Page 1


VISÃO FOKKA - COMUNICATION AGENCY


About Br. J. Anal. Chem. The Brazilian Journal of Analytical Chemistry (BrJAC) is a peer-reviewed scientific journal intended for professionals and institutions acting mainly in all branches of analytical chemistry. BrJAC is an open access journal which does not charge authors an article processing fee. Scope BrJAC is dedicated to the diffusion of significant and original knowledge in all branches of Analytical Chemistry. BrJAC is addressed to professionals involved in science, technology and innovation projects in Analytical Chemistry at universities, research centers and in industry. BrJAC publishes original, unpublished scientific articles and technical notes that are peer reviewed in the double-blind way. In addition, it publishes reviews, interviews, points of view, letters, sponsor reports, and features related to analytical chemistry. Manuscripts submitted for publication in BrJAC cannot have been previously published or be currently submitted for publication in another journal. For manuscript preparation and submission, please see the Guidelines for the Authors section at the end of this edition. When submitting their manuscript for publication, the authors agree that the copyright will become the property of the Brazilian Journal of Analytical Chemistry, if and when accepted for publication. BrJAC is Published by: VisĂŁo Fokka Communication Agency Publisher Lilian Freitas MTB: 0076693/ SP lilian.freitas@visaofokka.com.br Advertisement Luciene Campos luciene.campos@visaofokka.com.br ISSN 2179-3425 printed

Editorial Assistant Silvana Odete Pisani brjac@brjac.com.br Art Director: Adriana Garcia WebMaster: Daniel Letieri ISSN 2179-3433 digital

BrJAC’s website: www.brjac.com.br Like BrJAC on Facebook: https://www.facebook.com/brjachem

BrJAC is covered in the Clarivate Analytics Emerging Sources Citation Index Av. Washington Luiz, 4300 - Bloco G - 43 Campinas - SP - Brazil Zip Code 13042-105 BrJAC is associated to the Brazilian Association of Scientific Editors

+55 (19) 98322-7040 / +55 (19) 99817-0405 contato@visaofokka.com.br www.visaofokka.com.br


Editorial Board Editor-in-Chief

Marco Aurélio Zezzi Arruda Full Professor / Institute of Chemistry, University of Campinas, Campinas, SP, BR

Associate Editors

Cristina Maria Schuch Analytical Department Manager / Solvay Research & Innovation Center, Paris, FR Elcio Cruz de Oliveira Technical Consultant / Technol. Mngmt. at Petrobras Transporte S.A. and Aggregate Professor at the Post-graduate Program in Metrology, Pontifical Catholic University, Rio de Janeiro, RJ, BR Fernando Vitorino da Silva Chemistry Laboratory Manager / Nestle Quality Assurance Center, São Paulo, SP, BR Mauro Bertotti Full Professor / Institute of Chemistry, University of São Paulo, São Paulo, SP, BR Pedro Vitoriano Oliveira Full Professor / Institute of Chemistry, University of São Paulo, São Paulo, SP, BR Renato Zanella Full Professor / Dept. of Chemistry, Federal University of Santa Maria, Santa Maria, RS, BR

Advisory Board

Adriano Otávio Maldaner Criminal Expert / Forensic Chemistry Service, National Institute of Criminalistics, Brazilian Federal Police, Brasília, DF, BR Auro Atsushi Tanaka Full Professor / Dept. of Chemistry, Federal University of Maranhão, São Luís, MA, BR Carlos Roberto dos Santos Director of Engineering and Environmental Quality of CETESB, São Paulo, SP, BR Gisela de Aragão Umbuzeiro Professor / Technology School, University of Campinas, Campinas, SP, BR Janusz Pawliszyn Professor / Department of Chemistry, University of Waterloo, Ontario, Canada Joaquim de Araújo Nóbrega Full Professor / Dept. of Chemistry, Federal University of São Carlos, São Carlos, SP, BR José Anchieta Gomes Neto Associate Professor / São Paulo State University (UNESP), Inst. of Chemistry, Araraquara, SP, BR José Dos Santos Malta Junior Pre-formulation Lab. Manager / EMS / NC Group, Hortolandia, SP, BR Lauro Tatsuo Kubota Full Professor / Institute of Chemistry, University of Campinas, Campinas, SP, BR Luiz Rogerio M. Silva Quality Assurance Associate Director / EISAI Lab., São Paulo, SP, BR Márcio das Virgens Rebouças Global Process Technology / Specialty Chemicals Manager - Braskem S.A., Campinas, SP, BR Marcos Nogueira Eberlin Full Professor / School of Engineering, Mackenzie Presbyterian University, São Paulo, SP, BR Maria das Graças Andrade Korn Full Professor / Institute of Chemistry, Federal University of Bahia, Salvador, BA, BR Ricardo Erthal Santelli Full Professor / Analytical Chemistry, Federal University of Rio de Janeiro, RJ, BR


Contents

Br. J. Anal. Chem., 2019, 6 (22)

Editorial 19 ENQA & 7th CIAQA — Innovation for Sustainable Analytical Chemistry.....................................2-3 th

Wendell Karlos Tomazelli Coltro

Interview Professor José Luís Costa Lima, with an extensive and prestigious academic career, collaborated and continues to collaborate with many Brazilian research groups.........................................................4-7 Points of View Portable Analytical Techniques for Forensic Applications..................................................................8-9 Thiago R. L. C. Paixão

Women in Science - Current Status, Challenges, and Trends in Brazilian Analytical Chemistry....... 10-11 Márcia Foster Mesko

Letter Biomarkers of oxidative/nitrosative/carbonyl Stress: How important are they and where to go in their analyses?......................................................................................................................................12-13 Monika B. dos Santos, Jadriane A. Xavier, Ana Caroline F. Santos, Fabiana A. Moura, Marília O. F. Goulart

Articles Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design.....................................................14-28 de Sousa, P. A. R.; Furtado, L. T.; Neto, J. L. L.; de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

Development of a Prototype Management Software for Testing Laboratories – Quality Control under ISO/IEC 17025:2017 Standard......................................................................................................29-38 Sales, D. M.; Alves, R. A. S.; Rocha, J. C. P.

Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran samples by HPLC.............................................................................................................................................39-51 Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Fast and Simple Spectrophotometric Procedure for Determination of TiO2 in Paint Samples......52-59 Reis, F. E.; Maringolo, V.; Diogo Librandi Rocha, D. L.

Magnetic Solid Phase Microextraction using CoFe2O4 Nanoparticles for Determination of Cu, Cd, Pb and V in Sugar Cane Spirit Samples by Energy Dispersive X-Ray Fluorescence Spectrometry.............60-66 Meira, L. A.; Almeida, J. S.; Dias, F. S.; Teixeira, L. S. G.

Electrode Modified with 1,3-bis (4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) ions in Cabbage Cultivated with Bordeaux Syrup....................................67-79 Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability......80-90 Casanova, M. C. R.; Ferreira, G. S.; de Abreu, A. N.; Damasceno, D.


Contents

Feature 19 ENQA was a Milestone in Sustainability.................................................................................91-97 th

Sponsor Reports Discovery of emerging disinfection by-products in water using gas chromatography coupled with Orbitrap-based mass spectrometry.............................................................................................98-105 Thermo Scientific

Monitoring Inorganic Anions and Cations During Desalination................................................. 106-115 Thermo Scientific

Determination of Mercury in Soil Samples Using Direct Mercury Analysis............................... 116-117 Milestone

Releases Don’t miss the Largest Meeting of Analytical Chemistry in Latin America - The 6th Analitica Latin America Congress............................................................................................................................ 118 Thermo Scientific Exactive GC Orbitrap GC-MS System - The Frontier of Routine GC-MS............ 120 Thermo Scientific Dionex ICS-6000 HPIC System - The Freedom to Explore................................. 122 DMA-80 - The most successful Hg Analyzer in the market.............................................................. 124 Pittcon is the world’s leading annual conference and exposition for laboratory science.................. 126 SelectScience® Pioneers Online Communication and Promotes Scientific Success since 1998................................................................................................................................................. 128 CHROMacademy Helps Increase your Knowledge, Efficiency and Productivity in the Lab............. 130 Women in Science: The Federal University of Pelotas discusses the Challenges and Perspectives of Including New Talent........................................................................................................................ 132 Notices of Books

....................................................................................................133-134

Periodicals & Websites ........................................................................................................... 135 Events

....................................................................................................136-137

Guidelines for the Authors ...............................................................................................138-140


Editorial

Br. J. Anal. Chem., 2019, 6 (22) pp 2-3 DOI: 10.30744/brjac.2179-3425.editorial.wktcoltro

19th ENQA & 7th CIAQA — Innovation for Sustainable Analytical Chemistry

Wendell Karlos Tomazelli Coltro BrJAC’s Guest Editor Associate Professor Institute of Chemistry, Federal University of Goias Goiânia, GO, Brazil wendell@ufg.br The National Meeting on Analytical Chemistry (ENQA) is organized by the Analytical Chemistry Division of the Brazilian Chemical Society. ENQA’s main goal is to present and discuss the latest advances in analytical chemistry in Brazil. Since 1982, when the first ENQA was held, the event has traditionally been held every two years in different regions of Brazil. The 19th ENQA was organized and held jointly with the 7th Ibero-American Congress on Analytical Chemistry (7th CIAQA) from 16 to 19 September 2018 at the city of Caldas Novas, Goias. This was the first edition of ENQA to be held in the midwest region of Brazil. Caldas Novas is a touristic city and has the largest thermal water spring in the world. The meeting was a great forum to review recent scientific contributions on electrochemistry, atomic spectrometry, mass spectrometry, analytical instrumentation, separation methods, sample preparation, environmental chemistry, energy, microfluidics, chemometrics as well as other topics in analytical chemistry. The 19th ENQA & 7th CIAQA received more than 1,100 submitted abstracts and was attended by over 1,200 participants who came from 25 states and Federal District in Brazil, and 3 other countries. The conference theme was focused on “Innovation for Sustainable Analytical Chemistry” and offered 5 short courses, 2 workshops, 4 symposia, 9 plenary talks, 2 round tables, 3 themed sessions, 4 technical talks, 80 oral presentations, 3 poster sessions and several social integration activities. The meeting also presented tribute and book release sessions. In parallel with scientific programming, the meeting also promoted a 3-day exposition of companies associated with the analytical chemistry field, making possible interaction with technical experts to accomplish the latest instrumental advances and find solutions for all routine laboratory challenges. Due to the remarkable indicators, the 19th ENQA can be considered one of the largest editions since 1982. The organizing committee gratefully acknowledges all sponsors including funding agencies, companies, the Royal Society of Chemistry and the National Institutes of Science and Technology (INCTBio, INCTAA, INCT-E&A and INCT-DATREM), who contributed to support the invited national and international speakers. It is important to highlight some activities realized during the 19th ENQA. The themed session dedicated to “Women in Analytical Chemistry” was very successful and received over 250 participants. The integration with high school students also deserves mention. The activity named “ENQA in the Schools” provided a series of experiments with simple or no instrumentation and visual impact to demonstrate concepts and applications involving analytical chemistry. Overall, more than 500 students participated in this pioneering interaction. Other social activities included the donation of chemistry books. Around 90 books were received and donated to a charity organization. These actions were considered important for the host city. 2


Editorial

For this special issue, we thank all authors for submitting their contributions and all reviewers for sharing their time and expertise to contribute to the quality of the issue dedicated to the 19th ENQA & 7th CIAQA. Lastly, we recognize the organizing and scientific committees and the overall staff for their support. Enjoy reading.

3


Interview

Br. J. Anal. Chem., 2019, 6 (22) pp 4-7 DOI: 10.30744/brjac.2179-3425.interview.jlclima

Professor José Luís Costa Lima, with an extensive and prestigious academic career, collaborated and continues to collaborate with many Brazilian research groups

José Luís Costa Lima Emeritus Professor Faculty of Pharmacy, University of Porto, Portugal limajlfc@ff.up.pt Professor José Luís Costa Lima was born in Cidade do Porto, Portugal, and graduated in Chemistry at the Faculty of Sciences of the University of Porto, where he also obtained a PhD degree with a thesis titled “Ion-selective electrodes with conductive resin support”. In 1986, he joined the Faculty of Pharmacy of the University of Porto (FFUP) as an assistant professor and participated in the founding of a group in the area of Analytical and Applied Chemistry that resulted in the creation of a true “School of Analytical Chemistry”, generating more than 40 PhDs, whom Professor Costa Lima affectionately calls “scientific children”. In 1992, he began to work as an associate professor at FFUP and in 1996 as full professor. On December 4, 2015 he gave his last lecture at the Noble Hall of the Abel Salazar Institute of Biomedical Sciences (ICBAS) / FFUP complex. Throughout his academic career in the Faculty of Pharmacy, Costa Lima has advised several PhD students in exchange programs with Spanish and Brazilian universities. He was responsible for the disciplines of “Analytical Chemistry and Instrumental Methods of Analysis”, “Chemical and Physical Control” and “Methods of Analysis in Analytical Toxicology” at undergraduate and postgraduate levels from 2009 to 2015. He has held several management positions: as Chairman of the Board of Directors (1998–1999), President of the Scientific Council (2000– 2001) and Director of the Faculty of Pharmacy (2011–2015). Outside the University of Porto, he collaborated with the Superior School of Biotechnology of the Catholic University, Porto, Portugal, where he was responsible for the discipline of Analytical Chemistry and Instrumental Methods (1985–2011). He was president of the Institute of Agrarian Sciences and Technologies and Agrifood (1998–2012) and member of the Scientific and Technical Committee of REQUIMTE (Network of Chemistry and Technology), Associated Laboratory for Green Chemistry (2001– 2008), all in Portugal. He was the coordinator and executive investigator of more than four dozen research projects on the automation of chemical and biochemical analyses. He developed, with the collaboration of Professors Elias Zagatto and Boaventura Freire dos Reis, both from the University of São Paulo (Brazil), the multiple switching in flow networks by multiswitch and multi-impulsion, two automation techniques based on conditions of chemical non-equilibrium 4


Interview

at the time of execution of the analytical measurements. These techniques were then used internationally in the development of new analytical methods. Professor Costa Lima is the author or co-author of more than 500 scientific papers published in more than 100 Portuguese and foreign journals, in the areas of Fundamental Analytical Chemistry, and Food, Biological and Environmental Control Analytical Chemistry. He has made more than 1000 communications at national and international congresses, and his h index (ISI) equals 45 with over 16,500 citations. In 2016, he was honored by the Division of Analytical Chemistry of the Brazilian Chemical Society, in recognition of his contribution to teaching and research. In March 2017, in the commemorations of the University of Porto Day, he was distinguished with the title of Professor Emeritus of the University of Porto. Since 2005, Professor Costa Lima has been a foreign member of the Brazilian Academy of Sciences and of numerous other scientific societies, such as the Portuguese Society of Chemistry (vice-president, 2004–2006; president of the Division of Analytical Chemistry, 1996–1998 and 2000–2003; and president of the “Porto” Delegation, 2007–2012), the Portuguese Society of Electrochemistry, the Spanish Society of Analytical Chemistry, and the International Society of Electrochemistry. He was also president of the Portuguese Society of Pharmaceutical Sciences (2010–2015) and the Portuguese Society of Electrochemistry (2000–2002). Which factors influenced your education? What motivates you in analytical chemistry? Throughout my school education, a set of facts that led me to Analytical Chemistry came together. My entrance to the university, with facilities that do not exist today, has resulted from an occasional choice for the Chemical Sciences. In my undergraduate course, the final term paper that was assigned to me (at the time the students’ choices were not considered) was an analytical application of electrochemistry, which contributed decisively to consolidate my connection with Analytical Chemistry. What are your lines of research? What work are you currently …“the execution of a project developing? funded by the European Space In Portugal, a large part of the research management and funding Agency has further aroused structure occurs in parallel with the university teaching career. my interest in chemistry and Thus, it was possible for me to maintain the links with the Research analytical instrumentation in Center to which I have always belonged, so that I maintain the same the absence of gravity”… lines of research that I followed before my retirement. Recently, the execution of a project funded by the European Space Agency has further aroused my interest in chemistry and analytical instrumentation in the absence of gravity. Do you keep informed about the progress of chemistry research? What is your opinion about the current progress of research in chemistry in the Ibero-American region? What are the latest advances and challenges in instrumentation for flow injection analysis? As I have already mentioned, my research activity has not significantly changed in recent years, which leads me to systematically follow the enormous growth of chemistry research in the Ibero-American region. It should, however, be emphasized that it could be even more significant if collaboration between the various countries of the region were encouraged in some way. Concerning the second part of the question, I think it is difficult to find significant instrumental advances related to Flow Injection Analysis, except those concerning miniaturization. From the strategic point of view, it is worth noting the rupture with the original and traditional concept of a laminar flow-based transport in favor of the advantageous alternative of the use of pulsed flows.

5


Interview

For you, what have been the most important achievements in the analytical research field recently? What were the landmarks? What are the latest advances and challenges in analytical chemistry? It is tempting and easy to answer the formulated question referring to the advent or refinement of analytical techniques that have allowed reductions in the limits of detection and increases in the selectivity of the methods. From my point of view, the most important achievements in the analytical field is the increasing democratization of the use of instrumentation; that is, the ease of access to equipment, both in teaching and scientific research, and even in companies, compared to the existing situation in the last 20 years. In addition to this achievement, miniaturization has enabled the individual use of equipment to monitor relevant parameters of the health status of its bearer. “From my point of view, the most important achievements in the analytical field is the increasing democratization of the use of instrumentation”…

There are several meetings of chemistry experts that take place around the world. Last year, for example, the 19th Brazilian Meeting on Analytical Chemistry (ENQA) and 7th Ibero-American Congress on Analytical Chemistry (CIAQA) focused on Innovation for Sustainable Analytical Chemistry. What is the importance of these meetings to the development of the area? My response is supported by my participation in all ENQAs over the past 30 years as well as in the seven CIAQAs that have already taken place. My presence at these events allowed me to note that the ongoing research in Latin America and the growing participation of young researchers are very significant, but the same growth has not been detected with regard to collaborative work among institutions in the same country or among institutions in different countries. Particularly in the case of the CIAQA, it is necessary for the societies involved in its organization to be more active in creating conditions for the movement and participation of its members in the congress, and it is urgent that, at the central level, projects are implemented to increase the internationalization of research. Currently, you are an Emeritus Professor at the Faculty of Pharmacy at the University of Porto. In addition, do you perform other jobs? How many scientific papers have you published and can you share any highlights with us? As I have already mentioned, my connection with research has not changed significantly in recent years, since I remain full time and exclusively dedicated to the Faculty of Pharmacy at the University of Porto and consequently do not have any additional job. My research activity developed so far has resulted in more than 518 indexed articles that originated more than 16,500 citations. I cannot fail to point out that, among these works, 89 were published with groups from Brazil, reflecting partnerships of colleagues in Brazilian cities such as João Pessoa, Recife, Salvador, São Carlos, Campinas, Araraquara, São Paulo and especially Piracicaba, where I established a fantastic partnership and friendship with Professor Elias Zagatto and colleagues. It all started at a congress held in Cordoba (Spain) in 1989, where we assumed the commitment to start a collaboration between Brazil and Portugal in the field of analytical chemistry, a commitment that was always cherished by Professor Henrique Bergamin Filho until his death. What sort of a career could someone expect in the field of analytical chemistry? What advice would you give to a newcomer to this area? The speed of technological evolution recommends moderation in the predictions that can be made regarding any activity. I would stress, however, that given the nature and areas of intervention of analytical chemistry, it will always need specialists who respond to society’s growing concerns in areas such as food safety and environmental control, as well as public health. Such a scenario assures newcomers good perspectives and a lot of work, whether they face their future activity in teaching, 6


Interview

research or control, or whether they work in public or private entities. Do you believe that the current graduate programs produce quality researchers in the field of analytical chemistry? Is there need for further integration? My knowledge of undergraduate and postgraduate programs that I have been able to follow in Brazil over the past 30 years shows that the evolution was remarkable, with an ever-growing number of excellent and committed students who, in most cases, can be recommended as candidates for the highlevel postgraduate courses that many universities offer. With regard to this last aspect, I should point out that it is desirable that the training system assign greater importance to the tutorial role of supervisors. For you, what is the importance of the support of funding agencies for the scientific development of the country? As is usual to say (and governments are well aware), research spending is not an expense but an investment. However, in all countries, there is a tendency to lament the supposedly small volume of investment mobilized by the funding agencies, and Brazil is no exception. However, as an external observer, it seems to me that there are aspects that significantly affect the profitability of the financial resources made available. Managers of science and technology who simplify the execution of the projects, along with agile ways of acquiring the required means for the development of the programs would be very significant improvements and would be advantageous alternatives to the injection of larger funds. You have also received some awards in more than one category. What is it like to receive this recognition? What is the importance of these awards in the development of new technologies? In fact, throughout my career, I was honored with certain awards, such as the Galician-Portuguese Chemistry Prize awarded by the National Association of Chemists of Spain (1991), the Prize for Excellence in Research by the Foundation for Science and Technology (2004), the FIA Honor Award for Science by the Japanese Association for Flow Injection Analysis (2008), the Ferreira da Silva Prize (career award) and as Honorary Member of the Portuguese Chemical Society (2012 and 2016). These awards were a great satisfaction to me and correspond to peer recognition, but I must point out that my greatest personal satisfaction resulted in being a foreign member of the Brazilian Academy of Sciences (2015).

7


Point of View

Br. J. Anal. Chem., 2019, 6 (22) pp 8-9 DOI: 10.30744/brjac.2179-3425.point-of-view-trlcpaixao

Portable Analytical Techniques for Forensic Applications

Thiago R. L. C. Paixão Associate Professor Department of Fundamental Chemistry, Institute of Chemistry University of São Paulo, SP, Brazil trlcp@iq.usp.br Forensic chemistry is defined as the science that deals with the analysis, classification, and quantification of elements or substances during the investigation of crime scenes, so that they could be used as valid evidence during subsequent legal proceedings. A variety of professionals from the field of chemistry are involved in forensics, including organic, inorganic, physical and analytical chemists. Analytical chemists occupy an important position in the field of forensic chemistry, because most investigations require the development or application of a technique pertaining to analytical chemistry for the examination, identification, and/or comparison of materials collected from crime scenes. In some cases, real-time analyses of the materials collected in-situ from crime scenes are suitable by using portable devices or methods. The concept of using analytical chemistry as a method to establish evidence (or otherwise) against/ in favor of the accused was pioneered in London for the trial of John Bodle in 1832, who was accused of murdering his grandfather by arsenic poisoning. The British chemist James Marsh proposed the use of chemical techniques to detect traces of arsenic in the stomach of the corpse. Although Marsh was successful in determining the presence of arsenic, but the test results had deteriorated before they could be presented to the jury and the judge. As a result, Bodle was acquitted, although he confessed to the murder later. Looking for a more reliable test in crime investigation, Marsh proposed the Marsh test. It was an improvement over the Scheele’s test that involved the reaction of arsenic powder with metallic zinc and nitric acid in the presence of heat to form arsine gas (AsH3). Marsh confined the formed arsine gas inside a funneled tube and re-heated it. The trapped arsine gas was decomposed into a gray metallic film, forming an “arsenic mirror” that could be used as evidence in the courtroom [1]. This test was used to establish the guilt of Marie LaFarge, who was accused of using arsenic to poison her husband. Hence, the development and use of analytical techniques occupy an important position in contemporary crime investigation as tools to detect and quantify chemicals found in crime scenes. For example, most modern analytical laboratories use sophisticated methods such as atomic absorption spectrometry and inductively coupled plasma mass spectrometry to detect arsenic in a biological sample. Apart from the methods listed above, some non-standard techniques are being increasingly used in forensic analysis because of their enhanced portability and reduced costs [2,3]. The portable techniques could be very helpful for in-situ forensic analysis at crime scenes. For example, if a large amount of evidence is uncovered from a crime scene, conventional analytical methods would involve the investment of a lot of time and effort in performing definitive analyses of all the substances in order to classify them and determine their nature. A batch of seized material presumed to be cocaine could end up being something that is entirely irrelevant and/or harmless, thus rendering the entire endeavor wasted. Hence, quick preliminary field analyses are extremely important to reduce the number of definitive analyses. As a result, portable techniques are applicable 8


Point of View

because they are widely used as an initial step to analyze suspicious materials or illicit substances. Thus, portable techniques minimize the necessity of storing a large number of samples, which is a requirement when conventional methods of analysis are applied. This field has garnered considerable research interest, and consequently the number of publications in analytical chemistry literature about the portable techniques is increasing steadily [2,3]. However, these methods need further development to be readily applicable in the field of forensic analysis. 1. Marsh, J. Edinburgh New Philos. J., 1836, 21, pp 229–236. 2. Oliveira, L. P.; Rocha, D. P.; Araujo, W. R.; Muñoz, R. A. A.; Paixão, T. R. L. C.; Salles, M. O. Anal. Methods, 2018, 10, pp 5135–5163. 3. Araujo, W. R.; Cardoso, T. M. G.; Rocha, R. G.; Santana, M. H. P.; Muñoz, R. A. A.; Richter, E. M.; Paixão, T. R. L. C.; Coltro, W. K. T. Anal. Chim. Acta, 2018, 1034, pp 1–21.

9


Point of View

Br. J. Anal. Chem., 2019, 6 (22) pp 10-11 DOI: 10.30744/brjac.2179-3425.point-of-view-mfmesko

Women in Science: Current Status, Challenges, and Trends in Brazilian Analytical Chemistry Márcia Foster Mesko Associate Professor Centro de Ciências Químicas, Farmacêuticas e de Alimentos Universidade Federal de Pelotas – UFPel Pelotas, RS, Brazil marcia.mesko@pq.cnpq.br The worldwide discussion regarding gender equity in science has grown in recent years. In Brazil, due to several recent actions, discussions about ensuring inequality reduction and the integration of minorities into society and diverse environments, including chemistry, have clearly increased. In chemistry, as in many other areas of science in Brazil, few women hold prominent positions. However, the number of women who choose careers in the exact sciences and engineering, for example, is increasing, and this is probably related to various actions that stimulate and encourage women to choose such careers. Therefore, we must reflect on educational processes that begin in childhood, when girls are often discouraged from playing games or participating in activities simply because they are girls. From my point of view, small changes to outdated habits can significantly influence the transformations we wish to promote. Nowadays, this is also evident in the scientific community, where the number of women who are active researchers and who occupy leadership positions is increasing. We must reflect on this and understand that gender differences promote diversity of thoughts, perceptions, and methods, which contributes significantly to the field. In the scientific community, and in Brazilian chemistry specifically, more women are now prominent researchers, and this will certainly influence new generations of students. In particular, I believe that female chemists today play a key role in shaping the future of new scientists. We must, therefore, get rid of the preconceptions that still exist and, above all, continue to show that we are capable of pursuing any career we wish until everything happens naturally. In my opinion, increasing initiatives and projects aimed at achieving gender equity in science remains fundamental to ensuring we have more opportunities to acquire leadership positions and pursue successful careers. We must think more about acknowledging the demands of women, who often care for their families and work twice as much as men to consolidate their careers. Moreover, in Brazil the difference between regional and racial issues must also be considered to correct historical misconceptions. In this context, actions that reduce public investment in education, science, and technology in our country are lamentable, as this leads to less social and economic development and decreases the chances of expanding opportunities for women working for scientific and technological development. Various actions and programs have been proposed, and many of these are in evidence, such as maternity leave for scholarship researchers. In addition, gender diversity has been prioritized in the constitution of scientific committees, among other representative places. This will lead to new reflections that inform future actions. Unfortunately, the number of female analytical chemists in such places is still low.

10


Point of View

Furthermore, programs like “For Women in Science,” promoted by L’Oréal, the Brazilian Academy of Sciences, and United Nations Educational, Scientific and Cultural Organization, recognize scientists throughout the country. Besides encouraging women to continue their research, the program also promotes the dissemination of each winner’s scientific activities to society. Such actions draw attention to female scientists, bringing science closer to society and allowing more women to imagine themselves as scientists. It is also important to mention the increasing number of female analytical chemists in Brazil. In this way, the Brazilian Chemical Society and its Analytical Chemistry Division have motivated discussions about this issue in recent years. Among such actions, the successful section dedicated to “Women in Analytical Chemistry: challenges and perspectives” during the 19th National Meeting of Analytical Chemistry and the 7th Ibero-American Congress of Analytical Chemistry is quite relevant. A surprising number of male and female participants discussed the current state of gender equity in the Brazilian analytical chemistry community. In my opinion, this type of action motivates and encourages young female researchers to continue their careers. I usually emphasize that gender equity is important to the sciences and society because male and female perceptions are complementary when observing the same phenomena. Moreover, in my opinion, the sciences have grown significantly in Brazil in recent decades, and to achieve better results, government investments in education, science, and technology are essential. It is likewise important to mention that the number of female researchers in chemistry and analytical chemistry is growing and that public politics are essential to creating more opportunities for women. I hope to see gender equity achieved in the coming years. Therefore, from my point of view reflections, discussions, and actions are essential for the promotion of necessary transformations in society and the sciences, especially regarding the inclusion of minorities. We must continue to show that gender diversity among professionals contributes to society and science in a meaningful way. Thus, in my opinion, it is still necessary to emphasize that it does not mean occupying the other’s space, but that each has the right to occupy the space regardless of gender, race or skin color.

11


Letter

Br. J. Anal. Chem., 2019, 6 (22) pp 12-13 DOI: 10.30744/brjac.2179-3425.letter.mofgoulart

Biomarkers of oxidative/nitrosative/carbonyl stress: How important are they and where to go in their analyses?

Monika B. dos Santos, Jadriane A. Xavier, Ana Caroline F. Santos, Fabiana A. Moura, Marília O. F. Goulart*

Laboratory of Electrochemistry and Oxidative Stress, Institute of Chemistry and Biotechnology, Federal University of Alagoas, Maceió, AL, CEP: 57072-970, Brazil *mofg@qui.ufal.br /

Life in aerobic environments inevitably leads to the formation of reactive oxygen species (ROS). When in low concentrations, they are essential for redox signaling (“eutress”), and cell homeostasis. On the other hand, in higher concentrations, they can cause irreversible damage to macromolecules, leading to benefits (for instance, in cancer treatments, and as antibacterial or parasiticidal agents) or harm, in a process known as oxidative stress (OS) (“distress”) [1]. Other species of strong relevance in this context are reactive nitrogen species (RNS), mixed reactive oxygen and nitrogen ones (RONS), reactive sulfur species (RSS) and reactive selenium species (RSeS) [1]. Oxidative stress, an imbalance between oxidants and antioxidants in favor of the oxidants, leading to a disruption of redox signaling and control and/or molecular damage [1], is the biochemical basis of aging and of a number of diseases, including cancer [2] and gastrointestinal [3], cardiometabolic [4] and neurodegenerative [5] diseases. In many cases, OS can lead to the increased formation of reactive carbonyl species (RCS), especially in conditions of high level of glycemia, which contribute greatly to the generation and aggravation of these diseases, giving rise to the term carbonyl stress (CS), related to various forms of metabolically generated aldehydes and electronically excited (triplet) carbonyls [1]. There is a strong connection between RONS, RCS and disease. This area is of increasing clinical interest and presents several scientific and technological challenges, including a detailed understanding of the link between OS and pathogenesis. The aim is to assess disease status and to develop preventive and therapeutic strategies in humans [1,6-8]. To achieve these goals, a series of biomarkers have been employed [6-8]. A single parameter as gold standard for defining redox status in clinical samples has not yet been reported [8]. In fact, the assessment of OS in clinical samples involves: (1) direct measurement of RONS levels, (2) detection of the resulting oxidative damage to biomolecules (RNA/DNA, lipids, sugars and proteins), and (3) the determination of antioxidant status (enzymatic antioxidant activities, nonenzymatic antioxidant levels or total antioxidant capacity) [8]. As representatives of approach (1), major analysed species are H2O2, HOCl, peroxynitrite and 12


Letter

others. In approach (2), principal biomarkers include: carbonylated proteins; advanced glycation end products (AGEs, derived from RCS); 3-nitrotyrosine; 3-chlorotyrosine; oxidized low-density lipoprotein (ox-LDL); other lipid oxidation products such as 4-hydroxy-nonenal (4-HE) and malondialdehyde (MDA); F2-isoprostanes; DNA/RNA oxidation products such as 8-oxo-deoxyguanosine; methionine sulfoxide and others. In approach (3), total thiols, glutathione reduced/oxidized ratio (GSH/GSSG) and cysteine/ cystine redox couples, superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx) activities, antioxidant index, measured through different methods, and several others have been used. The vast diversity in OS between diseases and conditions has to be taken into account when selecting the most appropriate biomarkers. Despite the recognition of these biomarkers as being relevant for diagnosis, several drawbacks are still experienced in this area: the use of different biomarkers and protocols of analysis in the literature, revealing data fragmentation; and the measurement of biomarkers using nonspecific methods, as specific ones are too sophisticated or laborious for routine clinical use. There is a considerable data variability across laboratories. As such, no adequate comparison has yet been performed between different biomarkers and the methodologies used to measure them, making it difficult to conduct a conclusive analysis of findings from different laboratories. Recommendations, critical evaluation and adaptation of proposed methodologies available in the literature are urgently required, to enable the investigators to choose the most suitable procedure for each chosen biomarker. Measurement of larger panels of biomarkers in key conditions will help to give a more comprehensive picture of their significance. In parallel with the exciting developments in ROSvalidated targets and clinical indications, those markers and patterns that correlate best with treatment efficacy or mortality will eventually advance the field of ROS biomarkers. Therefore, an integrative approach, with simultaneous multiple biomarkers’ analysis, examining both pro- and antioxidant reactions, as shown before, will lead to a comprehensive score with higher sensitivity to physiological and pathological alterations. The field is open for new methodologies and innovations, especially in vivo and in a non-invasive way, which require interdisciplinary knowledge in the search for selectivity, sensitivity and good analytical performance. The use in public health, for instance in point-of care devices, demands cheap assays, small sample amounts and portability, especially for in situ analysis. This arena will become the place where science meets technology, leading to evolution. This is urgent, since the earlier diseases are discovered, the higher the chance of treatment and cure. REFERENCES 1. Sies, H.; Berndt, C.; Jones, D.P. Annu. Rev. Biochem., 2017, 86, pp 715-748. 2. Sosa, V.; MolinÊ, T.; Somoza, R.; Paciucci, R.; Kondoh, H.; Lleonart, M. E. Ageing Research Rev., 2013, 12 (1), pp 376-390. 3. Moura, F. A.; de Andrade, K. Q.; dos Santos, J. C.; Araujo, O. R.; Goulart, M. O. F. Redox Biol., 2015, 6, pp 617-639. 4. Tenorio, M. B.; Ferreira, R. C.; Moura, F. A.; Bueno, N. B.; Goulart, M. O. F.; Oliveira, A. C. M. Nutr. Metab. Cardiovasc. Dis., 2018, 28 (9), pp 865-876. 5. Swomley, A. M.; FÜrster, S.; Keeney, J. T.; Triplett, J.; Zhang, Z.; Sultana, R.; et al. Biochim. Biophys. Acta, 2013, 1842 (8), pp 1248-1257. 6. Griffiths, H. R.; Moller, L.; Bartosz, G.; Bast, A.; Bertoni-Freddari, C.; et al. Mol. Aspects Med., 2002, 23, pp 101-208. 7. Frijhoff, J.; Winyard, P. G.; Zarkovic, N.; Davies, S. S.; Stocker, R.; et al. Antioxid. Redox Signal., 2015, 23, pp 1144-1170; 8. Katerji, M.; Filippova, M.; Duerksen-Hughes, P. Oxid. Med. Cell. Longevity, 2019, Article ID 1279250. 13


Article

Br. J. Anal. Chem., 2019, 6 (22) pp 14-28 DOI: 10.30744/brjac.2179-3425.AR.119-2018

Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media — Study based on Factorial Design Priscila Afonso Rodrigues de Sousa1*, Liliam Tavares Furtado1, João Luiz Lima Neto1, Fabiano Mendonça de Oliveira2, José Guilherme Martins Siqueira1, Luiz Fernando Silva1, Luciana Melo Coelho1 1

Federal University of Goiás, Regional Catalão, Catalão, GO, 75704-020, Brazil. *rodriguessousa41@hotmail.com Federal University of Uberlândia, Monte Carmelo Campus, IQUFU, Monte Carmelo, MG, 38500-000, Brazil.

2

Graphical Abstract

Adsorption of emergent contaminants using banana peel as adsorbent and factorial planning method with response surface analysis

A simple procedure was developed with the adsorption of the compounds estrone (E1), 17α-ethinylestradiol (EE2), and sulfamethoxazole (SMX) in aqueous solutions using banana peel as an adsorbent material. Adsorbent mass, contact time, and granulometry were studied through multivariate design. The proposed adsorbent was advantageous, with removal exceeding 80% for E1 and EE2 and 70% for SMX in the analysed samples. Studies of adsorption isotherms demonstrate adequacy compared to the Freundlich model, and kinetic studies indicate adsorption through the pseudosecond order model (E1 = 0.9999, EE2 = 0.9999, and SMX = 0.9999). The developed method was successfully applied in supply water samples and accuracy was evaluated through recovery tests, with recovery ranging from 70% to 96%.

Keywords: Adsorption, emerging contaminant, multivariate design, hormone, antibiotic INTRODUCTION The contamination of water resources has long been a major concern. According to the World Health Organization (WHO), since 1970 intense modifications observed in the environment have been caused by the presence of natural and synthetic contaminants, especially in groundwater and surface waters, at concentrations of pg L–1 to ng L–1. Compounds arising from human activities and found in the environment are known as emerging contaminants [1]. Many compounds are classified as emerging contaminants, particularly toiletries, pharmaceuticals, hormones, products for veterinary use, drugs, additives, and beauty and cleaning products [2]. Antibiotics used in the treatment of infections and pharmaceuticals represent a class of emerging contaminants classified as endocrine disrupters or endocrine interfering. According to the Environmental Protection Agency (EPA), “disrupter or endocrine interfering are exogenous agents that interfere in the synthesis, secretion, transport, binding, action or elimination of natural hormones in the body which are responsible for the maintenance, reproduction, development and behaviour of organisms” [3]. Estrone (E1) and 17α-ethinylestradiol (EE2) compounds are classified as endocrine disruptors when found in the environment. 14


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

Estrone is a derivative of the hormone 17β-estradiol, which is present in females and males organisms [4]. The daily excretion of this compound in domestic sewage is variable; pregnant women excrete 600 μg per day, while men excrete only 3.9 μg per day [5,6]. The compound 17α-ethinylestradiol (EE2) is a synthetic hormone found in contraceptive pills, which are being discarded in the environment through urine and feces [7]. The sulfonamides are compounds that act as microbial inhibitor agents on the bacteria in the treatment of intestinal and respiratory infections [8,9]. The antibiotic sulfamethoxazole (SMX) is a compound of the sulfonamide class with bacteriostatic function that is consumed by patients with intestinal infections [11]. This compound is found in urine at concentrations of 10–30% of the initial concentration consumed [12]. The study of these compounds is necessary because they can be found in the environment due to the excretion of animals or indiscriminate disposal of sewage. Antibiotics, such as sulfamethoxazole, were found in effluents from different countries (France, Greece, and Germany) at concentrations of 0.01–0.41 µg L–1 [16]. The compound EE2 was found at concentrations of 0.2–0.45 µg L–1 in Italy, the Netherlands, England, and Germany. Estrone was found at concentrations of 0.5– 0.027 µg L–1 in Italy, the Netherlands, and Germany [17]. The conventional treatment of water, sewage and industrial effluents are not efficient in the removal of these compounds, requiring the development of more efficient techniques. A proposed method to remove these compounds from aqueous environments is the use of natural adsorbents for the treatment of contaminated water [18–20]. Activated carbon is an adsorbent efficiently used for the removal of different compounds (organic or metallic). However, its cost is higher than most of the natural adsorbent materials cited in the scientific literature. In this context other natural adsorbents have been extensively researched, such as coconut shell, palm and bamboo, orange skin, and rice husk [21–24]. Banana peel, which is usually used as fertilizer or animal feed [25], is a type of natural adsorbent that has been used in the development of analytical methods. Several studies have shown the use of banana peels to remove organic compounds and metals, demonstrating the efficacy of this adsorbent material in the removal of different compounds. Gupta [26] proposed an efficient and inexpensive approach to remove polycyclic aromatic hydrocarbons from an aqueous system using activated charcoal synthesized from banana peel. The results demonstrated the removal of up to 95% of the hydrocarbons at a concentration of 20 mg L–1 when using around 2 mg of adsorbent material and a contact time of 80 min. Silva et al. [27] developed a method using banana peel in the removal of the pesticides atrazine and ametryne from river and treated waters. In their study, low limit of quantification (LOQ) values were achieved (0.10 and 0.14 μg L–1) for both pesticides with removal efficiency greater than 90%, thus demonstrating the efficiency of banana peel as a bioadsorbent for aqueous systems. The potentiality of the banana peel as adsorbent material was also evaluated by the adsorption of Congo red dye from an aqueous solution [28]. This adsorption study was performed through the evaluation of operational variables such as pH (pH 10), adsorbent concentration (increasing the adsorbent concentration from 0.5 g / 80 mL to 1.5 g / 80 mL resulted in the percentage of adsorption ranging from 63.32% to 75.26%), contact time (90 minutes) and temperature (40 ºC). The adsorption equilibrium of the dye was evaluated by the Freundlich and Langmuir isothermal models. The results revealed that the isotherm and the adsorption kinetics of the dye fit well with the Langmuir isotherm and the pseudo-second order kinetics, respectively. The adsorption capacity of the dye was recorded as 1.727 mg/g [28]. A bibliographic search in the Web of Science database for the keywords “banana peel”, “sulfamethoxazole”, “estrone”, and “ethinylestradiol” showed no published research article in which banana peel is used for the adsorption of E1, EE2, or SMX, demonstrating the possibility and necessity of studying the potential of banana peels in the removal of these compounds. Thus, in this study a methodology for the removal of the emerging contaminants estrone, ethinyl estradiol, and sulfamethoxazole in water was developed using banana peel as a biosorbent. The determination of the organic compounds in water samples was performed by high performance liquid chromatography (HPLC). Parameters influencing adsorption were studied through multivariate design. 15


Article

de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

MATERIALS AND METHODS Solutions and adsorbent material preparation The compounds estrone (E1) (≥ 99% purity), 17α-ethinylestradiol (EE2) (≥ 98% purity), and sulfamethoxazole (SMX) (99% purity) were acquired from Sigma-Aldrich. The working solutions were obtained by diluting a stock solution of 100.0 mg L–1 of each compound prepared with ultrapure water obtained by a water purification system from Gehaka (São Paulo, Brazil). Before use, the laboratory glassware was left in a 10% (v/v) aqueous solution of nitric acid overnight, and rinsed with deionized water the next day. The adsorbent material was purchased from a trade, washed with distilled water and oven dried for 24 h at 105 °C. After drying, the peels were crushed in a blender (Black & Decker, São Paulo, Brazil) and sieved in different grades (60 to 100 mesh). This material, designated as “banana peel in natura”, was submitted to physical-chemical analysis and used in adsorption tests. High performance liquid chromatography (HPLC) A high-performance liquid chromatography system (Shimadzu Model SPD-20A) coupled with an UV–Vis detector was used for the chromatographic analyses. The column used was octadecyl (C18) (250 × 460 mm ID, 5 µm), the mobile phase was MeCN/H2O (50:50 v/v), the flow rate was 1.0 mL min–1, the injection volume was 20.0 μL, and the wavelength was 212 nm. The quantification was performed by external standardization through the calibration curve for each compound at different concentration values, prepared by diluting the stock solution at a concentration of 100.0 mg L–1 of each compound. The retention times of E1, EE2, and SMX were 5.3, 4.8, and 3.2 min, respectively. Adsorbent characterization The functional groups present on the surface of the adsorbent were identified by infrared spectroscopy. An IR Prestige-21 infrared spectrophotometer (Shimadzu) was used in this study. The adsorbent material was compressed in a KBr tablet (10:1 KBr/sample) and the analyses were performed in the wavelength range of 4000–500 cm–1 with a resolution of 4 cm–1. Scanning electron microscopy (SEM) was performed for observation and analysis of the microstructural characteristics of the adsorbent under study. The micrographs were obtained using a scanning electron microscope (model JSM-6610, Jeol) equipped with EDS (energy dispersive spectroscopy) (NSS Spectral Imaging, Thermo Scientific) in the High Resolution Microscopy Laboratory of the Federal University of Goiás (LabMic, UFG), Samambaia Campus (Goiânia, GO, Brazil). Prior to the analyses, the samples were coated with a thin film of gold using a deposition system (Desk V, Denton Vaccum). The samples were fixed in a copper sample port with the aid of carbon tape. Study of pH influence on adsorption The influence of pH on the adsorption was studied by tests performed with 500.0 mg of the adsorbent (100 mesh) and 25.0 mL of the water sample at different pH values (2, 4, 6, and the natural pH of the mixture of E1, EE2, and SMX in water, pH = 5.25), and fortified with E1, EE2, and SMX at a concentration of 1.0 mg L–1. The samples were shaken at 150 rpm for 60 min using an orbital shaker table, filtered and analysed by HPLC. All tests were performed in triplicate (n=3) at room temperature (Tamb = 25 ºC). Optimization strategy for the adsorption of E1, EE2, and SMX After the pH optimization, a 23 factorial design [three variables, at two levels with their coded values (+) and (–)] was used to evaluate additional adsorption parameters, such as adsorbent mass (0.250 g and 0.500 g), granulometry (60 mesh and 100 mesh), and contact time (30 min and 60 min). Ten experiments were performed with two central points for each parameter. 16


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

The factorial design experiments were made with 25.0 mL of a solution containing a mixture of E1, EE2, and SMX at a concentration of 500 µg L–1. The mixtures in the test conditions were placed on an orbital shaker table at 150 rpm, with subsequent filtration and quantification by HPLC. Isotherms, adsorption kinetics, and thermodynamic parameters The adsorption kinetics tests were done using 25.0 mL of the solution containing E1, EE2, and SMX at a concentration of 500.0 µg L–1, and the mass was defined by factorial design studies at the following different shaking times: 5, 10, 15, 30, 45, 60, 75, 90, 120, 180, and 240 min. The solutions were filtered and analysed by HPLC. The adsorption isotherms were obtained using the mass and the optimized contact time through a factorial design with 25.0 mL of the solution containing the three compounds in different concentration ranges for E1 (1.5–12.0 mg L–1), EE2 (1.5–4.0 mg L–1), and SMX (1.5–10.0 mg L–1). The amount of compound adsorbed at the equilibrium time represents the adsorption capacity, Qe (mg/g), determined by equation (1) as follows:

Qe = (C0 – Ce) V W

(1)

where C0 and Ce (mg L-1) are the initial and equilibrium adsorbate concentrations, respectively; V is the volume of the solution (L); and W is the mass of the adsorbent (g). Samples The water samples were collected after treatment at the Water Treatment Station (ETA) in the city of Catalão, GO, Brazil, and before distribution to the population of this city. A total of three samples were collected. The samples were loaded in amber glass bottles with caps, properly identified with name, collection place, date and time, and were kept in a Styrofoam container with ice for transportation. In the laboratory, the capped amber glass bottles were placed in a refrigerator at approximately 4 ºC. The samples were analysed in less than 24 h after collection. Prior to the analyses, the water samples were filtered through 0.45 μm membranes to remove suspended particles. The pH of the samples was measured and corrected to 6.0 using NaOH or HCl (0.1 mol L–1) solutions. Aliquots were removed for analysis. RESULTS AND DISCUSSION Adsorbent characterization The spectrum obtained in the medium infrared region (FT-MIR) shows the functional groups present in the studied adsorbent (Figure 1).

17


Article

de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

Figure 1. Infrared spectrum of the banana peel.

The infrared spectrum of the banana peel shows the presence of some bands typical of different functional groups. The band at 884 cm–1 can be attributed to amine deformations, according to Memon et al. [29], and primary and secondary alcohols cause the band at 1059 cm–1. The band at 1104 cm–1 can be attributed to chemical bonding S–OH or –P=O groups, according to Corti et al. [30]. The carboxyl group is indicated by the band at 1300 cm–1. Vibration bands at 1525 cm–1, reported by Akhter et al. [31], are assigned to –NO2 groups. Bands at 1625 cm–1 may be assigned to a combination of C=C stretching vibrations of the aromatic ring structures or to systems such as diketone, ketoester, and quinone [32]. The band at 1734 cm–1 can be attributed to axial deformation vibrations of C=O in carboxylic acids or esters presents in the banana peel [25]. The band at 1750 cm–1 can be attributed to an ester, the band at 2927 cm–1 is due to methylcellulose, and the band at 3400 cm–1 is assigned to hydroxylic groups [33]. SEM analyses identified the morphological properties of the adsorbent material surface. Figure 2 shows an irregular porous surface (micro and macro pores) with the presence of some cracks and recesses, characteristics that favour adsorption. In the analysis of other materials (sugar cane and vegetable sponge) used in adsorption studies, similar results were observed [34,35].

Figure 2. Scanning electron microscopy (SEM) micrographs of banana peel. 18


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

Influence of pH on adsorption The biomass surface is composed of proteins, lipids, and carbohydrates, which are responsible for the surface charge of particles due to the dissociation of functional groups. This dissociation is pH dependent. To evaluate the influence of pH on the adsorption of compounds E1, EE2, and SMX, adsorption tests were made with solutions at different pH values. The results are shown in Figure 3.

Figure 3. Study of the influence of pH on the adsorption process of the compounds estrone (E1), ethinylestradiol (EE2), and sulfamethoxazole (SMX) (n=3).

Good removal rates of the compounds studied (>70%) were observed. The study of adsorption as a function of pH variation shows that from the initial concentration of 1.0 mg L-1 for each compound, the maximum amount of adsorption of compounds EE2, E1 and SMX was 0.93 mg L-1; 0.88 mg L-1 and 0.82 mg L-1, respectively, demonstrating efficient removal. This is due to the presence of a greater amount of hydroxyl and carbonyl groups on the surface of the adsorbent material, which was observed in the infrared spectrum. The variation of the adsorption rate of each compound in the different pH values was small, not exceeding 10%. Therefore, considering that the pH of a sample for HPLC chromatographic column analysis should not be too acidic nor too basic, the pH 6.0 was chosen for the analyses because it was close to the pH of the samples in which the method would be applied and the removal rate was greater than 80%. The pH of the solution was above the point of zero charge (PZC) of the biomass (pH=5.6) obtained experimentally by the authors, and surface negative charges were present predominantly in dissociated carboxyl and hydroxyl groups, interacting more satisfactorily with positively charged compounds. Bajpai and Rajpoot (1996) [36] reported that in solutions where the adsorbent is protonated, release of nitrogen-bound hydrogen in the SMX occurs, allowing the electrostatic attraction between the protonated functional group present on the surface of the adsorbent and negatively charged SMX. At pH values above 7, interaction of the deprotonated groups present on the surface of the adsorbent occurs with the hydrogen bound to the amino group. At a pH of 8, the neutral or deprotonated form (presence of negative charge) prevails, with interaction through hydrogen bonding as well as electrostatic interactions between the deprotonated functional group and the H present in SMX. According to Han et al. [37], hydrogen bonding interactions can occur between the phenolic hydroxyl 19


Article

de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

of EE2 and E1 and the amide groups present in the active sites of the adsorbents. These interactions are stable between pH values of 4.8 and 9.1. Furthermore, because of the bioaccumulation capacity of these compounds, they have a strong affinity for solids insoluble in aqueous solutions, contributing to the adsorption [37]. At higher pH values, there is less protonation of the functional groups, which could lead to greater interaction. In basic medium, there is competition between the hydroxyls and the compounds with the adsorption sites. According to Marques et al. [38], different interaction mechanisms can occur through hydrogen bonding with primary and secondary amine molecules, as well as hydrophobic interactions by Van der Waals forces and hydrogen bonds [39]. Study of chemical variables in the adsorption process The significance of each parameter in adsorption (adsorbent mass, time contact, granulometry) and interactions were determined using 23 complete factorial experiments and the response was the adsorption capacity, which is the amount of each compound adsorbed per unit mass of the adsorbent (Qe). An analysis of variance (ANOVA) test was performed to determine if the studied experimental factors were significant (with a value of 0.05) in the performance of the adsorption system. The main effects and their interactions are described in the Pareto graphs shown in Figure 4. The experiments were performed in triplicate and the lack of adjustment was evaluated through the ANOVA table, where the R-sqr value was 0.88066 and residual MS was equal to 0.0007841.

(a)

(b)

(c) Figure 4. Pareto chart of the standardized effects for the variables of adsorption systems E1 (estrone) (a), EE2 (ethinylestradiol) (b), and SMX (sulfamethoxazole) (c) with the banana peel adsorbent (n=3). 20


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

Analysing the Pareto graphics for the isolated variables (1, 2, and 3), it was observed that the adsorbent mass variable was significant for the three compounds studied and the contact time variable was only significant for the compound SMX. As the granulometry variable had no significant effect on the adsorption of the compounds, its value was defined based on the lower reagent consumption, and the adsorbent was used in the 100 mesh granulometry for the other analyses. Considering the interactions between the variables (1:2; 1:3; 2:3) in the pareto graph, only the interaction mass and time (1:3) presented significance (p > 0.5), thus requiring a study to obtain optimum final conditions. The other interactions (mass versus granulometry and time versus granulometry) had no significant effect on any of the compounds. The interaction between mass and time was evaluated through the construction of the response surface using CCD (central composite designer). The ten experiments required to construct the response surface, as well the obtained Qe values, are shown in Table I. Table I. Matrix for the optimization of adsorbent mass and contact time (n=3) Experiment

Mass (mg)

Time (min)

E1 qe (mg g–1)

EE2 qe (mg g–1)

SMX qe (mg g–1)

1

0.2500

30.0

0.235

0.226

0.186

2

0.2500

60.0

0.418

0.416

0.368

3

0.5000

30.0

0.306

0.315

0.285

4

0.5000

60.0

0.425

0.389

0.409

5

0.1981

45.0

0.178

0.156

0.117

6

0.5562

45.0

0.267

0.273

0. 253

7

0.3750

24.7

0.290

0.280

0.207

8

0.3750

68.3

0.278

0.269

0.382

9 (0)

0.3750

45.0

0.346

0.357

0.368

10 (0)

0.3750

45.0

0.349

0.350

0.367

qe: quantity adsorbed in equilibrium (mg g ) –1

After obtaining the results, a response surface was generated for each compound using the Lagrange criterion, obtaining the maximum and critical values of each variable: mass 0.391, 0.390 and 0.710 mg; time 58.663, 53.250 and 62.000 min; 100, 100 and 100 mesh granulometry, respectively, compounds estrone, ethinylestradiol and sulfamethoxazole. The pareto graph (Figure 4) showed a negative standardized effect for the mass and time interaction for the compounds E1 (-3.52083) and EE2 (-3.45336), indicating that if the adsorbent mass increased, the contact time between the adsorbent and adsorbate must decrease for adsorption to be effective, or vice versa. For SMX, the positive value of the 1:3 interaction (5.932718) indicates that the adsorbent mass and the contact time must be increased simultaneously for adsorption be significant. Thus, as the values of mass and time are similar for the compounds E1 and EE2 and different for the SMX, and analysing the significance generated by the pareto graph (Figure 4) for the three compounds, the results obtained for the SMX compound were considered as optimized conditions, since the interaction significance for the compounds E1 and EE2 was minimal when compared to the interaction result obtained for the SMX. As a result of the optimization procedures, the following working conditions were selected: adsorbent mass of 0.710 mg, adsorbent granulometry of 100 mesh, and contact time of 62 min.

21


Article

de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

Adsorption isotherms The adsorption isotherms show the equilibrium between the maximum amount of compound (mg) that is adsorbed by a certain adsorbent mass (g) under certain operating conditions. This allows the observation of the adsorption process equilibrium that occurs without the compound presence in the system solid and liquid phases. The adsorption data of isotherms were applied to the linearized model of Langmuir (equation 2), Freundlich (equation 3) and Dubinin-Radushkevich (equation 4) represented by the equations:

đ??śđ?‘“ 1 đ??śđ??š = + đ?‘„đ?‘’ đ?‘„đ?‘€đ?‘Žđ?‘Ľ đ?‘? đ?‘„đ?‘€đ?‘Žđ?‘Ľ

(2)

(3)

(4)

where QMax is the Langmuir adsorption capacity parameter (L mg–1), b is the Langmuir constant related to adsorption energy (L mg–1), Cf is the concentration of the substance in the solution when in equilibrium (mg L–1), n is the adsorption efficiency (absorption intensity) (mg g–1), Kf is an indicator of adsorption capacity of the material (L mg–1), qe is the concentration of the adsorbate present in the adsorbent when in equilibrium (mmol g–1), Xm is the adsorption capacity (mmol g–1), k is the constant bonded to the energy free of sorption (E) (mol2 kJ–2), and E is the Potential of Polanyi (kJ mol–1). The Langmuir model indicates adsorption per monolayer on the adsorbent surface due to the presence of homogeneous sites of the same energy. The Freundlich isotherm admits a multilayer adsorption process and predicts the heterogeneity of the adsorption sites on the adsorbent surface. The Dubinin–Radushkevich (D–R) isotherm was developed to overcome the limitation of the Langmuir and Freundlich models. The D–R model does not consider the homogeneity of the process and admits that the adsorption potential is constant. Table II shows the parameters obtained when applying the data obtained with the Langmuir and Freudlich models. Note that the results for the adsorption of E1, EE2, and SMX by the banana peel were not adequately described by the Langmuir model (E1 = 0.861, EE2 = 0.548, SMX = 0.676), but by the Freudlich model, indicating that the adsorption is not limited to a monolayer; saturation occurs, forming other layers (multilayer). The values of n for compounds E1, EE2, and SMX were 1.138, 1.364, and 1.246, respectively. If n is greater than 1, this indicates that the high energy sites are occupied by others of lower energy and intensity and the adsorption of the three compounds is favourable. The Kf values indicate low adsorption of the compounds, as well as a good linearity, indicating that adsorbent–adsorbate interactions occur [40]. The value of the division 1/n was less than 1, indicating low heterogeneity of the surface sites and stronger interaction between the adsorbent and the adsorbate. The Kf values indicate low adsorption of the compounds, as well good linearity, indicating that the adsorbent–adsorbate interactions may be of a physical nature [40]. Analysing the two factors (n and Kf), it was observed that the adsorption process occurs in multiple layers, which is more appropriate for the Freudlich model.

22


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

Table II. Adsorption parameters, E1 (estrone), EE2 (ethinylestradiol) and SMX (sulfamethoxazole) using banana peel as adsorbent (n=3) LANGMUIR

FREUNDLICH

QMax

B

RL

R

n

1/n

Kf

R

E1

-2.4929

-0.2525

0.8608

0.5820

1.1378

0.8789

0.6007

0.9868

EE2

1.1783

-1.9186

0.5479

0.9307

1.3639

0.7331

0.3089

0.9948

SMX

0.9219

0.1323

0.6756

0.6403

1.2458

0.8027

0.1073

0.9889

DUBININ–RADUSHKEVICH Xm

k

E

R

E1

2.0793

3.10-8

4.083

0.9926

EE2

-0.2037

7. 10-9

7.453

0.9899

SMX

-0.2427

1 .10-8

7.071

0.9960

By analysing the parameters obtained with the Dubinin–Radushkevich isotherm (Table II), physical adsorption is observed since physical adsorption occurs when an E value of less than 8 kJ mol–1 is obtained. The chemical adsorption presents values for E between 8 and 16 kJ mol–1 [41]. The best fit (R) by the Freundlich and D–R models for the compounds under analysis are expected due to the heterogeneous surface of the adsorbent material resulting from the distribution of the active sites after the adsorption of E1, EE2, and SMX [42]. Adsorption kinetics The adsorption kinetics represent the amount of each free compound that is adsorbed in the banana peel, considering the time. The kinetic study of the adsorption of E1, EE2, and SMX with banana peel shows that the removal of the compounds in solution increased with the in contact time, reaching a time of equilibrium of 90 min and a maximum removal of 0.387 mg g–1 for E1, 0.420 mg g–1 for EE2, and 0.141 mg g–1 for SMX. The models used to describe adsorption kinetics were: pseudofirst order models (5), pseudosecond order (6) and intraparticle diffusion (7) analysis which describe the adsorption mechanism of the adsorbent-adsorbate systems. The kinetic parameters (Table III) for adsorption were obtained by linear regression using the equations:

log(qe – qt) = log(qe) – k1t/2.303

(5)

t/qt = 1/(k2qe2) + t/qe

(6)

qt = kdift1/2 + C

(7)

where qe (mg g–1) and qt (mg g–1) are the amounts of E1, EE2 e SMX adsorbed per unit mass of adsorbent at equilibrium and at any time t, respectively, k1 (min–1) is the constant of the pseudofirst order adsorption rate, k2 (g mg–1 min–1) is the constant of the pseudosecond order adsorption rate, which is obtained by the angular coefficient of the curve, Kdif (mg g–1 min–1/2) is the constant of the intraparticle diffusion rate, and C is the coefficient of linear regression. 23


de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

Article

Table III. Kinetic parameters of adsorption of compounds E1 (estrone), EE2 (ethinylestradiol) and SMX (sulfamethoxazole) models by pseudofirst order, pseudosecond order and intraparticle diffusion (n=3) Pseudofirst Order Parameters Compound

k1 (min–1)

qe (exp) (mg g–1)

qe (calc) (mg g–1)

R

E1

0.0292

0.0387

0.00275

0.6875

EE2

0.0108

0.0420

0.00150

0.6314

SMX

0.0972

0.0413

0.02840

0.9542

Parameters Intraparticle Diffusion

Pseudosecond Order Parameters Compound

k2 (g mg–1 min–1)

qe (exp) (mg g–1)

qe (calc) (mg g–1)

h (mg g–1 min–1)

R

C (mg g–1)

Kdif (mol g–1 min–1/2)

R

E1

16.371

0.0387

0.0391

0.02507

0.9999

0.0355

0.000239

0.9223

EE2

38.359

0.0420

0.0421

0.06805

0.9999

0.0389

0.000323

0.9128

SMX

8.914

0.0413

0.0426

0.01621

0.9998

0.0344

0.000609

0.8262

Table III shows that the most suitable model for kinetic adsorption studies is the pseudosecond order model (E1 = 0.9999, EE2 = 0.9999, SMX = 0.9999). One factor that corroborates this situation is the proximity between the values of the calculated q and the experimental q of each compound. The constant of adsorption (k2) of each compound (E1=16.371, EE2=38.359, SMX=8.914) indicates a fast adsorption rate in banana peel. The suitability of the pseudosecond order model indicates that adsorption depends on the amount of the compound and the active sites present in the adsorbent material. Chemisorption can be explained by an ion exchange process between the compounds and the deprotonated hydroxyl groups of the adsorbent material. Intraparticle diffusion values in Table III show that the Qt versus t0.5 graphs did not pass through the origin (C value other than zero), indicating that this mechanism is not determinant in the adsorption process. Other mechanisms, such as intermolecular interactions, must act in the adsorption and mass transfer process [43]. Thermodynamic parameters The values of the thermodynamic parameters were calculated according to the following equations: Kd = Cequlibrium /Cf

(8)

∆G = -RT ln Kd

(9)

∆Gº ads /T= ∆Sºads

(10)

where Cequilibrium is the concentration of organic banana peel compounds at equilibrium (mg L–1), Kd is the apparent equilibrium constant, ΔG is the Gibbs free energy (J mol–1), R is the universal gas constant (JK–1 mol–1), T is the system absolute temperature (K), and ΔSºads is the entropy involved in the adsorption system (J mol–1 K–1). The results obtained indicate that the adsorption process is a spontaneous process [negative ΔG values for estrone (-6.992), ethinylestradiol (-4.528), and sulfamethoxazole (-1.403)]. The positive 24


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

entropy values (E1 = 23.310, EE2 = 15.092, SMX = 4.676) indicated that the adsorbent material has a substantial number of active sites, that is, adsorption occurs not only on the surface of the adsorbent material, but also in other internal regions [44]. Validation of some analytical method parameters Some validation parameters of the analytical method were determined from analyses carried out under the optimized HPLC conditions previously presented in this paper. The limit of detection (LOD) was considered as the lowest concentration of E1 (0.03 mg L–1), EE2 (0.03 mg L–1), and SMX (0.02 mg L–1) that could be detected considering 3 times the signal-to-noise ratio, and the limit of quantification (LOQ) as 5 times the signal noise (E1 = 0.06 mg L–1, EE2 = 0.07 mg L–1, SMX = 0.06 mg L–1). A satisfactory correlation coefficient was obtained for the analytical signal up to the concentration of 4.0 mg L–1 (E1 = 0.9978, EE2 = 0.9947, and SMX = 0.9987). The repeatability of the proposed method was assessed by performing ten consecutive adsorption steps at a concentration level of 500 μg L–1 of the compound mixture, and the result was expressed in terms of the relative standard deviation (that value was equal to 2.42%). The specificity was investigated to verify the existence of interfering agents in the matrix analyzed. Due to the absence of a certified material for determination of accuracy, recovery tests were performed using water samples from the public supply system. The samples were fortified by adding 5.0 mL of an analytical standard of each compound in 20.0 mL of matrix, corresponding to three levels of the standard curve. As can be seen in Table IV, recovery rates of 70–96% were achieved. Table IV. Relative recovery rates of estrone (E1), ethinylestradiol (EE2) and sulfamethoxazole (SMX) in the samples subjected to the proposed extraction method (n=3) Sample

1

2

3

Added (mg L–1)

Removed (mg L–1)

Recovery (%)

R. S. D. (%)

E1

EE2

SMX

E1

EE2

SMX

E1

EE2

SMX

E1

EE2

SMX

0.5

0.5

0.5

0.36

0.38

0.35

72

76

70

0.89

0.77

0.46

1.0

1.0

1.0

0.84

0.92

0.8

84

92

80

0.22

0.42

0.84

2.0

2.0

2.0

1.44

1.88

1.67

72

94

83.5

0.24

0.29

0.33

0.5

0.5

0.5

0.4

0.44

0.36

80

88

72

0.26

0.19

0.47

1.0

1.0

1.0

0.86

0.9

0.73

86

90

73

0.55

0.57

0.67

2.0

2.0

2.0

1.78

1.92

1.47

89

96

73.5

0.75

0.76

0.66

0.5

0.5

0.5

0.37

0.41

0.39

74

82

78

0.49

0.62

0.14

1.0

1.0

1.0

0.82

0.94

0.86

82

94

86

0.38

0.84

0.74

2.0

2.0

2.0

1.84

1.59

1.42

92

79.5

71

0.73

0.76

0.67

The literature presents adsorption studies of the same compounds investigated in this work, but with different adsorbents, and percentages of removal very close to the values presented in this work with banana peel. As is the case with the use of active charcoal for estrone with removal between 88.0 and 94.0% [44], Polyamide 612 with 72.5% removal of ethinylestradiol [37], and removal of 68.0% of sulfamethoxazole using activated carbon [45]. The adsorbent under study is advantageous with removal of more than 80% for E1 and EE2 and 70% for SMX in the samples analyzed. Note that the percentages of removal mentioned above are close to the values found in this study with the use of the banana peel, a fact that shows that this natural adsorbent is as effective as the others found in the literature.

25


Article

de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

CONCLUSION The proposed method was suitable for adsorption and quantification of compounds E1, EE2, and SMX in aqueous solutions. The banana peel sample was efficient in the adsorption process, with removal percentages higher than 70%. The suitability of the Freundlich model showed that adsorption occurs in several layers. The results concerning kinetic adsorption showed a better fit to the pseudo-second order model. The results of the thermodynamic parameters indicate spontaneous adsorption. Based on the reported data, it can be inferred that the banana peel proved to be a natural adsorbent suitable to be used efficiently in the removal of E1, EE2, and SMX from aqueous matrices.

Manuscript submitted: Oct. 19, 2018; revised manuscript submitted: Dec. 31, 2018; revised for the 2nd time submitted: March 18, 2019; revised for the 3rd time submitted: May 5, 2019; accepted: June 10, 2019; published online: July 04, 2019. REFERENCES 1. Lei, M.; Zhang, L.; Lei, J.; Zong, L.; Li, J.; Wu, Z.; Wang, Z. Biomed. Res. Int. 2015, 1, pp 1-12 (DOI: http://dx.doi.org/10.1155/2015/404796). 2. Geissen, V.; Mol, G.; Klumpp, E.; Umlauf, G.; Nadal, M.; Van der Ploeg, M.; Van de Zee, S. E. A. T. M.; Ritsema, C. J. International Soil and Water Conservation Research. 2015, 3 (1), pp 57-65 (DOI: http://dx.doi.org/10.1016/j.iswcr.2015.03.002). 3. Bennasroune, A.; Rojas, L.; Foucaud, L.; Goulaouic, S.; Laval-Gilly, P.; Fickova, M.; Couleau, N.; Durandet, C.; Henry, S.; Falla, J. Int. J. Immunopathol. Pharmacol. 2012, 25 (2), pp 1-12 (DOI: http://dx.doi.org/10.1177/039463201202500206). 4. Vihma, V.; Wanga, F.; Savolainen-Peltonena, H.; Turpeinend, U.; Hämäläinend, E.; Leideniuse, M.; Mikkolaa, T. S.; Tikkanena, M. J. J. Steroid. Biochem. Mol. Biol. 2016, 155, pp 120-125 (DOI: http://dx.doi.org/10.1016/j.jsbmb.2015.10.004). 5. Lark, S. M. The estrogen decision self help book. Celestial Arts: New York. 320, 1999. 6. Johnson, A. C.; Belfroid, A.; Di Corcia, A. Sci. Tot. Environ. 2000, 256, pp 163-173 (DOI: http:// dx.doi.org/10.1016/S0048-9697(00)00481-2). 7. Brunton, L. L.; Lazo, J. S.; Parker, K. L. Goodman & Gilman as bases farmacológicas da terapêutica. Rio de Janeiro: McGraw-Hill, 2007, p 1821. 8. Ariese, F.; Wilfried, H. O. E.; Dick, T. H. M.; Sijm, C. Environ. Toxicol. and Pharmacol. 2001, 10, pp 65-80 (DOI: http://dx.doi.org/10.1016/S1382-6689(01)00090-4). 9. Errayess S. A.; Lahcen A. A.; Idrissi L.; Marcoaldi C.; Chiavarini S.; Amine A. Spectrochim. Acta, Part A, 2017, 181 (15), pp 276-285 (DOI: http://dx.doi.org/10.1016/j.saa.2017.03.061). 10. Fent, K.; Weston, A. A.; Caminada, D. Aquatic. Toxicol. 2006, 76, pp 122-159 (DOI: http://dx.doi. org/10.1016/j.aquatox.2005.09.009). 11. Khalaf, H. S.; Dikran, S. B.; Mohammed, A. K. Jour. for Pure & Appl. Sci. 2014, 27 (3), pp 365379 (DOI: http://dx.doi.org/10.13140/RG.2.1.2209.4488). 12. Iquego: sulfametoxazol+trimetoprima. Dra. Maria Aparecida Rodrigues. Goiás. Bula de remédio. Indústria Química do Estado de Goiás S. A. 13. Reis Filho, R. W.; Araújo, J. C.; Vieira, E. M. Quím. Nova. 2006, 29 (4), pp. 817-822 (DOI: http:// dx.doi.org/10.1590/S0100-40422006000400032).  14. Rovani, S.; Censi, M. T.; Pedrotti, S. L.; Lima, E. C.; Cataluna, R.; Fernandes, A. N. J. Hazard. Mater. 2014, 271, pp. 311- 320 (DOI: http://dx.doi.org/10.1016/j.jhazmat.2014.02.004). 15. Cordeiro, G. A.; Zamora, P. P.; Nagata, N.; Pontarollo, R. Quim. Nova. 2008, 31 (2), pp. 254-260 (DOI: http://dx.doi.org/10.1590/S0100-40422008000200012).  26


Evaluation of the Adsorption Capacity of Banana Peel in the Removal of Emerging Contaminants present in Aqueous Media – Study based on Factorial Design

Article

16. Melo, S. A. S.; Trovó, A. G.; Bautitz, I. R.; Nogueira, R. F. P. Quím. Nova. 2009, 32, pp 188-197 (DOI: http://dx.doi.org/10.1590/S0100-40422009000100034). 17. Bila, D. M.; Dezotti, M. Quím. Nova. 2003, 26, pp 523-530 (DOI: http://dx.doi.org/10.1590/ S0100-40422003000400015). 18. Bhatnagar, A.; Sillanpääb, M. Chem. Eng. J. 2010, 157, pp 277-296 (DOI: http://dx.doi.org/10.1016/j.cej.2010.01.007). 19. Zhang, Y.; Zheng, R.; Zhao, J.; Ma, F.; Zhang, Y.; Meng, Q. Biomed. Res. Int. 2014, 12 (2) (DOI: http://dx.doi.org/10.1155/2014/496878). 20. Gil, A.; Taoufik, N.; García, A. M.; Korili, A. S. Environ. Technol. 2018, 19, pp 1-14. (DOI: http:// dx.doi.org/10.1080/09593330.2018.1464066). 21. Sousa, F. W.; Oliveira, A. G.; Ribeiro, J. P.; Rosa, M. F.; Keukeleire, D.; Nascimento, R. F. J Environ Manage. 2010, 91 (8), pp 1634 – 1640 (DOI: http://dx.doi.org/10.1016/j.jenvman.2010.02.011). 22. Abdelwahab, O.; Nasr, S. M.; Thabet, W. M. Alexandria Eng. J. 2017, 56 (4), pp 749-755 (DOI: http://dx.doi.org/10.1016/j.aej.2016.11.020). 23. Wang, F. Y.; Wang, H.; Ma, J. W. J Hazard Mater. 2010, 177, pp 300-306 (DOI: http://dx.doi.org/10.1016/j.jhazmat.2009.12.032). 24. Mafra, M. R.; Mafra, L. I.; Zuim, D. R.; Vasques, É. C.; Ferreira, M. A. Braz. J. Chem. Eng. 2013, 30 (3), pp 657 – 665 (DOI: http://dx.doi.org/10.1590/S0104-66322013000300022). 25. Hussein, H. S.; Shaarawy, H. H.; Hussien, N. H.; Hawash, S. I. Bulletin of the National Research Centre. 2019, 43 (26), pp 1-9 (DOI: http://dx.doi.org/10.1186/s42269-019-0058-1). 26. Gupta, H.; Gupta, B. Desalin. Water Treat. 2015, 57 (20), pp 1-12 (DOI: http://dx.doi.org/10.1080/19443994.2015.1029007). 27. Silva, C. R.; Gomes, T. F.; Andrade, G. C. R. M.; Monteiro, S. H.; Dias, A. C. R.; Zagatto, E, A. G.; Tornisielo, V. L. J. Agric. Food Chem., 2013, 61 (10), pp 2358–2363 (DOI: http://dx.doi.org/10.1021/jf304742h). 28. Mondal, N. K.; Kar, S. Appl. Water Sci. 2018, 8 (6), pp 1-12. (DOI: http://dx.doi.org/10.1007/s13201-018-0811-x). 29. Memon, J. R.; Memon, S. Q.; Bhanger, M. I.; Memon, Z.; Turki, A. EI.; Allen, G. C. Colloids Surf B Biointerfaces. 2008, 66, pp. 260-265 (DOI: http://dx.doi.org/10.1016/j.colsurfb.2008.07.001) 30. Corti, G. S.; Botaro, V. R.; Gil, L. F.; Gil, R. P. F. Polímeros: Ciência e Tecnologia. 2004, 14 (5), pp 313–317 (DOI: http://dx.doi.org/10.1590/S0104-14282004000500007). 31. Akhter, M. S.; Chughtai, A. R.; Smith, D. M. J. Phys. Chem.1984, 88, pp. 5334 – 5342 (DOI: http://dx.doi.org/10.1021/j150666a046). 32. Fanning, P. E.; Vannice, M. A. A. Carbon. 1993, 31, pp.721-730 (DOI: http://dx.doi.org/10.1016/0008-6223(93)90009-Y). 33. Gomez-Serrano, V.; Pastor-Villegas, J.; Perez-Florindo, A.; Duran-Valle, C.; Valen–Calahorro, C. J. Anl. Appl. Pyrol. 1996, 36, pp 71-80 (DOI: http://dx.doi.org/10.1016/0165-2370(95)00921-3). 34. Ribeiro, A. V. F. N.; Belisário, M.; Galazzi, R. M.; Balthazar, D. C.; Pereira, M. G.; Ribeiro, J. N. Electron. J. Biotechn. 2011, 114, pp 1-10 (DOI: http://dx.doi.org/10.2225/vol14-issue6-fulltext-8). 35. Ribeiro, A. V. F. N.; Silva, A, R.; Cunha, T. P.; Santos, R. T. L.; Oliveira, J. P.; Pereira, E. V.; Licinio, M. V. V. J.; Pereira, M. G.; Santos, A. V.; Ribeiro, J. N. J. Environ. Prot. 2016, 7, pp 1850-1859 (DOI: http://dx.doi.org/10.4236/jep.2016.712147 ). 36. Bajpai, A. K.; Rajpoot, M. Adsorption Behavior of Sulfamethoxazole Onto na Alumina- Solution Interface. Bull. Chem. Soc. Jpn. 1996, 69 (3), pp 521-527 (DOI: http://dx.doi.org/10.1246/bcsj.69.521). 37. Han, J.; Qui, W.; Cao, Z.; Hu, J.; Gao, W. Water Res. 2013, 47, pp 2273- 2284 (DOI: http:// dx.doi.org/10.1016/j.watres.2013.01.046).

27


Article

de Sousa, P. A. R.; Furtado, L. T.; Lima Neto, J. L. ;de Oliveira, F. M.; Siqueira, J. G. M.; Silva, L. F.; Coelho, L. M.

38. Marques, N. J. O.; Bellato, C. R.; Milagres, J. L.; Kenia, D. P.; Alvarenga, E. S. J. of the Brazil. Chem. Society. 2013, 24, pp 121-132 (DOI: http://dx.doi.org/10.1590/S0103-50532013000100017). 39. Dash, M.; Chiellini, F.; Ottenbrite, R. M.; Chielline, E. Progr. in Polym. Sci. 2011, 36, pp 9811014 (DOI: http://dx.doi.org/10.1016/j.progpolymsci.2011.02.001). 40. Martínez, J. I.; Calle-Vallejo, F.; García-Lastra, J. M.; Rossmeisl, J.; Koper, M. T. M. Phys. Rev. Lett. 2012, 108, pp 103-116 (DOI: http://dx.doi.org/10.1103/PhysRevLett.108.116103). 41. Sljivić, M.; Smičiklas, I.; Pejanović, S.; Plećaš, I. Comparative study of Cu2+ adsorption on a zeolite, a clay and a diatomite from Serbia. Applied Clay Science. 2009, 43, pp 33-40 (DOI: https://doi.org/10.1016/j.clay.2008.07.009). 42. Oliveira, T.; Guégan, R.; Thiebault, T.; Milbeau, C.; Muller, F.; Teixeira, V.; Giovanela, M.; Boussafir, M. J Hazard Mater. 2017, 323, pp 558-566 (DOI: http://dx.doi.org/10.1016/j.jhazmat.2016.05.001). 43. Febrianto, J.; Kosasih, A. N.; Sunarso, J.; Ju, Y. H.; Indraswati, N.; Ismadji, S. J. Hazard. Mater. 2009, 162, pp 616-645 (DOI: http://dx.doi.org/10.1016/j.jhazmat.2008.06.042). 44. Gökçe, C. E.; Arayici, S. Desalin. Water Treat., 2015, 57 (6), pp. 2503-2514 (DOI: http://dx.doi.org/10.1080/19443994.2015.1034183). 45. Lember, E.; Pachel, K.; Loigu, E. “Environmental Engineering” 10th International Conference, 2017 (DOI: http://dx.doi.org/10.3846/enviro.2017.082).

28


Br. J. Anal. Chem., 2019, 6 (22) pp 29-38

Article

DOI: 10.30744/brjac.2179-3425.AR.121-2018

Development of a Prototype Management Software for Testing Laboratories Quality Control under ISO/IEC 17025:2017 Standard Desirée Marianne Sales* Rodrigo Augusto da Silva Alves Janice Cardoso Pereira Rocha Centro Federal de Educação Tecnólogica de Minas Gerais, Avenida Amazonas, 5253, Belo Horizonte, MG, Brazil *desireemsales@outlook.com

Graphical Abstract

Creation process of Software Solution, a quality management program for testing laboratories, focused on compliance with ISO/IEC 17025:2017 standard. The image also highlights the programming languages used for the development and a screenshot of the final result.

In the so-called Total Quality Era, it is necessary to implement standardized and recognized experimental procedures around the world. When testing laboratories are adapted to the requirements set forth in ISO/IEC 17025:2017 standard, the evaluation of results and the exchange of knowledge becomes easier and more dynamic. This adaptation can be simplified and accelerated through the use of a data management software. Thus, the objective of this work was to develop a platform for quality control of a chemical testing laboratory, focusing on compliance with managerial and technical requirements of ISO/IEC 17025:2017 standard. The developed software allows not only data recording, but also the comparison of the analysis results with limit values established by current legislation, guaranteeing greater reliability of the reports issued. The created prototype is useful in ensuring high efficiency of the activities of chemical testing laboratories, making the workflow faster and safer, aside from guaranteeing compliance with the requirements of ISO/IEC 17025:2017 standard. Keywords: accreditation, quality management system, chemical testing laboratory

29


Article

Development of a Prototype Management Software for Testing Laboratories — Quality Control under ISO/IEC 17025:2017 StandardQuality Control under ISO/IEC 17025:2017 Standard

INTRODUCTION Nowadays, in the so-called Total Quality Era, the control tools usually seek to solve problems and integrate processes, with the main goal of controlling the variability of results, maintaining the development of services and products in the company under stable control [1]. Global sharing of test and calibration results is facilitated when the companies meet the technical and managerial requirements established in ISO/IEC 17025:2017, an international standard that establishes “General requirements for the competence of testing and calibration laboratories”. This adaptation facilitates collaboration, commercialization and communication between laboratories, making it easier to exchange information and harmonize experiences of their procedures [2]. According to information available on the website of the National Institute of Metrology, Quality and Technology of Brazil (Inmetro), there were, in 2018, 1039 accredited independent laboratories in the country that meet the requirements of ISO/IEC 17025. In relation to 2015, this number showed a growth of more than 100 percent, when there were only 438 accredited companies. This strong growth is a direct response to the demand of an increasingly globalized market, that seeks to improve the quality of its procedures and aims at the reliability of their services’ results [3]. Procedures that follow internationally recognized standards are of uppermost importance in many areas within a testing laboratory. According to Batista and colleagues (2008), volumetric verification of pipettes is an example of standardized procedure that exists in many laboratories. However, these type of verification and validation routines are not satisfactorily standardized, because usually they are not performed regularly [4]. With the technology evolution witnessed today, it is fundamental to modernize even a small or medium-sized laboratory, evolving from a system managed with printed documents and forms to a digital and automated system, that assists in the process of quality management and control [5]. The use of a digital management system is generally also linked to minimization of waste production, and, according to the principles of Green Chemistry, minimizing the waste is preferable than treating them after their generation [6]. Therefore, this work aimed at developing a software to facilitate the planning and accomplishment of a chemical testing laboratory activities, in order to avoid losses during the whole process. The Brazilian national market in the field of quality management software for testing laboratories is heated due to the need to provide services that meet the requirements of ISO/IEC 17025:2017. What differentiates the software created in the present work from the already existing in corporate market is the possibility of integration between managerial and technical activities, in accordance with the guidelines set forth by the standard. MATERIALS AND METHODS For the development of the management software, it became necessary the detailed knowledge of the company routine and operational flow. Over two months, the routine of small laboratory that works with physical-chemical and microbiological tests of waters, effluents, foods and oils was monitored. All activities developed within the company were identified, step by step, from the contact of a client requesting a budget until the invoice issued after the completion of the services. This audit and control allowed for the identification of the procedures that were most susceptible to generating errors and, therefore, could make it difficult to implement and maintain an efficient quality management system. With this previous work it was possible to gather and systematize the main information of the step by step of the different analysis. It was, then, set up the planning and layout of a computer program that met the needs of the company and could assist in the adaptation of its procedures to ISO/IEC 17025:2017 standard.

30


Sales, D. M.; Alves, R. A. S.; Rocha, J. C. P.

Article

RESULTS AND DISCUSSION The implementation of the prototype hereby presented made easier to ensure quality control in different stages within the laboratory. Gaining organizational performance, security and reliability in routine activities at various levels and functions within the company allows for the issuance of reports with greater reliability [7]. Analysis of the Laboratory The analysis of the laboratory’s documents and records led to the identification of the most performed physicochemical tests in 2016, involving classical analytical techniques, such as gravimetric and titrimetric methods, and three instrumental techniques, as listed below: 1. 2. 3. 4. 5. 6. 7. 8. 9.

Determination of chloride by Mohr Method Determination of total hardness by titration with EDTA Determination of pH by potentiometric method Determination of total solids by gravimetric method Determination of dissolved solids by gravimetric method Determination of suspended solids by gravimetric method Determination of aluminum by UV-Vis spectrophotometric method Determination of ammonia by UV-Vis spectrophotometric method Determination of iron by UV-Vis spectrophotometric method

Based on the findings above, three tests were selected as pilot, which means that they were the first procedures managed by the prototype software developed in this work, called Software Solution. These procedures were selected based on the number of tests performed in one month, so that they can put the maximum of significance on the Software Solution, and based on their nature, so that the pilot tests are diverse and cover the main types of analytical methods (gravimetric, titrimetric and instrumental methods). The pilot tests used for the development of the prototype are shown below: • Determination of chloride by Mohr Method (Titrimetric) • Determination of total solids by gravimetric method (Gravimetric) • Determination of nitrate by UV-Vis spectrophotometric method (Instrumental) The studied laboratory presents a daily routine without major changes, being the stages of budgeting, traceability of measurements and issuance of reports the three crucial stages the makes it hard to maintain a management system focused on quality control and governed by ISO/IEC 17025:2017 standard. Planning Software Solution In order to objectively plan the development of the Software, it was determined the topics of ISO/IEC 17025:2017 that would be initially addressed and controlled by its pilot version. Figure 1 below shows the essential features present in Software Solution, which covers the main categories of activities performed in the laboratory, all according to ISO/IEC 17025:2017 standard.

31


Article

Development of a Prototype Management Software for Testing Laboratories — Quality Control under ISO/IEC 17025:2017 StandardQuality Control under ISO/IEC 17025:2017 Standard

Figure 1. Essential categories developed in Software Solution.

After the survey and a detailed analysis of the requirements for the Software, a description of ‘minimundo’ was created, which can be defined as the instructions in words of what will be represented in the database, and makes it possible to create an entity–relationship diagram (ERD). The ERD model was developed using an online program called “ERDPlus”, and contains the connection between the Software entities and their relationships of dependency. Figure 2 presents an example of a diagram created for Software Solution. Technical Aspects and Languages The main language used on the development of Software Solution was HTML5, a markup language that allows for online use of the platform. This means that anywhere with an Internet connection is the perfect place to view and manage the laboratory activities, controlling the most important tasks at any time, and bringing efficiency to the routine of all employees. The security of data accessed from outside of the laboratory is ensured by mainly three processes: 1. Daily backups of all the files from the server to a local computer stored on a safe place; 2. Authenticity confirmation, requesting usernames and passwords to access the pages; and 3. Encryption procedures at the beginning and at the end of the files’ path from the server. According to Shacham and colleagues (2012), HTML5 offers a set of specifications that provide for structured data storage, as well as benefits such as the possibility of using geolocation services and the ability to manipulate browser history and cache [8]. The software has two main building blocks: a back-end and a front-end. The back-end was developed with PHP language and MySQL server, as the front-end was mainly written in HTML, CSS and JavaScript, using Admin LTE as a base code for programming. As the development was done under a widely used framework, Admin LTE, it can be said that the software works in the main browsers of the market — Google Chrome®, Mozilla Firefox® and Internet Explorer®, and provides a unique environment with useful resources to manage a testing laboratory. The Software’s database was developed using SQL language, and its management was done with MySQL, a free and open source program widely used in professional applications.

32


Figure 2. Entity-relationship diagram (ERD) of gravimetric method.

Sales, D. M.; Alves, R. A. S.; Rocha, J. C. P.

Article

33


Article

Development of a Prototype Management Software for Testing Laboratories — Quality Control under ISO/IEC 17025:2017 StandardQuality Control under ISO/IEC 17025:2017 Standard

Software Solution has a user-friendly and responsive interface for a smoother user experience, which makes the platform adaptable to all devices (desktops, tablets and phones), using CSS3 and HTML5 technologies to create well-designed pages that give a clean look to the software. Functionalities The final version of the prototype Software Solution is able to control customer records, budgets and internal tests. It can also compare a result with the limit value established in specific legislation, as well as aid in the creation of budgets, presentation of up-front technical analysis of results and generation of reports. In order to detail the functionalities of the software and its approach to ISO/IEC 17025:2017, the following pages present the items from the Standard, their characteristics and how they will be treated in the platform. Item “Test Method”, as shown below in Figure 3. • The Standard Operating Procedure is presented and instructed to the technician responsible for the analysis. • Data processing security is ensured with backup, authenticity confirmation, and encryption procedures.

Figure 3. Test registration screen — determination of total fixed solids by gravimetric method. 34


Sales, D. M.; Alves, R. A. S.; Rocha, J. C. P.

Article

Item “Quality Assurance of Results”, as shown below in Figure 4. • A comparison is made between the value found in the test and the reference value established by the legislation.

Figure 4. Tests page, highlighting the comparison between the value found as result and the reference value established by current legislation.

Item “Results presentation”, as shown below in Figure 5. • Test results are recorded on electronic forms.

Figure 5. Tests page, highlighting the button to print the electronic form registered with the information of the test and its results and conclusions.

Its responsive layout and online nature, with cloud operation, allows access to the software through different platforms, like desktops and smartphones. This brings several benefits to the laboratory, such as registration of analysis in loco. All procedures managed by the Software are in accordance with ISO/IEC 17025:2017, focusing primarily on items that relate to measurement traceability and reporting, which have been found to be the main sources of errors in the studied laboratory. The Software provides a concise way for implementing and simplifying quality systems using automated and interactive processes, making it possible to manage, track and report quality indicators. The Figures S1, S2, S3 and S4 are shown in the Supplementary Material section in order to illustrate the Software’s functionalities and screens. The implementation of the digital system also ensures 35


Article

Development of a Prototype Management Software for Testing Laboratories — Quality Control under ISO/IEC 17025:2017 StandardQuality Control under ISO/IEC 17025:2017 Standard

compliance with ISO/IEC 17025:2017 and helps to conduct continuous improvement processes throughout the organization. CONCLUSION The implementation of Software Solution resulted in an improvement of the laboratory’s routine and consequent fulfillment of international standard requirements. Daily monitoring of the routine was essential for the identification of procedures’ different stages, as well as for the recognition of the main laboratory needs. Evaluation at the laboratory as well as integration between technical knowledge of Chemistry and Information Technology areas were essential factors for proper planning and development of Software Solution. Prospects for future research include expanding Software’s functionalities, as well as performing comparative tests of laboratory dynamics before and after the digital implementation. Acknowledgements The authors thank the Centro Federal de Educação Tecnológica de Minas Gerais for laboratory and field facilities. Manuscript submitted: Oct. 19, 2018; revised manuscript submitted: March 11, 2019; manuscript accepted: April 29, 2019; published online: July 04, 2019. REFERENCES 1. Veras, C. M. A. Gestão da Qualidade. Instituto Federal de Educação, Ciência e Tecnologia do Maranhão, São Luis, MA, 2009. 2. International Organization for Standardization. ISO 17025. General requirements for the competence of testing and calibration laboratories. Geneva, CH: ISO, 2017. 3. http://www.inmetro.gov.br/laboratorios/rble/ [Accessed 13 September 2018]. 4. Batista, E.; Filipe, E.; Mickan, B. Accreditation Qual. Assur., 2008, 13 (4), pp 261-266 (DOI: http://dx.doi.org/10.1007/s00769-008-0362-1). 5. Rocha, E. P. Processo de Acreditação de um Laboratório de Ensaios Físico-Químicos. Undergraduate thesis, 2016, Centro Federal de Educação Tecnológica de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. 6. Lenardão, E. J.; Dabdoub, M. J.; Batista, C. F. Quim. Nova. 2003, 26 (1), pp 123-129 (DOI: http://dx.doi.org/10.1590/s0100-40422003000100020). 7. Elmasri, R.; Navathe, S. Sistemas de Banco de Dados. Pearson Addison Wesley, São Paulo, 2005. 8. Mowery, K.; Shacham, H. Pixel Perfect : Fingerprinting Canvas in HTML5. Proceedings of the Web 2.0 Security and Privacy., 2012, pp 1-12. 9. Feinber, M.; Laurentie, M. Accredit. Qual. Assur., 2006, 11 (1-2), pp 3-9 (DOI: http://dx.doi.org/10.1007/s00769-005-0081-9). 10. Stangegaard, M.; Hansen, A. J.; Froslev, T. G.; Morling, N. J. Lab. Autom., 2011, 16 (5), pp 381386 (DOI: http://dx.doi.org/10.1016/j.jala.2009.06.004). 11. Wang, J. Acc. Chem. Res., 2002. 35 (9), pp 811-816. (DOI: http://dx.doi.org/10.1021/ar010066e) 12. Galuszka, A.; Migaszewski, Z.; Namiesnik, J. TrAC, Trends Anal. Chem., 2013, 50, pp 78-84 (DOI: http://dx.doi.org/10.1016/j.trac.2013.04.010). 13. Newman, S.G.; Jensen, K.F. Green Chem., 2013, 15 (6), pp 1456-1472 (DOI: http://dx.doi.org/10.1039/c3gc40374b).

36


Sales, D. M.; Alves, R. A. S.; Rocha, J. C. P.

Article

SUPPLEMENTARY MATERIAL

Figure S1. Home page of Software Solution.

Figure S2. Sampling page of Software Solution.

37


Article

Development of a Prototype Management Software for Testing Laboratories — Quality Control under ISO/IEC 17025:2017 StandardQuality Control under ISO/IEC 17025:2017 Standard

Figure S3. Materials page of Software Solution.

Figure S4. Equipment page of Software Solution.

38


Article

Br. J. Anal. Chem., 2019, 6 (22) pp 39-51 DOI: 10.30744/brjac.2179-3425.AR.122-2018

Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC Cristiane Canan¹*, Fernanda Delaroza², Daneysa Lahis Kalschne¹, Marinês Paula Corso¹, Elza Iouko Ida³ ¹Departamento Acadêmico de Alimentos, Programa de Pós-Graduação em Tecnologia de Alimentos, Universidade Tecnológica Federal do Paraná, Avenida Brasil, Parque Independência, 4232, 85884-000, Medianeira, PR, Brazil. ²Centro de Ciências Exatas, Programa de Pós-Graduação em Química, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, Pr 445, Km 380, 86057-970, Londrina, PR, Brazil. ³Centro de Ciências Agrárias, Programa de Pós-Graduação em Ciência de Alimentos, Universidade Estadual de Londrina, Rodovia Celso Garcia Cid, Pr 445, Km 380, 86057-970, Londrina, PR, Brazil. *canan@utfpr.edu.br

Phytic acid (PA) or myo-inositol-1,2,3,4,5,6-hexakisphosphoric acid (IP6) can be hydrolyzed into inositol phosphates, such as inositol pentaphosphate (IP5), inositol tetraphosphate (IP4), inositol triphosphate (IP3) and possibly inositol di- and monophosphates (IP2 and IP1) by phytases (enzyme) during grains and seeds storage and fermentation. Chromatographic conditions of mobile phase, sample diluent, column and ionic par, for IP6 determination in defatted rice bran and purified PA from rice bran, were studied in this research. Linearity, repeatability, recovery, and limit of detection (LOD) and limit of quantification (LOQ) of the method were evaluated. The best resolution occurred with the use of both C18 columns (Shim-pack CLC-ODS and Novapak) at a 45 °C oven temperature and mobile phase A (32.50% methanol and 1.45% TBAH) and sample diluent da (32.50% methanol and 1.45% TBAH) and db (32.10% methanol and 1.20% TBAH). The R2 of calibration curve was 0.9988, confirming the linearity in the PA range of 1.5 to 10 mg mL-1 (r = 0.9993; p < 0.0000). Intra-day repeatability presented relative standard deviations (RSD) of 3.43, 2.37 and 1.88% for 8, 5, and 3 mg mL-1 of PA concentrations, respectively. Inter-day intermediate precision RSD values were 0.93, 1.38, and 3.50% for each PA concentration, 8, 5, and 3 mg mL-1 respectively. RSD values were lower than 4% for both studies, demonstrating adequate repeatability and intermediate precision for the analytical method proposed. A 91% IP6 recovery was obtained and the LOD and LOQ were 0.05 and 0.15 mg mL-1, respectively. The IP6 content in defatted rice bran and purified PA from rice bran samples were 3.90 and 420 mg 100 g-1, respectively. Keywords: analytical method, high-performance liquid chromatography, inositol phosphates, myoinositol-1,2,3,4,5,6-hexkisphosphate, purified rice bran. INTRODUCTION Myo-inositol-1,2,3,4,5,6-hexakisphosphoric acid (IP6), also known as phytic acid (PA) [1], is a constituent commonly found in plants, and is the main storage form of inositol and phosphate in grains and plant seeds, accumulated during maturation period. PA constitutes 1 to 5% (w/w) of most oilseeds, legumes, cereals, nuts, and pollen [2,3] representing 50-80% of total phosphorus level in seeds [4]. In brown rice (unpolished), the total phosphorous content was around 0.38 g 100 g-1, while phytate form corresponds the majority (73.7%) of phosphorus content (0.28 g 100 g-1) and the PA was equivalent of 0.99 mg 100 g-1 [5]. Insoluble salts are formed as a result of PA interaction with cations, named phytates [6] and chelates food micronutrients, making them non-absorbable by the intestine and thereby reducing their bioavailability [4,7]. However, these effects are associated with a diet poor in trace-elements and based on high PA intake [8], influenced by micronutrients linkage with other food components [9], thus, the metal ion : PA molar ratio should be considered [10]. However, PA physiological effects on health have also been studied, showing a suitable anti-oxidative effect on preventing gastrointestinal cancer [11], reducing induced-cancer in lab rats [12], potential antimicrobial effect [13,14], prevention of diabetes 39


Article

Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC

[15], Parkinson’s disease [16], allergens complexation [17], and heart disease [18]. The molecular mass of PA is 660.04 g mol-1 and its structure has 12 ionizable protons [19] and it has a potent chelating potential due to its unique structure (Figure 1), having a high affinity for polyvalent cations such as calcium, zinc, and iron [20]. Three of the ionisable protons are weakly acidic (pKa 5.7–7.6), three others are very weakly acid (pKa 10.0–12.0), and the remaining six ionisable protons, one from each phosphate group, are strongly acid (pKa 1.1–2.1) [21]. Thus, under physiological pH conditions phytic acid is greatly ionized, becoming negatively charged, and is able to easily react with positively charged substances [20,22]. The PA solubility depends on pH, it being soluble at a pH < 2 [10]. Therefore, acidic solutions are widely used in its extraction, including hydrochloric acid (from 0.5 to 2.4 mol L-1) [23–26], acetic, sulphuric, phosphoric [27,28], and trichloroacetic acids [29].

Figure 1. Phytic acid molecular structure.

Prior to PA determination, a sample preparation method of at least three steps is necessary, including the extraction, concentration and purification from vegetable sources. The rice bran PA acid direct extraction are mainly employed, and are dependent of some variables such as acid concentration, temperature, pH, solid-liquid ratio, and extraction time [26,28]. Most used methods for IP6 extraction requires 1 to 3 h of extraction time with hydrochloric acid, followed by concentration and purification stages performed by ion exchange or precipitation as iron phytate [26,30]. The ion exchange chromatography method developed by Harland and Oberleas [30] is currently adopted by Association of Official Analytical Chemists (AOAC) for PA purification [31]. It is based on the hydrochloric acid extraction from the sample followed by ion exchange column purification by PA elution with 0.7 mol L-1 sodium chloride (non-linear gradient) and digestion of eluate to inorganic phosphate; the phytate content was determined colorimetrically. However, this method determination might lead to PA overestimation since it includes other non-distinguishable inositol phosphates (penta, tetra, tri, bi, and mono) [24,32]. PA determination techniques in cereals were briefly reviewed, demonstrating their evolution, which began with a simple acidic insoluble ferric phytate precipitation method and progressed through instrumental methods, such as colorimetric, high performance liquid chromatography (HPLC), synchronous fluorescence spectroscopy (SFS), and isotachophoresis [33]. Among HPLC-used methods, a quantitative method with prior PA precipitation with ferric chloride followed by conversion to phytate was described [34]. Phytate was injected onto a reversed-phase C18 column and determined by atomic absorption spectrometry. It was found that PA extraction in wheat bran with 3% sulphuric acid was more efficient than the one with 3% trichloroacetic acid. In this case, PA recovery ranged from 99 to 103%. The HPLC procedures are quite sensitive and selective, and today the modern chromatographic 40


Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Article

systems allow rapid analysis and no longer at high costs like in the past. Additionally, HPLC procedures allow PA identification and quantification including its dephosphorylated derivatives, either by adding standards in reverse phase chromatography or by post-column reactions in ion exchange chromatography. However, several interferences were found using HPLC for IP6 and its dephosphorylated identification and determination, such as negative peaks, lack of stability in the peaks quantification, sample diluent interference with refraction index detector (RI) [24,35,36]. The PA determination methods by liquid chromatography coupled to mass spectrometry (LC-MS) was now available for blood and plasma. The LC-MS is now the reference method for small analyte determination, with lower LOD (30 to 80 ng mL-1) and LOQ (500 ng mL-1) for PA determination [37,38]. However, the application of LC-MS is limited because is more complex and sophisticated [39]. Thus, the aim of this study was to evaluate pH, size and column type, column temperature, methanol and tetrabutylammonium hydroxide concentration in both the mobile phase and in the sample diluent for IP6 determination by HPLC. After standardization of these variables, the linearity, repeatability, intermediate precision, limits of detection and quantification, and recovery of IP6 from rice bran were evaluated. Additionally, defatted rice brand and purified PA from rice bran were analysed in terms of IP6 content. MATERIALS AND METHODS Materials, reagents, standards, and samples The PA was extracted and purified from rice bran obtained from rice cultivar IRGA 417 provided by the Instituto Rio Grandense do Arroz (IRGA) in the municipality of Cachoeirinha, RS, Brazil. The solvents used on mobile phase preparation were: methanol, formic acid, and sulfuric acid (Merck, Darmstat, Germany), all with chromatographic grade and ethylenediamine tetra acetic acid (EDTA) (Synth, Diadema, Brazil). The deionized water was Milli-Q® grade (Millipore, Billencia, USA). The mobile phases used were filtered in Millipore vacuum filtration system using 0.45 μm membranes (Millipore, Billencia, USA). Myo-inositol (I5125), D-myo-inositol 1,4,5-trisphosphate hexasodium (I9766), and rice dodecasodium phytate (P0109) from Sigma (Saint Louis, USA) and 50% (v/v) PA solution in water from Sigma-Aldrich (593648) (Saint Louis, USA), all of analytical grade, were the standards employed. The other chromatographic-graded reagents used were from different commercial brands. Sample preparation steps for IP6 determination by HPLC A defatted rice bran sample and a purified PA from rice bran one, were analyzed in order to determine the IP6 content by HPLC. Additionally, IP6 standard (P0109) was applied in order to optimize the chromatographic conditions. Each sample has a specific extraction process described in the sequence and all the samples were submitted to ion exchange column passage before the HPLC analysis. Defatted rice bran: the PA from rice bran sample was extracted according to Lehrfeld [35] with some modifications. A 500 mg sample aliquot was weighted and diluted in 10 mL of 0.5 mol L-1 HCl and the mixture was sonicated for 5 min, centrifuged at 25000 g for 20 min and 5.0 mL of supernatant was diluted to 10 mL with Milli-Q® water, which was then eluted in ion exchange column (described in the sequence). Purified PA: the PA was purified from rice bran with 1.0 mol L-1 HCl (1:10 w/v) at 25 ºC with 2 g agitation in a Bench Incubator (MA830/A, Marconi, Piracicaba, Brazil), followed by pH adjustment, precipitation with a 1.5 mol L-1 Na2CO3 solution, filtration through qualitative filter paper Whatman # 3 (the filtered solution was discarded), and drying for 24 h in an oven at 60 ºC for purification, according to method by Canan et al. [26]. The purified PA (300 mg) was diluted to 10 mL with Milli-Q® water and eluted in an ion exchange column. IP6 standard (P0109): The purification process was skipped since the sample was obtained in its purified form (purity > 90%). A 300 mg IP6 standard aliquot was diluted with 10 mL Milli-Q® water and eluted in an ion exchange column. 41


Article

Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC

Ion-exchange column process: the supernatant containing the PA was eluted with anion-exchange resin to remove the inorganic phosphorous and other interfering compounds. Thus, a Dowex-AGX-4 ion-exchange column was previously prepared with 0.60 g resin, submitted to successive elutions with 10 mL Milli-Q® water, 10 mL of 0.7 mol L-1 NaCl, and 10 mL of Milli-Q® water [40]. Thus, each diluted 10 mL sample was applied to the column, eluted with 10 mL of 0.05 mol L-1 HCl and 2 mL of 2.0 mol L-1 HCl and collected a 2 mL fraction of the last eluate. For each sample prepared, 500 μL eluate aliquots were transferred to 2 mL Eppendorf tubes and concentrated in a Speed Vac vacuum centrifuge (RC 1022, Jouan, Darmstadt, Germany) at 40 ºC, until obtaining a solid residue. In order to obtain the IP6 hydrolyzed, the last eluate collected from the Dowex-AGX-4 ion- exchange column obtained from IP6 standard (P0109) was autoclaved at 120 ºC for 1 h and subsequently transferred to 2 mL Eppendorf tubes and concentrated in a Speed Vac vacuum centrifuge (RC 1022, Jouan, Darmstadt, Germany) at 40 ºC until obtaining a solid residue. The residue was resuspended in Milli-Q® water or mobile phase and injected into HPLC. Chromatographic conditions Chromatographic analysis was performed using a Shimadzu liquid chromatograph (Kyoto, Japan), consisting of a LC-10AD system solvent pump, automatic injector SIL-10A with 20 μL maximum capacity, a DGU-2A degassing unit, a CTO-10A oven, and a 10A refractive index detector. A Shim-pack CLC G-ODS pre-column (1 cm x 4.0 mm I.D.) was used and combined with three reverse phase analytical columns: a PRP1 (150 mm x 4.1 mm) (Hamilton, Reno, NE); a Shim-pack CLC-ODS (150 mm x 4.6 mm, I.D.) (Shimadzu, Kyoto, Japan), both with a 5 μm particle size; and a C18 Novapak (150 mm × 3.9 mm I.D., n° 86344) with a 4 μm particles size (Waters, Milford, USA). An isocratic elution mode, a 0.4 mL min-1 flow rate and a 20 μL injected volume were utilized. Different analytical conditions were tested to find the best chromatographic conditions for separation and determination of IP6 and its inositols, as described in the following items. Organic modifier (methanol) in the mobile phase optimization In order to obtain the best chromatographic conditions, 27.5 and 32.5% concentration levels for organic modifier methanol were initially tested in the mobile phase. On both mobile phases, 1.45% tetrabutylammonium hydroxide (TBAH) and 0.035 mol L-1 formic acid were used. Hydrolyzed IP6 standard (10 mg mL-1) diluted in Milli-Q® water and PRP1 column were used in this step. Sample diluent, mobile phase pH, and column temperature optimization After establishing the best mobile phase, the Milli-Q® water sample diluent and mobile phase (32.5% methanol) sample diluent were compared. Subsequently, the mobile phase pH (from 4.0 to 4.5) and the column temperatures (35, 40, and 45 ºC) were evaluated. PRP1 column was used for these steps. Column optimization For better resolution and retention time, three different columns arrangements were evaluated using the mobile phase with 32.5% methanol. The columns used alone were a PRP1 polystyrene resin used by Lehrfeld [35] and a Shim-pack CLC-ODS column. In order to increase the separation efficiency, the analytical course increased from 15 to 30 cm, which was performed by the coupling of two columns, a C18 Shim-pack CLC-ODS and a C18 Novapak. The Shim-pack and Novapak columns were used due to the higher separation efficiency observed. Optimization of Ionic pair (tetrabutylammonium hydroxide) in the mobile phase and sample diluent The ionic pair (TBAH) concentration effect on the mobile phase and sample diluent was evaluated in order to improve the chromatographic profile selectivity. Lehrfeld and Morris [41] suggested that reconstituting the sample with TBAH the ghost peaks should be minimized. Thus, three mobile phases 42


Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Article

named A, B, and C were tested with 3 TBAH percentage levels, 1.45, 1.20, and 0.77%, respectively (Table I). Table I. Mobile phases A, B and C employed to evaluate three percentage levels of ion pair (tetrabutylammonium hydroxide) Mobile phase

A

B

C

Methanol (%)

32.50

32.10

30.93

Formic acid 0.035 mol L-1 (%)

66.05

66.70

68.30

Tetrabutylammonium hydroxide (%)

1.45

1.20

0.77

100.00

100.00

100.00

Total (%)

Three samples diluents formed by the mobile phases (A, B, and C), named da, db, and dc, and a fourth sample diluent (X) with no ion pair (dx, without TBAH and composed by methanol/Milli-QÂŽ water (1:5, v/v/)), were evaluated. The dx was prepared and tested so that the blank (obtained by injection of mobile phase) had no positive peaks and vacancies with the mobile phase. The different sample diluents (da, db, dc, and dx) were tested on 12 chromatography assays in duplicates (Figure 2) for each mobile phase (A, B, and C). The combination of two C18 columns (Shim-pack CLC-ODS and Novapak) and a 4 mL min-1 flow rate at 45 ÂşC oven temperature was used in this step.

Figure 2. Samples and blank (mobile phase) elutions diagram in HPLC IP6 determination.

This assay was done in triplicate in order to evaluate the blank (mobile phase), the external standard, and the hydrolyzed sample. For blank, the interference from the mobile phase peak at the retention times of interest for inositol phosphate was evaluated; the external standard was used for IP6 quantification, and peaks selectivity was evaluated for hydrolyzed samples. In order to examine possible mobile phases discriminations in different eluates, the scanned chromatograms were placed in the 24 x 1750 matrix (three mobile phases, each one tested with 4 sample diluents including the analyte in duplicate). The data were submitted to Q type PCA, loadings, and hierarchical analysis (AH). Separation factor in chromatographic profiles optimization This optimization was performed in order to verify the chromatographic separation of IP3, IP4 and IP5 inositols from the hydrolyzed IP6 standard. The mobile phase and sample diluent selection was based on the separation factor. Numerical representation of chromatogram quality was laborious due to the 43


Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC

Article

absence of absolute standards (IP2 and IP4), which could be used to measure the peaks resolution and separation factor. Therefore, for each chromatogram the various values for separation factor between adjacent peaks were reduced to a single number by the chromatographic response function (CRF), defined by Equation 1 [42]. k

CRF = ln

â&#x2C6;&#x2018; (P ) i

i =1

Equation 1

where: CRF is chromatographic response function; Pi is the separation measure between adjacent peaks in a chromatogram for k peak pairs, where k is less than the peaks total number. Figures of merits The method evaluation was performed according to AOAC guidelines [31], including linearity, repeatability, intermediate precision, recovery, and LOD and LOQ estimative. Linearity: It was determined by analysis in triplicate of standard mixtures at six different concentrations ranging from 1.5 to 10.0 mg mL-1, by constructing the external calibration curve and by calculating the coefficient of determination (R2) and significance level (p). Repeatability and intermediate precision: Five different extractions from the same sample, subject to the same extraction and analysis conditions, were analyzed using the same equipment, in short time frame. Intra-day repeatability was also studied; the extraction of the same sample was evaluated with five replicates during the day. Additionally, an inter-day repeatability (intermediate precision) was performed by analyzing a standard mixture of compounds (5 mg mL-1), which was prepared and injected at 24 h intervals for 5 days. The repeatability and intermediate precision results were expressed in terms of relative standard deviation (RSD). Recovery (accuracy): It was determined by adding the test substance standard to the purified PA sample prior to analysis. Firstly, the IP6 content in the purified PA was estimated, obtaining a content of 39 mg 100 g-1. The analysis was repeated by adding the PA standard amount corresponding to 50% of the purified PA initial concentration. The analyses were performed in triplicate. Limit of detection (LOD) and limit of quantification (LOQ): was estimated by the ratio between the standard deviation (SD) of the calibration curve and its slope, using the suggested multiplier factor by the ICH norm [43] (Equation 2 and 3, respectively).

LOD = 3.33SD/b

Equation 2

LOQ = 10SD/b

Equation 3

where: LOD is limit of detection, LOQ is limit of quantification, SD is calibration curve standard deviation and b is calibration curve angular coefficient. IP6 quantification and statistical analysis IP6 quantification was performed by external standardization. The calibration curves were constructed considering that the chromatographic peak was proportional to the injected standard concentrations. IP6 content in defatted rice bran determined by HPLC (proposed method) was compared with the content determined by a colorimetric method [44]. Computer software Arthur, modified for microcomputers [45], was used for preprocessing calculations and Principal Component Analysis (PCA). Statistica 6.0 and Origin 7 programs were used on graphic plotting. CRF calculations were performed by AutoCad 2009.

44


Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Article

RESULTS AND DISCUSSION For IP6 determination, the variation of chromatographic conditions showed important changes in the profile of chromatograms, as described in detail for each evaluated parameter. Organic modifier (methanol) as mobile phase and sample diluent The mobile phase with 32.5% methanol showed a chromatographic profile with better resolution of the peaks related (Figure 3b). Two peaks were detected in retention times of 7.33 and 8.41 min (Figure 3b), while for the mobile phase with 27.5% methanol only one peak (10.09 min retention time) and a negative one (8.56 min retention time) were detected (Figure 3a). The occurrence of negative peaks in PA chromatograms is not desirable, specially the adversely affect the separation and quantification of inositol phosphates. However, some other similar studies have reported the occurrence of negative peaks [24,35,36]. According to Hamada et al. [36], the TBAH increase in mobile phase (from 0.6 to 1.0%) reduce the negative peaks and improve the peak resolution. Ultra-pure water and mobile phase have been used as sample diluent for HPLC analysis [46,47]. However, in the proposed method, the mobile phase with 32.5% methanol used as sample diluent presented a better chromatographic profile, obtaining a new profile with two peaks (3.27 and 6.24 min retention times) and a vacancy between them (Figure 3c). Mobile phase pH and column temperature There were no changes in the chromatographic profiles in the 4.0 to 4.5 pH range, hence, pH 4.3 was selected. According to previous studies, a loss in chromatogram resolution would occur should the mobile phase pH increase from 4.3 to 5.2, reducing the number of peaks from 4 to 2 [35]. For column temperature, the optimal condition was observed at 45 °C. This temperature reduced the pressure column and this result is in agreement with previous studies [48]. Columns The PRP1 column replacement by the Shim-pack CLC-ODS column eliminated the vacancy between the peaks of interest, resulting in 4 peaks in the retention times of 5.70, 6.45, 7.11 and 1.35 min (Figure 3d). The use of a longer length applying two combined C18 columns, a Shim-pack CLC-ODS, and a Novapak, proved an interesting alternative to IP6 determination. Ionic pair (tetrabutylammonium hydroxide) in the mobile phase and sample diluent Evaluating only the blank (reading the sample diluent in the mobile phase), interfering peaks were observed in the sample diluents carrying the ion exchanger (da, db, and dc). The db and dc sample diluents behaved similarly in mobile phases A and B, with a blank detected at 7.1 min. A peak delay was noticed in sample diluent da, which presented the greatest ionic pair strength in the three mobile phases used (A, B, and C) with 11.5, 11.7, and 12.7 min, respectively. The chromatographic profile for mobile phase C with db and dc diluents was limited to 5.7 min for IP2, IP3, IP4, IP5 and IP6 inositol readings, with the blank detected at 7.1 and 12.8 min. No peak of interference for sample diluent dx occurred at the time of interest. Figure 4 shows the three mobile phases (A, B, and C) variation with the IP6 standard elution in da, db, dc, and dx.

45


Article

Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC

Figure 3. (a) Hydrolyzed IP6 standard eluted in the mobile phase with 27.5% methanol and Milli-QÂŽ water as sample diluent and PRP1 column; (b) hydrolyzed IP6 standard eluted in mobile phase A (32.5% methanol), diluted with Milli-QÂŽ water and PRP1 column; (c) hydrolyzed IP6 standard eluted in mobile phase A (32.5% methanol), diluted with mobile phase A and PRP1 column; (d) hydrolyzed IP6 standard eluted in mobile phase A (32.5% methanol), diluted with mobile phase A and a C18 Shim-pack CLC-ODS column. 46


Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Article

Figure 4. PCA plot (PC3 x PC4) for the sample diluents a (da), b (db), c (dc), and x (dx) eluted in mobile phases A, B, C, and X.

The PCA required 10 principal components (PC) in order to explain 99% of the total data variance. Figure 4 shows PC3 x PC4 plot, which represents 5.96% of total variance. It is possible to notice, in the loading plot in Figure 5, the formation of three groups that distinguished the three mobile phases (A, B, and C).

Figure 5. Loading plot (PC3 x PC4) for sample diluents a (da), b (db), c (dc), and x (dx) eluted in mobile phases A, B, C, and X.

The samples eluted in the mobile phase C differed from the other samples (eluted in A and B) by the positive PC3, which presented the highest impact at 14 and 12 min retention times. Mobile phase C chromatograms showed the worst selectivity, with peaks IP3 and IP4 coeluted. Mobile phase A showed the greatest discrepancy between the strength of sample diluent, separated by the PC4. As previously discussed, the blank peak was detected at 7.1 min in db and dc sample diluents and at 11.5 min in da sample diluent, obtaining an optimal discrimination for this phase. However, the great interest for inositol detection are the peaks after 7.1 min, 10.8, 10.3, 12.01, 12.2, and 11.7 min for instance, and some peaks of lower responses not shown in Figure 5, in mobile phases A and B with the db and dc sample diluents since they are peaks without organic solvent interferers. By the dendogram analysis (Figure 6), the distinction of the three groups at the 0.9 distance confirms the previously discussed analysis.

47


Article

Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC

Figure 6. Dendrogram based on data from sample diluents a (da), b (db), c (dc), and x (dx) eluted in mobile phases A, B, and C.

Thus, the mobile phase and the sample diluent choice by the chromatographic profiles quality evaluation using the CRF, showed da and db sample diluents and mobile phase A as the best conditions in this study (Figure 7). Therefore, the mobile phase A and db were the chromatographic conditions used for the continuity in the inositol quantification.

Figure 7. Chromatographic response function study in mobile phases A, B, and C and da, db, dc, and dx sample diluents.

Method evaluation The myo-inositol standard peak was identified at 7.0 min, the IP3 standard peak at 6.7 min, and the IP6 standard peak at 9.8 min in chromatograms. Similarly, Frontela et al. [47] employed the same method proposed by Lehrfeld [35] for PA determination in infant cereals, and the retention time of PA was 9.2 min in a reverse-phase C18 column. The method was shown to be linear (r = 0.9993; p < 0.0000) over the range 1.5 to 10.0 mg mL-1 for PA. The calibration curve demonstrated in Figure 8 had a R2 = 0.9988.

48


Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Article

Figure 8. Calibration curve for IP6 determination (1.5 to 10.0 mg mL-1 range) (R2 = 0.9988).

The intra-day repeatability presented RSD values of 3.43, 2.37, and 1.88% for the 5 replicates of each concentration, 8, 5, and 3 mg mL-1 respectively. Inter-day intermediate precision RSD values were 0.93, 1.38, and 3.50% for each PA concentration – 8, 5, and 3 mg mL-1, respectively – evaluated for 5 different days. RSD values were lower than 4% on both intra and inter-day studies, demonstrating adequate repeatability and intermediate precision for the analytical method of PA quantification proposed. A 91% IP6 recovery was obtained. The recovery obtained was lower compared with the range of 99 to 103% reported for a quantitative method by atomic absorption spectrometry in wheat bran; in this case the sample preparation method was performed by PA extraction with sulphuric acid, precipitation with ferric chloride followed by conversion to phytate [34]. In contrast, the recovery of 90% was reported by Frontela et al. [47] employing HPLC PA determination method proposed by Lehrfeld [35]. The LOD of proposed method was 0.05 and the LOQ was 0.15 mg mL-1. Similarly, a LOD of 0.04 mg mL-1 was reported [47] for HPLC PA determination using the method proposed by Lehrfeld [35]. IP6 quantification in defatted rice bran and purified PA samples PA content was 3.90 mg 100 g-1 for defatted rice bran (Table II), while it was 6.0 mg 100 g-1 when determined by a colorimetric method [44] (IP6 overestimation of 35%), suggesting that other inositols were quantified together with IP6. Similarly, an overestimation of 27% in the PA content of infant foods were reported by the comparison of HPLC and colorimetric method [24]. The determination of PA based on the phosphorus content – as performed in colorimetric method – overestimate the real PA content because processed foods often contain partially phosphorylated inositols formed by hydrolysis of PA [41]. Additionally, the PA content in defatted rice bran (3.90 mg 100 g-1) was slightly higher than the PA content of whole rice bran (3.65 mg 100 g-1) [5]. Purified PA from rice bran presented 420 mg 100 g-1 PA content; the result obtained was in the range of PA content in purified PA from rice bran (335 to 708 mg 100 g-1) described by Canan et al. [26]. The purification step of the rice bran guaranteed around four times higher PA content compared to rice infant cereal and rice flour (Table II). It was not possible to quantify other inositols.

49


Chromatographic Conditions Evaluation for Phytic Acid (IP6) Determination in Rice Bran Samples by HPLC

Article

Table II. PA content comparison with literature data Method

IP6 content (mg 100 g-1)

LOD (mg mL-1)

LOQ (mg mL-1)

Defatted rice bran

HPLC

3.90

0.05

0.15

Defatted rice bran

Colorimetric

6.0

HPLC

420

0.05

0.15

Purified PA from rice bran [26]

Colorimetric

335 - 708

Rice bran [5]

Colorimetric

3.65

HPLC

107.3

Colorimetric

75.14

Sample

Purified PA from rice bran

Rice infant cereal [47] Rice flour [49]

0.04

CONCLUSIONS A series of complex equilibrium are linked to ion pair chromatography, in this case, a good organic modifier/sample diluent/column interaction evaluation was crucial for developing this study. The evaluation using modifier methanol varying 5% resulted in a chromatographic profile improvement, as well as PRP1 column replacement by combined C18 columns, a Shim-pack CLC-ODS, and a Novapak, increasing the analytical course. The mobile phase (A, B, and C) and sample diluent (da, db, and dc), with a 1.57% ion exchanger variation (mobile phase A to mobile phase C), had a negligible difference in the chromatographic profiles. Thus, the difference in the profiles was not only between the mobile phases, showing the ionic pair percentage relevance eluted with the sample. Among the profiles studied, a loss of up to 2 peaks in the chromatographic profiles occurred. CRF showed differences in profile selectivity, where the maximum reached was at 2.08 (mobile phase A and db) and the minimum was at 1.01 (mobile phase C and da). Mobile phase A and the da and db sample diluents provided the best responses in the chromatographic profiles. IP6 calibration curve R2 was 0.9988 and intra-day and inter-day studies showed RSD values lower than 4% in all cases, showing adequate repeatability and intermediate precision for the analytical method proposed. A 91% IP6 recovery was achieved and the LOD and LOQ were 0.05 and 0.15 mg mL-1, respectively. The IP6 content in defatted rice bran was 3.90 g 100 g-1 and in purified PA from rice bran sample was 420 mg 100 g-1. The great contribution of the developed chromatographic method is the PA overestimation solution. Manuscript submitted: Oct. 19, 2018; revised manuscript submitted: Jan. 1, 2019; manuscript accepted: Feb. 7, 2019; published online: June 11, 2019. REFERENCES 1. Kumar, V.; Sinha, A. K.; Makkar, H. P. S.; Becker, K. Food Chem., 2010, 120, pp 945-959. 2. Graf, E.; Eaton, J. W. Free Radic Biol Med., 1990, 8, pp 61-69. 3. Duong, Q. H.; Clark, K. D.; Lapsley, K. G.; Pegg, R. B. J Food Compos Anal., 2017, 59, pp 74-82. 4. Thavarajah, D.; Thavarajah, P.; See, C. T.; Vandenberg, A. Food Chem., 2010, 122, pp 254-259. 5. Ravindran, V.; Ravindran, G.; Sivalogan, S. Food Chem., 1994, 50 (2), pp 133-136. 6. Hurrell, R. F. Int J Vitam Nutr Res., 2004, 74, pp 445-452. 7. Bhagyawant, S. S.; Bhadkaria, A.; Gupta, N.; Nidhi, S. J Food Biochem., 2018 (DOI: http://dx.doi.org/10.1111/jfbc.12678). 8. Vucenik, I.; Shamsuddin, A. M. Nutr Cancer., 2006, 55, pp 201-209. 9. Lopez, H. W.; Leenhardt, F.; Coudray, C.; Remesy, C. J. Food Sci. Technol., 2002, 37, pp 727-739. 50


Canan, C.; Delaroza, F.; Kalschne, D. L.; Corso, M. P.; Ida, E. I.

Article

10. Champagne, E. T.; Hinojosa, O. J Inorg Biochem., 1987, 30, pp 15-33. 11. Law, B. M. H.; Waye, M. M. Y.; So, W. K. W. Int J Mol Sci., 2017, 18, pp 1-20. 12. Norazalina, S.; Norhaizan, M. E.; Hairuszah, I.; Norashareena, M. S. Exp Toxicol Pathol., 2010, 62, pp 259-268. 13. Canan, C.; Bloot, A. P. M.; Baraldi, I. J.; Colla, E.; Feltrin, V. P.; Corso, M. P.; Habu, S.; Nogues, D. R. N.; Kalschne, D. L.; Silva-Buzanello, R. A. Composição antimicrobiana a base de fitato, e seu uso. BR 10 2018 006228 0, March 27, 2018, UTFPR, Medianeira, PR, BR. 14. Kim, N. H.; Rhee, M. S. Int J Food Microbiol., 2016, 227, pp 17-21. 15. Kim, S. M.; Rico, C. W.; Lee, S. C.; Kang, M. Y. J Clin Biochem Nutr., 2010, 47, pp 12-17. 16. Xu, Q.; Kanthasamy, A. G.; Reddy, M. B. Toxicology, 2008, 245, pp 1-2. 17. Chung, S. Y.; Champagne, E. T. J Agric Food Chem., 2007, 55, pp 9054-9058. 18. Obata, T.; Nakashima, M. Eur J Pharmacol., 2016, 774, pp 20-24. 19. Costello, A. J.; Glonek, T.; Myers, T. C. Carbohydr Res., 1976, 46, pp 159-171. 20. Nolan K. B.; Duffin, P. A. J. Nutr., 1984, 114 (7), pp 1192-1198. 21. Fuh, W. S.; Chiang, B. H. J. Sci. Food Agric., 2001, 81 (15), pp 1419-1425. 22. Persson, H.; Turk, M.; Nyman, M.; Sandberg, A. S. J Agric Food Chem., 1999, 46, pp 3194-3200. 23. Blaabjerg, K.; Hansen-Møller, J.; Poulsen, H. D. J. Chromatogr. B, 2010, 878 (3-4), pp 347-354. 24. Park, H. R.; Ahn, H. J.; Kim, S. H.; Lee, C. H.; Byun, M. V.; Lee, G. W. Food Control, 2006, 17 (9), pp 727-732. 25. Phillippy, B. Q.; Wyatt, C. J. J. Food Sci., 2001, 66 (4), pp 535-539. 26. Canan, C.; Cruz, F. T. L.; Delaroza, F.; Casagrande, R.; Sarmento, C. M. P.; Shimokomaki, M.; Ida, E. I. J Food Compos Anal., 2011, 24, pp 1057-1063. 27. Han, Y. W. J. Agric. Food Chem., 1988, 36 (6), pp 1181-1183. 28. Sha, R.; Wu, D.; Wang, W.; Wang, S.; Cai, C.; Mao, J. Waste Biomass Valor., 2017 (DOI: 10.1007/s12649-017-0092) 29. Pande, R.; Mishra, H. N. Food Chem., 2015, 172, pp 880-884. 30. Harland, B. F.; Oberleas D. Journal-Association off Anal Chem., 1986, 69, pp 667-670. 31. AOAC. American Organization of Analytical Chemists. Official Methods of Analysis of the Association of Official Analytical Chemists. AOAC, Arlington, 2005. 32. Harland, B. F.; Oberleas, D. World Rev. Nutr. Diet., 1987, 52, pp 235-259. 33. Wu, P.; Tian, J. C.; Walker, C. E.; Wang, F. C. Int J Food Sci Technol., 2009, 44, pp 1671-1676. 34. Camire, A. L.; Clydesdale, F. M. J Food Sci., 1982, 47, pp 575-578. 35. Lehrfeld, J. Cereal Chem., 1989, 66, pp 510-515. 36. Hamada, J. S. J. Chromatogr. A, 2002, 944 (1-2), pp 241-248. 37. Tur, F.; Tur, E.; Lentheric, I.; Mendoza, P.; Encabo, M.; Isern, B.; Grases, F.; Maraschiello, G. J. Chromatogr. B, 2013, 928, pp 146-154. 38. Rougemont, B.; Fonbonne, C.; Lemoine, J.; Bourgeaux, V.; Salvador, A. J. Liq. Chromatogr. Relat. Technol., 2009, 39 (8), pp 408-414. 39. Lanças, F. M. Sci. Chromatogr., 2009, 5 (1), pp 27-46. 40. Ellis, R.; Morris, E. R. Cereal Chem., 1986, 63, pp 58-59. 41. Lehrfeld, J.; Morris, E, R. J Agric Food Chem., 1992, 40 (11), pp 2208–2210. 42. Glajch, J. L.; Kirkland, J. J.; Squire, K. M.; Minor, J. M. J Chromatogr A., 1980, 199, pp 57-79. 43. ICH. Q2B Validation of Analytical Procedures: Methodology. ICH, London, 1996. 44. Latta, M.; Eskin, M. J Agric Food Chem., 1980, 28, pp 1313-1315. 45. Scarminio, I. S.; Bruns, R. E. TrAC - Trends Anal Chem., 1989, 8, pp 326-327. 46. Nappi, G. U.; Ribeiro-Cunha, M. R.; Coelho, J. V.; Jokl, L. Ciência e Tecnol Aliment., 2006, 26, pp 811-820. 47. Frontela, C.; García-Alonso, F. J.; Ros, G.; Martínez, C. J Food Compos Anal., 2008, 21, pp 343-350. 48. Burbano, C.; Muzquiz, M.; Osagie, A.; Ayet, G.; Cuadrado, C. Food Chem., 1995, 52, pp 321-325. 49. Norhaizan, M. E.; Nor Faizadatul Ain, A. W. Mal J Nutri, 2009, 15 (2), pp 213-222. 51


Article

Br. J. Anal. Chem., 2019, 6 (22) pp 52-59 DOI: 10.30744/brjac.2179-3425.AR.131-2018

Fast and Simple Spectrophotometric Procedure for Determination of TiO2 in Paint Samples Felipe Eduardo Reis, Vivian Maringolo,

Diogo Librandi Rocha*

Center for Natural Sciences and Humanities, Federal University of ABC, Avenida dos Estados, 5001, BangĂş, 09210-580, SĂŁo Paulo, SP, Brazil. *d.rocha@ufabc.edu.br

Graphical abstract

Titanium dioxide is separated from other components in paint samples, and solubilized. After the addition of hydrogen peroxide, a colored complex with absorption maximum at 435 nm is obtained. Thus, spectrophotometric analytical response can be registered, yielding a simpler, inexpensive, and faster analysis than the titrimetric reference procedure.

Paints are commonly used to protect solid surfaces and to cover imperfections. The composition alters the characteristics of the paint such as brightness, and resistance to abrasion. An important component of paints is TiO2, which yields a strong white color and opacity. Due to the cost of this raw material, its employment is limited. The determination of TiO2 is important for quality control and for developing formulations with lower content of TiO2. Additionally, deformulation studies are generally carried out aiming at aiding market assessment. The reference procedure for determination of TiO2 is based on a volumetric method using highly unstable species such as Ti(III) and Fe(II), making it extremely susceptible to systematic errors. Alternative procedures with atomic absorption or emission techniques are expensive for research laboratories in the industry, especially when the determination of a few metals is required. In this sense, a simple spectrophotometric procedure for TiO2 determination in paint samples is herein proposed, based on the reaction between Ti(IV) and H2O2 that yield a soluble complex with absorption maximum at 435 nm. The univariate optimization of the parameters was carried out aiming at best sensitivity and analytical frequency, and minimum reagent consumption and waste generation. Linear response was observed between 6.0 and 60 mg L-1 Ti. Detection limit (n = 20, 99.7% confidence level) and coefficient of variation (n = 20) were estimated at 2.8 mg L-1 and 1.2 %, respectively. Sample preparation was based on ashing, and dissolution in hot mixture of sulfuric and hydrochloric acids. The analysis of the digests by the proposed and the titrimetric reference procedures agreed at the 95% confidence level. The developed procedure is a faster, low-cost, reliable and cleaner alternative for determination of TiO2 in paint samples. Keywords: titanium, pigments, spectrophotometry, paints, deformulation. 52


Fast and Simple Spectrophotometric Procedure for Determination of TiO2 in Paint Samples

Article

INTRODUCTION Paints are defined as a dispersion of pigments in the presence of polymers [1]. On principle, they were conceived to enhance esthetics, but in actual days they are also used for other ends such as protection. The heterogenous mixture produces a dried thin coat that covers the substrate and yields different characteristics depending on the composition. The formulations show some common components, such as additives, resins, pigments, and fillers that are varied depending on the specific purpose of the final product, such as resistance to abrasion, higher yield after drying, and brightness [2]. The formation of the coating over the substrate depends on physical and chemical phenomena that occur after the application. The solvent, which is the volatile fraction of the paint, assures adequate homogenization of the mixture, dissolving some components and allowing the equal distribution of particles. Additionally, the viscosity of the paint depends on the solvent, influencing its stability and performance. The additives, such as defoamers, humectants and dispersers, and resins are important for enhancing the fabrication process, the stability, and the application of the paint. Fillers and pigments generally form a suspension, and they are responsible for color, opacity and resistance of the paint. Additionally, the content and refraction index of these components affect efficiency of the coating and brightness. The most used pigment in paint samples is TiO2 that yields high efficient coating and whiteness [3]. Titanium dioxide shows adequate stability, reflectance and opacity, and low toxicity, making it suitable for producing paints. The crystalline forms of TiO2 are anatase, rutile, and brookite, but important physical properties of the pigment are not significantly altered with the crystalline form. The best coating conditions using TiO2 is evidenced by comparing refraction indexes (RIs). The forms anatase and rutile show 2.55 and 2.73, respectively, indicating the wider use of the rutile form [3]. The RI of TiO2 is 1.7-fold and 1.4-fold higher than of calcium carbonate and zinc oxide, respectively. However, the use of TiO2 is limited by its cost. Generally, low-cost fillers substitutes, such as CaCO3 and SiO2, are generally used to reduce the price, and to yield different properties to paints. Therefore, investigating the formulation of paints of different brands through deformulation enhances the competition in the market and aids research and development to optimize the performance of the product. Additionally, quality control also requires monitoring of TiO2. Deformulation comprises decomposition of the sample aiming at identifying and characterizing its contents [4]. The reverse engineering is used as a tool for marketing and for studies in the technical area. For paint samples, a common strategy for deformulation is thermal decomposition, in which groups of chemicals are eliminated by increasing temperature. By reaching 900 ºC, the digests basically comprise silicates, and metal oxides, including TiO2, which is submitted to chemical analysis. The determination of Ti in paints can be carried out according to recommended protocols based on titrimetric analysis after the dissolution of ashes in hot concentrated sulfuric acid [5]. After cooling down, the digest is mixed with aluminum foils under heating for Ti(IV) reduction to Ti(III). The reaction must be carried out under an oxygen-free atmosphere (saturation with CO2 is generally exploited) due to instability of Ti(III). The derivatized analyte is then titrated with a Fe(III) solution using NH4SCN as indicator. Therefore, the end point occurs when an excess Fe(III) yields the red [Fe(SCN)]2+. The detection of the end point is difficult because of the grayish color that the mixture assumes due to excess of aluminum foil in the solution. Additionally, analytical frequency is not suitable for laboratories with high demand for analysis. In general, inductive coupled plasma optical emission spectrometry (ICP OES) and mass spectrometry (ICP-MS) are alternatives for Ti determination [6-8]. Despite the possible multielementary determinations of ICP OES and ICP-MS, such variety of elemental analysis is not required, as well as high sensitivity procedures for analysis of paint samples. Therefore, the cost of acquisition and maintenance of the equipment are too high for implementation in those analytical laboratories. Spectrophotometric procedures require lower-cost instrumentation, but Ti determination is carried out with selective reagents, such as ponceau S [9], and 4´-dimethylphenylazo-6-hydroxypyrimidine53


Article

Reis, F. E.; Maringolo, V.; Rocha, D. L.

2,4-dione [10]. These chemicals make the procedures expensive and might show higher toxicity. Therefore, selective and low-cost reagents for Ti determination is sought. An alternative has been used for determination of Ti in digests of aluminum foils [11]. Hydrogen peroxide was used for generating a colored complex with Ti, and a hot concentrated nitric acid was employed prior to the addition of the reagent for a nitration step that took 10 min, hindering analytical frequency. In this work, a simple spectrophotometric procedure is proposed based on the reaction between Ti(IV) and H2O2, generating a coordination compound with absorption maximum at 435 nm. The colorimetric reagent is cheap, and easy to find and to discard in comparison to organic reagents used for spectrophotometric determination of TiO2. MATERIALS AND METHODS Reagents and solutions All solutions were prepared with analytical grade reagents, and deionized water. The stock solution of Ti(IV) was prepared by addition of 100 mg of titanium dioxide (99.8% w/w, Synth), in 10 mL of concentrated H2SO4 and of HCl (both Merck). The mixture was heated until rising of white fumes, and kept under heating for 30 min. The dissolution of TiO2 was observed during the process. After cooling down, 70 mL of deionized water was carefully added to the solution, transferred to a 100 mL volumetric flask, and diluted up to the mark with water, and kept in a dark flask. Reference solutions were prepared by adequate dilution of the stock. H2O2 0.3% (v/v) solution was daily prepared by dilution of the concentrated reagent (30%, Merck) in water. White paint samples were furnished by BASF S.A. Apparatus Spectrophotometric responses were obtained with a modular spectrophotometer comprising a tungsten-halogen light source (Ocean Optics), a support with a 10 mm optical path quartz cuvette, and a multichannel spectrometer based on charge-coupled devices (Ocean Optics), allowing acquisition of spectra between 200 and 800 nm. Optical fiber cables were used to transport the radiation from the light source to the cuvette and to the spectrometer. For data acquisition, a microcomputer Intel Pentium IV (Hewlett-Packard), and the software SpectraSuite (Ocean Optics) were used. For sample preparation, a multiprocessing oven (Quimis, model Q318M35T) was employed. Proposed procedure The proposed procedure for TiO2 determination in paint samples is schematically described in Figure 1.

Figure 1. Schematic representation of the proposed procedure for TiO2 determination in paint samples.

For sample preparation, ca. 4.0 g of paint sample was weighted in a porcelain crucible and heated at 900 ยบC for 2 h. After cooling down, the ashes were macerated, and 100 mg of the fine powder was 54


Fast and Simple Spectrophotometric Procedure for Determination of TiO2 in Paint Samples

Article

weighted and transferred to an Erlenmeyer. Afterwards, 10 mL of concentrated sulfuric acid and of hydrochloric acid were added to the ashes. The mixture was heated until white fumes were observed and kept under heating for 30 min. After cooling down, ca. 50 mL of water was added. The solution was quantitatively filtered, transferred to a 100 mL volumetric flask, and diluted with deionized water. For spectrophotometric determination, 1.0 mL of the diluted digest and 300 ÂľL of 1.2 mmol L-1 (0.3% v/v) H2O2 were transferred to a 10 mL volumetric flask and diluted with water. Afterwards, the spectrophotometric detection was assessed at 435 nm. Reference procedure For determination of TiO2 with the reference procedure, sample preparation was also based on ashing as described in the above mentioned section. The ashes were weighted (200 mg) and transferred to a 500 mL Erlenmeyer followed by the addition of 20 mL of concentrated H2SO4, and 8.0 g of ammonium sulfate. The mixture was heated until white fumes were observed, and kept under heating for 20 min. Afterwards, 120 mL of water and 20 mL of concentrated HCl were carefully added. The mixture was boiled again for another 20 min. After cooling down, 1.0 g of aluminum foil was added to the digest. The flask was closed with a stopper coupled to the end of a U-shaped tube. The other end of the tube was used to close an Erlenmeyer containing boiling NaHCO3 solution. In this way, the CO2 generated was transferred to the reaction flask. After dissolution of the aluminum foil, the mixture was boiled for 5 min and cooled down to 60 ÂşC. The indicator NH4SCN was added to the digest, which was titrated with a standardized FeNH4(SO4)2.12H2O solution. The end-point was observed by the rising of a reddish color of the titrate. RESULTS AND DISCUSSION The procedure for the determination of TiO2 was based on the reaction between Ti(IV) and H2O2, yielding a yellow solution with absorption maximum at 435 nm. In the literature, more than one structure has been proposed for the complex, such as [TiO2]2+ [12], TiO(H2O2)2+ [13], and TiO2+ [14], being reaction 1 the most accepted. Nevertheless, the works agreed that reaction stoichiometry Ti(IV):H2O2 is 1:1. Additionally, the reaction is selective, fast, and pH-dependent.

Ti4+ + H2O2

[TiO2]2+ + 2H+

(Reaction 1)

Optimization The optimization was carried out with the univariate method aiming at maximum sensitivity and precision, and minimum waste generation and reagent consumption. The initial conditions were 1.2 mmol L-1 Ti (60 mg L-1), 1.2 mmol L-1 H2O2, and pH 1.0 adjusted with sulfuric acid. Readings were carried out at 435 nm. The first study was a simple kinetic assessment carried out for 20 min to evaluate reaction rate (Figure S1 in Supplementary Material). Spectrophotometric readings were performed right after mixing analyte and reagent solutions (after less than 3 s). It was not observed significant variation of the signal during the study for Ti(IV) and blank solutions. Therefore, readings were carried out right after mixing sample and reagent. The effect of H2O2 concentration on the analytical response was evaluated between 0.70 and 2.0 mmol L-1 (Figure 2A). Best response was observed with 1.1 mmol L-1, indicating quantitative conversion following the stoichiometry 1:1 Ti(IV):H2O2 previously proposed [12,14,15]. Higher amounts of the reagent did not alter the response significantly due to the lack of Ti(IV). Despite this observation, 1.2 mmol L-1 H2O2 was used for further experiments to assure enough amount of reagent as H2O2 is susceptible to degradation. The use of higher concentrations of H2O2 is also recommended as analytical signal is not significantly affected.

55


Article

Reis, F. E.; Maringolo, V.; Rocha, D. L.

Figure 2. Variation of analytical (-â&#x2013;Ą-) and blank (-â&#x2014;&#x2039;-) signals with H2O2 concentration (A), and pH (B). The responses were obtained with 60 mg L-1 Ti(IV) solutions.

As pH is a critical chemical parameter, its effect on the analytical signal was also evaluated from 1.0 to 8.0 (Figure 2B). The adjustment was carried out by using proper amounts of 2.0 mol L-1 NaOH solution. Lower analytical signals were observed at higher pH because Ti(IV) hydrolysis is favored in alkaline medium. Therefore, soluble molecular species of Ti(IV) associated to hydroxyl or oxygen were formed [13], hindering the formation of Ti/H2O2 complex. The evidence of hydrolysis was reinforced at pH higher than 7.0 because it was observed the formation of TiO2 that caused light scattering and consequently increased absorbance readings [16]. Therefore, pH 1.0 was chosen for further experiments. Analytical features and interference studies After optimization, it was observed linear response between 6.0 and 60 mg L-1 Ti (0.12 and 1.2 mmol L-1), described by equation A = 0.0082 CTi + 0.053 (R2 = 0.999), where A is absorbance at 435 nm, and CTi is Ti(IV) concentration in mg L-1. The analytical curve is presented in Figure S2 in Supplementary Material. The coefficient of variation (n = 20, 30 mg L-1 Ti), and the detection limit (n = 20, 99.7% confidence level) were estimated at 1.2% and 2.8 mg L-1, respectively. The analysis of the samples 1-3 and 4-6 were performed in different days and changing the analyst and the equipment. The coefficients of variation remained < 7.0% in both cases (standard deviation < 0.2% w/w, except for sample 3). The variation of the signals obtained with reference solutions was < 5.0%. Per determination, 0.40 mg of H2O2 was consumed. Paint samples show some elements that yield oxides during sample preparation, being Fe the main concomitant. Other elements are negligible in view of the mass of sample and dilutions applied in the procedure, especially for white paints. As iron content can reach up to 0.1% (w/w), the influence of this metal ion on the analytical response was evaluated at 1.0 mg L-1 in the presence of 30 mg L-1 Ti(IV), which represents an excess of fivefold in relation to the expected concentration of Fe. Both Fe(II) and Fe(III) were evaluated and signal variations were < 1.0%, indicating that interference was not significative (< 5.0%). Application and critical evaluation For accuracy assessment, six paint samples were analyzed by the proposed and reference procedures [5]. The results obtained by both procedures (Table I) agreed at the 95% confidence level, showing relative errors < 4.7%. In comparison to the reference procedure [5], the proposed procedure minimized reagent consumption. Waste generation was reduced threefold, and analytical frequency was drastically enhanced, demonstrating that this procedure is more suitable for quality control of paints in the industry. Additionally, tiring and time-consuming steps were eliminated, such as the generation of inert atmosphere and heating for analyte reduction.

56


Fast and Simple Spectrophotometric Procedure for Determination of TiO2 in Paint Samples

Article

Table I. Main values and uncertainties for TiO2 determination in white paint samples by the proposed and reference procedures TiO2 (% w/w) Sample

Proposed procedure

Reference procedure [5]

Relative Error (%)

1 2 3 4 5 6

12.5 ± 0.2 12.8 ± 0.2 11.0 ± 0.5 16.5 ± 0.1 17.9 ± 0.2 5.6 ± 0.2

12.6 ± 0.3 12.7 ± 0.2 11.3 ± 0.2 16.6 ± 0.2 17.1 ± 0.2 5.4 ± 0.4

0.79 0.78 2.6 0.60 4.7 3.7

The content of TiO2 in % w/w was calculated based on the use of 4.0 g of paint sample, and solubilization of 100 mg of ashes in 100 mL of acidic mixture, as described in the experimental section.

Procedures based on ICP OES, and flame atomic absorption spectrometry (FAAS) techniques for Ti determination in cement [17] required similar sample preparation applied to paint samples in this work, except for the employment of HF for dissolving SiO2. The proposed procedure showed higher detection limits, which is not critical for paint analysis. The employment of special gases for ICP OES and FAAS techniques increased the cost per analysis due to maintenance of the equipment. Additionally, HF was used for sample preparation, increasing the hazards associated to this step. Acidic digestion with nitric acid has also been exploited for sample preparation prior to determination of Ti in cosmetics by ICP OES [6], but the time for digestion was not significantly reduced compared to ashing of the sample generally used for TiO2 determination. ICP-MS has also been used for Ti determination in ceramic materials [8]. Despite the low detection limit for Ti (0.11 µg L-1), which is not strictly necessary due to the content of TiO2 in paint samples, acquisition and maintenance costs of the equipment hinders its employment. Spectrophotometric procedures required lower cost instrumentation, but a step for chemical derivatization is often necessary. Organic ligands have been employed for the determination of Ti in several types of samples, such as 5-(2’,4’-dimethylphenylazo)-6-hydroxipyrimidine-2,4-dione [10], and 4-(2-pyridilazo) resorcinol [18]. Despite efficient and with proper quantification limits, the use of those reagents increases the cost of the analysis due to acquisition of chemicals and waste treatment. Alternatively, a flow-based spectrophotometric procedure has been proposed for determination of TiO2 in sunscreens [19]. In this case, sample preparation was based on microwave digestion for approximately 1 h. In spite of the reduction on analytical frequency, HF was employed for dissolving the sample, requiring a step for eliminating the mineral acid. Additionally, chromotropic acid was used as colorimetric reagent. These characteristics show that the herein developed batch procedure is more environment-friendly. CONCLUSIONS The proposed procedure for the spectrophotometric determination of TiO2 in paint samples was developed in view of the analysis in quality control and deformulation laboratories. Cost, waste generation, and reagent consumption were minimized in relation to the reference and alternative procedures. Additionally, analytical frequency was drastically increased in comparison to titrimetric determinations. Procedures based on atomic spectrometry can be used for determination of Ti, but the cost of acquisition and maintenance hinders their applications mainly in deformulation laboratories. The proposed procedure requires a spectrophotometer that shows lower cost, and the detection can also be carried out in lab-made devices. The use of one low-cost colorimetric reagent is also advantageous, also in view of waste treatment. Additionally, H2O2 can be easily standardized by spectrophotometric methods to evaluate the purity of 57


Article

Reis, F. E.; Maringolo, V.; Rocha, D. L.

the reagent that eventually is stored for long periods. In summary, the developed procedure is a fast, reliable, and low-cost alternative for determination of TiO2 in paint samples, attending to the demand of routine laboratories and for deformulation studies. Acknowledgements This research was funded by São Paulo Research Foundation (FAPESP), grant numbers 2015/12172-6 and 2018/05559-0, and in part by the Coordination for the Improvement of Higher Education Personnel - Brazil (CAPES) - Finance Code 001. The authors would like to thank BASF S.A. for furnishing paint samples, for the application of the reference procedure, and for sample preparation. Manuscript received: Nov. 22, 2018; revised manuscript received: Dec. 14, 2018; manuscript accepted: Jan. 10, 2019; published online: June 11, 2019. REFERENCES 1. Brazilian National Standards Organization NBR 12554: Non-industrial buildings paints Terminology. Brazil, 2013. 2. Müller, B.; Poth, U. Coatings Formulation: An International Textbook. Vincentz Network, Hanover, 2011. 3. Amorim, S. M.; Suave, J.; Andrade, L.; Mendes, A. M.; José, H. J.; Moreira, R. F. P. M. Prog. Org. Coatings, 2018, 118, pp 48-56. 4. Gooch, J. W. Analysis and deformulation of polymeric materials. Kluwer Academic, New York, 2002. 5. Brazilian National Standards Organization NBR 15438: Horizontal roadmarking - Traffic paints Testing methods. Brazil, 2013. 6. Salvador, A.; Pascual-Martí, M. C.; Adell, J. R.; Requeni, A.; March, J. G.; J. Pharm. Biomed. Anal., 2000, 22, pp 301-306. 7. Santos, E. J.; Santos, M. P.; Herrmann, A. B.; Sturgeon, R. E. Anal. Meth., 2016, 8, pp 6463-6467. 8. Packer, A. P.; Ere, D.; Li, C.; Chen, M.; Fawcett, A.; Nielsen, K.; Mattson, K.; Chatt, A.; Scriver, C.; Erhardt, L. S. Anal. Chim. Acta, 2007, 588, pp 166-172. 9. Mastoi, G. M.; Khuhawar, M. Y.; Abbasi, K.; Akhtar, M.; Naz, S.; Khan, H.; Mallah, A.; Memon, Z. African J. Pharm. Pharmacol., 2011, 5, pp 1182-1184. 10. Amin, A. S. Quim. Anal., 2002, 20, pp 217-222. 11. Du, X.; Xu, Y.; Qin, L.; Lu, X.; Liu, Q.; Bai, Y. Am. J. Anal. Chem., 2014, 5, pp 149-156. 12. Izci, A.; Hosģün, H. L. Turkish J. Chem., 2007, 31, pp 493-499. 13. Matsubara, C.; Takamura, K. Anal. Chim. Acta, 1975, 77, pp 255-262. 14. Lewis, D. J. Phys. Chem., 1958, 62, pp 1145-1146. 15. Noack, S. R.; Smernik, R. J.; McBeath, T. M.; Armstrong, R. D.; McLaughlin, M. J. Talanta, 2014, 126, pp 122-129. 16. Doty, P.; Steiner, R. F. J. Chem. Phys., 1950, 18, pp 1211-1220. 17. Franco-Jr., J. O.; Korn, M. G. A.; Costa, A. C. S.; Santos-Jr., A. F.; Teixeira, L. S. G. Quim. Nova, 2001, 24, pp 195-199. 18. Masrournia, M.; Vaziry, A. J. Anal. Chem., 2018, 73, pp 128-132. 19. Páscoa, R. N. M. J.; Tóth, I. V; Almeida, A. A.; Rangel, A. O. S. S. Sensors Act. B. Chem., 2011, 157, pp 51-56.

58


Fast and Simple Spectrophotometric Procedure for Determination of TiO2 in Paint Samples

Article

SUPPLEMENTARY MATERIAL In this section, the data related to the kinetic study and analytical curve are presented in Figures S1 and S2, respectively.

Figure S1. Variation of the response of analyte (-â&#x2013;Ą-) and blank (-â&#x2014;&#x2039;-) solutions with time for the kinetic study on the reaction between Ti(IV) and H2O2. Conditions: 60 mg L-1 Ti(IV) in 1.8 mol L-1 H2SO4; 1.2 mmol L-1 H2O2.

Figure S2. Analytical curve obtained for determination of TiO2 in paint samples. Conditions: Ti(IV) solutions in 1.8 mol L-1 H2SO4 and 1.2 mmol L-1 H2O2.

59


Article

Br. J. Anal. Chem., 2019, 6 (22) pp 60-66 DOI: 10.30744/brjac.2179-3425.AR.133-2018

Magnetic Solid Phase Microextraction using CoFe2O4 Nanoparticles for Determination of Cu, Cd, Pb and V in Sugar Cane Spirit Samples by Energy Dispersive X-Ray Fluorescence Spectrometry Lucilia A. Meira1,

Jorge S. Almeida1,2*, Fábio de S. Dias3, Leonardo S. G. Teixeira1,2

Universidade Federal da Bahia, Instituto de Química, Departamento de Química Analítica, Campus Universitário de Ondina, 40170-115, Salvador, BA, Brazil. *jorgealmeidas@hotmail.com 2 INCT de Energia e Ambiente - Universidade Federal da Bahia, Instituto de Química, Campus Universitário de Ondina, 40170-115, Salvador, BA, Brazil. 3 Universidade Federal do Recôncavo da Bahia, Centro de Ciências Exatas e Tecnológicas, Campus Universitário de Cruz das Almas, 44380-000, Cruz das Almas, BA, Brazil. 1

Graphical Abstract

Determination of Cu, Cd, Pb and V in sugar cane spirit samples by EDXRF after preconcentration using CoFe2O4

A method for the determination of Cu, Cd, Pb and V in Brazilian sugarcane spirit (“cachaça” in Brazil) using CoFe2O4 nanoparticles impregnated with 1-(2-pyridylazo)-naphthol (PAN) for extraction of the metals with posterior determination by X-ray fluorescence spectrometry directly in the solid phase is described. The recommended conditions for extraction were: pH 6.0 (1.0 mol L−1 hexamethylenetetramine (HMTA)/ nitric acid buffer solution); sample volume, 25 mL; and nanoparticle mass, 100 mg. The precisions for the determination of each element, expressed as relative standard deviations (RSD) of standard solutions containing 0.20 mg L−1 of each analyte, were 1.5, 1.8, 1.2 and 2.9% (n = 10), respectively. Limits of detection of 0.032, 0.038, 0.016 and 0.028 mg L-1 were obtained for Cu, Cd, Pb and V, respectively. Addition and recovery tests were performed, and the results ranged from 97 to 115% for Cu, 85 to 115% for Cd, 85 to 99% for Pb and 85 to 110% for V. The method was successfully applied in extraction and determination of Cd, Pb, Cu and V in sugar cane spirit samples from Brazil. Keywords: sugar cane spirit; energy dispersive X-ray fluorescence spectrometry; multi-element determination; magnetic solid-phase microextraction. INTRODUCTION The sugar cane spirit (usually known as “cachaça” in Brazil) is the typical and exclusive denomination of cane brandy produced in Brazil, with an alcoholic content of 38-48% (v v-1) and peculiar sensorial characteristics [1,2]. The cachaça is the third most consumed distilled beverage in the world, and in 60


Magnetic Solid Phase Microextraction using CoFe2O4 Nanoparticles for Determination of Cu, Cd, Pb and V in Sugar Cane Spirit Samples by Energy Dispersive X-Ray Fluorescence Spectrometry

Article

Brazil, occupies the first place [3]. Metals can be introduced in sugar cane spirit during the production process, transport and tankage due to the oxidation of parts of the metallic equipment’s or with the use of raw material with inorganic contaminants [4]. The quantification of metallic specie is important for product quality control, observing the inorganic composition assurance and the presence of toxic elements to humans [5]. These determinations are routinely performed by flame atomic absorption spectrometry (F AAS), [69], inductively coupled plasma mass spectrometry (ICP-MS) [10], electrothermal atomic absorption spectrometry ET AAS [2,4,11,12,13] and UV-Vis spectrophotometry [14,15]. However, the energy dispersive X-ray fluorescence spectrometry (EDXRF) has not been explored for determination of inorganic species in sugar cane spirit. Energy dispersive X-ray fluorescence spectrometry is a successful technique, since it allows multielement determination with sufficient spectral resolution in metals determination. However, EDXRF has low sensitivity and it may be difficult to use liquid and volatile samples, such as sugar cane spirit. Thus, it is common to include a step for metal extraction and preconcentration prior the determinations using the EDXRF [16-21]. Extraction and pre-concentration of metals using magnetic nanoferrites have been explored in association with different analytical techniques of detection [22], including EDXRF [17]. In the latter case, the possibility of association of magnetic nanoparticles with EDXRF for ethanolic matrix analysis (specifically, fuel ethanol) was shown. The objective of this work was to verify the possibility of expanding the application of the extraction and determination of Cu, Cd, Pb and V in sugar cane spirit samples using magnetic solid phase dispersive microextraction with CoFe2O4 nanoparticles (NPs) as solid support for measurements by EDXRF. MATERIALS AND METHODS Instrumentation An energy dispersive X-ray spectrometry S2 Ranger (Bruker, Billerica, MA, USA) was used for the measurements. The equipment has a palladium-targeted X-ray tube. The equipment calibration was performed using a copper disk (40 mm diameter). After the extraction procedure, nanoferrites rich in metals of interest were placed in the center of a polyethylene cup spectrometer cell and the sample holder was sealed with a Mylar® film. The instrumental conditions were: irradiation time, 90 s; tube tension, 40 kV; tube current, 30 mA; and a helium atmosphere. The analytical lines used were: Cd, 23.1 keV (Kα); Pb, 10.6 keV (Lα); Cu, 8.04 keV (Kα) and V, 5.00 keV (Kα). A model 827 digital pH meter (Metrohm Ltd., Switzerland) with a combined glass electrode was used in the pH adjustments of the solutions. An ultrasonic bath (model 75D from VWR International™, Cortland, New York) of 60 kHz and 2 L of power and internal capacity, respectively, was used to accelerate CoFe2O4 impregnation with PAN. An analytical balance (model TE214 S from Sartorius, Goettingen, Germany) with an accuracy of ± 0.1 mg was used for weighing of the masses of substances used. Centrifuge conical tubes with internal capacity of 50 mL were used in the experiments. A Varian Vista (Mulgrave, Australia) simultaneous inductively coupled plasma optical emission spectrometer instrument with axial viewing, equipped with charge coupled device (CCD), and a V-Groove nebulizer, was used as a comparative method for determination of Cu, Cd, Pb e V. The metal determinations were carried in the following conditions: power (1.4 kW), plasma gas flow (15.0 L min−1), nebulizer gas flow (0.7 L min−1), and auxiliary gas flow (1.5 L min−1). The emission lines used in the determination were: Cu (324.752 nm), Cd (214.439 nm), Pb (220.353 nm) and V (318.397 nm). Reagents, solutions and samples All reagents used were at least of analytical grade. Water with a resistivity of 18.2 MΩ cm was obtained from a Milli-Q system (Millipore, Bedford, MA, USA) and used in all solution preparation. Nitric 61


Article

Meira, L. A.; Almeida, J. S.; Dias, F. S.; Teixeira, L. S. G.

acid was purified by double sub-boiling distillation in a quartz still (Kürner Analysentechnik, Rosenheim, Germany). All flasks were cleaned by soaking in a 1.4 mol L-1 HNO3 solution for at least 24 h and rinsed abundantly with high-purity deionized water before use. All solvents and reagents were of the highest commercially available purity grade. Mixed working standard solutions for Cd, Pb, Cu and V (0.20 mg L−1) were prepared by dilution from 1000 mg L−1 stock solutions (Specsol Quimlab, Brazil). The solutions of each element were prepared by dilution in 1.0 mol L−1 hexamethylenetetramine (HMTA)/nitric acid buffer solution and ethyl alcohol PA. Nanoferrites were synthesized from their metal precursors in the form of nitrate (Exodus Científica, Brazil) and impregnated with 1-(2-pyridylazo)-naphthol (PAN) (0.005 mol L-1) (Merck, Darmstadt, Germany) as previously described [17,23,24]. Unaged sugar cane spirit (cachaça) samples were obtained from different industrial producers in Brazil. The samples were transparent and were produced for immediate consumption, without going through aging process in wooden barrels. They were purchased in supermarkets in the metropolitan region of Salvador, Bahia, Brazil, and stored in a refrigerator at 4 °C until analysis. Synthesis and impregnation of CoFe2O4 nanoparticles The CoFe2O4 nanoparticles were synthesized following a co-precipitation procedure as described in a previous work [17]. Briefly, iron nitrate and cobalt nitrate solutions were mixed in an stoichiometry ratio of 2:1 (Fe:Co) in the presence of a sucrose solution. Then, NaOH solution was added until precipitate formation. After filtration, the precipitate was washed, heated and calcined. Once synthesized, the nanoparticles were impregnated with the reagent 1-(2-pyridylazo)-naphthol (PAN). A mass of 2.0 g of CoFe2O4 was immersed in 20 mL of PAN solution (0.005 mol L-1) and 10 mL of sodium dodecyl sulfate (SDS) solution (0.018 mol L-1) in a glass vessel of 100 mL of internal capacity. The mixture was sonicated for 20 min. After impregnation, the nanoferrites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanoparticles presented a particle size of (8.5 ± 2.8) nm. More detailed information of the synthesis and characterization of the nanoferrites used in this work are described in a previous work [17]. General procedure A volume of 22.0 mL of each sugar cane spirit sample was added directly into a centrifuge tube. Subsequently, 3.0 mL of 0.1 mol L-1 HMTA /nitric acid buffer solution (pH 6.0) was added to the medium. Then, 100 mg of CoFe2O4 NPs was added to the medium and the mixture was stirred manually for 10 min. Then, the NPs were separated from the supernatant with the aid of a magnet. Subsequently, the solid phase was conducted to the drying stage at room temperature and then subjected to the determination of the metal ions contained in the solid support itself (nanoferrite) using EDXRF. Calibration curves were prepared in alcoholic medium attending a concentration range of 0.107– 1.000, 0.127–1.000, 0.053–1.000 and 0.093–1.000 mg L−1 for Cu, Cd, Pb and V respectively. The alcohol content of the reference solutions was adjusted to (40 ± 5)% (v v-1), to simulate the matrix of the samples, using PA hydrated ethyl alcohol (Merck, 95.1%). The blank solutions were prepared through the same procedure using pure hydrated ethanol (95.1%, Merck, Germany) with the addition of the buffer solution giving solutions with final ethanol content of (40 ± 5)% (v v-1). Blank solutions were analyzed by EDXRF and the analytical signals were low and comparable to background signals. All standard solutions, including blanks, were subjected to the extraction procedure for the purpose of constructing the calibration curve. Comparative method The comparative method for the determination of Cu, Cd, Pb and V in sugar cane samples was performed using the inductively coupled plasma optical emission spectrometry (ICP OES) technique. The external calibration in acid medium (HNO3 0.01 mol L-1) was used for all the elements. Samples of 62


Magnetic Solid Phase Microextraction using CoFe2O4 Nanoparticles for Determination of Cu, Cd, Pb and V in Sugar Cane Spirit Samples by Energy Dispersive X-Ray Fluorescence Spectrometry

Article

sugar cane spirit were pretreated prior to determination of the metals by evaporation to near dryness at constant temperature, thereafter they were adjusted to known volumes using dilute nitric acid. In this way, it was possible to obtain sufficient conditions to allow the analysis by ICP OES. RESULTS AND DISCUSSION The instrumental conditions of the equipment operation were established previously when ethanol fuel analysis by EDXRF was proposed: irradiation time, 90 s; tube voltage, 40 kV; current, 30 mA and atmosphere helium condition [17]. In solid phase microextraction, the pH value plays a critical role in the extraction of metals. The surface charge density of CoFe2O4/NPs is a major factor affecting the extraction of the analytes and their amount varies strongly with the pH values [24]. In this way, the extraction capacity of the metals at pH 1-12 was evaluated. Practically, no extraction for the metals investigated was observed for pH values between 1-3. Low pH values make the surface of the nanoparticle positive, leading to low metal retention [25-27]. The analytical signals for all metals increase significantly from pH 5 and highest extractions were obtained in the pH range of 5-7. For pH above 8, a decrease in analytical signals was observed, possibly due to the formation of metal hydroxides, which compromises the extraction of the ions. Thus, the pH of the samples was adjusted to 6.0 for extraction of all metals in accordance with the previous work when ethanol fuel was analyzed [17]. The total sample volume was evaluated in the range 3-100 mL. Firstly, the test was performed keeping the analyte mass constant in order to verify if an increase of sample volume affects the extraction efficiency. In addition, the formation of particle agglomerates can occur, varying the contact surface of the nanoparticles and sample [28]. The results indicated that there was no significant difference in the analytical signals when sample volumes in the range 3-100 mL were employed. However, when different volumes with constant concentrations are used the analyte signal increases linearly up to the volume of 25 mL. Thus, to guarantee the sensitivity of the developed method, 25 mL of sample were used. Using a 25 mL volume, the contact time between sample and nanoparticles was evaluated for 5-20 min, and it was noted that there was no significant variation in the results for contact times greater than 10 min. The ethanol content is another important variable to be investigated, because, depending on the alcoholic content of the medium, there may be release of the PAN from the nanoparticle to the solution. Previous works report the stability of the nanoferrite in the presence of organic solvents, such as ethanol [17,29]. However, a release of PAN was visually observed for ethanol content above 70% (v v-1) [17]. Considering that the concentration of alcohol in sugar cane spirit is typically 38-48% (v v-1), the concentration of ethanol was adjusted in this range in the standard solutions for calibration purpose For use of CoFe2O4 nanoparticles in the pre-concentration of metals and direct determination on the solid support by X-ray fluorescence spectrometry, it is necessary to establish the mass of the NPs suitable for the procedure. A small mass is insufficient to retain a significant amount of metals. In addition, there is a difficulty in working with EDXRF using low amounts of solid support, because affects the accuracy of the measurements. High mass of CoFe2O4 nanoparticle can generate physical interference [27]. In this way, the nanoparticle mass was evaluated from 100-800 mg and through the results obtained 100 mg was choose (Figure 1).

63


Meira, L. A.; Almeida, J. S.; Dias, F. S.; Teixeira, L. S. G.

Article

Figure 1. Effect of the mass of the magnetic nanoferrite on the analytical signal for determination of Cu (■), Cd (●), Pb (◄) and V(○)in sugar cane spirit samples. Conditions: concentration of all metals, 0.20 mg L−1; pH 6.0; buffer solution HMTA/nitric acid, 1.0 mol L−1; contact time, 10 min; sample volume, 25 mL; ethanol content, 35% (v v-1).

Analytical features and application Using the general procedure, a series of experiments was performed to obtain the calibration graph, linear range, precision, limit of detection and limit of quantification for determination of the analytes. The relative standard deviation (RSD) was obtained for the repetitive determinations of 0.2 mg L–1 of all metals (n = 10). The limit of detection (LOD) and quantification (LOQ) were calculated using the criterion 3xSb/m and 10xSb/m, where Sb is the standard deviation of the blank measurements and m is the calibration slope. The analytical characteristics of the proposed method are shown in Table I. The sugar cane spirit samples were analyzed using spike recovery tests. These results were obtained as the averages of three replicates of each sample. As shown in Table II, the recoveries varied from 97 to 115% for Cu, 85 to 115% for Cd, 85 to 99% for Pb and 85 to 110% for V. Good agreement was found between the results obtained using the proposed method and the comparative method for the results of concentrations of the analytes. Table I. Analytical characteristics of the proposed method for the determination of Cu, Cd, Pb and V in sugar cane spirit samples Parameters Calibration curve Coefficient of correlation Linear range, mg L

Cu

Cd

Pb

V

I = 0.491x + 1.085

I = 0.376x + 0.123

I= 1.525x + 2.073

I= 1.402x + 0.956

0.994

0.996

0.993

0.996

0.107-1.000

0.127-1.000

0.053-1.000

0.093-1.000

-1

LOD, mg L

0.032

0.038

0.016

0.028

LOQ, mg L-1

0.107

0.127

0.053

0.093

1.5

1.8

1.2

2.9

-1

RSD, % (0.2 mg L-1; n = 10)

LOD: limit of detection; LOQ: limit of quantification; RSD: relative standard deviation; I: intensity of fluorescence, cps; x: concentration of the respective analyte, mg L−1. 64


Magnetic Solid Phase Microextraction using CoFe2O4 Nanoparticles for Determination of Cu, Cd, Pb and V in Sugar Cane Spirit Samples by Energy Dispersive X-Ray Fluorescence Spectrometry

Article

Table II. Determination of Pb, Cd, Cu and V in sugar cane spirit samples by EDXRF after magnetic solid-phase microextraction procedure and by the comparative method (n= 3) Concentration (mg L-1) Sample without lead addition Sample with lead addition* Recovery (%)

Sample 1

Sample 2

Sample 3

Sample 4

<LQ

<LQ

0.075 ± 0.002

0.081 ± 0.002

0.17 ± 0.05

0.18 ± 0.02

0.25 ± 0.02

0.28 ± 0.02

85

90

88

99

Comparative methoda

<LQ

<LQ

0.102 ± 0.025

0.08 ± 0.02

Sample without cadmium addition

<LQ

0.17 ± 0.02

<LQ

<LQ

0.202 ± 0.005

0.39 ± 0.05

0.17 ± 0.02

0.23 ± 0.04

Sample with cadmium addition* Recovery (%)

101

110

85

115

Comparative methoda

<LQ

0.17 ± 0.01

<LQ

<LQ

Sample without copper addition Sample with copper addition* Recovery (%) Comparative method

a

Sample without vanadium addition Sample with vanadium addition* Recovery (%) Comparative methoda a

0.25 ± 0.05

0.21 ± 0.05

0.86 ± 0.04

<LQ

0.444 ± 0.001

0.44 ± 0.01

1.08 ± 0.02

0.21 ± 0.06

97

115

110

105

0.32 ± 0.05

0.23 ± 0.03

0.76 ± 0.12

<LQ

<LQ

<LQ

<LQ

0.11 ± 0.01

0.17 ± 0.02

0.17 ± 0.05

0.18 ± 0.02

0.33 ± 0.02

85

85

90

110

<LQ

<LQ

<LQ

0.10 ± 0.02

Determination by ICP OES; *Recovery tests: 0.2 mg L-1 of each metal.

CONCLUSION The proposed method provides a highly sensitive and simple approach for the determination of copper, cadmium, lead and vanadium in sugar cane spirit samples by EDXRF after the application of a magnetic solid-phase dispersive microextraction procedure. The method is simple and does not require a drastic pretreatment with the use of concentrated acids or long time for analysis. Acknowledgments The authors are grateful to “Fundação de Amparo à Pesquisa do Estado da Bahia” (FAPESB), “Conselho Nacional de Desenvolvimento Científico e Tecnológico” (CNPq) and “Coordenação de Aperfeiçoamento de Pessoal de Nível Superior” (CAPES) for providing grants, fellowships and financial support. Manuscript submitted: Nov. 30, 2018; revised manuscript submitted: Feb. 14, 2019; manuscript accepted: Feb. 18, 2019; published online: June 11, 2019. REFERENCES 1. Brazil, Leis, decretos, etc. Decreto Nº 6.871, de 4 de junho de 2009. Regulamento da Lei nº 8.918, de 14 de julho de 1994. 2. Caldas, M. N.; Filho, V. R. A.; Neto. J. A. G. At. Spectrosc., 2007, 28, p 5. 3. Tavares, E. F. L.; Okumura, L. L.; Cardoso, M. G.; Oliveira, M. F.; Magriotisa, Z. M.; Saczk, A. A. J. Braz. Chem. Soc., 2012, 23, pp 1614-1622. 4. Canuto, M. H.; Siebald, H. G. L.; Lima, G. M.; Silva, J. B. B. J. Anal. At. Spectrom., 2003, 18, pp 1404–1406. 65


Article

Meira, L. A.; Almeida, J. S.; Dias, F. S.; Teixeira, L. S. G.

Canuto, M. H.; Siebald, H. G. L.; Beinner, M. A.; Silva, J. B. B. IOSR-JESTFT, 2015, 9, pp 55-61. Pinto, F. G.; Rocha, S. S.; Canuto, M. H., Siebald, H. G. L.; Silva, J. B. B. Analytica, 2005, 17, p 48. Souza, J. C.; Toci, A. T.; Beluomini, M. A.; Eiras, S. P. Eclet. Quím., 2017, 42, pp 33-39. Peña, Y. P.; Paredes, B.; Rondón, W.; Bueguera, M.; Bueguera, J. L.; Rondón, C.; Carrero, P.; Capote, T. Talanta, 2004, 64, pp 1351. 9. Catarino, S.; Pinto, D.; Curvelo-Garcia, A. S. Ciên. Téc. Vitiv., 2003, 18, p 65. 10. Wang, X.; Deng, C.; Yin, J.; Tang, X. Environ Earth Sci., 2018, 108, pp 42-59. 11. Oshita, D.; Oliveira, A. P.; Neto, J. A. G, Moraes, M. Eclet. Quím., 2003, 28, p 91. 12. Caldas, N. M.; Raposo, J. L.; Neto, J. A. G.; Barbosa, F. Food Chem., 2009, 113, pp 1266–1271. 13. Froes, R. E. S.; Windmöller, C. C.; Silva, J. B. B. Analytica, 2006, 23, p 23. 14. Azevedo, S. M.; Cardoso, M. G.; Pereira, N. E.; Ribeiro, C. F. S.; Silva, V. F.; Aguiar, F. C. Cienc. Agrotecnol., 2003, 27, pp 618-624. 15. Soares, S. A. R.; Costa, S. S. L.; Araujo, R. G. O.; Teixeira, L. S. G.; Dantas, A. F. J. AOAC Int., 2018,101, pp 876-882. 16. Marguí, E.; Grieken, R. V.; Fontàs, C.; Hidalgo, M.; Queralt, I. App Spectrosc. Rev., 2010, 45, pp 179–205. 17. Meira, L. A.; Almeida, J. S.; Dias, F. S.; Pedra, P. P.; Pereira, A. L. C.; Teixeira, L. S. G. Microchem J., 2018, 142, pp 144–151. 18. Teixeira, L. S. G.; Santos, E. S.; Nunes, L. S. Anal. Chim. Acta, 2012, 722, pp 29–33. 19. Teixeira, L. S. G.; Rocha, R. B. S.; Sobrinho, E. V.; Guimarães, P. R. B.; Pontes, L. A. M.; Teixeira, J. S. R. Talanta, 2007, 72, pp 1073–1076. 20. Kocot, K.; Leardi, R.; Walczac, B.; Sitko, R. Talanta, 2015, 134, pp 360–365. 21. Kocot, K.; Sitko, R. Spectrochim. Acta B, 2014, 95, pp 7–13. 22. Xie, J.; Zhang, X.; Wang, H.; Zheng, H.; Huang, Y. Trac-Trend. Anal. Chem., 2012, 39, pp 114– 129. 23. Maaz, K.; Mumtaz, A.; Hasanain, S. K.; Ceylan, A. J. Magn. Magn. Mater., 2007, 308, pp 289– 295. 24. Abdolmohammad-Zadeh, H.; Rahimpour, E. Anal. Chim. Acta, 2015, 881, pp 54–64. 25. Jiang, H.; Yang, T.; Wang, Y.; Lian, H.; Hu, X. Talanta, 2013, 116, pp 361–367. 26. Firouzabadi, D. Z.; Shabani, A. M. H.; Dadfarnia, S.; Ehrampoush, M. H. Microchem. J., 2017, 130, pp 428–435. 27. Baalousha, M. Sci. Total Environ., 2009, 407, pp 2098–2101. 28. Nurmi, N. T.; Tratnyek, P. G.; Sarathy, V.; Baer, D. R.; Amonette, J. E.; Pecher, K.; Wang, C.; Linehan, J. C.; Matson, D. W.; Penn, R. L.; Driessen, M. D. Environ. Sci. Technol., 2005, 39, pp 1221-1230. 29. Corsini, I. M. Y.; Fernando, Q.; Freiser, H. Anal. Chem., 1962, 34, pp 190–193. 5. 6. 7. 8.

66


Article

Br. J. Anal. Chem., 2019, 6 (22) pp 67-79 DOI: 10.30744/brjac.2179-3425.AR.134-2018

Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup Jonatas de Oliveira S. Silva1, Jéssica B. S. Lima3, Sanny W. M. M. de Carvalho1,2, Mércia V. S. Sant’Anna1,2, José C. S. Júnior1,2, Ravir R. Farias3, Maurício M. Victor3, Eliana Midori Sussuchi1,2* Corrosion and Nanotechnology Laboratory/NUPEG, Federal University of Sergipe, São Cristóvão, SE, 49100000, Brazil. *esmidori@gmail.com 2 Postgraduate Program in Chemistry, Department of Chemistry, Federal University of Sergipe, Av. Marechal Rondon, S/N, São Cristóvão, SE, 49100-000, Brazil. 3 Department of Organic Chemistry, Chemistry Institute, Federal University of Bahia, Salvador, BA, 40170-115, Brazil. 1

Graphical Abstract

The modified electrode with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl) propan-2-ol ligand (CPE/BT) was applied to determinate Cu(II) ions in cabbage cultivated with the use of Bordeaux syrup.

The modified electrode with 1,3-bis(4-butyl-1H-1,2,3triazol-1-yl)propan-2-ol ligand (CPE/BT) was applied to determinate Cu(II) ions in cabbage cultivated with the use of Bordeaux syrup. The parameters optimization resulted in better analytical signals in B-R buffer solution at pH 5.00, potential of -0.4 V for 900 s on preconcentration, scan rate of 10 mV s-1 and amount of modifier of 5%. Under the electroanalytical method obtained linear behavior in the range of 1.00 x 10-8 to 1.30 x 10-7 mol L-1, with a correlation coefficient of 0.994. The limit of detection (LOD) and the limit of quantification (LOQ) for determination of copper were with 1.67 x 10-9 mol L-1 and 5.05 x 10-9 mol L-1, respectively. The electrode was successfully applied in the determination of Cu2+ on cabbage (“couve”) cultivated with Bordeaux syrup and the quantity of copper found was 8.05 µg kg-1, which is within the standards stipulated by ANVISA.

Keywords: Modified electrode, bistriazoles ligand, copper(II), Bordeaux syrup. INTRODUCTION The development of technologies to improve organic crops, in order to produce healthy foods, has been scientifically and socioeconomically important over the years [1,2]. Phytoprotective syrups, such as the Bordeaux blend (Bordeaux syrup), has as main objective the diseases’ control and pests at the farms. Discovered in France in 1882, consists in the mixture of calcium oxide and copper(II) sulphate and has fungicidal and bactericidal actions [3]. Although they provide an improvement in agricultural production, excessive copper accumulation in plants may cause adverse effects on the human body representing risks to the kidneys, liver, and central nervous system, beyond increased blood pressure and respiration rate [4]. The Brazilian National Health Surveillance Agency (ANVISA) delimits the maximum limit for copper ions in 10 mg kg-1 per vegetable [5], and its determination has 67


Article

Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup

been investigated by several analytical techniques such as atomic absorption spectroscopy, coupled plasma-mass spectrometry, UV spectrophotometry, fluorescence and electrochemical techniques [612]. Analyzes using the electrochemical techniques present advantages when compared to others analytical techniques. According to Skoog [13], the main advantage of electrochemical procedures is the possibility to determinate the concentration of same element’s metal ions with different oxidation states. Besides, they are more accessible due its low costs. The electrochemical techniques have a high application in the monitoring of metals ions employing adsorptive stripping voltammetry as a powerful technique for determination of metals. The low limits of detection are determined by stripping techniques which is based on the adsorption accumulation of metal ions and suitable complexing agent (ligand) on the electrode’s surface [14-16]. The use of chemical species as a surface modifier of the conventional carbon, silver, gold, platinum electrodes, among others, provides greater selectivity and reactivity when in contact with the desired analyte [17]. The carbon paste electrodes (CPEs) are an alternative to replace the electrodes containing toxic metals, such as mercury. CPEs are produced from powdered graphite and mineral oil, acting as a binder and promoting the immiscibility of the electrode in the solution. In addition, the development of chemically modified carbon paste electrodes presents ease in the preparation, modification and renewal of their surface [18]. A sensitivity’s increase and a lower detection limit can be achieved with the use of voltammetric detectors along with a preconcentration step for the deposition of electroactive species on the electrode’s surface prior to its electroanalytical determination. An important tool to preconcentrate an analyte and to study the electrochemical behavior of the species is Stripping Voltammetry. Anodic Stripping Voltammetry of copper(II) ions involves preconcentration of the metal at the electrode’s surface by the application of a sufficiently negative potential for the copper to reduce at it. Then the potential sweep is carried out in the anodic direction, oxidizing the previously deposited copper. The current recorded in the anodic stage is used as analytical signal, as long as the peak current be proportional to the concentration of the species in solution. In this context, the triazolic compounds were used as modifier of carbon paste electrodes, due to their ability to complexation with copper(II) ions [19-20]. In this work, to enhance the Cu(II) ions detection, the differential pulse stripping voltammetry technique was proposed based on the complexation of 1,3-bis(4butyl-1H-1,2,3-triazol-1-yl)propan-2-ol (BT) ligand with Cu(II) ions on the carbon paste electrode. The peak currents of Cu(II) ions were evaluated within a wide concentration range, with high selectivity and sensitivity suitable for investigation of real samples in cabbage cultivated with Bordeaux syrup and produced on the irrigated perimeter of the Piauí city, located in the Sergipe state’s countryside. MATERIALS AND METHODS Materials Graphite powder (C), cadmium chloride (CdCl2), zinc(II) acetate dihydrate (Zn(CH3COO)2.2H2O), epichlorohydrin, sodium azide (NaN3), copper(II) sulphate (CuSO4.5H2O) and mineral oil were purchased from Sigma-Aldrich. Sodium phosphate monobasic monohydrate (NaH2PO4.H2O), copper(II) nitrate trihydrate (Cu(NO3)2.3H2O), sodium phosphate dibasic anhydrous (Na2HPO4) and phosphoric acid (H3PO4) were purchased from Synth. Sodium hydroxide (NaOH) was purchased from IMPEX. Potassium hexacyanoferrate(III) (K3Fe(CN)6) was purchased from Baker. Glacial acetic acid (CH3COOH), lead(II) acetate trihydrate (Pb(CH3COO)2.3H2O), iron(II) chloride tetrahydrate (FeCl2.4H2O), manganese(II) acetate tetrahydrate (Mn(CH3COO)2.4H2O) were purchased from Vetec. Sodium acetate trihydrate (Na(CH3COO).3H2O) and Boric acid (H3BO3) were purchased from Reagen. Acetonitrile was used in HPLC grade. Analytical thin layer chromatography (TLC) and TLC plates pre-coated with silica gel 60 F254 (250 μm thickness) were performed on E. Merck. Ultrapure water was in-laboratory produced from deionized water using an ultrapure water generator device (Millipore). The melting points were uncorrected and determined on a MQAPF-302 apparatus. Nuclear Magnetic Resonance spectra was 68


Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

Article

recorded on Varian spectrometer model Inova-500 in deuterated solvents (Figures S1–S2). Electrospray high-resolution mass spectra (HR-MS) was obtained using an Agilent 6550 Q-TOF MS instrument in the positive mode (Figure S3). IR spectra was measured using a Shimadzu IR-Affinity spectrophotometer (Figure S4). Synthesis of 1,3-bis (4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol The synthesis of ligant BT was reached in two steps from epichlorohydrin according to literature described proceedings [20-21]. Synthesis of 1,3-diazide propan-2-ol To a stirred solution of epichlorohydrin (2.00 mL, 25.5 mmol) in a mixture of acetonitrile and water (7:3) sodium azide (4.00 g, 61.6 mmol) was added at room temperature and the mixture was refluxed overnight at 90 °C. The solvent was removed under reduced pressure and the aqueous layer was extracted with dichloromethane (3 X 10 mL). The combined organic layer was dried over anhydrous sodium sulphate. The pure compound (2.97 g, 20.9 mmol) was obtained after removing the solvent under reduced pressure as a transparent viscous liquid. The compound shows single point in ethyl acetate by thin layer chromatography at rf 0.8. Yield: 82%. Synthesis of 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol 1,3-Diazide propan-2-ol (0.5 mmol) and hex-1-yne (1.5 mmol) were suspended in a 1:1 mixture of water and tert-butyl alcohol (2 mL). Sodium ascorbate (0.2 mmol, 200 μL of freshly prepared solution in water) was added, followed by copper(II) sulfate pentahydrate (0.02 mmol in 67 μL of water). The heterogeneous mixture was stirred vigorously overnight at 40 ºC, which in that point it cleared and TLC analysis indicated complete consumption of the reactants. The reaction mixture was diluted with water (8 mL), cooled in ice, and the white precipitate was collected by filtration. After washing the precipitate with cold water (2 x 4 mL), it was dried under vacuum and recrystallized with EtOAc:hexanes mixtures furnishing ligant BT as a white solid. Yield: 85%. Mp 153.0-154.5 ºC; FTIR (KBr) νmax (cm-1) 3284, 3140, 3115, 3064, 1550; 1H NMR (500 MHz, CDCl3) δ 0.94 (t, 6H, J = 7.4 Hz), 1.39 (sex, 4H, J = 7.4 Hz), 1.65 (quint, 4H, J = 7.5 Hz), 2.68 (t, 4H, J = 7.7 Hz), 4.34 (dd, 2H, J = 6.4 and 14.1 Hz), 4.47 (dd, 2H, J = 4.3 and 14.1 Hz), 4.54-4.62 (m, 1H), 5.11 (s, 1H), 7.47 (s, 2H); 13C NMR (125 MHz, CDCl3) δ 13.8, 22.3, 25.3, 31.4, 53.0, 68.8, 122.7, 148.4; ESI-HRMS m/z 329.20663 (observed), 329.20658 (required for [M+Na]+). Modified electrodes Unmodified carbon paste electrodes containing 7:3 m/m (solid:liquid) of graphite powder:mineral oil per weight were used for the sake of comparison. The modified carbon paste electrodes containing 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol (CPE/BT) were prepared by mixing graphite powder:BT:mineral oil (6.5:0.5:3 ratio). The carbon paste mixture holder was constructed using a thickwalled glass tube with 0.40 cm internal diameter. A copper sleeve equipped with a copper wire plunger was mounted at the top of the glass tube. By rotating the sleeve, the plunger extruded a used paste layer which was sliced off to form a fresh surface and was made by hand-polishing on a weighing paper. The electrodes used in the experiments were stored in a refrigerator at 5 ºC and the measurements were performed at room temperature. Instrumentation The electrochemical measurements were carried by using an Autolab 100N Potentiostat/Galvanostat. Cyclic and differential pulse voltammetrics experiments were performed in a one-compartment cell using a carbon paste working electrode, a platinum wire auxiliary electrode and Ag/AgCl/KCl (3.00 mol L-1) reference electrode. The differential pulse voltammetry parameters used were: 5 mV step potential, 69


Article

Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup

50 mV modulation amplitude, 0.01 s pulse modulation and 0.1 s interval times. Experiments were performed at 25 ± 1 ºC in B-R buffer, acetate or phosphate buffer solution. The B-R buffer (µ= 2.0 mol L-1) was obtained as described in the literature and pH was adjusted adding sodium hydroxide. The preconcentration step of the system was maintained under stirring all the time. The Scanning Electron Microscopy (SEM) images were obtained using a SEM of the HITACHI model TM 3000. Using a sample holder by means of a carbon tape, the samples were adhered and gold-plated and subsequently subjected to equipment. Stock Solutions A stock solution of hydrate cooper(II) nitrate (0.01 mol L-1) was prepared and aliquots were diluted with B-R buffer solution pH = 5.0 (µ = 2.0 mol L-1) to obtain the concentration range of 1.00 x 10-8 1.30 x 10-7 mol L-1. The Cu2+ determinations were carried out by stripping voltammetric analysis. All measurements were performed at room temperature. Real samples In this work, two methods of preparation were used to prepare cabbage samples: a) the samples (59.8810 g) were ground in 70.00 mL of ultrapure water, then the mixture was centrifuged in two 1200 s cycles at 4000 rpm s-1 and the solution obtained was analyzed; and b) the cabbage samples were ground and stirred for 24 hours in B-R buffer solution pH 5.0 (µ = 2.0 mol L-1). After stirring, the obtained mixture was centrifuged for 1200 s cycles at 4000 rpm s-1 and, after filtered, the solution was analyzed. However, this later method of preparation did not present reproducible results, being discarded. RESULTS AND DISCUSSION The electrochemical behavior of the modified carbon paste electrode was evaluated in K3Fe(CN)6 (1.0 mmol L-1) in KCl. The cyclic voltammograms revealed a linear correlation between the scan rates (ν1/2), anodic and cathodic peak currents (Ipa and Ipc), typical behavior of reversible electrochemical processes presenting diffusional control (Figure 1). Using the Randles-Sevcik equation, it was possible to determine the effective electrode’s area [22]. The modified electrode presented a response surface of 0.27 cm2, higher than its geometric area (0.12 cm2).

Figure 1. Cyclic voltammograms of CPE/BT in K3Fe(CN)6 solution (1.0 mmol L-1) in 1.0 mol L-1 KCl, scan rate range 10 - 300 mV s-1.

Confirming, along with the results shown in cyclic voltammograms, the scanning electron microscopy (SEM) images (Figure 2) corroborate with the data obtained through the cyclic voltammograms. When compared to that of the carbon paste electrode without modifier (a), the modified surface electrode (b) presents greater roughness and porosity, such characteristics can provide a greater surface area, causing the rapid diffusion of the analyte in the support solution which generates the increase of the analytical signal. 70


Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

(a)

Article

(b)

Figure 2. SEM images of CPE (a) and CPE/BT (b).

The CPE’s electrochemical behavior (absence of modification) and CPE/BT (Figure 3) in presence of a fixed amount of copper(II) were performed to determine the variation in the anodic peak currents and the method’s sensitivity. The presence of the -OH group and triazoles rings of the ligand’s molecular structure contribute to their ability to complexate with copper(II) ions, increasing the intensity of the anodic peak current and a shift to lower potential value.

Figure 3. Differential pulse voltammograms of CPE in Cu2+ absence (black line), CPE/BT in Cu2+ absence (red line), CPE (blue line) and CPE/BT (green line) in the presence of Cu2+ 1.0 x 10-5 mol L-1. Conditions: preconcentration potential -0.5 V for 300 s in phosphate buffer (pH = 6.0); ν= 10 mV s-1.

The optimization of an electrochemical parameter is very important in order to improve the analytical response profile, furnishing better results for application in real samples. The electrolyte evaluation was performed using B-R, acetate and phosphate buffer solutions at pH 5.0, with a higher signal intensity when the analyzes were performed in B-R buffer solution (Figure 4). The study of the behavior by pH variation was obtained in B-R buffer solutions (µ = 2.0 mol L-1) with pH range from 2.00 to 8.00. Figure 5 shows the displacement of the copper anodic peak potential to negative potential values indicating that oxidation is facilitated with increasing pH. However, the highest intensity of anodic peak current 71


Article

Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup

was observed at pH 5.0. This behavior may be explained by the presence of protons and its influence on the triazole ligand’s chelating ability. At pH 5.0 favors the desorption of copper in the oxidation stage, while the excess of H+ (pH < 5) leads to the competition of H+ and Cu2+ ions during the adsorption step, reducing the detection of copper ions. The decrease of the anodic peak currents obtained in alkaline media is justified by the presence of hydroxyl ions in solution, leading to the formation of Cu(OH)2, which decreases its availability in solution for its determination [23,24].

Figure 4. Differential pulse voltammograms of CPE/BT in the detection of 1.0 x 10-5 mol L-1 Cu+2 in different buffer solutions pH 5.0. Conditions: preconcentration time 300 s; ν = 10 mV s-1 and preconcentration potential -0.5 V.

Figure 5. Differential pulse voltammograms of CPE/ BT in the detection of 1.0 x 10-5 mol L-1 Cu+2 in B-R buffer pH 2.0 – 8.0 range (µ = 2.0 mol L-1). Conditions: preconcentration time 300 s; ν = 10 mV s-1 and preconcentration potential -0.5 V.

The effect of the modifier on the CPE/BT composition was studied by varying the modifier’s proportion from 2.5 to 7.5% (w/w) in the electrode composition. The highest response was obtained using 5% (w/w) modifier and values above 5% were responsible for noticeable the reduction in current intensity. This effect could be attributed to the decrease in the presence of graphite (that is conductive) and the addition of modifier, which decreases the conductivity of the electrode. The influence of the preconcentration time on the electrochemical sensor response in times between 30 and 900 s, revealed 72


Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

Article

a greater intensity of anodic peak current in 900 s (Figure 6). The system also showed a linear behavior between the anodic peak currents and the preconcentration time.

Figure 6. Differential pulse voltammograms of CPE/BT in the detection of 1.0 x 10-5 mol L-1 Cu+2 at different preconcentration times. Conditions: B-R buffer solution pH 5.0 (µ= 2.0 mol L-1); ν = 10 mV s-1 and preconcentration potential -0.4 V. Inset: Current anodic peak (Ipa) versus preconcentration time.

The data obtained to study the influence of preconcentration potential (Figure 7) revealed a better signal when applied a potential of -0.4 V (vs. Ag/AgCl). The study of scan rate was performed from 5 to 30 mV s-1 scan rate range. The differential pulse voltammograms showed a better analytical response to 30 mV s-1, which caused a widening of the signal that could evidence the presence of possible contaminants. Therefore, the scan rate of 10 mV s-1 was chosen for future studies.

Figure 7. Differential pulse voltammograms of CPE/BT in the detection of 1.0 x 10-5 mol L-1 Cu+2 in different preconcentration potentials. Conditions: B-R buffer solution pH 5.0 (µ= 2.0 mol L-1); ν = 10 mV s-1 and preconcentration time 900 s.

Interference study The selectivity of the proposed method was investigated in a range of 0.1:1, 1:1, 10:1 (M2+:Cu2+) proportions (Table I). The anodic peak currents were monitored and compared to those from pure Cu2+ solution, revealing the interference of the ions following the order Cd2+> Zn2+> Mn2+> Fe2+> Pb2+. The higher interference of Cd2+ and Zn2+ ions can be justified by competition with copper ions and their preference to coordinate to triazole ligand. In order to measure the magnitude of the interference ions 73


Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup

Article

on a real sample, aliquots of the ion (1:1) were added to the electrochemical cell containing 10% (w/w) of the cabbage. Differential pulse voltammograms revealed a decrease in the anodic peak current in all the evaluated ions, being the reduction of 25.04%, 17.37% and 27.36%, for Cd2+, Fe2+ and Zn2+, respectively, demonstrating that the interference in the real sample is smaller and the method can be applied in the presence of other metal ions. Table I: Variation of the anodic peak currents using the fixed concentration of Cu2+ ions and varying the interferents’ concentration according to the proportions Variation of anodic peak current (%) M2+:Cu2+ (mol L-1)

Cd2+

Fe2+

Mn2+

Pb2+

Zn2+

0

0

0

0

0

0.1:1

+52.33

+10.02

-15.19

+12.90

+4.42

1:1

+78.00

+5.25

-17.81

-12.36

+14.75

10:1

+109.01

-20.04

-23.48

-18.81

+71.54

0:1

The repeatability of the method was evaluated in six analyses at concentration 0.10 μmol L-1 of copper(II) solution under the optimized conditions. The relative standard deviation (RSD) was 4.3% (n= 6) indicating good repeatability of the modified electrode (CPE/BT). The reproducibility study was performed in three modified electrodes, prepared separately on the same day and the analyses were obtained in triplicate. The results obtained showed a standard deviation of 3.3% demonstrating the viability of the proposed method for the determination of Cu2+ ions. Detection of Cu2+ in real sample The analytical curve obtained by the standard addition method under optimized conditions (Figure 8) revealed a linear relationship between the anodic peak currents and Cu2+ concentrations ranging from 1.0 x 10-8 to 1.3 x 10-7 mol L-1. The linear regression equation is described by Ipa = 52.50 [Cu2+] – 9.14 x 10-7, where Ipa is the anodic peak current and [Cu2+] is concentration of copper(II) ions, with a correlation coefficient of 0.994 (n=7), and showing detection limit at 1.67 x 10-9 mol L-1 and quantification limit at 5.05 10-9 mol L-1 (LOD = 3.3 σ /α, LOQ = 10 σ /α, where σ is standard deviation, α is slope of the line). Therefore, the LOD and LOQ values of copper(II) ions using the modified electrode demonstrate that it is possible to detect this metal in real samples. Additionally, the results obtained here were comparable to other modified electrodes (Table II). The electrochemical signal of Cu2+ in cabbage cultivated with the use of Bordeaux syrup was observed by the increase of the anodic peak currents around -0.19 V (E vs Ag/AgCl) and its quantification was performed by the standard addition method. An amount of 6.89 µmol L-1 of Cu2+ was determined by extrapolating the calibration curve (Figure 9), described by Ipa= 22.68 [Cu2+] – 8.60 x 10-6, R2= 0.992. The method using modified electrode CPE/BT indicated that the analyzed sample contains 8.05 µg kg-1 of copper(II), which is lower than the limit established by the Brazilian resolution (10.0 mg kg-1).

74


Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

Article

Figure 8. Differential pulse voltammograms of CPE/ BT in the detection of different Cu2+ concentrations. Conditions: B-R buffer solution pH 5.0 (µ= 2.0 mol L-1); ν= 10 mV s-1, preconcentration potential -0.4 V for 900 s. Inset: analytical curve.

Table II: Efficiency comparison of some modified electrodes used in the determination of Cu2+ Linear range (mol L-1)

Limit of detection (mol L-1)

References

MS4/QD

5.0 x 10-8 – 2.3 x 10-6

6.4 x 10-8

[25]

FMC

5.0 x 10-7 – 1.7 x 10-6

8.2 x 10-8

[26]

MCPE-CNT

6.3 x 10-8 – 3.1 x 10-5

1.7 x 10-8

[27]

Cu-DPABA–NA/GCE

15 x 10-8 – 5.6 x 10-5

8.9 x 10-8

[15]

BTPSBA-MCPE

8.0 x 10-7 – 1.0 x 10-5

2.0 x 10-7

[16]

CPE/BT

1.0 x 10-8 – 1.3 x 10-7

1.67 x 10-9

This work

Modified electrodes

Figure 9. Differential pulse voltammograms of CPE/ BT in different Cu2+ concentrations. a) blank; b) 5% real sample. Conditions: 5% sample, 95% B-R buffer solution pH 5.0 (µ= 2.0 mol L-1), ν = 10 mV s-1, preconcentration potential -0.4 V for 900 s. Inset: variation of the anodic peak currents as a function of the Cu2+ concentrations.

75


Article

Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup

CONCLUSIONS The new modified carbon paste electrode with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol ligand was successfully applied for Cu2+ determinations in cabbage cultivated with the use of Bordeaux syrup. Optimizations of the analysis parameters enabled the elaboration of an analytical curve with linear coefficient within the ANVISA standards for n ≥ 5. Finally, the new methodology aplication in real samples showed its validity by evaluating it within the standards for human consumption. Acknowledgements Authors are grateful to Brazilian funding agencies CNPq, CAPES, FAPITEC/SE and National Institute of Science and Technology of Energy and Environment for financial support. Manuscript submitted: Nov. 30, 2018; revised manuscript submitted: March 19, 2019; revised for the 2nd time submitted: June 6, 2019; manuscript accepted: June 11, 2019; published online: June 21, 2019. REFERENCES 1. Peruch, A. M. L.; Bruna, E. D. Revista Ciência Rural. 2008, 38 (9), pp 2413-2418 (https://doi. org/10.1590/S0103-84782008000900001). 2. Wang, Q. Y.; Sun, J. Y.; Xu, X. J.; Yu, H. W. Ecotoxicol. Environ. Saf. 2018, 161, pp 662–668 (https://doi.org/10.1016/j.ecoenv.2018.06.041). 3. Martins, V.; Teixeira, A.; Bassil, E.; Blumwald, E.; Gerós, H. Plant Physiol. Biochem. 2014, 82, pp 270–278 (https://doi.org/10.1016/j.plaphy.2014.06.016). 4. Liu, J.; Wang, J.; Lee, S.; Wen, R. PLoS One. 2018, 13 (9), e0203612 (https://doi.org/10.1371/ journal.pone.0203612). 5. Conselho do Mercado Comum. MERCOSUL/GMC/RES. Nº 102/94. 1995. 1-3. Available from: http://www.inmetro.gov.br/barreirastecnicas/PDF/GMC_RES_1994-102.pdf [acessed 15 August 2018]. 6. Khayatian, G.; Jodan, M.; Hassanpoor, S.; Mohebbi, S. J. Iran. Chem. Soc. 2016, 13 (5), pp 831839 (https://doi.org/10.1007/s13738-015-0798-2). 7. Bahar, S.; Karami, F. J. Iran. Chem. Soc. 2015, 12 (12), pp 2213-2220 (https://doi.org/10.1007/ s13738-015-0699-4). 8. Salinas-Castillo, A.; Ariza-Avidad, M.; Pritz, C.; Camprubi-Robles, M.; Fernandez, B.; RuedasRama, M. J.; Megia-Fernández, A.; Lapresta-Fernández, A.; Santoyo-Gonzalez, F.; SchrottFischer, A.; et al. Chem. Comm. 2013, 49 (11), pp 1103-1105 (https://doi.org/10.1039/ c2cc36450f). 9. Mazloum-Ardakani, M.; Amini, M. K.; Dehghan, M.; Kordi, E.; Sheikh-Mohseni, M. A. J. Iran. Chem. Soc. 2014, 11 (1), pp 257-262. (https://doi.org/10.1007/s13738-013-0295-4). 10. Cui, L.; Wu, J.; Li, J.; Ge, Y.; Ju, H. Biosens. Bioelectron. 2014, 55, pp 272-277. (https://doi. org/10.1016/j.bios.2013.11.081). 11. Majidian, M.; Raoof, J. B.; Hosseini, S. -R.; Ojani, R. J. Iran. Chem. Soc. 2017, 14 (6), pp 1263– 1270 (https://doi.org/10.1007/s13738-017-1077-1). 12. Dugandžić, V.; Kupfer, S.; Jahn, M.; Henkel, T.; Weber, K.; Cialla-Maya, D.; Popp, J. Sens. Actuators, B. 2019, 279, pp 230-237 (https://doi.org/10.1016/j.snb.2018.09.098). 13. Skoog, D. A.; Holler, F. J.; Nieman, T. A. Principios de Análisis Instrumental. Quinta edición. 2001. 14. Azhari, S.; Ahamad, R.; Ahmad, F. Malaysian Journal of Analytical Sciences, 2015, 19 (2), pp 309317. Available from: https://www.researchgate.net/publication/282053739 [Acessed 21 May 2019].

76


Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

Article

15. Stankivic, D.; Roglic, G.; Andjelkovic, I.; Skrivanj, S.; Mutic, J.; Manojlovic, D. Anal. Bioanal. Electrochem. 2011, 3 (6), pp 556-564 Available from: https://www.researchgate.net/publication/281925094 [Acessed 21 May 2019]. 16. Cesarino, I.; Marino, G.; Matos, J.R.; Cavalheiro, E.T.G. Talanta. 2008, 75 (1), pp 15-21 (https:// doi.org/10.1016/j.talanta.2007.06.032). 17. Souza, M. F. B. Quim. Nova. 1997, 20(2), pp 191-195 (https://doi.org/10.1590/S010040421997000200011). 18. Wang, Y.; Wu, Y.; Xie, J.; Hu, X. Sens. Actuators, B. 2013, 177, pp 1161-1166 (https://doi. org/10.1016/j.snb.2012.12.048). 19. Christensen, A. J.; Fletcher, J. T. Tetrahedron Lett. 2014, 55 (33), pp 4612-4615 (https://doi. org/10.1016/j.tetlet.2014.06.059). 20. Victor, M. M.; Farias, R. R.; Silva, D. L.; Carmo, P. H. F.; Resende-Stoianoff, M. A.; Viegas Jr., C.; Espuri, P. F.; Marques, M. J. Med. Chem. 2019, 15 (4), pp 400-408 (https://doi.org/10.2174/15734 06414666181024111522). 21. Priyanka, K. G.; Mishra, A. K.; Kantheti, S.; Narayan, R.; Raju, K. V. S. N. J. Appl. Polym. Sci. 2012, 126 (6), pp 2024-2034 (https://doi.org/10.1002/app.36921). 22. Li, Y.; Jiang, Y.; Mo, T.; Zhou, H.; Li, Y.; Li, S. J. Electroanal. Chem. 2016, 767, pp 84–90 (https:// doi.org/10.1016/j.jelechem.2016.02.016). 23. Oliveira, P. R.; Lamy-Mendes, A. C.; Rezende, E. I.; Mangrich, A. S.; Junior, L. H. M.; Bergamini, M. F. Food Chem. 2015, 171, pp 426–431 (https://doi.org/10.1016/j.foodchem.2014.09.023). 24. Mehta, V. N.; Kumar, M. A.; Kailasa, S. K. Ind. Eng. Chem. Res. 2013, 52 (12), pp 4414−4420 (https://doi.org/10.1021/ie302651f). 25. Carvalho, S. W. M. M.; Matos, C. R. S.; Santana, T. B. S.; Souza, A. M. G. P.; Costa, L. P.; Sussuchi, E. M.; Gimenez, I. F. J. Porous Mater. 2019, 26 (4), pp 1157–1169 (https://doi.org/10.1007/s10934-018-00717-3). 26. Santos, J. C.; Matos, C. R. S.; Pereira, G. B. S.; Santana, T. B. S.; Souza Jr, H. O.; Costa, L. P.; Sussuchi, E. M.; Souza, A. M. G. P.; Gimenez, I. F. Microporous Mesoporous Mater. 2016, 221, pp 48 – 57 (https://doi.org/10.1016/j.micromeso.2015.09.024). 27. Nasiri-Majd, M.; Taher, M. A.; Fazelirad, H. Ionics. 2016, 22 (2), pp 289–296 (https://doi. org/10.1007/s11581-015-1533-9).

77


Article

Electrode Modified with 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol for Electrochemical Determination of Cu(II) Ions in Cabbage Cultivated with Bordeaux Syrup

Supplementary Material

Figure S1. 1H NMR (500 MHz, CDCl3) of 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol.

Figure S2. 13C NMR (125 MHz, CDCl3) of 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol.

78


Silva, J. O. S.; Lima, J. B. S.; de Carvalho, S. W. M. M.; Sant’Anna, M. V. S.; Júnior, J. C. S.; Farias, R. R.; Victor, M. M.; Sussuchi, E. M.

Article

Figure S3. ESI-HRMS of 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol.

Figure S4. FTIR (KBr) of 1,3-bis(4-butyl-1H-1,2,3-triazol-1-yl)propan-2-ol.

79


Article

Br. J. Anal. Chem., 2019, 6 (22) pp 80-90 DOI: 10.30744/brjac.2179-3425.AR.136-2018

Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability Monise Cristina Ribeiro Casanova*, Gabriella Silva Ferreira, Amanda Novais de Abreu, Deangelis Damasceno Instituto Federal de Educação, Ciência e Tecnologia de Goiás - Senador Canedo, Senador Canedo, 75261-331, Goiás, Brazil. *monise.coltro@ifg.edu.br

Nanomaterials, especially silver nanoparticles (AgNps) offer unique optical, chemical and physical properties when compared to properties of bulk materials due to their plasmonic ressonance band. Despite AgNps synthesis by chemical reduction is not new, their stability is a crucial factor for a good applicability. AgNps were characterized by UV-vis spectroscopy. Different reports found in literature related to concentrations of used reagents in nanoparticles synthesis are scares when one take into account the high control that is required to avoid nanoparticles aggregation. This study aims to evaluate the concentrations of the reducing agent – NaBH4 (factor a), stabilizing agent – PVA (factor b) and AgNO3 (factor c) through a factorial design 23 with three center points of face centered to evaluate the influence of reagents and their concentrations on AgNps stability. The interaction between factors “a” and “c” showed a positive significant value when concentrations are modified from level (-) to level (+) of these two variables. It can be observed an increase of plasmonic band absorption peaks of 18.4% indicating synergism between variables a and c. However, one can notice a decrease of 3.91% of peak’s incidence when factor “b” concentrations are increased. It can be inferred that low PVA concentrations (≤ 0.5%) assist the AgNps stability and above this value PVA acts as a chemical inhibitor. Analysis of variance indicated a coded quadratic model of second order. Plots of response surface showed that the ideal synthesis of AgNps happens on the ratio NaBH4 (mmol) : PVA (%) : AgNO3 (mmol) of 4:1:2. Keywords: Chemometrics, Nanotechnology, Nanoscale, Spectroscopy. INTRODUCTION Nanotechnology is a rapidly expanding field, focused on the creation of functional materials, devices, and systems through the control of matter on the nanometer scale, and the exploitation of novel phenomena and properties at that length scale [1]. It is a target of interest of the scientific community in the last decade. The term is defined as the control of matter in the atomic or molecular level in the size range where at least one of the nanomaterials dimensions is between 1 and 100 nanometers [1]. When dimensions of a material decrease to a smaller size, its properties remain the same at first but have small changes. But then, decreasing size to less than 100 nm, properties of the materials change drastically. Nanomaterials have an outstanding behavior for having a broad range of applications in areas like medicine, agriculture, pharmacy and cosmetics [2] among others. In food industry, e.g. it helps to keep food in ideal conservatory conditions [3,4] or flexibility properties improvement for food packaging, in pharmaceutical area it can be used as vectorization of anticancer drugs and antibiotics [5,6] for example, and in medical field being used for the treatment of cavities interrupting the process of inflammation either preventing cavities or detecting them in early stages [7,8]. Among metallic nanoparticles, silver nanoparticles stand out once in nanometric scale they have a variety of applications in sensors, electronic chips among others. Besides, in the medical field, they have bactericidal [9] and fungicide properties. Nowadays, AgNps are used in the treatment of mycoses and cavities. Since antiquity, silver properties were already known by Greeks and Romans who used it as antibiotics. 80


Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability

Article

Its great advantage lies in the fact that individuals throughout life need long term use of antibiotics which brings the emergence of resistant super bacteria to antibiotics [10], then the use of nanoparticles is a very promising alternative. Silver nanoparticles are being used in numerous technologies and incorporated into a wide array of consumer products that take advantage of their desirable optical, conductive, and antibacterial properties. For diagnostic applications, silver nanoparticles are used in biosensors where they can be used as biological tags for quantitative detection. For antibacterial applications, silver nanoparticles are incorporated in apparel, footwear, paints, wound dressings, appliances, cosmetics, and plastics for their antibacterial properties [10]. AgNps can also be used in conductive inks and integrated into composites to enhance thermal and electrical conductivity. Silver nanoparticles can be prepared by chemical and physical methods. Among chemical methods, electrochemical and photochemical methods stand out. Studies show that experimental conditions, interaction kinetics of metallic ions with reducing agents, and adsorption processes of the stabilizing agents with nanoparticles influence size, stability, and properties of metallic nanoparticles [11]. Therefore, choosing the preparing method of nanoparticles as well as reducing agent and the stabilizing agent is essential for a successful synthesis. The chemical reduction method is the most used one to prepare silver nanoparticles as colloidal dispersions in water or organic solvents. This method outstands itself among others once it is fast, cheap and does not require organic solvents, becoming a method less harmful for the environment. It consists of chemical reduction of silver ions – which comes from the used silver salt – to silver atoms followed by agglomeration in “clusters” [12]. As the synthesis of silver nanoparticles is a redox reaction, it is crucial to choose the most appropriate reducing agent. Reducing agents that are commonly used are sodium borohydride, sodium citrate, ascorbic acid, and hydrogen. Previous studies show that the use of strong reducing agents besides increasing the redox reaction velocity, as sodium borohydride, form monodisperse smaller particles, but larger nanoparticles are more difficult to control [11,13]. On the other hand, the use of weaker reducing agents leads to larger nanoparticles with wider size distribution [14]. To synthesize silver nanoparticles through chemical reduction method it is extremely important to apply a stabilizing agent capable of restraining nanoparticles aggregation/agglomeration of colloids. The chosen stabilizing agent was polyvinyl alcohol (PVA). According to Sharma and coworkers [15], PVA is an environment friendly polymer once it is water soluble and it has extremely low toxicity. It is often used as a stabilizer due to its optical clarity [16], which allows investigation of nanoparticles formation. Despite silver nanoparticles synthesis is not new, their stability is a crucial factor for their good applicability. Factors such as reagents concentration is one of them. The synthesis of AgNps is related to obtaining of AgNps with uniform distribution and high stability due to their tendency of agglomeration in aqueous solutions. In this matter, AgNps were prepared and characterized by UV-vis spectroscopy – an indicative of chemical stability of AgNps are narrow peaks with high absorbance values. Studies in literature make use of reagents concentrations for AgNps synthesis following protocols previously established based on empiric nanoparticles size and format results or scarse reports in synthesis procedures details or either the choice of reagents concentrations seems mechanic or random if one takes into account the required high control level to avoid particles aggregation. Optimization of synthesis parameters such as reagents concentrations allows the obtaining of silver nanoparticles with high stability which is very important to several silver nanoparticles applications. As nature and concentration of reducing and stabilizing agents greatly influence the functional properties of silver nanoparticles and as we deal with different parameters to synthesize stable nanoparticles, a factorial design seems proper to give us the optimum ratio between reagents concentrations. For that matter, factorial design was shown to be an important tool to increase the sensitivity of an analytical method, enabling optimization of the concentrations of reagents used to obtain silver nanoparticles or either optimize production levels of stabilizers for silver nanoparticles synthesis. 81


Article

Casanova, M. C. R.; Ferreira, G. S.; de Abreu, A. N.; Damasceno, D.

As an example, Bittar and coworkers [17] were successful on the determination of the optimized experimental conditions for the development of a simple and low-cost process for the production of stable silver nanoparticles using factorial design (central composite design with five levels with four central points) for the determination of melamine in milk products at concentrations that may be harmful to human health. They found the best reagents concentrations for AgNps synthesis were AgNO3 and NaBH4 were 3.00 × 10−3 mol L−1 and 1.25 × 10−3 mol L−1, respectively. El-Naggar et al. [18] have chosen factorial design to determine the combined effects of four process variables (AgNO3 concentration, incubation period, pH level and inoculum size) on the extra-cellular biosynthesis of silver nanoparticles by Streptomyces viridochromogenes. Results showed that the maximum biosynthesis of silver nanoparticles was achieved at a concentration of 0.5% (v/v) of 1 mM AgNO3, an incubation period of 96 h, an initial pH of 9 and inoculum size of 2% (v/v). After optimization, the biosynthesis of silver nanoparticles was improved by approximately 5-fold as compared to that of the unoptimized conditions. Sathiyanarayanan and coworkers [19] used a central composite design (CCD) of 32 experiments (5-level-4-factorial) with six central points to statistically optimize the production of a bioflocculant from marine sponges – used as a stabilizer – with most significant factors such as palm jaggery, NH4NO2, K2HPO4 and NaCl for the synthesis of silver nanoparticles. The maximum bioflocculant production obtained with statistically optimized medium was 13.42 g L-1. Therefore, this study aims to evaluate silver nitrate (AgNO3), reducing agent (NaBH4) and stabilizing agent (PVA) through a factorial design 23 with three central points face centered to evaluate the influence of reagents and their respective concentrations on AgNps stability. MATERIALS AND METHODS Chemicals PVA (MW 61,000) and sodium borohydride granulate (10-40 mesh, 98%) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Silver nitrate was purchased from Vetec (Duque de Caxias, RJ, Brazil). All chemicals were used as received, without further purification. Methods Characterization For characterization of AgNps, UV-vis spectroscopy was used to evaluate Nps optical characteristics as well as size. Transmission Electron Microscopy (TEM) was used to evaluate the size and shape of synthesized silver nanoparticles. Silver nanoparticles synthesis To synthesize silver nanoparticles, 10 mL of silver nitrate solution (solution a) were added to an Erlenmeyer. Then, 2 mL of polyvinyl alcohol solution (solution b) was added to solution a. And finally, a sodium borohydride solution was added slowly (drop wise) to the mixture (solution a and solution b) until a light-yellow color could be observed indicating the formation of silver nanoparticles. These reagents concentrations (solution a, b and c) were varied. UV-vis spectroscopy Silver nanoparticles solutions were diluted in deionized water (1:10 v/v) to obtain UV-vis spectra. Readings were performed in quartz bucket on UV-vis Hitachi spectrophotometer. Transmission Electron Microscopy Transmission electron microscopy (TEM) study for the characterization of particles were carried out by placing a drop of silver solution onto a carbon film supported on a copper grid followed by solvent evaporation under vacuum. Samples were studied using Jeol, JEM-2100 TEM, equipped with EDS, Thermo Scientific. 82


Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability

Article

Design Factor For statistical analysis MATLAB® - based program was used to study the effects of the reagent concentrations on the formation of the Ag nanoparticles. A complete factorial design 23 was prepared, with three centric face centered. The use of a complete factorial design provides an extended study of the influence of each variable, providing a mathematical model and a response surface that allows to establish greater control of the working conditions. Table I shows the studied factors and their respective levels. Experiments were performed randomly to avoid systematic errors. The measured responses were the absorbance peaks with wavelengths between 300 and 500 nm, corresponding to the maximum absorption of the synthesized silver nanoparticles Table I. Real and encoded levels for factorial design 23 Factor

Variable

Level (-)

Level (0)

Level (+)

A

NaBH4 (mmol)

2.0

3.0

4.0

B

PVA (% m/v)

0.5

1.0

1.5

C

AgNO3 (mmol)

1.0

1.5

2.0

Data in factorial design were statistically evaluated through analysis of variance (ANOVA) and used for the construction of response surface plots. RESULTS AND DISCUSSION Silver nanoparticles synthesis Silver nanoparticles were obtained through oxidation reduction reaction between silver nitrate (oxidant agent) and sodium borohydride (reducing agent) according to the chemical reaction in Equation 1. AgNO3(aq) + NaBH4(aq) → Ag + ½ H2(g) + ½ B2H6(g) + NaNO3(aq)

(Eq. 1)

After the synthesis of silver nanoparticles, a yellow color was observed indicating their formation. When colloidal particles are much smaller than visible light wavelength, solutions present a yellow color with an intense plasmonic band in the range from 380 to 400 nm and others less intense bands in the absorption spectra [15]. As the chemical reaction for synthesis of silver nanoparticles is an oxidation reduction reaction, the reagents silver nitrate (oxidizing agent), sodium borohydride (reducing agent) are essential for the formation of silver nanoparticles. However, one can notice a low stability, which means their nanoparticles aggregate easily. The latter can be observed for silver nanoparticles that make use of only silver nitrate and sodium borohydride, where the solution shows a grey color, indicating aggregation and coalescence of nanoparticles. Due to the later, the use of a stabilizing agent was chosen, capable of containing nanoparticles aggregation. The chosen stabilizing agent was PVA. According to Sharma and coworkers [15], PVA is a very interesting polymer to be used once it is water soluble and has extremely low toxicity. It is frequently used as a stabilizer due to its optical clarity, which allows investigation of nanoparticle formation. Solutions prepared with PVA showed a dark yellow color. Despite silver nanoparticles synthesis via chemical reduction is not new, stability is a crucial factor for their good applicability. On this purpose, a great variety of variables can influence silver nanoparticles stability such as reagents concentration, temperature, stocking conditions. A successful synthesis of AgNps is attached to obtaining AgNps with uniform distribution and high stability due to its tendency of agglomerate in aqueous solutions. In this study, concentration of silver 83


Article

Casanova, M. C. R.; Ferreira, G. S.; de Abreu, A. N.; Damasceno, D.

nitrate, sodium borohydride and PVA varied during synthesis in order to understand the influence of their concentrations on AgNps stability and to find the great ratio between reagents concentrations that synthesize the smaller and most stable AgNps. Silver nanoparticles characterization Synthesized AgNps were characterized through transmission electron microscopy (TEM) and UVvis spectroscopy. Through UV-vis analysis, spectra showed surface plasmonic bands characteristics of silver nanoparticles. Figure 1 shows spectra in the UV-vis region of synthesized AgNps. AgNps solutions that contain PVA in their composition showed a narrower surface plasmonic band when compared to the AgNps solution without PVA, indicating the formation of smaller AgNps thus more stable due to the presence of PVA. Besides, in the solutions where concentrations of AgNO3 was 2 mM and NaBHâ&#x201A;&#x201E; was 4 mM it was noticed a bigger influence of PVA on AgNPs stability.

Figure 1. UV/Vis spectra recorded for solutions A (2 mM AgNO3, 4 mM NaBH4), B (1 mM AgNO3, 2 mM

NaBH4, 0.5% m/v PVA), C (1 mM AgNO3, 4 mM NaBH4, 0.5% m/v PVA), D (1 mM AgNO3, 2 mM NaBH4, 1.5% m/v PVA), E (2 mM AgNO3, 4 mM NaBH4, 0.5% m/v PVA) and F (2 mM AgNO3, 4 mM NaBH4, 1.5% m/v PVA).

Transmission electron microscopy (TEM) images of AgNps solutions were obtained as shown in Figure 2. AgNps without PVA agglomerate more when compared to others with PVA and AgNps with PVA concentration 1.5% are more disperse than the ones with PVA concentration 0.5%.

Figure 2. Transmission electron microscopy of AgNps solutions A (2 mM AgNO3, 4 mM NaBH4),

B (2 mM AgNO3, 4 mM NaBH4, 0,5% m/v PVA) and C (2 mM AgNO3, 4 mM NaBH4, 1,5% m/v PVA).

Although concentrations of silver nitrate, sodium borohydride and PVA varied for silver nanoparticles synthesis, UV-vis spectra and transmission electron microscopy images were not enough to provide a detailed picture of the influence of these reagent concentrations on the stability of silver nanoparticles.

84


Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability

Article

Factorial design Therefore, in this study a factorial design 2Âł with 03 centric face centered was performed to evaluate the influence of reagents and their respective concentrations on AgNps stability [20]. The studied variables and their respective levels are presented in Table II, besides absorbance results. With factorial design it was verified that absorbance values increased with the increase of concentrations of factor a and c, besides the interaction of these independent variables. This can be better noticed in Figure 3, where variables effect and their interactions is presented showing the standardized values (absolute values) obtained in factorial design of each parameter. The size of the bars shows the impact of the parameters in the process. These three parameters exceed the t-value limit [21] and have significant positive values which indicates increase of AgNps stability. It is remarkable that the interaction between factors a and c present a significant and positive value when concentrations modify from level (-) to level (+) of these two variables. Table II: Real and coded values for factorial design 2Âł with 03 centric face centered for AgNps synthesis and absorbance results Factors Xa

Xb

Xc

Absorbance responses (a.u.)

1

-1

-1

-1

0.650

2

1

-1

-1

0.435

3

-1

1

-1

0.452

4

-1

-1

1

0.396

5

1

1

-1

0.440

6

1

-1

1

0.804

7

-1

1

1

0.457

8

1

1

1

0.751

9

0

0

0

0.881

10

0

0

0

0.872

11

0

0

0

0.813

12

-1

0

0

0.770

13

1

0

0

0.660

14

0

-1

0

0.712

15

0

1

0

0.603

16

0

0

-1

0.732

17

0

0

1

0.773

Experiments

85


Casanova, M. C. R.; Ferreira, G. S.; de Abreu, A. N.; Damasceno, D.

Article

Figure 3. Pareto chart with standardized effects for factorial design performed for silver nanoparticle synthesis.

It was observed an increase of absorbance peaks of plasmonic resonance bands of 18.4% indicating synergism between these two variables. However, there was a decrease of 3.91% on peaks incidence when there is an increase on factor b concentrations. It can be inferred that low concentrations of PVA (â&#x2030;¤ 0.5%) support AgNps stability and above this value, PVA acts as an inhibitor in the formation of AgNPs. Model was validated through analysis of variance (ANOVA), in Table III. Table III. ANOVA results for second-order non-linear model DF

Adj. SS

Adj. MS

F-value

P-value

Model

10

0,402517

0,040252

7,32

0,012

(a)

1

0,013309

0,013309

2,42

0,171

(b)

1

0,00867

0,00867

1,58

0,256

(c)

1

0,022178

0,022178

4,03

0,091

(ab)

1

0,00098

0,00098

0,18

0,688

(ac)

1

0,107882

0,107882

19,61

0,004

(bc)

1

0,005043

0,005043

0,92

0,375

(abc)

1

0,012442

0,012442

2,26

0,183

(aa)

1

0,020704

0,020704

3,76

0,1

(bb)

1

0,056289

0,056289

10,23

0,019

(cc)

1

0,006721

0,006721

1,22

0,311

Error

6

0,033012

0,005502

Lack of fit

4

0,0303

0,007575

5,59

0,158

Pure Error

2

0,002712

0,001356

Total

16

0,43553

According to Table III, ANOVA interpretation indicates that the model is well adjusted (p value < 0.05). The curvature on the response surface was statistically significant (p value > 0.05), indicating that the model did not show a lack of fit. Figure 4 shows random behavior of the residues along the absorbance values predicted by the model. 86


Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability

Article

Figure 4. Residues chart according to the absorbance values predicted by the model.

Considering the statistical relevance between the factors and their interactions described in Table III, Equation 2 represents the second-order non-linear coded model which describes the absorbance response due to the interaction of concentrations of NaBH4 and AgNO3, with values of R2 and adjusted R² respectively. Ab = 0.825 (±0.077) + 0.1161 (±0.063)ac - 0.1449 (±0.1101)b2

(Eq. 2)

where Ab is absorbance (a.u.), a represents NaBH4 concentration, c is AgNO3 concentration, and b is PVA concentration, R² is 92,42% and adjusted R² is 79,79%. Equation 2 shows the strong influence of the increase of concentration of these two factors and also that silver nanoparticles stability was significantly influenced by decrease of PVA concentration. Response surface plots [22-24] using quadratic models were proposed to describe the behavior of silver nonoparticulate synthesis where two variables fluctuate along the experimental levels. Figure 5 shows absorbance variation when AgNO3 concentration is fixed on (-) Figure 5a , (0) Figure 5b and (+) Figure 5c. The vertex corresponding to level (+1) of the factor increases with increase of factor c. Throughout the experiment, this difference increases, corroborating to the synergism between factors a and c. When analyzing Figure 5a and setting AgNO3 concentration to its lowest value, the stability of AgNps are favored in lower concentrations of NaBH4 and PVA. It is inferred that PVA at lower concentrations functions as a surfactant aiding the stability of AgNps. In Figures 5b and 5c one can notice that PVA still favors the obtaining of stable AgNps until its concentration reaches the center point and above that point the AgNps aggregate. It could be noticed that PVA concentration (factor b) contributed to the AgNps stabilization until level (0). Above this level, one can infer high concentration of PVA polymer inhibits AgNps synthesis.

87


Article

Casanova, M. C. R.; Ferreira, G. S.; de Abreu, A. N.; Damasceno, D.

Figure 5. Response surface plots to the quadratic model as a function of factors “a” and “b” and factor “c” fixed on (A) level (-), (B) level (0) and (C) level (+).

According to this study, it can be noticed that synthesis of AgNps happens on the ratio NaBH4 (mmol) : PVA (%) : AgNO3 (mmol) of 4:1:2, which will generate smaller and more stable AgNps. CONCLUSIONS We have successfully reported herein the use of complete factorial design 23 with three centric face centered for evaluation of the influence of the reducing agent – NaBH4 (factor a), stabilizing agent – PVA (factor b) and AgNO3 (factor c) concentrations on silver nanoparticles stability. UV-vis spectra showed 88


Factorial Design for Evaluation of Reagent Concentrations on Silver Nanoparticles Stability

Article

characteristic surface plasmonic bands of AgNps, indicating successful nanoparticles synthesis. The presence of PVA in composition lead to smaller and more stable nanoparticles. Factorial design results showed that the interaction between factors a and c present a significant and positive value when concentrations modify from level (-) to level (+) of these two variables. Besides, absorbance peaks of plasmonic resonance bands analysis infers that low concentrations of PVA (≤ 0.5%) support AgNps stability and above this value, PVA acts as an inhibitor in the formation of AgNPs. Response surface plots using quadratic models described that PVA concentration (factor b) contributed to the AgNps stabilization until level (0). Above this level, one can infer high concentration of PVA polymer inhibits AgNps synthesis. Therefore, it can be suggested that synthesis of AgNps happens on the ratio NaBH4 (mmol) : PVA (%) : AgNO3 (mmol) of 4:1:2, which will generate smaller and more stable AgNps. Manuscript submitted: Dec. 2, 2018; revised manuscript submitted: Feb. 12, 2019; manuscript accepted: March 11, 2019; published online: June 21, 2019. REFERENCES 1. Bhushan, B. Introduction to Nanotechnology. In: Handbook of nanotechnology. 4th Edition. Springer, 2017. 2. Sharma, G.; Kumar, A.; Sharma, S.; Naushad, M.; Dwivedi, R. P.; Alothman, Z. A.; Mola, G. T. J. King Saud Univ., Sci. In Press, 2017 (DOI: https://doi.org/10.1016/j.jksus.2017.06.012). 3. Souza, V. G. L.; Fernando, A. L. Food Packaging and Shelf Life, 2016, 8, pp. 63-70 (DOI: https://doi.org/10.1016/j.fpsl.2016.04.001). 4. Moura, M. R.; Mattoso, L. H. C.; Zucolotto, V. J. Food Eng., 2012,109 (3), pp. 520-524 (DOI: https://doi.org/10.1016/j.jfoodeng.2011.10.030). 5. Kim, T.; Braun, G. B.; She, Z.; Hussain, S.; Ruoslahti, E.; Sailor, M. J. ACS Appl. Mater. Interfaces, 2016, 8 (44), pp 30449–30457 (DOI: https://doi.org/10.1021/acsami.6b09518). 6. Hussain, S.; Joo, J.; Kang, J.; Kim, B.; Braun, G. B.; She, Z.; Kim, D.; Mann, A. M.; Mölder, T.; Teesalu, T.; Carnazza, S.; Guglielmino, S.; Sailor, M. J.; Ruoslaht, E. Nature Biom. Eng., 2018, 2, pp 95-103 (DOI: https://doi.org/10.1038/s41551-017-0187-5). 7. Noronha, V. T.; Paula, A. J.; Durán, G.; Galembeck, A.; Cogo-Muller, K.; Franz-Montan, M.; Durán, N. Dent. Mater., 2017, 33 (10), pp 1110-1126 (DOI: https://doi.org/10.1016/j.dental.2017.07.002). 8. Freire, P. L. L.; Stamford, T. C. M.; Albuquerque, A. J. R.; Sampaio, F. C.; Cavalcante, H. M. M.; Macedo, R. O.; Galembeck, A.; Flores, M. A. P.; Rosenblatt, A. Int. J. Antimicrob. Agents., 2015, 45 (2) pp 183-187 (DOI: https://doi.org/10.1016/j.ijantimicag.2014.09.007). 9. Prabhu, S.; Poulose, E. Int Nano Lett, 2012, 2:32, pp 1-10. (DOI:https://doi.org/10.1186/22285326-2-32) 10. Abou El-Nour, K. M. M.; Eftaiha, A.; Al-Warthan, A.; Ammar, R. A. A. Arabian J. Chem., 2010, 3 (3), pp 135-140 (DOI: https://doi.org/10.1016/j.arabjc.2010.04.008). 11. Rafique, M.; Sadaf, I.; Rafique, M. S.; Tahir, M. B. Artif. Cells, Nanomed., Biotechnol., 2017, 45 (7), pp. 1272-1291 (DOI: https://doi.org/10.1080/21691401.2016.1241792). 12. Ozyurek, M.; Gungor, N.; Baki, S.; Guçlu, K.; Apak, R. Anal. Chem., 2012, 84 (18), 8052-8059 (DOI: https://doi.org/10.1021/ac301925b). 13. Kakkar, R.; Sherly, E. D.; Madgula, K.; Devi, D. K.; Sreedhar, B. J. Appl. Polym. Sci., 2012, 126, pp 154-161 (DOI: https://doi.org/10.1002/app.36727). 14. Lee, P. C.; Meisel, D. J. Phys. Chem., 1982, 86 (17), pp 3391-3395 (DOI: https://doi.org/10.1021/j100214a025). 15. Sharma, V., Yngard, R., Lin, Y. Adv. Colloid Interface Sci., 2009,145, pp 83-96 (DOI: https://doi.org/10.1016/j.cis.2008.09.002). 89


Article

Casanova, M. C. R.; Ferreira, G. S.; de Abreu, A. N.; Damasceno, D.

16. Hallensleben, M.; Fuss, R.; Mummy, F. Polyvinyl Compounds, Others. Ullman’s Encyclopedia of Industrial Chemistry. Wiley Library, UK, 2015, pp 1-23. 17. Bittar, D. B.; Catelani, T. A.; Nigoghossian, K.; Barud, H. S.; Ribeiro, S. J. L.; Pezza, L.; Pezza, H. R. Anal. Lett., 2017, 50 (5), pp 829-841. (DOI: https://doi.org/10.1080/00032719.2016.1196213) 18. El-Naggar, N. E.; Abdelwahed, N. A. M. J. Microbiol., 2014, 52 (1), pp. 53–63 (DOI: https://doi.org/10.1007/s12275-014-3410-z). 19. Sathiyanarayanan, G.; Kiran, G. S.; Selvin, J. Colloids Surf. B., 2013, 102 (1), pp 13-20 (DOI: https://doi.org/10.1016/j.colsurfb.2012.07.032). 20. Breitkreitz, M., Souza, A., Poppi, R. Quim. Nova. 2014, 37 (3), pp 564-573 (DOI: https://doi.org/10.5935/0100-4042.20140071). 21. Rigon, R. B.; Gonçales, M. L.; Severino, P.; Alves, D. A.; Santana, M. H. A.; Souto, E. B.; Chorilli, M. Colloids Surf., B., 2018,171, pp 501-505 (DOI: https://doi.org/10.1016/j.colsurfb.2018.07.065). 22. Wang, C.; Wang, H.; Zhao, D.; Wei, X.; Li, X.; Liu, W.; Liu, H. Sensors, 2019, 19 (3), 615 (DOI: https://doi.org/10.3390/s19030615). 23. Aly-Eldeen, M. A.; El-Sayed, A. A. M.; Salem, D. M. S. A.; Zokm, G. M. Egypt. J. Aquat. Res., 2018, 44, pp 179-186 (DOI: https://doi.org/10.1016/j.ejar.2018.09.001). 24. Vicentini, F. C.; Figueiredo-Filho, L. C. S.; Janegitz, B. C.; Santiago, A., Pereira-Filho, E. R.; Fatibello-Filho, O. Quim. Nova. 2011, 5, pp 825-830 (DOI: https://doi.org/10.1590/S010040422011000500018).

90


Feature

Br. J. Anal. Chem., 2019, 6 (22) pp 91-97

19th ENQA was a Milestone in Sustainability The 19th Brazilian Meeting on Analytical Chemistry (ENQA) focused on “Innovation for Sustainable Analytical Chemistry”

19th ENQA Opening Ceremony - Photo: ENQA 2018

With the support of the Royal Society of Chemistry, several social and environmental actions were carried out during the event, generating a sustainability seal for ENQA. “We had selective garbage collection, use of reusable cups, donation of books, and inclusion of secondary schools,” said ENQA general coordinator Professor Wendell Coltro. The event was held from 16 to 19 September, 2018 at the city of Caldas Novas, Goiás, Brazil, along with the 7th Ibero-American Congress on Analytical Chemistry (CIAQA). In all, there were more than 1200 attendees from 25 Brazilian states and the Brazilian Federal District. Internationally, the event was attended by speakers and participants from different countries such as Argentina, Portugal, Canada and the United States. In all, 1112 scientific posters were presented, which is the highest number on record in the history of ENQAs. The ENQA meetings have been held every two years. One of the main reasons for the purpose of the ENQA is to promote a discussion forum on the advances in Analytical Chemistry. For that reason, there were conferences, lectures, coordinated sessions, technical lectures, workshops, mini-courses, and presentations of works in poster sessions. “The event exceeded expectations, everything worked well, the rooms were full since 8:00 a.m. and we had more abstracts submitted than at the last Annual Meeting of the Brazilian Chemical Society,” said Coltro.

91


Feature

Poster Session - Photo: ENQA 2018

The ENQA also allowed direct interaction between participants and companies dedicated to the Research & Development and Quality Control sector in Analytical Chemistry. This interaction was made possible by the exposition of analytical instrumentation that occurred simultaneously with the scientific meeting. Companies like Metrohm, Waters, Agilent, Analítica, Bruker, Allcrom, and PerkinElmer, among others — see the complete list here — were present exposing their innovations in instrumentation for chemical analysis laboratories.

Booths of some of the companies that were present at the 19th ENQA and overview of the exhibition area - Photo: ENQA 2018

92


Feature

The Analítica company held a raffle to give an ENQA attendee a copy of the book ICP Mass Spectrometry Handbook, edited by Simon M. Nelms and an issue of the Brazilian Journal of Analytical Chemistry with the journal’s mascot.

In the center is the winner of the book drawn by Analitica company - Photo: ENQA 2018

On the first day, before the official opening, two workshops and five short courses were held. In all, about 400 congress attendees participated in these activities. The workshops covered topics related to sample preparation and chemical imaging, and the short courses covered the areas of metrology, forensic chemistry, chemometrics, separations, and electroanalytical chemistry. The opening conference was held by Prof. Dr. Érico Marlon de Moraes from the Department of Chemistry, Federal University of Santa Maria, RS, Brazil. The theme was “Microwave in Analytical Chemistry: Solutions for Analysis of Common and Uncommon Samples”. Homage Session Soon after the opening ceremony, some honors were held. The following professors were honored: Prof. Dr. Auro Atsushi Tanaka, Department of Chemistry, Federal University of Maranhão, São Luís, MA; Prof. Dr. Elias Ayres Guidetti Zagatto from the Center for Nuclear Energy in Agriculture (CENA), Piracicaba, SP; and Prof. Dr. Ieda Spacino Scarmínio, Department of Chemistry, State University of Londrina, Londrina, PR. Also some medals were awarded The Janusz Pawliszyn medal was awarded to Prof. Dr. Maria Eugênia Queiroz, Faculty of Philosophy Sciences and Letters, University of São Paulo, Ribeirão Preto, SP. The Adilson José Curtius medal was 93


Feature

awarded to Prof. Dr. Marco Aurélio Zezzi Arruda from the Institute of Chemistry, State University of Campinas, SP. The Carol Hollingworth Collins medal was awarded to Prof. Dr. Érico Marlon de Moraes Flores, Federal University of Santa Maria, Santa Maria, RS. Finally, the 1st Metrohm Young Chemist Award Brazil was presented to Lucyano Jefferson Alves de Macedo, a doctoral student at the Institute of Chemistry of São Carlos, University of São Paulo, São Carlos, SP. Book Launches Another important highlight of ENQA was the launch of the books: “Metallomics: The Science of Biometals”, edited by Prof. Marco Aurélio Zezzi Arruda and collaborators, and “Ciências do vinho: Noções básicas de enologia para curiosos enófilos”, author Prof. Dr. Eric de Souza Gil.

Prof. Wendell Coltro, general coordinator of ENQA, was with Prof. Dr. Marco Aurélio Zezzi and Prof. Dr. Eric de Souza Gil to celebrate the launch of their books. - Photos: ENQA 2018

The book launches were held in the exhibition area of the event, and all of the attendees present had the opportunity to honor the books’ authors and to discuss the subjects addressed with them. Symposiums and Thematic Sessions Four symposiums were held in which the following topics were addressed: “Innovation and Entrepreneurship”, “Passive Sampling in Environmental Chemistry”, “Advances in Spectrometric Analysis & Recent Advances in Analytical Instrumentation” and “Development of Chemical Sensors”. All the symposiums had the participation of renowned researchers in the respective areas, and the rooms where they were held were crowded. The Symposium “Advances in Spectrometric Analysis” was dedicated to the memory of Professor Bernhard Welz, who died on June 2, 2018. The Thematic Sessions were also highlighted. In all, there were three thematic sessions. One of them was named “Meet the Editor Session” which was furthered by the Royal Society of Chemistry and 94


Feature

had the participation of the following editors: Dr. Carlos D. Garcia (associate editor of RSC Advances), Dr. Susan M. Lunte (former editor-in-chief of Analytical Methods) and Dr. Jailson Bittencourt de Andrade (associate editor of Analytical Methods). The audience present had the opportunity to discuss general and ethical aspects regarding “What to publish”, “Where to publish” and “How to publish with quality”. One of the great novelties of the ENQA 2018 was undoubtedly the session entitled “Women in Analytical Chemistry: Challenges and Perspectives”, which received over 250 participants. This session had lectures by Professors Márcia Foster Mesko (Federal University of Pelotas, RS and Director of the Analytical Chemistry Division of the Brazilian Chemical Society), Maria das Graças Andrade Korn (Federal University of Bahia), Maria Valnice Boldrin Zanoni (São Paulo State University - UNESP), and Maria Zaira Turchi (Goias Federal University and President of the State of Goiás Research Foundation - FAPEG). In general, the scenarios of analytical chemistry in different regions of Brazil, the challenges, and examples of success obtained by women in this area of chemistry were discussed.

Thematic Session “Women in Analytical Chemistry: Challenges and Perspectives” - Prof. Dr. Márcia Foster Mesko (left) and Prof. Dr. Maria das Graças Andrade Korn (right) - Photos: ENQA 2018

Another thematic session was devoted to Multidisciplinary Analytical Techniques, providing an overview of the use of flow analysis, spot tests, mobile applicative, and molecular fluorescence systems for different analytical applications. Round Table Discussions During the event, two round tables were held. The first one addressed the theme “Teaching of Analytical Chemistry: Panoramas, Trends and Challenges” and had the participation of Prof. Dr. Maria Fernanda Silva (National University of Cuyo, Argentina) and Prof. Dr. Orlando Fatibello Filho (Federal University of São Carlos) and Prof. Dr. Mauro Korn (State University of Bahia). The second round table focused on “Contribution of the National Institutes of Science and Technology (INCTs) for Brazilian Analytical Chemistry” and counted on the participation of Prof. Dr. Lauro Kubota and Prof. Dr. Célio Pasquini, both from the State University of Campinas (Unicamp), Prof. Dr. Maria Valnice Boldrin Zanoni from the São Paulo State University (UNESP), and Prof. Dr. Jailson Bittencourt de Andrade from the Federal University of Bahia and the coordinators of the National Institutes of Science 95


Feature

and Technology of Bioanalytics (INCT-Bio), National Institute of Sciences and Advanced Analytical Technologies (INCTAA), National Institute of Alternative Technologies for Detection, Toxicological Evaluation and Removal of Emerging and Radioactive Contaminants (INCT-DATREM), and National Institute of Science and Technology of Energy and Environment (INCT E&A). ENQA in the Schools ENQA in the Schools was an activity dedicated to the students of the secondary schools of the city of Caldas Novas, Goiás. With the help of the teacher Pedro Henrique Alves de Araújo of the “Colégio Vetor” of Caldas Novas and under the coordination of Prof. Dr. Andréa Rodrigues Chaves (Federal University of Goiás), more than 500 students from six Caldas Novas schools had the opportunity to follow a sequence of six experiments organized by researchers from the universities of Goiás (UFG), Brasília (UnB), Santa Cruz do Sul (UNISC-RS), Rio Grande do Sul (UFRGS) and the State of Bahia (UNEB). The high school students had the opportunity to interact with several researchers, visit the exhibition fair of instruments for laboratories, and were delighted with the experimental activities carried out. In parallel with ENQA in the Schools, a joint action of INCTBio and the project “Chemistry does good” from the Federal University of Minas Gerais, made possible the exhibition of approximately 15 posters that presented works developed by INCTBio with a language directed to high school students.

High school students participating in the activities developed at the ENQA at Secondary School - Photos: ENQA 2018

96


Feature

BrJAC at ENQA The BrJAC was present at the event to disseminate the work of the journal. To honor its readers, raffles of editions and mascots of the journal were made.

Winners of BrJAC editions and mascots — Photos: Lilian Freitas

Book Donation One of the social actions undertaken during the ENQA was the collection and subsequent donation of books on chemistry. Approximately 100 books were received from ENQA’s attendees. This collection was donated to the “Associação Centro Juvenil pela Vida” (ACEJUVI), a non-profit-making charity organization that develops social assistance and cultural activities with the needy population of the City of Caldas Novas, Goiás, Brazil. Bookshelf with books on chemistry for donation Photo: ENQA 2018

97


Sponsor Report

Br. J. Anal. Chem., 2019, 6 (22) pp 98-105 PDF

This section is dedicated for sponsor responsibility articles.

Discovery of Emerging Disinfection by-products in Water using Gas Chromatography coupled with Orbitrap-based Mass Spectrometry Cristian Cojocariu1, Cristina Postigo2, Susan D. Richardson3, Damia Barcelo2,4, and Paul Silcock1 Thermo Fisher Scientific, Runcorn, UK. 2Institute of Environmental Assessment and Water Research, (IDAEACSIC) Water and Soil Quality Research Group, Department of Environmental Chemistry, Barcelona, Spain. 3 University of South Carolina, Department of Chemistry and Biochemistry, Columbia, SC, U.S.A. 4 Catalan Institute for Water Research (ICRA), Parc Científic i Tecnològic de la Universitat de Girona, 17003 Girona, Spain 1

Keywords: Iodinated disinfection by-products, water, accurate mass, high resolution, Q Exactive GC INTRODUCTION The disinfection of drinking water is required in order to protect consumers from potential waterborne infectious and parasitic pathogens. Water is commonly treated by adding chemical disinfectants, such as free chlorine, chloramines, chlorine dioxide, and ozone. However, although very effective in removing disease-causing microorganisms, these disinfectants can react with naturally occurring materials in the water and can form disinfection by-products (DBPs) which can be harmful to human health. In particular, compounds containing an iodo-group, i.e., iodinated DBPs (iodo-DBPs), may pose a greater health risk for the population exposed to them than their brominated and chlorinated analogues [1]. In recent years, several chemical classes of low molecular weight iodo-DBPs have been reported; however, many more may be still present in the unknown fraction (~50%) of halogenated material formed during disinfection treatments [2]. Therefore, complete characterization of iodo-DBPs present in DBP mixtures is crucial to further investigate their occurrence in disinfected waters and potential toxicity effects. The identification of emerging iodinated DBPs in water is difficult due to the complexity of this matrix and the low concentrations of these compounds. For this, analytical techniques with high resolving power, high mass accuracy and sensitivity are required. In this work, a novel gas chromatography (GC), coupled with high-resolution accurate mass Orbitrap mass spectrometer (the Thermo Scientific™ Q Exactive™ GC hybrid quadrupole-Orbitrap mass spectrometer), has been used for iodo-DBPs detection and accurate mass identification in chlorinated and chloraminated water samples. EXPERIMENTAL Sample Preparation The formation of DBPs is mainly related to the type of the disinfection treatment applied, and the nature of the water source in terms of natural organic matter (NOM) characteristics, as well as the bromide and iodide content. In order to study the formation of iodo-DBPs in iodine-containing waters, lab-scale chlorination and chloramination reactions were performed. The tested water was a Milli-Q® water solution containing NOM from the Nordic reservoir (NL) (Vallsjøen, Skarnes, Norway), which is a reference material from the International Humic Substances Society (IHSS), fortified with bromide (500 ppb, added as KBr) and iodide (50 ppb, added as KI). Following disinfection reactions with chorine and monochloramine, the water samples were extracted onto XAD resins, and analytes retained were eluted with ethyl acetate. After drying and concentration of these extracts, they were directly injected into the Q Exactive GC system for analysis of iodo-DBPs. Details about the procedures followed to perform the disinfection reactions and DBP analysis can be found elsewhere [3]. 98


Sponsor Report

A procedural blank, i.e., untreated water concentrated in the same manner as the treated samples, was used to investigate whether the compounds detected and identified were generated during disinfection treatments or were artifacts generated during the sample preparation treatments. GC-MS conditions Compound separation and detection was achieved using a Thermo Scientific™ TRACE™ 1310 GC system coupled with a Thermo Scientific Q Exactive GC hybrid quadrupole-Orbitrap mass spectrometer. Sample introduction was performed using a Thermo Scientific™ TriPlus™ RSH autosampler. The analytical column used was a Thermo Scientific™ TG-5MS, 60 m × 0.25 mm ID × 0.25 μm film thickness (P/N: 26096-1540). Additional details of instrument parameters are shown (Tables I and II).

Table I. GC Temperature program TRACE 1310 GC System Parameters

Table II. Mass spectrometer parameters Q Exactive GC Mass Spectrometer Parameters

Injection Volume (μL):

1.0

Transfer Line (°C):

280

Liner:

Single taper, wool

Ionization Type:

EI & CI (methane)

Inlet (°C):

280

Ion Source (°C):

230 (El), 185 (CI)

Inlet Mode:

Splitless

Electron Energy (eV):

70

Carrier Gas, (mL/min):

He, 1.2

Acquisition Mode:

Full-scan

Mass Range (Da):

50 - 650

(P/N 453A0924-Ul)

Oven Temperature Program Temperature 1 (°C):

40

Resolving Power (FWHM at m/z 200):

60,000

Hold Time (min):

1

Lockmass, Column Bleed (m/z):

207.03235

Temperature 2 (°C):

325

Rate (°C/min):

15

Hold Time (min):

10

Data processing Data was acquired and processed using Thermo Scientific™ TraceFinder™ software that allowed peak detection with spectral deconvolution and tentative compound identification against a commercial spectral library (NIST). In order to reduce chemical interferences from the matrix, a mass window of ± 2 ppm was always used to enable generation of highly selective extracted ion chromatograms. Semi-quantitative information (peak area) was also obtained and a sample comparison was conducted in order to find chemicals that are only present in the treated samples analyzed. RESULTS AND DISCUSSION The DBP mixture concentrates obtained from the lab-scale chlorination and chloramination reactions were analyzed in full scan mode. An example of chromatographic separation is shown in Figure 1 for untreated-control and chlorinated samples. Compound discovery workflow The workflow used for the detection and molecular structure characterization of iodo-DBPs is schematically represented in Figure 2. Data acquired in full scan using electron ionization (EI) was processed in TraceFinder for peak detection and spectral deconvolution followed by compound identification using a library (NIST) search and high-resolution filtering (HRF) of the candidate compounds. 99


Sponsor Report

The deconvolution software uses a HRF score for the library searches. For each compound with a library match, the HRF represents the relative number of explainable ions in the measured spectra as compared to the proposed elemental composition of the best (based on the forward search index SI value) library match [4]. Consequently, the confidence in compound identification is dramatically increased as the analyst does not only rely on a library matching score (such as the forward SI). Data processing was simultaneously performed for all DBP mixtures generated (i.e., untreated NL NOM, chlorinated NL NOM and chloraminated NL NOM). A large number of peaks were detected subsequent to deconvolution (e.g. >2,500 peaks were found in the chloraminated NL NOM extract using a total ion current (TIC) intensity threshold of 500,000 and a signal-to-noise (S/N) threshold of 10:1). Having a high number of component peaks is clearly beneficial for comprehensive characterization of a sample. However, it is also essential for users to quickly isolate the peaks of interest, either within a sample or between sample groups. To facilitate this, TraceFinder has a variety of filters that can be used to isolate particular features in the data. In this example, an exact mass filter was used to isolate only the compounds containing iodine (exact mass m/z 126.90392). This reduced the total list of iodine containing chemicals detected to only 15 main peaks in the aforementioned example, i.e., chloraminated NL NOM extract. An example of peak deconvolution in the TraceFinderâ&#x20AC;&#x2122;s browser is shown in Figure 3 for chlorodiiodomethane. The samples of interest (a) were deconvoluted and a list of peaks was generated (b). Tentative compound identification was made by searching the NIST library, taking into account the forward search index (SI). In addition, an HRF score was used to determine the percentage of the mass fragments in the acquired spectrum that can be explained by the chemical formula of the molecular ion proposed from the library match, in this case CHCII2 for chlorodiiodomethane. This resulted in a combined total score indicating the quality of match between this library hit and the deconvoluted measured spectrum. This functionality makes this software a very powerful and unique tool that can be used for compound identification and confirmation.

Figure 1. Overlayed extracted ion chromatograms (m/z 126.90392, iodine) of Milli-Q water spiked with natural organic matter (NL NOM) subjected to chlorination (red) and control of untreated water (blue) showing an increase in both the number and intensity of iodinecontaining peaks in the chlorinated water as compared to the control.

100


Sponsor Report

Figure 2. Compound discovery workflow used for iodo-DBPs peak detection with spectral deconvolution and tentative compound identification.

Figure 3. Deconvolution browser showing chlorodiiodomethane identification based on library (NIST) match search index, SI 963), fragment rationalization with an HRF> 99% and mass accuracies of measured fragments (e.g., molecular ion m/z 301.78513 ppm = 0.23). Samples processed (a), peaks detected (b), identified chemicals (c), and deconvoluted mass spectra for chlorodiiodomethane (d) with the measured and theoretical ions including mass errors are indicated.

Identification of Iodo-DBPs with no library match However, many emerging chemical contaminants do not have a match in NIST (or similar MS libraries) and in this case a different approach has to be used to determine their identity (elemental 101


Sponsor Report

composition and chemical structure). This is where obtaining high mass accuracy becomes critical as only with appropriate mass spectral data is it possible to clearly determine the elemental composition of an unknown chemical. In this work, the EI mass spectra of the compounds detected in the treated water samples did not provide a sufficient match in the NIST library, and were interrogated using a pre-determined set of chemical elements (C-50, H-50, Br-5, Cl-10, I-10, O-10, and N-10). The molecular ion of the target compound was confirmed using positive chemical ionization (PCI) with methane. In addition, authentic standards were analyzed to confirm the identities using the retention time, EI mass spectral match, and mass accuracy of the measured ions. An example of unknown identification for compounds with no spectral match in the NIST library is shown in Figure 5 for iodoacetaldehyde.

Figure 4. Ion mass spectrum, corresponding accurate masses (ppm) and elemental composition of chlorodiiodomethane (RT= 8.77 min) a) in the chloraminated NL NOM extract and b) MS library match. Data acquired in EI at 60,000 resolution (FWHM, at m/z 200). Annotated are the acquired fragment ions that can be explained from CHClI2 proposed by NIST. Automatic elemental composition calculation is determined for each ion in the spectra in addition to exact mass calculations and mass difference (ppm error).

Figure 5. Confirmation of iodoacetaldehyde identification with authentic solvent standard (a) and NL treated samples (c) based on RT and mass accuracy measurements. Positive chemical ionization (PCI) mass spectrum (b) confirms mass of molecular ion [M+H]+ with 0.06 ppm mass accuracy.

102


Sponsor Report

Sample comparison and fold-change of Iodo-DBPs As an additional approach to identifying peaks of interest, TraceFinder software also allows for sample grouping and facilitates the analysis and data visualization of fold changes of the analytes detected. Detected peaks in all the samples were retention time aligned and the peak areas automatically compared, resulting in the generation of a heat map (Figure 6). This semi-quantitative approach allows the researcher to easily visualize and report the levels of detected chemicals.

Figure 6. TraceFinder browser showing the heat map with the peak areas of detected peaks (a), and as an example, the increased concentration of a compound eluting at RT = 7.46 min, the corresponding extracted peak chromatogram (b), and the abundance of this chemical in the samples analyzed (c).

Increased levels of iodo-DBPs were observed following chloramination (NH2Cl) reactions, in agreement with what was previously reported [5]. Following the identification workflow described above, a total of eight different iodo-DBPs were confidently identified in the extracts analyzed. Chemical structures were proposed for all compounds after applying the workflow described in the previous section. Experimental and theoretical masses of molecular ions from both EI and PCI with methane, the mass difference (Î&#x201D; ppm), the assigned elemental compositions for each diagnostic ion, and the proposed chemical structure for the identified DBPs are shown in Table III. Sample comparisons revealed that significantly higher levels of DBPs were observed in the chloraminated samples compared to the chlorinated extracts. Peak areas (XIC of m/z 126.90392) in the chloraminated extract were 8 to 66-fold higher as compared to the chlorinated extract, and up to 145 in the case of diiodomethane (Figure 7).

103


Sponsor Report

Table III. Iodo-DBPs identified and confirmed in disinfected NL NOM waters RT (min)

Identity

Elemental Composition

Theoretical m/z (EI)

Measured m/z (EI)

Δ (ppm)

Theoretical m/z [M+H]+

Measured m/z [M+ H]+

Δ (ppm)

3.71

Iodomethane

CH3I

141.92739

141.92745

0.4

142.93522

142.93522

0.0

5.36

Chloroiodomethane

CH2ClI

175.88842

175.88839

0.2

176.89625

176.89620

0.3

5.76

Iodoacetaldehyde

C2H3IO

169.92231

169.92234

0.2

170.93013

170.93014

0.06

7.36

Diiodomethane

CH2I2

267.82404

267.82424

0.8

268.83186

268.83192

0.2

8.03

Ethyl iodoacetate

C4H7IO2

213.94852

213.94840

0.6

214.95635

214.95627

0.4

8.14

Ethyl β-iodopropionate

C2H9IO2

n.d.

n.d.

228.97200

228.97198

0.07

8.77

Chlorodiiodomethane

CHClI2

301.78507

301.78509

0.1

301.78507

301.78511

0.1

9.85

Bromodiiodomethane

CHBrI2

345.73455

345.73459

0.1

345.73455

345.73446

0.3

Figure 7. Fold increase of iodo-DBPs detected and identified in chloraminated DBP mixture concentrates as compared to chlorinated ones.

CONCLUSIONS This work has shown the successful application of the Q Exactive GC system for the characterization of iodo-DBPs in disinfected water extracts. A large number of peaks were detected in the samples analyzed and an exact mass filter in TraceFinder was used to isolate only the compounds containing iodine. Higher concentrations of iodoDBP were found in the samples exposed to chloramination compared to chlorination treatments. The EI data obtained can be used for candidate compound identification against existing commercial libraries. Importantly, as often the chemicals detected are not included in such libraries, the consistent sub-ppm mass accuracy measurements will unambiguously determine the elemental composition and subsequent structural elucidation of unknown chemicals. Moreover, softer ionization such as positive chemical ionization with methane can be used to confirm the elemental composition of the molecular ion of a chemical. The Q Exactive GC mass spectrometer and the compound discovery and identification workflow described here allow for rapid detection and confident identification of unknown DBPs in disinfected water, enabling researchers to reliably and timely report the identities of the unknown chemicals.

104


Sponsor Report

Acknowledgements C. P. acknowledges support provided by the European Union 7th R&D Framework Programme (FP7/2007e2013) under grant agreement 274379 (Marie Curie IOF) and the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the COFUND programme of the Marie Curie Actions of the EU’s FP7 (2014 BP_B00064). This work has been financially supported by the Generalitat de Catalunya (Consolidated Research Groups “2014 SGR 418 - Water and Soil Quality Unit” and 392 2014 SGR 291 - ICRA) and by the European Union’s FP7 for research, technological development and demonstration under grant agreement nº 603437 (SOLUTIONS). The EU is not liable for any use that may be made of the information contained therein. REFERENCES 1. Richardson, S. D.; Fasano, F.; Ellington, J. J.; Crumley, F. G.; Buettner, K. M.; Evans, J. J.; Blount, B. C.; Silva, L. K.; Waite, T. J.; Luther, G. W.; McKague, A. B.; Miltner, R. J.; Wagner, E. D.; Plewa, M. J. Environ. Sci. Technol., 2008, 42, pp 8330–8338. 2. Richardson, S. D.; Plewa, M. J.; Wagner, E. D.; Schoeny, R.; Demarini, D. M. Mutat. Res., 2007, 636, pp 178-242. 3. Postigo, C.; Cojocariu, C. I.; Richardson, S. D.; Silcock, P.; Barcelo, D. Anal Bioanal Chem, 2016, 408, pp 3401-3411 (DOI: http://dx.doi.org/10.1007/s00216-016-9435-x). 4. Kwiecien, N. W.; Bailey, D. J.; Rush, M. J. P.; Ulbrich, A.; Hebert, A. S.; Westphall, M. S.; Coon, J. J. Accurate mass for improved metabolite identification via high-resolution GC/MS. Metabolomics 2015 (11th Annual International conference of the Metabolomics Society). June 29 - July 2, 2015. San Francisco Bay Area, CA. USA MOB: Informatics: Metabolomics. 5. Krasner, S. W.; Weinberg, H. S.; Richardson, S. D.; Pastor, S. J.; Chinn, R.; Sclimenti, M. J; Onstad, G. D.; Thruston, A. D. Jr. Environ. Sci. Technol., 2006, 40, pp 7175-7185.

This sponsor report is the responsibility of Thermo Fischer Scientific.

105


Sponsor Report

Br. J. Anal. Chem., 2019, 6 (22) pp 106-115 PDF

This section is dedicated for sponsor responsibility articles.

Monitoring Inorganic Anions and Cations During Desalination Lipika Basumallick and Jeff Rohrer Thermo Fisher Scientific, Sunnyvale, CA, USA

INTRODUCTION As of 2009, there were 14,450 desalination plants worldwide producing more than 60 million cubic meters of water a day.1 Because of the growing demand for water and the limited supply of fresh water, desalination increasingly is being used to produce potable and irrigation water from salty or brackish water. The global market for desalination to generate supplies of potable water is projected to grow at an annual rate of 10% over the next 10 years. Seawater desalination is a $10 billion industry today and is forecasted to reach $16 billion in 2020 [1]. A wide variety of desalination techniques are currently available and more are being developed. Most use distillation or membrane techniques. The performance of desalination processes is evaluated by monitoring the common anions and cations in the feed, intermediate, and final water product. For the final drinking water product, ion chromatography (IC) is approved for monitoring primary and secondary anions according to U.S. Environmental Protection Agency (EPA) Method 300.0 [2], and Federal and State regulatory agencies ensure that U.S. National Primary and Secondary Drinking Water Standards are met. Common cations, though not considered contaminants, are monitored and reported by many public water suppliers in the United States. Cations, particularly calcium and magnesium, are measured to determine water hardness. In addition to calcium and magnesium, ammonium is also measured and regulated in public water supplies in EU countries and Japan. During desalination, the levels of divalent cations affect performance of membrane processes like reverse osmosis (RO) [3]. High levels of calcium or magnesium result in frequent fouling of the membranes, which is highly undesirable. Therefore, it is critical to monitor anions and cations at all stages of desalination. Another challenge for the desalination of seawater is the removal of boron, which is typically found at concentrations of 4.5 mg/L. World Health Organization 2008 guidelines suggest a concentration of 0.5 mg/L [4], whereas the U.S. EPA recommends a maximum lifetime exposure of 0.6 mg/L [5]. Depending on pH levels, boron can exist in ionic and non-ionic forms. Above pH 8, the removal efficiency using RO is enhanced due to the formation of borate. RO membranes remove ions better than non-ionic forms of the same compounds. This suggests that raising the pH may improve the removal efficiency of boron. However, raising the pH too high results in the formation of scales formed by the precipitation of carbonate salts of calcium and magnesium, which can disrupt membrane performance. In addition to monitoring the pH, it is important to know the concentration of scale-forming divalent cations calcium and magnesium in order to maintain optimal RO membrane performance. Compared to traditional sources of water, desalination is an energy-intensive process that requires expensive infrastructure. The potential benefits of desalination are constantly being evaluated because of the high economic and environmental costs. Hence, efficient water monitoring techniques are needed to understand the robustness of desalination processes. This work describes an IC method using a Thermo Scientific™ Dionex™ ICS-6000 Reagent-Free™ Ion Chromatography (RFIC™) system with Thermo Scientific™ Dionex™ IonPac™ AS18 anionexchange and Dionex IonPac CS12A cation-exchange columns, electrolytically generated hydroxide and methanesulfonic acid eluents, and suppressed conductivity detection to simultaneously measure the common anions and cations in water samples obtained from desalination processes. This method 106


Sponsor Report

uses a 2 mm column format for anion separations, a 3 mm column format for cation separations, and electrolytically generated eluents that require only the addition of deionized water for continuous operation. The linearity, method detection limits (MDLs), precision, and recovery of anions and cations in saline and drinking water matrices for this method are discussed here. This IC method supports all the monitoring needs of a desalination facility because it can measure anions and cations in diverse matrices ranging from seawater to drinking water MATERIALS AND METHODS Equipment Dionex ICS-6000 RFIC system with eluent generation (RFIC-EG) including the Thermo Scientific™ itens: Dionex DP Dual Pump module; Dionex EG Eluent Generator module; Dionex DC Detector/ Chromatography module (single- or dual-temperature zone configuration); Dionex AS Autosampler (with Simultaneous Injection Upgrade Kit); Dionex EGC II KOH cartridge; Dionex CR-ATC Continuously Regenerated Anion Trap Column; Dionex EGC II MSA cartridge; Dionex CR-CTC Continuously Regenerated Cation Trap Column; Dionex™ Chromeleon™ 6.8 Chromatography Data System (CDS) Workstation; Nalgene™ 125 mL Narrow-Mouth HDPE Bottles; Nalgene 250 mL Narrow-Mouth HDPE Bottles; Nalgene™ 250 mL 0.2 µm nylon filter units; Nalgene 1000 mL 0.2 µm nylon filter units. Polystyrene Autoselect vials with caps and septa, 10 mL. Reagents and Standards • Deionized water, Type I reagent grade, 18 MΩ cm resistivity or better, filtered through a 0.2 μm filter immediately before use. • Fluoride, chloride, nitrite, bromide, sulfate, nitrate, phosphate, lithium, sodium, ammonium, potassium, magnesium, and calcium standards (1000 mg/L). • Sodium chloride, sodium sulfate, sodium nitrite, sodium bromide, sodium nitrate, potassium phosphate monobasic, lithium chloride, ammonium chloride, potassium chloride, magnesium chloride hexahydrate, and calcium chloride dihydrate. • Combined Six Cation Standard-II and Seven Anion Standard. Conditions Anion Determinations Columns:

Dionex IonPac AG18, 2 × 50 mm Dionex IonPac AS18, 2 × 250 mm

Eluent:

22 mM KOH from 0–7 min, 22–40 mM KOH from 7–8 min, 40 mM KOH from 8–18 min*

Eluent Source:

Dionex EGC II KOH cartridge with Dionex CR-ATC column

Injection Volume:

4 μL

Flow Rate:

0.25 mL/min

Detection:

Suppressed conductivity, Thermo Scientific™ Dionex™ ASRS™ 300 Anion Self-Regenerating suppressor, 2 mm, recycle mode, suppressor current 15 mA

Background Conductance:

< 1 μS

107


Sponsor Report

Cation Determinations Columns:

Dionex IonPac CG12A-5 μm, 3 × 30 mm Dionex IonPac CS12A-5 μm, 3 × 150 mm

Eluent:

20 mM MSA

Eluent Source:

Dionex EGC II MSA cartridge with Dionex CR-ATC column

Injection Volume:

10 μL

Flow Rate:

0.50 mL/min

Detection:

Suppressed conductivity, Thermo Scientific™ Dionex™ CSRS™ 300 Cation Self-Regenerating suppressor, 2 mm, recycle mode, suppressor current 30 mA

Background Conductance:

<0.5 μS

Both Anion and Cation Determinations Temperature:

30 °C (column and detector compartment)

Noise:

~0.5–1.0 nS (conductivity)

System Backpressure:

~2500 psi

Run Time:

20 min (including column equilibration time)

* The column equilibrates for 2 min at 22 mM KOH prior to injection.

Preparation of Solutions and Reagents Eluent Solutions Generate potassium hydroxide (KOH) and methanesulfonic acid (MSA) eluents online by pumping high-quality degassed, deionized (DI) water through the Dionex EGC II KOH and Dionex EGC II MSA cartridges, respectively. Chromeleon CDS software tracks the amount of KOH and MSA used and calculates the remaining lifetime. Although electrolytic eluent generation delivers the best performance, manually prepared eluents may be used, if needed. Stock Standard Solution Certified standard solutions can be purchased from Thermo Scientific or other commercial sources. When commercial standards are not available, 1000 mg/L stock standard solutions can be prepared by dissolving appropriate amounts of the required analyte in DI water in a plastic volumetric flask (Table I). Store in plastic containers at 4 ºC. Stock standards are stable for at least 3 months. Working Standard Solutions Prepare composite working standards at lower analyte concentrations by diluting appropriate volumes of the 1000 mg/L stock with DI water. Prepare working standards containing <100 mg/L anions or cations daily. Store standard solutions at <6 ºC when not in use.

108


Sponsor Report

Table I. Mass of compound required to prepare 1 L of 1000 mg/L stock standard solutions Analyte

Compound

Fluoride

Sodium fluoride (NaF)

2.210

Chloride

Sodium chloride (NaCl)

1.648

Nitrite

Sodium nitrite (NaNO2-N)

4.926

Sodium bromide (NaBr)

1.288

Sodium nitrate (NaNO3-N)

6.068

Potassium phosphate monobasic (KH2PO4-P)

4.394

Bromide Nitrate Sulfate

Amount (g)

Sodium sulfate (Na2SO4)

1.479

Lithium chloride (LiCl)

6.108

Sodium

Sodium chloride (NaCl)

2.542

Ammonium

2.965

Potassium

Ammonium chloride (NH4Cl)

Potassium chloride (KCl)

1.907

Magnesium

Magnesium chloride hexahydrate (MgCl2 • 6H2O)

8.365

Phosphate Lithium

Calcium

Calcium chloride dihydrate (CaCl2 • 2H2O)

3.668

Sample Preparation Artificial Seawater Prepare simulated seawater by diluting the salts listed in Table II into 1 L of DI water following the method of Kester et al. [6] with the exclusion of strontium chloride. This yields a solution with approximately 3.5% salinity. Table II. Salts added to form simulated seawater (1 L) Compound

Amount (g)

Sodium chloride

2.393

Sodium sulfate

4.008

Potassium chloride

0.677

Sodium bicarbonate

0.196

Potassium bromide

0.098

Boric acid

0.026

Sodium fluoride

0.003

Commercial Aquarium Sea Salt Follow package directions (1/2 cup of salt per gallon of DI water) to prepare commercially available synthetic sea salt, creating a solution of approximately 3.5% salinity. Prepare a 1 L portion with 30 g of aquarium salt. (A sea salt density of approximately 2.2 g/cm3 was used to convert the preparation directions to metric units. [7]) Seawater (From California’s San Francisco Bay) Collect surface seawater in a Nalgene 250 mL HDPE bottle that has been precleaned before sample collection. Store the sample on ice until it can be filter sterilized through a Nalgene 250 mL, 0.2 μm nylon filter unit. After filtration, store the sample at <6 °C. Filter all samples through a 0.2 μm nylon filter unit before injection. 109


Sponsor Report

System Preparation and Configuration Configure the Dionex AS autosampler for simultaneous injection into the anion and cation detection systems. In the simultaneous mode, the Dionex AS autosampler delivers sample to two independent IC systems. The sample is injected simultaneously and equally to both systems (two injection valves are required). Dual analyses can be performed with only one sample. A 5 or 10 mL syringe and an 8.5 mL sampling needle assembly are required for simultaneous injections. Full-loop injections are required for this mode. Using Chromeleon CDS software, configure the two chromatography systems and the Dionex AS autosampler into a single timebase and assign each system a unique device name and channel. Use one control panel to monitor and control both systems and all samples in one sequence. The system also may be configured for sequential injection into the two IC systems. In the sequential option, the sample is delivered to the first system, flow is rerouted (diverted), and then sample is delivered to the second system [8]. RESULTS AND DISCUSSION Using the Dionex IonPac CS12A and Dionex IonPac AS18 columns, the common anions and cations were easily resolved in 20 min (Figure 1 A and B). Note that this method provided good resolution between sodium and ammonium, the two analytes that can be challenging to resolve, especially when one is in a large excess relative to the other. This method also achieved good retention time for fluoride, which was well resolved from the void volume.

Figure 1. Separation of common A) anions using the Dionex IonPac AS18 column and B) cations using the Dionex IonPac CS12A column.

Table III summarizes the calibration data, the method detection limits (MDLs), retention time, and peak area precisions for the common anions and cations. MDLs and precision data were obtained from seven replicate injections of the MDL and QCS standards, respectively, prepared in DI water. Anion and cation MDL standards were prepared at concentrations of 3â&#x20AC;&#x201C;5x the estimated method detection limits. Correlation coefficient values obtained from the calibration plots were between 0.9994 and 0.9999. The calibration curves were linear for all anions and cations except ammonium. Analytes that form weak acids or bases in the suppressor are known to exhibit nonlinear behavior. A quadratic curvefitting function was used for ammonium. The retention time precision ranged from <0.01â&#x20AC;&#x201C;0.07%, and 110


Sponsor Report

the peak area precision ranged from 0.04–0.97%. The high retention time precisions are attributed to consistent generation of high-purity KOH and MSA using the eluent generator module and the respective continuously regenerated trap columns (Dionex CR-ATC and Dionex CR-CTC columns). Table III. Linear range, MDLs, and precisions for anions and cations QCS (mg/L)

Retention Time Precision (RSD)b

Peak Area Precision (RSD)b

0.08

1

0.07

0.20

4

0.13

4

<0.01

0.29

0.9997

5

0.10

5

<0.01

0.97

0.9997

10

0.10

10

0.03

0.61

0.02–80

0.9998

5

0.53

5

0.03

0.09

Calcium

0.02–80

0.9999

5

0.36

5

0.04

0.15

Fluoride

0.08–100

0.9996

10

0.62

2

0.05

0.05

Chloride

0.24–300

0.9999

10

0.66

20

0.02

0.04

Nitrite (-N)

0.08–100

0.9994

20 (67 as NO3-)

0.51 (-N)

2 (6.7 as NO3-)

0.03

0.07

Bromide

0.08–100

0.9994

25

0.46

2

0.02

0.05

Sulfate

0.16–201

0.9994

20

0.67

2

0.01

0.07

Phosphate (-P)

0.03–33

0.9999

27 (70 as PO43-)

0.15 (-P)

0.7 (2 as PO43-)

0.04

0.14

Analyte

Range (mg/L)

Corr. Coeff. (r2)

MDL Standard (μg/L)

MDL (μg/L)a

Lithium

0.02–16

0.9999

1

Sodium

0.10–100

0.9999

Ammoniumc

0.01–8

Potassium

0.02–16

Magnesium

MDL = (t) × (S) where t = Student’s t value for a 99% confidence level and a standard deviation estimate with n - 1 degrees of freedom [t = 3.14 for seven replicates of the MDL Standard], and S = standard deviation of the replicate analysis. b Relative standard deviation, n = 7 c Quadratic fit a

Method performance was evaluated by measuring recoveries in samples of spiked saline (Table IV) and drinking water (Table V). Samples were spiked with analytes at a level that was 50–100% of the amount determined in the original sample. The between-day precision for anions and cations in the spiked samples ranged from < 0.01–1.6% over three days.

111


Sponsor Report

Table IV. Between-day (n = 3) retention time (RT) and peak area precisions (triplicate injections of spiked sample) Cations

Anions San Francisco Bay Water

Analyte

RT (min)

RT Precision (RSD)

Peak Area (ÎźS* min)

Peak Area Precision (RSD)

RT (min)

RT Precision (RSD)

Peak Area (ÎźS* min)

Peak Area Precision (RSD)

Lithium

2.57

<0.01

0.72

0.13

Fluoride

3.63

<0.01

0.39

0.57

Sodium

3.19

0.06

18.4

0.07

Chloride

5.45

0.00

40.3

0.31

Ammonium

3.61

0.02

Potassium

4.59

0.03

0.32

0.20

Nitrite

6.77

0.02

0.61

0.64

0.51

0.40

Bromide

9.63

0.03

0.14

0.82

Magnesium

7.87

0.02

4.31

0.12

Sulfate

10.53

0.01

5.14

0.20

Calcium

9.96

0.02

0.91

0.38

Nitrate

11.57

0.01

0.26

0.63

Phosphate

15.44

0.03

0.09

0.65

Analyte

Commercial Aquarium Sea Salt Lithium

2.57

0.05

0.72

0.15

Fluoride

3.63

0.05

0.37

0.52

Sodium

3.19

0.02

18.4

0.05

Chloride

5.45

0.02

40.2

0.18

Ammonium

3.61

<0.01

0.29

0.54

Nitrite

6.77

0.02

0.63

0.79

Potassium

4.59

0.03

0.52

0.30

Bromide

9.63

0.01

0.14

0.63

Magnesium

7.91

0.02

4.32

0.09

Sulfate

10.54

0.03

5.11

0.26

Calcium

10.08

0.01

0.88

0.41

Nitrate

11.57

0.01

0.26

0.68

Phosphate

15.45

0.02

0.09

1.01

Artificial Seawater Lithium

2.57

0.05

0.71

0.22

Fluoride

3.63

<0.01

0.37

0.39

Sodium

3.20

0.04

21.2

0.05

Chloride

5.45

0.01

45.83

0.22

Ammonium

3.61

<0.01

0.31

0.52

Nitrite

6.77

0.02

0.62

0.61

Potassium

4.59

0.03

0.58

0.37

Bromide

9.63

0.01

0.15

0.62

Magnesium

7.91

0.01

4.56

0.36

Sulfate

10.52

0.02

3.92

0.27

Calcium

10.07

0.03

0.94

0.50

Nitrate

11.57

0.01

0.27

0.24

Phosphate

15.44

0.02

0.09

0.55

112


Sponsor Report

Table V. Between-day (n = 3) retention time (RT) and peak area precisions (triplicate injections of spiked sample) Cations

Anions Tap Water Peak Area Peak Area Precision (μS* min) (RSD)

RT (min)

RT Precision (RSD)

Peak Area (μS* min)

Peak Area Precision (RSD)

Fluoride

3.63

0.04

0.82

0.34

0.10

Chloride

5.47

0.01

7.47

0.32

0.48

0.14

Nitrite

6.78

0.01

0.29

0.46

<0.01

0.27

0.15

Bromide

9.64

0.02

0.12

0.76

0.02

4.11

0.19

Sulfate

10.53

0.03

5.13

0.34

0.01

6.57

0.18

Nitrate

11.56

0.01

0.31

0.66

Phosphate

15.44

0.01

0.09

0.89

Analyte

RT (min)

RT Precision (RSD)

Lithium

2.57

0.05

0.75

0.13

Sodium

3.16

0.04

8.34

Ammonium

3.61

0.02

Potassium

4.59

Magnesium

7.91

Calcium

9.97

Analyte

Bottled Mineral Water Lithium

2.57

0.03

0.75

0.13

Fluoride

3.63

0.04

0.90

0.49

Sodium

3.16

<0.01

8.57

0.07

Chloride

5.47

0.01

6.12

0.33

Ammonium

3.61

0.04

0.29

0.54

Nitrite

6.76

0.02

0.22

0.65

Potassium

4.59

0.01

0.61

0.09

Bromide

9.61

0.01

0.12

0.76

Magnesium

7.80

0.02

11.4

0.12

Sulfate

10.44

0.03

8.52

0.50

Calcium

9.73

0.01

18.5

0.21

Nitrate

11.52

0.02

0.74

0.34

Phosphate

15.51

0.03

0.09

0.53

Figure 2 shows the separation of A) anions and B) cations in water from California’s San Francisco Bay. The bay water sample is representative of the typical feed water into a desalination plant. The bay water sample was diluted 200-fold so that measured levels were within the calibrated range. The major inorganic anions in bay water are chloride and sulfate, and the major inorganic cations are sodium, potassium, magnesium, and calcium.

Figure 2. San Francisco, CA bay water: determination of common A) inorganic anions using the Dionex IonPac AS18 column and B) cations using the Dionex IonPac CS12A column. 113


Sponsor Report

As seen in Figure 2 and Table VI, all anions and cations were well resolved and had acceptable recoveries (80â&#x20AC;&#x201C;120%) using the criteria outlined in U.S. EPA Method 300.0. Table VI. Between-day (n = 3) retention time (RT) and peak area precisions (triplicate injections of spiked sample) San Francisco Bay Water Analyte

Artificial Seawater

Commercial Aquarium Sea Salt

Bottled Mineral Water

Tap Water

Amount Added (mg/L)

Recovery* (%)

Amount Added (mg/L)

Recovery* (%)

Amount Added (mg/L)

Recovery* (%)

Amount Added (mg/L)

Recovery* (%)

Amount Added (mg/L)

Recovery* (%)

Lithium

1

93.5

1

92.4

1

98.1

1.0

96.9

1

97.2

Sodium

40

89.9

40

95.3

40

90.9

20.1

93.1

20

96.6

Ammonium

1

108.3

1

105.7

1

105.9

1.0

97.9

1

99.9

Potassium

2

94.5

2

96.7

2

99.6

1.0

94.9

1

95.7

Magnesium

5

97.2

5

97.4

5

97.6

5.0

94.6

5

97.1

Calcium

2

88.4

2

83.7

2

82.8

15.0

95.7

15

85.6

Fluoride

1

109.6

1

107.0

1

106.9

1

98.1

1

98.7

Chloride

74

87.2

74

92.7

74

89.7

16

84.2

16

85.9

Nitrite (-N)

1

100.7

1

101.7

1

105.3

1

37.2

1

41.5

Bromide

1

84.4

1

83.6

1

84.1

1

87.9

1

88.4

Sulfate

16

81.2

16

83.9

16

84.9

16

93.9

16

84.4

Nitrate (-N)

0.2

98.4

0.2

103.7

0.2

100.0

0.2

100.9

0.2

101.3

Phosphate (-P)

0.3

88.0

0.3

84.3

0.3

86.6

0.3

88.4

0.3

85.0

Figure 3 (A and B) shows the chromatogram for all anions and cations in Sunnyvale, CA drinking water. Tap water samples have fluoride, chloride, and sulfate as the predominant inorganic anions. Table VI lists the recoveries of anions and cations in the drinking water matrices. All anions and cations were well resolved and, with the exception of nitrite, had acceptable recoveries (80â&#x20AC;&#x201C;120%). The low recovery of nitrite can be attributed to biological activity in these samples (which is minimal in the high saline matrices) and the instability of nitrite in oxidizing environments, such as chlorinated water or other oxidizing disinfectants in drinking water. In summary, the current methods using the Dionex IonPac AS18 and Dionex IonPac CS12A columns provide acceptable recoveries for anions and cations in both saline and drinking water matrices. This work shows methods that can be used for diverse matrices that are typically encountered in a desalination plant.

Figure 3. Sunnyvale, CA tap water: determination of common A) inorganic anions using the Dionex IonPac AS18 column and B) cations using the Dionex IonPac CS12A column.

114


Sponsor Report

CONCLUSION Dionex IonPac AS18 and Dionex IonPac CS12A columns with electrolytically generated hydroxide and MSA eluents can simultaneously determine anions and cations in saline and drinking water matrices. The capacities of the Dionex IonPac AS18 and Dionex IonPac CS12A columns allow sample analysis with minimal sample pretreatment. The RFIC-EG system allows continuous operation of the instrument with minimal maintenance. Only water for eluent generation and suppressor regeneration must be added to keep the instrument running for sample analysis. Additionally, the smaller column format generates less waste and uses less eluent, saving both time and money. The methods were shown to be accurate by the good recovery of anions and cations in a wide variety of samples including natural and artificial seawater and drinking water. These methods are robust for all ionmonitoring needs of a typical desalination facility and support a varying range of matrices from seawater to drinking water. REFERENCES 1. Information released during the International Desalination Organization (IDA) World Congress held by the IDA and Global Water Intelligence, Dubai, UAE, Nov 2009. www.workingwithwater. net/view/5177/global-waterintelligence-report-shows-296-increase-in-seawaterdesalination-plants/ (accessed June 4, 2010). 2. U.S. Environmental Protection Agency. Method 300.0. The Determination of Inorganic Anions in Water by Ion Chromatography. Cincinnati, Ohio, 1993. www.epa.gov/waterscience/methods/method/ files/300_1.pdf (accessed June 4, 2010). 3. Potts, D. E.; Ahlert, R. C.; Wang, S. S. Desalination, 1981, 36 (3), pp 235–264. 4. Kester, D. R.; Duedall, I. W,; Connors, D. N.; Pytkowicz, R. M. Limnology and Oceanography, 1967, 12, p 176. 5. World Health Organization. Guidelines for Drinking Water Quality. Geneva, Switzerland, 2008. www.who.int/water_sanitation_health/dwq/gdwq3rev/en/index.html 6. U.S. Environmental Protection Agency. Drinking Water Health Advisory for Boron. Cincinnati, Ohio, 1993. http://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P1000ZWU.txt 7. Lewis, E. R.; Schwartz, S. E. Atmospheric Environment, 2006, 40 (3), pp 588-590. 8. Dionex (now part of Thermo Scientific) Operator’s Manual: AS Autosampler Operator’s Manual. Document No. 065051-03, January 2008, Sunnyvale, CA.

This sponsor report is the responsibility of Thermo Fischer Scientific.

115


Sponsor Report

Br. J. Anal. Chem., 2019, 6 (22) pp 116-117 PDF

This section is dedicated for sponsor responsibility articles.

Determination of Mercury in Soil Samples Using Direct Mercury Analysis Mercury analysis of soil and sediment samples is becoming increasingly important due to mercury’s toxicity and the adverse effects it can have on human health. Dumping of contaminated wastes, effluents from manufacturing processes, and combustion of fossil fuels are a few common sources of soil contamination. Remediation of mercury contaminated sites require specific procedures which vary based on the levels of mercury found in the soil and sediment samples from the site. Conventionally, to analyze mercury in soils and sediments, the samples need to be digested in acid and are then analyzed using either cold vapor atomic absorption spectroscopy (CVAA) or an ICP system. While these are tried and tested methodologies, the need to digest samples prior to analysis proves to be a very costly and a time and labor-intensive step. Additionally, the user is required to ensure that the digestion unit is properly maintained, safe working protocols are followed, and waste acids are properly disposed. This ultimately hinders the productivity of the lab. Direct mercury analysis eliminates these challenges completely, while providing accurate and reproducible data. MATERIALS AND METHODS Instrumentation Direct mercury analysis, as described in U.S. EPA Method 7473, is a cost effective, proven alternative to these labor-intensive, wet chemistry techniques. Direct Mercury Analysis involves an integrated sequence of combustion, catalytic conversion, amalgamation and detection using Atomic Absorption. Direct analysis affords the laboratory many benefits including: • • • • •

Reduced Sample Turnaround (6 minutes) No Sample Preparation Reduced Hazardous Waste Generation Reduction of Analytical Errors General Cost Savings (70% vs. CVAA)

The Milestone DMA-80 direct mercury analyzer provides a highly flexible platform with an extremely wide dynamic detection range to analyze soil samples with varying mercury levels. Additional features such as internal temperature monitoring, auto-blanking and preheated cuvettes ensure a complete and safe decomposition of the highly organic and oily samples without any contamination or memory effects. The DMA-80 features a circular, stainless steel, interchangeable 40-position autosampler for virtually limitless throughput and can accommodate both nickel (500 mg) and quartz boats (1500 uL) depending on the requirements of the application. It operates from a single-phase 110/220V, 50/60 Hz power supply and requires regular grade oxygen as a carrier gas. Calibration The DMA-80 can be calibrated using aqueous standards or Standard Reference Materials (SRM’s). The DMA-80 used for this experiment had a tri-cell spectrophotometer and covered a dynamic range of 0.0015-1200 ng Hg. Calibration was performed using different volumes of 1ppm and 0.1 ppm stock solutions, prepared from an NIST traceable 1000 ppm stock solution (VHG Labs). RESULTS AND DISCUSSION In this experiment, 5 different soil samples were analyzed 4 times to study the concentration range of mercury in soil. 116


Sponsor Report

A standard solution of 0.500 ppm was analyzed before and after the sample analysis. The results and profile are shown in Tables I and II. Table I. Analysis of Unknown Soil Samples

Table II. Profile

Concentration (ppm)

Step

Time (hh:mm:ss)

Temperature (ยบC)

0.491

1

00:00:10

250

A

0.0940+/-0.02

2

00:00:30

250

B

0.1228+/-0.02

3

00:01:30

650

C

0.1423+/-0.02

4

00:01:30

650

D

0.0900+/-0.02

E

0.9620+/-0.02

Sample Standard Precheck (0.500 ppm)

Standard Postcheck (0.500 ppm)

0.495

Max Start Temperature: 250 ยบC Catalyst Temperature: 600 ยบC Purge Time: 60 seconds Amalgamation Time: 12 seconds at 900 ยบC Oxygen Flow: 120 mL/m

CONCLUSION A lab analyzing mercury in soil samples is required to maintain high throughput while keeping its costs under control. The DMA-80 is an excellent tool as it yields results in ~6 min/sample and proves to be profi cient, matrix-independent and cost effective while completely eliminating the sample preparation challenges posed by conventional mercury analysis techniques.

This sponsor report is the responsibility of Milestone.

117


Release

Br. J. Anal. Chem., 2019, 6 (22)

Don’t miss the largest meeting of Analytical Chemistry in Latin America

6th Analitica Latin America Congress September 24-26, 2019 São Paulo Expo, São Paulo, SP, Brazil The goal of the Analitica Latin America Congress (ALAC) is the integration of professionals from both the academic and industrial sectors. To assist in achieving this idealistic purpose of integration, BrJAC was launched soon after the 1st edition of ALAC, in 2010, with an Editorial Board of professionals from the analytical chemistry field in academia, private companies and public institutions. Since then, the BrJAC has maintained a close partnership with ALAC and provides a scientific platform to researchers involved in science, technology and innovation projects on analytical chemistry to disseminate their studies developed at universities, research centers and in industry. The 6th ALAC will include Innovation in Analytical Chemistry, Artificial Intelligence, Blockchain, Big Data, Nanotechnology, Forensics, and Startup Labs as the main themes. In addition to lectures and round-tables, the ALAC has specific sessions for the discussion of posters, and technical talks on new technologies in analytical instrumentation and new procedures in the lab. A highlight of this event is the Live Lab, a laboratory fully equipped with instruments to carry out realtime analysis demonstrating the usability of state-of-the-art equipment. In the Live Lab of the 6th ALAC, analysis using GC-MS, LC-MS, HPLC, IC, ICP, UV and other analytical techniques will be performed.

Log in to the BrJAC website and have 10% discount on congress registration! After login, register at the Analytical Congress here

118


SEPTEMBER

24 TO 26 SÃ&#x192;O PAULO EXPO SP - BRASIL

15th International Laboratory Technology, Analysis, Biotechnology and Quality Control Fair

2019 1 PM TO 9 PM

THE BEST REFERENCE IN INNOVATION AND TRENDS IN ANALYTICAL CHEMISTRY.

500

EXHIBITORS BRANDS

7.500

+

QUALIFIED VISITORS

Join the largest multi-sectoral

meeting of analytical chemistry!

analitica@nm-brasil.com.br | +55 11 3205-5023

www.analiticanet.com.br Organization and Promotion:

Parallel Events:

Venue:


Release

Br. J. Anal. Chem., 2019, 6 (22)

Thermo Scientific Exactive GC Orbitrap GC-MS System The Frontier of Routine GC-MS The power of multi-award winning Orbitrap GC-MS technology has so far allowed research scientists to break new ground in gaining a broader and deeper understanding of their samples through the use of high-resolution, accurate-mass (HR/AM) analysis. The introduction of the Thermo Scientific™ Exactive™ GC Orbitrap™ GC-MS system brings that power into the routine environment for the first time. This system allows scientists working in fields like food safety, environmental, industrial, forensics and anti-doping to revolutionize their workflows by taking their analytical capability to the next level. The Exactive GC system is an easy-to-use, dedicated GC-MS that provides an unprecedented level of highly sensitive, routine grade performance for both targeted and non-targeted analysis, along with high confidence quantitation for the ultimate sample analysis workflow. This is achieved through the superior resolving power, mass accuracy, linear dynamic range and sensitivity that only Orbitrap technology can deliver, combined with the intelligent data processing workflows provided by Thermo Scientific™ TraceFinder™ software. Performance benefits • Resolving power of up to 50,000 (FWHM) at m/z 272 • Routine sub ppm mass accuracy • < 6 fg OFN Instrument Detection Limit • EI/CI Thermo Scientific ExtractaBrite ion source removable under vacuum through vacuum interlock • Vent-free column exchange with source plug Some Hardware Specifications Ion Source • Thermo Scientific ExtractaBrite Electron Ionization (EI) source • Ion source includes ion volume, repeller, source lenses, RF lens and dual filaments in all ionization modes, programmable from 50 °C to 350 °C • Chemical Ionization (CI) source for acquisition with Positive Ion Chemical Ionization (PCI) and Negative Ion Chemical Ionization (NCI) • Remove entire ion source or change to CI source in under 2 minutes without venting • Vent-free column exchange with new, patented source plug • Combination EI/PCI/NCI ion volume can be used without need for source interchange MS Ion Optics • Advanced pre-filtering and axial field bent flatapole ion guide reduces noise by eliminating neutrals. Orbitrap Mass Analyzer • Nitrogen-filled C-Trap • Highly efficient ion transfer to Orbitrap mass analyzer • Low-noise image current preamplifier • 16-bit signal digitalization 120


Redefine your GC-MS Analysis A comprehensive understanding of samples has been out of reach for GC-MS users for too long. The Thermo Scientific™ Q Exactive™ GC Orbitrap™ GC-MS/MS system and the new Thermo Scientific™ Exactive™ GC Orbitrap™ GC-MS system have changed all of that. The Q Exactive GC Orbitrap GC-MS/MS system is here with the superior resolving power, mass accuracy and ™ Orbritrap™ technology can deliver. And the Exactive GC Orbitrap GC-MS sensitivity that only Thermo Scientific system brings the power of high-resolution, accurate-mass (HR/AM) analysis into the routine environment for the first time. Both systems allow scientists working in the fields of food safety, environmental, industrial, forensics and anti-doping to revolutionize their workflows by taking their analytical capability to the next level.

VIDEO

Find out more at thermofisher.com/OrbitrapGCMS ©2016 Thermo Fisher Scientific Inc. All rights reserved. All trademarks are the property of Thermo Fisher Scientific and its subsidiaries unless otherwise specified. AD10525-EN 0616S

WEBSITE


Release

Br. J. Anal. Chem., 2019, 6 (22)

Thermo Scientific Dionex ICS-6000 HPIC System The Freedom to Explore When solving ion analysis challenges, there are sometimes more questions than answers. The ability to develop and run different methods for a single sample or for different samples is increasingly important for analytical laboratories. A highly flexible ion chromatography (IC) system provides you with the freedom to develop, explore, and run different methods simultaneously. The Thermo Scientific™ Dionex™ ICS-6000 HPIC™ system is a truly modular, highly configurable, high-performance system. The robust system design enables operation at up to 5000 psi and produces consistent, reliable results. As a topof-the line ion chromatography system, it is designed for users who want to push the boundaries of what is possible in ion analysis. Accelerate your Productivity • Single- and dual-channel system configuration options • Finger-tight connections that minimize dead volume and make connections easier • Automated tracking of the usage and performance of IC consumables • Automated eluent preparation using Reagent-Free IC-Eluent Generation (RFIC-EG™) technology • Tablet control of the IC system, to easily monitor sample runs • An optional, always ready capillary IC configuration to perform 24/7 sample analysis • IC columns featuring 4 μm particles to optimize chromatographic efficiency with shorter sample run times and/or improved resolution Explore the Possibilities The Dionex ICS-6000 HPIC system is available in a variety of configurations, including: • Standard bore, microbore, and capillary formats • Multiple, flexible detector options Discover Ion Chromatography-Mass Spectrometry The Dionex ICS-6000 HPIC system is compatible with single quadrupole, triple quadrupole, and high-resolution accurate-mass (HRAM) Thermo Scientific™ Orbitrap™ mass analyzer-based mass spectrometers for performing powerful ion chromatography-mass spectrometry (IC-MS) analyses. Solve Complex Analysis Challenges The Dionex ICS-6000 HPIC system can address the full range of IC analysis applications. It is suitable for techniques from 2-D ion chromatography for trace-level analysis to high-performance anionexchange chromatography with pulsed amperometric detection (HPAE-PAD) for complex carbohydrate analyses.

122


Br. J. Anal. Chem., 2019, 6 (22)

Release

DMA-80 - The most successful Hg analyzer in the market The Milestone DMA-80 is a direct mercury analyzer of solid, liquid, and gas samples, based on the principles of sample thermal decomposition, mercury amalgamation and atomic absorption detection. Analysis time is 5 minutes only and no sample preparation is required. With over 1300 units installed in 80 different countries worldwide, the DMA-80 is the most successful direct mercury analyzer in the market.

8 good reasons to choose the Milestone DMA-80 No sample preparation - The DMA-80 does not require any sample preparation or other wet chemistry prior the analysis. This means ease of use, low running cost and no need for hazardous chemicals to purchase, handle and dispose. Best analytical performance - Combining an innovative mercury measuring system with a unique optical path spectrophotometer, the DMA-80 achieves a detection limit as low as 0.001 nanograms of mercury and is capable of measuring up to 30,000 nanograms of mercury, equivalent to a concentration of 300 mg/kg (300 ppm) on a 100 mg sample analysis. Ease of use - Just weigh your sample, load it onto the built-in auto-sampler and press ‘start’. The DMA80 is so simple to use that it can be operated in the field, not only in the analytical laboratory. High productivity - The DMA-80 is incredibly fast. A complete analysis -start to finish, takes 5 minutes. Sample weight is automatically transferred from the analytical balance. The dual-tray auto-sampler allows sample loading ‘on-the-fly’, for a continuous operation of the instrument. Lowest cost of analysis - Ease of use, speed of analysis, catalyst and amalgamator long lifetime, sample boats durability and the possibility of using air as combustion and carrier gas minimize the DMA-80 cost of analysis. Easy maintenance - All the DMA-80 components, such as the catalytic furnace, amalgamator and spectrophotometer, are easily accessible for routine cleaning and maintenance. Largest installed base - With over 1300 units installed in 80 different Countries worldwide, Milestone is the acknowledged market leader in direct mercury determination. Our extensive experience enables us to provide the highest level of application and service support. Official methods compliance - The DMA-80 has been used to develop the US EPA method 7473 (Mercury in solids and solutions by thermal decomposition, amalgamation, and atomic absorption spectrophotometry). It is furthermore compliant with ASTM method D-6722-01 (Total mercury in coal and coal combustion residues) and ASTM method D-7623- 10 (Total mercury in crude oil).

124


Release

Br. J. Anal. Chem., 2019, 6 (22)

Pittcon Conference & Expo Pittcon is the worldâ&#x20AC;&#x2122;s leading annual conference and exposition for laboratory science.

Pittcon not only covers analytical chemistry and spectroscopy, but also showcases developments made in the field of food safety, environmental sciences, bioterrorism, pharmaceuticals, and more. Pittcon attracts attendees from industry, academia and government from more than 90 countries worldwide. It is a great opportunity to network with colleagues. Cutting Edge Research The high-caliber technical program features scientists from around the world. With more than 2,000 technical sessions, Pittcon makes it easy for you to get connected to the latest research and developments from leading scientists from around the world. The robust technical program offers the latest research covering a diverse selection of methodologies and applications. Skill-Building Short Courses Offered at beginner and intermediate levels. With more than 100 from which to choose, there are a wide variety of classes covering relevant analytical topics in food science, water/wastewater, environmental, life science, pharmaceutical. Courses for broad-based application and general lab functions include lab management, quality control, technical writing, statistics, data management, and lab safety. 3 Day Expo This global exposition gives you the opportunity to get a hands-on look at the latest laboratory instrumentation, participate in live demos and product seminars, talk with technical experts, and find solutions to all your laboratory challenges.

For more information, please visit https://pittcon.org

126


The robust technical program oďŹ&#x20AC;ers the latest research in more than 2,000 technical presentations covering a diverse selection of methodologies and applications.

Pittcon also oďŹ&#x20AC;ers more than 100 skill -building short courses in a wide range of topics

Opportunity to network with colleagues.

What is Pittcon? Pittcon is the worldâ&#x20AC;&#x2122;s leading annual conference and exposition on laboratory science. Pittcon attracts attendees from industry, academia and government from over 90 countries worldwide.


Release

Br. J. Anal. Chem., 2019, 6 (22)

SelectScience® pioneers online communication and promotes scientific success since 1998 Working with Scientists to Make the Future Healthier SelectScience® promotes scientists and their work, accelerating the communication of successful science. SelectScience® informs scientists about the best products and applications through online peer-to-peer information and product reviews. Scientists can make better decisions using independent, expert information and gain easy access to manufacturers. SelectScience® informs the global community through Editorial, Q&A and Application Articles, Featured Topics, Event Coverage, Video and Webinar programs. Some recent contributions from SelecScience® to the scientific community • Editorial Feature How Scientists Can Predict the Properties of Energy Crops for Efficient Conversion of Biomass Feedstock Learn how FTIR technology is helping to build chemometric models to predict quality parameters of energy grasses. As energy producers move towards biomass as an energy source, there is an increasing need to produce a sustainable supply of quality energy crops. This requires the ability to accurately measure and predict the chemical qualities of this fuel type to ensure efficient energy conversion. Read this full text here • Materials Update Technologies Enhancing the Metals and Mining Industry Mining, analysis and production of metals require a broad range of instrumentation and technology to ensure quality control and analysis of raw materials. In this Materials Update article, SelectScience® brings together all the latest news, application notes and videos in the metals and mining community. Read this full text here The future is closer than you think For two decades, SelectScience has been publishing news and content from the front line of scientific advancement, improving communication between leading scientists and the biggest and best manufacturers across the globe, as we work towards one common goal - making the future healthier. In 2040 - where will we be – a disease-free humanity, producing super-foods, or even super-humans? We welcome you to explore what the future of science could like, meet the people making that happen, and discover how they intend to do it. Access “The Future of Science - How science could change your life by 2040” here

128


SelectScienceÂŽ is the leading independent online publisher connecting scientists to the best laboratory products and applications. Access 2 Million+ Decision Makers

Working with Scientists to Make the FutWorking with Scientists to Make the Future Healthier. Informing scientists about the best products and applications. Connecting manufacturers with their customers to develop, promote and sell technologies.ure Healthier.


Release

Br. J. Anal. Chem., 2019, 6 (22)

CHROMacademy helps increase your knowledge, efficiency and productivity in the lab

CHROMacademy is the world’s largest eLearning website for analytical scientists. With a vast library of high-quality animated and interactive eLearning topics, webcasts, tutorials, practical information and troubleshooting tools CHROMacademy helps you refresh your chromatography skills or learn something completely new. A subscription to CHROMacademy provides you with complete access to all content including: • Thousands of eLearning topics covering HPLC / GC / Sample Prep / Mass Spec / Infrared / Basic Lab Skills / Biochromatography Each channel contains e-Learning modules, webcasts, tutorials, tech tips, quick guides and interactive tools and certified assessments. • Video Training Courses Each course contains 4 x 1.5-hour video training sessions, released over 4 weeks, with full tutor support and certification. • Ask the Expert – 24-hour Chromatography Support A team of analytical experts are on hand to help fix your instrument and chromatographic problems, offer advice on method development & validation, column choice, data analysis and much more. • Assessments Test your knowledge, certificates awarded upon completion. • Full archive of Essential Guide Webcasts and Tutorials Over 70 training topics covered by industry experts. • Application Notes and LCGC Articles The latest application notes & LCGC articles. • Troubleshooting and Virtual Lab Tools Become the lab expert with our HPLC and GC Troubleshooters. • User Forum Communicate with others interested in analytical science. Lite members have access to less than 5% of CHROMacademy content. Premier members get so much more!

For more information, please visit www.chromacademy.com/subscription.html 130


Release

Br. J. Anal. Chem., 2019, 6 (22)

Women in Science: The Federal University of Pelotas discusses the Challenges and Perspectives of Including New Talent September 25 and 26, 2019 The Pelotense Public Library (opening ceremony), and the Auditorium of the UFPel Arts Center in Pelotas, RS, Brazil

Discussion is growing worldwide on the role of women in science and on the discrepancies in gender equity. Currently, women make up only 30 percent of the worldâ&#x20AC;&#x2122;s scientific community. The Federal University of Pelotas will on 25 and 26 September 2019 hold an event to discuss the general panorama of womenâ&#x20AC;&#x2122;s activities in science and encourage the inclusion of new talent. The event will consist of roundtables where prominent national and international professionals will address the main challenges and perspectives on the role of women in the labor market. In addition, there will be four lectures featuring representatives of governmental and scientific bodies, during which inclusive, interdisciplinary and dynamic themes will be addressed to encourage participant interest and reflection on important scientific aspects affecting daily life that are not usually highlighted. This event will have a significant impact on the scientific community and local society, and may stimulate the development of other activities in inclusive and egalitarian actions related to gender. Approximately 150 participants will attend including teachers and researchers, undergraduate and postgraduate students from various institutions, as well as other members of the community who are interested in the subject.

Register online at: https://wp.ufpel.edu.br/elasnaciencia/

132


Notices of Books

Br. J. Anal. Chem., 2019, 6 (22)

Green Analytical Chemistry, 2nd Edition

Mihkel Koel, Mihkel Kaljurand, Authors March 2019. Publisher: Royal Society of Chemistry Chemical analysis requires solvents, reagents and energy, and generates waste. The main goal of green analytical chemistry is to avoid or reduce the undesirable environmental side effects of chemical analysis, while preserving the classic analytical parameters of accuracy, sensitivity, selectivity and precision. This book focuses on sample preparation techniques minimizing solvent consumption or using alternative solvents, concepts and methods of improving the ‘greenness’ of instrumental analysis where miniaturization is an important part, separation methods from the perspective of green analytical chemistry and chemometrics approaches, which can reduce or can even remove the need for conventional steps in chemical analysis. Read more

HPLC and UHPLC for Practicing Scientists, 2nd Edition

Michael W. Dong, Author August 2019. Publisher: John Wiley & Sons A concise yet comprehensive reference guide on HPLC/UHPLC that focuses on its fundamentals and latest developments. Written for practitioners by an expert practitioner, this new edition adds numerous updates to its coverage of HPLC, including comprehensive information on UHPLC and the continuing migration of HPLC to UHPLC, the modern standard platform. In addition to introducing readers to HPLC’s fundamentals, applications, and developments, the book describes basic theory and terminology for the novice, and reviews relevant concepts, best practices, and modern trends for the experienced practitioner. Read more

Mass Spectrometry: An Applied Approach, 2nd Edition

Marek Smoluch, Giuseppe Grasso, Piotr Suder, Jerzy Silberring Editors July 2019. Publisher: John Wiley & Sons This book provides a comprehensive description of mass spectrometry basics, applications, and perspectives. It describes everything readers need to know about mass spectrometry — from the instrumentation to the theory and applications. It looks at all aspects of mass spectrometry, including inorganic, organic, forensic, and biological MS. It also contains a list of key terms for easier and faster understanding of the material by newcomers to the subject and test questions to assist lecturers. Read more

Practical Inductively Coupled Plasma Spectrometry, 2nd Edition

John R. Dean, Author March 2019. Publisher: John Wiley & Sons The second edition of this book discusses many of the significant developments in the field which have expanded ICP spectrometry from a useful optical emission spectroscopic technique for trace element analysis into a source for both atomic emission spectrometry and mass spectrometry, capable of detecting elements at subppb (ng mL−1) levels with good accuracy and precision. Comprising nine chapters, this new edition has been fully revised and up-dated in each chapter. Read more

133


Notices of Books

Books launched at the 19th ENQA Metallomics - The Science of Biometals

Marco Aurélio Zezzi Arruda, Editor June 2018, Springer International Publishing As Metallomics is intrinsically a transdisciplinary area, this book is authored by experts in Environmental, Nuclear, and Human Metallomics fields. Within these topics metals play important role, as being part of biomolecules, controlling different biochemical process, being signaling agents, being catalyst of biochemical reactions, among others. This volume demonstrates the importance of more investigation about metals and their interactions with biomolecules. Read more

Ciências do vinho: Noções básicas de enologia para curiosos enófilos

Eric de Souza Gil, Author 2018. Publisher: Editora da Universidade Federal de Goiás This book stands out with respect to the rigor given to the oenology, in particular to the Brazilian oenology, the number of grape varieties contemplated, the detail given to the techniques of production and quality control of wines, as well as to relate succinctly the chemical and its biological properties, including sensory properties. This book was written by post-graduate oenophiles in the areas of human, exact and biological. Read more

134


Periodicals & Websites

Br. J. Anal. Chem., 2019, 6 (22)

American Laboratory The American Laboratory® publication is a platform that provides comprehensive technology coverage for lab professionals at all stages of their careers. Unlike singlechannel publications, American Laboratory® is a multidisciplinary resource that engages scientists through print, digital, mobile, multimedia, and social channels to provide practical information and solutions for cutting-edge results. Addressing basic research, clinical diagnostics, drug discovery, environmental, food and beverage, forensics, and other markets, American Laboratory combines in-depth articles, news, and video to deliver the latest advances in their fields. Read more LCGC Chromatographyonline.com is the premier global resource for unbiased, peerreviewed technical information on the field of chromatography and the separation sciences. Combining all of the resources from the regional editions (LCGC North America, LCGC Europe, and LCGC Asia-Pacific) of award winning magazines, Chromatographyonline delivers practical, nuts-and-bolts information to help scientists and lab managers become more proficient in the use of chromatographic techniques and instrumentation, thereby making laboratories more productive and businesses around the world more successful. Read more Scientia Chromatographica Scientia Chromatographica is the first and to date the only Latin American scientific journal dedicated exclusively to Chromatographic and Related Techniques (Mass Spectrometry, Sample Preparation, Electrophoresis, etc.). With a highly qualified and internationally recognized Editorial Board, it covers all chromatography topics (HPLC, GC, SFC) in all their formats, in addition to discussing related topics such as “The Pillars of Chromatography”, Quality Management, Troubleshooting, Hyphenation (GC-MS, LC-MS, SPE-LC-MS/MS) and others. It also provides columns containing general information, such as: calendar, meeting report, bookstore, etc. Read more Select Science SelectScience® promotes scientists and their work, accelerating the communication of successful science. SelectScience® informs scientists about the best products and applications through online peer-to-peer information and product reviews. Scientists can make better decisions using independent, expert information and gain easy access to manufacturers. SelectScience® informs the global community through Editorial, Features, Video and Webinar programs. Read more Spectroscopy Spectroscopy’s mission is to enhance productivity, efficiency, and the overall value of spectroscopic instruments and methods as a practical analytical technology across a variety of fields. Scientists, technicians, and laboratory managers gain proficiency and competitive advantage for the real-world issues they face through unbiased, peer-reviewed technical articles, trusted troubleshooting advice, and best-practice application solutions. Read more

135


Events

Br. J. Anal. Chem., 2019, 6 (22)

2019 February 11 - 13 Brazilian Congress of Materials Microscopy - XV Micromat Brazilian Nanotechnology National Laboratory (LNNano), Campinas, SP, Brazil https://www.sbmm.org.br/ February 28 – March 1th 10th Edition of International Conference on Analytical Chemistry London, UK https://analyticalchemistry.euroscicon.com/ March 17 - 21 PITTCON Conference and Expo 2019 Pennsylvania Convention Center, Philadelphia, PA, USA https://pittcon.org/pittcon-2019/ March 25-28 35th International Symposium on Microscale Separations and Bioanalysis CH2M HILL Alumni Center, Oregon State University, Corvallis, Oregon, USA https://msb2019.org/ May 12 – 18 43rd International Symposium on Capillary Chromatography & 16th GCxGC Syposium Hilton Fort Worth, Fort Worth, TX, USA https://www.isccgcxgc.com/ May 27 - 30 42nd Annual Meeting of the Brazilian Chemical Society (42nd RASBQ) Centro de Convenções Expoville, Joinville, SC, Brazil http://www.sbq.org.br/reunioes-anuais June 16 - 20 48th International Symposium on High-Performance Liquid Phase Separations and Related Techniques (HPLC 2019) University of Milano-Bicocca, Milan, Italy https://www.hplc2019-milan.org/ July 7-12 IUPAC 47th World Chemistry Congress Palais des Congrès, Paris, FR www.iupac2019.org July 14 - 19 Latin American Congress on Chromatography and Related Techniques (COLACRO XVII) Unit – Universidade Tiradentes, Aracaju, SE, Brazil https://www.colacro2019.com

136


Events

September 1 - 5 Brazilian Symposium of Electrochemistry and Electroanalysis - XXII SIBEE Convention Center Ribeirão Preto, Ribeirão Preto, SP, Brazil www.xxiisibee.com.br September 1 - 5 Euroanalysis XX - Europe’s Analytical Chemistry Meeting Istanbul, Turkey http://euroanalysis2019.com/ September 3 - 5 Brazilian Meeting on Chemical Speciation - EspeQBrasil-2019 Universidade Federal da Bahia, Campus de Ondina, Salvador, BA, Brazil http://www.espeqbrasil2019.ufba.br/ September 8 - 11 133rd AOAC Annual Meeting & Exposition Sheraton Denver Downtown Hotel, Denver, CO, USA http://www.aoac.org September 24 - 26 15th Analitica Latin America Expo & 6th Analitica Congress Centro de Exposições São Paulo Expo, São Paulo, SP, Brazil https://www.analiticanet.com.br/en September 25 - 26 Women in Science: The Federal University of Pelotas discusses the Challenges and Perspectives of Including New Talent Pelotense Public Library (opening ceremony) and the Auditorium of the UFPel Arts Center, Pelotas, RS, Brazil https://wp.ufpel.edu.br/elasnaciencia/ October 28 - 31 XXI Brazilian Congress of Toxicology & XV The International Association of Forensic Toxicologists (TIAFT) Latin-American Regional Meeting Águas de Lindóia, SP, Brazil http://www.cbtox-tiaft.org/ November 5 - 8 9th International Symposium on Recent Advances in Food Analysis - RAFA 2019 Prague, Czech Republic http://www.rafa2019.eu November 6 - 8 XIV Latin American Symposium on Environmental Analytical Chemistry (LASEAC) & IX National Meeting on Environmental Chemistry (ENQAmb) Bento Gonçalves, RS, Brazil http://www.laseac2019.furg.br

137


Guidelines for Authors

Br. J. Anal. Chem., 2019, 6 (22) pp 138-140 PDF

Scope The Brazilian Journal of Analytical Chemistry (BrJAC) is dedicated to the diffusion of significant and original knowledge in all branches of Analytical Chemistry. BrJAC is addressed to professionals involved in science, technology and innovation projects in Analytical Chemistry, at universities, research centers and in industry. Professional Ethics Manuscripts submitted for publication in BrJAC cannot have been previously published or be currently submitted for publication in another journal. BrJAC publishes original, unpublished scientific articles and technical notes that are peer reviewed in the double-blind way. Review process BrJAC’s review process begins with an initial screening of the manuscripts by the editor-in-chief, who evaluates the adequacy of the study to the journal scope. Manuscripts accepted in this screening are then forwarded to at least two reviewers who are experts in the related field. As evaluation criteria, the reviewers employ originality, scientific quality, contribution to knowledge in the field of Analytical Chemistry, the theoretical foundation and bibliography, the presentation of relevant and consistent results, compliance to the BrJAC’s guidelines, and the clarity of writing and presentation. BrJAC is a quarterly journal that, in addition to scientific articles and technical notes, also publishes reviews, interviews, points of view, letters, sponsor reports, and features related to analytical chemistry. Brief description of the documents that can be submitted by the authors • Articles: Full descriptions of an original research finding in Analytical Chemistry. Articles undergo double-blind full peer review. • Reviews: Articles on well-established subjects, including a critical analysis of the bibliographic references and conclusions. Manuscripts submitted for publication as reviews must be original and unpublished. Reviews undergo double-blind full peer review. • Technical Notes: Concise descriptions of a development in analytical method, new technique, procedure or equipment falling within the scope of BrJAC. Technical notes also undergo doubleblind full peer review. The title of the manuscript submitted for technical note must be preceded by the words “Technical note”. • Letters: Discussions, comments, suggestions on issues related to Analytical Chemistry, and consultations to authors. Letters are welcome and will be published at the discretion of the BrJAC editor-in-chief. • Points of view: The expression of a personal opinion on some relevant subject in Analytical Chemistry. Points of View are welcome and will be published at the discretion of the BrJAC editor-in-chief. • Releases: Articles providing new and relevant information for the community involved in Analytical Chemistry. Download a template here Path: Log In / Manuscript Submission / Online Submission

Manuscript (MS) preparation • Language: English is the language adopted by BrJAC. • Required items: the MS must include a title, a graphical abstract, an abstract, keywords, and the following sections: Introduction, Materials and Methods, Results and Discussion, Conclusion, and References. • Identification of authors: the MS must NOT contain the authors’ names nor affiliations. This information must be in the cover letter to the editor-in-chief. This rule is necessary because the MS is subjected to double-blind review. • Layout: the lines in the MS must be numbered consecutively and double-spaced throughout the text. 138


Guidelines

• Graphics and Tables: must appear close to the discussion about them in the text. For figures use Arabic numbers, and for tables use Roman numbers. • Permission to use content already published: for figures, graphs, diagrams, tables, etc. identical to others previously published in the literature, the author must ask for publication permission from the company or scientific society holding the copyrights, and send this permission to the BrJAC editor-in-chief with the final version of the manuscript. • Chemical nomenclature: should conform to the rules of the International Union of Pure and Applied Chemistry (IUPAC) and Chemical Abstracts Service. It is recommended that, whenever possible, authors follow the International System of Units, the International Vocabulary of Metrology (VIM) and the NIST General Table of Units of Measurement. Abbreviations are not recommended except those recognized by the International Bureau of Weights and Measures or those recorded and established in scientific publications. • References: must be cited by numbers in square brackets. It is recommended that references older than 5 (five) years be avoided, except in relevant cases. Include references that are accessible to readers. References should be thoroughly checked for errors by the authors before submission. See how to format the references in the following item. Examples of reference formatting Journals 1. Orlando, R. M.; Nascentes, C. C.; Botelho, B. G.; Moreira, J. S.; Costa, K. A.; Boratto, V. H. M. Anal. Chem. 2019, 91 (10), pp 6471-6478 (https://doi.org/10.1021/acs.analchem.8b04943).

• Publications with more than 10 authors, list the first 10 authors followed by a semicolon and et al. • Titles of journals must be abbreviated as defined by the Chemical Abstracts Service Source Index (http:// cassi.cas.org/search.jsp).

Electronic journals 2. Sapozhnikova, Y.; Hoh, E. LCGC North Am. 2019, 37 (1), pp 52-65. Available from: http:// www.chromatographyonline.com/suspect-screening-chemicals-food-packaging-plastic-filmcomprehensive-two-dimensional-gas-chromatogr [Accessed 20 January 2019]. Books 3. Burgot, J.-L. Ionic Equilibria in Analytical Chemistry. Springer Science & Business Media, New York, 2012, Chapter 11, p 181. 4. Griffiths, W. J.; Ogundare, M.; Meljon, A.; Wang, Y. Mass Spectrometry for Steroid Analysis. In: Mike, S. L. (Ed.). Mass Spectrometry Handbook, v. 7 of Wiley Series on Pharmaceutical Science and Biotechnology: Practices, Applications and Methods. John Wiley & Sons, Hoboken, N.J., 2012, pp 297-338. Standard methods 5. International Organization for Standardization. ISO 26603. Plastics — Aromatic isocyanates for use in the production of polyurethanes — Determination of total chlorine. Geneva, CH: ISO, 2017. Master’s and doctoral theses or other academic literature 6. Dantas, W. F. C. Application of multivariate curve resolution methods and optical spectroscopy in forensic and photochemical analysis. Doctoral thesis, 2019, Institute of Chemistry, University of Campinas, Campinas, SP, Brazil. Patents 7. Trygve, R.; Perelman, G. US 9053915 B2, June 9, 2015, Agilent Technologies Inc., Santa Clara, CA, US. 139


Guidelines

Web pages 8. http://www.chromedia.org/chromedia [Accessed 10 January 2019]. Unpublished source 9. Viner, R.; Horn, D. M.; Damoc, E.; Konijnenberg, A. Integrative Structural Proteomics Analysis of the 20S Proteasome Complex (WP-25). Poster presented at the XXII International Mass Spectrometry Conference (IMSC 2018) / August 26-31, 2018, Florence, IT. 10. Author, A. A. J. Braz. Chem. Soc., in press. 11. Author, B. B., 2017, submitted for publication. 12. Author, C. C., 2018, unpublished manuscript. Note: Unpublished results may be mentioned only with express authorization of the author(s). Personal communications can be accepted exceptionally.

Download templates here Path: Log In / Manuscript Submission / Online Submission Manuscript submission Three different files, as described below, must be sent online through the website www.brjac.com.br 1. A Cover Letter (PDF file): addressed to the editor-in-chief, with the manuscript title, the full names of the authors and their affiliations, and the complete contact information of the corresponding author, including the ORCID iD. This letter should also inform to which section of the BrJAC the manuscript is being submitted (e.g. Article, Review, Technical Note, Point of View or Letter). The cover letter should also contain a statement that the article has not been previously published and is not under consideration for publication elsewhere. 2. The manuscript PDF file that must NOT mention the names of the authors nor their affiliations. 3. A similarities analysis report on the manuscript obtained through an anti-plagiarism software. (BrJAC indicates CopySpiderŠ freeware to support similarities checking analyzes. Download the CopySpider freeware at: www.copyspider.com.br

Revised manuscript submission Based on the comments and suggestions of the reviewers and editors a revision of the manuscript may be requested to the authors. A revised manuscript should be submitted by the authors, containing the changes made in the manuscript clearly highlighted. Letters to the reviewers, one to each reviewer, must also be submitted answering in detail to the questions made by them, and describing the changes made in the manuscript. Copyright When submitting their manuscript for publication, the authors agree that the copyright will become the property of the Brazilian Journal of Analytical Chemistry, if and when accepted for publication. The copyright comprises exclusive rights of reproduction and distribution of the articles, including reprints, photographic reproductions, microfilms or any other reproductions similar in nature, including translations. Final Considerations Whatever the nature of the submitted manuscript, it must be original in terms of methodology, information, interpretation or criticism. As to the contents of published articles, the sole responsibility belongs to the authors, and Br. J. Anal. Chem. and its editors, editorial board, employees and collaborators are fully exempt from any responsibility for the data, opinions or unfounded statements. BrJAC reserves the right to make, whenever necessary, small alterations to the manuscripts in order to adapt them to the journal rules or make them clearer in style, while respecting the original contents. The article will be sent to the authors for approval prior to publication.

140


Profile for BrJAC

BrJAC - N22  

BrJAC - N22