Contents
Contributorsxi
1.Milestonesinthedevelopmentofgas chromatography
WALTERG.JENNINGSANDCOLINF.POOLE
1.1Introduction1
1.2Theinventionofgaschromatography1
1.3Earlyinstrumentation2
1.4Earlycolumndevelopments3
1.5Interfacingglasscapillarycolumnstoinjectorsand detectors6
1.6TheHindelangconferencesandthefused-silica column7
1.7Increasingsophisticationofinstrumentation9
1.8Declineintheexpertiseoftheaveragegas chromatographer15
References16
Furtherreading17
2.Theoryofgaschromatography
LEONIDM.BLUMBERG
2.1Introduction19
2.2Nomenclatureandotherconventions20
2.3Generaldefinitionsandconventions23
2.4Solute columninteraction23
2.5Propertiesofidealgas29
2.6Flowofidealgasinopentubes33
2.7Solutemigrationandelution37
2.8Peakspacingandreversalofelutionorder45
2.9Peakwidth48
2.10Performancemetrics67
2.11Optimization73 References92
3.Columntechnology:open-tubular columns
FRANKL.DORMANANDPETERDAWES
3.1Introduction99
3.2Overviewofthefused-silicadrawingprocess100
3.3Thepreform rawmaterial100
3.4Surfacechemistry101
3.5Drawingofthecapillaryfromthepreform101
3.6Protectivecoating103
3.7Alternativeprotectivecoatings104
3.8Cleanroomenvironment105
3.9Qualitymonitoring105
3.10Observationsonhandlingoffused-silicacapillary tubing107
3.11Columntechnology coatingthestationary phase108
3.12Stationaryphases111
3.13Coatingtechniques112
3.14Columntechnology qualityevaluation114
3.15Columntechnology summary116 References116
4.Columntechnology:porouslayer open-tubularcolumns
JAAPDEZEEUW
4.1Introduction117
4.2Challengesinporouslayeropen-tubular(PLOT) columnchemistry117
4.3MeasurementofrestrictionofPLOTcolumns119
4.4ManufactureofPLOTcolumns119
4.5Stabilizationofadsorptionlayers121
4.6Behaviorofadsorbents122
4.7PLOTcolumnsingaschromatography mass spectrometry123
4.8Typesofcapillarytubing123
4.9Mostcommonlyusedadsorbents124
4.10Summary138 References140
5.Columntechnology:packedcolumns COLINF.POOLE
5.1Introduction141
5.2Gas liquidchromatography142
5.3Gas solidchromatography158 References161
6.Columnclassificationandstructureretentionrelationships
COLINF.POOLE
6.1Introduction165
6.2Stationary-phaseclassi fication167
6.3Structure retentionrelationships181 References186
7.Multidimensionalandcomprehensivegas chromatography
JOHNV.SEELEY
7.1Introduction191
7.2Agraphicalrepresentationof2DGC separations193
7.3Backflushing2DGC195
7.4Heartcutting2DGC200
7.5Comprehensive2DGC203
7.6Conclusions211
References213
8.Sampleintroductionmethods ANDREWTIPLER
8.1Introduction217
8.2Choosingasampleintroduction system218
8.3Supportingdevices218
8.4Thecoldon-columninjector223
8.5The flashvaporizationinjector229
8.6Thesplit/splitlessinjector231
8.7Theprogrammable-temperaturevaporizing(PTV) injector240
8.8Thegassamplingvalve246
8.9Theliquidsamplingvalve247 Acknowledgments247 References249
9.Headspacegaschromatography
MICHAELJ.SITHERSINGHANDNICHOLASH.SNOW
9.1Introduction251
9.2Fundamentalsofheadspaceextraction253
9.3Instrumentationandpractice257
9.4Methoddevelopmentconsiderations262 Acknowledgments264 References264
10.Thermaldesorptiongaschromatography ELIZABETHWOOLFENDEN
10.1Generalintroductiontothermaldesorption267
10.2Briefhistoryofthermaldesorption essential functionsandperformancecharacteristics270
10.3TheevolutionofTDtechnology important milestones276
10.4Usingthermaldesorptiontoenhanceanalysisof complexliquidandsolidsamples285
10.5Samplingoptionsforthermaldesorption288
10.6Anintroductiontothermaldesorption applications288
10.7Breathmonitoring290
10.8Airmonitoring291
10.9Chemicalemissionsfromeverydayproductsto indoorandin-vehicleair295
10.10Toxicchemicalagentsandcivildefense299
10.11Directthermaldesorptionofresidual volatiles299
10.12Odor/fragranceprofilingandVOC “fingerprinting” 301
10.13Forensicapplications306
10.14Monitoringmanufacturingandotherindustrial chemicalprocesses309 AppendixA309 AppendixB314 References316
11.Pyrolysis-gaschromatography KAREND.SAM
11.1Introduction325
11.2Moleculartheory326
11.3Instrumentation329 11.4Applications330 References342
12.Conventionaldetectorsforgas chromatography COLINF.POOLE
12.1Introduction343
12.2Ionization-baseddetectors345
12.3Bulkphysicalpropertydetectors358
12.4Opticaldetectors360
12.5Electrochemicaldetectors366 References367
13.Molecularspectroscopicdetectorsforgas chromatography
ARIELM.O’BRIENANDKEVINA.SCHUG
13.1Introduction371
13.2Milestones372
13.3GaschromatographyFouriertransforminfrared spectroscopy373
13.4Gaschromatographyvacuumultraviolet spectroscopy382
13.5Comparisonoftechniques390
13.6Conclusionsandfuture outlook394
References394
14.Massspectrometricdetectorsforgas chromatography
DAVIDJ.HARVEY
14.1Introduction399
14.2Gaschromatography massspectrometry interfaces399
14.3Ionizationtechniques402
14.4Methodsofmassseparation409
14.5Modesofoperation414
14.6Dataanalysis417
14.7Samplepreparation420
14.8Conclusions420
References423
15.Ionmobilitydetectorsforgas chromatography
MARIAJOSECARDADOR,NATIVIDADJURADO-CAMPOSAND LOURDESARCE
15.1Introduction425
15.2IMSoperation426
15.3IMSdevicecomponents427
15.4TypesofIMSinstruments430
15.5LimitationsofIMS432
15.6FundamentalsofGC-IMS432
15.7TypesofIMScoupledtoGC433
15.8DataobtainedfromGC-IMS instruments434
15.9TreatmentofIMSdata435
15.10AdvantagesanddisadvantagesofGC-IMS analysis438
15.11Applications439 References442
16.Speciationandelement-selectivedetection bygaschromatography
QILINCHANANDJOSEPHA.CARUSO
16.1Introductiontoplasma-baseddetectors449
16.2GC-ICPMS451
16.3GC-MIPandGC-GD454
16.4SamplepreparationforGC plasma spectroscopy457
16.5AdvancesinapplicationsofGC plasma spectroscopy457
16.6Conclusionsandperspectives462 References462
17.Fieldandportableinstrumentsforgas chromatography
STANLEYD.STEARNS
17.1History469
17.2Designchallenges472
17.3Sampleintroduction472
17.4Columnconfigurations474
17.5Detectors476
17.6Gassupply477
17.7Powermanagement478
17.8Prototyping481
17.9CommercialportableGCscurrentlyavailable482
17.10Futuretrends482
Acknowledgments485 References485
18.Preparativegaschromatography
LEESUNKIMANDPHILIPJ.MARRIOTT
18.1Introduction487
18.2Applicationscaleofpreparativegas chromatography488
18.3Experimentaltechniquesforanalytical-scale prep-GC489
18.4Casestudies:applications494
18.5Conclusions502
Acknowledgments502 References502
19.Dataacquisitionandintegration
YURIKALAMBET
19.1Introduction505
19.2Equipmentcontrolandsignalmeasurement506
19.3Peaksearch508
19.4Errorscausedbydiscretization(datarate)and conversion(bitpricevalue)512
19.5Smoothing514
19.6Peakidentification517
19.7Quantification518 References521
20.Dataanalysismethodsforgas chromatography
KARISAM.PIERCE,TIMOTHYJ.TRINKLEIN,JEREMYS.NADEAU ANDROBERTE.SYNOVEC
20.1Introduction525
20.2Preprocessing527
20.3Patternrecognition533
20.4Calibration540
20.5Experimentalmethodoptimization541
20.6Conclusion542 References542
21.Validationofgaschromatographic methods
BIEKEDEJAEGHER,JOHANNASMEYERS-VERBEKEAND YVANVANDERHEYDEN
21.1Introduction547
21.2Regulatoryaspects548
21.3Methodvalidationitems548
21.4Accuracypro files559 References559
22.Physicochemicalmeasurements(inversegas chromatography)
ADAMVOELKEL
22.1Introduction561
22.2Gas solidinversegaschromatography562
22.3Bulkpropertiesofpolymersandpolymers blends569 References573
23.Separationofstereoisomersbygas chromatography
CECILIACAGLIERO,BARBARASGORBINI,CHIARACORDERO, ERICALIBERTO,PATRIZIARUBIOLOANDCARLOBICCHI
23.1Introduction581
23.2Chiralstationaryphasesforenantioselectivegas chromatography583
23.3Determinationoftheenantiomeric distribution595
23.4Strategyforachievingchiralrecognition596
23.5Totalanalysissystemsandchiralrecognitionof complexsamples604
23.6Micropreparativeenantioselectivegas chromatography604
23.7Conclusions606
References606
24.Samplepreparationforgaschromatography COLINF.POOLE
24.1Introduction615
24.2Isolationandconcentrationtechniquesusing physicalmethods616
24.3Samplecleanupbycolumnchromatography635
24.4Microchemicalreactionsformodificationoftarget compound638
References648
25.Petrochemicalapplicationsofgas chromatography
JULIANACRUCELLO,NATHALIADEAGUIARPORTO, ROGÉRIOMESQUITACARVALHO, ALEXANDREDEANDRADEFERREIRA, CARLOSALBERTOCARBONEZIAND LEANDROWANGHANTAO
25.1Introduction655
25.2Columnselectionaccordingtosample volatility659
25.3Introductiontoorganicgeochemicalanalyses660
25.4Refineryoilassays663
References669
26.Gaschromatographicanalysisof essentialoils
K.HUSNUCANBAŞERANDTEMEL OZEK
26.1Definitions:whatisessentialoil?Whatare fragrances?675
26.2GCphasesusedintheanalysisofessentialoilsand aromachemicals676
26.3Separationcriteriaandtechniques676
26.4Retentionindex679
26.5Qualitativeandquantitativeaspects679
26.6GC-MSlibraries679
26.7Conclusions680
References681
27.Gaschromatographicanalysisoflipids
CRISTINACRUZ-HERNANDEZANDFRÉDÉRICDESTAILLATS
27.1Introduction683
27.2FattyacidanalysisbyGCasmethylester derivatives684
27.3Analysisoffreefattyacidsandacylglycerols690
27.4Analysisofsterols,sterolesters,stanylesters,and sterylglycosides691
27.5Analysisofwaxes693 References693
28.Gaschromatographicanalysisof carbohydrates
A.C.SORIA,A.MENA,A.I.RUIZ-MATUTEANDM.L.SANZ
28.1Introduction703
28.2Samplepreparation704
28.3Derivatization708
28.4Chromatographicconditionsfortheanalysisof carbohydrates713
28.5Structuralelucidationoflow-molecular-weight carbohydrates716
28.6GC-MSanalysisofoligo-andpolysaccharides719
28.7Comprehensivetwo-dimensionalgas chromatography720 References721
29.Gaschromatographicapplicationsin metabolomics
SZEHANLEE,MAINAKMAL,KISHOREKUMARPASIKANTIAND ERICCHUNYONGCHAN
29.1Overviewofmetabonomics727
29.2Analyticaltoolsinmetabonomicresearch728
29.3GC-MS-basedmetabonomics728
29.4Metabonomicsofsolidsamples733
29.5Metabonomicsofliquidsamples735
29.6Futuredirections737 References737
30.Applicationsofgaschromatographyin forensicscience
ABUZARKABIRANDKENNETHG.FURTON
30.1Introductionandscope745
30.2Analysisofbulkdrugforidentification,impurity profiling,anddrugintelligencepurpose747
30.3Gaschromatographyinforensictoxicology753
30.4Analysisofignitableliquidresiduesfrom fire debris760
30.5Analysisofexplosives761
30.6Gaschromatographicanalysisoforganicgunshot residues(OGSRS)764
30.7Analysisofforensictraceevidence767
30.8Forensicenvironmentalanalysis768
30.9Analysisofhumanodorprofi le772
30.10Analysisofhumandecompositionproducts774
30.11Field-portablegaschromatographforonsite sampleanalysis776
30.12Gaschromatographyinfoodforensics777
30.13Analysisofchemicalwarfareagents (CWAS)778
30.14Newdevelopmentsingaschromatographywith forensicimplications779 References780
31.Applicationsofgaschromatographyto multiresiduemethodsforpesticidesandrelated compoundsinfood
MILAGROSMEZCUA,M.ANGELESMARTINEZ-UROZAND AMADEOR.FERNANDEZ-ALBA
31.1Introduction793
31.2Multiresiduemethodsforpesticidesincrops794
31.3Multiresiduemethodsforpesticidesinanimalorigin products798
31.4Multiresiduemethodsforpesticidesinprocessed food799
31.5Multiresiduemethodsforpesticidesinbaby food802
31.6Conclusions804 Acknowledgments804 References804
32.Gaschromatographicanalysisofwine SUSANE.EBELER
32.1Introduction807
32.2Stationaryphases808
32.3Multidimensionalseparations810
32.4Detectorsandhyphenatedtechniques812
32.5Samplepreparation815 Summary821 References822
33.Gaschromatographicanalysisofemerging andpersistentenvironmental contaminants
FRANKL.DORMANANDERICJ.REINER
33.1Introduction836
33.2Polychlorinatedbiphenyls838
33.3Dioxins843
33.4Organochlorinepesticides848
33.5Halogenated flameretardants851
33.6Polybrominateddiphenylethers853
33.7Otherhalogenated flameretardants853
33.8Perfluorinatedcompounds859
33.9Polycyclicaromatichydrocarbons859
33.10Othercompoundsnotspecifically discussed861
33.11Summary861 References862
34.Gaschromatographyinspaceexploration
MARIACHIARAPIETROGRANDE
34.1Introduction865
34.2Technologicalandoperatingconstraintsinspace GC866
34.3PrebioticchemistryinTitan’satmosphere:the Cassini Huygensmission867
34.4Prebioticchemistryincometenvironments:Rosetta mission867
34.5Searchforkeychemicalbiomarkers:Mars exploration869
34.6Searchforchiralityinspace871
34.7Conclusionsandperspectives872 References872
35.Gaschromatographicanalysisofchemical warfareagents
PHILIPA.SMITH
35.1Introductionandbackground875
35.2Analyticalconsiderationsforsamplingandgas chromatographicanalysisofCWA-related compounds887
35.3GCapplicationsforbiomedicalCWA analyses895
35.4Conclusion896 References896
Index901
Contributors
LourdesArce DepartmentofAnalyticalChemistry, UniversityofCordoba,InstituteofFineChemistry andNanochemistry,Cordoba,Spain
CarloBicchi DipartimentodiScienzaeTecnologia delFarmaco,UniversityofTorino,Torino,Italy
LeonidM.Blumberg Advachrom,Wilmington,DE, UnitedStates
CeciliaCagliero DipartimentodiScienzaeTecnologiadelFarmaco,UniversityofTorino,Torino,Italy
K.HusnuCanBaşer AnadoluUniversity,Eskisehir, TR,Turkey
CarlosAlbertoCarbonezi DivisionofGeochemistry,PETROBRASResearchandDevelopment Center(CENPES),PETROBRAS,RiodeJaneiro, RJ,Brazil
MariaJoseCardador DepartmentofAnalytical Chemistry,UniversityofCordoba,Instituteof FineChemistryandNanochemistry,Cordoba, Spain
JosephA.Caruso UniversityofCincinnati,Cincinnati,OH,UnitedStates
RogérioMesquitaCarvalho DivisionofChemistry, PETROBRASResearchandDevelopmentCenter (CENPES),PETROBRAS,RiodeJaneiro,RJ,Brazil
QilinChan UniversityofCincinnati,Cincinnati, OH,UnitedStates
EricChunYongChan DepartmentofPharmacy, NationalUniversityofSingapore,Singapore
ChiaraCordero DipartimentodiScienzaeTecnologiadelFarmaco,UniversityofTorino,Torino,Italy
JulianaCrucello InstituteofChemistry,University ofCampinas(UNICAMP),Campinas,SP,Brazil
CristinaCruz-Hernandez NestléResearch,VersChez-Les-Blanc,Lausanne,Switzerland
PeterDawes AnalyticalScience,SGE,Ringwood, VIC,Australia
NathaliadeAguiarPorto InstituteofChemistry, UniversityofCampinas(UNICAMP),Campinas, SP,Brazil
AlexandredeAndradeFerreira Divisionof Geochemistry,PETROBRASResearchandDevelopmentCenter(CENPES),PETROBRAS,Riode Janeiro,RJ,Brazil
BiekeDejaegher DepartmentofAnalyticalChemistry,AppliedChemometricsandMolecularModelling,VrijeUniversiteitBrussel(VUB),Brussels, Belgium
FrédéricDestaillats NestléNutritionResearch, Vevey,Switzerland
JaapdeZeeuw RestekCorporation,Middelburg, TheNetherlands
FrankL.Dorman BiochemistryandMolecular Biology,ThePennsylvaniaStateUniversity,UniversityPark,PA,UnitedStates
SusanE.Ebeler DepartmentofViticultureand Enology,OneShieldsAvenue,UniversityofCalifornia,Davis,CA,UnitedStates
AmadeoR.Fernandez-Alba PesticideResidue ReseachGroup,UniversityofAlmeria,LaCanada deSanUrbano,Almeria,Spain
KennethG.Furton DepartmentofChemistryand Biochemistry,FloridaInternationalUniversity, Miami,FL,UnitedStates
LeandroWangHantao InstituteofChemistry,UniversityofCampinas(UNICAMP),Campinas,SP, Brazil
DavidJ.Harvey TargetDiscoveryInstitute, NuffieldDepartmentofMedicine,Universityof Oxford,Oxford,UnitedKingdom
WalterG.Jennings FoodScience,Universityof California,Davis,CA,UnitedStates
NatividadJurado-Campos DepartmentofAnalyticalChemistry,UniversityofCordoba,Instituteof FineChemistryandNanochemistry,Cordoba, Spain
AbuzarKabir DepartmentofChemistryand Biochemistry,FloridaInternationalUniversity, Miami,FL,UnitedStates
YuriKalambet AmpersandLtd.,Moscow,Russian Federation
LeesunKim UlsanNationalInstituteofScienceand Technology,Ulsan,SouthKorea
SzeHanLee DepartmentofPharmacy,National UniversityofSingapore,Singapore
EricaLiberto DipartimentodiScienzaeTecnologia delFarmaco,UniversityofTorino,Torino,Italy
MainakMal DepartmentofPharmaceuticalTechnology,BrainwareUniversity,Kolkata,India
PhilipJ.Marriott SchoolofChemistryMonash University,Clayton,VIC,Australia
M.AngelesMartinez-Uroz PesticideResidue ReseachGroup,UniversityofAlmeria,LaCanada deSanUrbano,Almeria,Spain
A.Mena InstitutodeQuímicaOrganicaGeneral (CSIC),Madrid,Spain
MilagrosMezcua PesticideResidueReseachGroup, UniversityofAlmeria,LaCanadadeSanUrbano, Almeria,Spain
JeremyS.Nadeau DepartmentofChemistry, UniversityofWashington,Seattle,WA,UnitedStates
ArielM.O’Brien DepartmentofChemistry& Biochemistry,TheUniversityofTexas,Arlington, TX,UnitedStates
Temel Ozek AnadoluUniversity,Eskisehir,TR, Turkey
KishoreKumarPasikanti AcceleratingTherapeuticsforOpportunitiesinMedicine(ATOM)Consortium,SanFrancisco,CA,UnitedStates
KarisaM.Pierce DepartmentofChemistryand Biochemistry,SeattlePacificUniversity,Seattle, WA,UnitedStates
MariaChiaraPietrogrande DepartmentofChemistry,UniversityofFerrara,Ferrara,Italy
ColinF.Poole DepartmentofChemistry,Wayne StateUniversity,Detroit,MI,UnitedStates
EricJ.Reiner BiochemistryandMolecularBiology, ThePennsylvaniaStateUniversity,University Park,PA,UnitedStates
PatriziaRubiolo DipartimentodiScienzaeTecnologiadelFarmaco,UniversityofTorino,Torino,Italy
A.I.Ruiz-Matute InstitutodeQuímicaOrganica General(CSIC),Madrid,Spain
KarenD.Sam ApplicationsLab,CDSAnalytical, Oxford,PA,UnitedStates
M.L.Sanz InstitutodeQuímicaOrganicaGeneral (CSIC),Madrid,Spain
KevinA.Schug DepartmentofChemistry& Biochemistry,TheUniversityofTexas,Arlington, TX,UnitedStates
JohnV.Seeley OaklandUniversity,Departmentof Chemistry,Rochester,MI,UnitedStates
BarbaraSgorbini DipartimentodiScienzaeTecnologiadelFarmaco,UniversityofTorino,Torino, Italy
MichaelJ.Sithersingh KRConsultants,Parsippany, NJ,UnitedStates
JohannaSmeyers-Verbeke DepartmentofAnalyticalChemistry,AppliedChemometricsandMolecularModelling,VrijeUniversiteitBrussel(VUB), Brussels,Belgium
PhilipA.Smith USDepartmentofLabor,Saltlake TechnicalCenter,Sandy,UT,UnitedStates
NicholasH.Snow ChemistryandBiochemistry, SetonHallUniversity,SouthOrange,NJ,United States
A.C.Soria InstitutodeQuímicaOrganicaGeneral (CSIC),Madrid,Spain
StanleyD.Stearns ValcoInstrumentsCo.Inc., Houston,TX,UnitedStates
RobertE.Synovec DepartmentofChemistry,UniversityofWashington,Seattle,WA,UnitedStates
AndrewTipler PerkinElmerInc.,Shelton,CT, UnitedStates
TimothyJ.Trinklein DepartmentofChemistry, UniversityofWashington,Seattle,WA,United States
YvanVanderHeyden DepartmentofAnalytical Chemistry,AppliedChemometricsandMolecular Modelling,VrijeUniversiteitBrussel(VUB),Brussels,Belgium
AdamVoelkel InstituteofChemicalTechnology andEngineering,PoznanUniversityofTechnology, Poznan,Poland
ElizabethWoolfenden MarkesInternational Limited,1000CentralPark,WesternAvenue, Bridgend,UnitedKingdom
Milestonesinthedevelopmentofgas chromatography
WalterG.Jennings1,y,ColinF.Poole2
1FoodScience,UniversityofCalifornia,Davis,CA,UnitedStates; 2DepartmentofChemistry, WayneStateUniversity,Detroit,MI,UnitedStates
1.1Introduction
Thisarticlewasstartedbytheseniorauthor WalterJennings,whowasunabletocomplete itduetopoorhealth.Walterpassedawayin thesummerof2012. Sections1.2 1.6 areapersonalaccountoftheearlydaysofgaschromatographyseenthroughtheeyesofoneofthe majorpioneersandinnovatorsinthis field. Withonlyminoreditorialchangesmadebythe juniorauthor,thesearepresentedasWalter intended.Asthejuniorauthor,Iamresponsible for Sections1.7and1.8.Thesesectionsextend Walter'scommentsontheearlydaysofgaschromatographytothepresentdayandbene fited fromthedetailednotesheprovidedmewith.
1.2Theinventionofgaschromatography
In1952,A.J.P.MartinandR.L.M.Syngewere bothawardedNobelPrizesfortheirworkinthe fieldofliquid/solidchromatography.Martin,in
y AuthorW.G.Jenningsisdeceased.
hisawardaddress,suggesteditmightbe possibletouseavaporasthemobilephase. Someyearslater,JamesandMartinusedethyl acetatevaportodesorbamixtureoffattyacids thathadbeenaffixedtoanadsorbentandplaced inatube.Thevaporstreamelutingfromthat tubewasdirectedtoanautomatedtitration apparatus,resultinginagraphshowingaseries of “steps” thatreflectedthesequentialadditions ofbaseaseachelutedacidwasneutralizedby automatedtitration[1].Manypractitioners haveforfartoolongconsideredthisasthestartingpointofgaschromatography.
In2008,LeslieEttrepublishedanarticlein whichhestated, “ theactivitiesofProfessor ErikaCremerandherstudentsattheUniversity ofInnsbruck,Austria,intheyearsfollowingthe SecondWorldWar,representedthetruestartof theircontinuousinvolvementingaschromatography” [2].AfterexploringEttre'sargumentsand conductingsomeresearchmyself,Ifullyagree withhisconclusions.Inowbelievethatthe
1.Milestonesinthedevelopmentofgaschromatography
theoreticalbasisforgaschromatographywas firstconceivedbyErikaCremer,anAustrianscientistattheUniversityofInnsbruck,Austria,in thelate1940sduringtheperiodoftheSecond WorldWar.AsEttrepointsout,thiswasaperiod whenwomen,especiallyinGermaniccountries, wereexpectedtoconfinetheiractivitiesto “children,church,andkitchen”.Inspiteofher “ superbPh.D.thesiswork,” shehadgreat difficultyin findingaposition.Heropportunity camein1940whenthewarstarted,anduniversityteachersweredrafted.SheobtainedanacademicpositionattheUniversityofInnsbruck, Austria(thenapartofGermany),intheInstitute ofPhysicalChemistry.Itwasherethatsheand herstudents(withmajorcredittoFritzPrior) constructedthe firstprototypeofagaschromatograph(GC)(Fig.1.1)and,afteralongdelay thatwasprobablyattributabletothewar,publishedtheresultsoftheirresearchin1951[3,4]. Atthistimeshewaspromotedtoprofessor and,some20yearslater,todirectorofthe
University'sInstituteofPhysicalChemistry.ProfessorDr.Cremer,byallaccountsabrilliant womanscientist,diedin1996.
1.3Earlyinstrumentation
By1953,severalpetroleumcompanies,primarilyinGreatBritainandtheNetherlands, wereexploringthisnewanalyticaltechnique, andin1954,afew flavorchemists(including thisauthor)werebuildingcrudechromatographs,manyofthembasedonanarticlebyN. H.Ray[5].Rayinsertedthermalconductivity cellsintoaWheatstonebridge,whoseoutletconnectedtoastripchartrecorder,thusgeneratinga Gaussianpeakforeachelutingsolute;thiswas (tomyknowledge)the firstgaschromatogram asweknowittoday.TheschematicsandchromatogramspublishedbyRayencourageda numberofreaders(includingtheauthor)to buildsimilarchromatographs.Almostevery partofthesecrudeinstrumentshadtobe
FIGURE1.1 ThegaschromatographicsystemusedinPrior’ work,in1945 1947.(A)adsorbentforpurificationofthe carriergas(hydrogen);(B)sampleinletsystem;(C)buretcontainingmercurywithniveauglassforsampleintroduction; (D)Dewar flask;(E)separationcolumn(containingsilicagelonactivatedcarbon);and(F)thermalconductivitydetector. FromRef.O.Bobleter,Exhibitionofthe firstgaschromatographicworkofErikaCremerandFritzPrior,Chromatographia43(1996) 444 446;CopyrightFriedr.ViewegandSohn.
self-designedandself-made,butthisintroduced thedaysofthepackedcolumn;supports,suchas granulesofdiatomaceousearth,werecoated withavarietyofhigh-boiling fluids(e.g.,diethyleneglycolsuccinate,DEGS)and,inourearliest efforts,packedintocoppercolumns,typically 3 6mlongwithinternaldiametersofabout 6mm,and(usually)coiled.Itwassoonrecognizedthatcoppercolumnswerequiteactive, andmostworkersswitched, firsttostainless steelandthentocoiledglasstubingofsimilardimensions.Thereminiscencesofmanyofthe earlypioneersingaschromatographicinstrumentationaresummarizedinRef.[6].
1.3.1Earlycommercialinstruments
The firstcompaniestomanufactureGCsin EuropewereGriffinandGeorge(London)and MetropolitanVickersElectric(Manchester),but theUSinstrumentcompanieshadagreater impactonthedevelopmentofthisnewarea [7].PerkinElmerwasoneofthe firstcompanies tomarketaGC;inMayof1954,theyintroduced theirModel154VaporFractometer.Thetemperatureofthecolumnovenwasadjustablefrom roomtemperatureto150 C,anditoffereda “flashvaporizer” witharubberseptumpermittingsyringeinjectionintothecarriergasstream. Thedetectorwasathermalconductivitycell.The instrumentwasagreatsuccessandsoldwidely [8].Inearly1956,PerkinElmerfollowedup withtheirModel154-B,withatemperature rangefromroomtemperatureto225 Cand couldbe fittedwithanoptionalrotaryvalveofferingavarietyofsampleloopsfortheinjection ofgassamples.
1.4Earlycolumndevelopments
Alloftheearlyinstrumentsutilizedpacked columns,somecoiled,someU-shaped.Packed columnsallhaveonethingincommon:they possessahighresistancetogas flow,andthis
limitsthepracticallengthofthecolumn,usually toafewmeters.Inmuchlaterdays,somepacked columnsapproachedanef ficiencyequivalentto ourcurrent0.32mminternaldiametercapillary columns(ca.3000platespermeter),butbecause oftheirlengthlimitations,theycouldachieve perhaps35,000theoreticalplateswhilea30m open-tubular0.25mminternaldiametercolumn shouldbecapableofthreetimesthatefficiency, merelybecauseitisthreetimeslonger.
Itwasatthe1958SecondInternationalSymposiumonGasChromatographyinAmsterdam thatMarcelGolay,whowasthenaconsultantto PerkinElmer,introducedthetheoryofopentubularcapillarycolumnsanddemonstrated theirsuperioritytopackedcolumns[9].(There isnoconnectionbetweentheoldPerkinElmerreferred tohereandthePerkinElmeroftoday,theyareentirely differentcompanies.)Thesecolumnsdemanded muchsmallersampleinjections,necessitating moresensitivedetectorsthanthethermalconductivitydetectorsthatwereincommonuseat thetime.Fortunately,JamesE.Lovelockhad inventedanelectron-capturedetectorin1957 [10],andin1958the flameionizationdetector appeared;somecreditthistoHarley,Nel,and Pretorious[11],andotherstoMcWilliamsand Dewer[12,13];theseincreaseddetectorsensitivitiesbyca.103 106.Theinventionanddevelopmentofthe flameionizationdetectorare discussedinmoredetailinRef.[14].Earlycapillarycolumnswereofplasticandcoppertubing; theformerhadserioustemperaturelimitations andthelatterwasactive;thisledtostainlesssteel tubing.PerkinElmerhad filedforandbeen grantedpatentsontheopen-tubularconcept, essentiallyworldwide.IpurchasedtwoPerkinElmerwall-coatedopen-tubular(WCOT)columnsatdifferenttimes,onlyto findthatthe columnsavailablefromthemproducedabominableresults.PerkinElmerapparentlyrecognizedthisfact,becausetheyessentially abandonedtheirresearcheffortsonWCOTcolumns,outsourcedtheirproduction,andredirectedtheireffortstocolumnswhoseinteriors
were firstcoatedwithasupportmaterial(e.g., diatomaceousearth)andthenwiththestationaryphase.Theseweredubbed “supportcoated open-tubular(SCOT)columns.” PerkinElmer continuedtorigorouslyenforcethepatenton WCOT(andSCOT)columns,butunderconsiderablepressure(especiallyfromtheapplicant) theywereforcedtoissueonelicense,toHansjurgJaeggi,aformerassistantofKurtGrobin Switzerland.UnderSwisslaw,ifapatentbars aSwissfromconductinghisorherbusiness,alicensemustbeissued.Jaeggihadbeenandstill wasmakingexcellentglassWCOTcolumns. ThehighqualityofhiscolumnsledPerkinElmer tolaterproposethattheycollaborate,but,probablybecauseoftheacrimoniousbattlehehad gonethroughtoobtainhislicense,hewanted nothingmoretodowithPerkinElmerand refusedtheiroffer.Hisobituary,writtenbyKonradGrob,makesinterestingreading[15].
1.4.1Do-it-yourselfglasscapillary columns
In1965,Destyetal.inventedanelegantlysimple machinefordrawinglonglengthsofcoiledglass capillaries[16].Besidesthefactthatthiswasmuch lessexpensivetubing,italsohadasmootherinterior anditwastransparent.Forthe firsttime,itwas possibletoscrutinizethelayerofstationaryphase asitexistedonthecolumnwall;soonitwasobvious thatwhenanewunusedcolumnexhibitingathin uniform filmofstationaryphasewasexposedto highertemperatures,thestationaryphasecollected intobeadsthatwererandomlyscatteredovertheinnersurface.Almostimmediatelyscoresofscientists realizedthatmanyofthelow-viscosity fluidsthat workedwellinpackedcolumnswereunsatisfactoryforWCOTcolumnsandshouldbereplaced withhigh-viscositymaterialsthatwouldretaintheir highviscosityevenathighertemperatures.Lowviscositysilicone fluids(e.g.,OV101)werereplaced withhigh-viscositysilicones(e.g.,OV30,aviscous paste-likesilicone),and experimenterssoonbegan producingmuchmorestablecolumns.
1.4.2Thepositiveresultsofpatent enforcement
ThelowqualityofthePerkinElmerWCOT columnsandenforcementoftheirpatentled manyscientiststobeginmakingtheirowncolumnsfortheirownuse.Thiscausedinvestigatorsinmanyother fields,whowouldhave preferredtopurchaseuseablecolumnsfroman outsidesourceandconfinetheirresearchto someother field,tonowhavetomakecolumns; scoresofscientistswerenowstudyingandpublishingonmethodsofpretreating,deactivating, andcoatingcolumns.Theircombinedresults wereresponsibleformanyoftheadvancesin columnimprovements,andtheysoonsurpassed theresultsthathadbeengeneratedbyPerkin Elmer[17].
1.4.3MilepostsincoatingWCOT capillarycolumns
Golayhadcoatedhisoriginalglassopentubularcolumnsbycompletely fillingthemwith adilutesolutionofstationaryphaseinalowboilingsolvent,sealingoneend,andthendrawing thecolumn,openend first,throughanoven[18]. AsusedbyGolay,thecolumncouldbecoiled onlyaftercoating,adistinctdrawback.The methodwasimprovedbyIlkovaandMistrykov [19],whocoiledandthen filledthecolumnand sealedoneend.Theopenendofthe filledcolumn wasfedintoaheatedovenbysupportingthecolumnonarotatingrod fittedwithadriverollerat theentrancetothecolumnoven,thusliterally screwingtherestofthecolumnintotheoven.
Upuntiljustafewyearsago,allchemistrydepartmentsatthemulticampusUniversitiesof Californiasystemfrownedonappliedresearch, andchemistrydepartmentfacultiesdrifting awayfrompureorganicchemistryorpurephysicalchemistryrarelysurvivedtotenure.Analyticalchemistrywasessentiallyforbidden.There weremanyfacultymembersscatteredthrough variousotherdepartmentswhowereanalytical
chemists,andeventuallytheyformeda “Group inAnalyticalandEnvironmentalChemistry,” opentoanyoneinanydepartmentwhohadinterestsintheanalyticalside.AtonetimeIchaired thatgroupforseveralyearsanditstillexists.At thistime,mytitlewas “ProfessorofFoodScience andTechnologyandChemistintheExperiment Station.” Thishadseveraladvantages:forone thing,thosewithjusttheacademictitleworked 9monthsperyear,whiletheExperimentStation operated11monthsayear.Mydepartment chairmantoleratedwhathecalledmy “dabbling” ingaschromatography,butinsisted thatIshouldalsobeworkingonsubjects “ more alignedwiththefoodindustries”;hesuggested “circulationcleaning,” whichwasjustemerging. SwallowingwhatIwantedtosay,Iassigneda newPh.D.student(MalcolmBourne)totheproject,builtaminiaturecirculationpipeline,and helpedhimbakeradiolabeledtristearinonto glassmicroscopeslidesandstripsofstainless steelofsimilarwidthandlength.Thesewere insertedintotherapidcirculatingsystem,and thelevelsofradioactivitymeasuredevery2minutes.Inevitably,semilogplotsofourcleaning curvesshowedarapidlydroppingcurvethat terminatedinastraightlinewithaslightdownwardslope.AllatonceBournerealizedthathe waslookingattwo first-orderreactionsthat wereoccurringsimultaneously.Thebaked film oftristearinexistedonlyatoneoftwoenergy levels,alooselyboundsystem,andamuch moretightlyboundsystem nothinginbetween. Spatialestimatesindicatedthatthetightlybound formwasnotamonolayer,butcouldbeuptoat least20molecularthicknesses[20 22].Healso discoveredthatbymanipulatingtimeandtemperature,hecouldchangetheratioofthetwo species.Bournewentontostudythekineticsof cleaninginmuchgreaterdepthandmadequite anameforhimself.Iwentbacktomy “dabbling,” thenslowlyrealizedthatmynewly gainedknowledgeonremovalofthin filmswas justthereverseofachievingmorestablecoatings ofstationaryphasestothecolumnsurface.
ThismayhaveguidedmeasIattemptedto modifyourcolumncoatingapparatus.After replacingtheopaquelidoftheovenwithaglass lid,itwasobviousthatthesolutionwassuperheatedandevaporatedinaseriesofminor explosions,leavingblotchesofstationaryphase randomlyscatteredoverthesurfaceofthecolumn.Idecidedtointroducethecolumninto theoventhroughapreheatermadefromashort curvedlengthof1/8inchstainlesssteeltubing laggedwithanelectricallyheatedwireandheatedto150 C:thecolumn'spassagethroughthe curvedpreheaterwasnotsmooth;indeed,it scrapedthewallsandvibrated.Toavoid breakage,Iintroducedgraphitepowderinto theloop.Thecolumncontinuedtovibrate,but moregently.Inretrospect,thatvibrationatthis pointonitspassageintotheovenwouldalso discouragesuperheating.Itmayhavebeen dumbluck,butfromthenon,theevaporation ofthesolventoccurredsmoothly.Wewere routinelyproducingverystablecolumnswith uniformlythincoatings.
1.4.4Commercialcolumn manufacturers
Atthispoint,oneofmyPh.D.students,RobertWohleb,suggestedthatwehadamarketable productandshouldestablishacolumnproductioncompany.WhenIbroachedthissuggestion withmydepartmentchairman,hecalledinthe dean.Aftermuchdiscussion,theyagreedthatI couldengageinthisactivityonlyifIagreedto severalrestrictions:(1)aslongasIwasafulltimeprofessor,Icouldreceivenoremuneration fromthisventure;(2)therecouldbenoconnectionbetweenmyuniversityresearchand activitiesofthecompany;(3)Icouldnotget involvedintheday-to-dayactivitiesofthe company.Icould, onmyowntime,answer trouble-shootingquestionsandengageineducationalactivities.J&WScientificwasfoundedin 1974;Iconstructedtwodrawingmachinesin mymachineshopathomeandleftthemwith
WohlebasIdepartedonmysecondsabbatical leave,thistimeinKarlsruhe,Germany.Sandy Lipskyhadlaunchedhiscompany,Quadrex, slightlyaheadofJ&W.
1.4.5Bonded,cross-linked,and/or immobilizedstationaryphases
In1975,J&Wnoticedasuddendropincolumn salesfromseveralregularcustomers;fortunately, wehadbeenusing(andsaving)barcodestotrace everystepeachcolumnwentthrough.Thebar codesonallofthecolumnsthosecustomershad beenbuyingshowedtheyhadallgonethrough thesamecoatingmachineinthesamegeneral timeperiod.Icalledseveralofthebuyersand askediftheywerehavingproblemswithourcolumnsandwasshockedwhentheyreplied, “ no, thecolumnsaregreat theyneverwearout.” Thiswasserious,wewereputtingourselvesout ofbusiness.Incheckingthatcoatingmachine,it wasdiscoveredthatthethermocoupleonthepreheaterthroughwhichthecolumnenteredthe ovenhadfailedsometimeagoandwasgiving muchlowerreadings.Overthepastfewweeks, thetechnicianonthemachinehadsimply compensatedforthelowreadingbyboosting thevoltage.Insteadof150 C,thatpreheater wascloseto300 C.Thestationaryphasewe wereusing(SE-54)contained1%vinyl.Our R&Dhead,RandJenkins,realizedthatserendipityhadsmiledonus!Heimmediatelyordered materialsandbeganaddingvinyl-containing compounds,toourcoatingsolutions,hoping thatthephasewouldnotonlycross-linkbut alsoconnectwithsomesurfacehydroxyls.With someprettyharshtesting,wefoundthatthecolumnsexposedtothesehigherpreheatertemperaturesweremuchmorerugged,andthedeposited phasecouldnotberemovedwithsolventrinsing. Atthenext “AdvancesinChromatography” meetinginHouston,weannouncedthe “Bonded PhaseColumn.” Ifthetechnicianonthatmachine hadreportedthefailingthermocouple,wewould simplyhavereplaceditandnoneofthiswould
havehappened.ItturnedoutthatKurtGrobin Switzerlandhad(independently)beenworking alongthesesamelines.Checkingonthedates thatbothpartieshadorderedvinylchemicals, Randwasjustabout5daysahead.
1.4.6Furtherimprovementsin stationaryphases
Inthelate1950sandextendingintothe1960s, gaschromatographersdealtwithaplethoraof stationaryphases.Petroleumchemists,dealing withnonpolarproducts,favoredphasessuch assqualane,afullysaturatedhydrocarbon (C30H62)onthebasisoflike-attracts-like.TheuppertemperaturelimitforSqualaneis125degrees,andahighertemperatureparaffin, Apolane87(C87H176),wassometimesused instead.Chemistsdealingwithmorepolarproductsneededmorepolarstationaryphases,and theyturnedtohigh-boilingesterssuchasdiethyleneglycolsuccinate(DEGS).Asmoreand morescientistsenteredthe field,therangeofstationaryphasesexplodedtoover200different phases,mostofwhichweregraduallydiscarded. Thepolysiloxanestationaryphasesarenow widelyusedandhavebeenreviewedbyBlomberg[23]andHaken[24].
1.5Interfacingglasscapillarycolumnsto injectorsanddetectors
Attachingtheserelativelyfragileglass capillariestoinjectorsanddetectorsvialeakproofconnectionssoonbecameaproblem; someworkerspunchedholesinsmalldisksof siliconerubber,whichwerethensubstituted fortheferrulessuppliedwith1/16inchSwagelok fittings,butalltoofrequently,asthenuton theSwagelok fittingwastightenedtothepoint thattherewerenoleaks,thecompressivestrain ontheglasscausedbreakageatthatpoint. Otherstriedleaddisks,withsimilareffects.I wasonsabbaticalleaveatthenuclearresearch
instituteinKarlsruhe,Germany,whenaclerkin thesupplyroomcalledmyattentiontoasheetof plasticheavilyinfusedwithgraphite.After slidingSwagelokcapsontobothcolumnends, Iwoundsmallstripsofthisaroundbothends ofaglasscapillary,removedthestockferules fromtheSwagelokconnectorstotheinletand detector,andconnectedthecolumn.AsItightenedtheconnectionstoapointwherethere wasnoleakageandfoundthatthecolumnwas stillintact,Iwasdelighted.Thecompanythat madethesegraphitizedsheetswasjustafew milesoutsideofKarlsruhe,andIpaidthema visit.Theywereverycordialandgavemea numberofsamples.OnmyreturntotheUnited States,J&Worderedseveralsteeldiesdimensionedontheinnermeasurementsofa1/16 inchSwagelok fittingandbeganpressingferrules.Thesewentonthemarketin1975;they wereagreatsuccess,andIhavealwaysregretted myfailuretopatentthatproduct.
1.6TheHindelangconferencesandthe fused-silicacolumn
The firstsymposiumrestrictedtoopentubular(capillary)columnswasorganizedby RudolfKaiserandchairedbyDennisDestyin 1975;thiswasthe firstofthefourHindelangconferencesandwasheldinanisolatedvillagein theBavarianAlps.EttrevisitedKaiser, firstto voicehisoppositiontoholdingthemeeting, andthenproposedadelay,arguingthatitwas beingheld “fartooearly,” butmanyother workersinthe fieldwereenthusedbytheidea. Istillregardthe firstHindelangconferenceas themostexcitingmeetingIhaveeverattended. Itattractednearlyeverybodythatwasworking withglasscapillarycolumns.Welistenedtopresentationsfromourassociatesinthemorning andspentafternoonsandeveningsgathered aroundtablesseatingperhapseightparticipants, drinkingstrongGermanbrewsandexchanging viewsonchromatography,withtheemphasis onWCOTcolumns.ItwasthenthatGolay approachedme;hewasfeebleatthetimeand steadiedbyEttre.HewantedtotalkaboutJ&W0 s methodofcoatingcolumns.Iexplainedthatthe firststepwashisideaoffeedinga filledcolumn, openend first,intoaheatedoven.Ilkovaand Mistrykov'sideaofscrewingthecoiledcolumn intotheovenshowedrealingenuity:mypreheatercontributionwouldhavebeenproposed byanyonethatcouldactuallyseetheoperation takingplace.NowthatIhavereached(andprobablysurpassed)Golay'sageatthetime,Ibelieve Icannowunderstandhiscuriosity,andIhope herealizedthatanotherofhisbrilliantideas hadbornefruit.Hedepartedcourteously,andI waslefttocontinuemyattemptstovisitevery tableandmeeteveryparticipant.Ididmeet virtuallyalltheexperts,absorbedagreatdeal ofknowledge,andleft filledwithnewideas andadesiretogethomequicklywhereIcould getbacktoworkinmyownlab.
Therearemanytypesofglass,butwewill restrictourintereststothosestudiedfortheir chromatographicinterestbyDandeneauand Zerenner:sodalime,borosilicate,uranium,potashsodalead,andfusedsilica(Table1.1)[25]. AtthethirdHindelangconference,Ipresented apaperonmultipleshort-passcapillarychromatography,inwhichoneofmyPh.D.students (JamesA.Settlage)hadrecycledabutaneinjection16timesthroughtwo7.5mcolumnsto achieve1170theoreticalplatespersecondand generated850,000theoreticalplatesinthose16 passesinlessthan12min[26];asI finished, severalmembersoftheaudiencerushedtothe podiumwithcongratulations;ata finalsynopsis ofthemeeting,Destycitedalsothispaper,butI knewtheywereallwrong.Themostsigni ficant paperwasthatofDandeneauandZerenner [25],releasingthefused-silicacolumn.When Dandeneaupresentedhispaper,veryfewpeople realizeditsimportance.SandyLipsky,whohad startedQuadrexaboutthesametimethatJ&W wasfounded,wasone,andIwasanother.Both LipskyandIhadbeentryingtoconvert
TABLE1.1 Approximatecompositionsforglassmaterialsusedforcapillarycolumnfabrication.
Borosilicate812413
Uraniumglass76342141
Potashsodalead5624929
Fusedsilicaa 100
a Typicallycontainslessthan1ppmtotalmetals.
industrialanalyststoWCOTglasscapillaries, withbutscantsuccess.Industrialanalystsrealizedthesuperiorityofresultsgeneratedbythese columns,buttheyalsorecognizedtheirfragility. Downtimeisrarelycriticalinacademia,butin industryitcanbeveryserious;glasscapillaries breakeasily,packedcolumnslastedlonger. However,thisfused-silicacolumnchanged everything!Herewasacapillarycolumnthat wasbothstrongand flexible,butbecauseit wasbothlabor-intensiveandmaterialsintensive,itwasmuchmoreexpensive.
Fused-silicacolumnshaveimmensetensile strength,permittinganextremelythincolumn wall,whichinturnmakesa flexiblecolumn. Thispermitteddrawinglonglengthsofstraight tubing,whichcanthenbecoiled.Interfacing thesetodetectorsandinjectorswasnowasimple task;nolongermustwe flamestraightenthe endsofthecolumn,itwasalreadyinherently straight!Buttheoutersurfaceofdrawnsilicarequiresprotection.Likeallsilica-basedglasses, fusedsilicaissubjectto flawsatitssurface,and flawsgrowataratedeterminedbystress and coilingthislongstraightpieceoffusedsilicaplacesitunderstress asthe flawgrowslarger,the columnsnapsatthatpoint.Toprotecttheouter surface,HewlettPackard firstcoatedthecolumnswithacoatingofpolysiloxane,butthis endedupasaverystickycolumn.DuPontthen cameforwardwithapolyamidecoatingthat wasappliedduringthedrawingprocess.Later
theychangedtoapolyimide;thissealssurface flawsinthetubing.Itisusuallyappliedin severalthincoatsduringthedrawingprocess. Noteveryonerecognizedtheadvantagesof thefused-silicacolumn;indeed,inspiteofmy vigorousprotests,mypartnersatJ&Wdismissed itas “agimmick.” 2weekslater,itwasimpossibletogive,letalonesell,aglasscapillarycolumn,andJ&Wmadetheconversiontofused silica.Atthispoint,thingsbecamevery “touchy.” Thevastmajorityofscientistsworking ingaschromatographyhadcareersbasedon glasscapillarycolumns drawing,deactivation, coating,etc. nowthosecareerswerepasse.I hadaseminarscheduledforMilan,Italy,where Iwaswarmlyreceived untilmy firstslidewas shown.Itwasafused-silicacolumn.Severalattendeeslefttheroom,andtheatmospheretook onachill.Veryfewinthisaudiencewantedto hearhowtheirfuturesmightbeaffected.Shortly thereafter,GeorgesGuiochonorganizedachromatographysymposiuminCannes,France. TheGCcolumnportionofthemeetingwas chairedbyGerhardtSchomburg.Ashecalled themeetingtoorder,heannouncedthatthere wouldbe “nodiscussionoffused-silicacolumns. ” Asthemeetingproceeded,severalattendeesexpressedtheirobjectionstothe openingrestrictionandannouncedthatthey hadcometothemeetingjusttolearnmoreabout thefused-silicacolumn.Withobviousdistaste, Schomburgturnedtomeandsaid, “tellthem
somethingaboutfusedsilica.” Atthistime,Ihad beenexploringon-columninjectionswithfused silica,sometimestrappingsampleswithinthe fused-silicatubingbyfoldingthe flexibletube intoa “U” shapeinaDewar flask filledwith liquidnitrogen,thenwithdrawingthe “U” and reinsertingitintoa flaskofheatedoilforinjection.Thisapproachdemandeda flexibletube andwouldhavebeenimpossiblewithglass capillarytubing.Anobviouslyuncomfortable Schomburginterruptedmewiththeobservation that “flexibilityappealsonlytoAmericans,and onlybecausetheyaretooclumsytohandle glass.” Afewmonthslater,J&Wwasselling Schomburgfused-silicacolumns.
1.7Increasingsophisticationof instrumentation
Table1.2 providesatimelineforimportant developmentsininstrumentation[8,26,27].The essentialelementsofinstrumentsweredevelopedbytheearly1960s,withfurtherdevelopmentsoccurringinshortburstsofinnovation andadvancesintechnologyfollowedbylonger periodsofevolutionarychangesandconsolidation.Manyadvanceswerecatalyzedbyadvancesincolumntechnologyorelectronics.For example,theadventofthemicroprocessor broughtaboutaradicalchangeininstrument designanduse.Fromthispointonward,instrumentfunctionsweremonitoredandcontrolled bynetworksofcircuitscommunicatingwith eachotherandwithacentralcontroller.This pavedthewayfortheemergenceofthe keyboardinstrumentcontrolledbysoftware runningonapersonalcomputer,whichdominatedinstrumentsforlaboratoryusebytheearly 1990s.Asigni ficantmilestoneinachievingfull automationofinstrumentoperationwasthe introductionofelectronicpressurecontrolin theearly1980s.Thisallowedcarriergasandsupportgaspressureand flowratestobesetand monitoredbyelectromechanicaldevices
communicatingwithacentralprocessor.With theintroductionofroboticautosamplersat aboutthesametime,theGCcouldnowoperate withouthumanintervention,24hoperation becamestandardpracticeforroutineanalysis inhighsamplethroughputenvironments,and GCsweredeployedtoremotelocationsand monitoredelectronicallywithonlyoccasional visitsforserviceandroutinemaintenance.Electronicpressurecontrolwascentraltoaseriesof advancesinprogrammedandlarge-volumeinjectiontechniques,multidimensional-column chromatography,andretention-timelocked methods.Thecomplexfunctionsofgaschromatographyhadbeenreducedtothoseofablack boxanalyzer50yearsafteritsinvention,butstill evolutionarychangescontinueintechnology withtheviewofminimizingtheimportanceof theskillandknowledgeoftheoperatorinthe productionofdata[27].
1.7.1Columnheating
Apartfromtheuseofliquidthermostatsin theearlydaysofgaschromatography,thecolumnheaterinaGCistypicallyaforcedcirculationairoven,thetemperatureofwhich canbechangedinacontrolledmannerwith timefortemperature-programmedseparations. Goodtemperaturecontrolisessentialtoobtain reproducibleretentiontimesandtoavoidpeak distortionsassociatedwithtemporalandspatial oventemperaturegradients.Alowthermalmass fortheovenisalsoimportantsinceitallows rapidcoolingaftertemperatureprogramming. Typically,forcedair-circulationovenscanmaintainahigherrateofheatingatlowertemperaturesthanhighertemperaturesduetothe greateramountofheatlosttothesurrounding environmentasthetemperaturerampprogresses.Forfastgaschromatography,some manufacturershaveaddressedthisproblem withtheoveninsideanovenconceptormore directlyusingresistiveheatingachievedthrough
TABLE1.2 Importantadvancesintechnologythatimpactedgaschromatography.
1955Firstcommercialinstrument(thermalconductivitydetection)
1955 60Rapidgrowthintechnology
Inventionofionizationdetectors
Interfacesforcouplingtomassspectrometry
Microsyringesproducedcommercially
Temperatureprogrammingintroduced
1960 70Periodoftechnicaladvances
Firstopen-tubularcolumnsintroduced
Transistorsreplacevacuumtubes
Improvementsindetectortechnology
StablerubidiumsourcesintroducedforTID
ImprovedFPD(severaldesigns)
PulsedECDintroduced
1970 80Periodofconsolidationandrefinement
Microprocessor-basedinstrumentsintroduced
Self-madeglassopen-tubularcolumnsincreasinglyused
Computingintegratorsintroducedfordatahandling
Fused-silicaopen-tubularcolumnsintroducedin1979andcatalyzesfurtherchangesincolumnand instrumenttechnology
1980 90Periodoftechnicaladvances
Gumandimmobilizedphasesdeveloped
Columnswiththick-filmstationaryphasesdeveloped
Wide-boreopen-tubularcolumnsdeveloped
Fundamentalbasisforinjectionmechanismsdeveloped
On-columnandPTVinjectiondeveloped
Large-volumeinjectiondescribed
Autosamplersforunattendedinjectiondeveloped
1990 2000Periodofconsolidationandrefinement
Keyboardinstrumentation(PCcontrolofoperationanddatahandling)
Electronicpneumaticcontrol
Selectableelementaldetection(SED)
Pulsed flamephotometricdetectordeveloped(FPD)
TABLE1.2 Importantadvancesintechnologythatimpactedgaschromatography. cont'd
1955Firstcommercialinstrument(thermalconductivitydetection)
Electron-capturedetectorwithpulseddischargesourcedeveloped(ECD)
Moreversatileandaffordablespectroscopicdetectors(MS,FTIR)
Solid-phasemicroextractionaffordsanewapproachtosamplingandsampleintroduction
Firstmicrofabricatedgaschromatographonachipintroducedbutfailscommercially
Fieldportableinstrumentsmovegaschromatographyoutofthelaboratory
Introductionofcomprehensivetwo-dimensionalgaschromatography
2000 PresentSlowingdowninthegrowthoftechnology
Micro-GCinstrumentsforfastgaschromatographydeveloped
Capillarycolumnswithionicliquidstationaryphasesintroduced
Gasgeneratorsstarttoreplacepressurizedgascylinders
Programmableroboticsystemsusedtoautomatesamplepreparation
Resistiveheatingofcolumnsintroducedasanalternativemeansoftemperaturecontroltoconvectionovens
theuseofametallicheatingelementtotransfer heattothecolumnbyconduction[28].Fastgas chromatographymakesuseofshortcolumnsof smallinternaldiameter,thin filmcolumns, highercarriergas flowrates,andfasttemperatureprogramrates(Table1.3)[29].Forthefastest separations,thelimitinginstrumentconditions becometheavailablecolumninletpressure, maximumoventemperatureprogramrate,
TABLE1.3 Instrumentalparametersforfastgas chromatography.
(i)Fastgaschromatography(separationtimes <10min)
Peakwidths0.5 2s
Columns5 15mwithI.D.0.25 0.1mm
Temperatureprogramrates20 60 Cmin 1
Columninletpressure <15barDataacquisitionrate50Hz
Mobilephasevelocity1.4 uopt
(ii)Veryfastgaschromatography(separationtimein seconds)
Peakwidths50 200ms
Columns2 10mandI.D.0.1 0.05mm
Temperatureprogramrates >60 Cmin 1
Dataacquisitionrates50 200Hz
maximumdetectorsamplingrate,detectorsensitivityandnoiselevel,andsampleintroduction (initialbandwidth).Contemporarylaboratory instrumentscanusuallymeettherequirements forfastgaschromatography(firstentryin Table1.3),butspecial-purposeinstrumentsare requiredforveryfastgaschromatography (secondentryin Table1.3).Theentriesin Table1.3 reflectwhatiswithinthecapabilityof commercialinstrumentswithlittlemodification (firstentry)andthelimitsofcurrenttechnology requiringspecialpurposingofinstruments (secondentry).Fromtheperspectiveofseparationspeed,thecapabilityofgaschromatographicinstrumentslimitsperformancemore sothancolumntechnologyincontemporary practice.
1.7.2Sampleintroduction
Thelimitedsamplecapacityandlowcarrier gas flowratesassociatedwithopen-tubularcolumnsmakesampleintroductionmoredifficult thanforpackedcolumns.Athermostated flash
vaporizationchamberinwhichtheevaporated sampleismixedwithcarriergasanddividedbetweenastreamenteringthecolumn(carriergas flow)andastreamventedtowaste(split flow) wasthe firstpracticalsolutiontothisproblem. Splitinjectioncanbeusedtogenerateextremely smallbandwidthsforhighpeakcapacityseparationsbutdiscriminatesagainstlessvolatilecompoundsandthequantitativeanalysisofwide boiling-pointmixturesisdifficult,andforsamplespresentindilutesolution,detectabilityis limitedbythesmallamountofsampletransferredtothecolumn.Thesplitlessinjectiontechniquewasdevised(actuallydiscovered accidentally[30])toovercomesomeofthedeficienciesofsplitinjectionfortheanalysisofmixturesindilutesolutionthroughthetransferof relativelylargesamplevolumestothecolumn. Thegas flowthroughasplitlessinjectorisrelativelylow,andthesampleisintroducedinto thecolumnoveracomparativelylongtime (30 60s),relyingoncoldtrappingand/orsolventeffectstorefocusthecompoundsatthe headofthecolumn.Theimportanceofthese refocusingmechanismswasnotfullyunderstoodat firstandmuchofourcurrentknowledgeoftheinjectionmechanismowesagreat dealtotheexemplarystudiesofKonradGrob andthepublicationin1986ofhisclassicbook onsplitandsplitlessinjection[30].
Theprogrammed-temperaturevaporizer (PTV)injectorisperhapsthemostversatile injectordevelopedforgaschromatography.Itfacilitatessplitandsplitlessinjectionaswellasnew approachesforlarge-volumeinjectionwithsolventelimination[31].ThePTVinjectorhasa lowthermalmasstoallowrapidheatingand cooling.Thesampleisintroducedatarelatively lowtemperatureandthenraisedballisticallytoa temperaturesufficientforrapidvolatilizationof thehighest-boilingsamplecomponents.Slow sampleintroductionatalowtemperaturewith solventeliminationfacilitatestheinjectionof
largesamplevolumes(usually <1mL)fortrace analysis.ThePTVinjectorwasoriginallyintroducedinEuropeinthe1980s,butitwasovera decadelaterbeforeitgainedtractioninthe UnitedStates.Formuchofthistimeitwasanoptionbutnotheavilypromotedorsupportedby instrumentcompaniesbasedintheUnited States.Thiswasprobablyduetoacombination ofcommercialpreferencesandthenotinvented-heresyndrome.
Theproductionofwide-borefused-silica capillarycolumnscoatedwithimmobilizedstationaryphasesintheearly1980sallowedthesyringeneedletobeintroduceddirectlyintothe columnandeliminatedtheproblemofremoval ofthestationaryphasebytherelativelylarge volumeofsolventreleasedinsidethecolumn bythesyringe[32].Theseadvancesincolumn technologyfacilitatedthedevelopmentofcold on-columninjectionwherethesampleisintroducedasaliquidintothecolumninletandsubsequentlyvaporized.Discriminationbecauseof volatilitydifferenceswasvirtuallyeliminated andtheriskofsampledecompositionminimized.Withsecondarycoolingoftheinjector, theoventemperaturecouldbekeptwellabove theboilingpointofthesolventwhilemaintainingthecolumninletatamuchlowertemperature.Thisisimportantforusingon-column injectioninhigh-temperaturegaschromatography.Dirtysamplespresentaproblemowing tocontaminationofthesampleintroduction zone,whichleadstopoorchromatographyand unreliablequanti fication.Bothon-columnand PTVinjectionaffordhighaccuracyandprecision.Theseinjectorsalsofacilitatedthedirect couplingofotherchromatographicsystemsto gaschromatography,suchasliquidchromatographyandsupercritical fluidchromatography [33].Inthe1980s,CarloErbamanufacturedan instrumentforon-lineliquidchromatography gaschromatography,buttheuptakewaspoor andthesystemwasdiscontinued.
