Rodrigo Porcionato, Danielle Polidório Íntima, Cassiana Seimi Nomura
0.30
A
-1) Integrated Absorbance/sample mass (s mg
Results showed that all standards presented homogeneity factors of about 10 (HE < 10) for Cd and Pb, indicating acceptable homogeneity for microanalysis.
0.25
Integrated Absorbance (s)
Table III. Homogeneity results for Cd and Pb in ceramics Cd Pb m (mg) HE
m (mg) HE
Standard 1
0.662 ± 0.142
Standard 2
0.081 + 0.021
2.4 0.173 + 0.074 11
Standard 3
0.085 + 0.026
2.6 0.101 + 0.091 5.0
Standard 4
0.077 + 0.024
2.8 0.052 + 0.027 7.6
2.2
0.157 ± 0.049
13
0.20
0.15
0.10
0.05
0.00
B 2.0
1.5
1.0
0.5
0.0 0
20
40
60
80
100
120
0
Calibration Analytical calibration curves for Cd and Pb made by increasing the mass of one calibrating standard are shown in Figures 1a (y = 1.942 ± 0.0386 x, R2 = 0.9956 ± 0.0087) and 2a (y = 0.00222 ± 0.00004 x, R2 = 0.9962 ± 0.0079) respectively. The analytical calibration curves using four calibrating standards containing different concentration of Cd and Pb are shown, respectively, in Figures 1b (y = 0.00883 ± 0.00006 x, R2 = 0.9999 ± 0.0033) and 2b (y = 0.00190 ± 0.00006 x, R2 = 0.9983 ± 0.0539) for Pb. Analytical calibration curves were also performed with aqueous solutions that showed the same behaviors as those obtained using solid calibrating standards for Cd (y = 0.00900 ± 0.00009 x, R2 = 0.9992 ± 0.0045) and for Pb (y = 0.00193 ± 0,000024 x, R2 = 0.9991 ± 0.0033). In this specific case, the determinations of Cd and Pb by SS-GFAAS could be done using aqueous calibrations.
0.5
A -1) Integrated absorbance / sample mass (A mg
0.05
Integrated Absorbance (s)
0.04
0.03
0.02
0.01
0.00 1
2
3
4
5
a
50
60
Cd (mg kg-1)
calibration curves for
Cd: (a)
increasing sample
containing different concentrations of
Cd
Pb: (a)
increasing sample
Pb
CRM MESS-1 BCSS-1 SRM2703 CPIII* SRM 1648a PACS 2 SRM 1944 TH-1 TH-2 MESS-1 BCSS-1 TH-1 TH-2 PACS 2 SRM 1944 TH-1 TH-2 PACS 2 SRM 1944
Cd (mg kg-1) Certified value Found Value 0.59 ± 0.10 0.25 ± 0.04 0.25 ± 0.04 0.26 ± 0.03 0.811 ± 0.076 0.77 ± 0.04 0.40 ± 0.01 0.35 ± 0.09 73.7 ± 2.3 79.9 ± 11.5 2.11 ± 0.10 2.3 ± 0.3 8.8 ± 1.4 9.8 ± 1.8 5.41 ± 1.83 6.2 ± 0.4 5.22 ± 0.46 4.9 ± 0.6 Pb (mg kg-1) 34.0 ± 6.1 35.1 ± 8.9 22.7 ± 3.4 23.4 ± 1.3 257 ± 69 267 ± 25 194 ± 14 198 ± 22 183 ± 8 191 ± 29 330 ± 48 341 ± 37 257 ± 69 246 ± 5 194 ± 14 184 ± 16 183 ± 8 188 ± 20 330 ± 48 301 ± 32
Calibration type 1 (using increasing sample mass of one calibrating standard) b
40
mass of one calibrating standard, and (b) four calibrating standards
52
T Y P E 2
0.1
Cd (ng)
Figure 1. Analytical
T Y P E 1
T Y P E 2
30
1000
1). increasing sample mass of calibrating standard containing 0.44 ± 0.05 mg Cd and 506 ± 21 mg kg-1 of Pb; 2). similar sample masses of calibrating standards containing different concentration of Cd and Pb
0.2
20
800
kg-1 of
0.3
10
600
Table IV. CRM analysis using ceramics impregnated with Cd and Pb standards for analytical calibration curves:
B
0
calibration curves for
containing different concentrations of
0.4
6
400
mass of one calibrating standard, and (b) four calibrating standards
T Y P E 1
0.0 0
Figure 2. Analytical
200
Pb (mg kg-1)
Pb (ng)
Calibration type 2 (using four calibrating standards containing different concentration of Cd and Pb)
Analysis of CRMs The applicability of the proposed ceramics spiked with different concentration of Cd and Pb as a synthetic calibrating standard was checked by the analysis of environmental CRMs. The CRM results using calibration with increasing mass of one standard (type 1) and using four
Br J Anal Chem