A Study of the Critical Uncertainty Contributions in the Analysis of PCBs in Ambient Air
Table 5
(a) Table calculating the uncertainty in the mass concentration of PCB in the SRM using (6) and the third approach (gravimetric preparation: calculations in the mass concentration domain).
Quantity
Symbol
Value
Sensitivity coefficient
Uncertainty
Probability distribution
Divisor
Contribution to standard uncert
Mass fraction of PCB in the extract (ng⋅mL−1)
5.640
4.76
0.593
Normal
1
2.821
Total volume of extract (mL)
1.244
21.6
0.006
Normal
1
0.121
Extraction efficiency (no units)
0.658
−40.8
0.028
Normal
1
−1.139
Mass of SRM extracted (g)
0.397
−67.6
0.001
Normal
1
−0.034
Mass fraction of PCB in the SRM (ng⋅g−1)
26.853
—
—
Normal
1
3.045
(b) Table calculating the uncertainty in the measured mass concentration of PCB in the extract using (7) and the third approach (gravimetric preparation: calculations in the mass concentration domain).
Quantity
Symbol
Value
Sensitivity coefficient
Uncertainty
Probability distribution
Divisor
Contribution to standard uncert
Average injection standard corrected peak area of PCB in the extract (no units)
0.0213
265
0.0021
Normal
1
0.564
Gradient of the calibration curve for the PCB (mL⋅ng−1)
0.00378
−1494
0.00012
Normal
1
−0.182
Measured mass concentration of PCB in the extract (ng⋅mL−1)
5.640
—
—
Normal
1
0.593
(c) Table calculating the uncertainty in extraction efficiency using (8) and the third approach (gravimetric preparation: calculations in the mass concentration domain).
Quantity
Symbol
Value
Sensitivity coefficient
Uncertainty
Probability distribution
Divisor
Contribution to standard uncert
Average, injection standard-corrected, peak area of the internal standard in the extract (no units)
0.298
2.21
0.007
Normal
1
0.016
Mass concentration of the internal standard in a calibration solution (ng⋅mL−1)
36.79
0.018
0.83
Normal
1
0.015
Average, injection standard-corrected, peak area of the internal standard in a calibration solution (no units)
0.489
−1.35
0.012
Normal
1
−0.016
Theoretical mass concentration of the internal standard in the extract (assuming complete recovery) (ng⋅mL−1)
