Validation of the determination of lead in whole blood by ICP-MS

Validation of the determination of lead in whole blood by ICP-quadrupole MS has been performed. Blood was 1:45 v/v diluted in an aqueous solution containing 0.1 mg l(-1) NH4OH, 0.1 g l(-1) EDTA, 5 mg l(-1) n-butanol and 0.1% Triton X 100. It was verified that a synthetic matrix made of 7.5 g l-(1) NaCl and 0.5 g l(-1) CaCl2 behaved similarly to the whole blood and to QC samples. Limits of detection and of quantitation were determined by plotting the RSD of the net signal as a function of the concentration, and were 0.01 and 0.1 mug l(-1), respectively, which was below the lowest Pb concentration in blood, i.e., 0.2 mug l(-1) after dilution. Uncertainty of the centroid of the calibration graph was preferred to the evaluation of the linearity with ANOVA to validate the calibration procedure. At 95% confidence level, a warning limit was set up at 5% uncertainty, while rejection was decided on for 20% uncertainty. Internal standardization based on the use of Re-187 provided improvement in the uncertainty and the reproducibility. Intra- and inter-day reproducibilities were evaluated. Good agreement was observed between the concentrations obtained by ICP-MS and GF-AAS.