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

Abstract

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 µg l⁻¹, respectively, which was below the lowest Pb concentration in blood, i.e., 0.2 µg 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 ¹⁸⁷Re 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.