Determination of lead in whole blood using inductively coupled argon plasma mass spectrometry with isotope dilution

Abstract

An accurate and simple method for determination of lead in whole blood using inductively coupled argon plasma mass source mass spectrometry (ICP-MS) was developed. Determination of lead was by stable isotope dilution, using a spiking material from the National Institute of Standards and Technology (NIST), Standard Reference Material (SRM) 983, Radiogenic Lead Isotopic Standard, enriched to 92.15 at.% lead 206 (206Pb). Two aliquots of each whole blood specimen were taken (about 0.50 g) and weighed accurately by difference. One of the aliquots was then spiked with about 100 mg of a solution prepared from SRM 983; about 1 µg g–1 of Pb in concentration. Both aliquots were then digested with ultrapure, concentrated nitric acid in a microwave oven. The digestate was cooled, diluted, and both unspiked and spiked digests were aspirated into the ICP-MS instrument and isotope ratios of lead 208 : lead 206 were measured. The amount and concentration of lead was calculated as µg of lead per g sample, and multiplied by 100 to give µg of lead per 100 g of sample. This mass-basis measurement (µg per 100 g) was then converted to mass per volume (µg dl–1) using the measured density of the whole blood specimen as a correction factor. The method has been evaluated using SRM 955a to determine accuracy. The proposed method provides a standard of accuracy for determination of lead in blood in a nationally based standardization programme, the Blood Lead Laboratory Reference System (BLLRS).