DETERMINATION OF LEAD IN URINE AND WHOLE-BLOOD BY STABLE-ISOTOPE DILUTION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

A stable isotope dilution gas chromatography-mass spectrometry (CC-MS) method is described for the determination of lead (Pb) in urine and w hole blood. The use of lithium bis(trifluoroethyl)dithiocarbamate Pb(F DEDTC) as a chelating agent showed strong memory effect, restricting t he range of Pb isotope ratios that can be measured in unknown samples. To overcome this carryover problem, we further derivatized the Pb(FDE DTC)(2) chelate with 4-fluorophenyl magnesium bromide to form Pb(FC6H4 )(4). The sequential analyses of solutions of natural Pb and enriched Pb-204 With Pb(FC6H4)(4) chelate by GC-MS demonstrated no observable m emory effect. Precision and accuracy of Pb isotope ratio measurements with Pb(FC6H4)(4) were established, and the isotope dilution GC-MS met hod was validated by determining Pb concentrations in urine standards from the National Institute of Standards and Technology, urine and blo od reference materials from the New York State Department of Health, a nd blood Pb survey samples from the College of American Pathologists.