THE DETERMINATION OF LEAD IN BLOOD USING ISOTOPE-DILUTION INDUCTIVELY-COUPLED PLASMA-MASS SPECTROMETRY

Isotope dilution inductively coupled plasma mass spectrometry (ID-ICP- MS) was applied to the certification of Pb in four levels of NIST bloo d SRM, 955a. This standard reference material (SRM) represents a signi ficant improvement over the previous blood reference material and will greatly aid method development. The lowest level, 47.76 ng/g Pb was d etermined with an analysis uncertainty (95% Cl, ID-ICP-MS uncertaintie s) of less than 1% and the highest level, 517.9 ng/g Pb to 0.3%. Uncer tainty in the lowest level was due to sample inhomogeneity and variabi lity in the analytical blank as the RSD on ratio measurements was typi cally better than 0.2%. Properly applied isotope dilution coupled with careful isotope ratio measurements on the ICP-MS offers precision and accuracy for blood Pb analyses beyond what is currently obtainable wi th routine methods.