DETERMINATION OF BLOOD LEAD BY ELECTRON-CAPTURE NEGATIVE CHEMICAL-IONIZATION GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

An electron-capture negative chemical ionization (NCI) gas chromatogra phy-mass spectrometry (GC-MS) method for determination of lead (Pb) in blood samples is described, Extraction of Pb from the sample does not involve hot digestion but is based on treatment at ambient temperatur e. The blood sample is supplemented with a known amount of internal st andard (Pb-204) for isotope dilution and is treated with concentrated nitric acid, After adjusting the pH to 7, the Pb is extracted into tol uene as the pyrrolidine-dithiocarbamate chelate, Samples are then deri vatized with 4-fluorophenylmagnesium bromide to form Pb(FC6H4)(4). The use of NCI offers enhanced sensitivity (by 75-fold better than previo usly used electron ionization), gives good precision and accuracy, and has no observable memory effect, The isotope dilution GC-MS methodolo gy typically agreed within 2-3% of expected values for the College of American Pathologists blood Pb specimens and the National Institute of Standards and Technology Standard Reference Material 955a.