Selectivity of negative ion chemical ionization mass spectrometry for benzo[a]pyrene

Abstract

Gas chromatography/negative ion chemical ionization mass spectrometry (GC/NICIMS) was used as a selective and sensitive technique for the detection of benzo(a)pyrene (BaP). Under optimized conditions, the molecular anion, M/sup -/, of BaP was more than 3 orders of magnitude more abundant than that of its isomer benzo(e)pyrene (BeP) using methane as the reagent gas. Quantities of BaP as low as 1 pg can easily be detected in the selected ion monitoring mode and the response vs. concentration was linear over a range of 3 orders of magnitude. The absolute sensitivity and the selectivity for detection were found to depend on the pressure and temperature in the ion source of the mass spectrometer. NICIMS was used for the quantitative determination of BaP, indeno(1,2,3-cd)pyrene, and benzo(ghl)perylene in a sample of petroleum crude oil as part of the process of certifying the oil as a Standard Reference Material.