Liquid chromatography-mass spectrometry with collision-induced dissociation of conjugated metabolites of benzo[a]pyrene

Benzo[a]pyrene (BP) metabolites conjugated with glutathione, cysteine- glycine, cysteine, N-acetylcysteine, and sulfuric and glucuronic acids have been studied by microcolumn liquid chromatography-electrospray mass spectrometry with collision-induced dissociation (CID) on a hybrid double focusing magnetic sector-orthogonal time-of-flight tandem mass spectrometer equipped with a focal plane array detector. Negative-ion electrospray mass spectra of the conjugated BP metabolites showed strong [M - H]^- ions. When the array detector was used, spectra were obtained from femtomoles of sample infused at mass resolutions of 5000 (full width at half maximum). Cone voltage fragmentation spectra show [M - H]^- ions and fragment ions indicative of the BP moiety and/or the conjugating group. Linked scan CID spectra at constant B/E were found to contain structurally informative product ions from infusion of as little as 1 pmol of sample. CID spectra were also recorded by using the double focusing sectors for precursor ion selection and the orthogonal time-of-flight analyzer for product ion mass separation. The method was applied to the analysis of conjugated BP metabolites in the urine of germ-free rats given a single intraperitoneal dose of BP.