Characterization of amino polyaromatic hydrocarbon–DNA adducts using continuous‐flow fast atom bombardment and collision‐induced dissociation: Positive and negative ion spectra

Continuous-flow fast atom bombardment (CF FAB) mass spectrometry has been investigated for the detection and structural characterization of amino polyaromatic hydrocarbon DNA nucleoside adducts. Full scan CF FAB mass spectra can be recorded using fewer than 50 ng, and corresponding tandem mass spectra are obtained from only 20–40 ng of adduct. This represents a 20-30-fold increase in sensitivity over single-scan spectra recorded using a static FAB probe. The flow injection nature of the apparatus simplifies the handling of samples. Positive ion spectra generally exhibit protonated molecular species, [MH]+, and protonated aglycone species, [AH2]+, resulting from loss of the deoxyribose sugar. Further structural detail is provided by collision-induced dissociation (CID) of the appropriate ion with B/E linked scans. By recording the CID spectra of both the [MH]+ and the [AH2]+ions, information about the base, sugar, polyaromatic hydrocarbon xenobiotic and site of covalent linkage may be obtained. Additionally, reaction monitoring of the metastable transition from [MH]+ to [AH2]+ provides a reliable method of detection for these adducts at picogram levels with the potential for even lower detect limits. CF FAB spectra acquired in the negative ion mode exhibit interesting features when compared with positive ion spectra. Included among these is an enhancement in the relative intensity of the [M - H]− ion for most adducts and complementary fragmentation in certain cases.