TANDEM MASS-SPECTROMETRY STUDY OF C-PHENYL-N-TERT-BUTYL NITRONE SPIN ADDUCTS FROM IN-VITRO RAT-LIVER MICROSOMAL METABOLISM OF BROMOTRICHLOROMETHANE AND CARBON-TETRACHLORIDE

Electron ionization and thermospray were used in conjunction with tandem mass spectrometry methods to identify trichloromethyl/C-phenyl-N-teut-butyl nitrone (PBN) spin adducts produced in rat liver microsomal dispersions that had been treated with reduced nicotinamide adenine dinucleotide phosphate (NADPH)-generating system and BrCCl3 (or CCl4). In the identification of PBN spin adducts, a scan of precursors of m/z 57 was utilized to confirm the presence of PBN spin adducts, because PBN spin adducts produce m/z 57 from tert-butyl as a characteristic fragment. Use of deuterated PBN (PBN-d(9) deuterated at tert-butyl; PBN-d(14) deuterated at both phenyl and tert-butyl) improved the recognition of PBN adducts in mixtures by precursor ion scans, because m/z 66 (which corresponds to the deuterated tert-butyl group) is characteristic and, unlike m/z 57, it is not a common fragment for any other compounds. Two new PBN spin adducts that were not detected before by electron paramagnetic resonance or mass spectrometry were identified by these methods for the first time.