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 tand em mass spectrometry methods to identify trichloromethyl/C-phenyl-N-te ut-butyl nitrone (PBN) spin adducts produced in rat liver microsomal d ispersions that had been treated with reduced nicotinamide adenine din ucleotide phosphate (NADPH)-generating system and BrCCl3 (or CCl4). In the identification of PBN spin adducts, a scan of precursors of m/z 5 7 was utilized to confirm the presence of PBN spin adducts, because PB N spin adducts produce m/z 57 from tert-butyl as a characteristic frag ment. 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 (wh ich corresponds to the deuterated tert-butyl group) is characteristic and, unlike m/z 57, it is not a common fragment for any other compound s. Two new PBN spin adducts that were not detected before by electron paramagnetic resonance or mass spectrometry were identified by these m ethods for the first time.