Combined liquid chromatography/electron paramagnetic resonance spectrometry/electrospray ionization mass spectrometry for radical identification.

Electron paramagnetic resonance (EPR) spectrometry and mass spectrometry (MS) have been coupled together on-line with liquid chromatography (LC)/UV detection. These combined techniques have been applied to the determination of spin-trapped radical adducts, including phenyl, 2-, 3-, and 4-chlorophenyl, and 2-bromophenyl radicals trapped with alpha-(1-oxo-4-pyridyl)-N-tert-butylnitrone (4-POBN), and phenyl radicals trapped with 2-methyl-2-nitrosopropane (MNP), alpha-phenyl-N-tert-butylnitrone (PBN), and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Oxidized and reduced forms of the radical adducts were also detected by the on-line LC/EPR/MS system.