ELECTRON-CAPTURE NEGATIVE CHEMICAL-IONIZATION MASS-SPECTROMETRY AND TANDEM MASS-SPECTROMETRY ANALYSIS OF BETA-CAROTENE, ALPHA-TOCOPHEROL AND THEIR OXIDATION-PRODUCTS

The biological antioxidants alpha-tocopherol, 1, and beta-carotene, 4, and products of their antioxidant reactions are potentially important indicators of biological antioxidant status and functions. Electron c apture by compounds 1 and 4 and their oxidation products yields intens e molecular anions with little fragmentation. Collision-induced dissoc iation of the molecular anions was studied by linked-scaning (B/E = co nstant) on a reverse-geometry magnetic-sector mass spectrometer. Both 1 and 4 and their products undergo extensive diagnostic cleavages of t heir hydrocarbon chains, apparently via charge-remote fragmentation. E lectron capture negative chemical ionization mass spectrometry appears uniquely suited to structure identification studies of antioxidants a nd their oxidation products. This methodology is used to identify oxid ation products of 1 and 4 from a model biological membrane system subj ected to peroxyl radical attack.