SUPPRESSION EFFECTS ON A REDUCTION PROCESS IN FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

Various methods of suppression of the reduction process occurring in f ast-atom bombardment (FAB) mass spectrometry have been studied, using the organic dyes rhodamine B and methylene blue as reference compounds . Our results indicate that transition metal chlorides have a strong i nfluence on the suppression of the reduction process, while stannous c hloride exhibits a remarkable suppression effect despite being a stron g reducing agent. We suggest that the metal radicals generated in glyc erol solution are responsible for these suppression effects. This phen omenon strongly supports the mechanism of hydrogen radical addition to the substrate molecules, postulated earlier as the cause of the reduc tion process. Co-solvents in the matrix have also been found to suppre ss the reduction ions along with other matrix-interfering ions. These studies help shed some light on the FAB ionization mechanism.