Aspects of the Production of FAB and SIMS Mass Spectra

Article abstract of DOI:10.1021/ja00241a013

It is shown that reduction is a common process in FAB mass spectra and that these processes are frequently consistent with one-electron reductions.The model previously presented by Cooks et al. to rationalize features of SIMS (and, by analogy, FAB) spectra obtained from a matrix is developed in terms of qualitative energetic considerations.It is shown that the population of ions observed is consistent with the formation of gas-phase ions whose energies are in the approximate range 0-3 eV (and not>8 eV).From an analysis of the ratio of singly to doubly charged ions in FAB spectra, it is deduced that in the positive ion spectra of highly basic compounds (e.g., arginine-containing peptides), comparable amounts of the analyte are desorbed as ions and neutrals.In contrast, it is concluded that polyhydroxy compounds lacking a highly basic site are largely desorbed as neutral species, with a consequent loss in sensitivity.