Reduction processes in the fast atom bombardment mass spectra of pyridinium salts. The effect of reduction potential and concentration

The enhancement of the (C + 1)/C ratio in the fast atom bombardment mass spectra of seven pyridinium cations has been measured. No dependence of the enhancement on the cation reduction potential could be identified. The N-methyl pyridinium cation, which showed no enchancement under matrix-free conditions, exhibited an increase in the (C + 1)/C ratio with decreasing concentration. This concentration dependence was eliminated when the bombardment energy was reduced from 9 to 5 keV. Possible mechanisms for the concentration dependence and the variation with bombardment energy are proposed. Keywords: fast atom bombardment, reduction, pyridinium salts.