Liquid secondary ion mass spectra and fast atom bombardment mass spectra of diquaternary pyridinium oxime salts

Positive-ion mass spectra of diquaternary pyridinium oxime salts were measured using fast atom bombardment and liquid secondary ion mass spectrometry in different laboratories to establish both the characteristic behavior and the spectral variability of this class of compounds. Molecular ions observed in these mass spectra include the one-electron reduced doubly charged cation, the deprotonated double charged cation and the anion-reduced doubly charged cation. Common fragment ions include the products of simple cleavages along the aliphatic bridge between the heterocyclic rings. Concomitant loss of hydrogen and cyclization of the bridge can occur, along with losses of OH, NOH and CHNOH from various fragment ions. A nitrobenzyl alcohol matrix generally gave superior results to glycerol and thioglycerol in all laboratories, although the use of additive surfactant acids such as p-toluenesulfonic acid or camphorsulfonic acid in glycerol could provide useful results.