POSITIVE ION LIQUID SECONDARY ION MASS SPECTRA OF AROMATIC SULFONIUM SALTS

Abstract

Organic sulfonium salts exist as pit-charged species in the matrices normally used for liquid secondary ionization mass spectrometry. Positive ion LSIMS mass spectra of the sulfonium salts therefore exhibit the intact cation (C⁺) as the dominant ion species. Generally, the fragment ions are of 30–40% relative intensity and are formed through simple cleavages and rearrangements. Cluster ions such as CAC⁺ and C₃A₂ ⁺ are also present in the mass spectra (A is the counter ion of the salt). These cluster ions provided confirmation of the molecular weight. Adduct ions are formed between organic sulfonium salts and matrices used in LSIMS such as diethanolamine and triethanolamine. Beam-induced reactions are identified by comparison of mass spectra obtained with electrospray ionization, and by changes in ion products with changes in solvent matrix.

Key Words:

• Mass spectrometry
• LSIMS
• sulfonium salts
• electrospray