Silver cationization of thia fatty acids and esters in laser desorption/ionization time-of-flight mass spectrometry

A laser desorption/ionization (LDI) time-of-flight mass spectrometric (TOF- MS) technique was used for the molecular mass analysis of thia fatty acids and esters, samples without appreciable light absorption at the laser wavel ength. After a sample overlayer is deposited by solvent evaporation on a th in silver film substrate, it is subjected to 355 or 532 nm Nd:YAG laser irr adiation. Photoablation of the Ag film substrate occurs with sufficient las er fluence, producing silver cluster cations, which can react with the deso rbed thia fatty acid or ester molecules in the gas phase. Silver cation att achment of thia fatty esters may produce a silver-cationized analyte and fr agments of structural diagnostic value, whereas thia fatty acids would not. With oxygen(s) present on the sulfur in sulfoxy fatty acids and esters, a silver-cationized analyte and additional fragments are produced. Formation of these fragments is consistent with charge-remote mechanisms through simp le cleavage and rearrangement pathways. The structural reactivity of these compounds with ablated silver cations is hence comprehensively analyzed, Co pyright (C) 1999 John Wiley & Sons, Ltd.