A fast atom bombardment and matrix-assisted laser desorption/ionization mass spectrometry study of doubly charged porphyrins

In this mass spectrometry (MS) study of doubly charged porphyrin salts, fas t atom bombardment (FAD) and matrix-assisted laser desorption/ionization (M ALDI) MS techniques are utilized to examine several unique ionic species. T he predominant transformation of preformed doubly charged ions in the desor ption/ionization mechanism of FAB and MALDI is the result of deprotonation reactions to form singly charged ions of the type [M2+-H+](+) and of one-el ectron reductions to form radical cations [M2++e(-)](+.). The dependence of this phenomenon and the formation of a number of additional ionic species on the different matrices and the FAB-matrix additive benzoquinone is exami ned. The significant analogous behavior of doubly charged porphyrins in FAB - and MALDI-MS leads to the conclusion that one-electron reductions are of distinct relevance in the desorption/ionization mechanism of MALDI. Copyrig ht (C) 2001 John Wiley & Sons, Ltd..