A new kind of metal incorporation in porphyrins during mass spectrometric analysis: cation exchange between lithium halide or transition-metal halide surfaces and metalloporphyrins in field desorption

Abstract

Under conditions normally used for cationisation field desorption, cations from some metal salts replace central metal ions in representative porphyrin complexes. Lithium ions replace weakly bound central metal cations, such as Cd, but not more strongly bound ions such as Cu. The transition-metal cations, on the other hand, not only replace weakly bound metals in the metalloporphyrin complex, but can also replace cations normally considered ‘strongly bound.’ Cation-exchange reactions in field desorption are thus more general than those found in electron ionization and define a limit of usefulness of the cationisation field desorption technique.