Cationization of simple organic molecules by singly-charged Ag-3(+) cluster ions in matrix-assisted laser desorption/ionization mass spectrometry: Metal cluster-molecule interactions

摘要

It was found earlier that under matrix-assisted laser desorption/ionization (MALDI) conditions several organic compounds which produce adduct with silver ions, are also capable of forming adducts with Ag-3(+) cluster ions under appropriate conditions. The Ag-3(+) cluster ion can be in situ generated under the MALDI analysis conditions from silver trifluoroacetate cationization agent in the presence of organic MALDI matrices. In this article the fragmentation of a commercial plasticizer, a peracetylated isoflavone glycoside and a pyrazolylphenyl disulfide derivative cationized with silver ions and Ag-3(+) cluster ions are compared. It was observed that the complexes of Ag-3(+) are less fragmented than the corresponding adduct ions with Ag+. The presumable fragmentation channel of [M + Ag-3(+)] is the elimination of Age units from these complexes. No significant dissociation of [M + Ag-3(+)], into M and Ag-3(+) takes place, indicating a tight connection between the corresponding molecule and Ag-3(+) cluster ion. However, with a compound carrying very labile groups, such as the pyrazolylphenyl disulfide derivative, intramolecular cleavages can occur prior to significant dissociation of the Ag-3(+) cluster ion.(C) 2004 American soociety for Mass Spectrometry.