Fragmentation of Doubly-Charged Negative Ions of Dicarboxylic Acids under Collision-Induced Dissociation Conditions

The conditions for recording electrospray ionization mass spectra of dicarboxylic acids are selected to ensure the generation of doubly-charged negative ions of compounds containing more than 14 carbon atoms in the chain. The fragmentation of such ions under the conditions of collision-induced activation is described. It is shown that the main decomposition route is associated with the break of C–C bonds in the hydrocarbon skeleton of molecules. Thus, in contrast to the fragmentation of singly charged negative ions, the forced decomposition of bis-deprotonation products of decarboxylic acids makes it possible to obtain information about the structure of the molecular skeleton.