Quadrupole Ion Trap Time-of-Flight MALDI Mass Spectrometry: Hydration of Ions of Hydroxyl-Containing Compounds

A possibility of artifact formation associated with ion hydration in quadrupole ion trap MALDI mass spectra is shown for the first time on an example of a number of natural hydroxyl-containing compounds from various classes. It was found that, in using tandem mass spectrometry, both precursor ions and product ions are involved in the formation of adducts with water. The main source of water for ion-molecular interactions in the ion trap is provided by buffer and collision gases. The role of metal cations in the formation of analyte adducts with water is noted. For the majority of the studied hydroxyl-containing compounds, hydration proceeds most actively in cationization with lithium ions, with the peak of the [M+H2O+Li]+ ion dominating in the mass spectra.