Mobility shifts when buffer gas temperature increases in ion mobility spectrometry are affected by intramolecular bonds

Abstract

When buffer gas temperatures increase in ion mobility spectrometry (IMS), ions lose hydration molecules and their mobilities increase. Also, shift reagents (SRs, dopants or modifiers) introduced in the buffer gas, form adducts with the ions and their ion mobilities decrease. Some ions, such as methionine and diamines, are not largely influenced by the introduction of SRs or the buffer gas temperatures because they form intramolecular hydrogen bonds (IHBs). We used electrospray ionization IMS coupled to quadrupole mass spectrometry to study the drift behavior of these ions using data obtained at different temperatures or with different SRs. In this study, we explain the unusually small mobility shifts in methionine and diamine ions when buffer gas temperature increases in IMS based on the breaking of IHBs that increase the ions’ collision cross-sections. We also explain the small mobility shifts in these ions when buffer gas SRs are introduced in the drift tube based on the formation of these IHBs, This study is important because when temperature increases in IMS, mobility shifts had been considered to be affected exclusively by declustering and the increase in collision frequency. This information will help understand the behavior of IHB-forming ions in IMS at different temperatures and when buffer gas SRs are introduced in the drift tube, and could be used to demonstrate the presence of these bonds and measure their binding energy.