Preferential Ion Microsolvation in Mixed-Modifier Environments Observed Using Differential Mobility Spectrometry
The preferential solvation behavior for eight different derivatives of protonated quinoline was measured in a tandem differential mobility spectrometer mass spectrometer (DMS-MS). Ion-solvent cluster formation was induced in the DMS by the addition of chemical modifiers (i.e., solvent vapors) to the N2 buffer gas. To determine the effect of more than one modifier in the DMS environment, we performed DMS experiments with varying mixtures of water, acetonitrile, and isopropyl alcohol solvent vapors. The results show that doping the buffer gas with a binary mixture of modifiers leads to the ions binding preferentially to one modifier over another. We used density functional theory to calculate the ion-solvent binding energies, and in all cases, calculations show that the quinolinium ions bind most strongly with acetonitrile, then isopropyl alcohol, and most weakly with water. Computational results support the hypothesis that the quinolinium ions bind exclusively to whichever solvent they have the strongest interaction with, regardless of the presence of other modifier gases.
KeywordsDifferential ion mobility DMS Ion mobility Modifiers Preferential solvation Gas-phase solvation DFT Ion-solvent clustering
The authors acknowledge high-performance computing support from the SHARCNET consortium of Compute Canada. WSH acknowledges financial support from the Natural Sciences and Engineering Research Council (NSERC) via the Discovery Grant and Collaborative Research and Development Grant schemes. WSH also acknowledges financial support from the Ontario Centres of Excellence in the form of a VIP-II grant, as well as the government of Ontario for an Ontario Early Researcher Award. MJL acknowledges financial support from the NSERC for a Vanier Graduate Scholarship.
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