Queuing Theory-based Predictions Ion Mobility Shifts via Vapor Clustering at Arbitrary Field Strength

TOMOYA TAMADATE, Christopher J. Hogan, Kanazawa University

     Abstract Number: 272
     Working Group: Aerosol Physics

Abstract
Ion mobility spectrometry (IMS) enables the separation of gas-phase ions based on their electrophoretic velocity per unit electric field strength in a bath gas of controlled composition, i.e. based upon their ion mobilities (or mobility diameters). More advanced separation methodologies incorporate high electric field strengths and the introduction of condensable vapor molecules, which selectively cluster with gas-phase ions. In this study, we develop and implement a queuing theory-based framework to predict ion mobilities under arbitrary electric field strengths and in the presence of condensable vapors. The theoretical approach is validated through comparison with molecular dynamics (MD) simulations of doubly charged bradykinin ions in a nitrogen atmosphere (1 atm), with methanol introduced as a condensable vapor. Simulations span a range of electric field strengths extending beyond the zero-field limit (up to 76 kV/cm). The MD results capture typical ion mobility responses to variations in both field strength and vapor pressure. Comparison between the queuing theory model and MD simulations reveals that key statistical parameters, such as vapor arrival time, binding duration, and the number of binding vapor molecules, are well represented by appropriate probability distributions. These findings support the use of the queuing theory approach for mobility prediction, contingent only upon well-defined input parameters.