Solving the “General Elution Problem” of Ion Mobility Spectrometry: Single-Run Voltage Sweep

While modern mobility methods have shifted toward vacuum-based techniques that allow advanced ion manipulations to improve resolution, atmospheric pressure ion mobility spectrometry (IMS) cells continue to find utility in primary security and screening applications. These small units generally demonstrate low resolution due to both their size and inability to perform advanced ion manipulations at atmospheric pressure. Existing drift time IMS cells utilize a static voltage typically tuned to optimize both total signal and separation efficiency for the ions of particular interest in a given application. These static voltage IMS cells suffer from a phenomenon similar to the general elution problem of chromatography, wherein the separation conditions are optimized for a particular species at the expense of the other analytes in the system. Through the application of an external high voltage sweep (VS) tuned to match the theoretical optimum potential at every drift time, this work solves the General Elution Problem of IMS. In comparison to static mode, VSIMS demonstrates significantly improved resolution and resolving power while maintaining fidelity in reduced mobility measurements. When applied to a library of IMS standards, VSIMS demonstrates consistent, reproducible resolving powers regardless of the mobility of the ion introduced to the instrument.