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.