A substitute for ion gating in ion mobility spectrometry

Abstract

Miniaturized ion mobility spectrometry (IMS) presents several advantages as portable chemical detection tools. They are fast, simple and inexpensive. However, the implementation of ion gates in miniaturized designs is difficult. Studies also showed that ion gates leads to electrostatic effects that negatively impacts the performance of IMS. This paper presents an alternative which eliminates ion gates by using the pulsating regimes of electrospray to generate small ion packets and a current-based measurement method to monitor drift times. A feedback loop was designed to control the number of pulsations generated by the electrospray. The results demonstrate that pulses of the axial spray mode I generate ion emissions of about 200 μs in ambient gas, which is comparable to conventional gating methods. The measured mobility is roughly 2.5 times higher than with conventional gating methods, so a new library of ion mobilities for this new method must be created for reference. The method presented is inexpensive and can be easily implemented in microfabricated IMS and similar devices.