Achieving high gating performance for ion mobility spectrometry by manipulating ion swarm spatiotemporal behaviors in the vicinity of ion shutter.

Abstract

Ion shutter is one of the key components of the drift-tube types of ion mobility spectrometer, which affects both the resolving power and sensitivity of an ion mobility spectrometer. In this work, a spatiotemporal model was built to understand the behaviors of the ion swarms around the ion shutter. For simplicity, a Tyndall-Powell gate (TPG) was chosen as the gating disturbance to the field on the two sides of ion shutter could be separated. It can be inferred from the spatiotemporal model that the ion swarm could be diluted in front of the TPG when the gate closing voltage (GCV) was superposed on the grid facing the ionization region, while it could be compressed behind the TPG when the GCV was superposed on the other grid. These inferences conformed to the narrower and higher ion peaks obtained at GCV superposed on the latter grid and were further verified by the ion distribution profiles obtained at a wide gate opening pulse width. Finally, the product of the resolving power and the gating efficiency was proposed to evaluate the gating performance of an ion shutter. At GCV superposed on the grid facing the drift region, the best gating performance of 42 was obtained with peak height of 1.63\u202fnA and resolving power of 57.2, and was almost twice as high as the optimal gating performance at GCV superposed on the other grid.