Gas-phase ion dynamics in a periodic-focusing DC ion guide

In this work, we provide a comprehensive understanding of the radial ion focusing mechanism in the periodic-focusing DC ion guide (PDC IG) The PDC IG was developed in our laboratory to improve the sensitivity and throughput orlon mobility spectrometry (IMS) with respect to conventional uniform field IMS. Radial ion focusing, which is responsible for the sensitivity improvement, is attributed to the presence of effective potentials created by the fringing electric fields of thick ring electrodes and collisional cooling of the ions with the neutral buffer gas. The ion focusing mechanism is affirmed by investigating the variations in the effective ion temperature (T-eff) which are dependent upon axial position in the device. The concepts derived herein outline guidelines for the design of high performance PDC IG ion mobility instruments and other ion optical devices such as periodic-focusing DC ion funnels (C) 2010 Elsevier B V All rights reserved