Compact and Sensitive Dual Drift Tube Ion Mobility Spectrometer with a New Dual Field Switching Ion Shutter for Simultaneous Detection of Both Ion Polarities

Abstract

Ion mobility spectrometers (IMS) with field switching ion shutters are an excellent choice for trace gas detection, being extremely sensitive while having fast response times. However, as different target molecules may form positive, negative, or even ions of both polarities, it is beneficial to simultaneously detect both ion polarities. Here, we present a dual drift tube IMS with a new dual field switching ion shutter for gating both ion polarities and an X-ray ionization source in orthogonal configuration. The dual field switching ion shutter allows significantly improved ion gating and ion accumulation due to improved shielding of the ionization region from the drift field. Equipped with two 75 mm long high-performance drift tubes, the dual IMS reaches high resolving power of R = 90 with detection limits in the lower pptv range for different ketones, chlorinated hydrocarbons and methyl salicylate that forms ions in both polarities.

Ultrasensitive Ion Source for Drift Tube Ion Mobility Spectrometers Combining Optimized Sample Gas Flow with Both Chemical Ionization and Direct Ionization

“…It consists of a main body and a thin metal grid with 200 μm diameter holes arranged in a 12 × 12 pattern. The ion source is designed completely symmetrically, allowing the pusher electrode to be replaced by a second ion shutter and drift tube, forming an axially arranged dual drift tube IMS with two extended field ion switching shutters . Using two ratios allows describing the various gas flows shown in Figure b) more easily.…”

“…The ion source is designed completely symmetrically, allowing the pusher electrode to be replaced by a second ion shutter and drift tube, forming an axially arranged dual drift tube IMS with two extended field ion switching shutters. 30 Using two ratios allows describing the various gas flows shown in Figure 1b) more easily. The outlet to inlet factor k OI between the sample gas outlet flow Q sample,out and the sample gas inlet flow Q sample,in as given by eq 1 is a measure for the amount of clean gas used to focus the sample gas and ranges from 0 ≤ k OI < ∞.…”

Miniaturized Drift Tube Ion Mobility Spectrometer with Ultra-Fast Polarity Switching

“…22−30 However, a dual drift tube approach is fraught with challenges as well, including the uniform transfer of ions into each individual drift tube which may require completely new ion shutter designs to remedy. 27 Furthermore, the size reduction of two single IMS is limited as still two drift tubes and two sets of control electronics are required.…”

An atmospheric pressure ion funnel with a slit entrance for enhancing signal and resolution in high resolution differential ion mobility mass spectrometry

“…IM approaches can be broadly classified into linear and non-linear methods. In linear methods, such as drift tube IMS (DTIMS), 4,5 travelling wave IMS, 6,7 and trapped IMS, 8,9 ions are separated under a relatively weak electric field ( E ) such that their mobilities ( K ) increase proportionally with the electric field. In low field IM methods, ion separation depends strongly on the cross section and reduced mass of the ion-neutral collision pair, and the charge state of the ion.…”