Maximizing Ion Transmission in Differential Mobility Spectrometry

Abstract

We provide modeling and experimental data describing the dominant ion-loss mechanisms for differential mobility spectrometry (DMS). Ion motion is considered from the inlet region of the mobility analyzer to the DMS exit, and losses resulting from diffusion to electrode surfaces, insufficient effective gap, ion fragmentation, and fringing field effects are considered for a commercial DMS system with 1-mm gap height. It is shown that losses due to diffusion and radial oscillations can be minimized with careful consideration of residence time, electrode spacing, gas flow rate, and waveform frequency. Fragmentation effects can be minimized by limitation of the separation field. When these parameters were optimized, fringing field effects at the DMS inlet contributed the most to signal reduction. We also describe a new DMS cell configuration that improves the gas dynamics at the mobility cell inlet. The new cell provides a gas jet that decreases the residence time for ions within the fringing field region, resulting in at least twofold increase in ion signal as determined by experimental data and simulations. Graphical Abstract ᅟ.

Differential mobility spectrometry/mass spectrometry history, theory, design optimization, simulations, and applications

“…This goal has been achieved, and some practical examples of their utility have been shown in this review. Research moves forward on instrument design, and considers different geometries (Jakubowska et al, ), improved transmission (Schneider, Nazarov, & Covey, ), faster filtering (Shvartsburg et al, ), better selectivity (Schneider et al, ; Menlyadiev, Stone, & Eiceman, ), more advanced instrument integration (Schneider et al, ), and low pressure operation (Papanastasiou et al, ). Lagging behind these advances is a more thorough, quantitative understanding of the physical chemical principles that underlie the separation process when clustering modifiers are added to the transport gas, although research in this regard progresses (Kafle et al, ; Campbell, Zhu, & Hopkins, ; Auerbach, Aspenleiter, & Volmer, ).…”

Differential Mobility Spectrometry-Mass Spectrometry (DMS-MS) for Uranium Ion Prefiltration to Improve Isotope Ratio Analysis

“…It is also imperative to mention that there is reduced ion transmission when DMS is coupled to MS, as described in previous literatures. 47,48 For our planar DMS design, ion signal was reduced by a factor of ~10. However, increasing sample concentration can compensate for the ion loss.…”

Automated chemical identification and library building using dispersion plots for differential mobility spectrometry

“…Differential mobility spectrometry (DMS) is a variation of IMS, where ions are characterized while drifting between two planer electrodes that establish an asymmetric waveform with electric fields reaching ~30 kV/cm at MHz frequency (6, 7). The ions are differentiated by the differences of the ion mobility coefficients (ΔK) in the low and high electric fields.…”

“…The ions are differentiated by the differences of the ion mobility coefficients (ΔK) in the low and high electric fields. DMS devices can be miniaturized easily due to the less complicated design structure without ion shutters, and notably ions of both polarities can be detected simultaneously (7, 8). DMS has additional advantages compared to IMS as DMS can scan both the compensation voltage (CV) and radio Frequency (RF) voltage simultaneously to filter ions that are being passed through the drift region (6–8).…”

“…α n (E/N) n . This α function is unique for each ion in a DMS spectrum and may be used to identify ions (7, 8).…”