Characterization of Traveling Wave Ion Mobility Separations in Structures for Lossless Ion Manipulations

Abstract

We report on the development and characterization of a traveling wave (TW)-based Structures for Lossless Ion Manipulations (TW-SLIM) module for ion mobility separations (IMS). The TW-SLIM module uses parallel arrays of rf electrodes on two closely spaced surfaces for ion confinement, where the rf electrodes are separated by arrays of short electrodes, and using these TWs can be created to drive ion motion. In this initial work, TWs are created by the dynamic application of dc potentials. The capabilities of the TW-SLIM module for efficient ion confinement, lossless ion transport, and ion mobility separations at different rf and TW parameters are reported. The TW-SLIM module is shown to transmit a wide mass range of ions (m/z 200–2500) utilizing a confining rf waveform (~1 MHz and ~300 Vp-p) and low TW amplitudes (<20 V). Additionally, the short TW-SLIM module achieved resolutions comparable to existing commercially available low pressure IMS platforms and an ion mobility peak capacity of ~32 for TW speeds of <210 m/s. TW-SLIM performance was characterized over a wide range of rf and TW parameters and demonstrated robust performance. The combined attributes of the flexible design and low voltage requirements for the TW-SLIM module provide a basis for devices capable of much higher resolution and more complex ion manipulations.

Achieving High Resolution Ion Mobility Separations Using Traveling Waves in Compact Multiturn Structures for Lossless Ion Manipulations

“…18,33,44 At TW speeds lower than a threshold only very narrow peaks with no separation are observed due to ion confinement in traveling traps (sometimes referred to as “surfing”). In this work, we use the resolution of m/z 622 and 922 ions ( R 622–922 ) obtained from Agilent low concentration tune mix to evaluate separation quality 33 using eq 2 $$R_{622-922}=\frac{2(t_{922}-t_{622})}{\Delta t_{922}+\Delta t_{622}}$$ where t 922 and t 622 represent the arrival times of m/z 922 and 622 ions while Δ t 922 and Δ t 622 are the fwhm of the m/z 922 and 622 peaks, respectively. The factors that affect the resolution in the TW-SLIM multiturn module included TW sequence, TW amplitude, guard bias, RF amplitude, TW speed, and SLIM surface gap spacing.…”

“…TW sequences, the voltages applied in a repeating pattern to each set of eight electrodes (Figure 2A), included two up and six down (11000000) to six up and two down (11111100) yielded similar ion mobility resolutions of 10.4 ± 0.1 which were also similar to those previously reported results for a straight TW-SLIM module. 33 A symmetric TW with a sequence of 11110000 at a TW speed of 90 m/s was used at TW amplitudes from 15 to 60 V, with the optimum resolution of 10.4 ± 0.1 at 30 V (Figure 2B). The guard bias and the applied RF had no significant effect on the resolution over a wide range (Figures 2C and 2D).…”

“…In this work, the TW was created by switching the DC (on and off) to individual electrodes of each eight electrode set. 33 The TW sequence was varied between 10000000 and 11111100, where 0 corresponds to 0 V and 1 to the application of the TW amplitude (e.g., 30 V) to the electrode set, and stepped one electrode at a time in the direction of ion motion. The gap between the two TW-SLIM surfaces was varied by changing the size of aluminum spacers (McMaster-Carr, Los Angeles, CA).…”

A Structures for Lossless Ion Manipulations (SLIM) Module for Collision Induced Dissociation

“…In this work, we introduce a new structures for lossless ion manipulations (SLIM) CID module for CID/MS. SLIM devices have been previously demonstrated for ion mobility (IM) separations[25–28], mobility-based ion selection[29], and ion trapping[30]. In this study, we demonstrate that SLIM is adaptable (and highly suitable) to applications outside of IM.…”

Spatial Ion Peak Compression and its Utility in Ion Mobility Spectrometry

“…using SLIM devices [27-32], the reduced peak intensities and mobility range with increasing numbers of passes presents significant challenges. We have recently described travelling wave-based SLIM devices that can potentially provide very high mobility resolution using long drift paths [33] over a much greater range of mobilities, including much longer multi-pass designs, but diffusional broadening for greatly extended drift lengths would remain problematic.…”