Solvent vapor effects on planar high-field asymmetric waveform ion mobility spectrometry

Rorrer, Leonard C.; Yost, Richard A.

doi:10.1016/j.ijms.2010.04.002

Cited by 66 publications

(78 citation statements)

References 23 publications

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“…The number of ion-neutral collisions during the low-field segment of the waveform was well below 1, and the observed behaviour consequently cannot be described as a cluster-decluster mechanism with modification of the alpha-function. Modification of the alpha function was observed at higher vapour levels as seen in Figures 1 and 2, where a cool ion can be solvated through 2 or more collisions [37,38,39,40]. It is helpful to emphasise the convergence of the protonated monomer maximum to the proton bound dimer compensation field maximum must be due to ion molecule collisions over time periods greater than 600 ns (the duration of the low field segment of the dispersion waveform) and is consistent with residence time of ions in the drift tube (1 to 2 ms).…”

Section: Concentration Dependence Of Differential Mobility Spectra Ofmentioning

confidence: 99%

Fragmentation, auto-modification and post ionisation proton bound dimer ion formation: the differential mobility spectrometry of low molecular weight alcohols

Ruszkiewicz

Thomas

Eiceman

2016

Analyst

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Section: Concentration Dependence Of Differential Mobility Spectra Ofmentioning

confidence: 99%

Fragmentation, auto-modification and post ionisation proton bound dimer ion formation: the differential mobility spectrometry of low molecular weight alcohols

Ruszkiewicz

Thomas

Eiceman

2016

Analyst

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“…The addition of chemical modifiers to a DMS system induces the dynamic cluster/decluster phenomenon, where ions may cluster with polar neutral molecules during the low field portion of the waveform and decluster during the high field portion [6]. This mechanism imparts chemical selectivity to DMS separations and has been shown to dramatically improve many separations [7,18,20,21,26,27]. An example of the change in separation mechanism that can occur in the presence of chemical modifiers is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The spacing between the parallel plates in a DMS analyzer can be generally referred to as the gap height (h). The literature contains examples of numerous atmospheric pressure DMS devices that include gap heights ranging from approximately 35 μm [14][15][16] to 2 mm [17,18]. Three of these publications have attempted to compare the separation capability of devices with different gap heights.…”

Section: Introductionmentioning

confidence: 99%

Comparison of the peak capacity for DMS filters with various gap height: experimental and simulations results

Schneider

Nazarov

Londry

et al. 2015

Int. J. Ion Mobil. Spec.

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Differential Mobility Spectrometry (DMS) devices have been integrated with mass spectrometers to provide an orthogonal pre-separation for targeted quantitation. The distance between the DMS electrodes, referred to as the gap height, is a critical parameter for optimization of DMS performance. The literature includes descriptions of various atmospheric pressure DMS devices with gap heights spanning a range of approximately 0.035 to 2 mm. However, despite the presence of numerous publications describing different gap height devices, there is no systematic investigation that describes the effect of DMS gap height on separation peak capacity. This paper summarizes the results from experimental investigations of the effect of gap height on analytical performance (peak capacity and speed) for DMS devices with gap heights that range from 100 μm to 1.5 mm. In addition, this manuscript provides computer simulations of ion motion that shed some light on the relationship between DMS gap height, waveform frequency, and ion transmission. In order to provide accurate and precise experimental data for use in the simulations and development of models, a custom waveform generator has been designed to maintain separation waveform shape regardless of the capacitive load of the DMS cell and the separation waveform amplitude. The differential mobility function (alpha) has been calculated from experimentally measured compensation fields with each of the cells. When the experimental conditions were constant for a given compound, all tested cells provided similar alpha functions, confirming that similar separation mechanisms are observed regardless of gap height. On the basis of these comprehensive experimental data, it is suggested that a phenomenological model can be used for prediction of peak position for particular ion species in planar DMS devices with different gap height. A number of examples will be presented illustrating peak capacity and speed for separations at fixed E/N ratios, as well as at the maximum E/N achievable for each differential mobility filter.

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“…It is well documented [18,19] that FAIMS separation power in general can be improved significantly by adding chemical modifiers to the transport gas. This is a possibility which can be applied also in the presented setup.…”

Section: Resultsmentioning

confidence: 99%

Transient simulation of moving ion clouds in time-of-flight ion mobility spectrometers operating with DC and AC fields

Allers

Bohnhorst

Kirk

et al. 2015

Int. J. Ion Mobil. Spec.

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Ion mobility spectrometers can be divided by their principle of ion separation. For example, classical drift tube time-of-flight Ion Mobility Spectrometers (IMS) separate ions by the absolute value of their low field ion mobility; Field Asymmetric Ion Mobility Spectrometers (FAIMS) separate ions by the field dependence of their ion mobility. However, the low field mobilities and the field dependence of the mobility vary only within a limited range for different ions, leading to a limited peak capacity of stand-alone drift tube IMS and FAIMS. Combining both types leads to orthogonal data and thus enhances the selectivity in comparison with standalone devices. In this work, a new approach of enhancing the separation power of a classical drift tube IMS by integrating a field asymmetric waveform ion separation region in longitudinal direction into the drift tube is discussed. This additional separation region is realized by superimposing the constant drift field of a drift tube IMS with an asymmetric parallel AC field using two additional grids inside the drift tube. Since the ions are exposed alternately to high field and low field strengths on their way through the additional separation region, the resulting drift time is affected. Hence, two ion species having the same low-field mobility, but showing a different field dependence of the mobility have different drift times in the enhanced IMS. In order to analyze the ion movement inside such a modified ion mobility spectrometer, the finite element method (FEM) software Comsol Multiphysics is used. Therefore, an existing drift tube IMS model which perfectly agrees with experimental results and considers field inhomogenieties, diffusion, Coulomb repulsion and ion losses at metallic surfaces, is expanded in order to simulate the ion movement in AC fields. This enhanced model provides visualization of the location and shape of the ion cloud during DC/ AC operation. Particular attention is given to the increased broadening of the ion cloud due to field inhomogenieties in the additional AC field. Furthermore, ion losses inside the drift tube caused by the AC field and the additional grids are considered. In this work, simulations are used to theoretically investigate our new separation approach to give a first impression of the possible analytical performance.

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Solvent vapor effects on planar high-field asymmetric waveform ion mobility spectrometry

Cited by 66 publications

References 23 publications

Fragmentation, auto-modification and post ionisation proton bound dimer ion formation: the differential mobility spectrometry of low molecular weight alcohols

Fragmentation, auto-modification and post ionisation proton bound dimer ion formation: the differential mobility spectrometry of low molecular weight alcohols

Comparison of the peak capacity for DMS filters with various gap height: experimental and simulations results

Transient simulation of moving ion clouds in time-of-flight ion mobility spectrometers operating with DC and AC fields

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