Differential mobility spectrometry DMS

Fig. 6. Schematic of a differential mobility spectrometer showing the principles of ion separation in a differential mobility spectrometry (DMS) drift tube. Ion paths are governed by both the asymmetric electric field and field dependence of mobility for an ion. The inset displays the asymmetric waveform of separation electric field used in the DMS drift tube. The waveforms shown are theoretical (top part) and actual or experimental (bottom part) used in these experiments.

Kolakowski, B.M., Mester, Z. (2007). Review of applications of high-field asymmetric waveform ion mohility spectrometry (FAIMS) and differential mobility spectrometry (DMS). Analyst 132 842-64. 

The application of GC for the introduction of complex samples into field asymmetric IMS (FAIMS) and differential mobility spectrometry (DMS) instruments is also used extensively. Fast capillary chromatography in which relatively simple mixtures can be separated in less than a second provides a rapid separation-and-introduction method for DMS. One specific advantage of FAIMS (or DMS) as a chromatographic detector is that both positive and negative ions can be monitored simultaneously from the GC effluent. Figure 3.10 provides a schematic of a typical capillary GC/DMS instrument in which SPME is used to inject semivolatile compounds into the capillary column with DMS detection. 

While time-dispersive ion mobility devices of the type used for drift tube IMS require aperture grids prior to the Faraday plate to preserve the resolving power of the instrument, ion filters and scanning mobility spectrometry such as differential mobility spectrometry (DMS), field asymmetric IMS (FAIMS), differential mobility analysis (DMA), and aspiration IMS (alMS) do not require an aperture grid and can efficiently detect ions with a simple Faraday plate. In these devices, ions do not travel as a discrete swarm, and the exact arrival time of the ions is not critical. Figure 7.3 shows a schematic of a typical differential ion mobility spectrometer (DIMS) in... 

As described in previous chapters, there are many different types of ion mobility methods. These include drift tube ion mobility spectrometry (DTIMS), traveling wave ion mobility spectrometry (TW-IMS), differential mobility spectrometry (DMS), differential mobility analysis (DMA), and aspiration ion mobility spectrometry (alMS). All of these IMS methods have been interfaced to MSs. 

Differential mobility spectrometry (DMS) and FAIMS find thdr niche as mobility filters for MSs. They were first interfaced to MS by Guevermont et aL they demonstrated an... 

Combining high-speed gas chromatography (GC) with differential mobility spectrometry (DMS) was used to determine mixtures of several explosives, including PETN, RDX, Tetryl, and peroxides, in solution. The use of GC for preseparation of the sample improved the DMS response, and distinct patterns were found for each of the compounds. The authors concluded that additional selectivity may be achieved by use of several differential mobility detectors operated in parallel or series with characteristic separation voltages. ... 

Several review papers on the application of ion mobility spectrometry (IMS) and differential mobility spectrometry (DMS) for detection of chemical warfare agents (CWAs) and their simnlants have been published during the last decade. " The comprehensive review by Sferopoulos on detector technologies and commercial devices for detection of CWAs is especially noteworthy as it surveyed all the different techniques and included a chapter on IMS-based instrumentation. ... 

Molina, M.A. Zhao, W Sankaran, S. Schivo, M. Kenyon, N.J. Davis, C. E., Design-of-experiment optimization of exhaled breath condensate analysis using a miniature differential mobility spectrometry (DMS), Anal. Chim. Acta 2008, 628, 185-161. 

Thomas, C.L.P., Mohammad, A., Examination of the effects of inter- and intra-molecular ion interactions in differential mobility spectrometry (DMS). Int. J. Ion Mobility Spectrom. 2006, 9. 

Differential Mobility-MS for Explosive Threat Detection Differential mobility spectrometry (DMS), also known as FAIMS, is a technique closely related to IMS [191-192]. In this system, the ratio of the electric field strength (E, V/cm) applied to the electrodes to the drift gas number density (N, cm" ) is increased to a level beyond that used in DT-IMS (the most common configuration of IMS systems) so that the mobility of the ion (K) is no longer constant but is dependent on the strength of E/N (Townsend [Td]) [192]. 

Ion-mobility mass spectrometry (IM-MS) has emerged as an important analytical method in the last decade [74]. In IM-MS, ions are generated by pyrolysis, electrospray, laser desorption, or other ionization techniques prior to their entry into a gas-filled mobility drift cell. In this cell, ions drift at a velocity obtained from an electric field based on their shapes or dipoles in the case of differential mobility spectrometry (DMS). The greater the cross section of an analyte is (i.e., the larger the ion... 

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