Tandem Drift Tubes in Mobility Spectrometry

Ion mobility spectrometers are sufficiently simple and inexpensive that several drift tubes can be combined for sequential measurements of ions or for characterization 

A surge of interest has occurred in the interest in and use of mobility methods to provide additional ion filtering between ESI sources and mass spectrometers and to explore gas phase ions of biomolecules for shape, size, and transformations. This was simulated by availability of commercial instruments, including the ThermoFisher FAIMS/MS, AB SCIEX SelexION, the Owlstone pFAIMS/MS, and 

Waters Corporation Synapt. The samples are solutions of biological material, and the ion sources are uniformly EIS, nanospray ionization, or matrix-assisted laser desorption and ionization as described in Chapters 4,9,15, and 18. Studies with the Synapt traveling wave instrument have revealed details of biomolecular ions in the gas phase that are not available by MS alone or by other methods. The full meaning of such studies and relevance for in vivo biomolecular activity is currently under discussion and debate nonetheless, IM-MS for explorations of biomolecules certainly has affected the visibility of mobility as a measurement method and the level of technology that has been advanced through pharmaceutical and medical concerns. 

Electrospray ion sources initiated the current revolution in biological and medical uses of MS, yet the chanistry of these sources is complex, and the number of useful ions derived from a sample can be few amid a complex mixture of interfering ions. When placed between the ESI source and the mass spectrometer, EAIMS and DMS instruments can isolate ions of importance, significantly simplifying mass spectra and improving signal-to-noise ratios in quantitative measurements. - This was initiated with EAIMS instruments and is now complimented with ultraFAlMS and DMS. A direct and near-immediate use of IMS in medical research has arisen with the development of cUnical applications of IMS, as described in Section 1.3. 

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