title: Improving FAIMS sensitivity using a planar geometry with slit interfaces.
abstract: Differential mobility spectrometry or field asymmetric waveform ion mobility spectrometry (FAIMS) is gaining broad acceptance for analyses of gas-phase ions, especially in conjunction with largely orthogonal separation methods such as mass spectrometry (MS) and/or conventional (drift tube) ion mobility spectrometry. In FAIMS, ions are filtered while passing through a gap between two electrodes that may have planar or curved (in particular, cylindrical) geometry. Despite substantial inherent advantages of the planar configuration and its near-universal adoption in current stand-alone FAIMS devices, commercial FAIMS/MS systems have employed curved FAIMS geometries that can be more effectively interfaced to MS. Here we report a new planar (p-) FAIMS design with slit-shaped entrance and exit apertures that substantially increase ion transmission in and out of the analyzer. The entrance slit interface effectively couples p-FAIMS to multi-emitter electrospray ionization (ESI) sources, improving greatly the ion current introduced to the device and allowing liquid flow rates up to approximately 50 microL/min. The exit slit interface increases the transmission of ribbon-shaped ion beams output by the p-FAIMS to downstream stages such as a MS. Overall, the ion signal in ESI/FAIMS/MS analyses increases by over an order of magnitude without affecting FAIMS resolution.
authors.affiliation: Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
authors.forename: Ridha
authors.initials: R
authors.lastname: Mabrouki
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Kelly
authors.forename: David C
authors.initials: DC
authors.lastname: Prior
authors.forename: Alexandre A
authors.initials: AA
authors.lastname: Shvartsburg
authors.forename: Keqi
authors.initials: K
authors.lastname: Tang
authors.forename: Richard D
authors.initials: RD
authors.lastname: Smith
mesh_terms: D004867:Equipment Design; D019544:Equipment Failure Analysis; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation*; D014159:Transducers