Here we present a guide to ion mobility mass spectrometry experiments, which covers both linear and nonlinear methods: what is measured, how the measurements are done, and how to report the results, including the uncertainties of mobility and collision cross section values. The guide aims to clarify some possibly confusing concepts, and the reporting recommendations should help researchers, authors and reviewers to contribute comprehensive reports, so that the ion mobility data can be reused more confidently. Starting from the concept of the definition of the measurand, we emphasize that (i) mobility values (K0) depend intrinsically on ion structure, the nature of the bath gas, temperature, and E/N; (ii) ion mobility does not measure molecular surfaces directly, but collision cross section (CCS) values are derived from mobility values using a physical model; (iii) methods relying on calibration are empirical (and thus may provide method-dependent results) only if the gas nature, temperature or E/N cannot match those of the primary method. Our analysis highlights the urgency of a community effort toward establishing primary standards and reference materials for ion mobility, and provides recommendations to do so.
Bibliographical noteFunding Information:
The EU COST action BM1403 ?Native Mass Spectrometry and Related Methods for Structural Biology? is acknowledged for supporting meetings at which these recommendations were discussed, and for supporting the open access charges for this paper.
Valerie Gabelica, Carlos Afonso, Perdita Barran, Justin L. P. Benesch, Christian Bleiholder, Michael T. Bowers, Aivett Bilbao, Matthew F. Bush, Iain D. G. Campuzano, Colin S. Creaser, Edwin De Pauw, Johann Far, Francisco Fernandez-Lima, Hugh I. Kim, Kevin Pagel, Frederic Rosu, Frank Sobott, Konstantinos Thalassinos and Thomas Wyttenbach declare no conflicts of interest. Alexandre A. Shvartsburg has interest in Heartland MS that provides the ion funnel and FAIMS systems for various mass spectrometers (including those mentioned in the article) and receives royalties from Battelle on licensed IP implemented in commercial IMS/MS instruments (including the Agilent 6560 and Bruker timsTOF mentioned in the article). He also holds a faculty appointment at the Moscow Engineering Physics Institute (MEPhI), Russia. Tim Causon and Stephan Hann are recipients of a University Relations Grant from Agilent Technologies (#4240). Brian H. Clowers receives royalties from licensed intellectual property held by Battelle Memorial Institute (US7888635B2), which is used in commercial IMS/MS instruments. Christopher J. Hogan Jr. receives royalties on a commericial IMS (Kanomax-FMT) coupled to a condensation particle counter for nanoparticle and macromolecular analyte detection. Drs. John A. McLean and Jody C. May have collaborative agreements in place with Agilent Technologies (Santa Clara, CA) and Waters Corporation (Milford, MA). The Center for Innovative Technology at Vanderbilt University is designated a Waters Center of Innovation and acknowledge financial support in the form of an Agilent Thought Leader Award. Stephen J. Valentine receives royalties from Waters for patents related to the IMS-TOF technology. J. Larry Campbell is an employee of SCIEX, a manufacturer of Differential Mobility Spectrometry (DMS) technology. K Giles and K Richardson are employees of Waters Corporation, Wilmslow UK who design, develop and sell mass spectrometry instruments utilizing the traveling wave ion mobility separators discussed in this article. John C. Fjeldsted and Ruwan T. Kurulugama are employed by Agilent Technologies, a commercial supplier of Ion Mobility Mass Spectrometry instrumentation and informatics products. Mark E. Ridgeway is an employee of Bruker Daltonics, a manufacturer of TIMS ion mobility technology. Michael Groessl is consulting for Tofwerk, a commercial supplier of ion mobility mass spectrometry instrumentation.
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