Recommendations for Reporting Ion Mobility Mass Spectrometry Measurements

Abstract

Here we present a guide on 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 on 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 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 towards establishing primary standards and reference materials for ion mobility, and provides recommendations to do so. <br><br><br>

An emerging powerful technique for distinguishing isomers: Trapped ion mobility spectrometry time‐of‐flight mass spectrometry for rapid characterization of estrogen isomers

“…The resolving power in a TIMS instrument is calculated according to Equation : It should be noted that, despite resolving powers up to 350 being reported using TIMS devices, 11,12 the experimental resolving power is highly dependent on the species being studied. Indeed, the ion diffusion phenomenon and eventually the existence of different ion structures (various charge locations for polyfunctional compounds) lead to an increased ion mobility peak width (large ion population for one species) which results in a decrease in the detected ion mobility resolving power 35 . In our study, isomer separations were achieved with a resolving power ranging from 80 to a maximum of 180, depending on the ion mobility mode used (see below) and the compounds studied.…”

Shotgun ion mobility mass spectrometry sequencing of heparan sulfate saccharides

“…CCSs are generally given in units of ångström squared (Å 2 ) and serve as molecular descriptors that can be stored in databases and used for the identification of analytes 32 . Depending on the utilized IMMS technique, CCSs can be directly calculated from the applied instrumental parameters as performed here (for details see Methods) or obtained from calibration 33 . The resulting CCS values derived from the 36 HS standards (#1-#36) and their fragments (See Supplementary Tables 1 and 2) demonstrated the ability of IMMS to distinguish between intact structures, different sized fragment ions, charge states and isomeric structures (See Supplementary Table 2).…”

Computational Strategies and Challenges for Using Native Ion Mobility Mass Spectrometry in Biophysics and Structural Biology

“…While calibration of the m/z axis is straightforward, in order to transform the mobility information (typically acquired in the form of an arrival time distribution, ATD) into a CCS axis, a calibration procedure is typically required 16 . In the overwhelming majority of cases, this is achieved using reference standards appropriate to the target analyte 17 .…”