Control of Ion Distortion in Field Asymmetric Waveform Ion Mobility Spectrometry via Variation of Dispersion Field and Gas Temperature

Journal Article · Wed Oct 01 00:00:00 EDT 2008 · Analytical Chemistry, 80(19):7508-7515

DOI:https://doi.org/10.1021/ac800655d· OSTI ID:946649

Robinson, Errol W.; Shvartsburg, Alexandre A.; Tang, Keqi; Smith, Richard D.

Field asymmetric waveform ion mobility spectrometry (FAIMS) has emerged as an analytical tool of broad utility, especially in conjunction with mass spectrometry. Of particular promise is the use of FAIMS and 2-D ion mobility methods that combine it with conventional IMS to resolve and characterize protein and other macromolecular conformers. However, FAIMS operation requires high electric fields and ions are inevitably heated by above-thermal collisions with buffer gas molecules. This may induce ion isomerization and dissociation that distort separation properties determined by FAIMS and subsequent stages and/or reduce instrumental sensitivity. As FAIMS employs a periodic waveform, the ion temperature can be characterized at the maximum or average field intensity (E). Which method is most applicable to temperature sensitive ions, such as protein ions, has been debated. Here we address this issue by measuring the unfolding of compact ubiquitin ion geometries as a function of waveform amplitude (dispersion field, ED) and gas temperature, T. The field heating is quantified by matching the dependences of structural transitions on ED and T. Increasing ED from 12 to 16 or from 16 to 20 kV/cm is equivalent to heating the (N2) gas by ~15 - 25 oC. The magnitude of field heating for any E can be calculated using the two-temperature theory, and raising ED by 4 kV/cm augments heating by ~15 - 30 oC for maximum and ~4 - 8 oC for average E in the FAIMS cycle. Hence, isomerization of ions in FAIMS appears to be governed by the maximum internal temperature at waveform peaks.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 946649
• Report Number(s): PNNL-SA-59851; 400412000
• Journal Information: Analytical Chemistry, 80(19):7508-7515, Vol. 80, Issue 19
• Country of Publication: United States
• Language: English