Differential Ion Mobility Separations in up to 100% Helium Using Microchips
The performance of differential IMS (FAIMS) analyzers is much enhanced by gases comprising He, especially He/N2 buffers. However, electrical breakdown has limited the He fraction in those mixtures to ~50 - 75%, depending on the field strength. By Paschen law, the threshold field for breakdown increases at shorter distances. This allows FAIMS using chips with microscopic channels to utilize much stronger field intensities (E) than “full-size” analyzers with wider gaps. Here we show that those chips can employ higher He fractions up to 100%. Use of He-rich gases improves the resolution and resolution/sensitivity balance substantially, although less than for full-size analyzers. The optimum He fraction is ~80%, in line with first-principles theory. Hence one can now measure the dependences of ion mobility on E in pure He, where ion-molecule cross section calculations are much more tractable than in other gases that form deeper and more complex interaction potentials. This capability may facilitate quantitative modeling of high-field ion mobility behavior and thus FAIMS separation properties, which would enable a priori extraction of structural information about the ions from FAIMS data.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1130228
- Report Number(s):
- PNNL-SA-97871; 47418; 48135; 400412000
- Journal Information:
- Journal of the American Society for Mass Spectrometry, 25(3):480-489, Journal Name: Journal of the American Society for Mass Spectrometry, 25(3):480-489
- Country of Publication:
- United States
- Language:
- English
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