Differential Ion Mobility Separations in the Low-Pressure Regime.

Area of Science:

• Analytical Chemistry
• Biophysical Chemistry

Background:

• Ion mobility spectrometry coupled with mass spectrometry (IMS/MS) is a powerful analytical platform.
• Field asymmetric waveform ion mobility spectrometry (FAIMS) offers greater orthogonality to MS than linear IMS.
• Integrating FAIMS with MS is challenging due to its atmospheric pressure operation.

Purpose of the Study:

• To demonstrate FAIMS operating at reduced pressure (15-30 Torr) within an MS instrument.
• To enhance separation speed and ion collection efficiency for FAIMS/MS.
• To showcase the potential of low-pressure FAIMS for complex biological samples, such as in proteomics.

Main Methods:

• Implementation of a planar-gap FAIMS stage inside the MS instrument envelope.
• Operation at reduced buffer gas pressure (15-30 Torr) enabling higher electric fields (up to ~300 Td).
• Evaluation of separation speed, resolution, and ion collection efficiency at low pressure.

Main Results:

• Achieved rapid FAIMS separations in ~10 ms and full scans in under 5 seconds.
• Demonstrated efficient ion collection at low pressure, minimizing ion losses.
• Observed separation characteristics mirroring ambient pressure FAIMS, validating the approach.
• Successfully separated isomeric peptides with varying post-translational modifications, highlighting proteomic applications.

Conclusions:

• Reduced pressure FAIMS integrated into MS is feasible and offers significant advantages in speed and efficiency.
• This approach overcomes previous integration challenges and maintains separation quality.
• Low-pressure FAIMS/MS holds great promise for high-throughput biological and environmental analyses, particularly in proteomics.