Using gas modifiers to significantly improve sensitivity and selectivity in a cylindrical FAIMS device

Area of Science:

• Analytical Chemistry
• Spectrometry

Background:

• Gas additives improve performance in Differential Mobility Spectrometry (DMS) with planar electrodes.
• Previous studies suggested similar benefits were not achievable with Field Asymmetric Ion Mobility Spectrometry (FAIMS) due to non-homogeneous electric fields in cylindrical electrodes.

Purpose of the Study:

• To modify a FAIMS system for controlled gas additive delivery.
• To investigate the distinction between contaminant and controlled gas modifiers.
• To demonstrate that FAIMS can achieve analytical benefits from gas additives.

Main Methods:

• Modified a FAIMS system for controlled gas additive delivery.
• Simulated contamination by adjusting electrospray ionization (ESI) needle position.
• Introduced acetonitrile vapor as a gas modifier.
• Analyzed 15 positive ions (m/z 90-734).

Main Results:

• Controlled gas modifier delivery yielded reproducible CV spectra, unlike contamination.
• Acetonitrile vapor significantly improved peak capacity and ion transmission, even at trace levels.
• Signal intensity increased 10- to 100-fold for low m/z ions, matching or exceeding ESI without FAIMS.

Conclusions:

• Controlled gas additive delivery is crucial for reproducible FAIMS analysis.
• FAIMS with non-homogeneous electric fields benefits from gas modifiers, similar to DMS devices.
• Trace levels of acetonitrile vapor significantly enhance FAIMS performance.