Collisional Cross-Sections with T-Wave Ion Mobility Spectrometry without Experimental Calibration

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Computational Chemistry

Background:

• Traveling-wave ion mobility spectrometry (TWIMS) is a powerful technique for separating ions.
• Relating TWIMS drift times to collisional cross-sections (CCS) is crucial for structural analysis.
• Existing methods often require calibration with other ion mobility devices.

Purpose of the Study:

• To develop and validate a computational method for deriving CCS from TWIMS drift times.
• To assess the impact of wave velocity on CCS measurements.
• To eliminate the need for external calibration of TWIMS data.

Main Methods:

• Utilized SIMION modeling to simulate the TWIMS potential wave.
• Employed equations describing ion velocity in electric fields.
• Compared CCS derived from TWIMS with static drift tube measurements for 70 reference ions.

Main Results:

• The computational method accurately determines CCS at low wave velocities (average difference of 0.3% vs. static drift).
• High wave velocities resulted in significantly larger CCS, particularly for buffered aqueous solution ions.
• Discrepancies at high wave velocities may indicate unmodeled high-order effects or ion unfolding.

Conclusions:

• CCS can be accurately obtained from single TWIMS drift time measurements using the presented computational method.
• Low wave velocities and gentle instrument conditions are recommended to minimize uncertainties.
• This method removes the necessity of calibrating TWIMS drift times with data from other ion mobility techniques.