Determination of Collision Cross Sections Using a Fourier Transform Electrostatic Linear Ion Trap Mass Spectrometer

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Spectroscopy

Background:

• Collision cross sections (CCSs) are crucial for characterizing molecular size and shape.
• Traditional methods for CCS determination can be complex and time-consuming.
• Developing novel, high-throughput methods for CCS measurement is essential.

Purpose of the Study:

• To establish a method for determining collision cross sections (CCSs) from frequency-domain linewidths in an electrostatic linear ion trap.
• To validate the accuracy and reproducibility of this novel CCS determination technique.
• To correlate CCS measurements from the ion trap with those obtained from drift-tube ion mobility spectrometry.

Main Methods:

• Utilized a Fourier transform electrostatic linear ion trap to record transients at varying background pressures.
• Employed an energetic hard-sphere ion-neutral collision model to relate image charge to CCS.
• Developed a Lorentzian fitting algorithm incorporating known isotopic abundances to extract linewidths, minimizing ion loss and experimental error.

Main Results:

• Established an excellent correlation (R² ≈ 0.9999) between CCSs measured in the ion trap and drift-tube ion mobility spectrometry.
• Demonstrated that corrected CCS values for [angiotensin II]2+ and reserpine closely matched reported ion mobility spectrometry CCSs.
• Achieved high reproducibility (within a fraction of a percent) for CCS determinations, comparable to dedicated ion mobility instruments.

Conclusions:

• Frequency-domain linewidths in an electrostatic linear ion trap provide a reliable method for determining collision cross sections.
• The developed method, when corrected using a linear correlation, yields accurate and highly reproducible CCS values.
• This technique offers a promising alternative for molecular characterization, complementing existing ion mobility spectrometry approaches.