Ion-Ion Interactions in Charge Detection Mass Spectrometry

Area of Science:

• Analytical Chemistry
• Physical Chemistry
• Mass Spectrometry

Background:

• Charge detection mass spectrometry (CDMS) is a single-particle technique for determining ion masses.
• Ions are typically trapped in an electrostatic linear ion trap (ELIT) and their oscillations analyzed.
• Previous studies questioned the impact of multiple ion trapping events on CDMS results.

Purpose of the Study:

• To assess the influence of ion-ion interactions on CDMS measurements.
• To evaluate how multiple highly charged ions affect ELIT performance.
• To quantify the impact of these interactions on mass-to-charge ratio (m/z) accuracy.

Main Methods:

• Trajectory calculations were performed to simulate ion behavior within an ELIT.
• The study analyzed the effects of simultaneous trapping of multiple ions.
• Fast Fourier Transforms (FFTs) were implicitly considered in the analysis of oscillation signals.

Main Results:

• Ion-ion interactions cause fluctuations in ion trajectories and energy.
• These fluctuations lead to variations in oscillation frequencies, degrading m/z precision and accuracy.
• Peak shapes exhibit tails, and the average m/z shifts higher with increased ion numbers.

Conclusions:

• Ion-ion interactions significantly impact CDMS measurements in ELITs.
• The observed effects are proportional to ion charges and the square root of ion numbers.
• These interactions limit the m/z resolving power to several hundred for homogeneous ion populations.