Simulation of the Effect of Mechanical Misalignment on High M/Z Resolution Cdms Trap Solutions

Significance of the Topic

Charge detection mass spectrometry CDMS enables direct mass measurement of large heterogeneous ions by trapping single ions in an electrostatic linear ion trap ELIT and recording induced charge signals. High m z resolution is essential to reduce uncertainty in frequency measurements and achieve accurate charge assignment. Improvements in trap geometry and construction tolerance can unlock resolutions above 200 000 and enhance capacity for complex ion ensembles

Objectives and Study Overview

The study examines how realistic mechanical misalignments in trap electrodes affect high m z resolution CDMS performance. A Monte Carlo approach is used to simulate assembly tolerances, quantify stability and resolution losses and identify trap designs that maintain performance under practical build deviations

Methodology and Instrumentation

Three candidate trap geometries were evaluated 96 mm short three electrode 150 mm long three electrode and 140 mm four electrode designs. Electrode models and electric fields were generated using SIMION 2020 and Laplace equation solutions saved as field dat files. A Monte Carlo simulation introduced random x y z offsets with a standard deviation of 16 microns and tilts up to 0.2 degrees between trap halves. Ion trajectories were calculated with a fourth order Runge Kutta integrator implemented in PyCUDA leveraging CUDA GPU acceleration. Ions of 340 kDa charge plus 40 and axial kinetic energy mean 130 eV per charge were tracked over 500 ms or 100 oscillation passes to derive stability and m z resolution as frequency divided by two times peak width at 10 percent peak height

Main Results and Discussion

The current prototype trap achieved resolution of 120 with stability above 99 percent. The short three electrode design reached approximately 25 000 resolution the long three electrode about 30 000 and the four electrode design about 193 000 under ideal alignment. Monte Carlo offsets caused severe stability and resolution loss for the short three electrode trap with up to 10 percent assemblies unstable and two thirds below 50 percent stability. The long three electrode trap was more tolerant but still showed up to 20 percent assemblies with resolution below 100 000. The four electrode trap remained above 99.5 percent stability and lost less than 10 percent resolution under offsets. Voltage retuning recovered performance in many cases. Realistic tilts and offsets of half assemblies below 0.2 mm or 0.2 degrees did not significantly impact stability for any design and produced at most 10 percent resolution loss for the four electrode design

Benefits and Practical Applications

High m z resolution traps enable accurate charge detection and improved mass measurement of large biomolecules viral capsids and heterogeneous complexes. Robust designs tolerant to mechanical misalignment reduce manufacturing complexity and increase experimental yield. The four electrode trap offers a route to routine resolutions above 100 000 with standard assembly tolerances

Future Trends and Potential Uses

Future efforts may focus on optimizing electrode shapes and spacing for even higher tolerance and resolution at lower cost. Integration of real time GPU based trajectory feedback and adaptive voltage control could enhance stability and throughput. Applications may extend to high precision analysis of complex therapeutic molecules native protein assemblies and intact viruses

Conclusion

A Monte Carlo analysis of electrode misalignment demonstrates that a four electrode CDMS trap design delivers both high m z resolution and exceptional tolerance to realistic mechanical deviations. This approach guides the development of robust mass analyzers for advanced bioanalytical and industrial applications

Used Instrumentation

• SIMION 2020 for electric field modeling and Laplace solutions
• PyCUDA with CUDA GPU acceleration for trajectory simulation

References

• D Reitenbach Botamanenko Miller Jarrold Anal Chem 2024 96 14060 14067
• D Langridge Richardson Brown Giles MP 394 ASMS 2023
• SIMION 2020 Scientific Instrument Services Inc