Improved performance of linear ion trap mass spectrometer with added octopole and dodecapole fields

Significance of the topic

In linear ion trap mass spectrometry, controlling higher-order multipole fields is critical to achieving high mass resolution and efficient ion trapping. Introducing tailored octopole and dodecapole field components can sharpen resonance edges, improving mass isolation selectivity and trap sensitivity.

Study objectives and overview

This work evaluates a modified linear ion trap design with optimized electrode geometry to balance positive octopole and negative dodecapole components. Numerical simulations and experimental validation assess improvements in mass isolation performance and trap efficiency.

Methodology and instrumentation

• Field calculation: Surface charge method and multipole expansion up to 100th order for fast and accurate electric field evaluation.
• Trajectory simulation: 2D LabVIEW program with Runge-Kutta integration and 3D GPU-accelerated model using NVIDIA Quadro GP100 for realistic ion motion analysis.
• Instrument construction: Modified LCMS-8050 platform incorporating custom electrode set (Model D) in place of the collision cell, with argon cooling gas at 0.1 Pa and dipole excitation via isolation transformer.

Main results and discussion

• Simulations identified Model D geometry yielding equal magnitude of A4/A2 and A6/A2 ratios with opposite sign, producing sharp resonance edges on both high and low frequency sides.
• Experimentally, mass isolation of m/z 921–923 via FNF waveform showed improved peak separation compared to the standard trap.
• CID efficiency test with precursor m/z 555 revealed the modified trap required three times higher excitation voltage, indicating enhanced ion confinement and sensitivity.

Benefits and practical applications

• Enhanced mass isolation improves analysis of complex mixtures in proteomics and metabolomics.
• Increased trap efficiency supports lower detection limits and wider dynamic range for QA/QC and trace analysis.
• Optimized trap design can be integrated into commercial LC–MS instruments for advanced research uses.

Future trends and possibilities

• Real-time adaptive control of multipole fields via dynamic electrode biasing.
• Integration with high-throughput and imaging mass spectrometry platforms.
• Further electrode design optimization using machine learning for tailored field distributions.

Conclusion

Balancing octopole and dodecapole components through precise electrode geometry modifications significantly enhances mass isolation resolution and trap efficiency in linear ion trap mass spectrometers. Numerical and experimental results demonstrate the potential for advanced analytical applications.

Reference

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