A Robust C-Trap Ion Injection Method Incorporating Electrodynamic Squeezing

Importance of Topic

The injection of ions into the C-Trap of Orbitrap mass analyzers governs key performance metrics such as sensitivity, contamination control and resolution. Optimizing ion admission and trapping ensures stable operation during extended runs, reduces maintenance and supports reliable analysis in research and industrial settings.

Objectives and Study Overview

This study aimed to develop a robust ion injection method for Thermo Scientific Orbitrap Exploris instruments by incorporating electrodynamic squeezing in the C-Trap and testing an intermediate voltage pulsing step. Continuous infusion of ubiquitin was employed to simulate prolonged usage and lens contamination, allowing evaluation of transmission stability over time.

Methodology

Key experimental steps included:

• Continuous infusion of 3 μmol ubiquitin at 10 ml/min over up to 97 hours to induce lens contamination.
• Regular scanning of C-Trap exit lens voltage during ion purge and measurement of transmitted ion intensity across m/z ranges.
• Implementation of dynamic DC ramping (0.8 V/ms for 3 ms) of the Ion Routing Multipole and exit lens during ion transfer.
• Testing an additional brief −20 V intermediate offset on the IRM prior to purge to enhance focusing.

Used Instrumentation

Instruments and components:

• Prototype Thermo Scientific Orbitrap Exploris Mass Spectrometer.
• Collision cell acting as Ion Routing Multipole conjoined to the C-Trap.
• Electrospray ion source with S-lens/Funnel and bent flatapole.
• Resolving quadrupole and Orbitrap analyzer.

Main Findings and Discussion

Study results demonstrated that dynamic electrodynamic squeezing significantly widened the exit lens voltage window for efficient ion transmission and minimized shifts of tuning curves under prolonged contamination. The intermediate −20 V IRM offset further broadened this acceptance range, particularly benefiting higher m/z ions by improving overlap across the mass range and reducing lens charging effects.

Benefits and Practical Applications

The optimized injection approach offers:

• Enhanced instrument robustness with reduced lens contamination and maintenance intervals.
• Simplified tuning procedures due to wider voltage tolerances.
• Stable performance in high-throughput proteomics, QA/QC and industrial analytics.

Future Trends and Potential Applications

Emerging opportunities include:

• Full integration of dynamic ramping in commercial Orbitrap Exploris platforms.
• Adaptation of electrodynamic squeezing techniques to other trap-based mass analyzers.
• Development of advanced voltage control schemes for further optimization of ion injection and contamination mitigation.

Conclusion

The combination of electrodynamic squeezing and an intermediate IRM offset pulse presents a robust ion injection strategy that enhances C-Trap lens tolerance to contamination and broadens transmission windows. Implementing this method in Orbitrap Exploris instruments will improve long-term performance and reliability for diverse analytical applications.