IMSC: A New Design of Ion Lens and Collision/Reaction Cell for ICP-MS

Importance of the Topic

The accurate removal of spectral interferences in inductively coupled plasma mass spectrometry (ICP-MS) is critical for reliable multi-element analysis in complex matrices. Polyatomic overlaps can bias quantification, particularly in environmental, pharmaceutical, and industrial testing. The novel ORS3 collision/reaction cell design addresses these challenges by enhancing interference removal without compromising analyte sensitivity.

Aims and Study Overview

This study presents the design and performance evaluation of the third-generation ORS3 collision/reaction cell for the Agilent 7700 Series ICP-MS. It compares interference removal efficiency in no gas, hydrogen (H₂) mode, and helium (He) collision mode across multiple sample matrices, demonstrating the cell’s capability to maintain low detection limits and high data integrity.

Methodology and Instrumentation

• Instrument: Agilent 7700 Series ICP-MS equipped with ORS3 cell.
• Cell design enhancements: 18% longer octopole rods, 15% smaller internal diameter, 16% higher cell gas pressure, 20% higher RF frequency.
• Collision gases tested: no gas, H₂ (reactive mode), He (inert collision mode).
• Energy discrimination: large kinetic energy discrimination (KED) voltage step at cell exit to reject low-energy polyatomic ions.
• Sample matrices: seven individual matrices (HNO₃, HCl, H₂SO₄, IPA and combinations) plus mixed acid matrix, unspiked blanks and spiked standards.

Main Results and Discussion

• No gas mode: widespread polyatomic interferences observed on nearly every mass, leading to elevated apparent concentrations.
• H₂ mode: partial removal of some interferences but creation of new overlapping species (e.g., ⁴⁵Sc by ⁴⁴CaH), and poor sensitivity for certain analytes (e.g., Cu reaction with H₂).
• He mode with ORS3: complete removal of polyatomic interferences in all tested matrices; consistent low blank levels for 14 analytes; preservation of analyte signal due to inert gas chemistry; narrow ion energy spread and high collision frequency preferentially attenuate larger molecular species.
• KED bias step effectively discriminates residual low-energy polyatomics while transmitting high-energy analyte ions.

Benefits and Practical Application

The ORS3 cell in He mode delivers robust interference suppression across diverse and unknown sample types without generating new overlaps or sacrificing sensitivity. This enables accurate, high-throughput multi-element analysis in environmental monitoring, food safety, clinical testing, and quality control laboratories.

Future Trends and Applications

• Integration with high-resolution and tandem mass analyzers for enhanced selectivity.
• Development of alternative inert collision gases or gas mixtures to further refine molecular dissociation.
• Automation and AI-based data correction algorithms to streamline method development and real-time interference identification.
• Miniaturization of collision cell hardware for portable ICP-MS applications in field analysis.

Conclusion

The third-generation ORS3 collision/reaction cell significantly improves polyatomic interference removal in ICP-MS using He collision mode. Its advanced cell geometry, higher gas pressure, and large energy discrimination step enable accurate multi-element quantification in complex and variable matrices, ensuring high data integrity and reliable analytical performance.

References

• Wahlen R., McCurdy E. A New Design of Ion Lens and Collision/Reaction Cell for ICP-MS. Agilent Technologies (UK) Ltd.