WCPS: Application of Collision/Reaction Cell ICP-MS to the Analysis of Variable and Unknown Samples

Importance of the Topic

Collision/reaction cell inductively coupled plasma mass spectrometry (ICP-MS) offers a universal solution for trace-element analysis in unknown or variable sample matrices without extensive tuning. By using an inert cell gas and energy discrimination, this approach overcomes the limitations of conventional ICP-MS and reactive-gas cell modes, enabling reliable, multi-element screening in diverse matrices.

Objectives and Study Overview

This work evaluates the application of a collision/reaction octopole cell in the Agilent 7500c ICP-MS to:

• Demonstrate matrix-independent interference removal using a single inert gas and fixed cell conditions.
• Assess the capacity to analyze first-row transition metals, arsenic, selenium and other elements simultaneously in high-matrix samples.
• Compare the performance to conventional ICP-MS and reactive-gas modes in terms of sensitivity, interference suppression and method development burden.

Methodology and Instrumentation

The study employed an Agilent 7500c ICP-MS equipped with an octopole collision/reaction cell and a shielded torch to minimize ion-energy spread. Key features include:

• Inert Helium cell gas at controlled flow (e.g., 5 mL/min) and energy discrimination (ED) of ca. 4 V at the cell exit.
• Shielded torch configuration to ensure ions enter the cell with uniform energy, critical for effective ED-based interference removal.
• Semi-quantitative calibration using a limited set of reference elements and constant corrections for isotope abundance and ionization efficiency.

Key Results and Discussion

• In comparison to conventional ICP-MS, He collision mode with ED effectively reduced all polyatomic interferences (ArO, Ar2, SO, S2, SO2, ArS, S2O, SO3) in a 2 % H2SO4 matrix, enabling trace-level measurement of first-row transition metals, As and Se.
• Reactive-gas modes often require multiple gases or generate new cluster interferences; the inert-gas approach removed these complications and eliminated the need for analyte- or matrix-specific tuning.
• Semi-quantitative analyses of reference materials (NIST 1640, SLRS-4, LGC drinking water and landfill leachate) showed agreement within analytical uncertainty across a wide element range under a single set of cell conditions.
• The ion-filtering mechanism relies on the larger collisional cross-sections of polyatomic species, which lose more energy and are rejected via ED, while monatomic analyte ions remain largely unaffected.

Benefits and Practical Applications

• Universal cell conditions simplify method development, reduce analysis time and support unknown sample screening.
• Elimination of interference correction equations improves robustness and ease of use in QA/QC, environmental, industrial and clinical laboratories.
• Multi-element capability under fixed conditions facilitates high-throughput workflows and broad-spectrum monitoring.

Future Trends and Opportunities

• Integration with automated sample introduction and data-processing pipelines for real-time decision support.
• Extension to more challenging matrices such as high-salt, organic or solid digests by coupling with advanced sample-preparation techniques.
• Further refinement of cell design and discrimination electronics to push detection limits and reduce sensitivity losses for poorly ionizing elements.

Conclusion

Inert-gas collision cell ICP-MS with energy discrimination provides a versatile, matrix-independent strategy for trace-element analysis. By removing all polyatomic interferences under single, fixed conditions, it streamlines multi-element measurements in unknown samples, delivering reliable semi-quantitative results without elaborate tuning or correction protocols.

Reference

Agilent Technologies. Application of Collision/Reaction Cell ICP-MS to the Analysis of Variable and Unknown Samples Without Requiring Matrix-Specific or Element-Specific Tuning and Cell Conditions, Pub No. 5989-0664EN.