WCPS: Performance evaluation of Helium Mode ICP-MS for high-matrix sample types in a high-throughput European laboratory

Significance of the Topic

High-matrix samples like wastewater digests require robust removal of spectral interferences and minimal sample handling to maintain throughput and accuracy in environmental monitoring and industrial QA/QC. The integration of aqua regia digestion with advanced ICP-MS collision/reaction cell technology can streamline workflows and meet stringent regulatory limits.

Objectives and Study Overview

This study aimed to validate a direct analysis method for over 30 elements in high-acid wastewater digests prepared according to NEN7777 (Dutch regulation AS3000). A 30-day trial involving 18 sample types assessed method detection limits, spike recoveries, and certified reference material accuracy using an Agilent 7700x ICP-MS equipped with ORS3 cell in Helium mode and High-Matrix Introduction.

Methodology and Instrumentation

• Sample Digestion: Aqua regia (6 mL HCl and 2 mL HNO3) in a CEM Mars microwave system; cooled and diluted to 50 mL.
• ICP-MS Analysis: Agilent 7700x with ORS3 collision cell operated in Helium mode, Burgener MiraMist nebulizer, RF power 1600 W, carrier gas 0.6 L/min, dilution gas 0.4 L/min, helium flow 4.3 mL/min.
• Calibration and Quality Control: Multi-element standards from 0.002 microg/L to 1000 mg/L; low and high level spikes at 10x and 100x regulatory limits; certified reference materials BCR-145R and FeNeLab for accuracy verification.

Main Results and Discussion

• Method detection limits were 2 to 100 times below required reporting limits for elements including Be, P, S, V, As, Se, Cd, and Hg.
• Spike recoveries ranged between 80% and 110% for nearly all analytes in the high-acid matrix.
• Certified reference material analysis exhibited excellent agreement with certified values for interfered elements such as P, V, Cr, Mn, Fe, Ni, Cu, Zn, As, and Se.
• Calibration check stability over a 12-hour period confirmed consistent instrument performance.
• Total analysis time per sample, including rinse and multi-isotope confirmation, was five minutes.

Benefits and Practical Applications

The combined high-matrix introduction and ORS3 Helium mode remove the need for separate ICP-OES, atomic fluorescence, or dedicated mercury analyzers, reduce sample dilution steps, and support high-throughput analysis of complex environmental and industrial matrices.

Future Trends and Potential Uses

Expected developments include extension to solid matrices such as soils and sludges, further automation of digestion and introduction workflows, and optimization of collision cell gases for ultra-trace analysis in challenging samples.

Conclusion

This validation demonstrates that the Agilent 7700x ICP-MS in Helium mode with high-matrix introduction enables accurate, efficient direct analysis of high-matrix aqua regia digests, meeting stringent regulatory requirements and enhancing laboratory productivity.

Reference

Wahlen R and Proper W Performance evaluation of Helium mode ICP-MS for high-matrix sample types 2010 Winter Conference on Plasma Spectrochemistry