Direct Analysis of Undiluted Soil Digests Using the Agilent High Matrix Introduction Accessory with the 7500cx ICP-MS

Importance of Topic

High total dissolved solids (TDS) samples such as undiluted soil digests, seawater, and heavy matrix groundwaters pose significant challenges in ICP-MS analysis due to matrix suppression, oxide interferences, and potential instrument contamination. Robust and automated sample introduction strategies are critical to maintain sensitivity, accuracy, and sample throughput in environmental and industrial laboratories.

Study Objectives and Overview

This study evaluates the performance of the Agilent High Matrix Introduction (HMI) accessory coupled to the 7500cx ICP-MS for direct analysis of undiluted soil digests and other high TDS matrices. The main goals are to assess matrix tolerance, long-term stability, detection limits under regulatory requirements, and overall method robustness compared to standard sample dilution protocols.

Methodology and Instrumentation

• Instrument: Agilent 7500cx ICP-MS equipped with High Matrix Introduction (HMI) aerosol dilution accessory.
• Sample types: Neat seawater, undiluted soil digests, high TDS groundwaters, TCLP leachates, geological fusions, RoHS and high-purity metal samples.
• Operating conditions: RF power 1600 W; carrier gas ~0.28 L/min; HMI dilution gas ~0.67 L/min; aerosol dilution factor 1/12; sample uptake 0.17 mL/min; helium collision mode (4 mL/min He, 2 V KED) and hydrogen mode (4 mL/min H₂, 2 V KED).
• Validation: Certified reference materials (river clay, sewage sludge) and spiked samples analyzed over 30 days to evaluate recovery, precision, and CCV stability.

Main Results and Discussion

• Matrix tolerance: Effective analysis of samples up to 3 % TDS with typical oxide ratio (CeO⁺/Ce⁺) reduced to ~0.3 % under HMI conditions versus ~1 % with standard setup.
• Long-term stability: Over 30 days, replicate measurements of reference materials yielded recoveries between 90 % and 108 %, demonstrating excellent precision.
• Spike recoveries: Low-level and high-level spikes for 25 elements returned recoveries of 93–108 %, confirming method accuracy across a wide concentration range.
• Detection limits: Compliant with Dutch regulatory guidelines for soil, achieving method detection limits below required thresholds without manual dilution.
• CCV stability: Continuous calibration verification showed minimal drift across 235 samples, indicating reliable performance in high-throughput operations.
• Operational simplicity: Switching between HMI and conventional modes showed reproducible performance without hardware changes, reducing downtime.

Benefits and Practical Applications

• Eliminates manual dilution, reducing contamination risk and pipetting errors.
• Maintains high throughput by avoiding additional sample preparation steps.
• Enhances plasma robustness and reduces oxide and polyatomic interferences.
• Applicable to diverse high-matrix applications in environmental analysis, regulatory testing, and industrial quality control.

Future Trends and Applications

• Integration with automated sample handling systems for fully unattended operation.
• Expansion to bioanalytical and pharmaceutical matrices requiring minimal sample manipulation.
• Development of advanced collision/reaction cell chemistries to further suppress remaining interferences.
• Coupling HMI-enabled ICP-MS with chromatographic separation techniques for speciation and trace organic analysis in complex matrices.

Conclusion

The Agilent HMI accessory for the 7500cx ICP-MS provides a robust, automated solution for direct analysis of undiluted high-matrix samples. It achieves regulatory detection limits, stable long-term performance, and operational simplicity without compromising instrumental lifetime or data quality. This approach streamlines workflows in environmental, industrial, and research laboratories facing challenging sample matrices.

Reference

No formal literature references were provided in the source document.