Maximizing productivity for high matrix sample analysis using the Agilent 7900 ICP-MS with ISIS 3 discrete sampling system

Significance of the topic

Environmental laboratories frequently analyze complex matrices such as soils, sediments and sludges for trace and mineral elements. High matrix tolerance, regulatory compliance and rapid turnaround are essential to meet contractual and cost demands. This study addresses these challenges by combining advanced collision cell technology, aerosol dilution and discrete sampling to deliver fast, robust and accurate ICP-MS analysis in high matrix samples.

Objectives and study overview

The main goal was to demonstrate EPA 6020A compliant multi-element analysis in less than 90 seconds per sample using the Agilent 7900 ICP-MS equipped with ORS4 helium mode, Ultra High Matrix Introduction and the new ISIS 3 discrete sampling system. A continuous sequence of 383 samples—including certified reference materials, matrix spikes, calibration checks and blanks—was run over 9 hours 35 minutes to evaluate throughput, data quality and long-term stability.

Methodology

Interference removal was achieved using the Octopole Reaction System in helium mode for all polyatomic overlaps, while low mass elements were measured in no gas mode. The UHMI option provided precise aerosol dilution up to 100× and automated plasma optimization to ensure robust conditions. ISIS 3 discrete sampling separated sample uptake from acquisition, reducing stabilization time, minimizing sample exposure and enabling fast cell gas switching between modes. A full QA/QC schema of low level and continuing calibration verifications, interference checks, matrix spikes and duplicates was integrated into the run to assess accuracy, precision and compliance.

Used instrumentation

An Agilent 7900 ICP-MS fitted with standard nickel cones, a glass concentric nebulizer, the UHMI aerosol dilution module and the ISIS 3 discrete sampling accessory was employed. The ISIS 3 system includes a high-speed piston pump, a seven-port valve for sample loop injection and an automated three-port valve for online internal standard addition and tuning solution switching.

Main results and discussion

• Sample throughput reached 383 analyses in 9 h 35 min, equivalent to a 90 s cycle time and a ~30 % increase compared to a 7700x system.
• Method detection limits were in the sub-ppb range for most trace metals and 1–10 ppb for high-abundance elements, meeting EPA requirements without matrix-matched calibration.
• Low level initial calibration verifications showed recoveries within ±30 %; initial calibrations were within ±10 % of target.
• Continuing calibration checks maintained recoveries within ±10 % for all 28 replicates; internal standard recoveries remained stable across the sequence.
• Certified reference materials and matrix spikes returned mean recoveries of 90–110 % with RSDs <5 % and MS/MSD RPDs <2 %, demonstrating high accuracy and precision across diverse matrices.

Benefits and practical applications of the method

• High throughput reduces analysis cost and workload in service laboratories
• Enhanced matrix tolerance extends maintenance intervals and minimizes downtime
• Automated sample introduction and tuning simplifies operation and reduces human error
• Single-cell gas mode strategy streamlines method setup for interfered and un-interfered elements

Future trends and possible applications

Further integration of discrete sampling with laboratory automation and robotics can deliver walk-away workflows. Combining fast ICP-MS with front-end separations enables speciation and screening in environmental, food, clinical and industrial matrices. Advances in software-driven method development and real-time data analytics will continue to boost laboratory productivity and data confidence.

Conclusion

The synergy of ORS4 helium collision cell, UHMI aerosol dilution and ISIS 3 discrete sampling on the Agilent 7900 ICP-MS provides a powerful solution for high matrix sample analysis. It achieves EPA 6020A compliance in under 90 s per sample while maintaining excellent accuracy, precision and long-term stability.

References

• Steve Wilbur and Craig Jones – Simple Reliable Analysis of High Matrix Samples According to US EPA Method 6020A using the Agilent 7700x ICP-MS, Agilent Technologies publication 5990-5514EN 2010
• Steve Wilbur Takeo Kuwabara and Tetsushi Sakai – High-Speed Environmental Analysis Using the Agilent 7500cx with Integrated Sample Introduction System Discrete Sampling ISIS DS, Agilent Technologies publication 5990-3678EN 2009
• Steve Wilbur and Craig Jones – Maximizing Productivity in High Matrix Samples using the Agilent 7700x ICP-MS with ISIS Discrete Sampling, Agilent Technologies publication 5990-5437EN 2010