Automated Analysis of Low-to-High Matrix Environmental Samples Using a Single ICP-MS Method

Importance of the topic

Accurate multi-element analysis of environmental samples is critical for monitoring water quality, assessing soil and sediment contamination, and ensuring regulatory compliance. Inductively coupled plasma mass spectrometry (ICP-MS) offers low detection limits, a wide dynamic range, and high throughput, but handling diverse matrices often requires laborious manual dilution and calibration steps. Integrating automated dilution with ICP-MS promises greater efficiency, reduced error rates, and cost savings in routine environmental testing laboratories.

Objectives and study overview

This study evaluated the performance of an Agilent 7850 ICP-MS combined with the Agilent Advanced Dilution System 2 (ADS 2) and SPS 4 autosampler. The goals were to demonstrate a single-method workflow for waters, sediments, soils, and synthetic seawater; to assess dilution accuracy over a 1× to 400× range; and to verify long-term stability and quality control over an eight-hour run including prescriptive and reactive autodilution functions.

Instrumentation used

The setup comprised:

• Agilent 7850 ICP-MS with octopole reaction system (ORS4)
• Advanced Dilution System 2 (two-syringe autodilutor, up to 400× dilution)
• Agilent SPS 4 autosampler
• Concentric MicroMist nebulizer, temperature-controlled quartz spray chamber, quartz torch with 2.5 mm injector
• Ultra High Matrix Introduction (UHMI) for robust plasma with high total dissolved solids

Methodology and instrumentation

All standards and samples were acidified with 1% HNO₃ and 0.5% HCl. A single mixed stock standard was autodiluted by ADS 2 to prepare nine calibration levels (undiluted to 400× dilution). The ORS4 cell operated in no-gas mode for Be, He collision mode for most elements, and high-energy He for Se. The sequence included initial and continuing calibration blanks (ICB/CCB), calibration verifications (ICV/CCV), certified reference materials (CRMs) for water, wastewater, river sediment, and soil, plus a synthetic seawater spike. Prescriptive dilution was applied to high-matrix samples, and reactive dilution was triggered when analyte signals exceeded calibration limits or internal standard recovery tolerances.

Main results and discussion

The instrument detection limits ranged from 0.0001 µg/L (Th, U) to 4.9 µg/L (Ca). All calibration curves from 1× to 400× dilution exhibited linearity coefficients > 0.9995. CRM recoveries for 26 elements fell within 90–110%, with most within 95–105%. Seawater spike recoveries ranged from 93% to 102%. Over an eight-hour, 140-sample run, CCV recoveries remained within ±10% and internal standard recoveries stayed within ±25% without retuning, demonstrating excellent stability and robustness.

Benefits and practical applications of the method

Implementing ADS 2 with the 7850 ICP-MS offers:

• Fully automated calibration from a single stock, reducing standard preparation time
• Prescriptive autodilution of high-matrix samples, eliminating manual dilution steps
• Reactive dilution for out-of-range samples, avoiding repeat runs
• Enhanced throughput and lower cost per sample by minimizing analyst intervention and error

Future trends and possibilities for use

Further developments may include tighter integration with laboratory information management systems (LIMS), automated real-time data correction using machine learning, expanded application to more complex matrices (e.g., biological fluids, industrial wastes), and coupling ICP-MS with chromatographic separation for speciation analysis. Miniaturized autosampling and dilution modules could enable decentralized or field-deployable elemental testing.

Conclusion

The Agilent 7850 ICP-MS with the ADS 2 and SPS 4 autosampler provides a robust, high-throughput solution for trace and major element analysis across diverse environmental matrices. Automated autocalibration, prescriptive dilution, and reactive dilution significantly streamline workflows, improve data quality, and reduce labor-intensive steps, making this integrated system well suited for routine environmental monitoring and compliance testing.

Reference

• Agilent Technologies. Agilent Advanced Dilution System (ADS 2) – Technical overview. Publication 5994-7211EN.
• Yamanaka K., Wilbur S. Maximizing Productivity for High Matrix Sample Analysis using the Agilent 7900 ICP-MS with ISIS 3 Discrete Sampling System. Agilent 5991-5208EN.
• Kubota T. Routine Analysis of Soils using ICP-MS and Discrete Sampling. Agilent 5994-2933EN.