Routine Analysis of Soils using ICP-MS and Discrete Sampling

Importance of the topic

Routine analysis of soils and sediments is critical for environmental monitoring, regulatory compliance, and pollution assessment. High matrix samples such as digested soils present challenges for inductively coupled plasma mass spectrometry (ICP-MS) due to signal suppression, spectral interferences, and instrument maintenance demands. Developing a robust, high-throughput workflow that ensures data accuracy and long-term stability addresses the needs of commercial and research laboratories performing large-scale environmental testing.

Objectives and study overview

This application note evaluates the performance of the Agilent 7850 ICP-MS coupled with the ISIS-3 discrete sampling system and ICP-MS MassHunter software for routine multi-element analysis of soil and sediment digests. Key goals include demonstrating matrix tolerance without extensive sample dilution, assessing signal stability over long runs, validating accuracy with certified reference materials (CRMs) and spikes, and showcasing automated maintenance alerts to optimize instrument uptime.

Methodology and Instrumentation

Instrumentation used

• Agilent 7850 ICP-MS with Ultra High Matrix Introduction (UHMI) aerosol dilution.
• ORS 4 helium collision/reaction cell for polyatomic interference control.
• ISIS-3 discrete sampling system and SPS 4 autosampler for rapid sample introduction.
• ICP-MS MassHunter software (v5.1+) with IntelliQuant, autotuning, and early maintenance feedback (EMF).

Sample and calibration preparation

• Soil and sediment digests predigested to 1% HNO₃/0.5% HCl matrix.
• Calibration with multi-element standards and single-element solutions for selected analytes.
• Internal standards Li, Y, In, Bi added online via the seventh port.
• CRMs (River Sediments A/B, Estuarian Sediment, Soils A/B) diluted 2×.
• Matrix spike recoveries assessed at 100 µg/L (Zn at 150 µg/L, Hg at 2 µg/L).

Main results and discussion

Analytical figures of merit

• Limits of detection in low ng/L (ppt) range for trace elements, confirming high sensitivity.
• ISTD recoveries remained within 70–130% across >130 samples, with no mass-dependent drift.
• CRM recoveries for certified elements were within ±10% after dilution correction.
• Matrix spike and duplicate recoveries mostly within ±10%, with relative percent differences below 10%.

Interference control

• UHMI reduced sample matrix loading, minimizing drift and maintenance frequency.
• ORS 4 in He mode effectively suppressed polyatomic overlaps under a single cell condition.
• Automated half-mass mode and M²⁺ correction ensured accurate As and Se quantification in the presence of rare earth elements.

Maintenance optimization

• EMF counters and post-run tune checks notified analysts when interface cleaning or tubing replacement was needed.
• Scheduling maintenance by sample count preserved performance and avoided unnecessary downtime.

Benefits and practical applications

The combined hardware and software approach delivers

• High matrix tolerance without individual sample dilutions or matrix-matched standards.
• Streamlined method development using presets, autotune, and IntelliQuant screening.
• Reliable long-term stability for high-throughput environmental testing.
• Automated alerts that balance maintenance needs with productivity.

Future trends and opportunities

Looking ahead, laboratories may benefit from

• Enhanced automation of sample preparation and data review using robotics and machine learning.
• Advanced real-time diagnostics to predict maintenance and prevent downtime before QC failures occur.
• Integration of streaming data analytics for rapid decision-making in field-based deployments.
• Continued miniaturization of ICP-MS components for portable environmental monitoring.

Conclusion

The Agilent 7850 ICP-MS with ISIS-3 discrete sampling and MassHunter software provides a robust, efficient solution for routine soil and sediment analysis. UHMI aerosol dilution and ORS 4 collision cell ensure accurate multi-element data in high matrix samples. IntelliQuant screening, automated interference correction, and EMF maintenance alerts further streamline the workflow, delivering reproducible results with minimal downtime.

References

1. Kubota T.; Yan D. China Soil Pollution Survey: Elemental Analysis of Soil and Sediment Digests by ICP-MS; Agilent publication 5994-0309EN.
2. Kubota T. Simple and Reliable Soil Analysis using the Agilent 7800 ICP-MS with ISIS 3; Agilent publication 5991-8674EN.
3. Yamanaka K.; Wilbur S. Maximizing Productivity for High Matrix Sample Analysis using the Agilent 7900 ICP-MS with ISIS 3 Discrete Sampling System; Agilent publication 5991-5208EN.
4. Agilent Technologies. Plasma Robustness and Matrix Tolerance, Agilent ICP-MS technology brief 5994-1173EN.
5. Agilent Technologies. Agilent IntelliQuant for ICP-MS; Agilent publication 5994-2796EN.
6. Agilent Technologies. Smart Self-Health Checks for ICP-MS Instruments; Agilent publication 5994-2780EN.
7. Agilent Technologies. Fast, Accurate Analysis of 28 Elements in Water using ISO Method 17294-2; Agilent publication 5994-2804EN.