Analysis of Environmental Samples with the Agilent 730-ES Following US EPA Guidelines

Significance of the Topic

Accurate trace-level measurement of inorganic contaminants in water and soil is critical for environmental risk assessment, regulatory compliance and remediation decision-making. The US EPA/CLP protocols define stringent performance criteria for detection limits, precision and accuracy across 23 target elements, including mercury and cyanide. Implementing a robust, streamlined method that meets these guidelines reduces analysis time and cost while ensuring data quality for emergency response and enforcement actions.

Aims and Study Overview

This study demonstrates the application of the Agilent 730-ES simultaneous ICP-OES to perform US EPA/CLP-compliant multi-element analysis of aqueous environmental samples. The objectives were to:

• Validate method detection limits (MDLs) and contract required detection limits (CRDLs) for 23 elements.
• Evaluate linear dynamic range and the MultiCal approach for high-concentration elements.
• Assess precision, accuracy and long-term stability under routine operating conditions.

Methodology and Used Instrumentation

All samples, calibration and QC solutions were prepared in ultrapure water acidified with 1% v/v HNO₃ and 5% v/v HCl. An online 1% w/v Cs buffer was added to suppress ionization interferences. Key instrumentation components:

• Agilent 730-ES ICP-OES with custom CCD detector and axial plasma view.
• ICP Expert II software with MultiCal feature for extended linear range.
• Agilent Switching Valve System (SVS) and SPS 3 autosampler for rapid sample introduction and washout.
• Glass cyclonic spray chamber, SeaSpray nebulizer, standard axial torch.
• Superfund CLP ICP calibration kits and NIST 1643e reference material for LCS.

Main Results and Discussion

Method detection limits ranged from sub-µg/L for Be and Ag to low mg/L for major elements, meeting or exceeding ILM05.3 requirements. Recoveries for calibration verification (ICV/CCV) and contract quantitation check (CRI) standards fell within 92–110% for most elements. Reproducibility was demonstrated by:

• Reagent blank spikes at 5 µg/L showing <0.5 µg/L MDLs and RSDs below 0.5%.
• Duplicate sample RPDs well under the 20% control limit for both NIST 1643e and local tap water.
• Matrix spike recoveries between 93–119% across all analytes.
• Long-term stability tests over an eight-hour run yielding <1% RSD for key wavelengths.

MultiCal extended the linear range for Na, K, Ca and Fe up to 2 000 mg/L without additional sample dilution. Interference check samples (ICSA/ICSAB) passed the ±2× CRQL and ±20% recovery criteria without applying IEC factors. The total analysis time, including all QC checks, was reduced to approximately 2 min 25 s per run.

Benefits and Practical Applications

The Agilent 730-ES method offers:

• Single-plasma axial measurement of all target elements, eliminating the need for dual-view systems.
• Automated QC and EPA protocol workflows within ICP Expert II, ensuring compliance and traceability.
• Enhanced throughput through rapid valve switching and autosampler-driven dilution.
• Cost savings by minimizing re-runs and reagent consumption.

Future Trends and Possibilities

Emerging directions include integration with high-resolution mass spectrometry for ultra-trace analysis, cloud-based data management for real-time compliance reporting, and portable ICP-OES platforms for field screening. Continued automation of EPA QC protocols and advanced interference suppression techniques will further streamline environmental monitoring workflows.

Conclusion

The Agilent 730-ES ICP-OES, equipped with simultaneous CCD detection, MultiCal linearity extension and automated EPA QC protocols, successfully meets all US EPA ILM05.3 requirements for water analysis. Its combination of precision, speed and ease of use makes it a powerful tool for environmental laboratories tasked with regulatory compliance and contamination assessment.

References

1. United States Environmental Protection Agency. Multi-Media, Multi-Concentration, Inorganic Analytical Service for Superfund (ILM05.3). EPA 540-F-04-001, 2004.
2. Dubuisson C., Poussel E., Mermet J.M. Comparison of axially viewed and radially viewed ICP-AES in terms of signal-to-background ratio and matrix effects. J. Anal. At. Spectrom. 1997, 12, 281–286.
3. US EPA Contract Laboratory Program, Statement of Work for Inorganics, Multi-Media, Multi-Concentration, ILM05.3, 2004.
4. EPA Superfund Contract Laboratory Program CLP Guidance: http://www.epa.gov/superfund/programs/clp/ilm5.htm