Automating EPA 6020 Compliant Analysis with the Agilent 7900 ICP-MS and ESI prepFAST Autodilution System

Importance of the Topic

Environmental monitoring of trace and major elements is essential for assessing pollution, regulatory compliance, and public health. EPA Method 6020A provides a performance-based ICP-MS approach capable of quantifying over 60 elements in diverse matrices such as water, soils, and sludges. However, high sample throughput, matrix interferences, and stringent quality control requirements pose challenges for routine laboratories. Automating critical steps—calibration, dilution, and internal standard addition—can enhance efficiency, data quality, and compliance with regulatory protocols.

Study Objectives and Overview

This application note demonstrates the integration of Elemental Scientific’s prepFAST M5 autodilution system with the Agilent 7900 ICP-MS to achieve fully automated EPA 6020A-compliant analysis. Key goals include:

• Automated preparation of multi-point calibration standards from a single stock
• Automated dilution of high-concentration or over-range samples
• Evaluation of method detection limits, precision, accuracy, and long-term stability

An 8-hour sequence of 230 soil and sediment digest samples was analyzed to assess productivity and performance.

Methodology and Instrumentation

• Sample Preparation: All solutions prepared in 2% HNO₃ and 1% HCl. Six certified reference materials (CRMs) representing water, sediments, and soils were digested and spiked with an internal standard mix (⁴⁵Sc, ⁷²Ge, ⁸⁹Y, ¹⁰³Rh, ¹⁷⁵Lu).
• Instrument Configuration:
  • Agilent 7900 ICP-MS with nickel cones, ORS4 helium collision cell, and UHMI aerosol dilution (constant 10× setting)
  • PFA-ST nebulizer and UHMI system for high-matrix tolerance up to 25% dissolved salts
  • ESI prepFAST M5 autodilution system with dual syringe loops and S500V2 syringe pump (±0.05% RSD, ±0.2% bias)
  • MassHunter software with a custom ESI plug-in for seamless control of autocalibration and autodilution
• Auto-Calibration: Seven-level calibration from a single mixed stock standard (100× to undiluted). No matrix matching required.
• Gas Modes: Helium collision mode for most elements; no-gas mode for beryllium. Rapid cell gas stabilization enabled gas-mode switching during loop injection.
• Sequence Design: Periodic insertion of CCV and QC samples after every 10 real samples to meet EPA 6020A quality control criteria.

Key Results and Discussion

• Linearity and Detection Limits: All calibration curves exhibited correlation coefficients of 1.000. Method detection limits ranged from 0.01 ppb (Be) to 7.8 ppb (K).
• Quality Control: ISTD recoveries remained above 30%, and CCV recoveries stayed within ±10% throughout the 8-hour run (230 analyses).
• Accuracy: Recoveries for CRMs were within ±10% of certified values for the majority of elements. Deviations for a few analytes were traced to CRM contamination.
• Matrix Spike Recoveries: Most spike recoveries fell within the EPA acceptance range of 75–125%; deviations occurred only when spike levels were less than one-tenth of the native concentration.
• Automatic Over-Range Dilution: Soil B CRM initially over-range at 10× dilution was successfully reanalyzed at an automatically calculated 200× dilution, yielding recoveries within 92–102% of expected values.
• Throughput: Average analysis time per sample was 150 s, including any necessary autodilution reruns.

Benefits and Practical Applications

• Fully automated calibration and dilution workflows reduce hands-on time and potential for human error.
• High matrix tolerance via UHMI and helium collision cell ensures robust performance with complex environmental digests.
• Seamless software integration under MassHunter provides intuitive method setup and control.
• Compliance with EPA 6020A QC criteria and accurate quantitation supports contract laboratories and regulatory monitoring programs.
• Rapid sample throughput meets the demands of high-volume environmental testing.

Future Trends and Applications

Automation in ICP-MS is expected to advance through:

• Integration with robotic sample preparation platforms and laboratory information management systems (LIMS).
• Expansion to additional regulatory methods and specialized matrices (e.g., biological, industrial effluents).
• Use of advanced data analytics and machine learning for predictive maintenance, method optimization, and outlier detection.
• Development of multi-element speciation protocols via coupling with separation techniques and automated dilution.

Conclusion

The combined Agilent 7900 ICP-MS and ESI prepFAST M5 system delivers a highly automated, EPA 6020A-compliant workflow for multi-element analysis of environmental samples. It achieves excellent accuracy, precision, and throughput, even for high-matrix digests, while fully satisfying regulatory QC requirements. This approach streamlines laboratory operations and ensures consistent data quality in demanding analytical environments.

References

1. Schultz A., Field P., prepFAST ICP-MS: Environmental, Elemental Scientific, 2017.
2. U.S. EPA Method 6020A (SW 846), Inductively Coupled Plasma Mass Spectrometry, Revision 1, 1998.
3. Yamanaka K., Wilbur S., Maximizing productivity for high matrix sample analysis using the Agilent 7900 ICP-MS with ISIS 3, Agilent Technologies, 2014.