Robust analysis of a variety of water, wastewater, and soil samples according to U.S. EPA Method 6020B (SW-846)

Importance of Topic

Monitoring of trace metals in water, wastewater, and soil is critical to evaluate environmental pollution from industrial, agricultural, and urban sources.
EPA Method 6020B provides a standardized approach for multi element analysis using ICP-MS but requires enhanced matrix tolerance and rigorous quality control to deliver reliable data.

Objectives and Study Overview

This study evaluated the Thermo Scientific iCAP MSX ICP-MS for routine compliance testing of diverse environmental samples under the requirements of US EPA Method 6020B.
The performance was assessed across water, wastewater, and soil digest matrices, focusing on linearity, detection limits, sample throughput, and instrument robustness.

Methods and Instrumentation

The iCAP MSX ICP-MS system features High Matrix mode, Argon Gas Dilution, and intelligent matrix handling to limit sample matrix load on the plasma and interface.
A Thermo Scientific iSC-65 Autosampler enabled unattended runs.
Key operating parameters included RF power of 1550 W, nebulizer flow of 0.279 L/min, AGD at dilution Level 25, helium collision gas in KED mode at 4.2 mL/min, and cyclonic quartz spray chamber at 2.7 °C.
Soil samples were digested by SW-846 Method 3010A using nitric acid and peroxide, diluted to 50 mL.
Wastewater matrices were simulated with high levels of major ions and analyzed via online argon dilution.
Calibration covered 24 elements in eight standards up to 250 mg/L for trace metals and 250,000 mg/L for major elements.
QC protocols included initial and continuing calibration blanks and verifications (ICB, CCB, ICV, CCV), interference check solutions (ICSA, ICSAB), matrix spikes, and duplicates.

Key Results and Discussion

All analytes displayed excellent linearity (R2 > 0.999) and low detection limits (LODs in the µg/L to low mg/L range).
Calibration blank carryover remained below half the lowest quantitation limit throughout 480 samples over two days.
ICV and CCV standards yielded 90–110% recoveries, confirming calibration stability over extended runs.
Interference checks demonstrated effective removal of polyatomic overlaps using helium KED in single cell mode.
Matrix spike recoveries and duplicate precision met EPA criteria (±25% recovery, <20% RPD) for both soil digests and wastewater.
Internal standard signals stayed within 80–120% over 12 hours with up to 1.7% total dissolved solids, indicating high robustness.

Benefits and Practical Applications

The iCAP MSX ICP-MS workflow enables rapid, high-throughput analysis of complex environmental matrices without frequent maintenance.
Automated argon dilution and intelligent matrix handling reduce matrix deposition, signal drift, and downtime.
Compliance with EPA Method 6020B is achieved with minimal sample preparation effort and consistent data quality.

Future Trends and Applications

Further automation of matrix dilution and online sample preparation may enhance throughput.
Advances in collision/reaction cell technology could extend interference removal capabilities.
Integration with chromatographic separation and field-portable ICP-MS systems may broaden on site monitoring.

Conclusion

The Thermo Scientific iCAP MSX ICP-MS delivers reliable performance for multi element determination in water, wastewater, and soil according to EPA Method 6020B.
Its combination of high matrix tolerance, robust QC, and unattended operation supports efficient regulatory compliance testing.

Použitá instrumentace

• Thermo Scientific iCAP MSX ICP-MS with High Matrix mode and Argon Gas Dilution
• Thermo Scientific iSC-65 Autosampler
• Qtegra ISDS Software for instrument control, data acquisition, and QC management

Reference

• US EPA. Method 6020B: Inductively Coupled Plasma-Mass Spectrometry. US Environmental Protection Agency.
• US EPA. Contract Laboratory Program Quality Assurance and Quality Control Guidelines, Document ISM23D.