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

Significance of the Topic

Environmental monitoring of water and wastewater is critical to protect ecosystems and human health. U.S. EPA Method 6020B defines robust procedures for trace and major element analysis by ICP-MS, addressing increasing waste loads from industrialization, population growth, and climate impacts. Reliable, high-throughput measurement of complex matrices ensures regulatory compliance and informs remediation strategies.

Objectives and Study Overview

This application note evaluates the Thermo Scientific iCAP RQplus ICP-MS coupled with Qtegra ISDS Software for:

• Performing direct analysis of water and wastewater samples across a wide concentration range.
• Meeting all performance criteria of EPA Method 6020B over a three-day sequence (600 samples).
• Demonstrating instrument robustness, accuracy, and precision without maintenance downtime.

Methodology

Samples and standards were prepared according to EPA guidelines, including calibration blanks, initial/continuing calibration verification (ICV/CCV), interference check solutions (ICSA/ICSAB), and matrix spikes/duplicates. Key aspects:

• Multi-element calibration with eight standards covering trace to major levels.
• Online addition of internal standards (Li, Sc, Y, Rh, In, Tb, Ho, Bi).
• Kinetic Energy Discrimination (KED) mode with helium collision gas to remove polyatomic interferences.
• Automated QC checks in Qtegra ISDS Software to flag any deviations in real time.

Instrumentation

The iCAP RQplus ICP-MS was configured with:

• MicroMist nebulizer and cyclonic quartz spray chamber (400 µL/min).
• Quartz injector (2.5 mm i.d.) and torch.
• Ni-tipped sample/skimmer cones and high-matrix skimmer insert.
• Argon Gas Dilution (AGD) system for direct handling of high TDS samples.
• RF power 1,550 W, auxiliary gas 0.8 L/min, cool gas 14 L/min.

Results and Discussion

Detection limits (IDLs) met or exceeded EPA targets for 24 analytes, with R2 > 0.9995. Lower limits of quantification (LLOQs) were established for all elements. Linear ranges extended up to 1,000 mg/L for major elements, reducing the need for sample re-dilution. QC checks showed:

• ICB and CCB blanks below half LLOQ, confirming minimal carry-over.
• ICV and CCV recoveries between 90–110% over three days.
• Interference checks (ICSA/ICSAB) recoveries 90–110%, validating KED mode effectiveness.
• Matrix spikes and duplicates met ±25% recovery and <20% RSD criteria, even in high‐TDS samples.
• Internal standard responses remained within 75–125% across a 10-hour run, illustrating robustness without maintenance.

Benefits and Practical Applications

This workflow delivers:

• High sample throughput with up to 200 analyses per day without maintenance interruptions.
• Accurate multi‐element data for trace and major constituents in complex matrices.
• Automated compliance with EPA Method 6020B via built-in QC functions in Qtegra ISDS Software.
• Reduced sample preparation and re-analysis through wide linear ranges and AGD system.

Future Trends and Opportunities

Advances in ICP-MS will focus on:

• Further automation and remote operation for 24/7 monitoring.
• Integration of real-time data analytics and predictive maintenance.
• Enhanced interference removal via novel collision/reaction cell chemistries.
• Miniaturized and field-deployable platforms for on-site environmental assessments.

Conclusion

The Thermo Scientific iCAP RQplus ICP-MS with Argon Gas Dilution and Qtegra ISDS Software reliably meets EPA Method 6020B requirements for water and wastewater analysis. It achieves excellent detection limits, stability, and throughput over extended runs with minimal maintenance. This solution enhances laboratory productivity and data integrity for environmental compliance.

References

• EPA Method 6020B, Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency.
• Thermo Fisher Scientific iCAP RQplus ICP-MS Product Manual.