Analysis of 23 Elements in Wastewater by U.S. EPA Method 6020B Using ICPMS-2050

Importance of Topic

The monitoring of heavy metals in wastewater is critical due to their persistence, toxicity and potential ecological and human health impacts. Climate change, industrial expansion and population growth drive increasing contaminant loads, making reliable multi-element analysis essential for regulatory compliance and environmental protection.

Study Goals and Overview

This work evaluates the Shimadzu ICPMS-2050 for analysis of 23 elements in wastewater following U.S. EPA Method 6020B. Key objectives include verifying detection limits, assessing spectral interference removal strategies, and demonstrating accuracy, precision and long-term stability in real and reference samples.

Methodology and Instrumentation

• Calibration and QC standards prepared in 1% HNO₃/0.5% HCl matrix, covering analyte ranges from ultra-trace to high concentration.
• Sample types: spectral interference check (SIC) solution, simulated wastewater reference materials (JEMCA 0001-6 and 0001-7), and two factory wastewater samples.
• ICPMS-2050 configuration: DC04 nebulizer, cyclone chamber, mini torch, nickel skimmer cone, AS-20 autosampler and online internal standard kit (Bi, Ga, In, Sc).
• Collision/reaction cell optimization: H₂ reaction mode for MoO interference on ¹¹¹Cd and He collision mode for chlorine oxide interference on ⁵¹V.
• Calibration verification: multi-point curves, LLOQ set as lowest standard, verified by seven replicates (RSD ≤20%, recovery ±35%).

Main Results and Discussion

• Optimized H₂ reaction conditions reduced MoO interference on ¹¹¹Cd from 0.514 to 0.003 µg/L while preserving 10 µg/L Cd signal.
• Instrument detection limits (IDLs) met or exceeded EPA requirements (e.g., Cd 0.01 µg/L, Pb 0.003 µg/L, Se 0.06 µg/L).
• SIC solution spike recoveries ranged 89–105%, satisfying EPA QC (100 ± 25%).
• Reference materials analysis achieved recoveries within ±5% of certified values for Mn, Fe, Cu and Cd.
• Real wastewater samples showed %RPD ≤6.5% for duplicates and spike recoveries of 87–104%, meeting QC criteria.
• Long-term stability over 9 h: CCV recoveries within 90–110% and internal standard fluctuations within 70–130%, confirming method robustness.

Benefits and Practical Applications

• Enables simultaneous quantification of trace and high-concentration metals in complex wastewater matrices.
• Effective interference removal using tailored cell gases enhances accuracy for critical elements like Cd and V.
• Built-in Internal Standard Intensity Fluctuation Graph facilitates real-time QC monitoring.
• Mini-torch design reduces argon consumption and operating costs, supporting routine environmental analysis and compliance testing.

Future Trends and Potential Applications

• Automation of sample introduction and data processing for higher throughput in environmental laboratories.
• Expansion to speciation analysis and emerging contaminant monitoring using advanced cell gas chemistries.
• Adoption in other high-matrix analyses such as sludge, soil extracts and industrial effluents.
• Instrument enhancements to further lower detection limits and improve interference management through novel interface innovations.

Conclusion

The ICPMS-2050, operated with a mini torch and optimized collision/reaction cell conditions, successfully met EPA Method 6020B quality control requirements for 23 elements in wastewater. The system demonstrated low detection limits, high accuracy, excellent precision and stability over extended runs, offering a cost-effective solution for environmental monitoring and regulatory compliance.

Reference

1. EPA Method 6020B, Inductively Coupled Plasma – Mass Spectrometry, U.S. Environmental Protection Agency, July 2014.