Determination of Trace Level Lead (Pb) in Drinking Water Using a Mercury-Free Electrode and a Portable Instrument According to the Requirements of USEPA Lead and Copper Rule

Significance of the Topic

Lead contamination in drinking water poses severe health risks due to its neurotoxic effects and cumulative bioaccumulation. Regulatory frameworks such as the USEPA Lead and Copper Rule impose an action limit of 15 µg/L, necessitating reliable, on-site analytical methods.

Objectives and Study Overview

This study evaluates a mercury-free anodic stripping voltammetry (ASV) approach using a portable voltammetric analyzer to determine trace levels of lead directly at the sampling site. The goal is to assess method sensitivity, accuracy, precision, and compliance with USEPA requirements.

Methodology and Instrumentation

Anodic stripping voltammetry enables the preconcentration of Pb²⁺ ions onto a silver-modified gold micro-wire electrode, followed by oxidative stripping for quantification. Standard additions calibrate the measurement. The 946 Portable VA Analyzer (battery-powered) and scTRACE Gold sensor (gold working electrode modified with a silver film, Ag/AgCl reference, carbon auxiliary) provide a fully mercury-free system.

Main Results and Discussion

• Method Detection Limit (MDL): 1.72 µg/L (t = 3.143, S = 0.55 µg/L), Minimum Level (ML): 5.47 µg/L.
• Accuracy: Recovery between 88.6% and 98.5% (mean 95.4%), within the acceptance range of 80–120%.
• Precision: Relative standard deviation of ±3.4%, surpassing the ±20% acceptance criterion.
• Quality Control: Certified reference yielded 66.9 µg/L Pb (105.1% recovery), meeting the 55.3–71.9 µg/L acceptance range.
• Fortified real-world samples (tap and mineral water at 15 µg/L spike) achieved recoveries up to 98.7%.

The portable ASV method demonstrates robust performance under field conditions, confirming its suitability for regulatory compliance.

Benefits and Practical Applications

• Environmental Safety: Completely mercury-free analysis mitigates secondary contamination risks.
• On-Site Monitoring: Portable instrumentation allows immediate, point-of-use determination without laboratory support.
• Regulatory Compliance: Sensitivity and precision meet or exceed USEPA Lead and Copper Rule criteria.
• Operational Efficiency: Rapid 30-second deposition step and standard additions streamline workflow.

Future Trends and Potential Applications

Advancements may include integration with wireless data transmission for real-time reporting, multi-element detection capabilities, further miniaturization of electrode sensors, and automation for high-throughput field surveys. Ongoing research may push detection limits lower and expand applications to other environmental matrices.

Conclusion

The mercury-free ASV method with the 946 Portable VA Analyzer and scTRACE Gold electrode offers a sensitive, precise, and accurate solution for lead monitoring in drinking water. It fulfills USEPA requirements and supports rapid, on-site decision making for water quality management.

References

• United States Environmental Protection Agency. Lead and Copper Rule. EPA Ground Water and Drinking Water Division.
• Metrohm Application Bulletin 433/1 – Determination of lead in water using the scTRACE Gold electrode.
• Metrohm Application Work AW VA CH4-0587-092019 – Determination of Pb in acidified water samples at a silver-film electrode using the 946 Portable VA Analyzer.
• EPA Protocol for the Evaluation of Alternate Test Procedures for Organic and Inorganic Analytes in Drinking Water (EPA 815-R-15-007), 2015.
• EPA Protocol for Review and Validation of New Methods for Regulated Organic and Inorganic Analytes in Wastewater Under EPA’s Alternate Test Procedure Program (EPA 821-B-18-001), 2018.