Global Best Practices for High Quality Analysis of Waters for Trace Metals & Mercury

Significance of the Topic

Water analysis for trace metals and mercury requires stringent sampling protocols to avoid contamination and ensure reliable detection at ultra-low levels. Clean sample containers and proper preservation methods are essential to prevent false positives or negatives and to maintain sample integrity from collection to analysis.

Aims and Study Overview

This study assessed global best practices for high-quality water sampling for trace metals and mercury analysis. ALS conducted comparative tests of over forty sample containers sourced from seven countries, using two laboratories (Vancouver and Lulea) offering some of the lowest detection limits worldwide. The investigation also evaluated field versus laboratory preservation techniques to optimize data quality and sampling logistics.

Methodology and Sample Handling

Ultratrace metals testing was performed down to one tenth of standard detection limits, involving short- and long-term leaching studies with acidified samples. Suitability testing for pre-charged containers with concentrated nitric acid was included to simulate practices in different regions. Preservation methods compared lab-based acidification with field approaches using pre-charged bottles or nitric acid vials. Mercury sampling employed pre-charged glass vials with HCl to stabilize dissolved mercury as a chloride complex.

Main Results and Discussion

Testing revealed that plastic containers pre-charged with concentrated nitric acid leached higher metal concentrations (notably chromium), compromising reliable detection limits. Specially selected ultra-clean bottles and rigorous proofing protocols enabled lower and more consistent limits of detection. Lab preservation with high-grade nitric acid reduced field handling risks and contamination, and offered improved detection limits, especially for chromium. For mercury, glass vials pre-charged with HCl provided stable samples and faster turnaround by eliminating lengthy equilibration steps.

Benefits and Practical Applications of the Method

• Enhanced detection sensitivity and reliability at trace levels.
• Reduced contamination risks through controlled laboratory preservation and bottle proofing.
• Simplified field operations by avoiding handling of concentrated acids on-site.
• Optimized turnaround times for mercury analysis using pre-charged glass vials.

Future Trends and Applications

Advances in container materials, proofing processes, and automated acid dosing are expected to further lower detection limits and streamline sampling workflows. Integration of real-time monitoring and digital traceability can enhance sample chain of custody. Sustainable container designs and alternative preservation chemistries may reduce environmental impact.

Conclusion

Implementing ultra-clean containers combined with laboratory-based acid preservation significantly improves the quality and reliability of trace metals and mercury analysis in water. These best practices minimize contamination, lower detection limits, and increase sampling efficiency, supporting robust environmental monitoring and regulatory compliance.