Analysis of volatile organic compounds in drinking water according to U.S. EPA Method 524.4

Importance of the Topic

Volatile organic compounds (VOCs) are widespread environmental contaminants that can adversely affect human health when present in drinking water. Regulatory agencies, including the U.S. EPA, mandate sensitive and accurate methods to monitor these compounds. U.S. EPA Method 524.4 introduces flexibility in purge-and-trap parameters and permits the use of nitrogen as purge gas, reducing reliance on helium.

Objectives and Study Overview

This study demonstrates an analytical workflow that complies with U.S. EPA Method 524.4 for quantifying 75 VOCs in drinking water. The goals were to evaluate instrument sensitivity, linearity, method detection limits (MDLs), precision, accuracy, robustness over extended sequences, and cost reduction via helium-saving technology.

Methodology and Instrumentation

A purge-and-trap concentrator (Teledyne LABS Tekmar Lumin P&T) coupled with an AQUATek LVA autosampler processed water samples spiked with internal and surrogate standards. Key steps:

• Calibration range: 0.2–50 ppb using P&T-grade methanol standards.
• MDL and MRL determination via seven replicates at 0.5 ppb.
• Precision and accuracy tested at 10 ppb over seven injections.
• Extended robustness test: 185 consecutive injections (representing three days of analysis) without maintenance.

Instrumentation:

• GC: Thermo Scientific™ TRACE™ 1610 with HeSaver-H2Safer split/splitless injector.
• Column: TraceGOLD™ TG-VMS (30 m × 0.25 mm, 1.4 μm film).
• MS: Thermo Scientific™ ISQ™ 7610 single-quadrupole with full-scan (35–260 amu) or optional SIM mode.
• Data system: Thermo Scientific™ Chromeleon™ CDS v7.3 controlled the entire setup.

Main Results and Discussion

• Linearity: All 75 VOCs achieved r² ≥ 0.995 across 0.2–50 ppb.
• Sensitivity: MDLs ranged near 0.04–0.14 ppb; MRLs passed strict confirmation criteria.
• Precision & Accuracy: Seven replicates at 10 ppb yielded average RSD 3.25% and accuracy 102% (±20% allowed).
• Robustness: Over 185 injections, RSDs for all compounds were < 30% (method limit) with average RSD 6.6%.
• Water interference: Minimal peak distortion, confirming effective matrix management.

Benefits and Practical Applications

• Reliable quantitation of trace VOCs in drinking water for compliance and quality control.
• Reduced helium consumption by a factor of four using HeSaver-H2Safer technology, lowering operational costs.
• Automated purge-and-trap cleanup sequence minimizing carryover and maintenance downtime.
• Single software control simplifies data acquisition and reporting.

Future Trends and Opportunities

• Broader adoption of nitrogen as an alternative purge gas to conserve helium.
• Integration of advanced autosampler designs for faster throughput and lower carryover.
• Application of high-resolution MS or tandem MS for increased selectivity.
• Development of predictive maintenance algorithms based on extended sequence performance metrics.

Conclusion

The combined Tekmar Lumin P&T concentrator with TRACE 1610 GC–ISQ 7610 system meets or exceeds U.S. EPA Method 524.4 requirements. The workflow delivers excellent sensitivity, reproducibility, and linearity while achieving significant cost savings through helium-saving technology. This robust solution supports routine drinking water monitoring and ensures regulatory compliance.

References

• U.S. EPA Method 524.2. Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry.
• Thermo Fisher Scientific Application Note 000525: Uninterrupted analysis of volatile organic compounds in drinking water using single quadrupole GC-MS.
• Thermo Fisher Scientific Application Note 002952: Adhering to U.S. EPA Method 524.2 for the analysis of volatile organic compounds in drinking water.
• Thermo Fisher Scientific Helium Saver Calculator tool.