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

Importance of the topic

Volatile organic compounds (VOCs) in drinking water present significant health and environmental concerns. Regular monitoring of VOCs is mandated by regulatory agencies to protect public health. U.S. EPA Method 524.4 provides a standardized approach for quantifying trace levels of 75 VOCs, ensuring reliable detection, minimized false positives, and adherence to stringent quality control requirements.

Study Objectives and Overview

This application note aimed to demonstrate the performance of U.S. EPA Method 524.4 using a Teledyne Tekmar Atomx XYZ purge and trap (P&T) system coupled to a Thermo Scientific TRACE 1610 gas chromatograph and ISQ 7610 single quadrupole mass spectrometer. Key objectives included evaluating method linearity, detection limits, precision, accuracy, and robustness over an extended sequence of injections.

Used Instrumentation

• Teledyne Tekmar Atomx XYZ Purge & Trap System with chilled tray upgrade
• Thermo Scientific TRACE 1610 Gas Chromatograph (GC)
• Thermo Scientific ISQ 7610 Single Quadrupole Mass Spectrometer (MS) with NeverVent™ VPI and ExtractaBrite™ ion source
• TraceGOLD TG-VMS GC column (20 m × 0.18 mm, 1 µm film)
• Chromeleon™ Chromatography Data System (version 7.3)

Methodology

Sample Preparation:

• Calibration standards (0.2–50 ppb) and spiking of internal and surrogate standards in methanol.
• Seven replicates at 0.5 ppb and seven at 10 ppb in deionized water for MDL, MRL, accuracy, and precision.

Instrument Conditions:

• Purge and trap parameters: 5 mL sample, 8 min purge at 55 mL/min, desorb at 250 °C for 2 min.
• GC oven program: 35 °C hold 3 min, ramp 12 °C/min to 85 °C, then 25 °C/min to 225 °C (total 14.8 min).
• MS acquisition: full scan 35–260 amu, 0.15 s dwell time, solvent delay 0.5 min.

Main Results and Discussion

Linearity and Sensitivity:
All 75 target VOCs achieved regression coefficients (r²) ≥ 0.995 across 0.2–50 ppb. Method detection limits ranged from 0.02 to 0.17 ppb with minimal water interference.

Precision and Accuracy:
Seven injections of a 10 ppb standard yielded average precision of 3.4% RSD and accuracy of 95%, well within method criteria of ≤ 20% RSD and ± 30% recovery.

Robustness:
An extended sequence of 245 consecutive injections (40 calibration checks) over four days showed RSDs below 30% for all compounds and an average RSD of 9%, indicating stable performance without maintenance interruptions.

Benefits and Practical Applications

• Reliable quantitation of trace-level VOCs in drinking water samples.
• Minimized downtime and maintenance through stable purge and trap operation.
• Compliance with U.S. EPA Method 524.4 quality control requirements.
• Unified control and data processing using Chromeleon CDS for both GC-MS and P&T systems.

Future Trends and Opportunities

Advancements in purge and trap automation and high-throughput workflows are expected to further reduce analysis time. Integration of selective ion monitoring (SIM) or high-resolution MS can enhance selectivity and lower detection limits. Emerging data analytics tools may improve real-time QC monitoring and predictive maintenance.

Conclusion

The combined Teledyne Tekmar Atomx XYZ P&T with Thermo Scientific TRACE 1610 GC-ISQ 7610 MS system meets U.S. EPA Method 524.4 requirements, offering excellent linearity, sensitivity, precision, accuracy, and long-term stability for VOC analysis in drinking water.

Reference

1. U.S. EPA Method 524.2. Measurement of Purgeable Organic Compounds in Water by Capillary Column Gas Chromatography/Mass Spectrometry.
2. Thermo Scientific Application Note 000525: Uninterrupted analysis of volatile organic compounds in drinking water using single quadrupole GC-MS.