US EPA Method 624 – Teledyne Tekmar Atomx XYZ and Agilent 7890B GC/5977A MSD

Significance of the Topic

Determining trace levels of volatile organic compounds (VOCs) in environmental water samples is critical for regulatory compliance, public health protection, and process monitoring. US EPA Method 624 provides a standardized protocol for detecting purgeable organics, ensuring consistent results across laboratories. Improvements in purge-and-trap (P&T) technology that enhance water removal and reduce cycle time can increase sample throughput while maintaining analytical precision and sensitivity.

Aims and Overview of the Study

This application note evaluates the performance of the Teledyne Tekmar Atomx XYZ P&T system paired with an Agilent 7890B gas chromatograph and 5977A mass spectrometer for analyzing VOCs in wastewater according to EPA Method 624. The main objectives were to:

• Establish linear calibration curves over a wide concentration range (0.5–200 ppb).
• Determine method detection limits (MDLs) and assess accuracy and precision at a low-level spike (0.5 ppb).
• Demonstrate the Atomx XYZ’s ability to remove excess water vapor and resolve interferences.

Methodology and Instrumentation

Water samples and calibration standards were prepared in methanol, using Restek® multi-component mixes to yield 31 target VOCs. Internal standards and surrogates ensured reliable quantitation and quality control. Seven replicate 0.5 ppb samples were analyzed to calculate MDLs, accuracy, and precision.

• Teledyne Tekmar Atomx XYZ P&T system: Multi-matrix design with enhanced moisture control, rapid trap cooling, and an 84-position autosampler. Key parameters included a 5 mL purge volume, 11 min purge time, water bake rinse, and helium purge gas.
• Agilent 7890B GC/5977A MSD: Rtx-VMS capillary column (20 m × 0.18 mm, 1 µm film), helium carrier at 1 mL/min. Oven ramp from 35 °C to 225 °C over 14 min. Mass spectrometer scanned m/z 35–260.

Main Results and Discussion

Calibration curves for all compounds exhibited relative standard deviations (RSDs) below 20 %, meeting EPA requirements. MDLs ranged from 0.08 to 0.28 ppb, demonstrating high sensitivity. Accuracy for the 0.5 ppb spikes fell within 89–122 % recovery, and precision (RSD) was ≤15.4 % for all analytes, well under the 20 % threshold. A representative total ion chromatogram of a 50 ppb standard showed clear peak resolution with no detectable water interference, confirming the efficacy of the moisture control system.

Key findings:

• Consistent linear response across the calibration range with low variability.
• Low MDLs enabled detection near regulatory limits.
• Effective elimination of water vapor peaks, protecting the GC/MS system and extending column life.

Benefits and Practical Applications

The Atomx XYZ P&T system, combined with Agilent GC/MS, provides reliable, high-throughput analysis of VOCs in water matrices. Laboratories can achieve a 14 % reduction in cycle time compared to earlier models, increasing the number of samples processed per shift. Enhanced water removal reduces maintenance frequency and improves long-term method robustness. This workflow supports environmental monitoring, wastewater compliance testing, and quality control in industrial settings.

Future Trends and Potential Applications

Advances in P&T technology may focus on further automation, miniaturization, and coupling with high-resolution mass spectrometry for non-target screening. Integration with online sampling and data analytics platforms will enable real-time monitoring of emerging contaminants. Adaptation of this approach to other matrices, such as soil leachate or air emissions, could broaden its application in environmental forensics and occupational safety.

Conclusion

This study confirms that the Teledyne Tekmar Atomx XYZ purge-and-trap system, in conjunction with an Agilent 7890B GC/5977A MS, meets or exceeds EPA Method 624 performance criteria for VOC analysis in water. The method delivers precise, accurate quantitation at sub-ppb levels while effectively controlling moisture interference. Increased throughput and reduced maintenance make it a valuable tool for environmental and industrial laboratories.

References

1. Appendix A to Part 136 - Methods for Organic Chemical Analysis of Municipal and Industrial Wastewater - Method 624: Purgeables; US EPA, Promulgated 1984.