Analysis of volatile organic compounds in water using purge and trap coupled to single quadrupole GC-MS

Significance of the Topic

Volatile organic compounds in water are critical environmental pollutants that contribute to ground level ozone formation and pose health risks. Sensitive and robust analytical methods are needed to monitor these contaminants in groundwater, surface water, and wastewater according to regulatory standards such as the Chinese Method HJ 639 and US EPA Method 8260.

Objectives and Study Overview

This study evaluates the performance of a purge and trap system coupled to a single quadrupole GC MS for determination of 66 target VOCs in water. Key performance metrics including method detection limits, linearity, precision, accuracy, and long term robustness were examined against acceptance criteria specified in HJ 639.

Instrumentation

• Teledyne Tekmar Atomx XYZ purge and trap concentrator with efficient trap cooling and moisture control
• Thermo Scientific Trace 1610 gas chromatograph equipped with a TraceGOLD TG VMS capillary column
• Thermo Scientific ISQ 7610 single quadrupole mass spectrometer with NeverVent vacuum probe interlock and ExtractaBrite ion source
• Chromeleon Chromatography Data System with ePanel and eWorkflow for integrated control, acquisition, and reporting

Methodology

Water samples and calibration standards were prepared by spiking reagent water with certified VOC mixes and internal standards. Nine calibration levels ranged from 0.5 to 200 µg/L. Purge parameters included an 11 minute nitrogen purge at 40 mL/min followed by dry purge and thermal desorption at 250 °C. GC oven programming achieved full separation in under 15 minutes. Mass spectrometer data were collected in scan and selected ion monitoring modes.

Key Results and Discussion

• Linearity was excellent over 0.5 to 200 µg/L with R2 values above 0.99 and response factor RSD below 20
• Method detection limits were below 0.27 µg/L for most analytes, exceeding the HJ 639 criterion of 0.6 µg/L
• Precision and accuracy for seven replicate injections at 20 µg/L showed recoveries within ±20 and RSDs under 7
• Robustness was demonstrated by 137 consecutive injections over four days with average peak area RSD of 7.9 and average recovery of 98 without system intervention

Benefits and Practical Applications

• Automated instrument control minimizes downtime and user error
• Effective water removal extends column life and improves sensitivity
• Wide linear dynamic range allows quantitation from sub µg/L to hundreds of µg/L
• Proven robustness supports high throughput environmental monitoring

Future Trends and Potential Applications

• Integration of advanced data analytics for real time quality control
• Application of similar P T GC MS workflows to emerging contaminants and non VOC targets
• Further miniaturization and field deployable purge and trap systems
• Expansion of library based identification with high resolution mass spectrometry coupling

Conclusion

The combined Atomx XYZ purge and trap concentrator, Trace 1610 GC, and ISQ 7610 MS meets and exceeds the Chinese HJ 639 requirements for VOC analysis in water. The system delivers low detection limits, excellent linearity, reproducibility, and unattended operation capability, making it a reliable solution for environmental laboratories.

References

1. Method 8260 Measurement of Volatile Organic Compounds in Water by Capillary Column Gas Chromatography Mass Spectrometry U S EPA Method 8260 Revision D
2. Thermo Scientific AppsLab Library