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

Significance of the topic

Volatile organic compounds in soil pose environmental and health risks by migrating into air and groundwater and contaminating food chains. Accurate quantitation of these compounds is critical for regulatory compliance and risk assessment.

Objectives and study overview

This work evaluates the performance of the Teledyne Tekmar Atomx XYZ purge and trap system coupled to a Thermo Scientific TRACE 1610 gas chromatograph and ISQ 7610 single quadrupole mass spectrometer. The method is validated against Chinese MEE HJ 605 requirements, assessing linearity, detection limits, precision, accuracy, and robustness for 66 target VOCs in soil.

Methodology and instrumentation

Soil and water standards were prepared from certified VOC mixes diluted in methanol and reagent water. Eight-point calibration curves (1 to 200 ppb) included internal standards and surrogates at 25 ppb. The purge and trap system parameters were optimized for trap cooling, purge flow, bake conditions, and moisture removal. GC separation used a 20 m TraceGOLD TG VMS column under a temperature program from 35 to 225 C with helium carrier. The ISQ 7610 MS operated in full scan mode (40 to 270 amu) with electron ionization and an extended dynamic range detector.

Results and discussion

All 66 VOCs were resolved within 12 minutes with sharp peaks and minimal water interference. Calibration linearity exceeded R2 of 0.99 and response factor precision below 20% across the full range. Method detection limits averaged 0.2 ppb with precision under 4%. At 20 ppb, recoveries fell within 20% of nominal and RSDs remained below 7%. A two-day sequence of 77 injections demonstrated stable peak areas with RSDs under 10% without user intervention, confirming robustness.

Benefits and practical applications

The integrated P&T GC-MS workflow delivers rapid, fully automated soil VOC analysis with high sensitivity and reproducibility. The vacuum probe interlock feature minimizes downtime, supporting high sample throughput in environmental testing laboratories.

Future trends and potential applications

Ongoing improvements in detector technology and data system integration can further enhance sensitivity, dynamic range, and ease of reporting. Expanding the method to include emerging contaminants and portable field units may broaden its environmental monitoring capabilities.

Conclusion

The validated purge and trap GC-MS method exceeds HJ 605 criteria for soil VOC analysis, demonstrating excellent linearity, sensitivity, accuracy, and long-term stability. It offers a robust solution for routine environmental surveillance.

References

• US EPA Method 8260 Measurement of Volatile Organic Compounds by Gas Chromatography-Mass Spectrometry
• Chinese Ministry of Ecology and Environment Method HJ 605 for Soil Volatile Organic Compounds
• Thermo Scientific AppsLab Application Notes Repository