A consolidated method for the analysis of VOCs in soil by HS-GC-MS in analytical testing laboratories

Significance of the topic

Volatile organic compounds in soil present significant environmental and health concerns due to their toxicity, mobility, and regulatory limits. Accurate measurement of these contaminants is critical for informed site remediation decisions. Traditional analytical workflows often require multiple methods and extended instrument time, resulting in increased labor, costs, and delayed results. A consolidated headspace GC-MS approach addresses these challenges by streamlining sample preparation and analysis into a single, efficient protocol.

Objectives and study overview

• Combine U.S. EPA 5021 and Chinese standards HJ642-2013 and HJ736-2015 into one method
• Simultaneously quantify 61 VOCs in soil samples
• Reduce run time and per-sample cost
• Validate performance against regulatory criteria

Methodology and Instrumentation

The consolidated method utilized a Thermo Scientific TriPlus 500 headspace autosampler, TRACE 1310 gas chromatograph, and ISQ 7000 single quadrupole mass spectrometer. Samples consisted of 2 g soil mixed with an acidified sodium chloride matrix modifier at pH 2. Headspace extraction was conducted by incubating vials at 60 °C for 30 minutes under 160 kPa with medium agitation. Chromatographic separation employed a TraceGOLD TG-624 60 m × 0.25 mm × 1.4 µm column. The MS operated in full-scan mode (35–300 m/z) with electron ionization at 70 eV.

Main Results and Discussion

Baseline separation of all 61 compounds was achieved in a 30-minute run. Identification criteria included retention time windows (±0.05 min), characteristic ion ratios (±30 %), and NIST library matching. Calibration over 10–500 µg/kg yielded R² > 0.999 and average factor RSD < 5 %. Method detection limits were ≤ 2 µg/kg (average 0.9 µg/kg). Precision at 100 and 200 µg/kg showed RSD < 12 %. Spike recoveries in soil ranged from 70 % to 130 %. Robustness testing over 128 injections in 4.5 days without maintenance demonstrated stable recoveries (RSD < 20 %). Retention time alignment software maintained peak windows after column trimming, preserving method consistency.

Benefits and Practical Applications

This consolidated HS-GC-MS method merges three regulatory procedures into a single 30-minute sequence, saving over 24 hours of instrument time per 20-sample batch. It reduces equipment and staffing needs, lowers per-sample costs, and accelerates data turnaround. Automated eWorkflows and intelligent run control ensure reproducible results, streamlined data processing, and full traceability.

Future Trends and Applications

Advances may include coupling with high-resolution mass spectrometry, expanding compound libraries, fully automated sample preparation, and on-site field deployable systems. Applications could extend to additional environmental matrices and real-time contaminant monitoring.

Conclusion

The validated headspace GC-MS method meets U.S. EPA and Chinese regulatory requirements for 61 soil VOCs, offering high sensitivity, precision, and linearity within a 30-minute run. This consolidated workflow delivers significant improvements in throughput, cost efficiency, and operational simplicity for environmental testing laboratories.

Instrumentation Used

• Thermo Scientific TriPlus 500 headspace autosampler
• Thermo Scientific TRACE 1310 gas chromatograph
• Thermo Scientific ISQ 7000 single quadrupole mass spectrometer
• TraceGOLD TG-624 60 m × 0.25 mm × 1.4 µm column

References

• US EPA. What is the definition of VOC? 2020.
• US EPA. Impact of VOCs on indoor air quality. 2020.
• Thermo Fisher Scientific. Application Note AN73415: Routine analysis of purgeable organic compounds in drinking water with ISQ 7000 GC-MS. 2020.
• Thermo Fisher Scientific. Application Note AN10729: Analysis of VOCs in soil by HS-GC-MS. 2020.
• US EPA. SW-846 Test Method 8260D: Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry. 2020.
• US EPA. Method 5021: Volatile Organic Sampling and Preparation Procedure for VOA Analysis. 1996.