Determination of Volatile Organic Compounds in Water by Purge and Trap Gas Chromatography/Mass Spectrometry

Importance of the Topic

Volatile organic compounds (VOCs) are regulated contaminants in drinking and environmental waters due to their potential health risks and strict regulatory limits. Accurate and sensitive analysis of VOCs supports water quality protection, regulatory compliance, and risk assessment. Purge and trap gas chromatography–mass spectrometry (P&T GC/MS) remains a gold standard for trace-level VOC determination.

Objectives and Study Overview

This work evaluates the performance of an Agilent Intuvo 9000 GC coupled with an Agilent 5977B GC/MSD and a Teledyne Tekmar Atomx XYZ purge and trap sampler for the analysis of 57 VOCs in water. The protocol follows Chinese Ministry of Environmental Protection method HJ 639-2012. Key goals include assessing linearity, repeatability, and detection limits in both full-scan and selected ion monitoring (SIM) modes.

Methodology

Water samples (5 mL) were spiked automatically with two internal standards (fluorobenzene and 1,4-dichlorobenzene-d4) and three surrogate compounds. A purge at 40 mL/min for 11 minutes transferred VOCs to a sorbent trap, followed by bake and desorb steps. The GC oven program started at 35 °C (2 min), ramped at 5 °C/min to 120 °C, then 10 °C/min to 220 °C (2 min). Mass spectrometric detection used electron impact ionization with scan or SIM acquisition, solvent delay of 2 minutes, and established tune settings.

Instrumentation Used

• Teledyne Tekmar Atomx XYZ purge and trap system (5 mL vessel, trap #9)
• Agilent Intuvo 9000 GC with Ultra Inert inlet and J&W DB-624 UI column (30 m × 0.25 mm, 1.4 µm)
• Agilent 5977B GC/MSD (EI source, 230 °C; quad 150 °C)
• Helium carrier gas at 1 mL/min constant flow
• Internal standards: fluorobenzene, 1,4-dichlorobenzene-d4; surrogates: dibromofluoromethane, toluene-d8, 4-bromofluorobenzene

Key Results and Discussion

Calibration in scan mode (5–200 µg/L) and SIM mode (1–40 µg/L) yielded correlation coefficients (R²) ≥ 0.9989 for all 57 compounds. Repeatability (n=8) at 5 µg/L (scan) showed area percent RSD between 0.9 % and 7.6 %. Detection limits in scan mode were ≤ 1.6 µg/L, while SIM mode achieved LODs ≤ 0.33 µg/L, with most compounds below 0.2 µg/L. These metrics meet or exceed the requirements of method HJ 639-2012.

Benefits and Practical Applications

P&T GC/MS with automated sample preparation offers high sensitivity, broad analyte coverage, and reproducible quantitation. The dual-mode acquisition enables both comprehensive screening and targeted quantitation. This workflow supports environmental laboratories, regulatory monitoring, and quality control in water analysis laboratories.

Future Trends and Opportunities

Advances may include integration of high-resolution mass spectrometry for improved selectivity, further miniaturization of P&T modules, expanded analyte libraries, and enhanced data analytics with machine learning. Online and real-time monitoring systems could leverage similar sampling principles for continuous water quality surveillance.

Conclusion

The combination of the Agilent Intuvo 9000 GC, 5977B GC/MSD, and Teledyne Tekmar P&T system successfully fulfills HJ 639-2012 performance criteria for 57 VOCs in water. Excellent linearity, precision, and low detection limits demonstrate the robustness of this automated P&T GC/MS approach for routine environmental analysis.

References

1. Chinese Ministry of Environmental Protection. HJ 639-2012: Determination of Volatile Organic Compounds in Water by Purge and Trap/Gas Chromatography–Mass Spectrometry.