Volatile Organic Compounds Analysis in Drinking Water with Headspace GC/MSD Using Hydrogen Carrier Gas and HydroInert Source

Significance of the Topic

Monitoring volatile organic compounds (VOCs) in drinking water is essential to safeguard public health, meet regulatory requirements, and detect contamination from industrial or disinfection by-products. Traditionally, helium has been used as the carrier gas in headspace GC/MS analyses, but recent shortages and cost increases have driven laboratories to seek alternatives. Hydrogen offers comparable or superior chromatographic speed and resolution, provided that in-source reactions are controlled to maintain spectral fidelity.

Objectives and Study Overview

This study aimed to develop and validate a rapid static headspace GC/MS method for the quantitation of 80 VOCs in drinking water using hydrogen as the carrier gas. Key goals included evaluating a new HydroInert electron ionization (EI) source optimized for hydrogen, achieving baseline separation of target analytes within a seven-minute runtime, and demonstrating reliable identification and quantitation in both scan and selected ion monitoring (SIM) modes over concentrations ranging from 0.05 to 25 µg/L.

Methodology and Instrumentation

Sample preparation involved spiking 20 mL headspace vials with VOC standards (including internal and surrogate standards) and 5 g of sodium sulfate to enhance partitioning. An Agilent 8697 headspace sampler was set to 75 °C with 12 minutes equilibration and pulsed split injection (21:1 split ratio) into an Agilent 8890 GC equipped with a multimode inlet and a 20 m × 0.18 mm, 1 µm DB-624 Ultra Inert column. Hydrogen was delivered at 0.95 mL/min constant flow. The GC was coupled to an Agilent 5977C Inert Plus MSD retrofitted with a HydroInert EI extractor source and 9 mm extractor lens. Mass spectra were acquired in scan mode (35–260 Da) and SIM mode with optimized dwell times. Data processing employed Agilent MassHunter Workstation with Unknowns Analysis for spectral deconvolution and NIST20 library searches.

• Agilent 8890 GC with multimode inlet and Ultra Inert splitless straight liner (1.0 mm id)
• Agilent DB-624 UI column, 20 m × 0.18 mm, 1 µm
• Agilent 8697 headspace sampler
• Agilent 5977C MSD with HydroInert EI source and extractor lens
• MassHunter Unknowns Analysis and Quantitative Analysis software

Main Results and Discussion

The optimized method resolved 80 VOCs in under seven minutes. In scan mode, the average calibration range was 0.16–25 µg/L with a mean R2 of 0.9978. The average relative standard deviation of response factors (RF RSD) was below 20% for 76 analytes; polar compounds such as acetone exhibited the highest variability and required careful blank correction. Deconvoluted spectra matched NIST20 library entries with an average match score of 94, confirming spectral fidelity despite potential in-source reactions. SIM mode provided enhanced sensitivity, with an average calibration range of 0.07–24 µg/L, mean R2 of 0.9990, and average method detection limit (MDL) of 0.026 µg/L. A subset of analytes required quadratic fitting to meet the 20% relative standard error criterion.
Analysis of tap water samples from two regions demonstrated detection of common disinfection by-products (trihalomethanes) at concentrations up to 44 µg/L and trace levels of industrial VOCs such as cis-1,2-dichloroethylene and methyl tert-butyl ether (MTBE). Spectral deconvolution and SIM qualifier/quantifier ratio checks confirmed compound identities at low µg/L levels.

Benefits and Practical Applications

The hydrogen-based headspace GC/MS method offers rapid throughput, high resolution, and cost savings without sacrificing analytical performance. The HydroInert source effectively mitigates hydrogen-induced in-source reactions, preserving spectral integrity for reliable library matching. Laboratories facing helium constraints can adopt this workflow for routine drinking water monitoring, environmental screening, and regulatory compliance testing.

Future Trends and Opportunities

As hydrogen use in GC/MS expands, further enhancements in source design and materials are anticipated to reduce background noise and broaden analyte scope. Coupling hydrogen-based separations with tandem MS (MS/MS) and advanced deconvolution algorithms will improve selectivity for complex matrices. Expanded multiclass pollutant screening, integration with sample preparation automation, and real-time data analytics will drive higher throughput in environmental and industrial laboratories. Method harmonization and regulatory acceptance of hydrogen carrier gas protocols are expected to facilitate broader adoption.

Conclusion

This application note demonstrates that hydrogen is a viable alternative to helium for static headspace GC/MS analysis of VOCs in drinking water when used with an optimized HydroInert EI source. The method achieves rapid separation of 80 compounds, robust calibration in scan and SIM modes, low MDLs, and reliable spectral fidelity. Implementation can alleviate helium supply concerns while maintaining high analytical performance for environmental and quality control testing.

References

1. US EPA Method 524.2: Successful Measurement of Purgeable Organic Compounds in Drinking Water by Agilent 8860/5977B GC/MSD. Agilent Technologies appl. note, 5994-0833EN, 2019.
2. Improved Volatiles Analysis Using Static Headspace, Agilent 5977B GC/MSD, and High-Efficiency Source. Agilent appl. note, 5991-6539EN, 2016.
3. Fast VOC Analysis of Drinking Water Using Agilent 8697 HS Sampler with Intuvo 9000 GC and 5977B GC/MSD. Agilent appl. note, 5994-4449EN, 2021.
4. Agilent Inert Plus HydroInert GC-MS System: Applying H2 Carrier Gas to Real-World GC-MS Analyses. Agilent tech. overview, 5994-4889EN, 2022.