Analysis of Semivolatile Organic Compounds with Hydrogen Carrier Gas and HydroInert Source by Gas Chromatography/Triple Quadrupole Mass Spectrometry (GC/MS/MS)

Importance of the Topic

Environmental monitoring of semivolatile organic compounds (SVOCs) relies heavily on gas chromatography–mass spectrometry (GC/MS). Traditional methods use helium as the carrier gas, but global supply concerns and rising costs have driven the search for alternatives. Hydrogen offers an attractive option due to its fast diffusivity and low cost. Yet, its reactivity in mass spectrometer ion sources can lead to unwanted hydrogenation or dechlorination of analytes. The Agilent HydroInert source design addresses these challenges and enables robust SVOC analysis under U.S. EPA Method 8270E using hydrogen carrier gas.

Objectives and Study Overview

The core aim of this study was to demonstrate that a GC/triple quadrupole MS system equipped with the HydroInert source can meet the stringent calibration, sensitivity, and spectral fidelity requirements of EPA Method 8270E when using hydrogen carrier gas. Key goals included:

• Extending the calibration range from 0.02 to 100 µg/mL for a representative set of 120 SVOCs plus surrogates and internal standards.
• Verifying minimal hydrogenation or dechlorination of sensitive functional groups (e.g., nitro and halogenated compounds).
• Maintaining isomer resolution, method run time, and mass spectral libraries established under helium-based methods.

Methodology and Instrumentation

A comprehensive standard mixture containing 120 target SVOCs and surrogates was prepared in dichloromethane, with nominal calibration levels ranging from 0.02 up to 100 µg/mL. An Agilent 8890B GC equipped with a multimode inlet (MMI) and an Agilent J&W DB-5ms Ultra Inert column (20 m × 0.18 mm, 0.18 µm) delivered efficient separations under a 12-minute temperature program. Hydrogen carrier gas was held at a constant 1.2 mL/min.

The MS system consisted of an Agilent 7000E Inert Plus triple quadrupole mass spectrometer fitted with the HydroInert source and a 9 mm HydroInert extractor lens. Electron ionization at 70 eV was used, and dynamic multiple reaction monitoring (dMRM) transitions were drawn from existing libraries and reoptimized as needed. Periodic autotunes with perfluorotributylamine ensured mass accuracy and stability.

Main Results and Discussion

Initial calibration showed that 92.5 % of the 120 compounds could be quantified over the full extended range (0.02–100 µg/mL) under hydrogen carrier gas with less than 20 % relative standard deviation (RSD) of average response factors (RFs). Only 16 compounds required linear or quadratic curve fits, compared to eight in prior helium-based triple quadrupole work. Key observations included:

• DFTPP tune ion ratios met EPA Method 8270E criteria, confirming inlet and column integrity despite hydrogen use.
• Critical isomer pairs (e.g., phenanthrene/anthracene, benz[a]anthracene/chrysene) maintained baseline or near-baseline resolution in the 12-minute run.
• Overlay of quantifier and qualifier MRM transitions for nitrobenzene and hexachlorobenzene showed no evidence of hydrogenation or dechlorination, with transition ratios matching those from helium methods.
• Comparison of RF guidance values indicated similar sensitivity to traditional helium-based single quadrupole systems for most compounds.

Matrix repeatability experiments, involving 10 replicate injections of a 0.4 µg/mL calibration verification spike into an extracted soil composite, yielded RSDs below 10 % for over 95 % of compounds. Recovery of the calibration check standard in matrix was within ±20 % for more than 85 % of the analytes, demonstrating robust performance in environmental samples.

Benefits and Practical Application of the Method

The integration of hydrogen carrier gas with the HydroInert source onto a GC/MS/MS platform delivers several advantages:

• Reduced reliance on helium supply chains and lower operating costs.
• Shortened analysis time (12 minutes) without compromising resolution of critical SVOC isomers.
• Retention of existing calibration libraries and MRM methods developed under helium, minimizing revalidation effort.
• High sensitivity and mass spectral fidelity essential for regulatory compliance under EPA Method 8270E.

Laboratories conducting QA/QC, solid waste, soil, sediment, water, and air analyses can adopt this workflow to maintain performance while transitioning to hydrogen.

Future Trends and Possible Applications

Advances in source design and gas delivery will likely expand hydrogen use across other GC/MS applications, including ultra-trace pesticide, dioxin, and emerging contaminant screening. Real-time monitoring of SVOCs with hydrogen may benefit from faster cycle times. Integration with automated sample prep, AI-driven data processing, and coupling to high-resolution MS could further enhance detectability and reduce turnaround. Exploration of other inert gas replacements (e.g., nitrogen) and continued optimization of split/splitless inlets will support diverse environmental, food safety, and forensic analyses.

Conclusion

This study demonstrates that a GC/triple quadrupole MS system equipped with Agilent’s HydroInert source can successfully employ hydrogen as a carrier gas to meet EPA Method 8270E requirements for SVOCs. The method offers equivalent or improved sensitivity, robust spectral fidelity, and efficient isomer resolution in a 12-minute run, while alleviating helium supply concerns. The approach is readily transferable to routine environmental laboratories seeking cost-effective, high-throughput analyses.

Reference

1. U.S. Environmental Protection Agency. Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS); Method 8270D. Revision 4, February 2007.
2. U.S. Environmental Protection Agency. Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS); Method 8270E. Revision 4, June 2018.
3. Churley M., Quimby B., Andrianova A. A Fast Method for EPA 8270 in MRM Mode Using the 7000 Series Triple Quadrupole GC/MS. Agilent Technologies Application Note 5994-0691EN, 2019.