Analysis of Semivolatile Organic Compounds Using Hydrogen Carrier Gas and the Agilent HydroInert Source by Gas Chromatography/Mass Spectrometry

Significance of the Topic

Gas chromatography–mass spectrometry (GC/MS) is the cornerstone for semivolatile organic compound (SVOC) analysis in environmental and industrial matrices. Recent global helium (He) shortages have driven the exploration of hydrogen (H₂) carrier gas. However, conventional GC/MS sources often suffer from loss of sensitivity and unwanted hydrogenation or dechlorination of analytes. The Agilent HydroInert source offers a technical solution, preserving mass spectral fidelity and method performance while enabling use of H₂ as carrier gas.

Objectives and Study Overview

This study evaluated whether the Agilent 5977B Inert Plus GC/MSD equipped with the HydroInert source could:

• Maintain mass spectral integrity of nitro- and halogenated compounds when using H₂ carrier gas.
• Meet the calibration and performance criteria of U.S. EPA Method 8270E across a broad concentration range (0.1–100 µg/mL).
• Deliver rapid analysis (12-minute run) with adequate resolution of critical isomer pairs.
• Demonstrate tuning, calibration linearity, and repeatability in a soil matrix.

Methodology and Instrumentation

A comprehensive mixture of 119 target SVOCs and surrogates, ranging from nitrosamines and phenols to PAHs and heavily chlorinated species, was prepared in dichloromethane. Calibration standards spanned 0.1–100 µg/mL with internal standards at 40 µg/mL.

Instrumentation:

• Agilent 8890 GC with J&W DB-5ms Ultra Inert column (20 m × 0.18 mm, 0.36 µm).
• Agilent 5977B Inert Plus MS with HydroInert source and 9 mm extraction lens.
• Injection: 1 µL, split 10:1, inlet at 230 °C.
• Oven program: 40 °C (0 min) to 320 °C at 30 °C/min (2 min hold).
• Carrier gas: H₂ at 1.2 mL/min constant flow.
• MS conditions: transfer line 320 °C, source 300 °C, quadrupole 150 °C, scan 35–500 m/z, etune.u.

Results and Discussion

Mass Spectral Fidelity:
An extractor source showed extensive hydrogenation of nitrobenzene to aniline (m/z 93) under H₂, whereas the HydroInert source preserved the native nitrobenzene spectrum (m/z 123), demonstrating retention of key functional groups.

Tuning and Performance:
DFTPP tuning met all ion-ratio criteria of EPA 8270D/E. DDT breakdown stayed below 0.2%, and tailing factors for benzidine and pentachlorophenol were under 1.4.

Resolution of Critical Isomers:
Baseline or >50% resolution was achieved for phenanthrene/anthracene, benz[a]anthracene/chrysene, and benzo[b]/benzo[k]fluoranthene in the 12-minute run.

Calibration and Linearity:
Initial calibration covered 0.1–100 µg/mL for 119 compounds. 87% passed with average RF %RSD <20%. Fourteen compounds required linear fits and one quadratic fit. Comparison with He methods showed only minor differences in response factors.

Matrix Repeatability:
A 15 µg/mL soil extract spike analyzed nine times yielded average recoveries within ±20% for all but two compounds (within ±25%) and RSDs below 7%, confirming method robustness.

Benefits and Practical Applications

• Enables transition from He to H₂ without revising existing mass spectral libraries.
• Preserves spectral fidelity of labile functional groups in SVOCs.
• Meets regulatory method 8270 criteria in a shortened, 12-minute analysis.
• Reduces reliance on scarce helium and lowers operational costs.
• Maintains sensitivity and calibration range comparable to He methods.

Future Trends and Applications

Further adoption of H₂ carrier gas will be driven by helium supply constraints and sustainability goals. Advances may include temperature-programmable inlets to enhance heavy analyte performance, integration with multimode inlets, and wider application to other GC/MS methods. Continued optimization of source design and data processing will extend the approach to emerging contaminants and high-throughput laboratories.

Conclusion

The Agilent HydroInert source coupled with H₂ carrier gas successfully maintains spectral integrity, sensitivity, and regulatory compliance for EPA 8270 SVOC analysis in a rapid 12-minute GC/MS method. This development offers laboratories a viable alternative to helium, enabling cost savings and method flexibility without sacrificing performance.

Reference

1. EPA Method 8270D: Semivolatile Organic Compounds by GC/MS, Revision 4, February 2007.
2. EPA Method 8270E: Semivolatile Organic Compounds by GC/MS, Revision 4, June 2018.
3. Smith Henry A., Analysis of Semivolatile Organic Compounds with Agilent Sintered Frit Liner by GC/MS, Agilent Technologies Application Note 5994-0953EN, 2019.
4. Ciotti R., EPA 8270E with Pulsed Split Injection and Retention Time Locking on an 8890GC with 5977 Series MSD, Application Note 5994-1500EN, 2020.