A More Sustainable Analysis of Ethylene Oxide and 1,4-Dioxane in Surfactants with Hydrogen Carrier Gas

Importance of the Topic

This application note addresses the need for precise, sustainable detection of ethylene oxide and 1,4-dioxane in surfactant products. Both compounds are regulated due to their potential health risks and can be present at trace levels following alkoxylation and sulfation steps in surfactant manufacture. Traditional methods rely on helium carrier gas, but a global helium shortage and environmental considerations have driven interest in hydrogen as an alternative.

Objectives and Study Overview

The study aims to develop and validate a headspace gas chromatography/mass spectrometry (HS-GC/MS) method using hydrogen carrier gas and an Agilent HydroInert source. Key goals include achieving limits of quantification (LOQs) at or below regulatory thresholds (around 0.1 ppm), demonstrating linearity, precision, and accuracy comparable to helium-based methods, and ensuring spectral fidelity for quantitation and confirmation.

Methodology

Surfactant samples were spiked with internal standards and analyzed using HS-GC/MS. Separate GC systems were configured with helium or hydrogen carrier gas. Calibration standards covering 0.016 to 5.0 ppm were prepared in water with 1,4-dioxane-d8 as the internal standard. Method validation followed criteria for linear regression, residual normality, homoscedasticity, LOQ, precision, and recovery.

Used Instrumentation

• Agilent 7890 GC with helium carrier gas
• Agilent 8890 GC with hydrogen carrier gas equipped with HydroInert source
• Agilent 5977B GC/MSD detector
• PAL3 autosampler for headspace sampling
• Agilent J&W DB-624 column (60 m × 0.25 mm × 1.40 μm)

Main Results and Discussion

Both helium and hydrogen methods exhibited excellent linearity (R² > 0.99) over the calibration range for ethylene oxide and 1,4-dioxane. Residual analysis confirmed normal distribution and homoscedasticity. LOQs of 30–40 ppb were achieved for both analytes with signal-to-noise ratios above 10. Precision at LOQ and three spiking levels met acceptance criteria (< 11% RSD), and accuracy ranged from 80 to 110% recovery. The HydroInert source preserved spectral quality in hydrogen mode, enabling the use of the same quantifier and qualifier ions as in helium.

Benefits and Practical Applications

• Eliminates dependence on scarce helium without sacrificing analytical performance
• Meets stringent regulatory requirements for trace-level detection in consumer products
• Maintains spectral library compatibility and method transferability
• Supports quality control in surfactant manufacturing and environmental monitoring

Future Trends and Opportunities

Further applications may extend to other volatile analytes where hydrogen can replace helium. Integration with automated headspace systems and expanded method scopes could improve throughput. Development of hydrogen-compatible sources for other detectors may broaden sustainable analytical workflows in pharmaceutical, environmental, and industrial laboratories.

Conclusion

The validated HS-GC/MS method using hydrogen carrier gas and an Agilent HydroInert source delivers performance equivalent to helium-based protocols for ethylene oxide and 1,4-dioxane analysis. It offers a sustainable alternative in response to helium shortages and stringent regulatory demands, maintaining sensitivity, accuracy, and spectral fidelity.

References

1. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 100F, International Agency for Research on Cancer, 2012.
2. U.S. Department of Health and Human Services. 14th Report on Carcinogens, National Toxicology Program, 2016.
3. European Chemicals Agency. Guidance on the Application of the CLP Criteria, ECHA, 2017.
4. Liptak BG. Handbook of Analytical Instrumentation. CRC Press, 2017.
5. Review of the Current State-of-the-Art for Precise Measurement of 1,4-Dioxane Concentration in Cleaning Products. J Surfactants Detergents 2022;25:729–741.