Ethylene oxide in Ethanol

Importance of Topic

Reliable measurement of trace-level ethylene oxide and related epoxides is critical for residuum control in pharmaceutical, food and industrial products. Ethylene oxide is a potent sterilant and classified as a carcinogen, making its accurate quantitation in alcohol-based matrices a regulatory requirement. Headspace gas chromatography with flame ionization detection (HS-GC-FID) offers a streamlined approach for volatile residual solvent analysis, and the use of inert, high-performance capillary columns helps minimize sample interaction and improve sensitivity.

Study Objectives and Overview

The primary aim of this application note is to demonstrate a robust HS-GC-FID method using an InertCap WAX column for simultaneous separation and quantitation of ethylene oxide, propylene oxide and 2-chloroethanol in ethanol solutions. The study highlights chromatographic conditions, sample preparation and performance characteristics for routine laboratory implementation in quality control environments.

Methodology and Instrumentation

• Sample Preparation: 10 mL of ethanol spiked with 1 mg/L ethylene oxide, 5 mg/L propylene oxide and 50 mg/L 2-chloroethanol were equilibrated in a 22 mL headspace vial. A 30 min incubation at 70 °C generated the headspace gas.
• Injection: 0.5 mL headspace gas injected via split mode (11 mL/min split flow) into the GC.
• Chromatographic Conditions: InertCap WAX, 0.25 mm ID × 60 m, 0.50 µm film. Column oven: 40 °C (5 min hold) → 10 °C/min to 200 °C (9 min hold). Carrier gas helium at 150 kPa.
• Detection: Flame ionization detector at 220 °C, sensitivity range set to 10⁰.

Instrumentation Used

• Gas chromatograph equipped with headspace autosampler (HT3).
• InertCap® WAX capillary column (GL Sciences, Cat. No. 1010-67164).
• Flame ionization detector (FID).

Results and Discussion

The chromatogram exhibited three well-resolved peaks corresponding to ethylene oxide, propylene oxide and 2-chloroethanol, with retention times of approximately 5, 12 and 20 min, respectively. Peak shapes were symmetrical and free of tailing, indicating minimal interaction with column surfaces. Signal intensities increased proportionally with analyte concentration, suggesting linear detector response within the tested range. The inert stationary phase effectively reduced adsorption of reactive epoxides, ensuring reproducible quantitation.

Benefits and Practical Applications

• Fast, reliable separation of structurally similar epoxides and chlorohydrin compounds.
• Minimal sample handling and reduced risk of artefact formation.
• Applicable to pharmaceutical QA/QC, environmental monitoring and food safety analysis.

Future Trends and Applications

Advances may include coupling headspace sampling with mass spectrometry for lower detection limits and enhanced selectivity. Miniaturized or real-time headspace analysis modules could permit in-line monitoring of sterilization processes. Integration of automated data processing and cloud-based reporting will improve laboratory throughput and regulatory compliance.

Conclusion

This application demonstrates that HS-GC-FID using an InertCap WAX column provides a straightforward, high-performance solution for trace analysis of ethylene oxide and related compounds in ethanol. The method delivers sharp, reproducible peaks and sufficient sensitivity for compliance testing in pharmaceutical and industrial contexts.