Quantitation of Ethylene Oxide (EtO) and 2-Choloro Ethanol(2-CE) in sesame seeds by using dynamic headspace GC-MS/MS

Significance of the Topic

Ethylene oxide (EtO) is a widely used fumigant with potent antimicrobial properties but is classified as a human carcinogen and mutagen. Its small molecular size ensures deep penetration into dry food matrices, making it effective for disinfestation but raising safety concerns due to genotoxic impurities. Quantifying EtO and its by-product 2-chloroethanol (2-CE) in food items like sesame seeds is critical to ensure consumer safety and regulatory compliance.

Study Objectives and Overview

This work aimed to develop a robust, sensitive, and matrix-independent method for simultaneous quantitation of EtO and 2-CE in sesame seeds. Three dynamic headspace GC-MS/MS protocols were optimized on the Shimadzu GCMS-TQ8050 NX with HS-20 NX sampler. The study assessed method performance against EU maximum residue limits (MRLs) and compared three headspace approaches to overcome challenges of liquid-injection techniques in fatty matrices.

Methodology and Instrumentation

Certified reference standards of EtO and 2-CE were used to optimize MS/MS multiple reaction monitoring (MRM) transitions and collision energies. Sample vials containing ground sesame seeds and water/NaCl were incubated and purged with inert gas; analytes were concentrated on a trap and thermally desorbed into the GC inlet. Key instrument settings:

• GC-MS/MS: Shimadzu GCMS-TQ8050 NX
• Sampler: HS-20 NX dynamic headspace
• Autosampler: AOC-20i/AOC-20s
• Column: Rtx-624 or equivalent low-bleed phase
• MRM transitions optimized for EtO and 2-CE with segmented acquisition

Main Results and Discussion

All three dynamic headspace methods achieved excellent linearity (r2 > 0.99) over relevant concentration ranges. Method 1 provided a 10 ppb LOQ for both EtO and 2-CE in a single run. Method 2 improved 2-CE detection to 5 ppb, and Method 3 achieved a 6 ppb LOQ for EtO. Precision (n=6) showed relative standard deviations below 5%, and accuracy (n=3) yielded recoveries within 80–120%. Compared to liquid injection, headspace sampling eliminated cleanup reagents, reduced matrix interferences, and delivered better sensitivity.

Benefits and Practical Applications

• Simple sample preparation without extraction salts or cleanup chemicals.
• Reduced matrix effects and instrument contamination.
• Simultaneous quantitation of EtO and 2-CE at trace levels below regulatory limits.
• High throughput suitable for routine QA/QC in food testing laboratories.

Future Trends and Application Potential

Advances in headspace automation and trap technologies will further improve sensitivity and reduce cycle times. Coupling dynamic headspace with high-resolution MS may enable screening of additional volatile genotoxic impurities. Expanded application to other low-moisture, high-fat food matrices and integration with data-handling software will streamline regulatory compliance workflows.

Conclusion

The optimized dynamic headspace GC-MS/MS methods on Shimadzu GCMS-TQ8050 NX offer a sensitive, reliable, and matrix-robust solution for trace-level quantitation of EtO and 2-CE in sesame seeds. These protocols exceed current regulatory requirements and facilitate rapid, high-throughput testing without extensive sample cleanup.

References

1. EURL-SRM Analytical Observation Report, Version 1.1, December 2020.