Trace level quantitation of Ethylene Oxide (EtO) and 2-Chloroethanol (2-CE) in sesame seeds by using various GCMS/MS techniques with their own merits and demerits

Importance of the Topic

Ethylene oxide (EtO) is a widely used fumigant and sterilizing agent valued for its high diffusivity and antimicrobial efficacy. However, its classification as carcinogenic, mutagenic and genotoxic impurity at trace levels makes its quantitation in food matrices critical for consumer safety. 2-Chloroethanol (2-CE), a primary reaction product of EtO, also poses genotoxic and carcinogenic risks. Regulatory bodies have set stringent maximum residue levels (MRLs) for the sum of EtO and 2-CE in food commodities, necessitating analytical methods capable of trace-level quantitation without compromising accuracy or sample throughput.

Objectives and Study Overview

This study aimed to develop and compare three dynamic headspace methods and a liquid injection method for the quantitation of EtO and 2-CE in sesame seeds at levels below established MRLs. Key goals included:

• Achieving low limits of quantitation (LOQs) without derivatization.
• Minimizing sample preparation and matrix interferences.
• Evaluating precision, accuracy and linearity according to ICH guidelines.

Methodology

Samples of sesame seeds were spiked with standard mixtures of EtO and 2-CE and processed by two approaches:

• Liquid injection: Acetonitrile extraction, cleanup reagent addition, vortexing, centrifugation and direct GC-MS/MS injection.
• Dynamic headspace injection: Direct transfer of analytes from heated sample vials into the GC-MS/MS using optimized headspace parameters.

Optimized MRM transitions were established for EtO (44>29, 44>28, 44>14) and 2-CE (80>31, 80>44, 82>31). Performance was assessed at multiple concentration levels (LOQ to 50 ppb) in solvent and matrix-matched standards.

Used Instrumentation

• Gas Chromatograph-Triple Quadrupole Mass Spectrometer: Shimadzu GCMS-TQ8050 NX
• Dynamic Headspace Sampler: HS-20 NX
• Liquid Autosamplers: AOC-20i and AOC-20s
• Capillary Column: Restek RTX-VMS (60 m × 0.45 mm × 2.55 µm)
• Carrier Gas: Helium
• Ionization Mode: Electron Ionization (EI)

Main Results and Discussion

All methods demonstrated excellent linearity (r2 > 0.997) and precision (%RSD < 10% for LOQ levels). Key performance characteristics included:

• Liquid injection LOQs: 10 ppb (w.r.t. sample) for both EtO and 2-CE, with recoveries of 73–98%.
• Dynamic headspace (single run for EtO + 2-CE): LOQ 10 ppb, recoveries 91–121%.
• Dynamic headspace for 2-CE alone: LOQ 5 ppb, recoveries 98–102%.
• Dynamic headspace for EtO alone: LOQ 6 ppb, recoveries 82–91%.

Comparative data showed dynamic headspace methods reduced matrix effects, simplified preparation and extended consumable life by avoiding direct injection of lipids.

Benefits and Practical Applications

• No derivatization required, reducing sample handling errors.
• Trace-level quantitation well below EU-MRLs for spices, nuts and oilseeds.
• Dynamic headspace minimizes matrix contamination of the GC system.
• High throughput: sample preparation time reduced by 30–50% compared to liquid injection.

Future Trends and Potential Applications

Advancements may include automated headspace extraction coupled with enhanced ion source designs for even lower detection limits. Integration of real-time monitoring interfaces and multi-analyte panels could expand application to other fumigants and food matrices. Emerging HRAM-MS technologies may further improve selectivity and robustness in complex matrices.

Conclusion

The Shimadzu GCMS-TQ8050 NX platform combined with dynamic headspace sampling provides a powerful, sensitive and efficient solution for trace-level EtO and 2-CE analysis in sesame seeds. Dynamic headspace methods outperform liquid injection in terms of matrix cleanliness, ease of preparation and quantitation limits, ensuring compliance with stringent regulatory standards.