Interlaboratory comparison study of two gas chromatography injection techniques viz. liquid and dynamic headspace for trace level quantification of Ethylene Oxide (EtO) and 2-Chloroethanol (2-CE) in ginger powder sample by using tandem mass spectrometry

Significance of the Topic

The determination of trace level residues of Ethylene Oxide (EtO) and its metabolite 2-Chloroethanol (2-CE) in food commodities is of high importance due to their carcinogenic and genotoxic properties. Regulatory agencies worldwide have established very low maximum residue limits (MRLs) to protect human health. Accurate, reliable, and robust analytical methods are essential to ensure compliance with these limits and to safeguard consumer safety.

Objectives and Study Overview

This interlaboratory comparison aimed to evaluate and compare two gas chromatography injection techniques—liquid injection following solvent extraction and dynamic headspace sampling—for quantifying EtO and 2-CE at trace levels in ginger powder. Multiple laboratories participated in standardized experiments to assess method performance, linearity, sensitivity, extraction efficiency, and reproducibility.

Instrumentation

• GC-MS/MS system: Shimadzu GCMS-TQ8050 NX
• Liquid sampler: AOC-20i/s autosampler
• Dynamic headspace sampler: HS-20 NX
• Column: SH-502.2, 60 m × 0.25 mm I.D., 1.4 μm film thickness
• Carrier gas: Helium at 2.0 mL/min
• Ionization: Electron ionization (EI) at 70 eV; interface temp 250 °C; ion source 240 °C
• MRM transitions optimized for EtO (44>29, 44>28, 44>14) and 2-CE (80>31, 80>44, 82>31)

Methodology

The study compared two sample preparation and injection workflows:

• Liquid injection method:
  
  • Solvent extraction with acetonitrile and dispersive SPE cleanup (MgSO4, PSA, C18, GCB)
  • Vial incubation at varying temperatures (65 °C to 125 °C) with vortexing or sonication
  • Split injection (10:1) into GC-MS/MS
• Dynamic headspace method:
  
  • Direct headspace sampling of homogenized sample in 20 mL vial
  • Equilibration at 65 °C or 125 °C for 25 min
  • Multiple injection count (MIC up to 10) and split ratio 20:1

Calibration standards ranged from 5 ppb to 1600 ppb for both analytes, prepared in matrix-matched samples. Linearity was assessed by plotting peak area versus concentration.

Main Results and Discussion

Both methods achieved excellent linearity with correlation coefficients (r²) exceeding 0.999 for EtO and 2-CE. Key findings include:

• Dynamic headspace sampling provided more consistent recoveries and required fewer cleanup steps, reducing variability across laboratories.
• Liquid injection required optimization of extraction conditions (temperature, time, vortex/sonication) to achieve comparable recoveries.
• Limits of quantification were below EU MRLs (0.02–0.10 mg/kg), demonstrating high method sensitivity.
• Reproducibility across laboratories was high, though dynamic headspace showed slightly tighter interlaboratory precision.

Benefits and Practical Applications

The validated methods enable reliable monitoring of EtO and 2-CE residues in spices and other food matrices at trace levels. Laboratories can choose dynamic headspace for streamlined sample preparation and rapid analysis or liquid injection when headspace equipment is unavailable. Both approaches support regulatory compliance and quality control in food safety testing.

Future Trends and Opportunities

Emerging developments may include:

• Integration of automated sample preparation platforms to further reduce manual handling.
• Miniaturized headspace devices and micro-extraction techniques for lower solvent use.
• Advanced data processing and chemometric tools for enhanced signal deconvolution.
• Extension of methods to a broader range of commodities and matrices, including high-fat or complex samples.

Conclusion

The interlaboratory study demonstrates that both liquid injection and dynamic headspace GC-MS/MS methods are fit for purpose in quantifying trace levels of EtO and 2-CE in ginger powder. Dynamic headspace offers advantages in ease of use and consistency, while liquid injection remains a robust alternative. Adoption of either method can ensure compliance with stringent regulatory limits and support ongoing food safety monitoring.

References

• [1] EURL-SRM – Analytical Observation Report, Version 1.1 (December 2020)