This study from Issue 14 of the Analytix Reporter presents the development and optimization of an HS-SPME-GC-MS method for the analysis of 2-chloroethanol in sesame seeds. A Carboxen®-PDMS phase on a nitinol SPME fiber core, providing more robustness and reproducibility, was found to be the most effective fiber coating.
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Abstract
The main goal of this work was to develop and optimize an HS-SPME-GC-MS sampling method to measure 2-chloroethanol as a marker of ethylene oxide in sesame seed samples. The developed method was then applied to quantify the marker in a variety of sesame seeds of different origins. It was found that 2-chloroethanol was present in two of the samples with concentrations in the range of 84-151 ng/g, values above the permitted concentration levels established by the Europe Union regulation (EC) No 396/2005 in oil seeds.
Introduction
Ethylene oxide (EO) gas is used as a fumigant for the control of insects and microorganisms in food commodities. It reacts with natural chlorides present in the food matrix to form 2-chloroethanol, a known carcinogen, that may persist in the food product for long periods of time, even throughout food processing. Due to the demonstrated harmful health effects of these compounds, the employment of EO as a fumigant for food commodities is being progressively regulated or banned in several countries. Currently, Europe controls the use of this fumigant in food by regulation (EC) 396/2005, which defines its concentration as a sum of EO and 2-chloroethanol, with a permissible concentration of 0.05 mg/kg in nuts, oil fruits, and oil seeds. The aim of this study was to develop a high- throughput HS-SPME-GC-MS method to detect and quantify 2-chloroethanol as a marker for EO fumigation in sesame seeds.
Four commercially available SPME fibers were used to determine the selectivity of the SPME fiber coating for the headspace extraction of sesame seeds followed by GC-MS analysis. Carboxen-PDMS coating on a nitinol core was more effective in the extraction and desorption of 2-chloroethanol, and the optimized HS-SPME-GC-MS method demonstrated overall good linearity, reproducibility, and sensitivity. This shows that the method exhibits great potential as a quality control methodology for the fast screening of 2-chloroethanol. Additionally, this method was successfully applied for analyzing 2-chloroethanol in 3 sesame samples of different origins.
Experimental Conditions
The HS-SPME method optimization was achieved using sesame seed samples obtained from a local market with an undetectable GC-MS level of 2-chloroethanol. During the method development, fiber selectivity, extraction time (1, 2, 5, 10, 15, 20 min), and temperature (30, 40, 50, and 60 °C) parameters were studied. For this purpose, 1 g of 2-chloroethanol-free sesame seeds were spiked with 1 µL of a 20 ng/g solution of 2-chloroethanol prepared in methanol. For a summary of the HS-SPME-GC-MS method please refer to Tables 1 and 2 in the full article.
Results and Discussion
HS-SPME Method Optimization Procedure
Coating Selectivity
Initial tests were conducted using 4 different fibers including PDMS, DVB/PDMS, CAR/PDMS, and DVB/CAR/ PDMS to evaluate the performance and effectiveness of each fiber coating material for the headspace extraction of 2-chloroethanol in sesame seed samples. The extraction conditions were as follows: equilibrium time of 2 min, extraction time of 10 min, and extraction temperature of 40 °C. Further sample preparation conditions are mentioned in the experimental section.
Conclusions
This study developed and optimized an HS-SPME- GC-MS method using a Carboxen®-PDMS fiber on a nitinol core for the analysis of 2-chloroethanol as a marker of ethylene oxide in sesame seeds. The SPME method yielded good sensitivity, accuracy, and reproducibility when applied to the analysis of sesame seed samples. The Carboxen®-PDMS chemistry allows the efficient retention and release of small analytes such 2-chloroethanol due to the presence of micropores such 2-chloroethanol due to the presence of micropores in the fiber structure.
This study demonstrated that HS-SPME-GC-MS employing a CAR/PDMS fiber can be used as a quality control methodology for fast screening of 2-chloroethanol as a marker of ethylene oxide in food commodities.
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