High levels of ethylene oxide (EtO) and 2-chloroethanol (2-CE) present in sesame seeds and other agricultural products have led to multiple product recalls throughout the European Union (EU). Here, we show headspace–trap with multi-step enrichment (MSE) on the Centri® platform to quantitatively determine the contaminants at the required 0.05 mg/kg (50 ppb) reporting threshold or maximum residue limit (MRL) without extensive and manual sample preparation. Excellent chromatographic performance is shown with the linearities of ethylene oxide and 2-chloroethanol at R2 = 0.9983 and R2 = 0.9995, respectively, within a single GC–MS analysis, and reproducibility with relative standard deviation (RSD) ≤ 5%. We also demonstrate the enhancement in sensitivity provided by this technique to go beyond the regulation, reaching lower levels of detection for reliable determination.
Introduction
Ethylene oxide (EtO) is used in many regions around the world as a fumigant to eliminate insects in seasonings, spices and foodstuffs; due to its strained three-membered ring structure, EtO is highly reactive, leading to effective bactericidal, fungicidal and sporicidal disinfection.1 However, its use is banned in the EU due to its highly toxic properties as a carcinogen, mutagen and reproductive toxicant.2 Since August 2020, European countries have flagged concerns of alarming levels of EtO present in various exports of sesame seeds, triggering global recalls of food products. The high reactivity of EtO means that it is prone to degradation, and so produces 2-chloroethanol (2-CE) as a by-product, which is also a toxic chemical restricted by the EU. This has led to regulation of both compounds – they have a combined maximum residue limit (MRL) of 0.05 mg/kg (50 ppb).3
Current methods for sample preparation include lengthy, cumbersome and solvent-heavy extraction procedures. They are manual, can be prone to human error and have expensive disposal costs associated with the harmful solvents used. Solvents used for extraction of target analytes may also extract unwanted components that enter the analytical system during sample injection and can cause contamination of subsequent analyses. To detect these lower concentrations without the need for complex sample preparation, headspace–trap (HS–trap) was investigated as a viable option for volatile contaminant detection to ensure imported foodstuffs meet safety requirements.
In this study, HS–trap with multi-step enrichment (MSE) (Figure 1) coupled with gas chromatography–mass spectrometry (GC–MS) was investigated and is shown to provide efficient extraction of EtO and 2-CE from sesame seeds without the need for solvents, whilst providing much cleaner sample extracts and meeting the regulatory requirement of 0.05 mg/kg.
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