Simultaneous determination of ethyl carbamate and 4‐(5‐)methylimidazole in yellow rice wine and soy sauce by gas chromatography with mass spectrometry

We developed a new method, based on alkaline diatomite solid‐phase extraction followed by gas chromatography with mass spectrometry, for the simultaneous determination of the toxic contaminants ethyl carbamate (EC) and 4‐(5‐)methylimidazole (4‐MEI) in yellow rice wine and soy sauce. The optimal extraction conditions were defined. With the application of alkaline diatomite solid‐phase extraction, damage to the capillary column by organic acids was greatly reduced. With deuterated EC used as the internal standard, the linearity of the calibration curves for EC and 4‐MEI was good with correlation coefficient above 0.99. In a spiked experiment with EC and 4‐MEI in yellow rice wine and soy sauce, recovery of the added EC was 80.5–102.5% and that of 4‐MEI was 78.3–92.8%. The limit of quantification and limit of detection for EC were 6.0 and 2.0 μg/kg, respectively, and for 4‐MEI were 15.0 and 5.0 μg/kg, respectively. The validation results demonstrate that the method is fast, simple, and selective, and therefore is suitable for simultaneously determining the presence of EC and 4‐MEI in fermented food.