Determination of Ethyl Carbamate in Various Fermented Foods by Selected Ion Monitoring

A simple and sensitive method for the determination of ethyl carbamate (urethane) in various fermented foods has been developed. Twenty g of sample was homogenized and extracted with 150 ml of acetone. Twenty ml of water was added to the extract which was then evaporated to remove organic solvent. The residual aqueous solution was extracted three times with 100 ml of dichloromethane. The organic layer was concentrated by rotary evaporator and was charged on an acid-celite column. After washing the column with 100 ml of pentane and 100 ml of pentane-dichloromethane mixture (80:20), ethyl carbamate was eluted with 60 ml of dichloromethane. The eluant was concentrated to 1 ml using a rotary evaporator, and ethyl carbamate was determined by gas chromatography-mass spectrometry in the selected ion monitoring mode. For liquid samples, extraction with acetone was not necessary. The column purification step was also unnecessary for alcoholic beverages. The detection limit for this procedure was 0.5 ppb/sample, and the recovery was 70 to 105% for miso, moromi, natto, soy sauce, sake, yogurt, and bread when they were fortified with 5 to 50 ppb of ethyl carbamate. Ethyl carbamate levels in various fermented foods including yogurt, bread, mirin, or sakekasu were determined by this method. Relatively high levels of ethyl carbamate were detected in sake and soy sauce.