Determination of ethyl carbamate in alcoholic beverages using ethanol-K_2HPO_4-H_2O aqueous two-phase extraction combined with gas chromatography/mass spectrometry

In this paper ethanol in alcoholic beverages was used as an extraction solvent. Based on the ethanol-K2HPO4-H2O aquatic two phase system( ATPS) coupled with GC/MS,an effective sample pretreatment method was developed for the analysis of ethyl carbamate. The influence factors on formation of ethanol-salt-H2O system were discussed in depth. Meanwhile,the influence of the ethanol- K2HPO4-H2O aquatic two phase system on extraction of ethyl carbamate in alcoholic beverages was detailedly investigated. The results showed that ethyl carbamate was extracted into upper phase with high efficiency. When K2HPO4was added in alcoholic beverage to form aqueous two phase system,the most of polarity chemical impurities such as sugar,protein,tannin and pigment were distributed in lower phase,and ethyl carbamate was extracted in up phase. Because of the higher chemical polarity of ethanol,the lipid-soluble impurities are extracted less in up phase of ATPS. Therefore the purification steps were greatly simplified. The anhydrous magnesium sulfate( MgSO4) and primary secondary amine( PSA) were added in upper phase to eliminate the moisture and other impurities. Then,the ethyl carbamate in extract( upper phase) was directly analyzed by GC/MS with the internal standard method( tertbutyl carbamate as an internal standard). This proposed approach was satisfactorily applied to the determination of ethyl carbamate in white spirit,brandy,geneva,grape and rice wine. The recoveries were 91. 6% ~113. 9%,with relative standard deviations of 0. 70% ~ 5. 9%,and the detection limit was 1. 3 μg/L.