GC-MS Determination of Residual Ethylene-thiourea in Vegetables and Fruits

Gas chromatography was applied to the determinations of residual ethylene-thiourea in vegetables and fruits. The samples were extracted with methanol,the extract obtained was derivatized with benzyl chloride to form ethylene-benzyl thiourea. The ethylene-benzyl thiourea was purified with dichloromethane and derivatized again with trichloroacetic anhydiride. The product was used for GC-MS analysis. External standard calibration was adopted in the determination. Linear relationship between peak areas and mass concentrations of derivative of ethylene-thiourea was obtained within the range of 2.0 mg·L-1. Detection limit (3S/N) of the method was 0.01 mg·kg-1. Tests for recovery and precision were made by standard addition method at 3 different concentration levels,values of recovery found were in the range of 87.9%-95.8% and values of RSD′s (n=6) were less than 7.5%.