GC/ECD determination of ethylenethiourea residues in tobacco leaves

Ethylenethiourea (ETU) is one of the degradation products of ethylene-bisdithiocarbamates (EBDCs), a largely used fungicide in agricultural crops. Since its recognized carcinogenic toxicity to humans, accurate and reliable determination of the residue level of ETU in food and agricultural products has become of great importance. Tobacco leaves before and after treatment with increasing rates of a formulation of Mancozeb (a commercial dithiocarbamate) were extracted for ETU and its trifluoroacetylated S-benzyl derivative analyzed by gas chromatography with an electron capture detector (GC/ECD). This method is precise and sensitive for small amounts of ETU residues and represents a valid alternative to traditional spectrophotometric analysis of CS, which is the other degradation product of dithiocarbamates. Particular care must be paid to analyze the ETU derivative right after synthesis because of its rapid degradation with time.