Determination of ETU in tomatoes and tomato products by HPLC-PDA. Evaluation of cleanup procedures

HPLC-PDA method for the determination of ethylenethiourea (ETU), the main d egradation product of the organic fungicides ethylene bis(dithiocarbamate)s (EBDCs), in tomatoes and tomato products is reported. Solid-matrix liquid- liquid (l-l) partitioning and separatory funnel l-l partitioning for the cl eanup were examined. The effect of salt addition, pH, and phase ratio on an alyte recovery at the cleanup step was studied. It was found that solid-mat rix l-l partitioning afforded higher precision and more selective separatio n of the analyte. According to the method proposed, the samples were extrac ted with methanol/water (3:1, v/v) and cleaned up on an Extrelut 20 column. ETU was eluted with dichloromethane and separated on a reversed phase HPLC column. For tomato products with degrees Brix > 20 further purification th rough silica cartridge was adopted. The method was validated over the follo wing ranges of concentrations: 0.01-0.5 mg/kg for tomatoes, 0.01-0.1 mg/kg for tomato juice, and 0.05-0.25 mg/kg for tomato paste. The accuracy (recov eries > 70%) and the precision obtained (%RSD < 10%) were satisfactory.