DETERMINATION OF ETHYLENETHIOUREA AND PROPYLENETHIOUREA IN TOMATO PRODUCTS AND IN FRUIT PUREES

An analytical method was developed for determining ethylenethiourea and propylenethiourea in tomato products (tomato pulp, tomato puree, tomato paste of 28-degrees and 36-degrees Brix, peeled tomatoes and ketchup) and in fruit purees (apricot, pear, peach, apple). The residues were extracted with dichloromethane on an Extrelut column and clean-up was carried out using a Sep-Pak C18 cartridge before injection into a liquid chromatograph with an electrochemical detector (coulometer). With this method 100 samples of commercial tomato products were analysed. The positive samples were confirmed by capillary gas chromatography with flame photometric detector (sulphur mode filter). The sensitivity of the method is 3 mug kg-1 in the case of tomato products (peeled and strained tomatoes, tomato pulp) with a total solids content similar to that of fresh tomatoes and of fruit purees with a soluble solids content of 10-degrees Brix.