RESIDUES OF TECNAZENE AND ITS METABOLITES IN POTATOES IN COMMERCIAL STORES

Potato samples were taken from nine commercial stores at approximately 2-monthly intervals from November 1990 to June 1991. Three different types of store were sampled - bulk ambient, box ambient and box refrig erated. Tecnazene had been applied as a sprout suppressant, according to the product label recommendations, to some or all of the tubers in each store and residues of the pesticide and its metabolites were meas ured in samples collected from each store. Tecnazene residues were all well below the UK advisory maximum residue limit of 5 mg kg-1 on a wa shed whole-tuber basis, the highest level detected being 2.73 mg kg-1. The tecnazene metabolites 2,3,5,6-tetrachloroaniline and 2,3,5,6-tetr achlorothioanisole were found in all treated potatoes, at low levels r elative to tecnazene. The conditions maintained in the various types o f store did not appear to influence the levels of tecnazene, nor the p roportions of the metabolites produced. As the metabolites were found at the first sampling date that occurred after the end of any curing p eriod, it is evident that they were formed rapidly after store loading .