Photolysis of metribuzin in oxygenated aqueous solutions

The photochemical behaviour of metribuzin [4-amino-6-(1.1-dimethylethyl)-3-methylthio-1.2.4-triazin-5(4H)-one] and its known metabolites desaminometribuzin (DA), diketometribuzin (DK) and desaminodiketometribuzin (DADK) was investigated in aqueous oxygenated solutions at various pH values. The photochemical degradation of metribuzin over time and the formation and further fate of DA, DK and DADK were elucited. Both side-chain degradation and ring opening were detected as a result of photolysis. Six unknown metabolites as a result of side-chain degradation, including 6-azauracile, 6-azathymine and 4-aminosubstituted derivatives, were identified as very stable photodegradation products. Furthermore, some inorganic and organic ionic compounds were detected such as monocarboxylic, dicarboxylic and ketocarboxylic acids formed by side-chain degradation and ring cleavage.