The photochemical behaviour of metribuzin methylethyl)-3-methylthio-1.
2.4-triazin-5(4H)-one] and its known metabolites desaminometribuzin (D
A), diketometribuzin (DK) and desaminodiketometribuzin (DADK) was inve
stigated in aqueous oxygenated solutions at various pH values. The pho
tochemical degradation of metribuzin over time and the formation and f
urther fate of DA, DK and DADK were elucidated. Both sidechain degrada
tion and ring opening were detected as a result of photolysis. Six unk
nown metabolites as a result of side-chain degradation, including 6-az
auracile, 6-azathymine and 4-aminosubstituted derivatives, were identi
fied as very stable photodegradation products. Furthermore, some inorg
anic and organic ionic compounds were detected such as monocarboxylic,
dicarboxylic and ketocarboxylic acids formed by side-chain degradatio
n and ring cleavage. (C) 1998 Elsevier Science Ltd.