Photodegradation of Metribuzin in Sunlight Sensitized by TiO₂

Photodegradation of the herbicide metribuzin in methanol using TiO₂ as sensitizer under sunlight is reported. In presence of TiO₂ after 72 hours of sunlight irradiation, 52.79% dissipation of metribuzin was observed in comparison with 26.29% without any sensitizer, depicting half-life (t_½) values of 3.14 and 12.54 days respectively. Out of the four photoproducts identified by GC-MS analysis, three compounds namely S-(4-amino-6-(1, 1dimethylethyl)-5-oxo-4, 5-dihydro-1, 2, 4-triazin-3-yl) thioformate, 6-(1, 1-dimethylethyl)-5-oxo-4, 5-dihydro-1, 2, 4triazine-3-sulfenic acid and 6-(1, 1-dimethylethyl)-4-nitro-5-oxo-4, 5-dihydro-1, 2, 4-triazine-3-sulfenic acid were found to be new.