Abiotic degradation of imazethapyr in aqueous solution

The photodegradation of imazethapyr [2-(4,5-dihydro-4-méthyl-4-(1-méthylethyl)-5-oxo-1H-imidazol-2-yl)-5-ethyl-3-pyridinecarboxylic acid] in aqueous solution in the presence of titranium dioxide (TiO2) and humic acids (HA) at different ratios of herbicide/TiO2 and herbicide/humic acids was studied at pH 7.0. Irradiation was carried out with polychromatic light using Heraeus apparatus equipped with xenon lamp to simulate sunlight having a spectral energy distribution similar to solar irradiation (>290 nm). The concentration of remaining herbicide was followed using a High Pressure Liquid Chromatograph (HPLC) equipped with UV detector at 230 nm. In pure aqueous solution imazethapyr degrades slowly and the photodegradation leads to the formation of two metabolites labelled A and B. The presence of TiO2 caused enhancement of the degradation rate. The presence of HA induced an increase of the photodegradation of the pesticide with respect to pure aqueous solution.