Photostabilization of the herbicide bensulfuron-methyl by using organoclays.

Photostable formulations of the herbicide bensulfuron-methyl [BSM, 2-(4,6-dimethoxypyrimidin-2-carbamoylsulfamoyl)-o-toluic acid methyl ester] were achieved by adsorbing it on clays or on clays pre-adsorbed with the organic cation malachite green (MG). Fourier-transform infra-red (FTIR) spectra showed the existence of strong interactions between the pre-adsorbed MG and the herbicide. The photostabilization of BSM obtained with clay-MG was mainly due to pacification of clay surface by MG and a deactivation mechanism via energy transfer between the two organic molecules adsorbed on the surface of the clay.