Sorption and desorption of pesticide in the octadecylsilyl-silica gel/water system by single microparticle injection and absorption microspectroscopy

The sorption and desorption processes of a pesticide between a single octadecylsilyl (ODS)-silica gel microparticle and the surrounding water phase were kinetically analyzed by absorption microspectroscopy combined with a single microparticle injection method. 2-Amino-3-chloro-1,4-naphthoquinone (quinoclamine) sorbed into the microparticle was completely desorbed into the water phase, and both the sorption and desorption processes could be analyzed by the intraparticle diffusion model. 5-Dipropylamino-α,α,α-trifluoro-4,6-dinitro-o-toluidine (prodiamine) sorbed into the microparticle partially remained for the desorption process. These results are discussed in terms of pore/surface diffusion and adsorption of the pesticide on ODS and silanolate groups in the pores of the ODS-silica gel.