The sorption of rhodamine 6G from water into a single silica gel microparticle was analyzed using microcapillary manipulation/injection and microabsorption methods. The rate-determining step of the sorption process was diffusion of the cationic dye in the particle interior, and the intraparticle diffusion coefficient was highly dependent on the pH and the ionic strength of the water phase. The adsorption coefficient of the dye determined from the Langmuir adsorption isotherm was also influenced by the pH and the ionic strength. The relationship between these kinetic and isotherm parameters was quantitatively discussed based on a pore diffusion model.