Com. SiO2 was modified with R2N(CH2)(3) (MeO)(3)Si (I), (R = H or Me) in dry PhMe and used for adsorption of sinapic acid from its i-PrOH soln. The adsorption isotherms were described with a variety of models. Their applicability decreased in series Dubinin-Astakhov > Redlich-Peterson > Langmuir > Freundlich. Max. adsorption capacities (Dubinin-Astakhov model) for SiO2 modified with I (R = H) and I (R = Me) were 154.4 and 112.5 mg/g, resp.