The effects of organosulphonate groups oil the ion-exchange and ion-transport properties of silica hydrogels have been investigated by using Ru(NH3)(6)(3+), Ru(bpy)(3)(2+) and Fe(CN)(6)(3-) redox probes. Silica and sulphonated ormosil hydrogels, were prepared by using tetramethyl orthosilicate as a silica precursor and 2(4-chlorosulphony] phenyl)ethyl-trichlorosilane to provide sulphonate functionality for ion-exchange and ion conductivity. Both gels act as cation-exchangers and exclude Fe(CN)(6)(3-). Partition coefficients are higher for the ormosil and for the more highly charged Ru(NH3)(6)(3+) versus Ru(bPY)(3)(2+). Diffusion coefficients are higher for the unmodified silica, which is consistent with weaker interactions between the cationic probes and less anionic gel network. (c) 2007 Elsevier Ltd. All rights reserved.