Equilibrium diagrams have been obtained for the ionic exchange that occurs between Fe3+ ions in solution and the protons present in a chelating ion exchange resin, in water, in alcohol and in hydroalcohol solvents. These diagrams have also been obtained for a natural complex solvent (a wine matrix). A mathematical model has been developed to predict this equilibria which gives a good fit for the experimental data in the first three types of solvents studied and, after making some modifications, also in the last case. It has been observed that the type of solvent influences not only the resin equivalent capacity but also the equilibrium parameters of the system. In the case of the wine matrix used as the solvent it has been found that other factors influence the equilibrium diagram, i.e., the presence of quelating compounds. (c) 2005 Elsevier Ltd. All rights reserved.