The interaction between the [Co(en)(2)Cl-2](+) trans-dichlorobis cobalt(III)bis(ethylenediammine) and an anionic micelle of sodium dodecyl sulphate (SDS) is considered in the framework of the exponential mean spherical approximation (EMSA) in order to obtain the equilibrium binding constant between the metal complex ion and the micelle. This calculation has been carried out at different [SDS] concentrations as well as at different [NaCl] concentrations. The objective was to compare with previous experimental data in order to check if only considerations of electrostatic interactions are able to explain the behaviour of charged metal ions in the presence of micelles of SDS. (c) 2006 Elsevier B.V. All rights reserved.