Simultaneous measurement of the faradaic impedance and electrogravimetric transfer function during the redox reactions of a polymer in HClO4 allows anions, cations and solvent contributions to the charge compensation processes to be separated and their insertion/expulsion rate to be evaluated. A model of the transport processes in the polymer and the charge transfer kinetics of the ions and solvent at the polymer/solution interface is proposed. For the polymers and experimental conditions investigated, it was shown that the anions are generally inserted and the solvent generally expelled. Concerning the cations or species related to cations. e.g. hydronium ions, they can be either inserted or expelled.