Mobile species transfer accompanying the redox switching of poly(vinylferrocene) (PVF) in aqueous perchlorate solutions of four cations was investigated using the electrochemical quartz crystal microbalance (EQCM). Cyclic voltammetry in 0.05 M solutions containing hydronium, sodium, rubidium or tetraethylammonium cation was employed. The mass transients could not be explained solely in terms of anion and solvent transport processes. EQCM transient data showed that the cation as well as perchlorate and water transport participated in the redox switching process in the four bathing solutions. Results and interpretation of the experimental approach are presented. (c) 2005 Elsevier Ltd. All rights reserved.