This paper shows the application of conducting polymers (CPs) for constructing model biological membranes in order to study potential formation mechanism. Two amino acids, asparagine and glutamine, were incorporated in the poly(pyrrole) matrix during electrochemical polymerization. The polymer film was characterized by infrared and X-ray photoelectron spectroscopy. The film morphology was studied by atomic force microscopy. The ion-exchange behavior of PPy-Asn and PPy-Gln membranes in dependence on the conditioning solution are characterized using an open circuit potentiometric measurements. Close-to-Nernstian sensitivity was observed for the films under equilibrium. During equilibration provoked by the change in concentration of magnesium and/or calcium ions, the differences in the shape and evolution of the potential response with time were observed. The varying potential-time behavior after a bulk concentration change has been explained by a different participation of the magnesium and calcium ions on the ground diffusion layer model (DLM). (c) 2005 Elsevier Ltd. All rights reserved.