The impedance of an ion-selective electrode (ISE) to potassium with valinomycin as the ionophore and KBPhi(4) as the ionic sites was measured. The membrane was made of PVC with DNP as a plasticizer. The influence of the content of the plasticizer and the membrane thickness was investigated. The concentrations of the ionophore and the ionic sites were changed to modify the response on the ISE. Finally, the selectivity was tested in terms of impedance. All impedance experiments were correlated to the potentiometric curves plotted under the same experimental conditions. The measured impedances were compared to the model proposed in the previous paper (paper I). A good agreement was found. (C) 2004 Elsevier B.V. All rights reserved.