We investigated conductometric analysis of electro-inactive metal ions at high concentration based on nanoporous electrodes by electrochemical impedance spectroscopy (EIS). The three dimensional interconnected nanoporous Pt (L-2-ePt) was found to enable significantly sensitive and selective conductometric detection of alkali and alkaline earth metal ions of high concentration at low frequency without any additional surface modification, which can be hardly done by flat Pt. The extremely large surface area of L-2-ePt remarkably suppressed the electrode impedance and the pore effect was additional positive contribution to selective ion sensing by conductometry at low frequency. Importantly. L-2-ePt allowed recognition of fractional ratio reversal of Na+ to K+ ions in a mixed solution at physiological concentration maintaining the constant total ionic strength. The results suggest the possibility of real time extracellular monitoring of instantaneous ion exchange near ion channels of a cell membrane such as action potential propagation along axons in a neuronal system. (C) 2010 Elsevier Ltd. All rights reserved.