A neutral redox-active receptor (ferrocene functionalized calix[4]pyrrole) was used as an active component in carbon paste electrodes and ion-selective electrodes ISEs, for the detection of anions in aqueous solution. Measurements with the carbon paste electrodes were conducted using Osteryoung square-wave voltammetry. At the surface of the modified electrode the redox potential of ferrocene-substituted calix[4]pyrrole was found to be at ca. 400 mV. Amongst the anions studied, dihydrogen phosphate and fluoride caused the strongest decrease of peak current (approximately 25%), followed by bromide and chloride. This sensitivity sequence was compared with that obtained with ISEs containing the ferrocene-substituted calix[4]pyrrole. The influence of the interface between host molecule environment and aqueous solution containing target anion on the molecular recognition process and electrochemical signal generation has been investigated. (c) 2006 Elsevier B.V. All rights reserved.