Ferrocene-substituted calix[4]pyrrole modified carbon paste electrodes for anion detection in water

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.