A chronopotentiometric approach for measuring chloride ion concentration

In this paper, a novel approach is reported for the electrochemical measurement of chloride ions in aqueous solution. This sensor is based on the stimulus/response principle of chronopotentiometry. A current pulse is applied at the Ag/AgCl working electrode and the potential change is measured with respect to another identical Ag/AgCl electrode in the bulk electrolyte. The potential difference is related to the Clˉ ion concentration via the Nernst equation and follows an inverse logarithmic trend. By varying the applied current pulse, the sensitivity of the sensor is tunable to different concentration ranges. The potential response is also influenced by the pH of the electrolyte, this effect is pronounced at lower concentration of Clˉ ions (<1 mM KCl) and at high pH values (>12 pH). The advantage of this approach is the use of a bare Ag/AgCl electrode as a pseudo-reference electrode, which enables this system for long term application such as the in situ measurement of Clˉ ions in concrete.