Derivative dynamic response of ion-selective electrodes. Application to the precipitate-based iodide-selective electrode in the presence of interfering ions

The concept of the derivative dynamic response (dE/dt) of ion-selective electrodes is introduced to study the response of a precipitate-based iodide-selective electrode in the presence of interfering ion, using a flow injection system and a flow-through cell. A type of concentration perturbation is assayed in which the primary ion is completely removed while the interfering ion is introduced. The effects of interfering ion concentration and flow rate on the derivative dynamic signals are studied. A new well-defined peak appears in the presence of bromide interfering ion. The peak height increases with bromide concentrations in the range of 10−5 to 10−2 M. In the case of chloride interfering ion the new peak is only appreciable at ≥ 10−2 M.