Flow-injection approach for the determination of the dynamic response characteristics of ion-selective electrodes. Part 2. Application to tubular solid-state iodide electrode

Abstract

The flow-injection approach proposed in Part 1 for investigating the dynamic behaviour of flow-through detectors was applied to the study of a tubular iodide electrode prepared from a pressed precipitate of silver iodide. It was found that the electrode response cannot be described by either of the models developed in Part 1 on the basis of the concepts in the literature for the transient response mechanism of ion-selective electrodes. Scratches and microcavities in the electrode bore were observed under the microscope, most probably resulting from bore drilling. These surface non-idealities make the accessibility of the electrode surface to the analyte variable. A mathematical model developed on the basis of the assumption that part of the electrode surface is directly exposed to the flow while the remainder of the surface incorporates all microcavities in which ideal mixing exists, describes fairly successfully the experimentally obtained potential—time transients. Moreover, this study shows that the rate of response of solid-state ion-selective electrodes is in principle comparable to that of other electrochemical sensors.