Response characteristics and application of chalcogenide glass Cr(VI) selective electrode

Abstract A chalcogenide glass Cr(VI) selective electrode has been tested. The Nernst plot is S-shaped, and the slope of the mid linear portion is about 90 mV decade −1 . An analytically useful potential change from about 10 −6 –10 −3 M Cr(VI) results. The response is related to a surface sensing mechanism, which is of redox nature. The electrode is generally sensitive towards compounds with high oxidising and reducing powers but insensitive towards ions with poor oxidising or reducing capacities. The response is slow and depends on the reduction potential of the analyt compounds, the exposure time and the concentration level. Therefore a flow-Injection-Analyser-system (FIA) is developed for the determination of Cr(VI) in aqueous environments. For the reduction of response times thereby enhancing the performance of the electrode reducing agents or electrochemical reduction between FIA injections were successfully employed. It is concluded, that to a large extend the FIA-system can be optimised to aqueous environments with Cr(VI) concentrations down to 10 −6 M. Special applications is under development for on-line measurements of Cr(VI) for production control in the electroplating industries.