RESPONSE CHARACTERISTICS AND APPLICATION OF CHALCOGENIDE GLASS CR(VI)SELECTIVE ELECTRODE

A chalcogenide glass Cr(VI) selective electrode has been tested. The N ernst plot is S-shaped, and the slope of the mid linear portion is abo ut 90 mV decade(-1). An analytically useful potential change from abou t 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 general ly sensitive towards compounds with high oxidising and reducing powers but insensitive towards ions with poor oxidising or reducing capaciti es. The response is slow and depends on the reduction potential of the analyt compounds, the exposure time and the concentration level. Ther efore a flow-Injection-Analyser-system (FIA) is developed for the dete rmination of Cr(VI) in aqueous environments. For the reduction of resp onse times thereby enhancing the performance of the electrode reducing agents or electrochemical reduction between FIA injections were succe ssfully employed. It is concluded, that to a large extend the FIA-syst em can be optimised to aqueous environments with Cr(VI) concentrations down to 10(-6) M. Special applications is under development for on-li ne measurements of Cr(VI) for production control in the electroplating industries. (C) 1997 Elsevier Science S.A. All rights reserved.