Copper(I) electrode function of two types of copper(II) ion-selective electrodes.
The response of two types of solid-state copper ion-selective electrodes with homogeneous membranes of CuAgSe and Cu(2-x)Se has been investigated in copper(I) solutions, prepared electrochemically by insitu generation from a copper anode in chloride medium. The selectivity coefficient K(pot)(Cu+, Cu(2+)) both types of electrodes has been determined. It is 10(-5.7) for the copper selenide sensor, and 10(-6.2) for the copper silver selenide one. These values are very close to that calculated for an exchange reaction proceeding on the electrode surface. The similarity in K(pot)(Cu+ ,Cu(2+)) values for different chalcogenidebased sensors suggests a common potential-generating mechanism. High chloride concentration does not interfere with the electrode response towards Cu(I), but distorts the electrode response to Cu(II).
Diffusion-layer model for copper solid-state chalcocite membrane electrode; sensitivity to copper(II) ions.
The diffusion-layer model for the chalcocite (Cu(2)S) membrane electrode is discussed. It is equivalent to a simpler model based on exchange reactions at the electrode surface. The chalcocite is sensitive to copper(I) and copper(II) ions and the theoretically predicted response is in good agreement with experimental data. The membrane is a conductor, but this does not significantly affect its function as an ion detector. The limitation of the electrode is the membrane solubility as shown when Cu(II) ions in contrast to copper(I) ions are strongly complexed.
Studies of copper(II) sulphide ion-selective electrodes.
Changes in liquid junction potentials in copper(II) solutions were measured when different reference electrodes were used. The slope and intercept of a calibration curve for a copper-selective electrode will depend on the selection of reference electrode. The condition of the electrode surface of an Orion copper-selective electrode was studied microscopically and the influence of redox potential on stability of the electrode against corrosion is discussed. Oxidizing solutions will produce pits at dislocations in the material and there will be a mixed electrode potential. The slope, stability, and speed of response are much lower when the surface contains pits. Diamond-polishing was shown to improve the electrode significantly.