Study of the pH function of a mechanically renewed graphite-quinhydrone indicator electrode

Abstract

A composition of quinhydrone and spectral graphite powders and also an epoxy resin with polyethylene polyamine as a binder is studied for fabricating a solid indicator electrode, renewed by mechanically cutting a thin surface layer, intended for measurements of the pH of solutions. It is shown that after the renewal of the electrode surface, the dissolution of the components of quinhydrone occurs in the near-electrode layer and the electrode potential depends on the pH of the solution and the time of the contact of the electrode with the solution. The pH dependence of potentials (Et) at t = const in the pH range 2.0–7.0 is linear and close to the theoretical one. In the pH range 7.0–13.9, the results of measurements of Et by the proposed carbon-quinhydrone electrode, in contrast to the traditional quinhydrone electrode, are well reproducible and linearly depend on pH. This opens up the possibility of using the electrode for the determination of Et also in alkaline media.