A theory based on the establishment of a diffusion layer between the electrode surface and the bulk of solution, and the attainment of chemical equilibrium at the electrode surface is used to explain quantitatively the behavior of solid-state cupric ion-selective electrodes in chloride media: Cu(II) from the bulk of solution is reduced at the electrode surface to Cu(I), which is stabilized by chloride complexation. The theory was experimentally verified: in solutions with different concentrations of Cu2+, Cl-, and Cu2+-complexing ligands; with an alternate Cu(I) stabilizing agent, CH3CN; with cupric ion selective electrodes of different standard potentials (a sulfur-rich graphite contacted electrode and a silver contacted electrode). The onset of interference of chloride ion is described as a function of concentrations of Cu2+, Cl-, and Cu2+-complexing ligands, and the standard potential of the electrode. The general unsuitability of the electrode for measurement of cupric ion activity in seawater is accounted for by this theory.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry