Specific influence of electrolysis potential on the Zn-peak in chronovoltamperometry on the HMDE

Abstract

Summaryo1.Adsorption on the Hg hanging drop electrode, established during the preliminary electrolysis, influences the Ep and σ of the anodic peak during the subsequent stripping process.2.In the particular case of zinc ions in alkaline solutions, at a low electrolysis potential (Eel), Zn(OH)2 is formed as an intermediate and is adsorbed at the electrode interface. At higher potentials this layer disappears. These potentials are ca. — 1.92 V (SCE) in 0.1–1 N KOH or — 1.82 V (SCE) in 1.5–3 N KOH. The influence of this layer in the stripping process is similar to that of other adsorbed layers, e.g. of gelatine.3.The effect described is of importance in the selection of optimum conditions in the technique of anodic stripping voltammetry.4.Although observed in the case of zinc ions, the effect described may also occur in other systems. Therefore a study of the influence of Eel on Ep and σ is always advisable and should not be limited to the influence on h. Adsorption on the Hg hanging drop electrode, established during the preliminary electrolysis, influences the Ep and σ of the anodic peak during the subsequent stripping process. In the particular case of zinc ions in alkaline solutions, at a low electrolysis potential (Eel), Zn(OH)2 is formed as an intermediate and is adsorbed at the electrode interface. At higher potentials this layer disappears. These potentials are ca. — 1.92 V (SCE) in 0.1–1 N KOH or — 1.82 V (SCE) in 1.5–3 N KOH. The influence of this layer in the stripping process is similar to that of other adsorbed layers, e.g. of gelatine. The effect described is of importance in the selection of optimum conditions in the technique of anodic stripping voltammetry. Although observed in the case of zinc ions, the effect described may also occur in other systems. Therefore a study of the influence of Eel on Ep and σ is always advisable and should not be limited to the influence on h.