Introduction rotating disk electrode

Figure 7.12 A schematic rotating disk electrode (or rotrode) used for the introduction of hquid samples into an electrical discharge. The system is used primarily for the determination of metals in oils.

As mentioned in the introduction of the amperometry techniques, the voltammetry with periodical renewal of the diffusion layer is particularly effective in monitoring a process differently involving an electroactive species, e.g., in the already mentioned amperometric titrations, in the determination of the stability of a species, etc. In particular cases, also simple chronoamperometry, i.e., at a fixed, suitably chosen potential, may be effective to this purpose. Noteworthy, it will be clear in the following that the much more widely diffused linear potential scan and cyclic voltammetric techniques are not always suitable to substitute for voltammetry with periodical renewal of the diffusion layer to the purpose of monitoring electroactive species during their transformation. Voltammetry with periodical renewal of the diffusion layer, as well as the voltammetry at rotating disk electrode, only allows the estimation of the concentrations of both partners of a redox couple, on the basis of the ratio between the anodic and cathodic limiting currents. 

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