Rotating Disc Electrode is the working electrode for an amperommetry method. In this method, the working electrode spins at approximately 600 rpm, which creates a convection current in the electrochemical cell. This brings the analyte up toward the electrode, and allows the redox reaction to take place. Once the redox reaction begins, a density gradient is created as the oxidant near the electrode is depleted and reductant near the electrode is produced. The oxidant is the analyte we are looking for. Since the analyte has been depleted near the electrode, more analyte will flow toward the electrode. This moving charge increases the current toward the electrode. The limiting current, Ilim, is the difference between the initial current and the final current which has been influenced by the density current. It can be used in the following equation to fing the diffusion coefficient, D, or the concentration, C, of the analyte:
where n is the number of electrons, F is the Faraday constant, A is the active electrode area, v is the solution kinematic viscosity, and w is the electrode rotation speed.
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