Electroanalysis using differential pulse methods at a rotating disk electrode

Application of a differential pulse waveform to a rotating disk electrode (RDE) results in a peaked response for amperometric redox reactions. Based on this observation two models were proposed which describe the limiting cases. Model 1 assumes that the current subsequent to the pulse dominates, while Model 2 assumes that the pulse width is sufficiently long to allow a steady-state current to exist during the pulse width. Simulations of the derivative of the equation describing the sigmoidal response were also carried out. Model 1 was found to be unsuitable for the system studied here (pulse width: 55 ms) and is more suited to systems where shorter pulse widths are used. The correlation between peak current heights returned by Model 2 and those recorded experimentally was poor but the theoretical results followed the same trends as those observed experimentally. This technique was found to have a limit of detection of 2.3 × 10^-5 M and a limit of quantitation of 7.68 × 10^-5 M for the [Fe(CN)₆]^4- system.