Large amplitude square wave voltammetric experiments have been undertaken with model electrochemical system comprising aqueous solutions of tris(2,2-bipyridine)osmium(II/III) and tris(2,2-bipyridine)iron(II/III) redox couples, both of which exhibit reversible behaviour. Analysis of the current responses in the frequency domain were performed by means of Fourier transformation. Excellent agreement was obtained between the experimental voltammograms and those predicted by theory, both for single component solutions and for mixtures.