Electrochemical oxidation of ferrocene in naturally occurring molecular assemblies at microdisc electrodes. An application to dairy products

The oxidation of ferrocene was studied by using both micro- and macro-platinum electrodes in natural organized assemblies like milk, cream and butter. At the microelectrode, the oxidation of ferrocene was found to be reversible, whereas at the conventional electrode it was affected by capacitive currents, the ohmic resistance and kinetics which led, generally, to responses of very low quality. At the microdisc, the oxidation of ferrocene has been assumed to occur at the interface of the electrode with either phase. The half-wave potential of the electrochemical process involved was found to depend on the fat percentage of the samples. This effect has been attributed to a change in the micelle or emulsion equilibrium phase exchange constant, K. The K values were evaluated either from the reversible half-wave potentials of the ferrocene/ferricinium couple obtained in the emulsion and in water, or from the concentrations of the saturated solutions of ferrocene. The diffusion coefficients and saturation concentrations of the probe molecule in these media were estimated and the relevant results are also discussed critically. © 1990