Application of several multipotential step techniques to the study of multicenter molecules at spherical electrodes of any size

Several multipotential step techniques such as staircase voltammetry (SCV), additive differential staircase voltammetry (ADSCV) and cyclic voltammetry (CV) have been applied to the study of the reversible reduction/oxidation of molecules with multiple redox centers (interacting or not) using spherical electrodes of any size. The theoretical predictions have been tested with two experimental systems: quinizarine in acetonitrile and pyrazine in aqueous acid media, founding an excellent agreement between theory and experiments. A critical analysis of the response with each technique allows us to conclude that, although all of them are powerful qualitative tools, ADSCV, proposed in this paper, is the most suitable technique to study such multistep processes quantitatively, and it can be used to determine the formal potentials easily for any number of electrochemical steps in the case of molecules with strongly interacting centers, and also in the case of molecules with two redox centers whatever the interaction degree between them. The formal potentials for the systems mentioned above have been evaluated with this technique. The advantages of using microelectrodes in order to obtain characteristic parameters of the system are also discussed.