An analytical explicit expression for the current obtained with the well-known multipulse technique square wave voltammetry (SWV), corresponding to the reversible reduction/oxidation of multicenter redox molecules whose centers may or may not interact, has been given in Appendix. This equation is valid for spherical electrodes of any size, including planar electrodes (r 0 f ∞) and ultramicroelectrodes (r 0 f 0) as limit cases, and it also permits us to deduce the behavior of these processes at the limit situations corresponding to small and great square wave amplitudes. For the sake of simplicity, we have analyzed the behavior of bicenter molecules, ranging from noninteracting centers, for which the square wave current obtained is twice that corresponding to a single E mechanism, to strongly interacting centers which present two successive and well-separated signals of one electron each. The results obtained here are easily extendable to molecules with any number of redox centers. The theoretical predictions have been tested with two experimental systems, quinizarine in acetonitrile and pyrazine in aqueous acid media, and an excellent agreement between theory and experiments is found.

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An explicit analytical equation applicable to the study of reversible ion transfer at systems with two liquid/liquid polarizable interfaces is presented. This expression is valid for any multipotential step technique, which are all very adequate for the determination of standard transfer potentials and transport parameters of ions. The expression of the I/E response for linear sweep voltammetry and cyclic voltammetry can also be deduced as a particular case of this equation. The general solution given here is formally similar to that obtained for the application of any multipotential step sequence to a system with a single polarizable interface, since the method followed here is based on the same premises.

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A general analytical expression has been deduced for the I/E response of the square wave voltammetry corresponding to ion transfer processes in systems with two liquid/liquid polarized interfaces. This expression has been evaluated through the experimental study of a series of quaternary ammonium cations and metal chloro complex anions. We have found that systems with two liquid/liquid polarizable interfaces present the striking advantage that the difference between peak potentials of square wave voltammograms of cations and anions with similar standard ion transfer potential is much greater than in systems with a single polarizable one.

A simple analytical expression for the response of the double-pulse technique differential pulse voltammetry (DPV) corresponding to ion transfer processes in systems with two liquid/liquid polarizable interfaces has been deduced. This expression predicts lower and wider curves than those obtained with a membrane system with a single polarizable interface. Moreover, the peak potential of these systems is shifted 13 mV from the half-wave membrane potential. We have applied this expression to study the ion transfer of drugs with different pharmacological activities (verapamil, clomipramine, tacrine, and imipramine), at a solvent polymeric membrane ion sensor.

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