Removal of electroanalytical interferences using thermodynamic and kinetic effects induced by in situ electrogeneration of protons

This articles describes a new method to resolve overlapped voltammetric peaks by selectively shifting the redox potential E°′ of a target species in a mixture. The shift is due to a combined kinetic and thermodynamic effect induced by H+ electrogenerated in situ. The H+ are produced from a sacrificial source which is present in solution and could be the solvent or an added reagent. The principle implemented in this work, relies on the notion whereby the ΔG° or E°′ of a reaction can be favorably shifted through stabilization of a product by a subsequent reaction that contributes with negative ΔG° (in this case the protonation of a base produced in the electrochemical step). The selectivity in the redox shift occurs due to a significant difference in the rates at which H+ stabilizes the formation of protonatedproducts for the electrochemical reactions in the mixture. Literature and estimated values of rate constants support the conclusion that the kinetics of the subsequent protonation reaction is what determines the appearance of the shift. A magnitude difference of about 1010 in the rate constants for the protonation reactions was found for the two model compounds considered for this proof of concept.