Protolysis studies and quantification of acids and bases in aqueous solutions by microelectrode voltammetry

Acid-base equilibria are generally studied and taught at universities using approaches and techniques that include the use of dyes, spectrophotometry, conductometry and potentiometry. Instead, voltammetric techniques, although employed for research purposes for acid-base investigations, have rarely been included in electrochemical curricula. In this article we highlight the potential of microelectrode voltammetry in studying acid-base equilibria, their kinetics and the acid and base content in aqueous solutions by exploiting the hydrogen and oxygen evolution reactions. Microelectrodes are used as they allow the attainment of reproducible and well-defined convergent mass-transport conditions and the achievement of steady-state diffusion regimes in short times. The resulting steady-state limiting current is proportional to bulk concentration, diffusion coefficient and electrode radius, which is useful for a more precise evaluation of each of latter quantities. Mention is also made on how mathematical treatments and digital simulation procedures can help in the classification and parameterization of the electrode processes involved.