Separation of migrational and chemical components in voltammetric currentsof the reduction of weak acids at microelectrodes

The influence of the increase in concentration of a buffering salt present as supporting electrolyte on the height of voltammetric waves of weak acids has been investigated experimentally at platinum disk microelectrodes. The following weak acids have been examined: trichloroacetic, chloroacetic, ac etic, formic and propionic. The wave height of all acids decreased more wit h the addition of buffering salts compared to the case of unbuffering, neut ral salts. It has been shown that this difference is caused by a decrease i n the acid dissociation progress and by a large difference in the diffusion coefficients of the hydrogen ion and the undissociated acid molecule. The obtained results are at odds with some theoretical predictions available in the literature.