Rotating ring-disk voltammetric investigations on the degradation rate of the nickel(III)-glycylglycyl-L-histidine complex

Abstract

The voltammetric behavior of the Ni(II)/glycylglycyl-L-histidine complex and the degradation of the electrogenerated Ni(III) species were investigated by cyclic voltammetry. Results of electrochemical and spectrophotometric experiments indicated some differences in the nature and reactivity of Ni(III) complexes formed by two independent routes, i.e., anodic oxidation of Ni(II) and homogeneous oxidation by an autocatalytic reaction in a medium containing oxygen and S(IV) (H2SO3, HSO[Formula: see text], and SO[Formula: see text]). The Ni(III) species formed electrochemically reacts in a fast chemical process (EC mechanism) and the observed rate constant of the degradation (k = 0.17 s–1) was determined by a rotating ring-disk electrode technique measuring kinetic collection efficiency values as a function of the rotation rate. Key words: nickel, glycylglycyl-L-histidine, sulfite, degradation reaction, rotating ring-disk voltammetry.