Electrochemical behavior of histidine on gold

Cyclic voltammetry at the stationary and rotating disk electrodes and the spectroscopy techniques are used to study adsorption and specific electrooxidation of histidine at the gold electrode in solutions of various pH that correspond to prevalence of all existing forms of this amino acid. The adsorption mechanism is shown to depend on solution pH, which leads to participation of various functional groups of histidine in the adsorption process. On the basis of the polarization measurements, UV spectroscopy, and mass spectrometry, a scheme is proposed for a consecutive two-electron oxidation of histidine in weakly acidic, high-concentration solutions, with allowance made for the influence exerted by additives of propylene carbonate on the reaction order.