A study on electrochemistry of histidine and its metabolites based on the diazo coupling reaction.

The diazo coupling reaction of diazotized p-aminoacetophenone (DPAAP) with histidine and its metabolites form the basis of the differential pulse adsorption stripping voltammetry (DPASV) method for determination of histidine and its metabolites. The adsorption and electrochemical reaction mechanism of the coupling products were studied in detail by structure analysis, cyclic voltammetry, chronocoulometry, control potential electrolysis, electrocapillary curves, UV spectroscopy and the effect of temperature and surfactants. The adsorption of azo-histidine was found to obey Frumkin adsorption isotherm. The calculation results of the maximum surface excess (Gamma(m)=3.08x10(-11) mol cm(2)), diffusion coefficient (D=2.27x10(-6) cm(2) s(-1)), adsorption coefficient (beta=1.06x10(7)) and interactive factor (gamma=0.9900) showed that the azo-histidine conjugation molecules adsorbed on the mercury electrode surface were attracted each other and the electrode process was adsorption controlled.