Effect of Anodic Surface Treatment on the Oxidation of Catechols at UltrasmallCarbon Ring Electrodes

摘要

Electrochemical anodic treatment at ultrasmall carbon ring electrodes appears toresult in the formation of an oxide film which displays charge-selective and pH dependent enhancement in the pH 7.4 citrate-phosphate buffer and is more Nernstian for dopamine (DA) and less Nernstian for 3,4-dihydroxyphenylacetic acid (DOPAC). However, oxidation in pH 2.8 buffer gives rise to voltammetry which is less Nernstian for both DA and DOPAC. Extensive surface oxidation in potassium hydroxide apparently forms a thick layer which acts like a thin layer reservoir for adsorbed analyte. Voltammetry following extensive treatment is attenuated and peak shaped. Minimal surface oxidation in KOH results in more Nernstian sigmoidal voltammetry with only slight current attenuation. The data suggest that an oxide layer formed following anodic treatment is non-uniform and leaves sites of activated carbon exposed on the surface.