Determination of 5-Hydroxyindole Acetic Acid by Electrochemical Methods with an Oxidized Glassy Carbon Electrode

The concentration of 5-hydroxyindole acetic acid (5-HIAA), the major metabolite of serotonin, might be the diagnosis basis for some cranial nerve pathology. An oxidized glassy carbon electrode (named OGCE) was employed to detect 5-HIAA with electrochemical methods. Multi-peaks appeared from the second cycle in range of 0.10-0.55 V (vs. AgCl/Ag) were assigned to the oxidative intermediates and products of 5-HIAA after the electrochemically driven oxidation at over 0.6 V in the first cycle. Kinetics studies show that all of these electrode reactions are adsorption-controlled processes, which are contributed to the strong hydrogen-bond interaction of these intermediates with the negatively charged hydroxyl and carboxyl groups on the surface of OGCE. Based on the square wave voltammetry (SWV) method, the linear relationship was shown between the peak current at 0.7 V and the concentration of 5-HIAA in range of 1.56-58.6 μmol/L, so 5-HIAA could be determined with limit of 0.917 μmol/L (S/N = 3) even certain interference were co-existed.