Graphitized mesoporous carbon modified glassy carbon electrode for selective sensing of xanthine, hypoxanthine and uric acid

Abstract

An efficient electrochemical sensor for simultaneous electrochemical sensing of three purine compounds, uric acid (UA), xanthine (X) and hypoxanthine (HX), using a graphitized mesoporous carbon (GMC) modified glassy carbon electrode (GCE/GMC) has been demonstrated in pH 7 phosphate buffer solution without any enzyme, prior to electrode activation, surfactant and sample pre-concentration step. Electrochemical investigation of the GCE/GMC with [Fe(CN)₆]³⁻ indicates metallic conductor like surface features of the modified electrode. A diffusion controlled reaction mechanism was identified for the electro-oxidation of the three purine compounds with an electrocatalytic pathway, except for the UA, where it shows a surface area effect with a mixed-diffusion and adsorption controlled mechanism at higher scan rates (>70 mV s⁻¹). Calculated full-width of the half maximum values for the simultaneous detection of the three purine compounds are 42, 53 and 64 mV respectively and these are the lowest values ever reported in the literature, suggesting effective electron-transfer behaviour of the modified electrode for the purine oxidations. Calibration plots for the simultaneous detection of the purine compounds were linear in the concentration range of 20–400 μM, 20–320 μM and 20–240 μM for UA, X and HX with detection limit values of 110 nM, 388 nM, and 351 nM respectively. Selective sensing of the purine compounds in human blood-plasma, urine and fish samples was successfully demonstrated with recovery values ∼100%.