Analysis of reaction of luminol at an indium-tin oxide anode by cyclic voltammetry

In the present study, cyclic voltammograms obtained with an indium-tin oxide (ITO) anode were compared with those obtained with a platinum anode. The peak currents generated by luminol oxidation at the platinum anode showed convex curves facing upwards with increasing luminol concentration, as the result of the prevention of the oxidation of the platinum electrode by the presence of luminol. With the ITO anode, no current due to electrode oxidation or reduction was detected. The peak current intensity of luminol oxidation was proportional to the luminol concentration, but the peak current was also in a linear relationship with the square root of the scan rate. However, the intercept current was largely deviated from zero. The deviation suggests radial diffusion of luminol at the ITO anode which has a small active point density. In conclusion, the ITO anode is useful for accurate measurement of the rate of luminol oxidation, but radial diffusion of luminol in the vicinity of the ITO surface should be taken into consideration in analysis of luminol oxidation.