Kinetics Simulation of Luminol Chemiluminescence Based on Quantitative Analysis of Photons Generated in Electrochemical Oxidation

The kinetics of electrogenerated chemiluminescence (ECL) of luminol at a gold electrode in alkaline solution was investigated by measuring the absolute number of photons emitted in an integrating sphere. The ECL efficiency as the ratio of photon to electric charge was 0.0004 in cyclic voltammography and 0.0005 in chronoamperometry. By numerically solving the rate equations based on a diffusion layer model, the observed time profile of the luminescence intensity could be successfully simulated from the oxidation current of luminol in the chronoamperometry. In the simulation, the rate constant for the oxidation of luminol by superoxide radicals in alkaline solution was determined to be 6 × 10⁵ M^–1 s^–1. The present methodology and the achievement could be widely applicable to various analytical techniques using chemiluminescence