ENZYME GAS-DIFFUSION ELECTRODES ― MATHEMATICAL MODELLING

摘要

A mathematical model of an enzyme-gas diffusion electrode for detection of phenol in solution described previously is used. Two step enzymatic reaction turns the phenol consecutively to catehol (stage 1) and to o-quinone (stage 2), the latter being converted by the electrochemical indicator electrode reaction back to catehol which can be looped again in the stage 2 of the enzymatic reaction; this can result in an internal gain of the am-perometric signal. The system of partial differential equations is solved numerically for discrete moments of time and spatial distributions of the concentrations of phenol, catechol and o-quinone into the membrane and the enzyme layers are obtained, as well as the current of the electrode. From the values of the steady-state current, a calibration curve, which shows good correlation with experimental data, is built. The concentration profiles of the species involved, as well as the spatial distribution in the layers of the rate of the enzyme reactions obtained at different moments of time are compared for two significantly different values of the initial concentration of phenol in the solution. It is shown that loop of the product of the indicator reaction again in the enzymatic reaction makes the electrode more sensitive to lower phenol concentrations in the bulk solution.