This paper reports on a study by reflectometry of the adsorption process of phenolic compounds electrochemically oxidized on glassy carbon electrodes. This technique provides information about the adsorption rate and the maximum adsorbed amount. The adsorption process depends on several variables like adsorbent concentration, solution pH and working potential, while ionic strength has no significant influence. The best adsorption conditions were obtained at high phenolic concentrations (0.1 M), high pH values (>10) and working potential values higher than 0.600 V. The adsorption process on glassy carbon electrodes showed irreversible behavior, reaching the maximum adsorbed amount at relatively short times (less than 100 s).