The electrochemical oxidation of the hormone ethinylestradiol in an aqueous-methanolic medium by the application of a constant current of 40？mA？cm？2 in a flow cell with a commercial Ti/Ru0.3 Ti0.7O2 electrode was evaluated. The effect caused by the use of NaCl as a support electrolyte was also investigated. Hence, HPLC-UV analyses revealed that ethinylestradiol was almost totally consumed after a 60？min reaction time in the presence of NaCl. Conversely, much lower degradation rates were obtained when NaCl was not employed. Moreover, direct infusion ESI-MS and GC-MS analysis revealed that apparently no degradation products had been formed under these conditions. Hence, this study clearly demonstrated that such electrochemical treatment can be efficiently used to promote the complete degradation (and probably mineralization) of the hormone ethinylestradiol. 1. Introduction It has been profusely reported that several pharmaceuticals, including the endocrine disrupting compounds (EDCs), are directly released into water bodies, such as rivers and lakes, thus representing a serious risk to the natural ecosystems [1]. These substances, which cannot be completely eliminated by the conventional treatment procedures, have been detected in drinking water and are potentially dangerous to the human health [1–3]. The presence of estrogens in the effluents of sewage treatment plants has been reported in many countries [4]. Ethinylestradiol (Figure 1), a synthetic steroidal estrogen, is a common component widely used as the active principle of many contraceptive agents and therapy drugs. The occurrence of estrogen hormones in natural systems, such as surface waters, soils, and sediments, has become a subject of major concern. Many problems, for instance the feminization of male fishes, the lower sperm counts in adult males, and an increasing incidence of cancer, have been related to the existence of these hormones in natural waters [4]. Figure 1: Chemical structure of the synthetic hormone ethinylestradiol. Advanced oxidative processes (AOPs) have been widely applied for the disinfection (elimination of undesired micropollutants) from drinking and waste waters [5, 6]. Ozone, chlorine, and chlorine dioxide are the most used reactants for such purpose. In AOPs, hydroxyl radicals, very reactive species that ultimately account for the oxidation of target compounds, are secondary oxidants that can be produced in situ by the decomposition of ozone or mainly from combined systems as Fenton, UV/H2O2, and UV/TiO2 [7, 8]. The interest in using electrochemical techniques to
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