Electrochemical monitoring of ethinylestradiol oxidation by the horseradish peroxidase enzyme in water

SCALA L; NOELIA A. MARTINEZ; PEREIRA S; RABA J; MESSINA G

Cordoba

Congreso; RICIFA; 2014

Ethinylestradiol (EE2) is a synthetic estrogen used in contraceptive therapy. The presence of this compound in the environment has been attributed to their incomplete removal in wastewater treatment plant processes. The purpose of this research was to optimize the Horseradish peroxidase (HRP) enzyme-catalyzed process for removal of EE2 from synthetic water (purified deionized water) and the monitoring of the enzymatic process by square-wave voltammetry (SWV). In this study, HRP catalyzes the oxidation of EE2 in presence of H2O2 and the products formed are polymerized through a non-enzymatic process which leads to the formation of high molecular weight polymers. These low-solubility polymers can be removed from wastewater by co-precipitation, sorption to solids, sedimentation or filtration. The reaction mixture was prepared by diluting stock solution of a EE2 to a concentration of 0.5 µM, in 10 mL of 0.01 M citrate buffer pH 5.0 containing HRP 0.02 U mL-1. The reaction was initiated by adding 1 mM of H2O2. Then, after stirring for 10 min, the sample was centrifugated and EE2 was quantified by SWV. The enzymatic process was monitored by SWV using a three electrodes system: glassy carbon working electrode, Ag|AgCl|3M NaCl reference electrode and Pt counter electrode. For the measurement of EE2 by SWV a calibration equation was ΔI (µA) = 1.436 + 2.382 CEE2 with a correlation coefficient of 0.998, over the concentration range of 0.3?50 µM with a limit of detection of 0.11µM. Our analysis demonstrated that EE2 disappeared almost completely in the reaction mixture after 10 min treatment. These results strongly suggest that HRP is effective in removing the estrogenic activities of EE2 in water samples.