Electroanalytical Determination of Estrone in Seawater Samples Using Functionalized Multiwalled Carbon Nanotubes

In this work, a glassy carbon electrode (GCE) modified with multiwalled carbon nanotubes functionalized with carboxylic groups (MWCNT?COOH) was used to determine the hormone estrone in seawater samples. Modification of the electrode was optimized using three successive 10-μL aliquots of the MWCNT?COOH dispersion in ethanol (1 : 5 mL). The cyclic voltammetry results showed an oxidation peak at 0.59 V with characteristics of an irreversible process, pH dependent and controlled by adsorption of species. The results of square-wave voltammetry showed that the intensities of peak currents for the MWCNT?COOH/GCE were about 2.5 times higher than for GCE. The calibration curve showed a linearity of 0.9981 and a sensitivity of 0.1521 μA/mol L^?1. The limits of detection and quantification were 0.117 and 0.392 μmol L^?1, respectively. The recovery obtained using seawater samples was 91%, indicating the applicability of the method in marine environments.