Adsorptive stripping voltammetric determination of gallic acid using an electrochemical sensor based on polyepinephrine/glassy carbon electrode and its determination in black tea sample

An efficient adsorptive stripping voltammetric (AdSV) method for determination of gallic acid, GA, was developed by using an electrochemical sensor based on polyepinephrine/glassy carbon electrode, PEP/GCE. Modification of GCE with PEP was done by electropolymerization of epinephrine, EP, in 0.2 M phosphate buffer solution using cyclic voltammetry, cv. A well-defined redox cv wave of epinephrine in potential range of −0.10 to 0.70 V was obtained. It corresponds to oxidation of EP to PEP. The formed PEP was characterized by cv, FE-SEM and in situ UV–vis spectroelectrochemistric spectral methods. Gallic acid at the modified electrode shows an irreversible well-defined adsorption-controlled redox cv wave. At optimal conditions, the anodic square wave, SW, peak current correlates linearly with GA concentration from 1.0 to 20.0 μM with detection limit of 6.63 × 10−7 M. It was found that ascorbic and caffeic acids do not interfere with the voltammetric response of GA. Gallic acid content in black tea sample was successfully determined on applying the prepared sensor.