Evaluating the antioxidant activity of different species using a novel reagentless chronopotentiometric method

Abstract

Antioxidants are substances that even in low concentrations can delay or prevent unwanted oxidizing processes. In this way, they can prevent or treat certain diseases in a physiological environment. The presence, amount, concentration and activity of these compounds in foods, beverages and in living tissues are therefore important parameters. Many methods have been developed for assessing antioxidant activity or capacity in different samples.Recently we introduced a new, reagentless, chronopotentiometric method for antioxidant measurement that was tested by measuring L-ascorbate in aqueous samples. The method uses a carbon working electrode chemically modified by a thin reversible redox mediator layer on its measuring surface. A simple, two-step procedure is used for the determination. First, in a short, controlled potential step, the mediator layer is converted into its oxidized state. In the second step, the potential control is terminated and the open cell redox potential value is recorded over time to obtain an analytical signal.In this paper, results obtained in further experiments using the novel method are described. An electrochemically formed graphene docking layer was employed to increase the stability of the redox mediator layer. The performance of the method has been tested using different antioxidant species. The influence of redox layer thickness on the sensitivity has been studied. The expected shapes of the chronopotentiometric function (E–t) and the calibration curve (ΔE/Δtinitial–canalyte) were predicted using a rough model. The calculated and measured curves were compared.