Increased sensitivity of ascorbate detection by mediated oxidation in confined electrochemical cells

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Abstract

In this work, the EC’ mechanism involving ascorbate (AA−) and the oxidized form of ferrocenemethanol (FcMeOH) was explored as an analytical strategy to monitor AA− at low concentration levels. The feasibility of this approach was investigated at different mass transport regimes utilizing macro- (glassy carbon) and ultramicroelectrodes (5 μm radius carbon disk). Cyclic voltammograms (CV) were recorded in acetate buffer solution (pH 3.7) using a glassy carbon electrode, and an expressive increase in the anodic peak current (and decrease in the cathodic peak) was noticed in the CV in a solution containing both FcMeOH and ascorbate, confirming the presence of an electrocatalytic process (EC’). The current increase was more pronounced when the reactants and products were confined in a thin solution layer, which was created by approaching an ultramicroelectrode close to an insulator surface. At optimized experimental conditions, a correlation between ascorbate concentration and the steady-state current measured at the ultramicroelectrode was established, allowing the development of an analytical method for ascorbate detection in the micromolar range. The proposed approach was used to quantify ascorbate in a commercial juice sample.

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