Electroanalysis of Naringin at Electroactivated Pencil Graphite Electrode for the Assessment of Polyphenolics with Intermediate Antioxidant Power

Abstract

A simple and rapid differential pulse voltammetric (DPV) method using a single-use electroactivated pencil graphite electrode (PGE*) is proposed for the rapid screening of the total content of polyphenolics (TCP) with intermediate antioxidant power (AOP) in grapefruit peel and fresh juice. The results were compared and correlated with those provided by the HPLC-DAD-MS method. NG voltammetric behavior at PGE* was studied by cyclic voltammetry and an oxidation mechanism was suggested. The experimental conditions (type of PGE, electroactivation procedure, pH, nature and concentration of supporting electrolyte) for NG DPV determination were optimized. The NG peak current varied linearly with the concentration in the ranges 1.40 × 10−6–2.00 × 10−5 and 2.00 × 10−5–1.40 × 10−4 mol/L NG and a limit of detection (LoD) of 6.02 × 10−7 mol/L NG was attained. The method repeatability expressed as relative standard deviation was 7.62% for the concentration level of 2.00 × 10−6 mol/L NG. After accumulation for 240 s of NG at PGE* the LoD was lowered to 1.35 × 10−7 mol/L NG, the linear range being 6.00 × 10−7–8.00 × 10−6 mol/L NG. The developed electrochemical system was successfully tested on real samples and proved to be a cost-effective tool for the simple estimation of the TCP with intermediate AOP in citrus fruits.

Voltammetric Investigation of Ferulic Acid at Disposable Pencil Graphite Electrode

“…The solid electrodes consisting of glassy carbon (GCE) and platinum (Pt) with a diameter of 0.30 cm and the corresponding geometrical surface area (A g ) of 0.0707 cm 2 were employed for comparison. The PGE (Figure S2) was prepared as described in a previous paper [19] and every time, 1.00 cm of the graphite lead was introduced in the solution so that the A g was always constant (0.1589 cm 2 ), thus ensuring the reproducibility of the measurements.…”

“…Thus, this paper presents for the first time the results of FA voltammetric analysis at an unmodified, disposable sensor and discusses it in comparison to similar reports previously published in the literature. To the best of our knowledge, the composite graphite material used in the PGE was not exploited till now for FA electroanalysis, despite the fact that this electrode has a very large applicability in voltammetry, including the polyphenolics analysis [19], due to its positive above-mentioned electrochemical and economic advantages [16][17][18]. Moreover, often using unmodified PGE, analytical performances similar to those reported for modified electrodes are obtained, but with a smaller number of steps and a lower consumption of reagents.…”

Curcumin Electrochemistry—Antioxidant Activity Assessment, Voltammetric Behavior and Quantitative Determination, Applications as Electrode Modifier

“…Thus, based on the different reducing power of the various molecules, reflected in their oxidation (peak) potential, Blasco et al [120] pointed out that electrochemical methods, i.e., amperometry, may have a certain degree of selectivity, and defined the "electrochemical index" according to which, by selecting the proper detection potential of 0.800, 0.500, and 0.300 V (versus Ag/AgCl, PBS pH 7.00), a distinction between the "Total natural antioxidant index", "Intermediate antioxidant species", and "High antioxidant compounds", respectively, can be made. It was recently reported that DPV was able to discriminate between phenolics with high (polyphenolic acids like caffeic and gallic acid) and intermediate (naringin and naringenin bioflavonoids) AOA [121]. However, very often, the advantages of experimental methods (spectroscopic, chromatographic, electrochemical) and theoretical calculations are exploited together in order to establish the AOC of a sample.…”