Voltammetric analysis of naringenin at a disposable pencil graphite electrode – application to polyphenol content determination in citrus juiceElectronic supplementary information (ESI) available. See DOI: 10.1039/c8ay02281j

The electrochemical behaviour of the flavonoid naringenin (NGN) was investigated for the first time by cyclic voltammetry (CV), using a disposable electroactivated pencil graphite electrode (PGE*). In this electrochemical sensor, NGN is irreversibly oxidized, giving rise to two pH-dependent peaks due to mixed (diffusion- and adsorption-controlled) electrode processes involving the same number of electrons and protons, namely two and one, respectively. Exploiting these peaks, differential pulse voltammetry (DPV) and square wave voltammetry (SWV) at PGE* in 0.05 mol L−1potassium hydrogen phthalate were applied for quantitative determination of NGN. The new proposed methods presented linear ranges covering more than three orders of magnitude (7.86 × 10−8to 1.82 × 10−4mol L−1NGN for DPV and 7.50 × 10−8to 1.00 × 10−4mol L−1NGN for SWV) and low limits of detection (LoD) and quantification (LoQ) (LoD = 3.06 × 10−8mol L−1, LoQ = 1.02 × 10−7mol L−1NGN for DPV and LoD = 4.40 × 10−8mol L−1, LoQ = 1.11 × 10−7mol L−1NGN for SWV), similar to or better than those reported in the literature. The developed voltammetric methods were applied with good results to determine the intermediate antioxidant power polyphenolics content expressed as mg naringenin equivalent per L grapefruit juice.