Determination of Quercetin by a Siloxane-Polyester/Poly-L-Lysine Nanocomposite Modified Glassy Carbon Electrode

Abstract

Poly-L-lysine incorporated in the nanocavities of polysiloxane-poly(propylene) oxide is reported as an electrochemical sensor for quercetin. A glassy carbon electrode coated by poly-L-lysine/polysiloxane-poly(propylene) oxide accumulated quercetin through hydrogen bonding in pH 2 ethanol/Britton-Robinson buffer. The catecol oxidation was monitored at 0.45 V as a reversible two electron peak. The voltammetric response using the film electrode was 80% higher compared to a bare electrode. Square wave voltammetry was employed using an accumulation time of 8 min and a linear relationship was obtained for concentrations of quercetin from 1.0 × 10−8 mol L−1 to 1.0 × 10−6 mol L−1. The limit of detection was 2.76 ± 0.5 × 10−9 mol L−1. The method was employed to determine quercetin in green tea, but did not show selectivity to catechin, which was oxidized at a similar potential. The measurements were validated by high-performance liquid chromatography.