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

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 0.45V 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 8min and a linear relationship was obtained for concentrations of quercetin from 1.0x10(-8)mol L-1 to 1.0x10(-6)mol L-1. The limit of detection was 2.76 +/- 0.5x10(-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.