Determination of quercetin using a photo-electrochemical sensor modified with titanium dioxide and a platinum(II)-porphyrin complex

A glassy carbon electrode (GCE) was modified with a film containing titanium dioxide and a Pt(II)-porphyrin complex, and its response to quercetin was investigated employing cyclic voltammetry and chronoamperometry. The oxidation current caused by quercetin is largely enhanced under UV illumination. The effects of pH value, mass of TiO2 in the film, UV illumination time and applied potential were studied. Under optimized conditions, the peak current at a typically applied voltage of +0.4 V depends linearly on the concentration of quercetin in the 0.002 to 50 mg L-1 range. The detection limit (at an SNR of 3) is 0.8 mu g L-1. The method was successfully applied to the determination of quercetin in (spiked) samples of tea and apple juice.