Quantitative Determination of Quercetin in Black Tea and Beet Juice Using SWAdSV onto The Pencil Graphite Electrode Surface

In this study, a new electroanalytical method has been developed for the determination of quercetin (Que), an important flavonoid derivative, in natural samples. Pencil graphite electrode (PGE) was used for the determination of Que in black tea and beet juice samples, these determinations were done by square wave adsorptive stripping voltammetry method (SWAdSV). When using the PGE, which has a wide and active surface, a significant increase was observed in the oxidation peak current of Que. Calibration graphs were drawn in the range from 9.67 ng mL−1 to 411 ng mL−1 (from 3.2×10-8 mol L-1 to 1.36×10-6 mol L-1) using 0.1 M PBS at the optimum parameters determined for quantitative determination of Que. Thus, the amount of Que in beet juice and black tea samples was determined as 10.33 ng mL−1 (3.42×10-8 M) and 16.0 ng mL−1 (5.3×10-8 M), respectively. As a result of these processes using the SWAdSV technique, Limit of Detection (LOD) and Limit of Quantification (LOQ) values were calculated as 0.51 ng mL-1 (1.7×10−9 M) and LOQ 1.54 ng mL-1 (15.1×10−9 M), respectively. With this study, the determination of Que in natural samples without any interference effect has been demonstrated with the method developed using the PGE, which is very easy to access renewable and also cheap.