Electrochemical Determination of Flavonoid Fisetin in Commercial Dietary Supplements Using a Boron-Doped Diamond Electrode

For the first time, a boron-doped diamond electrode was utilized to quantitatively determine flavonoid fisetin (FST). Cyclic voltammetric studies have shown that the electrochemical oxidation of FST is irreversible and well-separated two peaks (P-A1 and P-A2) in 0.1 MHNO3 solution. The effects of electrode pretreatment, solution pH, nature of the supporting electrolyte, and instrumental variables on the peak current and potentials of the FST were investigated by square-wave voltammetry (SWV) and then optimum ones were determined. It was observed that the cathodically pre-treated BDD (CPT-BDD) electrode's performance was better than the other pre-treatment procedures for increasing the FST oxidation signal. Under optimized conditions and using the SWV technique, the response of the first anodic peak (P-A1) of the FST was proportional in a concentration range of 0.5-20.0 mu g mL(-1) (1.7x10(-6)-6.9x10(-5) mol L-1) with a detection limit of 0.08 mu gm L-1 (2.8 x 10(-7) mol L-1). Also, it was successfully demonstrated that the proposed method is applicable in commercial nutritional supplement formulations.