The Use of Boron‐Doped Diamond Electrodes for the Amperometric Determination of Flavonoids in a Flow Injection System

This paper describes the use of boron‐doped diamond electrode for the amperometric detection and quantification of flavonoids in tea samples using a flow injection system. Flavonoids are phenol derivates widely distributed in fruits, nuts, seeds, flowers, vegetable peels, and beverages; they are known to exhibit high antioxidative activities. After optimization, the experiments were performed at a fixed potential of 0.42 V vs Ag/AgCl with a flow rate of 2.5 ml min−1 in a Britton‐Robinson buffer at pH 5.0. The results revealed that the peak current increases linearly with rutin concentration in the interval 0.1–2.5×10−4 mol L−1 and the detection limit was 7.7×10−6 mol L−1. The method was used for the determination of rutin in three different green tea (Camellia sinensis) infusions by the direct addition of 150 µL of untreated sample. The repeatability of current responses for injections of 150 µL rutin was evaluated to be 2.1% (n=20) and the analytical frequency was 100 Hz h−1. The results were compared with the results obtained by high‐performance liquid chromatrography‐diode ray detector.