Development of a novel voltammetric sensor for the determination of quercetin on an electrochemically pretreated carbon-paste electrode

Abstract

In this work, a simple, cheap and sensitive sensor for quercetin voltammetric determination was developed. Quercetin is a flavonoid that is widely distributed in plants. The antioxidant, anti-cancer, antibacterial and anti-inflammatory activities of quercetin make it an important biologically active substance. Therefore, the development of new methods for its rapid and inexpensive determination is an urgent task. The presence of a large number of hydroxyl groups in quercetin makes its accumulation possible due to hydrogen bonding. Using the electrochemical activation of a carbon-paste electrode, a sensor with great ability for quercetin adsorption has been developed. Using the proposed sensor, the electrochemical behavior of quercetin has been investigated. The adsorption nature of the current was established. After pre-accumulation on the sensor, quercetin is oxidized reversibly. Using SWVs under optimal conditions (electrochemical pretreatment of the CPE was carried out in 1 M NaOH solution at 1.5 V for 120 seconds; quercetin adsorption at 0 mV for 300 s from Britton–Robinson buffer solution with pH 3 and a sweep rate of 200 mV s⁻¹, an amplitude of 50 mV, and a frequency of 30 Hz), it is possible to determine quercetin in the concentration range of 0.06–2 μM, with the LOD and LOQ equal to 1.6 × 10⁻³ μM and 5.2 × 10⁻³ μM, respectively, and a sensitivity of 19.9 μA μM⁻¹. The developed sensor was satisfactorily used for the determination of quercetin in pharmaceuticals and extracts of green and black tea with a RSD of 3.5%.