Voltammetric Determination of Flavonoids in Medicinal Plant Materials Using Electrodes Modified by Cerium Dioxide Nanoparticles and Surfactants

Methods for the voltammetric determination of flavonoids (rutin and quercetin) using electrodes modified with CeO2 nanoparticles and various surfactants have been developed . The voltammetric characteristics of analytes are most properly recorded on a glassy carbon electrode modified with CeO2 nanoparticles dispersed in anionic sodium dodecyl sulfate. The electro-oxidation of quercetin and rutin is adsorption-controlled and proceeds with the participation of two electrons and two protons. Under conditions of differential pulse voltammetry in a Britton-Robinson buffer solution with pH 2.0, the analytical ranges are 0.01-1.0 and 1.0-250 mu M for quercetin and 0.10-100 mu M for rutin with the limits of detection (S/N = 3) of 2.9 and 28 nM, respectively. The proposed approaches were tested in analyzing water and alcohol extracts from medicinal plant materials (St. John's wort herb, marigold flowers, and bearberry leaves). The conditions for the extraction of flavonoids from raw materials with ethanol are found. The results of the voltammetric determination of quercetin and rutin in plant raw materials correlate with the total flavonoids according to spectrophotometry: r = 0.929 with r(crit) = 0.521 for n = 11 in the case of quercetin and r = 0.951 at r(crit) = 0.729 for n = 6 for rutin.