Multi-wall carbon nanotube paste electrode for adsorptive stripping determination of quercetin: A comparison with graphite paste electrode via voltammetry and chronopotentiometry

Adsorptive-stripping voltammetry and chronopotentiometry were used to study the adsorption and oxidation of quercetin at both graphite-nujol paste electrode (GPE) and carbon nanotubes-nujol paste electrode (CNTPE) for the potential application of carbon nanotube to flavonoids determination. As compared with GPE, CNTPE showed very great power to adsorb quercetin and resulted in a considerable signals enhancement. The adsorption isotherm of quercetin on CNTPE was of Langmuir type, and the stripping of quercetin adsorbed on CNTs showed a quasi-reversible oxidation reaction involving two-electron and two-proton. The high adsorbtive activity of CNTPE was contributed to the high specific surface area and the special surface characteristics of carbon nanotubes. The peak current response of differential pulse voltammetry depended linearly on quercetin concentration. A linear equation I-p (mu A) = 0.987c(mu mol L-1) + 0.023 with a correlation coefficient of 0.994 was obtained over the concentration range 0.1 - 1.0 mu mol L-1.