Simultaneous determination of quercetin and rutin at a multi-wall carbon-nanotube paste electrodes by reversing differential pulse voltammetry

A reversing differential pulse voltammetry (RDPV) with a pre-accumulation step has been developed for simultaneous determination of quercetin and rutin in a mixture. A multi-wall carbon-nanotube paste electrode (CNTPE) was used for this purpose. Quercetin presented two oxidation steps at Em of 0.155 and Epa of 0.360 V versus SCE, and rutin presented only one oxidation step at Em of 0.316 V at the CNTPE. Strong adsorption and favorable assembly process of these species were observed on the electrode surface, based on which these species could be significantly pre-accumulated at the electrode for determination, resulting in considerably increased signals with well separated voltammetric peaks, allowing simultaneous detection. RDPV technique was used to select the first anodic peak of quercetin and the re-reduction peak of rutin for the determination, avoiding the peak overlap interferences. The electrochemical system was optimized for the selection of a suitable buffer system and pre-accumulation parameters such as adsorption potential and time duration. Finally, the multi-wall CNT paste electrode, as an electrochemical sensor, gave detecting sensitivities as high as 4.90 μA/(μM quercetin) in the linear range of 0.05–5 μM (in the presence of 10 μM rutin) and 2.43 μA/(μM rutin) in the linear range of 0.1–10 μM (in the presence of 10 μM quercetin). The applicability of the method to real sample analysis was also evaluated.