Development of an electrochemical sensor for the determination of the flavonoid luteolin in peanut hull samples

We describe the development of an electrochemical sensor based on glassy carbon electrodes modified with multiwalled carbon nanotubes dispersed in low molecular weight polyethylenimine for the determination of luteolin in peanut hulls. A well defined quasi-reversible surface redox couple was found using cyclic and square wave voltammetries for luteolin in 1.0 mol L-1 HClO4 aqueous solutions. The best accumulation potential and the accumulation time were 0.55 V and 20 min, respectively. An optimal ratio of 1:5 for multiwalled carbon nanotubes/polyethylenimine was used to prepare dispersions. The linear range was from 2.4 x 10(-3) to 1.75 mu mol L-1. The luteolin contents determined in two peanut hull samples were (1.18 +/- 0.08) and (1.47 +/- 0.09) g per 100 g of sample, being in very good agreement with those values obtained from the same samples using HPLC. The limits of detection and quantification were 5.0 x 10(-10) and 1.5 x 10(-9) mol L-1, respectively. The reproducibility and the repeatability were 8.0 and 7.3%, respectively. The modified glassy carbon electrode was stable even after 23 days. (C) 2014 Elsevier B.V. All rights reserved.