The studies of composite pencil graphite (CPG) lead at different hardness as substrate electrodes are presented. In a reversible redox system, Fe(CN)(6)(4-/3-), the CPG electrode (CPGE) is superior than the conventional graphite electrodes. The carboxylic multi-walled carbon nanotube (c-MWCNT) modified CPGE (c-MWCNT/CPGE) had even far better performances than the CPGE. The c-MWCNT/CPGE has been found to improve current density, lower the onset potentials and charge transfer resistances. This could be due to better electrocatalytic effect of c-MWCNT, for it had relatively good graphitic orientation, richness in oxygen-containing surface functional groups and high mesoporous 3D structure. The surface morphologies of the electrodes were studied by using field emission scanning electron microscopy. The electrochemically accessible surface area and charge transfer resistances were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The c-MWCNT/CPGE has been used to study the oxidation behavior of five kinds of flavonoids with satisfactory result. (C) 2012 Elsevier Ltd. All rights reserved.