Abstract: A new method for determination of nitrophenols was presented based on polyvinylpyrrolidone modified carbon paste electrode coupled to a dual-electrode and dual-channel electrochemical detection system of capillary electrophoresis. In this system, two working electrodes and two amperometric detector were employed. The oxidative and reductive detection potentials were set at +0.5 V and -1.4 V vs. SCE, respectively. The ratio of reductive and oxidative current response(N_c=i_r/i_o) obtained at each electrode was also used to verify sample purity. Four nitrophenols were determined with oxidation and reduction at the same time. Efficient, rapid and versatile electrophoretic conditions were obtained with 25 mmol/L Tris-2.85 mmol/L citric acid-10 mmol/L β-CD-10% ethanol. The effects of the working electrode, detection potential, buffer, the concentration of β-CD and ethanol on the separation were investigated. The output signal was processed by spline wavelet least square, which can extract useful information from high noise signals. The method was applied to separation and determination of sample of environment with satisfactory results.

Key words: Dual-channel amperometric detection for capillary electrophoresis, Polyvinylpyrrolidone modified carbon paste electrode, Nitrophenols, Spline wavelet least square