Determination of Trace Copper by Adsorptive Voltammetry Using a Multiwalled Carbon Nanotube Modified Carbon Paste Electrode

A new method for the determination of trace copper was described. A multiwalled carbon nanotube modified carbon paste electrode was prepared and the adsorptive voltammetric behavior of copper‐alizarin red S (ARS) complex at the modified electrode was investigated. By use of the second‐order derivative linear sweep voltammetry, it was found that in 0.04 mol/L acetate buffer solution (pH 4.2) containing 4×10 −6  mol/L ARS, when accumulation potential is 0 mV, accumulation time is 60 s and scan rate is 100 mV/s, the complex can be adsorbed on the surface of the electrode, yielding one sensitive reduction peak at −172 mV (vs. SCE). The peak current of the complex is proportional to the concentration of Cu(II) in the range of 2.0×10 −11 –4.0×10 −7  mol L −1 with a detection limit ( S / N =3) of 8.0×10 −12  mol/L (4 min accumulation). The proposed method was successfully applied to the determination of copper in biological samples with satisfactory results, the recoveries were found to be 96%–102%.