Copper dispersed into polyaniline films as an amperometric sensor in alkaline solutions of amino acids and polyhydric compounds

A chemically modified electrode composed of copper microparticles dispersed into a polyaniline (PANI) film was investigated as an amperometric sensor of scarcely electroactive compounds possessing -OH and -NH2 groups. Glassy carbon was used as an electrode material and modified firstly by a PANI film, then allowed to stand in contact with a solution of copper ions, and finally, the electroreduction was done at -0.3 V. The electrochemical behaviour of the resulting modified electrode in alkaline medium was examined by cyclic voltammetry and flow-injection amperometry. Using some representative compounds, the effect of copper loading and pH on the electrode response was investigated. Constant-potential amperometric detection was applied in conjunction with anion-exchange chromatographic (AEC) separations of amino acids and carbohydrates. At an applied potential of 0.55 V vs. Ag/ AgCl, the detection limits (S/N=3) for all analytes investigated ranged 5-15 pmol, and the linear dynamic range was three-four orders of magnitude above the detection limits. The resulting modified electrode was found to retain 95% of its initial response in flowing streams for 3 h of operating time.