USING AN ACTIVATED COPPER MICROELECTRODE FOR VOLTAMMETRIC DETERMINATION OF ALCOHOLS

Abstract

A method for fabricating a copper microdisk electrode of an original design based on 50 μm diameter wire sealed in borosilicate glass is described. The electrochemical properties of the copper microelectrode were studied by the method of steady-state voltammetry in a 2 M NaOH solution in the potential range from -1.1 to 0.8 V (versus saturated Ag/AgCl-electrode). In order to improve the electrochemical response a method for two-stage electrode activation based on a copper dissolution / redeposition procedure followed by polarization in an alkaline medium is suggested. Morphological and physico-chemical changes on copper surface after activation were examined by atomic force microscopy and X-ray photoelectron spectroscopy. After this procedure, the electrode showed a heterogeneous morphology with coarse texture and high roughness parameters, and a layer of catalytically active Cu(III) species was formed on copper surface. The best results were achieved with an activation time of 60 s and a polarization potential of -0.3 V. The effectiveness of the activation procedure was tested during the chronoamperometric determination of methanol, ethanol and ethylene glycol. Factors affecting the formation of the analytical signal of alcohols were studied, and optimal conditions of amperometric measurements were selected on their basis. Under optimal conditions, the metrological characteristics of the method were determined. The peak current response increases linearly with alcohols concentration over the range 0.01 - 0.45 M (0.04 - 3% v/v). The repeatability of the electrode response was evaluated as 3.8% (n = 10). The activated copper microelectrode was used for the determination of ethanol in pharmaceutical and other products.

Keywords

• copper microelectrode
• electrochemical activation
• x-ray photoelectron spectroscopy
• cyclic voltammetry
• alcohols