engleski

ELECTROCHEMICAL INVESTIGATION OF ANTIOXIDANTS ON MICRO AND MACRO ELECTRODES

The electrochemical oxidation of ascorbic and uric acid on carbon paste electrodes of macroscopic dimensions, as well as improvement that makes the transition to a microscopic level was investigated. Measurements were performed in phosphate buffer saline simulating physiological environment in the concentration range present in blood plasma. Electrodes with diameters of 3 mm, 1 mm and 100 m were employed in order to investigate effect of spherical diffusion on the electrode processes and to examine the possibility of reducing electrolyte volume. Electrochemical method of cyclic voltammetry was used due to its suitability for determination of the redox properties of antioxidant molecules in solution. Based on the criteria of irreversibility, it was concluded that the electrochemical oxidation reaction of ascorbic and uric acid are irreversible at the carbon paste electrode in the physiological pH conditions. Following electrochemical parameters were determined from cyclic voltammograms: peak potential (Ep), peak current (Ip) and peak charge (Qp). Linear dependence of Ep and Ip on the scan rate (1/2) indicates dependence of the electrode processes on the reaction kinetics. Linearity of the Ip and Qp vs. concentration shows that Randles-Sevcik equation is valid in the studied concentration range. Application of micro electrode resulted in ten times higher current densities compared to the macrodimenzion electrodes. Such effect was attributed to the contribution of spherical diffusion phenomena to the electrode processes.

cyclic voltammetry; carbon paste; ascorbic and uric acid

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