Flow Injection Analysis of Allopurinol by Enzymeless Approach at Glassy Carbon Electrodes

Abstract

Allopurinol is a pharmaceutical drug mainly used for the treatment of chronic gout. It is an antioxidant as well as a powerful inhibitor of xanthine oxidase. Very few electroanalytical assays were reported for allopurinol detection so far. No faradic process of allopurinol was observed by cyclic voltammetry at a glassy carbon electrode. A systematic decrease in current signal of ascorbic acid was observed upon the addition of allopurinol due to the inhibitory action. By taking ascorbic acid as the mobile phase, the above property was utilized to develop a sensitive detection scheme for allopurinol by flow injection analysis. Possible inhibition pathway is derived in terms of radical coupling mechanism. Under optimized conditions, the calibration plot showed a linear range up to 150 μM with a detection limit (S/N=3) of 0.5 μM (i.e., 1.3 ng in 20 μL sample loop). The precision for 18 successive injection of 0.1 mM allopurinol showed a relative standard deviation of less than 2%. The proposed method is used to detect the amount of allopurinol in a commercially available pharmaceutical drug to show its potential use in real applications.