Abstract

A simple, sensitive and accurate spectrophotometric method has been proposed for the determination of isoniazid in pharmaceutical formulations. The method is based on the oxidation of tiron by potassium periodate followed by coupling with isoniazid in alkaline medium leading to the formation of a red coloured product having maximum absorbance at 505 nm. The reaction conditions were optimized to obtain the maximum colour intensity. The absorbance was found to increase linearly with increase in concentration of isoniazid, which was corroborated by the calculated correlation coefficient (0.9991). The system obeyed Beer's law in the concentration range of 1.5-18 μg/ml. The common excipients and additives used in pharmaceutical formulations do not interfere with the proposed method. The method was successfully applied for the assay of INH in various pharmaceutical formulations and the results compare favorably with those of theofficial method.