Oxidative Coupling-Base Reaction for the Indirect Spectrophotometric Determination of Paracetamol in Drug Formulations

Abstract

A simple, rapid, and specific spectrophotometric method was developed for the determination of paracetamol  in pure form and drug formulations. The method depended on the hydrolysis of paracetamol to p-aminophenol, which, oxidized under the effect of dissolved oxygen to benzoquinoneimine. In the alkaline medium, benzoquinoneimine reacts with Methyldopa to produce a high stabile indophenol dye. The absorbance was measured at 580 nm, and the molar absorptivity was found to be 7.75 x 10^-5 L/(mol cm). Paracetamol was determined in pharmaceutical products in the 10–100 μg.mL^-1 concentration range with a detection limit of 1.5 μg.mL^-1 PAP. The developed method can be applied to the determination of both paracetamol and p-aminophenol in the presence of each other without prior separation. The proposed method is successfully employed for the determination of paracetamol in various synthetic mixtures and pharmaceutical preparations. Our obtained results were statistically compared with those given by the similar methods and the procedures evaluated as regards to both figures of merit and ease of applicability.