Spectrophotometric Determination of Phenylephrine Hydrochloride in Pharmaceutical Formulations Using an Oxidative Coupling Reaction

This study presents a simple and accurate analytical method for the quantitative determination of selected decongestants and cough suppressants, specifically phenylephrine hydrochloride, in both pure form and pharmaceutical formulations. The method is based on an oxidative coupling reaction with p-aminophenol using potassium iodate as an oxidizing agent in a hydrochloric acid medium. Key experimental parameters including reagent concentrations, acid strength, temperature, reaction time, and stability were thoroughly investigated and optimized. The developed method demonstrated excellent linearity in the range of 5–50 µg/mL at a wavelength of 548 nm, with high precision, accuracy, and sensitivity evidenced by a low limit of detection (LOD) of 0.1207 µg/mL and a limit of quantitation (LOQ) of 0.3659 µg/mL . Successful application to a commercial syrup formulation yielded high recovery percentages, confirming the method's accuracy and revealing no significant interference from common excipients. Consequently, this proposed method is straightforward, cost-effective, and highly suitable for routine quality control analysis in pharmaceutical laboratories.