SPECTROPHOTOMETRIC DETERMINATION OF PARACETAMOL IN PHARMACEUTICALS BY DIAZOTIZATION AND COUPLING REACTION WITH RESORCINOL AND 1-NAPHTHOL

A simple, accurate, and sensitive spectrophotometric method has been developed for the quantitative determination of acetaminophen (paracetamol, PAR) in pharmaceutical formulations including tablets, syrups, and injectable solutions. The method involves acid hydrolysis of PAR to yield p-aminophenol, which is subsequently subjected to diazotization to form a diazonium salt. This diazonium intermediate reacts with resorcinol and 1-naphthol to form colored azo dyes, exhibiting maximum absorbance at 480 nm and 510 nm, respectively. The method adheres to Beer’s law over concentration ranges of 3–15 μg/mL for the resorcinol system and 2.5–20 μg/mL for the 1-naphthol system. The calculated molar absorptivity values were 18.5 × 10³ and 9.8 × 10³ L·mol⁻¹·cm⁻¹, with corresponding Sandell’s sensitivities of 0.008 and 0.015 μg·cm⁻², respectively. Method validation demonstrated satisfactory accuracy, with mean percentage recoveries ranging from 94.78% to 105.73%. Furthermore, the method exhibited good linearity, low limits of detection and quantification, and minimal relative error, underscoring its reliability and suitability for routine quality control analysis of PAR in commercial pharmaceutical preparations.