Impurity profiling of paracetamol toxic impurities in pharmaceutical combination with ibuprofen and chlorzoxazone using HPLC and TLC densitometric methods

This work presents two methods for the simultaneous determination of ibuprofen (IBU), paracetamol (PAR), and chlorzoxazone (CHZ) in the presence of three PAR impurities: p-aminophenol (PAP), p-nitrophenol (PNP), and p-chloroacetanilide (PCA). Furthermore, both methods attempt to quantify these hazardous impurities. The first method is a thin layer chromatography densitometric method (TLC), where separation was achieved on silica gel 60 F₂₅₄ plates using a mobile phase consisting of chloroform, toluene, ethanol, and ammonia (7.0: 1.0: 1.6: 0.2, by volume). Densitometric detection was performed at 220.0 nm. The second method is a high-performance liquid chromatographic method (HPLC), in which the analytes were separated on an Xterra C8 column (150 × 4.6 mm, 5 µm) using an isocratic mobile phase of acetonitrile and phosphate buffer (pH 7.5) in a 30:70 (v/v) ratio. The UV detector was set at 220.0 nm, and the flow rate was maintained at 0.7 mL/min. Both methods were validated following ICH guidelines and successfully applied to the determination of IBU, PAR, and CHZ in their commercial tablet formulations. A statistical comparison with a previously reported method confirmed no discernible differences in the results, demonstrating the reliability and accuracy of the proposed techniques.