UV-Vis and HPLC Analysis of the Content of Commercially Available Paracetamol and Aspirin

The objective of this study was to determine the actual active pharmaceutical ingredient (API) content in commercial aspirin and paracetamol tablets using ultraviolet-visible (UV-Vis) spectrophotometry and High-Performance Liquid Chromatography (HPLC) and to assess whether the measured values comply with pharmacopeial standards. The experiment involved preparing a series of standard solutions, generating calibration curves, and analyzing triplicate samples of each tablet type to evaluate methods’ linearity and precision. Standard solutions of 4-acetamidophenol were prepared and analyzed to establish a calibration curve at 242 nm. Samples from two brands of paracetamol tablets (A: Shanxi Fen he Pharmaceutical Co. and B: Sichuan Tong yuan Pharmaceutical Group Co.) were accurately weighed, diluted, and analyzed under identical spectrophotometric conditions. Results demonstrated a strong linear relationship between absorbance and API concentration. However, significant deviations in the measured API content were observed in Brand A, attributed primarily to undissolved particulate matter and possible volumetric dilution errors during sample preparation. Conversely, Brand B exhibited relatively consistent API content, with only minor deviations slightly exceeding the Paracetamol limit (±5%), but still within the safe therapeutic dosage range; The HPLC method showed excellent performance, with both aspirin (Kunming Yunjian Pharmaceutical Co.) and paracetamol (Sichuan Tong yuan Pharmaceutical Group Co.) displaying strong linear relationships across replicate measurements. Although the measured API contents were approximately 5.7–6% lower than the labeled values, they remained within the ±10% range permitted by the Chinese Pharmacopoeia.