Estimation of Antimicrobial Agent (Sorbic Acid) in Semisolid Dosage Form (Gel) Using Liquid Chromatography and Evaluation of Its Stability in the Presence of Steroids, Polymers, and Low pH

The stability of sorbic acid as a preservative in pharmaceutical semisolid dosage forms has not been adequately characterized. In this study, the degradation behavior of sorbic acid was systematically investigated in a model semisolid formulation containing progesterone, polymeric excipients, oils, glycerine, and water. A stability-indicating liquid chromatographic method was developed and validated for the quantitative determination of sorbic acid. Chromatographic separation was achieved under isocratic conditions using 0.1% orthophosphoric acid and acetonitrile at a flow rate of 1.0 mL/min, with UV detection at 254 nm. The method demonstrated clear separation of sorbic acid from degradation products and formulation components and was validated for specificity, linearity, precision, accuracy, and robustness in accordance with ICH Q2(R2), Chinese Pharmacopoeia ⟨9101⟩, and United States Pharmacopoeia ⟨1225⟩ guidelines. Stability studies revealed a significant decline in sorbic acid content during storage, which was strongly influenced by the presence of the steroidal drug, polymeric excipients, and acidic pH of the semisolid matrix. These findings highlight the need for careful preservative stability evaluation during semisolid formulation development.