AQbD-Optimised Stability-Indicating Green RP-HPLC Method for Simultaneous Determination of Adapalene and Benzoyl Peroxide in Topical Gel

Abstract

A tetrahydrofuran-free, stability-indicating reversed-phase HPLC method was developed for simultaneous determination of adapalene and benzoyl peroxide in a commercial topical gel. Analytical Quality by Design (AQbD) was used to define the analytical target profile, identify high-risk chromatographic variables, and evaluate aqueous-phase pH, acetonitrile content, ethanol content, flow rate, and column temperature. Separation was achieved on an RP-C18 column (150 × 4.6 mm, 5 µm) using 0.1% acetic-acidified water, acetonitrile, and ethanol (28:52:20, v/v/v) at 1.0 mL/min, 30 °C, and 272 nm. Benzoyl peroxide and adapalene eluted at approximately 3.18 and 7.11 min, respectively, within a 10 min run. The method was linear over 125–375 µg/mL for benzoyl peroxide and 5–15 µg/mL for adapalene, with coefficients of determination above 0.99999. Recoveries were 99.63–100.22% and 99.68–100.31%, while repeatability RSD values were 0.57% and 0.74%, respectively. Forced degradation produced resolved degradants under acid, alkali, oxidation, heat, light, and neutral hydrolysis; peak purity passed and mass balance remained 97.8–99.4%. The commercial gel assayed at 99.42% benzoyl peroxide and 100.18% adapalene. An AGREE score of 0.66 reflected improved environmental performance through removal of tetrahydrofuran, simultaneous analysis, and a short isocratic run.