Stability-indicating Isocratic RP-HPLC Method for Simultaneous Quantification of Olaparib and Paracetamol: Development, Validation and Forced Degradation Study

Abstract

An isocratic reversed-phase HPLC (RP-HPLC) method with UV detection was developed and validated for the simultaneous quantification of olaparib (OLA) and paracetamol (PCM) in laboratory-prepared mixtures, with demonstration of stability-indicating performance. Chromatographic separation was achieved on a C18 column (250 × 4.6 mm, 5 µm) using a mobile phase of acetonitrile and 0.02 M phosphate buffer (55:45, v/v; pH 3.0 ± 0.1) at a flow rate of 1.0 mL/min, column temperature of 30 °C and detection at 250 nm. Retention times were approximately 3.18 min for PCM and 6.45 min for OLA, with resolution >4 between peaks. The method was validated according to ICH Q2 (R1) for specificity, linearity, accuracy, precision, sensitivity and robustness. Linearity was established over 5–50 µg/mL for OLA and 2.5–25 µg/mL for PCM with regression coefficients >0.999. Recoveries at 80–120% levels were 99.40–99.75% for OLA and 99.58–99.63% for PCM, with %RSD <1.0. Intra- and inter-day precision studies provided assay %RSD ≤0.71 for both analytes. LOD/LOQ values were approximately 0.5/1.5 µg/mL for OLA and 0.3/1.0 µg/mL for PCM. Forced degradation under acidic, alkaline, oxidative, neutral, thermal and photolytic stress produced 2.2–19.4% degradation, while analyte peaks remained well resolved from degradation peaks and mass balance approached 100%. The validated method is suitable for routine assay, compatibility studies and stability testing of OLA–PCM mixtures.