Development and Validation of an RP-HPLC Method for Simultaneous Determination of Methylparaben and Propylparaben in Pharmaceutical Syrup Formulations"

A rapid, selective, and accurate reversed-phase high-performance liquid chromatography (RP-HPLC) method was developed and validated for the simultaneous determination of methylparaben (MP) and propylparaben (PP) in pharmaceutical syrup formulations. A systematic optimization study revealed that mobile phase composition (methanol-to-water ratio) was the most critical parameter for separation, followed by flow rate, pH, and column temperature. Optimal separation was achieved on a Kromasil C18 column (150 mm × 4.6 mm, 5 µm) using an isocratic mobile phase of methanol and water (70:30, v/v) at pH 6.5. The method operated at a flow rate of 1.5 mL/min with the column maintained at 35°C, employing detection at 254 nm. These conditions resulted in excellent resolution of MP and PP, with retention times of 2.213 and 4.370 minutes, respectively. The method was validated per ICH Q2(R1) guidelines. Linearity was excellent over the range of 6–30 µg/mL for MP (R² > 0.999) and 1–5 µg/mL for PP (R² > 0.995). Precision was high, with both intra-day and inter-day relative standard deviations (RSD) below 2.0%. Accuracy, confirmed via recovery studies, showed mean recoveries between 98.5% and 101.1%. Sensitivity was established with limits of detection (LOD) of 0.69 µg/mL for MP and 0.29 µg/mL for PP, and limits of quantification (LOQ) of 2.1 µg/mL for MP and 0.88 µg/mL for PP.