New Validated Stability Indicating Rp-HPLC Method for the Simultaneous Estimation of Valproate and Lamotrigine in Combined Pharmaceutical Dosage Forms

Abstract

The present research focuses on the development and validation of a Reverse Phase High-Performance Liquid Chromatography (RP-HPLC) method for the simultaneous estimation of Valproate and Lamotrigine in combined pharmaceutical dosage forms. The primary objective of this study was to establish a simple, accurate, precise, and cost-effective analytical method suitable for routine quality control and stability analysis. Chromatographic separation was achieved using a Discovery C18 column (250 × 4.6 mm, 5 µm) with a mobile phase consisting of phosphate buffer and acetonitrile in the ratio of 60:40 v/v, pH was adjusted to 3 with 0.1% Ortho phosphoric acid, at a flow rate of 1.0 mL/min. Detection was performed at a wavelength of 230 nm, where both drugs exhibited significant absorbance. Under the optimized chromatographic conditions, sharp and symmetrical peaks were obtained with retention times of 2.365 minutes for Valproate and 3.423 minutes for Lamotrigine, showing excellent resolution and separation. The developed method was validated as per the International Council for Harmonisation (ICH Q2 R1) guidelines. The method demonstrated good linearity over the concentration range of 25–150 µg/mL for Valproate and 12.5–75 µg/mL for Lamotrigine, with correlation coefficients (R²) greater than 0.999. Accuracy studies showed mean recoveries between 98% and 102%, while precision results confirmed reproducibility with %RSD values below 2. The method also proved to be robust and specific, showing no interference from excipients or degradation products. Hence, the developed RP-HPLC method is rapid, reliable, and suitable for routine simultaneous analysis of Valproate and Lamotrigine in combined dosage forms.