Stability-Indicating UPLC Method for the Simultaneous Estimation of Foscarbidopa and Foslevodopa in Bulk and Pharmaceutical Dosage Form

ABSTRACTA simple, rapid, precise, sensitive, and reproducible Ultra-Performance Liquid Chromatography (UPLC)method has been developed and validated for the simultaneous quantitative analysis of Foslevodopa andFoscarbidopa in bulk and pharmaceutical dosage forms. Chromatographic separation was achieved on a WatersACQUITY UPLC system using a Phenomenex C18 column (50 × 2.1 mm, 1.7 µm) with an isocratic mobilephase consisting of Acetonitrile and 0.1% Trifluoroacetic acid (TFA) in water (40:60 % v/v) at a flow rate of0.5 mL/min. Detection was carried out at an isosbestic wavelength of 228 nm using a photodiode array (PDA)detector at ambient temperature. The retention times for Foslevodopa and Foscarbidopa were 1.625 min and2.931 min, respectively, with a total run time of 5.0 min. System suitability parameters demonstratedtheoretical plate counts exceeding 2000 (15,634 for Foslevodopa and 8,305 for Foscarbidopa) and tailingfactors below 2.0 (0.92 and 0.98, respectively), with peak resolution reaching 6.67. Linearity was establishedover concentration ranges of 30.0–180.0 µg/mL (R² = 0.9995) for Foslevodopa and 1.5–9.0 µg/mL (R² =0.9998) for Foscarbidopa. The LOD and LOQ were determined as 0.36 µg/mL and 1.20 µg/mL forFoslevodopa, and 0.18 µg/mL and 0.60 µg/mL for Foscarbidopa. Forced degradation studies under acid, alkali,peroxide, reduction, thermal, photolytic, and hydrolytic conditions confirmed that degradation products werewell-resolved from parent drug peaks, establishing the stability-indicating capacity of the proposed method inaccordance with ICH guidelines.