Determination of betamethasone disodium phosphate in the in vitro media of PLGA microspheres by high-performance liquid chromatography

Betamethasone disodium phosphate is a kind of corticosteroid, which is commonly used in the intralesional treatment of keloids. In this work, polymeric microspheres loaded with betamethasone disodium phosphate were fabricated to design a sustained-release system. A validated HPLC technique for determination of betamethasone disodium phosphate in in vitro media of the polymeric microspheres has been developed. The operation conditions were optimized. The analytical column was ZORBAX® Bonus-RP column with 4.6×150 mm ID and a particle size of 5 μm. The mobile phase consisted of acetonitrile-0.01% phosphoric acid water solution (40:60, v/v). The flow rate was 1.0 ml/min and injection volume was 50 μl. The elutes were detected at 240 nm. Linearity, repeatability, inter- and intra-assay precision and accuracy of the method were evaluated. The liner range was obtained in a concentrated range of 20-1000 μg/ml, with a coefficient of correlation r=0.999978. The limit of detection for betamethasone disodium phosphate in the in vitro test samples was 0.25 μg. Recovery of betamethasone disodium phosphate from the in vitro test samples was 99.7±5.2% (mean±SD). Stability of betamethasone disodium phosphate at different pH values and temperatures were also investigated.