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 x 150 mm ID and a particle size of 5 microm. 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 microl. 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 microg/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 microg. 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.