title: High-performance liquid chromatographic separation and identification of epimeric 17-ketone impurities in commercial sample of dexamethasone sodium phosphate.
abstract: A commercial sample of dexamethasone sodium phosphate solution for injection was found to contain 56% of the label concentration and to be extensively contaminated (approximately 50%) with a white insoluble solid, which was identified as a mixture of the 16 alpha- and 16 beta-methyl epimers of 9-fluoro-11 beta-hydroxy-16-methylandrosta-1,4-diene-3,17-dione. High-performance liquid chromatography (HPLC) was used to separate, identify, and quantitate these epimers and to determine their presence in commercial samples. One epimer was identified by HPLC comparison with a synthesized specimen of 9-fluoro-11 beta-hydroxy-16 alpha-methylan-drosta-1,4-diene-3,17-dione. The second peak was identified as the 16 beta-epimer by epimerization of the synthesized alpha-component with alkali to obtain a product whose chromatogram matched that of the impurity. These conclusions are supported by data obtained by IR and UV spectrophotometry, TLC, and the blue tetrazolium test.
mesh_terms: D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003907:Dexamethasone / Q000032:analysis*; D004340:Drug Contamination; D007536:Isomerism; D007659:Ketones / Q000032:analysis*; D008722:Methods
chemical_list: D007659:Ketones; D003907:Dexamethasone