highperformance liquid chromatographic separation and identification of epimeric 17ketone impurities in commercial sample of dexamethasone sodium phosphate 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 betamethyl epimers of 9fluoro11 betahydroxy16methylandrosta14diene317dione highperformance 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 9fluoro11 betahydroxy16 alphamethylandrosta14diene317dione the second peak was identified as the 16 betaepimer by epimerization of the synthesized alphacomponent 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