ANALYSIS OF STEROIDS .43. ESTIMATION OF IMPURITY PROFILES OF DRUGS AND RELATED MATERIALS .8. COMBINED APPLICATION OF HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY AND NMR-SPECTROSCOPY IN THE IMPURITY PROFILING OF DRUGS

The usefulness of the joint application of HPLC and NMR spectroscopy in drug impurity profiling is demonstrated by the following examples: (1) identification of Z and E isomers of 17-alpha-ethynyl-4-oestrene-3-beta,17-diol-3-acetate-17-(3'-acetoxy-2'-butenoate) in ethynodiol diacetate; (2) identification of the p-tolyl analogue as the impurity of enalapril maleate; (3) identification and quantification of 2'-dehydro-pipecuronium bromide in pipecuronium bromide. The possibilities of utilizing NMR spectroscopy for the identification and quantification of the impurities with and without their isolation are discussed.