PROFILING 19-NORSTEROIDS .2. TANDEM MASS-SPECTROMETRIC CHARACTERIZATION OF THE HEPTAFLUOROBUTYRYL ESTER AND PENTAFLUOROBENZYLOXIME HEPTAFLUOROBUTYRYL ESTER DERIVATIVES OF 19-NORANDROSTERONE USING COLLISIONLY ACTIVATED DISSOCIATION

Tandem mass spectrometric methods for the identification of 19-norandrosterone (3 alpha-hydroxy-5 alpha-estran-17-one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxine heptafluorobutyryl (PFBO-HFB) ester derivatives of 19-norandrosterone (3 alpha-hydroxy-5 alpha-estran-17-one) in particular were studied for the purpose to select characteristic ions. The HFB ester was analyzed by collisionly activated dissociation (CAD) following electron impact in order to fragment the steroid nucleus, The formation of D-ring fragments, i.e. the ring containing the keto function, was typical for this type of derivative, Cleavages of fragments with an intact D-ring were also prominent, The PFBO-HFB ester was formed to create a derivative, which could capture electrons and be analyzed in the Electron Capture Negative Chemical Ionization (ECNCI) mode. Besides fragmentations originating in the groups coupled to the steroid by derivatization, also characteristic D-ring fragments were observed by CAD following ECNCI. Accordingly, of both methods evaluated only CAD following EI of the HFB derivative of 19-norandrosterone provided a characteristic MS/MS procedure for the identification of 19-norandrosterone under the conditions studied.