Isolation and structural analysis by mass analysed ion kinetic energy spectroscopy of diverse sidechains from steroids of similar tetracyclic carbon skeletons.

The technique of mass analysed ion kinetic energy spectroscopy has been applied to the structural determination of five different substituent sidechains from five steroids of similar ring anatomy. A mass spectrometer of reversed geometry, which permits ion selection according to its mass-to-charge ratio before the ions enter the electric sector, was used to isolate the ion corresponding to the mass of each particular sidechain. Subsequent mass analysed ion kinetic energy spectra of the selected ion demonstrated daughter ions whose compositions were compatible with the structures of the model compounds. This ability to determine the structure of a specific portion of a large molecule and to permit differentiation of minor structural features in a series of compounds, whose major framework is similar, adds a new dimension to the powerful mass analysed ion kinetic energy spectroscopy technique for structural analysis of complex biological molecules.