Direct analysis of steroid conjugates: the use of secondary ion mass spectrometry

Data are presented on the mass spectrometry of intact steroid conjugates. The principal technique used was secondary ion mass spectrometry (SIMS) using a Cs+ ion beam for ionization, although comparable data were obtained by fast atom bombardment (FAB) using a Xeo beam. In both techniques the samples were analyzed in a liquid matrix (glycerol). Positive and negative ion spectra have been obtained, the latter being most useful for steroid sulfate and glucuronide analysis. The negative ion spectra are dominated by a pseudomolecular ion at m/z [M-H]- (M of free acid) and the lack of marked fragmentation permits mixtures of steroids to be resolved in a single spectrum, providing they differ in mass. Preliminary data on the separate analysis of individual components from urine and plasma of patients with assorted disorders of steroid synthesis and metabolism are presented. This technique shows great promise for the clinical analysis of steroid conjugates without the need for enzymic hydrolysis or chromatographic separation of individual steroids.