Collision-induced dissociation-mass-analysed ion kinetic energy (CID-MIKE) analysis of ions generated by fast atom bombardment of isomeric bile salts.

Molecular protonated ions and alkali attachment ions, generated by fast atom bombardment of isomeric bile salts, were analysed by collision-induced dissociation-mass-analysed ion kinetic energy (CID-MIKE) spectroscopy. Within each series of isomers, CID-MIKE spectra were similar, but showed subtle differences in the middle mass region. The most abundant ions were formed by fragmentation of the side chain. The positive charge was found to reside on the sulfonate or carboxylate moiety of the ionized salts and did not seem to migrate to other functional groups. Ions in the middle mass region were probably formed by fragmentation in the steroid ring system and therefore reflected structural differences of the bile conjugates. The usefulness of CID-MIKE spectroscopy in the structural analysis of isomeric materials was demonstrated.