Separation of steroid isomers by ion mobility mass spectrometry

• We report a reliable, fast and repeatable method to separate steroid isomers.
• We compare two different drift gases in order to achieve optimum separation.
• Different drift gas pressures were studied for optimum separation.
• The separation efficiencies of the steroid isomers are increased by derivatization.

Ion mobility mass spectrometry performed in a compact traveling wave cell (TWIM-MS) is shown to provide a reliable, fast and repeatable method to separate derivatized steroid isomers. Three steroid isomer pairs were analyzed in their native form and as their p-toluenesulfonyl isocyanate derivatives. The native steroids were separated from each other, but no separation could be attained for the isomers. The derivatized steroid isomers were, however, properly separated by TWIM-MS with peak-to-peak resolutions close to or as high as baseline resolution (Rp − p = 0.77–1.08).