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). (C) 2013 Elsevier B.V. All rights reserved.1310133137FinPharma Doctoral Program (FPDP)Magnus Ehrnrooth Foundation [ke2011n1]Academy of Finland [251575, 257685]Magnus Ehrnrooth Foundation [ke2011n1]Academy of Finland [251575, 257685]