Application of Group I Metal Adduction to the Separation of Steroids by Traveling Wave Ion Mobility Spectrometry
Steroids represent an interesting class of small biomolecules due to their use as biomarkers and their status as scheduled drugs. Although the analysis of steroids is complicated by the potential for many isomers, ion mobility spectrometry (IMS) has previously shown promise for the rapid separation of steroid isomers. This work is aimed at the further development of IMS separation for the analysis of steroids. Here, traveling wave ion mobility spectrometry (TWIMS) was applied to the study of group I metal adducted steroids and their corresponding multimers for five sets of isomers. Each set of isomers had a minimum of one dimeric metal ion adduct that exhibited a resolution greater than one (i.e., approaching baseline resolution). Additionally, ion-neutral collision cross sections (CCSs) were measured using polyalanine as a calibrant, which may provide an additional metric contributing to analyte identification. Where possible, measured CCSs were compared to previously reported values. When measuring CCSs of steroid isomers using polyalanine as the calibrant, nitrogen CCS values were within 1.0% error for monomeric sodiated adducts and slightly higher for the dimeric sodiated adducts. Overall, TWIMS was found to successfully separate steroids as dimeric adducts of group I metals.
KeywordsSteroids Metal ion adduction Isomer discrimination Ion mobility spectrometry Collision cross section
This work was supported in part by funding from the National Science Foundation, Division of Chemistry, through the Chemical Measurement and Imaging Program (Award Number 1507989) and through the Research Experiences for Undergraduates Program (Award Number 1460829). Funding from the National Institutes of Health, National Institute of General Medical Sciences, was received through a fellowship to A.L.R. from the Molecular Mechanisms of Disease Predoctoral Training Program (Award Number T32GM107001). Finally, the authors thank Jessica L. Minnick and Katherine N. Schumacher for constructive comments on a draft of the manuscript.
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