Anabolic androgenic steroids (AASs) are the most commonly detected prohibited substances in anti-doping testing. Despite the number of positive test results for anabolic steroids, current methodology, even with lengthy chromatographic separation, is unable to detect all AAS compounds, in part due to the large number exogenous AASs that are isomeric with endogenous steroids. However, the integration of ion mobility (IM) with liquid chromatography-mass spectrometry (LC-MS) testing protocols can improve the resolution of isomeric species without lengthening the required data acquisition time.<br/>Ion mobility-mass spectrometry (IM-MS) analysis of isomeric steroids reveals that under electrospray conditions sodiated dimer adducts of some isomeric steroids separate by ion mobility with baseline resolution. This separation is further improved by the addition of alternative metal cations, such as group I, group II, and transition metal cations. For example, the zinc dimer adducts of 1-testosterone and 5β-androst-1-en-17β-ol-3-one, whose sodiated dimers do not separate, are nearly baseline resolved.<br/>In this study, IM was integrated with an existing LC-MS method; due to the rapid timescale of ion mobility separation, analysis time including chromatography was reduced to as little as four minutes. However, some steroid isomers were not resolved using this combined liquid chromatography-ion mobility-mass spectrometry (LC-IM-MS) method. Alternative cation (AC) steroid dimer adducts were observed when ACs were directly added to both LC mobile phases, and as expected enhanced mobility separation was observed for some isomeric steroids. This improved mobility separation also revealed previously obscured drift peaks, which arise from isomeric heterodimers. Finally, this study has examined the potential effects of isomeric heterodimerization on LC-IM-MS analysis of isomeric AASs.

Liquid chromatography-ion mobility-mass spectrometry for the improved analysis of isomeric anabolic androgenic steroids

2019 Spring National Meeting

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