Session: Advances in Mass Spectrometry:

Mass-Spectrometry-based methods have become the gold standard for quantification of prohibited anabolic steroids. However, despite the advantages of high resolution and tandem MS, definitive identification of potentially novel, or ‘designer’, compounds remain challenging due to their structural similarity to other steroids and low concentrations. Our group has recently investigated selective reactions that can potentially provide more structural information about steroids. One promising example is the Paternò-Büchi (PB) reaction, a photochemical reaction where a radical carbonyl compound (formed by exposure to UV radiation) attacks a C=C double bond to form an oxetane ring derived from cycloaddition. This reaction is commonly used with tandem mass spectrometry to locate the C=C double bond in unsaturated lipids. During this research, we initially investigate the use of the Paternò-Büchi reaction with the simplest carbonyl, acetone, for the separation of steroid isomers using ion mobility-mass spectrometry (IM-MS). This research focuses on isomers of both endogenous steroids and anabolic androgenic steroids prohibited by the World Anti-Doping Agency (WADA). One important isomer pair is testosterone/epitestosterone, which displays nearly identical MS/MS fragmentation pattern and collision cross section (CCS). However, after undergoing the PB reaction (at nearly 50% efficiency) testosterone adopts a new CCS of 205.3 Å², while epitestosterone presents three unique drift peaks at CCS of 181.9, 190.4, and 202.2 Å². Several endogenous pairs, including aldosterone/cortisone and 17-hydroxyprogesterone/21-hydroxyprogesterone, were also shown to demonstrate unique ion mobility fingerprint patterns. Studies are currently underway to investigate the patterns observed for PB reaction products of over two dozen other WADA-prohibited anabolic steroids. Additionally, we will also investigate the use of other carbonyl compounds (e.g., butanone, pentanone, etc.). The overall goal of the research is to gain more confidence in the identification and resolution of steroid isomers in a variety of applications.

Christopher Chouinard

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