Study examines accuracy of GC–combustion–isotope ratio MS doping control analysis
A team at the Olympic Athletic Center of Athens, Greece, has found that kinetic isotope effects do not bias doping control analysis results as originally suspected.
Researchers at the Doping Control Laboratory at the Olympic Athletic Center of Athens, based in Greece, have carried out a study to examine whether or not kinetic isotope effects impact the accuracy of results obtained from GC–combustion–isotope ratio MS doping control analysis.
In carrying out doping control analysis, endogenous androgenic anabolic steroids, and their metabolites, are commonly acetylated using acetic anhydride reagent, thereby incorporating exogenous carbon, which contributes to the measured isotope ratio. In order to compare the endogenous δ13C of free, mono-, and di-acetylated steroids, corrections must be performed, typically through the use of the mass balance equation.
The team, led by Yiannis Angelis, hypothesized that steroid structure may ensue in variation in the kinetic isotope effects (KIEs), causing fractionation of endogenous steroid carbon and consequently, inaccurate results.
To test if this was indeed the case, acetic anhydride of graded isotope ratio, within the natural abundance range, was used under normal derivatization conditions to test for linearity.
Results of the investigation demonstrated a linear relationship between the measured steroid acetate δ13C versus acetic anhydride δ13C and similar KIEs in all cases, following a regression analysis of the Δδ13C of enriched acetic anhydrides versus Δδ13C of derivatized steroids. The team concluded that the δ13C, calculated from the mass balance equation, is independent of the δ13C of the acetic anhydride reagent, and that net KIEs, under normal derivatization conditions, do not bias the final reported steroid δ13C.
The investigation was carried out in collaboration with the University of Athens (Greece), Cornell University (Ithaca, NY, USA) and the Anti-Doping Laboratory of Qatar (Doha, Qatar).
Source: Angelis YS, Kioussi MK, Kiousi P, Brenna JT, Georgakopoulos CG. Examination of the kinetic isotopic effect to the acetylation derivatization for the gas chromatographic-combustion-isotope ratio mass spectrometric doping control analysis of endogenous steroids. Drug Test. Anal. 4(12), 923–927 (2012).
