Gas chromatography/combustion/isotope ratio mass spectrometry to control the misuse of androgens in breeding animals:: new derivatisation method applied to testosterone metabolites and precursors in urine samples

A new derivatisation reaction applied to the analysis of steroids by gas chromatography/combustion/ isotope ratio mass spectrometry (GC/C/IRMS) was studied. The trimethylsilylated steroids were characterised by well-resolved chromatographic signals, no peak tailing, reproducible C-13/C-12 measurements (0.32 parts per thousand, n = 28), good signal-to-noise ratio and absolute intensity (5 x 10(-9) A, 20 ng), and a slow degradation of copper oxide pellets in the combustion furnace. In addition, two new metabolites and one precursor of testosterone in bovine have been brought into consideration and used for GC/C/IRMS measurements, namely, 3 beta -hydroxy-5 alpha -androstan-17-one (epiandrosterone), 3 beta ,17 alpha -dihydroxy-5 alpha -androstane, and 3 beta ,17 alpha -dihydroxy-5-androstene. The new findings have been applied to an elimination study in bovine of testosterone metabolites after an intramuscular injection of testosterone enanthate. Significant differences (up to 4 parts per thousand) between testosterone metabolites and precursor were detectable at least three weeks after administration. Copyright (C) 2001 John Wiley & Sons, Ltd.