Development of a gas chromatographic-mass spectrometric method using multiple analytes for the confirmatory analysis of anabolic steroids in horse urine. I. Detection of testosterone phenylpropionate administrations to equine male castrates.

A gas chromatographic-mass spectrometric (GC-MS) method using three analytes to detect and confirm the administration to equine male castrates of veterinary pro-drugs based upon esters of testosterone is described. The method involves extraction of steroid conjugates from horse urine by C18-bonded cartridges and fractionation into glucuronic acid and sulpho-conjugates by Sephadex LH-20 column chromatography. After deconjugation, the free neutral steroids were partially purified by thin-layer chromatography and following derivatization (methyloxime-trimethylsilyl ether) were analysed by capillary GC-MS in the selected-ion or full-scan mode. Of the three analytes, 5 alpha-androstane-3 beta, 17 alpha-diol could be detected in the glucuronic acid fraction for about ten days and 5 alpha-androstane-3 beta,17 beta-diol and testosterone could be detected in the sulpho-conjugate fraction for up to nineteen days after administration of a single therapeutic dose (50 mg) of testosterone phenylpropionate to cross-bred and thoroughbred castrated male horses. The reasons for development of such a method, its validation and its potential for the detection of neutral metabolites of other veterinary anabolic steroids in horse urine are discussed.