Carbon isotope mass spectrometry in doping control

A procedure that makes it possible to establish the origin of endogenous steroids present in human urine by the determination of the ¹³C/¹²C carbon isotope ratio is described. A combination of solid-phase and liquid-liquid extraction, as well as semipreparative liquid chromatography, was used to separate fractions containing testosterone, 5α- and 5β-androstane-3α, 17β-diols, androsterone, ethiocholanolone, 5β-pregnane-3α, 20S-diol, and 16(5α)-androstene-3α-ol. More than 100 samples were analyzed by gas chromatography coupled with isotope mass spectrometry. The resulting values of ¹³C/¹²C were statistically processed, and the ranges required for the interpretation of the results were found. The procedure was certified and accredited in accordance with ISO 17025 requirements.