Clenbuterol - regional food contamination a possible source for inadvertent doping in sports

The misuse of the sympathomimetic and anabolic agent clenbuterol has been frequently reported in professional sport and in the livestock industry. In 2010, a team of athletes returned from competition in China and regular doping control samples were taken within the next two days. All urine samples contained low amounts (pg/ml) of clenbuterol, drawing the attention to a well‐known problem: the possibility of an unintended clenbuterol intake with food. A warning that Chinese meat is possibly contaminated with prohibited substances according to international anti‐doping regulations was also given by Chinese officials just before the Bejing Olympic Games in 2008. To investigate if clenbuterol can be found in human urine, a study was initiated comprising 28 volunteers collecting urine samples after their return from China. For the quantification of clenbuterol at a low pg/ml level, a very sensitive and specific isotope dilution liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) assay was developed using liquid/liquid re‐extraction for clean‐up with a limit of detection and quantification of 1 and 3 pg/ml, respectively. The method was validated demonstrating good precision (intra‐day: 2.9–5.5 %; inter‐day: 5.1–8.8%), accuracy (89.5–102.5%) and mean recovery (81.4%). Clenbuterol was detectable in 22 (79%) of the analyzed samples, indicating a general food contamination problem despite an official clenbuterol prohibition in China for livestock. Copyright © 2012 John Wiley & Sons, Ltd.