Quantification and enantiomeric distribution of clenbuterol in several bovine tissues using UHPLC-tandem mass spectrometry: Evaluation of a risk factor associated with meat contamination.

Clenbuterol (Clb) (4-amino-α-[(tert-butylamine) methyl]-3,5-dichlorobenzyl alcohol) is a sympathomimetic agent that exhibits β2-agonist activity. It is applied as a bronchodilatory, tocolytic, and mucolytic agent and is authorized for clinical management in both human and veterinary therapeutics as a racemic mixture. However, its use is strictly prohibited in animals destined for food production in countries in the European Union and in the United States and Mexico, among many others. The R-(-) enantiomer in clenbuterol stimulates β2-receptors, whereas the S-(+) enantiomer blocks the effect of β1-receptors. The aims of this study were to develop a method for detecting and quantifying Clb and its enantiomeric distribution in several bovine tissues. The UHPLC-MS/MS method developed to quantify the target compound at trace levels in these tissues combines high sensitivity with good selectivity and short chromatographic run time. The tissue samples tested were found to contain racemic Clb in concentrations of 5-447 pg g . The enantiomeric analysis of Clb showed that R-(-)-Clb is present at higher concentrations in some tissues, whereas S-(+)-Clb was detected in a ratio of 55/45 in the liver and heart tissues.