External contamination of bovine hair with β2-agonist compounds: evaluation of decontamination strategies

Hair analysis has shown great potential in the control of illegal use of veterinary drugs such as β2-agonists. However, it has been shown that hair can be externally contaminated with drugs which can lead to false positive results. Exposure of bovine hair to aqueous solutions of β2-agonist compounds results in incorporation of these drugs into the hair. Standard hair washing procedures found in the literature: detergent (Tween-20), phosphate buffer or organic solvents (dichloromethane or methanol) cannot eliminate this external contamination. β2-Agonists can be extracted from hair very efficiently with 0.1 M HCl, the extraction kinetics of externally and endogenously accumulated clenbuterol at room temperature are different which makes it feasible to discriminate between them. Treatment of hair samples with a 0.1 M HCl solution for 2 h at room temperature results in a ratio of clenbuterol content in the wash solution to clenbuterol content in the washed hair equal to or less than 0.25 for samples from treated cattle; whereas this ratio is equal to or higher than 0.70 for externally contaminated samples. The design of the study was intended to resemble the plausible scenario of hair being sampled a short time after external contamination. A similar study to detect external contamination for hair sampled a long time after exposure is in progress.