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 beta(2)-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 beta(2)-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. beta(2)-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. (C) 2002 Elsevier Science B.V. All rights reserved.