Detection of illegal clenbuterol use in calves using hair analysis. Application in meat quality control

This study describes a real-life situation involving nine calves, 106 days old, which received oral doses of clenbuterol administered through their milk. Powdered skim milk containing 6.7 mg of clenbuterol was given daily for fifteen days under supervision (i.e. 100 mg per calf for the whole study) to seven calves, and two calves did not receive the drug. Hair samples and urine were taken and subjected to analysis by gas chromatography-mass spectrometry. Hairs were pulverized in a ball mill and 100 mg were incubated in a mildly acidic medium. The sample clean-up procedure involved solid-phase extraction on C18 cartridges. Metoprolol was used as the internal standard for quantitation, after formation of methylboronate derivatives. The calibration curve for clenbuterol in hair was linear in the range 20-5000 pg/mg. The limit of detection of clenbuterol was 16 pg/mg in hair and 0.14 ng/ml in urine. Hair testing was effective after 7-10 days of treatment, and concentrations were in the range of 20 to 4372 pg/mg. Urinalysis can detect clenbuterol for up to two weeks after discontinuation of the drug. Conveniently, this is around the time when the hair samples attain greatest sensitivity. Therefore, the combination of the two matrices appears to be the method of choice for testing for the illegal use of drugs in meat-producing animals.