Determination of clenbuterol residues in bovine hair by using diphasic dialysis and gas chromatography–mass spectrometry

A method for the determination of clenbuterol (4-amino-3,5-dichloro-α(tert.-butylamino)methyl]-benzyl alcohol hydrochloride) in hair of living cows has been developed. Hair samples were digested in an alkaline medium. The diphasic dialysis technique is a semi-permeable membrane technology developed for the direct extraction of relatively low-molecular-mass analytes such as clenbuterol. In this case, we used sodium citrate buffer to homogenize the digested hair, dichloromethane was used as the extraction solvent at 37°C, and stirring was applied at 150 rpm for 4 h. The analysis was carried out using gas chromatography–mass spectrometry. The calibration curve for clenbuterol in hair was linear in the range from 12.5 to 400 ng g⁻¹. The detection limit of clenbuterol was 5 ng g⁻¹ and the quantification limit was 12.5 ng g⁻¹, in hair. A good inter-day reproducibility was obtained (R.S.D.=7.08%). The repeatability and intra-day reproducibility (50 ng g⁻¹ of hair, n=10) show R.S.D.s of 7.1 and 9.5%, respectively.