Determination of clenbuterol residues in bovine urine by optical immunobiosensor assay

Clenbuterol (CBL) is an orally active beta (2)-adrenoceptor agonist which h as been used in veterinary medicine as a broncodilator and an agent of uter ine relaxation. It has however become better known as a drug used illegally to promote growth in farm animals. A rapid and sensitive biosensor assay w as developed to detect CBL residues in bovine urine. The method involved a simple extraction procedure using tert-butyl methyl ether followed by analy sis on the biosensor with results obtained against a buffer calibration cur ve. The assay allowed up to 88 samples to be analyzed per working day, with each cycle on the biosensor taking approximately 7 min to complete. The li mit of detection (LOD) was determined as 0.27 ng/mL using 20 EU reference b lank urine samples. The intra-assay Sr ranged from 4.7-7.6% for 3 control s amples while the interassay S-r ranged from 9.2-12.7%. The recovery was fou nd to be approximately 95%. A series of incurred urine samples were assayed and the results compared by Enzyme immunoassay (EIA), radio-immunoassay (R IA), and gas chromatography/mass spectrometry (GC/MS) analysis. Urine sampl es taken from local abattoirs were also analyzed by the biosensor method an d by EIA analysis. The antibody used in the biosensor test exhibited high c ross reactivity with at least 7 other beta -agonists allowing detection of these compounds at less than 1 ng/mL in bovine urine.