Determination of carazolol residues in porcine tissue by radioreceptor assay Original Research Article

A radioreceptor assay was developed for the determination of the β-blocker carazolol in porcine muscle and kidney. The method involves a simple alkaline extraction procedure using diethyl ether followed by a competitive assay between carazolol residues and [3H]-dihydroalprenolol ([3H]-DHA) using solubilised β2-adrenoceptors isolated from a transfected cell line. The limit of detection (LOD) was determined using 20 reference blank samples of pig kidney and pig muscle. LODs for muscle (0.93 μg kg−1) and kidney (1.47 μg kg−1) were well below their respective European community maximum residue limits, (MRLs 5 and 25 μg kg−1, respectively). The assay was used to investigate if carazolol residues persisted in pig tissues for up to 30 h post-intramuscular injection at the recommended dose rate (10 μg carazolol/kg body weight). The highest mean±S.D. concentrations were detected at 1 h post-injection in kidney (10.84±1.3 μg kg−1) and muscle (3.59±0.2 μg kg−1) which were less than the respective MRLs. It is concluded that this method offers a robust and rapid alternative to other methods for the screening of carazolol residues in pig meat.