Dexamethasone and clenbuterol detection by enzyme immunoassay in bovine liver tissue: A new multiresidue extraction procedure

A fast and simple extraction procedure was developed for simultaneous deter mination in bovine liver of two veterinary dress, widely used as growth pro moters in meat production: dexamethasone (a synthetic corticosteroid drug) and clenbuterol (a beta(2)-adrenergic agonist drug). Liver samples were ext racted by acetonitrile, without any clean-up step. Two different ELISAs, sp ecific for the two classes of drugs, were used to determine the residue con centration in the extracts. The intra- and inter-extraction variability was determined at different concentrations: the intra-extraction coefficients of variation (CT's) were between 2.5 and 17.7% for dexamethasone and betwee n 0.9 and 9.8% for clenbuterol; the inter-extraction CVs were between 2.0 a nd 16.8% for dexamethasone and between 0.5 and 10.8% for clenbuterol. Recov ery ranged from 92 to 154% for dexamethasone and from 78 to 105% for clenbu terol. The limit of detection was 1.43 ng g(-1) and 0.43 ng g(-1) respectiv ely. The limit of quantification for dexamethasone was 2.09 ng g(-1) and fo r clenbuterol was 0.72 ng g(-1). The combination of the new extraction proc edure with an ELISA detection permitted the rapid semi quantitative determi nation of both dexamethasone at its maximum residue level (MRL: 2.5 ng g(-1 ) in liver tissue), and clenbuterol at low concentration level.