Liver concentrations of clenbuterol, a β2-adrenergic agonist, were measured by enzyme-linked immunosorbent assay (ELISA) in 12 female pigs on days 0, 7, 14 and 21 after prolonged administration of a growth-promoting dose of clenbuterol. The analytical procedure showed good recovery (>80 %), while intra-assay results showed acceptable variation in individual measurements for all samples to which 0.5, 2 or 5 ng/g clenbuterol were added (RSD <10 %). The assay detection limit was 0.13 ng/g and

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... ification limit 0.16 ng/g. The results indicated that >80 % clenbuterol depletion in pig liver occurred during the first 7 days after cessation of administration, however, more than 14 days were required for the clenbuterol concentration to fall below the maximal residual level of 0.5 ng/g. On day 21 of clenbuterol discontinuation, residues of the drug were detectable in pig liver (0.22 ng/g), suggesting that clenbuterol residues persist in liver as an edible tissue and may induce a risk for consumer health.