Residues of oxytetracycline and its 4'-epimer in edible tissues from turkeys.

Francesca Capolongo, Annalisa Santi, Luciana Tomasi, Paola Anfossi, Mauro Missagia, Clara Montesissa

Index: J. AOAC Int. 85(1) , 8-14, (2002)

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Abstract

Residues of oxytetracycline (OTC) in edible tissues (muscle, liver, and kidney) of 18 turkeys were determined after continuous administration of the drug for 3 days in drinking water at the maximum recommended concentration of 400 mg/L. The European Union (EU) maximum residue limits (MRLs) set for OTC are 100 microg/kg in muscle tissues, 300 microg/kg in liver, and 600 microg/kg in kidney, as the sum of the parent compound and its derivative 4'-epi-oxytetracycline (4-epi-OTC). Cleanup of tissue samples was performed by metal chelate affinity chromatography (MCAC), but the original technique was miniaturized by the adoption of a mini solid-phase extraction column, allowing reduction of solvents, time, and hazardous waste. OTC and its 4'-epimer were quantitated by an isocratic liquid chromatography elution with UV detection. After 1 day of withdrawal, OTC plus 4-epi-OTC residues were greater than MRL values in muscle and liver; 3 days after the end of treatment, all tissue residues were far lower than the MRL values. At the first day after the end of treatment, 4-epi-OTC was detected at very low concentrations only in muscle, in liver after 1 and 3 days of withdrawal, and in kidney at all sampling times. The withdrawal time was calculated according to EU recommendations and was set at 5 days.