Quantitative determination of Closantel residues in milk by high-performance liquid chromatography with fluorescence detection

A HPLC method with fluorescence detection for quantitative determination of Closantel residues in milk has been developed and validated. The proposed cleaning procedure with acetonitrile and acetone extraction, and solid-phas e clean-up with Florisil enables concentrations of Closantel below 50 mu g/ l to be determined. The method was shown to be sufficient, precise, accurat e, selective and rugged. The method was applied in the regular monitoring o f Closantel residues in milk and of the pharmacokinetic behavior of Closant el in sheep. (C) 1999 Elsevier Science B.V. All rights reserved.