DETERMINATION OF FLORFENICOL AMINE IN SWINE MUSCLE BY HYDROPHILIC INTERACTION LIQUID CHROMATOGRAPHY–TANDEM MASS SPECTROSCOPY

Abstract

Nuflor (florfenicol) Premix for Swine is approved by the U.S. Food and Drug Administration (FDA) and the same regulatory agencies from many other countries for control of swine respiratory disease. A simple and fast LC-MS/MS method for the assay of florfenicol amine, the marker residue of florfenicol in swine muscle is described. A 24-hr strong acid hydrolysis of tissue residues converts florfenicol and its known metabolites into florfenicol amine and also fully releases florfenicol amine from florfenicol residues covalently bound to the swine muscle. The majority of fatty acids and lipids are removed via hexane extraction. Then, the pH of the extracted hydrolysate is adjusted to 11 and florfenicol amine is extracted by ethyl acetate. A portion of ethyl acetate extract is dried under nitrogen and reconstituted with 1 mL acetonitrile. Dispersive solid-phase extraction is used for cleanup in which 100 mg primary secondary amine sorbent is mixed with the extract. After the centrifugation, the supernatant is diluted 20-fold for a hydrophilic interaction LC-MS/MS analysis. No matrix effect is observed in the LC-MS/MS assay and the recovery is nearly 100%. In the comparison with the current US FDA Center for Veterinary Medicine regulatory surveillance method, the new method is simple, fast, and accurate. The validated method is used to investigate the depletion of florfenicol from the swine administrated with Nuflor (florfenicol) Premix.