Liquid Chromatographic Determination of Multiresidue Fluorescent Derivatives of Lonophore 1 Compounds, Monensin, Salinomycin, Narasin, and Lasalocid, in Beef Liver Tissue

Abstract

A liquid chromatographic (LC) method with fluorometric detection was developed to quantitatively determine residue levels of monensin, salinomycin, narasin, and lasalocid in beef liver tissue. The ionophores are extracted from the tissue, purified by both alumina and Sephadex LH-20 column chromatography, and then derivatized. Lasalocid was directly esterified with 9-anthryldiazomethane (ADAM), but monensin, salinomycin, and narasin were first acetylated with acetic anhydride and then esterified with ADAM. The ADAM derivatives were purified on a silica gel column and separated by LC using an RP C-8 5 micron column. A fluorescence detector set at 365 nm (excitation) and 418 nm (emission) was used to monitor the column effluent. The detection limits were 0.15 ppm, and the calibration curves were linear between 0.5 and 5.0 ppm for all 4 ionophores. Mean recoveries were 57, 70, 75, and 90% for lasalocid (5 ppm), monensin (2.5 ppm), salinomycin (2.5 ppm), and narasin (2.5 ppm), respectively. The ionophores were also separated and semiquantitated by using bioautography and thin layer chromatography with a vanillin spray.