IMPROVEMENT OF CHEMICAL-ANALYSIS OF ANTIBIOTICS .21. SIMULTANEOUS DETERMINATION OF 3 POLYETHER ANTIBIOTICS IN FEEDS USING HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH FLUORESCENCE DETECTION

A simultaneous determination of three polyether antibiotics (PEs), salinomycin, monensin, and lasalocid, in feeds has been established by high-performance liquid chromatography with a precolumn reaction system using 1-(bromoacetyl)pyrene as a fluorescence reagent. PEs were extracted from feeds with acetonitrile and cleaned up using prepacked silica gel cartridges to eliminate coexisting materials such as fatty acids. An addition of triethylamine into the reaction solution was essential to derivatize efficiently. The separation was performed on Develosil 5 C-18 (5 mu m, 250 X 4.6 mm) with methanol/water (97:3) as a mobile phase, and the separated PEs were detected at lambda(x) 360 nm and lambda(m) 420 nm. The internal standard, 18,19-dihydrosalinomycin, was effective for the simultaneous determination of PEs, and the recoveries of PEs from various feeds fortified at levels from 25 to 100 ppm were 95-100%.