EVALUATION OF A LIQUID-CHROMATOGRAPHIC METHOD FOR THE DETERMINATION OF FUMONISINS IN CORN, POULTRY FEED, AND FUSARIUM CULTURE MATERIAL

The performance of a liquid chromatographic method for determining fum onisins in corn, animal feeds, and culture material was evaluated. Eff iciencies of extractions with the following solvent systems were deter mined: acetonitrile-water (50 + 50, v/v), methanol-water (75 + 25, v/v ), and 100% water. The acetonitrile solvent gave both higher extractio n efficiencies and faster extraction times than the other 2 solvents. Extraction was followed by C-18 solid-phase extraction column cleanup. Fumonisin B-1 (FB1), fumonisin B-2 (FB2), and fumonisin B-3 (FB3) wer e measured by precolumn derivatization with o-phthalaldehyde followed by isocratic separation on a C-18 reversed-phase column with a mobile phase of 50 mM potassium dihydrogen phosphate (pH 3.3)-acetonitrile (6 0 + 40). Commercially prepared poultry feed, corn, and Fusarium spp. c orn cultures were analyzed at the following levels: FB1, 1.5 to 15 000 mu g/g; FB2, 0.5 to 4000 mu g/g; FB3, and 0.17 to 1 500 mu g/g. Recov eries were 91-94%, 90-100%, and 81-93% for FB1, FB2, and FB3, respecti vely. Precision (coefficient of variation) was determined with pooled field samples and ranged from 2% at 19 mu g/g for FB1 to 9% at 0.17 mu g/g for FE(3). Time and pH studies of the formation of the fluorescen t derivative and its stability were conducted. Complete reaction occur red at pHs above 7.9, with optimal pH for chromatography between 8.0 a nd 8.5. No statistically significant response differences were detecte d for reaction times ranging from 4 to 40 min; however, the detector s ignal was significantly reduced when reaction times were shorter than 4 min. Chromatograms of samples were free of interferences for all fee ds, corn, and culture material tested. Quantitation limits for the 3 f umonisins were of the same magnitude and were estimated to be 0.1 mu g /g for FB1 and 0.2 mu g/g for FB2 and FB3.