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 fumonisins in corn, animal feeds, and culture material was evaluated. Efficiencies of extractions with the following solvent systems were determined: acetonitrile-water (50 + 50, v/v), methanol-water (75 + 25, v/v), and 100% water. The acetonitrile solvent gave both higher extraction 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) were 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 (60 + 40). Commercially prepared poultry feed, corn, and Fusarium spp. corn 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. Recoveries were 91-94%, 90-100%, and 81-93% for FB1, FB2, and FB3, respectively. 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 fluorescent derivative and its stability were conducted. Complete reaction occurred at pHs above 7.9, with optimal pH for chromatography between 8.0 and 8.5. No statistically significant response differences were detected for reaction times ranging from 4 to 40 min; however, the detector signal was significantly reduced when reaction times were shorter than 4 min. Chromatograms of samples were free of interferences for all feeds, corn, and culture material tested. Quantitation limits for the 3 fumonisins 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.