Liquid chromatographic method for fumonisin B1in sorghum syrup and corn-based breakfast cereals

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Abstract
The fungus Fusarium verticillioides has been found on corn and sorghum, so it is possible that one or more of these toxins may be found in corn products such as breakfast cereals and syrup prepared from sorghum. Published methods when applied to syrups spiked with fumonisins gave low recoveries, less than 50%. A method was therefore developed which would be applicable to the syrup and breakfast cereals as well. Test samples were extracted with methanol-0.1M sodium phosphate buffer (pH3) (1 + 1). The extract was diluted with water and applied to a 1g C18 column. The column was washed with acetonitrile-water (2 + 8). Fumonisin B1 (FB1) was eluted with acetonitrile- trifluoroacetic acid (1000 + 1). The purified extract was evaporated and the toxin was derivatized with ophthaldialdehyde mercaptoethanol. The reaction mixture was resolved on a C18 liquid chromatographic column using acetonitrile-water-acetic acid (500 + 550 + 10.5) as the mobile phase at 37oC, and FB1 measured with a fluorescence detector (excitation 335nm, emission 440nm). Recoveries of FB1 added to samples of sorghum syrup at levels ranging from 0.1 to 1.0 mu g/g were 94-132%. Recoveries of FB1 added to samples of breakfast cereal (corn flakes) at levels ranging from 0.2 to 1.6 mu g/g were 96-100%. The method was applied to the analysis of 35 samples of sorghum syrup collected from 15 states in the US. One sample was found to contain FB1 at 0.12 mu g/g. A total of 32 samples of breakfast cereals collected by the Food and Drug Administration inspectors from grocery stores around the Kansas City area were analysed; no FB1 was found in the breakfast cereals (< 0.01 mu g/g). Results of this study indicated that FB1 possibly is not a problem in sorghum syrup and corn-based breakfast cereals in the US.