Liquid Chromatographic Determination of Fumonisins with 4-Fluoro-7-nitrobenzofurazan

Abstract

Abstract Fumonisins B1 and B2 are closely related mycotoxins produced by Fusarium moniliforme, F. proliferatum, and related species. Disadvantages of 2 fluorescence derivatizing reagents currently used for liquid chromatography (LC) are instability of the derivatives (with o-phthaldialdehyde-mercaptoethanol) and formation of 2 peaks (with fluorescamine). 4-Fluoro-7-nitrobenzofurazan (4-fluoro-7- nitrobenz-2-oxa-1,3-diazole; NBD-F) was, therefore, investigated. Although a larger molar excess of this reagent is required for fumonisins than for amino acids, the derivatives formed are moderately stable, and as little as 1 ng fumonisins B1 or B2 can be detected, with a linear response up to at least 50 ng injected. Reversed-phase LC (C18 column) was carried out with a mobile phase of methanol- 0.05M sodium dihydrogen phosphate adjusted to pH 5 (1 -1-1), which was mixed with an equal volume of acetonitrile-water (8 + 2) after 5 min. Using a modification of a strong anion exchange cleanup procedure, good recoveries (averages of 94 and 80%, respectively) of fumonisins B1 and B2 from ground corn, corn meal, and corn flakes in the 125̶ 5000 ng/g range were generally obtained; the limit of detection of the overall method was about100 ng/g. Similar results were obtained in studies with ground corn, corn meal, and corn flakes using naphthalene-2,3-dicarboxaldehyde-potassium cyanide (NDA-KCN) for derivatization; average recoveries of fumonisins B1 and B2 were 94 and 83%, respectively.