RESUMO
A thin layer chromatography (TLC) method was developed for the detection of fumonisin B1 and B2 in corn and corn-based feedstuffs. Finely ground samples were extracted with acetonitrile:water (1:1), filtered, and applied to C18 cleanup columns. The columns were washed with 1% aqueous KCl followed by acetonitrile: 1% aqueous KCl (1:9), and the fumonisins were eluted with acetonitrile:water (7:3). The eluants were concentrated and spotted on reverse-phase C18 TLC plates along with fumonisin B1 and B2 standards, and the plates were developed in methanol: 4% aqueous KCl (3:2). The fumonisins were visualized by spraying the TLC plates successively with 0.1 M sodium borate buffer, fluorescamine, and 0.01 M boric acid. The plates were then dried and examined under longwave ultraviolet light. Fumonisin B1 and B2 appeared as bright yellowish-green fluorescent bands at Rfs of 0.5 and 0.1, respectively. The detection limit for the fumonisins on the TLC plate was 0.1 ppm in corn. Recoveries from spiked samples averaged greater than 80%. The identification of the fumonisins was confirmed by hydrolyzing the parent compounds of B1 and B2 to their respective C22 amino-alcohols and reexamining by TLC with the same visualizing reagents. This procedure was used to survey 193 corn samples collected from University of Missouri test plots in 1990 for fumonisin B1. Fumonisin B1 was detected in 15% of the corn samples.
