Rapid Quantitation and Confirmation of Aflatoxins in Corn and Peanut Butter, Using a Disposable Silica Gel Column, Thin Layer Chromatography, and Gas Chromatography/Mass Spectrometry

Abstract

Abstract Asimple, rapid, and solvent-efficient method for determining aflatoxins in corn and peanut butter is described. Aflatoxins B1, B2, G1, and G2 were extracted from SO g sample with 200 mL methanol-water (85 + 15). A portion of the extract was diluted with 10% NaCl solution to a final concentration of 50% methanol, and then defatted with hexane. The aflatoxins were partitioned into chloroform. The chloroform solution was evaporated, and the residue was placed on a 0.5 g disposable silica gel column. The column was washed with 3 mL each of hexane, ethyl ether, and methylene chloride. Aflatoxins were eluted with 6 mL chloroform-acetone (9 + 1). The solvent was removed by evaporation on a steam bath, and the aflatoxins were determined using thin layer chromatography (TLC) with silica gel plates and a chloroform-acetone (9 + 1) developing solvent. Overall average recovery of aflatoxin B] from corn was 82%, and the limit of determination was 2 ng/g. For mass spectrometric (MS) confirmation, aflatoxin B1, in the extract from 3 g sample (20 ng/g) was purified by TLC and applied by direct oncolumn injection at 40°C into a 6 m fused silica capillary gas chromatographic column. The column was connected directly to the ion source. After injection, the temperature was rapidly raised to 250¯C, and the purified extract was analyzed by negative ion chemical ionization MS.