Rapid liquid chromatographic determination of aflatoxins in heavily contaminated corn

A procedure is described for rapid, quantitative determination of aflatoxins B1, B2, G1, and G2 in heavily contaminated corn (greater than 500 micrograms B1/kg) from field, greenhouse, and growth chamber experiments employing artificial inoculation of corn with Aspergillus flavus. Whole kernel corn is ground to pass a 1 mm screen and mixed before extraction of a water-wetted (25 mL) 50 g subsample with 250 mL chloroform. The filtered extract is diluted 1:1 with hexane and applied to a hexane-wetted (10 mL) disposable silica cartridge. Interferences are removed with chloroform-hexane (1 + 3), and aflatoxins are quantitatively eluted with hexane-acetone (1 + 1). Aflatoxins B1 and G1 are converted to the more intensely fluorescent hemiacetals, B2a and G2a, by treatment with trifluoroacetic acid-water. Derivatized aflatoxins are separated by reverse phase liquid chromatography (LC) and quantitated fluorometrically. Compared with AOAC method I (CB) for corn, using samples containing approximately 50 and 10 000 micrograms B1/kg, agreement between methods was good at the lower level while the rapid method yielded a considerably larger mean at the higher level. A precision study of 30 replicate samples produced a coefficient of variation of 8.46% at a mean value of 1066 micrograms B1/kg. The cartridge method was developed for LC analysis of samples that contain greater than 500 micrograms aflatoxin B1/kg corn, but it may be used to quantitate as little as 10 micrograms B1/kg with no modification.