Quantification of aflatoxins in organic corn grains by a pre-column derivatization HPLC-FLD method

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Aflatoxins (B1, B2, G1 and G2) are the secondary metabolites of pathogenic molds, Apergillus flavus and Apergillus parasiticus and they are classified as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC). Among these toxins, Aflatoxin B1 (AFB1) is the most toxic and widely present in cereal grains, peanuts, tree nuts and other oil seeds. Accurate determination of aflatoxin content is extremely important to the trade of cereals and safety of human food and animal feed. Due to the ban of most fungicide in organic farming, organic cereal grains may contain higher aflatoxins than conventional cereal grains. The objective of this study was to optimize the extraction and purification procedures for the HPLC quantification of aflatoxins in organic corn grains. The ground corn grains (25g each) was extracted with 100 ml of 80% methanol, 70% methanol with and without 4% NaCl, separately. The extracts were purified with Florosil SPE column conditioned with methanol, acetonitrile and the mixture of methanol and hexane (1:1), separately followed by elution with the mixture of acetone/DI water/formic acid (96:3.7:0.3) at different solvent to sample ratios. After purification, the elutes were dried under nitrogen flush, reconstituted in 40% acetonitrile, and then derivatized with triflouroacetic acid for HPLC analysis. The results indicate that 80% methanol was the best for extraction solvents which resulted in clean peaks of all aflatoxins; 100% methanol was the best conditioning solution for SPE column, and the elution solvent to sample ratio of 6:5 (v/v) gave highest recovery. Under the optimized the extraction and purification condition, the recoveries of aflatoxin B1, B2, G1 and G2 from ground organic corn grains were 96.01%, 89.04%, 85.09% and 85.01%, respectively.