Screening method for the detection of aflatoxins in mixed feeds and other agricultural commodities with subsequent confirmation and quantitative measurement of aflatoxins in positive samples.

The method described will detect total aflatoxins (B1, B2, G1, and G2) in mixed feeds, grains nuts, and fruit products in samples containing as little as 5-15 mug/kg. In addition, the presence of aflatoxins in the positive samples can be confirmed and the toxins can be quantitatively measured, using the same extract as that used for the screening method. In the screening method, aflatoxins are extracted with acetone-water (85+15), and interferences are removed by adding cupric carbonate and ferric chloride gel. The aflatoxins are extracted from the aqueous phase with chloroform and the chloroform extract is washed with a basic aqueous solution. A Velasco-type minicolumn is used to further purify the extract and capture the aflatoxins in a tight band. The screening method has been successfully applied to 24 different agricultural commodities. Quantitative thin layer chromatography was also performed with extracts of each of these commodities. An average recovery of 94% B1, 108% B2, 130% G1, and 103% G2 was obtained compared to the official final action AOAC method for cottonseed products, 26.048-26.056. Within-laboratory coefficients of variation of 10-15% were obtained for each of the aflatoxins and total aflatoxins in a sample of peanut meal naturally contaminated with 11 mug B1+3 mug B2+11 mug G1+5 mug G2/kg.