Determination of aflatoxins B1, B2, G1, and G2 in foodstuffs

Formed by the metabolism of the mold fungi Aspergillus flavus and parasiticus, aflatoxins are carcinogenic and waken the immune system. The most important naturally occurring aflatoxins are B1, B2, G1, and G2 . Of this the commonest and most potent is aflatoxin B1 . The limit concentrations to be monitored in spices, for example, are 5ppb for aflatoxin B1 and 5ppb for the sum of aflatoxins B2, G1, and G2 . In nuts the limits are 1ppm for B1 and 5ppb for the sum of aflatoxins B2, G1, and G2 .
The mycotoxins are isolated from the matrix by liquid/liquid extraction. In the case of critical matrices, a solid phase extraction step is employed. They are chromatographed on silica gel, simultaneously eluted matrix being first removed by prechromatography with diethyl ether, after which the mycotoxins are separated with chloroform – acetone – water. Densitometric evaluation is performed by fluorescence measurement at 366/>400 nm. Positive results can be confirmed by additional prechromatographic derivatization.