High pressure liquid chromatographic determination of aflatoxins in peanut products

A precise and sensitive high pressure liquid chromatographic method is proposed for determining aflatoxins B1, B2, G1, and G2 in all types of peanut products. The method is based on acidified aqueous methanol extraction, partition of aflatoxins into dichloromethane, and purification of the extract on a 2 g silica gel column. Aflatoxins in the purified extract are completely resolved on a microparticulate (10 micron) porous silica gel column in approximately 10 min with a water-saturated chloroform-cyclohexane-acetonitrile solvent. The preferred detection system, B1, and B2 by ultraviolet absorbance at 360-365 nm and G1 and G2 by fluorescence, allows accurate and sensitive detection of all 4 aflatoxins at levels as low as 0.3-1.0 microgram/kg. Repetitive assay of 3 samples of naturally contaminated peanut butters containing total aflatoxins (B1 + B2 + G1 + G2) at levels of 5, 10, and 15 microgram/kg gave within-laboratory coefficients of variation of 11, 5, and 5% respectively.