This International Standard specifies a high-performance liquid chromatographic (HPLC) method for the determination of aflatoxin B1 content of animal feeding stuffs including those containing citrus pulp. The lower limit of determination is 1 μg/kg. NOTE 1 This International Standard may be applicable for the determination of the aflatoxin B1 content of a number of raw materials and straight feeding stuffs such as corn gluten, groundnut, palm kernel, copra, citrus pulp, tapioca, soya bean, rice bran, pollard, rape seed, niger seed and cotton seed (see references [1] and [2]). These materials were, however, not included in the collaborative testing of the method. NOTE 2 This International Standard may also be applicable for the determination of the content of the sum of the aflatoxins B1, B2, G1 and G2. However, the method has not been validated for this parameter by collaborative testing.