This International Standard specifies a method for the determination of aflatoxin B1 in animal feeding stuffs using high-performance liquid chromatography with post-column derivatization. It is applicable to animal feeding stuffs with a fat content of up to 50 %. The limit of quantification of this method has been demonstrated to be better than 0,5 µg/kg for aflatoxin B1 for a signal-to-noise ratio of 6. NOTE The method is based on that given in Reference [1].