International mycotoxin check sample program: Part II. Report on laboratory performance for determination of aflatoxin M1 in milk.

A sample of aflatoxin M1-contaminated lyophilized cow's milk was analyzed by 80 laboratories in 30 countries. Sufficient data were obtained to permit a statistical comparison of the performance of laboratories using AOAC methods I and II and those using high performance liquid chromatography for quantitation. A significant difference was noted between means for laboratories using AOAC method I as opposed to those using HPLC methods. Overall reproducibility (between- plus within-laboratory precision) was best for laboratories using HPLC methods and poorest for those using AOAC method II.