Liquid Chromatographic Determination of Aflatoxin M1 in Milk Powder Using Immunoaffinity Columns for Cleanup: Interlaboratory Study

Abstract

A liquid chromatographic method for determining low aflatoxin M₁ concentrations in milk was evaluated in an International Dairy Federation (IDF) interlaboratory study. The study involved 16 participants from 11 countries. The method, chosen after a comparison of several methods by a preparatory group, uses an immunoaffinity column for cleanup. As the sample passes through the column, antibodies selectively bind with aflatoxin M₁ (antigen) present and form an antibody-antigen complex. All other components of the sample matrix are washed off the column with water. Then, aflatoxin M₁ is eluted from the column with acetonitrile, which is collected. Final determination is carried out by reversed-phase liquid chromatography with fluorescence detection. Over the tested range (80-600 ng aflatoxin M₁/kg milk powder), an RSDR ranging from 11 to 23% was obtained by analyzing 24 samples (blind duplicates), 2 samples of which were blanks.