Use of immunoaffinity chromatography as a purification step for the determination of aflatoxin M1 in cheeses.

A method using immunoaffinity as a purification step for the determination of aflatoxin M1 in cheese is described. A simple solvent extraction with dichloromethane followed by a washing step with N-hexane gives a prepurified extract. A comparison between two ways of aflatoxin M1 purification, by solid-phase extraction clean-up and by immunoaffinity, was carried out. The use of immunoaffinity columns containing monoclonal antibodies against aflatoxin M1 gives the best result, i.e. a very clean preparation containing purified aflatoxin M1. The quantification of aflatoxin M1 is then performed by high performance liquid chromatography using fluorometric detection. This method was successfully carried out on naturally-contaminated and spiked cheeses. Recoveries are about 75%. The limit of quantification is 0.020 microgram of aflatoxin M1 per kg of cheese. This method seems suitable for use in monitoring programmes for aflatoxin M1 contamination in dairy products such as cheese.