Chromatographic method for the determination of aflatoxin M1 in cheese, yogurt, and dairy beverages.

The aim of this work was to develop and validate a method to determine aflatoxin M1 (AFM1) in cheese, yogurt, and dairy beverages. The method consisted of aqueous methanol extraction, immunoaffinity column purification and isolation, RPLC separation, and fluorescence detection. The four types of cheese samples were classified according to moisture and fat content. The mean recoveries were 71% for cheese at spiked levels from 100 to 517 ng/kg, and 76% for yogurt and dairy beverages spiked at levels from 66 to 260 ng/kg. The mean RSDs were 5.9% for cheese, and 10% for yogurt and dairy beverages. The LOD was 3 ng/kg and the LOQ was 10 ng/kg for all test commodities. To test the applicability of the developed method, a small survey of the presence of AFM1 in cheese, yogurt, and dairy beverages purchased in Ribeirão Preto-SP, Brazil, was conducted. AFM1 was detected (> 3 ng/kg) in all samples. Twenty cheese samples (83%) were contaminated with AFM1 in the range of 13-304 ng/kg. In yogurt and dairy beverages, the contamination was lower (13-22 ng/kg) in five samples (42%). The results indicated that the method is adequate for the determination of AFM1 in these four types of cheese, as well as in yogurt and dairy beverages.