Method for determination of aflatoxin M 1 in cheese and butter by HPLC using an immunoaffinity column

Abstract

A rapid, sensitive convenient method for determination of aflatoxin M1 (AFM1) in cheese and butter by HPLC was developed and validated. The method employs a safe extraction solution (mixture of acetonitrile, methanol and water) and an immunoaffinity column (IAC) for clean-up. Compared with the widely used method employing chloroform and a Florisil column, the IAC method has a short analytical time and there are no interference peaks. The limits of quantification (LOQ) of the IAC method were 0.12 and 0.14 μg/kg, while those of the Florisil column method were 0.47 and 0.23 μg/kg in cheese and buffer, respectively. The recovery and relative standard deviation (RSD) for cheese (spiked at 0.5 μg/kg) in the IAC method were 92% and 7%, respectively, while for the Florisil column method the corresponding values were 76% and 10%. The recovery and RSD for butter (spiked at 0.5ng/kg) in the IAC method were 97% and 9%, and those in the Florisil method were 74% and 9%, respectively. In the IAC method, the values of in-house precision (n = 2, day = 5) of cheese and butter (spiked at 0.5 μg/kg) were 9% and 13%, respectively. The IAC method is superior to the Florisil column method in terms of safety, ease of handling, sensitivity and reliability. A survey of AFM 1 contamination in imported cheese and butter in Japan was conducted by the IAC method. AFM 1 was not detected in 60 samples of cheese and 30 samples of butter.