Simultaneous determination of aflatoxins B1, B2, G1 and G2 in commercial rices using immunoaffinity column clean-up and HPLC-MS/MS

Rice is frequently contaminated with aflatoxins, that are highly toxic fungal substances and strongly involved on hepatic cancer. In this work, different extraction and clean-up methods were evaluated for the simultaneous extraction and clean-up of aflatoxins B1, B2, G1 and G2 from rice. Favourable results were obtained by using methanol - water (80:20, v/v) extraction followed by immunoaffinity columns for clean-up, with recoveries of 86-92%, standard deviations between 5 and 11%, LOD ranged between 0.09 and 0.32 mu g/kg, and LOQ between 0.31 and 1.06 mu g/kg. Method validation and sample analysis were performed by using HPLC-MS/MS. Nine rice samples from different origin, varieties and specific characteristics, acquired in Spanish supermarkets were analysed. In two basmati samples from the same batch aflatoxin B1 was detected at (1.62 +/- 0.08) mu g/kg and (0.77 +/- 0.03) mu g/kg, both lower than the levels established by European Regulation for aflatoxin B1 in cereals.