The residues which showed the presence of aflatoxins were further purified using a silica gel G-60 mini column (15 cm height, 0•5 cm internal diameter) and 100 μl of CHCl3. The column was washed successively three times with 1•5 ml of (i) n-hexane, (ii) diethyl ether (iii) CHCl3 : methanol (97 : 3). The last three fractions were collected, combined and evaporated at 40°C using a rotary evaporator. The residues were saved for high performance liquid chromatography (HPLC).