2.4. Extraction and clean-up
The method as described by Akiyama and co-workers was used with minor modifications (Akiyama, Chen, Miyahara, Toyoda, &Saito, 1996). A 20 g of sample was extracted with 80 mL acetonitrile:
water (9:1) mixture for 30 min by shaking under high speed,and then filtering using a No. 4 Whatman filter paper. A 1-mL portion of the filtrate was loaded on the MFC and passed through at a flow rate of 2 mL min1 (the column had previously been preconditioned with 5 mL methanol and 5 mL acetonitrile:water (9:1)).Next, 1 mL of acetonitrile:water (9:1) was applied to the column
to ensure all the aflatoxins are collected. This step was repeated five times and the filtrates were combined and evaporated to dryness under nitrogen in amber bottles (5 mL capacity) and the residue was used for the derivatisation.