**3.2 Assay protocol for aflatoxins**

200 μL conjugate solution was pipetted into dilution wells. 100 μL of each standard or sample extract was added into the dilution wells. The mixture was mixed well and 100 μL of the mixture (conjugate and standard or samples) was transferred into antibody-coated wells. The plate was then incubated for 15 min with slow shaking and washed with distilled water for 5 times. The plate was then tap dried. 100 μL of substrate solution was pipetted into antibody coated wells. The plate was incubated with shaking for 5 min. 100 μL of stop solution was pipetted into antibody coated wells. The absorbance of each well was read at 450 nm with a differential filter at 630 nm. As the aflatoxin limit was (0–40) ppb but we found more than that which was diluted by dilution factor in three regions (Bogura, Nilphamari, Rangpur) by four times dilution.
