For samples outside the range of detection
(0e100 mg/kg and 0e300 mg/kg for peanut and maize products,
respectively) filtrate was further diluted 1:5 (10 ml dilute filtrate
and 40 ml de-ionized water) or 1:10 (5 ml dilute filtrate and 45 ml
de-ionized water). The column was washed with de-ionized water
twice and eluted into a borosilicate culture tube with 1.0 ml of
HPLC-grade methanol. To the eluate was added 1.0 ml of brominated
water, and the sample was vortexed. After 1.0 min, fluorescence
of the sample was read (Excitation: 360 nm, Emission:
440 nm)