Rapid Determination of Aflatoxin B₁ in Corn Meal by Light- Emitting Diode Excited Fluorescence Spectrometry after Pyridine Tribromide Derivatization

A light-emitting diode (LED) excited micro fluorescence spectrum detection device was constructed with LED as the excitation light source and optical fiber spectrometer as the detection equipment. Aflatoxin B₁ (AFB₁) could produce strong fluorescence signal after pyridine tribromide derivation, and a method for the rapid determination of AFB₁ in corn meal was proposed. The sample (5 g) was taken, and 25 mL of 80% (volume fraction) methanol solution and 1.0 g of sodium chloride powder were added. The mixture was extracted ultrasonically for 20 min and filtered, and an aliquot (5 mL) of the filtrate was taken and passed through C₁₈ cartridge. An aliquot (2 mL) was taken, and 1 mL of 200 mg·L^-1 pyridine tribromide solution was added, and the derivative reaction was conducted at 60 ℃ for 4 min. The fluorescence intensity of the system at 429 nm was recorded under the LED excitation wavelength of 370 nm. It was shown that linear relationship between mass concentration of AFB₁ and fluorescence intensity of the system was kept in the range of 10-500 μg·L^-1, with detection limit (3s/k) of 3.47 μg·L^-1. Test for recovery was made on the actual sample, and the recoveries of AFB₁ were in the range of 80.1%-109%, with RSDs (n=5) of the determined values ranged from 2.4% to 7.7%.