Development of a new analytical method for the determination of fumonisins B1 and B2 in food products based on high performance liquid chromatography and fluorimetric detection with post-column derivatization

A sensitive and selective analytical method was developed for the quantitative determination of fumonisins B1 and B2 in maize-based foods for direct human consumption. The method, based on high-performance liquid chromatography and fluorescence detection, presents a rapid and automated on-line post-column derivatization, performed with o-phtalaldehyde and N,N-dimethyl-2-mercaptoethylamine. Several factors affecting the separation and detection of fumonisins were investigated, including mobile phase composition, column features, derivatization agent flow-rate and both the excitation and the emission wavelengths. Optimal fluorescence detection was obtained by using a λexc of 343 nm and a λem of 445 nm. Under the optimized experimental conditions, a complete separation of fumonisins was obtained in less than 13 min by using a C18 column and a gradient elution at 0.8 mL/min with methanol and 0.1 M phosphate buffer at pH 3.15. The limits of detection for FB1 and FB2 were 4 and 5 μg/L corresponding to 5 and 6 μg/kg in matrix. Each fumonisin was determined in the range 40–320 μg/L that correspond to 50–400 μg/kg in matrix. The necessary requirements for accuracy, reproducibility and sensitivity were fulfilled and recovery values ranged from 87 to 94% for FB1 and from 70 to 75% for FB2 in cornflake samples at three fortification levels in the range 100–300 μg/kg. The potential of this method, combined with a simple clean-up procedure, was assessed by the measurements of FB1 and FB2 in maize-based products, such as maize flour, “polenta”, tortillas and cookies.