Determination of fumonisins B1 and B2 in cornflakes by high performance liquid chromatography and immunoaffinity clean-up.

The determination of fumonisins in cornflakes is a challenging matter as the actually available methods for the analysis of corn do not perform well when applied to this more complex matrix. After testing several factors that may affect the analytical performance, an accurate method for the determination of fumonisin B1 (FB1) and B2 (FB2) in cornflakes has been developed. The method uses immunoaffinity chromatography for clean-up and high performance liquid chromatography (HPLC) for quantification of the toxins. Samples were extracted twice with acetonitrile-methanol-water (25:25:50) and the combined extracts were diluted with phosphate buffered saline (PBS) and applied to a FumoniTest immunoaffinity column. After washing with PBS, fumonisins were eluted from the column with methanol and reacted with o-phthaldialdehyde/2-mercaptoethanol to form fluorescent derivatives. Fumonisin derivatives were analysed by reversed phase HPLC with fluorometric detection using methanol-0.1 M phosphate buffer (77:23; pH adjusted at 3.35) as mobile phase. The average recoveries for FB1 and FB2 spiked in the ranges of 0.33 2.80 microg/g and 0.17-1.40 microg/g were 102.6% and 95.1%, respectively, with average relative standard deviations of 9% and 8%. The limit of quantification for FB1 and FB2 was 0.005 microg/g based on a signal-to-noise ratio of 6.1 by using a sensitive fluorescence detector. The method was used to analyse 18 cornflakes and cornflake cereals samples/for FB1 and FB2 contamination. All but one sample were found to be contaminated, with maximum FB1 and FB2 concentrations of 1.092 microg/g and 0.235 microg/g, respectively. Mean FB1 and FB2 concentrations were 0.157 microg/(g and 0.036 microg/g, respectively.