Determination of fumonisins B-1 and B-2 in cornflakes by high performance liquid chromatography and immunoaffinity clean-up

The determination of fumonisins in cornflakes is a challenging matter as th e actually available methods for the analysis of corn do not perform well w hen applied to this more complex matrix. After testing several factors that may affect the analytical performance, an accurate method for the determin ation of fumonisin B-1 (FB1) and B-2 (FB2) in cornflakes has been developed . The method uses immunoaffinity chromatography for clean-up and high perfo rmance liquid chromatography (HPLC) for quantification of the toxins. Sampl es were extracted twice with acetonitrile-methanol-water (25:25:50) and the combined extracts were diluted with phosphate buffered saline (PBS) and ap plied to a FumoniTest(TM) immunoaffinity column. After washing with PBS, fu monisins were eluted from the column with methanol and reacted with o-phtha ldialdehyde/2-mercaptoethanol to form fluorescent derivatives. Fumonisin de rivatives were analysed by reversed phase HPLC with fluorometric detection using methanol-0.1 M phosphate buffer (77:23; pH adjusted at 3.35) as mobil e phase. The average recoveries for FB1 and FB2 spiked in the ranges of 0.3 3- 2.80 mug/g and 0.17-1.40 mug/g were 102.6% and 95.1%, respectively, with average relative standard deviations of 9% and 8%. The limit of quantifica tion for FB1 and FB2 was 0.005 mug/g based on a signal-to-noise ratio of 6: 1 by using a sensitive fluorescence detector. The method was used to analys e 18 cornflakes and cornflake cereals samples for FB1 and FB2 contamination . All but one sample were found to be contaminated, with maxi-mum FB1 and F B2 concentrations of 1.092 mug/g and 0.235 mug/g, respectively. Mean FB1 an d FB2 concentrations were 0.157 mug/g and 0.036 mug/g, respectively.