A LC/MS/MS method for the simultaneous quantification of free and masked fumonisins in maize and maize-based products

An LC-ESI-MS/MS method for the simultaneous detection of the main fumonisins and their hydrolysed derivatives is described, allowing for a simplified sample preparation without previous clean up. The method has a very low quantification limit (10 mu g/kg for FB1, 12 mu g/kg for FB2 and FB3, 70 mu g/kg for HFB1, HFB2 and HFB3 in maize flour) and a very good recovery for all the analytes. The method has been applied to check several maize-based foods for the presence of free and bound forms of fumonisins, the latter being determined after alkaline hydrolysis as hydrolysed derivatives. Bound fumonisins were found to be present not only in thermally treated maize-based products but also in mild processed or even raw products (pasta, bread, cakes, crisps, flour) and they were always present in almost similar or even higher amounts than the free forms. Osborne fractions of maize proteins showed that fumonisins were particularly bound to prolamins and glutelins. Model systems and extracts of these protein fractions gave positive response to ELISA tests, thus confirming the cross reactivity of these masked forms.