Liquid chromatographic method for determining added folic acid in fortified cereal products

Reversed-phase ion-pair high-performance liquid chromatography (HPLC) was coupled with detection by UV absorption (280 nm) for separation and quantitation of added folic acid (FA) in fortified cereal based foods. A simple and rapid liquid-solid extraction method, combined with enzymatic digestion, to recover FA from the sample matrices is also presented. The quantitation of added FA was achieved in products including corn (maize), wheat-, rice- and oat-based cereal breakfast foods fortified at 25% and 100% of the reference daily intake (RDI). The retention time for FA was ca. 15 min, and the detection limit was 2 ng/20 microliters injection for standard FA. When FA was added to unfortified samples of wheat flour at concentrations of 3.08 or 20.0 micrograms/g, recoveries were 93% and 96%, respectively. Comparison of HPLC results with those of a standard microbiological assay has shown quite good agreement (r = 0.998). A solid-phase extraction clean-up procedure has also been developed for use with samples fortified with low levels of FA, where interferences may otherwise hinder quantitation.