Determination of folic acid in fortified wheat flours

A reversed-phase high-performance liquid chromatography (HPLC) method with ultraviolet detection to determine folic acid (FA) in fortified wheat flour is described. The method includes FA extraction with tetraborate and trichloroacetic acid buffer solution and purification by solid-phase extraction with strong anion-exchange cartridges. Good results were obtained with respect to repeatability (relative standard deviation ⩽8.8) and recovery (⩾97%). Detection and quantification limits were 0.06 and 0.19 μg g−1, respectively. The comparison between the HPLC method and both microbiological and immunoenzymatic assays revealed similar results. FA determination results on 33 wheat flours samples revealed that 51% of these samples had below 1.50 μg g−1 FA concentration added, the enrichment level established by Brazilian Regulation.