Development of ic-ELISA and lateral-flow immunochromatographic assay strip for the detection of folic acid in energy drinks and milk samples

Folic acid (FA) is an important vitamin for human growth and development, especially for pregnant women. A sensitive, rapid, and accurate FA detection method is required to assess the nutritional quality and safety of foods. A monoclonal antibody against FA was prepared for the development of indirect competitive enzyme-linked immunosorbent assay (ic-ELISA) and lateral-flow immunochromatographic assay (ICA) strip. The 50% inhibitory concentration and limit of detection of ic-ELISA were 0.12 and 0.018 ng/ml, respectively. The visual limit of detection and cut-off values of the lateral-flow ICA strip were 0.5 and 2.5 ng/ml, respectively. Using the ICA strip, FA recovery rates were 89–98% from energy drinks and 73–87% for milk samples and were in good agreement with those obtained from the conventional microbiological assay method. Our developed methods are sensitive, convenient, effective, and suitable for on-site detection and rapid mass screening of food samples.