Selective and Sensitive Determination of Folic Acid Based on Molecularly Imprinted Poly (o-aminophenol) and Reduced Graphene Oxide Decorated with Au Nanoparticles

Background: Folic acid (pteroylglutamic acid, FA), known as a water-soluble vitamin of B complex family, plays an important role in the human body. However, excess intake of FA would mask the vitamin B12 deficiency symptoms, which may lead to other health risks. Therefore, it is very important to develop a method for the sensitive and selective determination of FA in natural sources, fortified foods and multivitamin preparations. Methods: An electrochemical sensor was fabricated for the analysis of FA, which was based on electropolymerized molecularly imprinted poly (o-aminophenol) film and reduced graphene oxide decorated with Au nanoparticles composites (rGO-AuNPs). The transmission electron microscope, cyclic voltammetry, electrochemical impedance spectroscopy and differential pulse voltammetry were utilized for the characterization of the imprinted polymer film. Results: Under the optimized experimental conditions, the proposed sensor exhibited two distinct linear responses ranging from 0.02 to 0.8 mu mol L-1 and 0.8 to 10 mu mol L-1 towards the concentrations of FA, and the detection limit was found to be 2.8 nmol L-1 (S/N=3). The molecularly imprinted film proposed was also found to exhibit comparatively high selectivity toward folic acid against structurally similar analogues, and the preparation of the sensor was simple and reproducible. Conclusion: In this work, a molecularly imprinted film fabricated on an rGO-AuNPs modified electrode was developed for the sensitive and selective determination of FA. Furthermore, the method was applied to the detection of FA in infant formula milk, multivitamin tablets and blood serum sample with satisfactory results.