Electrochemical Sensor Based on Covalent Organic Framework for Detection of Folic Acid

Folic acid (FA) is an essential nutrient to human and plays an important role in hematopoietic system. Covalent organic frameworks (COFs) are porous crystalline polymers composed of organic molecular units connected by covalent bonds. The porous structure endows them with large specific surface area, which is helpful for the enrichment of target onto the electrode surface and the electrochemical reaction when it is modified on electrode surface. In this work, TAPB-DMTP-COF was first synthesized with 1,3,5-tri (4-aminophenyl) benzene (TAPB) and 2,5-dimethoxybenzene-1,4-diformaldehyde (DMTP) as precursor monomer. The obtained COF was characterized by electron microscopy, X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The electrochemical properties of COF were characterized, and the results proved that TAPB-DMTP-COF had good electrocatalytic activity towards oxidation of FA. With TAPB-DMTP-COF as modified material, an electrochemical sensor was constructed for detection of FA. Using differential pulse voltammetry (DPV) as detection method, under optimal conditions, this sensor exhibited a wide linear response range (1-800 & mu;mol/L) to FA with a detection limit of 0.3 & mu;mol/L (SIN=3). This sensor also exhibited good anti-interference ability and reproducibility. The sensor was used to detect FA in apple juice, and the recoveries were 103.4%-105.2%.