Development of a folic acid molecularly imprinted polymer and its evaluation as a sorbent for dispersive solid-phase extraction by liquid chromatography coupled to mass spectrometry

This work shows the development of a molecularly imprinted polymer to determine folic acid (FA) in food extracts by using dispersive solid-phase extraction and liquid chromatography coupled to mass spectrometry (LC-MS). Herewith, combinations of monomers (methacrylic acid (MAA), 4-vinylpyridine (4VPy) and vinylbenzyl trimethylammonium chloride (VBTMAC)) and crosslinkers (ethylene glycol dimethacrylate (EGDMA) and divinyl benzene (DVB)) were tested in appropriate solvents. Isotherm tests revealed that the MIP with the highest affinity was obtained by combining VBTMAC and EGDMA. Having checked the appropriate template-monomer-crosslinker ratio, the FA MIP was analyzed for its kinetic and equilibrium binding properties, proving very high affinity (more than 2.5 mmol g^-1) and MIP/NIP ratio (up to 37). The FA MIP was used to selectively isolate the compound of interest from lettuce and cookies matrices using a dispersive solid-phase extraction protocol (which exhibited appropriate recovery and repeatability, ≥79.50% and ≤13.41 (%RSD in terms of area values), respectively, as well as absence of matrix effect); the resulting extracts were analyzed by a rapid and reliable LC-MS method.