Magnetic molecularly impri̇nted polymer synthesi̇s for selecti̇ve separati̇on of flavonoi̇ds

Molecularly imprinted polymers (MIPs) are artificial polymers which are formed in the presence of a target molecule that finally is removed by the proper solvents; therefore, the obtained specific cavities are complement to the target molecule in shape, size and functional groups. MIPs are used many areas such as extraction, sensor construction catalysis and drug delivery. In recent years, the use of magnetic molecular imprinted polymers (MMIP) for separation, purification and concentration has become a growing concern. Apart from the advantages of high affinity and specificity of traditional MIPs, MMIPs can be rapidly and easily separated using an external magnetic field with high efficiency and low cost. So, easy and efficient separation can be performed with an external magnetic field without any additional centrifugation or filtration procedures. Quercetin (BUE), is the most active compound in flavone family, widely occurring in leaves, fruits, and flowers of many plants. This compound has become the topic of increasing interest based on its antioxidant, antiviral and antitumor properties. So, the isolation of quercetin from various plant matrices is becoming an important research area. In this study, the conditions of MMIPs synthesis and their use for QUE recovery were examined. Iron (II) chloride tetrahydrate (FeCl2.4H2O) and iron (III) chloride hexahydrate (FeCl3.6H2O) were used to prepare magnetic nanoparticles and Fe3O4 was synthesized. Tetraethyl ortho silicate (TEOS) was used to coat the resulting Fe3O4 surface with silane. [3-(methacryloxy) propyl] trimethoxysilane (γ-MPS) was used to functionalize the surface of the formed Fe3O4@TEOS structure. Synthesis was carried out using QUE as template molecule; tetra hydrofuran (THF), ethanol (EtOH), asetone:acetonitrile (ACN) (3:1, v/v) solvent mixture as porogen solvents; acrylamide (AM), metacrylic acid (MAA), 4-vinyl pyridine (4-VP) as functional monomers; ethyleneglycol dimethacrylate (EDMA) as cross-linker and 2,2'-azobisizobutironitril (AIBN) as initiator at different molar ratios (template:monomer:cross-linker; 1:4:20, 1:8:20 and 1:8:40). The recognition and selectivity properties of these polymers were determined from the absorbance values at 370 nm obtained with equilibrium assays using QUE solutions prepared in THF, ACN and %50 EtOH solvent mixtures at different ratios. It was established that the magnetic imprinted polymer prepared in %50 EtOH solvent mixture with a molar ratios of 1:8:40 (QUE:4-VP: EDMA) had the highest adsorption capacity and imprinting factor. Using the prepared QUE-MMIP, QUE was obtained with 33% efficiency from red onion skin extract.