Preparation Of Magnetic Dopamine Surface Molecularly Imprinted Polymers For Quinolones Adsorption

Dopamine monomers can self-polymerize to form highly cohesive polydopamine（PDA）under alkaline conditions.PDA has been widely used in membrane separation engineering,biosensors,solid-phase extraction,and other fields owing to its simple synthesis method and multiple surfactant active groups.In this study,two types of molecularly imprinted materials were prepared based on polydopamine,and their performance in extracting quinolone（FQ）residues from complex substrates such as food and environmental samples was investigated.These results can provide a reference for the development of solid-phase extraction materials.The main research contents and results are as follows.（1）Magnetic Fe₃O₄as the core,PDA as the shell,gatifloxacin as the template molecule,and a magnetic surface molecule-imprinted polymer with a core-shell structure Fe₃O₄@PDA@MIPs were prepared.The synthesized materials were characterized by Fourier transform infrared spectroscopy（FTIR）,transmission electron microscopy（TEM）,thermogravimetric analysis（TGA）,and Brunauer-Emmett-Teller（BET）surface area analysis.We studied and evaluated the performance of Fe₃O₄@PDA@MIPs in the extraction of FQs,and the results showed that Fe₃O₄@PDA@MIPs had a large specific surface area,good magnetic properties,and excellent target molecule selectivity.The effects of p H and the amount of Fe₃O₄@PDA@MIPs on solid-phase extraction were investigated.The results showed that the maximum adsorption capacity of Fe₃O₄@PDA for gatifloxacin was 51.9 mg/g,the adsorption equilibrium was achieved within 30 min,and the selective imprinting factor was 2.24.The results of Fe₃O₄@PDA@MIPs cycling showed that the adsorption capacity of Fe₃O₄@PDA@MIPs did not decrease significantly after six cycles.This study further established an Fe₃O₄@PDA@MIPs solid-phase extraction/HPLC method for the analysis of residual FQs in water samples.The results revealed that the recovery rate of the method was between 84.1%and 91.9%,and limit of detection and limits of quantitation were 6.4 ng/m L and 34.5 ng/m L,respectively.（2）In this study,Fe₃O₄@PDA was coated with nano-sized titanium dioxide,and a core-shell structure Fe₃O₄@PDA@Ti O₂was obtained.The Fe₃O₄@PDA@Ti O₂@MIPs surface molecularly imprinted polymer was synthesized using Fe₃O₄@PDA@Ti O₂as the carrier and enrofloxacin as the template molecule.The materials were characterized by FTIR,scanning electron microscopy（SEM）,TEM,BET specific surface area analysis,and magnetic property tests.The results showed that Fe₃O₄@PDA@Ti O₂@MIPs had good magnetic properties and a high specific surface area.The adsorption process of enrofloxacin on Fe₃O₄@PDA@Ti O₂@MIPs conformed with the Freundlich adsorption isotherm model,and equilibrium adsorption was reached within 10 min.The maximum adsorption capacity was 118.6 mg/g,and the selective imprinting factor was 2.66.The experimental results of adsorption-desorption recycling showed that after five cycles of Fe₃O₄@PDA@Ti O₂@MIPs,the decrease in adsorption capacity was less than 20%.Based on Fe₃O₄@PDA@Ti O₂@MIPs solid-phase extraction,an HPLC method was established to detect quinolones,and the recovery rate was between 79.6%and 98.8%.