In this work, a novel mixed non-covalent and semi-covalent molecularly imprinted membrane (MIM) with hierarchical pores was prepared by cryopolymerization at −18 °C and using PEG2000 and dimethyl sulfoxide ice crystals as the pore templates. The free-standing MIM was characterized by scanning electron microscope and nitrogen adsorption-desorption isotherms, and the results confirmed the formation of the hierarchical pore structure . In the static adsorption, membrane permeation and dead-end filtration experiments, the results indicated that the mixed non-covalent and semi-covalent molecular imprinting was a good method to improve the performance of MIM which had a good adsorption selectivity toward genistein due to the presence of the imprinted sites in MIM and possessed strong imprinting efficiency toward genistein even in some similar compound mixture or extract of Radix Puerariae Lobatae.
Lu Wang,Hongyuan Yan,Chunliu Yang,Zan Li,Fengxia Qiao
A mimic molecularly imprinted ordered mesoporous silica (MIOMS) adsorbent was prepared utilizing a thermally reversible semicovalent approach. The thermally reversible covalent template-monomer complex was firstly synthesized by employing 4,4′-sulfonyldiphenol (BPS) and (3-isocyanatopropyl) triethoxysilane (ICPTES) as template and monomer, respectively. The template-monomer complex was incorporated into ordered mesoporous silica via a simple self-assembly process. The adsorption experiment illustrated that the imprint-removed silica (MIOMS-ir) had higher special recognition ability (250 μg g −1 ) for estradiol (E2) than the non-imprinted silica (NIOMS-ir) (25 μg g −1 ). MIOMS-ir was applied as an adsorbent in pipette-tip solid-phase extraction (PT-SPE) coupled with liquid chromatography-fluorescence detector (LC-FLD) for determination of E2 in milk samples. Under the optimized conditions, only 3 mg of the adsorbent, 0.3 mL of water as washing solvent, and 0.5 mL of acetonitrile-acetic acid (96:4, v/v) as elution solvent were used in the pretreatment procedure of milk samples. Good calibration linearity was obtained in a range of 25 ng L −1 to 1000 ng L −1 , and the recoveries at three spiked levels were ranged from 95.4% to 107.0% with relative standard deviations (RSDs) ≤3.1% (n = 3). The proposed MIOMS-ir-PT-SPE-LC-FLD method combined the advantages of PT-SPE and ordered mesoporous material such as ease assembly, low cost, high extraction efficiency and large specific surface area, so it is a potential pretreatment strategy for the extraction and determination of E2 in complex milk samples.
A novel mesoporous fluorescent molecularly imprinted sensor for selective detection of bisphenol A (BPA) in food materials was fabricated via a semi-covalent imprinting method. The imprinting precursor that served as an alternative template molecule for BPA was prepared via thermally reversible isocyanate bonding, which effectively improved the imprinting efficiency for the molecularly imprinted sensor. Carbon dots (CDs) were embedded in mesoporous silica as signal recognition elements that exhibited quenching upon BPA binding. Subsequently, through the sol–gel process, the molecularly imprinted layer was coated on the CDs silica layer and provided specific recognition sites for BPA. The composite of CDs embedded in the mesoporous molecularly imprinted polymer (CDs@MIP) was characterized with scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer–Emmett–Teller measurements and thermogravimetric analysis. The mechanism of carbon dots quenching and the high selectivity of CDs@MIP towards BPA were explored. The linear response range of the sensor was from 0.025 mg L−1 to 2 mg L−1 with a limit of detection of 0.016 mg L−1. The method was successfully applied for the determination of food samples and recoveries ranged from 92.5% to 101.1%. The BPA contents in actual samples were determined using high performance liquid chromatography and the proposed sensor, showing no significant difference between the two methods.
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