Magnetic Non-imprinted Polymer Research Articles

Molecularly imprinted polymer coating with fluorescence on magnetic particle

In this research, molecular imprinting technology was employed to prepare magnetic, fluorescent molecularly imprinted polymer microspheres (fluorescent M-MIP) for recognition and separation of endocrine disrupting chemicals. The fluorescent M-MIP were prepared using Fe3O4@SiO2 magnetic nanoparticles combined with fluorescein (isothiocyanate) as fluorescent material with the surface molecularly imprinting method. The magnetic fluorescent molecularly imprinted polymers were characterized by fluorescence spectrophotometer, X-ray powder diffraction, vibration sample magnetic field meter, scanning and transmission electron microscopic methods. The results showed that the fluorescent M-MIP not only had excellent superparamagnetism and maintained the crystalline structure of the magnetic nanoparticles, but also stable fluorescence. The recognition selectivity of the magnetic fluorescence polymer was studied for template molecule and analogues. The results indicated that the fluorescent quenches of bisphenol A (the selective target) for fluorescent M-MIP were higher than that of the structural analogues, which illustrated the recognition selectivity for bisphenol A. Simultaneously, the fluorescent magnetic non-imprinted polymers (M-NIPs) had much higher fluorescent quenches than the fluorescent M-NIPs in the processes of rebinding. Therefore, the fluorescent M-MIP technology can be used for the recognition, magnetic separation and detection of bisphenol A by fluorescence spectrometry without any time-consuming elution. Open image in new window

Preparation of a magnetic molecularly imprinted polymer with pseudo template for rapid simultaneous determination of cyromazine and melamine in bio-matrix samples

A magnetic molecularly imprinted polymer (M-MIP) for cyromazine and melamine was prepared by simple suspension polymerization using a pseudo template, 2-(4,6-diamino-1,3,5-triazin-2-ylamino)ethanethiol disulfide. The M-MIP was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, and vibrating sample magnetometry. Molecular recognition properties and binding capability to cyromazine and melamine were evaluated by adsorption testing, which showed the M-MIP had better affinity and selectivity than the magnetic non-imprinted polymer (M-NIP) for cyromazine and melamine. A method based on molecularly imprinted solid-phase extraction assisted by magnetic separation was developed for extraction of cyromazine and melamine from bio-matrix samples. Various conditions, for example desorption conditions, amount of M-MIP, extraction time, and sample pH were optimized. High-performance liquid chromatography with UV detection was used to determine cyromazine and melamine after extraction. The proposed method was successfully applied to determination of cyromazine and melamine in egg and milk samples. Recovery of standard spiked cyromazine and melamine from these samples was between 71.86 and 80.57%, with intraday and interday relative standard deviation ranging from 3.45 to 6.39% and from 3.95 to 7.84%, respectively. The results indicate that the pseudo template M-MIP can be used for preconcentration, purification, and analysis of cyromazine and melamine in bio-matrix samples.

Selective recognition of 2,4,5-trichlorophenol by temperature responsive and magnetic molecularly imprinted polymers based on halloysite nanotubes

Fe3O4/Halloysite nanotube magnetic composites (MHNTs) were firstly prepared via an effective polyol-medium solvothermal method, and then the surface of the MHNTs was endowed with reactive vinyl groups through modification with 3-(methacryloyloxy)propyl trimethoxysilane (MPS). Based on the MHNTs-MPS, temperature responsive and magnetic molecularly imprinted polymers (t-MMIPs) were further synthesized by adopting methacrylic acid (MAA) and N-isopropylacrylamide (NIPAM) as the functional monomer and temperature responsive monomer, respectively. The as-prepared t-MMIPs were characterized by FT-IR, TEM, TGA and VSM, which indicated that the t-MMIPs exhibit magnetic sensitivity (Ms = 2.026 emu g−1), magnetic stability (especially in the pH range of 4.0–8.0) and thermal stability and are composed of an imprinted layer. The molecular interaction between 2,4,5-trichlorophenol (TCP) and MAA was investigated by 1H-NMR spectroscopy and ultraviolet absorption spectroscopy, which suggest that hydrogen bonding may be largely responsible for the recognition mechanism. The t-MMIPs were then applied to selectively recognise and release TCP molecules at 60 °C and 20 °C, respectively. The maximum amount of binding at 60 °C was 197.8 mg g−1 and 122.6 mg g−1 for t-MMIPs and temperature responsive and magnetic non-imprinted polymers (t-MNIPs), respectively. At 20 °C, about 32.3%–42.7% of TCP adsorbed by t-MMIPs was released, whereas 25.3%–39.9% of TCP was released by t-MNIPs. The selective recognition experiments demonstrated the high affinity and selectivity of t-MMIPs towards TCP over competitive phenolic compounds, and the specific recognition of binding sites may be based on the distinct size, structure and functional group to the template molecules.

Novel Cu (II) magnetic ion imprinted materials prepared by surface imprinted technique combined with a sol–gel process

A novel Cu (II) magnetic ion-imprinted polymer (MIIP) was synthesized by surface imprinting technique combined with a sol–gel process. The adsorbent of Cu (II)-MIIP shows higher capacity and selectivity than that of magnetic non-imprinted polymers (MNIP). Adsorption capacities of Cu (II)-MIIP and MNIP are 24.2 and 5.2 mg/g for Cu (II) ions, respectively. The selectivity coefficients of the Cu (II)-MIIP for Cu (II)/Zn (II) and Cu (II)/Ni (II) are 91.84 and 133.92, respectively. Kinetics studies show that the adsorption process obeys pseudo-second-order rate mechanism with an initial adsorption rate of 132.48 for Cu (II)-MIIP and 2.41 mg g −1 min −1 for MNIP. In addition, no obvious decrease was observed after up to five adsorption cycles, indicating that the Cu (II)-MIIP is of high stability.

Simultaneous determination of trace sterols in complicated biological samples by gas chromatography–mass spectrometry coupled with extraction using β-sitosterol magnetic molecularly imprinted polymer beads

In this paper, an efficient and sensitive analytical method for the simultaneous determination of three trace sterols including ergosterol, stigmasterol and β-sitosterol in complicated biological samples was developed by gas chromatography–mass spectrometry (GC–MS) coupled with extraction using novel β-sitosterol magnetic molecularly imprinted polymer (mag-MIP) beads. Physical tests suggested that β-sitosterol mag-MIP beads prepared by a rapid microwave synthesis method possessed the porous morphology, narrow size distribution, stable chemical and thermal property. Due to the greatly enlarging surface area and the strong recognition to the target molecules, β-sitosterol mag-MIP beads have a higher enrichment factor for β-sitosterol (∼20-fold) and the higher selectivity for β-sitosterol and its analogs than that of β-sitosterol magnetic nonimprinted polymer (mag-NIP) beads. Under the optimum analytical conditions, all the target compounds achieved good chromatographic separation and sensitive detection without matrix interference. It was interesting that three target sterols were actually found in mushroom samples, and stigmasterol and β-sitosterol were actually found in serum and watermelon samples. The recoveries of spiked sample tests were in range of 71.6–88.2% with RSDs of 2.4–10.0% ( n = 3). This method is reliable and applicable for the simultaneous determination of trace sterols in real biological samples based on the β-sitosterol mag-MIP bead extraction.

Selective Separation of Cu(II) from Aqueous Solution with a Novel Cu(II) Surface Magnetic Ion-Imprinted Polymer

A novel Cu(II) magnetic ion-imprinted polymer (MIIP) was prepared via the sol−gel method. The Cu(II)-MIIP exhibited good magnetic property and thermal stability. The binding characteristics of Cu(II)-MIIP were studied by adopting both static and dynamic adsorption experiments. The maximum adsorptions calculated from the Langmuir isotherm are 58.20 and 23.10 mg/g for Cu(II)-MIIP and magnetic nonimprinted polymer (MNIP), respectively. The kinetics studies showed that the adsorption process obeyed a pseudo-second-order kinetic model. The selectivity coefficients of the Cu(II)-MIIP for Cu(II) in the presence of Zn(II) and Ni(II) are 49.44 and 50.38, respectively. The relative selectivity coefficients of Cu(II)-MIIP for Cu(II)/Zn(II) and Cu(II)/Ni(II) are 12.36 and 8.73, respectively. Moreover, Cu(II)-MIIP could be used five times without obvious deterioration in their adsorption capacities.