A magnetic molecularly imprinted polymer for enriching low-concentration hexabromocyclododecane and a preparation method and application thereof

Abstract

This invention discloses a magnetic molecularly imprinted polymer, its preparation method, and its applications. First, Fe3O4 nanoparticles are prepared via co-precipitation. Then, the Fe3O4 nanoparticles are surface-modified with tetraethyl orthosilicate and 3-(trimethoxysilyl)propyl methacrylate to obtain Fe3O4@SiO2@CH2=CH2 nanoparticles. Using these as the magnetic core of the molecularly imprinted polymer, hexabromocyclododecane is used as the template molecule, 4-vinylpyridine as the functional monomer, azobisisobutyronitrile as the initiator, ethylene glycol dimethacrylate as the crosslinking agent, and acetonitrile as the porogen, to prepare the magnetic molecularly imprinted polymer. The magnetic molecularly imprinted polymer prepared by this invention can rapidly separate hexabromocyclododecane under an external magnetic field with good specificity, exhibiting excellent adsorption and desorption effects. It has low preparation cost, can be recycled, and has good application prospects.

Description

Technical Field

[0001] This invention belongs to the field of molecular imprinted materials technology, specifically relating to a magnetic molecular imprinted polymer enriched with low concentrations of hexabromocyclododecane, its preparation method, and its application. Background Technology

[0002] Hexabromocyclododecanes (HBCDs) are alicyclic hydrocarbon compounds containing polybrominated groups. As the world's third largest brominated flame retardant, they are widely used in electronics, plastics, textiles, and construction. HBCDs readily enter the environment through various pathways, exhibiting long residual periods, high detection rates, and biotoxicity. Furthermore, HBCDs can enter organisms through migration via soil and water pollution, inhalation, and food, accumulating through the food chain and seriously endangering human health. In May 2013, HBCDs were officially included in the Stockholm Convention on Persistent Organic Pollutants.

[0003] my country first issued a national standard for the detection of HBCDs in electronic and electrical products (GB / T 29785-2013) in 2013, which sets a detection limit of 50 mg / kg for HBCDs. Currently, commonly used HBCDs pretreatment methods include Soxhlet extraction, ultrasound-assisted extraction, accelerated solvent extraction, solid-phase extraction, and liquid-liquid extraction. However, these methods generally suffer from drawbacks such as cumbersome procedures, high costs, and lack of specificity. There is an urgent need for a new, rapid, efficient, and reusable method for the enrichment and detection of HBCDs.

[0004] Molecular imprinting is a novel solid-phase extraction technique based on the antigen-antibody specific recognition mechanism simulated by molecularly imprinted polymers. Magnetic molecularly imprinted polymers (MMIPs) are produced by synthesizing molecularly imprinted shells on the surface of magnetic nanomaterials, enabling solid-liquid separation via an external magnetic field, overcoming the cumbersome separation process of traditional molecularly imprinted materials. Magnetic molecular imprinting technology is widely used by researchers due to its advantages such as strong enrichment capacity, high specificity, high adsorption capacity, structural stability, and resistance to strong acids and alkalis. Summary of the Invention

[0005] The purpose of this invention is to provide a method for enriching low concentrations of HBCDs from a medium. This method has the advantages of high specificity, short processing time, and good reusability. The prepared molecularly imprinted polymer is magnetic and can be separated under an external magnetic field.

[0006] To achieve the above objectives, the technical solution adopted by this invention is summarized as follows:

[0007] This invention provides a method for preparing a magnetically imprinted polymer enriched with low concentrations of HBCDs from a medium, comprising the following steps: (1) Magnetic Fe3O4 nanoparticles were prepared by coprecipitation method; (2) Using tetraethyl orthosilicate as the silicon source, a SiO2 layer was coated on the surface of the magnetic Fe3O4 nanoparticles to prepare Fe3O4@SiO2 nanoparticles; then, the Fe3O4@SiO2 nanoparticles were surface modified by 3-(trimethoxysilyl)propyl methacrylate to prepare Fe3O4@SiO2@CH2=CH2 nanoparticles. (3) The magnetic molecularly imprinted polymer was prepared by using the Fe3O4@SiO2@CH2=CH2 nanoparticles as the magnetic core of the molecularly imprinted polymer, hexabromocyclododecane as the template molecule, 4-vinylpyridine as the functional monomer, azobisisobutyronitrile as the initiator, ethylene glycol dimethacrylate as the crosslinking agent, and acetonitrile as the pore-forming agent.

[0008] Further, in step (1), the specific method for preparing magnetic Fe3O4 nanoparticles using the co-precipitation method is as follows: Take water-soluble Fe... 3+ Salt and Fe 2+ Salt was dispersed in water, and then ammonia was added under heating and stirring at 70°C. The temperature was raised to 80°C, and the reaction was continued for 30 min. After the reaction was completed, the mixture was cooled to room temperature, and Fe3O4 was separated from the solution using a magnet to obtain magnetic Fe3O4 nanoparticles.

[0009] According to one embodiment of the present invention, the method for preparing magnetic Fe3O4 nanoparticles by coprecipitation is as follows: 4.7 g of FeCl3·6H2O and 1.72 g of FeCl2·4H2O are weighed and ultrasonically dispersed in 200 mL of ultrapure water. 10 mL of 25% ammonia solution is added under heating and stirring conditions at 70 °C, and the temperature is raised to 80 °C. The reaction is continued with stirring for 30 min. After the reaction is complete and cooled to room temperature, Fe3O4 is separated from the solution using a magnet. The nanoparticles are repeatedly washed with deionized water and ethanol until neutral, and then vacuum dried to obtain Fe3O4 nanoparticles.

[0010] Further, in step (2), the SiO2 layer is coated on the surface of the magnetic Fe3O4 nanoparticles by the hydrolysis and condensation of the tetraethyl orthosilicate; the hydrolysis and condensation conditions are: using anhydrous ethanol-water mixed solution as the reaction medium, under alkaline conditions, and stirring at room temperature for 24 h.

[0011] According to one embodiment of the present invention, the preparation method of the Fe3O4@SiO2 nanoparticles is as follows: 1.0 g of magnetic Fe3O4 nanoparticles are weighed and added to 100 mL of ethanol-water solution. After ultrasonic dispersion for 30 min, 3 mL of 25% ammonia water and 4 mL of tetraethyl orthosilicate are added. The mixture is stirred and reacted at room temperature for 24 h. After the reaction is completed, the precipitate is separated from the solution by a magnet, washed repeatedly with methanol, and dried under vacuum to obtain Fe3O4@SiO2 nanoparticles. The ethanol-water solution is obtained by mixing ethanol and ultrapure water at a volume ratio of 15:4.

[0012] Further, in step (2), 3-(trimethoxysilyl)propyl methacrylate is used to react with the silanol groups on the surface of SiO2 to undergo silanization modification reaction; the conditions for the silanization modification reaction are: using acetic acid-water solution as the reaction medium, stirring at 50-70℃ for 4-6 hours.

[0013] According to an embodiment of the present invention, the preparation method of the Fe3O4@SiO2@CH2=CH2 nanoparticles is as follows: 0.5g of Fe3O4@SiO2 nanoparticles are weighed and placed in 100 mL of acetic acid-water solution, and 150 μL of 3-(trimethoxysilyl)propyl methacrylate is added. The mixture is stirred and reacted in a water bath at 60 °C for 5 h. After the reaction is completed, the precipitate is separated from the solution by a magnet, washed three times with water and methanol, and dried under vacuum to obtain Fe3O4@SiO2@CH2=CH2 nanoparticles.

[0014] Further, in step (3), the molar ratio of the template molecule, the functional monomer, and the crosslinking agent is 1:(3-5):(18-22); the mass-volume ratio of the functional monomer to the porogen is 1mg:(0.075-0.15)mL; the initiator is 10-15% of the mass of the functional monomer; and the mass ratio of the Fe3O4@SiO2@CH2=CH2 nanoparticles to the functional monomer is 1:(2-3).

[0015] According to one embodiment of the present invention, the specific preparation method of the magnetic molecularly imprinted polymer is as follows: 240 mg of HBCDs were weighed and added to 15 mL of acetonitrile, followed by the addition of 157 mg of 4-vinylpyridine, and prepolymerized by sonication for 20 min. Subsequently, 75 mg of Fe3O4@SiO2@CH2=CH2 nanoparticles, 1.4 mL of ethylene glycol dimethacrylate, and 20 mg of azobisisobutyronitrile were added, followed by sonication for 15 min and nitrogen deoxygenation. Then, the mixture was stirred at 60 °C for 24 h. After the reaction was completed, the mixture was separated using a magnet, washed, and dried to obtain the magnetic molecularly imprinted polymer HBCDs-MMIPs.

[0016] Preferably, the nitrogen degassing time is 10 min.

[0017] Preferably, in the preparation method of the magnetic molecularly imprinted polymer, the washing method is to first perform Soxhlet extraction with methanol-acetic acid (9:1, v / v) solution for 24 h, and then perform Soxhlet extraction with methanol solution for 24 h.

[0018] The magnetic molecularly imprinted polymers prepared by the above method are also within the scope of protection of this invention.

[0019] Furthermore, the particle size of the magnetic molecularly imprinted polymer is 50-100 nm.

[0020] This invention also protects a method for enriching low concentrations of HBCDs from a medium.

[0021] The method includes the following steps: mixing the magnetic molecularly imprinted polymer with a methanol sample containing hexabromocyclododecane (HBCDs), shaking at room temperature for 45-75 min, then separating the magnetic molecularly imprinted polymer using an external magnetic field, adding an elution solvent after decanting the supernatant, shaking at room temperature for 20-40 min, separating the magnetic molecularly imprinted polymer using an external magnetic field, and collecting the supernatant, which is the HBCDs enrichment solution; wherein, the elution solvent is a methanol-acetic acid mixture with a volume ratio of 9:1.

[0022] Furthermore, the methanol sample containing hexabromocyclododecane (HBCDs) is extracted from any of the following samples containing hexabromocyclododecane: environmental samples and blood samples.

[0023] Furthermore, the concentration of hexabromocyclododecane (HBCDs) in the methanol sample containing hexabromocyclododecane (HBCDs) is 50-400 μg / mL.

[0024] Furthermore, the ratio of the magnetic molecularly imprinted polymer to the methanol sample containing hexabromocyclododecane (HBCDs) is (5-10) mg: 1 mL.

[0025] Compared with the prior art, the present invention has the following beneficial effects: (1) The HBCDs magnetic molecular imprinted polymer prepared by the present invention has good specificity and short enrichment time.

[0026] (2) The HBCDs magnetic molecular imprinted polymer prepared by the present invention has a particle size of nanometer and is magnetic, and can be separated by an external magnetic field.

[0027] (3) The HBCDs magnetic molecular imprinted polymer prepared by the present invention has the advantages of simple preparation, low cost, easy storage, good reusability and high stability. Attached Figure Description

[0028] Figure 1 Scanning electron microscope (SEM) images of different products from the preparation process ((A) Fe3O4; (B) Fe3O4@SiO2; (C) Fe3O4@SiO2@CH2=CH2; (D) HBCDs-MMIPs). Figure 2 Fourier transform infrared spectra of different products from the preparation process; Figure 3 Magnetometer plots of vibrating samples of materials synthesized in each step; Figure 4 Figure 1 shows the optimization results of HBCDs-MMIPs preparation and adsorption conditions ((A) Functional monomer optimization; (B) Extraction solvent optimization; (C) Elution solvent optimization). Figure 5 The dynamic adsorption curve of HBCDs adsorbed by HBCDs-MMIPs. Figure 6 The first-order and second-order kinetic fitting plots of the dynamic adsorption curve are shown in ((A) first-order kinetic fitting; (B) second-order kinetic fitting). Figure 7 Isothermal adsorption curves of HBCDs adsorbed by HBCDs-MMIPs; Figure 8 Langmuir and Freundlich fits of the isothermal adsorption curves are shown in the figures ((A) Langmuir fit of HBCDs-MMIPs; (B) Langmuir fit of HBCDs-MNIPs; (C) Freundlich fit of HBCDs-MMIPs; (D) Freundlich fit of HBCDs-MNIPs). Figure 9 This is a specific adsorption diagram of HBCDs-MMIPs on HBCDs; Figure 10 The graph shows the cyclic performance of HBCDs-MMIPs. Detailed Implementation

[0029] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0031] The room temperature mentioned in the following examples refers to 25°C.

[0032] Example 1 A method for preparing HBCDs magnetic molecularly imprinted polymers (HBCDs-MMIPs) includes the following steps: (1) Preparation of magnetic Fe3O4 nanoparticles by coprecipitation: 4.7 g FeCl3·6H2O and 1.72 g FeCl2·4H2O were weighed and dissolved in 200 mL of ultrapure water by ultrasonication. After stirring and heating to 70 °C, 10 mL of 25% ammonia solution was added, and then the temperature was raised to 80 °C and the reaction was continued by stirring for 30 min. After the reaction was completed, the mixture was cooled to room temperature, and Fe3O4 was separated from the solution using a magnet. Fe3O4 was washed repeatedly with deionized water and ethanol until neutral, and then dried under vacuum at 55 °C to obtain magnetic Fe3O4 nanoparticles. The particle size was 10 nm.

[0033] (2) Synthesis of silanized Fe3O4 nanoparticles: 1.0 g of Fe3O4 nanoparticles were weighed and added to 100 mL of ethanol-water (15:4, v / v) solution. After ultrasonic dispersion for 30 min, 3 mL of 25% ammonia solution and 4 mL of tetraethyl orthosilicate were added. The mixture was stirred at room temperature for 24 h. After the reaction was completed, the precipitate was separated from the solution by a magnet. The precipitate was washed three times with methanol and dried under vacuum at 55 °C to obtain Fe3O4@SiO2 nanoparticles.

[0034] (3) Synthesis of vinyl-modified Fe3O4@SiO2 nanoparticles: 0.5 g of Fe3O4@SiO2 was weighed and placed in 100 mL of acetic acid-water (1:9, v / v) solution, and 150 μL of 3-(trimethoxysilyl)propyl methacrylate was added. The mixture was stirred in a water bath at 60 °C for 5 h. After the reaction was completed, the precipitate was separated from the solution by a magnet, washed three times with water and methanol, and dried under vacuum at 55 °C to obtain Fe3O4@SiO2@CH2=CH2 nanoparticles.

[0035] (4) Preparation of HBCDs magnetic molecularly imprinted polymer: 240 mg of HBCDs were weighed and added to 15 mL of acetonitrile, followed by 157 mg of 4-vinylpyridine as a functional monomer. The mixture was sonicated for 20 min for prepolymerization. Then, 75 mg of Fe3O4@SiO2@CH2=CH2 nanoparticles were added as a magnetic core, 1.4 mL of ethylene glycol dimethacrylate as a crosslinking agent, and 20 mg of azobisisobutyronitrile as an initiator. After sonication for 15 min, nitrogen gas was introduced for 10 min to remove oxygen. The mixture was then stirred at 60 °C for 24 h. After the reaction was completed, the product was separated from the solvent using a magnet. Soxhlet extraction was performed using methanol-acetic acid (9:1, v / v) solution for 24 h, followed by Soxhlet extraction using methanol solution for 24 h to remove excess acetic acid. After drying, the HBCDs magnetic molecularly imprinted polymer (HBCDs-MMIPs) was obtained.

[0036] Example 2 The HBCDs-MMIPs prepared in Example 1 were used as materials for characterization.

[0037] (1) Scanning electron microscope The materials synthesized in each step were characterized by scanning electron microscopy (SEM), and the results are as follows: Figure 1 As shown, Fe3O4 synthesized by coprecipitation is spherical particles in an irregular aggregated state; Fe3O4@SiO2 and Fe3O4@SiO2@CH2=CH2 have SiO2 produced by the hydrolysis of tetraethyl orthosilicate on their surfaces, so their surfaces are smooth, their particle size is increased, and they are in an irregular aggregated state; HBCDs-MMIPs have a relatively rough surface because their outer layer is wrapped by a molecularly imprinted layer.

[0038] (2) Infrared spectrum The materials synthesized in each step were characterized by Fourier transform infrared spectroscopy (FTIR), and the results are as follows: Figure 2 As shown, Fe3O4 at 564 cm⁻¹ -1 The presence of a characteristic peak representing the stretching vibration of the Fe-O bond at 1096 cm⁻¹ confirms the successful synthesis of Fe₃O₄ nanomaterials. Fe₃O₄@SiO₂ exhibits a characteristic peak at 1096 cm⁻¹, indicating the successful synthesis of Fe₃O₄ nanomaterials. -1 The presence of a characteristic peak representing the stretching vibration of the Si-O bond at this location proves that SiO2 was successfully coated on the Fe3O4 surface. The Fe3O4@SiO2@CH2=CH2 peak at 1621 cm⁻¹ -1 The presence of characteristic peaks representing carbon-carbon double bonds indicates that vinyl groups were successfully grafted onto the Fe3O4@SiO2 surface. HBCDs-MMIPs at 1729 cm⁻¹ -1The characteristic peak at this location represents the stretching vibration of the C=O bond in the crosslinking agent ethylene glycol dimethacrylate, proving that the molecularly imprinted layer polymerized on the surface of Fe3O4@SiO2@CH2=CH2. Therefore, Fourier transform infrared spectroscopy characterization confirms the successful synthesis of HBCDs molecularly imprinted polymers.

[0039] (3) Vibrating sample magnetometer The magnetic properties of the materials synthesized in each step were characterized using a vibrating sample magnetometer (VSM), and the results are as follows: Figure 3 As shown, all four hysteresis loops are symmetrical to the origin, indicating that the material exhibits superparamagnetism. With the addition of non-magnetic surface modifiers and polymer coatings on the magnetic core surface, the magnetic strength of the material decreases with the increase of the polymer shell structure. The saturation magnetization of Fe3O4, Fe3O4@SiO2, Fe3O4@SiO2@CH2=CH2, and HBCDs-MMIPs are 63.23, 27.92, 25.67, and 5.91 emu / g, respectively.

[0040] Example 3 Preparation and adsorption conditions were optimized.

[0041] Functional monomers form complexes with HBCDs in molecularly imprinted polymers (HBCDs-MMIPs) through hydrogen bonding and hydrophobic interactions, thereby enabling HBCDs-MMIPs to adsorb HBCDs. Therefore, selecting suitable functional monomers is crucial. Following the method described in Example 1, HBCDs-MMIPs were prepared using equimolar amounts of 4-vinylpyridine (4-VP), acrylamide (AM), and methacrylic acid (MAA) as functional monomers. Adsorption capacity was measured according to the method in Example 4. The results are as follows... Figure 4 As shown in Figure A, the HBCDs-MMIPs prepared with 4-VP as the functional monomer have the optimal adsorption capacity for HBCDs.

[0042] Extraction solvent is a crucial factor in enabling molecularly imprinted polymers to function. HBCDs standards dissolved in methanol, acetonitrile, and ethanol were prepared, respectively. Using the HBCDs-MMIPs prepared in Example 1 as the material, the adsorption capacity was determined according to the method in Example 4. The results are as follows: Figure 4 As shown in Figure B, HBCDs-MMIPs exhibit the highest adsorption capacity for HBCDs dissolved in methanol, indicating that methanol is the optimal extraction solvent.

[0043] The purpose of the elution solvent is to elute the adsorbed HBCDs molecules from HBCDs-MMIPs for subsequent detection. Methanol, ethanol, and methanol-acetic acid (9:1, v / v) solutions were selected as elution solvents. Using the HBCDs-MMIPs prepared in Example 1 as the material, the adsorption experiment was conducted according to the method in Example 4. After separating the HBCDs-MMIPs and decanting the supernatant, 4 mL of elution solvent was added. After shaking at room temperature for 30 min, the HBCDs-MMIPs were separated by an external magnetic field. The concentration of HBCDs in the supernatant was collected, and the results are as follows: Figure 4 As shown in Figure C, the methanol-acetic acid (9:1, v / v) solution is the optimal elution solvent because acetic acid competes with HBCDs for binding sites on HBCDs-MMIPs, resulting in more complete elution of HBCDs from HBCDs-MMIPs.

[0044] Example 4 The adsorption efficiency was tested using HBCDs-MMIPs prepared in Example 1 as the material. Following the method in Example 1, HBCDs-MNIPs were prepared as a control material without adding the template molecule HBCDs during the preparation of the molecularly imprinted polymer.

[0045] (1) Dynamic adsorption Adsorption kinetics experiments were conducted on the molecularly imprinted polymer. A methanol standard solution with an HBCD concentration of 200 μg / mL was prepared. 20.0 mg of HBCDs-MMIPs or HBCDs-MNIPs were weighed and added to 3 mL of the HBCDs standard solution. The mixture was shaken at room temperature for 0, 10, 20, 30, 40, 60, and 90 min to allow HBCDs to adsorb onto the surface. Subsequently, an external magnetic field was used to separate the HBCDs-MMIPs or HBCDs-MNIPs. The supernatant was poured into a 5 mL centrifuge tube, and the HBCDs content in the solution before and after adsorption was measured. The amount of HBCDs adsorbed in the magnetically imprinted polymer was calculated. The results are as follows: Figure 5 As shown, the adsorption capacity of HBCDs-MMIPs and HBCDs-MNIPs increased with increasing adsorption time, and the adsorption capacity stopped increasing at 60 minutes, indicating that the recognition sites on their surfaces were completely occupied; therefore, 60 minutes was selected as the optimal adsorption time. Under this condition, the maximum adsorption capacities of HBCDs-MMIPs and HBCDs-MNIPs were 2.6 and 1.5 mg / g, respectively.

[0046] To further investigate the adsorption of HBCDs by HBCDs-MMIPs and HBCDs-MNIPs, experimental data from dynamic adsorption curves were analyzed using first-order and second-order kinetic models, respectively. The results are as follows: Figure 6As shown, the second-order dynamic fitting parameters (Ri) of HBCDs-MMIPs and HBCDs-MNIPs are... 2 The values ​​are all greater than the first-order kinetic fitting parameters, indicating that the adsorption process involves both chemical adsorption and physical adsorption, and that there are HBCDs-specific adsorption sites on the polymer surface.

[0047] (2) Isothermal adsorption Isothermal adsorption experiments were conducted on the molecularly imprinted polymer. Methanol standard solutions with HBCD concentrations of 50, 100, 150, 200, 250, 300, and 400 μg / mL were prepared. 20.0 mg of HBCDs-MMIPs or HBCDs-MNIPs were weighed and added to 3 mL of each HBCD standard solution. The mixture was shaken at room temperature for 60 min to allow HBCDs to adsorb onto the surface. Subsequently, an external magnetic field was used to separate the HBCDs-MMIPs or HBCDs-MNIPs. The supernatant was poured into a 5 mL centrifuge tube, and the HBCDs content in the solution before and after adsorption was measured. The amount of HBCDs adsorbed in the magnetically imprinted polymer was calculated. The results are as follows: Figure 7 As shown, the adsorption capacity of both HBCDs-MMIPs and HBCDs-MNIPs increases with increasing HBCDs concentration. When the HBCDs concentration exceeds 300 μg / mL, the adsorption capacity of HBCDs-MMIPs reaches its maximum and no longer increases, with a maximum adsorption capacity of 4.24 mg / g. When the HBCDs concentration exceeds 200 μg / mL, the adsorption capacity of HBCDs-MNIPs also reaches its maximum and no longer increases, with a maximum adsorption capacity of 1.98 mg / g.

[0048] The adsorption results were further analyzed using Langmuir and Freundlich models. The Langmuir model represents homogeneous adsorption of the target substance on the polymer surface, indicating monolayer adsorption. The Freundlich isotherm model, on the other hand, represents heterogeneous phase adsorption, indicating a multilayer adsorption structure. The results are as follows: Figure 8 As shown, the fitting results of HBCDs-MMIPs to the Freundlich model (R0) are displayed. 2 =0.9759) is better than the fitting result for the Langmuir model (R = 0.9759). 2 =0.9678), indicating that the adsorption of HBCDs by HBCDs-MMIPs is more consistent with the Freundlich model, belonging to multilayer adsorption. The fitting result of HBCDs-MNIPs to the Langmuir model (R² = 0.9678) shows that the adsorption of HBCDs by HBCDs-MMIPs is more consistent with the Freundlich model, belonging to multilayer adsorption. 2 =0.9088) is better than the fitting result of the Freundlich model (R = 0.9088). 2=0.9006), indicating that the adsorption of HBCDs by HBCDs-MNIPs is more consistent with the Langmuir model and belongs to monolayer adsorption.

[0049] (3) Specific adsorption To investigate the specificity of HBCDs-MMIPs, cyclododecanone (CDON) and tetrabromobisphenol A (TBBPA) were selected as structural analogs of HBCDs and environmental interfering substances, respectively, for adsorption studies. The results are as follows: Figure 9 As shown in Figure A, the adsorption capacity of HBCDs-MMIPs for HBCDs is higher than that for TBBPA and CDON, indicating that HBCDs-MMIPs has a certain specificity for HBCDs. The imprinting factors for HBCDs, TBBPA, and CDON are 1.54, 1.27, and 1.05, respectively, and the selectivity factors for TBBPA and CDON are 1.21 and 1.47, respectively. Furthermore, comparing the HBCDs concentration in the adsorption-elution products of HBCDs-MMIPs and HBCDs-MNIPs yields the following results: Figure 9 As shown in Figure B, HBCDs-MMIPs exhibit higher adsorption efficiency for HBCDs.

[0050] (4) Reusability The reusability of molecularly imprinted polymers is an important performance indicator. The experimental results for the reusability of HBCDs-MMIPs are as follows: Figure 10 As shown, after 5 adsorption-elution cycles, the adsorption amount of HBCDs-MMIPs is approximately 82% of the initial adsorption amount, indicating that the HBCDs-MMIPs structure is stable and can be reused multiple times.

[0051] Example 5 Enrichment and separation of HBCDs in samples (1) Preparation of spiked serum samples Aspirate 1.5 ml of serum, add different concentrations of HBCDs standards, then add 150 μL of hydrochloric acid (6 M) and mix the sample using a vortex mixer. Add 1 ml of isopropanol and mix again. Extract the sample three times with n-hexane-MTBE (1:1, v / v) solution. Combine the organic phases, evaporate under mild nitrogen, and resuspend in 4 mL of methanol.

[0052] (2) Enrichment of HBCDs by molecular imprinting method Weigh 20.0 mg of HBCDs-MMIPs and add them to 3 mL of spiked sample. Shake at room temperature for 60 min. Then, separate HBCDs-MMIPs using an external magnetic field. After decanting the supernatant, add 4 mL of elution solvent (methanol-acetic acid (9:1, v / v) solution). Shake at room temperature for 30 min. Then, separate HBCDs-MMIPs using an external magnetic field and collect the supernatant.

[0053] (3) Spike recovery rate detection The supernatant was dried under mild nitrogen, resuspended in methanol, filtered through a 0.22 μm filter, and then analyzed by HPLC. HPLC conditions: C18 column (4.6 × 250 mm, 5 μm), mobile phase: water-methanol (6:94, v / v), flow rate: 0.6 mL / min, column temperature: 25 °C. o C, the injection volume is 20 μL, and the ultraviolet detection wavelength is 208 nm.

[0054] The results are shown in Table 1. The recoveries at spiked concentrations of 50, 100, and 200 μg / mL were 89.2%-115.1%, 79.8%-110.6%, and 88.4%-100.4%, respectively, indicating that HBCDs-MMIPs can effectively enrich HBCDs from real samples and have high specificity and selectivity.

[0055] Table 1. Spiking recoveries of HBCDs

[0056] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.

Claims

1. A method for preparing a magnetically imprinted polymer, comprising the following steps: (1) Magnetic Fe3O4 nanoparticles were prepared by coprecipitation method; (2) Using tetraethyl orthosilicate as the silicon source, a SiO2 layer was coated on the surface of the magnetic Fe3O4 nanoparticles to prepare Fe3O4@SiO2 nanoparticles; then, the Fe3O4@SiO2 nanoparticles were surface modified by 3-(trimethoxysilyl)propyl methacrylate to prepare Fe3O4@SiO2@CH2=CH2 nanoparticles. (3) The magnetic molecularly imprinted polymer was prepared by using the Fe3O4@SiO2@CH2=CH2 nanoparticles as the magnetic core of the molecularly imprinted polymer, hexabromocyclododecane as the template molecule, 4-vinylpyridine as the functional monomer, azobisisobutyronitrile as the initiator, ethylene glycol dimethacrylate as the crosslinking agent, and acetonitrile as the pore-forming agent.

2. The production method according to claim 1, characterized by: In step (1), the specific method for preparing the magnetic Fe3O4 nanoparticles by co-precipitation is as follows: taking water-soluble Fe 3+ salt and Fe 2+ salt into water, then adding ammonia water under the condition of heating and stirring at 70°C, increasing the temperature to 80°C, continuing to stir for 30 min, cooling to room temperature after the reaction is completed, separating Fe3O4 from the solution using a magnet, and obtaining magnetic Fe3O4 nanoparticles.

3. The production method according to claim 1 or 2, characterized by: In step (2), a SiO2 layer is coated on the surface of magnetic Fe3O4 nanoparticles by the hydrolysis and condensation of tetraethyl orthosilicate; the hydrolysis and condensation conditions are: using anhydrous ethanol-water mixed solution as the reaction medium, under alkaline conditions, and stirring at room temperature for 24 h.

4. The production method according to any one of claims 1 to 3, characterized by: In step (2), 3-(trimethoxysilyl)propyl methacrylate is used to react with the silanol groups on the surface of SiO2 to undergo silanization modification reaction; the conditions for the silanization modification reaction are: using acetic acid-water solution as the reaction medium, stirring at 50-70℃ for 4-6 hours.

5. The production method according to any one of claims 1 to 4, characterized by: In step (3), the molar ratio of the template molecule, the functional monomer and the crosslinking agent is 1:(3-5):(18-22). And / or, the mass-to-volume ratio of the functional monomer to the porogen is 1 mg: (0.075-0.15) mL; And / or, the initiator is 10-15% of the mass of the functional monomer; And / or, the mass ratio of the Fe3O4@SiO2@CH2=CH2 nanoparticles to the functional monomers is 1:(2-3).

6. The production method according to any one of claims 1 to 5, characterized by: The step (3) also includes a step of washing the obtained magnetic molecularly imprinted polymer. The washing method is as follows: first, Soxhlet extraction is performed for 24 h using a methanol-acetic acid (9:1, v / v) solution, and then Soxhlet extraction is performed for 24 h using a methanol solution.

7. The magnetic molecularly imprinted polymer prepared by the method according to any one of claims 1-6.

8. A method for enriching low concentration hexabromocyclododecane (HBCDs) from medium, comprising the following steps: mixing the magnetic molecularly imprinted polymer with HBCDs-containing methanol sample, shaking at room temperature for 45-75 min, then separating the magnetic molecularly imprinted polymer using an external magnetic field, adding elution solvent after pouring the supernatant, shaking at room temperature for 20-40 min, then separating the magnetic molecularly imprinted polymer using an external magnetic field, and collecting the supernatant, which is the HBCDs enrichment solution; wherein, The elution solvent is a mixed solution of methanol and acetic acid in a volume ratio of 9:

1.

9. The method according to claim 8, characterized in that: The methanol sample containing HBCDs was extracted from any of the following samples containing HBCDs: environmental samples or blood samples.

10. The method according to claim 8, characterized in that: The concentration of hexabromocyclododecane (HBCDs) in the methanol sample containing hexabromocyclododecane (HBCDs) was 50-400 μg / mL; And / or, the ratio of the magnetic molecularly imprinted polymer to the methanol sample containing hexabromocyclododecane (HBCDs) is (5-10) mg: 1 mL.

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