Br-COF magnetic nanoparticle solid-phase microextraction material as well as preparation method and application thereof

Abstract

The invention discloses a Br-COF magnetic nanoparticle solid-phase microextraction material as well as a preparation method and application thereof, and relates to the technical field of material preparation and application. The preparation method comprises the following steps: firstly, by utilizing a hydrothermal synthesis method and taking FeCl3. 6H2O as an iron source, partially reducing ferric ions into ferrous iron by ethylene glycol under high-temperature and alkaline conditions, so as to generate magnetic nanoparticles Fe3O4; then, 1, 3, 5-tri (4-aminophenyl) benzene and 2, 5-dibromo terephthalaldehyde are used as monomers, the surface of the magnetic nano Fe3O4 is modified with Br-COF through a solvothermal method, and the cross-linked magnetic extraction material with excellent dispersity is obtained. The COF material structurally contains aromatic rings, bromine atoms and a large conjugated system, the specific adsorption capacity on polybrominated diphenyl ether compounds can be enhanced, the enrichment multiple and extraction selectivity are improved, and therefore the requirement for detecting low-concentration target objects in water environment samples is met.

Description

Technical Field

[0001] This invention relates to the field of materials preparation and application technology, specifically to a Br-COF magnetic nanoparticle solid-phase microextraction material, its preparation method, and its application. Background Technology

[0002] With the development of industry, agriculture, and textiles, a large number of organic chemicals are widely used. However, many organic chemicals are directly discharged into aquatic environments without treatment or due to improper disposal, leading to water pollution and making it a global problem. Polybrominated diphenyl ethers (PBDEs) are a class of synthetic compounds widely used as flame retardant additives. It is well known that these compounds, as additives, are not chemically bonded to the product structure, thus easily released into the environment and entering organisms and humans through the food chain. Epidemiological studies have shown that PBDEs have persistent adverse effects on human health and the environment, such as endocrine disruption, reproductive toxicity, immunotoxicity, and neurotoxicity. These effects are serious and difficult to remove, and they are classified as persistent organic pollutants. Therefore, it is necessary to detect PBDEs in the environment.

[0003] Currently, polybrominated diphenyl ethers (PBDEs) are typically present at extremely low concentrations in environmental samples, and the matrices are complex, necessitating sample pretreatment before detection. Existing pretreatment methods include liquid-liquid extraction, solid-phase extraction, and liquid-liquid microextraction. However, these methods generally suffer from drawbacks such as time-consuming steps, insufficient selectivity, significant matrix effects, and high organic solvent consumption. Therefore, developing efficient, sensitive, and environmentally friendly pretreatment methods is of great significance.

[0004] Magnetic solid-phase extraction (MSPE) offers advantages such as simplicity, environmental friendliness, high extraction efficiency, and easy material recovery. Fe3O4-based magnetic nanoparticles, due to their ease of functionalization to enhance selectivity for target analytes, have been widely used in the analysis of complex matrices, including food, environmental samples, and biological systems. In MSPE, the extraction efficiency largely depends on the surface modification coating. Therefore, developing coating materials with high extraction rates and enrichment efficiencies is of great significance for the efficient enrichment of polybrominated diphenyl ethers (PBDEs) in complex matrices. Summary of the Invention

[0005] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a Br-COF magnetic nanoparticle solid-phase microextraction material, its preparation method and application. Specifically, the first purpose of this invention is to provide a Br-COF brominated functionalized covalent organic framework material, the second purpose is to provide a magnetic solid-phase extraction material, and the third purpose is to provide an application of the magnetic solid-phase extraction material in the detection of polybrominated diphenyl ether compounds.

[0006] This invention first utilizes a hydrothermal synthesis method, using FeCl3·6H2O as the iron source. Under high temperature and alkaline conditions, ferric ions are partially reduced to ferrous ions by ethylene glycol, thereby generating magnetic nanoparticles Fe3O4. Subsequently, using 1,3,5-tris(4-aminophenyl)benzene and 2,5-dibromo-terephthalaldehyde as monomers, Br-COF is modified on the surface of Fe3O4 via a solvothermal method to obtain a cross-linked magnetic extraction material with excellent dispersibility. The COF material structure of this invention contains aromatic rings, bromine atoms, and a large conjugated system, which can enhance the specific adsorption capacity for polybrominated diphenyl ethers and improve the enrichment factor and extraction selectivity, thus meeting the needs of detecting low concentrations of target analytes in aquatic environmental samples.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing Br-COF magnetic nanoparticle solid-phase microextraction materials, comprising the following steps: Using a hydrothermal synthesis method with FeCl3·6H2O as the iron source, ferric ions were partially reduced to ferrous ions under high temperature and alkaline conditions to generate magnetic nanoparticles Fe3O4. Using 1,3,5-tris(4-aminophenyl)benzene and 2,5-dibromo-terephthalaldehyde as monomers, Br-COF was modified on the surface of the magnetic nanoparticles Fe3O4 by a solvothermal method to obtain Br-COF magnetic nanoparticle solid-phase microextraction material.

[0008] Optionally, the preparation method of the magnetic nanoparticles Fe3O4 includes the following specific steps: Sodium poly(4-styrenesulfonic acid-copolymer-maleic acid), ethylene glycol, FeCl3·6H2O and anhydrous sodium acetate were mixed to obtain a mixture. The mixture was reacted at 150-200 °C for 6-12 h. After the reaction was completed, it was cooled to room temperature, the product was separated, and the product was washed and dried to obtain magnetic nanoparticles Fe3O4.

[0009] Optionally, the molar ratio of FeCl3·6H2O to sodium poly(4-styrenesulfonic acid-copolymer-maleic acid) is 1:1 to 3, more preferably 1:1; the molar ratio of FeCl3·6H2O to anhydrous sodium acetate is 1:10 to 16, more preferably 1:13; and the addition ratio of FeCl3·6H2O to ethylene glycol is 0.4 to 0.6 g: 10 to 50 mL, more preferably 0.54 g: 20 mL.

[0010] Optionally, the preparation method of Br-COF magnetic nanoparticle solid-phase microextraction material includes the following specific steps: 1,3,5-tris(4-aminophenyl)benzene, 2,5-dibromo-terephthalaldehyde and the magnetic nanoparticles Fe3O4 were mixed, and then n-butanol, water and glacial acetic acid were added. The mixture was reacted at 50-70 °C for 12-20 h. After the reaction was completed, the product was separated, washed and dried to obtain Br-COF magnetic nanoparticle solid-phase microextraction material.

[0011] Optionally, the molar ratio of 1,3,5-tris(4-aminophenyl)benzene to 2,5-dibromo-terephthalaldehyde is 2:3, the mass ratio of 1,3,5-tris(4-aminophenyl)benzene to magnetic nanoparticles Fe3O4 is 15~25:20~50, and the addition ratio of 1,3,5-tris(4-aminophenyl)benzene, n-butanol, water and glacial acetic acid is 15~25mg:1~2mL:0.2~0.3mL:0.4~0.6mL.

[0012] Optionally, a method for preparing a Br-COF magnetic nanoparticle solid-phase microextraction material includes the following steps: Step 1: Preparation of Fe3O4 magnetic nanoparticles Sodium poly(4-styrenesulfonic acid-copolymer-maleic acid) was placed in ethylene glycol and stirred for 30 min to disperse it evenly. FeCl3·6H2O and anhydrous sodium acetate were added to the above solution and stirred for 30 min. The resulting mixed solution was transferred to a reaction vessel and reacted at 150~200 ℃ for 6~12 h. After the reaction was completed, the mixture was cooled to room temperature, and the product was separated by a magnet. The product was washed 3~5 times with deionized water and ethanol, and then dried under vacuum at 50 ℃ for 8~12 h to obtain Fe3O4 magnetic nanoparticles with uniform particle size distribution.

[0013] Step 2: Preparation of Fe3O4@Br-COF magnetic solid-phase extraction material 1,3,5-tris(4-aminophenyl)benzene, 2,5-dibromo-terephthalaldehyde and Fe3O4 particles were added to a pressure-resistant bottle in a certain proportion, followed by the addition of n-butanol, water and glacial acetic acid. The mixture was reacted at 50-70 °C for 12-20 h. After the reaction was completed, the mixture was separated by an external magnetic field and washed 3-5 times with methanol to obtain Fe3O4@Br-COF.

[0014] Secondly, the present invention provides a Br-COF magnetic nanoparticle solid-phase microextraction material, which is obtained by the preparation method described above.

[0015] This invention modifies the surface of magnetic nanoparticles Fe3O4 with Br-COF. Br-COF is a porous material containing aromatic rings and bromine atoms. It has a large conjugated system and multiple recognition sites, and can adsorb polybrominated diphenyl ether compounds through mechanisms such as π-π stacking, hydrophobic interaction and halogen atom interaction.

[0016] Thirdly, the present invention provides the application of the Br-COF magnetic nanoparticle solid-phase microextraction material in the enrichment of trace polybrominated diphenyl ether pollutants.

[0017] The coating of the magnetic nanoparticles utilizes the Br-COF magnetic nanoparticle solid-phase microextraction material described in this invention. In practical applications, the Fe3O4@Br-COF magnetic solid-phase extraction material can be used to enrich and extract trace amounts of polybrominated diphenyl ethers (including TPB, BBPE, TBBPA, and PBDE) in the aqueous environment. The enrichment and extraction conditions are: extraction time 1–30 min, pH 4.0–9.0, and extraction material dosage of 0.5–2.0 mg per 5 mL of water sample. More preferably, the extraction time is 10 min; the extraction pH is 6; and the extraction material dosage is 1.0 mg per 4 mL of water sample.

[0018] Fourthly, this invention provides the application of the Br-COF magnetic nanoparticle solid-phase microextraction material combined with HPLC-DAD in the detection of polybrominated diphenyl ether pollutants.

[0019] This invention uses Br-COF magnetic nanoparticle solid-phase microextraction material to extract and enrich polybrominated diphenyl ether (PBDE) pollutants. After enrichment and extraction, the pollutants are eluted with an elution solvent, and then the eluent is detected by HPLC-DAD. This allows for the detection of PBDE pollutants.

[0020] Optionally, after enrichment extraction, elution is performed with an elution solvent, methanol, for 1 to 30 minutes. More preferably, the elution time is 10 minutes.

[0021] Optionally, after elution, the eluent is detected by HPLC-DAD. The HPLC conditions are as follows: C18 column parameters are 150 mm × 4.6 mm and 5 µm; mobile phase A is a 0.1% formic acid aqueous solution and mobile phase B is acetonitrile. Isocratic elution is used with a flow rate of 1 mL / min and an injection volume of 20 μL.

[0022] Fifthly, the present invention provides a method for detecting polybrominated diphenyl ether (PBDE) contaminants, comprising the following steps: The Br-COF magnetic nanoparticle solid-phase microextraction material was mixed with the test solution to extract and enrich polybrominated diphenyl ether pollutants in the test solution. After extraction and enrichment, the Br-COF magnetic nanoparticle solid-phase microextraction material was separated, the water sample was discarded, methanol was added for elution, and the eluent was collected after elution. The eluent was filtered through a filter membrane and then detected by a high-performance liquid chromatography-diode array detector. Mobile phase A was an aqueous solution of formic acid with a volume fraction of 0.1%; mobile phase B was acetonitrile, and isocratic elution was used.

[0023] Optionally, the extraction and enrichment conditions include: an extraction and enrichment time of 1-30 min, a pH of 4.0-9.0, and an extraction material dosage of 0.5-2.0 mg of Br-COF magnetic nanoparticle solid-phase microextraction material per 5 mL of test solution; The elution time is 1~30 min; Using 150 mm × 4.6 mm, 5 µm C 18 Separation was performed using a chromatographic column at a flow rate of 1 mL / min and an injection volume of 20 μL.

[0024] This invention has at least one of the following beneficial effects: This invention prepares Br-COF magnetic nanoparticle solid-phase microextraction material by modifying the surface of Fe3O4 magnetic nanoparticles with Br-COF. Specifically, the Br-COF modified on the surface of Fe3O4 magnetic nanoparticles is a porous material containing aromatic rings and bromine atoms. It has a large conjugated system and multiple recognition sites, and can adsorb polybrominated diphenyl ethers through mechanisms such as π-π stacking, hydrophobic interaction, and halogen atom interaction. This enables high-throughput adsorption and enrichment of trace polybrominated diphenyl ethers in complex aquatic matrices, achieving high-precision detection. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the synthesis and extraction process of the Fe3O4@Br-COF magnetic solid phase extraction material described in Example 1 of the present invention.

[0026] Figure 2 The infrared spectra of Br-COF, the synthetic monomer, Fe3O4, and Fe3O4@Br-COF in Example 1 of this invention are shown, where (a) Br-COF and the synthetic monomer, and (b) Br-COF, Fe3O4, and Fe3O4@Br-COF.

[0027] Figure 3 The images shown are scanning electron microscope (SEM) characterization images of Br-COF, Fe3O4, and Fe3O4@Br-COF in Example 1 of this invention, where (a) Br-COF, (b) Fe3O4, and (c) Fe3O4@Br-COF.

[0028] Figure 4 The X-ray photoelectron spectroscopy characterization diagrams of Br-COF, Fe3O4, and Fe3O4@Br-COF in Example 1 of the present invention are shown.

[0029] Figure 5 The X-ray diffraction characterization patterns of Fe3O4 and Fe3O4@Br-COF in Example 1 of this invention are shown.

[0030] Figure 6 The image shows the hysteresis curves of Fe3O4 and Fe3O4@Br-COF in Example 1 of this invention.

[0031] Figure 7 This is a repeatability graph of the Fe3O4@Br-COF magnetic solid-phase extraction material used in Example 2 of the present invention.

[0032] Figure 8 This is a comparison chart showing the detection effects of Fe3O4@Br-COF magnetic solid phase extraction material in Example 2 and Fe3O4@COFTABT-DPTA magnetic solid phase extraction material in Comparative Example 2 on polybrominated diphenyl ether compounds. Detailed Implementation

[0033] To make the technical problems solved, technical solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0034] Example 1 This embodiment provides a method for synthesizing Br-COF magnetic nanoparticle solid-phase microextraction materials. In this embodiment, the Br-COF magnetic nanoparticle solid-phase microextraction material is specifically Fe3O4@Br-COF magnetic solid-phase extraction material. Figure 1 This is a schematic diagram of the synthesis and extraction process of the Fe3O4@Br-COF magnetic solid phase extraction material in this embodiment.

[0035] The synthesis method of Fe3O4@Br-COF magnetic solid-phase extraction material in this embodiment includes the following steps: I. The Fe3O4 magnetic nanoparticles of this invention are prepared by the following method: 0.5 g of sodium poly(4-styrenesulfonic acid-copolymer-maleic acid) was placed in 20 mL of ethylene glycol and stirred for 30 min to disperse it evenly, thus obtaining a sodium poly(4-styrenesulfonic acid-copolymer-maleic acid) solution. Subsequently, 0.54 g of FeCl3·6H2O and 2.5 g of anhydrous sodium acetate were added to the above sodium poly(4-styrenesulfonic acid-copolymer-maleic acid) solution and stirred for 30 min. The resulting mixed solution was transferred to a reaction vessel and reacted at 180 °C for 10 h. After cooling to room temperature, the mixture was washed three times with deionized water and three times with ethanol. The mixture was collected under an external magnetic field, separated, and dried at 50 °C for 12 h to obtain black Fe3O4 magnetic nanoparticles.

[0036] II. The Fe3O4@Br-COF magnetic solid-phase extraction material of the present invention is prepared by the following method: 1,3,5-tris(4-aminophenyl)benzene (TABT, 21.2 mg, 0.06 mmol), 2,5-dibromo-terephthalaldehyde (DBTA, 26.2 mg, 0.09 mmol), black Fe3O4 magnetic nanoparticles (40 mg), n-butanol (1500 μL), water (250 μL), and glacial acetic acid (18 M, 500 μL) were added to a pressure-resistant bottle. The mixture was sonicated for 10 min, reacted with magnetic stirring at 70 ℃ for 16 h, washed three times with anhydrous methanol, separated by an external magnetic field, and dried at 80 ℃ for 12 h to obtain Fe3O4@Br-COF magnetic solid-phase extraction material.

[0037] In comparison, this embodiment also provides a method for preparing Br-COF material, including the following steps: 1,3,5-tris(4-aminophenyl)benzene (TABT, 21.2 mg, 0.06 mmol), 2,5-dibromo-terephthalaldehyde (DBTA, 26.2 mg, 0.09 mmol), n-butanol (1500 μL), water (250 μL), and glacial acetic acid (18 M, 500 μL) were added to a pressure-resistant bottle. The mixture was sonicated for 10 min and reacted with magnetic stirring at 70 ℃ for 16 h. The mixture was washed three times with methanol and dried at 80 ℃ for 12 h to obtain the Br-COF material.

[0038] III. Characterization of Fe3O4@Br-COF magnetic solid-phase extraction materials 1. FT of Br-COF and its synthetic monomers IR spectrum such as Figure 2 As shown in (a), by Figure 2 From (a), we can see that 1685 cm in DBTA 1 The characteristic C=O peaks at this location weaken, as do the peaks at 3457, 3323, and 3208 cm⁻¹ in TAPT. 1 The NH characteristic peak at 1623 cm⁻¹ weakened, while the characteristic peak of C=N appeared in Br-COF (1623 cm⁻¹). 1 This indicates that Br-COF was successfully synthesized via the Schiff base reaction. The FT-IR spectra of Br-COF, Fe3O4, and Fe3O4@Br-COF are shown below. Figure 2 As shown in (b), the Fe3O4@Br-COF magnetic solid-phase extraction material at 585 cm⁻¹ -1The characteristic peaks are related to the stretching vibrations of the Fe-O-Fe bonds, thus proving the presence of Fe3O4. Compared with the bare Fe3O4 core, the Fe3O4@Br-COF composite nanomaterial exhibits higher activity at 1625 cm⁻¹. -1 The presence of a characteristic absorption peak at C=N indicates the successful preparation of Fe3O4@Br-COF composite nanomaterials.

[0039] 2. Scanning electron microscopy results of Br-COF, Fe3O4, and Fe3O4@Br-COF are shown in [reference needed]. Figure 3 . Figure 3 (a) shows that Br-COF exhibits a tubular network structure. Figure 3 (b) shows that the Fe3O4 magnetic nanoparticles are uniformly spherical. Figure 3 (c) shows that the Fe3O4@Br-COF composite material exhibits a cross-linked polymer structure.

[0040] 3. The X-ray photoelectron spectroscopy results of Br-COF, Fe3O4, and Fe3O4@Br-COF are shown in [reference needed]. Figure 4 .Depend on Figure 4 It can be seen that, compared with the XPS full spectrum of Fe3O4 and Br-COF alone, the Fe3O4@Br-COF composite material simultaneously exhibits characteristic energy spectrum peaks of Fe 2p, O 1s, N 1s, C1s and Br 3d, confirming the presence of the corresponding elements in the Fe3O4@Br-COF composite material and indicating the successful preparation of the cross-linked polymer material.

[0041] 4. X-ray diffraction results of Fe3O4 and Fe3O4@Br-COF are shown in [reference needed]. Figure 5 The main characteristic peaks of Fe3O4 are located at 30.5°, 35.9°, 43.5°, 57.5°, and 63.1°, which are consistent with the (220), (311), (400), (511), and (440) crystal planes in the standard pure phase of Fe3O4. A characteristic diffraction peak at 25.9° appeared in the Br-COF modified composite material, indicating the successful preparation of the cross-linked polymer material.

[0042] 5. The magnetization curves of Fe3O4 and Fe3O4@Br-COF are shown in [reference needed]. Figure 6 The saturation magnetization of Fe3O4@Br-COF is 20 emu / g. Compared with the magnetic strength of Fe3O4 material (50 emu / g), the magnetization of the composite material is reduced, which may be related to the encapsulation of COF.

[0043] In summary, the above characterization results confirm the successful preparation of Fe3O4@Br-COF composite nanomaterials, laying the foundation for their adsorption and enrichment of polybrominated diphenyl ether compounds.

[0044] Comparative Example 1 In Example 1, the COF synthesis ligand 2,5-dibromo-terephthalaldehyde was replaced with terephthalaldehyde (DPTA), and Fe3O4@COF TABT-DPTA magnetic solid phase extraction material was prepared using the same method.

[0045] Example 2 This embodiment provides a method for detecting trace polybrominated diphenyl ethers (PBEs) in an aquatic environment. Specifically, the Fe3O4@Br-COF magnetic solid-phase extraction material synthesized in Example 1 is applied to the enrichment and detection of trace PBEs in an aquatic environment. The structures of the four PBEs detected in this embodiment are shown in Table 1. Table 1 I. This invention, based on Fe3O4@Br-COF composite nanomaterials and HPLC-DAD technology, constructs a method for detecting trace polybrominated diphenyl ether compounds in the aquatic environment. Combined with... Figure 1 The law includes the following testing content: 1. Sample preparation: Take 4 mL of actual water sample or standard working solution containing polybrominated diphenyl ethers, add 1 mg of the black-brown powdered Fe3O4@Br-COF composite nanomaterial prepared in Example 1, and shake at 250 rpm for 10 min at room temperature for adsorption.

[0046] 2. Separation, Elution, and Detection: Fe3O4@Br-COF composite nanomaterials were adsorbed using a magnet, eluted with 500 μL of methanol for 10 min, and the eluent was analyzed using HPLC-DAD. Phase A was a 0.1% (v / v) formic acid aqueous solution, and phase B was 100% acetonitrile. A 150 mm × 4.6 mm, 5 µm C microscope was used. 18 Chromatographic column separation was performed using isocratic elution at a flow rate of 1 mL / min and an injection volume of 20 μL. The type and concentration of pollutants were determined by DAD detection of peak time and peak area.

[0047] 3. Method validation: The limits of detection (LODs, S / N=3), limits of quantitation (LOQs, S / N=10), linear range, linear correlation coefficient R, and precision were examined.

[0048] The results are shown in Table 2. The results indicate that TPB, BBPE, TBBPA, and PBDE were within the range of 0.5–250 ng·mL. -1 The linear relationship was good within the range, with linear correlation coefficients (R) all above 0.99. The LODs of TBBPA were 0.05 ng·mL⁻¹. -1 The LODs of TPB, BBPE, and PBDE were 0.1 ng·mL.-1 The LOQs of the four substances were in the range of 0.2–0.5 ng·mL. -1 The precision of the method was evaluated by calculating the relative standard deviations (RSDs) of multiple sets of experiments. The intra-day precision (n = 3) was 1.4-3.0%, the inter-day precision (n = 3) was 1.2-3.6%, and the inter-batch precision (n = 3) was less than 5.7%, indicating that the method has good repeatability.

[0049] Table 2 4. Validation of actual water samples: Mixed working solution was added to actual samples and spike recovery tests were conducted. The results are shown in Table 3. The results show that the spike recovery rate was in the range of 81.6-103.8% and the RSDs were less than 6.53%, indicating that the method has high accuracy and can be used for reliable detection of polybrominated diphenyl ether compounds in aquatic environmental matrices.

[0050] Table 3 5. Reproducibility: This example also investigated the reproducibility of the Fe3O4@Br-COF magnetic solid-phase extraction material. The Fe3O4@Br-COF prepared in Example 1 was repeatedly used for the extraction of four polybrominated diphenyl ether compounds, with identical extraction conditions each time. After each extraction, the material was rinsed with methanol and allowed to dry before the next extraction. The results of this repeated use are shown in [Figure 1]. Figure 7 .Depend on Figure 7 It can be seen that, under the same extraction conditions, after being used 5 times, the enrichment efficiency of the Fe3O4@Br-COF magnetic solid phase extraction material did not decrease significantly, indicating that the extraction material of the present invention has good reusability.

[0051] Comparative Example 2 The Fe3O4@COF TABT-DPTA magnetic solid-phase extraction material prepared in Comparative Example 1 was applied to the enrichment and detection of trace polybrominated diphenyl ether compounds in an aqueous environment according to the method in Example 2. The detection results are as follows: Figure 8 As shown, by Figure 8It can be seen that the Fe3O4@COF TABT-DPTA magnetic solid-phase extraction material prepared in Comparative Example 1 showed poorer detection performance for the four polybrominated diphenyl ether compounds than the Fe3O4@Br-COF prepared in Example 1. This indicates that the enrichment and extraction performance of Fe3O4@COF TABT-DPTA for the four polybrominated diphenyl ether compounds in Comparative Example 1 was inferior to that of Fe3O4@Br-COF prepared in Example 1. Therefore, compared with the Fe3O4@Br-COF described in Example 1, the extraction performance of the Fe3O4@Br-COF extraction material is superior to that of Fe3O4@COF TABT-DPTA. This result demonstrates that the introduction of bromine-containing groups can provide halogen atom interaction forces, thereby further improving the extraction selectivity of the material.

[0052] In summary, the method for detecting trace polybrominated diphenyl ethers (PBDEs) in the aquatic environment based on Fe3O4@Br-COF magnetic solid-phase extraction material of this invention not only exhibits a good linear range, but also has high sensitivity, high accuracy and good repeatability, and can be used for high-precision detection of PBDEs in the aquatic environment.

[0053] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing Br-COF magnetic nanoparticle solid-phase microextraction materials, characterized in that, Includes the following steps: Using a hydrothermal synthesis method with FeCl3·6H2O as the iron source, ferric ions were partially reduced to ferrous ions under high temperature and alkaline conditions to generate magnetic nanoparticles Fe3O4. Using 1,3,5-tris(4-aminophenyl)benzene and 2,5-dibromo-terephthalaldehyde as monomers, Br-COF was modified on the surface of the magnetic nanoparticles Fe3O4 by a solvothermal method to obtain Br-COF magnetic nanoparticle solid-phase microextraction material.

2. The preparation method according to claim 1, characterized in that, The preparation method of the magnetic nanoparticles Fe3O4 includes the following specific steps: Sodium poly(4-styrenesulfonic acid-copolymer-maleic acid), ethylene glycol, FeCl3·6H2O and anhydrous sodium acetate were mixed to obtain a mixture. The mixture was reacted at 150-200 °C for 6-12 h. After the reaction was completed, it was cooled to room temperature, the product was separated, and the product was washed and dried to obtain magnetic nanoparticles Fe3O4.

3. The preparation method according to claim 2, characterized in that, The molar ratio of FeCl3·6H2O to sodium poly(4-styrenesulfonic acid-copolymer-maleic acid) is 1:1~3; the molar ratio of FeCl3·6H2O to anhydrous sodium acetate is 1:10~16; and the addition ratio of FeCl3·6H2O to ethylene glycol is 0.4~0.6 g:10~50 mL.

4. The preparation method according to claim 1, characterized in that, The preparation method of Br-COF magnetic nanoparticle solid-phase microextraction material includes the following specific steps: 1,3,5-tris(4-aminophenyl)benzene, 2,5-dibromo-terephthalaldehyde and the magnetic nanoparticles Fe3O4 were mixed, and then n-butanol, water and glacial acetic acid were added. The mixture was reacted at 50-70 °C for 12-20 h. After the reaction was completed, the product was separated, washed and dried to obtain Br-COF magnetic nanoparticle solid-phase microextraction material.

5. The preparation method according to claim 4, characterized in that, The molar ratio of 1,3,5-tris(4-aminophenyl)benzene to 2,5-dibromo-terephthalaldehyde is 2:3; the mass ratio of 1,3,5-tris(4-aminophenyl)benzene to magnetic nanoparticles Fe3O4 is 15~25:20~50; and the addition ratio of 1,3,5-tris(4-aminophenyl)benzene, n-butanol, water, and glacial acetic acid is 15~25 mg:1~2 mL:0.2~0.3 mL:0.4~0.6 mL.

6. A Br-COF magnetic nanoparticle solid-phase microextraction material, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 5.

7. The application of the Br-COF magnetic nanoparticle solid-phase microextraction material according to claim 6 in the enrichment of trace polybrominated diphenyl ether pollutants.

8. The application of the Br-COF magnetic nanoparticle solid-phase microextraction material as described in claim 6 combined with HPLC-DAD in the detection of polybrominated diphenyl ether pollutants.

9. A method for detecting polybrominated diphenyl ether (PBDE) pollutants, characterized in that, Includes the following steps: The Br-COF magnetic nanoparticle solid-phase microextraction material described in claim 6 is mixed with the test solution to extract and enrich polybrominated diphenyl ether pollutants in the test solution. After extraction and enrichment, the Br-COF magnetic nanoparticle solid-phase microextraction material was separated, the water sample was discarded, methanol was added for elution, and the eluent was collected after elution. The eluent was filtered through a filter membrane and then detected by a high-performance liquid chromatography-diode array detector. Mobile phase A was an aqueous solution of formic acid with a volume fraction of 0.1%; mobile phase B was acetonitrile, and isocratic elution was used.

10. The method according to claim 9, characterized in that, The extraction and enrichment conditions include: an extraction and enrichment time of 1-30 min, a pH of 4.0-9.0, and an extraction material dosage of 0.5-2.0 mg of Br-COF magnetic nanoparticle solid-phase microextraction material per 5 mL of test solution. The elution time is 1~30 min; Using 150 mm × 4.6 mm, 5 µm C 18 Separation was performed using a chromatographic column at a flow rate of 1 mL / min and an injection volume of 20 μL.

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