COF-coated BDTP-coated Fe3O4 nano material as well as synthesis method and application thereof

Abstract

The invention discloses a COF-coated BDTP-coated Fe3O4 nano material as well as a synthesis method and application thereof. The nano material is obtained by wrapping the surface of aminated nanoscale Fe3O4 with a covalent organic framework material with high porosity and high crystallinity during synthesis, the nano material can effectively adsorb chloramphenicol, the maximum adsorption saturation of every 10 mg of the nano material to chloramphenicol is 9.89-10.4 mu g / mL, and the adsorption repeatability is good. Based on the obtained nano material, the invention also provides a pretreatment method for detecting chloramphenicol by using high performance liquid chromatography. Compared with a traditional pretreatment method, the pretreatment method has the advantages that the use amount of organic reagents is greatly reduced, the pretreatment cost is reduced, the pretreatment time is shortened, and the pretreatment method has good applicability, stability and feasibility, is beneficial to accurate detection of residual chloramphenicol in agricultural and sideline products and guarantees food safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of the synthesis of nanomaterials and the detection of drug residues. More specifically, it relates to a COF@BDTP@Fe3O4 nanomaterial, a synthesis method thereof, and an application thereof. Background Art

[0002] Chloramphenicol (CAP) is a broad-spectrum antibiotic, mainly used for treating infectious diseases caused by various bacteria, and is widely used in livestock farming. Chloramphenicol has serious toxic and side effects on the human body, and can cause adverse reactions such as aplastic anemia and abnormal liver function. Chloramphenicol residues in agricultural and sideline products can enter the human body through the food chain, and long-term micro-intake may lead to serious health problems. Therefore, the detection of chloramphenicol residues in agricultural and sideline products is an important link to ensure food safety.

[0003] Commonly used detection methods for chloramphenicol residues include high-performance liquid chromatography detection, etc. Among them, high-performance liquid chromatography detection has good accuracy and high sensitivity, but its pretreatment process is complex and not conducive to practical applications.

[0004] Covalent organic framework (COF) materials are crystalline porous polymer materials composed of organic molecules connected by covalent bonds. Compared with traditional materials, COF materials have advantages such as low density, high specific surface area, multiple active sites, adjustable porosity, and good thermal stability. Although there are already reports on using COF materials to detect organophosphorus pesticides and acetamiprid, etc., the adsorption effects of the same COF material on different substances are different. During the high-performance liquid chromatography detection process, when using COF materials for pretreatment for different detection targets, the required COF materials are also different. At present, there is no report on a COF material that can be applied to the pretreatment process of high-performance liquid chromatography detection of chloramphenicol. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the present invention provides a COF@BDTP@Fe3O4 nanomaterial, a synthesis method thereof, and an application thereof.

[0006] The first object of the present invention is to provide a synthesis method of a COF@BDTP@Fe3O4 nanomaterial.

[0007] The second object of the present invention is to provide a COF@BDTP@Fe3O4 nanomaterial obtained by synthesizing with the above method.

[0008] The third object of the present invention is to provide the application of the COF@BDTP@Fe3O4 nanomaterial in adsorbing chloramphenicol or in preparing a product for adsorbing chloramphenicol.

[0009] The fourth object of the present invention is to provide the application of the COF@BDTP@Fe3O4 nanomaterial in the preparation of a pretreatment product for detecting chloramphenicol by high performance liquid chromatography.

[0010] The fifth object of the present invention is to provide a pretreatment method for detecting chloramphenicol by high performance liquid chromatography.

[0011] The sixth object of the present invention is to provide a high performance liquid chromatography detection method for chloramphenicol.

[0012] The above objects of the present invention are achieved by the following technical solutions:

[0013] By adjusting the dosages of benzidine and phloroglucinol trialdehyde, the present invention synthesizes a COF material with high porosity and high crystallinity, and wraps the COF material on the surface of amino-functionalized nanoscale Fe3O4 during synthesis, thereby obtaining a COF@BDTP@Fe3O4 nanomaterial that can effectively adsorb chloramphenicol. Based on the COF@BDTP@Fe3O4 nanomaterial, the present invention also develops a pretreatment method for detecting chloramphenicol by high performance liquid chromatography, which greatly reduces the use of organic reagents, reduces costs and shortens the pretreatment time. Therefore, the present invention claims the COF@BDTP@Fe3O4 nanomaterial, its synthesis method and application.

[0014] The present invention provides a synthesis method of the COF@BDTP@Fe3O4 nanomaterial, specifically: dispersing amino-functionalized nanoscale Fe3O4 in 1,4-dioxane at a ratio of 15 - 25 mg / mL, adding phloroglucinol trialdehyde at a ratio of 0.4 - 0.8 mg / mL, adding 1 - 3‰ volume of acetic acid at the same time, mixing evenly and reacting at 115 - 125 °C for 2.4 - 2.6 h. After washing the reaction product, add 0.8 - 1.2 mL of mesitylene and 0.8 - 1.2 mL of 1,4-dioxane to every 200 - 210 mg of the product respectively, then add 75 - 85 mg of benzidine and 55 - 65 mg of phloroglucinol trialdehyde, as well as 0.4 - 0.6 mL of acetic acid solution with a concentration of 8 - 10 mol / L, mix evenly and react at 115 - 125 °C for 46 - 50 h. After washing and drying the reaction product, the COF@BDTP@Fe3O4 nanomaterial is obtained.

[0015] More specifically, the synthesis method is as follows: The amino-functionalized nanoscale Fe3O4 is dispersed in 1,4-dioxane at a ratio of 18 - 22 mg / mL, then phloroglucinol trialdehyde is added at a ratio of 0.5 - 0.7 mg / mL, and at the same time, 1.5 - 2.5‰ volume of acetic acid is added. After mixing evenly, the reaction is carried out at 118 - 122 °C for 2.4 - 2.6 h. After the reaction product is washed, for every 200 - 210 mg of the product, 1 mL of mesitylene and 1 mL of 1,4-dioxane are added respectively, then 75 - 85 mg of benzidine and 55 - 65 mg of phloroglucinol trialdehyde are added, as well as 0.4 - 0.6 mL of acetic acid solution with a concentration of 8 - 10 mol / L. After mixing evenly, the reaction is carried out at 118 - 122 °C for 46 - 50 h. After the reaction product is washed and dried, the COF@BDTP@Fe3O4 nanomaterial is obtained.

[0016] In a specific embodiment of the present invention, the synthesis method is as follows: The amino-functionalized nanoscale Fe3O4 is dispersed in 1,4-dioxane at a ratio of 20 mg / mL, then phloroglucinol trialdehyde is added at a ratio of 0.6 mg / mL, and at the same time, 2‰ volume of acetic acid is added. After mixing evenly, the reaction is carried out at 120 °C for 2.5 h. After the reaction product is washed with absolute ethanol and water, for every 200 mg of the product, 1 mL of mesitylene and 1 mL of 1,4-dioxane are added respectively, then 4 mL of deionized water containing 75 - 85 mg of benzidine and 55 - 65 mg of phloroglucinol trialdehyde is added, as well as 0.5 mL of acetic acid solution with a concentration of 9 mol / L. After mixing evenly, the reaction is carried out at 120 °C for 48 h. After the reaction product is washed and dried, the COF@BDTP@Fe3O4 nanomaterial is obtained.

[0017] More specifically, for every 200 mg of the product, 1 mL of mesitylene and 1 mL of 1,4-dioxane are added respectively, then 4 mL of deionized water containing 80 mg of benzidine and 60 mg of phloroglucinol trialdehyde is added.

[0018] Specifically, the particle size of the amino-functionalized nanoscale Fe3O4 is 180 - 220 nm.

[0019] More specifically, the particle size of the amino-functionalized nanoscale Fe3O4 is 200 nm.

[0020] Specifically, when acetic acid is added for the first time, the concentration of the acetic acid is 17.5 mol / L.

[0021] The amino-functionalized nanoscale Fe3O4 used in the above synthesis method can be purchased as commercially available amino-functionalized Fe3O4 magnetic beads, or can be prepared by oneself. In a specific embodiment of the present invention, the preparation method of the amino-functionalized nanoscale Fe3O4 includes the following steps:

[0022] S1. Preparation of nanoscale Fe3O4: Dissolve 180 - 220 mg of ferric chloride hexahydrate in 8 - 12 mL of ethylene glycol, then add 0.4 - 0.6 mL of 0.1 M sodium acetate dissolved in ethylene glycol. After mixing evenly, add 4 - 6 mL of polyethylene glycol and stir to fully dissolve and react. Transfer the reacted liquid to a high-pressure reactor, heat it at 180 - 200 °C for 12 - 14 h and then cool it. Wash the product repeatedly with ethanol and deionized water and then place it in a vacuum drying oven for drying to obtain the product nanoscale Fe3O4. The obtained product is then passed through a 200 nm polycarbonate membrane, and nanoscale Fe3O4 with a particle size of 200 nm is obtained by filtration and stored for later use;

[0023] S2. Preparation of amino-functionalized Fe3O4: Take 1 - 1.2 g of the prepared Fe3O4 with a particle size of 200 nm and add it to 100 - 120 mL of 80% ethanol. Add 0.4 - 0.6 mL of ammonia water and 0.2 - 0.3 mL of tetraethoxysilane. After ultrasonic treatment until the solution is completely dispersed and uniform, shake it at a constant temperature of 70 °C in a water bath shaker for 5 - 7 h. The product is washed with absolute ethanol and deionized water and then added to 100 - 120 mL of 80% ethanol, 0.4 - 0.6 mL of ammonia water and 0.2 - 0.3 mL of aminopropyltriethoxysilane. After ultrasonic treatment until the solution is completely dispersed and uniform, shake it at a constant temperature of 70 °C in a water bath shaker for 5 - 7 h. The product is washed with absolute ethanol and deionized water and then placed in a vacuum drying oven for drying to obtain amino-functionalized nanoscale Fe3O4, which is stored at 4 °C for later use.

[0024] Specifically, in S1, the obtained product is passed through a 200 nm polycarbonate membrane and filtered at a speed of 0.5 mL / min to obtain nanoscale Fe3O4 with a particle size of 200 nm.

[0025] The present invention also provides a COF@BDTP@Fe3O4 nanomaterial synthesized by using the said synthesis method.

[0026] The COF@BDTP@Fe3O4 nanomaterial of the present invention can effectively adsorb chloramphenicol, and the maximum adsorption saturation of chloramphenicol per 10 mg of the nanomaterial is 9.89 - 10.4 μg / mL. Therefore, the present invention requests protection for the application of the COF@BDTP@Fe3O4 nanomaterial in adsorbing chloramphenicol or in the preparation of products for adsorbing chloramphenicol.

[0027] The present invention also requests protection for the application of the said COF@BDTP@Fe3O4 nanomaterial in the preparation of a pretreatment product for detecting chloramphenicol based on high performance liquid chromatography.

[0028] Based on the COF@BDTP@Fe3O4 nanomaterial of the present invention, the present invention also provides a pretreatment method for detecting chloramphenicol based on high performance liquid chromatography, including the following steps:

[0029] S1. If the sample to be tested is a liquid, add water and mix well according to the volume ratio of the sample to be tested to water of 1:1 - 2, adjust the pH to 5 - 7, add 5 - 10 g of the COF@BDTP@Fe3O4 nanomaterial, and let it stand for adsorption for 60 - 100 min; if the sample to be tested is a solid, add water and grind it into a homogenate according to the mass - volume ratio of the sample to be tested to water of 1:1 - 2, adjust the pH to 5 - 7, add 5 - 10 g of the COF@BDTP@Fe3O4 nanomaterial, and let it stand for adsorption for 60 - 100 min;

[0030] S2. Take out the COF@BDTP@Fe3O4 nanomaterial after the standing adsorption in S1 and place it in another container, add a desorbent and desorb for 20 - 30 min, and filter the desorbed solution through a filter membrane;

[0031] Among them, the desorbent is methanol, acetonitrile, a mixed solution of methanol and formic acid, or a mixed solution of acetonitrile and acetic acid.

[0032] Specifically, in S1, adjust the pH to 6 ± 0.5.

[0033] More specifically, in S1, adjust the pH to 6.

[0034] Specifically, the standing adsorption time is 60 - 80 min.

[0035] Preferably, the standing adsorption time is 60 min. Under this time condition, the COF@BDTP@Fe3O4 nanomaterial can already adsorb chloramphenicol to the maximum extent, and with the extension of time, the adsorption amount of chloramphenicol will not increase significantly anymore.

[0036] Specifically, the reaction temperature during the standing adsorption is 25°C - 35°C.

[0037] More specifically, the temperature is 28°C - 32°C.

[0038] Specifically, in the mixed solution of methanol and formic acid, the volume ratio of methanol to formic acid is 95 - 97:3 - 5; in the mixed solution of acetonitrile and acetic acid, the volume ratio of acetonitrile to acetic acid is 95 - 97:3 - 5.

[0039] More specifically, in the mixed solution of methanol and formic acid, the volume ratio of methanol to formic acid is 96:4; in the mixed solution of acetonitrile and acetic acid, the volume ratio of acetonitrile to acetic acid is 97:3.

[0040] Specifically, when adding the desorbent, the mass (g) - volume (mL) ratio of the COF@BDTP@Fe3O4 nanomaterial to the desorbent is 4 - 6:2 - 3.

[0041] More specifically, the mass-volume ratio of the COF@BDTP@Fe3O4 nanomaterial to the desorbent is 2.5 g / mL.

[0042] Specifically, after adding the desorbent, desorption is carried out for 25 - 30 min.

[0043] Preferably, after adding the desorbent, desorption is carried out for 25 min.

[0044] Specifically, the filter membrane is a 0.22 μM filter membrane.

[0045] More specifically, the filter membrane is a 0.22 μm PTFE organic phase microporous filter membrane.

[0046] The present invention also provides a high performance liquid chromatography detection method for chloramphenicol, specifically: after pretreating the sample to be tested by the pretreatment method of the present invention, taking the filtrate obtained by filtering through the filter membrane for high performance liquid chromatography detection; the chromatographic conditions used are as follows: a C18 reversed-phase chromatographic column, the column temperature is 28 - 32 °C; the mobile phase is a 50% methanol solution, isocratic elution, the flow rate of the mobile phase is 1.0 mL / min; the injection volume is 20 μL; the detector is a DAD detector, and the detection wavelength is 280 nm.

[0047] Specifically, the specifications of the chromatographic column are: 5 μm, 250 mm × 4.6 mm.

[0048] The present invention has the following beneficial effects:

[0049] By adjusting the dosages of benzidine and phloroglucinol trialdehyde, the present invention synthesizes a COF material with high porosity and high crystallinity, and wraps the COF material on the surface of amino-functionalized nanoscale Fe3O4 (amino-functionalized Fe3O4 magnetic beads) during synthesis to obtain a COF@BDTP@Fe3O4 nanomaterial. The nanomaterial of the present invention can effectively adsorb chloramphenicol, and the maximum adsorption saturation of chloramphenicol per 10 mg of the nanomaterial is 9.89 - 10.4 μg / mL, and the adsorption repeatability is good. Based on the obtained nanomaterial, the present invention also provides a pretreatment method for detecting chloramphenicol by high performance liquid chromatography. Compared with the traditional pretreatment method, the pretreatment method of the present invention greatly reduces the usage amount of organic reagents, reduces the pretreatment cost and shortens the pretreatment time, has good applicability, stability and good feasibility, is conducive to the accurate detection of residual chloramphenicol in agricultural and sideline products, and ensures food safety. Description of the Drawings

[0050] Figure 1Scanning electron microscope images of the nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials synthesized in this invention; the scanning electron microscope images of the nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials are shown as A - C in the figure in sequence.

[0051] Figure 2 Schematic diagram of the synthesis process of the COF@BDTP@Fe3O4 nanomaterial and the schematic diagram of detection after adsorbing chloramphenicol with it.

[0052] Figure 3 X - ray diffraction patterns of the nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials synthesized in this invention.

[0053] Figure 4 Fourier transform infrared spectroscopy characterization diagrams of the nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials synthesized in this invention.

[0054] Figure 5 Test results of the adsorption effect of the COF@BDTP and COF@BDTP@Fe3O4 nanomaterials synthesized in this invention on chloramphenicol (chromatogram of the remaining CAP in the solution).

[0055] Figure 6 Test results of the maximum adsorption capacity of the COF@BDTP@Fe3O4 nanomaterial synthesized in this invention for chloramphenicol.

[0056] Figure 7 Effect of the reuse of the COF@BDTP@Fe3O4 nanomaterial synthesized in this invention on the adsorption effect of chloramphenicol.

[0057] Figure 8 Test results of the stability of the COF@BDTP@Fe3O4 nanomaterial synthesized in this invention.

[0058] Figure 9 Effect of pH on the adsorption effect of the COF@BDTP@Fe3O4 nanomaterial synthesized in this invention on chloramphenicol.

[0059] Figure 10 Effect of the static adsorption time on the adsorption effect of the COF@BDTP@Fe3O4 nanomaterial synthesized in this invention on chloramphenicol.

[0060] Figure 11 Effect of the desorbent type on the adsorption effect of the COF@BDTP@Fe3O4 nanomaterial synthesized in this invention on chloramphenicol.

[0061] Figure 12 Effect of desorption time on the adsorption effect of chloramphenicol by the COF@BDTP@Fe3O4 nanomaterial synthesized in the present invention. Specific embodiments

[0062] The present invention will be further described below in conjunction with the specification drawings and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0063] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0064] Example 1 Synthesis of COF@BDTP@Fe3O4 nanomaterial

[0065] The synthesis method of the COF@BDTP@Fe3O4 nanomaterial described in the present invention includes the following steps:

[0066] S1. Preparation of nanoscale Fe3O4: Dissolve 200 mg of ferric chloride hexahydrate (FeCl3·6H2O) in 10 mL of ethylene glycol, then add 0.5 mL of 0.1 M sodium acetate, stir evenly and then add 5 mL of polyethylene glycol, and stir with a magnetic particle stirrer for 30 min to fully dissolve and react; transfer the reacted liquid to a high-pressure reaction kettle, heat at 180 °C for 12 h and then cool, repeatedly rinse the product 3 times with ethanol and deionized water and then place it in a 60 °C vacuum drying oven for drying for 6 h to obtain the product nanoscale Fe3O4; the obtained product is then filtered through a 200 nm polycarbonate membrane (as a filter membrane) at a speed of 0.5 mL / min to obtain Fe3O4 with a particle size of 200 nm, and store it for later use;

[0067] S2. Preparation of amino-functionalized Fe3O4 (Fe3O4-NH2): Take 1 g of the prepared Fe3O4 with a particle size of 200 nm and add it to 100 mL of 80% ethanol, add 0.5 mL of ammonia water and 0.25 mL of tetraethoxysilane, ultrasonicate for 1 h until the solution is completely dispersed and uniform, and then shake it at a constant temperature of 70 °C in a water bath shaker for 6 h. The product is rinsed 3 times with anhydrous ethanol and deionized water and then added to 100 mL of 80% ethanol, 0.5 mL of ammonia water and 0.25 mL of aminopropyltriethoxysilane, ultrasonicate for 1 h, and then shake it in a 70 °C water bath for 6 h. The product is rinsed 3 times with anhydrous ethanol and deionized water and then dried in a 60 °C vacuum for 6 h to obtain Fe3O4-NH2, and store it at 4 °C for later use;

[0068] Preparation of S3.COF@BDTP@Fe3O4 nanomaterials: Take 200 mg of the prepared Fe3O4-NH2 and disperse it in 10 mL of 1,4-dioxane. Add 6 mg of phloroglucinol trialdehyde (TP) and 50 μL of acetic acid (17.5 mol / L). After ultrasonic mixing for 10 min, put it into a reaction kettle and react at 120 °C for 2.5 h to obtain a preliminary reaction product. After washing the reaction product with absolute ethanol and deionized water, add 1 mL of mesitylene and 1 mL of 1,4-dioxane, then add 4 mL of deionized water containing 80 mg of benzidine (BD) and 60 mg of TP, as well as 0.5 mL of 9 mol / L acetic acid solution. Stir evenly and ultrasonically for 10 min, then transfer it into the reaction kettle and react at 120 °C for 48 h. After the reaction is completed, take out the brown-yellow product, wash it 3 times with absolute ethanol and deionized water, and dry it in vacuum at 60 °C for 6 h to obtain brown-yellow COF@BDTP@Fe3O4 nanomaterials, and store them at 4 °C for later use.

[0069] In addition to synthesizing COF@BDTP@Fe3O4 nanomaterials, the present invention also synthesized COF@BDTP, and its synthesis method is the same as the above method, and the only difference is that Fe3O4-NH2 is not added. The synthesized nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials were respectively subjected to electron microscopy scanning, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) analysis.

[0070] The scanning electron microscope images of the prepared nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials are successively as shown in Figure 1 A - C in. As can be seen from Figure 1 , the nanoscale Fe3O4 prepared in the present invention is in the form of microsphere aggregates ( Figure 1 A in), and COF@BDTP shows the characteristics of being irregular but having many micropores ( Figure 1 B in). As can be seen from Figure 1 C, Fe3O4 is well wrapped inside by COF@BDTP, indicating that the COF@BDTP@Fe3O4 nanomaterials are successfully synthesized.

[0071] The schematic diagram of the synthesis process of the COF@BDTP@Fe3O4 nanomaterials is as shown in Figure 2 .

[0072] The X-ray diffraction patterns of the prepared nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials are as shown in Figure 3 . As can be seen from Figure 3It can be seen that strong diffraction peaks appear at 2θ = 18.40°, 30.30°, 35.50°, 43.25°, 53.54°, 57.13°, and 62.65° for the COF@BDTP@Fe3O4 nanomaterial, corresponding to the diffraction peaks of the 220, 311, 400, 422, 511, and 440 crystal planes of nanoscale Fe3O4 (Fe3O4 NPs), respectively. In addition, a weak diffraction peak appears at 2θ = 5.92°, which may be due to the low crystallinity of the generated COF, consistent with the literature reports on the synthesis of COF by the hydrothermal synthesis method. Combining the results of transmission electron microscopy (TEM), it can be seen that the COF@BDTP@Fe3O4 composite material was successfully synthesized.

[0073] The Fourier transform infrared spectroscopy characterization diagrams of the prepared nanoscale Fe3O4, COF@BDTP, and COF@BDTP@Fe3O4 nanomaterials are as Figure 4 shown. From Figure 4 it can be seen that the COF@BDTP@Fe3O4 nanomaterial shows a stretching vibration absorption peak of Fe-O-Fe at a wavenumber of 587 cm -1 and a stretching vibration absorption peak of Si-O-Si at 1014 cm -1 . Also, from Figure 4 it can be seen that the absorption peaks of amino and aldehyde groups that should have been at 3406 cm -1 and 2890 cm -1 disappear, and a new absorption peak of the formed C-N bond appears at 1682 cm -1 for the COF@BDTP@Fe3O4 nanomaterial, further indicating that the COF@BDTP@Fe3O4 nanomaterial has been successfully synthesized.

[0074] Example 2

[0075] The difference between the synthesis method of the COF@BDTP@Fe3O4 nanomaterial described in this example and the method described in Example 1 lies in that in S3, after obtaining the preliminary reaction product, the amounts of benzidine and phloroglucinol trialdehyde used are different; the amount of benzidine used is 75 mg; the amount of phloroglucinol trialdehyde used is also 55 mg. The appearance of the prepared COF@BDTP@Fe3O4 nanomaterial has no obvious difference from that of Example 1.

[0076] Example 3

[0077] The difference between the synthesis method of the COF@BDTP@Fe3O4 nanomaterial described in this example and the method described in Example 1 lies in that in S3, after obtaining the preliminary reaction product, the amounts of benzidine and phloroglucinol trialdehyde used are different; the amount of benzidine used is 85 mg; the amount of phloroglucinol trialdehyde used is also 65 mg. The appearance of the prepared COF@BDTP@Fe3O4 nanomaterial has no obvious difference from that of Example 1.

[0078] Comparative Example 1

[0079] The difference between the synthesis method of the COF@BDTP@Fe3O4 nanomaterial described in this comparative example and the method described in Example 1 lies in that in S3, the dosages of benzidine and phloroglucinol trialdehyde are different; the dosage of benzidine is 50 mg; the dosage of phloroglucinol trialdehyde is also 50 mg.

[0080] The color of the final product synthesized in this comparative example is dark brown, and it is judged that the reason is incomplete Fe3O4 coating.

[0081] Comparative Example 2

[0082] The difference between the synthesis method of the COF@BDTP@Fe3O4 nanomaterial described in this comparative example and the method described in Example 1 lies in that in S3, the dosages of benzidine and phloroglucinol trialdehyde are different; the dosage of benzidine is 40 mg; the dosage of phloroglucinol trialdehyde is also 80 mg.

[0083] The color of the final product synthesized in this comparative example is dark brown, and it is judged that the reason is incomplete reaction.

[0084] Experimental Example 1 Adsorption Performance and Stability Test of COF@BDTP@Fe3O4 Nanomaterial on Chloramphenicol

[0085] Taking the COF@BDTP@Fe3O4 nanomaterial synthesized in Example 1 as an example, its adsorption performance and stability on chloramphenicol were tested.

[0086] 1. Adsorption Effect Test on Chloramphenicol

[0087] (1) To test whether the synthesized nanomaterial has an adsorption effect on chloramphenicol (CAP), the CAP standard solution with a concentration of 1 mg / mL was diluted to 10 μg / mL; 2 mL of the diluted solution was respectively placed into centrifuge tubes containing equal amounts of COF@BDTP@Fe3O4 nanomaterial and COF@BDTP, as well as an empty centrifuge tube (as a control). After waiting for 1 h, the adsorption solution was taken, filtered through a 0.22 μm PTFE organic phase microporous filter membrane, and then the change in the CAP concentration in the solution before and after adsorption was detected and compared by HPLC.

[0088] The test results of the adsorption effect of the synthesized COF@BDTP and COF@BDTP@Fe3O4 nanomaterials on chloramphenicol are as Figure 5 shown. From Figure 5It can be seen that both COF@BDTP and COF@BDTP@Fe3O4 nanomaterials have an adsorption effect on CAP. Among them, the adsorption effect of COF@BDTP@Fe3O4 nanomaterials is more obvious. The reason may be that the encapsulation of Fe3O4 by COF expands the specific surface area of COF, thereby increasing the porosity and enhancing the intermolecular force and π-π interaction.

[0089] (2) To test the maximum adsorption capacity of the synthesized nanomaterials for CAP, the synthesized nanomaterials were evenly divided into six parts with an analytical balance, each part being 10.0 mg. CAP standard solutions with concentrations of 1, 5, 10, 15, 20, and 25 μg / mL in equal volumes were added respectively. After waiting for 1 h, the adsorption solutions were respectively taken and filtered through a 0.22 μm PTFE organic phase microfiltration membrane, and then detected by HPLC to calculate the maximum adsorption capacity range of each 10 mg of the nanomaterials for CAP.

[0090] The test results of the adsorption capacity of the synthesized COF@BDTP@Fe3O4 nanomaterials for chloramphenicol are as Figure 6 shown. It can be Figure 6 seen that as the concentration of CAP in the solution increases, the adsorption capacity of the nanomaterials for CAP gradually reaches a saturation state. After calculation, the maximum adsorption saturation of each 10 mg of COF@BDTP@Fe3O4 nanomaterials for CAP is between 9.89 and 10.4 μg / mL, and the maximum adsorption saturation of each mg of nanomaterials for CAP is 0.89 - 1.04 μg / mL.

[0091] 2. Stability test

[0092] (1) Through multiple adsorption-desorption cycle experiments, the change in the adsorption efficiency of the synthesized nanomaterials during repeated use was tested. The experiment was carried out under the same conditions, and the same batch of synthesized nano-adsorption materials was subjected to 6 repeated adsorption-desorption experiments.

[0093] The influence of the repeated use of the synthesized COF@BDTP@Fe3O4 nanomaterials on the adsorption effect of chloramphenicol is as Figure 7 shown (n = 3). It can be Figure 7 seen that the adsorption efficiency range of the six experiments of the nanomaterials is 93.50% - 94.38%, and the RSD is 0.28%. It can be concluded that as long as the synthesized nanomaterials do not undergo oxidation reactions, their repeated use effects are relatively stable, indicating that the repeatability of the adsorption materials is good.

[0094] (2) To test the stability of the synthesized nanomaterials, they were stored at 4 °C for one month, and the adsorption efficiency of the nanomaterials for CAP was tested under the same conditions every week. The stability test results of the synthesized COF@BDTP@Fe3O4 nanomaterials are as shown in Figure 8 (n = 3). As can be seen from Figure 8 , for the COF@BDTP@Fe3O4 nanomaterials synthesized in the present invention, the adsorption rate was stable above 92% before 14 days. After 21 days, it began to decrease to 89%. This may be because a small part of the material was oxidized, resulting in a decrease in the adsorption efficiency. However, based on the above data, it can be seen that the COF@BDTP@Fe3O4 nanomaterials synthesized in the present invention have relatively good stability.

[0095] Experimental Example 2 Construction and Optimization of the Pretreatment Method for Detecting Chloramphenicol by High Performance Liquid Chromatography

[0096] As can be seen from the results shown in Experimental Example 1, the COF@BDTP@Fe3O4 nanomaterials synthesized in the present invention can adsorb chloramphenicol. Based on this, the present invention provides a pretreatment method for using the COF@BDTP@Fe3O4 nanomaterials synthesized in Example 1 of the present invention to pretreat the sample to be tested so as to detect the chloramphenicol contained therein by high performance liquid chromatography.

[0097] Using the COF@BDTP@Fe3O4 nanomaterials, the pretreatment method for detecting chloramphenicol based on high performance liquid chromatography preliminarily established in the present invention is as follows:

[0098] Weigh 5 g of the sample to be tested (such as pork, chicken), add 10 mL of water and grind it into a homogeneous slurry state. Add an excessive amount (at least 5 mg) of COF@BDTP@Fe3O4 nanomaterials, mix evenly, and then stand and adsorb at 25 °C - 35 °C for at least 60 min; after the adsorption is completed, take out the COF@BDTP@Fe3O4 nanomaterials with a magnet, put them into a centrifuge tube, add 2 mL of desorbent, after desorbing for 15 min, take out the desorbing solution with a 1 mL syringe, filter it through a membrane and put it into an injection vial, and then perform on-machine inspection.

[0099] The liquid chromatography conditions are as follows: The chromatographic column is a C18 reverse phase chromatographic column, specifications: 5 μm, 250 mm × 4.6 mm; the volume ratio of the mobile phase: methanol: water = 1:1, isocratic elution; the flow rate of the mobile phase: 1.0 mL / min; the column temperature: 30 °C; the injection volume: 20 μL (controlled by the quantitative loop); the detector: DAD detector, detection wavelength: 280 nm. All the analyzed samples are filtered through a 0.22 μm microporous membrane before use.

[0100] 1. Influence of pH on the Adsorption Effect of COF@BDTP@Fe3O4 Nanomaterials

[0101] To test the influence of the pH value of the sample solution to be measured on the adsorption effect of the synthesized COF@BDTP@Fe3O4 nanomaterial on chloramphenicol during adsorption, in this invention, the pH of the water sample containing 10 μg / mL chloramphenicol was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, and 10 respectively using 2M HCl solution or NaOH solution. Equal amounts of COF@BDTP@Fe3O4 nanomaterials were respectively added into 9 water samples with the above different pH values, and adsorption was carried out under the same conditions. After 1 hour of adsorption, the adsorption solutions of each water sample were respectively taken, passed through a microporous filter membrane and then added into a 2 mL injection vial, and analyzed by liquid chromatography. The absorption concentration and absorption efficiency were calculated according to the standard curve to determine the optimal pH.

[0102] The stability of chloramphenicol in solutions with different pH values showed significant differences. In the range of pH 2 - 7, the influence of pH on the hydrolysis rate of chloramphenicol was relatively small. When the pH was lower than 2 or higher than 8, the hydrolysis rate of chloramphenicol would increase significantly. In addition, under the condition of pH greater than 8, chloramphenicol might also undergo dechlorination reaction, resulting in inactivation. The influence of pH on the adsorption effect of the synthesized COF@BDTP@Fe3O4 nanomaterial on chloramphenicol is as Figure 9 shown (n = 3). As Figure 9 can be seen, after pH > 7, due to the hydrolysis of chloramphenicol, the adsorption decreased significantly; when the pH was 6, the adsorption rate reached the highest, which was 86%. Therefore, in subsequent experiments, the pH of the sample solution to be measured was adjusted to 6.

[0103] 2. Influence of adsorption time on the adsorption effect of COF@BDTP@Fe3O4 nanomaterial

[0104] Take six 2 mL water samples each containing 10 μg / mL chloramphenicol, after adjusting the pH to 6, add equal amounts of the synthesized COF@BDTP@Fe3O4 nanomaterials respectively, and let them stand for adsorption for 0, 20, 40, 60, 80, and 100 min respectively. Take the adsorption solutions of each, pass through a microporous filter membrane and then add into a 2 mL injection vial, and measure the concentration of the remaining chloramphenicol in the adsorption solution by high performance liquid chromatography, and calculate the adsorption efficiency at different adsorption times.

[0105] The influence of adsorption time on the adsorption effect of the synthesized COF@BDTP@Fe3O4 nanomaterial on chloramphenicol is as Figure 10 shown (n = 3). As Figure 10 can be seen, under the same conditions, the adsorption of the nanomaterial on CAP gradually reached complete adsorption after 40 min of adsorption, and was basically completely adsorbed after 60 min. The standing adsorption time for subsequent experiments was all 60 min.

[0106] 3. Influence of the type of desorbent on the adsorption effect of COF@BDTP@Fe3O4 nanomaterial

[0107] Take six 2-mL water samples containing 10 μg / mL chloramphenicol, adjust the pH to 6, and then add equal amounts of the synthesized COF@BDTP@Fe3O4 nanomaterial and let it stand for adsorption for 60 min. After the adsorption is completed, use a desorbent to elute the chloramphenicol adsorbed on the nanomaterial. Collect the desorption solution, filter it through a microporous filter membrane, and then perform high-performance liquid chromatography analysis. Calculate and compare the recovery rates of different desorbents to determine the optimal desorbent. The desorbents used in this experiment are: acetonitrile, methanol, methanol:formic acid (v:v) = 96:4, acetonitrile:acetic acid (v:v) = 97:3, phosphate buffer:acetonitrile (v:v) = 1:1, and phosphate buffer, a total of 6 kinds.

[0108] The present invention compares the effects of different desorbents (acetonitrile, methanol, methanol:formic acid (v:v) = 96:4, acetonitrile:acetic acid (v:v) = 97:3, phosphate buffer:acetonitrile (v:v) = 1:1, and phosphate buffer) on the desorption efficiency of CPA. The results are as Figure 11 shown. As Figure 11 can be seen, the desorption effect is the best when using a mixture of acetonitrile and acetic acid (volume ratio 97:3) as the desorbent, and the final desorption efficiency can reach 87% (desorption efficiency = spiked concentration / adsorption concentration).

[0109] In subsequent experiments, a mixture of acetonitrile and acetic acid (volume ratio 97:3) is selected as the desorbent.

[0110] 4. Effect of desorption time on the adsorption effect of COF@BDTP@Fe3O4 nanomaterial

[0111] Prepare five 2-mL standard solutions with a CAP concentration of 10 μg / mL, adjust the pH to 6, add 10 mg of the synthesized COF@BDTP@Fe3O4 nanomaterial, vortex disperse it, and let it stand for adsorption in a 30°C water bath for 60 min. Then, take out the nanomaterial and perform desorption in 2 mL of acetonitrile-acetic acid desorbent (acetonitrile:acetic acid = 97:3) for 5, 10, 15, 20, 25, and 30 min respectively. After magnetic separation, collect the desorption solution and detect the CAP content in the desorption solution by liquid chromatography to investigate the effect of different desorption times on the desorption efficiency of CAP.

[0112] The effect of desorption time on the adsorption effect of the synthesized COF@BDTP@Fe3O4 nanomaterial on chloramphenicol is as Figure 12 shown (n = 3). As Figure 12 can be seen, there is an obvious equilibrium relationship between the desorption time and the desorption efficiency. Within a certain range, as the desorption time increases, the desorption efficiency increases significantly; however, when the desorption time exceeds a certain critical value, the increase in desorption efficiency tends to level off. As Figure 12As shown, when the desorption time is 20 min, the desorption gradually becomes flat, and complete desorption occurs at 25 min, with a desorption efficiency of 93.50%. In subsequent experiments, the desorption experiment is 25 min each time.

[0113] Based on the above optimization experiment results, the best pretreatment method for detecting chloramphenicol based on high performance liquid chromatography provided by the present invention includes the following steps:

[0114] S1. If the sample to be tested is a liquid, add water and mix evenly according to the volume ratio of the sample to be tested to water of 1:1 - 2, adjust the pH to 6, add 10 g of the COF@BDTP@Fe3O4 nanomaterial, and let it stand for adsorption for 60 min; if the sample to be tested is a solid, add water and grind it into a homogeneous slurry according to the mass - volume ratio of the sample to be tested to water of 1:1 - 2, adjust the pH to 6, add 10 g of the COF@BDTP@Fe3O4 nanomaterial, and let it stand for adsorption for 60 min;

[0115] S2. Take out the COF@BDTP@Fe3O4 nanomaterial after the static adsorption in S1 and place it in another container. Add 2 mL of acetonitrile - acetic acid desorbent (acetonitrile: acetic acid = 97:3) and desorb for 25 min. After filtering the desorbed solution through a membrane, perform detection.

[0116] Comparison of recovery rate and relative deviation between the pretreatment method described in Experimental Example 3 and the national standard detection method for chloramphenicol

[0117] The present invention prepared pig urine and chicken homogenates containing 5, 10, and 20 μg / mL chloramphenicol respectively. Taking these as samples to be tested, the recovery rate (%) and relative standard deviation (%) after liquid chromatography detection (repeated 3 times) under the same chromatographic conditions (shown in Experimental Example 2) were respectively tested after pretreatment of the samples to be tested using the best pretreatment method described in Experimental Example 2 of the present invention and the national standard detection method.

[0118] Prepare 5 mL of pig urine containing 5, 10, and 20 μg / mL chloramphenicol respectively, with 3 portions for each concentration; taking these as samples to be tested, pretreat them using the best pretreatment method described in Experimental Example 2 and then perform liquid chromatography detection on the machine; separately take another 3 portions of 5.00 g of blank chicken, add 5 mL of the prepared chloramphenicol standard solution containing 5, 10, and 20 μg / mL respectively, mix and grind them into a homogeneous slurry state, with 3 portions for each concentration; taking these as samples to be tested, pretreat them using the best pretreatment method described in Experimental Example 2 and then perform liquid chromatography detection on the machine; take the average value of the results.

[0119] It can be seen from the detection results that after being processed by the optimal pretreatment method described in the present invention, the recovery rate of chloramphenicol in pig urine is between 84.40% and 98.93%, and the relative standard deviation (RSD) is between 0.12% and 0.55%; the recovery rate of chloramphenicol in chicken is between 84.17% and 98.93%, and the RSD is between 0.66% and 1.59%.

[0120] Control example of national standard for pig urine (GB 31658.2-2021)

[0121] Prepare 5 mL of pig urine containing 5, 10, and 20 μg / mL chloramphenicol respectively, and use this as the sample to be tested. Pretreat it according to the pretreatment method in the national standard (GB31658.2-2021). The pretreatment method is as follows: Add 2 mL of 0.2 mol / L ammonium acetate (pH = 5.2) to the sample to be tested, then add 15 mL of ethyl acetate, vortex for 2 min and then shake for 10 min, centrifuge at 4000 r / min for 10 min, extract the supernatant into a 50 mL centrifuge tube, continue to add 15 mL of ethyl acetate to the remaining lower layer solution, repeat the above operation 2 times, combine the supernatants of the 2 times, shake well, take 6 mL and place it in a nitrogen blower to dry at 45 °C, add 1 mL of deionized water to re-dissolve, filter through a 0.22 μm filter membrane and then perform liquid chromatography detection on the machine. Repeat the above operation three times, take the average value of the results, and the resulting recovery rate is between 89.7% and 100.3%, and the RSD is between 0.5% and 10.4%.

[0122] Control example of national standard for chicken (GB 31658.2-2021)

[0123] Extraction: Take 5.0 g of the blank chicken sample that has been minced and place it in a 50 mL polypropylene centrifuge tube. Add the prepared chloramphenicol standard solution and mix it into a homogeneous state by grinding. Add 15 mL of ethyl acetate, 0.45 mL of ammonium hydroxide, and 5 g of anhydrous sodium sulfate, homogenize and extract for 30 s, centrifuge at 4000 r / min for 5 min, and transfer the supernatant to a 50 mL colorimetric tube; take another 50 mL centrifuge tube, add 15 mL of ethyl acetate and 0.45 mL of sodium hydroxide, wash and homogenize for 5 min, centrifuge at 4000 r / min for 5 min, and combine the supernatants into a 50 mL colorimetric tube; add 15 mL of ethyl acetate to the residue again, repeat the above operation, combine all the supernatants into a 50 mL colorimetric tube, make up the volume to 50 mL with ethyl acetate, shake well, transfer 10 mL of the ethyl acetate extract to a 25 mL pear-shaped flask and concentrate it to dry at 45 °C by rotary evaporation;

[0124] Purification: The residue in the Erlenmeyer flask was dissolved with 3 mL of water, sonicated for 5 min, 3 mL of n-hexane was added and vortex-mixed for 30 s, allowed to stand for phase separation, the upper layer of n-hexane was discarded, another 3 mL of n-hexane was added and vortex-mixed for 30 s, allowed to stand for phase separation, 1 mL of the aqueous phase was transferred to a 1.5 mL polypropylene centrifuge tube, centrifuged at 13000 r / min for 5 min, and the supernatant was filtered through a 0.22 μm filter membrane and then analyzed by liquid chromatography. The above operation was repeated three times, and the average value of the results was taken. The recovery rate of the results was between 89% and 113%, and the RSD was between 5.3% and 9.5%.

[0125] After the pretreatment of pig urine and chicken samples containing different concentrations of chloramphenicol by using the pretreatment method described in the present invention and the method recommended by GB / T 22338-2008, the recoveries and RSDs of liquid chromatography detection are summarized in Table 1 as follows.

[0126] Table 1 Recoveries and relative standard deviations (n = 3)

[0127]

[0128] As can be seen from Table 1, the recoveries of pig urine treated by using the pretreatment method described in the present invention are between 84.40% and 98.93%, and the RSDs are between 0.12% and 0.55%; the recoveries of chicken are between 84.17% and 98.93%, and the RSDs are between 0.66% and 1.59%, which are similar to those of the national standard, indicating that the method described in the present invention has good precision and accuracy.

[0129] Since the method recommended by GB 31658.2-2021 requires multiple additions of a large amount of organic solvents and a complex purification and nitrogen blowing concentration process, the time for treating samples by the national standard method is about 4 hours. However, the pretreatment method provided by the present invention has fewer steps and higher extraction efficiency. The advantage of the present invention lies in the pretreatment method before determination. Further research finds that the chloramphenicol drug residues can be basically separated by the pretreatment method of the present invention, and fewer organic reagents are required. The total pretreatment time only needs about 1.5 h, which greatly reduces the pretreatment time and cost.

[0130] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A synthesis method of COF@BDTP@Fe3O4 nanomaterials, characterized in that, Disperse the amino-functionalized nanoscale Fe3O4 in 1,4-dioxane at a ratio of 15 - 25 mg / mL, then add phloroglucinol trialdehyde at a ratio of 0.4 - 0.8 mg / mL, and simultaneously add 1 - 3‰ volume of acetic acid. After mixing evenly, react at 115 - 125 °C for 2.4 - 2.6 h. After washing the reaction product, add 0.8 - 1.2 mL of mesitylene and 0.8 - 1.2 mL of 1,4-dioxane to every 200 - 210 mg of the product respectively, then add 75 - 85 mg of benzidine, 55 - 65 mg of phloroglucinol trialdehyde, and 0.4 - 0.6 mL of acetic acid solution with a concentration of 8 - 10 mol / L. After mixing evenly, react at 115 - 125 °C for 46 - 50 h. After washing and drying the reaction product, the COF@BDTP@Fe3O4 nanomaterial is obtained.

2. The synthesis method according to claim 1, characterized in that, The particle size of the amino-functionalized nanoscale Fe3O4 is 180 - 220 nm.

3. The synthesis method according to claim 1, wherein The concentration of the acetic acid solution is 8.5 - 9.5 mol / L.

4. The COF@BDTP@Fe3O4 nanomaterial synthesized by the synthesis method described in any one of claims 1 - 3.

5. Use of the COF@BDTP@Fe3O4 nanomaterial described in claim 4 for adsorbing chloramphenicol or in the preparation of a product for adsorbing chloramphenicol.

6. Use of the COF@BDTP@Fe3O4 nanomaterial described in claim 4 in the preparation of a pretreatment product for detecting chloramphenicol based on high performance liquid chromatography.

7. A pretreatment method for detecting chloramphenicol by high performance liquid chromatography, characterized in that, Comprising the following steps: S1. If the sample to be tested is a liquid, add water and mix evenly according to the volume ratio of the sample to be tested to water of 1:1 - 2, adjust the pH to 5 - 7, add 5 - 10 g of the COF@BDTP@Fe3O4 nanomaterial described in claim 4, and let it stand for adsorption for 60 - 100 min; if the sample to be tested is a solid, add water and grind it into a homogeneous slurry according to the mass-volume ratio of the sample to be tested to water of 1:1 - 2, adjust the pH to 5 - 7, add 5 - 10 g of the COF@BDTP@Fe3O4 nanomaterial described in claim 4, and let it stand for adsorption for 60 - 100 min; S2. Take out the COF@BDTP@Fe3O4 nanomaterial after the static adsorption in S1 and place it in another container, add a desorbent and desorb for 20 - 30 min, and take the desorbed solution through a filter membrane; Wherein, the desorbent is methanol, acetonitrile, a mixed solution of methanol and formic acid, or a mixed solution of acetonitrile and acetic acid.

8. The pre-treatment method according to claim 7, characterized in that In S1, adjust the pH to 6 ± 0.

5.

9. The pretreatment method according to claim 7, wherein In the mixed solution of methanol and formic acid, the volume ratio of methanol to formic acid is 95 - 97:3 - 5; in the mixed solution of acetonitrile and acetic acid, the volume ratio of acetonitrile to acetic acid is 95 - 97:3 - 5.

10. A high performance liquid chromatography detection method for chloramphenicol, characterized in that, After pretreating the sample to be tested by the pretreatment method described in any one of claims 7 - 9, take the filtrate obtained through the filter membrane for high performance liquid chromatography detection; the chromatographic conditions used are as follows: a C18 reverse phase chromatographic column, the column temperature is 28 - 32 °C; the mobile phase is a 50% methanol solution, isocratic elution, the flow rate of the mobile phase is 1.0 mL / min; the injection volume is 20 μL; the detector is a DAD detector, and the detection wavelength is 280 nm.

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