Method for preparing covalent organic framework adsorbent and extracting and detecting paraben

Abstract

The invention relates to a method for preparing a covalent organic framework adsorbent and extracting and detecting paraben, and belongs to the technical field of adsorption materials. The preparation method comprises the following steps: dispersing Fe3O4 nanoparticles and an amino organic monomer containing ureido in an organic solvent, adding an aldehyde group organic monomer, sequentially carrying out primary ultrasonic operation, vortex operation and secondary ultrasonic operation, standing and reacting at room temperature for 1-1.5 hours, and carrying out magnetic separation to obtain a crude product; washing the crude product with N, N-dimethylformamide and ethanol in sequence; and drying the obtained product in vacuum to obtain the magnetic ureido covalent organic framework adsorbent. The adsorbent provides a hydrogen bond and pi-pi accumulation effect, and can perform high-selectivity extraction and detection on p-hydroxybenzoate in samples such as toning lotion and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of adsorption materials, and particularly relates to a method for preparing a covalent organic framework adsorbent and extracting and detecting parabens. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and is not necessarily to be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art.

[0003] Parabens, a general term for paraben compounds, are a class of commonly used preservatives. Due to their good anti-microbial and anti-fungal properties, they are widely used in the fields of cosmetics, food, and pharmaceuticals. However, according to literature reports, parabens have estrogenic effects and can interfere with the human endocrine system, causing disorders. Therefore, the extraction and quantitative detection of parabens in cosmetics are of great significance. However, the matrix of cosmetic samples is complex, and the efficient and selective extraction and detection of parabens are still challenges at present.

[0004] Magnetic solid-phase extraction (MSPE) is a sample pretreatment technology with great application potential, which has the advantages of easy separation, easy operation, and reusability, and has received much attention in the field of adsorption and detection of trace target substances. The MSPE adsorbent is composed of magnetic nanoparticles and the coated adsorption material, where the adsorption material is the core of the MSPE technology and the key factor affecting the adsorption characteristics of MSPE. In recent years, various materials such as carbon nanotubes, layered double hydroxides, and molecularly imprinted polymers have been used to prepare MSPE adsorbents.

[0005] As an emerging crystalline porous material, covalent organic frameworks (COFs) have received extensive attention due to their ordered porosity, designable structure, large surface area, and good stability. At present, COFs show great application potential in the fields of adsorption and separation, catalysis, and sensing. However, due to the relatively single interaction between COFs and parabens, the selectivity of their extraction still needs to be improved, and structural modification or functionalization is urgently needed. The present invention uses the urea group with dual properties of hydrogen bond donor and acceptor as an ideal functional group to construct a novel MSPE adsorbent, and improves the extraction efficiency and selectivity through intermolecular hydrogen bonding and π-π stacking interactions, so as to achieve the efficient and selective extraction and detection of parabens in lotion. Summary of the Invention

[0006] Based on the current technical status, the purpose of the present invention is to provide a method for preparing a covalent organic framework adsorbent and extracting and detecting parabens, which has high efficiency and high selectivity for the extraction and detection of parabens.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] In a first aspect, a method for preparing the above-mentioned covalent organic framework adsorbent includes the following steps:

[0009] Disperse Fe3O4 nanoparticles and amino organic monomers containing urea groups in an organic solvent, add aldehyde organic monomers, and perform first ultrasonic treatment, vortexing, and second ultrasonic treatment in sequence. Then, let it stand and react at room temperature for 1 to 1.5 h, and obtain a crude product through magnetic separation;

[0010] Wash the crude product with N,N-dimethylformamide and ethanol in sequence; vacuum dry the obtained product to obtain a magnetic urea-based covalent organic framework adsorbent.

[0011] In a second aspect, a covalent organic framework adsorbent obtained by the method for preparing the above-mentioned covalent organic framework adsorbent.

[0012] In a third aspect, a method for extracting and detecting parabens includes the following steps:

[0013] S1. Degas the sample to be tested under ultrasonic assistance, filter it through a filter membrane, and adjust the pH of the sample solution to 3 to 9;

[0014] S2. Add the above-mentioned covalent organic framework adsorbent to the sample solution, mix well on a shaker for extraction, and magnetically separate the adsorbed covalent organic framework adsorbent to obtain a residue;

[0015] S3. Wash the residue with pure water, add an eluent, disperse it ultrasonically, mix well on a shaker, and magnetically separate the covalent organic framework adsorbent to retain the supernatant;

[0016] S4. Detect the content of parabens in the supernatant to obtain a detection result.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention uses magnetic urea-based covalent organic frameworks as adsorbents to extract and detect parabens in lotion samples, and establishes a detection method for quickly analyzing parabens in lotions. This covalent organic framework adsorbent has a large specific surface area, good superparamagnetism and stability. The introduction of urea groups provides abundant hydrogen bond donor and acceptor sites. At the same time, combined with the structural characteristics of the covalent organic framework, with the help of intermolecular hydrogen bonds and π-π stacking, this adsorbent can be used as an MSPE adsorbent for highly selective extraction of parabens. The prepared adsorbent has a large adsorption capacity for parabens and a short adsorption time, can be used for the analysis of parabens in lotions, and can be recycled. The magnetic solid-phase extraction-high performance liquid chromatography-ultraviolet method of the present invention is simple and fast, with a short pretreatment time, which shortens the detection time and can reduce the detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The schematic diagrams in the specification accompanying the present invention, which form a part of the present invention, are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0020] Figure 1 They are the schematic flow diagrams in Example 1 and Example 2.

[0021] Figure 2 They are the characterization result diagrams in Example 1, where (a) is the X-ray powder diffraction pattern, (b) is the infrared spectrum, (c) is the hysteresis regression curve, and (d) is the thermogravimetric analysis curve.

[0022] Figure 3 They are the optimization result diagrams of extraction and detection conditions in Examples 2-5, where (a) is the adsorbent dosage, (b) is the extraction time, (c) is the solution pH, and (d) is the eluent type. DETAILED DESCRIPTION OF THE INVENTION

[0023] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0024] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0025] The reagents used in the following specific embodiments include:

[0026] 1,3-bis(4-aminophenyl)urea, CAS No.: 4550-72-5, with the structure:

[0027]

[0028] Trihydroxybenzene-1,3,5-tricarbaldehyde (1,3,5-triformylphloroglucinol), CAS No.: 34374-88-4, with the structure:

[0029]

[0030] o-Dichlorobenzene, CAS No.: 95-50-1.

[0031] N,N-Dimethylformamide, CAS No.: 68-12-2.

[0032] In a specific embodiment of the present invention, a preparation method of a ureido covalent organic framework adsorbent is provided, including the following steps:

[0033] Disperse Fe3O4 nanoparticles and amino organic monomers containing ureido groups in an organic solvent, preliminarily bond the amino organic monomers through the carboxyl groups on the surface of Fe3O4, add aldehyde organic monomers, and perform the first ultrasonic treatment, vortexing, and second ultrasonic treatment in sequence, then let it stand and react at room temperature for 1 - 1.5 h. Utilize the condensation reaction between aldehyde groups and amino groups, and obtain a crude product including a magnetic ureido covalent organic framework adsorbent through magnetic separation;

[0034] Wash the crude product with N,N-dimethylformamide and ethanol in sequence to remove unreacted monomers and solvents; vacuum dry the obtained product to obtain a magnetic ureido covalent organic framework adsorbent.

[0035] Optionally, the Fe3O4 nanoparticles are spherical particles with a size of ~200 nm.

[0036] Optionally, the amino organic monomers containing ureido groups include one or more of 1,3-bis(4-aminophenyl)urea and 1,1'-(1,4-phenylene)biurea.

[0037] Optionally, the organic solvent includes one or more of ethanol / o-dichlorobenzene binary solvents and n-butanol / o-dichlorobenzene binary solvents.

[0038] Optionally, the aldehyde organic monomers include one or more of trihydroxybenzene-1,3,5-tricarbaldehyde and benzene-1,3,5-tricarbaldehyde.

[0039] Optionally, the first ultrasonic treatment is performed for 1 - 5 min, and its function is to uniformly disperse the aldehyde organic monomers.

[0040] Optionally, the operation method of the vortex is: 4.5 rpm, 1 - 3 min, and the function is to achieve sufficient mixing of the reaction system.

[0041] Optionally, the secondary ultrasonic method is: 150 - 200 W, 1 - 5 min, and the function is to make the organic monomers and Fe3O4 nanoparticles attached to the inner wall return to the reaction system again.

[0042] In the specific implementation manner of the present invention, a covalent organic framework adsorbent prepared by the above preparation method is provided.

[0043] In the above structural units, the ureido group can provide rich hydrogen bond donor and acceptor sites. At the same time, combined with the structural characteristics of the covalent organic framework, the extraction and detection of hydroxybenzoate are realized by using intermolecular hydrogen bonds and π-π stacking interactions.

[0044] In the specific implementation manner of the present invention, a method for extracting and detecting hydroxybenzoate is provided, including the following steps:

[0045] S1. Degas the sample to be tested under ultrasonic assistance, and after filtering through a filter membrane, adjust the pH of the sample solution to 3 - 9;

[0046] S2. Add the above covalent organic framework adsorbent to the sample solution, mix well on a shaker for extraction, magnetically separate the covalent organic framework adsorbent after adsorption, and obtain the residue;

[0047] S3. Wash the residue with pure water and then add an eluent for ultrasonic dispersion, mix well on a shaker, magnetically separate the covalent organic framework adsorbent, and retain the supernatant;

[0048] S4. Detect the content of hydroxybenzoate in the supernatant to obtain the detection result.

[0049] Optionally, the hydroxybenzoate includes one or more of methyl hydroxybenzoate, ethyl hydroxybenzoate, propyl hydroxybenzoate, and butyl hydroxybenzoate.

[0050] Optionally, in S1, the sample to be tested is lotion, beverage, or environmental water sample.

[0051] Optionally, in S1, after filtering through a 0.20 - 0.40 μm filter membrane, the sample solution is stored at 0 - 4 °C for later use.

[0052] Optionally, in S2, the proportion of the covalent organic framework adsorbent added to the sample solution is 0.5 - 2 mg / mL, and the extraction time is 1 - 40 min.

[0053] Optionally, in S3, the eluent is any one of methanol, acetonitrile, isopropanol, and n-hexane, and the ratio of the eluent to the residue is 0.5 - 2 mL / mg.

[0054] Optionally, in S4, the detection method uses high performance liquid chromatography-ultraviolet detection analysis technology. The chromatographic column is a C18 column: 250 mm × 4.6 mm, 5 μm; the column oven temperature is 25°C; the flow rate is 1 mL / min; the injection volume is 20 μL; the mobile phase is: acetonitrile and water in a ratio of 45:55; the wavelength of the ultraviolet detector is 254 nm.

[0055] Example 1

[0056] A covalent organic framework adsorbent, as Figure 1 shown, the preparation method includes:

[0057] Disperse Fe3O4 nanoparticles (50 mg) and 1,3-bis(4-aminophenyl)urea (0.072 mmol) into a binary solvent ethanol / o-dichlorobenzene (V / V, 1 / 1, 0.24 ml), sonicate for 3 min, add 1,3,5-triformylphloroglucinol (0.072 mmol), after the first sonication (3 min), vortex (4.5 rpm, 1 min) and the second sonication (200 W, 3 min) operations, let it stand and react at room temperature for 1 h to generate a mixed solution containing the covalent organic framework adsorbent.

[0058] Obtain the crude product by magnetic separation. Wash the crude product successively with N,N-dimethylformamide and methanol, and then vacuum dry the obtained product to obtain the magnetic urea-based covalent organic framework adsorbent, which is the covalent organic framework adsorbent.

[0059] Among the raw materials used, the Fe3O4 nanoparticles are spherical particles with a specification of ~200 nm.

[0060] Characterization of the prepared magnetic urea-based covalent organic framework adsorbent includes:

[0061] The X-ray powder diffraction pattern is as shown in (a) of Figure 2 . The 16°, 30.2° and 35.6° in the figure prove the formation of crystalline covalent organic framework in the adsorbent.

[0062] The infrared detection pattern is as shown in (b) of Figure 2 . The 1589 cm -1 (Fe-O) and 587 cm -1 (C=O) prove the successful synthesis of Fe3O4@TFPBau; in the figure, TFPBau represents the urea-based covalent organic framework.

[0063] The detection result of the hysteresis regression curve Figure 2As shown in (c), it can be seen that the saturation magnetization intensities of the black lines representing Fe3O4 nanoparticles and the red lines representing the prepared products are 60.0 emu / g and 39.8 emu / g respectively. Although the coating of ureido-COFs results in partial loss of magnetization intensity, the magnetic ureido covalent organic framework adsorbent can still meet the requirements of rapid separation.

[0064] The thermogravimetric analysis curve is as Figure 2 shown in (d), which proves that the prepared magnetic ureido covalent organic framework adsorbent has good thermal stability.

[0065] Example 2

[0066] To study the application of the adsorbent in actual samples, it was combined with liquid chromatography-ultraviolet technology to investigate the extraction and detection of butyl p-hydroxybenzoate ( Figure 3 denoted as BP in Figure 1 ) in actual and spiked samples, as

[0067] shown, including the steps:

[0068] S1. The toner sample was ultrasonically degassed, filtered through a 0.22 μm filter membrane, and the filtrate was stored at 4 °C for later use. It was adjusted to the set pH before detection.

[0069] S2. The covalent organic framework adsorbent obtained in Example 1 was added to 3 mL of the sample solution, and the mixture was shaken evenly on a shaker for extraction and adsorption. The adsorbed covalent organic framework adsorbent was magnetically separated to obtain the residue.

[0070] S3. The residue was washed with pure water and then added with an eluent for ultrasonic dispersion. The mixture was shaken evenly on a shaker, and the covalent organic framework adsorbent was magnetically separated to retain the supernatant. The separated adsorbent was washed with pure water and ethanol and dried under vacuum, and could be recycled for use in step S2 of other detection processes.

[0071] Among them, the pH in S1 was adjusted according to Figure 3 (c); in S2, the dosage of the magnetic ureido covalent organic framework material was adjusted according to Figure 3 (a), the adsorption time was adjusted according to Figure 3 (b), and the eluent in S3 was according to Figure 3For the adjustment in (d), methanol (MeOH), acetonitrile (ACN), isopropanol (IPA), or n - hexane (NHE) was used respectively.

[0072] During the optimization process of the above conditions, when Figure 3 the dosage in (a) was the single variable, the adsorption time was 5 min, pH was 7.0, and the eluent was acetonitrile; when Figure 3 the dosage in (b) was the single variable, the adsorbent dosage was 4 mg, pH was 7.0, and the eluent was acetonitrile; when Figure 3 the dosage in (c) was the single variable, the adsorbent dosage was 4 mg, the adsorption time was 5 min, and the eluent was acetonitrile; when Figure 3 the dosage in (c) was the single variable, the adsorbent dosage was 4 mg, the adsorption time was 5 min, and pH was 7.0.

[0073] According to Figure 3 the recovery rate in, the optimal extraction and detection method for butyl p - hydroxybenzoate was obtained:

[0074] Adjust the pH of the sample pretreatment solution to 7.0, take 3 mL of the sample solution and add 4 mg of magnetic urea - based covalent organic framework composite material, ultrasonicate, and mix well on a shaker for 5 min. The magnetic urea - based covalent organic framework composite material reaches the adsorption equilibrium for methyl p - hydroxybenzoate in the solution, and the maximum recovery rate of butyl p - hydroxybenzoate is 105.1%; during the detection process, the best eluent is acetonitrile, and the dosage is 1 mL.

[0075] To verify the selectivity of the adsorbent, two other commonly used preservatives, sodium benzoate and potassium sorbate, were selected as interfering substances. Due to hydrogen bonding and π - π stacking interactions, the magnetic covalent organic framework adsorbent can highly selectively extract butyl p - hydroxybenzoate and effectively eliminate interference.

[0076] Example 3

[0077] Extraction and detection of methyl p - hydroxybenzoate ( Figure 3 denoted as MP in ) were carried out with the same steps as in Example 2, except that the toner sample contained methyl p - hydroxybenzoate.

[0078] According to Figure 3 the recovery rate in, the optimal extraction method for methyl p - hydroxybenzoate was obtained:

[0079] Adjust the pH of the sample pretreatment solution to 7.0, take 3 mL of the sample solution and add 4 mg of magnetic urea - based covalent organic framework composite material, ultrasonicate, and mix well on a shaker for 5 min. The magnetic urea - based covalent organic framework composite material reaches the adsorption equilibrium for methyl p - hydroxybenzoate in the solution, and the maximum recovery rate of methyl p - hydroxybenzoate is 66.3%; during the detection process, the best eluent is acetonitrile, and the dosage is 1 mL.

[0080] Example 4

[0081] Extraction and detection of ethyl p - hydroxybenzoate ( Figure 3 denoted as EP in

[0082] The steps and methods are basically the same as those in Example 2, except that the sample solution contains ethyl p - hydroxybenzoate.

[0083] According to Figure 3 the recovery rate in

[0084] obtain the optimal extraction method for ethyl p - hydroxybenzoate:

[0085] Adjust the pH of the sample pretreatment solution to 7.0, take 3 mL of the sample solution and add 4 mg of magnetic urea - based covalent organic framework composite material, ultrasonicate, and mix well on a shaker for 5 min. The magnetic urea - based covalent organic framework composite material reaches the adsorption equilibrium for methyl p - hydroxybenzoate in the solution, and the maximum recovery rate of ethyl p - hydroxybenzoate is 75.4%; during the detection process, the best eluent is acetonitrile, and the dosage is 1 mL.

[0085] Example 5

[0086] Extraction and detection of propyl p - hydroxybenzoate ( Figure 3 denoted as PP in

[0087] The steps and methods are basically the same as those in Example 2, except that the sample solution contains propyl p - hydroxybenzoate.

[0088] According to Figure 3 the recovery rate in

[0089] obtain the optimal extraction method for propyl p - hydroxybenzoate:

[0090] Adjust the pH of the sample pretreatment solution to 7.0, take 3 mL of the sample solution and add 4 mg of magnetic urea - based covalent organic framework composite material, ultrasonicate, and mix well on a shaker for 5 min. The magnetic urea - based covalent organic framework composite material reaches the adsorption equilibrium for methyl p - hydroxybenzoate in the solution, and the maximum recovery rate of propyl p - hydroxybenzoate is 87.9%; during the detection process, the best eluent is acetonitrile, and the dosage is 1 mL.

[0090] Example 6

[0091] Co - extraction of p - hydroxybenzoates.

[0092] The steps and methods are basically the same as those in Example 2, except that the sample solution contains methyl p - hydroxybenzoate, ethyl p - hydroxybenzoate, propyl p - hydroxybenzoate and butyl p - hydroxybenzoate simultaneously.

[0093] According to Figure 3 the recovery rate in

[0094] Adjust the pH of the sample pretreatment solution to 7.0. Take 3 mL of the sample solution and add 4 mg of magnetic urea-based covalent organic framework composite material. Ultrasonicate and mix well on a shaker for 5 min. The magnetic urea-based covalent organic framework composite material reaches the adsorption equilibrium for the p-hydroxybenzoates in the solution. The maximum recovery rates of methyl p-hydroxybenzoate, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, and butyl p-hydroxybenzoate are 61.8%, 68.8%, 82.2%, and 89.5% respectively. During the detection process, the best eluent is acetonitrile and the dosage is 1 mL.

[0095] Example 7

[0096] Co-detection of p-hydroxybenzoates

[0097] To test the detection effect of the magnetic urea-based covalent organic framework material for magnetic solid-phase extraction of p-hydroxybenzoates obtained in Example 1, according to the optimal extraction and detection methods obtained in Example 2, the liquid chromatography-ultraviolet detection analysis method and the standard addition recovery method were used to determine three different brands of toner lotions (with unknown p-hydroxybenzoate content). Each sample was determined in parallel 3 times, and the recovery rates and relative standard deviations of the spiked samples were obtained. The results are shown in Table 1. The recovery rates of the three toner lotions are relatively high, proving that the present invention has great application prospects in the detection and analysis of p-hydroxybenzoates in aqueous solutions.

[0098] Table 1

[0099]

[0100] a nd: not detected.

[0101] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a covalent organic framework adsorbent, characterized in that, It includes the following steps: Disperse Fe3O4 nanoparticles and amino organic monomers containing urea groups in an organic solvent, add aldehyde group organic monomers, and after performing the first ultrasonic treatment, vortexing, and second ultrasonic treatment in sequence, let it stand and react at room temperature for 1 - 1.5 h, and obtain a crude product through magnetic separation; Wash the crude product with N,N-dimethylformamide and ethanol in sequence; vacuum dry the obtained product to obtain a magnetic urea-based covalent organic framework adsorbent.

2. The preparation method of the covalent organic framework adsorbent according to claim 1, characterized in that, The amino organic monomers containing urea groups include one or more of 1,3-bis(4-aminophenyl)urea and 1,1'-(1,4-phenylene)diurea.

3. The preparation method of the covalent organic framework adsorbent according to claim 1, characterized in that, The organic solvents include one or more of ethanol / o-dichlorobenzene binary solvents and n-butanol / o-dichlorobenzene binary solvents.

4. The preparation method of the covalent organic framework adsorbent according to claim 1, characterized in that, The aldehyde group organic monomers include one or more of phloroglucinol trialdehyde and benzene-1,3,5-tricarbaldehyde.

5. The preparation method of the covalent organic framework adsorbent according to claim 1, wherein, The first ultrasonic treatment is for 1 - 5 min; Or, the operation method of vortexing is: 4.5 rpm, 1 - 3 min; Or, the vortex method of the second ultrasonic treatment is: 200 W, 1 - 5 min.

6. A covalent organic framework adsorbent obtained by the preparation method of the covalent organic framework adsorbent according to any one of claims 1 - 5.

7. A method for extracting and detecting parabens, characterized in that, It includes the following steps: S1. Degas the sample to be tested under ultrasonic assistance, and after filtering through a filter membrane, adjust the pH of the sample solution to 3 - 9; S2. Add the above-mentioned covalent organic framework adsorbent to the sample solution, mix well on a shaker for extraction, magnetically separate the covalent organic framework adsorbent after adsorption, and obtain a residue; S3. After washing the residue with pure water, add an eluent and disperse it ultrasonically, mix well on a shaker, magnetically separate the covalent organic framework adsorbent, and retain the supernatant; S4. Detect the content of parabens in the supernatant to obtain a detection result.

8. The method for extracting and detecting parabens according to claim 7, wherein, Parabens include one or more of methyl paraben, ethyl paraben, propyl paraben, and butyl paraben.

9. The method for extracting and detecting p-hydroxybenzoate according to claim 7, characterized in that, In S2, the proportion of adding the covalent organic framework adsorbent to the sample solution is 0.5 - 2 mg / mL, and the extraction time is 1 - 40 min.

10. The method for extracting and detecting p-hydroxybenzoate according to claim 7, characterized in that, In S3, the eluent is any one of methanol, acetonitrile, isopropanol, and n-hexane, and the ratio of the eluent to the residue is 0.5 - 2 mL / mg.

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