Quaternary ammonium type fluorinated magnetic microporous organic network for detecting perfluoroalkyl substances in food, environment and biological samples

Abstract

The invention provides a quaternary ammonium type fluorinated magnetic microporous organic network for detecting perfluoroalkyl substances in food, environment and biological samples, and belongs to the field of perfluoroalkyl substance detection. According to the method, a post-modification strategy is adopted, ferroferric oxide is taken as a magnetic source and a template, a fluorinated magnetic microporous organic network is firstly constructed, and then surface quaternization of the fluorinated magnetic microporous organic network is carried out by virtue of an alkylation reaction of tertiary amine with high reaction activity and iodo-alkane. The quaternary ammonium type fluorinated magnetic microporous organic network has F affinity action sites, a quaternary ammonium salt structure is formed through post-modification, electrostatic and ion exchange action sites are provided for PFAS, and the water dispersion capacity of the adsorbent is improved; and the microporous organic network skeleton can provide large specific surface area and high-density acting sites. The predesigned multiple action sites and magnetic separation capability are used for realizing efficient enrichment and sensitive detection of PFAS in various actual samples.

Description

Technical Field

[0001] The invention relates to a quaternary ammonium fluorinated magnetic microporous organic network for efficient and sensitive detection of perfluoroalkyl substances in food, environment and biological samples, belonging to the field of perfluoroalkyl substance detection. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance some understanding of the overall background of the invention and should not be necessarily regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Perfluoroalkyl substances (PFAS) are a class of synthetic compounds that have been widely used in textiles, food packaging, flame retardants and other fields since the 1950s, and can enter environmental media such as soil, water, and atmosphere through various pathways. Due to the rich CF bonds in its structure, PFAS is extremely stable in chemical properties and has the characteristics of being difficult to degrade, migrating over long distances, and accumulating in organisms along the food chain, making it detected in many environmental media and organisms, and even in the human body. Studies have shown that long-term exposure to PFAS, even at low concentrations, can still cause serious health problems, mainly manifested as liver damage, kidney damage, damage to reproductive cells, destruction of cell membrane structure, and cancer. In 2023, relevant departments included PFAS in the "List of New Pollutants under Key Control (2023 Edition)". In April 2024, the U.S. Environmental Protection Agency issued drinking water standards, stipulating that the concentration limit of six PFAS in drinking water is 4-10 ng L -1 Therefore, effective monitoring of PFAS in environmental water bodies is crucial for environmental water quality monitoring, pollution control, and aquatic food safety. At the same time, it is necessary to develop sensitive and efficient detection methods for trace amounts of PFAS in environmental, food, and biological samples.

[0004] Magnetic solid-phase extraction (MSPE) offers advantages such as ease of use, rapidity, and strong anti-interference capabilities. It is suitable for enriching trace targets in complex matrices and is currently one of the most widely used sample pretreatment methods. Adsorbents are the core of magnetic solid-phase extraction, and the development of highly effective MSPE adsorbents for PFAS is particularly important. In recent years, novel PFAS adsorbents have been developed based on the structural characteristics of PFAS. Currently, studies have utilized the FF interaction sites of materials such as fluorinated covalent organic frameworks, fluorinated metal-organic frameworks, and fluorinated adaptive cages; electrostatic interaction sites of materials such as cationic covalent organic frameworks and aminated covalent organic polymers; and host-guest interaction sites of β-CD polymers and cucurbituril-based materials to effectively detect and remove PFAS. However, the interaction sites of these adsorbents are relatively limited, making the recovery and reuse of non-magnetic adsorbents difficult. Summary of the Invention

[0005] As mentioned above, conventional adsorbents reported in previous studies have limitations, such as low adsorption capacity, long extraction times, weak binding affinity, and poor anti-interference capabilities. New PFAS adsorbents have improved these shortcomings to some extent, but the strong hydrophobicity of fluorinated porous materials hinders mass transfer of PFAS to the adsorbent in aqueous matrices. Cationic adsorbents are also inevitably affected by water salinity, acid radicals, and anionic contaminants. To overcome these shortcomings, the present invention aims to design a magnetic quaternary ammonium fluorinated MON (Fe3O4@quaternary ammonium FMON) with dual quaternary ammonium and fluorine functionalization. This quaternary ammonium fluorinated MON (Fe3O4@quaternary ammonium FMON) provides PFAS with multiple synergistic forces, including hydrophobic, hydrogen bonding, FF, electrostatic, and ion exchange, enabling efficient and sensitive detection of PFAS in environmental, food, and biological samples.

[0006] The technical solution adopted in the present invention is as follows: In the first aspect of the present invention, there is provided a quaternary ammonium fluoride compound having the general structural formula: Where R is an alkyl chain of different lengths, i.e. R=CH3, R=CH2CH3, R=(CH2)3CH3, R=(CH2)4CH3, R=(CH2)5CH3, R=(CH2)7CH3, R=(CH2) 11 CH3 or R=(CH2) 15 CH3.

[0007] The present invention provides a novel quaternary ammonium fluorinated magnetic microporous organic network material, which is not only resistant to matrix interference but also capable of highly efficient and sensitive detection of trace amounts of perfluoroalkyl substances in environmental, food and biological samples.

[0008] In a second aspect of the present invention, a method for preparing a magnetic microporous organic network material containing the above-mentioned quaternary ammonium fluorinated compound is provided, the method comprising the following steps: Considering the high reactivity of iodinated alkanes with tertiary amines, magnetic Fe3O4 nanoparticles were used as magnetic sources and substrate templates to first construct magnetic fluorinated MON containing tertiary amine groups (Fe3O4@FMON). Then, iodinated alkanes of different chain lengths were used as alkylating agents to quaternize the tertiary amine N on Fe3O4@FMON via the Menschutkin reaction to prepare Fe3O4@quaternary ammonium-type FMON, which is the quaternary ammonium-type fluorinated magnetic microporous organic network material with the above-mentioned general structure.

[0009] In one or some embodiments of the present invention, the preparation method of Fe3O4@FMON specifically includes: Ferroferric oxide (Fe3O4) and a catalyst are dispersed in an organic solvent. Then, the reaction monomers 4,4'-dibromooctafluorobiphenyl (DFBP) and tripropargylamine (TPA) are added and allowed to react after dispersion. After the reaction, the crude product is collected by an external magnet, washed, and dried to obtain Fe3O4@FMON.

[0010] Preferably, the mass ratio of Fe3O4, catalyst, 4,4'-dibromooctafluorobiphenyl (DFBP) and tripropargylamine (TPA) is (100-300): (10-40): (100-200): (10-50); more preferably, the mass ratio is 200:25.6:136.8:26.3.

[0011] Preferably, the catalyst is a mixture of Pd(PPh3)2Cl2 and CuI in a mass ratio of (1-5):(1-5); more preferably, the mass ratio is 3:1.

[0012] Preferably, the reaction conditions are stirring at 60-90 °C for 10-15 h.

[0013] In one or some embodiments of the present invention, the preparation method of Fe3O4@quaternary ammonium FMON includes: Fe3O4@FMON was dispersed in organic solvent 2, and an alkylating agent was added to react to obtain Fe3O4@quaternary ammonium FMON.

[0014] The alkylating agent is not particularly limited. Preferably, the alkylating agent is at least one of methyl iodide, ethyl iodide, butyl iodide, pentane iodide, hexane iodide, octane iodide, dodecane iodide, and hexadecane iodide. More preferably, the alkylating agent is methyl iodide, ethyl iodide, 1-butyl iodide, 1-pentane iodide, 1-hexane iodide, octane iodide, 1-dodecane iodide, or 1-hexadecane iodide.

[0015] Preferably, the feeding ratio of the Fe3O4@FMON and the alkylating agent is (100-300) mg: (1-10) mmol; more preferably, the feeding ratio is 200 mg: 5 mmol.

[0016] Preferably, the reaction conditions are 80-100° C. and stirring for 36-60 h.

[0017] In the present invention, the organic solvent 1 and the organic solvent 2 are not particularly limited, and are used for the purpose of dissolving the raw materials.

[0018] Preferably, the first organic solvent is a mixed solution of tetrahydrofuran and triethylamine.

[0019] Preferably, the second organic solvent is ethanol.

[0020] In a third aspect of the present invention, there is provided the use of the quaternary ammonium fluorinated compound and / or the magnetic microporous organic network material prepared by the above method in the detection of perfluoroalkyl substances in food, environmental and / or biological samples.

[0021] Preferably, the perfluoroalkyl substances (PFAS) include but are not limited to perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), perfluorobutane sulfonate (PFBS), etc.

[0022] Compared with the related art known to the inventors, one of the technical solutions of the present invention has the following beneficial effects: The present invention adopts a post-modification strategy, using ferrosoferric oxide as a magnetic source and template to first construct a fluorinated magnetic microporous organic network, and then facilitates the alkylation reaction of a highly reactive tertiary amine with an iodinated alkane to carry out surface quaternization of the fluorinated magnetic microporous organic network.

[0023] The quaternary ammonium fluorinated magnetic microporous organic network contains F-affinity sites, which, after post-modification, form a quaternary ammonium salt structure. This provides electrostatic and ion-exchange sites for PFAS and enhances the adsorbent's water dispersibility. Furthermore, the microporous organic network framework offers a large surface area and high-density sites. The pre-designed multiple sites and magnetic separation capabilities enable efficient enrichment and sensitive detection of PFAS in a variety of real-world samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which constitute a part of the specification of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 This is the Fourier infrared spectrum of Fe3O4@quaternary ammonium FMON prepared in Example 1.

[0026] Figure 2 Characterization of Fe3O4@FMON and Fe3O4@quaternary ammonium FMON prepared in Example 1: (a) is the scanning electron microscope image of Fe3O4@FMON, (b) is the scanning electron microscope image of Fe3O4@IM-FMON, (c) is the scanning electron microscope image of Fe3O4@IB-FMON, (d) is the scanning electron microscope image of Fe3O4@IH-FMON, (e) is the transmission electron microscope image of Fe3O4@FMON, and (f) is the transmission electron microscope image of Fe3O4@IM-FMON; (g) is the elemental mapping analysis image of Fe3O4@IM-FMON, and (h) is the water contact angle images of Fe3O4@FMON, Fe3O4@IM-FMON, Fe3O4@IB-FMON and Fe3O4@IH-FMON.

[0027] Figure 3 These are the hysteresis loops of Fe3O4@FMON and Fe3O4@quaternary ammonium FMON prepared in Example 1.

[0028] Figure 4 The extraction recovery rates of PFAS from different batches of Fe3O4@IM-FMON prepared in Example 1.

[0029] Figure 5 Comparison of the PFAS extraction recovery rates of Fe3O4@FMON and Fe3O4@quaternary ammonium FMON prepared in Example 2.

[0030] Figure 6 This is Example 3, in the presence of different coexisting interferents, the removal rate of PFOA by Fe3O4@IM-FMON is studied.

[0031] Figure 7 This is the reusability study of Fe3O4@IM-FMON in Example 4.

[0032] Figure 8 This is a diagram of the matrix effect of the actual sample in Example 5.

[0033] Figure 9 This is a synthetic route for quaternary ammonium fluorinated magnetic microporous organic networks. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are exemplary and 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 skilled in the art to which the present invention belongs.

[0035] 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 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 and / or combinations thereof.

[0036] In a typical embodiment of the present invention, the synthesis route of the quaternary ammonium fluorinated magnetic microporous organic network is as follows Figure 9 .

[0037] The quaternary ammonium fluorinated magnetic microporous organic network of the present invention has the ability to efficiently extract perfluorinated compounds in actual samples (environmental, food, biological samples), quickly recover and have good anti-interference properties. It is a magnetic microporous organic network with good magnetism and abundant action sites.

[0038] In the article, MON in “fluorinated MON” is the abbreviation of Micropore Organic Network.

[0039] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0040] Example 1

[0041] Preparation of Fe3O4@FMON Ferroferric oxide (Fe3O4, 200 mg), catalyst (Pd(PPh3)2Cl2, 19.2 mg and CuI, 6.4 mg) were ultrasonically dispersed in 30 mL of a solution of tetrahydrofuran: triethylamine = 1:1 (v / v). Then, the reaction monomers 4,4'-dibromooctafluorobiphenyl (DFBP, 136.8 mg) and tripropargylamine (TPA, 26.3 mg) were added. After ultrasonic dispersion, the mixture was heated at 70 o C for 12 h. After the reaction, the crude product was collected by an external magnet, washed with DMF and MeOH under reflux, and dried to obtain a reddish-brown solid, namely Fe3O4@FMON.

[0042] Preparation of Fe3O4@quaternary ammonium FMON Fe3O4@FMON (200 mg) was dispersed in 50 mL of ethanol solution, and a certain amount of methyl iodide, butyl iodide, and hexyl iodide (5 mmol) of different chain length alkylating agents were added at 90 o C for 48 h, and Fe3O4@quaternary ammonium FMON with different alkyl chain modifications were obtained, which were named Fe3O4@IM-FMON, Fe3O4@IB-FMON and Fe3O4@IH-FMON, respectively. Figure 1 .

[0043] The above preparation process was repeated four times, and the reproducibility of the adsorbent was investigated using the extraction recovery rate of PFAS as an indicator.

[0044] The results show that the prepared Fe3O4@quaternary ammonium FMON has a spherical core-shell structure with a shell of 15 nm, good water dispersibility, large saturation magnetization value, and good reproducibility. Figure 2 、 Figure 3 and Figure 4 .

[0045] Example 2

[0046] 4 mg of Fe3O4@IM-FMON was added to 20 mL of 5 μg L -1in a mixed solution of six PFAS. Under pH 6, after ultrasonic extraction for 6 min, Fe3O4@IM-FMON was collected with an external magnet and the supernatant was discarded. Subsequently, the PFAS extracted from Fe3O4@IM-FMON was ultrasonically eluted with 0.4 mL MeOH + 5% NH3 H2O (0.2 × 2 mL) for 4 min. Finally, the combined eluate was collected, concentrated to a final volume of 0.2 mL by nitrogen blowing, filtered through a nylon membrane filter (0.22 μm), and analyzed by HPLC-MS / MS. Magnetic adsorbents such as Fe3O4@FMON, Fe3O4@IB-FMON and Fe3O4@IH-FMON were sequentially subjected to the above-mentioned PFAS extraction-elution procedure. The extraction recovery rate of PFAS was used as an indicator to compare the extraction efficiency of different adsorbents. The results were consistent with expectations. Fe3O4@quaternary ammonium FMON modified with alkyl chains had a higher extraction recovery rate than Fe3O4@FMON. As Figure 5 .

[0047] Example 3

[0048] Taking PFOA as an example, the anti-interference ability of Fe3O4@IM-FMON on PFOA adsorption was studied. Considering the common organic compounds in water, phenol, OA, sodium 1-dodecylsulfonate (SDS), and humic acid (HA) were selected as coexisting organic matter. In the experiment, the Fe3O4@IM-FMON dosage was 5 mg, the initial solution pH was 6, and the initial PFOA concentration was 1000 μg L -1 , the volume is 10 mL, and the concentration of other organic compounds coexisting in the dual solute is 1000 μg L -1 PFOA removal rate was used as the anti-interference ability index. The results showed that in the presence of coexisting pollutants, the removal rate of PFOA by Fe3O4@IM-FMON did not change significantly and was still able to maintain a removal rate of more than 95%, indicating that Fe3O4@IM-FMON has good anti-interference ability. Figure 6 .

[0049] Example 4

[0050] After one extraction-desorption experiment, the recovered Fe3O4@IM-FMON was regenerated by adding regeneration solutions (desorption solvent: 10 mL 95% MeOH-5% NH3 H2O, MeOH / saturated KI solution) in sequence. First, Fe3O4@IM-FMON was added to the desorption solvent and sonicated for 15 minutes to remove any residual PFAS. Then, MeOH / saturated KI solution was added and shaken at 25 °C for 12 hours. The regenerated Fe3O4@IM-FMON continued to undergo extraction-desorption-regeneration cycles, and the above cycles were repeated 8 times to evaluate the effect of Fe3O4@IM-FMON on PFAS (5 μg L -1 ) reusability. The results show that the prepared Fe3O4@IM-FMON can be reused 6 times with a recovery rate of 80%, which has good reusability. Figure 7 .

[0051] Example 5

[0052] Various real samples (urine, blood, river water, lake water, fish, and shrimp) were pretreated, and working solutions with PFAS concentrations of 10, 50, and 100 ng L were prepared by spiking aqueous and matrix solutions. -1 The MSPE process in Example 2 was carried out to examine the influence of the matrix solution on the extraction efficiency, i.e., the matrix effect. Taking the average value of the ratio of the extraction recovery rate of PFAS at various concentrations in the matrix solution and the aqueous solution as an indicator, the ME% was between 80-120%, indicating that Fe3O4@IM-FMON has good resistance to matrix effects. Figure 8 .

[0053] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A quaternary ammonium fluoride compound, characterized in that: Its general structural formula is: Wherein R=CH3, R=CH2CH3, R=(CH2)3CH3, R=(CH2)4CH3, R=(CH2)5CH3, R=(CH2)7CH3, R=(CH2) 11 CH3 or R=(CH2) 15 CH3.

2. A method for preparing a magnetic microporous organic network material containing the quaternary ammonium fluoride compound according to claim 1, characterized in that: The method comprises the following steps: Using magnetic Fe3O4 nanoparticles as a magnetic source and substrate template, a magnetic fluorinated MON (Fe3O4@FMON) containing a tertiary amine group is first constructed, and then iodinated alkanes of different chain lengths are used as alkylating agents to quaternize the tertiary amine N on the Fe3O4@FMON through a Menschutkin reaction to prepare Fe3O4@quaternary ammonium FMON, which is a magnetic microporous organic network material containing the quaternary ammonium fluorinated compound described in claim 1.

3. The method for preparing a magnetic microporous organic network material according to claim 2, characterized in that: The preparation method of Fe3O4@FMON specifically includes: The method comprises the following steps: dispersing ferroferric oxide (Fe3O4) and a catalyst in an organic solvent, and then adding reaction monomers 4,4'-dibromooctafluorobiphenyl (DFBP) and tripropargylamine (TPA), and reacting the mixture after dispersion; after the reaction, collecting the crude product through an external magnet, washing it, and drying it to obtain Fe3O4@FMON.

4. The method for preparing a magnetic microporous organic network material according to claim 3, characterized in that: The mass ratio of Fe3O4, catalyst, 4,4'-dibromooctafluorobiphenyl (DFBP) and tripropargylamine (TPA) is (100-300): (10-40): (100-200): (10-50); The catalyst is a mixture of Pd(PPh3)2Cl2 and CuI, and the mass ratio thereof is (1-5): (1-5).

5. The method for preparing a magnetic microporous organic network material according to claim 3, characterized in that: The reaction conditions are stirring at 60~90 ℃ for 10~15 h.

6. The method for preparing a magnetic microporous organic network material according to claim 2, characterized in that: The preparation method of Fe3O4@quaternary ammonium FMON includes: Fe3O4@FMON was dispersed in organic solvent 2, and an alkylating agent was added to react to obtain Fe3O4@quaternary ammonium FMON.

7. The method for preparing a magnetic microporous organic network material according to claim 6, characterized in that: The alkylating agent is at least one of methyl iodide, ethyl iodide, butyl iodide, pentane iodide, hexane iodide, octane iodide, dodecane iodide and hexadecane iodide.

8. The method for preparing a magnetic microporous organic network material according to claim 6, characterized in that: The feeding ratio of the Fe3O4@FMON and the alkylating agent is (100-300) mg: (1-10) mmol.

9. The method for preparing a magnetic microporous organic network material according to claim 6, characterized in that: The reaction conditions are stirring at 80~100 ℃ for 36~60 h.

10. Use of the quaternary ammonium fluoride compound according to claim 1 and / or the magnetic microporous organic network material prepared by the method according to any one of claims 2 to 9 in the detection of perfluoroalkyl substances in food, environmental and / or biological samples.

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