Application of metal organic framework functionalized cashmere fiber as extraction material for perfluoroalkyl substances

Abstract

This invention belongs to the field of environmental analytical chemistry and functional materials technology, specifically relating to the application of metal-organic framework (MOF) functionalized cashmere fibers as extraction materials for perfluoroalkyl substances. The application method involves: activating the MOF functionalized cashmere fibers with a methanol-water solution, then extracting the sample solution containing the perfluoroalkyl substances to be enriched and / or detected, yielding MOF functionalized cashmere fibers enriched with perfluoroalkyl substances and a purified sample solution; subsequently, the MOF functionalized cashmere fibers enriched with perfluoroalkyl substances are eluted using an eluent for the detection of perfluoroalkyl substance content. This MOF functionalized cashmere fiber can effectively enrich perfluoroalkyl substances, exhibiting a large adsorption capacity and high extraction efficiency. Furthermore, after enrichment, the perfluoroalkyl substances are easily eluted, ensuring the accuracy of subsequent quantitative detection.

Description

Technical Field

[0001] This invention belongs to the field of environmental analytical chemistry and functional materials technology, specifically involving the application of metal-organic framework functionalized cashmere fibers as extraction materials for perfluoroalkyl substances (PFASs). Background Technology

[0002] Perfluoroalkyl substances (PFASs) are a new class of persistent organic pollutants with extremely high environmental persistence, bioaccumulation, and potential toxicity. PFASs were once widely used in textiles, non-stick cookware, and fire-fighting foam, and have been widely detected in various water bodies worldwide. Therefore, accurate monitoring of trace and even ultra-trace levels of PFASs in the environment is a prerequisite for assessing their ecological and human health risks.

[0003] Currently, the mainstream method for detecting PFASs is liquid chromatography-tandem mass spectrometry (LC-MS / MS). However, due to the extremely low concentration of PFASs and the complex matrix in environmental samples, enrichment and purification of the samples are usually required before detection. Solid phase extraction (SPE) is the most commonly used pretreatment technique. Although commercially available SPE columns (such as WAX and GBC) are widely used, they still have some limitations, such as limited adsorption capacity, slow flow rate, cumbersome operation steps, long operation time, and the use of large amounts of organic solvents which can easily cause secondary pollution. They also cannot effectively enrich perfluoroalkyl substances, which can further affect the accuracy of detection. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a solid phase extraction material based on metal-organic framework functionalized cashmere fiber to address the shortcomings of the prior art. This material can effectively enrich perfluoroalkyl substances, with large adsorption capacity and high extraction efficiency.

[0005] To address the technical problems proposed in this invention, this invention provides the application of metal-organic framework functionalized cashmere fibers as extraction materials for perfluoroalkyl substances; the metal-organic framework functionalized cashmere fibers are obtained by carboxylating cashmere fibers after alkali and acid treatment, and then preparing metal-organic framework material UiO-66-F4 in situ.

[0006] The preparation method of the above-mentioned metal-organic framework functionalized cashmere fibers includes the following steps: (1) Pretreatment: The cashmere (CSM) is soaked in alkaline solution and then taken out, then soaked in acid solution and taken out, washed and dried to obtain pretreated cashmere; (2) The pretreated cashmere was placed in a citric acid aqueous solution for two-stage heat treatment, then washed and dried to obtain carboxylated cashmere; (3) Dissolve zirconium oxychloride and acetic acid in water to obtain a precursor solution; then, immerse carboxylated cashmere in the precursor solution and sonicate and / or stir, then remove it and immerse it in a mixed aqueous solution of tetrafluoroterephthalic acid and NaOH (ligand solution) and sonicate and / or stir, then let it stand for a period of time. Pour the remaining precursor solution into the ligand solution and stir for a certain period of time. After washing with water and drying, solid phase extraction material (UIO-66-F4@CSM) based on metal-organic framework functionalized cashmere is obtained.

[0007] Furthermore, the diameter of raw cashmere is typically between 10 and 20 micrometers, and it is fibrous.

[0008] Further, in step (1), the alkaline solution is preferably a NaOH aqueous solution with a concentration of 0.05-0.2 M, and is generally soaked in the alkaline solution for 1.5-2.5 hours; the acid solution is preferably an HCl aqueous solution with a concentration of 0.05-0.15 M, and is generally soaked in the acid solution for 20-40 minutes.

[0009] Further, in step (2), the concentration of the citric acid aqueous solution is 0.2-0.8 M; the two-stage heat treatment process is as follows: first, heat the reaction at 40-60 ℃ for 20-28 hours, and then raise the temperature to 100-140 ℃ at 4-10 ℃ / min and keep the reaction at the temperature for 1-2 hours.

[0010] Further, in the precursor solution of step (3), the concentration of zirconium oxychloride is 0.1-0.3 M, and the volume percentage of acetic acid is 12-15%; in the mixed aqueous solution of tetrafluoroterephthalic acid and NaOH (i.e., the ligand solution), the concentration of tetrafluoroterephthalic acid is 0.1-0.2 M, and the concentration of NaOH is 0.16-0.22 M. The molar ratio of tetrafluoroterephthalic acid to NaOH is preferably 1:2, and the molar ratio between tetrafluoroterephthalic acid and zirconium oxychloride is preferably 1:1.

[0011] More preferably, in step (3), after the first immersion in the precursor solution and sonication for 5-15 minutes, the mixture is stirred for 0.5-1.5 hours; after sonication in the ligand solution for 5-15 minutes, the mixture is allowed to stand for 20-40 minutes; and after pouring in the remaining precursor solution, the mixture is stirred for 2-4 hours. This invention involves two immersions in the precursor solution, one before and one after immersion in the ligand solution. The first immersion in the precursor solution allows the carboxyl groups on the surface of the cashmere to be anchored to a layer of Zr under mild conditions. 4+ Ions form heterogeneous nucleation sites; subsequently, ligands are introduced to promote preferential orientation of MOF crystal nucleation on the fiber surface; finally, the remaining Zr is replenished by adding precursor solution again. 4+ This provides continuous nutrition to the crystal nucleus, enabling it to grow densely and uniformly into a film.

[0012] The aforementioned metal-organic framework-functionalized cashmere fibers can be used directly as solid-phase extraction materials for enriching perfluoroalkyl substances (PFASs), or they can be filled into packing media such as small columns to form solid-phase extraction columns. Therefore, the present invention also provides a solid-phase extraction column for enriching perfluoroalkyl substances, which is obtained by filling the aforementioned metal-organic framework-functionalized cashmere fibers.

[0013] Based on the above, the application of the metal-organic framework functionalized cashmere fiber of the present invention as an extraction material for perfluoroalkyl substances is as follows: the metal-organic framework functionalized cashmere fiber is activated with a methanol aqueous solution, and then extracted with a sample solution of perfluoroalkyl substances to be enriched and / or detected to obtain metal-organic framework functionalized cashmere fiber enriched with perfluoroalkyl substances and a purified sample solution; then the metal-organic framework functionalized cashmere fiber enriched with perfluoroalkyl substances is eluted with an eluent to detect the content of perfluoroalkyl substances.

[0014] Furthermore, the present invention provides an application method for enriching and / or detecting perfluoroalkyl substances (PFASs) in metal-organic framework functionalized cashmere fibers, comprising the following steps; 1) The metal-organic framework functionalized cashmere fibers are wetted with methanol aqueous solution to activate them, and then filled into a small column (or they can be filled into a small column first and then activated) to obtain a solid phase extraction column; 2) Add the sample solution of the perfluoroalkyl substances to be enriched and / or detected to the solid phase extraction column obtained in step 1), and let it flow through the solid phase extraction column to enrich the perfluoroalkyl substances in the sample solution in the solid phase extraction column, and obtain a solid phase extraction column enriched with perfluoroalkyl substances (at this time, the sample solution has removed the perfluoroalkyl substances and is converted into a purified sample solution). 3) The solid-phase extraction column enriched with perfluoroalkyl substances was eluted with an ammonia-methanol solution to obtain the eluent; 4) The eluent can be directly used as the loading solution for liquid chromatography-tandem mass spectrometry (LC-MS / MS) detection, or the eluent can be concentrated and reconstituted by nitrogen blowing before being used for LC-MS / MS detection.

[0015] According to the above scheme, the perfluoroalkyl substances of the present invention include perfluorobutyric acid (PFBA), perfluorovalerate (PFPA), perfluorohexanoic acid (PFHxA), perfluorobutyric acid (PFBS), perfluoroheptanoic acid (PFHpA), perfluoropentanesulfonic acid (PFPeS), 3H-perfluoro-4,8-dioxanonanoic acid (ADONA), perfluorooctanoic acid (PFOA), perfluorohexanesulfonic acid (PFHxS), perfluorononanoic acid (PFNA), perfluoroheptanesulfonic acid (PFHpS), perfluorodecanoic acid (PFDA), and perfluorooctanoic acid (PFOS). It includes one or more of the following: perfluoroundecanoic acid (PFUnDA), perfluorononylsulfonic acid (PFNS), 9-chlorohexadecano-3-oxanonane-1-sulfonic acid (9Cl-PF3ONS), perfluorododecanoic acid (PFDoA), perfluorodecylsulfonic acid (PFDS), perfluorotridecanoic acid (PFTriDA), 11-chloroeicosicofluoro-3-oxaundecane-1-sulfonic acid (11Cl-PF3OUdS), perfluorotetradecanoic acid (PFTeDA), perfluorohexadecanoic acid (PFHxDA), and perfluorooctadecaic acid (PFODA).

[0016] The above method can detect perfluoroalkyl substances in actual samples such as water samples, seafood, and agricultural products. In water samples, suspended solids are removed by filtration to obtain a sample solution; in seafood and agricultural products, perfluoroalkyl substances are extracted to obtain the test sample solution, which is then used for detection. Specifically, seafood and agricultural products are generally extracted with acetonitrile followed by centrifugation, nitrogen blowing, and reconstitution to obtain the test sample solution.

[0017] According to the above scheme, in step 1), the volume percentage of methanol in the methanol-water solution is 20-50%.

[0018] According to the above scheme, between steps 2) and 3), there is an additional step of aspirating an appropriate amount of methanol-water solution 2-3 times to wash away adsorbed non-target impurities and matrix. The methanol-water solution contains 20-50% methanol by volume.

[0019] According to the above scheme, in step 3), the ammonia-methanol solution is obtained by mixing ammonia and methanol at a volume ratio of 1:99-1:49, wherein the ammonia is industrial ammonia with a concentration of 25%-28%.

[0020] According to the above scheme, in step 4), redissolution can generally be achieved using a methanol-water solution. The methanol-water solution contains 20-50% methanol by volume.

[0021] Compared with the prior art, the beneficial effects of the present invention are: (1) The solid-phase extraction material of the metal-organic framework functionalized cashmere fiber of this invention uses carboxylated fiber as the active substrate and achieves Zr through chemical bonding. 4+This invention utilizes targeted anchoring and MOF-oriented heterogeneous nucleation to form a continuous and dense MOF functional membrane layer through stepwise controllable growth. It combines the synergistic effects of a flexible fiber matrix and a highly porous MOF active phase, enabling rapid enrichment of trace perfluoroalkyl substances with high adsorption capacity and extraction efficiency. Specifically, this invention uses cashmere fibers as a substrate and achieves carboxylation treatment with citric acid. A two-stage heat treatment process—first low-temperature permeation adsorption, then high-temperature covalent grafting—ensures that citric acid fully penetrates the cashmere fibers while efficiently achieving the carboxylation grafting reaction at high temperatures, minimizing fiber damage to obtain well-modified cashmere. Then, the modified cashmere fibers are treated with ligands and precursor solutions added sequentially. The precursor solution first anchors a layer of Zr on the cashmere surface under mild conditions. 4+ Ions form heterogeneous nucleation sites, followed by the introduction of ligands, which promote preferential orientation of MOF crystal nucleation on the fiber surface. The remaining Zr is then added via a precursor solution. 4+ This provides continuous nutrition to the crystal nuclei, enabling them to grow into a dense and uniform film. This results in a strong bond between the MOF layer and the cashmere fiber, a uniform and dense distribution, abundant adsorption sites, and excellent structural stability, significantly improving the adsorption capacity, extraction selectivity, and recyclability of the target analyte.

[0022] (2) The solid-phase extraction material based on metal-organic framework functionalized cashmere fibers described in this invention is easy to elute after enriching perfluoroalkyl substances, which can then ensure the accuracy of subsequent quantitative detection. Specifically, cashmere belongs to keratin, and cashmere fibers contain a large number of amino (-NH2), carboxyl (-COOH), and peptide bonds (-NH-CO-), etc. During the in-situ growth of UiO-66-F4, these groups on cashmere fibers can act as "anchors" to induce MOF crystals to nucleate uniformly and firmly, avoiding the problems of easy crystal shedding or uneven growth commonly found in cotton. Moreover, cashmere has a unique scaly structure. This rough surface provides more physical retention space and a larger specific surface area, which is beneficial for the embedding and loading of MOF particles; while the surface of fibers such as kapok contains more wax, is hydrophobic and smooth, which is extremely unfavorable for crystal growth in aqueous or solvothermal systems. This invention uses tetrafluoroterephthalic acid ligands, which bind to perfluoroalkyl substances mainly through fluorine-fluorine hydrophobic interactions and weak hydrophobic interactions. The interaction is mild and reversible, and can be rapidly desorbed under suitable elution conditions. It is not prone to irreversible strong chemical adsorption. Therefore, after the metal-organic framework functionalized cashmere fibers are enriched with perfluoroalkyl substances, they are easy to elute, which can ensure the accuracy of subsequent quantitative detection. Attached Figure Description

[0023] Figure 1 and Figure 2 SEM images of raw cashmere fibers at different magnifications.

[0024] Figure 3 and Figure 4 SEM images of the solid-phase extraction material (UIO-66-F4@CSM) of metal-organic framework functionalized cashmere fibers prepared for the example at different magnifications.

[0025] Figure 5 Infrared spectra of the solid-phase extraction material (UIO-66-F4@CSM) based on metal-organic framework functionalized cashmere prepared in Example 1 and the raw cashmere fibers.

[0026] Figure 6 The graph shows the adsorption results of the standard solution on the metal-organic framework functionalized cashmere (solid phase extraction material UIO-66-F4@CSM) prepared in Example 1.

[0027] Figure 7 The MRM spectra of each PFAS standard sample in Example 3 at a concentration of 5 ppb are shown.

[0028] Figure 8 The figure shows the spiked recovery results of the metal-organic framework functionalized cashmere (solid phase extraction material UIO-66-F4@CSM) prepared in Example 1.

[0029] Figure 9 The spiked recovery results of the metal-organic framework functionalized cashmere (solid phase extraction material UIO-66-F4@CSM) prepared in Example 1 and the solid phase extraction material (UIO-66-F4@CCF) with degreased cotton as carrier prepared in Comparative Example 1 are compared.

[0030] Figure 10 The graph shows a comparison of the spiked recovery results of the metal-organic framework functionalized cashmere (solid phase extraction material UIO-66-F4@CSM) prepared in Example 1, cashmere, and solid phase extraction materials (UiO-66@CSM, UiO-66-NH2@CSM) prepared in Comparative Example 2 using different organic ligands (terephthalic acid, 2-aminoterephthalic acid). Detailed Implementation

[0031] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0032] In the following examples, high-performance liquid chromatography (HPLC) was performed using an ACQUITY UPLC BEH C18 reversed-phase column with a particle size of 1.7 µm, a pore size of 130 Å, and column dimensions of 2.1 mm × 50 mm. The column flow rate was 0.3 mL / min. Mobile phase A was 5 mM ammonium acetate, and mobile phase B was pure methanol. The gradient elution program was as follows: 0–0.3 min, 95% A, balance mobile phase B; 0.9–9 min, 5% A; 9–12 min, 5% A; 12.0–12.1 min, 95% A; 12.1–14.0 min, 95% A.

[0033] In the following embodiments, triple quadrupole mass spectrometry uses an electron impact ionization (EI) source and multiple reaction monitoring (MRM) mode. The ion source temperature is set to 150°C, and selected specific precursor ions are subjected to collision-induced dissociation. Mass spectrometry signals are acquired only for selected specific daughter ions. The MRM parameters are shown in Table 1.

[0034] Table 1

[0035] Example 1 The preparation method of metal-organic framework functionalized cashmere includes the following steps: (1) Cashmere pretreatment: 5 g of cashmere (CSM) was soaked and stirred in 0.1 M NaOH solution (600 mL) for 2 hours, then taken out and soaked and stirred in 0.1 M HCl solution (600 mL) for 0.5 hours. Then it was washed with ultrapure water 3-4 times and dried at 60℃ overnight to obtain pretreated cashmere fibers.

[0036] (2) Immerse 4 g of pretreated cashmere fiber in 0.5 M citric acid solution (400 mL), stir and react at 50 °C for 24 hours, then gradually raise the temperature to 120 °C within 10 min, keep warm for 1.5 hours, cool to room temperature, wash 3-4 times with ultrapure water, and dry at 60 °C overnight to obtain carboxylated cashmere.

[0037] (3) Preparation of precursor solution: 6.708 g ZrOCl2·8H2O (0.02 mol), 25.58 mL acetic acid and 62.50 mL distilled water were added to a 250 mL round bottom flask, heated at 60 °C for 6 hours, cooled and diluted with 88 mL distilled water to about 170 mL to obtain the precursor solution; Preparation of ligand solution: 4.952 g tetrafluoroterephthalic acid (0.02 mol), 1.667 g NaOH (0.04 mol) and 104.17 mL distilled water were added to a 250 mL round-bottom flask, heated to 60 °C to dissolve, and after cooling, diluted with 104 mL distilled water to about 200 mL to obtain the ligand solution.

[0038] Preparation of UIO-66-F4@CSM: 3 g of carboxylated cashmere was immersed in the precursor solution, sonicated for 10 minutes, stirred for 1 hour and then removed. It was then immersed in the ligand solution, sonicated for 10 minutes and left to stand for 0.5 hours and then removed. The remaining precursor solution was then poured into the precursor solution and stirred for 3 hours. After washing several times with ultrapure water, it was dried at 60°C overnight to obtain metal-organic framework functionalized cashmere (solid phase extraction material UIO-66-F4@CSM).

[0039] Depend on Figure 1 It is known that cashmere fibers have a diameter of about 14-16 μm, which is much finer than ordinary wool. The surface is relatively smooth, and the scale layer on the fiber surface can be clearly seen. Figure 2 It presents the overall shape of multiple fibers, showing natural bending and twisting, with relatively uniform fiber diameter and interwoven fibers.

[0040] Depend on Figure 3 It can be seen that a large number of fine white particles are uniformly distributed on the surface of the cashmere fiber. These are metal-organic framework (MOF) nanoparticles loaded onto the cashmere fiber, with particle sizes ranging from nanometers to submicrometers. Furthermore, the scaly structure of the cashmere fiber itself is partially covered by MOF particles, making the fiber surface rougher, which is direct evidence of successful MOF loading. The MOF particles are tightly bonded to the fiber surface, indicating that this invention achieves good interfacial bonding between the two. Figure 4 It can be seen that the natural curvature and interlacing state of cashmere fibers are preserved, indicating that MOF functionalization treatment does not damage the basic morphology and mechanical properties of cashmere fibers; compared with untreated cashmere fibers ( Figure 2 In contrast, the surface gloss of fibers functionalized with metal-organic frameworks is reduced, resulting in a rougher texture, which is a macroscopic manifestation of the uniform coverage of MOF particles. Furthermore, the gaps between fibers still exist, which helps maintain the breathability and fluffiness of the material. At the same time, MOF particles may also be distributed in the fiber gaps, providing more active sites for subsequent enrichment of perfluoroalkyl substances.

[0041] Depend on Figure 5 It can be known that the original cashmere fiber is at 3280 cm. -1 (O–H) and 1640 cm -1The characteristic peaks at (C=O) all changed significantly after MOF functionalization, indicating that MOF is not simply physically adsorbed, but rather interacts with cashmere fibers through chemical bonds to achieve stable loading; and, 990 cm⁻¹ -1 (C–F) and 734 cm -1 (Zr–O) is a unique fingerprint peak of MOF materials. Its appearance on functionalized fibers is direct chemical evidence of successful MOF loading.

[0042] Example 2 The solid-phase extraction column was packed with the solid-phase extraction material based on metal-organic framework functionalized cashmere fiber prepared in Example 1. The specific process is as follows: 20 mg of the solid-phase extraction material based on metal-organic framework functionalized cashmere fiber prepared in Example 1 was taken and filled into a 100 μL pipette tip (the pipette tip is used as the packing medium for the solid-phase extraction column) to obtain the solid-phase extraction column.

[0043] Example 3 The application of metal-organic framework-functionalized cashmere fibers in the enrichment and detection of perfluoroalkyl substances includes the following steps; 1) Connect the solid-phase extraction column prepared in Example 2 to the lower end of a 10 ml pipette, and use a pipette to aspirate and push out 1 ml of 20% methanol aqueous solution 2-3 times to activate the solid-phase extraction column; 2) Using PFAS standards, a mixed standard solution of 23 PFAS standards and 13 internal standards was prepared using 1 mL of methanol and water as a mixed solvent (20% by volume of methanol) as a sample solution for the perfluoroalkyl substances to be enriched and detected, in order to test the enrichment effect of the solid phase extraction material based on metal-organic framework functionalized cashmere fiber described in this invention on perfluoroalkyl substances. 3) The solid-phase extraction column activated in step 1) was repeatedly aspirated and pushed out PFAS mixed standard solution 5 times at a slow and stable speed (1 mL / min) to obtain a solid-phase extraction column enriched with perfluoroalkyl substances. 4) After rinsing the solid-phase extraction column enriched with perfluoroalkyl substances by aspirating 1 ml of 40% methanol aqueous solution, slowly aspirate 1 ml of a mixed solution of industrial ammonia and methanol (ammonia concentration 25%, volume ratio of ammonia to methanol 1:99) for elution. Repeat 3 times to obtain the eluent. 5) The eluent was filtered through a 0.22 μm nylon needle filter, bottled, and analyzed by liquid chromatography-tandem mass spectrometry (LC-MS / MS). The results are as follows: Figure 6 As shown, the absolute recoveries of the 23 PFAS ranged from 40% to 80%, which meets the recovery requirements of solid-phase microextraction.

[0044] 6) Detect the standard solution obtained in step 2) using liquid chromatography-tandem mass spectrometry (LC-MS / MS). Acquire data according to the MRM mode of the mass spectrometer to obtain the MRM chromatogram, as shown below. Figure 7 As shown in Table 2, standard curves for various PFAS were obtained by plotting the concentration of each PFAS as the x-axis and the product of the ratio of the peak area of ​​the corresponding quantitative ion pair to the internal standard as the y-axis. The correlation coefficient R0 for each standard curve (calibrated at 8 points: 0.05, 0.1, 0.4, 0.6, 1, 5, 10, and 20 ng / mL) is shown in Table 2. 2 Between 0.9936 and 0.9998, the LOD was 0.01–0.15 ng / mL, and the LOQ was 0.03–0.27 ng / mL.

[0045] Table 2

[0046] Example 4 Based on Example 3, a spiked recovery experiment was conducted using honey as the actual sample to further confirm the application of metal-organic framework functionalized cashmere fibers in the enrichment and detection of perfluoroalkyl substances. The specific steps include the following: 1) Same as step 1) of Example 3, to obtain the activated solid-phase extraction column; 2) Honey pretreatment method: Weigh 2 g of honey sample into a centrifuge tube, add internal standards with a mass concentration of 10 ng / g and standard substances with a mass concentration of 5 ng / g, let stand for 10 min, then add 5 mL of ultrapure water and shake to dissolve, add 10 mL of acetonitrile and shake to extract, add 4 g of magnesium sulfate and 1 g of sodium chloride for salting out, shake thoroughly and centrifuge, take 5 mL of supernatant and blow with nitrogen, and redissolve with 1 mL of 20% methanol solution to obtain the loading solution; 3) The solid-phase extraction column activated in step 1) is repeatedly aspirated and pushed out 5 times at a slow and stable speed (1 mL / min) with the sample solution loaded in step 2). Then, an appropriate amount of 40% methanol solution is aspirated and pushed out 2-3 times each to wash away the adsorbed non-target impurities and matrix, so as to obtain a solid-phase extraction column enriched with perfluoroalkyl substances. 4) Same as step 4) of Example 3, to obtain the eluent; 5) Same as step 5) in Example 3, detect the concentration of PFAS in the eluent, and the spiked recovery results are as follows: Figure 8 As shown in the results, the recovery rates of the 23 PFAS were between 80% and 120%, which met the recovery rate requirements.

[0047] Example 5 The application of metal-organic framework functionalized cashmere fibers in the enrichment and detection of perfluoroalkyl substances in real samples includes the following steps; 1) Same as step 1) of Example 3, to obtain the activated solid-phase extraction column; 2) The test subjects were six honey samples from two different regions. The honey pretreatment method was as follows: 2 g of honey sample was weighed into a centrifuge tube, and internal standards with a mass concentration of 10 ng / g were added. The mixture was allowed to stand for 10 min, then 5 mL of ultrapure water was added and shaken to dissolve. 10 mL of acetonitrile was added and shaken to extract. 4 g of magnesium sulfate and 1 g of sodium chloride were added for salting out. After thorough shaking, the mixture was centrifuged, and 5 mL of the supernatant was taken and blown with nitrogen. The mixture was then reconstituted with 1 mL of 20% methanol solution to obtain the loading solution. 3) The solid-phase extraction column activated in step 1) is repeatedly aspirated and pushed out 5 times at a slow and stable speed (1 mL / min) with the sample solution loaded in step 2). Then, an appropriate amount of 40% methanol solution is aspirated and pushed out 2-3 times each to wash away the adsorbed non-target impurities and matrix, so as to obtain a solid-phase extraction column enriched with perfluoroalkyl substances. 4) Same as step 4) of Example 3, to obtain the eluent; 5) Same as step 5) of Example 3, the concentration of PFAS in the eluent was detected. The specific results are as follows: PFBA, PFPA, PFHxA, and PFOA were all detected in region 1, with mass concentrations between 0.1 and 1.0 ng / g; PFBA, PFPA, and PFOA were all detected in region 2, with mass concentrations between 0.05 and 1.1 ng / g. See Table 3 for details. 6) The solid phase extraction column can be regenerated by washing with methanol and water and then reused several times.

[0048] Table 3

[0049] Comparative Example 1 In this invention, the choice of substrate material has a significant impact on the adsorption effect of PFAS. The difference between this comparative example and Example 1 is that the same mass of degreased cotton fiber (CCF) is used as the carrier material. Otherwise, the synthesis method is exactly the same as in Example 1, thus synthesizing the solid-phase extraction material UiO-66-F4@CCF. Then, a spiked recovery experiment of UiO-66-F4@CCF was conducted according to Example 4. The spiked recovery results of the comparative example and Example 4 are as follows: Figure 9 As shown. By Figure 9 It can be seen that the adsorption effect of UiO-66-F4@CCF on 23 PFAS is much lower than that of UiO-66-F4@CSM, and the recovery rate of four short-chain PFAS is less than 10%, making it impossible to accurately determine multiple PFAS at the same time.

[0050] Comparative Example 2 In this invention, the selection of the organic ligand for MOF has a significant impact on the adsorption effect of PFAS. In this comparative example, the organic ligand tetrafluoroterephthalic acid in Example 1 was replaced with the same number of moles of terephthalic acid and 2-aminoterephthalic acid, respectively. All other steps were the same as in Example 1. Solid phase extraction materials UiO-66@CSM and UiO-66-NH2@CSM were synthesized in this way.

[0051] Spiked recovery experiments were conducted on four materials—cashmere, UiO-66@CSM, UiO-66-NH2@CSM, and UiO-66-F4@CSM—following the steps in Example 4. The results are as follows: Figure 10 As shown. By Figure 10 It is known that cashmere alone exhibits extremely low adsorption and recovery rates for most PFAS (especially short-chain PFAS), only around 10%-30%, which cannot meet the requirements for accurate determination. While the two comparative materials (UiO-66@CSM and UiO-66-NH2@CSM) showed slightly better performance for individual PFAS, their overall recovery rates fluctuated significantly, and their adsorption effect on short-chain PFAS was significantly lower than that of the material in the present invention (UiO-66-F4@CSM). The UiO-66-F4@CSM prepared in this invention shows relatively stable and high recovery rates for PFAS with different carbon chain lengths, enabling simultaneous efficient enrichment and accurate determination of multiple PFAS.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. The application of metal-organic framework functionalized cashmere fibers as extraction materials for perfluoroalkyl substances, characterized in that, The application method is as follows: the metal-organic framework functionalized cashmere fiber is activated with methanol aqueous solution, and then enriched with the perfluoroalkyl substance sample solution to be enriched and / or detected to obtain metal-organic framework functionalized cashmere fiber enriched with perfluoroalkyl substances and the purified sample solution; then the metal-organic framework functionalized cashmere fiber enriched with perfluoroalkyl substances is eluted with an eluent to detect the content of perfluoroalkyl substances.

2. The application of the metal-organic framework functionalized cashmere fiber according to claim 1 as an extraction material for perfluoroalkyl substances, characterized in that, The metal-organic framework functionalized cashmere fiber is obtained by carboxylating cashmere fiber after alkali and acid treatment, and then preparing metal-organic framework material UiO-66-F4 in situ.

3. The application of the metal-organic framework functionalized cashmere fiber according to claim 1 as an extraction material for perfluoroalkyl substances, characterized in that, The method for preparing the metal-organic framework functionalized cashmere fiber includes the following steps: (1) Pretreatment: The cashmere was soaked in alkaline solution and then taken out, then soaked in acid solution and taken out, washed and dried to obtain modified cashmere; (2) The pretreated cashmere was placed in a citric acid aqueous solution for two-stage heat treatment, then washed and dried to obtain carboxylated cashmere; (3) Dissolve zirconium oxychloride and acetic acid in water to obtain a precursor solution; then, immerse the carboxylated cashmere in the precursor solution for sonication and / or stirring, then remove it and immerse it in a mixed aqueous solution of tetrafluoroterephthalic acid and NaOH for sonication and / or stirring, then let it stand, pour the remaining precursor solution into the ligand solution and stir for a certain time, then wash and dry it to obtain metal-organic framework functionalized cashmere.

4. The application of the metal-organic framework functionalized cashmere fiber according to claim 3 as an extraction material for perfluoroalkyl substances, characterized in that, In step (1), the diameter of the raw cashmere is between 10 and 20 micrometers, and it is fibrous; In step (1), the alkaline solution is a NaOH aqueous solution with a concentration of 0.05-0.2 M, and the person is soaked in the alkaline solution for 1.5-2.5 hours; the acid solution is an HCl aqueous solution with a concentration of 0.05-0.15 M, and the person is soaked in the acid solution for 20-40 minutes.

5. The application of the metal-organic framework functionalized cashmere fiber according to claim 3 as an extraction material for perfluoroalkyl substances, characterized in that, In step (2), the concentration of the citric acid aqueous solution is 0.2-0.8 M; the two-stage heat treatment process is as follows: first, heat the reaction at 40-60 ℃ for 20-28 hours, and then raise the temperature to 100-140 ℃ at 4-10 ℃ / min and keep the reaction at the temperature for 1-2 hours.

6. The application of the metal-organic framework functionalized cashmere fiber according to claim 3 as an extraction material for perfluoroalkyl substances, characterized in that, In step (3), the concentration of zirconium oxychloride in the precursor solution is 0.1-0.3 M, and the volume percentage of acetic acid is 12-15%; in the mixed aqueous solution of tetrafluoroterephthalic acid and NaOH, the concentration of tetrafluoroterephthalic acid is 0.1-0.2 M, and the concentration of NaOH is 0.16-0.22 M. After the first immersion in the precursor solution, sonicate for 5-15 minutes and then stir for 0.5-1.5 hours; after sonicating in a mixed aqueous solution of tetrafluoroterephthalic acid and NaOH for 5-15 minutes, let stand for 20-40 minutes; and then stir in the precursor solution for 2-4 hours.

7. The application of the metal-organic framework functionalized cashmere fiber according to claim 1 as an extraction material for perfluoroalkyl substances, characterized in that, The perfluoroalkyl substances include one or more of the following: perfluorobutyric acid, perfluorovaleric acid, perfluorohexanoic acid, perfluorobutyric acid, perfluoroheptanoic acid, perfluoropentanesulfonic acid, 3H-perfluoro-4,8-dioxanonanoic acid, perfluorooctanoic acid, perfluorohexanesulfonic acid, perfluorononanoic acid, perfluoroheptanesulfonic acid, perfluorodecanoic acid, perfluorooctanoic acid, perfluoroundecanoic acid, perfluorononanesulfonic acid, 9-chlorohexadecano-3-oxononane-1-sulfonic acid, perfluorododecanic acid, perfluorodecanesulfonic acid, perfluorotridecanoic acid, 11-chloroeicosico-3-oxaundecane-1-sulfonic acid, perfluorotetradecanoic acid, perfluorohexadecanoic acid, and perfluorooctadecanic acid.

8. The application of the metal-organic framework functionalized cashmere fiber according to claim 1 as an extraction material for perfluoroalkyl substances, characterized in that, The metal-organic framework functionalized cashmere fibers were activated with an aqueous methanol solution and then used as a packing material to prepare a solid-phase extraction column for extracting perfluoroalkyl substances sample solutions to be enriched and / or detected; wherein the volume percentage of methanol in the aqueous methanol solution was 20-50%.

9. The application of the metal-organic framework functionalized cashmere fiber according to claim 1 as an extraction material for perfluoroalkyl substances, characterized in that, The elution was performed using an ammonia-methanol solution, wherein the ammonia-methanol solution was obtained by mixing ammonia and methanol in a volume ratio of 1:(49-99).

10. The application of the metal-organic framework functionalized cashmere fiber according to claim 1 as an extraction material for perfluoroalkyl substances, characterized in that, The eluent can be used directly as the sample loading solution for detection in liquid chromatography-tandem mass spectrometry (LC-MS / MS), or the eluent can be concentrated and reconstituted by nitrogen blowing before being used for detection in LC-MS / MS.

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