A surface coating material, a solid-phase microextraction probe, and a preparation method and application thereof

Abstract

The present invention relates to the technical fields of solid-phase microextraction probes and veterinary drug detection, and specifically relates to a surface coating material, a solid-phase microextraction probe, a preparation method and an application thereof. The surface coating material is prepared on the surface of a substrate by an electrospinning method after 2D-Ni-MOF material, polyacrylonitrile and N,N-dimethylformamide are mixed and stirred; the solid-phase microextraction probe comprises a substrate and a coating, and the coating is formed on the surface of the substrate by an electrospinning method. The solid-phase microextraction probe prepared by the present invention can perform quantitative analysis on sulfamethazine, thiabendazole and clenbuterol, and solves the problem in the prior art that different types of veterinary drugs cannot be detected at one time.

Description

Technical Field

[0001] The present invention relates to the technical fields of solid-phase microextraction probes and veterinary drug detection, and particularly relates to a surface coating material, a solid-phase microextraction probe, a preparation method and an application thereof. Background Art

[0002] Adding veterinary drugs in the production of animal food has become a standard practice for decades. The addition of these veterinary drugs not only increases the growth rate of animals, but also plays a key role in the prevention and control of animal diseases. However, the use of veterinary drugs may lead to residue problems in livestock and poultry products, posing obvious health risks to consumers. Therefore, monitoring veterinary drug residues has become increasingly important.

[0003] Common types of veterinary drug residues include: antibacterial drug residues, anti-parasitic drug residues, hormone and hormone drug residues, etc. Among them, antibacterial drug residues include residues of various antibiotics such as sulfamethazine, tetracycline, fluoroquinolone, sulfadimidine, etc. and antifungal drugs such as ketoconazole. These drugs are mainly used to treat microbial infections in animals, but improper use may leave residues in livestock and poultry products. Anti-parasitic drug residues include anti-helminth and anti-protozoal drugs, such as thiabendazole and benzothiazole compounds, etc. These drugs are mainly used to control parasitic infections in animals, but excessive use may lead to residues. Hormone and hormone drug residues include corticosteroids and β-agonists. For example, clenbuterol and ractopamine, etc. These drugs are usually used to increase the growth rate and meat quality, but may accumulate in the body and interfere with the human endocrine system. The widespread use of veterinary drugs in animal husbandry has increased the survival rate and growth efficiency of animals, significantly promoting the development of animal husbandry. However, unreasonable use, drug abuse and environmental persistence may lead to residues in livestock and poultry products, causing various health problems. Therefore, effectively managing these drugs, as well as developing and applying sensitive and reliable residue detection methods, are crucial for protecting consumer health and ensuring environmental safety.

[0004] To reduce matrix interference and selectively adsorb target analytes, sample pretreatment is required before instrumental analysis. Solid Phase Microextraction (SPME), whose English name is Solid Phase Microextraction and is abbreviated as SPME, has obvious advantages in terms of sensitivity, speed, and simplicity of operation. The basic principle of SPME is to adsorb target compounds from liquid samples onto a solid fiber, thereby separating them from the sample matrix and interfering compounds. Then, these adsorbed compounds are eluted by an eluent or thermally desorbed, allowing the separation and enrichment of the target compounds. The commercially available SPME probe in 2015 is a new type of SPME device that overcomes the limitations of traditional SPME fibers. It uses a stainless steel rod coated with a functional material as the matrix, significantly improving the robustness and extraction ability. Therefore, developing functional materials with excellent selectivity as the coating of SPME probes is crucial for improving extraction efficiency and analytical performance.

[0005] In recent years, various coating materials for SPME probes have been developed, including graphene and metal-organic frameworks. Among them, two-dimensional metal-organic framework nanosheets have attracted significant attention. Two-dimensional metal-organic framework nanosheets, abbreviated as 2D-MOFs, are a new type of ultrathin 2D nanostructure that combines the advantages of 2D nanostructures and MOF crystals. Compared with other nanostructures, 2D-MOFs have a large specific surface area, which is beneficial for the exposure of active sites, and due to their ultrathin characteristics, they have a high surface area-to-volume ratio. Therefore, using 2D-MOFs to prepare suitable coating materials and applying them to the preparation of SPME probes is the focus of current research.

[0006] However, currently, the SPME probes prepared using 2D-MOFs coating materials on the market are highly targeted, mostly used for adsorbing a certain substance or substances of the same type, and have relatively poor adsorption effects on different types of substances. Summary of the Invention

[0007] To solve the problem that the SPME probes prepared using 2D-MOFs coating materials currently have relatively poor adsorption effects on different types of substances, the purpose of the present invention is to provide a surface coating material, a solid-phase microextraction probe, a preparation method, and an application.

[0008] To achieve the above purpose, the technical solution of the present invention is as follows.

[0009] In the first aspect of the present invention, a surface coating material is provided. The surface coating material is prepared on the surface of a substrate by electrospinning after mixing and stirring a two-dimensional nickel-based metal-organic framework material, polyacrylonitrile, and N,N-dimethylformamide; the dosage ratio of the two-dimensional nickel-based metal-organic framework material, polyacrylonitrile, and N,N-dimethylformamide is 199 mg - 201 mg: 99 mg - 101 mg: 2 mL - 4 mL.

[0010] The present invention selects two-dimensional nickel-based metal-organic framework materials, polyacrylonitrile, and N,N-dimethylformamide as raw materials for the coating material. By adjusting the appropriate addition amount of the two-dimensional nickel-based metal-organic framework material in the electrospinning solution, nanofibers with advantages such as a high specific surface area and fast mass transfer kinetics are prepared by the electrospinning process, thereby significantly increasing the active adsorption sites of the obtained solid-phase microextraction probe and solving the problem that the SPME probe prepared using two-dimensional MOF coating materials has relatively poor adsorption effects on different types of substances.

[0011] Experimental analysis shows that when the addition amount of the two-dimensional nickel-based metal-organic framework material is too low, the surface coating of the metal rod will be unstable, which is mainly attributed to the low viscosity of the electrospinning solution components. On the contrary, excessive addition of the two-dimensional nickel-based metal-organic framework material will hinder the diffusion path and reduce the effective specific surface area of the surface coating. Therefore, selecting an appropriate addition amount of the two-dimensional nickel-based metal-organic framework material helps to form more effective adsorption sites on the surface coating.

[0012] Preferably, the conditions for electrospinning are: the voltage is 19.5 kV, the working rate is 15 µL·min -1 , and the electrospinning time is 50 min.

[0013] Preferably, the two-dimensional nickel-based metal-organic framework material is prepared by the following method: Mix N,N-dimethylformamide, ethanol, and water to obtain a mixed solution; add terephthalic acid and nickel salt to the mixed solution, mix and stir, then add triethylamine, and perform ultrasonic treatment. After washing and drying, the two-dimensional nickel-based metal-organic framework material is obtained; the volume ratio of N,N-dimethylformamide, ethanol, and water is 320:20:20; the dosage ratio of terephthalic acid, nickel salt, mixed solution, and triethylamine is 7.5 mmol:7.5 mmol:360 mL:8 mL. The two-dimensional nickel-based metal-organic framework material is obtained by ultrasonic treatment of terephthalic acid and nickel salt under the catalysis of triethylamine to promote the coordination reaction and form a two-dimensional nickel-based metal-organic framework material.

[0014] Preferably, the nickel salt is nickel chloride hexahydrate. Of course, other nickel salts can also be selected according to actual needs. Preferably, the substrate is a metal rod. Of course, an appropriate substrate and the corresponding substrate size can also be selected according to actual needs.

[0015] In the second aspect of the present invention, a solid-phase microextraction probe is provided, including a substrate and a two-dimensional nickel-based metal-organic framework coating. The two-dimensional nickel-based metal-organic framework coating is formed on the surface of the substrate by the electrospinning method, and the two-dimensional nickel-based metal-organic framework coating is the surface coating material.

[0016] Preferably, the thickness of the two-dimensional nickel-based metal-organic framework coating is 130 μm, and the length of the two-dimensional nickel-based metal-organic framework coating is 1 cm.

[0017] Preferably, the substrate is a metal rod, and the diameter of the metal rod is 991 µm.

[0018] The third aspect of the present invention provides a preparation method of the solid-phase microextraction probe described in the second aspect, comprising the following steps:

[0019] Mix and stir the two-dimensional nickel-based metal-organic framework material, polyacrylonitrile, and N,N-dimethylformamide to obtain an electrospinning solution; form a two-dimensional nickel-based metal-organic framework coating on the surface of the substrate by electrospinning the electrospinning solution, and then immerse the substrate with the two-dimensional nickel-based metal-organic framework coating in ethanol and dry it to obtain a solid-phase microextraction probe.

[0020] The fourth aspect of the present invention provides an application of the solid-phase microextraction probe described in the second aspect in veterinary drug detection, and the veterinary drugs are at least one of dimetridazole, thiabendazole, and clenbuterol.

[0021] Preferably, the veterinary drug detection is carried out by combining ultra-high performance liquid chromatography with a quadrupole time-of-flight mass spectrometer, and the quadrupole time-of-flight mass spectrometer is equipped with an electrospray ionization interface and operates in the positive ion mode.

[0022] Preferably, the chromatographic conditions for veterinary drug detection are as follows:

[0023] An Acquity UHPLC BEH C18 chromatographic column with a particle size of 1.7 μm and an inner diameter of 2.1 mm × 100 mm is used; the temperature is 30 °C, and the mobile phase: mobile phase A is an aqueous solution of 100 mmol / L ammonium acetate and mobile phase B is methanol, and the flow rate is 0.4 mL·min -1 ; The gradient program is: mobile phase B is 2% - 99% from 0 min to 4 min, B is 99% - 2% from 4 min to 8 min, and B is 2% from 8 min to 10 min.

[0024] Preferably, the mass spectrometry conditions for veterinary drug detection: the voltage is 1 kV, the ion source temperature is 120 °C, and the desolvation temperature is 500 °C; the scanning range is 50 m / z - 400 m / z; 99.9% nitrogen is used as the cone gas and the dissolving gas, and the flow rates are 20 L·h -1 and 1000 L·h -1 .

[0025] The beneficial effects of the present invention:

[0026] 1. The present invention selects two-dimensional nickel-based metal-organic framework materials, polyacrylonitrile, and N,N-dimethylformamide as raw materials for the coating material. By adjusting the appropriate addition amount of the two-dimensional nickel-based metal-organic framework material in the electrospinning solution, nanofibers with advantages such as a high specific surface area and fast mass transfer kinetics are prepared by the electrospinning process and formed on the surface of the substrate, thereby being able to significantly increase the active adsorption sites of the obtained solid-phase microextraction probe and solving the problem that the SPME probe prepared using 2D-MOFs coating materials has relatively poor adsorption effects on different types of substances. The solid-phase microextraction probe prepared by the present invention can perform quantitative analysis on sulfamethazine, thiabendazole, and clenbuterol.

[0027] 2. The solid-phase microextraction probe of the present invention can withstand up to 90 extraction and desorption cycles and is suitable for detection in milk and pork. The detection limit in milk is 0.001 μg·L -1 ~0.004 μg·L -1 and the detection limit in pork is 0.003 μg·L -1 ~0.007 μg·L -1 . The detection sensitivity and specificity are good, and the analysis results are highly reliable.

[0028] 3. The preparation method of the solid-phase microextraction probe of the present invention is simple and inexpensive. Compared with commercially available probes, the solid-phase microextraction probe prepared by the present invention has better extraction efficiency for veterinary drugs and can perform quantitative analysis on sulfamethazine, thiabendazole, and clenbuterol in combination with an ultra-high performance liquid chromatography-mass spectrometer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 are images of the surface coatings of different solid-phase microextraction probes. Among them, (a) is an image of a 2D-Ni-MOF coating; (b) is an image of a 2D-Mn-MOF coating; (c) is an image of 2D-Co-MOF.

[0030] Figure 2 is a comparison chart of the adsorption capacities of 2D-Ni-MOF-solid-phase microextraction probe, 2D-Mn-MOF-solid-phase microextraction probe, and 2D-Co-MOF-solid-phase microextraction probe for three target veterinary drugs.

[0031] Figure 3Total ion chromatograms of different samples processed by 2D-Ni-MOF solid-phase microextraction probes. Among them, (a) is the total ion chromatogram of the first spiked standard solution; (b) is the total ion chromatogram of the second spiked standard solution; (c) is the total ion chromatogram of a milk sample spiked with sulfamethazine, clenbuterol, and thiabendazole without pretreatment with a 2D-Ni-MOF-SPME probe; (d) is the total ion chromatogram of a milk sample spiked with sulfamethazine, clenbuterol, and thiabendazole that has been pretreated with a 2D-Ni-MOF-SPME probe; (e) is the total ion chromatogram of a pork sample spiked with sulfamethazine, clenbuterol, and thiabendazole without pretreatment with a 2D-Ni-MOF-SPME probe; (f) is the total ion chromatogram of a pork sample spiked with sulfamethazine, clenbuterol, and thiabendazole that has been pretreated with a 2D-Ni-MOF-SPME probe. Among them, the retention time of sulfamethazine is 2.60 minutes; the retention time of clenbuterol is 3.16 minutes; the retention time of thiabendazole is 3.48 minutes.

[0032] Figure 4 Curves for optimizing electrospinning conditions and solid-phase microextraction parameters. Among them, (a) is the mass percentage - absolute recovery curve of the 2D-Ni-MOF material; (b) is the electrospinning time - absolute recovery curve; (c) is the sample volume - absolute recovery curve; (d) is the NaCl concentration - absolute recovery curve; (e) is the stirring speed - absolute recovery curve; (f) is the extraction temperature - absolute recovery curve; (g) is the extraction time - absolute recovery curve; (h) is the desorption solvent - absolute recovery bar chart; (i) is the desorption time - absolute recovery curve.

[0033] Figure 5Scanning electron microscope images of the surface coatings of 2D-Ni-MOF solid-phase microextraction probes prepared at different electrospinning times at different magnifications. Among them, (a1) is the scanning electron microscope image of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 20 minutes and a thickness of 56 μm with part of the coating removed; (a2) is the scanning electron microscope image of the surface coating of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 20 minutes and a thickness of 56 μm; (a3) is a partial enlarged view of (a2); (b1) is the scanning electron microscope image of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 30 minutes and a thickness of 80 μm with part of the coating removed; (b2) is the scanning electron microscope image of the surface coating of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 30 minutes and a thickness of 80 μm; (b3) is a partial enlarged view of (b2); (c1) is the scanning electron microscope image of the 2D-Ni-MOF solid-phase microextraction probe with a thickness of 100 μm prepared with an electrospinning time of 40 minutes with part of the coating removed; (c2) is the scanning electron microscope image of the surface coating of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 40 minutes and a thickness of 100 μm; (c3) is a partial enlarged view of (c2); (d1) is the scanning electron microscope image of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 50 minutes and a thickness of 130 μm with part of the coating removed; (d2) is the scanning electron microscope image of the surface coating of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 50 minutes and a thickness of 130 μm; (d3) is a partial enlarged view of (d2); (e1) is the scanning electron microscope image of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 60 minutes and a thickness of 150 μm with part of the coating removed; (e2) is the scanning electron microscope image of the surface coating of the 2D-Ni-MOF solid-phase microextraction probe prepared with an electrospinning time of 60 minutes and a thickness of 150 μm; (e3) is a partial enlarged view of (e2).

[0034] Figure 6Figure showing the test results of the reusability of the 2D-Ni-MOF solid-phase microextraction probe. Among them, (a1) is the scanning electron microscopy image of the 2D-Ni-MOF solid-phase microextraction probe without cycling; (a2) is the enlarged view of the partial area of (a1); (a3) is the scanning electron microscopy image of the 2D-Ni-MOF solid-phase microextraction probe after 90 extraction-desorption cycles; (a4) is the enlarged view of the partial area of (a3); (b1) is the photo of the 2D-Ni-MOF solid-phase microextraction probe without cycling; (b2) is the photo of the 2D-Ni-MOF solid-phase microextraction probe after 90 extraction-desorption cycles; (c) is the column chart of the absolute recovery rate of the reusability of the 2D-Ni-MOF solid-phase microextraction probe; (d) is the column chart of the absolute recovery rate of the repeatability of the 2D-Ni-MOF solid-phase microextraction probes from the same batch and different batches; among them, 1, 2, and 3 are three solid-phase microextraction probes from the same batch; 4, 5, and 6 are three solid-phase microextraction probes from three different batches; (e) is the column chart of the absolute recovery rate of the residual test of the 2D-Ni-MOF solid-phase microextraction probe for extracting three target analytes.

[0035] Figure 7 Figure comparing the extraction efficiencies of the 2D-Ni-MOF solid-phase microextraction probe and four commercial solid-phase microextraction probes under the optimal extraction and desorption conditions. Among them, C1 is the 2D-Ni-MOF solid-phase microextraction probe; C2 is the PDMS / DVB solid-phase microextraction probe; C3 is the PDMS solid-phase microextraction probe; C4 is the PDMS / CAR / DVB solid-phase microextraction probe; C5 is the PA solid-phase microextraction probe.

[0036] Figure 8 Mass spectra of three veterinary drugs. Among them, (a) is the mass spectrum of thiabendazole; (b) is the mass spectrum of sulfamethazine; (c) is the mass spectrum of clenbuterol. Detailed implementation manners

[0037] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0039] In the following embodiments of the present invention, the 2D-Ni-MOF material is a two-dimensional nickel-based metal-organic framework material; the 2D-Ni-MOF coating is a two-dimensional nickel-based metal-organic framework coating; the 2D-Ni-MOF solid-phase microextraction probe is a two-dimensional nickel-based metal-organic framework-solid phase microextraction probe.

[0040] The 2D-Mn-MOF material is a two-dimensional manganese-based metal-organic framework material; the 2D-Mn-MOF coating is a two-dimensional manganese-based metal-organic framework coating; the 2D-Mn-MOF solid-phase microextraction probe is a two-dimensional manganese-based metal-organic framework-solid phase microextraction probe.

[0041] The 2D-Co-MOF material is a two-dimensional cobalt-based metal-organic framework material; the 2D-Co-MOF coating is a two-dimensional cobalt-based metal-organic framework coating; the 2D-Co-MOF solid-phase microextraction probe is a two-dimensional cobalt-based metal-organic framework-solid phase microextraction probe.

[0042] A suitable coating preparation method can not only make the coating more durable and long-lasting, but also reduce experimental errors. At present, the preparation methods of nanomaterial coatings include self-assembly method, electrochemical deposition method and electrospinning method. Among them, electrospinning stands out because it forms microfibers by electrostatic stretching from a viscous solution with a certain elasticity. This method is simple to operate, allows immediate adjustment of working parameters, and produces nanofibers with good uniformity and a large specific surface area, which is an effective method for preparing extraction coatings.

[0043] The surface coating material of the present invention is prepared from 2D-Ni-MOF material, polyacrylonitrile and N,N-dimethylformamide. The 2D-Ni-MOF material has a large specific surface area, which is beneficial to the exposure of active sites. And due to its ultrathin characteristics, it has a high surface area to volume ratio, so the extraction efficiency is relatively high. The electrospinning method has the advantages of uniform coating, economy, reusability and good stability. The prepared nanofibers have the advantages of a high specific surface area and fast mass transfer kinetics, etc., so that the active adsorption sites of the obtained solid-phase microextraction probe can be significantly improved.

[0044] The technical solution of the present invention will be further described below through specific embodiments. In the following embodiments, unless otherwise specified, the methods are all conventional methods; the reagents and materials, unless otherwise specified, can all be purchased on the market.

[0045] In the following examples, terephthalic acid, with the full English name of Terephthalic acid, abbreviated as H2BDC, has a purity of 99%; N,N-dimethylformamide, with the full English name of N,N-Dimethylformamide, abbreviated as DMF, has a purity of 99.5%; methanol, chromatographically pure, has a purity of ≥99.9%; ethanol, analytically pure, has a purity of ≥99.7%; manganese chloride tetrahydrate has a purity of 99%; nickel chloride hexahydrate has a purity of 99%; cobalt chloride hexahydrate has a purity of 99%; triethylamine, with the full English name of Triethylamine, abbreviated as TEA, has a purity of 99%; polyacrylonitrile, with the full English name of Polyacrylonitrile, abbreviated as PAN, has an average molecular weight of 85,000; all were purchased from Macklin Biochemical Technology Co., Ltd. in Shanghai, China.

[0046] In the following examples, thiabendazole and sulfamethazine were purchased from Yuanye in Shanghai, China. Clenbuterol was from TM Standard in Changzhou, China. Four commercially available solid-phase microextraction probes: PDMS / DVB-solid-phase microextraction probe; PDMS-solid-phase microextraction probe; PDMS / CAR / DVB-solid-phase microextraction probe; PA-solid-phase microextraction probe, were from Merck in Shanghai, China. Headspace vials and headspace caps were all purchased from Merck in Shanghai, China. The scanning electron microscope used the S-3700N instrument from Hitachi, Japan.

[0047] In the following examples, the room temperature was 25 ± 5°C. The preparation of 100 mmol / L ammonium acetate aqueous solution was obtained by dissolving 100 mmol of ammonium acetate in water and making up the volume to 1 L.

[0048] Example 1

[0049] A preparation method of a 2D-Ni-MOF-solid-phase microextraction probe includes the following steps:

[0050] Step 1, preparation of 2D-Ni-MOF material: Mix 320 mL of N,N-dimethylformamide, 20 mL of ethanol and 20 mL of deionized water to form a homogeneous solution; add 7.5 mmol of terephthalic acid and 7.5 mmol of nickel chloride hexahydrate to the above solution, stir for 30 min, then inject 8 mL of triethylamine into the solution; continuously ultrasonically treat the mixture for 8 hours; collect the prepared sample, wash it several times with ethanol and water, and dry it under vacuum at 60°C for 24 hours to obtain the 2D-Ni-MOF material.

[0051] Step 2, Preparation of electrospinning solution containing 2D-Ni-MOF: Mix polyacrylonitrile with N,N-dimethylformamide and assist with magnetic stirring to completely dissolve polyacrylonitrile and mix it evenly with N,N-dimethylformamide; then add the 2D-Ni-MOF material obtained in Step 1, mix and stir for 24 h to obtain an electrospinning solution containing 2D-Ni-MOF; in the electrospinning solution, the dosage ratio of the 2D-Ni-MOF material, polyacrylonitrile, and N,N-dimethylformamide is 200 mg: 100 mg: 3 mL.

[0052] Step 3, Formation of 2D-Ni-MOF coating on the metal rod surface: Repeatedly wash the metal rod surface with water and ethanol to remove oil stains and impurities, and dry it for standby. The diameter of the bare metal rod is 0.98 mm, as Figure 2 shown. Fix the washed metal rod on the motor, place the electrospinning solution containing 2D-Ni-MOF obtained in Step 2 in a handheld electrospinning instrument, perform electrospinning, and use the handheld electrospinning instrument to coat the metal rod surface to form a 2D-Ni-MOF coating on the metal rod surface. Among them, the voltage of electrospinning is 19.5 kV, the working rate is 15 μL·min -1 , the electrospinning time is 50 min; the distance from the tip of the syringe needle to the tip of the metal rod is 20 cm, and the inner diameter of the spinning instrument is 0.6 mm. The thickness of the 2D-Ni-MOF coating formed on the metal rod surface is 130 μm, and the length is 1 cm.

[0053] Step 4, Preparation of 2D-Ni-MOF-solid phase microextraction probe: Immerse the metal rod with 2D-Ni-MOF coating in ethanol for 1 h to promote the solvent exchange reaction. Then place it in a drying oven at 70 °C and dry for 12 h to obtain a 2D-Ni-MOF-solid phase microextraction probe.

[0054] Comparative Example 1

[0055] A preparation method of a 2D-Mn-MOF-solid phase microextraction probe includes the following steps:

[0056] Step 1, Preparation of 2D-Mn-MOF material: Mix 320 mL of N,N-dimethylformamide, 20 mL of ethanol, and 20 mL of deionized water to form a homogeneous solution; add 7.5 mmol of terephthalic acid and 7.5 mmol of manganese chloride tetrahydrate to the above solution, stir for 30 min, and then inject 8 mL of triethylamine into the solution; continuously ultrasonicate the mixture for 8 hours; collect the prepared sample, wash it several times with ethanol and water, and dry it under vacuum at 60 °C for 24 hours to obtain the 2D-Mn-MOF material.

[0057] Step 2, Preparation of electrospinning solution containing 2D-Mn-MOF: Mix polyacrylonitrile with N,N-dimethylformamide and assist with magnetic stirring to completely dissolve polyacrylonitrile and mix it evenly with N,N-dimethylformamide; then add the 2D-Mn-MOF material obtained in Step 1, mix and stir for 24 h to obtain an electrospinning solution containing 2D-Mn-MOF; in the electrospinning solution, the dosage ratio of the 2D-Mn-MOF material, polyacrylonitrile, and N,N-dimethylformamide is 200 mg: 100 mg: 3 mL.

[0058] Step 3, Formation of 2D-Mn-MOF coating on the metal rod surface: Repeatedly wash the metal rod surface with water and ethanol to remove oil stains and impurities, and dry it for later use. The diameter of the bare metal rod is 0.98 mm. Fix the washed metal rod on the motor, place the electrospinning solution containing 2D-Mn-MOF obtained in Step 2 in a handheld electrospinning instrument, perform electrospinning, and use the handheld electrospinning instrument for coating to form a 2D-Mn-MOF coating on the metal rod surface. Among them, the voltage of electrospinning is 19.5 kV, the working rate is 15 μL·min -1 , the electrospinning time is 50 min; the distance from the tip of the syringe needle to the tip of the metal rod is 20 cm, and the inner diameter of the spinning instrument is 0.6 mm. The thickness of the 2D-Mn-MOF coating formed on the metal rod surface is 130 μm, and the length is 1 cm.

[0059] Step 4, Preparation of 2D-Mn-MOF-solid phase microextraction probe: Immerse the metal rod with 2D-Mn-MOF coating in ethanol for 1 h to promote the solvent exchange reaction. Then place it in a drying oven at 70 °C and dry for 12 h to obtain a 2D-Mn-MOF-solid phase microextraction probe.

[0060] Comparative Example 2

[0061] A preparation method of a 2D-Co-MOF-solid phase microextraction probe includes the following steps:

[0062] Step 1, Preparation of 2D-Co-MOF material: Mix 320 mL of N,N-dimethylformamide, 20 mL of ethanol, and 20 mL of deionized water to form a homogeneous solution; add 7.5 mmol of terephthalic acid and 7.5 mmol of cobalt chloride hexahydrate to the above solution, stir for 30 min, and then inject 8 mL of triethylamine into the solution; continuously ultrasonically process the mixture for 8 hours; collect the prepared sample, wash it several times with ethanol and water, and dry it under vacuum at 60 °C for 24 hours to obtain the 2D-Co-MOF material.

[0063] Step 2, Preparation of electrospinning solution containing 2D-Co-MOF: Mix polyacrylonitrile with N,N-dimethylformamide and assist with magnetic stirring to completely dissolve polyacrylonitrile and mix it evenly with N,N-dimethylformamide; then add the 2D-Co-MOF material obtained in Step 1, mix and stir for 24 h to obtain an electrospinning solution containing 2D-Co-MOF; in the electrospinning solution, the component ratio of the 2D-Co-MOF material, polyacrylonitrile, and N,N-dimethylformamide is 200 mg: 100 mg: 3 mL.

[0064] Step 3, Formation of 2D-Co-MOF coating on the metal rod surface: Repeatedly wash the surface of the metal rod with water and ethanol to remove oil stains and impurities, and dry it for standby. The diameter of the bare metal rod is 0.98 mm. Fix the washed metal rod on the motor, place the electrospinning solution containing 2D-Co-MOF obtained in Step 2 in a handheld electrospinning instrument, perform electrospinning, and use the handheld electrospinning instrument for coating to form a 2D-Co-MOF coating on the metal rod surface. Among them, the voltage of electrospinning is 19.5 kV, the working rate is 15 μL·min -1 , the electrospinning time is 50 min. The distance from the tip of the syringe needle to the tip of the metal rod is 20 cm, and the inner diameter of the spinning instrument is 0.6 mm. The thickness of the 2D-Co-MOF coating formed on the metal rod surface is 130 μm, and the length is 1 cm.

[0065] Step 4, Preparation of 2D-Co-MOF-solid phase microextraction probe: Immerse the metal rod with 2D-Co-MOF coating in ethanol for 1 h to promote the solvent exchange reaction. Then place it in a drying oven at 70 °C and dry for 12 h to obtain a 2D-Co-MOF-solid phase microextraction probe.

[0066] Perform profile analysis on the surface coatings of different solid phase microextraction probes prepared in Example 1, Comparative Example 1, and Comparative Example 2, and the results are as Figure 1 shown. Figure 1 The results show that compared with Comparative Example 1 and Comparative Example 2, the 2D-Co-MOF coating in Example 1 is relatively flatter.

[0067] Select thiabendazole, sulfamethazine, and clenbuterol as target veterinary drugs, and compare the adsorption capacities of the 2D-Ni-MOF-solid phase microextraction probe in Example 1, the 2D-Mn-MOF-solid phase microextraction probe in Comparative Example 1, and the 2D-Co-MOF-solid phase microextraction probe in Comparative Example 2 for the three target veterinary drugs. The results are shown in Figure 2 . Figure 2 The results show that compared with Comparative Example 1 and Comparative Example 2, the 2D-Ni-MOF-solid phase microextraction probe prepared in Example 1 shows relatively higher adsorption capacities for all three target veterinary drugs.

[0068] To investigate the effect of the presence of other competing compounds on the selectivity of the 2D-Ni-MOF solid-phase microextraction probe prepared in Example 1 for three target veterinary drugs, 50 mg of each veterinary drug was dissolved in 50 mL of methanol to prepare a stock solution. 1 mL of sulfamethazine, clenbuterol, and thiabendazole were taken as the target veterinary drugs, and the stock solutions of sulfamethazine, clenbuterol, and thiabendazole were added to a 250 mL volumetric flask and made up to the mark with water to prepare the first spiked treatment standard solution. Taking two antibiotics, chloramphenicol and florfenicol, as competing compounds, 1 mL of the stock solutions of sulfamethazine, clenbuterol, thiabendazole, florfenicol, and chloramphenicol were added to a 250 mL volumetric flask and made up to the mark with water to prepare the second spiked treatment standard solution. The 2D-Ni-MOF solid-phase microextraction probe of Example 1 was used to perform selectivity tests on the first spiked treatment standard solution and the second spiked treatment standard solution respectively, and the results are shown in Figure 3 Figures (a) and (b) of

[0069] Example 2

[0070] A preparation method of a 2D-Ni-MOF solid-phase microextraction probe is basically the same as the method of Example 1, except that: the electrospinning conditions are different, as shown in Table 1 specifically.

[0071] Table 1 Parameter optimization conditions of electrospinning conditions

[0072]

[0073] Note: The dosage ratio of the electrospinning solution is the dosage ratio of the 2D-Ni-MOF material, polyacrylonitrile, and N,N-dimethylformamide. The mass percentage of the 2D-Ni-MOF material is the percentage of the mass of the 2D-Ni-MOF material in the total mass of the 2D-Ni-MOF material and polyacrylonitrile.

[0074] To investigate the effect of the composition of the electrospinning solution on the extraction of three target veterinary drugs by the 2D-Ni-MOF solid-phase microextraction probe, the corresponding 2D-Ni-MOF solid-phase microextraction probes were prepared according to the parameter optimization conditions in Table 1, and thiabendazole, sulfamethazine, and clenbuterol were selected as the target veterinary drugs, and the extraction efficiency of the corresponding 2D-Ni-MOF solid-phase microextraction probes was evaluated respectively, and the results are shown in Figure 4 Figures (a) and (b) of

[0075] As Figure 4 shown in Figure (a) below, when the dosage ratio of 2D-Ni-MOF material, polyacrylonitrile, and N,N-dimethylformamide is 200 mg: 100 mg: 3 mL, the best adsorption performance can be observed. It can be seen that at this ratio, it helps to form more effective adsorption sites on the 2D-Ni-MOF coating.

[0076] On the contrary, when the addition amount of 2D-Ni-MOF material is too low, the surface coating of the metal rod will be unstable, which is mainly attributed to the low viscosity of the electrospinning solution composition. On the contrary, excessive addition of 2D-Ni-MOF material will hinder the diffusion path and reduce the effective specific surface area of the surface coating. Therefore, the dosage ratio of 2D-Ni-MOF material, polyacrylonitrile, and N,N-dimethylformamide of 200 mg: 100 mg: 3 mL is selected as the dosage ratio of the best electrospinning solution for preparing 2D-Ni-MOF-solid phase microextraction probe.

[0077] As Figure 4 shown in Figure (b) below, as the electrospinning time is extended from 20 min to 60 min, the thickness of the surface coating increases from 56 µm to 150 µm. Correspondingly, the extraction ability of the 2D-Ni-MOF-solid phase microextraction probe for three target veterinary drugs is significantly improved. However, when the electrospinning time is further extended to more than 50 min, the extraction ability is not significantly improved, which may be due to the too thick surface coating hindering the diffusion path and slowing down the adsorption kinetics. Therefore, the electrospinning time of 50 min is selected as the best electrospinning time for preparing 2D-Ni-MOF-solid phase microextraction probe.

[0078] Scanning electron microscopy analysis of the surface coatings of 2D-Ni-MOF-solid phase microextraction probes prepared at different electrospinning times was carried out at different magnification levels, and the results are as Figure 5 shown. Figure 5 The results show that at different electrospinning times, the 2D-Ni-MOF coating is uniformly coated on the solid phase microextraction probe.

[0079] Example 3

[0080] The 2D-Ni-MOF-solid phase microextraction probe of Example 1 was used for the detection of veterinary drug residues. Among them, the initial conditions were a sample volume of 10 mL, no salt added, a stirring speed of 1500 revolutions per minute, extraction at room temperature, an adsorption time of one hour, methanol was used as the desorption solvent, and the desorption time was one hour. The conditions of the solid phase microextraction probe program were optimized, and the specific optimization methods are as follows:

[0081] (1)Optimization of sample solution conditions: To investigate the effect of the volume of the sample solution on the extraction efficiency of the 2D-Ni-MOF coating. Take 1 mL of the stock solutions of thiabendazole, sulfamethazine, and clenbuterol, add them to a 250 mL volumetric flask, and make up to the mark with water to prepare the sample solution. Select the volumes of the sample solution to be 5 mL, 10 mL, and 15 mL, and test the absolute recoveries of the 2D-Ni-MOF solid-phase microextraction probe for sample solutions of different volumes. The results are as shown in Figure 4 Figure (c) of Figure 4 Due to the strong turbulence effect, the diffusion rate of the target veterinary drug is relatively fast. Theoretically, a smaller volume of the sample solution can improve the extraction efficiency. However, the extraction efficiencies observed at sample volumes of 10 mL and 15 mL are comparable, as shown in

[0082] Figure (c) of Figure 4 Therefore, a sample solution volume of 10 mL was selected for subsequent experiments.

[0083] (2)Optimization of salt concentration conditions: To study the effect of the NaCl concentration on the adsorption of the 2D-Ni-MOF coating. Take 1 mL of the stock solutions of thiabendazole, sulfamethazine, and clenbuterol, add them to a 250 mL volumetric flask, and make up to the mark with water to prepare the sample solution. Divide the sample solution into 5 portions, and add different amounts of NaCl to adjust the NaCl concentrations in the corresponding sample solutions to 0 wt%, 10 wt%, 20 wt%, 30 wt%, and 40 wt%. Test the absolute recoveries of the corresponding sample solutions at different NaCl concentrations. The results are as shown in Figure 4 Figure (d) of

[0083] The results show that increasing the NaCl concentration from 0 wt% to 40 wt% has no significant effect on sulfamethazine and clenbuterol, but has a significant effect on the extraction of thiabendazole. This indicates that a higher ionic strength has a positive effect on the analyte adsorption. Therefore, a NaCl concentration of 40 wt% in the sample solution was selected for subsequent experiments.

[0083] (3)Optimization of stirring rate conditions: To investigate the effect of the stirring speed on the extraction efficiency. Take 1 mL of the stock solutions of thiabendazole, sulfamethazine, and clenbuterol, add them to a 250 mL volumetric flask, and make up to the mark with water to prepare the sample solution. And use stirring speeds of 0 r·min -1 , 600 r·min -1 , 800 r·min -1 , 1200 r·min -1 , 1500 r·min -1 , and test the absolute recoveries of the corresponding sample solutions at different stirring speeds. The results are as shown in Figure 4 Figure (e) of The results show that as the stirring speed increases from 0 r·min -1 to 1500 r·min -1, the extraction efficiency of the 2D-Ni-MOF solid-phase microextraction probe for three veterinary drugs has been improved. However, a further increase in the stirring speed will cause vortex phenomenon, resulting in the incomplete immersion of the 2D-Ni-MOF coating, thus reducing the extraction efficiency. Therefore, in the subsequent experiments, the optimal stirring speed selected was 1200 r·min -1 .

[0084] (4) Optimization of extraction temperature conditions: To study the effect of adsorption temperature on the extraction efficiency of the 2D-Ni-MOF coating. The adsorption temperatures were selected as 10°C, 25°C, 40°C, 50°C, 60°C, and 70°C, and the absolute recoveries of the corresponding sample solutions at different adsorption temperatures were tested. The results are as shown in Figure 4 Figure (f). The results show that the extraction efficiency decreases with the increase in temperature. This is because the exothermic nature of the adsorption process causes stronger thermal agitation of the analytes, followed by desorption, thus reducing the extraction efficiency. Therefore, the optimal extraction temperature selected was 25°C.

[0085] (5) Optimization of extraction time conditions: To explore the effect of extraction time on the extraction efficiency of the 2D-Ni-MOF coating. The extraction times selected were 5 min, 10 min, 20 min, 30 min, 40 min, 60 min, and 90 min, and the absolute recoveries of the corresponding sample solutions at different extraction times were tested. The results are as shown in Figure 4 Figure (g). Solid-phase microextraction is an equilibrium-driven process and usually reaches adsorption equilibrium within a certain time. The results show that the equilibrium was reached after 60 min of adsorption, and no further increase in adsorption efficiency was observed with the extension of adsorption time. Therefore, the optimal extraction time selected was 60 min.

[0086] (6) Optimization of desorption parameter conditions: To explore the effects of different desorption solvents and desorption times on the extraction efficiency. The desorption solvents selected were methanol, acetonitrile, and dichloromethane, and the absolute recoveries of the corresponding sample solutions with different desorption solvents were tested. The results are as shown in Figure 4 Figure (h). The results show that among the tested desorption solvents, methanol had the highest desorption efficiency. Therefore, methanol was selected as the optimal desorption solvent.

[0087] The desorption times selected were 5 min, 10 min, 20 min, 30 min, 40 min, 60 min, and 90 min, and the absolute recoveries of the corresponding sample solutions at different desorption times were tested. The results are as shown in Figure 4 Figure (i). The results show that 30 min was sufficient to achieve the maximum desorption amount of the target analytes. Therefore, the optimal desorption time selected was 30 min.

[0088] Example 4

[0089] Under the optimized conditions of Example 3, the reusability of the 2D-Ni-MOF solid-phase microextraction probe of Example 1 was tested as follows:

[0090] The appearance and scanning electron microscopy analysis of the 2D-Ni-MOF solid-phase microextraction probe before cycling and after 90 extraction-desorption cycles were carried out, and the results are as Figure 6 shown in Figures (a) and (b) of

[0091] Figure 6 Figures (a) and (b) of

[0092] describe the appearance and internal structure characteristics of the 2D-Ni-MOF solid-phase microextraction probe before and after 90 extraction and desorption cycles, respectively. The metal rod of the solid-phase microextraction probe has a uniform 2D-Ni-MOF coating. After 90 adsorption and desorption cycles, the changes in its appearance or internal structure are also minimal.

[0092] After the 2D-Ni-MOF solid-phase microextraction probe underwent 10 to 90 adsorption and desorption cycles, the absolute recoveries of the three target veterinary drugs were analyzed, and a column chart of the extraction efficiency trend was plotted, as shown in Figure 6 Figure (c) of Figure 6 Figure (c) of

[0093] verified the extraction efficiency trend of the three target veterinary drugs in 90 cycles, indicating that the extraction efficiency decreased slightly by the 90th cycle, but the 2D-Ni-MOF solid-phase microextraction probe could still effectively extract the target analytes, showing excellent reusability. Figure 6 Further reproducibility tests were carried out on the 2D-Ni-MOF solid-phase microextraction probes prepared in the same batch and different batches, including within-batch and between-batch reproducibility tests. The results are as shown in Figure (d) of

[0094] where 1, 2, and 3 are three solid-phase microextraction probes from the same batch; 4, 5, and 6 are three solid-phase microextraction probes from three different batches. The results showed that within the same batch, the relative standard deviation of reproducibility remained below 10.7%, indicating that the performance of the 2D-Ni-MOF solid-phase microextraction probe was stable. Similarly, the relative standard deviation between different batches also remained below 13.4%, indicating that the reproducibility between different batches was also very good. Figure 6 The desorption of the three target veterinary drugs was carried out for 30 min and 60 min, and the mass of the target compounds in the secondary re-desorption was compared with the mass of the initial 30-minute desorption, and the residual rate was quantified. The results are as shown in Figure (e) of

[0095] Example 5

[0096] The extraction performance of the 2D-Ni-MOF solid-phase microextraction probe of Example 1 was tested under the optimized conditions of Example 3, as follows:

[0097] Four commercial solid-phase microextraction probes were selected and purchased from Merck, China. The four commercial solid-phase microextraction probes were polydimethylsiloxane / divinylbenzene-solid-phase microextraction probe, abbreviated as PDMS / DVB-solid-phase microextraction probe; polydimethylsiloxane-solid-phase microextraction probe, abbreviated as PDMS-solid-phase microextraction probe; polydimethylsiloxane / carboxyl / divinylbenzene-solid-phase microextraction probe, abbreviated as PDMS / CAR / DVB-solid-phase microextraction probe; polyacrylate-solid-phase microextraction probe, abbreviated as PA-solid-phase microextraction probe.

[0098] Under the optimal extraction and desorption conditions, the 2D-Ni-MOF solid-phase microextraction probe was compared with the four commercial solid-phase microextraction probes, and the results are as Figure 7 shown. Among them, C1 is the 2D-Ni-MOF solid-phase microextraction probe; C2 is the PDMS / DVB solid-phase microextraction probe; C3 is the PDMS solid-phase microextraction probe; C4 is the PDMS / CAR / DVB solid-phase microextraction probe; C5 is the PA solid-phase microextraction probe.

[0099] From Figure 7 the results, it can be seen that among the four commercial solid-phase microextraction probes, the PDMS / DVB solid-phase microextraction probe has the highest extraction ability for the three target veterinary drugs. However, the extraction efficiency of the 2D-Ni-MOF solid-phase microextraction probe is much higher than that of the commercially available PDMS / DVB solid-phase microextraction probe. Compared with the commercially available solid-phase microextraction probes, the 2D-Ni-MOF solid-phase microextraction probe of Example 1 of the present invention shows excellent extraction ability and selectivity for the three target analytes.

[0100] Example 6

[0101] Method validation of the 2D-Ni-MOF solid-phase microextraction probe of Example 1 was carried out as follows:

[0102] Matrix effect is inevitable in analytical determination and will affect the accuracy and precision of the method. The matrix effect was evaluated by comparing the calibration curve slopes of the actual samples and the standard solutions. The calculation formula for the matrix effect is: ME = K1 / K2 × 100%; where ME is the matrix effect; K1 is the actual sample; K2 is the standard solution.

[0103] ME values between 80% and 120% indicate slight signal suppression or enhancement; while values below 80% or above 120% indicate significant signal suppression or enhancement. The matrix effects of the three target analytes in milk and pork were below 80%, as shown in Tables 2 and 3. It can be seen that the matrix effect has a great influence on the detection of analytes, such as Figure 3 in Figures (c) to (f) of

[0104] Ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry, abbreviated as UPLC-Q-TOF-MS. The 2D-Ni-MOF solid-phase microextraction probe of Example 1 was combined with UPLC-Q-TOF-MS for the analysis of target analytes. The target analytes were thiabendazole, sulfamethazine, and clenbuterol.

[0105] The verification results of the 2D-Ni-MOF solid-phase microextraction probe-UPLC-Q-TOF-MS method on milk and pork samples are shown in Tables 2 and 3.

[0106] Table 2 Results of milk matrix-matched calibration strategy

[0107]

[0108] Table 3 Results of pork matrix-matched calibration strategy

[0109]

[0110] The results showed that the correlation coefficients of the three target analytes were all greater than 0.9942. The detection limits of milk samples were in the concentration range of 0.001 μg·L –1 to 0.004 μg·L –1 with a signal-to-noise ratio of 3. The intraday precision ranged from 3.8% to 8.7%, and the intraday accuracy ranged from 5.1% to 9.5%. The detection limits of pork samples were in the range of 0.003 μg·L –1 to 0.007 μg·L –1 . The intraday precision ranged from 5.3% to 9.5%, and the intraday accuracy ranged from 6.9% to 11.5%. Thus, the method combining the 2D-Ni-MOF solid-phase microextraction probe with UPLC-Q-TOF-MS showed excellent performance in the quantitative analysis of target analytes in milk and pork samples, demonstrating high sensitivity, high precision, and high selectivity.

[0111] Example 7

[0112] Feasibility detection of ultra-high performance liquid chromatography-mass spectrometry was carried out as follows:

[0113] The detection conditions for ultra-high performance liquid chromatography-mass spectrometry were as follows: ultrapure water with a resistivity of 18.25 MΩ·cm was used, sourced from an ultrapure water system and purchased from Chengdu Yinghang Water Treatment Equipment Co., Ltd. The three target analytes were sulfamethazine, thiabendazole, and clenbuterol. 50 mg of each of the three target analytes was dissolved in 50 mL of methanol and stored at 4 °C. The stock solution was diluted with ultrapure water to obtain sample solutions of different target analytes with a concentration of 100 μg·mL -1 The feasibility of simultaneously detecting sulfamethazine, thiabendazole, and clenbuterol using an ultra-high performance liquid chromatography-mass spectrometry instrument was studied.

[0114] The detection was carried out using a combination of ultra-high performance liquid chromatography and a quadrupole time-of-flight mass spectrometer. The mass spectrometer was equipped with an electrospray ionization interface and operated in the positive ion mode.

[0115] Chromatographic conditions: An Acquity UHPLC BEH C18 column with a particle size of 1.7 μm and an inner diameter of 2.1 mm × 100 mm was used; the temperature was 30 °C; the mobile phase: mobile phase A was an aqueous solution of 100 mmol / L ammonium acetate, and mobile phase B was methanol; the flow rate was 0.4 mL·min -1 The gradient program was as follows: from 0 min to 4 min, mobile phase B was 2% - 99%; from 4 min to 8 min, B was 99% - 2%; from 8 min to 10 min, B was 2% to re-equilibrate the chromatographic column capillary.

[0116] Mass spectrometry conditions: The voltage was set at 1 kV, and the ion source and desolvation temperatures were 120 °C and 500 °C, respectively. The scanning range was 50 m / z - 400 m / z. 99.9% nitrogen was used as the cone gas and desolvation gas, with flow rates of 20 L·h -1 and 1000 L·h -1 respectively. The transitions of the three target analytes are shown in Table 4. The total ion chromatogram is as shown in Figure 3 Figure (a), and the mass spectrum is as shown in Figure 8 Figure.

[0117] The results showed that all three substances were successfully detected, and these results highlight the applicability of the ultra-high performance liquid chromatography-mass spectrometry instrument for simultaneously detecting three veterinary drugs.

[0118] Table 4 Transitions of the three target analytes

[0119]

[0120] Note: Different letters on top of each point in the table indicate significant differences between groups, such as a and b, b and c, a and c, etc. Determined by one-way ANOVA and Tukey's post hoc test. A P value < 0.05 is considered statistically significant. The same letter or one of the same letters on top of each point indicates no significant difference, such as a and ab, or b and ab.

[0121] Example 8

[0122] Using the optimized conditions of Example 3 and the 2D-Ni-MOF solid-phase microextraction probe of Example 1 for sample analysis, the specific sample analysis process is as follows:

[0123] Preparation of milk sample: In 50 mL of milk, add 0.5 g of zinc sulfate and 0.5 g of K4[Fe(CN)6]·3H2O. Vortex the resulting mixture for 20 seconds, and then centrifuge at 10000 rpm·min -1 for 3 minutes to remove the precipitate. This process is repeated six times until the residue is almost negligible. Then, filter the resulting supernatant through a 0.22-μm membrane and store it at 4°C. Then, take 10 mL of the filtrate obtained above, immerse the 2D-Ni-MOF solid-phase microextraction probe of Example 1 into it to enrich three target veterinary drugs, the extraction temperature is room temperature, and the stirring speed is 1200 rpm·min -1 , the extraction time is 60 min; then immerse the 2D-Ni-MOF solid-phase microextraction probe into an injection vial containing 200 μL of methanol solution at room temperature for static desorption, and the desorption time is 30 min; finally, analyze according to the conditions of the ultra-high performance liquid chromatography-mass spectrometry instrument of Example 7.

[0124] Example 9

[0125] Using the optimized conditions of Example 3 and the 2D-Ni-MOF solid-phase microextraction probe of Example 1 for sample analysis, the specific sample analysis process is as follows:

[0126] Preparation of pork sample: Use fresh or frozen pork, remove visible fat, and mix the meat evenly to obtain a pork sample. Weigh 10 g of the pork sample and put it into a 250 mL centrifuge tube, and add 50 mL of acetonitrile. Vortex the resulting mixture at 2000 rpm·min -1 for 1 minute to disperse the extract, and then at 10000 rpm·min -1Centrifuge for 10 minutes under the given conditions. Transfer the supernatant to a 250 mL separatory funnel, and add 100 mL of n-hexane for defatting. Shake the mixture thoroughly for 5 minutes, and then collect the lower layer solution. Transfer the lower layer solution to a 10 mL centrifuge tube, centrifuge multiple times, and then evaporate to dryness with nitrogen at 40 °C. Dissolve the residue in 1.0 mL of the initial mobile phase, which is 2% methanol and 98% aqueous solution of 100 mmol ammonium acetate, and filter through a 0.22 μm organic membrane. The pretreated sample is stored at 4 °C.

[0127] Before analysis, the sample is filtered through a 0.22 μm pore size organic membrane. Then, take 10 mL of the obtained filtrate, immerse the 2D-Ni-MOF solid-phase microextraction probe into it to enrich three target veterinary drugs. The extraction temperature is at room temperature, and the stirring speed is 1200 rpm·min -1 , and the extraction time is 60 min; then immerse the 2D-Ni-MOF solid-phase microextraction probe into a vial containing 200 μL of methanol at room temperature for static desorption, and the desorption time is 30 min; finally, analyze according to the conditions of the ultra-high performance liquid chromatography-mass spectrometry in Example 7.

[0128] The sample analysis results of Example 8 and Example 9 are as follows:

[0129] Since the target analytes were not initially detected in the sample, spiking was performed at three concentration levels. According to the Chinese national standard GB 31650, the maximum residue limit of sulfamethazine in meat is 100 μg·kg -1 , and the maximum residue limit of sulfamethazine in milk is 25 μg·kg -1 . Similarly, the maximum residue limit of thiabendazole in both meat and milk is 100 μg·kg -1 ; while clenbuterol requires zero detection. Therefore, the spiking levels of clenbuterol and sulfamethazine were set at 25 μg·kg -1 , 100 μg·kg -1 and 200 μg·kg -1 ; the spiking level of thiabendazole was set at 100 μg·kg -1 , 200 μg·kg -1 and 500 μg·kg -1 .

[0130] Table 5 Spiking Concentrations and Recoveries of Different Target Analytes in Milk and Pork

[0131]

[0132] The results in Table 5 show that the recoveries of milk samples were between 84.5% and 105.3%, and the relative standard deviations were between 3.6% and 9.3%. Similarly, the recoveries of pork samples were between 85.6% and 103.7%, and the relative standard deviations were between 3.3% and 10.5%. These results indicate that the 2D-Ni-MOF-solid phase microextraction probe-UPLC-Q-TOF-MS method exhibits good accuracy and precision in the detection and quantification of target compounds in complex food samples.

[0133] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A surface coating material applied to a solid-phase microextraction probe, characterized in that, The surface coating material is prepared on the surface of a substrate by electrospinning after mixing and stirring a two-dimensional nickel-based metal-organic framework material, polyacrylonitrile, and N,N-dimethylformamide; The dosage ratio of the two-dimensional nickel-based metal-organic framework, polyacrylonitrile, and N,N-dimethylformamide is 199 mg to 201 mg: 99 mg to 101 mg: 2 mL to 4 mL.

2. The surface coating material according to claim 1, characterized in that, The conditions for electrospinning are as follows: the voltage is 19.5 kV, the working rate is 15 µL·min -1 , and the electrospinning time is 50 min.

3. The surface coating material according to claim 1, characterized in that, The two-dimensional nickel-based metal-organic framework material is prepared by the following method: Mix N,N-dimethylformamide, ethanol, and water to obtain a mixed solution; Add terephthalic acid and nickel salt to the mixed solution. After mixing and stirring, add triethylamine and perform ultrasonic treatment. After washing and drying, obtain the two-dimensional nickel-based metal-organic framework material; The volume ratio of N,N-dimethylformamide, ethanol, and water is 320:20:20; The dosage ratio of terephthalic acid, nickel salt, the mixed solution, and triethylamine is 7.5 mmol: 7.5 mmol: 360 mL: 8 mL.

4. The surface coating material according to claim 3, characterized in that, The nickel salt is nickel chloride hexahydrate.

5. The surface coating material according to claim 1, characterized in that, The substrate is a metal rod.

6. A solid-phase microextraction probe, characterized in that, It includes a substrate and a two-dimensional nickel-based metal-organic framework coating. The two-dimensional nickel-based metal-organic framework coating is formed on the surface of the substrate by electrospinning, and the two-dimensional nickel-based metal-organic framework coating is the surface coating material described in Claim 1.

7. The solid phase microextraction probe according to claim 6, characterized in that, The thickness of the two-dimensional nickel-based metal-organic framework coating is 130 μm, and the length of the two-dimensional nickel-based metal-organic framework coating is 1 cm.

8. The solid-phase microextraction probe according to claim 6, characterized in that The substrate is a metal rod, and the diameter of the metal rod is 991 µm.

9. The preparation method of the solid-phase microextraction probe according to claim 6, characterized in that, It includes the following steps: Mix and stir the two-dimensional nickel-based metal-organic framework material, polyacrylonitrile, and N,N-dimethylformamide to obtain an electrospinning solution; Form a two-dimensional nickel-based metal-organic framework coating on the surface of the substrate by electrospinning the electrospinning solution, and then immerse the substrate with the two-dimensional nickel-based metal-organic framework coating in ethanol and dry it to obtain a solid-phase microextraction probe.

10. Use of the solid-phase microextraction probe according to claim 6 in veterinary drug detection, characterized in that, The veterinary drug is at least one of dimetridazole, thiabendazole, and clenbuterol.

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