Pyrenyl beta-cyclodextrin magnetic graphene oxide gel, preparation method thereof and application of pyrenyl beta-cyclodextrin magnetic graphene oxide gel in food safety detection

Abstract

The invention belongs to the field of chemical materials, particularly relates to pyrenyl beta-cyclodextrin magnetic graphene oxide gel, a preparation method of the pyrenyl beta-cyclodextrin magnetic graphene oxide gel and application of the pyrenyl beta-cyclodextrin magnetic graphene oxide gel in food safety detection, and discloses the pyrenyl beta-cyclodextrin magnetic graphene oxide gel. The gel is obtained by covalent bond connection and supramolecular interaction-host-guest assembly of magnetic graphene oxide, beta-cyclodextrin molecules and pyrene derivatives. The gel belongs to a lamellar stacked three-dimensional structure, and compared with traditional gel, the gel has the advantages that the overall pore diameter is increased, the separation flux is improved, the separation efficiency is improved, adsorption equilibrium can be quickly achieved within 0.5 min, and specific separation and adsorption of mycotoxin in a complex food sample are facilitated.

Description

Technical Field

[0001] The invention belongs to the field of chemical materials, and in particular relates to pyrene-based beta-cyclodextrin magnetic graphene oxide gel and a preparation method thereof and application thereof in food safety detection. Background Art

[0002] Natural toxins are produced by the metabolism of fungi, plants or microorganisms, and they pose a serious threat to human health. Mycotoxins are highly toxic secondary metabolites of fungi that can easily contaminate grains, feed and related foods. Contaminated foods accumulate through the food chain, causing serious health damage to humans and animals, such as gastrointestinal pain, edema, acute liver damage, and even death.

[0003] A large number of nanomaterials have been developed and utilized for trace mycotoxins of different structures in complex food matrices, such as carbon-based nanomaterials, covalent organic frameworks, inorganic hybrid nanopolymers, metal organic frameworks, and molecular imprinting monomers as adsorption materials. Compared with other materials, porous polymers have the advantages of rigid crystal structure, precise customization of functions, and adjustable pore size. In existing studies, gels are often used to support porous polymer materials. As a typical adsorption material, gels have hierarchical porosity and three-dimensional structure, and their mechanical properties are conducive to the rapid diffusion of target molecules into nanoporous structures. The advantages of porous polymer gels are as follows: 1. Reaction monomers can be designed to control the reaction pathway and promote gel formation. 2. Rich porous polymer morphologies can support the formation of various types of gels, such as membranes, fibers, and blocks. 3. Rich functional groups in porous polymers contribute to the formation of gel networks. 4. The firmness of the porous polymer structure gives the porous polymer gel good stability. However, the synthesis of porous polymer gels still requires multiple chemical reaction steps by modifying the polymer porous polymer, which is not conducive to large-scale preparation of materials and limits the industrial application of porous polymer gels.

[0004] The prior art has disclosed some adsorption of specific compounds by β-cyclodextrin / magnetic graphene oxide composite materials, such as the prior art "Adsorption of ofloxacin by β-cyclodextrin / magnetic graphene oxide" (Gong Qiaojuan, Zhao Xiaoyan, Han Haixia, et al. Adsorption of ofloxacin by β-cyclodextrin / magnetic graphene oxide [J]. Chemical Research and Application, 2022(002):034.) discloses that graphene oxide (GO) and β-cyclodextrin (β-CD) are used as raw materials to synthesize β-cyclodextrin / magnetic graphene oxide composite materials (β-CD / MGO) by chemical coprecipitation method, and the prior art "Adsorption performance and mechanism of magnetic graphene oxide / β-cyclodextrin composite materials for U (VI)" (Shi Dongfeng, Tang Zhenping, Huang Huayong, et al. Adsorption performance and mechanism of magnetic graphene oxide / β-cyclodextrin composite materials for U (VI) [J]. Atomic Energy Science and Technology, 2016, 50(009):1556-1564.DOI:10.7538 / yzk.2016.50.09.1556.) also discloses that ferroferric oxide nanoparticles are deposited on the surface of graphene oxide by an in-situ coprecipitation method to synthesize magnetic graphene oxide, and then β-cyclodextrin is loaded on the surface to obtain a magnetic graphene oxide / β-cyclodextrin composite material with high adsorption performance. The prior art Preparation of β-cyclodextrin / graphene oxide and its adsorption properties for methylene blue (Yang Z, Liu X, Liu X, et al. Preparation of β-cyclodextrin / graphene oxide and its adsorption properties for methylene blue[J]. Colloids and surfaces B: Biointerfaces, 2021(1):111605.DOI:10.1016 / j.colsurfb.2021.111605) discloses the preparation of graphene oxide from natural graphite powder by a modified Hummers method. β-CD / graphene oxide was prepared by modifying graphene oxide by β-cyclodextrin cross-linking method, and the adsorption performance of β-CD / graphene oxide composite material on organic dyes was studied. The results show that β-cyclodextrin / graphene oxide composite material has high adsorption performance and is a powder material.

[0005] However, since the adsorption / detection matrices of the above-mentioned prior arts are all simple matrices such as water, the adsorption / detection of trace fungal toxins with different structures in complex food matrices still needs to further eliminate the interference of macromolecular substances in the matrix and enhance the adsorption flux capacity of β-cyclodextrin-magnetic graphene oxide. Summary of the invention

[0006] In view of this, in order to solve the problems in the prior art, the present invention provides a pyrene-based β-cyclodextrin magnetic graphene oxide gel, a preparation method and its application in food safety detection, the gel of the present invention does not need to be prepared using any special equipment often required for the preparation of organic porous polymers, nor does it need to be modified after synthesis. The organic porous polymer and magnetic graphene oxide can be directly prepared into a composite gel material, which overcomes the poor processability of organic porous polymer powders in the prior art, and also overcomes the thin sheet stacking of magnetic graphene oxide blocking micropores, enhancing the underwater stability of the material and the characteristics of excluding macromolecular interferences. The overall pore size of the gel material of the present invention is increased, the separation flux is improved, the separation efficiency is increased, and its specific trace enrichment ability can improve the accuracy of quantitative trace substances.

[0007] The technical solution adopted by the present invention includes: The first aspect of the present invention discloses a pyrene-based β-cyclodextrin magnetic graphene oxide gel, comprising the following structure: ; Wherein, the L1 is selected from: , , C 1-6 Alkylene, -O-, -S-, , , , or One or more combinations of; A1 is cyclodextrin; L2 is selected from: single bond, -O-, -O-R1-O-, -C 1-6 The alkylene , 、-O-、-S-、 , , , or One or more combinations of; The R1 is selected from a single bond or C 1-6 of alkylene; The X1 includes the following structure: ; The R2 and R3 are selected from C 1-6 The alkylene , -O- or -S-; The L3 includes: ; The L4 is selected from: -O-R4-O-, -O-, -C 1-6 The alkylene , 、-O-、-S-、 , , , or A combination of one or more of the following; The R4 is selected from a single bond or C 1-6 of alkylene; The n1 is selected from an integer of 1 to 100; The n2 is selected from an integer of 1 to 300.

[0008] In some embodiments, the L1 is selected from: The R5 is selected from C 1-6 of alkylene; L2 is selected from: -O-R1-O-; The R1 is selected from a single bond or C 1-6 of alkylene; The X1 includes ; The L3 is selected from: ; The n1 is selected from an integer of 1 to 50; The n2 is selected from an integer of 1 to 200.

[0009] In some embodiments, the gel structure comprises the following structure: .

[0011] In some embodiments, the gel includes magnetic graphene oxide, β-cyclodextrin molecules and pyrene derivatives, and is obtained by covalently bonding and supramolecularly connecting the magnetic graphene oxide, β-cyclodextrin molecules and pyrene derivatives, and the supramolecular interaction includes host-guest assembly.

[0012] In some embodiments, the magnetic graphene oxide is composed of ferroferric oxide particles and graphene oxide chemically co-precipitated; The β-cyclodextrin molecule is epoxidized β-cyclodextrin, and the epoxidized β-cyclodextrin is composed of β-cyclodextrin grafted with epoxy molecules; The pyrene derivatives include substituted alkyl compounds with pyrene groups, and the substituents of the substituted alkyl compounds include one or more of alkyl groups, sulfonic acid groups, carboxyl groups, hydroxyl groups, phosphoric acid groups, halogen groups, aromatic groups or alkynyl groups.

[0013] In some embodiments, the gel is a three-dimensional layered structure of stacked sheets. The average adsorption pore size of the gel is 7.7-19.4 nm, the average desorption pore size of the gel is 12.2-20.3 nm, and the pore volume of the gel is 0.04-0.06 cm 3 / g, the magnetic intensity of the gel is 0.3-0.5 emu / g, and the specific surface area of ​​the gel is 11.4-54.2 m 2 g −1 .

[0014] The second aspect of the present invention provides a method for preparing the aforementioned gel, comprising: S1. Preparation of magnetic graphene oxide: chemically co-precipitating graphene oxide and ferrosoferric oxide particles and performing a first stirring to obtain a first mixture containing magnetic graphene oxide; S2. Preparation of epoxidized β-cyclodextrin: stirring β-cyclodextrin and the epoxy molecular derivative for a second time to obtain a second mixture containing epoxidized β-cyclodextrin; S3. Preparation of pyrene-based β-cyclodextrin magnetic graphene oxide gel: The first mixture and the second mixture are subjected to a third stirring with a pyrene derivative under the action of a crosslinker, an initiator, and an accelerator to obtain a uniformly dispersed hydrophilic colloid liquid, and the gel is obtained by reaction at 40-80°C.

[0015] In some embodiments, the ferrosoferric oxide particles in S1 are obtained by precipitation of ferric chloride hexahydrate and ferrous chloride tetrahydrate under the action of ammonia water, and the mass ratio of graphene oxide, ferric chloride hexahydrate and ferrous chloride tetrahydrate in S1 is (0.5-1): (8-10): (2-4); The chemical coprecipitation reaction in S1 is carried out under the condition of adding an ammonia solution, and 8 to 20 mL of a 28 to 30% ammonia solution is added for chemical coprecipitation; The mass ratio of β-cyclodextrin to epoxy molecular derivative in S2 is 1:(1-3); The mass ratio of the magnetic graphene oxide, epoxidized β-cyclodextrin crystals and pyrene derivative in the first mixture and the second mixture in S3 is (0.5-2): (0.5-2): (0.5-1); The reaction in S3 is carried out under sealed conditions.

[0016] In some embodiments, the crosslinking agent in S3 is N, N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the accelerator is N, N, N', N'-tetramethylethylenediamine, and the mass ratio of the three is 1: (0.5-2): (7-10); The stirring time of the first stirring in S1 is 10 to 40 minutes, and the stirring temperature is 70 to 90° C.; The second stirring in S2 is carried out in a sodium hydroxide solution with a mass percentage of 10-20% in the system, the stirring time is 110-130 minutes, and the stirring temperature is 40°C; The third stirring in S3 is carried out in anhydrous dimethylformamide and ethanol solution, the stirring time is 60 to 90 minutes, and the stirring temperature is room temperature; The reaction time in S3 is 720-900 minutes, and the reaction temperature is 40-55° C.; The rotation speeds of the first stirring, the second stirring and the third stirring are all in the range of 300-600 rpm.

[0017] A third aspect of the present invention provides an application of the aforementioned gel in food safety testing, wherein the application is to utilize the aforementioned gel to enrich and purify mycotoxins, wherein the mycotoxins are benzene ring-containing mycotoxins.

[0018] The present invention has at least the following beneficial effects: (1) The pyrene-based β-cyclodextrin magnetic graphene oxide gel of the present invention is obtained by covalently linking magnetic graphene oxide, β-cyclodextrin molecules and pyrene derivatives and supramolecular interaction-host-guest assembly. The unique structure of the gel of the present invention overcomes the problem of poor processability of organic porous polymer powder in the prior art, and also overcomes the problem of magnetic graphene oxide flakes stacking blocking micropores. It can effectively break through the technical bottleneck of traditional gel adsorbents with different adsorption amounts and small separation flux, improve separation efficiency, and quickly reach adsorption equilibrium. In addition, the specific modified pyrene group can further increase the selectivity of the gel for adsorption / enrichment of fungal toxins containing benzene rings.

[0019] (2) Under the premise that water is used as a dispersant, the zeta potential of the gel of the present invention is within the range of ±5 mV. In the sample solution of some embodiments, the granular dry gel can be uniformly dispersed and quickly agglomerated into blocks, thereby achieving sufficient contact with the target object, and facilitating the rapid separation of the adsorbed material from the actual sample, thereby shortening the sample pretreatment time.

[0020] (3) The gel of the present invention is used to perform solid phase microextraction of various fungal toxins present in complex samples. The gel of the present invention has strong adsorption capacity and short adsorption time. In some embodiments of the present invention, the adsorption efficiency reaches 80.1~92.8%, which is better than the adsorption capacity of pure magnetic graphene oxide (mGO) gel (53.9~86.7%). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying creative work.

[0022] Figure 1 Shown are scanning electron microscopic diagrams of mGO gel and β-mGOP gel in some embodiments of the present invention; Figure 2 Shown are schematic diagrams of XRD diffraction of magnetic graphene oxide particles, epoxidized β-cyclodextrin crystals, mGO gel and β-mGOP gel in some embodiments of the present invention; Figure 3 Shown are infrared spectra of epoxidized β-cyclodextrin crystals, mGO gel and β-mGOP gel in some embodiments of the present invention; Figure 4 Shown are nitrogen isothermal adsorption-desorption curves and pore size distribution diagrams of β-mGOP gel in some embodiments of the present invention; Figure 5 Shown are the magnetic measurement results of mGO gel and β-mGOP gel in some embodiments of the present invention; Figure 6a Shown is the adsorption equilibrium diagram of 11 fungal toxins by β-mGOP gel in some embodiments of the present invention; Figure 6b Shown are the adsorption kinetic curves of 11 fungal toxins by β-mGOP gel in some embodiments of the present invention; Figure 7 Shown is a graph showing the contact angle and surface tension measurement of β-mGOP gel in some embodiments of the present invention.

[0023] Figure 8 Shown is a schematic diagram of the reusability of β-mGOP gel in some embodiments of the present invention; Figure 9a Shown are structural diagrams of β-mGOP gels according to some embodiments of the present invention; Figure 9b Shown is a flow chart of a method for preparing a gel according to some embodiments of the present invention; Fig.10 Shown are the gel adsorption mechanisms in some embodiments of the present invention; Fig.11 Shown are Zeta potential analysis diagrams of mGO gel and β-mGOP gel in some embodiments of the present invention; Fig.12Schematic diagram showing the difference in adsorption efficiency between mGO gel and β-mGOP gel in some embodiments of the present invention. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the embodiments of the present invention are further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0025] It should be noted that all expressions using "first" and "second" in the embodiments of the present invention are for distinguishing two non-identical entities with the same name or non-identical parameters. It can be seen that "first" and "second" are only for the convenience of expression and should not be understood as limitations on the embodiments of the present invention. The subsequent embodiments will not explain this one by one.

[0026] The term "pyrene derivative" in the present invention refers to an alkyl compound having a pyrene group.

[0027] The term "β-cyclodextrin" in the present invention refers to a cyclic compound composed of 7 glucose residues connected by β-1,4-glycosidic bonds, which is extracted from starch after the action of microbial enzymes. It can form inclusion complexes with various compounds to stabilize and solubilize them, and is a new type of molecular encapsulation material.

[0028] The term "epoxy molecule derivative" in the present invention refers to an epoxy molecule derivative that is an alkylene oxide compound containing a leaving group. For example, in some embodiments of the present invention, the epoxy molecule derivative refers to epichlorohydrin.

[0029] In the present invention, the term "complex sample" includes food.

[0030] In the present invention, the term "adding 28-30% by mass of an ammonia aqueous solution" refers to commercially available concentrated ammonia water, in which the mass fraction of ammonia generally accounts for 28-30% of the total mass of the ammonia aqueous solution.

[0031] In the present invention, It represents the connection state of pyrene derivatives and cyclodextrin after supramolecular interaction-host-guest assembly.

[0032] In the present invention, C 1-6 The alkylene group refers to an alkylene group comprising 1, 2, 3, 4, 5 or 6 carbons.

[0033] The first aspect of the present invention provides a pyrene-based β-cyclodextrin magnetic graphene oxide gel, comprising the following structure: ; Wherein, the L1 is selected from: , , C 1-6 Alkylene, -O-, -S-, , , , or One or more combinations of; A1 is cyclodextrin; L2 is selected from: single bond, -O-, -O-R1-O-, -C 1-6 The alkylene , 、-O-、-S-、 , , , or ; The R1 is selected from a single bond or C 1-6 of alkylene; The X1 includes a combination of one or more of the following structures: , where the double bond is connected to L3; The R2 and R3 are selected from C 1-6 The alkylene , -O- or -S-; The L3 includes: , where the double bond is connected to X1; The L4 is selected from: -O-R4-O-, -O-, C 1-6 The alkylene , 、-O-、-S-、 , , , or A combination of one or more of the following; The R4 is selected from a single bond or C 1-6 of alkylene; The n1 is selected from an integer of 1 to 100; The n2 is selected from an integer of 1 to 300.

[0034] In some embodiments, the L1 is selected from: The R5 is selected from C 1-6 of alkylene; L2 is selected from: -O-R1-O-; The R1 is selected from a single bond or C 1-6 of alkylene; The X1 includes , wherein the double bond is connected to L3; The L3 is selected from: , where the double bond is connected to X1; The n1 is selected from an integer of 1 to 50; The n2 is selected from an integer of 1 to 200.

[0035] In some embodiments, n1 is selected from an integer of 1-40; n2 is selected from an integer of 1-150.

[0036] In some embodiments, the n1 is selected from an integer of 30 to 40, and the n1 is further selected from 35; The n2 is selected from an integer of 1 to 150, and the n2 is further selected from 135.

[0037] In some embodiments, the gel structure comprises the following structure: .

[0039] In some embodiments, the gel includes magnetic graphene oxide, β-cyclodextrin molecules and pyrene derivatives, which are obtained by covalent bonding and supramolecular bonding of magnetic graphene oxide, β-cyclodextrin molecules and pyrene derivatives, wherein the supramolecular action includes host-guest assembly, and the synthesis route is shown in FIG9 . The gel of the present invention is a gel with a three-dimensional layered structure, wherein β-cyclodextrin is the main molecule, and the pyrene derivative is the guest molecule, and an organic polyporous compound is formed by supramolecular force-host-guest assembly. Compared with the prior art, the macropore ratio of the gel of the present invention is increased, and at the same time, in the process of using the separation / enrichment of the target compound, the solvent directly passes through the organic porous polymer particles instead of flowing between the narrow graphene oxide layers, which greatly reduces the resistance of the solvent outflow pore size and improves the separation efficiency. The unique structure of the gel of the present invention overcomes the poor processability of the organic porous polymer powder in the prior art, and also overcomes the stacking of the thin sheets of magnetic graphene oxide that blocks the micropores. It can effectively break through the technical bottleneck of the traditional gel adsorbent with different adsorption amounts and small separation flux.

[0040] At the same time, since the gel of the present invention is obtained by covalently linking magnetic graphene oxide, β-cyclodextrin molecules and pyrene derivatives and supramolecular action-host-guest assembly, wherein the pyrene derivatives serve as guest molecules and form a stable host-guest complex with the hydrophobic cavity of epoxidized β-cyclodextrin, thereby enhancing the structural stability of the gel, and can also improve the selective adsorption and separation performance of the gel, and the pyrene derivative-modified gel can provide a strong π-π interaction force, the gel of the present invention can further increase its ability to adsorb benzene ring-containing fungal toxins, that is, selectivity, and enhance the mechanical properties of the gel in terms of microstructure under the synergistic effect of electrostatic interaction, hydrophobic interaction, π-π stacking / interaction and hydrogen bonding with specific benzene ring-containing fungal toxins.

[0041] In some embodiments, the magnetic graphene oxide is composed of ferroferric oxide particles and graphene oxide chemically coprecipitated. The magnetic graphene oxide is prepared by chemical coprecipitation, while maintaining the large specific surface area of ​​graphene, the magnetic properties of the material are improved, and it is convenient to self-heal and aggregate in a complex matrix and then quickly separate the gel. The pyrene-based β-cyclodextrin magnetic graphene oxide gel of the present invention, wherein the role of "host-guest assembly" is to improve the stability of the pyrene group in the gel. The present invention adopts a "gel" matrix, which is rarely disturbed by an external magnetic field. The gel matrix of the present invention can quickly aggregate and condense in the matrix to be tested (such as a food matrix) due to its own self-healing property generated by weak magnetism, and realizes the rapid separation characteristics from the food matrix solution; secondly, since the gel of the present invention belongs to an organic porous polymer-based gel, for complex matrices (such as food matrices), the large pore size of the gel layer is first used to interfere with the filtration of macromolecules, and then the target small molecules enter the gel and are specifically adsorbed by the organic porous polymer, so it is suitable for the enrichment and purification of fungal toxins in complex matrices such as food.

[0042] In some embodiments, the β-cyclodextrin molecule is epoxidized β-cyclodextrin, and the epoxidized β-cyclodextrin is composed of β-cyclodextrin grafted with epoxy molecules.

[0043] In order to further improve the adsorption, mechanical properties, selectivity and other properties of the gel of the present invention, in some embodiments, the β-cyclodextrin molecule is selected as an epoxidized β-cyclodextrin crystal, and the epoxidized β-cyclodextrin crystal is composed of epoxy molecules grafted on β-cyclodextrin. In some embodiments of the present invention, the epoxidized β-cyclodextrin can significantly improve its solubility and stability in hydrophilic colloids by introducing epoxy groups. This property enables it to be better dispersed and evenly distributed when synthesizing the aforementioned gel. In addition, the reason for the epoxidation of β-cyclodextrin is to better covalently link with the cross-linking agent during the synthesis of pyrene-based β-cyclodextrin magnetic graphene oxide gel. Compared with the amorphous epoxidized β-cyclodextrin crystalline polymer produced by the same reagent, the epoxidized β-cyclodextrin crystal has a more stable structure and better mechanical properties. In addition, based on the unique hydrophobic cavity structure of β-cyclodextrin, it can be included with small molecules, ions, etc. The present invention selects epoxidized β-cyclodextrin to provide abundant specific interaction sites, enhance the selective adsorption capacity of the gel for specific molecules, and epoxidized β-cyclodextrin can significantly improve the mechanical strength and stability of the gel by forming a strong covalent bond with the cross-linking agent in the gel, while providing more active sites for further chemical modification and functionalization. In some embodiments, "pyrene derivatives" are compounds containing a pyrene group, including substituted alkyl compounds containing a pyrene group, wherein the substituents of the substituted alkyl compounds include one or more of an alkyl group, a sulfonic acid group, a carboxyl group, a hydroxyl group, a phosphate group, a halogen group, an aromatic group, or an alkynyl group.

[0044] In some specific embodiments, the pyrene derivatives include pyrenebutyric acid, pyrenecarboxylic acid, and pyreneacetic acid.

[0045] The introduction of carbon chains improves the solubility of the gel in organic solvents and also promotes the covalent bond between the pyrene group and magnetic graphene oxide.

[0046] In some embodiments, the gel is a three-dimensional layered structure of stacked sheets. The average adsorption pore size of the gel is 7.7-19.4 nm, the average desorption pore size of the gel is 12.2-20.3 nm, and the pore volume of the gel is 0.04-0.06 cm 3 / g, the magnetic intensity of the gel is 0.3-0.5 emu / g, and the specific surface area of ​​the gel is 11.4-54.2 m 2 g −1 The present invention defines the gel as a specific three-dimensional layered structure, which provides the gel with excellent pore characteristics, including a high specific surface area and a suitable pore size, which is beneficial to improving the adsorption efficiency and selectivity, while the pore volume ensures a higher adsorption flux.

[0047] In some embodiments, the Zeta potential data of the gel when the dispersant is water is 4.17-4.86 mV, indicating that the gel will quickly condense into blocks in water (that is, when the gel of the present invention is a dry powder, when the Zeta potential is characterized, the material nanoparticle size and Zeta potential analysis are performed under the premise that the dispersant is water because the dry gel is in powder form, see Fig.11 ).

[0048] In some embodiments, in the contact angle surface tension measurement of the gel, the contact angle is 30-32°, indicating that the gel is lyophilic and is a super hydrophilic material.

[0049] In some embodiments, the gel can be reused at least 4 times.

[0050] like Figure 9b As shown, the second aspect of the present invention provides a method for preparing the aforementioned gel, comprising: S1. Preparation of magnetic graphene oxide: chemically co-precipitating graphene oxide and ferroferric oxide particles and performing a first stirring to obtain a first mixture containing magnetic graphene oxide; (In some embodiments of the present invention, the first mixture mainly comprises magnetic graphene oxide and a small amount of impurities) S2. Preparation of epoxidized β-cyclodextrin: a second stirring of β-cyclodextrin and an epoxy molecular derivative to obtain a second mixture containing epoxidized β-cyclodextrin; (in some embodiments of the present invention, the second mixture is mainly composed of epoxidized β-cyclodextrin and a small amount of impurities) S3. Preparation of pyrene-based β-cyclodextrin magnetic graphene oxide gel: The first mixture and the second mixture are subjected to a third stirring with a pyrene derivative under the action of a crosslinker, an initiator, and an accelerator to obtain a uniformly dispersed hydrophilic colloid liquid, and the gel is obtained by reaction at 40-80°C.

[0051] The preparation method of the present invention has mild synthesis conditions, green chemistry, simple operation, and no need for special equipment. The prepared β-mGOP gel has hierarchical porosity and three-dimensional structure, and its mechanical properties are conducive to the rapid diffusion of target molecules into the organic porous polymer nanoporous structure, the overall pore size is increased, the separation flux is improved, and the separation efficiency is increased.

[0052] In some embodiments, the ferrosoferric oxide particles in S1 are obtained by precipitation of ferric chloride hexahydrate and ferrous chloride tetrahydrate under the action of ammonia water, and the mass ratio of graphene oxide, ferric chloride hexahydrate and ferrous chloride tetrahydrate in S1 is (0.5-1): (8-10): (2-4); In some embodiments, the mass ratio of graphene oxide, ferric chloride hexahydrate and ferrous chloride tetrahydrate in S1 is 1:(8-10):(2-4).

[0053] In some embodiments, the mass ratio of graphene oxide, ferric chloride hexahydrate and ferrous chloride tetrahydrate in S1 is 1:9:4.

[0054] Since the finished products of ferroferric oxide and graphene oxide are both hydrophobic nanoparticles, it is difficult to form magnetic graphene oxide by direct reaction and the yield is not high. Therefore, the present invention uses trivalent iron and divalent iron ions under the action of ammonia water to chemically precipitate ferroferric oxide on graphene oxide. This synthesis method makes the material more uniform.

[0055] The chemical coprecipitation in S1 is carried out under the condition of adding an aqueous ammonia solution, and 8 to 20 mL of a 28 to 30% aqueous ammonia solution is added for chemical coprecipitation; in some embodiments, 10 mL of the aqueous ammonia solution is added.

[0056] The mass ratio of β-cyclodextrin to epoxy molecular derivative in S2 is 1:(1-3); In some embodiments, the mass ratio of β-cyclodextrin to epoxy molecule derivative in S2 is 1:(1-3) (including but not limited to 1:1, 1:2 or 1:3).

[0057] In some embodiments, the mass ratio of β-cyclodextrin to epoxy molecule derivative in S2 is 1:2.3 (i.e. 3:7); The mass ratio of the magnetic graphene oxide particles, epoxidized β-cyclodextrin crystals and pyrene derivatives in the first mixture and the second mixture in S3 is (0.5~2):(0.5~2):(0.5~1); in some embodiments, the mass ratio of the magnetic graphene oxide particles, epoxidized β-cyclodextrin crystals and pyrene derivatives in the first mixture and the second mixture in S3 is 1:1:(0.5~1); in some embodiments, the mass ratio of the magnetic graphene oxide particles, epoxidized β-cyclodextrin crystals and pyrene derivatives in the first mixture and the second mixture is 1:1:0.76.

[0058] The reaction in S3 is carried out under sealed conditions.

[0059] The present invention can obtain magnetic graphene oxide with more uniform magnetism and better dispersibility by optimizing the conditions of chemical coprecipitation and the ratio of reactants, and at the same time, the sealing reaction conditions are helpful to improve the yield and purity of the gel product.

[0060] In some embodiments, the crosslinker in S3 is N, N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the accelerator is N, N, N', N'-tetramethylethylenediamine, and the mass ratio of the three is 1: (0.5-2): (7-10); in some embodiments, the mass ratio of the three is 1: 1: 7.5. The specific crosslinker, initiator and accelerator system selected ensures the formation and stability of the gel network, and the precisely controlled stirring conditions ensure the uniform dispersion of the reactants and the uniform formation of the gel.

[0061] The stirring time of the first stirring in S1 is 10 to 40 minutes (including but not limited to 10, 15, 20, 25, 30, 35 or 40 minutes), and the stirring temperature is 70 to 90° C. (including but not limited to 70, 75, 80, 85 or 90° C.); in some embodiments, the stirring temperature is 80° C.; The second stirring in S2 is carried out in a sodium hydroxide solution with a mass percentage of 10-20% in the system, the stirring time is 110-130 minutes, and the stirring temperature is 40° C.; in some embodiments, the second stirring is carried out in a sodium hydroxide solution with a mass percentage of 15% in the system.

[0062] The third stirring in S3 is carried out in anhydrous dimethylformamide and ethanol solution, the stirring time is 60 to 90 minutes, and the stirring temperature is room temperature; because the solubility of the monomer epoxidized β-cyclodextrin and 1-pyrenebutyric acid is quite different, anhydrous dimethylformamide and ethanol (1:1, v:v) are added to achieve good solubility for a variety of organic compounds and inorganic compounds, which is convenient for the subsequent synthesis of gel.

[0063] The reaction time in S3 is 720-900 minutes, and the reaction temperature is 40-55° C.; in some embodiments, the reaction temperature is 50° C.; The rotation speeds of the first stirring, the second stirring and the third stirring are all within the range of 300-600 rpm. In some embodiments, the rotation speeds of the first stirring, the second stirring and the third stirring are all within the range of 450 rpm.

[0064] A third aspect of the present invention provides an application of the aforementioned gel in food safety testing, wherein the application is to enrich and purify mycotoxins using the aforementioned gel, wherein the mycotoxins are benzene ring-containing mycotoxins.

[0065] The method of the embodiment of the present invention has a strong ability to adsorb mycotoxins and a fast adsorption speed, and is particularly suitable for the rapid adsorption and separation of trace mycotoxins in complex samples.

[0066] In some embodiments, the benzene ring-containing fungal toxins include: aflatoxin B1 (AFB1), cytochalasin B (CB), tremor mycotoxin (TR1), stipetoxin (ST), ochratoxin A (OTA), ergosporine (ESN), alternating spore phenol (AOH), Beta-zearalenol (β-ZEN), Alpha-zearalenol (α-ZEN), Beta-zearalanol (β-ZAN), Alpha-zearalanol (α-ZAN).

[0067] In some embodiments of the present invention, the adsorption capacity of the gel is 80.1-92.8%. In contrast, the adsorption capacity of pure magnetic graphene oxide (mGO) gel is 53.9-86.7% (see Fig.12 ), the adsorption efficiency of the gel of the present invention is significantly improved, and the mGO gel is a gel formed without pyrene groups and epoxidized cyclodextrin, indicating that the main reason for the high-efficiency enrichment of benzene ring fungal toxins is the β-CD and pyrene host-guest structure inside the gel, rather than the magnetic graphene oxide.

[0068] In some embodiments, the gel is used as an adsorbent in the field of solid phase extraction.

[0069] The gel of the present invention can be used as a solid phase extraction adsorbent for efficient and specific enrichment of multiple fungal toxins in complex samples, and greatly simplifies the extraction and enrichment steps of existing solid phase extraction, with mild preparation conditions, greenness, fast adsorption speed and high extraction efficiency.

[0070] The scheme of the present invention will be explained below in conjunction with the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art (for example, refer to "Molecular Cloning Experiment Guide" by J. Sambrook et al., translated by Huang Peitang et al., third edition, Science Press) or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially, for example, they can be purchased from Illumina.

[0071] Example 1 Preparation of pyrene-based β-cyclodextrin magnetic graphene oxide gel (β-mGOP gel) material The reagents and instruments used in various embodiments of the present invention are shown in Table 1 and Table 2 below: Table 1 Reagents

[0072] Table 2 Instruments and equipment

[0073] According to the method of the embodiment of the present invention, magnetic graphene oxide particles, epoxidized β-cyclodextrin crystals and 1-pyrenebutyric acid are used as functional monomers to synthesize β-mGOP gel having a three-dimensional layer stacking structure, and the preparation process is as follows: (1) Preparation of magnetic graphene oxide (mGO): 0.2 g of graphene oxide powder was placed in a three-necked flask, and 200 mL of ultrapure water was added for ultrasonic dispersion for 1 h. Then, under the protection of N2, 1.8 g of FeCl3·6H2O and 0.8 g of FeCl2·4H2O were dissolved in 25 mL of ultrapure water and quickly added to the flask. Mechanical stirring was carried out at 450 r / min at 80 °C for 10 min. Subsequently, 10 mL of 28-30% (mass percentage) ammonia water was added, and vigorous stirring was continued for 30 min. After cooling to room temperature, the mGO particles were separated with a magnet, washed with ethanol and water several times to remove unreacted chemicals (neutral pH = 7), and the mGO was dried in a vacuum oven at 60 °C for 8 h.

[0074] (2) Preparation of epoxidized β-cyclodextrin (E-βCD) Weigh 3 g of β-cyclodextrin into a three-necked flask, add 12 mL of 15% (mass percentage) NaOH solution and stir to dissolve, heat to 40°C, add 6 mL of epichlorohydrin (i.e., about 7 g of epichlorohydrin) into the three-necked flask in three times, stir for 2 h, and after the reaction is completed, add cold acetone (4°C) and place at 4°C overnight, filter to remove unreacted impurities, and obtain a precipitate, which is freeze-dried at -50°C in a vacuum freeze-drying machine for 8 h to obtain white solid E-βCD.

[0075] (3) Preparation of β-mGOP gel In the first step, 0.2 g of E-βCD (epoxidized β-cyclodextrin) and 0.152 g of 1-pyrenebutyric acid were dissolved in 20 mL of anhydrous dimethylformamide / ethanol (1:1, v:v) solution and stirred evenly; in the second step, 10 mg / mL, 20 mL of mGO (magnetic graphene oxide) dispersed aqueous solution was added and stirred in a 50°C water bath for 30 min; in the third step, 200 mg of N, N'-methylenebisacrylamide was added and stirred evenly, and 200 mg of ammonium persulfate and 2 mL of N, N, N', N'-tetramethylethylenediamine (about 1.5 g of N, N, N', N'-tetramethylethylenediamine) were added and mixed in a three-necked flask and continued to stir evenly for 60 min. The uniformly dispersed hydrophilic colloid solution was added to the reactor, sealed with a tetrafluoroethylene container, and heated at 50°C for 12-15h to obtain a gel. The gel was taken out, filtered and washed with deionized water, and finally freeze-dried at -50°C under vacuum (<12Pa) for 12h to obtain a dry β-mGOP gel. Pure graphene oxide (mGO) gel (structural formula: Figure 9a As shown, according to the mass of monomers added in the previous step, it is calculated that the average number of n1 is about 35, and the average number of n2 is about 135).

[0076] Example 2 Characterization of β-mGOP gel A detailed characterization experiment was conducted on the pyrene-based β-cyclodextrin self-assembled magnetic graphene oxide (β-mGOP) gel prepared in Example 1 to demonstrate the successful preparation of the β-mGOP gel and its excellent physical and chemical properties. The details are as follows: (1) SEM characterization The mGO gel prepared in Example 1 and the β-mGOP gel prepared in Example 1 were analyzed by scanning electron microscopy. Figure 1 As shown, Figure 1 D. Figure 1 E and Figure 1 F is a scanning electron micrograph of the mGO gel of Example 1. Figure 1 D (2 μm), Figure 1 E (500 nm), Figure 1 The SEM image of F (200 nm) shows that the mGO gel of Example 1 has a compact polyhedral morphology and a small pore size. In contrast, the surface morphology of the β-mGOP gel has changed significantly. Figure 1 A. Figure 1 B and Figure 1 C is the scanning electron micrograph of the mGO gel of Example 1. Figure 1 A (2 μm), Figure 1 B (500 nm) and Figure 1 The scanning electron microscopy image of C (200 nm) further proves that β-mGOP gel has a three-dimensional layer stacking structure. Compared with mGO gel, the overall pore size of β-mGOP gel is larger, the separation flux is improved, and the separation efficiency is increased.

[0077] (2) XRD diffraction characterization The crystal structures of epoxidized β-cyclodextrin, magnetic graphene oxide particles, mGO gel and β-mGOP gel were analyzed by powder XRD diffraction experiment. Figure 2 As shown. Figure 2 It can be seen that in the XRD spectrum of epoxidized β-cyclodextrin, diffraction peaks can be observed at 27.2°, 31.4°, 45.4°, 56.4°, 66.2° and 75.1° at 2θ, but the gel material cannot maintain its original crystal structure after synthesis; the test results of magnetic graphene oxide particles, mGO gel and β-mGOP gel have uneven baselines and obvious data burrs. The results show that the β-mGOP gel material has poor crystallinity and more amorphous substances, and is a macromolecular polymer material.

[0078] (3) FTIR characterization The surface functional groups and chemical stability of epoxidized β-cyclodextrin crystals, mGO gel and β-mGOP gel were analyzed by Fourier transform infrared spectroscopy. Figure 3 ) can be clearly seen that the two substances have a –1 and 2944cm –1 There are characteristic absorption peaks at 1663cm-1, which are the vibration absorption peaks of OH and -CH. This result shows that β-cyclodextrin is successfully assembled on the gel. In the infrared spectra of mGO gel and β-mGOP gel, at 1663cm-1, −1 and 1529cm −1 The absorption peak at 1139 cm −1 The absorption peak at (NH) can be attributed to S=O vibration absorption. The results further show that the joint action of crosslinker, initiator and accelerator is the key to the formation of the two gels.

[0079] (4) BET and porosity characterization The specific surface area and porosity of β-mGOP gel were analyzed by N2 adsorption-desorption isotherm. Figure 4As shown in the figure, the N2 adsorption and desorption isotherms of β-mGOP gel are concave and have no inflection point. The number of adsorption layers is not limited, indicating that β-mGOP gel does not show adsorption saturation in the higher relative pressure region. The shape of the mesoporous hysteresis loop shows that the pore structure of β-mGOP gel is very irregular, belonging to a flat slit structure or crack structure. It is generally believed that the slit pores are formed by the accumulation of sheet materials. The pore size and shape of the β-mGOP gel were analyzed by pore size analyzer. The average adsorption pore size is 7.7~19.4 nm, the average desorption pore size is 12.2~20.3 nm, and the pore volume is 0.04~0.06 cm 3 / g; The specific surface area of ​​β-mGOP gel measured by BET specific surface area analyzer is 11.4~54.2 m 2 g −1 Compared with the prior art, the adsorption capacity of simple porous gel materials for various fungal toxins is not uniform, and the types of adsorption are few. The gel of the present invention shows that β-mGOP gel effectively breaks through the technical bottleneck of traditional gel adsorbents with different adsorption capacities and small separation flux.

[0080] (5) VSM analysis The magnetic properties of mGO gel and β-mGOP gel were analyzed by hysteresis loop test (VSM). Figure 5 As shown, the magnetic graphene oxide content of β-mGOP gel is low, which greatly reduces the saturation magnetization value of β-mGOP gel (0.4 emu / g) compared with the superparamagnetism of mGO gel (50 emu / g). However, β-mGOP gel has self-healing properties and is unstable in water or organic solvents and easily aggregates into blocks, which meets the requirements of rapid separation from the sample matrix and shortens the operation time of traditional sample pretreatment.

[0081] (6) DLS analysis The mGO gel and β-mGOP gel were analyzed by nanoparticle size and Zeta potential analysis (DLS). Fig.11 As shown in the figure, when the dispersant is water, the ζ potential of β-mGOP gel is 4.17-4.86mV, within the range of ±5mV, indicating that β-mGOP gel is unstable in water and tends to aggregate quickly, and the gel particle size is relatively large. The ζ potential of mGO gel is 11.5-12.1mV, within the range of ±10mV-±30mV, indicating that mGO gel begins to become unstable, but cannot be quickly aggregated into blocks, and requires the influence of an external magnetic field.

[0082] (7) CA analysis The contact angle surface tension test was used to analyze the β-mGOP gel using the sessile drop method. Figure 7As shown in the figure, the contact angle of β-mGOP gel is 30-32°, and θ is less than 90°. The results show that the gel is lyophilic and belongs to super-hydrophilic materials. It can be well dispersed in the sample solution. At the same time, because it is unstable in the solution and easily aggregates into blocks, it can achieve rapid separation from the sample matrix and shorten the operation time of traditional sample pretreatment. Therefore, β-mGOP gel shows great potential in enriching fungal toxins in liquid samples. Example 3 Feasibility study of the adsorption of mycotoxins by β-mGOP The feasibility of adsorption of aflatoxin B1 (AFB1), cytochalasin B (CB), tremor mycotoxin (TR1), stipetoxin (ST), ochratoxin A (OTA), ergosporine (ESN), alanine spore phenol (AOH), beta-zearalenol (β-ZEN), alpha-zearalenol (α-ZEN), beta-zearalenol (β-ZAN), alpha-zearalenol (α-ZAN) by the β-mGOP gel prepared in Example 1 was studied, as follows: The adsorption performance of β-mGOP gel for 11 kinds of mycotoxins was studied by static adsorption and dynamic adsorption experiments. Briefly, 1 mL of standard solutions containing the above target substances (11 kinds of mycotoxins) at concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L, 1000 μg / L, 2000 μg / L, 5000 μg / L and 8000 μg / L were prepared, and 5.0 mg of β-mGOP dry gel was added and shaken for adsorption for 60 minutes. The maximum adsorption capacity of β-mGOP gel for 11 kinds of mycotoxins was calculated by the following formula (1).

[0083] (1) Among them, Q e is the maximum adsorption capacity (μg / mg), C0 is the initial concentration of the adsorption solution (μg / L), C s is the target concentration (μg / L) when adsorption equilibrium is reached, m is the mass of β-mGOP gel (mg), and v is the volume of the adsorption solution (L).

[0084] For the adsorption kinetics experiment, 5.0 mg of β-mGOP gel was added to 1 mL of a mixed solution of 11 fungal toxins (100 μg / L) and adsorbed for different oscillation times (0.5 min, 1 min, 2 min, 5 min, 10 min, 20 min and 60 min). The results of this example were still calculated using formula (1) to calculate the maximum adsorption capacity of β-mGOP gel for 11 fungal toxins. from Figure 6a It can be seen that the adsorption capacity of β-mGOP gel as an adsorbent for 11 fungal toxins was studied through static equilibrium experiments at different initial concentrations. The rapid increase under low concentration conditions of the target verified the high adsorption efficiency of the material for trace fungal toxins. The adsorption curves of β-mGOP gel for 11 fungal toxins at different adsorption times are shown in Figure 2. Figure 6b As shown, the adsorption of 11 fungal toxins by β-mGOP gel is a rapid adsorption process, and the adsorption equilibrium is close to being reached in 0.5 minutes, which is consistent with the characteristics of rapid adsorption and separation materials.

[0085] Example 4 Study on the adsorption mechanism of 11 fungal toxins by β-mGOP gel Based on Example 3, the adsorption mechanism of 11 fungal toxins by the β-mGOP gel prepared in Example 1 was further studied by the Langmuir and Freundlich isotherm models. The Langmuir isotherm is based on the assumption that the target is covered with a single layer on the outer surface of the adsorbent. The linear form of the Langmuir isotherm is expressed as: (2) Another characteristic parameter of the Langmuir isotherm is the dimensionless factor R related to the shape of the isotherm. L (Separation factor). 0 <R L <1 indicates that adsorption is favorable, R L >1 indicates that adsorption is unfavorable, R L =0 indicates irreversible adsorption. L The calculation formula is: (3) In formula (2) and formula (3), C e (µg / L) is the equilibrium concentration, Q e (µg / mg) is the equilibrium adsorption capacity, Q s (µg / mg) is the theoretical saturated adsorption capacity, (L / µg) is the Langmuir constant. C0 (µg / L) is the maximum concentration of the target compound.

[0086] The Freundlich isotherm is based on multilayer adsorption on heterogeneous surfaces. The linear form of the Freundlich equation is: (4) Among them, K f and n are the Freundlich constant and the affinity constant of β-mGOP gel for the adsorption of 11 fungal toxins, respectively.

[0087] According to formula (3), R of AFB1, ESN, β-ZAN, α-ZAN, AOH, TR1, CB, ST, OTA, β-ZEN and α-ZEN L The values ​​were calculated to be 0.1125, 0.0553, 0.1210, 0.1274, 0.1538, 0.0630, 0.1928, 0.0832, 0.1226, 0.0997 and 0.0633, respectively. The RL values ​​in the range of 0.0553 to 0.1928 indicate that the Langmuir adsorption process is favorable but not dominant. The Freundlich isotherm has a better linear fit with a linear coefficient (R 2 >0.9052) is better than the linear coefficient of Langmuir isotherm (R 2 <0.8706). According to formula (4), the n values ​​of AFB1, ESN, β-ZAN, α-ZAN, AOH, TR1, CB, ST, OTA, β-ZEN and α-ZEN were calculated to be 1.481, 1.661, 1.436, 1.541, 1.633, 1.646, 1.533, 1.079, 1.682, 1.376 and 1.436, respectively. The n values ​​were all greater than 1, indicating that the Freundlich isotherm model was more suitable than the Langmuir model to describe the adsorption process. The results showed that the adsorption process was mainly completed by multiple interactions of different binding sites in heterogeneous forms. In addition to the strong π-π force provided by the pyrene group, graphene oxide can also have a π-π force on benzene ring-containing fungal toxins. The experimental data showed that the adsorption effect was more than 50%, while the adsorption effect of β-mGOP gel on benzene ring-containing fungal toxins was as high as more than 80%, and the specific adsorption was greatly improved. Therefore, combined with the adsorption mechanism diagram ( Fig.10 ) can show that the adsorption process is completed by multiple interactions at different binding sites.

[0088] Example 5 Adsorption kinetics of 11 fungal toxins by β-mGOP gel Based on Example 3, the adsorption behavior of 11 fungal toxins by the β-mGOP gel prepared in Example 1 was further studied by two conventional kinetic models, pseudo-first order and pseudo-second order. The pseudo-first order model is based on the assumption that adsorption is controlled by a diffusion step, i.e., physical adsorption behavior. The linear form of the pseudo-first order model is expressed as: (5) The pseudo-second-order model assumes that the adsorption rate is determined by the square of the number of unoccupied adsorption vacancies on the adsorbent surface, and the adsorption process is controlled by the chemical adsorption mechanism, that is, chemical adsorption behavior, which involves electron sharing or electron transfer between the adsorbent and the adsorbate.

[0089] (6) In equations (5) and (6), qe (µg / mg) and qt (µg / mg) are the adsorption capacities at equilibrium and time t, respectively, and k1 and k2 are the adsorption rate constants of pseudo-first-order and pseudo-second-order kinetics, respectively.

[0090] According to formulas (5) and (6), compared with the pseudo-first-order mode (R 2 <0.8582, the pseudo-secondary model has a higher coefficient of determination (R 2 >0.9083), indicating that the chemical adsorption process is the main rate-determining step in the interaction between β-mGOP gel and 11 fungal toxins. This fast adsorption kinetics should be due to the structural advantages of the multifunctional sites, such as Fig.10 As shown in the detailed adsorption mechanism diagram, the adsorption mechanism of β-mGOP gel includes: appropriate porosity, electrostatic interaction, hydrophobic interaction, π-π stacking / interaction and hydrogen bonding force. The synergistic effect of the above leads to faster binding of β-mGOP gel to the target.

[0091] Example 6 Study on the reusability of β-mGOP gel The reusability of the β-mGOP gel prepared in Example 1 was studied as follows: Disperse 5 mg of the β-mGOP gel prepared in Example 1 in 1 mL of the target aqueous solution, shake for adsorption, discard the supernatant, elute the target adsorbed on the β-mGOP gel with a desorption reagent (acetonitrile solution containing 5% formic acid), blow nitrogen, re-dissolve, pass the membrane, and test on the machine. Wash the above β-mGOP gel with the desorption reagent several times until it is rinsed clean; repeat the above experimental steps twice.

[0092] Plot the number of uses as the horizontal axis and the recovery rate as the vertical axis. The results are as follows: Figure 8 As shown, after being reused 4 times, the recovery rate began to decrease to below 80%, indicating that the β-mGOP gel can be reused at least 4 times.

[0093] The above results show that β-mGOP gel presents a similar adsorption process for 11 fungal toxins. The adsorption mechanism of β-mGOP gel for 11 fungal toxins is more consistent with the Freundlich isotherm model. This phenomenon may be explained as multilayer adsorption caused by hydrophobic interactions, hydrogen bonds, and π-π stacking forces between β-mGOP gel and the target. These results show that the β-mGOP gel of the embodiment of the present invention can be used as a high-throughput separation adsorbent for 11 fungal toxins in complex food samples.

[0094] The adsorption behavior of β-mGOP gel on 11 fungal toxins is more consistent with the pseudo-secondary model, and the interaction between β-mGOP gel and the target is chemical adsorption, such as the dominant π-π force. These results show that the β-mGOP gel of the embodiment of the present invention can be used as a specific separation adsorbent for 11 benzene ring-containing fungal toxins in complex food samples.

[0095] In summary, the β-mGOP gel of the embodiment of the present invention has excellent hydrophilicity, and at the same time, the overall pore size is increased, the separation flux is improved, the separation efficiency is increased, and the adsorption equilibrium is quickly reached in 0.5 minutes. It can be used as an adsorbent filler for specific rapid separation solid phase extraction (SPE) columns.

[0096] According to the results of Examples 3 to 5, it can be seen that according to the results of the aforementioned adsorption isotherms, it is determined that the adsorption process of the β-mGOP gel of the present invention is completed by multiple interactions of different binding sites on the heterogeneous surface, and at the same time, the adsorption capacity of fungal toxins shows a rapid increase trend at low concentrations, which is conducive to the specific enrichment and purification of trace substances. According to the results of adsorption kinetics, chemical adsorption is the main control process, indicating that the unique three-dimensional mechanical architecture of the gel: the sheet stacking structure has rapid adsorption kinetics, which is faster than simple pore adsorption, and there is no pore collapse. At the same time, the rich π-π conjugated groups present in the entire organic porous polymer molecules in the β-mGOP gel will greatly improve the high-throughput adsorption of 11 benzene ring-containing fungal toxins by the β-mGOP gel of the present invention. The β-mGOP gel of the present invention has a breakthrough potential in the adsorbent filler technology for realizing broad-spectrum specific rapid separation of solid phase extraction cartridges (SPE).

[0097] Comparative Example 1 Preparation of gel The instruments and reagents of this comparative example 1 refer to those of Example 1, with the only difference being that in step (3) of preparing mGO gel, 0.152 g of 1-pyrenebutyric acid and 0.2 g of E-βCD are not added, and the resulting gel structure is not only tightly arranged but also has a small overall pore size, a small separation flux, and a low separation efficiency. See Characterization for details. Figure 1 D, E, F.

[0098] Comparative Example 2 Adsorption capacity of gel The gel described in Comparative Example 1 was used for the experiment, wherein the adsorption feasibility study experimental steps and research process refer to Examples 3 to 5. The results show that the adsorption capacity of the gel in Comparative Example 1 for 11 specific fungal toxins is uneven and the adsorption efficiency is lower than that of the β-mGOP gel, which is only 53.9-86.7%. For details, see Fig.12 The above data show that the selectivity of the gel of Comparative Example 1 to mycotoxins is lower than that of the gel of Example 1.

[0099] in conclusion According to the above examples, the results show that the adsorption of β-mGOP gel material is mainly related to the specific benzene ring structural characteristics, and there are differences in the adsorption of α / β isomers. When mGO gel and β-mGOP gel were used to simultaneously test the adsorption of 11 benzene ring-containing fungal toxins, the adsorption efficiency of mGO gel for the 11 fungal toxins was 53.9~86.7%, while the adsorption efficiency of β-mGOP gel was as high as 80.18~92.74%, and the adsorption efficiency was significantly improved. ( Fig.12 (as shown) This indicates that the main reason for the high-efficiency enrichment of benzene ring fungal toxins is the β-CD and pyrene-based host-guest structure inside the gel, and the interaction force is π-π interaction, rather than the π-π interaction provided by magnetic graphene oxide in theory. In addition, compared with mGO gel, β-mGO gel cannot increase the adsorption amount of Alpha-configuration fungal toxins, but can further dynamically adsorb Beta-configuration fungal toxins based on the adsorption capacity of mGO gel. This shows that β-CD inside β-mGO gel has the function of further separating Alpha / Beta isomers, and the main adsorption site is located in the hydrophobic interaction within the organic structure of β-CD ( Fig.12 Therefore, β-mGOP gel with mechanical properties and rapid adsorption and desorption capabilities is expected to be prepared as a broad-spectrum chiral solid phase extraction SPF column adsorbent filler in subsequent experiments.

[0100] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A pyrene-based β-cyclodextrin magnetic graphene oxide gel, characterized in that: Includes the following structure: ； Wherein, the L1 is selected from: , , C 1-6 Alkylene, -O-, -S-, , , , or One or more combinations of; A1 is cyclodextrin; L2 is selected from: single bond, -O-, -O-R1-O-, -C 1-6 The alkylene , 、-O-、-S-、 , , , or One or more combinations of; The R1 is selected from a single bond or C 1-6 of alkylene; The X1 includes the following structure: ; The R2 and R3 are selected from C 1-6 The alkylene , -O- or -S-; The L3 includes: ; The L4 is selected from: -O-R4-O-, -O-, -C 1-6 The alkylene , 、-O-、-S-、 , , , or A combination of one or more of the following; The R4 is selected from a single bond or C 1-6 of alkylene; The n1 is selected from an integer of 1 to 100; The n2 is selected from an integer of 1 to 300.

2. The gel according to claim 1, characterized in that The L1 is selected from: R5 is selected from C 1-6 of alkylene; L2 is selected from: -O-R1-O-; The R1 is selected from a single bond or C 1-6 of alkylene; The X1 includes ; The L3 is selected from: ; The n1 is selected from an integer of 1 to 50; The n2 is selected from an integer of 1 to 200.

3. The gel according to claim 1, characterized in that The gel structural formula includes the following structure:

4. The gel according to claim 1, characterized in that The gel comprises magnetic graphene oxide, beta-cyclodextrin molecules and pyrene derivatives, and is obtained by connecting the magnetic graphene oxide, beta-cyclodextrin molecules and pyrene derivatives through covalent bonds and supramolecular interactions, wherein the supramolecular interactions include host-guest assembly.

5. The gel according to claim 4, characterized in that The magnetic graphene oxide is formed by chemical co-precipitation of ferroferric oxide particles and graphene oxide; The β-cyclodextrin molecule is epoxidized β-cyclodextrin, and the epoxidized β-cyclodextrin is composed of β-cyclodextrin grafted with epoxy molecules; The pyrene derivatives include substituted alkyl compounds with pyrene groups, and the substituents of the substituted alkyl compounds include one or more of alkyl groups, sulfonic acid groups, carboxyl groups, hydroxyl groups, phosphoric acid groups, halogen groups, aromatic groups or alkynyl groups.

6. The gel according to claim 5, characterized in that The gel is a three-dimensional layered structure of stacked sheets. The average adsorption pore size of the gel is 7.7-19.4 nm, the average desorption pore size of the gel is 12.2-20.3 nm, and the pore volume of the gel is 0.04-0.06 cm 3 / g, the magnetic intensity of the gel is 0.3-0.5 emu / g, and the specific surface area of ​​the gel is 11.4-54.2 m 2 g −1 .

7. A method for preparing the gel according to claim 5, characterized in that: include: S1. Preparation of magnetic graphene oxide: chemically co-precipitating graphene oxide and ferrosoferric oxide particles and performing a first stirring to obtain a first mixture containing magnetic graphene oxide; S2. Preparation of epoxidized β-cyclodextrin: stirring β-cyclodextrin and the epoxy molecular derivative for a second time to obtain a second mixture containing epoxidized β-cyclodextrin; S3. Preparation of pyrene-based β-cyclodextrin magnetic graphene oxide gel: The first mixture and the second mixture are subjected to a third stirring with a pyrene derivative under the action of a crosslinker, an initiator, and an accelerator to obtain a uniformly dispersed hydrophilic colloid liquid, and the gel is obtained by reaction at 40-80°C.

8. The preparation method according to claim 7, characterized in that: The ferroferric oxide particles in S1 are obtained by precipitation of ferric chloride hexahydrate and ferrous chloride tetrahydrate under the action of ammonia water, and the mass ratio of graphene oxide, ferric chloride hexahydrate and ferrous chloride tetrahydrate in S1 is (0.5-1): (8-10): (2-4); The chemical coprecipitation reaction in S1 is carried out under the condition of adding an ammonia solution, and 8 to 20 mL of a 28 to 30% ammonia solution is added for chemical coprecipitation; The mass ratio of β-cyclodextrin to epoxy molecular derivative in S2 is 1:(1-3); The mass ratio of the magnetic graphene oxide, epoxidized β-cyclodextrin crystals and pyrene derivative in the first mixture and the second mixture in S3 is (0.5-2): (0.5-2): (0.5-1); The reaction in S3 is carried out under sealed conditions.

9. The preparation method according to claim 7, characterized in that: The crosslinking agent in S3 is N, N'-methylenebisacrylamide, the initiator is ammonium persulfate, and the accelerator is N, N, N', N'-tetramethylethylenediamine, and the mass ratio of the three is 1: (0.5-2): (7-10); The stirring time of the first stirring in S1 is 10 to 40 minutes, and the stirring temperature is 70 to 90° C.; The second stirring in S2 is carried out in a sodium hydroxide solution with a mass percentage of 10-20% in the system, the stirring time is 110-130 minutes, and the stirring temperature is 40°C; The third stirring in S3 is carried out in anhydrous dimethylformamide and ethanol solution, the stirring time is 60 to 90 minutes, and the stirring temperature is room temperature; The reaction time in S3 is 720-900 minutes, and the reaction temperature is 40-55° C.; The rotation speeds of the first stirring, the second stirring and the third stirring are all in the range of 300-600 rpm.

10. Use of the gel according to claim 5 in food safety testing, characterized in that: The application is to use the gel described in claim 5 to enrich and purify mycotoxins, and the mycotoxins are mycotoxins containing benzene rings.

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