Applications of ZIF-67 derived carbon materials

Abstract

The present application relates to an application of a ZIF-67 derived carbon material, which is applied to a magnetic purifier for QuEChERS pesticide residue analysis, and the ZIF-67 derived carbon material is prepared by the following method: providing ZIF-67; annealing and carbonizing the ZIF-67 to obtain a ZIF-67 derived carbon material. The present application uses ZIF-67 derived carbon material to apply to a magnetic purifier for QuEChERS pesticide residue analysis, using ZIF-67 as a precursor, and high-temperature carbonization to construct ZIF-67 derived carbon, directly giving it sufficient magnetic strength, and only needing to apply an external magnetic field to achieve separation, and the operation is simple and fast. In addition, ZIF-67 derived carbon itself, as a porous carbon material, has excellent stability, has a strong adsorption effect on interfering substances in the pesticide analysis process, and does not adsorb target substances. Therefore, the present application applies ZIF-67 derived carbon material to the field of QuEChERS pesticide residue analysis, and provides a suitable QuEChERS magnetic purifier for it.

Description

Technical Field

[0001] The present application relates to the field of carbon materials, and in particular to organic metal framework-derived carbon materials. Background Art

[0002] QuEChERS is an important pretreatment method in the field of pesticide residue analysis. It is named for its characteristics of being quick, easy, cheap, effective, reliable and safe. This method creatively combines the extraction and purification steps. It uses organic solvents to extract the target substance and combines purification agents to remove interferences in the extraction solution, thereby realizing a method for pretreatment of pesticide residues in food samples. Among them, the purification step is mainly used to eliminate matrix interference, so the purification agent determines the purification effect and recovery rate of the method. Classic purification agents include N-propylethylenediamine bonded silica gel (PSA), C 18 and graphitized carbon black (GCB), etc., are often used to eliminate interferences such as organic acids, lipids, sugars and polar pigments.

[0003] Magnetic separation technology is a method of separating different magnetic materials under the action of an external magnetic field. The technology is simple and fast to operate. Magnetic separation technology is often introduced into the QuEChERS method. The synthesis of magnetic purifiers usually adopts the "one-pot" co-precipitation method, physical stacking method and post-modification method. The "one-pot" co-precipitation method is the most commonly used method to construct magnetic purifiers, that is, the magnetic source is directly mixed with nanomaterials, and the precipitate is generated by double decomposition reaction, such as magnetic multi-walled carbon nanotubes (MWCNTs), magnetic graphene oxide (GO), magnetic biochar and magnetic graphite phase carbon nitride. This method has the advantages of simple operation, rapid reaction and convenient mass production, but there are also shortcomings in the preparation process: on the one hand, the commonly used magnetic source Fe3O4 rapidly and briefly nucleates during the synthesis, and the sedimentation rate is difficult to control, resulting in uneven particle size distribution, poor dispersion and easy agglomeration; on the other hand, Fe3O4 is difficult to adhere to the surface of the functional material evenly by electrostatic action, and it will also occupy the active sites of the functional material, affecting the purification effect. The physical stacking method is a method of obtaining a magnetic purifier by directly mixing Fe3O4 with nanomaterials by mechanical grinding or ultrasonic mixing. At present, magnetic purifiers based on MWCNTs, PSA, GCB and GO have been successfully prepared by the physical stacking method. The preparation conditions of this method are mild, convenient and fast, but Fe3O4 is only combined with functional materials through physical action, and the binding force is weaker than that of chemical action. When used as a purifier, the stability is poor and Fe3O4 is easy to fall off, resulting in poor precision of the QuEChERS method. The post-modification method is a synthetic method of directly chemically bonding and modifying functional groups on the surface of pre-constructed Fe3O4, such as hyperbranched polyamide, n-octadecylamine and 2-methylacrylamide. Compared with the physical stacking method, although this method combines with functional groups through covalent bonds and constructs more stable purifiers, the preparation steps are cumbersome and complicated, and it takes a long time, which greatly increases the cost and time of the QuEChERS method. Therefore, there is currently a lack of QuEChERS magnetic purifiers that are simple to prepare, have excellent adsorption properties, and are easy and fast to operate. Summary of the invention

[0004] The embodiments of the present application provide an application of a ZIF-67 derived carbon material to solve the current technical problem of lack of a suitable QuEChERS magnetic purifier.

[0005] The present application embodiment provides an application of a ZIF-67-derived carbon material, wherein the ZIF-67-derived carbon material is used as a magnetic purifier in the field of QuEChERS pesticide residue analysis, and the ZIF-67-derived carbon material is prepared by the following method:

[0006] Provide ZIF-67;

[0007] The ZIF-67 is subjected to annealing and carbonization treatment to obtain a ZIF-67 derived carbon material.

[0008] In some embodiments of the present application, providing ZIF-67 comprises the following steps:

[0009] providing an alcohol solution of Co(NO3)2·6H2O and an alcohol solution of 2-methylimidazole;

[0010] The alcohol solution of Co(NO3)2·6H2O and the alcohol solution of 2-methylimidazole are mixed to obtain a mixed solution, wherein Co 2+ The molar ratio of ions to 2-methylimidazole molecules is 1:3;

[0011] The mixed solution forms a precipitate after reaction, and the precipitate is washed and dried to obtain ZIF-67.

[0012] In some embodiments of the present application, the mixed solution contains Co 2+ The concentration of ions is not less than 0.3mmol / L.

[0013] In some embodiments of the present application, the annealing and carbonization treatment of the ZIF-67 comprises the following steps:

[0014] The ZIF-67 was heated to 600-800° C. for 1-2 h in an inert atmosphere.

[0015] In some embodiments of the present application, the heating rate is 1-2°C / min.

[0016] In some embodiments of the present application, the QuEChERS pesticide residue analysis comprises the following steps:

[0017] Providing a sample to be tested, and crushing the sample to be tested to prepare a slurry;

[0018] adding the slurry into an acetic acid-acetonitrile solution to form a first mixed solution;

[0019] adding anhydrous magnesium sulfate and sodium chloride to the first mixed solution to form a second mixed solution;

[0020] collecting the clear liquid in the second mixed liquid as the first clear liquid, and adding the ZIF-67 derived carbon material to the first clear liquid for purification;

[0021] The ZIF-67-derived carbon material is separated by an external magnetic field to obtain a second clear liquid. The second clear liquid is filtered through an organic filter membrane, and then the obtained filtrate is analyzed for pesticide residues by liquid chromatography-tandem mass spectrometry.

[0022] In some embodiments of the present application, the slurry is added to an acetonitrile solution of acetic acid to form a first mixed solution, and 1 g of the slurry is added to every 1 mL of the acetonitrile solution of acetic acid.

[0023] In some embodiments of the present application, the slurry is added to an acetic acid acetonitrile solution to form a first mixed solution, and the mass concentration of the acetic acid acetonitrile solution is 1%.

[0024] In some embodiments of the present application, in the step of adding anhydrous magnesium sulfate and sodium chloride to the first mixed solution to form the second mixed solution, the mass ratio of the slurry, anhydrous magnesium sulfate and sodium chloride is 10:4:1.

[0025] In some embodiments of the present application, the ZIF-67 derived carbon material is added to the first clear liquid for purification:

[0026] Add at least 10 mg of the ZIF-67 derived carbon material per 1 mL of the first clear solution; and / or,

[0027] The purification method is vortex oscillation, and the duration is not less than 5 minutes.

[0028] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0029] The present application is applied to the QuEChERS pesticide residue analysis field by using ZIF-67 derived carbon material as magnetic purifier, with ZIF-67 as precursor, high temperature carbonization constructs ZIF-67 derived carbon, directly gives it sufficient magnetic strength, only needs to apply external magnetic field to achieve separation, and operation is simple and fast. In addition, ZIF-67 derived carbon itself, as porous carbon material, has excellent stability, has strong adsorption for the interference in the pesticide analysis process, and does not adsorb target. Therefore, the present application applies ZIF-67 derived carbon material to QuEChERS pesticide residue analysis, and provides a suitable QuEChERS magnetic purifier for it. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0031] In order to more clearly illustrate the embodiments of the present application 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, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1A schematic diagram of the preparation process of the ZIF-67-derived carbon material provided in the embodiments of the present application;

[0033] Figure 2 A schematic diagram of the process of providing ZIF-67 as described in this application;

[0034] Figure 3 A schematic diagram of the process of QuEChERS pesticide residue analysis provided in the embodiments of the present application;

[0035] Figure 4 The scanning electron micrographs of ZIF-67 and ZIF-67-derived carbon materials in Example 1;

[0036] Figure 5 The Fourier transform infrared spectra of the ZIF-67 derived carbon materials in Examples 1-3;

[0037] Figure 6 is the X-ray diffractometer image of the ZIF-67 derived carbon material in Examples 1-3;

[0038] Figure 7 The nitrogen adsorption-desorption curve of the ZIF-67 derived carbon material in Examples 1-3;

[0039] Figure 8 is a hysteresis curve diagram of the ZIF-67 derived carbon material in Examples 1-3;

[0040] Fig. 9 It is a curve diagram showing the maximum adsorption capacity of chlorophyll and xanthophyll of ZIF-67 derived carbon material changing with time;

[0041] Fig.10 Fitting curve of pseudo-second-order kinetic equation for adsorption of chlorophyll and xanthophyll by ZIF-67 derived carbon materials;

[0042] Fig.11 Fitting in-mold diffusion model curves for the adsorption of chlorophyll and xanthophyll by ZIF-67 derived carbon materials;

[0043] Fig.12 The Langmuir and Freundlich isotherm adsorption model curves of ZIF-67 derived carbon materials for chlorophyll and xanthophyll;

[0044] Fig.13 The chromatograms of chlorpyrifos, mefenpyr and isoprocarb obtained by liquid chromatography-tandem mass spectrometry analysis in Example 4;

[0045] Fig.14 The full wavelength scanning result diagram of the visible spectrophotometer of Examples 4-9 and Comparative Example 1;

[0046] Fig.15The curve diagram of the effect of purification time on the recovery rate of carbamate pesticides;

[0047] Fig.16 The full wavelength scanning result diagram of the visible spectrophotometer of Examples 10-14 and Comparative Example 1;

[0048] Fig.17 The figure is a curve showing the effect of the amount of ZIF-67 derived carbon material on the recovery rate of carbamate pesticides;

[0049] Fig.18 It is a full wavelength scanning curve diagram of the visible spectrophotometer of Example 4 and Comparative Examples 1-4;

[0050] Fig.19 This is a curve chart showing the effect of the type of purifier on the recovery rate of carbamate pesticides. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0052] Unless otherwise specified, the terms used herein should be understood as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. In the event of a conflict, this specification takes precedence.

[0053] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0054] Currently, in the field of pesticide residue analysis, there is a lack of technical problems in the QuEChERS magnetic purification agent that is simple to prepare, has excellent adsorption performance, and is simple and fast to operate.

[0055] The technical solution provided by the embodiments of the present application is to solve the above technical problems, and the overall idea is as follows:

[0056] The present application embodiment provides an application of a ZIF-67-derived carbon material, wherein the ZIF-67-derived carbon material is applied as a magnetic purifier for QuEChERS pesticide residue analysis. Figure 1 , the ZIF-67 derived carbon material is prepared by the following method:

[0057] S1: Provides ZIF-67;

[0058] S2: performing annealing and carbonization treatment on the ZIF-67 to obtain a ZIF-67 derived carbon material.

[0059] ZIF-67 is a known organic metal framework material. After annealing and carbonization, the organic metal framework material can obtain a porous carbon material with adjustable pore structure, large pore volume and specific surface area, excellent physical and chemical properties and regular morphology.

[0060] As an organic metal framework material, ZIF-67 is simple to prepare, cheap and readily available. The metal ion of ZIF-67 is divalent cobalt, which has magnetism after being reduced to cobalt, making ZIF-67-derived carbon materials useful as magnetic purifiers.

[0061] The present application is by applying ZIF-67 derived carbon material to the magnetic purifier of QuEChERS pesticide residue analysis, with ZIF-67 as precursor, high temperature carbonization constructs ZIF-67 derived carbon, directly gives it sufficient magnetic strength, only needs to apply external magnetic field to achieve separation, and operation is simple and fast. In addition, ZIF-67 derived carbon itself as porous carbon material, has excellent stability, has strong adsorption for the interference in pesticide analysis process, and does not adsorb target. Therefore, the present application applies ZIF-67 derived carbon material to QuEChERS pesticide residue analysis, and provides a suitable QuEChERS magnetic purifier for it.

[0062] In some embodiments of the present application, the ZIF-67 is provided, please refer to Figure 2 , including the following steps:

[0063] S11: providing an alcohol solution of Co(NO3)2·6H2O and an alcohol solution of 2-methylimidazole;

[0064] S12: Mix the alcohol solution of Co(NO3)2·6H2O and the alcohol solution of 2-methylimidazole to obtain a mixed solution, wherein Co 2+ The molar ratio of ions to 2-methylimidazole molecules is 1:3;

[0065] S13: After the mixed solution reacts, a precipitate is formed, and the precipitate is washed and dried to obtain ZIF-67.

[0066] Those skilled in the art will appreciate that the above method is one of the well-known methods for preparing ZIF-67 in the art.

[0067] In some embodiments of the present application, the mixed solution contains Co 2+ The concentration of ions is not less than 0.3mmol / L.

[0068] During the synthesis of ZIF-67, Co 2+ With the increase of concentration, the specific surface area and magnetic strength of the obtained ZIF-67-derived carbon material gradually increase. When used as a purifier, the higher the specific surface area, the higher the adsorption efficiency; the greater the saturation magnetic intensity, the faster the separation of the purifier and the sample matrix.

[0069] In some embodiments of the present application, the annealing and carbonization treatment of the ZIF-67 comprises the following steps:

[0070] The ZIF-67 was heated to 600-800° C. for 1-2 h in an inert atmosphere.

[0071] Those skilled in the art will appreciate that the inert gas may be, for example, a rare gas or nitrogen.

[0072] In some embodiments of the present application, the heating rate is 1-2°C / min.

[0073] In some embodiments of this application, please refer to Figure 3 The QuEChERS pesticide residue analysis includes the following steps:

[0074] S21: providing a sample to be tested, crushing the sample to be tested and preparing a slurry;

[0075] S22: adding the slurry into an acetic acid-acetonitrile solution to form a first mixed solution;

[0076] S23: adding anhydrous magnesium sulfate and sodium chloride to the first mixed solution to form a second mixed solution;

[0077] S24: collecting the clear liquid in the second mixed liquid as the first clear liquid, and adding the ZIF-67 derived carbon material to the first clear liquid for purification;

[0078] S25: After separating the ZIF-67-derived carbon material by an external magnetic field, a second clear liquid is obtained. After filtering the second clear liquid with an organic filter membrane, the obtained filtrate is subjected to pesticide residue analysis by liquid chromatography-tandem mass spectrometry.

[0079] Those skilled in the art will appreciate that acetonitrile is abbreviated as ACN, which is a commonly used solvent in standard analysis. ACN mentioned in this application refers to acetonitrile.

[0080] Those skilled in the art will appreciate that the samples to be tested are generally agricultural products that may be exposed to pesticides, such as vegetables and fruits.

[0081] In step S21, a person skilled in the art may crush the sample to be tested and prepare a slurry by conventional methods. As an example, the crushing of the sample to be tested and preparing a slurry may be performed by the following steps:

[0082] S211: cutting the sample to be tested into small pieces and placing them in a centrifuge tube;

[0083] S212: Use a homogenizer to grind until a uniform slurry is obtained.

[0084] In some embodiments of the present application, the slurry is added to an acetic acid acetonitrile solution to form a first mixed solution, and 1 g of the slurry is added to every 1 mL of acetic acid acetonitrile solution. Further, the slurry is added to an acetic acid acetonitrile solution to form a first mixed solution, and the mass concentration of the acetic acid acetonitrile solution is 1%. Further, anhydrous magnesium sulfate and sodium chloride are added to the first mixed solution to form a second mixed solution, and the mass ratio of slurry, anhydrous magnesium sulfate and sodium chloride is 10:4:1. Further, the ZIF-67 derived carbon material is added to the first clear solution for purification:

[0085] Add at least 10 mg of the ZIF-67 derived carbon material per 1 mL of the first clear solution; and / or,

[0086] The purification method is vortex oscillation, and the duration is not less than 5 minutes.

[0087] Under the aforementioned operating conditions, a good purification effect can be achieved by adding at least 10 mg of the ZIF-67-derived carbon material to every 1 mL of the first clear liquid and by a vortex oscillation lasting no less than 5 min.

[0088] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0089] Example 1

[0090] This embodiment provides a ZIF-67 derived carbon material that can be used as a QuEChERS magnetic purifier, which is prepared by the following steps:

[0091] Sa1: Weigh 3.05g Co(NO3)2·6H2O and 2.58g 2-methylimidazole and dissolve them in 35mL methanol. Slowly pour the 2-methylimidazole solution into the Co(NO3)2·6H2O solution to obtain a mixed solution. 2+The concentration is 0.3mmol / L;

[0092] Sb1: The mixed solution was magnetically stirred at 25°C for 24 hours, centrifuged at 7000r for 5 minutes, the purple precipitate was collected, washed with methanol until clear, and vacuum dried at 60°C to obtain ZIF-67;

[0093] Sc1: The obtained ZIF-67 is placed in a tubular furnace and heated to 700°C at a heating rate of 1.5°C / min under an argon protection environment, and maintained for 1.5 hours. After the reaction is completed, it is naturally cooled to room temperature and the black powder is collected, which is the ZIF-67-derived carbon material, i.e., the magnetic purifier.

[0094] Example 2

[0095] The difference between this embodiment and embodiment 1 is that step Sa1 is:

[0096] Weigh 1.08g Co(NO3)2·6H2O and 0.86g 2-methylimidazole and dissolve them in 35mL methanol. Slowly pour the 2-methylimidazole solution into the Co(NO3)2·6H2O solution to obtain a mixed solution. 2+ The concentration is 0.1mmol / L.

[0097] Example 3

[0098] The difference between this embodiment and embodiment 1 is that step Sa1 is:

[0099] Weigh 2.04 g Co(NO3)2·6H2O and 1.72 g 2-methylimidazole and dissolve them in 35 mL methanol. Slowly pour the 2-methylimidazole solution into the Co(NO3)2·6H2O solution to obtain a mixed solution. 2+ The concentration is 0.2mmol / L.

[0100] Example 4

[0101] This embodiment provides a QuEChERS pesticide residue analysis method, comprising the following steps:

[0102] Sa2: Provide fresh celery samples, cut the celery samples into small pieces, weigh 100 g and place them in a 50-mL centrifuge tube, and use a homogenizer to grind for 15 minutes until a uniform slurry is obtained;

[0103] Sb2: 10 g of the slurry was weighed and placed in a 50-mL centrifuge tube, 10 mL of ACN-1% HAC was added and shaken for extraction for 10 min, then 4 g of anhydrous magnesium sulfate and 1 g of sodium chloride were added, the mixture was shaken vigorously for 1 min, centrifuged at 4000 r / min for 5 min, and 1 mL of the supernatant was collected as the first supernatant;

[0104] Sc2: Add 10 mg of ZIF-67 derived carbon material, vortex oscillate for 5 min, apply an external magnetic field to separate the purifier from the sample solution to obtain a second supernatant, filter the second supernatant through an organic filter membrane, and perform liquid chromatography-tandem mass spectrometry analysis on the amount of carbamate pesticide residues.

[0105] Wherein, the ZIF-67 derived carbon material described in step Sc2 is the ZIF-67 derived carbon material provided in Example 1.

[0106] For liquid chromatography-tandem mass spectrometry analysis,

[0107] The liquid chromatography conditions are: the chromatographic column is C 18 Column (100 mm × 2.1 mm, 1.7 μm, Agilent, USA), mobile phases were (A) 0.1% formic acid aqueous solution and (B) ACN. Gradient elution program was 0-1.5 min, 25% B; 1.5-7.5 min, 25% B-85% B. Injection volume 10 μL, flow rate 0.3 mL / min, column temperature 35°C.

[0108] The mass spectrometry conditions were: electrospray ionization (ESI) source positive ion mode, capillary voltage 2.5 kV, RF lens voltage 0.5 V, ion source temperature 150 ° C, desolvation gas temperature 600 ° C, desolvation gas flow rate 1000 L / h, cone gas flow rate 50 L / h, multiplier voltage, 650 V, and detection mode was multi-segment multiple reaction monitoring (MRM). The retention time, qualitative ion pair, quantitative ion pair, cone voltage and collision energy reference values ​​of 8 carbamate pesticides are shown in the table below.

[0109] Table of retention time, qualitative ion pair, quantitative ion pair, cone voltage and collision energy of carbamate pesticides

[0110]

[0111] Example 5

[0112] The difference between this embodiment and embodiment 4 is only that:

[0113] In step Sc2, the vortex oscillation time is 1 min.

[0114] Example 6

[0115] The difference between this embodiment and embodiment 4 is only that:

[0116] In step Sc2, the vortex oscillation time is 2 minutes.

[0117] Example 7

[0118] The difference between this embodiment and embodiment 4 is only that:

[0119] In step Sc2, the vortex oscillation time is 3 minutes.

[0120] Example 8

[0121] The difference between this embodiment and embodiment 4 is only that:

[0122] In step Sc2, the vortex oscillation time is 4 minutes.

[0123] Example 9

[0124] The difference between this embodiment and embodiment 4 is only that:

[0125] In step Sc2, the vortex oscillation time is 6 minutes.

[0126] Example 10

[0127] The difference between this embodiment and embodiment 4 is only that:

[0128] In step Sc2, 2 mg of ZIF-67-derived carbon material was added and the vortex oscillation time was 8 min.

[0129] Embodiment 11

[0130] The difference between this embodiment and embodiment 10 is only that:

[0131] In step Sc2, 5 mg of ZIF-67 derived carbon material was added.

[0132] Example 12

[0133] The difference between this embodiment and embodiment 10 is only that:

[0134] In step Sc2, 15 mg of ZIF-67 derived carbon material was added.

[0135] Example 13

[0136] The difference between this embodiment and embodiment 10 is only that:

[0137] In step Sc2, 20 mg of ZIF-67 derived carbon material was added.

[0138] Comparative Example 1

[0139] The difference between this comparative example and Example 4 is only that:

[0140] In step Sc2, no ZIF-67 derived carbon material is added.

[0141] Comparative Example 2

[0142] The difference between this comparative example and Example 4 is only that:

[0143] In step Sc2, 10 mg of commercial octadecyl bond and silica gel (C 18 ) purifier instead of ZIF-67 derived carbon materials.

[0144] Comparative Example 3

[0145] The difference between this comparative example and Example 4 is only that:

[0146] In step Sc2, 10 mg of commercial N-propylethylenediamine bonded silica gel (PSA) purifier was used instead of the ZIF-67 derived carbon material.

[0147] Comparative Example 4

[0148] The difference between this comparative example and Example 4 is only that:

[0149] In step Sc2, 10 mg of commercial graphitized carbon black (GCB) scavenger was used instead of the ZIF-67 derived carbon material.

[0150] Related experiments and effect data:

[0151] The ZIF-67 and ZIF-67-derived carbon materials obtained in Example 1 were characterized by scanning electron microscopy. Figure 4 , Figure 4 (a) is a scanning electron microscope image of ZIF-67 in Example 1, Figure 4 (b) is a scanning electron microscope image of the ZIF-67 derived carbon material in Example 1. It can be seen that ZIF-67 is a regular dodecahedral structure, and after high-temperature calcination, the ZIF-67 derived carbon material retains the dodecahedral structure, but its surface is roughened.

[0152] The ZIF-67 derived carbon materials in Examples 1-3 were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. Figure 5 The Fourier transform infrared spectra of the ZIF-67 derived carbon materials in Examples 1-3 are shown in Table 1. All the synthesized products have an infrared spectrum at 1693 cm -1 and 572cm -1 There are bending vibration peaks of C=N and Co-N at all locations; Figure 6 The X-ray diffraction patterns of the ZIF-67 derived carbon materials in Examples 1-3 show typical diffraction peaks of the ZIF-67 derived carbon materials at 26.2° (002), 44° (111), 51° (200), and 76° (220). The above results confirm that different Co 2+ Concentrations of all kinds can be used to successfully construct ZIF-67-derived carbon materials.

[0153] The specific surface area of ​​the ZIF-67 derived carbon materials in Examples 1 to 3 was analyzed by nitrogen adsorption-desorption experiments to obtain nitrogen adsorption-desorption curves of the ZIF-67 derived carbon materials in Examples 1 to 3. Please refer to Figure 7 It can be seen that the nitrogen adsorption-desorption curves of the three ZIF-67 derived carbon materials are all type II curves. The specific surface areas of the ZIF-67 derived carbon materials in Example 2, Example 3, and Example 1 are 229.07, 233.78, and 256.51 m 2 / g, and the pore sizes are 3.39, 3.40 and 3.41 nm respectively.

[0154] Saturation magnetic intensity characterization: The ZIF-67 derived carbon materials in Examples 1 to 3 were characterized by a vibrating sample magnetometer to obtain a hysteresis curve of the purifier. Please refer to Figure 8 .Depend on Figure 8 It can be seen that the saturation magnetic intensities of the ZIF-67 derived carbon materials in Example 2, Example 3 and Example 1 are 37.64, 39.59 and 40.33 emu / g, respectively.

[0155] In summary, with the synthesis of ZIF-67, Co 2+ With the increase of concentration, the specific surface area and magnetic intensity of the calcined ZIF-67-derived carbon material gradually increase. When the ZIF-67-derived carbon material is used as a purifier, the higher its specific surface area, the higher its adsorption efficiency; the greater the saturation magnetic intensity, the faster the separation of the purifier and the sample matrix.

[0156] In many crops, such as celery, cabbage, cabbage, apples, bananas and oranges, natural pigments are the main interferences in the analysis of pesticide residues. Therefore, the ZIF-67-derived carbon materials in Examples 1 to 3 were taken to analyze their adsorption properties for chlorophyll and lutein:

[0157] 10 mg of ZIF-67-derived carbon material was dispersed in 6 mL of 100 μg / mL chlorophyll and lutein standard ACN solution, and after adsorption at a predetermined temperature for a predetermined time, an external magnetic field was applied to separate the ZIF-67-derived carbon material from the sample solution, and the supernatant was collected for UV spectrophotometric analysis. The maximum absorption wavelengths of chlorophyll and lutein in the UV spectrophotometer were 652 and 445 nm, respectively, and ACN was used for zero calibration.

[0158] The maximum adsorption capacity of ZIF-67 derived carbon materials at a certain time (t) is expressed as Q t It is expressed as follows:

[0159]

[0160] Ce is the initial concentration of chlorophyll (μg / mL); C t is the residual mass concentration of chlorophyll at time t (μg / mL); m is the mass of the ZIF-67 derived carbon material; V is the volume of the chlorophyll standard solution (mL).

[0161] Two groups of experiments were conducted. The first group of experimental conditions were as follows: the predetermined temperature was set to 25°C, and the predetermined time was set to 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15 and 20 min, respectively, to set up multiple groups of experiments to investigate the effect of the predetermined time on the maximum adsorption capacity of chlorophyll and lutein by ZIF-67 derived carbon materials.

[0162] The second set of experimental conditions is: setting the preset time to 10 minutes, and the preset temperatures to 25, 35, 45 and 55 °C, respectively, to set up multiple groups of experiments to investigate the effect of the preset temperature on the maximum adsorption capacity of chlorophyll and lutein by ZIF-67 derived carbon materials.

[0163] The above test was analyzed as follows:

[0164] ① Adsorption kinetics

[0165] For the first set of experiments, the adsorption capacity of chlorophyll and lutein on ZIF-67-derived carbon materials varied with time. Fig. 9 As shown in the figure, it can be seen that as the adsorption time increases from 1 min to 5 min, the adsorption of chlorophyll and lutein by ZIF-67-derived carbon materials quickly reaches saturation, with the maximum adsorption capacities of 29.89 and 22.28 mg / g, respectively. When the time continues to increase to 20 min, the adsorption capacity does not change significantly.

[0166] The pseudo-first-order and second-order kinetic equations were used to fit the adsorption behavior of ZIF-67-derived carbon materials on chlorophyll and lutein, as shown in the following table:

[0167] Kinetic parameters of chlorophyll and xanthophyll adsorption on ZIF-derived carbon materials

[0168]

[0169] The above table shows the correlation coefficient (R 2 ) is 0.984-0.998, which is greater than the pseudo-first-order kinetic equation fitting R 2 (0.194~0.459), indicating that the pseudo-second-order kinetic equation can better describe the adsorption process of ZIF-67 derived carbon materials. Fig.10The fitting curve of the quasi-second-order kinetic equation for the adsorption of chlorophyll and lutein by ZIF-67-derived carbon materials in the first group of experiments is shown. The theoretical maximum adsorption capacities of chlorophyll and lutein by ZIF-67-derived carbon materials calculated by the fitting equation are 30.5 and 25.8 mg / g, respectively, which are slightly different from the experimentally measured maximum adsorption capacities of 29.9 and 22.28 mg / g of ZIF-67-derived carbon materials, further indicating that the adsorption process of chlorophyll by ZIF-67-derived carbon materials is more in line with the quasi-second-order kinetic equation and is mainly chemical adsorption.

[0170] Fig.11 Qe versus t for fitting the pseudo-second-order kinetic equation for the adsorption of chlorophyll and xanthophyll by ZIF-67-derived carbon materials in the first set of experiments 0.5 The curve graph shows that the adsorption process of chlorophyll and lutein by ZIF-67 derived carbon material is divided into three stages: extramembrane diffusion, intramembrane diffusion and adsorption equilibrium. By comparing the slopes of the three, it can be seen that the extramembrane diffusion process is faster, indicating that the extramembrane diffusion process has a more obvious impact on the entire adsorption process.

[0171] ② Adsorption isotherm

[0172] The Langmuir and Freundlich isothermal adsorption models were used to describe the adsorption process of chlorophyll and lutein by ZIF-67 derived carbon materials in the first group of experiments. The following table shows the isothermal adsorption parameters of chlorophyll and lutein by ZIF-67 derived carbon materials. Fig.12 The Langmuir and Freundlich isotherm adsorption curves of chlorophyll and lutein on ZIF-67 derived carbon materials in the first group of experiments. The Freundlich adsorption isotherm model fitting R 2 The Langmuir adsorption isotherm model fitting R 2 The Langmuir isotherm adsorption equation is more suitable for describing the adsorption thermodynamic behavior of chlorophyll and lutein on ZIF-67 derived carbon materials. The adsorption equilibrium constant K L 0.037~0.097(0 <K L <1), indicating that the adsorption of chlorophyll and xanthophyll by ZIF-67-derived carbon materials is easy to occur, and the adsorption process tends to be monolayer adsorption, with chemical adsorption dominating.

[0173] Isothermal adsorption parameters of chlorophyll and xanthophyll on ZIF-67 derived carbon materials

[0174]

[0175] ③ Adsorption thermodynamics

[0176] For the second group of experiments, the study investigated the effect of adsorption temperatures of 25, 35, 45 and 55 ° C on the maximum adsorption capacity of ZIF-67 derived carbon materials. The thermodynamic equation was used to analyze the adsorption mechanism of ZIF-67 derived carbon materials on chlorophyll and lutein, and the Gibbs free energy change (ΔG, kJ / mol), enthalpy change (ΔH, kJ / mol) and entropy change ΔS (J / mol·K) were calculated. The results are shown in the table below. At different adsorption temperatures, ΔG is greater than 0, indicating that the adsorption of chlorophyll and lutein by ZIF-67 derived carbon materials is non-spontaneous. ΔH and ΔS are greater than 0, proving that the adsorption process is an endothermic and entropy increasing process.

[0177] Thermodynamic parameters of chlorophyll and xanthophyll adsorption on ZIF-67 derived carbon materials

[0178]

[0179] Liquid chromatography-tandem mass spectrometry analysis results:

[0180] Please refer to Fig.13 , Fig.13 The chromatograms of methiocarb, mefenamic acid and isoprocarb obtained by liquid chromatography-tandem mass spectrometry analysis in Example 4 show that the celery sample has no obvious matrix effect on methiocarb, mefenamic acid and isoprocarb, with values ​​of 0.58 to 0.72, and the method recovery rate is 95.4% to 101%, indicating that Example 4 can effectively purify impurities in vegetable samples and accurately analyze trace pesticide residues.

[0181] QuEChERS Conditions Study:

[0182] Purification time

[0183] Appropriate purification time is conducive to providing sufficient adsorption sites, ensuring full contact, and achieving excellent purification effect. The purification time (i.e., vortex oscillation time) of Example 5, Example 6, Example 7, Example 8, Example 4, and Example 9 is 1, 2, 3, 4, 5, and 6 minutes respectively, and other conditions are the same. The full wavelength scanning results of the visible spectrophotometer for Examples 4-9 and Comparative Example 1 are shown in FIG. Fig.14 Compared with comparative example 1 (corresponding to the curve "Without purification"), the impurity peak response decreases with the extension of purification time within 1 to 5 minutes, and continues to increase to 6 minutes, and the impurity peak response does not change significantly. At the same time, the inset results are consistent with the full wavelength scanning results.

[0184] The experiment further investigated the effect of purification time on the recovery rate of carbamate pesticides. Fig.15 The recovery rate of carbamate pesticides at different purification times is shown in the figure. Fig.15It shows that as the purification time increases from 1min to 5min, the recovery rates of 8 carbamate pesticides (Metolcarb, Bendiocarb, Pirimicarb, Trimenthacarb, Propoxur, xmc, Isoprocarb, Promecarb) gradually approach 100%, and the RSD decreases. When the purification time continues to increase, the recovery rate of the target does not change significantly. Therefore, the optimal purification time is not less than 5min.

[0185] The amounts of ZIF-67 derived carbon materials used in Examples 10-14 were 2, 5, 10, 15 and 20 mg respectively, and other conditions were the same. In addition, the purification time was fixed at 8 min in all experiments to ensure that the purification was fully carried out. The full wavelength scanning results of the visible spectrophotometer of Examples 10-14 and Comparative Example 1 are shown in FIG. Fig.16 As shown, compared with Comparative Example 1 (corresponding to the curve "Without purification" in the figure), when the amount of the purifier is 2-10 mg, as the amount of the purifier increases, the impurity peak response is significantly reduced, and the impurity peak response does not change significantly when the amount of the purifier is continued to increase to 20 mg. At the same time, it is found by naked eye observation that as the amount of the purifier increases from 2 mg to 10 mg, the celery sample solution gradually changes from green to transparent, and continues to increase to 20 mg, the color of the sample solution remains transparent. This shows that when the amount of the purifier is 10 mg, the ZIF-67 derived carbon material can effectively adsorb the interferences in the celery sample matrix.

[0186] At the same time, the experiment investigated the effect of the amount of ZIF-67 derived carbon material on the recovery rate of carbamate pesticides. Fig.17 As shown, Fig.17 The recovery rate of carbamate pesticides at different ZIF-67 derived carbon material dosages is a curve chart corresponding to Examples 10-14. When the purifier is 2-5 mg, the recovery rate of 8 carbamate pesticides is 83.1%-125%, and the RSDs are 1.4%-14.6%; when the purifier dosage is increased to 10-20 mg, the recovery rate of the target is 91.8%-107%, and the RSDs are 1.8%-9.8%, so the optimal dosage is not less than 10 mg.

[0187] Comparison with commercial purifiers

[0188] Comparative Examples 2-4 using commercial purifier C 18 , PSA, and GCB were used to purify the celery sample matrix instead of ZIF-67 derived carbon materials. First, it was observed by naked eyes that the purifier was C 18 When GCB and ZIF-67 derived carbon materials were used as purifiers, the supernatant of the celery sample was clear and transparent. Fig.18 The full wavelength scanning curves of the visible spectrophotometer of Example 4 and Comparative Examples 1-4 are shown. Compared with Comparative Example 1 (corresponding to the curve "Without purification"), when C 18 When and PSA were used as purifiers, the impurity peak response was reduced, but obvious impurity peaks could still be observed at 400 and 652 nm; when the purifiers were GCB and ZIF-67 derived carbon materials, the impurity peak response value was significantly reduced, and there was no obvious impurity peak at the same position, indicating that GCB and ZIF-67 derived carbon materials had the best purification effect on interferences in celery samples.

[0189] Fig.19 The recovery rate of carbamate pesticides under different purifiers is a curve chart corresponding to Example 4 and Comparative Examples 1-4. Fig.19 It shows that C 18 The recovery rates of ZIF-67 and PSA for 8 carbamate pesticides were 78.9% to 146% and 86.7% to 122%, respectively. Although the purification effects of ZIF-67-derived carbon materials and GCB were comparable, the recovery rate of GCB for the target was only 59.4% to 105%, while when the purifier was ZIF-67-derived carbon materials, the recovery rate was 91.8% to 107%. The above results show that, on the one hand, ZIF-67-derived carbon materials can effectively purify interferences in celery samples, the supernatant is clear, and the purification effect is comparable to GCB (transparent color), and is better than C 18 and PSA (light green). On the other hand, ZIF-67-derived carbon materials adsorbed the interferents without adsorbing the target, and the recovery rate of 8 carbamate pesticides was 91.8% to 107%, which was better than 59.4% to 105% of GCB. Therefore, ZIF-67-derived carbon materials can be used as excellent purifiers for the purification of carbamate pesticides.

[0190] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0191] In the present application, in the absence of any contrary description, the directional words used, such as "upper" and "lower", are specifically the directions of the drawings in the accompanying drawings. In addition, in the description of the present application specification, the terms "including", "comprising", etc. refer to "including but not limited to". Moreover, the terms "including", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. In this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent: A exists alone, A and B exist at the same time, and B exists alone. For the association relationship of more than three associated objects described by "and / or", it means that any one of these three associated objects can exist alone, or any at least two of them exist at the same time. For example, for A, and / or B, and / or C, it can be represented that any one of A, B, and C exists alone, or any two of them exist at the same time, or three of them exist at the same time. In this article, "at least one" refers to one or more, and "multiple" refers to two or more. "At least one", "the following at least one (individual)" or similar expressions refer to any combination of these items, including any combination of single (individual) or plural (individual). For example, "at least one (individual) of a, b, or c", or "at least one (individual) of a, b, and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, wherein a, b, and c can be single or multiple, respectively.

[0192] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. An application of a ZIF-67 derived carbon material, characterized in that: The ZIF-67 derived carbon material is used as a magnetic purifier in the QuEChERS pesticide residue analysis field. The ZIF-67 derived carbon material is prepared by the following method: Provide ZIF-67; The ZIF-67 is heated to 600-800° C. in an inert gas atmosphere for 1-2 hours at a heating rate of 1-2° C. / min to obtain a ZIF-67-derived carbon material; The ZIF-67 is prepared by the following method: providing an alcohol solution of Co(NO3)2·6H2O and an alcohol solution of 2-methylimidazole; The alcohol solution of Co(NO3)2·6H2O and the alcohol solution of 2-methylimidazole are mixed to obtain a mixed solution, wherein Co 2+ The molar ratio of 2-methylimidazole is 1:3; The mixed solution forms a precipitate after reaction, and the precipitate is washed and dried to obtain ZIF-67; The QuEChERS pesticide residue analysis includes the following steps: Providing a sample to be tested, and crushing the sample to be tested to prepare a slurry; The slurry is added to an acetonitrile solution containing acetic acid to form a first mixed solution, 1 g of the slurry is added to every 1 mL of the acetonitrile solution containing acetic acid, and the mass concentration of acetic acid in the acetonitrile solution containing acetic acid is 1%; adding anhydrous magnesium sulfate and sodium chloride to the first mixed solution to form a second mixed solution, wherein the mass ratio of the first mixed solution, anhydrous magnesium sulfate and sodium chloride is 10:4:1; The clear liquid in the second mixed liquid is collected as the first clear liquid, and the ZIF-67-derived carbon material is added to the first clear liquid for purification, at least 10 mg of the ZIF-67-derived carbon material is added per 1 mL of the first clear liquid, and the purification method is vortex oscillation, and the duration is not less than 5 minutes; After separating the ZIF-67-derived carbon material by an external magnetic field, a second clear liquid is obtained, and after filtering the second clear liquid with an organic filter membrane, the obtained filtrate is subjected to pesticide residue analysis by liquid chromatography-tandem mass spectrometry; The sample to be tested is selected from any one of celery, Chinese cabbage, cabbage, apple, banana or orange, and the pesticide is a carbamate pesticide.

2. The use of the ZIF-67 derived carbon material according to claim 1, characterized in that: The mixed solution contains Co 2+ The concentration of ions is not less than 0.3mmol / L.

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