Magnetic organic covalent framework material for extracting aflatoxin and precursor thereof from peanuts as well as preparation method and application of magnetic organic covalent framework material

Abstract

The invention relates to the technical field of magnetic organic covalent framework materials, in particular to a magnetic organic covalent framework material for extracting aflatoxin and a precursor thereof in peanuts as well as a preparation method and application of the magnetic organic covalent framework material, and the preparation method comprises the following steps: mixing Fe3O4 nanoparticles, 4, 4 '-(1, 3, 5-triazine-2, 4, 6-triyl) triphenylamine, 2, 3, 5, 6-tetrafluorop-dibenzaldehyde and an organic solvent; performing ultrasonic treatment on the mixture for 5 minutes, adding acetic acid, sealing in a reaction kettle, and heating at 120 DEG C for 24 hours; and filtering to obtain a purplish red precipitate, and washing with tetrahydrofuran and absolute ethyl alcohol respectively. And carrying out vacuum drying in a drying oven at 60 DEG C to finally obtain the amaranth F-COF-Fe3O4. The F-COF-Fe3O4 material prepared by the invention can realize efficient extraction of various aflatoxins and precursors thereof at the same time, has relatively strong matrix anti-interference capability and excellent enrichment and purification performance, and has the advantages of simple preparation method, relatively low cost and wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic organic covalent framework materials, and in particular to a magnetic organic covalent framework material for extracting aflatoxin and its precursors from peanuts, and a preparation method and application thereof. Background Art

[0002] The ubiquitous Aspergillus flavus and Aspergillus parasiticus are notorious for contaminating many major crops and food soils with the highly toxic and carcinogenic aflatoxin B1 (AFB1). Due to food safety concerns, maximum residual limits for AFB1 are mandated in various countries for crops and food plants. Extensive research on AFB1 has highlighted certain toxic biosynthetic precursors, such as averantin (AVN) and ster-igmatocystin (ST). These precursors also contaminate food, posing a threat to human health and global economic losses. However, in the early stages of contamination, concentrations of AFB1 and its precursors are extremely low, and their presence has been determined to be limited.

[0003] Effective sample preparation can avoid interference from the sample matrix and enrich the target. As a widely used sample preparation, dispersed solid phase extraction (DSPE) is performed by dispersing a solid adsorbent into a liquid sample solution, which has the advantages of large contact area, easy operation and time saving. Based on the structure of the target, the selection of an appropriate adsorbent is crucial for DSPE and enhancing the accuracy and sensitivity of subsequent detection technology. The AFB1 biosynthetic pathway involves a series of oxidative rearrangement reactions, so the structure of AFB1 is different from that of the resulting precursor. Due to the structural differences, the simultaneous and effective extraction of AFB1 and its precursor is a difficult task. This application developed a magnetic adsorbent Fe3O4 / ZIFs by combining MAG network solid phase (MSPE) to effectively extract AVN and ST in the grains, but at the same time effectively extract the precursors of AFB1 and its precursors. Therefore, the use of multifunctional groups to develop extraction materials is very necessary for the simultaneous and effective extraction of AFB1 and its precursors. Summary of the Invention

[0004] The purpose of the present invention is to address the shortcomings of the prior art and to propose a magnetic organic covalent framework material for extracting aflatoxins and their precursors from peanuts, as well as its preparation method and application. The prepared magnetic organic covalent framework material has excellent extraction and enrichment effects on aflatoxins and their precursors.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing a magnetic organic covalent framework material comprises the following steps:

[0007] Step 1: Fe3O4 nanoparticles, 4,4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,3,5,6-tetrafluorobenzaldehyde, 1,2-dichlorobenzene, and n-butanol were mixed, and then the mixture was ultrasonically treated for 5 minutes, 6M acetic acid was added, and the mixture was sealed in a reactor and reacted at 100-120°C for 24-48 hours;

[0008] Step 2: Obtain a reddish-brown precipitate by filtration, and then wash it with tetrahydrofuran (THF) and anhydrous ethanol respectively;

[0009] Step 3: After vacuum drying in an oven at 60°C, a reddish-brown magnetic organic covalent framework material, namely F-COF@Fe3O4, was finally obtained.

[0010] Preferably, in step 1, the amount ratio of Fe3O4 nanoparticles, 4,4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,3,5,6-tetrafluorobenzaldehyde and 1,2-dichlorobenzene, n-butanol and 6M acetic acid is 350-450 mg:150-200 mg:150-200 mg:15-20 mL:15-20 mL:1.5-2.2 mL, preferably 400:150:170:15:15:1.5 (mg:mg:mg:mL:mL); wherein the amount of 4,4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 2,3,5,6-tetrafluorobenzaldehyde is not zero.

[0011] Preferably, in step 1, the reaction is carried out in a reactor at 120° C. for 24 hours.

[0012] Preferably, in step 1, the preparation method of Fe3O4 nanoparticles is as follows:

[0013] The iron standard solution was added dropwise to the NaOH solution, stirred for reaction, cooled to room temperature after the reaction was completed, and then sodium citrate solution was added dropwise, mechanically stirred, and the product was magnetically separated, washed, and dried to obtain Fe3O4 nanoparticles.

[0014] Preferably, the usage ratio of the iron standard solution, NaOH solution and sodium citrate solution is 20-30:240-260:80-120, preferably 25:250:100 (mL:mL:mL).

[0015] Preferably, the formula of the iron standard solution is: 2.8g FeSO4·7H2O, 5.2g FeCl3·6H2O, and 0.85mL concentrated hydrochloric acid; in practical applications, the amount of each component can be simultaneously increased or decreased according to the formula.

[0016] Preferably, the stirring reaction conditions are selected from: stirring the reaction at 75-85° C. for 0.8-1.2 h; preferably: stirring the reaction at 80° C. for 1 h.

[0017] A magnetic organic covalent framework material F-COF@Fe3O4 is obtained by the above preparation method.

[0018] The present invention also provides an application of the magnetic organic covalent framework material F-COF@Fe3O4 in the extraction and enrichment of aflatoxins and their precursors; preferably, the application of the magnetic organic covalent framework material F-COF@Fe3O4 in the extraction and enrichment of aflatoxins and their precursors in peanuts.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The F-COF@Fe3O4 material prepared by the present invention can simultaneously achieve efficient extraction of multiple aflatoxins and their precursors, has strong matrix anti-interference ability, and excellent enrichment and purification performance. Its preparation method is simple, the cost is low, and it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope image of the F-COF@Fe3O4 material of the present invention;

[0022] Figure 2 This is the infrared spectrum of the F-COF@Fe3O4 material of the present invention. DETAILED DESCRIPTION

[0023] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings so that those skilled in the art can better understand the advantages and features of the present invention and thus more clearly define the scope of protection of the present invention. The embodiments described in the present invention are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative work shall fall within the scope of protection of the present invention.

[0024] In the present invention, the Chinese names and English abbreviations of the chemical components are as follows:

[0025] 4,4"-(1,3,5-Triazine-2,4,6-triyl)triphenylamine (TATB), 2,3,5,6-tetrafluorobenzaldehyde (TFTA), organic covalent framework (COF).

[0026] The other materials used in the present invention, unless otherwise stated, can be obtained through commercial channels. Unless otherwise specified, other terms used in the present invention generally have the meanings commonly understood by those of ordinary skill in the art. The present invention will be further described in detail below with reference to specific examples and data. The following examples are merely for illustration of the present invention and are not intended to limit the scope of the present invention in any way.

[0027] Example 1

[0028] The steps for preparing the magnetic organic covalent framework material F-COF@Fe3O4 are as follows:

[0029] 400mg of Fe3O4 nanoparticles, 150mg of TFTA, and 170mg of TATB were added to a 10.0ml Pyrex tube and dissolved in 15mL of 1,2-dichlorobenzene and 15mL of n-butanol. After sonicating the mixture for 5 minutes, 1.5mL of 6M acetic acid was added. The mixture was sealed in a reactor and heated at 120°C for 24h. A purple-red precipitate was obtained by filtration and then washed with tetrahydrofuran (THF) and anhydrous ethanol. After vacuum drying in an oven at 60°C, a purple-red F-COF was finally obtained.

[0030] The above-mentioned Fe3O4 nanoparticles are prepared by the following method:

[0031] Add 25 mL of iron standard solution (formula: 2.8 g FeSO₄·7H₂O, 5.2 g FeCl₃·6H₂O, 0.85 mL concentrated hydrochloric acid) dropwise to 250 mL of NaOH solution (0.5 mol / L). Stir at 80°C for 1 hour. After cooling to room temperature, add 100 mL of sodium citrate solution (0.3 mol / L) dropwise and mechanically stir for 1 hour. After magnetic separation, wash with water until neutral and freeze-dry for 24 hours.

[0032] Figure 1 The scanning electron microscope image of F-COF@Fe3O4 material is shown. Figure 1 It can be seen that a core-shell structure is formed on the surface of Fe3O4, indicating the successful synthesis of F-COF@Fe3O4.

[0033] Figure 2 This is the infrared spectrum of F-COF@Fe3O4 material. Figure 2 As can be seen, F-COF was characterized by Fourier transform infrared spectroscopy (FT-IR). A -C=N- peak (1624 cm-1) and a F (1020 cm-1) peak were observed in F-COF. In addition, the NH peaks of TATB (3406, 3343, and 3208 cm-1) and the C=O peak of TFTA (1702 cm-1) disappeared in F-COF, confirming the successful synthesis of F-COF.

[0034] Example 2

[0035] Extraction test of aflatoxins and their precursors:

[0036] 5 mg of F-COF@Fe3O4 material was added to 10 mL of a 0.1 μg / mL sample solution (containing AFB1, AVN, and ST) and shaken at room temperature for 30 minutes. The F-COF@Fe3O4 material was then separated using a magnet, and the supernatant discarded. The F-COF@Fe3O4 material was then added to 1 mL of acetonitrile and sonicated for 10 minutes to dissolve aflatoxins and their precursors in the acetonitrile. The F-COF@Fe3O4 material was then separated using a magnet, and the solution retained. Finally, the solution was filtered through a 0.22 μm membrane, and the peak areas of aflatoxins and their precursors were determined using HPLC (20 μL injection volume). The aflatoxins and their precursors content was calculated based on a standard curve.

[0037] The HPLC detection conditions are as follows:

[0038] C18 analytical column, specifications 250 mm × 4.6 mm, ID, 5 μm; mobile phase B: methanol, mobile phase C: water, mobile phase D: acetonitrile; gradient elution: 0-6 minutes, acetonitrile / methanol / water (30:30:40, v / v / v); 6–35 minutes, acetonitrile / methanol / water (35:35:30, v / v / v); mobile phase flow rate: 1.0 mL / min; column temperature: 40 °C; injection volume: 20 μL; UV detector, wavelength 330 nm.

[0039] The above standard curve construction method is as follows:

[0040] Using acetonitrile as the solvent, aflatoxin and its precursor concentration gradients were set, where the AFB1 concentration gradient was 1 μg / mL, 2 μg / mL, 3 μg / mL, 4 μg / mL, 5 μg / mL, 6 μg / mL, 7 μg / mL, 8 μg / mL, and 10 μg / mL; the ST concentration gradient was 1 μg / mL, 2 μg / mL, 3 μg / mL, 4 μg / mL, 5 μg / mL, 6 μg / mL, 7 μg / mL, 8 μg / mL, and 10 μg / mL; and the AVN concentration gradient was 1 μg / mL, 2 μg / mL, 3 μg / mL, 4 μg / mL, 5 μg / mL, 6 μg / mL, 7 μg / mL, and 8 μg / mL. HPLC was used to determine the peak areas of the above-mentioned aflatoxins and their precursors at various concentrations, and a standard curve was constructed with the concentration of aflatoxins and their precursors as the horizontal axis and the peak area as the vertical axis. As shown in Table 1 below:

[0041] Table 1

[0042]

[0043] As shown in Table 1, there is a linear relationship between the concentrations of the three aflatoxins and their precursors and the peak areas. After fitting, the fitting formula between the concentration and peak area of ​​AFB1 is: Y = 53843X - 10913, R 2 =0.9971; the fitting formula between ST concentration and peak area is: Y=73680X–51008, R 2 =0.9966; the fitting formula between AVN concentration and peak area is: Y=165080X–162476, R 2 =0.9906.

[0044] The peak area of ​​AFB1 in the sample solution was determined to be 17069, the peak area of ​​ST to be 31469, and the peak area of ​​AVN to be 57268. Calculation using the standard curves yielded concentrations of 0.52 μg / mL for AFB1, 1.12 μg / mL for ST, and 0.93 μg / mL for AVN. Compared to the pre-prepared sample solution, the recovery rates for AFB1, ST, and AVN were approximately 52.0%, 112.0%, and 93.0%.

[0045] Based on the above experiments, this example further studies the effect of the amount of extractant (F-COF@Fe3O4 material) on the recovery rates of AFB1, ST and AVN.

[0046] The test results are shown in Table 2:

[0047] Table 2

[0048]

[0049]

[0050] Table 2 shows that when the F-COF@Fe3O4 material (extractant) is used at a dosage of 7 mg, it achieves the highest extraction efficiency for aflatoxins and their precursors in a 10 mL sample. The high recovery rate also demonstrates that the F-COF@Fe3O4 material prepared by the present invention has excellent extraction efficiency for aflatoxins and their precursors, capable of extracting low doses of aflatoxins and their precursors from samples, enabling successful detection of aflatoxins and their precursors.

[0051] Application Examples

[0052] Peanuts, as a common nut, have many functions and effects. From a nutritional point of view, peanuts are rich in protein, unsaturated fatty acids, vitamins (such as vitamin E, B vitamins), and minerals such as calcium, phosphorus, and iron. Protein can provide the human body with a high-quality source of amino acids, which helps tissue repair and growth. Unsaturated fatty acids can lower cholesterol and are beneficial to cardiovascular health. In terms of health benefits, peanuts are high in zinc, which can enhance memory and delay brain function decline. The resveratrol it contains is a natural antioxidant with potential role in preventing tumors. In addition, peanut red skin can promote platelet production, which is helpful for patients with anemia. In terms of eating experience, peanuts can also play a role in strengthening the spleen and stomach, and can improve symptoms such as loss of appetite and indigestion caused by weak spleen and stomach. At the same time, eating peanuts in moderation can provide a sense of fullness, help control appetite, and assist in weight management.

[0053] Preparation of peanut sample solution:

[0054] Peanuts (purchased from Gansu Weishuiyuan Pharmaceutical Technology Co., Ltd.) were washed, cut into small pieces, and homogenized. A 100 g sample of homogenized peanuts was centrifuged at 8000 rpm for 10 min to collect the supernatant. The sample solution was filtered through a 0.22 μm aqueous filter and stored at 4°C. A 10-fold dilution was performed before extraction.

[0055] The peanut sample solution was extracted using the method described in Example 2, wherein the amount of F-COF@Fe3O4 material used was 7 mg. The extract was tested by HPLC with a sample load of 20 μL.

[0056] After testing, the peanut sample solution did not contain aflatoxin and its precursors, and verification using a C18 extraction column also proved that the peanut sample did not contain aflatoxin and its precursors.

[0057] Then, aflatoxin and its precursor standard samples were added to the peanut sample solution, and the spiked concentrations were set to 10, 50, and 100 μg / L. The samples were detected using F-COF@Fe3O4 and C18 extraction columns, respectively. The test results are shown in Tables 3 and 4 below.

[0058] Table 3 Detection of fenthion in peanut samples

[0059]

[0060] Table 4 Detection of fenitrothion in peanut samples

[0061]

[0062] As shown in Tables 3 and 4, the reliability of extracting aflatoxins and their precursors from actual samples (peanuts) using the magnetic organic covalent framework material prepared by the present invention is higher than that of the C18 extraction column commonly used in the prior art, and has good application prospects.

[0063] In summary, the F-COF@Fe3O4 material prepared in the present invention can simultaneously achieve efficient extraction of multiple aflatoxins and their precursors, has strong matrix anti-interference ability, and excellent enrichment and purification performance. Its preparation method is simple, the cost is low, and it has broad application prospects.

[0064] The descriptions and practices disclosed in this invention are easy to understand and comprehend for those skilled in the art, and modifications and refinements may be made without departing from the principles of the invention. Therefore, modifications and improvements made without departing from the spirit of the invention should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a magnetic organic covalent framework material, characterized in that: The steps include: Step 1: Fe3O4 nanoparticles, 4,4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,3,5,6-tetrafluorobenzaldehyde, 1,2-dichlorobenzene, and n-butanol were mixed, and then the mixture was ultrasonically treated for 5 minutes, 6M acetic acid was added, and the mixture was sealed in a reactor and reacted at 100-120°C for 24-48 hours; Step 2: Obtain a reddish-brown precipitate by filtration, and then wash it with tetrahydrofuran (THF) and anhydrous ethanol respectively; Step 3: After vacuum drying in an oven at 60°C, a reddish-brown magnetic organic covalent framework material, namely F-COF@Fe3O4, was finally obtained.

2. The method for preparing a magnetic organic covalent framework material according to claim 1, characterized in that: In step 1, the usage ratio of Fe3O4 nanoparticles, 4,4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 2,3,5,6-tetrafluorobenzaldehyde and 1,2-dichlorobenzene, n-butanol and 6M acetic acid is 350-450 mg: 150-200 mg: 150-200 mg: 15-20 mL: 15-20 mL: 1.5-2.2 mL, wherein the usage ratio of 4,4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 2,3,5,6-tetrafluorobenzaldehyde is not zero.

3. The method for preparing a magnetic organic covalent framework material according to claim 1, characterized in that: In step 1, the reaction was carried out in a reactor at 120° C. for 24 h.

4. The method for preparing a magnetic organic covalent framework material according to claim 1, characterized in that: In step 1, the preparation method of Fe3O4 nanoparticles is as follows: The iron standard solution was added dropwise to the NaOH solution, stirred for reaction, cooled to room temperature after the reaction was completed, and then sodium citrate solution was added dropwise, mechanically stirred, and the product was magnetically separated, washed, and dried to obtain Fe3O4 nanoparticles.

5. The method for preparing a magnetic organic covalent framework material according to claim 4, characterized in that: The usage ratio of the iron standard solution, the NaOH solution and the sodium citrate solution is 20-30:240-260:80-120.

6. The method for preparing a magnetic organic covalent framework material according to claim 4, characterized in that: The formula of the iron standard solution is: 2.8g FeSO4·7H2O, 5.2g FeCl3·6H2O, and 0.85mL concentrated hydrochloric acid.

7. The method for preparing a magnetic organic covalent framework material according to claim 4, characterized in that: The stirring reaction conditions are selected from: stirring the reaction at 75-85° C. for 0.8-1.2 h.

8. The magnetic organic covalent framework material F-COF@Fe3O4 obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the magnetic organic covalent framework material F-COF@Fe3O4 according to claim 8 in the extraction and enrichment of aflatoxins and their precursors in peanuts.

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