Preparation method and application of magnetic organic covalent framework material for extracting pyrethroid pesticide in peanuts

Abstract

The invention relates to the technical field of harmful substance detection, in particular to a preparation method and application of a magnetic organic covalent framework material for extracting pyrethroid pesticide in peanuts, and the preparation method comprises the following steps: step 1, dropwise adding an iron standard solution into a NaOH solution, stirring to react, cooling to room temperature after the reaction is finished, then dropwise adding a sodium citrate solution, mechanically stirring, and filtering to obtain a filtrate; magnetically separating a product, washing and drying to obtain Fe3O4 nanoparticles; step 2, mixing the Fe3O4 nanoparticles, DVA, TA, TAPT and acetonitrile, performing ultrasonic treatment, then adding acetic acid, oscillating the mixture, and then stirring and refluxing; the product is washed and dried, and COF coated Fe3O4 is obtained; step 3, uniformly dispersing COF coated Fe3O4 in an acrylamide solution, and then irradiating by a xenon lamp; and washing and drying the product to obtain the magnetic organic covalent framework material PAM-COF coated Fe3O4. The PAM-COF coated Fe3O4 material prepared by the preparation method disclosed by the invention can realize efficient extraction of various pyrethroid pesticides at the same time, and has relatively strong matrix anti-interference capability and excellent enrichment and purification performance.

Description

Technical Field

[0001] The invention relates to the technical field of harmful substance detection, and in particular to a preparation method and application of a magnetic organic covalent skeleton material for extracting pyrethroid pesticides in peanuts. Background Art

[0002] Pyrethroids are a class of synthetic pesticides that are similar in structure to natural pyrethroids of the genus Chrysanthemum. They produce neurotoxic effects by regulating the sodium channels of insect nerve axons. Compared with natural pyrethroids, pyrethroids have higher photostability and higher selectivity for target products. Compared with other insecticides such as organophosphorus and organochlorine, pyrethroids have broad-spectrum resistance to pests and are less toxic to humans. They are now widely used. However, long-term exposure to pyrethroids in humans can lead to chronic diseases, showing carcinogenicity and high toxicity. The matrix in actual samples is complex, and contaminants are usually present in low doses. Therefore, it is necessary to find a highly sensitive and selective method to detect pyrethroid pesticides in food.

[0003] Many sample pretreatment methods have been reported for the analysis of pyrethroid pesticides, such as solid phase extraction (SPE), liquid-liquid extraction (LLE), solid phase microextraction (SPME), and QuEChERS. However, the above methods are relatively cumbersome, resulting in a slow analysis process for pyrethroid pesticides. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a preparation method and application of a magnetic organic covalent framework material for extracting pyrethroid pesticides in peanuts. The prepared magnetic organic covalent framework material has excellent extraction and enrichment effects on pyrethroid pesticides.

[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 for extracting pyrethroid pesticides from peanuts comprises the following steps:

[0007] Step 1, adding the iron standard solution dropwise to the NaOH solution, stirring the reaction, cooling to room temperature after the reaction is completed, then adding the sodium citrate solution dropwise, mechanically stirring, magnetically separating the product, washing, and drying to obtain Fe3O4 nanoparticles;

[0008] Step 2, Fe3O4 nanoparticles, DVA, TA, TAPT and acetonitrile are mixed, ultrasonicated, and then acetic acid is added, and the mixture is shaken and then stirred and refluxed; the product is washed and dried to obtain COF@Fe3O4;

[0009] Step 3: evenly disperse COF@Fe3O4 in an acrylamide solution, and then irradiate with a xenon lamp; wash and dry the product to obtain a magnetic organic covalent framework material PAM-COF@Fe3O4.

[0010] Preferably, in step 1, the dosage ratio of the iron standard solution, the NaOH solution and the sodium citrate solution is 20-30:240-260:80-120, preferably 25:250:100 (mL:mL:mL).

[0011] Preferably, in step 1, the formula of the iron standard solution is: 2.8g FeSO4·7H2O, 5.2g FeCl3·6H2O, 0.85mL concentrated hydrochloric acid; in practical applications, the dosage of each component can be increased or decreased synchronously according to the formula. The reaction is stirred at 75-85°C for 0.8-1.2h, preferably at 80°C for 1h.

[0012] Preferably, in step 2, the dosage ratio of Fe3O4 nanoparticles, DVA, TA, TAPT, acetonitrile and acetic acid is 350-450:65-70:45-50:165-185:25-35:1.5-2.2, preferably 400:68:48:170:30:2 (mg:mg:mg:mg:mL:mL).

[0013] Preferably, in step 2, stirring and reflux are performed at 55-60° C. for 24-48 hours, preferably at 60° C. for 48 hours; and the washing is performed by washing the reaction product with THF and ethanol in sequence.

[0014] Preferably, in step 3, the ratio of COF@Fe3O4 to acrylamide solution is 350-450 mg:5-15 mL, preferably 400:10 (mg:mL); the concentration of acrylamide solution is one of 200 mg / mL, 250 mg / mL, and 300 mg / mL, preferably 250 mg / mL.

[0015] Preferably, in step 3, the xenon lamp irradiation condition is 1-3 hours, preferably 2 hours; and the washing is washing the reaction product with ethanol, distilled water and ethanol in sequence.

[0016] The present invention also provides an application of the magnetic organic covalent framework material PAM-COF@Fe3O4 obtained by the above-mentioned preparation method in the extraction and enrichment of pyrethroid pesticides in peanuts.

[0017] Preferably, the pyrethroid pesticide is selected from cypermethrin, fenvalerate, permethrin or bifenthrin.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The PAM-COF@Fe3O4 material prepared by the present invention can simultaneously realize the efficient extraction of multiple pyrethroid pesticides, has strong matrix anti-interference ability, and excellent enrichment and purification performance. The preparation method thereof is simple, the cost is low, and it has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a scanning electron microscope image of the PAM-COF@Fe3O4 material of the present invention;

[0021] Figure 2 This is a transmission electron microscope image of the PAM-COF@Fe3O4 material of the present invention;

[0022] Figure 3 This is the contact angle diagram of the PAM-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, thereby making a clearer definition of the protection scope of the present invention. The embodiments described in the present invention are only a part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are 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] 2,4,6-Tris(4-aminophenyl)-1,3,5-triazine (TAPT), 2,5-divinyl-1,4-benzaldehyde (DVA), organic covalent framework (COF), polyacrylamide (PAM).

[0026] Unless otherwise stated, other materials used in the present invention can be obtained through commercial channels. Other terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art.

[0027] Example 1

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

[0029] The AM monomer was dissolved in water at a concentration of 250 mg / mL, 400 mg of COF@Fe3O4 nanoparticles were added and dispersed in 10 mL of AM solution, and the polymerization was initiated by irradiation with a xenon lamp for 2 h.

[0030] The above COF@Fe3O4 is prepared by the following method:

[0031] 400 mg Fe3O4 nanoparticles, 68 mg DVA, 48 mg TA, 170 mg TAPT and 30 mL acetonitrile were added to a centrifuge tube and ultrasonicated for 1 min, 2 mL acetic acid (12 M) was added, and the mixture was vigorously shaken on a vortex mixer for 10 s, and then stirred and refluxed at 60 ° C for 48 h. The resulting precipitate was thoroughly washed with THF and ethanol, respectively, and vacuum dried at 80 ° C for 12 h to obtain COF@Fe3O4.

[0032] The above Fe3O4 nanoparticles are prepared by the following method:

[0033] 25 mL of iron standard solution (formula: 2.8 g FeSO4·7H2O, 5.2 g FeCl3·6H2O, 0.85 mL concentrated hydrochloric acid) was added dropwise to 250 mL of NaOH solution (0.5 mol / L), stirred at 80°C for 1 h, cooled to room temperature, and then 100 mL of sodium citrate solution (0.3 mol / L) was added dropwise, and mechanically stirred for 1 h. After magnetic separation, the mixture was washed with water until neutral, and freeze-dried for 24 h.

[0034] Figure 1 The SEM image of PAM-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 PAM-COF@Fe3O4.

[0035] Figure 2 This is a transmission electron microscope image of PAM-COF@Fe3O4 material. Figure 2 It can be seen that a core-shell structure is formed on the surface of Fe3O4, indicating the successful synthesis of PAM-COF@Fe3O4.

[0036] Figure 3 This is the contact angle diagram of PAM-COF@Fe3O4 material. Figure 3 It can be seen that the hydrophilicity of PAM-COF@Fe3O4 material is higher than that of COF@Fe3O4 material, indicating that hydrogel is successfully synthesized on the surface of COF@Fe3O4.

[0037] Example 2

[0038] Extraction test of pyrethroid pesticides:

[0039] 10 mg of PAM-COF@Fe3O4 material was added to 10 mL of 0.1 μg / mL sample solution (containing cypermethrin, cypermethrin, permethrin, and bifenthrin) and shaken at room temperature for 30 min. Then, the PAM-COF@Fe3O4 material was separated by a magnet and the supernatant was discarded. Then, the PAM-COF@Fe3O4 material was added to 3 mL of acetonitrile and ultrasonicated for 10 min to dissolve the pyrethroids in acetonitrile, and the PAM-COF@Fe3O4 material was separated by a magnet, and the solution was retained. Finally, the solution was filtered through a 0.22 μm membrane, and the peak area of ​​pyrethroids was determined by HPLC (injection volume of 20 μL), and the pyrethroid content was calculated according to the standard curve.

[0040] The detection conditions of HPLC are as follows:

[0041] C18 analytical column, specification 250mm×4.6mm, id, 5μm; mobile phase A: methanol, mobile phase B: water; isocratic elution: the volume ratio of methanol: water is 87:13; mobile phase flow rate: 1.0mL / min; column temperature: 30℃; injection volume: 20μL; UV detector, wavelength 225nm.

[0042] The above standard curve construction method is as follows:

[0043] Using acetonitrile as solvent, a pyrethroid concentration gradient was set, wherein the concentration gradients of the four pesticides were 0.5 μg / mL, 0.75 μg / mL, 1 μg / mL, 1.25 μg / mL, 1.5 μg / mL, 2 μg / mL, and 2.5 μg / mL. The peak areas of the above pyrethroid pesticides at each concentration were measured by HPLC, and a standard curve was constructed with the pyrethroid concentration as the abscissa and the peak area as the ordinate. As shown in Table 1 below:

[0044] Table 1

[0045]

[0046] As shown in Table 1, there is a linear relationship between the concentration and peak area of ​​the four pyrethroids. After fitting, the fitting formula between the concentration and peak area of ​​cypermethrin is: Y = 66203X-6153.6, R 2 =0.9916; the fitting formula between fenvalerate concentration and peak area is: Y=106131X-9272.7, R 2 =0.9967; the fitting formula between the concentration of permethrin and the peak area is: Y = 72073X-6536.1, R 2 =0.9951; the fitting formula between the concentration of bifenthrin and the peak area is: Y = 133442X-12488, R 2=0.9948.

[0047] It was determined that the peak area of ​​cypermethrin in the sample solution was 15377, the peak area of ​​fenvalerate was 26829, the peak area of ​​cypermethrin was 16122, and the peak area of ​​bifenthrin was 28811. Calculation according to the above standard curve showed that the concentrations of cypermethrin, fenvalerate, permethrin, and bifenthrin were 0.33 μg / mL, 0.34 μg / mL, 0.31 μg / mL, and 0.31 μg / mL, respectively. Compared with the sample solution prepared in advance, the recovery rates of cypermethrin, fenvalerate, permethrin, and bifenthrin were about 97.6%, 102.0%, 94.3%, and 92.8%, respectively.

[0048] Based on the above experiments, this example further studies the effect of the amount of extractant (PAM-COF@Fe3O4 material) on the recovery rate of four pyrethroid pesticides.

[0049] The test results are shown in Table 2:

[0050] Table 2

[0051]

[0052] It can be seen from Table 2 that when the dosage of PAM-COF@Fe3O4 material (extractant) is 10 mg, its extraction efficiency of pyrethroids in 10 mL sample is the highest. At the same time, the high recovery rate also shows that the PAM-COF@Fe3O4 material prepared by the present invention has an excellent pyrethroid extraction effect, and can extract low-dose pyrethroid pesticides in the sample, thereby achieving successful detection of pyrethroid pesticides.

[0053] Application Examples

[0054] Peanuts are a major source of edible oil, protein and other essential nutrients and are widely grown worldwide. As one of the leading peanut producers, China plays an important role in shaping the peanut production landscape. The nutritional components of peanuts include oil, protein, fiber, unsaturated fatty acids, vitamins and minerals. This example uses PAM-COF@Fe3O4 material to identify whether peanuts contain pyrethroid pesticides.

[0055] Preparation of peanut sample solution:

[0056] The peanuts were dried in an oven and crushed into powder. The baby cabbage was completely chopped for later use. 1 g of peanut powder was dissolved in 10 mL of a mixed solution of ethanol / water (70:30, v / v), shaken in a water bath for 2 h, centrifuged, and the supernatant was dried in an oven overnight, dissolved in 100 mL of deionized water, filtered through a 0.22 μm membrane, and used for HPLC analysis.

[0057] The Codonopsis pilosula sample solution was extracted using the method in Example 2, wherein the amount of PAM-COF@Fe3O4 material used was 10 mg. The extract was tested by HPLC, and the sample loading amount was 20 μL.

[0058] After testing, the peanut sample solution did not contain pyrethroids, and verification using a C18 extraction column also proved that the Codonopsis pilosula sample did not contain pyrethroids.

[0059] Then, pyrethroid 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 PAM-COF@Fe3O4 and C18 extraction columns, respectively. The test results are shown in Tables 3 and 4 below.

[0060] Table 3 Detection of cypermethrin in peanut samples

[0061]

[0062] Table 4 Detection of cypermethrin in Codonopsis samples

[0063]

[0064] Table 5 Detection of permethrin in Codonopsis samples

[0065]

[0066]

[0067] Table 6 Detection of bifenthrin in Codonopsis samples

[0068]

[0069] It can be seen from Tables 3 and 4 that the reliability of using the magnetic organic covalent framework material prepared by the present invention to extract pyrethroid pesticides in actual samples (peanuts) is higher than that of the C18 extraction column commonly used in the prior art, and has good application prospects.

[0070] In summary, the PAM-COF@Fe3O4 material prepared in the present invention can simultaneously achieve efficient extraction of multiple pyrethroid pesticides, 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.

[0071] The description and practice disclosed in the present invention are easy to think and understand for ordinary technicians in the technical field, and several improvements and modifications can be made without departing from the principles of the present invention. Therefore, modifications or improvements made without departing from the spirit of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts, characterized in that: The steps include: Step 1, adding the iron standard solution dropwise to the NaOH solution, stirring the reaction, cooling to room temperature after the reaction is completed, then adding the sodium citrate solution dropwise, mechanically stirring, magnetically separating the product, washing, and drying to obtain Fe3O4 nanoparticles; Step 2, Fe3O4 nanoparticles, DVA, TA, TAPT and acetonitrile are mixed, ultrasonicated, and then acetic acid is added, and the mixture is shaken and then stirred and refluxed; the product is washed and dried to obtain COF@Fe3O4; Step 3: evenly disperse COF@Fe3O4 in an acrylamide solution, and then irradiate with a xenon lamp; wash and dry the product to obtain a magnetic organic covalent framework material PAM-COF@Fe3O4.

2. The method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts according to claim 1, characterized in that: In step 1, the usage ratio of the iron standard solution, the NaOH solution and the sodium citrate solution is 20-30:240-260:80-120.

3. The method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts according to claim 1, characterized in that: In step 1, the formula of the iron standard solution is: 2.8 g FeSO4·7H2O, 5.2 g FeCl3·6H2O, 0.85 mL concentrated hydrochloric acid; stir the reaction at 75-85°C for 0.8-1.2 h.

4. The method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts according to claim 1, characterized in that: In step 2, the usage ratio of Fe3O4 nanoparticles, DVA, TA, TAPT, acetonitrile and acetic acid is 350-450 mg: 65-70 mg: 45-50 mg: 165-185 mg: 25-35 mL: 1.5-2.2 mL.

5. The method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts according to claim 1, characterized in that: In step 2, the reaction mixture is stirred and refluxed at 55-60° C. for 24-48 hours, and the reaction product is washed with THF and ethanol in sequence.

6. The method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts according to claim 1, characterized in that: In step 3, the ratio of COF@Fe3O4 to acrylamide solution is 350-450 mg:5-15 mL; the concentration of acrylamide solution is one of 200 mg / mL, 250 mg / mL, and 300 mg / mL.

7. The method for preparing a magnetic organic covalent framework material for extracting pyrethroid pesticides from peanuts according to claim 1, characterized in that: In step 3, the xenon lamp irradiation condition is 1-3 hours; and the washing is washing the reaction product with ethanol, distilled water and ethanol in sequence.

8. Use of the magnetic organic covalent framework material PAM-COF@Fe3O4 obtained by the preparation method according to any one of claims 1 to 7 in the extraction and enrichment of pyrethroid pesticides in peanuts.

9. The use according to claim 8, characterized in that: The pyrethroid pesticide is selected from cypermethrin, fenvalerate, permethrin or bifenthrin.

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