A carbon nanotube monolithic column, its preparation method and application

Abstract

The present invention discloses a carbon nanotube monolithic column, a preparation method thereof and an application thereof, belonging to the technical field of solid-phase extraction materials. The preparation method comprises the following steps: carrying out a polymerization reaction on carbon nanotubes and a polymerization solution in the column cavity of a solid-phase extraction column, and then removing a second solvent in the polymerization solution; the components of the polymerization solution include a first monomer, a second monomer, a first solvent, a second solvent and an initiator; wherein, the first monomer is styrene, the second monomer is divinylbenzene, the first solvent is toluene, the second solvent is dodecanol, and the initiator includes azobisisobutyronitrile. The carbon nanotube monolithic column prepared by the above preparation method has the advantages of low cost, low column back pressure, high flow rate, high efficiency, etc., and can be used for screening pesticides, such as fluazinam and unknown metabolites of fluazinam.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-phase extraction materials, and more particularly, to a carbon nanotube monolithic column, a preparation method thereof, and an application thereof. Background Art

[0002] There is a wide variety of pesticides with different physical and chemical properties, and there are multiple pesticide residues in agricultural products. Synchronous screening and analysis of multiple categories of pesticides are crucial for ensuring food safety. Modern precision instrument technologies such as mass spectrometry provide a strong technical foundation for high-throughput screening of risk factors in agricultural products. Before instrumental analysis, the sample purification step is essential because matrix interferents such as pigments, polysaccharides, and oils in agricultural products will seriously affect the sensitivity, accuracy, and precision of detection and analysis.

[0003] Solid-phase extraction technology is one of the most common sample purification technologies. Currently, there are a wide variety of solid-phase extraction materials, which can be divided into monolithic columns and packed columns according to their different preparation methods. However, the types of current monolithic columns are still relatively limited compared to packed columns, and there are limitations such as low purification efficiency and high cost.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] One of the purposes of the present invention is to provide a preparation method of a carbon nanotube monolithic column, which is simple and can prepare a carbon nanotube monolithic column with advantages such as low cost, low column back pressure, fast flow rate, and high efficiency.

[0006] Another purpose of the present invention is to provide a carbon nanotube monolithic column prepared by the above preparation method.

[0007] A third purpose of the present invention is to provide an application of the above carbon nanotube monolithic column.

[0008] The present application can be implemented as follows:

[0009] In a first aspect, the present application provides a preparation method of a carbon nanotube monolithic column, including the following steps: performing a polymerization reaction on carbon nanotubes and a polymerization solution in the column cavity of a solid-phase extraction column, and then removing the second solvent in the polymerization solution;

[0010] The components of the polymerization solution include a first monomer, a second monomer, a first solvent, a second solvent, and an initiator; wherein, the first monomer is styrene, the second monomer is divinylbenzene, the first solvent is toluene, the second solvent is dodecanol, and the initiator includes azobisisobutyronitrile.

[0011] In an alternative embodiment, the polymerization reaction is carried out at 75 - 85 °C for 20 - 28 h.

[0012] In an alternative embodiment, in the polymerization solution, the dosage ratios of the first monomer, the second monomer, the first solvent, the second solvent, and the initiator are successively 1.4 - 1.8 mL : 2.2 - 2.6 mL : 1.6 - 2 mL : 4 - 4.5 mL : 0.08 - 0.12 g.

[0013] In an alternative embodiment, 0.2 g of carbon nanotubes is used corresponding to every 1.4 - 1.8 mL of the first monomer.

[0014] In an alternative embodiment, the carbon nanotubes include at least one of multi - walled carbon nanotubes, single - walled carbon nanotubes, amino - functionalized multi - walled carbon nanotubes, and carboxylated carbon nanotubes.

[0015] In a second aspect, the present application provides a carbon nanotube monolithic column prepared by the preparation method of any one of the foregoing embodiments.

[0016] In a third aspect, the present application provides the application of the carbon nanotube monolithic column of the foregoing embodiment, and the carbon nanotube monolithic column is used for screening pesticides.

[0017] In an alternative embodiment, the carbon nanotube monolithic column is used for screening fluazinam and unknown metabolites of fluazinam.

[0018] In an alternative embodiment, the unknown metabolites of fluazinam include at least one of mercapto - fluazinam, hydroxy - fluazinam, and amino - fluazinam;

[0019] Among them, the chemical structural formulas of mercapto - fluazinam, hydroxy - fluazinam, and amino - fluazinam are successively:

[0020] and

[0021] In an alternative embodiment, the substance to be screened is agricultural products.

[0022] In an alternative embodiment, the agricultural products are fruits and / or vegetables.

[0023] In an alternative embodiment, the screening includes: flowing a sample to be screened prepared from the substance to be screened through the carbon nanotube monolithic column, and collecting the outflowing liquid for subsequent detection.

[0024] In an alternative embodiment, the sample to be screened flows through the carbon nanotube monolithic column at a flow rate of 0.45 - 0.55 mL / min.

[0025] In an alternative embodiment, after the sample to be screened flows through the carbon nanotube monolithic column, it further includes: eluting the carbon nanotube monolithic column with an eluent, collecting the eluted eluent, and combining the outflowing liquid and the eluent for subsequent detection.

[0026] In an alternative embodiment, the eluent is a mixed solution of toluene and acetonitrile.

[0027] The beneficial effects of this application include:

[0028] Through the preparation method provided by this application, the first monomer and the second monomer in the polymerization solution can undergo a polymerization reaction under the initiation of an initiator. Among them, divinylbenzene contains two double bonds, which can endow the polymer after polymerization with a three-dimensional porous structure. When the second solvent is removed, the positions originally occupied by the second solvent form micropores.

[0029] The carbon nanotube monolithic column prepared by this application has both a macroporous framework and a small microporous structure, and has the characteristics of low column back pressure, strong permeability, fast flow rate, and high efficiency. Moreover, during the screening process of the analyte to be screened, no pressurization operation is required by a mechanical pump or the like, and the operation is simple and convenient. This carbon nanotube monolithic column can be used for screening pesticides and can effectively screen out fluazinam and unknown metabolites of fluazinam. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0031] Figure 1 It is a physical diagram of the carbon nanotube monolithic column prepared in Example 1 of this application;

[0032] Figure 2 It is a high-resolution tandem mass spectrum of fluazinam in the test example of this application;

[0033] Figure 3 It is a high-resolution tandem mass spectrum of mercaptofluazinam in the test example of this application;

[0034] Figure 4 It is a high-resolution tandem mass spectrum of hydroxyfluazinam in the test example of this application;

[0035] Figure 5 It is a high-resolution tandem mass spectrum of amino fluazinam in the test example of this application. Detailed Embodiments

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0037] The carbon nanotube monolithic column provided by the present application, its preparation method and application will be specifically described below.

[0038] The present application provides a method for preparing a carbon nanotube monolithic column, which includes the following steps: carrying out a polymerization reaction between carbon nanotubes and a polymerization solution in the column cavity of a solid-phase extraction column, and then removing the second solvent in the polymerization solution.

[0039] The above-mentioned carbon nanotubes may include at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, amino-functionalized multi-walled carbon nanotubes, and carboxyl-functionalized carbon nanotubes.

[0040] The components of the polymerization solution include a first monomer, a second monomer, a first solvent, a second solvent, and an initiator.

[0041] Among them, the first monomer is styrene, the second monomer is divinylbenzene, the first solvent is toluene, the second solvent is dodecanol, and the initiator includes azobisisobutyronitrile (AIBN).

[0042] The above-mentioned first solvent can effectively dissolve styrene and divinylbenzene, and the second solvent, as a poor solvent, acts similar to a pore-forming agent.

[0043] Under the initiation of the initiator, the first monomer and the second monomer can undergo a polymerization reaction. Among them, divinylbenzene contains two double bonds, which can make the polymer after polymerization have a three-dimensional porous structure. When the second solvent is removed, the positions originally occupied by the second solvent form micropores.

[0044] That is to say, the carbon nanotube monolithic column prepared in the present application has both a macroporous framework and a small microporous structure, and has the characteristics of low column back pressure, strong permeability, fast flow rate, and high efficiency. Moreover, during the screening process of the substance to be screened, no pressurization operation is required by a mechanical pump or the like, and the operation is simple and convenient.

[0045] As a reference, the polymerization reaction can be carried out at 75 - 85 °C (such as 75 °C, 76 °C, 77 °C, 78 °C, 79 °C, 80 °C, 81 °C, 82 °C, 83 °C, 84 °C or 85 °C, etc.) for 20 - 28 h (such as 20 h, 21 h, 22 h, 23 h, 24 h, 25 h, 26 h, 27 h or 28 h, etc.).

[0046] In some specific embodiments, the polymerization reaction is carried out at 80 °C for 24 h.

[0047] It should be noted that the above polymerization reaction can adopt the traditional free radical polymerization method or the living / controlled radical polymerization method, etc.

[0048] As a reference ground, in the above polymerization solution, the dosage ratios of the first monomer, the second monomer, the first solvent, the second solvent, and the initiator may be 1.4 - 1.8 mL (such as 1.4 mL, 1.5 mL, 1.6 mL, 1.7 mL, or 1.8 mL, etc.): 2.2 - 2.6 mL (such as 2.2 mL, 2.3 mL, 2.4 mL, 2.5 mL, or 2.6 mL, etc.): 1.6 - 2 mL (such as 1.6 mL, 1.7 mL, 1.8 mL, 1.9 mL, or 2 mL, etc.): 4 - 4.5 mL (such as 4 mL, 4.1 mL, 4.2 mL, 4.3 mL, 4.4 mL, or 4.5 mL, etc.): 0.08 - 0.12 g (such as 0.08 g, 0.09 g, 0.1 g, 0.11 g, or 0.12 g, etc.).

[0049] For every 1.4 - 1.8 mL of the first monomer, 0.2 g of carbon nanotubes can be correspondingly used. In other words, the dosage ratio of carbon nanotubes to the first monomer can be 0.2 g:1.4 mL, 0.2 g:1.5 mL, 0.2 g:1.6 mL, 0.2 g:1.7 mL, or 0.2 g:1.8 mL, etc.

[0050] In some specific embodiments, the polymerization solution is obtained by mixing 1.6 mL of styrene, 2.4 mL of divinylbenzene, 1.8 mL of toluene, 4.2 mL of dodecanol, and 0.1 g of azobisisobutyronitrile. The amount of carbon nanotubes used correspondingly is 0.2 g.

[0051] In this application, it is preferred to first add carbon nanotubes into the polymerization solution and ultrasonicate (such as for 30 min) to make the carbon nanotubes uniformly dispersed in the polymerization solution, obtaining a black mixed dispersion. Subsequently, add the mixed dispersion into the column cavity of the solid-phase extraction column, seal both ends of the solid-phase extraction column, so that the mixed dispersion undergoes in-situ polymerization in the column cavity of the solid-phase extraction column, and adheres to the column wall of the solid-phase extraction column during the polymerization swelling process to form the initial column of the monolithic column. Subsequently, rinse the initial column with toluene and acetone to remove both the unreacted residues and the second solvent, thereby obtaining the required monolithic column.

[0052] The above process avoids the problem of the complex packing process existing in the packed column, and the shape of the monolithic column material can fit different molds, including pipette tips, capillaries, needle filters, syringes, etc., with strong applicability.

[0053] Correspondingly, this application provides a carbon nanotube monolithic column, which is prepared by the above preparation method.

[0054] The obtained carbon nanotube monolithic column has the advantages of low cost, low column back pressure, fast flow rate, high efficiency, etc., and can be used for screening pesticides, such as fluazinam and unknown metabolites of fluazinam.

[0055] In addition, the present application also provides the application of the above carbon nanotube monolithic column, such as using it for screening pesticides in agricultural products.

[0056] For reference, the carbon nanotube monolithic column provided by the present application can be used for screening fluazinam and unknown metabolites of fluazinam.

[0057] Among them, the unknown metabolites of fluazinam include at least one of mercaptofluazinam, hydroxyfluazinam, and amino fluazinam; the chemical structural formulas of mercaptofluazinam, hydroxyfluazinam, and amino fluazinam are as follows:

[0058] and

[0059] The above substances to be screened can be agricultural products, specifically fruits and / or vegetables.

[0060] In the present application, the screening includes: flowing a sample to be screened prepared from the substance to be screened through the carbon nanotube monolithic column, and collecting the outflowing liquid for subsequent detection.

[0061] During this process, the carbon nanotube monolithic column can adsorb interfering substances in the sample to be screened.

[0062] Exemplarily, the above sample to be screened can be obtained in the following manner:

[0063] Accurately weigh 10.0 g of the substance to be screened into a 50 mL centrifuge tube, add 15 mL of 1% acetonitrile in acetic acid and the QuEChERS extraction package P-QuEChERS-AOAC1202, shake vigorously for 1 min, vortex for 1 min, centrifuge at 8000 rpm for 2 min, and take the upper clear liquid (such as 5 mL) as the sample to be screened.

[0064] For reference, the sample to be screened flows through the carbon nanotube monolithic column at a flow rate of 0.45 - 0.55 mL / min (preferably 0.5 mL / min).

[0065] After the sample to be screened flows through the carbon nanotube monolithic column, it further includes: eluting the carbon nanotube monolithic column with an eluent, collecting the eluted liquid, and combining the outflowing liquid and the eluted liquid for subsequent detection.

[0066] Among them, the eluent can be a mixed solution obtained by mixing toluene and acetonitrile in a volume ratio of 1:1.

[0067] This process can complete the desorption process of pesticide residues.

[0068] Furthermore, the combined solution of the outflowing liquid and the eluted liquid is rotary evaporated to dryness, redissolved with acetonitrile (such as 2 mL) and filtered through a membrane (such as 0.2 μm), and high performance liquid chromatography or gas chromatography is used to detect and analyze the pesticide residues in the desorbed solution.

[0069] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0070] Embodiment 1

[0071] This embodiment provides an integrated carbon nanotube column, as Figure 1 shown, which is prepared by the following method:

[0072] Step (1): Mix 1.6 mL of styrene, 2.4 mL of divinylbenzene, 1.8 mL of toluene, 4.2 mL of dodecanol and 0.1 g of azobisisobutyronitrile (AIBN) uniformly to obtain a polymerization solution.

[0073] Step (2): Weigh 0.2 g of multi-walled carbon nanotubes and add them to the polymerization solution, and ultrasonicate for 30 min to uniformly disperse the multi-walled carbon nanotubes in the polymerization solution, and prepare a black mixed dispersion.

[0074] Step (3): Take a certain amount of the above mixed dispersion and add it to the column cavity of an empty solid-phase extraction column, seal both ends of the solid-phase extraction column, and heat it in a water bath at 80 °C for 24 h to in-situ polymerize the mixed dispersion in the column cavity of the solid-phase extraction column.

[0075] Step (4): After the polymerization reaction is completed, rinse the integrated carbon nanotube column with toluene and acetone in sequence to remove unreacted residues, and obtain the integrated carbon nanotube column.

[0076] Embodiment 2

[0077] This embodiment provides an integrated carbon nanotube column, which is prepared by the following method:

[0078] Step (1): Mix 1.4 mL of styrene, 2.2 mL of divinylbenzene, 1.6 mL of toluene, 4 mL of dodecanol and 0.08 g of azobisisobutyronitrile (AIBN) uniformly to obtain a polymerization solution.

[0079] Step (2): Weigh 0.2 g of multi-walled carbon nanotubes and add them to the polymerization solution, and ultrasonicate for 28 min to uniformly disperse the multi-walled carbon nanotubes in the polymerization solution, and prepare a black mixed dispersion.

[0080] Step (3): Take a certain amount of the above mixed dispersion and add it to the column cavity of an empty solid-phase extraction column, seal both ends of the solid-phase extraction column, and heat it in a water bath at 75 °C for 28 h to in-situ polymerize the mixed dispersion in the column cavity of the solid-phase extraction column.

[0081] Step (4): After the polymerization reaction is completed, rinse the integrated carbon nanotube column with toluene and acetone in sequence to remove unreacted residues, and obtain the integrated carbon nanotube column.

[0082] Example 3

[0083] This example provides an integrated carbon nanotube column, which is prepared by the following method:

[0084] Step (1): Mix 1.8 mL of styrene, 2.6 mL of divinylbenzene, 2 mL of toluene, 4.5 mL of dodecanol, and 0.12 g of azobisisobutyronitrile (AIBN) evenly to obtain a polymerization solution.

[0085] Step (2): Weigh 0.2 g of multi-walled carbon nanotubes and add them to the polymerization solution. Ultrasonic for 32 min to make the multi-walled carbon nanotubes evenly dispersed in the polymerization solution, and prepare a black mixed dispersion.

[0086] Step (3): Take a certain amount of the above mixed dispersion and add it to the column cavity of an empty solid-phase extraction column. Seal both ends of the solid-phase extraction column and heat it in a water bath at 85 °C for 20 h to in-situ polymerize the mixed dispersion in the column cavity of the solid-phase extraction column.

[0087] Step (4): After the polymerization reaction is completed, rinse the integrated carbon nanotube column with toluene and acetone in sequence to remove unreacted residues, and obtain the integrated carbon nanotube column.

[0088] Example 4

[0089] This example provides an application of the integrated carbon nanotube column, which is as follows:

[0090] Accurately weigh 10.0 g of the analyte to be screened into a 50 mL centrifuge tube, add 15 mL of 1% acetonitrile in acetic acid and the QuEChERS extraction kit P-QuEChERS-AOAC1202, shake vigorously for 1 min, vortex for 1 min, centrifuge at 8000 rpm for 2 min, take 5 mL of the upper clear liquid and flow it through the integrated carbon nanotube column provided by any one of Examples 1-3 at a rate of 0.5 mL / min, collect the outflowing liquid, and take another 10 mL of toluene-acetonitrile (1 / 1, v / v) as the eluent and flow it through the integrated column, collect the eluted liquid. Combine the above outflowing liquid and eluted liquid, rotary evaporate and concentrate to dryness, re-dissolve with 2 mL of acetonitrile, filter through a membrane (0.2 μm), and use ultra-high performance liquid chromatography-high resolution mass spectrometry to screen and identify fluazinam and its unknown metabolites.

[0091] Test Example

[0092] Taking the integrated carbon nanotube column provided in Example 1 as an example, according to the application method provided in Example 4, fluazinam and its metabolites are used as the analytes to be screened.

[0093] The detection conditions of ultra-high performance liquid chromatography-high resolution mass spectrometry screening are as follows:

[0094] Chromatographic column: Agilent XDB C18 (2.1 mm × 150 mm, 3.5 μm); Mobile phase: 5 mmol ammonium formate aqueous solution (A), 5 mmol ammonium formate methanol solution (B).

[0095] Elution gradient: 0.00 min - 1.00 min, 5.0% B; 1.01 min - 2.00 min, 5.0% B - 60.0% B; 2.01 min - 3.00 min, 60.0% B - 70.0% B; 3.01 min - 9.00 min, 70.0% B - 95.0% B; 9.01 min - 12.00 min, 95.0%; 12.01 min - 14.00 min, 5.0% B; 14.01 min, stop.

[0096] Flow rate: 0.4 mL / min; Full scan mass-to-charge ratio range: 80 - 1000; Full scan mass spectrometry resolution: 70000; MS / MS scan resolution: 17500; Ion spray voltage: 3.5 kV; Capillary temperature: 300 °C; Auxiliary gas flow rate: 1.0 L / min.

[0097] Through structural analysis, fluazinam and its three new unknown metabolites were identified as mercaptofluazinam, hydroxyfluazinam, and aminofluazinam. The high-resolution MS / MS spectra of fluazinam, mercaptofluazinam, hydroxyfluazinam, and aminofluazinam are as Figures 2 to 4 shown.

[0098] The m / z corresponding to fluazinam is Figure 2 462.944 in 13 H 3 Cl 2 F 6 N 4 O 4 - ; The m / z corresponding to mercaptofluazinam is Figure 3 460.9547 in 13 H 4 ClF 6 N 4 O 4 S - ; The m / z corresponding to hydroxyfluazinam is Figure 4 444.9778 in 13 H 4 ClF 6 N 4 O 5 - ; The m / z corresponding to aminofluazinam is Figure 5 432.9690 in 13 H5 Cl 2 F 6 N 4 O 2 - 。

[0099] In summary, the preparation method provided by this application can prepare a carbon nanotube monolithic column with the advantages of low cost, low column back pressure, high flow rate, high efficiency, etc. It can be used for screening pesticides and can effectively screen out fluazinam and unknown metabolites of fluazinam.

[0100] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application of a carbon nanotube monolithic column, characterized in that, the carbon nanotube monolithic column is used for screening fluazinam and unknown metabolites of fluazinam; the unknown metabolites of fluazinam include at least one of mercaptofluazinam, hydroxyfluazinam and amino fluazinam; the chemical structural formulas of mercaptofluazinam, hydroxyfluazinam and amino fluazinam are as follows: , and ; The preparation of the carbon nanotube monolithic column includes the following steps: polymerize carbon nanotubes and a polymerization solution in the column cavity of a solid-phase extraction column, and then remove the second solvent in the polymerization solution; the components of the polymerization solution include a first monomer, a second monomer, a first solvent, a second solvent and an initiator; wherein, the first monomer is styrene, the second monomer is divinylbenzene, the first solvent is toluene, the second solvent is dodecanol, and the initiator includes azobisisobutyronitrile; the polymerization reaction is carried out at 75-85 °C for 20-28 h; in the polymerization solution, the dosage ratios of the first monomer, the second monomer, the first solvent, the second solvent and the initiator are 1.4-1.8 mL: 2.2-2.6 mL: 1.6-2 mL: 4-4.5 mL: 0.08-0.12 g in sequence; 0.2 g of the carbon nanotubes are used for every 1.4-1.8 mL of the first monomer.

2. The application according to claim 1, characterized in that, the carbon nanotubes include at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, amino-functionalized multi-walled carbon nanotubes and carboxylated carbon nanotubes.

3. The application according to claim 1, characterized in that, the screening includes: flowing a screening sample prepared from a substance to be screened through the carbon nanotube monolithic column, and collecting the outflowing liquid for subsequent detection.

4. The application according to claim 3, characterized in that, the screening sample flows through the carbon nanotube monolithic column at a flow rate of 0.45-0.55 mL / min.

5. The application according to claim 3 or 4, characterized in that, after the screening sample flows through the carbon nanotube monolithic column, it further includes: eluting the carbon nanotube monolithic column with an eluent, collecting the eluted eluent, and combining the outflowing liquid and the eluent for subsequent detection.

6. The application according to claim 5, characterized in that, the eluent is a mixed solution of toluene and acetonitrile.

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