CN115554730A - Carbon nanotube monolithic column and preparation method and application thereof - Google Patents

Abstract

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

Description

A kind of monolithic column of carbon nanotubes and its preparation method and application

technical field

The invention relates to the technical field of solid phase extraction materials, in particular to a carbon nanotube monolithic column and its preparation method and application.

Background technique

There are a wide variety of pesticides with different physical and chemical properties, and there are many kinds of pesticide residues in agricultural products. Synchronous screening and analysis of multiple types of pesticides is critical to ensure food safety. Modern mass spectrometry and other sophisticated instrument technologies provide a strong technical basis for high-throughput screening of agricultural product risk factors. Before instrumental analysis, sample purification steps are essential, because matrix interferences such as pigments, polysaccharides, and oils in agricultural products will seriously affect the sensitivity, accuracy, and precision of detection and analysis.

Solid phase extraction is one of the most common sample cleanup techniques. At present, there are many kinds of solid phase extraction materials, which can be divided into monolithic columns and packed columns according to their different preparation methods. However, compared with packed columns, the types of monolithic columns are relatively limited at present, and there are limitations such as low purification efficiency and high cost.

In view of this, the present invention is proposed.

Contents of the invention

One of the purposes of the present invention is to provide a method for preparing a monolithic column of carbon nanotubes, which is simple and capable of preparing monolithic columns of carbon nanotubes with the advantages of low cost, low column back pressure, fast flow rate, and high efficiency.

The second object of the present invention is to provide a monolithic column of carbon nanotubes prepared by the above preparation method.

The third object of the present invention is to provide an application of the above monolithic column of carbon nanotubes.

This application can be implemented like this:

In the first aspect, the present application provides a method for preparing a monolithic column of carbon nanotubes, comprising the following steps: polymerizing carbon nanotubes and a polymerization solution in the column chamber of a solid-phase extraction column, and then removing the second carbon nanotube in the polymerization solution. solvent;

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, and the first solvent is Toluene, the second solvent is dodecyl alcohol, and the initiator includes azobisisobutyronitrile.

In an optional embodiment, the polymerization reaction is carried out at 75-85° C. for 20-28 hours.

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

In an optional embodiment, 0.2 g of carbon nanotubes is used for every 1.4-1.8 mL of the first monomer.

In an optional embodiment, the carbon nanotubes include at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, aminated multi-walled carbon nanotubes and carboxylated carbon nanotubes.

In a second aspect, the present application provides a monolithic column of carbon nanotubes, which is prepared by the preparation method in any one of the foregoing embodiments.

In a third aspect, the present application provides the application of the carbon nanotube monolithic column as in the aforementioned embodiment, and the carbon nanotube monolithic column is used for screening pesticides.

In an optional embodiment, the carbon nanotube monolithic column is used for screening fluazinam and unknown metabolites of fluazinam.

In an optional embodiment, the unknown metabolites of fluazinam include at least one of mercaptofluazinam, hydroxyfluazinam and aminofluazinam;

Among them, the chemical structural formulas of mercaptofluazinamine, hydroxyfluazinamine and aminofluazinamine are as follows:

及

and

In an optional embodiment, the object to be screened is an agricultural product.

In alternative embodiments, the agricultural products are fruits and/or vegetables.

In an optional embodiment, the screening includes: flowing the sample to be screened made from the substance to be screened through a carbon nanotube monolithic column, and collecting the effluent that flows out for subsequent detection.

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

In an optional embodiment, after the sample to be screened flows through the monolithic column of carbon nanotubes, it also includes: eluting the eluent from the monolithic column of carbon nanotubes, collecting the eluted eluate, and combining the effluents and eluent for subsequent detection.

In an optional embodiment, the eluent is a mixture of toluene and acetonitrile.

The beneficial effects of the application include:

Through the preparation method provided by this application, the first monomer and the second monomer in the polymerization liquid can undergo a polymerization reaction under the action of the initiator, wherein divinylbenzene contains two double bonds, which can make the polymerized Polymers have a three-dimensional porous structure. When the second solvent is removed, micropores are formed at the positions originally occupied by the second solvent.

The carbon nanotube integral column prepared by 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, in the process of screening the object to be screened, no mechanical pump or the like is required for pressurization operation, and the operation is simple and convenient. The carbon nanotube monolithic column can be used for screening pesticides, and can effectively screen out fluazinam and unknown metabolites of fluazinam.

Description of drawings

In order to illustrate the technical solutions of the embodiments of the present invention more clearly, the accompanying drawings 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 thus It should be regarded as a limitation on the scope, and those skilled in the art can also obtain other related drawings based on these drawings without creative work.

Fig. 1 is the physical picture of the carbon nanotube monolithic column prepared in Example 1 of the present application;

Fig. 2 is the high-resolution secondary mass spectrogram of fluazinam in the test example of the present application;

Fig. 3 is the high-resolution secondary mass spectrogram of mercaptofluazinam in the test example of the present application;

Fig. 4 is the high resolution secondary mass spectrogram of hydroxyfluazinam in the test example of the present application;

Fig. 5 is a high-resolution MS/MS spectrum of aminofluazinam in the test example of the present application.

detailed description

In order to make the purpose, 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 who do not indicate the specific conditions in the examples are carried out according to the conventional conditions or the conditions suggested by the manufacturer. The reagents or instruments used were not indicated by the manufacturer, and they were all conventional products that could be purchased from the market.

The carbon nanotube monolithic column provided in the present application and its preparation method and application are described in detail below.

The present application proposes a method for preparing a monolithic column of carbon nanotubes, which includes the following steps: polymerizing carbon nanotubes and a polymerization solution in a column chamber of a solid-phase extraction column, and then removing the second solvent in the polymerization solution.

The above-mentioned carbon nanotubes may include at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, aminated multi-walled carbon nanotubes, and carboxylated carbon nanotubes.

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 dodecyl alcohol, and the initiator includes azobisisobutyronitrile (AIBN).

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

The first monomer and the second monomer can undergo a polymerization reaction under the action of the initiator, wherein the divinylbenzene contains two double bonds, which can make the polymer after polymerization have a three-dimensional porous structure. When the second solvent is removed, micropores are formed at the positions originally occupied by the second solvent.

That is to say, the monolithic column of carbon nanotubes 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, in the process of screening the object to be screened, no mechanical pump or the like is required for pressurization operation, and the operation is simple and convenient.

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.) 20-28h (such as 20h, 21h, 22h, 23h, 24h, 25h, 26h, 27h or 28h, etc.).

In some specific embodiments, the polymerization reaction is carried out at 80° C. for 24 hours.

It should be noted that the above-mentioned polymerization reaction may adopt a traditional free radical polymerization method, or a living controllable free radical polymerization method and the like.

As a reference, in the above-mentioned polymerization liquid, the usage ratio of the first monomer, the second monomer, the first solvent, the second solvent and the initiator can be 1.4-1.8mL (such as 1.4mL, 1.5mL, 1.6mL, 1.7mL or 1.8mL, etc.): 2.2-2.6mL (such as 2.2mL, 2.3mL, 2.4mL, 2.5mL or 2.6mL, etc.): 1.6-2mL (such as 1.6mL, 1.7mL, 1.8mL, 1.9mL or 2mL, etc. ): 4-4.5mL (such as 4mL, 4.1mL, 4.2mL, 4.3mL, 4.4mL or 4.5mL, etc.): 0.08-0.12g (such as 0.08g, 0.09g, 0.1g, 0.11g or 0.12g, etc.).

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

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

In the present application, it is preferable to first add the carbon nanotubes into the polymerization solution, and ultrasonically (for example, 30 minutes) to uniformly disperse the carbon nanotubes in the polymerization solution to obtain a black mixed dispersion. Subsequently, the mixed dispersion is added to the column cavity of the solid phase extraction column, and the two ends of the solid phase extraction column are sealed, so that the mixed dispersion is polymerized in situ in the column cavity of the solid phase extraction column, and during the polymerization expansion process The initial column that adheres to the column wall of the solid phase extraction column to form a monolithic column. Subsequently, the initial column was washed with toluene and acetone to remove unreacted residues and the second solvent, thereby obtaining the desired monolithic column.

The above process avoids the problem of complex filling process in the packed column, and the shape of the overall column material can fit in different molds, including pipette tips, capillaries, needle filters, syringes, etc., and has strong applicability.

Correspondingly, the present application provides a monolithic column of carbon nanotubes, which is prepared by the above preparation method.

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.

In addition, the present application also provides the application of the carbon nanotube monolithic column, such as using it to screen pesticides in agricultural products.

As a reference, the carbon nanotube monolithic column provided by the present application can be used to screen fluazinam and unknown metabolites of fluazinam.

Among them, the unknown metabolites of fluazinam include at least one of mercaptofluazinamine, hydroxyfluazinamine and aminofluazinamine; the chemical structural formulas of mercaptofluazinamine, hydroxyfluazinamine and aminofluazinamine are as follows:

及

and

The aforementioned objects to be screened may be agricultural products, specifically fruits and/or vegetables.

In the present application, the screening includes: flowing the sample to be screened made from the substance to be screened through the monolithic column of carbon nanotubes, and collecting the effluent that flows out for subsequent detection.

During this process, the monolithic column of carbon nanotubes can adsorb the interfering substances in the sample to be screened.

Exemplarily, the above-mentioned samples to be screened can be obtained in the following ways:

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

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).

After the sample to be screened flows through the monolithic column of carbon nanotubes, it also includes: eluting the eluent from the monolithic column of carbon nanotubes, collecting the eluted eluent, and combining the effluent and eluent for subsequent use detection.

Wherein, the eluent may be a mixed solution obtained by mixing toluene-acetonitrile at a volume ratio of 1:1.

This process can complete the pesticide residue desorption process.

Further, the combined solution of the effluent and the eluate is concentrated to dryness by rotary evaporation, reconstituted with acetonitrile (such as 2 mL) and filtered through a membrane (such as 0.2 μm), and the desorption solution is desorbed by high performance liquid chromatography or gas chromatography. analysis of pesticide residues.

The characteristics and performance of the present invention will be described in further detail below in conjunction with the examples.

Example 1

This embodiment provides a carbon nanotube monolithic column, as shown in Figure 1, which is prepared in the following manner:

Step (1): 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) were uniformly mixed to obtain a polymerization solution.

Step (2): Weighing 0.2 g of multi-walled carbon nanotubes into the polymerization liquid, and ultrasonicating for 30 minutes, so that the multi-walled carbon nanotubes are uniformly dispersed in the polymerization liquid, and a black mixed dispersion liquid is prepared.

Step (3): Take a certain amount of the above-mentioned mixed dispersion liquid 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 hours to make the mixed dispersion liquid In situ polymerization in the column cavity of the solid phase extraction column.

Step (4): After the polymerization reaction is completed, wash the monolithic column of multi-walled carbon nanotubes with toluene and acetone in order to remove unreacted residues to obtain the monolithic column of carbon nanotubes.

Example 2

This embodiment provides a carbon nanotube monolithic column, which is prepared in the following manner:

Step (1): 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) were uniformly mixed to obtain a polymerization liquid.

Step (2): Weighing 0.2 g of multi-walled carbon nanotubes into the polymerization solution, and ultrasonicating for 28 minutes, so that the multi-walled carbon nanotubes are uniformly dispersed in the polymerization solution, and a black mixed dispersion is prepared.

Step (3): Take a certain amount of the above-mentioned mixed dispersion liquid 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 hours, so that the mixed dispersion liquid In situ polymerization in the column cavity of the solid phase extraction column.

Step (4): After the polymerization reaction is completed, wash the monolithic column of multi-walled carbon nanotubes with toluene and acetone in order to remove unreacted residues to obtain the monolithic column of carbon nanotubes.

Example 3

This embodiment provides a carbon nanotube monolithic column, which is prepared in the following manner:

Step (1): 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) were uniformly mixed to obtain a polymerization liquid.

Step (2): Weighing 0.2 g of multi-walled carbon nanotubes and adding them into the polymerization liquid, and ultrasonicating for 32 minutes, so that the multi-walled carbon nanotubes are uniformly dispersed in the polymerization liquid, and a black mixed dispersion liquid is prepared.

Step (3): Take a certain amount of the above-mentioned mixed dispersion liquid and add it to the column chamber 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 hours to make the mixed dispersion liquid In situ polymerization in the column cavity of the solid phase extraction column.

Step (4): After the polymerization reaction is completed, wash the monolithic column of multi-walled carbon nanotubes with toluene and acetone in order to remove unreacted residues to obtain the monolithic column of carbon nanotubes.

Example 4

This embodiment provides an application of a carbon nanotube monolithic column, specifically as follows:

Accurately weigh 10.0g of the substance to be screened in a 50mL centrifuge tube, add 15mL of 1% acetic acid acetonitrile and QuEChERS extraction package P-QuEChERS-AOAC1202, shake vigorously for 1min, vortex for 1min, centrifuge at 8000rpm/min for 2min, and take 5mL of the supernatant Flow through the monolithic column of carbon nanotubes provided by any of Examples 1-3 at 0.5mL/min, collect the effluent, and take 10mL of toluene-acetonitrile (1/1, v/v) as an eluent to flow through Monolithic column, collect the eluted eluent, combine the above effluent and eluent, concentrate to dryness by rotary evaporation, redissolve with 2mL acetonitrile, filter membrane (0.2μm), use ultra-high performance liquid chromatography-high resolution mass spectrometry The screen identified fluazinam and its unknown metabolites.

Test case

Taking the monolithic column of carbon nanotubes provided in Example 1 as an example, according to the application method provided in Example 4, fluazinam and its metabolites were used as the substances to be screened.

The detection conditions of ultra-high performance liquid chromatography-high resolution mass spectrometry sieve are as follows:

Chromatographic column: Agilent XDBC18 (2.1 mm×150 mm, 3.5 μm); mobile phase: 5 mmol ammonium formate aqueous solution (A), 5 mmol ammonium formate methanol solution (B).

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

Flow rate: 0.4mL/min; full scan mass-to-charge ratio range: 80-1000; full scan mass spectrometry resolution: 70000; secondary scan resolution: 17500; ion spray voltage: 3.5kV; capillary temperature: 300°C; auxiliary gas flow rate : 1.0L/min.

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

The m/z corresponding to fluazinamine is 462.944 in Figure 2, and its molecular formula is C ₁₃ H ₃ Cl ₂ F ₆ N ₄ O ₄ ^- ; the corresponding m/z of mercaptofluazinamine is 460.9547 in Figure 3, and its molecular formula is is C ₁₃ H ₄ ClF ₆ N ₄ O ₄ S ^- ; the m/z corresponding to hydroxyfluazinamine is 444.9778 in Figure 4, and its molecular formula is C ₁₃ H ₄ ClF ₆ N ₄ O ₅ ^- ; The m/z of is 432.9690 in Fig. 5, and its molecular formula is C ₁₃ H ₅ Cl ₂ F ₆ N ₄ O ₂ ^- .

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, fast flow rate, and high efficiency, which can be used for screening pesticides, and can effectively screen out fluoropyridine Amines and unknown metabolites of fluazinam.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A preparation method of a carbon nano tube monolithic column is characterized by comprising the following steps: carrying out polymerization reaction on the carbon nano tube and the polymerization solution in a column cavity of a solid-phase extraction column, and then removing a second solvent in the polymerization solution;

the components of the polymerization liquid comprise a first monomer, a second monomer, a first solvent, a second solvent and an initiator; the first monomer is styrene, the second monomer is divinylbenzene, the first solvent is toluene, the second solvent is dodecanol, and the initiator comprises azobisisobutyronitrile.

2. The method of claim 1, wherein the polymerization is carried out at 75-85 ℃ for 20-28 hours.

3. The production method according to claim 1 or 2, wherein the amount ratio of the first monomer, the second monomer, the first solvent, the second solvent, and the initiator in the polymerization solution is 1.4 to 1.8mL in this order: 2.2-2.6mL:1.6-2mL:4-4.5mL:0.08-0.12g.

4. The method of claim 3, wherein 0.2g of the carbon nanotubes is used per 1.4-1.8mL of the first monomer;

preferably, the carbon nanotubes comprise at least one of multi-walled carbon nanotubes, single-walled carbon nanotubes, aminated multi-walled carbon nanotubes and carboxylated carbon nanotubes.

5. A carbon nanotube monolithic column produced by the production method according to any one of claims 1 to 4.

6. The use of the carbon nanotube monolith column of claim 5, wherein the carbon nanotube monolith column is used for screening pesticides.

7. The use according to claim 6, wherein the carbon nanotube monolith column is used for screening fluazinam and unknown metabolites of fluazinam;

preferably, the unknown metabolite of fluazinam comprises at least one of mercaptofluazinam, hydroxyfluazinam and aminofluazinam;

the chemical structural formulas of the sulfydryl fluazinam, the hydroxyl fluazinam and the amino fluazinam are as follows in sequence:

and

preferably, the object to be screened is an agricultural product;

preferably, the produce is a fruit and/or vegetable.

8. The use of claim 6, wherein screening comprises: and (3) enabling a sample to be screened, which is prepared from the substance to be screened, to flow through the carbon nano tube monolithic column, and collecting effluent liquid flowing out for subsequent detection.

9. The use of claim 8, wherein the sample to be screened is flowed through the carbon nanotube monolith at a flow rate of 0.45-0.55 mL/min.

10. The use of claim 8 or 9, wherein after the sample to be screened flows through the carbon nanotube monolithic column, further comprising: eluting the carbon nano tube monolithic column by using an eluent, collecting the eluted eluent, and combining the effluent liquid and the eluent for subsequent detection;

preferably, the eluent is a mixed solution of toluene and acetonitrile.

Images