Nano-composite hydrogel modified silica gel as well as preparation method and application thereof

Abstract

The invention discloses nano composite hydrogel modified silica gel as well as a preparation method and application thereof. The method comprises the following steps: (1) preparing carbon nanoparticles; (2) preparing a polyvinyl alcohol aqueous solution and a pre-polymerized solution of carbon nanoparticles and hydrogel; (3) preparation of nano-composite hydrogel modified silica gel: adding the pre-polymerized liquid and silica gel into the polyvinyl alcohol aqueous solution under stirring, adding an initiator, carrying out hot bath, carrying out condensation reflux in an inert atmosphere for reaction, and then adding a polyvinyl alcohol cross-linking agent and an HCl aqueous solution for reaction; and after the reaction is finished, centrifugally washing and drying to obtain the nano-composite hydrogel modified silica gel. The nano-composite hydrogel modified silica gel has excellent hydrophilicity, can be used as a hydrophilic mode liquid chromatography filler, and has great development space and application potential in the field of chromatographic separation and analysis.

Description

Technical Field

[0001] This invention belongs to the field of high performance liquid chromatography separation and analysis technology, specifically relating to a nanocomposite hydrogel-modified silica gel, its preparation method, and its application. Background Technology

[0002] The separation and analysis of polar compounds is crucial in various fields such as environmental monitoring, pharmaceutical analysis, and food safety. Reversed-phase liquid chromatography (RPLC) and normal-phase liquid chromatography (NPLC) are currently the most widely used methods for separating polar compounds. However, they suffer from limitations in retention capacity and selectivity, as well as poor solubility and reproducibility, which restrict their application in the separation and analysis of polar compounds. In contrast, hydrophilic mode liquid chromatography (HILIC) uses water in its mobile phase, ensuring complete dissolution of polar compounds. Furthermore, HILIC exhibits excellent retention capacity, effectively solving the separation challenges of polar compounds in RPLC and NPLC.

[0003] In recent years, researchers have discovered that hydrogels can be used as functional groups in hydrophilic mode chromatography. Hydrogels are three-dimensional network polymers formed through monomer crosslinking. They can swell to equilibrium in water and retain a large amount of water without dissolving in water. They exhibit different hydrophilicity / phobicity, shrinkage / swelling properties, and volume variations for different types of polar compounds, and offer a rich variety of response types and control methods, demonstrating strong adaptability. They have broad application prospects in the field of separation and analysis.

[0004] However, the high swelling and water absorption, poor mechanical stability, and non-specific adsorption properties of traditional hydrogels limit their application as functional groups for stationary phases in hydrophilic mode chromatography. To improve these properties, the most common method is to add different nanomaterials to the hydrogel system through chemical or physical processes to prepare nanocomposite hydrogels. Compared to traditional hydrogels, nanocomposite hydrogels can effectively improve the swelling, mechanical, and adsorption properties of hydrogels. Based on the differences in the chemical composition and structure of polar compounds, the targeted design and control of the type and amount of nanocomposite materials, the type of hydrogel monomers, and external stimuli (such as pH, temperature, ionic strength, light, and electricity) are of great significance for achieving efficient and rapid separation and analysis of polar compounds with diverse structures.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a nanocomposite hydrogel-modified silica gel, its preparation method, and its application. This invention solves the problem of high swelling of functional groups in traditional hydrogels when used as stationary phases in hydrophilic chromatography. The nanocomposite hydrogel-modified silica gel of this invention has excellent hydrophilicity and can be used as a packing material in hydrophilic liquid chromatography, showing great development potential and application prospects in the field of chromatographic separation and analysis.

[0007] To achieve the above objectives, the present invention provides a method for preparing nanocomposite hydrogel-modified silica gel, the method comprising: (1) Preparation of carbon nanoparticles Carbon nanoparticles were prepared by fully dissolving the monomers in deionized water and then reacting them hydrothermally. (2) Preparation of polyvinyl alcohol aqueous solution and prepolymer solution of carbon nanoparticles and hydrogel The hydrogel monomer polyvinyl alcohol was dissolved in deionized water and heated with stirring to obtain a polyvinyl alcohol aqueous solution. The other monomer of the hydrogel, acrylic acid, and its crosslinking agent are fully dissolved in deionized water. Carbon nanoparticles and polymerization reaction promoters are added and stirred evenly to obtain a prepolymer solution of carbon nanoparticles and hydrogel. (3) Preparation of silica gel modified with nanocomposite hydrogel Under stirring, the prepolymer liquid and silica gel are added to the polyvinyl alcohol aqueous solution, an initiator is added and a hot bath is used. The reaction is carried out under an inert atmosphere by reflux condensation. Then, a polyvinyl alcohol crosslinking agent is added and the reaction is carried out in an acidic environment. In an acidic environment, the reaction between the polyvinyl alcohol crosslinking agent (such as glutaraldehyde) and polyvinyl alcohol molecules can be accelerated, the density and degree of crosslinking can be increased, thereby enhancing the stability and mechanical properties of the crosslinked structure.

[0008] After the reaction was complete, the silica gel was centrifuged, washed, and dried to obtain the silica gel modified with nanocomposite hydrogel.

[0009] The method of this invention utilizes acrylic acid and its crosslinking agent (such as N,N'-methylenebisacrylamide) to form polyacrylic acid, and further utilizes polyvinyl alcohol and its crosslinking agent (such as glutaraldehyde) to form a crosslinked structure. Under acidic conditions, polyacrylic acid, polyvinyl alcohol, and carbon nanoparticles are modified on the surface of silica gel through physical interactions (such as hydrogen bonding) to prepare a nanocomposite hydrogel-modified silica gel. The addition of carbon nanoparticles effectively increases the retention time of analytes, achieving better separation results.

[0010] Preferably, the monomers for synthesizing carbon nanoparticles are selected from citric acid and ethylenediamine, and carbon nanoparticles prepared from citric acid and ethylenediamine are simple, readily available, and stable; or / and, the temperature of the hydrothermal reaction is 200 °C; or / and, after the hydrothermal reaction is completed, the reaction solution is placed in a dialysis bag for dialyzing, and the liquid in the dialysis bag is dried to obtain carbon nanoparticles.

[0011] Preferably, the mass ratio of citric acid to ethylenediamine is 3.5:1; or / and, the hydrothermal reaction time is 5 h; or / and, the molecular weight cutoff of the dialysis bag is 3500; or / and, the liquid inside the dialysis bag is dried in a vacuum drying oven at 85~95 ℃ for 22~26 h.

[0012] Preferably, the mass ratio of polyvinyl alcohol to acrylic acid is 2~3:1; or / and, the molecular weight of the polyvinyl alcohol is 67000. Polyvinyl alcohol with different molecular weights has different degrees of crosslinking. The polyvinyl alcohol with a molecular weight of 67000 selected in this invention can well meet the requirements of this method; or / and, the crosslinking agent of the acrylic acid is selected from N,N'-methylenebisacrylamide; or / and, the accelerator is selected from tetramethylethylenediamine; or / and, the mass ratio of the acrylic acid to its crosslinking agent, carbon nanoparticles and accelerator is 1:0.1~0.2:0.5~0.6:0.3~0.4; or / and, the preparation of the aqueous solution of polyvinyl alcohol is carried out at a heating temperature of 70~90 °C.

[0013] Preferably, the mass ratio of silica gel to polyvinyl alcohol is 1:8~10. The amount of polyvinyl alcohol added as a hydrogel monomer affects the retention of substances. The separation and analysis of the target analyte can be achieved within the range of polyvinyl alcohol:silica gel = 1:8~1:10, but increasing the content of polyvinyl alcohol is beneficial to the retention of analytes and the separation effect is better; or / and, the initiator is ammonium persulfate; or / and, the mass ratio of the initiator to acrylic acid is 0.4~0.5:1; or / and, the reflux temperature is 50 ℃; or / and, the reflux time is 24 h; or / and, the polyvinyl alcohol crosslinking agent is selected from glutaraldehyde aqueous solution; or / and, the acidic environment is adjusted by any one or more of HCl, acetic acid, sulfuric acid, phosphoric acid and citric acid. Specifically, a 1 N HCl aqueous solution can be used; or / and, the preparation of the nanocomposite hydrogel modified silica gel involves washing with water by centrifugation after the reaction is completed, and drying in a vacuum drying oven at 85~95 ℃ for 22~26 h.

[0014] Preferably, the concentration of the glutaraldehyde aqueous solution is 25%; or / and the ratio of the amounts of polyvinyl alcohol, glutaraldehyde aqueous solution, and HCl aqueous solution is 3 g: 1 mL: 1 mL.

[0015] A second objective of this invention is to provide silica gel modified with nanocomposite hydrogels obtained by the preparation method described above.

[0016] A third objective of this invention is to provide a liquid chromatography column prepared using the aforementioned nanocomposite hydrogel-modified silica gel as a hydrophilic mode liquid chromatography packing material.

[0017] Preferably, the liquid chromatography column is prepared by high-pressure homogenization.

[0018] More preferably, in the high-pressure homogenization method, both the dispersion and the displacement liquid are methanol, and the pressure is 40 MPa.

[0019] A fourth objective of this invention is to provide the application of the aforementioned liquid chromatography column in the field of chromatographic separation.

[0020] Preferably, the application is selected from any one of the following: (1) Application in the separation of nucleosides and / or bases; (2) Application in the separation of sulfonamide compounds; (3) Application in the separation of organic acid compounds; (4) Application in the isolation of antibiotic compounds; (5) Application in alkaloid separation.

[0021] More preferably, the nucleoside is selected from any one or more of 2'-deoxyuridine, 5-methyluridine, uridine, inosine, cytosine nucleoside, and guanosine; the base is selected from any one or more of thymine, adenine, hypoxanthine, and cytosine; the sulfonamide compound is selected from any one or more of sulfadimethylpyrimidine, sulfadiazine, sulfadimidine, sulfamethoxypyrimidine, and sulfisoxazole; the organic acid compound is selected from any one or more of salicylic acid, 4-chlorobenzoic acid, trans-cinnamic acid, benzoic acid, p-hydroxybenzoic acid, and 2,3,5,6-terephthalic acid; the antibiotic compound is selected from any one or more of tinidazole, metronidazole, cefpirome sulfate, enrofloxacin, pefloxacin, levofloxacin, and ciprofloxacin; and the alkaloid is selected from any one or more of piperine, caffeine, theobromine, matrine, and theophylline.

[0022] More preferably, for the separation of nucleosides and / or bases, and sulfonamides, the mobile phase is acetonitrile / water at a volume ratio of 90 / 10; for the separation of organic acids, the mobile phase is acetonitrile / 200 mM ammonium acetate solution at a volume ratio of 74 / 26; for the separation of antibiotics, the mobile phase is acetonitrile / water at a volume ratio of 70 / 30; and for the separation of alkaloids, the mobile phase is acetonitrile / 125 mM ammonium acetate solution at a volume ratio of 90 / 10.

[0023] Specifically, the separation of nucleosides and / or bases, and sulfonamides was performed under the following chromatographic conditions: mobile phase: acetonitrile / water (90 / 10 v / v); flow rate: 1.0 mL / min; UV detector: 254 nm; injection volume: 20 µL. The separation of organic acids was performed under the following conditions: mobile phase: acetonitrile / 200 mM ammonium acetate solution (74 / 26 v / v); flow rate: 1.0 mL / min; UV detector: 268 nm; injection volume: 20 µL. The separation of antibiotics was performed under the following conditions: mobile phase: acetonitrile / water (70 / 30 v / v); flow rate: 1.0 mL / min; UV detector: 254 nm; injection volume: 20 µL. The separation of alkaloids was performed under the following conditions: mobile phase: acetonitrile / 125 mM ammonium acetate solution (90 / 10 v / v); flow rate: 1.0 mL / min; UV detector: 223 nm. nm; injection volume is 20 µL.

[0024] The present invention relates to nanocomposite hydrogel-modified silica gel, its preparation method, and its application, which solves the problem of high swelling of functional groups in traditional hydrogels when used as stationary phases in hydrophilic chromatography, and has the following advantages: (1) The silica gel modified by the nanocomposite hydrogel of the present invention is obtained by modifying the silica gel surface with a nanocomposite hydrogel made of carbon nanoparticles formed by citric acid and ethylenediamine and hydrogel formed by polyvinyl alcohol and polyacrylic acid through physical interaction. This modified layer formed by the nanocomposite hydrogel has different active sites, which can realize the separation and analysis of compounds with different polarities in hydrophilic chromatography mode. (2) The silica gel modified by the nanocomposite hydrogel of the present invention improves the swelling effect of traditional hydrogels. In actual separation, the problem of the mobile phase not being able to flow through the chromatographic column due to excessive column pressure will not occur. Moreover, the mechanical stability is improved through the cross-linking structure of the polymer. (3) Due to its excellent hydrophilicity, the nanocomposite hydrogel modification of the present invention can be used as a hydrophilic mode liquid chromatography packing material. It has great development space and application potential in the field of chromatographic separation and analysis. It can be used for the separation and analysis of compounds with different polarities, including the separation of compounds such as nucleosides / bases, sulfonamides, organic acids, antibiotics, alkaloids, etc. It can realize the separation and analysis of compounds with different polarities in hydrophilic chromatographic mode and has good separation selectivity. (4) The preparation method of the present invention is simple and can achieve efficient modification of the surface of the silica gel with nanocomposite hydrogel. Attached Figure Description

[0025] Figure 1SEM images of silica gel modified with nanocomposite hydrogel and bare silica gel prepared in Example 1 of this invention; (a) bare silica gel; (b) silica gel modified with nanocomposite hydrogel; scale bar in the figures is 1 μm.

[0026] Figure 2 This is a fluorescence confocal microscope image of the silica gel modified with nanocomposite hydrogel prepared in Example 1 of the present invention.

[0027] Figure 3 Thermogravimetric analysis (TGA) diagrams of the nanocomposite hydrogel-modified silica gel, unmodified carbon nanoparticle silica gel, and bare silica gel prepared in Example 1 of this invention.

[0028] Figure 4 This is a liquid chromatogram of the separation of nucleosides / bases in Example 3 of the present invention.

[0029] Figure 5 This is a liquid chromatogram of the separation of sulfonamide compounds in Example 3 of the present invention.

[0030] Figure 6 This is a liquid chromatogram of the organic acid compounds in Example 5 of the present invention.

[0031] Figure 7 This is a liquid chromatogram of the antibiotic compound in Example 6 of the present invention.

[0032] Figure 8 This is a liquid chromatogram of the alkaloids in Example 7 of the present invention.

[0033] Figure 9 The above are liquid chromatograms of the nanocomposite hydrogel with carbon nanoparticles and the hydrogel modified silica gel without carbon nanoparticles in Example 8 of the present invention for nucleosides / bases.

[0034] Figure 10 This is the chromatographic separation diagram of nucleosides / bases when polyvinyl alcohol:silica gel = 1:8 in Example 9 of the present invention. Detailed Implementation

[0035] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] It should be noted that: Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0037] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0038] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0039] Example 1 A nanocomposite hydrogel-modified silica gel, the preparation method of which includes the following steps: (1) Preparation of carbon nanoparticles 2.1 g of citric acid and 670 μL of ethylenediamine were dissolved in deionized water and hydrothermally reacted in a muffle furnace at 200 °C for 5 h. After the reaction was completed, the resulting solution was dialyzed in a 3500 MwCO dialysis bag for 24 h. The liquid in the dialysis bag was then dried in a vacuum drying oven at 85-95 °C for 22-26 h to obtain carbon nanoparticles. (2) Preparation of polyvinyl alcohol aqueous solution and prepolymer solution of carbon nanoparticles and hydrogel Weigh 0.3 g of hydrogel monomer polyvinyl alcohol (molecular weight Mw=67000) into 80 mL of deionized water, and stir magnetically at 90 °C for 2 h to fully dissolve it to obtain a polyvinyl alcohol aqueous solution. Measure 0.1 mL of the other monomer of the hydrogel, acrylic acid, and its crosslinking agent (0.02 g N,N'-methylenebisacrylamide) and dissolve them in 10 mL of deionized water. Then add 0.06 g of carbon nanoparticles and polymerization promoter (0.05 mL tetramethylethylenediamine), stir evenly, and obtain a prepolymer solution of carbon nanoparticles and hydrogel. (3) Preparation of silica gel modified with nanocomposite hydrogel Under magnetic stirring, the prepolymer obtained in step (2) and 3.0 g of silica gel were added to a polyvinyl alcohol aqueous solution. An initiator (0.05 g of ammonium persulfate) was added and the mixture was placed in a hot bath. Under an inert atmosphere, the mixture was refluxed at 50 °C for 24 h. Then, under magnetic stirring, an appropriate amount of polyvinyl alcohol crosslinking agent (0.1 mL of 25% glutaraldehyde aqueous solution) and 0.1 mL of 1 N HCl aqueous solution were added to the reaction solution and the mixture was refluxed at 50 °C for 2 h. After the reaction is complete, the silica gel is washed five times by centrifugation with deionized water and then dried in a vacuum drying oven at 85-95 ℃ for 22-26 h to finally obtain the nanocomposite hydrogel modified silica gel, denoted as Sil@PVA / PAA / CDs.

[0040] Example 2 A nanocomposite hydrogel-modified silica gel, the preparation method of which includes the following steps: (1) Preparation of carbon nanoparticles 2.1 g of citric acid and 670 μL of ethylenediamine were dissolved in deionized water and hydrothermally reacted in a muffle furnace at 200 °C for 5 h. After the reaction was completed, the resulting solution was dialyzed in a 3500 MwCO dialysis bag for 24 h. The liquid in the dialysis bag was then dried in a vacuum drying oven at 85-95 °C for 22-26 h to obtain carbon nanoparticles. (2) Preparation of polyvinyl alcohol aqueous solution and prepolymer solution of carbon nanoparticles and hydrogel Weigh 0.375 g of hydrogel monomer polyvinyl alcohol (molecular weight Mw=67000) into 80 mL of deionized water, and stir magnetically at 90℃ for 2 h to fully dissolve it to obtain a polyvinyl alcohol aqueous solution. Measure 0.1 mL of the other monomer of the hydrogel, acrylic acid, and its crosslinking agent (0.02 g N,N'-methylenebisacrylamide) and dissolve them in 10 mL of deionized water. Then add 0.06 g of carbon nanoparticles and polymerization promoter (0.05 mL tetramethylethylenediamine), stir evenly, and obtain a prepolymer solution of carbon nanoparticles and hydrogel. (3) Preparation of silica gel modified with nanocomposite hydrogel Under magnetic stirring, the prepolymer obtained in step (2) and 3.0 g of silica gel were added to a polyvinyl alcohol aqueous solution. An initiator (0.05 g of ammonium persulfate) was added and the mixture was placed in a hot bath. Under an inert atmosphere, the mixture was refluxed at 50 °C for 24 h. Then, under magnetic stirring, an appropriate amount of polyvinyl alcohol crosslinking agent (0.1 mL of 25% glutaraldehyde aqueous solution) and 0.1 mL of 1 N HCl aqueous solution were added to the reaction solution and the mixture was refluxed at 50 °C for 2 h. After the reaction is complete, the silica gel is washed five times by centrifugation with deionized water and then dried in a vacuum drying oven at 85-95 ℃ for 22-26 h to finally obtain the nanocomposite hydrogel modified silica gel.

[0041] Comparative Example 1 The hydrogel prepared by modifying the surface of unmodified carbon nanoparticle silica gel with only polyvinyl alcohol and polyacrylic acid includes the following methods: (1) Preparation of polyvinyl alcohol aqueous solution and hydrogel prepolymer solution Weigh 0.3 g of hydrogel monomer polyvinyl alcohol (molecular weight Mw=67000) into 80 mL of deionized water, and stir magnetically at 90 °C for 2 h to fully dissolve it to obtain a polyvinyl alcohol aqueous solution. Measure 0.1 mL of the other monomer of the hydrogel, acrylic acid, and its crosslinking agent (0.02 g N,N'-methylenebisacrylamide) and dissolve them in 10 mL of deionized water. Then add the polymerization accelerator (0.05 mL tetramethylethylenediamine) and stir until homogeneous to obtain the prepolymer solution of the hydrogel. (2) Preparation of silica gel modified with nanocomposite hydrogel Under magnetic stirring, the prepolymer obtained in step (1) and 3.0 g of silica gel were added to a polyvinyl alcohol aqueous solution. An initiator (0.05 g of ammonium persulfate) was added and the mixture was placed in a hot bath. Under an inert atmosphere, the mixture was refluxed at 50 °C for 24 h. Then, under magnetic stirring, an appropriate amount of polyvinyl alcohol crosslinking agent (0.1 mL of 25% glutaraldehyde aqueous solution) and 0.1 mL of 1 N HCl aqueous solution were added to the reaction solution and the mixture was refluxed at 50 °C for 2 h. After the reaction is complete, the product is washed five times by centrifugation with deionized water and then dried in a vacuum drying oven at 85-95 ℃ for 22-26 h to obtain unmodified carbon nanoparticle silica gel, denoted as Sil@PVA / PAA.

[0042] like Figure 1 As shown, SEM images of the nanocomposite hydrogel-modified silica gel and bare silica gel prepared in Example 1 of this invention are shown. (a) is bare silica gel and (b) is the prepared filler. It can be seen that the surface of the prepared filler is rough compared with the smooth surface of bare silica gel, which proves that the surface of silica gel has been successfully modified.

[0043] like Figure 2 The image shown is a fluorescence confocal microscope image of the silica gel modified with nanocomposite hydrogel prepared in Example 1 of this invention at 400 nm. It can be seen that the nanocomposite hydrogel emits blue light under 400 nm excitation light, which proves that the synthesized carbon nanoparticles were successfully modified onto the silica gel surface.

[0044] like Figure 3 The figure shows the thermogravimetric analysis (TGA) of silica gel modified with nanocomposite hydrogel, unmodified carbon nanoparticle silica gel, and bare silica gel prepared in Example 1 of this invention. The horizontal axis represents temperature (°C), and the vertical axis represents the percentage of remaining mass of the sample (%). It can be seen that the weight losses of the three are 6.6 wt%, 9.1 wt%, and 14.6 wt%, respectively, which proves that the nanocomposite hydrogel formed by carbon nanoparticles and hydrogel was successfully modified on the surface of silica gel.

[0045] The nanocomposite hydrogel-modified silica gel prepared in the embodiments of the present invention is used as a hydrophilic liquid chromatography column packing material and applied in the field of chromatographic separation. Specific applications are shown in Examples 3 to 9.

[0046] Example 3 The application of nanocomposite hydrogel-modified silica gel as a hydrophilic mode liquid chromatography column packing material in nucleoside / base separation is as follows: (1) Preparation of hydrophilic mode liquid chromatography column The hydrophilic-mode liquid chromatography packing material prepared in Example 1 was packed into a 150 × 4.6 mm stainless steel liquid chromatography column using a high-pressure homogenization method for the separation and analysis of nucleosides / bases (thymine, 2'-deoxyuridine, 5-methyluridine, uridine, adenine, hypoxanthine, cytosine, inosine, cytosine nucleoside, and guanosine). During packing, both the dispersion and displacement solvent were methanol, and the pressure was 40 MPa.

[0047] (2) Chromatographic separation of nucleosides / bases The chromatographic conditions were as follows: mobile phase: acetonitrile / H2O (90 / 10, v / v); flow rate: 1.0 mL / min; UV detector: 254 nm; injection volume: 20 µL.

[0048] like Figure 4 The figure shows the liquid chromatogram for the separation of nucleosides / bases in Example 3 of this invention. The analytes corresponding to each peak are: 1. Thymine; 2. 2'-deoxyuridine; 3. 5-methyluridine; 4. Uranidine; 5. Adenine; 6. Hypoxanthine; 7. Cytosine; 8. Inosine; 9. Cytosine nucleoside; 10. Guanosine. As can be seen from the figure, this hydrophilic liquid chromatography packing material exhibits excellent separation selectivity for nucleosides / bases, with a column efficiency of 56688.9 for 2'-deoxyuridine and 62204.7 for cytosine nucleoside. Furthermore, the resolution R = 5.47 for thymine and 2'-deoxyuridine successfully achieved baseline separation.

[0049] Example 4 The application of nanocomposite hydrogel-modified silica gel as a hydrophilic mode liquid chromatography column packing material in the separation of sulfonamide compounds is as follows: (1) Preparation of hydrophilic mode liquid chromatography column The hydrophilic-mode liquid chromatography packing material prepared in Example 1 was packed into a 150 × 4.6 mm stainless steel liquid chromatography column using a high-pressure homogenization method for the separation and analysis of sulfonamide compounds (sulfadimethylpyrimidine, sulfadiazine, sulfamididine, sulfamethoxypyrimidine, and sulfisoxazole). During packing, both the dispersion and displacement solvent were methanol, and the pressure was 40 MPa.

[0050] (2) Chromatographic separation of sulfonamide compounds The chromatographic analysis conditions were as follows: mobile phase: acetonitrile / water (90 / 10, v / v); flow rate: 1.0 mL / min; UV detector: 254 nm; injection volume: 20 µL.

[0051] like Figure 5 The figure shows the liquid chromatogram of sulfonamide compounds separated in Example 4 of this invention. The analytes corresponding to each peak are: 1. sulfadimethylpyrimidine; 2. sulfadiazine; 3. sulfamethoxypyrimidine; 4. sulfamethoxypyrimidine; 5. sulfaisoxazole. As can be seen from the figure, this hydrophilic liquid chromatography packing material has excellent separation selectivity for sulfonamide compounds, with a column efficiency of 47063.5 for sulfadiazine and 33417.9 for sulfamethoxypyrimidine. Furthermore, the resolution R = 3.89 for sulfadiazine and sulfamethoxypyrimidine, successfully achieving baseline separation.

[0052] Example 5 The application of nanocomposite hydrogel-modified silica gel as a hydrophilic mode liquid chromatography column packing material in the separation of organic acid compounds is as follows: (1) Preparation of hydrophilic mode liquid chromatography column The hydrophilic-mode liquid chromatography packing material prepared in Example 1 was packed into a 150×4.6 mm stainless steel liquid chromatography column using a high-pressure homogenization method for the separation and analysis of organic acid compounds (salicylic acid, 4-chlorobenzoic acid, trans-cinnamic acid, benzoic acid, p-hydroxybenzoic acid, and 2,3,5,6-terephthalic acid). During packing, both the dispersion and displacement solvent were methanol, and the pressure was 40 MPa.

[0053] (2) Chromatographic separation of organic acid compounds The chromatographic analysis conditions were as follows: mobile phase was acetonitrile / 200 mM ammonium acetate solution (74 / 26, v / v); flow rate was 1.0 mL / min; UV detector was 268 nm; and injection volume was 20 µL.

[0054] like Figure 6 The figure shows the liquid chromatogram of organic acid compounds in Example 5 of this invention. The analytes corresponding to each peak are: 1. Salicylic acid; 2. 4-chlorobenzoic acid; 3. trans-cinnamic acid; 4. Benzoic acid; 5. p-hydroxybenzoic acid; 6. 2,3,5,6-terephthalic acid. As can be seen from the figure, this hydrophilic liquid chromatography packing material exhibits excellent separation selectivity for organic acid compounds, with a column efficiency of 34337.6 for 4-chlorobenzoic acid and 39546.4 for benzoic acid. Furthermore, the resolution R = 2.90 for trans-cinnamic acid and benzoic acid, successfully achieving baseline separation.

[0055] Example 6 The application of nanocomposite hydrogel-modified silica gel as a hydrophilic mode liquid chromatography column packing material in the separation of antibiotic compounds is as follows: (1) Preparation of hydrophilic mode liquid chromatography column The hydrophilic-mode liquid chromatography packing material prepared in Example 1 was packed into a 150×4.6 mm stainless steel liquid chromatography column using a high-pressure homogenization method for the separation and analysis of antibiotic compounds (tinidazole, metronidazole, cefpirome sulfate, enrofloxacin, pefloxacin, levofloxacin, and ciprofloxacin). During packing, both the dispersion and displacement solvent were methanol, and the pressure was 40 MPa.

[0056] (2) Chromatographic separation of antibiotic compounds The chromatographic analysis conditions were as follows: mobile phase: acetonitrile / water (70 / 30, v / v); flow rate: 1.0 mL / min; UV detector: 254 nm; injection volume: 20 µL.

[0057] like Figure 7 The figure shows the liquid chromatogram of antibiotic compounds in Example 6 of this invention. The analytes corresponding to each peak are: 1. Tinidazole; 2. Metronidazole; 3. Cefpirome sulfate; 4. Enrofloxacin; 5. Pefloxacin; 6. Levofloxacin; 7. Ciprofloxacin. As can be seen from the figure, this hydrophilic liquid chromatography packing material has excellent separation selectivity for antibiotic compounds, with a column efficiency of 24756.5 for metronidazole and 39497.5 for cefpirome sulfate. Furthermore, the resolution R = 2.26 for cefpirome sulfate and enrofloxacin, successfully achieving baseline separation.

[0058] Example 7 The application of nanocomposite hydrogel-modified silica gel as a hydrophilic mode liquid chromatography column packing material in the separation of alkaloids is as follows: (1) Preparation of hydrophilic mode liquid chromatography column The hydrophilic-mode liquid chromatography packing material prepared in Example 1 was packed into a 150×4.6mm stainless steel liquid chromatography column using a high-pressure homogenization method for the separation and analysis of alkaloids (piperine, caffeine, theobromine, matrine, and theophylline). During packing, both the dispersion and displacement solvent were methanol, and the pressure was 40 MPa.

[0059] (2) Chromatographic separation of alkaloids The chromatographic analysis conditions were as follows: mobile phase was acetonitrile / 125 mM ammonium acetate solution (90 / 10, v / v); flow rate was 1.0 mL / min; UV detector was 223 nm; and injection volume was 20 µL.

[0060] like Figure 8The figure shows the liquid chromatogram of alkaloids in Example 7 of this invention. The analytes corresponding to each peak are: 1. Piperine; 2. Caffeine; 3. Theobromine; 4. Matrine; 5. Theophylline. As can be seen from the figure, this hydrophilic liquid chromatography packing material exhibits excellent separation selectivity for alkaloids, with a column efficiency of 28470.5 for piperine and 16898.1 for theobromine. Furthermore, the resolution R = 3.26 for caffeine and theobromine, successfully achieving baseline separation.

[0061] Example 8 The performance of silica gel modified with nanocomposite hydrogel as a hydrophilic mode liquid chromatography column packing material was compared with that of unmodified silica gel modified with carbon nanoparticles, as follows: Using nucleosides / bases as analytes, chromatographic separation was performed on silica gel modified with nanocomposite hydrogel as the packing material for hydrophilic mode liquid chromatography and silica gel modified with unmodified carbon nanoparticles. The separation conditions were the same as in Example 3.

[0062] like Figure 9 As shown, in the separation process of nucleosides / bases, the chromatographic column packing with added carbon nanoparticles enhances the retention of nucleosides / bases and is more conducive to achieving baseline separation of nucleosides / bases. Furthermore, the prepared nanocomposite hydrogel maintains a column pressure within 6 MPa during the separation process, effectively avoiding the problem that the column pressure often exceeds 10 MPa during chromatographic separation due to the excellent water absorption properties of traditional hydrogels. This indicates that the hydrophilic mode liquid chromatography column packing prepared by modifying silica gel with nanocomposite hydrogel in this invention is more conducive to achieving the separation and analysis of target analytes in hydrophilic mode.

[0063] Example 9 The application of the nanocomposite hydrogel-modified silica gel prepared in Example 2 as a hydrophilic liquid chromatography column packing material in nucleoside / base separation is as follows: Nucleosides / bases were used as analytes, and silica gel modified with nanocomposite hydrogel prepared in Example 2 was used as the packing material for hydrophilic liquid chromatography column. The separation conditions were the same as in Example 3.

[0064] like Figure 10 As shown, when polyvinyl alcohol:silica gel = 1:8, it can separate 10 nucleosides / bases. Figure 4 The comparison shows that under the separation condition of polyvinyl alcohol: silica gel = 1:10, better separation effect was achieved for the 10 target analytes. This indicates that the separation and analysis of target analytes can be achieved within the range of polyvinyl alcohol: silica gel = 1:8 to 1:10. However, increasing the content of polyvinyl alcohol is beneficial to the retention of analytes and the separation effect is better.

[0065] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing silica gel modified with nanocomposite hydrogel, characterized in that, The method includes: (1) Preparation of carbon nanoparticles Carbon nanoparticles were prepared by fully dissolving the monomers in deionized water and then reacting them hydrothermally. (2) Preparation of polyvinyl alcohol aqueous solution and prepolymer solution of carbon nanoparticles and hydrogel The hydrogel monomer polyvinyl alcohol was dissolved in deionized water and heated with stirring to obtain a polyvinyl alcohol aqueous solution. The other monomer of the hydrogel, acrylic acid, and its crosslinking agent are fully dissolved in deionized water. Carbon nanoparticles and polymerization reaction promoters are added and stirred evenly to obtain a prepolymer solution of carbon nanoparticles and hydrogel. (3) Preparation of silica gel modified with nanocomposite hydrogel Under stirring, the prepolymer liquid and silica gel are added to the polyvinyl alcohol aqueous solution, an initiator is added and a hot bath is provided, and the reaction is carried out under an inert atmosphere by reflux. Then, a polyvinyl alcohol crosslinking agent is added and the reaction is carried out in an acidic environment. After the reaction was complete, the silica gel was centrifuged, washed, and dried to obtain the silica gel modified with nanocomposite hydrogel.

2. The preparation method according to claim 1, characterized in that, The monomers for synthesizing carbon nanoparticles are selected from citric acid and ethylenediamine; Or / and, the temperature of the hydrothermal reaction is 200 °C; Or / and, after the hydrothermal reaction is completed, the reaction solution is placed in a dialysis bag for dialysis, and the liquid in the dialysis bag is dried to obtain carbon nanoparticles.

3. The preparation method according to claim 2, characterized in that, The mass ratio of citric acid to ethylenediamine is 3.5:1; Or / and, the hydrothermal reaction time is 5 h; Or / and, the molecular weight cutoff of the dialysis bag is 3500; Or / and, the liquid inside the dialysis bag is dried in a vacuum drying oven at 85~95 ℃ for 22~26 h.

4. The preparation method according to claim 1, characterized in that, The mass ratio of polyvinyl alcohol to acrylic acid is 2~3:1; Or / and, the molecular weight of the polyvinyl alcohol is 67,000; Or / and, the crosslinking agent for the acrylic acid is selected from N,N'-methylenebisacrylamide; Or / and, the promoter is selected from tetramethylethylenediamine; Or / and, the mass ratio of the acrylic acid to its crosslinking agent, carbon nanoparticles and accelerator is 1:0.1~0.2:0.5~0.6:0.3~0.4; Or / and, the preparation of the aqueous solution of polyvinyl alcohol is carried out at a heating temperature of 70~90 ℃.

5. The preparation method according to claim 1, characterized in that, The mass ratio of the silicone to polyvinyl alcohol is 1:8~10; Or / and, the initiator is selected as ammonium persulfate; Or / and, the mass ratio of the initiator to acrylic acid is 0.4~0.5:1; Or / and, the temperature of the reflux condensation is 50 °C; Or / and, the condensation reflux time is 24 h; Or / and, the polyvinyl alcohol crosslinking agent is selected from glutaraldehyde aqueous solution; Or / and, the acidic environment is adjusted by any one or more of HCl, acetic acid, sulfuric acid, phosphoric acid and citric acid; Or / and, the preparation of the nanocomposite hydrogel-modified silica gel involves washing with water by centrifugation after the reaction is complete, and drying in a vacuum drying oven at 85~95 ℃ for 22~26 h.

6. The preparation method according to claim 5, characterized in that, The concentration of the glutaraldehyde aqueous solution is 25%; Or / and, the ratio of the amounts of polyvinyl alcohol, glutaraldehyde aqueous solution and HCl aqueous solution is 3 g: 1 mL: 1 mL.

7. Silica gel modified with nanocomposite hydrogel obtained by the preparation method according to any one of claims 1 to 6.

8. A liquid chromatography column prepared using the nanocomposite hydrogel-modified silica gel as described in claim 7 as a hydrophilic mode liquid chromatography packing material.

9. The application of the liquid chromatography column as described in claim 8 in the field of chromatographic separation.

10. The application according to claim 9, characterized in that, The application is selected from any of the following: (1) Application in the separation of nucleosides and / or bases; (2) Application in the separation of sulfonamide compounds; (3) Application in the separation of organic acid compounds; (4) Application in the isolation of antibiotic compounds; (5) Application in alkaloid separation.

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