Preparation method and application of sodium alginate / silica gel composite material

Abstract

The present invention relates to the technical field of composite material preparation, specifically a preparation method and application of a sodium alginate / silica gel composite material. After sodium silicate is dissolved in deionized water, sodium alginate is added and stirred to form a uniform mixed solution. The pH of the mixed solution is adjusted to 5.0 ± 0.1, and the solution gradually changes from transparent to a milky white sol; urea is added to the obtained sol, and the obtained mixture is transferred to a hydrothermal reactor for hydrothermal reaction. After the reaction is completed, the reactor is naturally cooled to room temperature, and the product is taken out for suction filtration, washing, and drying to obtain a sodium alginate / silica gel composite material. The preparation method of the present invention is simple and efficient. The obtained sodium alginate / silica gel composite material combines the rigid porous structure of silica gel and the rich functional groups of sodium alginate, has excellent enrichment ability for clenbuterol hydrochloride, and establishes a detection and analysis method for clenbuterol hydrochloride in combination with high performance liquid chromatography analysis, with the advantages of low detection limit and high sensitivity.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and particularly relates to a preparation method and application of a sodium alginate / silica gel composite material. Background Art

[0002] Food safety has received significant attention in recent years. The illegal addition of clenbuterol (such as clenbuterol hydrochloride and ractopamine) to livestock and poultry production poses a serious threat to consumer health. While clenbuterol promotes growth and increases lean meat content in animals, its residues can cause symptoms such as palpitations, headaches, and even poisoning in humans. Therefore, establishing an efficient and sensitive method for detecting clenbuterol is crucial to ensuring food safety.

[0003] Currently, the main methods for detecting clenbuterol include enzyme-linked immunosorbent assay (ELISA), gas chromatography-mass spectrometry (GC-MS), and high-performance liquid chromatography (HPLC). HPLC is widely used due to its high separation efficiency and detection accuracy. However, the detection of trace clenbuterol in complex food matrices still faces challenges such as cumbersome sample pretreatment and low enrichment efficiency.

[0004] Solid-phase extraction (SPE) is an efficient sample pretreatment technique, in which the properties of the adsorption material are crucial to the extraction effect. Although traditional silica gel adsorbents have a large specific surface area, their selectivity is poor. Biopolymer adsorption materials such as sodium alginate (SA) have good biocompatibility and modifiability, but lack mechanical strength. Therefore, the development of composite materials with high adsorption capacity, good selectivity and high mechanical strength has become a research hotspot. Sodium alginate / silica gel composites combine the rigid porous structure of silica gel with the rich functional groups of sodium alginate, and are expected to improve the specific adsorption capacity for clenbuterol. At present, there are no reports on the effective preparation method of this composite material and its application in food safety testing. Summary of the Invention

[0005] In response to the above problems, the present invention provides a preparation method and application of a sodium alginate / silica gel composite material. The sodium alginate / silica gel composite material is prepared by a hydrothermal method, and the microstructure and surface properties of the sodium alginate / silica gel composite material are regulated by optimizing the synthesis conditions. On this basis, an efficient solid-phase extraction method based on the sodium alginate / silica gel composite material is developed. Combined with high-performance liquid chromatography (HPLC) technology, a detection and analysis method for clenbuterol hydrochloride in food is established, which solves the problems of insufficient sensitivity and high cost in detecting trace amounts of clenbuterol hydrochloride in food.

[0006] The present invention is specifically achieved through the following technical solutions. According to the present invention, a method for preparing a sodium alginate / silica gel composite material comprises the following steps:

[0007] (1) A certain amount of sodium silicate was dissolved in deionized water. After complete dissolution, sodium alginate powder was added and stirred until a uniform mixed solution was formed. Subsequently, a concentrated hydrochloric acid solution with a mass concentration of 37% was added dropwise to the mixed solution to adjust the pH of the solution to 5.0±0.1. At this time, the mixed solution gradually changed from transparent to a milky white sol, indicating that sodium silicate was hydrolyzed to generate silicic acid and initially cross-linked with sodium alginate.

[0008] (2) adding a certain amount of urea to the sol obtained in step (1), and regulating the pore structure and interfacial bonding strength of the material by the NH3 and CO2 gases generated by the high-temperature decomposition of urea; transferring the obtained mixture to a high-pressure hydrothermal reactor lined with polytetrafluoroethylene after stirring, and placing the reactor in a blast drying oven after sealing, and reacting at a constant temperature of 160°C for 24 hours; during this process, the silicic acid further condenses to form a three-dimensional porous skeleton, while the sodium alginate molecular chain is embedded in the silica gel network through hydrogen bonding and electrostatic interaction, and the gas generated by the decomposition of urea assists in forming a mesoporous structure, and finally obtaining a product with rigid-flexible synergistic properties;

[0009] (3) After the hydrothermal reaction is completed, the reactor is cooled naturally to room temperature, the product is taken out and filtered, and the filtered product is washed with deionized water 3 to 5 times. The washed and filtered product is transferred to a vacuum drying oven for drying to obtain a light yellow solid, namely sodium alginate / silica gel composite material, recorded as SA / SiO2.

[0010] In the aforementioned method for preparing the sodium alginate / silica gel composite material, in step (1), the mass ratio of sodium alginate to sodium silicate is 1:(20-50), preferably 1:25.

[0011] In the aforementioned method for preparing the sodium alginate / silica gel composite material, the volume ratio of the mass of sodium alginate to deionized water in step (1) is: 0.068 g: 10 mL.

[0012] In the aforementioned method for preparing the sodium alginate / silica gel composite material, the mass ratio of urea to sodium silicate is 1:8.5.

[0013] In the aforementioned method for preparing the sodium alginate / silica gel composite material, the product in step (3) is dried in a vacuum drying oven at 60-80°C for 12-24 hours.

[0014] The sodium alginate / silica gel composite material prepared by the aforementioned method has a uniform porous network structure with a pore size distribution of 2 to 15 nm.

[0015] The present invention also provides a method for detecting clenbuterol in meat using the sodium alginate / silica gel composite material prepared by the aforementioned method. The method uses the sodium alginate / silica gel composite material as a solid-phase extraction adsorbent, and solid-phase extraction combined with high-performance liquid chromatography (HPLC) is used to detect clenbuterol in meat, particularly clenbuterol in pork. The sample solution preparation method comprises: thoroughly mincing an appropriate amount of pork and homogenizing the mixture. Accurately weigh the minced pork sample into a centrifuge tube, adding an acetonitrile-water mixture (acetonitrile:water volume ratio of 8:2) and a 10% NaCl solution by mass, vortexing for 10-20 minutes, ultrasonically treating the mixture for 15-30 minutes, and then centrifuging at 8000 rpm for 5 minutes at 4°C. The supernatant is collected into a centrifuge tube, carbon tetrachloride is added, and the mixture is allowed to stand for 30 minutes. The supernatant is then removed and dried with nitrogen. The residue is then fully dissolved in acetonitrile to obtain the sample solution to be tested.

[0016] Furthermore, in the aforementioned sample solution treatment method, taking a 1.0 g minced pork sample as an example, the volume of the acetonitrile-water mixture added was 15 mL, the volume of the 10% NaCl solution added was 1 mL, and the volume of carbon tetrachloride added was 15 mL. The residue was fully dissolved in 1 mL of acetonitrile. In other implementation cases, this can be used as a benchmark for scaling up the same amount.

[0017] Solid phase extraction methods for sample solutions include:

[0018] S1. Column filling: Take an empty polypropylene solid phase extraction column, pad the bottom of the polypropylene solid phase extraction column with absorbent cotton, weigh 2 mg of sodium alginate / silica gel composite material as solid phase extraction adsorbent, and evenly fill it into the solid phase extraction column. Cover the adsorbent with the same absorbent cotton;

[0019] S2. Activation: Use 1 mL of anhydrous ethanol as an activating agent and flow through the column at a flow rate of 50 μL / min;

[0020] S3. Sample loading: 1 mL of the sample solution to be tested was loaded at a flow rate of 50 μL / min;

[0021] S4. Blow dry: Use an empty syringe to connect air to the top of the solid phase extraction cartridge to drain the residual liquid in the cartridge;

[0022] S5. Elution: Use 1 mL of a methanol / acetic acid mixture as the eluent. The volume ratio of methanol to acetic acid in the mixture is 9:1. Elute at a flow rate of 50 μL / min. Collect 50 μL of the eluate. After the eluate is dried with nitrogen, the residue is reconstituted with 50 μL of deionized water and analyzed by high-performance liquid chromatography.

[0023] The volume used in the above solid phase extraction method and the amount of the sodium alginate / silica gel composite material used are not considered to be limitations of the present invention.

[0024] When the content of clenbuterol hydrochloride in food was detected according to the above solid phase extraction method combined with high performance liquid chromatography analysis, the detection limit of clenbuterol hydrochloride was 7.52 ng / g and the quantification limit was 15.99 ng / g.

[0025] Compared with the prior art, the present invention has obvious advantages and beneficial effects. By means of the above technical solution, the present invention can achieve considerable technological advancement and practicality, and has a wide range of utilization value. It has at least the following advantages:

[0026] The preparation method of the present invention is simple and efficient, has mild preparation conditions, does not require large-scale equipment, and is easy to implement. By optimizing the synthesis conditions to regulate the microstructure and surface properties of the sodium alginate / silica gel composite material, the prepared sodium alginate / silica gel composite material combines the rigid porous skeleton of silica gel with the rich functional groups of sodium alginate, thereby improving the specific adsorption capacity for clenbuterol hydrochloride and clenbuterol hydrochloride, breaking through the bottleneck of low adsorption capacity and poor selectivity of a single material, and providing new ideas for the development of functional adsorption materials.

[0027] The prepared sodium alginate / silica gel composite material was used as a solid phase extraction adsorbent and combined with high performance liquid chromatography analysis to establish a detection and analysis method for clenbuterol hydrochloride. The detection limit was 7.52 ng / g and the quantification limit was 15.99 ng / g. This analytical method has high sensitivity and provides new materials and new technical support for the detection of clenbuterol hydrochloride in food, solving the problems of insufficient sensitivity and high cost in the detection of trace clenbuterol hydrochloride in food. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 1 is a Fourier transform infrared spectrum of silica gel and the sodium alginate / silica gel composite material prepared in Example 1.

[0029] Figure 2 This is an X-ray diffraction analysis (XRD) diagram of the sodium alginate / silica gel composite material prepared in Example 1.

[0030] Figure 3 This is a scanning electron microscope (SEM) image of the sodium alginate / silica gel composite material prepared in Example 1.

[0031] Figure 4 This is a comparison chart of chromatographic peak areas obtained by performing solid phase extraction of clenbuterol hydrochloride using the sodium alginate / silica gel composite materials prepared in Examples 1 to 8 as adsorbents and then performing high performance liquid chromatography analysis.

[0032] Figure 5This is a comparison chart of chromatographic peak areas obtained by performing solid phase extraction of clenbuterol hydrochloride using the sodium alginate / silica gel composite materials prepared in Example 1 and Examples 9-10 as adsorbents and then performing high performance liquid chromatography analysis.

[0033] Figure 6 This is a comparison chart of chromatographic peak areas obtained by high performance liquid chromatography analysis after solid phase extraction of clenbuterol hydrochloride using different amounts of sodium alginate / silica gel composite materials as adsorbents in Application Examples 1 to 3.

[0034] Figure 7 This is a comparison chart of chromatographic peak areas obtained by high performance liquid chromatography analysis of solid phase extraction of clenbuterol hydrochloride using sodium alginate / silica gel composite material as adsorbent under different eluent conditions in Application Examples 1 and Application Examples 4-6.

[0035] Figure 8 This is a standard curve diagram of sodium alginate / silica gel composite material for detecting clenbuterol hydrochloride based on SPE-HPLC analysis method. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] The present invention is described in detail below with reference to specific examples. In the following examples, if no specific conditions are specified, the experiments were carried out according to conventional conditions or those recommended by the manufacturer. Raw materials and reagents used, if the manufacturer is not specified, are all commercially available conventional products.

[0038] (1) Preparation of sodium alginate / silica gel composite materials

[0039] Example 1

[0040] (1) Dissolve 1.7 g of sodium silicate in 10 mL of deionized water. After complete dissolution, add 0.068 g of sodium alginate powder (the mass ratio of sodium alginate to sodium silicate is 1:25) and continue stirring until a uniform mixed solution is formed. Add a 37% concentrated hydrochloric acid solution dropwise to the mixed solution and adjust the pH of the mixed solution to 5.0±0.1. At this time, the mixed solution gradually changes from transparent to a milky white sol, indicating that sodium silicate is hydrolyzed to generate silicic acid and is initially cross-linked with sodium alginate.

[0041] (2) Add 0.2 g of urea to the sol obtained in step (1), stir evenly, and transfer the resulting mixture to a high-pressure hydrothermal reactor lined with polytetrafluoroethylene. The reactor is sealed and placed in a forced air drying oven for constant temperature reaction at 160°C for 24 h. During this process, silicic acid further condenses to form a three-dimensional porous skeleton, while the sodium alginate molecular chain is embedded in the silica gel network through hydrogen bonding and electrostatic interaction. The gas generated by the decomposition of urea assists in the formation of a mesoporous structure, and finally a product with rigid-flexible synergistic properties is obtained.

[0042] (3) After the hydrothermal reaction is completed, the reactor is cooled naturally to room temperature, and the product is taken out and filtered. The filtered product is washed three times with deionized water to remove unreacted ions and organic residues. After washing and filtering, the obtained product is transferred to a vacuum drying oven and dried at 80 °C for 12 h to obtain a light yellow powder, namely sodium alginate / silica gel composite material, recorded as SA / SiO2.

[0043] Figure 1 The following are Fourier infrared spectra of silica gel and the sodium alginate / silica gel composite material finally prepared in Example 1. By comparison, it can be seen that in the infrared spectrum of silica gel, at 480 cm -1 、808 cm -1 、3287 cm -1 There is a strong absorption peak at 480 cm -1 、808 cm -1 The absorption peak at 3287 cm corresponds to the stretching vibration peak of Si-O-Si in silica gel. -1 The absorption peak at 1700 cm corresponds to the stretching vibration peak of -OH. -1 、3410 cm -1 、2978 cm -1 The stretching vibrations of -C=O and -OH in sodium alginate-COOH and the stretching vibrations of CH bonds are shown in the figure. The results show that SA is successfully composited with SiO2.

[0044] Figure 2 This is an X-ray diffraction analysis (XRD) diagram of the sodium alginate / silica gel composite material prepared in Example 1, indicating that the introduction of sodium alginate does not change the crystal form of silica gel.

[0045] Figure 3 3 is a scanning electron microscope (SEM) image of the sodium alginate / silica gel composite material prepared in Example 1. It can be seen that the sodium alginate / silica gel composite material has a uniform porous network structure with a pore size distribution of 2 to 15 nm.

[0046] Example 2

[0047] The mass of sodium silicate is 0.68 g, the mass ratio of sodium alginate to sodium silicate is 1:10, and the remaining preparation processes and parameters are the same as those in Example 1.

[0048] Example 3

[0049] The mass of sodium silicate is 1.02 g, the mass ratio of sodium alginate to sodium silicate is 1:15, and the remaining preparation processes and parameters are the same as those in Example 1.

[0050] Example 4

[0051] The mass of sodium silicate is 1.36 g, the mass ratio of sodium alginate to sodium silicate is 1:20, and the remaining preparation processes and parameters are the same as those in Example 1.

[0052] Example 5

[0053] The mass of sodium silicate is 2.04 g, the mass ratio of sodium alginate to sodium silicate is 1:30, and the remaining preparation processes and parameters are the same as those in Example 1.

[0054] Example 6

[0055] The mass of sodium silicate was 2.38 g, the mass ratio of sodium alginate to sodium silicate was 1:35, and the remaining preparation processes and parameters were the same as in Example 1.

[0056] Example 7

[0057] The mass of sodium silicate is 2.72 g, the mass ratio of sodium alginate to sodium silicate is 1:40, and the remaining preparation processes and parameters are the same as those in Example 1.

[0058] Example 8

[0059] The mass of sodium silicate is 3.4 g, the mass ratio of sodium alginate to sodium silicate is 1:50, and the remaining preparation processes and parameters are the same as those in Example 1.

[0060] Example 9

[0061] The amount of urea added in step (2) of this embodiment is 0, specifically as follows:

[0062] (1) Dissolve 1.7 g of sodium silicate in 10 mL of deionized water. After complete dissolution, add 0.068 g of sodium alginate powder (the mass ratio of sodium alginate to sodium silicate is 1:25) and continue stirring until a uniform mixed solution is formed. Add a 37% concentrated hydrochloric acid solution dropwise to the mixed solution and adjust the pH of the solution to 5.0±0.1. At this time, the mixed solution gradually changes from transparent to a milky white sol, indicating that sodium silicate is hydrolyzed to generate silicic acid and is initially cross-linked with sodium alginate.

[0063] (2) The sol obtained in step (1) was transferred to a high-pressure hydrothermal reactor lined with polytetrafluoroethylene. The reactor was sealed and placed in a forced air drying oven for reaction at 160°C for 24 h.

[0064] (3) After the hydrothermal reaction is completed, the reactor is cooled naturally to room temperature, the product is taken out and filtered, and the filtered product is washed three times with deionized water. The washed and filtered product is transferred to a vacuum drying oven and dried at 80 °C for 12 h to obtain a sodium alginate / silica gel composite material.

[0065] Example 10

[0066] The amount of urea added in step (2) is 0.4 g, and the remaining preparation processes and parameters are the same as those in Example 1.

[0067] (2) Application of sodium alginate / silica gel composite materials

[0068] The sodium alginate / silica gel composite materials prepared in Examples 1 to 10 were used as solid phase extraction (SPE) adsorbents to enrich and purify clenbuterol hydrochloride in samples.

[0069] The sample solution preparation steps include thoroughly mincing an appropriate amount of pork and homogenizing it. Accurately weigh 1.0 g of the minced pork sample into a 25 mL centrifuge tube, add 15 mL of an acetonitrile-water mixture (acetonitrile:water volume ratio of 8:2) and 1 mL of a 10% NaCl solution, vortex for 10 minutes, and then sonicate for 15 minutes. The solution is then centrifuged at 8000 rpm for 5 minutes at 4°C. The supernatant is then transferred to a 25 mL centrifuge tube and 15 mL of carbon tetrachloride is added. After standing for 30 minutes, the supernatant is removed, dried with nitrogen, and the residue is thoroughly dissolved in 1 mL of acetonitrile to obtain the sample solution for column cleanup.

[0070] Application Example 1

[0071] The specific operations of solid phase extraction include:

[0072] S1. SPE column filling: Take an empty polypropylene solid phase extraction column, pad the bottom of the polypropylene solid phase extraction column with absorbent cotton, weigh 2 mg of the sodium alginate / silica gel composite material powder prepared in Example 1 as a solid phase extraction adsorbent, and evenly fill it into the solid phase extraction column. Cover the upper layer of the adsorbent with the same absorbent cotton;

[0073] S2. Activation: Use 1 mL of anhydrous ethanol as an activator and flow it through the column at a flow rate of 50 μL / min to activate the adsorbent in the column and remove impurities;

[0074] S3. Sample loading: 1 mL of the sample solution to be tested was loaded at a flow rate of 50 μL / min. The carboxyl and silanol groups on the surface of the sodium alginate / silica gel composite material formed hydrogen bonds and electrostatic adsorption with the amino and hydroxyl groups of the analyte clenbuterol hydrochloride.

[0075] S4. Blow dry: Use an empty syringe to connect air to the top of the solid phase extraction cartridge to drain the residual liquid in the cartridge to avoid diluting the subsequent eluent or introducing interference;

[0076] S5. Elution: Use 1 mL of a methanol / acetic acid mixture (methanol and 10% acetic acid, 9:1 by volume) as the eluent at a flow rate of 50 μL / min. Collect 50 μL of the eluate, dry it with nitrogen, and reconstitute the residue with 50 μL of deionized water for high-performance liquid chromatography (HPLC) analysis. Chromatographic conditions: Column: ZORBAX-SB-C18 (4.6 mm × 150 mm, particle size: 5 mm); Injection volume: 20 μL; Column temperature: 30°C; Detection wavelength: 243 nm; Flow rate: 1.0 mL / min; Mobile phase: 0.005 mol / L potassium dihydrogen phosphate solution: acetonitrile (77:23 by volume); UV detector.

[0077] Following the above procedures, solid-phase extraction (SPE) of clenbuterol hydrochloride was performed using the sodium alginate / silica gel composite materials prepared in Examples 1-10 as solid-phase extraction adsorbents, followed by high-performance liquid chromatography (HPLC) analysis. The extraction performance of the sodium alginate / silica gel composite materials prepared in different examples for clenbuterol hydrochloride was investigated by comparing HPLC peak areas.

[0078] Figure 4 This is a comparison of chromatographic peak areas obtained by high performance liquid chromatography analysis after solid phase extraction of clenbuterol hydrochloride using the sodium alginate / silica gel composite materials prepared in Examples 1 to 8 as adsorbents. The abscissa represents the mass ratio of sodium alginate to sodium silicate in different Examples, and the ordinate represents the high performance liquid chromatography peak area. It can be seen that the sodium alginate / silica gel composite materials prepared in Examples 1 and Examples 4 to 8 have better extraction effects on clenbuterol hydrochloride than those prepared in Examples 2 and 3. Among them, the sodium alginate / silica gel composite material prepared in Example 1 has the best extraction effect on clenbuterol hydrochloride, with a mass ratio of sodium alginate to sodium silicate of 1:25.

[0079] Figure 5The chromatographic peak area comparison chart is obtained by performing solid phase extraction of clenbuterol hydrochloride using the sodium alginate / silica gel composite materials prepared in Example 1 and Examples 9-10 as adsorbents and then performing high performance liquid chromatography analysis. It is obvious that when the mass of urea added in step (2) is 0.2 g, the sodium alginate / silica gel composite material has the best extraction effect on clenbuterol hydrochloride.

[0080] Application Example 2

[0081] In step S1, 1 mg of the sodium alginate / silica gel composite material powder prepared in Example 1 was weighed as a solid phase extraction adsorbent, and the remaining operations and steps were the same as those in Application Example 1.

[0082] Application Example 3

[0083] In step S1, 3 mg of the sodium alginate / silica gel composite material powder prepared in Example 1 was weighed as a solid phase extraction adsorbent, and the remaining operations and steps were the same as those in Application Example 1.

[0084] Application Example 4

[0085] In step S5, 1 mL of methanol solution was used as the eluent, and the remaining operations and steps were the same as those in Application Example 1.

[0086] Application Example 5

[0087] In step S5, 1 mL of acetonitrile solution was used as the eluent, and the remaining operations and steps were the same as those in Application Example 1.

[0088] Application Example 6

[0089] In step S5, 1 mL of a methanol / ammonia aqueous solution (the volume ratio of methanol to ammonia aqueous solution is 9:1) is used as the eluent, and the remaining operations and steps are the same as those in Application Example 1.

[0090] Figure 6 This is a comparison of chromatographic peak areas obtained from high-performance liquid chromatography analysis of solid-phase extraction of clenbuterol hydrochloride using different amounts of the sodium alginate / silica gel composite material (Example 1) as an adsorbent in Application Examples 1-3. It can be seen that the best extraction efficiency for clenbuterol hydrochloride was achieved when the sodium alginate / silica gel composite material was used at a dosage of 2 mg. This may be because the sodium alginate / silica gel composite material had fewer adsorption sites when used at a dosage of 1 mg, reducing the extraction efficiency of clenbuterol hydrochloride. When the sodium alginate / silica gel composite material was used at a dosage of 3 mg, the adsorbent layer was too thick, increasing mass transfer resistance and resulting in poor extraction efficiency.

[0091] Figure 7This is a comparison chart of chromatographic peak areas obtained by high performance liquid chromatography analysis of solid phase extraction of clenbuterol hydrochloride using the sodium alginate / silica gel composite material prepared in Example 1 as an adsorbent under different eluent conditions in Application Examples 1 and Application Examples 4 to 6. It can be seen that when a methanol / ammonia mixed solution or a methanol / acetic acid mixed solution is used as the eluent, the extraction effect is better. However, in comparison, the best effect is achieved when a methanol / acetic acid mixed solution (methanol and 10% by mass acetic acid solution are mixed in a volume ratio of 9:1) is used as the eluent.

[0092] (III) Establishment of SPE-HPLC analysis method based on sodium alginate / silica gel composite material

[0093] Using blank pork as the matrix, after mincing the blank pork, weigh 6 pork samples of equal mass (for example, 1.0 g each), add equal volumes of clenbuterol hydrochloride standard solutions of different concentrations to each sample, stir evenly, and make the clenbuterol hydrochloride concentrations in the 6 pork samples of equal mass be 50 ng / g, 100 ng / g, 200 ng / g, 400 ng / g, 800 ng / g, and 2000 ng / g, respectively. Then transfer the 6 pork samples to 6 25 mL centrifuge tubes, add 15 mL of acetonitrile-water mixture (acetonitrile:water volume ratio of 8:2) and 1 mL of 10% NaCl solution to each centrifuge tube, vortex for 10 minutes, then ultrasonicate for 15 minutes, and centrifuge at 8000 r / min for 5 minutes at 4°C. Take the supernatant after centrifugation and transfer it to another set of 25 mL centrifuge tubes. Add 15 mL of carbon tetrachloride to each centrifuge tube and let it stand for 30 minutes. After 1 minute, the supernatant was taken and dried with nitrogen. The residue was fully dissolved in 1 mL of acetonitrile to obtain 6 test sample solutions. The clenbuterol hydrochloride in the 6 test sample solutions was enriched according to the solid phase extraction method of Application Example 1 and analyzed by high performance liquid chromatography. The chromatographic conditions were as described above. The concentration of clenbuterol hydrochloride in the 6 pork samples was used as the horizontal axis (ng / g) and the chromatographic peak area of ​​clenbuterol hydrochloride after extraction was used as the vertical axis to draw a standard curve, as shown in the figure below. Figure 8 The results showed that the linear range of clenbuterol hydrochloride was 15.99-2000 ng / g, the regression equation was y=13.66x+1.4537, and the correlation coefficient R²=0.9983. Calculations showed that the limit of detection (LOD) of clenbuterol hydrochloride using the SPE-HPLC analysis method prepared by the present invention was 7.52 ng / g, and the limit of quantification (LOQ) was 15.99 ng / g, demonstrating high sensitivity.

[0094] When the sodium alginate / silica gel composite material of the present invention is used as a solid phase extraction adsorbent for actual sample analysis, the actual sample is treated according to the preparation method of the test sample solution described above, the obtained test sample solution is subjected to solid phase extraction according to the method of Application Example 1, and high performance liquid chromatography analysis is performed. The obtained chromatographic peak area is substituted into the regression equation, and the clenbuterol hydrochloride content in the sample is obtained by calculation.

[0095] The above description is merely an embodiment of the present invention and does not constitute any form of limitation to the present invention. The present invention may also have other forms of embodiments based on the above structures and functions, which are not listed here one by one. Therefore, any simple modification, equivalent changes, and modifications made to the above embodiments by any person skilled in the art in accordance with the technical essence of the present invention without departing from the scope of the technical solution of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. Application of sodium alginate / silica gel composite material in the detection of clenbuterol, characterized in that: The sodium alginate / silica gel composite material is prepared according to the following method: (1) Sodium silicate was dissolved in deionized water. After it was completely dissolved, sodium alginate was added. The mass ratio of sodium alginate to sodium silicate was 1:(20-50). The mixture was stirred until a uniform mixed solution was formed. The pH of the mixed solution was adjusted to 5.0±0.

1. The mixed solution gradually changed from transparent to milky white sol. (2) adding urea to the sol obtained in step (1) with a mass ratio of urea to sodium silicate of 1:8.5, transferring the resulting mixture to a polytetrafluoroethylene-lined high-pressure hydrothermal reactor, sealing the reactor and reacting at a constant temperature of 160°C for 20 to 24 hours; (3) After the hydrothermal reaction is completed, the reactor is cooled naturally to room temperature, the product is taken out and filtered, the filtered product is washed with deionized water, and then vacuum dried to obtain a light yellow solid, namely, sodium alginate / silica gel composite material.

2. The use of the sodium alginate / silica gel composite material in the detection of clenbuterol according to claim 1, characterized in that: The mass ratio of sodium alginate to sodium silicate in step (1) is 1:

25.

3. The use of the sodium alginate / silica gel composite material in the detection of clenbuterol according to claim 1, characterized in that: The product in step (3) is dried in a vacuum drying oven at 60-80°C for 12-24 h.

4. The use of the sodium alginate / silica gel composite material in the detection of clenbuterol according to claim 1, characterized in that: The sodium alginate / silica gel composite material has a uniform porous network structure, and the pore size distribution is 2-15 nm.

5. The use of the sodium alginate / silica gel composite material in the detection of clenbuterol according to claim 1, characterized in that: Solid phase extraction combined with high performance liquid chromatography was used to detect the content of clenbuterol.

6. The use of the sodium alginate / silica gel composite material in the detection of clenbuterol according to claim 5, characterized in that: Solid phase extraction methods include: S1. Column filling: Take an empty polypropylene solid phase extraction column, pad the bottom of the polypropylene solid phase extraction column with absorbent cotton, and evenly fill the solid phase extraction column with sodium alginate / silica gel composite material as a solid phase extraction adsorbent, and cover the upper layer of the adsorbent with the same absorbent cotton; S2, activation: use anhydrous ethanol as the activating agent and flow through the column at a flow rate of 50 μL / min; S3, sample loading: the sample to be tested was loaded at a flow rate of 50 μL / min; S4. Blow dry: Use an empty syringe to connect air to the top of the solid phase extraction cartridge to drain the residual liquid in the cartridge; S5. Elution: Use a methanol / acetic acid mixed solution as the eluent, with a volume ratio of methanol to acetic acid of 9:1 in the mixed solution, and elute at a flow rate of 50 μL / min. Collect the eluate, blow dry with nitrogen, and reconstitute the residue with deionized water for high performance liquid chromatography analysis.

7. Use of the sodium alginate / silica gel composite material according to claim 5 or 6 in the detection of clenbuterol, characterized in that: Clenbuterol is clenbuterol hydrochloride.

8. The use of the sodium alginate / silica gel composite material in the detection of clenbuterol according to claim 7, characterized in that: The detection limit of clenbuterol hydrochloride was 7.52 ng / g, and the quantification limit was 15.99 ng / g.

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