A carboxyl-cyano bifunctional group-modified silica material, and its preparation and application

Abstract

The present invention discloses a carboxyl-cyano bifunctional group-modified silica material with adjustable polarity, and its preparation and application. In order to solve the problem that the cyano solid phase extraction column has a poor enrichment effect on cationic targets during sample pretreatment, a carboxyl-cyano bifunctional group-modified silica material is prepared by acidifying the cyano-modified silica with a sulfuric acid solution. By changing the concentration of the sulfuric acid solution and the acidification temperature, the carboxyl bonding amount can be adjusted to control the surface polarity of the material, so that the material can achieve the enrichment of non-ionic polar targets and cationic targets in polar solutions.

Description

Technical Field

[0001] The invention relates to a solid phase extraction material, in particular to a bifunctional group-modified silica material, and preparation and application thereof. Background Art

[0002] Since silica has a diverse pore structure, high specific surface area, excellent thermal and hydrothermal stability, and abundant silanol groups on its surface that can serve as bonding sites (O'Mahony TF, Morris M A. Hydroxylation methods for mesoporous silica and their impact on surface functionalisation[J]. Microporous and Mesoporous Materials, 2021, 317:110989.), it is often used as a carrier and modified with functional groups for the enrichment of target substances in sample pretreatment.

[0003] However, during the sample pretreatment process, the target compounds often have different polarities. When they are collected step by step, the pretreatment process is complicated and consumes more reagents. In order to simplify the pretreatment steps, target compounds of different polarities are enriched at the same time. At this time, materials modified with a single functional group are often not competent. For example, cyano-modified silica, as a classic adsorbent, is often used for the enrichment of non-ionic polar compounds, such as the detection of organophosphorus pesticides in environmental water (Soutoudehnia Korrani Z, Wan Ibrahim WA, Rashidi Nodeh H, et al. Simultaneous preconcentration of polar and non-polar organophosphorus pesticides from water samples by using a new sorbent based on mesoporous silica[J]. Journal of Separation Science, 2016, 39(6): 1144-1151.). But in fact, different types of pesticides are used in agricultural production, and cationic pesticides such as diquat and paraquat may also exist. The single cyano-modified material has a poor adsorption effect on cationic compounds in polar solvents. If different solid phase extraction fillers are used to collect multiple target compounds in steps, the processing steps will be complicated, more reagents will be consumed, and the detection cost will increase.

[0004] In order to more effectively monitor toxic substances in the environment, simplify the pretreatment process and reduce costs, there is a need in the art to improve the original single functional group modified materials to achieve the simultaneous enrichment of polar compounds and cationic compounds for detection. Summary of the invention

[0005] The purpose of the present invention is to provide a bifunctional group-modified silica material to solve the problem of simultaneously enriching polar compounds and cationic compounds.

[0006] Another object of the present invention is to provide a method for preparing the bifunctional group-modified silica material.

[0007] Another object of the present invention is to provide use of the bifunctional group-modified silica material.

[0008] In a first aspect of the present invention, a bifunctional group-modified silica material is provided; the bifunctional group is a carboxyl-cyano bifunctional group, and the bifunctional group-modified silica material comprises: silica as a carrier; and a carboxyl functional group and a cyano functional group bonded to the surface of the silica.

[0009] In a preferred embodiment, the particle size of the silicon dioxide is 30 to 300 μm, preferably 50 to 150 μm.

[0010] In a preferred embodiment, the specific surface area of ​​the silicon dioxide is 200 to 600 m 3 / g, preferably 250-450 m 3 / g.

[0011] In some embodiments, the particle size of the silica includes 55, 60, 65, 70, 80, 90, 120 μm, etc.

[0012] In some embodiments, the specific surface area of ​​the silicon dioxide includes, for example, 280, 300, 350, 400, 420 m 3 / g, etc.

[0013] In a preferred embodiment, in the bifunctional group-modified silica material, the nitrogen element accounts for 0.12 to 3.50 wt %, preferably 0.3 to 2.5 wt %, of the total amount of the bifunctional group-modified silica material.

[0014] In a preferred embodiment, in the bifunctional group-modified silica material, the ion exchange capacity (bonding amount of carboxyl groups) is 0.12 to 2.5 mmol / g, preferably 0.5 to 2.5 mmol / g.

[0015] In a preferred embodiment, in the bifunctional group-modified silica material, the molar ratio of the cyano group to the carboxyl group is 0.1-10, preferably 2-8.

[0016] In some embodiments, the nitrogen element accounts for 0.2, 0.3, 0.8, 1, 1.5, 2, 2.5, 3, 3.45 wt % of the total amount of the bifunctional group-modified silica material.

[0017] In some embodiments, the ion exchange capacity (bonding amount of carboxyl groups) is, for example, 0.6, 0.8, 1, 1.2, 1.5, 1.8, 2, 2.2, or 2.4 mmol / g.

[0018] In some embodiments, the molar ratio of the cyano group to the carboxyl functional group is, for example, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, or 9.

[0019] In a preferred embodiment, the bifunctional group-modified silica material is prepared by the following method: using silica as a carrier, bonding a carboxyl functional group and a cyano functional group to the surface of the silica; preferably, the method includes the step of controlling the acidification process and the reaction temperature to control the conversion amount of cyano groups to carboxyl groups; specifically, the method includes: (1) dispersing silica in a solvent, adding a cyanosilane coupling agent dropwise therein, to obtain cyano-modified silica; (2) preparing a sulfuric acid solution, dispersing the cyano-modified silica therein, and reacting sufficiently to obtain a carboxyl-cyano bifunctional group-modified silica material.

[0020] In a second aspect of the present invention, a method for preparing a bifunctional group-modified silica material is provided, comprising using silica as a carrier and bonding two functional groups, carboxyl and cyano, to the surface of the silica.

[0021] In a preferred embodiment, the method comprises the steps of controlling the acidification process and the reaction temperature to control the conversion amount of cyano groups to carboxyl groups; specifically comprising: (1) dispersing silica in a solvent, and adding a cyanosilane coupling agent dropwise therein to obtain cyano-modified silica; and (2) preparing a sulfuric acid solution, dispersing the cyano-modified silica therein, and reacting the solution sufficiently to obtain a carboxyl-cyano bifunctional group-modified silica material.

[0022] In a preferred embodiment, in (2), the concentration of the sulfuric acid solution is 10% to 75% (wt%), preferably 18% to 70% (wt%).

[0023] In a preferred embodiment, the dosage ratio of the cyano-modified silica to the sulfuric acid solution is 1 g: 1-10 mL; preferably 1 g: 1-5 mL.

[0024] In a preferred embodiment, the sufficient reaction comprises: reacting at 25-80° C. for 1-16 hours, preferably reacting at 50-70° C. for 2-6 hours.

[0025] In a preferred embodiment, the silicon dioxide is spherical silica gel or amorphous silica gel.

[0026] In some embodiments, the concentration of the sulfuric acid solution is, for example, 19%, 20%, 30%, 40%, 50%, 60%, 70%, or 75% (wt%).

[0027] In some embodiments, the usage ratio of the cyano-modified silica: sulfuric acid solution is, for example, 1 g:2 mL, 1 g:4 mL, 1 g:5 mL, 1 g:6 mL, 1 g:8 mL, 1 g:9 mL.

[0028] In some embodiments, the cyano-modified silica is dispersed in a sulfuric acid solution and then reacted at, for example, 30, 40, 50, 60, or 70°C.

[0029] In some embodiments, the cyano-modified silica is dispersed in the sulfuric acid solution and reacted for, for example, 2, 4, 6, 8, 10, 12, or 15 hours.

[0030] The bifunctional group-modified silica material is used to calculate the bonding amount (mmol / g) of the carboxyl and cyano functional groups on the surface of the carrier silica by the mass fraction (wt%) of the nitrogen element and the ion exchange capacity (mmol / g). The specific calculation formula is as follows:

[0031] The bonding amount of cyano group = the mass fraction of nitrogen element / the relative atomic mass of nitrogen element

[0032] The amount of carboxyl bonding = ion exchange capacity

[0033] In some embodiments, in (1), the silica is dispersed in the solvent by mechanical stirring.

[0034] In some embodiments, in (2), the cyano-modified silica is dispersed in the sulfuric acid solution by mechanical stirring.

[0035] In a preferred embodiment, the solvent is any one of benzene, toluene or acetonitrile or a combination thereof.

[0036] In a preferred embodiment, the silane coupling agent is any one of trichloro-2-cyanoethylsilane, (3-cyanopropyl)methylchlorosilane, 2-cyanoethyltriethoxysilane or cyanotrimethoxysilane, or a combination thereof (such as two).

[0037] In a preferred embodiment, the usage ratio of the solvent: silane coupling agent: silicon dioxide is 2~5 mL: 0.1~0.5 g: 0.2~1 g.

[0038] As a preferred embodiment of the present invention, in step (1), the volume mass ratio of the solvent: silane coupling agent: silicon dioxide is 4~5 mL: 0.4~0.5 g: 0.8~1 g.

[0039] In the third aspect of the present invention, the bifunctional group-modified silica material is used for solid phase extraction or chromatography filler.

[0040] In a fourth aspect of the present invention, a solid phase extraction column is provided, which is filled with the bifunctional group-modified silica material of the present invention.

[0041] In the fifth aspect of the present invention, a method for solid phase extraction or further analysis of the extraction product is provided, comprising: (a) the solid phase extraction column as described above; (b) adding a sample containing or potentially containing the target analyte to the solid phase extraction column of (a) to extract the target analyte; preferably, it also comprises qualitative or quantitative analysis (such as chromatographic analysis) of the extraction product.

[0042] The present invention selects common medium polarity organophosphorus pesticides parathion and fenthion, and cationic pesticides paraquat and diquat as target compounds, and investigates the adsorption performance of carboxyl-cyano bifunctional group modified silica materials.

[0043] Under the optimal conditions, the silica filler modified with carboxyl-cyano bifunctional groups has a surface cyano / carboxyl molar ratio of 2-8, which can effectively adsorb medium-polarity, high-polarity and cationic targets, and the recovery rates of targets such as parathion and fenthion, paraquat and diquat are all greater than 95%.

[0044] Based on this, the present invention prepares a polarity-adjustable carboxyl-cyano bifunctional group-modified silica material. The bonding amount of the carboxyl functional group on the filler surface is adjusted by controlling the acidification conditions, thereby adjusting the surface polarity of the filler. Under preferred conditions, the bifunctional group-modified silica material has good selective adsorption performance for medium-polarity, high-polarity compounds and cationic compounds. This solves the problem of simultaneously processing polar compound and cationic compound sample adsorption. The present invention simplifies the sample pretreatment steps, improves the sample pretreatment efficiency, and also makes up for the shortcomings of similar fillers on the market. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the preparation process of the carboxyl-cyano bifunctional group modified silica material of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following general description and definition of the terms and uses mentioned in the specification and claims are provided. Unless otherwise specified, the technical and scientific terms used herein are the common meanings understood by those skilled in the art for the present invention. In case of conflict, the definitions in this specification shall prevail.

[0047] In this document, all features defined in the form of numerical ranges or percentage ranges, such as values, quantities, contents and concentrations, are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0048] The above-mentioned features mentioned in the present invention or the features mentioned in the embodiments can be combined in any way. All the features disclosed in the specification of this case can be used in combination with any combination form. As long as there is no contradiction in the combination of these features, all possible combinations should be considered to be within the scope of this specification. Each feature disclosed in the specification can be replaced by any alternative feature that can provide the same, equal or similar purpose. Therefore, unless otherwise specified, the disclosed features are only general examples of equal or similar features.

[0049] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] The present invention is described in detail below in conjunction with embodiments, but the implementation of the present invention is not limited thereto. Example

[0051] Take 50 g of silica (particle size 40 μm; specific surface area 247 m3 / g, amorphous silica gel), disperse it in 100 mL of toluene by mechanical stirring. Add 5 g of 2-cyanoethyltriethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter by suction, and dry at 60°C for 12 hours to obtain cyano-modified silica.

[0052] Take 50 g of the above cyano-modified silica, disperse it in 100 mL of 10% sulfuric acid solution (wt%) by mechanical stirring, heat it to 60 °C and continue stirring for 6 hours, and the reaction is completed. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups. Example

[0053] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene by mechanical stirring. Add 25 g of 2-cyanoethyltriethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter by suction, and dry at 60°C for 12 hours to obtain cyano-modified silica.

[0054] Take 50 g of the cyano-modified silica, disperse it in 50 mL of 10% sulfuric acid solution (wt%) by mechanical stirring, heat it to 60 °C and continue stirring for 6 hours, and the reaction is completed. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups. Example

[0055] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene with mechanical stirring. Add 10 g of cyanotrimethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter and dry at 60 °C for 12 hours to obtain cyano-modified silica.

[0056] Take 50 g of the cyano-modified silica, disperse it in 50 mL of 10% sulfuric acid solution (wt%) by mechanical stirring, heat it to 60 °C and continue stirring for 2 hours, and the reaction is completed. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups. Example

[0057] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene with mechanical stirring. Add 10 g of cyanotrimethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter and dry at 60 °C for 12 hours to obtain cyano-modified silica.

[0058] Take 50 g of the cyano-modified silica, disperse it in 70 mL of 20% sulfuric acid solution (wt%) by mechanical stirring, heat it to 60 °C and continue stirring for 7 hours, and the reaction is finished. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups. Example

[0059] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene with mechanical stirring. Add 10 g of cyanotrimethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter and dry at 60 °C for 12 hours to obtain cyano-modified silica.

[0060] Take 50 g of the cyano-modified silica, disperse it in 70 mL of 20% sulfuric acid solution (wt%) by mechanical stirring, heat it to 60 °C and continue stirring for 7 hours, and the reaction is finished. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups. Example

[0061] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene with mechanical stirring. Add 10 g of cyanotrimethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter and dry at 60 °C for 12 hours to obtain cyano-modified silica.

[0062] Take 50 g of the cyano-modified silica, disperse it in 70 mL of 40% sulfuric acid solution (wt%) by mechanical stirring, heat it to 60 °C and continue stirring for 7 hours, and the reaction is completed. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups. Example

[0063] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene with mechanical stirring. Add 10 g of cyanotrimethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter and dry at 60 °C for 12 hours to obtain cyano-modified silica.

[0064] Take 50 g of the cyano-modified silica, disperse it in 70 mL of 50% sulfuric acid solution (wt%) by mechanical stirring, heat it to 70 °C and continue stirring for 7 hours, and the reaction is completed. Filter it by suction, and dry it at 60 °C for 12 hours to obtain carboxyl-cyano functional group-modified silica. Example

[0065] Take 50 g of silica (particle size 60 μm; specific surface area 350 m3 / g, amorphous silica gel), disperse it in 250 mL of toluene with mechanical stirring. Add 10 g of cyanotrimethoxysilane, continue stirring for 5 hours, and the reaction is completed. Filter and dry at 60 °C for 12 hours to obtain cyano-modified silica.

[0066] Take 50 g of the cyano-modified silica, disperse it in 80 mL of 70% sulfuric acid solution (wt%) by mechanical stirring, heat it to 70 °C and continue stirring for 7 hours, and the reaction is completed. Filter it by suction, and dry it at 60 °C for 12 hours to obtain silica modified with carboxyl-cyano functional groups.

[0067] Application Examples

[0068] The intermediate products prepared in Examples 1 to 8 were used as solid phase extraction fillers to perform recovery experiments and analyses of mixed solutions of organophosphorus pesticides and cationic pesticides. The intermediate products were cyano-modified silica. The mixed solutions of pesticides included parathion, fenthion, paraquat and diquat.

[0069] The carboxyl-cyano functional group-modified silica material prepared in Examples 1 to 8 was used as a solid phase extraction filler to perform an experimental analysis of the recovery of the pesticide mixture.

[0070] The specific steps are as follows:

[0071] (1) Sample solution preparation: Using ethanol as solvent, prepare a 5 ppm mixed solution of organophosphorus pesticides and cationic pesticides (10 mL, including parathion, fenthion, paraquat and diquat) as the sample solution;

[0072] (2) Take 0.5 g of the target product carboxyl-cyano functional group-modified silica material in Examples 1 to 8 and load it into a solid phase extraction column; take 500 mg of the intermediate product (cyano-modified silica material) in Examples 1 to 8 and load it into a solid phase extraction column (capacity 500 mg, 6 mL). Take two commercially available cyano SPE columns (Sep-Pakyanopropyl (CN) purchased from Waters, Bond Elut cyano (CN) purchased from Agilent) as controls;

[0073] (3) Activate and equilibrate the four columns in step (2) with 5 mL of methanol and 5 mL of ethanol, respectively;

[0074] (4) Load 10 mL of pesticide mixed standard loading solution;

[0075] (5) Add 5 mL of acetonitrile for elution, and the eluate is filtered through a membrane and then analyzed by liquid chromatography.

[0076] Analytical methods

[0077] The nitrogen element of the filler is measured by an element analyzer. In the raw materials used, cyano group is the only source of nitrogen element, and the bonding amount of cyano group can be calculated by the content of nitrogen element.

[0078] The ion exchange capacity is measured according to the national standard GB / T 8144-2008 "Cation Resin Exchange Capacity Determination Method". The carboxyl group is the only group in the filler that contributes to the ion exchange capacity. The bonding amount of the carboxyl group can be calculated based on the ion exchange capacity. The greater the ion exchange capacity of the material, the more carboxyl bonding amount it has, and the greater the polarity of the silica material.

[0079] With reference to relevant patents and standards, liquid chromatography-mass spectrometry was used to quantitatively analyze the target substances (Zhang Yurong, Liang Chen, Ye Haiying, et al. Qualitative screening method for 242 compounds simultaneously by liquid chromatography-mass spectrometry:, CN101398414 B[P].; Determination of paraquat and diquat residues in exported plant-derived foods by liquid chromatography-mass spectrometry / mass spectrometry, SN / T 0293-2014). A Waters Alliance 2695 / Quattro Premier XE tandem quadrupole liquid-mass spectrometer (Waters, USA) was used, the chromatographic column was C18 5μm2.1×150mm (Waters), the column temperature was 45°C, the mobile phase was A: 2mM ammonium formate and 0.05% formic acid in water (0.126g ammonium formate and 500μL formic acid, add water to 1000mL); B: 2mM ammonium formate and 0.05% formic acid in acetonitrile (0.126g ammonium formate and 500μL formic acid dissolved in 40mL water, add 960mL acetonitrile), the flow rate was 0.2 mL / min. The gradient program is as follows:

[0080] Table 1 Gradient elution program

[0081] Time (min) Mobile phase A (%) Mobile phase B (%) 0.00 95.0 5.0 0.50 95.0 5.0 1.00 90.0 10.0 5.00 80.0 20.0 10.00 50.0 50.0 18.00 30.0 70.0 20.00 0.0 100.0

[0082] The mass spectrometry conditions were: positive and negative ion simultaneous scanning mode, spray voltage 3200 V, and ion source temperature 105 °C. The specific MRM parameters are as follows

[0083] Table 2 MSM specific parameters

[0084] Target Precursor ion pair (m / z) Product ion pair (m / z) Collision voltage (V) Parathion 293.1 237.1 17 Fenthion 280.2 170.1 20 Diquat 185.0 169.7 19 Paraquat 183.1 156.9 20

[0085] Table 3 Characterization of adsorption capacity and ion exchange capacity of intermediate product fillers of Examples 1 to 8

[0086] batch number Recovery rate of parathion (%) Fenthion recovery rate (%) Paraquat recovery rate (%) Diquat recovery rate (%) Ion exchange capacity (mmol / g) Nitrogen content (wt%) Example 1 - Intermediate Product 82.2 81.5 30.2 15.9 0.01 1.62 Example 2 - Intermediate Product 98.1 95.2 36.3 23.8 0.01 4.45 Example 3 - Intermediate Product 85.2 82.4 22.3 23.3 0.02 3.43 Example 4 - Intermediate Product 90.9 91.5 24.5 29.4 0.01 3.44 Example 5 - Intermediate Product 95.3 93.0 21.2 23.9 0.01 3.49 Example 6 - Intermediate Product 97.7 94.2 27.0 24.2 0.01 3.49 Example 7 - Intermediate Product 96.3 95.8 24.5 24.3 0.01 3.41 Example 8 - Intermediate Product 98.1 96.1 25.4 21.9 0.02 3.49

[0087] Table 4 Characterization of adsorption capacity and ion exchange capacity of the bifunctional group modified silica fillers described in Examples 1 to 8

[0088] batch number Recovery rate of parathion (%) Fenthion recovery rate (%) Paraquat recovery rate (%) Diquat recovery rate (%) Ion exchange capacity (mmol / g) Nitrogen content (wt%) Cyano / Carboxyl (molar ratio) Example 1 87.2 86.5 32.0 17.1 0.56 0.83 1.94 Example 2 91.1 85.2 42.3 45.1 0.72 3.44 1.29 Example 3 88.2 86.4 41.3 39.3 0.77 2.35 1.46 Example 4 92.9 90.5 61.5 78.4 0.83 2.27 1.51 Example 5 93.3 94.0 72.2 84.8 1.21 1.79 1.94 Example 6 96.7 97.2 98.8 96.3 1.62 1.22 2.86 Example 7 98.3 96.8 95.8 95.3 2.10 0.47 7.26 Example 8 89.1 93.1 96.5 97.6 2.23 0.36 9.48 Sep-Pakyanopropyl(CN) 95.3 94.8 40.2 36.8 / / / Bond Elut Cyano(CN) 97.6 95.9 51.8 47.7 / / /

[0089] In Examples 1 to 8, the characterization results of the recovery rate, nitrogen content and ion exchange capacity of the intermediate product filler are shown in Table 3. The intermediate product filler without acidification has a good enrichment effect on medium polarity and polar targets (recovery rate 85-99%), but a poor enrichment effect on cationic targets (recovery rate <30%), which may be due to the fact that the material has no carboxyl modification and the surface polarity is small (ion exchange capacity <0.01).

[0090] In Examples 1-8, the characterization results of the recovery rate, nitrogen content and ion exchange capacity of the carboxyl-cyano stationary phase filler are shown in Table 4. For the material after sulfuric acid acidification, as the concentration of sulfuric acid solution and the acidification temperature increase, the carboxyl bonding amount increases, the cyano bonding amount decreases, the ion exchange capacity on the surface of the material increases, and the enrichment effect on the cationic target is enhanced. However, when the degree of acidification is further increased, the ion exchange capacity continues to increase, and the enrichment effect of the material on the medium polarity target is weakened. This may be due to the excessive surface polarity and the weak interaction between the medium polarity target, resulting in a lower recovery rate. This shows that by adjusting the concentration of sulfuric acid solution and the acidification temperature, the bonding amount of the carboxyl functional group on the surface of the material can be effectively controlled to adjust the polarity of the surface of the material. Under preferred conditions (Examples 6 and 7), the prepared carboxyl-cyano bifunctional group modified silica filler has a cyano / carboxyl molar ratio of 2 to 8, which can efficiently enrich medium polarity and polar targets, and its performance can be compared with commercial cyano fillers. At the same time, the prepared material can also efficiently enrich cationic targets (recovery rate>95%), and its performance is better than that of commercial cyano fillers.

[0091] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make some modifications and improvements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the definition of the claims.

Claims

1. A use of a bifunctional group-modified silica material, characterized in that: The bifunctional group is a carboxyl-cyano bifunctional group, and the bifunctional group-modified silica material includes: Silica as a support; and a carboxyl functional group and a cyano functional group bonded to the surface of the silica; The particle size of the silicon dioxide is 30 to 300 μm, and the specific surface area of ​​the silicon dioxide is 200 to 600 m 3 / g; Wherein, the nitrogen element accounts for 0.12 to 3.50 wt% of the total amount of the bifunctional group-modified silica material, and / or The ion exchange capacity is 0.12 to 2.5 mmol / g, and / or The molar ratio of the cyano group to the carboxyl functional group is 0.1 to 10; The silicon dioxide is spherical silica gel or amorphous silica gel; the ion exchange capacity is the bonding amount of the carboxyl group; The bifunctional group-modified silica material is used as a solid phase extraction filler to extract the target analyte; The target analytes are: parathion, fenthion, paraquat and diquat.

2. The use of the bifunctional group-modified silica material according to claim 1, characterized in that: The particle size of the silicon dioxide is 50 to 150 μm; The specific surface area of ​​the silicon dioxide is 250 to 450 m 3 / g.

3. The use of the bifunctional group-modified silica material according to claim 1, characterized in that: The nitrogen element accounts for 0.3 to 2.5 wt % of the total amount of the bifunctional group-modified silica material; and / or An ion exchange capacity of 0.5 to 2.5 mmol / g; and / or The molar ratio of the cyano group to the carboxyl functional group is 2-8.

4. The use of the bifunctional group-modified silica material according to claim 1, characterized in that: The bifunctional group-modified silica material is prepared by the following method: using silica as a carrier, and bonding a carboxyl functional group and a cyano functional group to the surface of the silica.

5. The use of the bifunctional group-modified silica material according to claim 4, characterized in that: The method comprises the steps of controlling the acidification process and the reaction temperature to control the conversion amount of cyano groups into carboxyl groups; specifically comprising: (1) dispersing silica in a solvent, and dropping a cyanosilane coupling agent therein to obtain cyano-modified silica; (2) preparing a sulfuric acid solution, dispersing the cyano-modified silica therein, and allowing the solution to react sufficiently to obtain a carboxyl-cyano bifunctional group-modified silica material.

6. The use of the bifunctional group-modified silica material according to claim 5, characterized in that: The method comprises the steps of controlling the acidification process and the reaction temperature to control the conversion amount of cyano groups into carboxyl groups; specifically comprising: (1) dispersing silica in a solvent, and dropping a cyanosilane coupling agent therein to obtain cyano-modified silica; In step (1), The solvent includes any one of benzene, toluene or acetonitrile or a combination thereof; The usage ratio of the solvent: cyanosilane coupling agent: silicon dioxide is 2~5 mL: 0.1~0.5 g: 0.2~1 g; (2) preparing a sulfuric acid solution, dispersing the cyano-modified silica therein, and allowing the solution to react sufficiently to obtain a carboxyl-cyano bifunctional group-modified silica material; Wherein, in step (2), The concentration of the sulfuric acid solution is 10% to 75% (wt%); or The dosage ratio of the cyano-modified silica: sulfuric acid solution = 1 g: 1-10 mL; or The sufficient reaction includes: reacting at 25-80° C. for 1-16 hours.

7. The use of the bifunctional group-modified silica material according to claim 6, characterized in that: In step (2), The concentration of the sulfuric acid solution is 18% to 70% (wt%); or The dosage ratio of the cyano-modified silica: sulfuric acid solution = 1 g: 1-5 mL; or The sufficient reaction includes: reacting at 50-70° C. for 2-6 hours.

8. The use of the bifunctional group-modified silica material according to claim 6, characterized in that: The cyanosilane coupling agent includes any one of trichloro-2-cyanoethylsilane, (3-cyanopropyl)methylchlorosilane, 2-cyanoethyltriethoxysilane, cyanotrimethoxysilane or a combination thereof.

9. The use of the bifunctional group-modified silica material according to claim 6, wherein the ratio of the solvent: cyanosilane coupling agent: silica is 4-5 mL: 0.4-0.5 g: 0.8-1 g.

10. The use of the bifunctional group-modified silica material according to claim 1, characterized in that: (a) using the bifunctional group-modified silica material of claim 1 as a filler to prepare a solid phase extraction column; (b) Adding a sample containing or potentially containing the target analyte to the solid phase extraction column of (a) to extract the target analyte.

11. The use of the bifunctional group-modified silica material according to claim 10, further comprising further using the target analyte for qualitative or quantitative analysis.

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