High surface area surface porous chromatographic stationary phase and method of making

Abstract

The application discloses a high specific surface area surface layer porous chromatographic stationary phase and a preparation method, and belongs to the technical field of liquid chromatography silica gel microspheres. The silica gel microspheres used in the stationary phase have two-stage pore structure with a great size difference, wherein the first-stage size large pore provides a mobile phase channel, and the second-stage size small pore provides specific surface area required by chromatographic separation. The application prepares rich small pores (second-stage pores) on the pore wall of the large pores (first-stage pores) of the microspheres, so that the second-stage effective separation pores of the microspheres are all located on the surface of the first-stage large pores. Compared with full-porous stationary phase microspheres, the application can reduce the adverse influence of vortex diffusion in the chromatographic separation process and greatly reduce the mass transfer resistance. Compared with traditional core-shell stationary phases, the application has lower column pressure and higher column efficiency, and has a larger sample loading amount. The application has significant advantages compared with traditional full-porous stationary phases and core-shell stationary phases.

Description

Technical Field

[0001] This invention relates to the field of silica microsphere technology for liquid chromatography, and more particularly to a high specific surface area porous surface chromatographic stationary phase and its preparation method. Background Technology

[0002] Liquid chromatography (LC) is a commonly used separation and analysis technique with advantages such as high resolution, high sensitivity, and wide applicability. The stationary phase is a crucial component in LC, and its performance directly affects the chromatographic separation effect. Existing stationary phases mainly include fully porous stationary phases and core-shell stationary phases; however, both have certain limitations. While fully porous stationary phases have a high specific surface area, they are prone to eddy diffusion during chromatographic separation, affecting the separation effect. Core-shell stationary phases, although able to reduce the influence of eddy diffusion, have a smaller specific surface area, with all pores existing only on the spherical surface of the microspheres, resulting in low sample loading capacity and making them unsuitable for preparative separation. Furthermore, most core-shell stationary phases consist of small-diameter microspheres (≤3 μm), leading to high back pressure and limiting their widespread application. Therefore, there is a need to develop a novel LC stationary phase structure to overcome the shortcomings of existing technologies. Summary of the Invention

[0003] The purpose of this invention is to solve the above-mentioned problems in the prior art and provide a high specific surface area surface porous chromatographic stationary phase and its preparation method. The silica microspheres used have a two-level pore structure with huge size differences, which can significantly reduce mass transfer resistance, while having a larger sample loading capacity, lower column pressure and higher column efficiency.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A high specific surface area porous chromatographic stationary phase comprises silica microspheres. The silica microspheres have a two-level pore structure, including primary macropores and secondary mesopores. The primary macropores have a pore size of 100–500 nm and serve as channels for the mobile phase during chromatographic separation. The secondary mesopores are distributed on the pore walls of the primary macropores and have a pore size of 5–30 nm, providing the specific surface area required for chromatographic separation.

[0006] The specific surface area of ​​the silica microspheres is 80–350 m². 2 / g, with a particle size of 1–10 μm.

[0007] The surface of the silica microspheres is bonded with functional groups.

[0008] The functional group includes C18.

[0009] The method for preparing the high specific surface area porous surface chromatographic stationary phase includes the following steps:

[0010] 1) The porous silica microspheres were mixed with a salt solution, dried, and then calcined at 500-700℃. After washing, silica microspheres with primary macropores were obtained.

[0011] 2) The primary macroporous silica microspheres obtained in step 1) are dispersed in an alcohol-water mixed solvent, a template agent and a silicon source are added, and a reaction is carried out to form a mesoporous coating on the pore walls of the primary macroporous channels. After filtration, washing and drying, the template agent is removed by calcination at 500-700℃ to obtain high specific surface area surface porous silica microspheres.

[0012] 3) Surface bonding modification is performed on the silica microspheres obtained in step 2) to obtain the chromatographic stationary phase.

[0013] In step 1), the porous silica microspheres have a pore size of 8–12 nm and a specific surface area of ​​300–400 m². 2 / g; the salt solution is a sodium chloride solution with a mass concentration of 5% to 15%; the calcination temperature is 600℃ and the time is 4 to 8 hours.

[0014] In step 2), the template agent is dodecylamine; the silicon source is tetraethyl silicate; the reaction includes ultrasonic treatment and a static settling process; the calcination temperature is 600℃ and the time is 8-12 hours.

[0015] In step 3), the surface bonding modification includes: activating the high specific surface area porous silica microspheres obtained in step 2) with acid, washing them with water until neutral and drying them, mixing them with toluene, and reacting them with octadecyldimethylchlorosilane in the presence of a catalyst to obtain a C18 bonded chromatographic stationary phase.

[0016] In step 1), the average pore size of the obtained primary macroporous silica microspheres is 100–500 nm, and the specific surface area is 15–40 m². 2 / g.

[0017] In step 2), the average pore size of the secondary channels of the high specific surface area porous silica microspheres is 5–30 nm, and the specific surface area is 80–350 m². 2 / g.

[0018] Compared with the prior art, the beneficial effects achieved by the technical solution of this invention are:

[0019] The silica microspheres have a two-level pore structure with significant size differences. The large primary macropores provide mobile phase channels, while the small secondary mesopores provide the specific surface area required for chromatographic separation. Compared with fully porous stationary phase microspheres, they significantly reduce mass transfer resistance while mitigating the adverse effects of eddy diffusion during chromatographic separation. Compared with traditional core-shell stationary phases, they offer lower column pressure and higher column efficiency, while also providing a larger sample loading capacity. Attached Figure Description

[0020] Figure 1 This is an electron microscope image of porous silica microspheres.

[0021] Figure 2 Electron micrograph of macroporous silica microspheres.

[0022] Figure 3 This is a statistical diagram of the pore size of porous silica microspheres with high specific surface area.

[0023] Figure 4 This is a statistical chart showing the specific surface area of ​​macroporous silica microspheres and high specific surface area porous silica microspheres.

[0024] Figure 5 This is a separation chromatogram of the high specific surface area porous surface chromatographic stationary phase C18. Detailed Implementation

[0025] To make the technical problems, technical solutions and beneficial effects of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0026] Unless otherwise specified in the embodiments, the techniques and conditions described in the literature in this field or the product instructions shall be followed. If the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased commercially.

[0027] Example 1

[0028] I. Preparation of Macroporous Silica Microspheres

[0029] S1: Take 200 g of porous silica microspheres ( Figure 1 Particle size 5 μm, pore size 10 nm, specific surface area 350 m² 2 / g);

[0030] S2: The porous silica microspheres in S1 were mixed with 1000 mL of 10%wt sodium chloride solution and stirred for 4 h. After filtration, the mixture was dried at 100℃.

[0031] S3: The porous silica microspheres treated in S2 were placed in a muffle furnace and heated at 600℃ for 6 h. They were then washed successively with large amounts of water and methanol to obtain macroporous silica microspheres. Figure 2 Particle size 5 μm, pore size 100 nm, specific surface area 20 m² 2 / g);

[0032] II. Preparation of high specific surface area porous silica microspheres

[0033] S1: Take 150 g of the prepared macroporous silica microspheres, disperse them in 600 mL of methanol and 200 mL of water, add 20 g of dodecylamine, mix and dissolve thoroughly, add 10 g of tetraethyl silicate, sonicate for 10 min, and let stand for 24 h.

[0034] S2: The macroporous silica microspheres treated by S1 were filtered through a sand core funnel and washed with a large amount of methanol. They were dried at 120°C for 24 h and then calcined in a muffle furnace at 600°C for 10 h to obtain high specific surface area porous silica microspheres.

[0035] III. Modification of C18 on the surface of high specific surface area porous silica microspheres

[0036] S1: Mix 100 g of high specific surface area porous silica microspheres with 10% hydrochloric acid solution and reflux for 24 h. After washing with pure water until neutral, dry at 125℃.

[0037] S2: The high specific surface area porous silica microspheres treated in S1 were mixed with 1000 mL of toluene, heated to reflux, triethylamine catalyst was added, and octadecyldimethylchlorosilane toluene solution was added dropwise. The mixture was refluxed for 24 h, washed successively with toluene, acetone and methanol, and dried to obtain C18 modified high specific surface area porous silica microspheres.

[0038] See Figure 3 The high specific surface area porous silica microspheres have a particle size of 5 μm, with macropores (primary pores) having a diameter of 101 nm and micropores (secondary pores) having a diameter of 13 nm. See also... Figure 4 The specific surface area of ​​the high specific surface area porous silica microspheres is 111 m². 2 / g.

[0039] IV. The test methods and results of C18-modified high specific surface area porous silica microspheres as C18 stationary phase are as follows.

[0040] The microspheres were subjected to column packing tests under the following conditions: column size 4.6 × 250 mm, methanol / water = 85:15 (v / v), column temperature 30℃, flow rate 1 mL / min, detection wavelength 254 nm, and the target analytes were uracil, acetophenone, benzene, toluene, and naphthalene.

[0041] Test results: Separation spectra as follows Figure 5 As shown, from Figure 5 As can be seen, although a conventional high-pressure high-performance liquid chromatography column was used for separation, five substances were rapidly separated within 3 minutes under low pressure, and the peaks were sharp and symmetrical, achieving the separation effect of an ultra-high pressure liquid chromatography column. This fully demonstrates the significant superiority of high specific surface area surface porous chromatographic stationary phases over fully porous stationary phases and core-shell stationary phases.

[0042] In this invention, large-diameter primary channels are prepared inside the silica microspheres. These channels are large enough to serve only as mobile phase pathways during chromatographic separation, and no mass transfer occurs within them. Small-diameter secondary channels are then prepared on the walls of the primary channels. These secondary channels are small enough to provide the specific surface area required for chromatographic separation, thus providing a site for mass transfer during the separation process. Compared to fully porous stationary phase microspheres, this invention significantly reduces mass transfer resistance while minimizing the adverse effects of eddy diffusion during chromatographic separation. Compared to traditional core-shell stationary phases, it offers lower column pressure and higher column efficiency, while allowing for a larger sample loading capacity.

[0043] The above-described embodiments are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A high specific surface area porous chromatographic stationary phase comprising silica microspheres, characterized in that: The silica microspheres have a two-level pore structure, including primary macropores and secondary mesopores. The primary macropores have a pore size of 100–500 nm and serve as channels for the mobile phase during chromatographic separation. The secondary mesopores are distributed on the pore walls of the primary macropores and have a pore size of 5–30 nm, which are used to provide the specific surface area required for chromatographic separation.

2. The high specific surface area porous surface chromatographic stationary phase as described in claim 1, characterized in that: The specific surface area of ​​the silica microspheres is 80–350 m². 2 / g, with a particle size of 1–10 μm.

3. The high specific surface area porous surface chromatographic stationary phase as described in claim 1, characterized in that: The surface of the silica microspheres is bonded with functional groups.

4. The high specific surface area porous surface chromatographic stationary phase as described in claim 3, characterized in that: The functional group includes C18.

5. The method for preparing the high specific surface area porous surface chromatographic stationary phase according to any one of claims 1 to 4, characterized in that, Includes the following steps: 1) The porous silica microspheres were mixed with a salt solution, dried, and then calcined at 500-700℃. After washing, silica microspheres with primary macropores were obtained. 2) The primary macroporous silica microspheres obtained in step 1) are dispersed in an alcohol-water mixed solvent, a template agent and a silicon source are added, and a reaction is carried out to form a mesoporous coating on the pore walls of the primary macroporous channels. After filtration, washing and drying, the template agent is removed by calcination at 500-700℃ to obtain high specific surface area surface porous silica microspheres. 3) Surface bonding modification is performed on the silica microspheres obtained in step 2) to obtain the chromatographic stationary phase.

6. The preparation method according to claim 5, characterized in that: In step 1), the porous silica microspheres have a pore size of 8–12 nm and a specific surface area of ​​300–400 m². 2 / g; the salt solution is a sodium chloride solution with a mass concentration of 5% to 15%; the calcination temperature is 600℃ and the time is 4 to 8 hours.

7. The preparation method according to claim 5, characterized in that: In step 2), the template agent is dodecylamine; the silicon source is tetraethyl silicate; the reaction includes ultrasonic treatment and a static settling process; the calcination temperature is 600℃ and the time is 8-12 hours.

8. The preparation method according to any one of claims 5 to 7, characterized in that, In step 3), the surface bonding modification includes: activating the high specific surface area porous silica microspheres obtained in step 2) with acid, washing them with water until neutral and drying them, mixing them with toluene, and reacting them with octadecyldimethylchlorosilane in the presence of a catalyst to obtain a C18 bonded chromatographic stationary phase.

9. The preparation method according to claim 5, characterized in that: In step 1), the average pore size of the obtained primary macroporous silica microspheres is 100–500 nm, and the specific surface area is 15–40 m². 2 / g.

10. The preparation method according to claim 5, characterized in that: In step 2), the average pore size of the secondary channels of the high specific surface area porous silica microspheres is 5–30 nm, and the specific surface area is 80–350 m². 2 / g.

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