Preparation method and application of capillary open-tube chromatographic column based on defect engineering metal organic framework-molecular imprinting composite nanomaterial

Abstract

The application discloses a capillary open-tube chromatographic column preparation method based on a defect engineering metal organic framework-molecular imprinting composite nanomaterial and application, and particularly relates to the field of chemical synthesis and analysis technology. A GLYMO-IDA-silane solution is used to flush a pretreated capillary, so that a carboxyl-modified capillary is obtained. Then, an N,N-dimethylformamide solution containing zirconyl chloride octahydrate, terephthalic acid, L-proline and hydrochloric acid is injected into the cysteine-modified capillary, and under a heating condition, a metal organic framework UiO-66-L-Pro is in-situ grown on the inner wall of the capillary. D-tryptophan and norepinephrine are dissolved in a neutral buffer solution, and after magnetic stirring for 30 min, ferrous sulfate is added and rapidly injected into the UiO-66-L-Pro-modified capillary, and then both ends are sealed, and reaction is carried out at room temperature for 24 h. An acetic acid / SDS solution mixture is used to flush the capillary for 1.5 h to elute the template molecules, and then nitrogen is used to blow dry, so that an MIP@UiO-66-L-Pro@capillary is prepared.

Description

Technical Field

[0001] This invention belongs to the field of chemical synthesis and analysis technology, specifically relating to a method for preparing and applying a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials. Background Technology

[0002] Chirality is widespread in biological systems, and most currently used drugs exhibit chiral characteristics. Chirality refers to a class of structures that are mirror images of each other but cannot be superimposed, such as the left and right hands; they have the same composition but differ in spatial arrangement. Such stereochemical properties can cause biologically active molecules to exhibit different, and possibly even opposite, physiological and pharmacological properties.

[0003] Because enantiomers with different configurations can exhibit significant differences in physiological and pharmacological properties, the separation and analysis of chiral compounds has always been an important research direction in analytical science. Common techniques for achieving chiral resolution include high-performance liquid chromatography (HPLC), gas chromatography (GC), and capillary electrochromatography (CEC). However, HPLC and GC columns are expensive, while fluorescence and electrochemical detection are easily interfered with by coexisting substances. Capillary electrochromatography (CEC) is a highly efficient and sensitive chiral resolution method that combines the characteristics of capillary electrophoresis (CE) and high-performance liquid chromatography (HPLC), offering advantages such as simple operation, small sample volume, high separation efficiency, and low cost. Based on the form of the stationary phase, capillary electrochromatography columns can be classified into packed columns, monolithic columns, and open columns (also known as coated columns). Among these, open columns are widely used in chiral resolution studies due to their simple preparation process, low clogging rate, and high column efficiency. However, open capillary electrochromatography still has limitations such as limited specific surface area and small column capacity. Introducing suitable materials into the stationary phase to increase the specific surface area is expected to improve the above problems to some extent.

[0004] Due to their tunable pore structures and diverse functional groups, chiral metal-organic frameworks (CMOFs) have been widely used as chiral stationary phases in capillary electrochromatography. Researchers have employed various strategies to introduce chiral groups into MOF structures and further coat them onto the inner walls of capillaries to achieve enantiomeric separation. In recent years, defect engineering has emerged as an effective structural control method, using modulators to regulate the formation of structural defects such as missing ligands or clusters in MOFs. When chiral molecules are introduced into MOFs as defect modulators, not only can chiral centers be constructed within the framework, but larger defect channels can also be formed simultaneously.

[0005] Some metal-organic frameworks (CMOFs) exhibit poor dispersibility in water and insufficient stability under physiological conditions, thus limiting their practical applications. To improve their interfacial stability, dopamine can undergo a self-polymerization reaction on the CMOF surface, forming a protective adhesive coating. Under optimized conditions, the introduction of template molecules can further enable the successful construction of molecularly imprinted polymers (MIPs). MIPs are a class of functional polymeric materials capable of selectively recognizing specific target molecules (template molecules). Polymers prepared using a single enantiomer of a chiral compound as a template are called chiral molecularly imprinted polymers (CMIPs). Due to the structural memory effect of their imprinted cavities on template molecules, CMIPs can specifically recognize target enantiomers, thereby achieving chiral resolution.

[0006] Previous studies have shown that chiral molecularly imprinted polymers (CMIPs) have good application potential in chiral separation, but problems such as uneven distribution of imprinted sites, limited binding capacity, and low separation degree still need to be overcome. Based on this, this invention proposes to construct novel nanomaterials by combining CMIPs with chiral defect-engineered metal-organic frameworks (CMOFs), and use these as stationary phases to prepare capillary open columns. To date, there are few reports related to this strategy in the international literature, indicating a significant amount of room for further research. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing a capillary open-tube chromatographic column based on a novel nanomaterial synthesized from defect-engineered metal-organic framework materials and chiral molecularly imprinted polymers. The prepared novel capillary open-tube column can be used to construct a chiral separation system for CEC to complete the enantiomer separation of chiral drugs / compound tryptophan, which can solve the technical problems of low chiral separation degree and low separation efficiency in existing CEC.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials includes the following steps:

[0010] (1) Preparation of GLYMO-IDA-silane solution: NaOH and iminodiacetic acid were dissolved in deionized water, and then 3-glycidoxypropyltrimethoxysilane was slowly added dropwise to obtain GLYMO-IDA-silane solution;

[0011] (2) Pretreatment of capillary tubes: Unmodified capillary tubes were rinsed in sequence with NaOH solution, ultrapure water, HCl solution, ultrapure water and methanol, then purged with nitrogen to remove residual liquid, dried and taken out for use.

[0012] (3) Carboxylation of capillary: The pre-prepared GLYMO-IDA-silane solution was introduced into the pretreated capillary, the two ends of the capillary were sealed and heated in a water bath. After the reaction was completed, the capillary was rinsed with methanol and dried with nitrogen to obtain COOH@capillary.

[0013] (4) Preparation of capillary modified with chiral defect engineering metal-organic framework: Metal salt, non-chiral organic ligand, chiral organic ligand and HCl were dissolved in N,N-dimethylformamide to prepare a clear precursor MOF solution. The solution was then injected into COOH@capillary to seal both ends of the capillary and placed in an oven for heating reaction. After the reaction was completed, the capillary was rinsed with methanol and dried with nitrogen to finally obtain the capillary modified with chiral defect engineering metal-organic framework.

[0014] (5) Preparation of capillary modified with defect-engineered metal-organic framework-molecularly imprinted composite nanomaterial: The template molecule and functional monomer were dissolved in Tris-HCl buffer solution and stirred to prepare a precursor molecularly imprinted solution. Then, a catalyst was added and stirred until completely dissolved. The resulting solution was introduced into a capillary modified with a chiral defect-engineered metal-organic framework. The two ends of the capillary were sealed and allowed to react. After the reaction was completed, the template molecule was removed by elution with an elution buffer. The capillary was then dried under a nitrogen flow to finally obtain a capillary open column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterial.

[0015] As a preferred technical solution of the present invention, the capillary in step (2) is a molten silica capillary with an inner diameter of 75 micrometers and without any modification.

[0016] As a preferred technical solution of the present invention, in step (4), the metal salt is zirconium oxychloride octahydrate, the non-chiral organic ligand is terephthalic acid, the chiral organic ligand is L-proline, and the molar ratio of the metal salt, the non-chiral organic ligand and the chiral organic ligand is 1:1:5.

[0017] As a preferred technical solution of the present invention, in step (5), the template molecule is D-tryptophan, the functional monomer is norepinephrine, the catalyst is ferrous sulfate heptahydrate, and the molar ratio of the template molecule to the functional monomer is 1:1.

[0018] As a preferred embodiment of the present invention, in step (5), the Tris-HCl buffer solution has a pH of 7.0 and a concentration of 10 mM.

[0019] As a preferred technical solution of the present invention, the eluent in step (5) is an acetic acid / SDS solution, wherein the concentration of acetic acid is 5% (v / v) and the concentration of SDS is 0.1% (w / v), and the rinsing time of the eluent is preferably 1.5 h.

[0020] As a preferred technical solution of the present invention, in step (5), the two ends of the sealed capillary are left to react for 24-36 hours.

[0021] Application of a capillary open-tube chromatographic column in the chiral resolution of DL-tryptophan.

[0022] As a preferred embodiment of the present invention, the test sample is dissolved in a methanol / water mixture, and phosphate buffer is used as the buffer solution. The capillary open column with an effective length greater than 29.5 cm is selected as the column of the CEC system. Before the CEC system is injected, the capillary column is flushed with the buffer solution to obtain a stable baseline. The operating voltage is 12.5-17.5 kV, the injection volume is 50 mbar × 3 s, the operating temperature is 25 ℃, and the CEC data are collected and analyzed at a wavelength of 210 nm.

[0023] As a preferred embodiment of the present invention, the test sample is DL-tryptophan, the volume ratio of methanol to water in the methanol / water mixed solution is 1:1, the concentration of the test sample is 0.2 mg / mL, the concentration of the phosphate buffer is 20 mM, the pH range is 6.5-7.5, and all solutions need to be filtered through a 0.45 μm organic filter membrane before injection.

[0024] The beneficial effects of this invention are as follows:

[0025] I. This invention involves the in-situ growth of chiral defect-engineered MOFs on a carboxylated capillary column under acidic conditions, followed by coating CMIPs onto the MOF-grown capillary column to prepare a MIP@UiO-66-L-Pro@capillary open column. Compared to using CMIPs and MOFs alone as the stationary phase in a capillary open column, the novel capillary open column using CMIPs@CMOFs as the stationary phase significantly improves the chiral separation ability of tryptophan enantiomers, increasing the resolution from 0.51 and 1.08 to 4.18. The introduction of the CMIPs layer enhances the stability of the CMIPs@CMOFs stationary phase; the large specific surface area of ​​CMOFs greatly increases the loading of CMIPs on the inner wall of the capillary, and the rigid framework of MOFs effectively prevents deformation of the CMIPs imprinted cavity. The preparation method of this invention is simple, reproducible, and uses inexpensive materials.

[0026] II. In this invention, the chiral molecule (L-proline) introduced as a defect modifier into MOFs not only constructs chiral centers within the framework but also simultaneously forms larger defect channels, resulting in an ultra-high specific surface area that significantly increases the loading capacity of CMIPs on the stationary phase. Its rigid framework effectively prevents structural deformation of the imprinted cavities, thus maintaining the integrity of the recognition sites. Simultaneously, the introduction of CMIPs enhances the overall stability of the CMIPs@CMOFs stationary phase. Leveraging these synergistic advantages, the method for constructing capillary stationary phases based on defect-engineered CMOFs-CMIPs composite nanomaterials is significantly innovative and demonstrates broad application prospects and development potential in the field of efficient separation of chiral drugs / compounds. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the preparation process of the capillary electrochromatographic open column MIP@UiO-66-L-Pro@capillary of the present invention.

[0028] Figure 2 The images shown are side-view optical micrographs of the novel capillary open column prepared according to the present invention. (A) is a 40× magnification optical micrograph of the unmodified capillary column; (B) is a 100× magnification optical micrograph of the unmodified capillary column; (C) is a 40× magnification optical micrograph of COOH@capillary; (D) is a 100× magnification optical micrograph of COOH@capillary; and (E) is a UiO-66-L-P... Image (F) is an optical micrograph of UiO-66-L-Pro@capillary at 40× magnification; Image (G) is an optical micrograph of the MIP@UiO-66-L-Pro@capillary column at 40× magnification; Image (H) is an optical micrograph of the MIP@UiO-66-L-Pro@capillary column at 100× magnification.

[0029] Figure 3Scanning electron microscope (SEM) images of the novel capillary open column prepared according to this invention: (A) SEM image of the unmodified capillary column at magnification × 2.00 k; (B) SEM image of the unmodified capillary column at magnification × 5.00 k; (C) SEM image of the unmodified capillary column at magnification × 20.00 k; (D) SEM image of UiO-66-L-Pro@capillary at magnification × 2.00 k; (E) SEM image of UiO-66-L-Pro@capillary at magnification × 5.00 k; (F) SEM image of UiO-66-L-Pro@capillary at magnification × 20.00 k; (G) SEM image of MIP@UiO-66-L-Pro@capillary at magnification × 2.00 k. The image is a 5.00 k SEM image of MIP@UiO-66-L-Pro@capillary. The image is a 20.00 k SEM image of MIP@UiO-66-L-Pro@capillary.

[0030] Figure 4 The X-ray diffraction patterns of UiO-66-L-Pro and MIP@UiO-66-L-Pro in the embodiments of the present invention are shown below.

[0031] Figure 5 The images show the CEC chiral resolution results of racemic drug / compound tryptophan using the novel capillary open column prepared in this invention, as well as the electrophoretic images of L-tryptophan and D-tryptophan.

[0032] Figure 6 This is a comparison of the CEC chiral resolution results of racemic drug / compound tryptophan using UiO-66-NH2 and MIP alone as stationary phases, and MIP@UiO-66-L-Pro and NIP@UiO-66-L-Pro open-cell columns in this invention. Detailed Implementation

[0033] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0034] Example 1

[0035] (1) Preparation of GLYMO-IDA-silane solution: 1.08 g of NaOH and 0.72 g of iminodiacetic acid (IDA) were dissolved in 20 mL of deionized water and stirred for 10 min under ice bath conditions. Then, 1.20 mL of 3-glycidoxypropyltrimethoxysilane (GLYMO) was slowly added dropwise, and stirring was continued at room temperature for 4 h, followed by heating at 65 °C overnight. The resulting GLYMO-IDA-silane solution was naturally cooled and stored at 4 °C, during which time it remained clear and stable, with no visible precipitation or self-polymerization.

[0036] (2) Pretreatment of capillary tubes: Unmodified fused silica capillaries were rinsed sequentially with NaOH solution (1 h), ultrapure water (5 min), HCl solution (30 min), ultrapure water (5 min), and methanol (30 min). Then, nitrogen gas was used to purge the residual liquid, and the capillaries were dried in an oven at 100 °C for 1 h.

[0037] (3) Carboxylation of capillary: The pre-prepared GLYMO-IDA-silane solution was introduced into the pretreated capillary, and the two ends of the capillary were sealed and heated in a 70°C water bath for 12 h. After the reaction was completed, the capillary was rinsed with methanol for 15 min and dried with nitrogen to obtain a carboxylated capillary column (COOH@capillary).

[0038] (4) Preparation of chiral defect-engineered metal-organic framework-modified capillary: 485 mg (1.5 mmol) of ZrOCl2·8H2O, 251 mg (1.5 mmol) of H2BDC, 866 mg (7.5 mmol) of L-Pro, and 0.65 mL (7.8 mmol) of HCl were dissolved in 20 mL of N,N-dimethylformamide (DMF) to prepare a clear precursor MOF solution. This solution was injected into COOH@capillary. The capillary was then sealed at both ends and heated in an oven at 120 °C for 4 days. After the reaction was completed, the capillary was rinsed with methanol for 15 min and dried with N2 to finally obtain UiO-66-L-Pro@capillary.

[0039] Figure 2 (B) and Figure 2 (F) Comparison shows that the inner surface of the capillary becomes a uniform black. Figure 3 (C) and Figure 3 (F) Comparison shows that particulate matter adhered to the inner surface of the capillary. This preliminarily indicates the successful preparation of UiO-66-L-Pro@capillary.

[0040] (5) Preparation of capillary modified with defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials: 25 mg (0.122 mmol) of D-Trp and 20 mg (0.118 mmol) of norepinephrine were dissolved in 10 mL of Tris-HCl buffer (10 mM, pH 7.0) and stirred for 30 min to obtain a prepolymerized MIP solution. Then, 10 mg of FeSO4·7H2O was added and stirring was continued until completely dissolved. The resulting solution was injected into a UiO-66-L-Pro modified capillary. After sealing both ends of the capillary, the reaction was allowed to proceed at room temperature for 24 h. After the reaction was completed, the template molecules were eluted with acetic acid / SDS elution buffer (5% (v / v) / 0.1% (w / v)) and the capillary was dried under a nitrogen flow to obtain MIP@UiO-66-L-Pro@capillary.

[0041] Figure 2 (F) and Figure 2 (H) Compared with the previous method, the graininess of the inner surface of the capillary is reduced. Figure 3 (F) and Figure 3 (I) By comparison, the morphology of the particulate matter on the inner surface of the capillary changed. This preliminarily indicates that the preparation of MIP@UiO-66-L-Pro@capillary was successful.

[0042] Figure 4 X-ray diffraction patterns of UiO-66-L-Pro and MIP@UiO-66-L-Pro were displayed. The patterns of UiO-66-L-Pro and MIP@UiO-66-L-Pro are basically consistent, with peak positions matching those of the computer-simulated UiO-66 pattern. This indicates that L-proline-induced chiral defect engineering and MIP modification did not alter the lattice characteristics of UiO-66. It confirms that the crystal structure of the particles attached to the inner surface of the capillary is indeed UiO-66-L-Pro. Further modification of MIP has a certain impact on the diffraction peak intensity, preliminarily indicating the attachment of MIP.

[0043] Example 2

[0044] (1) Preparation of GLYMO-IDA-silane solution: 1.08 g of NaOH and 0.72 g of iminodiacetic acid (IDA) were dissolved in 20 mL of deionized water and stirred for 10 min under ice bath conditions. Then, 1.20 mL of 3-glycidoxypropyltrimethoxysilane (GLYMO) was slowly added dropwise, and stirring was continued at room temperature for 4 h, followed by heating at 65 °C overnight. The resulting GLYMO-IDA-silane solution was naturally cooled and stored at 4 °C, during which time it remained clear and stable, with no visible precipitation or self-polymerization.

[0045] (2) Pretreatment of capillary tubes: Unmodified fused silica capillaries were rinsed sequentially with NaOH solution (1 h), ultrapure water (5 min), HCl solution (30 min), ultrapure water (5 min), and methanol (30 min). Then, nitrogen gas was used to purge the residual liquid, and the capillaries were dried in an oven at 100 °C for 1 h.

[0046] (3) Carboxylation of capillary: The pre-prepared GLYMO-IDA-silane solution was introduced into the pretreated capillary, and the two ends of the capillary were sealed and heated in a 70°C water bath for 12 h. After the reaction was completed, the capillary was rinsed with methanol for 15 min and dried with nitrogen to obtain a carboxylated capillary column (COOH@capillary).

[0047] (4) Preparation of chiral defect-engineered metal-organic framework-modified capillary: 485 mg (1.5 mmol) of ZrOCl2·8H2O, 251 mg (1.5 mmol) of H2BDC, 866 mg (7.5 mmol) of L-Pro, and 0.65 mL (7.8 mmol) of HCl were dissolved in 20 mL of N,N-dimethylformamide (DMF) to prepare a clear precursor MOF solution. This solution was injected into COOH@capillary. The capillary was then sealed at both ends and heated in an oven at 120 °C for 4 days. After the reaction was completed, the capillary was rinsed with methanol for 15 min and dried with N2 to obtain UiO-66-L-Pro@capillary.

[0048] (5) Preparation of capillary modified with defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials: 25 mg (0.122 mmol) of D-Trp and 20 mg (0.118 mmol) of norepinephrine were dissolved in 10 mL of Tris-HCl buffer (10 mM, pH 7.0) and stirred for 30 min to obtain a prepolymerized MIP solution. Then, 10 mg of FeSO4·7H2O was added and stirring was continued until completely dissolved. The resulting solution was injected into a UiO-66-L-Pro modified capillary. After sealing both ends of the capillary, the reaction was allowed to stand at room temperature for 36 h. After the reaction was completed, the template molecules were eluted with acetic acid / SDS elution buffer (5% (v / v) / 0.1% (w / v)) and the capillary was dried under a nitrogen flow to obtain MIP@UiO-66-L-Pro@capillary.

[0049] Example 3

[0050] Test samples (DL-tryptophan, D-tryptophan, L-tryptophan) were dissolved in a methanol / water mixture (1:1, V / V) at a concentration of 0.2 mg / mL. A 20 mM phosphate buffer was used as the run buffer, and the pH was adjusted to 7.0 with phosphate solution. All solutions were filtered through a 0.45 μm organic filter before injection. The total capillary length was 38 cm, with an effective length of 29.5 cm. Before injection into the CEC system, the capillary column was flushed with the buffer solution for 20 min to obtain a stable baseline. The operating voltage was 15 kV, the injection volume was 50 mbar × 3 s, the operating temperature was 25 ℃, and CEC data were collected and analyzed at a wavelength of 210 nm. Figure 5 As can be seen, MIP@UiO-66-L-Pro@capillary can achieve chiral separation of DL-tryptophan with a resolution of 4.18, achieving baseline separation. Furthermore, the two sample peaks of DL-tryptophan are attributed to L-tryptophan and D-tryptophan, respectively. The capillary used in this embodiment is the MIP@UiO-66-L-Pro@capillary prepared in Example 1.

[0051] Figure 6 This study presents comparisons of MIP@UiO-66-L-Pro@capillary with those achieved by immobilizing UiO-66-L-Pro alone on the inner surface of a capillary, polymerizing MIP alone on the inner surface, and modifying the inner surface of the capillary with both UiO-66-L-Pro and NIP. The capillary column with UiO-66-L-Pro immobilized alone on the inner surface of the capillary showed a resolution of 1.08 for DL-tryptophan, failing to reach baseline separation. The capillary column with MIP polymerized alone on the inner surface showed a resolution of 0.51 for DL-tryptophan, also failing to reach baseline separation. The capillary column modified with both UiO-66-L-Pro and NIP on the inner surface of the capillary showed a resolution of 0, also failing to reach baseline separation. This indicates that MIP and UiO-66-L-Pro have a synergistic effect on the resolution of DL-tryptophan.

[0052] Example 4

[0053] The test samples (DL-tryptophan, D-tryptophan, L-tryptophan) were dissolved in a methanol / water mixture (1:1, V / V) to a concentration of 0.2 mg / mL. A 20 mM phosphate buffer was used as the run buffer, and the pH was adjusted to 6.5 with phosphate solution. All solutions were filtered through a 0.45 μm organic filter membrane before injection. The total capillary length was 38 cm, with an effective length of 29.5 cm. Before injection into the CEC system, the capillary column was flushed with the buffer solution for 20 min to obtain a stable baseline. The operating voltage was 15 kV, the injection volume was 50 mbar × 3 s, and the operating temperature was 25 °C. CEC data were collected and analyzed at a wavelength of 210 nm. The results showed that DL-tryptophan was successfully resolved with a resolution of 1.86. The capillary used in this example was the MIP@UiO-66-L-Pro@capillary prepared in Example 2.

[0054] Example 5

[0055] The test samples (DL-tryptophan, D-tryptophan, L-tryptophan) were dissolved in a methanol / water mixture (1:1, V / V) at a concentration of 0.2 mg / mL. A 20 mM phosphate buffer was used as the run buffer, and the pH was adjusted to 7.5 with phosphate solution. All solutions were filtered through a 0.45 μm organic filter membrane before injection. The total capillary length was 38 cm, with an effective length of 29.5 cm. Before injection into the CEC system, the capillary column was flushed with the buffer solution for 20 min to obtain a stable baseline. The operating voltage was 15 kV, the injection volume was 50 mbar × 3 s, and the operating temperature was 25 °C. CEC data were collected and analyzed at a wavelength of 210 nm. The results showed that DL-tryptophan was successfully resolved with a resolution of 2.43. The capillary used in this example was the MIP@UiO-66-L-Pro@capillary prepared in Example 1.

[0056] Example 6

[0057] The test samples (DL-tryptophan, D-tryptophan, L-tryptophan) were dissolved in a methanol / water mixture (1:1, V / V) at a concentration of 0.2 mg / mL. A 20 mM phosphate buffer was used as the run buffer, and the pH was adjusted to 7 with phosphate solution. All solutions were filtered through a 0.45 μm organic filter membrane before injection. The total capillary length was 38 cm, with an effective length of 29.5 cm. Before injection into the CEC system, the capillary column was flushed with the buffer solution for 20 min to obtain a stable baseline. The operating voltage was 12.5 kV, the injection volume was 50 mbar × 3 s, and the operating temperature was 25 ℃. CEC data were collected and analyzed at a wavelength of 210 nm. The results showed that DL-tryptophan was successfully resolved with a resolution of 3.14. The capillary used in this example was the MIP@UiO-66-L-Pro@capillary prepared in Example 1.

[0058] Example 7

[0059] The test samples (DL-tryptophan, D-tryptophan, L-tryptophan) were dissolved in a methanol / water mixture (1:1, V / V) to a concentration of 0.2 mg / mL. A 20 mM phosphate buffer was used as the run buffer, and the pH was adjusted to 7 with phosphate solution. All solutions were filtered through a 0.45 μm organic filter membrane before injection. The total capillary length was 38 cm, with an effective length of 29.5 cm. Before injection into the CEC system, the capillary column was flushed with the buffer solution for 20 min to obtain a stable baseline. The operating voltage was 17.5 kV, the injection volume was 50 mbar × 3 s, and the operating temperature was 25 ℃. CEC data were collected and analyzed at a wavelength of 210 nm. The results showed that DL-tryptophan was successfully resolved with a resolution of 1.52. The capillary used in this example was the MIP@UiO-66-L-Pro@capillary prepared in Example 1.

[0060] The main pharmaceutical products used in this invention are:

[0061] Aminodiacetic acid (IDA, 98%), Shanghai Maclean Biochemical Technology Co., Ltd.

[0062] 3-Glycidoxypropyltrimethoxysilane (GLYMO, ≥97%), Shanghai Aladdin Biochemical Technology Co., Ltd.

[0063] L-Proline (L-Pro, 98%), Shanghai Aladdin Biochemical Technology Co., Ltd.

[0064] D-Tryptophan (D-Trp, 98%), Shanghai Mairui Chemical Technology Co., Ltd.

[0065] L-Tryptophan (L-Trp, 98%), Shanghai Mairui Chemical Technology Co., Ltd.

[0066] DL-Tryptophan (DL-Trp, 98%), Shanghai Mairui Chemical Technology Co., Ltd.

[0067] Norepinephrine (98%), Shanghai Titan Technology Co., Ltd.

[0068] The main experimental instruments used in this invention are:

[0069] Fused silica capillary tube, inner diameter 75μm, outer diameter 365μm, Ruifeng Chromatography Devices Co., Ltd., Yongnian District, Handan City

[0070] CEC system, Agilent 7100 CE system, Agilent Technologies

[0071] It should be noted that the above content merely illustrates the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. For those skilled in the art, various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials, characterized in that, Includes the following steps: (1) Preparation of GLYMO-IDA-silane solution: NaOH and iminodiacetic acid were dissolved in deionized water, and then 3-glycidoxypropyltrimethoxysilane was slowly added dropwise to obtain GLYMO-IDA-silane solution; (2) Pretreatment of capillary tubes: Unmodified capillary tubes were rinsed in sequence with NaOH solution, ultrapure water, HCl solution, ultrapure water and methanol, then purged with nitrogen to remove residual liquid, dried and taken out for use. (3) Carboxylation of capillary: The pre-prepared GLYMO-IDA-silane solution was introduced into the pretreated capillary, the two ends of the capillary were sealed and heated in a water bath. After the reaction was completed, the capillary was rinsed with methanol and dried with nitrogen to obtain COOH@capillary. (4) Preparation of capillary modified with chiral defect engineering metal-organic framework: Metal salt, non-chiral organic ligand, chiral organic ligand and HCl were dissolved in N,N-dimethylformamide to prepare a clear precursor MOF solution. The solution was then injected into COOH@capillary to seal both ends of the capillary and placed in an oven for heating reaction. After the reaction was completed, the capillary was rinsed with methanol and dried with nitrogen to finally obtain the capillary modified with chiral defect engineering metal-organic framework. (5) Preparation of capillary modified with defect-engineered metal-organic framework-molecularly imprinted composite nanomaterial: The template molecule and functional monomer were dissolved in Tris-HCl buffer solution and stirred to prepare a precursor molecularly imprinted solution. Then, a catalyst was added and stirred until completely dissolved. The resulting solution was introduced into a capillary modified with a chiral defect-engineered metal-organic framework. The two ends of the capillary were sealed and allowed to react. After the reaction was completed, the template molecule was removed by elution with an elution buffer. The capillary was then dried under a nitrogen flow to finally obtain a capillary open column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterial.

2. The method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials according to claim 1, characterized in that, In step (2), the capillary is a molten silica capillary with an inner diameter of 75 micrometers and without any modification.

3. The method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials according to claim 1, characterized in that, In step (4), the metal salt is zirconium oxychloride octahydrate, the achiral organic ligand is terephthalic acid, the chiral organic ligand is L-proline, and the molar ratio of the metal salt, the achiral organic ligand and the chiral organic ligand is 1:1:

5.

4. The method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials according to claim 1, characterized in that, In step (5), the template molecule is D-tryptophan, the functional monomer is norepinephrine, the catalyst is ferrous sulfate heptahydrate, and the molar ratio of the template molecule to the functional monomer is 1:

1.

5. The method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials according to claim 1, characterized in that, In step (5), the Tris-HCl buffer solution has a pH of 7.0 and a concentration of 10 mM.

6. The method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials according to claim 1, characterized in that, In step (5), the eluent is an acetic acid / SDS solution, wherein the acetic acid concentration is 5% (v / v) and the SDS concentration is 0.1% (w / v), and the preferred rinsing time of the eluent is 1.5 h.

7. The method for preparing a capillary open-tube chromatographic column based on defect-engineered metal-organic framework-molecularly imprinted composite nanomaterials according to claim 1, characterized in that, In step (5), the two ends of the sealed capillary tube are left to stand for 24-36 hours to react.

8. The application of a capillary open-tube chromatographic column as described in any one of claims 1-7 in the chiral resolution of DL-tryptophan.

9. The application according to claim 8, characterized in that, The test sample was dissolved in a methanol / water mixture, and phosphate buffer was used as the buffer solution. The capillary open column with an effective length greater than 29.5 cm was selected as the column for the CEC system. Before the CEC system injection, the capillary column was flushed with the buffer solution to obtain a stable baseline. The operating voltage was 12.5-17.5 kV, the injection volume was 50 mbar × 3 s, the operating temperature was 25 ℃, and the CEC data were collected and analyzed at a wavelength of 210 nm.

10. The application according to claim 9, characterized in that, The test sample is DL-tryptophan, the methanol / water mixture has a methanol to water volume ratio of 1:1, the test sample concentration is 0.2 mg / mL, the phosphate buffer concentration is 20 mM, the pH range is 6.5-7.5, and all solutions must be filtered through a 0.45 μm organic filter membrane before injection.

Images