High Performance Liquid Chromatographic Resolution Method of Xylene Isomers by Amidonaphthalenetube

Abstract

The present invention discloses a high-performance liquid chromatography reverse-phase separation method for separating xylene isomers. The method includes: modifying amide naphthalene tubes with different substituents through amide reaction, grafting the modified amide naphthalene tubes onto the surface of activated silica gel to obtain amide naphthalene tube silica gel packing; and applying the prepared amide naphthalene tube silica gel packing to high-performance liquid chromatography, separating a mixed solution of xylene isomers with an acetonitrile-water mixture or a methanol-water mixture as the mobile phase in the reverse-phase mode, and using an ultraviolet detector to detect the separation result. The present invention provides a method for efficiently separating a mixture of xylene isomers, which has simple operation and excellent separation effect, and provides an effective way to solve the separation of xylene isomers.

Description

Technical Field

[0001] The present invention relates to a method for separating mixtures, and particularly to a high performance liquid chromatography method for separating mixtures of xylene isomers using a novel amide naphthalene tube-bonded silica gel packing as a stationary phase. Background Art

[0002] Xylene isomers can be widely used as solvents in industries such as coatings, resins, dyes, and inks, as synthetic monomers or solvents in industries such as pharmaceuticals, explosives, and pesticides, as high-octane gasoline components, and can also be used to remove asphalt from vehicle bodies. In the pathology department of hospitals, it is mainly used for the transparency and dewaxing of tissues and sections, and is an important raw material for organic chemical industry. According to the difference in the substitution positions of two methyl groups on the benzene ring, it can be divided into three isomers: o-xylene, m-xylene, and p-xylene. However, due to the similar structures and physical and chemical properties of the three isomers, the research on the efficient separation of xylene isomers is of great significance and has received increasing attention in industrial production and other fields.

[0003] High performance liquid chromatography (HPLC) is widely used in the separation field due to its good selectivity and high sensitivity. Although there have been studies on separating xylene isomers in liquid chromatography using other stationary phases, the disadvantages such as unsatisfactory separation effect and poor reproducibility have hindered its wide separation application. Therefore, seeking a stationary phase with better separation effect and higher selectivity is the key to the efficient separation of xylene isomers. Summary of the Invention

[0004] In order to seek a stationary phase with better separation effect and higher selectivity, the present invention designs a method for separating xylene isomers by high performance liquid chromatography. The amide naphthalene tubes with different substituents are modified through an amide reaction, and the modified amide naphthalene tubes are grafted onto the surface of activated silica gel to obtain an amide naphthalene tube silica gel packing; and the prepared amide naphthalene tube silica gel packing is applied to high performance liquid chromatography, thereby realizing the efficient separation of xylene isomers.

[0005] To achieve the above object, the present invention provides a high performance liquid chromatography method for separating xylene isomers, which includes:

[0006] 1) Dissolve the xylene isomers to obtain a sample solution, use a reversed-phase chromatographic column packed with amide naphthalene tube-bonded silica gel, the separation conditions use a methanol-water mixture or an acetonitrile-water mixture as the mobile phase, the column temperature is 20 - 50 °C, the flow rate of the mobile phase is 0.3 - 1 mL / min, and use an ultraviolet detector to perform liquid chromatography detection on the separated xylene isomers.

[0007] The structural formula of the amide naphthalene tube-bonded silica gel material includes:

[0008]

[0009] Among them, R is -CH2COOH, -CH3, -CH2C6H6 or -(CH2)3CH3.

[0010] Optionally, the amide naphthalene tube-bonded silica gel material is used to separate a xylene isomer mixed solution in a reverse phase mode in high performance liquid chromatography.

[0011] Optionally, the detection wavelength of the ultraviolet detector is 220 - 400 nm.

[0012] Optionally, the mobile phase is acetonitrile: water = 100% - 0%: 40% - 60%, preferably acetonitrile: water = 70%: 30%. The aforementioned ratio is a volume ratio.

[0013] Optionally, the flow rate of the mobile phase is 0.3 - 1 mL / min, preferably 0.5 mL / min.

[0014] Optionally, the specific steps for obtaining the xylene isomer mixed solution include: separately dissolving o-xylene, m-xylene, and p-xylene in the same solvent to obtain three sample solutions with the same concentration; mixing the three sample solutions to obtain a xylene isomer mixed solution.

[0015] Optionally, the concentration of the o-, m-, and p-xylene mixture in the xylene isomer mixed solution is 0.03 mg / mL - 0.5 mg / mL.

[0016] The amide naphthalene tube-bonded silica gel material is prepared by the following steps:

[0017] 1) Dissolve the amide naphthalene tube and dicyclohexylcarbodiimide in dichloromethane, add 3-aminopropyltriethoxysilane. The amide naphthalene tube includes one of the substituents R being -CH2COOH, -CH3, -CH2C6H6, -(CH2)3CH3. The molar ratio of the amide naphthalene tube to the amino silane coupling agent is 1:2 - 1:4, and react at room temperature for 4 - 8 h. A modified amide naphthalene tube is obtained.

[0018] 2) Add the modified amide naphthalene tube and silica gel into anhydrous N,N-dimethylformamide. The amount of the modified amide naphthalene tube required for each gram of microsphere silica gel is 0.5 - 1 g. React at 60 - 110 °C for 24 - 48 h. An amide naphthalene tube-bonded silica gel material is obtained.

[0019] As a further improvement of the present invention, it includes the following:

[0020] In step 1) of the preparation of the amide naphthalene tube-bonded silica material, the side chain of the amide naphthalene tube used can be one of -CH2COOH, -CH3, -CH2C6H6, and -(CH2)3CH3.

[0021] In step 2) of the preparation of the amide naphthalene tube-bonded silica material, the microspherical silica used is a fully porous or core-shell structured silica sphere with a diameter of 2 - 30 μm and a pore size of 30 - 200 Å.

[0022] Compared with the prior art, the present invention provides a highly stable amide naphthalene tube-bonded silica material, which realizes the efficient and highly selective separation of xylene isomer mixtures in the reverse phase mode of high performance liquid chromatography, providing a new method for the separation of xylene isomer mixtures. Brief Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the preparation method of the amide naphthalene tube-bonded silica material of the present invention;

[0024] Figure 2 It is a chromatogram of the amide naphthalene tube-bonded silica material prepared in Example 1 of the present invention for separating o-, m-, and p-xylene mixtures;

[0025] Figure 3 It is a chromatogram of the cyclic amide naphthalene tube-bonded silica material prepared in Example 2 of the present invention for separating o-, m-, and p-xylene mixtures. Detailed Description of the Invention

[0026] Traditional macrocyclic molecules for molecular recognition can be mainly divided into two categories: one has only a hydrophobic cavity, and the recognition of guest molecules depends to a great extent on the shape and size of the guest; the other has only polar binding sites, narrowing the recognition range of guest molecules. The selectivity of these macrocycles for guest molecules is relatively poor.

[0027] As a new type of macrocyclic host, the amide naphthalene tube exhibits excellent separation ability for xylene isomers due to its special cavity structure. And when different side chains (the side chain groups are -CH2COOH, -CH3, -CH2C6H6, or -(CH2)3CH3) are changed, good separation performance is still maintained. This new type of macrocyclic molecule, the amide naphthalene tube, has polar binding sites in the hydrophobic cavity and can form tightly bound inclusion compounds with guest molecules through hydrogen bonding, hydrophobic interaction, N-H-O, C-H-O and other interactions, thus greatly improving the selective recognition ability for guest molecules.

[0028] The present invention provides a method for separating xylene isomers by high performance liquid chromatography. The amide naphthalene tubes with different substituents are modified by an amide reaction to obtain modified amide naphthalene tubes; the modified amide naphthalene tubes are grafted onto the surface of activated silica gel to obtain amide naphthalene tube silica gel fillers; and the prepared amide naphthalene tube silica gel fillers are applied to high performance liquid chromatography. In the reversed-phase mode, the separation conditions use a mixed solution of acetonitrile-water or methanol-water as the mobile phase, the column temperature is 20 - 50 °C, the flow rate of the mobile phase is 0.3 - 1 mL / min, and a UV detector is used to detect the separation effect of the xylene isomer mixed solution. Among them, the concentration of the sample solution is 0.03 mg / mL - 0.5 mg / mL; the mobile phase is acetonitrile: water = 100%: 0% to 40%: 60%, preferably acetonitrile: water = 70%: 30%; the flow rate of the mobile phase is 0.3 - 1 mL / min, preferably 0.5 mL / min; the detection wavelength of the UV detector is 220 - 400 nm; the amide naphthalene tube-bonded silica gel material chromatographic column separates the sample solution in the reversed-phase mode in high performance liquid chromatography.

[0029] The preparation method of the amide naphthalene tube-bonded silica gel material is as Figure 1 shown, and the steps are as follows:

[0030] 1) Dissolve the amide naphthalene tube and dicyclohexylcarbodiimide in dichloromethane, add 3-aminopropyltriethoxysilane, and at room temperature, an amide reaction occurs between the amide naphthalene tube and 3-aminopropyltriethoxysilane. React for 4 - 8 h, filter and concentrate to obtain the modified amide naphthalene tube. Among them, the amide naphthalene tube can include one of the following substituents: -CH2COOH, -CH3, -CH2C6H6 or -(CH2)3CH3. In the aforementioned reaction, the molar ratio of the amide naphthalene tube to 3-aminopropyltriethoxysilane is 1:2 - 1:4.

[0031] In the aforementioned reaction, dicyclohexylcarbodiimide is a dehydrating agent that can effectively promote the occurrence of the amide reaction. 3-aminopropyltriethoxysilane is a coupling agent. The amino end of its structure can undergo an amide reaction with the carboxyl group of the amide naphthalene tube, and the ethoxy group connected to silicon at the other end can be hydrolyzed and bonded to the silica gel surface through a hydroxyl reaction.

[0032] Taking the cis-amide naphthalene tube as an example, the structure of the amide naphthalene tube before modification is as follows:

[0033] ;

[0034] The R substituent therein is -CH2COOH, -CH3, -CH2C6H6 or -(CH2)3CH3.

[0035] The structure of the modified amide naphthalene tube is as follows:

[0036] .

[0037] (2) Add the modified amide naphthalene tube and microsphere silica gel into anhydrous N,N-dimethylformamide, and react at 60-110 o °C for 24-48 h. After the reaction is completed, wash the solid product with water, methanol, and acetone 2-3 times successively, and dry it under vacuum at 50-80 o °C to obtain the amide naphthalene tube-bonded silica gel material. Among them, the microsphere silica gel used is a fully porous or core-shell structured silica gel sphere with a diameter of 2-30 μm and a pore diameter of 30-200 Å. The amount of modified amide naphthalene tube required for each gram of microsphere silica gel is 0.5-1 g.

[0038] The following uses multiple examples to illustrate the high-performance liquid chromatography separation method for o-xylene, m-xylene, and p-xylene mixtures provided by the present invention.

[0039] Example 1

[0040] Take 1.5 g of cis-amide naphthalene tube and 0.65 g of dicyclohexylcarbodiimide and dissolve them in 80 mL of dichloromethane solution, add 0.9 mL of 3-aminopropyltriethoxysilane, and react at room temperature for 5 h. Filter and concentrate to obtain the modified amide naphthalene tube. Dissolve 1.5 g of the modified amide naphthalene tube and 2.0 g of silica gel in 20 mL of anhydrous N,N-dimethylformamide (DMF), and react at 110 o °C for 48 h. After the reaction is completed, wash with water, methanol, and acetone successively to finally obtain the amide naphthalene tube-bonded silica gel material.

[0041] Prepare the stationary phase according to the above method. Dissolve o-xylene, m-xylene, and p-xylene monomers respectively with a mixed solution of acetonitrile: water (v:v = 60:40) to obtain three solutions of 1 mg / mL. All the prepared samples are filtered through a 0.22 μm filter membrane. Take 0.5 mL of each of the three solutions, mix them evenly and load them into the injection vial. Use a reverse-phase chromatographic column filled with amide naphthalene tube-bonded silica gel. The particle size of the packing is 3 μm, the pore diameter is 100 Å, the diameter of the chromatographic column is 4.6 mm, and the length is 100 mm. The column temperature is 30 °C. Use a mixed solution of acetonitrile: water (v:v = 60:40) as the mobile phase, the flow rate of the mobile phase is 0.5 mL / min, the ultraviolet wavelength for detection is 242 nm, and the injection volume is 5 μL.

[0042] And perform liquid chromatography detection according to the above chromatographic conditions. The separation results are as Figure 2 shown.

[0043] Example 2

[0044] Dissolve 1.5 g of trans - amide naphthalene tube and 0.65 g of dicyclohexylcarbodiimide in 80 mL of dichloromethane solution, add 0.9 mL of 3 - aminopropyltriethoxysilane, and react at room temperature for 5 h. Filter and concentrate to obtain the modified amide naphthalene tube. Dissolve 1.5 g of the modified amide naphthalene tube and 2.0 g of silica gel in 20 mL of anhydrous N,N - dimethylformamide (DMF), and react at 110 o °C for 48 h. After the reaction is completed, wash successively with water, methanol, and acetone to finally obtain the amide naphthalene tube - bonded silica gel material.

[0045] Prepare the stationary phase according to the above method. Dissolve o - xylene, m - xylene, and p - xylene monomers respectively in acetonitrile: water (v:v = 50:50) to obtain three solutions with a concentration of 1 mg / mL. All the prepared samples are filtered through a 0.22 - μm filter membrane. Take 0.5 mL of each of the three solutions, mix them evenly and load them into a sample vial. Use a reversed - phase chromatographic column with amide naphthalene tube - bonded silica gel as the packing material. The particle size of the packing material is 3 μm, the pore size is 100 Å, the diameter of the chromatographic column is 4.6 mm, and the length is 100 mm. The column temperature is 25 °C. Use an acetonitrile - water mixture (v:v = 50:50) as the mobile phase, the flow rate of the mobile phase is 0.5 mL / min, the ultraviolet wavelength for detection is 250 nm, and the injection volume is 10 μL.

[0046] And carry out liquid chromatography detection according to the above chromatographic conditions. The separation results are as Figure 3 shown.

[0047] In summary, combining the above - mentioned multiple embodiments, it can be seen that the present invention provides a high - performance liquid chromatography method for separating o - xylene, m - xylene, and p - xylene mixtures, which has simple operation, excellent separation effect, and high stability, providing a new method for separating o - xylene, m - xylene, and p - xylene mixtures.

[0048] It should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0049] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not used to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A high performance liquid chromatography separation method using an amide naphthalene tube for separating xylene isomers, characterized in that, The method includes: Preparing a mixed solution of xylene isomers; Using a reversed-phase chromatographic column filled with amide naphthalene tube-bonded silica gel material, with an acetonitrile-water mixed solution or a methanol-water mixed solution as the mobile phase, a column temperature of 20 - 50 °C, and a mobile phase flow rate of 0.3 - 1 mL / min to separate the mixed solution of xylene isomers, and using an ultraviolet detector for detection; The structural formula of the amide naphthalene tube-bonded silica gel includes: wherein, R is -CH2COOH, -CH3, -CH2C6H6 or -(CH2)3CH3; wherein, the amide naphthalene tube-bonded silica gel material is used as the stationary phase to separate the mixed solution of xylene isomers in a reversed-phase mode in high performance liquid chromatography; wherein, the amide naphthalene tube-bonded silica gel material is prepared by the following steps: 1) Dissolving the amide naphthalene tube and dicyclohexylcarbodiimide in dichloromethane, adding 3-aminopropyltriethoxysilane, and reacting at room temperature for 4 - 8 h to obtain a modified amide naphthalene tube; wherein, the amide naphthalene tube has one of the substituents -CH2COOH, -CH3, -CH2C6H6 or -(CH2)3CH3, and the molar ratio of the amide naphthalene tube to the amino silane coupling agent is 1:2 - 1:4; 2) Adding the modified amide naphthalene tube and microsphere silica gel into anhydrous N,N-dimethylformamide, and reacting at 60 - 110 °C for 24 - 48 h to obtain the amide naphthalene tube-bonded silica gel material; wherein, the amount of the modified amide naphthalene tube required for each gram of microsphere silica gel is 0.5 - 1 g.

2. The high performance liquid chromatography separation method of xylene isomers according to claim 1, characterized in that: The specific steps for preparing the mixed solution of xylene isomers include: Dissolving o-xylene, m-xylene, and p-xylene separately with the same solvent to obtain three sample solutions with the same concentration; Mixing the three sample solutions to obtain a mixed solution of xylene isomers.

3. The high performance liquid chromatography separation method of xylene isomers according to claim 2, characterized in that: The concentration of the sample solution is 0.03 mg / mL - 0.5 mg / mL.

4. The high-performance liquid chromatography separation method of xylene isomers according to claim 1, characterized in that: The mobile phase is acetonitrile, or a mixed solution of acetonitrile and water, wherein the volume percentage of acetonitrile in the acetonitrile-water mixed solution is greater than or equal to 40%.

5. The high performance liquid chromatography separation method of xylene isomers according to claim 1, characterized in that: The mobile phase flow rate is 0.3 - 1 mL / min.

6. The high performance liquid chromatography separation method of xylene isomers according to claim 1, characterized in that: The detection wavelength of the ultraviolet detector is 220 - 400 nm.

7. The high performance liquid chromatography separation method of xylene isomers according to claim 1, characterized in that: The microsphere silica gel is a fully porous or core-shell structured silica gel small sphere, and the diameter of the microsphere silica gel is 2-30 μm, and the pore diameter is

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