Gas-phase capillary gas chromatographic column for alkane separation

Abstract

The invention relates to the technical field of capillary gas chromatography alkane separation, in particular to a gas-phase capillary gas chromatographic column for alkane separation, and a prepared capillary gas chromatography stationary phase based on a beta-cyclodextrin derivative shows excellent separation performance and is suitable for industrial production. The efficient and rapid separation of n-alkane mixtures and aromatic hydrocarbon mixtures can be realized; the capillary column prepared by the invention has the advantages of simple synthesis method, simple and easily available raw materials, low price and the like; the prepared stationary phase has good stability, is very suitable for preparing a capillary gas chromatographic column by adopting an in-situ bonding method, and is low in column preparation cost and good in column preparation reproducibility; the beta-cyclodextrin derivative capillary gas chromatographic column prepared by the invention has the characteristics of high separation speed, good separation effect, good stability, reusability and the like.

Description

Technical Field

[0001] The invention relates to the technical field of capillary gas chromatography alkane separation, in particular to a gas phase capillary gas chromatography column for alkane separation. Background Art

[0002] β-cyclodextrin is a cyclic oligosaccharide with a unique hydrophobic cavity, which gives it an exceptional ability to form stable inclusion complexes with a wide range of molecules. β-cyclodextrin and its derivatives can selectively interact with molecules based on size, polarity, and shape to form inclusion complexes. These interactions include dispersion, hydrogen bonding, dipole steric forces, electrostatic forces, and van der Waals forces. These properties allow β-cyclodextrin and its derivatives to be used to create channels with exceptional selectivity, making them suitable separation materials and, as such, are widely used as stationary phases. Tetrafluoroterephthalonitrile is a rigid, polysubstituted aromatic compound that readily cross-links with β-cyclodextrin through nucleophilic substitution reactions, forming cross-linked cyclodextrin complexes with high surface areas. Therefore, this chromatographic stationary phase can provide π-π interactions, hydrogen bonding, and steric exclusion for the separation and analysis of structural analogs. These interactions, synergistically with the inclusion complexes within the hydrophobic cavity of cyclodextrin, enhance selectivity for structural analogs.

[0003] Chromatographic columns prepared by dynamic coating or static coating methods have low column efficiency and poor reproducibility due to their unsatisfactory film-forming performance on the inner wall of the capillary column, which is not conducive to the mass transfer process of the analyte on the gas chromatography stationary phase. Summary of the Invention

[0004] The present invention aims to provide a gas-phase capillary gas chromatography column for alkane separation, aiming to solve the technical problem that chromatographic columns prepared by the dynamic coating method or the static coating method in the prior art have low column efficiency and poor reproducibility of column preparation due to their unsatisfactory film-forming performance on the inner wall of the capillary column, which is not conducive to the mass transfer process of the analyte on the gas chromatographic stationary phase.

[0005] To achieve the above-mentioned purpose, the present invention adopts a gas phase capillary gas chromatography column for alkane separation, which uses β-cyclodextrin and tetrafluoroterephthalonitrile as raw materials, 1,8-diazabicyclo[5.4.0]undec-7-ene as a catalyst to prepare a mixed solution, and a silanized capillary is filled with a syringe pump to prepare the mixed solution, and an in-situ bonding method is used to prepare a β-cyclodextrin derivative chromatographic stationary phase.

[0006] The preparation method of the gas phase capillary gas chromatography column for alkane separation includes the following two stages:

[0007] The first stage, pretreatment of capillary column;

[0008] In the second stage, based on the pretreated capillary column, an in-situ bonding method is used to prepare a gas phase capillary gas chromatography column for alkane separation.

[0009] The first stage of preparing a gas phase capillary gas chromatography column for alkane separation is as follows:

[0010] First, fill the capillary with 1 mol / L sodium hydroxide solution, seal both ends with rubber, store at room temperature for 12 hours, and then wash with ultrapure water to achieve neutrality;

[0011] The capillary was then washed with 1.0 mol / L HCl water, both ends were sealed with rubber, stored at room temperature for 12 h, and then washed with ultrapure water to achieve neutrality;

[0012] The dried capillary was dried with N2 for 15 min to expose the silanol functional groups, and then the dried capillary was silanized with a mixture of 3-glycidoxypropyltriethoxysilane and methanol and kept at 60°C for 12 h to silanize the inner surface of the capillary.

[0013] The second stage of preparing a gas phase capillary gas chromatography column for alkane separation is as follows:

[0014] Accurately weigh β-cyclodextrin, tetrafluoroterephthalonitrile, 1,8-diazabicyclo[5.4.0]undec-7-ene, and N,N-dimethylformamide into a centrifuge tube;

[0015] The resulting mixture was sonicated for 30 minutes to form a yellow, transparent, homogeneous solution. Subsequently, the capillary prepared in the first stage was filled with the prepared mixed solution using a syringe pump, both ends were sealed with rubber, and then heated in a water bath for reaction.

[0016] After the reaction is completed, the obtained capillary chromatographic column is flushed with methanol using a syringe pump to remove the remaining reaction solution and other residues.

[0017] In the second stage, the mass ratio of β-cyclodextrin to tetrafluoroterephthalonitrile is 2:1, and the reaction time and temperature are 48 h and 85° C.

[0018] The present invention discloses a gas phase capillary gas chromatography column for separating alkanes. The capillary gas chromatography stationary phase prepared by the present invention is based on a β-cyclodextrin derivative and exhibits excellent separation performance, and can achieve efficient and rapid separation of normal alkane mixtures and aromatic hydrocarbon mixtures. The capillary column prepared by the present invention has the advantages of a simple synthesis method, easy-to-obtain raw materials, and low price. The prepared stationary phase has good stability and is very suitable for preparing a capillary gas chromatography column using an in-situ bonding method, and the column preparation cost is low and the column preparation reproducibility is good. The β-cyclodextrin derivative capillary gas chromatography column prepared by the present invention has the characteristics of fast separation speed, good separation effect, good stability, and can be repeatedly used. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 The present invention is a schematic diagram of the synthesis route of a gas phase capillary gas chromatography column for alkane separation.

[0021] Figure 2 The present invention is a chromatogram of separation of a Grob reagent using a gas capillary gas chromatography column for alkane separation.

[0022] Figure 3 The present invention is a chromatogram of separation of a normal alkane mixture using the gas capillary gas chromatographic column for alkane separation of the present invention.

[0023] Figure 4 The present invention is a chromatogram of separation of a benzene mixture using the gas capillary gas chromatography column for alkane separation of the present invention. DETAILED DESCRIPTION

[0024] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0025] See also Figure 1 , Figure 1 The present invention is a schematic diagram of the synthesis route of a gas phase capillary gas chromatography column for alkane separation.

[0026] The invention provides a gas phase capillary gas chromatography column for alkane separation. The column comprises a silanized capillary filled with a syringe pump to prepare a mixed solution prepared by using beta-cyclodextrin and tetrafluoroterephthalonitrile as raw materials and 1,8-diazabicyclo[5.4.0]undec-7-ene as a catalyst, and an in-situ bonding method is used to prepare a beta-cyclodextrin derivative chromatographic stationary phase.

[0027] Specifically, the preparation method of the gas phase capillary gas chromatography column for alkane separation includes the following:

[0028] 1. Pretreatment of capillary column: Cut a 15m long quartz capillary column with an inner diameter of 250μm, fill the capillary with 1mol / L sodium hydroxide solution, seal both ends with rubber, store at room temperature for 12 hours, and then wash with ultrapure water to achieve neutrality. Then wash the capillary with 1.0mol / L HCl water, seal both ends with rubber, store at room temperature for 12 hours, and then wash with ultrapure water to achieve neutrality. Dry with N2 for 15 minutes to expose the silanol functional groups, thus obtaining a capillary column with a roughened inner wall.

[0029] 2. Silanization of the capillary column: Silanize the pretreated capillary with a mixture of 3-glycidyloxypropyltriethoxysilane and methanol (1:30) and keep it at 60°C for 12 hours to silanize the inner surface of the capillary.

[0030] 3. Prepare a capillary column: Accurately weigh β-cyclodextrin (360 mg), tetrafluoroterephthalonitrile (180 mg), 1,8-diazabicyclo[5.4.0]undec-7-ene (45 μL) and N,N-dimethylformamide (5 mL) into a centrifuge tube; ultrasonically treat the resulting mixture for 30 minutes to form a yellow, transparent, uniform solution. Subsequently, the prepared capillary was filled with the prepared mixed solution using a syringe pump, sealed at both ends with rubber, and then immersed in a pre-conditioned water bath at 85°C for 48 hours. After the reaction is completed, the resulting capillary column is then flushed with methanol using a syringe pump to remove the remaining reaction solution and other residues;

[0031] 4. Aging capillary column: The column is aged by heating at 40°C for 5 minutes, then raised to 185°C at a rate of 3°C / min and maintained for 280 minutes. Repeat this process three times for a total of 12 hours to obtain a β-cyclodextrin derivative capillary column.

[0032] See also Figures 2 to 4 , Figure 2 The present invention is a chromatogram of separation of a Grob reagent using a gas capillary gas chromatography column for alkane separation. Figure 3 The present invention is a chromatogram of separation of a normal alkane mixture using the gas capillary gas chromatographic column for alkane separation of the present invention. Figure 4The present invention is a chromatogram of separation of a benzene mixture using the gas capillary gas chromatography column for alkane separation of the present invention.

[0033] Application Example 1: The capillary gas chromatography column prepared in the above manner was used to perform a chromatographic separation test on Grob reagent to investigate its separation effect. The chromatographic conditions were as follows: high-purity nitrogen as carrier gas, flow rate 0.8 mL / min, temperature program: 30°C to 180°C at a rate of 30°C, injection port temperature 290°C, and detector temperature 290°C.

[0034] The results of the test are as follows Figure 2 As shown in the figure, chromatographic peaks 1 to 10 are decane, undecane, n-nonanal, 2,6-dimethylphenol, tetradecane, 2,3-butanediol, methyl decanoate, methyl undecanoate, methyl dodecanoate, and dicyclohexylamine. Grob reagent is a difficult-to-separate mixture. Components such as 2,3-butanediol, n-nonanal, and dicyclohexylamine are prone to severe adsorption, chromatographic peak deformation, and difficulty in separation, which poses challenges to the selectivity and inertness of the chromatographic column. Figure 2 It can be seen that the chromatographic column can separate all components with high selectivity, and the peak shapes of most chromatographic peaks are well symmetrical, indicating that the chromatographic column has high selective separation performance and good inertness for difficult-to-separate mixtures, and can meet the requirements of chromatographic analysis and determination of sample components.

[0035] Application Example 2: The capillary gas chromatography column prepared in the above manner was used to perform a chromatographic separation test on a mixture of normal alkanes to investigate its resolution performance. Chromatographic conditions were as follows: high-purity nitrogen as carrier gas, flow rate 0.8 mL / min, temperature program: 30°C for 1.2 min, then 50°C / min to 180°C, inlet temperature 260°C, and detector temperature 260°C.

[0036] The results of the test are as follows Figure 3 As shown in the figure, chromatographic peaks 1 to 9 are n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tridecane, and n-tetradecane, respectively.

[0037] Application Example 3: The capillary gas chromatography column prepared in the above manner was used to perform a chromatographic separation test on a benzene mixture to investigate its resolution performance. The chromatographic conditions were as follows: high-purity nitrogen as the carrier gas, flow rate 0.8 mL / min, temperature program: 30°C for 0.2 min, then 40°C / min to 180°C, inlet temperature 260°C, and detector temperature 260°C.

[0038] The results of the test are as follows Figure 4 As shown in the figure, chromatographic peaks 1 to 5 are benzene, toluene, ethylbenzene, n-propylbenzene, and n-butylbenzene, respectively.

[0039] When using the gas phase capillary gas chromatography column for alkane separation of the present invention, the capillary gas chromatography stationary phase based on the β-cyclodextrin derivative prepared by the present invention shows excellent separation performance during specific use, and can achieve efficient and rapid separation of normal alkane mixtures and aromatic hydrocarbon mixtures. The capillary column prepared by the present invention has the advantages of simple synthesis method, easy-to-obtain raw materials, and low price. The prepared stationary phase has good stability and is very suitable for preparing capillary gas chromatography columns using the in-situ bonding method, and the column preparation cost is low and the column preparation reproducibility is good. The β-cyclodextrin derivative capillary gas chromatography column prepared by the present invention has the characteristics of fast separation speed, good separation effect, good stability, and can be repeatedly used.

[0040] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A gas phase capillary gas chromatography column for alkane separation, characterized in that: A mixed solution prepared with β-cyclodextrin and tetrafluoroterephthalonitrile as raw materials and 1,8-diazabicyclo[5.4.0]undec-7-ene as catalyst was filled into a silanized capillary using a syringe pump, and a β-cyclodextrin derivative chromatographic stationary phase was prepared by an in situ bonding method.

2. The gas phase capillary gas chromatography column for alkane separation according to claim 1, wherein The preparation method of the gas phase capillary gas chromatography column for alkane separation includes the following two stages: The first stage, pretreatment of capillary column; In the second stage, based on the pretreated capillary column, an in-situ bonding method is used to prepare a gas phase capillary gas chromatography column for alkane separation.

3. The gas phase capillary gas chromatography column for alkane separation according to claim 2, wherein The first stage of preparing a gas phase capillary GC column for alkane separation is as follows: First, fill the capillary with 1 mol / L sodium hydroxide solution, seal both ends with rubber, store at room temperature for 12 hours, and then wash with ultrapure water to achieve neutrality; The capillary was then washed with 1.0 mol / L HCl water, both ends were sealed with rubber, stored at room temperature for 12 h, and then washed with ultrapure water to achieve neutrality; The dried capillary was dried with N2 for 15 min to expose the silanol functional groups, and then the dried capillary was silanized with a mixture of 3-glycidoxypropyltriethoxysilane and methanol and kept at 60°C for 12 h to silanize the inner surface of the capillary.

4. The gas phase capillary gas chromatography column for alkane separation according to claim 3, wherein The second stage of preparing a gas phase capillary GC column for alkane separation is as follows: Accurately weigh β-cyclodextrin, tetrafluoroterephthalonitrile, 1,8-diazabicyclo[5.4.0]undec-7-ene, and N,N-dimethylformamide into a centrifuge tube; The resulting mixture was sonicated for 30 minutes to form a yellow, transparent, homogeneous solution. Subsequently, the capillary prepared in the first stage was filled with the prepared mixed solution using a syringe pump, both ends were sealed with rubber, and then heated in a water bath for reaction. After the reaction is completed, the obtained capillary chromatographic column is flushed with methanol using a syringe pump to remove the remaining reaction solution and other residues.

5. The gas phase capillary gas chromatography column for alkane separation according to claim 4, wherein In the second stage, the mass ratio of β-cyclodextrin and tetrafluoroterephthalonitrile was 2:1, and the reaction time and temperature were 48 h and 85°C.

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