High performance liquid chromatography detection method for transesterification rate of dimethyl 2, 6-naphthalate

Abstract

The invention belongs to the field of detection of dimethyl 2, 6-naphthalate, and discloses a high performance liquid chromatography detection method for the transesterification rate of dimethyl 2, 6-naphthalate, which comprises the following steps: dissolving a dimethyl 2, 6-naphthalate (NDC) transesterification product sample by low-temperature heating of an aprotic polar solvent; octadecylsilane chemically bonded silica is used as a filling agent of a chromatographic column; the detector is an ultraviolet detector; the detection wavelength is 245 nm to 275 nm; the column temperature of the chromatographic column is 20-30 DEG C; the flow velocity of the mobile phase is 0.8-1.2 mL / min; the mobile phase comprises a mobile phase A and a mobile phase B, and gradient elution is adopted; wherein the mobile phase A is HPLC (High Performance Liquid Chromatography)-grade acetonitrile, and the mobile phase B is purified water; the gradient elution procedure is as follows: 0 to 2 minutes ((0 to 20): (100 to 80)), 2.01 to 5 minutes ((35 to 45): (65 to 55)), 5.01 to 12 minutes ((55 to 65): (45 to 35)), and 12.01 to 20 minutes ((65 to 75): (25 to 35)); the sample size is 10-40 [mu] L; according to the method, the effective separation of each component in the 2, 6-dimethyl naphthalate (NDC) ester cross-linking product can be realized, the RSD measured by continuously injecting a test sample for 6 times is less than 5%, the sample injection repeatability is good, and the accuracy is high.

Description

Technical Field

[0001] The present invention belongs to the field of detection of dimethyl 2,6-naphthalenedicarboxylate, and relates to a high performance liquid chromatography detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate. Background Art

[0002] Polyethylene naphthalate (PEN) is formed by polycondensation of dimethyl 2,6-naphthalenedicarboxylate (NDC) or 2,6-naphthalenedicarboxylic acid (NDA) and ethylene glycol (EG). It is a new type of excellent polymer, which has better physical and mechanical properties, gas barrier properties, chemical stability, heat resistance, ultraviolet resistance, radiation resistance and other properties compared with traditional polyester (PET). Therefore, PEN polyester has excellent comprehensive properties and broad potential market.

[0003] Using dimethyl 2,6-naphthalenedicarboxylate (2,6-NDC) and ethylene glycol (EG) as raw materials, BHEN is obtained through transesterification reaction, and then PEN is obtained by reduced pressure polycondensation. This is the main polymerization process for producing PEN. The content of 2,6-NDC in the transesterification product indirectly reflects the reaction degree of the transesterification reaction. The transesterification rate of the transesterification reaction can be calculated by detecting the content of 2,6-NDC in the transesterification product.

[0004] Common instrumental methods for the determination of organic components include gas chromatography, mass spectrometry, infrared spectroscopy, high performance liquid chromatography, etc.

[0005] Gas chromatography is suitable for substances with low boiling points, easy to vaporize and good thermal stability. The boiling point of dimethyl 2,6-naphthalenedicarboxylate (NDC) is 375.26 °C, and the boiling point of its transesterification product with ethylene glycol is even higher and cannot be vaporized. Therefore, from the perspective of sample composition, it is not suitable to use gas chromatography for determination.

[0006] The quantitative analysis of mass spectrometry mainly depends on high-resolution mass spectrometers. After the sample enters the mass spectrometer, it is ionized to generate ions, and then accelerated by an accelerator. The ions move in a magnetic field, and their trajectories are affected by the magnetic field. Ions of different masses will show different trajectories, thus realizing mass analysis. Finally, the ions will be detected and counted by the detection system to calculate the quantitative analysis result. However, mass spectrometers are expensive and require frequent maintenance and calibration, with high usage costs and are difficult to popularize.

[0007] Infrared spectroscopy is commonly used for qualitative analysis of organic compounds and can also be used for quantitative analysis. Its quantitative methods mainly include measuring the spectral band intensity and measuring the spectral band area, but generally the quantitative error is large, and it is not easy to find a suitable standard sample to make a working curve.

[0008] High performance liquid chromatography is based on the distribution behavior of the sample solution in the mobile phase. Through the separation and analysis of the sample, the quantitative and qualitative analysis of chemical components in the mixture can be achieved. The analysis process is not limited by the volatility and thermal stability of the sample, which can make up for the deficiencies of gas chromatography.

[0009] To sum up, in the determination of the content of dimethyl 2,6-naphthalenedicarboxylate (NDC) in its transesterification products, gas chromatography, mass spectrometry, and infrared spectroscopy all have limitations. As one of the commonly used quantitative analysis methods in the field of polyester analysis, high performance liquid chromatography is simple, fast, has a wide linear range, high accuracy and sensitivity, and has been widely used in polyester production, quality control, and the formulation of detection standards. However, there is currently no national standard or industry standard for testing the transesterification degree of 2,6-NDC in China, and no relevant literature reports have been found. Summary of the Invention

[0010] The object of the present invention is to provide a high performance liquid chromatography test method for the transesterification rate of 2,6-NDC with high precision, high accuracy, and good stability in view of the lack of standards for testing the transesterification rate of 2,6-NDC during the PEN polymerization process, so as to be simple and convenient to operate and shorten the detection time.

[0011] The present invention provides a high performance liquid chromatography analysis method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC).

[0012] The technical solution adopted by the present invention is as follows: A high performance liquid chromatography detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC) includes the following steps:

[0013] (1) Prepare a standard sample stock solution: Dissolve and make up the volume of the dimethyl 2,6-naphthalenedicarboxylate (NDC) standard sample by heating at low temperature with an aprotic polar solvent.

[0014] (2) Prepare a standard sample solution: Transfer a certain volume of the solution in step (1), dilute it with an aprotic polar solvent to obtain a standard sample solution, and keep the standard sample solution for use after passing through a membrane.

[0015] (3) Prepare a sample solution: Dissolve and make up the volume of the transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate (NDC) by heating at low temperature with an aprotic polar solvent, and keep the sample solution for use after passing through a membrane.

[0016] (4) Use high performance liquid chromatography to quantitatively analyze the transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate (NDC).

[0017] The method adopts high performance liquid chromatography, and the chromatographic conditions are as follows:

[0018] Chromatographic column: Octadecylsilane-bonded silica gel is used as the filler;

[0019] Detector: UV detector;

[0020] Detection wavelength: 245 nm - 275 nm;

[0021] Column temperature of the chromatographic column: 20 - 30 °C;

[0022] Flow rate of the mobile phase: 0.8 - 1.2 mL / min;

[0023] The mobile phase includes mobile phase A and mobile phase B, and gradient elution is adopted; wherein mobile phase A is HPLC-grade acetonitrile and mobile phase B is pure water; the program of gradient elution is as follows:

[0024]

[0025]

[0026] Sample injection volume: 10 - 40 μL.

[0027] Preferably, in the chromatographic conditions, the chromatographic column is Waters Spherisorb ODS2, 4.0×250 mm, 5 μm.

[0028] Preferably, in the chromatographic conditions, the detection wavelength is 250 ± 5 nm.

[0029] Preferably, in the chromatographic conditions, the column temperature of the chromatographic column is 25 ± 5 °C.

[0030] Preferably, in the chromatographic conditions, the flow rate of the mobile phase: 1.0 mL / min;

[0031] Preferably, the gradient elution conditions are as follows:

[0032] Time (minutes) Mobile phase A (volume%) Mobile phase B (volume%) 0 0 100 2 0 100 2.01 40 60 5 40 60 5.01 60 40 12 60 40 12.01 70 30 20 70 30

[0033] Preferably, the sample injection volume is 10 - 30 μL.

[0034] (5) Under the operating conditions of step (2), after the baseline of the high-performance liquid chromatograph is stable, inject several needles of standard sample solutions with different concentrations continuously, calculate the peak area of dimethyl 2,6-naphthalenedicarboxylate (NDC), and draw a standard curve with the peak area of the standard sample as the abscissa and the concentration of dimethyl 2,6-naphthalenedicarboxylate (NDC) in the standard sample as the ordinate.

[0035] (6) Under the operating conditions of step (3), after the baseline of the high-performance liquid chromatograph is stable, inject several needles of sample solutions continuously, calculate the peak area of dimethyl 2,6-naphthalenedicarboxylate (NDC), and calculate the concentration of dimethyl 2,6-naphthalenedicarboxylate (NDC) according to the standard curve. Calculate the transesterification rate according to this concentration, and the calculation formula is as follows:

[0036]

[0037] Among them, X is the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC), in %;

[0038] c is the sample concentration calculated according to the standard curve, in g / mL;

[0039] v is the sample constant volume, in mL;

[0040] n is the sample dilution factor;

[0041] m is the sample mass, in g.

[0042] Optimized, the specific method for preparing the standard sample stock solution in step (1) is: weigh 0.05 g of dimethyl 2,6-naphthalenedicarboxylate (NDC) standard sample, accurate to 0.0001 g, heat and dissolve it with an aprotic polar solvent at 40°C to 50°C, transfer it to a 50 mL volumetric flask, dilute it to the scale with an aprotic polar solvent, shake well and set aside. The standard sample stock solution is prepared.

[0043] Optimized, the specific method for preparing the standard sample solution in step (2) is: respectively pipette 0.50, 1.00, 2.00, 3.00, 4.00, 5.00 mL of the standard sample stock solution described in step (1) into a 10 mL volumetric flask, dilute it to the scale with an aprotic polar solvent, shake well and set aside. The standard sample solution is prepared.

[0044] Optimized, the specific method for preparing the sample solution in step (3) is: weigh 0.1 g of the ground sample, accurate to 0.0001 g, heat and dissolve it with an aprotic polar solvent at 40°C to 50°C, transfer it to a 50 mL volumetric flask, dilute it to the scale with an aprotic polar solvent, and shake well. Accurately pipette 1.00 mL into a 10 mL volumetric flask and dilute it to the scale with an aprotic polar solvent, shake well and set aside.

[0045] The beneficial effects of the present invention compared with the prior art are:

[0046] The present invention provides a high performance liquid chromatography analysis method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC), explores and summarizes the high performance liquid chromatography detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC), and obtains a test method using dimethyl sulfoxide as the solvent, 254 nm as the detection wavelength, and pure water and acetonitrile as the mobile phase; this method is more simple, rapid, safe and accurate for the detection of the transesterification rate, has higher measurement sensitivity and precision, ensures the accuracy of the detection, realizes the accurate detection of the transesterification rate, and has important significance for the control of the reaction process of preparing PEN by the transesterification method of dimethyl 2,6-naphthalenedicarboxylate (NDC). Description of the Drawings

[0047] Figure 1 is the chromatogram for system suitability of the test sample;

[0048] Figure 2 is the linear relationship diagram between the concentration of dimethyl 2,6-naphthalenedicarboxylate (NDC) and the peak area. Specific embodiments

[0049] The beneficial effects of the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0050] Example 1

[0051] In this example, for the transesterification product of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol, a high performance liquid chromatography analysis method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC) is provided, and the chromatographic conditions are as follows:

[0052] Chromatographic column: Waters Spherisorb ODS2, 4.0×250mm, 5μm;

[0053] Detector: Ultraviolet detector;

[0054] Detection wavelength: 254nm;

[0055] Column temperature: 25°C;

[0056] Composition of the mobile phase: Mobile phase A is HPLC-grade acetonitrile, and mobile phase B is pure water;

[0057] Flow rate: 1.0 mL / min;

[0058] The gradient elution conditions of the chromatographic column are:

[0059] Time (minutes) Mobile phase A (volume%) Mobile phase B (volume%) 0 0 100 2 0 100 2.01 40 60 5 40 60 5.01 60 40 12 60 40 12.01 70 30 20 70 30

[0060] In this example, the pretreatment method of the test sample is as follows: The transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate (NDC) is dissolved and made up to volume by heating with dimethyl sulfoxide at 40°C, and the obtained sample solution is filtered through a membrane and reserved for use.

[0061] In this example, the injection volume of the above test sample solution for each detection is 10 μL. The obtained chromatogram is as Figure 1 shown.

[0062] As Figure 1 can be seen, the separation degree of the test sample by the high performance liquid chromatography method adopted in this example is very good, and the specificity of this method is good.

[0063] Methodology verification:

[0064] 1. Linearity investigation:

[0065] According to the method of Example 1, establish the standard working curve of dimethyl 2,6-naphthalenedicarboxylate (NDC). The results are as Figure 2 shown.

[0066] 1.1 Preparation of standard sample stock solution: Weigh 0.05 g of dimethyl 2,6-naphthalenedicarboxylate (NDC) standard sample, accurate to 0.0001 g. Heat and dissolve it with dimethyl sulfoxide at 40 °C, transfer it to a 50 mL volumetric flask, dilute it to the mark with dimethyl sulfoxide, shake well and set aside. The standard sample stock solution is prepared.

[0067] 1.2 Preparation of standard sample solution: Transfer 0.50, 1.00, 2.00, 3.00, 4.00, 5.00 mL of the standard sample stock solution described in step (1) to 10 mL volumetric flasks respectively, dilute them to the mark with dimethyl sulfoxide, shake well and set aside. The standard sample solution is prepared.

[0068] 1.3 High performance liquid chromatography (HPLC) test: After the baseline of the HPLC instrument is stable, continuously inject several needles of standard sample solutions with different concentrations, calculate the peak area of dimethyl 2,6-naphthalenedicarboxylate (NDC), and draw a standard curve with the peak area of the standard sample as the abscissa and the concentration of dimethyl 2,6-naphthalenedicarboxylate (NDC) in the standard sample as the ordinate, as Figure 2 shown.

[0069] 2. Precision investigation:

[0070] 2.1 Preparation of precision solution: Take the transesterification product of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol, homogenize it, heat and dissolve it with dimethyl sulfoxide at 40 °C, cool it and then transfer and make up the volume to obtain the sample solution. After passing through the membrane, set it aside.

[0071] 2.2 High performance liquid chromatography (HPLC) test: After the baseline of the HPLC instrument is stable, conduct the sample solution test, calculate the peak area of dimethyl 2,6-naphthalenedicarboxylate (NDC), and calculate the concentration of dimethyl 2,6-naphthalenedicarboxylate (NDC) according to the standard curve. Calculate the transesterification rate according to this concentration. Prepare 6 parallel samples.

[0072] Investigate the precision of the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC) according to the method of Example 1. The results are shown in the following table.

[0073]

[0074] 3. Accuracy investigation

[0075] According to the method of Example 1, the recovery rates of dimethyl 2,6-naphthalenedicarboxylate (NDC) at different concentrations in the transesterification product of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol were investigated, and the results are shown in the following table.

[0076]

[0077] It can be seen that the test method provided in this example has high precision for the determination of the content of dimethyl 2,6-naphthalenedicarboxylate (NDC) in the transesterification product of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol, with RSD less than 5%. The accuracy is good, and the spiked recovery rate is between 90% and 110%. Therefore, the method provided by the present invention can simply, accurately and efficiently determine the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC), which is of great significance for characterizing the degree of transesterification reaction.

[0078] Example 2

[0079] In this example, for the initial product of the transesterification of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol, a high performance liquid chromatography analysis method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC) is provided, and the chromatographic conditions are as follows:

[0080] Chromatographic column: Waters Symmetry C18, 4.6×250mm, 5μm;

[0081] Detector: UV detector;

[0082] Detection wavelength: 245nm;

[0083] Column temperature: 20°C;

[0084] Mobile phase composition: Mobile phase A is HPLC-grade acetonitrile, and mobile phase B is pure water;

[0085] Flow rate: 1.0mL / min;

[0086] The gradient elution conditions of the chromatographic column are the same as those in Example 1.

[0087] The pretreatment method of the test sample in this example is: dissolving and volume-fixing the transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate (NDC) by heating with N,N-dimethylformamide at 50°C, and the obtained sample solution is reserved after passing through the membrane.

[0088] The injection volume of the above test sample solution for each detection in this example is 10μL. The test results are shown in the following table.

[0089]

[0090] Example 3

[0091] In this example, for the intermediate product of the transesterification of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol, a high performance liquid chromatography analysis method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC) is provided. The chromatographic conditions are as follows:

[0092] Chromatographic column: Waters Spherisorb ODS2, 4.0×250mm, 5μm;

[0093] Detector: Ultraviolet detector;

[0094] Detection wavelength: 275nm;

[0095] Column temperature: 20°C;

[0096] Mobile phase composition: Mobile phase A is HPLC-grade acetonitrile, and mobile phase B is pure water;

[0097] Flow rate: 0.8 mL / min;

[0098] The gradient elution conditions of the chromatographic column are the same as those in Example 1.

[0099] In this example, the pretreatment method of the test sample is as follows: The transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate (NDC) is dissolved and made up to volume by heating with dimethyl sulfoxide at 40°C, and the obtained sample solution is reserved after passing through a membrane.

[0100] In this example, the injection volume of the above test sample solution for each detection is 20 μL. The test results are shown in the following table.

[0101]

[0102] Example 4

[0103] In this example, for the final product of the transesterification of dimethyl 2,6-naphthalenedicarboxylate (NDC) and ethylene glycol, a high performance liquid chromatography analysis method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate (NDC) is provided. The chromatographic conditions are as follows:

[0104] Chromatographic column: Waters Spherisorb ODS2, 4.0×250mm, 5μm;

[0105] Detector: Ultraviolet detector;

[0106] Detection wavelength: 254nm;

[0107] Column temperature: 30°C;

[0108] Mobile phase composition: Mobile phase A is HPLC-grade acetonitrile, and mobile phase B is pure water;

[0109] Flow rate: 1.2 mL / min;

[0110] The gradient elution conditions of the chromatographic column were the same as those in Example 1.

[0111] In this example, the pretreatment method of the test sample was as follows: The dimethyl 2,6-naphthalenedicarboxylate (NDC) transesterification product sample was dissolved and made up to volume by heating with dimethyl sulfoxide at 40 °C, and the obtained sample solution was reserved after passing through a membrane.

[0112] In this example, the injection volume of the above test sample solution for each detection was 20 μL. The test results are shown in the following table.

[0113]

[0114] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. An HPLC detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate, characterized in that, It includes the following steps: (1) Prepare a standard sample stock solution: Dissolve and make up the volume of the dimethyl 2,6-naphthalenedicarboxylate standard sample by heating it in an aprotic polar solvent at low temperature. (2) Prepare a standard sample solution: Pipette a certain volume of the solution described in step (1), dilute it with an aprotic polar solvent to obtain a standard sample solution, and keep it for use after passing through a membrane. (3) Prepare a sample solution: Dissolve and make up the volume of the transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate by heating it in an aprotic polar solvent at low temperature, and keep it for use after passing through a membrane. (4) Perform quantitative analysis on the transesterification product sample of dimethyl 2,6-naphthalenedicarboxylate by high performance liquid chromatography. The quantitative analysis uses high performance liquid chromatography, and the chromatographic conditions are as follows: Chromatographic column: Octadecylsilyl-bonded silica gel is used as the packing material. Detector: Ultraviolet detector. Detection wavelength: 245 nm - 275 nm. Column temperature of the chromatographic column: 20 - 30 °C. Flow rate of the mobile phase: 0.8 - 1.2 mL / min. The mobile phase includes mobile phase A and mobile phase B, and gradient elution is adopted; where mobile phase A is HPLC-grade acetonitrile and mobile phase B is pure water; the program of gradient elution is as follows: Sample injection volume: 10 - 40 μL.

2. The HPLC detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, It also includes: (5) Under the operating conditions of step (2), after the baseline of the high performance liquid chromatograph is stable, continuously inject several needles of standard sample solutions with different concentrations, calculate the peak area of dimethyl 2,6-naphthalenedicarboxylate, and plot a standard curve with the peak area of the standard sample as the abscissa and the concentration of dimethyl 2,6-naphthalenedicarboxylate in the standard sample as the ordinate.

3. The HPLC detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1 or 2, characterized in that, It also includes: (6) Under the operating conditions of step (3), after the baseline of the high performance liquid chromatograph is stable, continuously inject several needles of sample solutions, calculate the peak area of dimethyl 2,6-naphthalenedicarboxylate, calculate the concentration of dimethyl 2,6-naphthalenedicarboxylate according to the standard curve, and calculate the transesterification rate according to this concentration. The calculation formula is as follows: Where, X - Transesterification rate of dimethyl 2,6-naphthalenedicarboxylate, unit %. c - Sample concentration calculated according to the standard curve, unit g / mL. v - Fixed volume of the sample, unit mL. n - Dilution factor of the sample. m - Mass of the sample, unit g.

4. The HPLC detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, The chromatographic column is Waters Spherisorb ODS2, 4.0 × 250 mm, 5 μm.

5. The HPLC detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, The column temperature of the chromatographic column is 25 ± 5 °C.

6. The HPLC detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, The detection wavelength is 250 ± 5 nm.

7. The high performance liquid chromatography detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, The flow rate of the mobile phase is 1.0 mL / min.

8. The high performance liquid chromatography detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, The gradient elution conditions are as follows:

9. The high performance liquid chromatography detection method for the transesterification rate of dimethyl 2,6-naphthalenedicarboxylate according to claim 1, characterized in that, Sample injection volume is 10 - 30 μL.

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