Gel permeation chromatographic analysis method of pentaerythritol stearate

Abstract

The invention relates to the technical field of analysis and detection, and provides a gel permeation chromatographic analysis method of pentaerythritol stearate. According to the method, the distribution of intermediates in the pentaerythritol stearate and the content of the residual stearic acid are analyzed by adopting the gel permeation chromatography, the product can be analyzed and detected, the method is also suitable for analyzing a central control sample in the synthesis process of the pentaerythritol stearate, and the sample composition and the content of the residual stearic acid are rapidly obtained; the monitoring of the reaction process and the control of the reaction endpoint are of great significance for improving the experiment efficiency and optimizing the experiment process. Moreover, by optimizing the chromatographic conditions, the effective separation of the pentaerythritol stearate and the intermediates thereof can be realized, so that the accuracy of an analysis result is improved.

Description

Technical Field

[0001] The invention relates to the technical field of analysis and detection, in particular to a gel permeation chromatography analysis method for pentaerythritol stearate. Background Art

[0002] Pentaerythritol stearate (PETS) is a white, high-melting-point hard waxy substance with good thermal stability, low volatility, good demoulding and flow properties. It is often used as a plasticizer and lubricant in the rubber and plastic industries.

[0003] The traditional preparation method of pentaerythritol stearate is to use pentaerythritol and stearic acid as raw materials, and dehydrate them by esterification reaction at high temperature under the action of a catalyst. However, pentaerythritol stearate is actually a mixture of four esters, which also contains incompletely reacted intermediates: pentaerythritol tristearate, pentaerythritol distearate and pentaerythritol monostearate.

[0004] Pentaerythritol stearate is not suitable for high performance liquid chromatography detection due to its absorption characteristics and solubility problems, and it cannot be detected by gas chromatography due to its high boiling point. At present, the detection of pentaerythritol stearate mainly involves the detection of physical properties such as acid value, hydroxyl value, saponification value and iodine value of the product. It is necessary to combine nuclear magnetic resonance technology to characterize the product composition, which is time-consuming and cumbersome to operate. It is not suitable for rapid analysis of central control samples during the experiment. Therefore, the current detection of pentaerythritol stearate is to detect the product, and it is impossible to monitor the reaction process.

[0005] In summary, there is an urgent need to provide a method that can monitor the reaction process of pentaerythritol stearate and quickly analyze and evaluate the product. Summary of the invention

[0006] In view of this, the present invention provides a gel permeation chromatography analysis method for pentaerythritol stearate. The analysis method provided by the present invention is simple to operate and has a fast analysis speed. It can not only analyze and detect the product, but also is suitable for analyzing the intermediate control sample in the synthesis process of pentaerythritol stearate, and quickly judges the conversion and distribution of various intermediates of pentaerythritol stearate in the synthesis process.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] A gel permeation chromatography analysis method for pentaerythritol stearate comprises the following steps:

[0009] Dissolving the sample to be tested in tetrahydrofuran to obtain a test solution;

[0010] The test solution is subjected to gel permeation chromatography analysis to obtain a gel permeation chromatogram; the composition of the test sample is determined according to the retention time of the chromatographic peak in the gel permeation chromatogram; the content of stearic acid in the test sample is determined according to the gel permeation chromatogram and a stearic acid standard curve;

[0011] The chromatographic conditions of the gel permeation chromatography analysis include: the mobile phase is tetrahydrofuran, the flow rate is 0.1-1 mL / min, the column temperature is 35-45° C., and the injection volume is 5-100 μL;

[0012] The sample to be tested is a mid-control sample in the synthesis process of pentaerythritol stearate, or is a pentaerythritol stearate product.

[0013] Preferably, the chromatographic column for gel permeation chromatography analysis is Agilent PLgel MIXED-E.

[0014] Preferably, the guard column for gel permeation chromatography analysis is PLHFIPgel.

[0015] Preferably, the washing conditions of the gel permeation chromatography include: the washing agent is tetrahydrofuran, and the column temperature is 35-45°C.

[0016] Preferably, the flushing procedure includes: first gradient flushing for 25 to 35 minutes, and then flushing for 25 to 35 minutes at the endpoint flushing rate of the gradient flushing; the initial flushing rate of the gradient flushing is 0.1 to 0.2 mL / min, and the endpoint flushing rate is 0.5 to 0.8 mL / min. During the gradient flushing process, the flushing rate changes linearly from the initial flushing rate to the endpoint flushing rate.

[0017] Preferably, the concentration of the sample to be tested in the test solution is 1 to 10 mg / mL.

[0018] Preferably, the method for obtaining the intermediate control sample is: during the synthesis process of pentaerythritol stearate, sampling the reaction liquid, hot filtering the obtained liquid sample, cooling the obtained filtrate, and obtaining the intermediate control sample.

[0019] Preferably, before the test liquid is sampled, the test liquid is further subjected to membrane filtration.

[0020] Preferably, the filtration accuracy of the membrane filter is 0.2 to 0.5 μm.

[0021] Preferably, the method for drawing the stearic acid standard curve comprises: using a stearic acid reference substance and tetrahydrofuran as a solvent to prepare a series of stearic acid solutions of different concentrations; performing gel permeation chromatography analysis on the stearic acid solutions to obtain chromatographic peak area values ​​corresponding to stearic acid solutions of different concentrations, and establishing a stearic acid standard curve with stearic acid concentration as the abscissa and the corresponding chromatographic peak area value as the ordinate.

[0022] The invention provides a gel permeation chromatography (GPC) analysis method of pentaerythritol stearate, comprising the following steps: dissolving a sample to be tested in tetrahydrofuran to obtain a liquid to be tested; performing gel permeation chromatography analysis on the liquid to be tested to obtain a gel permeation chromatogram; determining the composition of the sample to be tested according to the retention time of a chromatographic peak in the gel permeation chromatogram; determining the content of stearic acid in the sample to be tested according to the gel permeation chromatogram and a stearic acid standard curve; the chromatographic conditions of the gel permeation chromatography analysis include: a mobile phase of tetrahydrofuran, a flow rate of 0.1 to 1 mL / min, a column temperature of 35 to 45 DEG C, and an injection volume of 5 to 100 μL; and the sample to be tested is a mid-control sample in the synthesis process of pentaerythritol stearate, or a pentaerythritol stearate product. The invention adopts gel permeation chromatography to analyze the distribution of intermediates and the residual stearic acid content in pentaerythritol stearate, which can not only analyze and detect the product, but also is suitable for analyzing the intermediate control sample in the synthesis process of pentaerythritol stearate, quickly obtaining the sample composition and the residual stearic acid content, monitoring the reaction process and controlling the reaction end point, which is of great significance for improving the experimental efficiency and optimizing the experimental process.

[0023] In addition, since the molecular weights of pentaerythritol stearate and its intermediates are not much different and are difficult to be effectively separated, the present invention adopts gel permeation chromatography and obtains gel permeation chromatography analysis conditions for the pentaerythritol stearate system by optimizing the chromatographic conditions, thereby achieving effective separation of pentaerythritol stearate and its intermediates, thereby improving the accuracy of the analysis result.

[0024] Furthermore, since pentaerythritol stearate has a small molecular weight and good lubricity, it is easy to form a thin film in the pores of the gel during the gel permeation chromatography analysis, affecting the elution time of the components, thereby affecting the separation effect of the components. The present invention optimizes the chromatographic flushing conditions to obtain the gel permeation chromatography flushing conditions for the pentaerythritol stearate system, which can effectively clean the residues in the chromatographic column, thereby ensuring the separation effect of the components. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the GPC spectrum of the reference substance containing pentaerythritol stearate and various intermediates;

[0026] Figure 2 This is the GPC spectrum of stearic acid reference substance;

[0027] Figure 3 is the standard curve of stearic acid;

[0028] Figure 4 is the GPC spectrum of pentaerythritol stearate sample 1;

[0029] Figure 5is the GPC spectrum of pentaerythritol stearate sample 2;

[0030] Figure 6 This is the GPC spectrum of the 1h intermediate control sample;

[0031] Figure 7 This is the GPC spectrum of the 4h in-process control sample;

[0032] Figure 8 This is the GPC spectrum of the 6h in-process control sample;

[0033] Fig. 9 The GPC spectrum of the reference substance containing pentaerythritol stearate and various intermediates in Comparative Example 1;

[0034] Fig.10 It is the GPC spectrum of the reference substance containing pentaerythritol stearate and various intermediates in Comparative Example 2. DETAILED DESCRIPTION

[0035] The present invention provides a gel permeation chromatography analysis method for pentaerythritol stearate, comprising the following steps:

[0036] Dissolving the sample to be tested in tetrahydrofuran to obtain a test solution;

[0037] The test solution is subjected to gel permeation chromatography analysis to obtain a gel permeation chromatogram; the composition of the test sample is determined according to the retention time of the chromatographic peak in the gel permeation chromatogram; the content of stearic acid in the test sample is determined according to the gel permeation chromatogram and a stearic acid standard curve;

[0038] The chromatographic conditions of the gel permeation chromatography analysis include: the mobile phase is tetrahydrofuran, the flow rate is 0.1-1 mL / min, the column temperature is 35-45° C., and the injection volume is 5-100 μL;

[0039] The sample to be tested is a mid-control sample in the synthesis process of pentaerythritol stearate, or is a pentaerythritol stearate product.

[0040] The present invention dissolves the sample to be tested in tetrahydrofuran to obtain a liquid to be tested. In the present invention, the sample to be tested is a central control sample in the synthesis process of pentaerythritol stearate, or a pentaerythritol stearate product; specifically, the method for obtaining the central control sample is preferably: in the synthesis process of pentaerythritol stearate, the reaction liquid is sampled, the obtained liquid sample is subjected to heat filtration, and the obtained filtrate is cooled to obtain the central control sample; the temperature of the heat filtration is preferably 100-120°C, and the filter membrane accuracy of the heat filtration is preferably 0.2-0.5μm, more preferably 0.45μm; the present invention removes the catalyst in the liquid sample by heat filtration; and the melting point of pentaerythritol stearate is 60-66°C, and the melting point of stearic acid is 67-72°C. The present invention can avoid the precipitation of pentaerythritol stearate and stearic acid in the liquid sample by controlling the temperature of the heat filtration, which causes filtration difficulties; the central control sample in a solid state can be obtained after the filtrate obtained after filtration is cooled.

[0041] In the present invention, the concentration of the sample in the test solution is preferably 1-10 mg / mL, specifically 1 mg / mL, 3 mg / mL or 5 mg / mL. The present invention has no special requirements for the preparation method of the test solution, as long as the sample can be completely dissolved.

[0042] In the present invention, before the liquid to be tested is sampled, the liquid to be tested is preferably subjected to membrane filtration; the accuracy of the membrane filtration is preferably 0.2-0.5 μm, more preferably 0.45 μm.

[0043] After obtaining the liquid to be tested, the present invention performs gel permeation chromatography on the liquid to be tested to obtain a gel permeation chromatogram (GPC spectrum). In the present invention, the chromatographic conditions of the gel permeation chromatography include: the mobile phase is tetrahydrofuran (THF), the flow rate is 0.1-1 mL / min, more preferably 0.5 mL / min, the column temperature is 35-45°C, more preferably 40°C; the tetrahydrofuran is chromatographically pure tetrahydrofuran, and specifically commercially available chromatographically pure tetrahydrofuran with a stabilizer can be used; the chromatographic column of the gel permeation chromatography is preferably Agilent PL gel MIXED-E, and the specifications of the chromatographic column are preferably 7.5×300 mm, 3 μm; the protective column of the gel permeation chromatography is preferably PL HFIPgel, and the specifications of the protective column are preferably 7.5×50 mm, 9 μm; the injection volume of the gel permeation chromatography is 5-100 μL, preferably 50 μL.

[0044] In the present invention, the flushing conditions of the gel permeation chromatography include: the flushing agent is tetrahydrofuran, the tetrahydrofuran is chromatographically pure tetrahydrofuran, specifically commercially available chromatographically pure tetrahydrofuran with a stabilizer can be used, the column temperature is 35-45°C, more preferably 40°C; the flushing procedure preferably includes: first gradient flushing for 25-35min, preferably 30min, and then flushing at the endpoint flushing rate of the gradient flushing for 25-35min, preferably 30min; the initial flushing rate of the gradient flushing is preferably 0.1-0.2mL / min, more preferably 0.1mL / min, and the endpoint flushing rate is preferably 0.5-0.8mL / min, more preferably 0.5mL / min; during the gradient flushing process, the flushing rate changes linearly from the initial flushing rate to the endpoint flushing rate; in a specific embodiment of the present invention, the time of the gradient flushing, the initial flushing rate of the gradient flushing and the endpoint flushing rate can be directly set in the gel permeation chromatograph; in a specific embodiment of the present invention, preferably after the injection, the gel permeation chromatograph is flushed to remove the sample residue in the chromatographic column to prevent the subsequent analysis from being affected.

[0045] The stationary phase of gel permeation chromatography is a porous gel. Only components with diameters smaller than the pore size can enter the gel pores. Large components cannot enter the gel pores and are excluded. They can only pass through the gaps between the gel particles, so the largest components are eluted first. Small components can enter most of the gel pores, have a long residence time in the chromatographic column, and will be eluted more slowly. Solvent molecules can enter all gel pores due to their smallest volume, so they are eluted from the chromatographic column last. The present invention utilizes this characteristic of gel permeation chromatography, combined with the control of chromatographic conditions, to achieve effective separation of pentaerythritol stearate and its intermediates.

[0046] In the present invention, after obtaining the GPC spectrum, the composition of the sample to be tested is determined according to the retention time of the chromatographic peak in the GPC spectrum. In a specific embodiment of the present invention, it is preferred to first use a reference substance containing pentaerythritol stearate and various intermediates, and a stearic acid reference substance for gel permeation chromatography analysis to determine the retention time of the pentaerythritol stearate and various intermediates, and stearic acid, and then combine the GPC spectrum of the sample to be tested to determine the composition of the sample to be tested; the intermediates of pentaerythritol are pentaerythritol monostearate, pentaerythritol distearate and pentaerythritol tristearate.

[0047] In the present invention, after obtaining the GPC spectrum, the content of stearic acid in the sample to be tested is determined according to the GPC spectrum and the stearic acid standard curve. In the present invention, the chromatographic peak corresponding to stearic acid in the GPC spectrum of the sample to be tested is first determined, and then the stearic acid content in the sample to be tested is calculated according to the area value of the chromatographic peak and the stearic acid standard curve.

[0048] In the present invention, the stearic acid standard curve is a curve of the relationship between stearic acid concentration and chromatographic peak area value; in a specific embodiment of the present invention, the method for drawing the stearic acid standard curve preferably includes: using a stearic acid reference substance and tetrahydrofuran as a solvent to prepare a series of stearic acid solutions of different concentrations, and then performing gel permeation chromatography analysis to obtain chromatographic peak area values ​​corresponding to stearic acid solutions of different concentrations, and establishing a stearic acid standard curve with stearic acid concentration as the horizontal coordinate and the corresponding chromatographic peak area value as the vertical coordinate. In the present invention, the concentration range of the stearic acid solution is preferably 0 to 10 mg / mL, and the concentrations of the stearic acid solutions are preferably 0 mg / mL, 0.1 mg / mL, 0.2 mg / mL, 0.5 mg / mL, 1 mg / mL, 2 mg / mL, 4 mg / mL, 6 mg / mL, 8 mg / mL and 10 mg / mL, respectively; the stearic acid solution is preferably filtered using a 0.45 μm filter membrane before gel permeation chromatography detection; the chromatographic conditions and flushing conditions used for gel permeation chromatography analysis of the stearic acid solution are consistent with the above-mentioned scheme, which will not be repeated here.

[0049] In a specific embodiment of the present invention, the acid value of the sample to be tested can be calculated according to the content of stearic acid, and the degree of esterification can be calculated according to the acid value. The synthesis of pentaerythritol stearate is carried out by the esterification reaction of stearic acid and pentaerythritol. The esterification reaction is a reversible reaction, so the reactants cannot be completely converted. If you want to make the esterification rate higher, it can be known from the equilibrium principle that if one of the reactants is excessive, the equilibrium will shift to the right. Therefore, in the synthesis reaction of pentaerythritol stearate, stearic acid is usually excessive so that the pentaerythritol in the reaction is as completely reacted as possible. However, too much excess of acid will cause the acid value of the product to be high, which will bring difficulties to subsequent separation and purification; in addition, the excess of acid will also cause the saponification of the product during deacidification, affecting its anti-emulsification performance. Therefore, in the process of determining the process parameters, the acid value is an important physical property index, and the degree of esterification can be calculated according to the acid value to judge the degree of reaction. The present invention has no special requirements for the calculation method of acid value and degree of esterification, and can be used by those skilled in the art.

[0050] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] Example 1

[0052] (I) Preparation of reference solution

[0053] Products containing pentaerythritol stearate and various intermediates, and raw material stearic acid were selected as reference substances, dissolved in tetrahydrofuran to a concentration of 1 mg / mL, and filtered with a 0.45 μm filter membrane to obtain reference substance solutions.

[0054] (II) Analysis of the composition of reference substances

[0055] The above-prepared reference solution was analyzed by gel permeation chromatography, and the chromatographic analysis conditions were as follows: chromatographic column: Agilent PLgel MIXED-E (7.5×300mm, 3μm), guard column: PL HFIPgel (7.5×50mm, 9um), mobile phase: chromatographically pure THF (containing stabilizer), flow rate: 0.5mL / min, column temperature: 40°C, injection volume: 50μL.

[0056] The flushing conditions were as follows: chromatographic column: Agilent PLgel MIXED-E (7.5×300mm, 3μm), guard column: PLHFIPgel (7.5×50mm, 9μm), mobile phase: chromatographically pure THF (containing stabilizer), column temperature: 40°C, flow rate: gradient flushing for 30 min (the flushing rate linearly changed from 0.1 mL / min to 0.5 mL / min), 0.5 mL / min flushing for 30 min; flushing was performed once after each sample was tested.

[0057] Figure 1 This is the GPC spectrum of the reference substance containing pentaerythritol stearate and various intermediates. The large molecular weight is eluted first, and the small molecular weight is eluted later. Figure 1 The four peaks in the figure are, from left to right, pentaerythritol tetrastearate peak, pentaerythritol tristearate peak, pentaerythritol distearate peak, and pentaerythritol monostearate peak.

[0058] The GPC spectrum of stearic acid reference substance is as follows Figure 2 shown.

[0059] according to Figure 1 and Figure 2 The retention times of pentaerythritol stearate, various intermediates and stearic acid are obtained, as shown in Table 1.

[0060] Table 1 Retention time

[0061] Reference Retention time (min) Pentaerythritol monostearate 17.2 Pentaerythritol distearate 16.3 Pentaerythritol tristearate 15.8 Pentaerythritol tetrastearate 15.5 Stearic acid 17.6

[0062] (III) Establishment of stearic acid standard curve

[0063] Weigh 2.5 mg, 5 mg, 12.5 mg, 25 mg, 50 mg, 100 mg, 150 mg, 200 mg, and 250 mg of raw stearic acid respectively, dissolve in tetrahydrofuran and make up to volume in a 25 mL volumetric flask, filter with a 0.45 μm filter membrane, and perform gel chromatography. According to the GPC spectrum, the chromatographic peak area values ​​corresponding to stearic acid solutions of different concentrations are obtained, and a stearic acid standard curve is established with stearic acid concentration as the horizontal coordinate and the corresponding chromatographic peak area value as the vertical coordinate. The standard equation obtained according to the standard curve is: y = 352974x + 9753.6, R 2 =0.999, where y is the peak area of ​​stearic acid and x is the concentration of stearic acid; the standard curve of stearic acid is as follows Figure 3 shown.

[0064] (IV) Analysis of actual sample composition

[0065] Product: The samples to be tested are pentaerythritol stearate sample 1 and pentaerythritol stearate sample 2.

[0066] The analysis method is as follows: the sample to be tested is dissolved in tetrahydrofuran to prepare a sample solution with a concentration of 1 mg / mL, and filtered with a 0.45 μm filter membrane. After the instrument is stable, the same chromatographic analysis conditions as step (ii) are used to directly analyze and measure to obtain the GPC spectrum of the sample. The sample composition is obtained according to the retention time of each intermediate and stearic acid in Table 1.

[0067] Figure 4 is the GPC spectrum of pentaerythritol stearate sample 1, according to Figure 4 It can be seen that the pentaerythritol stearate sample is mainly composed of tetraester; Figure 5 is the GPC spectrum of pentaerythritol stearate sample 2, according to Figure 5 It can be seen that the pentaerythritol stearate sample is mainly triester.

[0068] Mid-control sample: In the presence of zinc chloride as a catalyst, pentaerythritol stearate is synthesized with pentaerythritol and stearic acid as raw materials. The reaction temperature is 220°C. Samples are taken at 1h, 4h and 6h of reaction time, respectively. The liquid sample is hot filtered with a 0.45μm filter membrane at a filtration temperature of 100°C. The filtrate is cooled to obtain a mid-control sample. The mid-control sample is dissolved in tetrahydrofuran to prepare a sample solution with a concentration of 1mg / mL, and filtered with a 0.45μm filter membrane. After the instrument is stable, the same chromatographic analysis conditions as in step (ii) are used to directly analyze and determine the GPC spectrum of the mid-control sample.

[0069] Figure 6 to Figure 8 The GPC spectra of the in-process control samples at 1h, 4h, and 6h are shown respectively. The composition of the in-process control samples can be obtained according to the retention time of each intermediate in Table 1, and the conversion of each intermediate in the reaction process can be determined; Figure 6 to Figure 8 It can be seen that after 1 hour of reaction, the product is mainly pentaerythritol monostearate. After 4 hours of reaction, pentaerythritol monostearate is significantly reduced, pentaerythritol tristearate and pentaerythritol tetrastearate are increased. After 6 hours of reaction, the product is mainly pentaerythritol tetrastearate.

[0070] According to the retention time of stearic acid in the GPC spectrum of the central control sample, the chromatographic peak area value of the remaining stearic acid in the sample is obtained, and the stearic acid standard curve is introduced to obtain the stearic acid concentration (as shown in Table 2) to monitor the reaction progress.

[0071] Table 2 Stearic acid concentration of the control sample

[0072]

[0073] According to the stearic acid concentration in Table 2, it can be seen that as the reaction time increases, the stearic acid in the reaction system gradually decreases, thereby determining the reaction progress.

[0074] Comparative Example 1

[0075] The reference substance containing pentaerythritol stearate and various intermediates in Example 1 was detected, and the chromatographic conditions were as follows: chromatographic column: Agilent PLgel MIXED-E (7.5×300 mm, 3 μm), guard column: PL HFIPgel (7.5×50 mm, 9 μm), mobile phase: chromatographically pure THF (containing stabilizer), flow rate: 1.5 mL / min, column temperature: 40°C, injection volume: 120 μL.

[0076] The obtained GPC spectrum is as follows Fig. 9 As shown. Fig. 9 It can be seen that after changing the chromatographic conditions, pentaerythritol stearate and its intermediates cannot be effectively separated. The above results show that the present invention can achieve effective separation of pentaerythritol stearate and its intermediates by optimizing the chromatographic conditions of gel permeation chromatography.

[0077] Comparative Example 2

[0078] The reference substance containing pentaerythritol stearate and various intermediates in Example 1 was tested. The chromatographic conditions used were the same as those in Example 1, except that the rinsing process was omitted. After one sample was tested, the next sample was tested directly. The results showed that after testing 7 samples in a row, the chromatographic peak separation became worse, and pentaerythritol stearate and various intermediates could not be effectively separated; Fig.10 The GPC chromatogram of the seventh sample is shown, where pentaerythritol stearate and the intermediates can no longer be effectively separated. The above results show that the present invention can effectively clean the residues in the chromatographic column by setting the flushing conditions, thereby ensuring the separation effect of the components.

[0079] It can be seen from the above examples that the gel chromatography analysis method provided by the present invention is not only suitable for the evaluation of pentaerythritol stearate products, but also suitable for monitoring the reaction process of pentaerythritol stearate, and can quickly determine the conversion and distribution of various intermediates of pentaerythritol stearate, which is of great significance for improving experimental efficiency and optimizing experimental process.

[0080] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A gel permeation chromatography analysis method for pentaerythritol stearate, characterized in that: The following steps are involved: Dissolving the sample to be tested in tetrahydrofuran to obtain a test solution; The test solution is subjected to gel permeation chromatography analysis to obtain a gel permeation chromatogram; the composition of the test sample is determined according to the retention time of the chromatographic peak in the gel permeation chromatogram; the content of stearic acid in the test sample is determined according to the gel permeation chromatogram and a stearic acid standard curve; The chromatographic conditions of the gel permeation chromatography analysis include: the mobile phase is tetrahydrofuran, the flow rate is 0.1-1 mL / min, the column temperature is 35-45° C., and the injection volume is 5-100 μL; The sample to be tested is a mid-control sample in the synthesis process of pentaerythritol stearate, or is a pentaerythritol stearate product.

2. The gel permeation chromatography analysis method according to claim 1, characterized in that: The chromatographic column for the gel permeation chromatography analysis is Agilent PLgel MIXED-E.

3. The gel permeation chromatography analysis method according to claim 1, characterized in that: The protective column for the gel permeation chromatography analysis is PLHFIPgel.

4. The gel permeation chromatography analysis method according to claim 1, characterized in that: The washing conditions of the gel permeation chromatography include: the washing agent is tetrahydrofuran, and the column temperature is 35-45°C.

5. The gel permeation chromatography analysis method according to claim 4, characterized in that: The flushing procedure includes: first gradient flushing for 25 to 35 minutes, and then flushing for 25 to 35 minutes at the endpoint flushing rate of the gradient flushing; the initial flushing rate of the gradient flushing is 0.1 to 0.2 mL / min, and the endpoint flushing rate is 0.5 to 0.8 mL / min. During the gradient flushing process, the flushing rate changes linearly from the initial flushing rate to the endpoint flushing rate.

6. The gel permeation chromatography analysis method according to claim 1, characterized in that: The concentration of the sample to be tested in the test solution is 1-10 mg / mL.

7. The gel permeation chromatography analysis method according to claim 1, characterized in that: The method for obtaining the intermediate control sample is as follows: during the synthesis process of pentaerythritol stearate, sampling the reaction liquid, hot filtering the obtained liquid sample, and cooling the obtained filtrate to obtain the intermediate control sample.

8. The gel permeation chromatography analysis method according to claim 1, characterized in that: Before the test liquid is sampled, the test liquid is filtered through a filter membrane.

9. The gel permeation chromatography analysis method according to claim 9, characterized in that: The filtration accuracy of the membrane is 0.2-0.5 μm.

10. The gel permeation chromatography analysis method according to claim 1, characterized in that: The method for drawing the stearic acid standard curve comprises: using a stearic acid reference substance and tetrahydrofuran as a solvent to prepare a series of stearic acid solutions with different concentrations; performing gel permeation chromatography analysis on the stearic acid solutions to obtain chromatographic peak area values ​​corresponding to stearic acid solutions with different concentrations, and establishing a stearic acid standard curve with stearic acid concentration as the horizontal coordinate and the corresponding chromatographic peak area value as the vertical coordinate.

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