Method for detecting organic acid impurities in succinic anhydride samples

Abstract

The application relates to the technical field of impurity detection, and discloses a method for detecting organic acid impurities in a succinic anhydride sample. The method comprises the following steps: (1) extracting the sample: mixing the succinic anhydride sample to be detected with an extracting agent and heating; (2) preparing a derivative solution: mixing the extracting agent, a derivative reagent and a catalyst and reserving; (3) preparing a mixed standard solution: adding target organic acid standard products into the extracting agent, dissolving and constant volume; (4) preparing an extraction derivative solution: performing a derivative reaction on the organic acid impurity extraction solution and the derivative solution; (5) preparing a mixed standard product derivative solution: performing a derivative reaction on the mixed standard solution and the derivative solution; (6) chromatographic analysis: respectively performing chromatographic analysis on the extraction derivative solution and the mixed standard product derivative solution, and obtaining a regression equation according to an analysis result; and then substituting chromatographic peak areas into the regression equation to calculate the content of each organic acid impurity derivative. The method improves the sensitivity and accuracy of organic acid gas chromatographic detection through the extraction and derivative steps.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for detecting organic acid impurities in a succinic anhydride sample. BACKGROUND

[0002] Succinic anhydride is an important organic synthesis intermediate and fine chemical raw material, which can undergo hydrolysis, alcoholysis, esterification, halogenation, acylation and other reactions, and is widely used in the fields of medicine, pesticide, food, petrochemical, building material, synthetic resin and dye. In China, succinic anhydride is mainly used in medicine and pesticide. In recent years, with the extension of the downstream industry chain of succinic anhydride, the demand for succinic anhydride in the petrochemical industry is showing a rapid growth trend. In the petrochemical industry, the downstream of succinic anhydride can extend dozens of basic chemical raw materials, such as γ-butyrolactone, 1,4-butanediol, tetrahydrofuran, etc. which are important organic raw materials. Their derivatives can be used as olefin polymerization catalysts, crosslinking agents for ester polymer condensates, light stabilizers for polymers, ultraviolet absorbers, etc. In the plastic industry, the polycondensation of succinic anhydride, the hydrolysis product of succinic anhydride, and butanediol can be used to prepare biodegradable plastic polybutylene succinate (PBS) with excellent performance. With the development of China's pesticide, pharmaceutical and petrochemical industries, the demand for succinic anhydride is increasing year by year.

[0003] The methods for preparing succinic anhydride mainly include maleic anhydride method, succinic acid dehydration method, acetylene carbonylation method, etc. The main industrial production methods are maleic anhydride method and succinic acid dehydration method. In these two methods, trace amounts of organic acids such as succinic acid may be produced or remain. At present, the determination of free succinic acid in succinic anhydride mainly adopts neutral potassium phthalate standard solution titration method (T / HNPCIA13-2019). The method is tedious, time-consuming, low in sensitivity and cannot identify the types of organic acid impurities. Therefore, it is of great significance to develop a qualitative and quantitative detection method for trace amounts of organic acids in succinic anhydride for product quality control. SUMMARY

[0004] The purpose of the present application is to overcome the above-mentioned problems of the prior art, and to provide a method for detecting organic acid impurities in a succinic anhydride sample.

[0005] In order to achieve the above-mentioned purpose, the present application provides a method for detecting organic acid impurities in a succinic anhydride sample, which comprises the following steps:

[0006] (1) Extracting the sample: mixing the succinic anhydride sample to be tested with an extractant and heating to obtain an organic acid impurity extract;

[0007] (2) Preparing a derivative solution: mixing the extractant, a derivative reagent and a catalyst and reserving;

[0008] (3) Preparing a mixed standard solution: dissolving and diluting the target organic acid standard to the extractant;

[0009] (4) preparing an extraction derivative solution: the organic acid impurity extraction solution obtained in step (1) is subjected to a derivative reaction with the derivative solution prepared in step (2) to obtain an extraction derivative solution;

[0010] (5) preparing a mixed standard derivative solution: the mixed standard solution prepared in step (3) is subjected to a derivative reaction with the derivative solution prepared in step (2) to obtain a mixed standard derivative solution;

[0011] (6) chromatographic analysis: the extraction derivative solution obtained in step (4) and the mixed standard derivative solution obtained in step (5) are subjected to chromatographic analysis, respectively, and a regression equation is obtained according to the chromatographic analysis result of the mixed standard derivative solution; then the content of each organic acid impurity derivative in the extraction derivative solution is calculated by substituting the chromatographic peak area of the extraction derivative solution into the regression equation.

[0012] In the present application, the organic acid impurities in succinic anhydride can react with the derivative reagent to form stable derivatives by reacting with the derivative solution, that is, the types and contents of the corresponding organic acid impurities can be obtained by detecting the types and contents of the derivatives by using the method of the present application. Taking acetic acid as an example, under the action of a catalyst, acetic acid reacts with the derivative reagent N,O-Bis[trimethylsilane] trifluoroacetate to form (CH3)COOSi(CH3)3.

[0013] The detection method for trace organic acids in succinic anhydride provided by the present application comprises extraction, derivation and determination steps. The sample is heated and dissolved to obtain an extraction solution, and the extraction solution is subjected to a derivatization reaction with a derivative reagent to obtain volatile organic acid derivative products. The derivatives are subjected to qualitative and quantitative analysis by gas chromatography to obtain the types and contents of each organic acid in the succinic anhydride product. The present application improves the content of organic acids in the extraction solution through the extraction step, and derives high-boiling and difficult-gasification organic acids into easy-gasification components through derivation. The combination of the two greatly improves the sensitivity and accuracy of organic acid gas chromatography detection, and provides a more sensitive and accurate detection method for the detection of trace organic acids in succinic anhydride. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the gas chromatogram of the succinic anhydride sample in Example 1 of the present application;

[0015] Figure 2 is the gas chromatogram of the succinic anhydride sample in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0016] The endpoints of the ranges and any values disclosed herein are not limited to the precise values recited as the exact dimensions are not considered critical for the purposes of the application. The endpoints of the ranges and any values are provided as approximations only and are understood to be encompassed within the range or value themselves. For numeric ranges, the endpoints of each range, the endpoints of each range and individual point values, and individual point values can be combined with one another to generate one or more new numeric ranges that are to be considered as specifically disclosed herein.

[0017] The application provides a method for detecting organic acid impurities in a succinic anhydride sample, comprising the following steps:

[0018] (1) Test sample extraction: mix the succinic anhydride sample to be tested with an extraction agent, and heat to obtain an organic acid impurity extraction solution;

[0019] (2) Preparation of derivatization solution: mix the extraction agent, derivatization reagent and catalyst, and reserve;

[0020] (3) Preparation of mixed standard solution: dissolve and dilute the target organic acid standard to the extraction agent;

[0021] (4) Preparation of extraction derivatization solution: derivatization reaction of the organic acid impurity extraction solution obtained in step (1) and the derivatization solution prepared in step (2) to obtain an extraction derivatization solution;

[0022] (5) Preparation of mixed standard derivatization solution: derivatization reaction of the mixed standard solution prepared in step (3) and the derivatization solution prepared in step (2) to obtain a mixed standard derivatization solution;

[0023] (6) Chromatographic analysis: chromatographic analysis of the extraction derivatization solution obtained in step (4) and the mixed standard derivatization solution obtained in step (5) respectively, and obtaining a regression equation according to the chromatographic analysis results of the mixed standard derivatization solution; then according to the chromatographic peak area of the extraction derivatization solution, the content of each organic acid impurity derivative in the extraction derivatization solution is calculated by substituting the regression equation.

[0024] In the application, chromatographically pure reagents conforming to national standards are used for detection and analysis, which are generally chromatographically special solvents or reagents.

[0025] According to the application, preferably, the extraction agent is acetonitrile.

[0026] According to the application, preferably, in step (1), the amount of the extraction agent is 2-5 mL per gram of the succinic anhydride sample to be tested.

[0027] According to the application, preferably, in step (1), the heating temperature is 65-85℃.

[0028] According to the present application, preferably, in step (2), the derivatization reagent is at least one of N,O-Bis[trimethylsilyl]trifluoroacetamide (BSTFA), N,O-Bis[trimethylsilyl]acetamide (BSA), Hexamethyldisilazane (HMDS), N-Methyl-N-trimethylsilyltrifluoroacetamide (MSTFA).

[0029] According to the present application, preferably, in step (2), the catalyst is at least one of trimethylsilyl chloride (TCMS), trimethylsilyl iodide (TMSI) or ammonium iodide (NH4I).

[0030] According to the present application, preferably, in step (2), the amount of derivatization reagent is 8-20 mL and the amount of catalyst is 0.01-0.05 mL per 100 mL of extractant.

[0031] According to the present application, preferably, in step (3), the concentration of organic acid in the mixed standard solution is 0.005-0.05 g / mL.

[0032] According to the present application, the sample to be tested can be commercially available succinic anhydride or laboratory-prepared succinic anhydride. Generally, succinic anhydride contains various organic carboxylic acid impurities. The target organic acid standard can be selected according to the types of organic acid impurities in the sample. Preferably, in step (3), the target organic acid standard is at least one of C1-C10 carboxylic acid, preferably formic acid, acetic acid, propylene acid, cis-butenedioic acid, trans-butenedioic acid and phthalic acid.

[0033] According to the present application, preferably, in step (4), the volume ratio of the organic acid impurity extraction solution to the derivatization solution is 0.8-1.2:1.

[0034] According to the present application, preferably, in step (4), the temperature of the derivatization reaction is 75-90℃ and the time of the derivatization reaction is 1-3 h.

[0035] According to the present application, preferably, in step (4), the derivatization reaction is carried out in the presence of a dehydrating agent, which is sodium bisulfate and / or anhydrous sodium sulfate.

[0036] According to the present application, preferably, in step (4), the reactor for the derivatization reaction is a tube or a clamp glass bottle, which is convenient for operation and reduces the influence of the volatilization of the derivatization reagent and the derivative on the results.

[0037] According to the present application, preferably, in step (5), the volume ratio of the mixed standard solution to the derivatization solution is 0.8-1.2:1.

[0038] According to the present application, preferably, in step (5), the temperature of the derivatization reaction is 75-90°C, and the time of the derivatization reaction is 1-3h.

[0039] According to the present application, preferably, in step (5), the derivatization reaction is carried out in the presence of a dehydrating agent, which is sodium bisulfate and / or anhydrous sodium sulfate.

[0040] According to the present application, preferably, in step (5), the reactor for the derivatization reaction is a tube with screw cap or a tube with clamp cap.

[0041] According to the present application, preferably, in step (6), the chromatographic analysis is carried out by using a gas chromatograph.

[0042] According to the present application, preferably, the chromatographic column of the gas chromatograph is a HP-5 chromatographic column, and the specification of the chromatographic column is 30m x 0.32mm (I.D) / 4μm.

[0043] According to the present application, preferably, the temperature program of the chromatographic column of the gas chromatograph comprises: keeping at 40-60°C (such as 40°C, 50°C, 60°C, etc.) for 1.5-3min, increasing the temperature to 100-120°C (such as 100°C, 110°C, 120°C, etc.) at a rate of 50-70°C / min (such as 50°C / min, 60°C / min, 70°C / min, etc.) and keeping for 0.4-0.6min, increasing the temperature to 200-220°C at a rate of 15-25°C / min (such as 15°C / min, 20°C / min, 25°C / min, etc.), and increasing the temperature to 230-250°C at a rate of 25-35°C / min.

[0044] According to the present application, preferably, the flow rate of the carrier gas of the gas chromatograph is 0.5-2mL / min.

[0045] According to the present application, preferably, the injection amount of the chromatographic analysis is 0.2-1μL, and the split ratio is 1:10-1:500.

[0046] In the present application, the mixed standard solution and the sample solution after derivatization are injected respectively, and an external standard curve is established by taking the concentration of the mixed standard as the abscissa and the corresponding chromatographic peak area as the ordinate. In the experiment, the standard curve of the component without standard substance is calculated by using the component with the closest retention time.

[0047] Specifically, the mixed standard derivatization solution is diluted step by step to the required concentration by using an extractant, and an external standard curve (regression equation) is established by taking the concentration of the mixed standard as the abscissa and the corresponding chromatographic peak area as the ordinate.

[0048] The external standard curve of the target substance is:

[0049] Formic acid: Y=3377.6X-3557.1, R2 = 0.9993;

[0050] Acetic acid: Y = 14182.3X - 58366.8, R 2 = 0.9990;

[0051] Acrylic acid: Y = 3377.6X - 3557.1, R 2 = 0.9982;

[0052] cis-Butenedioic acid: Y = 63936.4X + 64183.0, R 2 = 0.9988;

[0053] trans-Butenedioic acid: Y = Y = 51586.3X + 50828.6, R 2 = 0.9990;

[0054] Phthalic acid: Y = 4187.4X + 8828.6, R 2 = 0.9991; wherein X is the concentration, Y is the corresponding chromatographic peak area, and R 2 is the linear fitting correlation coefficient.

[0055] The extraction derivative solution is injected and brought into the regression equation to calculate the content of each organic acid impurity.

[0056] In the external standard curve, the abscissa concentration is the target (organic acid) concentration, and the derivative peak area in the derivative standard curve can be directly recorded as the corresponding organic acid.

[0057] The application will be described in detail below through examples. In the following examples, the experimental water is ultrapure water.

[0058] Example 1

[0059] (1) Test sample extraction: 1 g of the succinic anhydride sample to be tested (accurate value 0.0001 g) was placed in a tongs glass bottle, 3 mL of the extraction agent acetonitrile was accurately added, the tongs glass bottle was sealed and heated to 70°C, and after the succinic anhydride was dissolved, it was maintained for 30 min. After the extraction solution was cooled to room temperature, the extraction solution was filtered into a tongs glass bottle using a syringe equipped with a needle filter. The needle filter used a Millipore 0.2 μm polytetrafluoroethylene hydrophobic needle filter.

[0060] (2) Derivative solution preparation: 50 mL of acetonitrile was placed in a 100 mL brown volumetric flask, 10 mL of the derivative reagent BSTFA and 0.02 mL of the catalyst TCMS were accurately transferred into the above brown volumetric flask, and then acetonitrile was used to make up to 100 mL, and it was sealed and stored in the dark as the derivative solution.

[0061] (3) Configuration of mixed standard solution: before the start of the detection, including the preparation of mixed standard solution as follows, the standard solution includes: take 50 mg (accurate value 0.0001 g) of formic acid, acetic acid, acrylic acid, cis-butenedioic acid, trans-butenedioic acid, phthalic acid, respectively, into a 10 mL brown volumetric flask, dissolved with acetonitrile and constant volume to 10 mL, the concentration is 0.005 g / mL of mixed standard solution of organic acids, the mixed standard solution is sealed and stored in a dry environment away from light.

[0062] (4) Preparation of extraction derivative solution: take 1 mL of extraction solution in step (1) into a glass bottle, add 1 mL of derivative solution in step (2), mix after sealing, react at 80℃ for 2h, cool to room temperature and then enter the gas chromatograph for detection.

[0063] (5) Preparation of mixed standard derivative solution: take 1 mL of mixed standard solution prepared in step (3) into a glass bottle, add 1 mL of derivative solution in step (2), mix after sealing, react at 80℃ for 2h, cool to room temperature and then enter the gas chromatograph for detection.

[0064] (6) Chromatographic analysis:

[0065] The chromatographic detection conditions are: the chromatograph is selected as a gas chromatograph; the chromatographic column is HP-5 chromatographic column, 30 m x 0.32 mm (I.D) / 4 μm; the carrier gas is helium, the flow rate is 1 mL / min constant flow; the column temperature is 50℃ (maintained for 2 min), increased to 110℃ at the rate of 60℃ / min (maintained for 0.5 min), increased to 210℃ at the rate of 20℃ / min, increased to 240℃ at the rate of 30℃ / min; the ion source is 230℃, the quadrupole is 150℃; the injection volume is 0.5 μL; the split ratio is 1:100.

[0066] The mixed standard derivative solution is diluted with acetonitrile to 1000, 200, 100, 50, 10 μg / mL, respectively, according to the above gas chromatographic conditions, and the external standard curve is established with the mixed standard concentration as the abscissa and the corresponding chromatographic peak area as the ordinate.

[0067] The target external standard curve is:

[0068] Formic acid: Y=3377.6X-3557.1, R 2 =0.9993;

[0069] Acetic acid: Y=14182.3X-58366.8, R 2 =0.9990;

[0070] Acrylic acid: Y=3377.6X-3557.1, R 2 =0.9982;

[0071] maleic acid: Y = 63936.4X + 64183.0, R 2 =0.9988;

[0072] trans-butenedioic acid: Y = Y = 51586.3X + 50828.6, R 2 =0.9990;

[0073] Phthalic acid: Y = 4187.4X + 8828.6, R 2 =0.9991; where X is the concentration, Y is the corresponding chromatographic peak area, and R... 2 The correlation coefficient is the linear fit coefficient.

[0074] The extract containing the above derivatives was injected and the content of each organic acid impurity was calculated by substituting it into the regression equation.

[0075] The calculated contents of organic carboxylic acid impurities in the succinic anhydride sample were as follows: acetic acid 1.6 μg / g, acrylic acid 0.4 μg / g, maleic acid 3.5 μg / g, and trans-butenedioic acid 1.8 μg / g.

[0076] Comparative Example 1

[0077] The succinic anhydride sample to be tested was directly subjected to gas chromatography analysis.

[0078] Weigh 1g of the succinic anhydride sample to be tested in Example 1 (accurate value 0.0001g) into a 10mL volumetric flask, dissolve it in acetonitrile, and dilute to 10mL. Inject the sample for detection according to the chromatographic conditions in Example 1. The chromatogram of the sample is shown in [Figure 1]. Figure 2 .

[0079] Except for the succinic anhydride sample peak, no other organic acid impurities were detected in the chromatogram, indicating that the method of extraction, derivatization and then detection provided by the present invention greatly improves the sensitivity of organic acid impurity detection by gas chromatography.

[0080] Comparative Example 2

[0081] Trace organic acids in the succinic anhydride sample of Example 1 were detected using liquid chromatography-mass spectrometry (LC-MS). The LC-MS system was a Waters Xevo TQ-S (USA). The mass spectrometry conditions were: ESI-ionization mode, capillary voltage 3.0 kV, cone voltage 35 V, ion source temperature 150 °C, lysis temperature 350 °C, and cone gas flow rate 150 L / h. -1 Desolventizing gas flow rate: 650 L·h -1; Chromatographic conditions: column: Waters Acquity BEH HSS T3 (2.1 x 100 mm x 1.7 μm), column temperature: 30 ℃, injection volume: 1 μL, mobile phase: 30% acetonitrile-70% water, flow rate: 1.0 mL / min. The sample detection results are shown in Table 1.

[0082] Table 1

[0083]

[0084] The results of the method for liquid chromatography-mass spectrometry test in Comparative Example 2 were compared with the results of the test method of the present application, and it was found that the concentrations of each organic acid impurity detected by the two methods were basically consistent. It was indicated that the detection method provided by the present application was accurate and reliable.

[0085] The preferred embodiments of the present application are described in detail above, but the present application is not limited thereto. Within the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, including the combination of each technical feature in any other suitable manner, and these simple modifications and combinations should also be considered as the disclosed content of the present application, and all fall within the protection scope of the present application.

Claims

1. A method of detecting organic acid impurities in a sample of succinic anhydride, characterized by, The method comprises the following steps: (1) sample extraction: mix the sample to be tested with the extraction agent and heat to obtain an organic acid impurity extraction solution; (2) prepare a derivative solution: mix the extraction agent, the derivative reagent and the catalyst and reserve; (3) prepare a mixed standard solution: dissolve and dilute the target organic acid standard to the extraction agent; (4) prepare an extraction derivative solution: perform a derivative reaction on the organic acid impurity extraction solution obtained in step (1) and the derivative solution prepared in step (2) to obtain an extraction derivative solution; (5) prepare a mixed standard derivative solution: perform a derivative reaction on the mixed standard solution prepared in step (3) and the derivative solution prepared in step (2) to obtain a mixed standard derivative solution; (6) chromatographic analysis: perform chromatographic analysis on the extraction derivative solution obtained in step (4) and the mixed standard derivative solution obtained in step (5) respectively, obtain a regression equation according to the chromatographic analysis result of the mixed standard derivative solution, and then calculate the content of each organic acid impurity derivative in the extraction derivative solution by substituting the chromatographic peak area of the extraction derivative solution into the regression equation; wherein the concentration of the organic acid in the mixed standard solution is 0.005-0.05 g / mL; and the target organic acid standard is at least one of formic acid, acetic acid, acrylic acid, cis-butenedioic acid, trans-butenedioic acid and phthalic acid; wherein the chromatographic analysis is performed by using a gas chromatograph; the chromatographic column of the gas chromatograph is an HP-5 chromatographic column; the programmed temperature process of the chromatographic column of the gas chromatograph comprises: maintaining at 40-60℃ for 1.5-3 min, increasing the temperature to 100-120℃ at a rate of 50-70℃ / min, maintaining at 100-120℃ for 0.4-0.6 min, increasing the temperature to 200-220℃ at a rate of 15-25℃ / min, and increasing the temperature to 230-250℃ at a rate of 25-35℃ / min; the flow rate of the carrier gas of the gas chromatograph is 0.5-2 mL / min; and the injection amount of the chromatographic analysis is 0.2-1 μL, and the split ratio is 1:10-1:

500.

2. The method of claim 1, wherein, The extraction agent is acetonitrile; In step (1), the amount of the extraction agent is 2-5 mL per gram of the sample to be tested; In step (1), the heating temperature is 65-85℃.

3. The method of claim 1, wherein, In step (2), the derivative reagent is at least one of N,O-Bis[trimethylsilyl]trifluoroacetate, N,O-bis[trimethylsilyl]acetamide, hexamethyldisilazane and N-methyl-N-trimethylsilyltrifluoroacetamide; In step (2), the catalyst is at least one of trimethylchlorosilane, trimethylsilyl iodide and iodinated ammonia; In step (2), the amount of the derivative reagent is 8-20 mL and the amount of the catalyst is 0.01-0.05 mL per 100 mL of the extraction agent.

4. The method of claim 1, wherein, In step (4), the volume ratio of the organic acid impurity extraction solution to the derivative solution is 0.8-1.2:1; In step (4), the derivative reaction temperature is 75-90℃, and the derivative reaction time is 1-3 h.

5. The method of claim 1, wherein, In step (4), the derivatization reaction is carried out in the presence of a dehydrating agent, which is sodium bisulfate and / or anhydrous sodium sulfate; In step (4), the reactor for the derivatization reaction is a tube screw glass bottle or a clamp glass bottle.

6. The method of claim 1, wherein, In step (5), the volume ratio of the mixed standard solution to the derivatization solution is 0.8-1.2:

1. In step (5), the derivatization reaction is carried out at a temperature of 75-90℃ for 1-3h.

7. The method of claim 1, wherein, In step (5), the derivatization reaction is carried out in the presence of a dehydrating agent, which is sodium bisulfate and / or anhydrous sodium sulfate; In step (5), the reactor for the derivatization reaction is a tube screw glass bottle or a clamp glass bottle.

8. The method of claim 1, wherein, The specification of the HP-5 chromatographic column is 30m x 0.32mm / 4μm.

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