Method for detecting purity of stearic acid in distearoyl phosphatidylcholine

Abstract

The invention discloses a method for detecting the purity of stearic acid in distearoyl phosphatidylcholine, and relates to the technical field of detection, and the method comprises the following steps: weighing 40mg of distearoyl phosphatidylcholine, placing in a round-bottom flask, adding a sodium hydroxide methanol solution, adding isooctane, uniformly mixing, standing, and taking the supernatant to obtain a test solution; adding a sodium hydroxide methanol solution into a round-bottom flask, adding isooctane, uniformly mixing, standing, and taking supernatant to obtain a blank solution; analyzing and detecting the test solution and the blank solution by adopting a gas chromatographic method to obtain a chromatogram, and calculating the stearic acid purity of the test solution according to the peak area of the chromatogram; according to the method for detecting the purity of stearic acid in distearoyl phosphatidylcholine, efficient and safe determination of the purity of stearic acid is realized by optimizing methyl esterification reaction conditions, adopting a sodium hydroxide methanol solution for methyl esterification, then adding isooctane, uniformly mixing and standing, and combining chromatographic conditions of gas chromatography.

Description

Technical Field

[0001] The present invention relates to a detection technology, in particular to a method for detecting the purity of stearic acid in distearoylphosphatidylcholine. Background Art

[0002] Distearoylphosphatidylcholine (DSPC) is a phospholipid molecule composed of a glycerol backbone, two stearoyl chains, a phosphate group, and a choline head group. In medicine, it is primarily used as a pharmaceutical excipient in the preparation of liposomes or thermosensitive liposomes, improving liposome stability and encapsulation efficiency, enhancing drug delivery efficiency, and cellular activity.

[0003] The existing method for detecting stearic acid in DSPC uses a sodium hydroxide methanol solution for methyl esterification followed by the addition of a boron trifluoride (BF3) catalyst, followed by an extraction step to separate the target product. This method has the following problems: the use of a boron trifluoride catalyst, which is highly toxic, dangerous to operate, and poses a high risk of environmental pollution; and the extraction step is complex, which can easily introduce experimental errors or cross-contamination that affects detection accuracy. Summary of the Invention

[0004] The object of the present invention is to provide a method for detecting the purity of stearic acid in distearoylphosphatidylcholine to overcome the above-mentioned shortcomings in the prior art.

[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for detecting the purity of stearic acid in distearoylphosphatidylcholine, comprising the following steps:

[0006] S1. Weigh 40 mg of distearoylphosphatidylcholine and place it in a 50 ml round-bottom flask. Then add sodium hydroxide methanol solution and isooctane. Mix well and let stand. Take the upper layer to obtain the test solution.

[0007] S2. In a 50 ml round-bottom flask, add sodium hydroxide methanol solution and then add isooctane, mix well and let stand, and take the upper layer to obtain a blank solution;

[0008] S3. Analyze and detect the test solution and blank solution by gas chromatography to obtain a chromatogram, and calculate the stearic acid purity of the test solution according to the peak area of ​​the chromatogram.

[0009] Furthermore, the chromatographic conditions of the gas chromatography method in S3 are:

[0010] A polyethylene glycol column was used; the starting temperature was 70°C, maintained for 2 minutes, then increased to 240°C at a rate of 5°C per minute and maintained for 25 minutes; the injection port temperature was 220°C; the flow rate was 1.0 ml / min; and the carrier gas was nitrogen.

[0011] Furthermore, the concentration of the sodium hydroxide methanol solution in S1 is 0.5 mol / L, and the amount added is 4 ml.

[0012] Furthermore, the amount of isooctane added in S1 is 4 ml; and the standing time in S1 is 5 to 10 minutes.

[0013] Furthermore, the concentration of the sodium hydroxide methanol solution in S2 is 0.5 mol / L, and the amount added is 4 ml.

[0014] Furthermore, the amount of isooctane added in S2 is 4 ml; and the standing time in S2 is 5 to 10 minutes.

[0015] Furthermore, the detector of the gas chromatography method described in S3 is a hydrogen flame ionization detector.

[0016] Furthermore, the temperature of the hydrogen flame ionization detector is 250-260°C.

[0017] Furthermore, the hydrogen flow rate of the hydrogen flame ionization detector is 30 mL / min, and the air flow rate is 400 ml / min.

[0018] Furthermore, the injection volume of the gas chromatography method is 1 μl.

[0019] Compared with the prior art, the present invention provides a method for detecting the purity of stearic acid in distearoylphosphatidylcholine. By optimizing the methylation reaction conditions, such as using a sodium hydroxide methanol solution for methylation followed by adding isooctane for mixing and allowing to stand, combined with specific chromatographic conditions of gas chromatography, including the use of a polyethylene glycol chromatographic column, a specific temperature program, inlet temperature, flow rate, carrier gas, and detector conditions, efficient and safe determination of the purity of stearic acid is achieved.

[0020] This method not only reduces operational hazards and environmental pollution risks, but also simplifies the experimental process and reduces the number of experimental steps, thereby reducing the possibility of experimental errors and cross-contamination, effectively improving the accuracy and reliability of the test. Furthermore, the elimination of special catalysts and complex extraction equipment reduces testing costs, making the test method more economical and practical, and easy to promote and popularize in practical applications. This provides a more efficient, safe, accurate, and cost-effective solution for the determination of stearic acid purity in DSPC. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments described in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0022] Figure 1 A schematic diagram of the overall flow of the detection method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] Example 1:

[0025] See also Figure 1 A method for detecting the purity of stearic acid in distearoylphosphatidylcholine comprises the following steps:

[0026] S1. Weigh 40 mg of distearoylphosphatidylcholine and place it in a 50 ml round-bottom flask. Then add 4 ml of 0.5 mol / L sodium hydroxide methanol solution and 4 ml of isooctane. Mix well and let stand for 5 to 10 minutes. Take the upper layer to obtain the test solution.

[0027] S2. In a 50 ml round-bottom flask, add 4 ml of 0.5 mol / L sodium hydroxide methanol solution and 4 ml of isooctane, mix well and let stand for 5 to 10 minutes. Take the upper layer to obtain a blank solution.

[0028] S3. The test solution and the blank solution were analyzed and detected by gas chromatography to obtain a chromatogram, and the stearic acid purity of the test solution was calculated based on the peak area of ​​the chromatogram. The chromatographic conditions of the gas chromatography were as follows: a polyethylene glycol column was used; the starting temperature was 70°C, maintained for 2 minutes, increased to 240°C at a rate of 5°C per minute, and maintained for 25 minutes; the inlet temperature was 220°C; the flow rate was 1.0 ml / min; the carrier gas was nitrogen; the detector for the gas chromatography was a hydrogen flame ionization detector; the temperature of the hydrogen flame ionization detector was 250°C; the hydrogen flow rate of the hydrogen flame ionization detector was 30 mL / min, and the air flow rate was 400 ml / min; the injection volume for the gas chromatography was 1 μl.

[0029] The specific implementation method is as follows: 40 mg of distearoylphosphatidylcholine is accurately weighed on an analytical balance to ensure that the weighing is accurate, and is placed in a 50 ml round-bottom flask.

[0030] Use a pipette to accurately measure 4 ml of a 0.5 mol / L sodium hydroxide methanol solution and add it to the round-bottom flask. This step should be done slowly while gently shaking the flask to ensure full contact between the distearoylphosphatidylcholine and the sodium hydroxide methanol solution to initiate the saponification reaction.

[0031] Add another 4 ml of isooctane and continue to gently shake the flask to mix the solution evenly. At this time, the stearic acid and other components in the solution will undergo saponification reaction under the action of sodium hydroxide and gradually be extracted by isooctane.

[0032] The mixed solution was placed at room temperature and allowed to stand for 5 to 10 minutes to allow the system to fully separate into layers. The upper layer was taken to obtain the test solution. The choice of the standing time should be appropriately adjusted according to the experimental conditions and the actual observed separation effect to ensure that components such as stearic acid are completely extracted into the isooctane layer.

[0033] Prepare a blank solution: In a separate 50-ml round-bottom flask, follow the same steps as for the test solution, adding 4 ml of 0.5 mol / L sodium hydroxide in methanol and 4 ml of isooctane. Mix thoroughly and let stand for 5–10 minutes to create a blank solution. This blank solution is prepared to eliminate background interference and improve the accuracy of test results.

[0034] Gas chromatography analysis and detection: The chromatographic column used is a polyethylene glycol column, such as an HP-I NNOWax column (30m×0.25mm×0.25μm). This column has good separation performance for polar compounds such as fatty acids and can effectively separate stearic acid from other possible impurities.

[0035] Temperature program: Start at 70°C, hold for 2 minutes, then increase to 240°C at a rate of 5°C / minute and hold for 25 minutes. This temperature program setting can meet the separation requirements of components such as stearic acid. The initial low-temperature stage fully condenses the sample and initiates separation. As the temperature gradually increases, the components elute in sequence. Finally, the high-temperature stage ensures that all components are completely eluted, resulting in clear chromatographic peaks.

[0036] Inlet temperature: Set to 220℃ to ensure that the sample solution can be quickly vaporized after injection and enter the chromatographic column for separation.

[0037] Flow rate: The carrier gas (nitrogen) flow rate was set at 1.0 ml / min. A stable flow rate helps to ensure the repeatability of the chromatographic peak shape and retention time, thereby improving the reliability of the test results.

[0038] Detector: A hydrogen flame ionization detector (FID) was used, and its temperature was set to 260°C. Under this temperature condition, the hydrogen flame can be stably burned, and a sensitive response signal can be generated to organic compounds such as stearic acid, thereby ensuring the stability of the detection process.

[0039] Injection volume: Use a microinjector to accurately measure 1 μl of the test solution and blank solution for injection.

[0040] The test solution and blank solution are analyzed and tested according to the set chromatographic conditions. The instrument automatically collects data and generates a chromatogram. In the chromatogram, the chromatographic peak of the blank solution is mainly used to subtract the background signal. The chromatogram of the test solution will have multiple chromatographic peaks. The position of the chromatographic peak corresponding to stearic acid can be determined by comparison with the standard or by known retention time.

[0041] According to the chromatograms of the test solution and blank solution, determine the peak area of ​​stearic acid, and calculate the purity of stearic acid by the peak area according to the area normalization method.

[0042] Example 2:

[0043] This embodiment provides a technical solution based on the first embodiment: a repeatability test of the detection method:

[0044] 1. Chromatographic conditions are as follows:

[0045] Chromatographic column: polyethylene glycol (or similar polarity) column;

[0046] Heating program: starting temperature at 70°C, maintaining for 2 minutes, increasing to 240°C at a rate of 5°C per minute, maintaining for 25 minutes;

[0047] Inlet temperature: 220°C;

[0048] Detector temperature (FID): 250°C;

[0049] Injection volume: 1 μL;

[0050] Carrier gas: nitrogen;

[0051] Flow rate: 1.0ml / min.

[0052] 2. The solution is prepared as follows:

[0053] Diluent: Isooctane is selected as the diluent. It has stable chemical properties, good miscibility with fatty acid methyl ester compounds, and will not produce interference peaks in gas chromatography analysis. It can ensure the accurate preparation and stable storage of reference solution and test solution.

[0054] Reference Solution: Accurately weigh a certain amount of methyl butyrate, methyl caproate, methyl octanoate, methyl decanoate, methyl laurate, methyl myristate, methyl palmitate, methyl stearate, methyl oleate, methyl linoleate, methyl linolenate, methyl arachidate, and methyl behenate. Dissolve them in heptane to a precise concentration of 0.1 mg / ml or 0.3 mg / ml, respectively. This reference solution contains methyl stearate and its related impurities and is used as a qualitative and quantitative standard for gas chromatography analysis.

[0055] Repeatability solution: Take about 40 mg of this product, accurately weigh it, place it in a 50 ml round-bottom flask, add 4 ml of 0.5 mol / L sodium hydroxide methanol solution, then add 4 ml of isooctane, mix vigorously and let it stand for more than 5 minutes, take the upper layer of liquid as the test solution, and prepare 6 parallel portions.

[0056] Blank solution: In a 50ml round-bottom flask, add 4ml of 0.5mol / L sodium hydroxide methanol solution and then add 4ml of isooctane. Mix vigorously and let it stand for more than 5min. Take the upper layer as the blank solution and prepare 6 parallel portions.

[0057] 3. Determination method: Accurately measure 1 μl each of the blank solution, reference solution, and repeatability solution and inject them into the gas chromatograph. After the instrument stabilizes, record the chromatogram. Qualitative analysis of methyl stearate and its impurities is performed by comparing the retention time of the chromatographic peak with that of the reference solution. Calculate the purity of stearic acid by peak area normalization.

[0058] 4. The results of the 6 repeated samples are shown in the following table:

[0059]

[0060] As can be seen from the data in the table, the purity of stearic acid in all six repetitive samples was greater than 98.0%, and the RSD of the stearic acid purity in the six samples was only 0.01% (n=6). This shows that in multiple repeated experiments, the gas chromatography analysis method can stably and accurately determine the purity of stearic acid, and the repeatability and reliability of the data are extremely high. Therefore, it can be concluded that this method has good repeatability and is suitable for the determination of stearic acid purity. It can provide reliable technical support for the quality control and production process optimization of stearic acid.

[0061] Example 3:

[0062] This embodiment provides a technical solution based on the first embodiment: a specific test detection of the detection method.

[0063] 1. The chromatographic conditions are the same as those in the repeatability test.

[0064] 2. Solution preparation:

[0065] Methyl stearate positioning solution: Accurately weigh approximately 10 mg of methyl stearate reference substance into a 10 ml volumetric flask. Add an appropriate amount of isooctane to fully dissolve it. Continue diluting with isooctane to the mark and shake well. Subsequently, accurately measure 1 ml from this solution and transfer it to another 10 ml volumetric flask. Dilute again with isooctane to the mark to prepare a methyl stearate positioning solution with a concentration of approximately 0.1 mg / ml. This positioning solution serves as a characteristic marker for methyl stearate, used to determine its specific retention time in the chromatogram, providing a precise reference for subsequent analysis.

[0066] Test solution, reference solution and blank solution: their preparation methods are the same as those in the repeatability test.

[0067] 3. Determination Method: Analyze and test each solution using gas chromatography. Accurately measure 1 μl each of the blank solution, reference solution, test solution, and methyl stearate solution and inject them into the gas chromatograph inlet. Under the specified chromatographic conditions, the sample enters the chromatographic column along with the carrier gas for separation. Different components are separated due to their different interactions with the stationary phase. Finally, qualitative and quantitative analysis is performed based on the retention time and peak area of ​​each component, and the chromatogram is recorded.

[0068] 4. The specificity results obtained from the experiment are shown in the following table:

[0069]

[0070] From the results, it can be seen that no interfering peak appears in the blank solution near the retention time of methyl stearate, indicating that the blank solution does not interfere with the detection of methyl stearate in the test solution; the retention time of methyl stearate in the test solution and the retention time of methyl stearate in the reference solution are highly consistent with the retention time in the methyl stearate positioning solution, indicating that under the established gas chromatography analysis conditions, methyl stearate can be accurately identified and separated, and the test solution matrix has no significant interference with the detection of methyl stearate. This detection method has good specificity and can be used for the accurate determination of methyl stearate, providing a strong guarantee for the quality control of methyl stearate.

[0071] Example 4:

[0072] This embodiment provides a technical solution based on the first embodiment: the quantitative limit test of the detection method:

[0073] This experiment determined the limit of quantification (LOQ) of methyl stearate using gas chromatography. The goal was to determine the method's minimum detectable concentration, verify the sensitivity and reliability of the analytical method, and provide an accurate basis for the determination of methyl stearate content. The following are the experimental details and analysis of the results.

[0074] 1. The chromatographic conditions are the same as those in the repeatability test.

[0075] 2. Solution preparation:

[0076] Methyl stearate positioning solution: Accurately weigh approximately 10 mg of methyl stearate reference substance into a 10 mL volumetric flask. Add an appropriate amount of isooctane to fully dissolve the solution. Dilute to the mark with isooctane and shake well. Then, accurately measure 1 mL of this solution and transfer it to another 10 mL volumetric flask. Dilute to the mark with isooctane to prepare a methyl stearate positioning solution with a concentration of approximately 0.1 mg / mL. This positioning solution is used to determine the characteristic retention time of methyl stearate in the chromatogram and serves as a reference standard for subsequent quantitative analysis.

[0077] Limit of Quantitation Solution: Place 1.0 ml of the methyl stearate solution in a 10 ml volumetric flask. Dissolve and dilute to the mark with isooctane. Prepare six parallel quantitation solutions using the same method. Reduce the concentration of the quantitation solution to a level close to the limit of quantitation through serial dilution to assess the detection capability and precision of the method in the low concentration range.

[0078] 3. Determination method:

[0079] The prepared solution was analyzed using gas chromatography. 1 μl of each blank solution and limit of quantitation solution was accurately measured and injected into the gas chromatograph inlet. Under the established chromatographic conditions, the methyl stearate component in the sample was separated on the chromatographic column, detected by the detector, and the chromatogram was recorded. The detection performance of the limit of quantitation solution was evaluated based on the peak area and signal-to-noise ratio (S / N) of the methyl stearate peak in the chromatogram.

[0080] 4. The test results are as follows:

[0081] 4.1 Peak area test results are shown in the following table:

[0082]

[0083] The peak areas of methyl stearate in the six quantification limit solutions were 4.4967, 4.3455, 4.5345, 4.4743, 4.6251, and 4.2508, respectively, with an average of 4.4545 and an RSD of 3.0%. These results demonstrate that the peak area of ​​methyl stearate has good repeatability and precision at the quantification limit, and the RSD values ​​meet the acceptance criteria for method validation, demonstrating that this method is capable of stable and reliable detection of methyl stearate in a low concentration range.

[0084] 4.2 The concentration and test sample ratio are as follows:

[0085] name Sample weight mg purity% Dilution multiple Concentration μg / ml % of test sample concentration Methyl stearate 11.72 100.0 1000 11.7200 0.23

[0086] Calculations show that the sample weight of the methyl stearate quantification limit solution is 11.72 mg, with a purity of 100.0%. After 1000-fold dilution, the concentration is 11.7200 μg / ml, representing 0.23% of the test sample concentration. This concentration level reflects the minimum concentration range within which the method can accurately and quantitatively detect methyl stearate, providing a quantitative basis for the detection of trace amounts of methyl stearate in actual samples.

[0087] 4.3 The signal-to-noise ratio test results are as follows:

[0088]

[0089] The signal-to-noise ratio (S / N) is a key indicator for measuring the limit of quantification. In this experiment, the S / N ratios of methyl stearate in the six quantification limit solutions were 20.8, 15.4, 22.8, 20.5, 22.6, and 23.4, respectively, all no less than 10. This indicates that at this concentration level, the signal from methyl stearate is clearly distinguishable from background noise, ensuring the accuracy and reliability of the quantitative determination. A S / N ratio of no less than 10 is a commonly used criterion for determining the limit of quantification, and the results of this experiment met this requirement, further validating the quantification limit performance of this method.

[0090] The experimental results show that the signal-to-noise ratio of the quantification limit solutions for methyl stearate is no less than 10, and the RSD of the main peak area of ​​the six quantification limit solutions is 3.0%, indicating that the gas chromatography analysis method has good precision and sensitivity at the quantification limit concentration level. This proves that the established method can accurately and reliably detect the lowest concentration of methyl stearate, and the quantification limit meets the analytical requirements. It provides an effective means for the quality control and microanalysis of methyl stearate, ensuring the accurate determination of methyl stearate content in actual testing processes, even in the low concentration range, and meeting the requirements of the quality standard.

[0091] Embodiment 5:

[0092] This embodiment provides a technical solution based on the first embodiment: solution stability test.

[0093] This experiment used gas chromatography to investigate the stability of a methyl stearate sample solution. The goal was to determine the stability of the sample solution after being stored at room temperature for a certain period of time, ensuring the reliability of the solution and the accuracy of the measurement results during sample analysis. The following is a detailed description of the experimental process and results.

[0094] 1. The chromatographic conditions are the same as those in the repeatability test.

[0095] 2. The solution preparation steps are the same as those in the repeatability test.

[0096] 3. Determination method:

[0097] Analyze the test solution using gas chromatography. Accurately measure 1 μl of each blank solution and test solution and inject them into the gas chromatograph inlet. Record the chromatogram. Calculate the methyl stearate content in the test solution by comparing it with the reference solution and examine its stability at different time points.

[0098] 4. The results of the stability test of the test solution are as follows:

[0099] From the data in the table below, it can be seen that the purity of methyl stearate measured at each time point after the test solution was placed at room temperature for 31 hours was maintained between 99.02% and 99.05%. Compared with the purity at 0h, the ratio at each time point was 100.0%, indicating that after the test solution was placed at room temperature for a certain period of time, the content of methyl stearate remained stable and did not change significantly.

[0100]

[0101] After the test solution was stored at room temperature for 31 hours, the measured stearic acid purity was no less than 98.0%, and the purity ratio compared to the purity at 0 hours was within the range of 98.0%-102.0%. This demonstrates the excellent stability of the test solution at room temperature, ensuring reliability during sample analysis and the accuracy of measurement results. In actual testing, this stability data provides a scientific basis for scheduling the preparation, storage, and analysis of the test solution, helping to improve work efficiency and the credibility of the results.

[0102] Example 6:

[0103] This embodiment provides a technical solution based on the first embodiment: a durability experiment of the detection method:

[0104] This experiment aims to investigate the robustness of this method for determining the purity of stearic acid. The following is a detailed description of the experimental process and results.

[0105] The chromatographic conditions and solution preparation were the same as those in the repeatability test, in which the temperatures of the injection port and the detector were changed to test the stability and reliability of the method.

[0106] Accurately measure 1 μl each of the blank solution, reference solution and repeatability solution, inject them into the gas chromatograph, record the chromatogram, and calculate the purity of stearic acid.

[0107] The durability results are as follows:

[0108] Based on the original chromatographic conditions, the injection port temperature and detector temperature were appropriately adjusted to investigate the effects of different conditions on the determination results of stearic acid purity, as follows:

[0109] Under the original conditions, the purity of stearic acid was measured to be 99.03%, the average was 99.0%, and the RSD was 0.01%; when the injection port temperature was adjusted to 245°C, the purity of stearic acid was measured to be 99.03%; when the injection port temperature was adjusted to 255°C, the purity of stearic acid was measured to be 99.05%; when the detector temperature was adjusted to 255°C, the purity of stearic acid was measured to be 99.03%; when the detector temperature was adjusted to 265°C, the purity of stearic acid was measured to be 99.04%.

[0110]

[0111] The experimental results show that the RSD of stearic acid purity measured under the original conditions and various durability conditions is 0.01%, indicating that when the injection port temperature and detector temperature change to a certain extent, the determination results of stearic acid purity still have good consistency and repeatability.

[0112] In summary, this method demonstrates excellent robustness for determining stearic acid purity. After moderate adjustments to the inlet and detector temperatures within the experimental range, the results remained essentially unchanged, with low RSD values. This demonstrates that this method can stably and accurately determine stearic acid purity under various chromatographic conditions. This provides a basis for fine-tuning instrumental conditions during actual analysis, ensuring the method's practicality and reliability.

[0113] The above description is merely illustrative of certain exemplary embodiments of the present invention. It goes without saying that those skilled in the art will be able to modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and description are illustrative in nature and should not be construed as limiting the scope of protection of the claims.

Claims

1. A method for detecting the purity of stearic acid in distearoylphosphatidylcholine, characterized in that: The steps include: S1. Weigh 40 mg of distearoylphosphatidylcholine and place it in a 50 ml round-bottom flask. Then add sodium hydroxide methanol solution and isooctane. Mix well and let stand. Take the upper layer to obtain the test solution. S2. In a 50 ml round-bottom flask, add sodium hydroxide methanol solution and then add isooctane, mix well and let stand, and take the upper layer to obtain a blank solution; S3. Analyze and detect the test solution and blank solution by gas chromatography to obtain a chromatogram, and calculate the stearic acid purity of the test solution according to the peak area of ​​the chromatogram.

2. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The chromatographic conditions of the gas chromatography method described in S3 are: A polyethylene glycol column was used; the starting temperature was 70°C, maintained for 2 minutes, then increased to 240°C at a rate of 5°C per minute and maintained for 25 minutes; the injection port temperature was 220°C; the flow rate was 1.0 ml / min; and the carrier gas was nitrogen.

3. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The concentration of the sodium hydroxide methanol solution in S1 is 0.5 mol / L, and the amount added is 4 ml.

4. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The amount of isooctane added in S1 is 4 ml; the standing time in S1 is 5 to 10 minutes.

5. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The concentration of the sodium hydroxide methanol solution in S2 is 0.5 mol / L, and the amount added is 4 ml.

6. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The amount of isooctane added in S2 is 4 ml; the standing time in S2 is 5 to 10 minutes.

7. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The detector of the gas chromatography described in S3 is a hydrogen flame ionization detector.

8. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 7, wherein: The temperature of the hydrogen flame ionization detector is 250-260°C.

9. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 7, wherein The hydrogen flow rate of the hydrogen flame ionization detector was 30 mL / min, and the air flow rate was 400 ml / min.

10. The method for detecting the purity of stearic acid in distearoylphosphatidylcholine according to claim 1, wherein: The injection volume for the gas chromatography was 1 μl.

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