Method for measuring content of diclofenac diethylamine latex

Abstract

The invention provides a method for determining the content of diclofenac diethylamine latex. The determination method comprises the following steps: 1, preparing an internal standard solution, a test solution and a reference solution of the diclofenac diethylamine latex; 2, high performance liquid chromatography is adopted, and chromatographic conditions include that a chromatographic column is an octadecyl silane bonded silica gel chromatographic column, a methanol-phosphate buffer solution is used as a mobile phase, the detection wavelength is 254 nm, and isocratic elution is carried out; in the methanol-phosphate buffer solution, the volume ratio of methanol to the phosphate buffer solution is 80: 20. According to the determination method provided by the invention, the determination effects of simplicity and convenience in operation, high accuracy, strong anti-interference capability, good stability, strong applicability, economy and high efficiency are achieved by optimizing the preparation of the internal standard solution, the test solution and the reference solution and adopting high performance liquid chromatography in combination with specific chromatographic conditions.

Description

Technical Field

[0001] The invention relates to the technical field of chemical drug analysis, in particular to a method for determining the content of diclofenac diethylamine emulsion. Background Art

[0002] Diclofenac Diethylamine is a nonsteroidal anti-inflammatory drug (NSAID), mainly used to relieve mild to moderate pain and inflammation. Its structural formula is shown in formula (I):

[0003]

[0004] It is commonly used to treat symptoms caused by arthritis, musculoskeletal disorders, etc. The drug can be applied topically (e.g. in gel or cream form) to reduce pain and inflammation in a specific area, thus reducing the risk of systemic side effects.

[0005] The determination of the content of diclofenac diethylamine emulsion is a key step to ensure its product quality and efficacy. Accurate content determination can ensure that the active ingredients of the drug reach the specified concentration range, which is crucial to ensuring the safety and effectiveness of the drug. Through strict quality control, it can not only ensure that patients can obtain the expected treatment effect, but also avoid potential risks caused by excessive or low drug content, such as increased side effects or treatment failure. Therefore, content determination is an important link in the process of drug production and quality control, which helps to safeguard the health rights and interests of patients and enhance the market competitiveness of pharmaceutical companies.

[0006] The British Pharmacopoeia BP2024, the imported drug registration standards JX20100183 and JX20220123 all have methods for determining the content of diclofenac diethylamine emulsion, but these methods have certain limitations in practical applications. For example, the BP2024 method is cumbersome to operate and is not suitable for rapid testing of a large number of samples; the JX20220123 method may lead to inaccurate results due to solvent effects; and the JX20100183 method may cause content determination deviations due to the insoluble excipients occupying the volume of the volumetric flask.

[0007] Therefore, in order to improve detection efficiency and accuracy, it is necessary to optimize and improve the existing measurement methods to better serve the quality control and clinical application needs of drugs. Summary of the invention

[0008] In view of this, the present invention proposes a method for determining the content of diclofenac diethylamine emulsion, which can effectively avoid the above problems, while ensuring the quality and safety of diclofenac diethylamine emulsion products, and ensuring the treatment effect and medication safety of patients.

[0009] The present invention provides a method for determining the content of diclofenac diethylamine emulsion, the method comprising the following steps:

[0010] The first step is to prepare an internal standard solution, a test solution and a reference solution of diclofenac diethylamine emulsion;

[0011] The second step is to use high performance liquid chromatography, the chromatographic conditions include: the chromatographic column is an octadecylsilane bonded silica gel chromatographic column, methanol-phosphate buffer is used as the mobile phase, the detection wavelength is 254nm, and isocratic elution is performed;

[0012] In the methanol-phosphate buffer, the volume ratio of the methanol to the phosphate buffer is 80:20.

[0013] On the basis of the above technical solution, preferably, when preparing the internal standard solution of the diclofenac diethylamine emulsion, the internal standard is selected from biphenyl or benzophenone.

[0014] The structural formula of biphenyl is shown in formula (II):

[0015] The structural formula of benzophenone is shown in formula (III):

[0016] On the basis of the above technical solution, preferably, the internal standard is selected from benzophenone; and the mass concentration ratio of the diclofenac diethylamine to the benzophenone is 0.58:0.09.

[0017] On the basis of the above technical solution, preferably, the chromatographic column is of model YMC-Pack Pro C18, with a length of 250 mm, an inner diameter of 4.6 mm, and a filler particle size of 5 μm.

[0018] On the basis of the above technical solution, preferably, the filler is octadecylsilane bonded silica gel.

[0019] On the basis of the above technical solution, preferably, the phosphate buffer is prepared from phosphoric acid, sodium dihydrogen phosphate dihydrate and water in a mass-to-volume ratio of 0.5 g:0.8 g:1000 ml.

[0020] Based on the above technical solution, preferably, the flow rate of the mobile phase is 1 ml / min.

[0021] Based on the above technical solution, preferably, the temperature of the chromatographic column is 30°C.

[0022] On the basis of the above technical solution, preferably, the phosphate buffer is adjusted to a pH value of 2.5 using phosphoric acid.

[0023] In the present invention, a method for determining the content of diclofenac diethylamine emulsion specifically comprises:

[0024] Internal standard solution: Take 150 mg of benzophenone, place it in a 100 ml volumetric flask, add methanol to dissolve and dilute to the scale, shake well. (Contains about 1.5 mg / ml of benzophenone)

[0025] Test solution Take about 2.5g of diclofenac diethylamine latex (equivalent to 29mg of diclofenac diethylamine), weigh accurately, place in a 100ml volumetric flask, accurately add 3ml of internal standard solution, and then add about 60ml of methanol, vortex until the latex is evenly dispersed, add 5ml of saturated sodium chloride solution and shake until the flocculation of the auxiliary materials no longer increases, dilute to the scale with methanol, shake well, filter through a 0.22μm hydrophobic PTFE filter membrane (manufacturer: Shanghai Anpu, diameter 25mm), discard 2ml of the initial filtrate, and take the subsequent filtrate. (Contains about 0.29mg / ml of diclofenac diethylamine and about 0.045mg / ml of benzophenone)

[0026] Reference solution: Take 29 mg of diclofenac diethylamine reference substance, place it in a 100 ml volumetric flask, accurately add 3 ml of internal standard solution, add methanol to dissolve and dilute to the scale, shake well. (Contains about 0.29 mg / ml of diclofenac diethylamine and about 0.045 mg / ml of benzophenone)

[0027] The chromatographic conditions are as follows: octadecylsilane bonded silica gel is used as the filler; methanol-pH 2.5 phosphate buffer (take 0.5 g of phosphoric acid and 0.8 g of sodium dihydrogen phosphate dihydrate, add 1000 ml of water, stir to dissolve, and adjust the pH value to 2.5 with phosphoric acid) (80:20) is used as the mobile phase; the detection wavelength is 254 nm; the flow rate is 1.0 ml per minute; the column temperature is 30°C; and the injection volume is 20 μl.

[0028] Determination method: Accurately measure the test solution and the reference solution, inject them into the liquid chromatograph respectively, record the chromatogram, and calculate by peak area according to the internal standard method.

[0029] The specification of diclofenac diethylamine emulsion is 1% (20g: 0.2g, calculated as diclofenac sodium), so diclofenac diethylamine needs to be converted into diclofenac sodium. The conversion coefficient of diclofenac diethylamine (molecular weight 369) into diclofenac sodium (molecular weight 318) is 0.8618.

[0030] Specifically, the following calculation formula can be used:

[0031] (1) Calculate the correction factor f of the reference solution according to the following formula:

[0032]

[0033] In formula (IV): As: peak area of ​​benzophenone in reference solution; Ar: peak area of ​​diclofenac in reference solution; Ms: sample weight of benzophenone (mg); Mr: sample weight of diclofenac diethylamine reference substance (mg); Ws: content of benzophenone; Wr: content of diclofenac diethylamine reference substance; Vs: dilution multiple of benzophenone in reference solution; Vr: dilution multiple of diclofenac diethylamine in reference solution.

[0034] (2) According to the internal standard method, the absolute content and relative content of diclofenac sodium were calculated by peak area according to the following formula:

[0035]

[0036] In formula (V) and (VI): Ax: peak area of ​​diclofenac in the test solution; As': peak area of ​​benzophenone in the test solution; Ms: sample weight of benzophenone (mg); Ws: benzophenone content; Vs': dilution factor of benzophenone in the test solution; V: dilution factor of the test sample; f: correction factor; M: sample weight of the test sample (g); Bs: specification (1%); K: conversion factor.

[0037] The method for determining the content of diclofenac diethylamine emulsion provided by the present invention has the following beneficial effects compared with the prior art:

[0038] (1) The present invention provides a method for determining the content of diclofenac diethylamine emulsion, which achieves a determination effect with simple operation, high accuracy, strong anti-interference ability, good stability, strong applicability and economical and efficient performance by optimizing the preparation steps of internal standard solution, test solution and reference solution and adopting high performance liquid chromatography (HPLC) under specific chromatographic conditions.

[0039] (2) The determination method of the present invention not only simplifies the operation process, reduces complex manual operations, and improves the operability and repeatability of the experiment, but also effectively reduces the interference of the sample matrix and enhances the anti-interference ability of the method by selecting a suitable internal standard (such as benzophenone) and accurately controlling the mass concentration ratio.

[0040] (3) The present invention ensures the stable operation of the chromatographic system by optimizing the chromatographic column conditions and mobile phase parameters, avoids measurement errors caused by factors such as temperature fluctuations and flow rate changes, and improves the stability of the method.

[0041] (4) The determination method of the present invention is applicable to the content determination of various diclofenac diethylamine emulsion preparations, has wide applicability and promotion value, and conforms to international standards, ensuring the international recognition and mutual recognition of the determination results, and providing strong technical support for the quality control and clinical application of drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 This is a real shot of the test solution of the imported drug registration standard JX20100183 of the present invention;

[0044] Figure 2 It is a chromatogram overlay of the content determination of different internal standard solutions of the present invention;

[0045] Figure 3 A typical chromatogram of the content determination of the reference substance solution in the embodiment of the present invention; DETAILED DESCRIPTION

[0046] In order to reproduce the method for determining the content of diclofenac diethylamine in the British Pharmacopoeia (BP 2024), the inventors followed the following steps: First, diclofenac diethylamine emulsion containing 50 mg of diclofenac diethylamine was dissolved in 50 ml of acetone, filtered after shaking for 10 minutes, and the filtrate was evaporated to dryness, and then further dried under reduced pressure. Subsequently, the dried residue was dissolved in 100 ml of a mixed solvent consisting of methanol and water (ratio of 60:40). 1 ml was taken from the solution, diluted to 10 ml with mobile phase, and then filtered through a glass fiber filter to obtain the final test solution. However, in the actual operation process, the inventors found that this sample preparation method is more complicated and is not suitable for the detection of a large number of samples. In addition, due to manual operation errors in the filtering operation and the dissolution and transfer of the residue, the accuracy and repeatability of the results may be affected.

[0047] When trying to reproduce the determination method of diclofenac diethylamine content in the imported drug registration standard JX20220123, the inventor adopted similar steps: Similarly, 50 mg of diclofenac diethylamine emulsion of diclofenac diethylamine was dissolved in 50 ml of acetone, filtered and evaporated to dryness after shaking for 10 minutes, and then dried under reduced pressure. The dried residue was dissolved in 100 ml of methanol-water (60:40) mixed solvent, 1 ml was taken out, diluted to 10 ml with mobile phase, and filtered through a glass fiber filter to obtain a test solution. However, when using a methanol-phosphate solution system as a chromatographic analysis condition, the preparation of the above-mentioned test solution is prone to solvent effect, resulting in poor chromatographic peak shape, thereby affecting the accuracy of quantitative analysis.

[0048] For the determination method of diclofenac diethylamine content in the imported drug registration standard JX20100183, the inventors adopted the following strategy: accurately weigh 2.5 grams of sample, place it in a 100 ml volumetric flask, add about 90 ml of methanol, and stir with a magnetic stirrer until completely dissolved. Afterwards, dilute to the scale with methanol, shake well and centrifuge, and take the supernatant as the test solution. This method matches the adopted chromatographic system well, so the reproducible operation can be completed smoothly. In view of the accuracy and convenience of the operation, the inventors adopted a vortex mixing method during the sample dispersion and dissolution process to improve efficiency and reduce errors. This standard uses the external standard method to determine the content of diclofenac diethylamine, and the determination results are shown in Figure 1 As shown in Table 1 below:

[0049] Table 1 Measurement results

[0050]

[0051]

[0052] Depend on Figure 1 It can be seen that: by observing the solution phenomenon, it is found that there are obvious oil drops at the bottom of the measuring bottle. From the test results in Table 1, it can be seen that the test results of the reference preparation are high.

[0053] After analyzing the test results and solution phenomena, it is speculated that the high content may be caused by: when the solution is prepared, the insoluble excipients in diclofenac diethylamine emulsion, mainly the oil phase matrix (such as coconut oil decanoate and liquid paraffin), will occupy the volume of the volumetric flask, making the dilution volume less than 100ml, which may lead to a high content.

[0054] Therefore, in view of the fact that the prior art is not as good as the inventor's expectations, the inventor made the present invention through further research.

[0055] In order to solve the problem of high content that may exist under the preparation method of the test solution of the imported drug registration standard JX20100183, and at the same time solve the problem that the macromolecular compounds in the test solution block the chromatographic column and make the chromatographic column not durable, the inventors of the present invention adjusted the content calculation method (from the external standard method to the internal standard method), added an internal standard to eliminate the influence of the solution preparation to ensure accurate quantification, and in addition, added a saturated sodium chloride solution when preparing the test solution to cause the macromolecular excipients in the test solution to flocculate and settle to protect the chromatographic column.

[0056] The chromatographic conditions for measuring the content of diclofenac diethylamine of the present invention are shown in Table 2 below.

[0057] Table 2 Chromatographic conditions

[0058]

[0059] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments 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.

[0060] The following is a preparation example of the present invention, which provides an internal standard solution prepared using different internal standards to measure the content of diclofenac diethylamine.

[0061] The internal standard substances screened by the inventors in the early stage include: biphenyl, 4-aminobenzoic acid isobutyl ester, benzophenone, butyl p-hydroxybenzoate, and 4-hydroxybenzoic acid pentyl ester. The internal standard solutions of the above internal standard substances were prepared respectively in the following manner:

[0062] Weigh about 10 mg of each compound, place it in a 20 ml volumetric flask, dissolve it in methanol and dilute it to the mark, shake well, and you have it.

[0063] The prepared internal standard solutions were injected separately to obtain Figure 2 Chromatogram shown.

[0064] Depend on Figure 2 It can be seen that the solvent peak of the internal standard solution containing isobutyl 4-aminobenzoate is interfered, the impurity peak of the internal standard solution containing butyl p-hydroxybenzoate is interfered, the internal standard solution containing pentyl 4-hydroxybenzoate is interfered with by the impurity peak and an impurity peak appears before the pentyl 4-hydroxybenzoate peak; while the peak positions of biphenyl and benzophenone are suitable, not interfered by the blank solvent, and do not interfere with the main components and impurities, so biphenyl and benzophenone are used as internal standards to detect the content and compare the results.

[0065] Preparation Example 1

[0066] This preparation example provides a method for determining the content of diclofenac diethylamine using an internal standard solution containing benzophenone, specifically comprising:

[0067] Internal standard solution: Weigh 150 mg of benzophenone, place in a 100 ml volumetric flask, add methanol to dissolve and dilute to the scale, and shake well.

[0068] Reference solution: Weigh 29 mg of diclofenac diethylamine reference substance into a 100 ml volumetric flask, accurately add 3 ml of internal standard solution, add methanol to dissolve and dilute to the scale, and shake well.

[0069] Test solution: Take about 2.5g of diclofenac diethylamine emulsion, weigh it accurately, put it in a 100ml volumetric flask, accurately add 3ml of internal standard solution, add about 60ml of methanol, vortex until the latex is evenly dispersed, add 5ml of saturated sodium chloride solution and shake until the flocculation of the auxiliary materials no longer increases, dilute to the scale with methanol, shake well, filter through a 0.22μm hydrophobic PTFE filter membrane (manufacturer: Shanghai Anpu, diameter 25mm), discard 2ml of the initial filtrate, and take the subsequent filtrate.

[0070] Chromatographic conditions

[0071] Chromatographic column: YMC-Pack Pro C18 250mm×4.6mm, 5μm

[0072] Mobile phase: pH 2.5 phosphate buffer-methanol (20:80)

[0073] Detection wavelength: 210-400 nm (extraction 254 nm), column temperature: 30°C, flow rate: 1.5 ml / min, injection volume: 20 μl. The measurement results are shown in Table 3 below.

[0074] Table 3 Measurement results

[0075]

[0076] Preparation Example 2

[0077] This preparation example provides a method for determining the content of diclofenac diethylamine using an internal standard solution containing biphenyl, specifically comprising:

[0078] Internal standard solution: Weigh 150 mg of biphenyl, place in a 100 ml volumetric flask, add methanol to dissolve and dilute to the scale, and shake well.

[0079] Reference solution: Weigh 29 mg of diclofenac diethylamine reference substance into a 100 ml volumetric flask, accurately add 3 ml of internal standard solution, add methanol to dissolve and dilute to the scale, and shake well.

[0080] Test solution: Take about 2.5g of diclofenac diethylamine emulsion, weigh it accurately, put it in a 100ml volumetric flask, accurately add 3ml of internal standard solution, add about 60ml of methanol, vortex until the latex is evenly dispersed, add 5ml of saturated sodium chloride solution and shake until the flocculation of the auxiliary materials no longer increases, dilute to the scale with methanol, shake well, filter through a 0.22μm hydrophobic PTFE filter membrane (manufacturer: Shanghai Anpu, diameter 25mm), discard 2ml of the initial filtrate, and take the subsequent filtrate.

[0081] Chromatographic conditions

[0082] Chromatographic column: YMC-Pack Pro C18 250mm×4.6mm, 5μm

[0083] Mobile phase: pH 2.5 phosphate buffer-methanol (20:80)

[0084] Detection wavelength: 210-400 nm (extraction 254 nm), column temperature: 30°C; flow rate: 1.5 ml / min, injection volume: 20 μl.

[0085] The measurement results are shown in Table 4 below.

[0086] Table 4 Measurement results

[0087]

[0088] Combining Table 3 and Table 4, it can be seen that: with benzophenone and biphenyl as internal standards, the content results of self-developed and reference are basically consistent, and the difference between the results calculated by the two external standard methods is about 1%. The use of the internal standard method can eliminate the volume error, so the internal standard method is selected as the content detection method, and because the structural formula of benzophenone is more similar to that of diclofenac diethylamine, benzophenone is selected as the internal standard.

[0089] Since diclofenac diethylamine emulsion contains macromolecular compounds (such as carbomer, etc.), which are easy to clog the chromatographic column after entering the chromatographic column with the test solution, an appropriate amount of saturated sodium chloride solution is added to the test solution to precipitate the macromolecular excipients, promote their precipitation, and prevent the carbomer in the test solution from clogging the chromatographic column.

[0090] The following example is obtained in combination with Preparation Example 1.

[0091] Example

[0092] This embodiment provides a method for determining the content of diclofenac diethylamine emulsion, which specifically comprises:

[0093] The first step is to prepare an internal standard solution, a test solution and a reference solution of diclofenac diethylamine emulsion;

[0094] (1) Internal standard solution

[0095] Take 150 mg of benzophenone, place it in a 100 ml volumetric flask, add methanol to dissolve and dilute to the mark, shake well. (Contains about 1.5 mg / ml of benzophenone);

[0096] (2) Test solution

[0097] Take about 2.5g of diclofenac diethylamine latex (equivalent to 29mg of diclofenac diethylamine), weigh accurately, place in a 100ml volumetric flask, accurately add 3ml of internal standard solution, then add about 60ml of methanol, vortex until the latex is evenly dispersed, add 5ml of saturated sodium chloride solution and shake until the flocculation of the auxiliary materials no longer increases, dilute to the scale with methanol, shake well, filter through a 0.22μm hydrophobic PTFE filter membrane (manufacturer: Shanghai Anpu, diameter 25mm), discard 2ml of the initial filtrate, and take the subsequent filtrate. (Contains about 0.29mg / ml of diclofenac diethylamine and about 0.045mg / ml of benzophenone)

[0098] (3) Reference solution

[0099] Take 29 mg of diclofenac diethylamine reference substance, place it in a 100 ml volumetric flask, accurately add 3 ml of internal standard solution, add methanol to dissolve and dilute to the scale, shake well. (Contains about 0.29 mg / ml of diclofenac diethylamine and about 0.045 mg / ml of benzophenone);

[0100] The second step is to use high performance liquid chromatography, and the chromatographic conditions include: octadecylsilane bonded silica gel as filler; methanol-pH2.5 phosphate buffer (take 0.5g of phosphoric acid and 0.8g of sodium dihydrogen phosphate dihydrate, add 1000ml of water, stir to dissolve, and adjust the pH value to 2.5 with phosphoric acid) (80:20) as mobile phase; detection wavelength is 254nm; flow rate is 1.0ml per minute; column temperature is 30℃; injection volume is 20μl.

[0101] Step 3: Determination

[0102] Accurately measure the test solution and reference solution, inject them into the liquid chromatograph respectively, and record the chromatogram. Figure 3 Calculated by peak area using internal standard method.

[0103] Typical chromatogram of content determination (reference solution) is as follows Figure 3 shown.

[0104] The inventors further verified the accuracy of the above examples, and the chromatographic conditions were the same as above.

[0105] Accuracy solution preparation includes the following steps:

[0106] Diclofenac diethylamine stock solution: Accurately weigh 180 mg of diclofenac diethylamine, place in a 25 ml volumetric flask, dissolve and dilute to the scale with methanol, and shake well.

[0107] Internal standard solution: Accurately weigh 150 mg of benzophenone, place it in a 100 ml volumetric flask, dissolve it in methanol and dilute to the scale, and shake well.

[0108] Background test solution: Take about 2.5g of diclofenac diethylamine emulsion, weigh it accurately, put it in a 100ml volumetric flask, accurately add 3ml of internal standard solution, and then add about 60ml of methanol, vortex until the latex is evenly dispersed, add 5ml of saturated sodium chloride solution and shake until the flocculation of the excipients no longer increases, dilute to the scale with methanol, shake well, filter through a 0.22μm hydrophobic PTFE filter membrane (manufacturer: Shanghai Anpu, diameter 25mm), discard 2ml of the initial filtrate, and take the subsequent filtrate.

[0109] Accuracy solution-1, 2, 3: Take about 1.25g of diclofenac diethylamine emulsion, weigh accurately, put it in a 100ml volumetric flask, accurately add 2ml of diclofenac diethylamine stock solution, 3ml of internal standard solution, and then add about 60ml of methanol, vortex until the latex is evenly dispersed, add 5ml of saturated sodium chloride solution and shake until the flocculation of the auxiliary materials no longer increases, dilute to the scale with methanol, shake well, filter through a 0.22μm hydrophobic PTFE filter membrane (manufacturer: Shanghai Anpu, diameter 25mm), discard 2ml of the initial filtrate, and take the subsequent filtrate. The verification results are shown in Table 5 below.

[0110] Table 5 Accuracy results

[0111]

[0112] It can be seen from Table 5 that the recovery rate and average rate of the three accuracy solutions are between 98.0% and 102.0%, and RSD% is less than 2.0%, which meets the requirements, indicating that the accuracy of this method is good.

[0113] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for determining the content of diclofenac diethylamine emulsion, characterized in that: The method comprises the following steps: The first step is to prepare an internal standard solution, a test solution and a reference solution of diclofenac diethylamine emulsion; The second step is to use high performance liquid chromatography, the chromatographic conditions include: the chromatographic column is an octadecylsilane bonded silica gel chromatographic column, methanol-phosphate buffer is used as the mobile phase, the detection wavelength is 254nm, and isocratic elution is performed; In the methanol-phosphate buffer, the volume ratio of the methanol to the phosphate buffer is 80:

20.

2. The method according to claim 1, characterized in that When preparing the internal standard solution of the diclofenac diethylamine emulsion, the internal standard substance is selected from biphenyl or benzophenone.

3. The method according to claim 2, characterized in that The internal standard is selected from benzophenone; the mass concentration ratio of the diclofenac diethylamine to the benzophenone is 0.58:0.

09.

4. The method according to claim 1, characterized in that The model of the chromatographic column is Ultimate LP-C18, with a length of 250 mm, an inner diameter of 4.6 mm, and a filler particle size of 5 μm.

5. The method according to claim 4, characterized in that The filler is octadecylsilane bonded silica gel.

6. The method according to claim 1, characterized in that The phosphate buffer is prepared from phosphoric acid, sodium dihydrogen phosphate dihydrate and water in a mass-volume ratio of 0.5 g:0.8 g:1000 ml.

7. The method according to claim 1, characterized in that The flow rate of the mobile phase is 1 ml / min.

8. The method according to claim 1, characterized in that The temperature of the chromatographic column was 30°C.

9. The method according to claim 1, characterized in that The phosphate buffer solution uses phosphoric acid to adjust the pH value to 2.5.

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