Method for determination of carbomer content in preparation by high performance liquid chromatography-evaporative light scattering

Abstract

The present application belongs to the field of polymer detection, and particularly relates to a method for determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering, comprising the steps of chromatographic conditions, drawing a standard curve of the logarithm of the carbomer concentration versus the logarithm of the peak area, preparing a blank sample solution, preparing and detecting a test sample solution, and the like. The present method utilizes the linear relationship between the logarithm of the concentration of carbomer in an evaporative light scattering detector and the logarithm of the response value, and through a certain sample pretreatment method, the carbomer is quantitatively dissolved and uniformly dispersed in a solvent, and then enters the HPLC-ELSD chromatographic system, so as to achieve the purpose of quantitative detection. The detection method realizes the quantitative detection of the commonly used auxiliary material carbomer in an external semi-solid preparation, thereby effectively guiding the self-made preparation to be consistent with the prescription of the reference preparation.

Description

Technical Field

[0001] This invention belongs to the field of polymer detection, and specifically relates to a method for determining the carbomer content in a formulation by high performance liquid chromatography-evaporative light scattering. Background Technology

[0002] Carbomer is a polymer formed by the chemical crosslinking of acrylic acid or acrylate with allyl ether, including polyacrylic acid (homopolymer) and long-chain alkanol acrylate polymers (polymers). Its molecular structure contains 52-68% acid groups, thus exhibiting a certain degree of acidity and hydrophilicity, making it soluble in water, ethanol, and glycerol. Carbomer possesses thickening, suspending, system stabilizing, and water and active ingredient release regulating functions. Furthermore, it is simple to process and exhibits good stability, making it a widely used rheology-modified thickener in personal care products, pharmaceuticals, and other fields.

[0003] Depending on the degree of crosslinking and molecular weight, carbomer exists in various types, including traditional series such as Carbopol 910, 934, 934P, 940, 941, and 954, as well as newer polymers like Carbopol Ultrez 20 / 21, all of which are homopolymers. The different types of carbomer, due to variations in their suspension stability and the duration of flow change, lead to different applications across various industries.

[0004] Among the existing methods for quantitative detection of carbomer content in formulations, the commonly used methods are Raman spectroscopy and acid-base titration. However, Raman spectroscopy is an uncommon and expensive instrument, resulting in high detection costs. Acid-base titration has poor specificity and is only suitable for single-component quantitative detection. Since the formulation components are complex, it can interfere with quantitative detection. Furthermore, the experimental principle of this method is based on the reaction of sodium hydroxide with the carboxylic acid in the carbomer structure. Carbomer is a polymer, and its carboxylic acid content is within a range. Therefore, this method cannot achieve the purpose of quantitative detection, nor can it provide guidance on the consistency between self-made formulations and reference formulations, nor can it verify whether self-made formulations based on reference formulations can meet the standards. Summary of the Invention

[0005] To overcome the problems of high cost, poor specificity, and poor accuracy in the quantification of carbomer in mixed components in the prior art, this invention provides a method for the quantitative detection of carbomer excipients in formulations by high performance liquid chromatography-evaporative light scattering.

[0006] The specific technical solution adopted is: a method for determining the carbomer content in a preparation by high-performance liquid chromatography-evaporative light scattering, including the following steps:

[0007] Step 1. Chromatographic conditions: An octadecylsilane-bonded silica gel column was used as the chromatographic column; water or 0.02% formic acid aqueous solution was used as mobile phase A, acetone as mobile phase B, and ethanol as mobile phase C. Gradient elution was performed, and the gradient elution program is as follows:

[0008] 0–4 min: The proportion of mobile phase B is between 0% and 10%, the proportion of mobile phase C is 0%, and the remainder is mobile phase A;

[0009] 4–4.5 min: The proportion of mobile phase C changes from 0% to 85%–95%, mobile phase B becomes 0%, and the remainder is mobile phase A;

[0010] 4.5–8.5 min: Mobile phase C accounts for 95%, with the remainder being mobile phase A;

[0011] 8.5–8.6 min: The proportion of mobile phase B changes from 0% to 5%, mobile phase C becomes 0%, and the remainder is mobile phase A;

[0012] 8.6–17 min: The proportion of mobile phase B is a value between 0% and 10%, and is the same as the proportion of mobile phase B from 0 to 4 min. The proportion of mobile phase C is 0%, and the remainder is mobile phase A.

[0013] The flow rate of the mobile phase is 0.3–0.6 mL / min;

[0014] The detector is an evaporative light scattering detector;

[0015] Drift tube temperature: 45℃~65℃;

[0016] Nitrogen flow rate: 1.8–3.0 L / min;

[0017] Traffic splitting mode: Traffic splitting;

[0018] The injection volume is 5–20 μL;

[0019] Step 2. Plot a standard curve of the logarithm of carbomer concentration versus the logarithm of peak area: Accurately weigh 1 mg, 5 mg, 10 mg, 15 mg, and 20 mg of carbomer reference standard, respectively, and place them in different 100 ml beakers. Add water to make them fully swollen, and adjust the pH to 7.0 ± 0.2 with an alkaline solvent, such as 0.01 mol / L sodium hydroxide solution or triethanolamine. Then add tetrahydrofuran to dilute, and stir at low speed with a high-speed disperser to form a uniform and clear liquid. Accurately measure the solution and enter it into a high-performance liquid chromatography system to obtain the peak area of ​​carbomer in carbomer reference standard solutions of different concentrations.

[0020] A standard curve was plotted with the logarithm of concentration on the x-axis and the logarithm of peak area on the y-axis to obtain the standard curve equation; where concentration = carbomer reference sample weight / dilution volume, and the concentration range is 0.01 mg / ml to 0.2 mg / ml;

[0021] Step 3. Preparation of blank sample solution: Accurately weigh an appropriate amount of blank sample and place it in a volumetric flask. Add tetrahydrofuran and shake to disperse the blank sample evenly. Stir with a vortex mixer until a dilute solution is formed. Then, dilute to the mark of the volumetric flask with acetonitrile and filter to obtain the blank sample solution. Take the blank sample solution and enter the high performance liquid chromatography system. The blank sample is a sample obtained by mixing other formulation components, except for carbomer, according to the formulation ratio.

[0022] Step 4. Preparation and detection of the test solution: Accurately weigh an appropriate amount of the preparation to be tested and place it in a volumetric flask. Add tetrahydrofuran and shake to disperse the preparation evenly. Stir with a vortex mixer until a dilute solution is formed. Then, dilute to the mark of the volumetric flask with acetonitrile, filter, and take the filtrate to obtain the test solution. Take the test solution and enter it into a high-performance liquid chromatography system to obtain the peak area of ​​carbomer in the test solution.

[0023] Substituting the values ​​into the standard curve equation obtained in step 2, we get the logarithm of the carbomer concentration. Then, according to the formula: a = 10... b The concentration of carbomer in the formulation is calculated as a × dilution factor / sample weight × 100%; where a is the concentration of carbomer (mg / ml) and b is the logarithm of the carbomer concentration.

[0024] Furthermore, in step 1, the length of the chromatographic column is 150 mm to 250 mm, the inner diameter is 1.8 mm to 4.6 mm, and the inner diameter of the packing material is 3.5 μm to 5.0 μm.

[0025] Moreover, the best results are achieved under the following conditions: mobile phase flow rate of 0.4 mL / min, drift tube temperature of 60 °C, nitrogen flow rate of 2.4 mL / min, and injection volume of 10 μL in step 1.

[0026] Furthermore, in step 2, accurately measuring the solution means transferring the obtained clear liquids of different concentrations into different 100ml volumetric flasks, rinsing the beakers with 20ml of acetonitrile, combining the washings into the same volumetric flask, then making up to 100ml with acetonitrile, and then measuring 10μl of each into the high performance liquid chromatography system.

[0027] Furthermore, in step 4, accurately weighing an appropriate amount of the test preparation and placing it in a volumetric flask means calculating the required mass of the preparation based on the preparation ratio, ensuring that the concentration of carbomer in the test solution is within the range of 0.01 mg / ml to 0.2 mg / ml.

[0028] Furthermore, accurately weighing an appropriate amount of blank sample in step 3 means that the mass of the accurately weighed blank sample is the same as the mass of the accurately weighed preparation in step 5.

[0029] Furthermore, the volume of tetrahydrofuran added in step 3 is 20% of the volumetric flask volume.

[0030] Furthermore, the volume of tetrahydrofuran added in step 4 is 20% of the volumetric flask volume.

[0031] Furthermore, before plotting the standard curve of the logarithm of carbomer concentration versus the logarithm of peak area in step 2, the method specificity is verified as follows:

[0032] (1) Prepare blank solvent for use in high performance liquid chromatography system: Take 10 ml of the same mobile phase A as in step 1 and place it in a 100 ml volumetric flask. Adjust the pH to 7.0 ± 0.2 with the same alkaline solvent as in step 2. Add 20 ml of tetrahydrofuran and then make up to 100 ml with acetonitrile to obtain blank solvent, which is then used in high performance liquid chromatography system.

[0033] (2) Preparation of blank sample solution for high performance liquid chromatography system: The blank sample is a sample obtained by mixing other formulation components except carbomer according to the formulation ratio. Take an appropriate amount of blank sample and put it in a volumetric flask. Add tetrahydrofuran and shake to disperse the blank sample evenly. Stir with a vortex mixer until a dilute solution is formed. Then, dilute to the mark of the volumetric flask with acetonitrile, filter, and obtain blank sample solution, which is then introduced into the high performance liquid chromatography system.

[0034] Compared with existing technologies, the advantages of this technical solution are as follows: A standard curve is established by utilizing the linear relationship between the logarithm of the peak area and the logarithm of the concentration of carbomer in an evaporative light scattering detector, thereby achieving the purpose of quantitative detection of carbomer content in formulations. This detection method is highly sensitive, specific, precise, accurate, simple, and rapid to operate. Furthermore, it has wide applicability, low detection cost, and fast detection speed, enabling the quantitative detection of carbomer, a commonly used excipient in topical semi-solid preparations. This effectively guides the formulation of self-made preparations to achieve consistency with reference formulations. Attached Figure Description

[0035] Figure 1 The spectrum of the blank solvent in Example 1;

[0036] Figure 2 The spectrum is that of the blank sample solution in Example 1;

[0037] Figure 3 This is the standard curve graph from Example 2;

[0038] Figure 4 The spectrum is for the sample with 80% accuracy in Example 3;

[0039] Figure 5 The spectrum is for the 100% accuracy sample in Example 3;

[0040] Figure 6 The spectrum is for the sample with 120% accuracy in Example 3;

[0041] Figure 7 The chromatogram is of the self-made formulation 1 in Example 4;

[0042] Figure 8 This is the chromatogram of reference preparation 1 in Example 4. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. However, the scope of the present invention is not limited to the following embodiments.

[0044] The carbomer reference standard used in the following examples was obtained from Lubrizol Advanced Materials, Inc., lot number 0102509299, model number Carbomer 980. The HPLC-ELSD used was from Agilent Technologies. All water used was ultrapure water.

[0045] Chromatographic conditions: An octadecylsilane-bonded silica column (4.6 mm × 250 mm, 3.5 μm) was used as the chromatographic column; water or 0.02% formic acid aqueous solution was used as mobile phase A, acetone as mobile phase B, and ethanol as mobile phase C, with gradient elution. The gradient elution program is as follows:

[0046] 0–4 min: The proportion of mobile phase B is between 0% and 10%, the proportion of mobile phase C is 0%, and the remainder is mobile phase A;

[0047] 4–4.5 min: The proportion of mobile phase C changes from 0% to 85%–95%, mobile phase B becomes 0%, and the remainder is mobile phase A;

[0048] 4.5–8.5 min: Mobile phase C accounts for 95%, with the remainder being mobile phase A;

[0049] 8.5–8.6 min: The proportion of mobile phase B changes from 0% to 5%, mobile phase C becomes 0%, and the remainder is mobile phase A;

[0050] 8.6–17 min: The proportion of mobile phase B is a value between 0% and 10%, and is the same as the proportion of mobile phase B from 0 to 4 min. The proportion of mobile phase C is 0%, and the remainder is mobile phase A.

[0051] The flow rate of the mobile phase is 0.3–0.6 mL / min; among which 0.4 mL / min yields the best results.

[0052] The detector is an evaporative light scattering detector;

[0053] Drift tube temperature: 45℃~65℃; 60℃ is the optimal temperature.

[0054] Nitrogen flow rate: 1.8–3.0 L / min; with 2.4 mL / min yielding the best results;

[0055] Traffic splitting mode: Traffic splitting;

[0056] The injection volume is 5–20 μL; 10 μL yields the best results.

[0057] Example 1: Experimental verification of method specificity

[0058] 1. Blank solvent: Take 10 ml of mobile phase A and place it in a 100 ml volumetric flask. Adjust the pH to 7.0 ± 0.2 with triethanolamine, add 20 ml of tetrahydrofuran, and then dilute to 100 ml with water. Take 10 μl of this solution and inject it into the HPLC-ELSD chromatographic system. The chromatogram of the blank solvent is shown below. Figure 1 As shown in the figure, the blank solvent does not interfere with the detection of the standard curve solution.

[0059] 2. Blank sample detection: Accurately weigh approximately 1 g of blank sample and place it in a 25 ml volumetric flask. Add 5 ml of tetrahydrofuran and shake to disperse the blank sample evenly. Stir with a vortex mixer until a dilute solution is formed. Then, dilute to the mark of the volumetric flask with acetonitrile to obtain the blank sample solution. Accurately measure 10 μl of this solution and introduce it into the HPLC-ELSD chromatography system.

[0060] Because the self-made formulation to be tested is prepared based on the reference formulation, the formulation components and proportions will change when the reference formulation is different. The blank sample is a sample prepared according to the reference formulation, with all formulation components except carbomer mixed in the formulation proportions.

[0061] The blank sample formulations shown in Table 1 below are three reference formulations excluding carbomer, with specific formulation quantities as follows:

[0062] Table 1

[0063]

[0064]

[0065] Validation was performed using three different blank sample formulations, and none of the resulting chromatograms showed peaks that interfered with carbomer detection. Figure 2 It is the chromatogram of the blank sample prepared according to prescription one.

[0066] Therefore, the self-made formulation to be tested can be processed in the same way as blank samples, and this processing method will not produce peaks that interfere with carbomer detection.

[0067] The above two verifications of method specificity demonstrate that the method has good specificity.

[0068] Example 2: Plotting Standard Curves

[0069] Accurately weigh 1 mg, 5 mg, 10 mg, 15 mg, and 20 mg of carbomer reference standard, and place them in separate 100 ml beakers. Add 20 ml of water to each beaker and allow them to swell overnight. Then add 30 ml of water and adjust the pH to 7.0 ± 0.2 with triethanolamine. Add 20 ml of tetrahydrofuran and stir at low speed using a high-speed disperser to form a homogeneous, clear liquid. Transfer the resulting solutions of each concentration to separate 100 ml volumetric flasks. Wash the beakers with 20 ml of acetonitrile and combine the washings in the same volumetric flask. Then dilute to 100 ml with acetonitrile. Accurately measure 10 μl of the standard curve solution and inject it into the HPLC-ELSD chromatographic system to obtain the peak area of ​​carbomer in the carbomer reference standard solutions of different concentrations.

[0070] Plot a standard curve with the logarithm of concentration on the x-axis and the logarithm of peak area on the y-axis. Figure 3 The concentration is calculated as: Carbomer reference standard sample weight / dilution volume, as shown in Table 2 below.

[0071] Table 2. Carbomer Standard Curve

[0072]

[0073] As shown in the table above, within the concentration range of 0.01436 mg / ml to 0.2200 mg / ml, the logarithm of the carbomer concentration and the logarithm of the peak area are linearly correlated, with the linear equation being y = 0.8183x + 3.1902 and the linear correlation coefficient being 0.9995.

[0074] Example 3: Accuracy Test

[0075] Accurately weigh 20 mg of carbomer reference standard into separate 100 ml beakers. Add 20 ml of water to each beaker and allow to swell overnight. Then add 30 ml of water and adjust the pH to 7.0 ± 0.2 with triethanolamine. Add 20 ml of tetrahydrofuran and stir at low speed with a high-speed disperser to form a homogeneous clear liquid. Transfer the clear liquids of each concentration into separate 100 ml volumetric flasks. Wash the beakers with 20 ml of acetonitrile and combine the washings into the same volumetric flask. Then dilute to 100 ml with acetonitrile to obtain the accuracy stock solution.

[0076] Accurately weigh approximately 1 g of blank sample (see Table 1, Formula 1) and place it in a 25 ml volumetric flask. Add 5 ml of tetrahydrofuran to evenly disperse and dissolve the blank sample. Then add 8 ml of accuracy stock solution and dilute to the mark with acetonitrile to obtain an 80% accuracy solution. Prepare three parallel solutions.

[0077] Accurately weigh approximately 1 g of blank sample (see Table 1, Formula 1) and place it in a 25 ml volumetric flask. Add 5 ml of tetrahydrofuran to evenly disperse and dissolve the blank sample. Then add 10 ml of accuracy stock solution and dilute to the mark with acetonitrile to obtain a 100% accuracy solution. Prepare three parallel solutions.

[0078] Accurately weigh approximately 1 g of blank sample (see Table 1, Formula 1) and place it in a 25 ml volumetric flask. Add 5 ml of tetrahydrofuran to evenly disperse and dissolve the blank sample. Then add 12 ml of accuracy stock solution and dilute to the mark with acetonitrile to obtain a 120% accuracy solution. Prepare three parallel solutions.

[0079] The accuracy results are shown in Table 3 below. Figures 4 to 6 As shown:

[0080] Table 3

[0081]

[0082] The data above show that when the samples are processed using the above method, the recoveries are all between 90% and 110%, with an RSD of 3.0%, indicating good accuracy and repeatability.

[0083] Example 4: Detection of self-made formulation

[0084] According to the standard curve equation obtained in Example 2, the logarithm of carbomer concentration and the logarithm of peak area show good linearity within the concentration range of 0.01436 mg / ml to 0.2200 mg / ml. Therefore, the carbomer concentration in the test solution entering the HPLC-ELSD chromatographic system must be within the range of 0.01436 mg / ml to 0.2200 mg / ml. Each time a different reference formulation is tested, a blank sample solution needs to be prepared again, and the standard curve needs to be re-plotted. Therefore, the standard curve equation and concentration range are not completely fixed, but they generally meet the requirement that the carbomer concentration in the test solution entering the HPLC-ELSD chromatographic system be within the range of 0.01 mg / ml to 0.2 mg / ml.

[0085] The method for preparing the test solution is as follows: Weigh an appropriate amount of the preparation to be tested (approximately equivalent to 11 mg of carbomer) into a 25 ml volumetric flask, add 5 ml of tetrahydrofuran, shake to disperse evenly, and then stir with a vortex mixer until a dilute solution is formed. Then, dilute to the mark with acetonitrile, filter, and accurately measure an appropriate amount of the filtrate to dilute quantitatively 10 times to obtain the test solution. For example, if the carbomer content of the self-made preparation is 1.1%, weigh 1 g of the preparation to be tested, dilute to the mark of a 25 ml volumetric flask, and then dilute 10 times; this is equivalent to 11 mg of carbomer in 250 ml of test solution.

[0086] Meanwhile, to avoid interference from other factors in detecting the carbomer peak, a 10 μL blank sample solution can be introduced into the HPLC-ELSD system before the test solution enters the HPLC-ELSD system to eliminate interference. The blank sample solution is prepared as follows: accurately weigh a blank sample of the same mass as the preparation of the test solution, place it in a 25 mL volumetric flask, add 5 mL of tetrahydrofuran to evenly disperse and dissolve the blank sample, stir with a vortex mixer until a dilute solution is formed, then dilute to the mark with acetonitrile, filter, and obtain the blank sample solution.

[0087] The blank sample solution and the test solution are fed into the HPLC-ELSD chromatographic system in the above order to detect the amount of carbomer in the formulation sample.

[0088] The results of the two sets of experiments are shown in Table 4 below: (Self-made formulation 1 was prepared according to the formulation of reference formulation 1, and self-made formulation 2 was prepared according to the formulation of reference formulation 2; Reference formulation 1 in Table 4, excluding carbomer, is the same as formulation 1 in Table 1.) Table 4

[0089]

[0090] The chromatogram of self-made formulation 1 is as follows: Figure 7 The chromatogram of reference preparation 1 is shown in the figure. Figure 8 As shown, this indicates that the self-made formulation 1 is almost identical to the reference formulation 1, demonstrating good consistency.

Claims

1. A method for determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering, characterized in that Comprise the following steps: Step 1. Chromatographic conditions: octadecylsilane-bonded silica gel column as the chromatographic column; water or 0.02% formic acid aqueous solution as the mobile phase A, acetone as the mobile phase B, ethanol as the mobile phase C, gradient elution, the gradient elution program as follows: 0-4 min: mobile phase B accounted for 0% to 10% of one value, mobile phase C accounted for 0%; 4-4.5 min: mobile phase C accounted for 0% to 85%-95%, mobile phase B to 0%; 4.5-8.5 min: mobile phase C accounted for 95%; 8.5-8.6 min: mobile phase B accounted for 0% to 5%, mobile phase C to 0%; 8.6-17 min: mobile phase B accounted for 0% to 10% of one value, and the same as the value of 0-4 min mobile phase B, mobile phase C accounted for 0%; The flow rate of the mobile phase is 0.3-0.6 mL / min; The detector is an evaporative light scattering detector; Drift tube temperature: 45-65 DEG C; Nitrogen flow rate: 1.8-3.0 L / min; Split mode: split; The injection volume is 5-20 mu L; Step 2. Draw the standard curve of the logarithm of carbomer concentration and the logarithm of peak area: precisely take 1 mg, 5 mg, 10 mg, 15 mg, 20 mg of carbomer reference substance respectively, and place them in different 100 ml beakers, add water to swell fully, and adjust the pH to 7.0 ± 0.2 with an alkaline solvent, which is 0.01 mol / L sodium hydroxide solution or triethanolamine, then dilute with tetrahydrofuran, then stir with a high-speed dispersing machine at low speed to form a uniform clear liquid, and precisely take the solution into the high performance liquid chromatography system to obtain the peak area of carbomer in different concentrations of carbomer reference solution; Take the logarithm of concentration as the abscissa and the logarithm of peak area as the ordinate to draw the standard curve, and obtain the standard curve equation; wherein, concentration = carbomer reference sample weight / dilution volume, concentration range is 0.01 mg / ml-0.2 mg / ml; Step 3. Preparation of blank sample solution: precisely take an appropriate amount of blank sample into a volumetric flask, shake with tetrahydrofuran to disperse the blank sample uniformly, then stir with a vortex mixer to form a dilute solution, then dilute to the mark of the volumetric flask with acetonitrile, filter to obtain the blank sample solution, and take the blank sample solution into the high performance liquid chromatography system; the blank sample is a sample obtained by mixing other formulation components except carbomer according to the formulation proportion; Step 4. Preparation and detection of test sample solution: precisely take an appropriate amount of the preparation to be tested into a volumetric flask, shake with tetrahydrofuran to disperse the preparation uniformly, then stir with a vortex mixer to form a dilute solution, then dilute to the mark of the volumetric flask with acetonitrile, filter, and take the filtrate to obtain the test sample solution; take the test sample solution into the high performance liquid chromatography system to obtain the peak area of carbomer in the test sample solution; The standard curve equation obtained in step 2 is substituted to obtain the logarithm of the carbomer concentration, and the concentration of carbomer in the preparation is calculated according to the formula: a = 10 b b; the concentration of carbomer in the preparation is a x dilution multiple / sample weight of the test product x 100%; in the formula, a is the concentration of carbomer, mg / ml; b is the logarithm of the concentration of carbomer.

2. The method for determination of carbomer content in a formulation by high performance liquid chromatography-evaporative light scattering as claimed in claim 1, wherein: The length of the chromatographic column in step 1 is 150-250 mm, the inner diameter is 1.8-4.6 mm, and the filler inner diameter is 3.5-5.0 mu m.

3. The method for determination of carbomer content in a formulation by high performance liquid chromatography-evaporative light scattering as claimed in claim 1, wherein: The flow rate of the mobile phase in Step 1 is 0.4 mL / min, the drift tube temperature is 60℃, the nitrogen flow rate is 2.4 mL / min, and the injection volume is 10 μL.

4. The method of determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering according to claim 1, characterized in that: In Step 2, the precise measurement of the solution refers to transferring the obtained clear liquid of each concentration into different 100 mL volumetric flasks, respectively, washing the beaker with 20 mL of acetonitrile, combining the washing liquid into the same volumetric flask, then using acetonitrile to make up to 100 mL, and then measuring 10 μL into the high-performance liquid chromatography system.

5. The method of determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering according to claim 1, characterized in that: In Step 4, the precise measurement of the appropriate amount of preparation to be tested in the volumetric flask refers to calculating the required mass of the preparation based on the proportion of the preparation, and the mass of the preparation is such that the concentration of carbomer in the test solution is within the range of 0.01 mg / mL to 0.2 mg / mL.

6. The method of determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering according to claim 5, characterized in that: In Step 3, the precise measurement of the appropriate amount of blank sample refers to the mass of the blank sample being the same as the mass of the preparation measured precisely in Step 5.

7. The method of determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering according to claim 1, characterized in that: The volume of tetrahydrofuran added in Step 3 is 20% of the volume of the volumetric flask.

8. The method of determining the content of carbomer in a preparation by high performance liquid chromatography-evaporative light scattering according to claim 1, characterized in that: The volume of tetrahydrofuran added in Step 4 is 20% of the volume of the volumetric flask.

9. The method of determining the content of carbomer in a formulation by high performance liquid chromatography-evaporative light scattering as claimed in claim 1, wherein: Before drawing the standard curve of the logarithm of carbomer concentration versus the logarithm of peak area in Step 2, the steps for verifying the method specificity are: (1) Prepare the blank solvent for entering the high-performance liquid chromatography system: take 10 mL of the same mobile phase A as in Step 1 into a 100 mL volumetric flask, adjust the pH to 7.0±0.2 with the same alkaline solvent as in Step 2, add 20 mL of tetrahydrofuran, then use acetonitrile to make up to 100 mL to obtain the blank solvent, and enter the high-performance liquid chromatography system; (2) Prepare the blank sample solution for entering the high-performance liquid chromatography system: the blank sample is a sample obtained by mixing other preparation components except carbomer according to the proportion of the preparation, take an appropriate amount of blank sample into a volumetric flask, add tetrahydrofuran and shake to uniformly disperse the blank sample, then use a vortex mixer to stir until a dilute solution is formed, then use acetonitrile to make up to the mark of the volumetric flask, filter, and obtain the blank sample solution, which enters the high-performance liquid chromatography system.

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