Method for detecting impurities in topiramate oral liquid preparation

Abstract

The invention relates to the technical field of medicine detection, and discloses a method for detecting impurities in a topiramate oral liquid preparation. The detection method comprises the step of synchronously detecting the contents of impurities B and D of topiramate EP by adopting a high performance liquid chromatography, wherein the high performance liquid chromatography adopts an ultraviolet detector for detection. According to the detection method provided by the invention, by adopting an ultraviolet detector, a terminal absorption wavelength of 190nm, a proper chromatographic column, a proper mobile phase system and a gradient elution procedure, impurities B and D of topiramate EP can avoid interference of a large number of auxiliary material peaks in a topiramate oral liquid preparation and have a certain response value at the same time; the method has good specificity and sensitivity, and the problems that in a universal detector (such as a differential detector), impurities B and D of topiramate EP are difficult to position or are easily interfered by auxiliary materials, and the sensitivity of the detector is insufficient, and the detection requirement cannot be met are solved.

Description

Technical Field

[0001] This invention relates to the field of drug detection technology, and in particular to a method for detecting impurities in topiramate oral liquid formulations. Background Technology

[0002] Topiramate is a highly effective, broad-spectrum antiepileptic drug, mainly used as adjunctive therapy to other antiepileptic drugs. It is used for simple partial seizures, complex partial seizures, and generalized tonic-clonic seizures, and is particularly effective for Lennox-Gastaut syndrome and West syndrome (infantile spasms). It has no obvious tolerance and can be used as monotherapy in high doses, with good long-term efficacy.

[0003] Currently, the topiramate-related formulations listed in domestic and international pharmacopoeias include: USP43-NF38-topiramate capsules, topiramate tablets, topiramate compound oral suspension, IP2010-topiramate tablets, and the domestic new drug approval standard topiramate tablets. None of the pharmacopoeias in any country include quality standards for topiramate oral liquid formulations, nor do they provide detection methods for related substances. Furthermore, topiramate oral liquid formulations have complex compositions, containing various small and large molecular polymer matrices, and are viscous. Topiramate is a clear, dissolved substance within the matrix, making it difficult to remove through pretreatment processes such as extraction or salting out. This results in significant excipient interference in the determination of related substances in topiramate oral liquid formulations.

[0004] When using general-purpose detectors such as differential refractive index or evaporative light scattering to detect related substances, the raw materials and excipients in topiramate oral liquid formulation will all show peaks, which seriously interferes with the detection of impurities. When using a UV detector to detect related substances, the presence of preservatives and complex flavorings in the oral liquid formulation will also interfere with the detection of impurities. Furthermore, since the structure of topiramate drug does not contain chromophores, most related substances also have no UV absorption. Some polymer related substances have weak absorption due to the presence of unsaturated bonds in the sulfonic acid groups, but this also poses a significant challenge to the sensitivity of the method.

[0005] In the relevant raw material and formulation standards for topiramate, the known impurities are EP impurities A, B, C, D, and E. However, in the related substances methods of the raw material standards, only EP impurities A and E are measured, and in the relevant formulation standards, only EP impurity A is measured. This means that no pharmacopoeia in any country records the detection methods for EP impurities B and D in topiramate. Based on the synthetic and degradation pathways of topiramate, it is known that topiramate can generate intermediate product EP impurity B (C) during its synthesis. 17 H 30 N2O9S (CAS: 876403-98-4), the formation pathway is shown in formula (Ⅰ), and during storage, it can generate condensation product EP impurity D (C 25 H 39 NO15 S, CAS: 950603-46-0), the generation path is as shown in equation (II):

[0006]

[0007]

[0008] Therefore, there is an urgent need to develop a detection method for EP impurity B and EP impurity D in topiramate oral liquid formulations to improve the quality control of topiramate drugs. Summary of the Invention

[0009] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a method for detecting impurities in topiramate oral liquid formulations.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] This invention provides a method for detecting impurities in topiramate oral liquid formulations, comprising simultaneously detecting the contents of impurities B and D in topiramate EP using high performance liquid chromatography; wherein the high performance liquid chromatography uses an ultraviolet detector for detection.

[0012] In some embodiments of the present invention, the high performance liquid chromatography-ultraviolet detector method is used for sample injection detection in accordance with the General Chapter 0512 of Part IV of the Chinese Pharmacopoeia 2020.

[0013] In some embodiments of the present invention, the detection method specifically includes the following steps:

[0014] Preparation of the test solution: Take topiramate oral liquid preparation and mix it with acetonitrile aqueous solution to obtain the test solution;

[0015] Preparation of reference solution: Take the standards of impurities B and D of topiramate EP, mix them with aqueous acetonitrile solution to obtain the reference solution;

[0016] The test solution and the reference solution were injected into a high-performance liquid chromatograph, the chromatograms were recorded, and the contents of impurities B and D in topiramate EP were calculated using the external standard method.

[0017] Chromatographic conditions include:

[0018] Detector: Detection wavelength is 190±5nm;

[0019] Column: Octadecylsilane-bonded silica gel packed column;

[0020] Mobile phase A: Potassium dihydrogen phosphate buffer and acetonitrile are mixed at a volume ratio of (80-85):(15-20);

[0021] Mobile phase B: Potassium dihydrogen phosphate buffer and acetonitrile are mixed at a volume ratio of (15-20):(80-85);

[0022] Gradient elution program: 0-10 min, 0% A → 100% A; 10-50 min, 100% A → 0% A; 60.1-75 min, 100% A.

[0023] In some embodiments of the present invention, the topiramate EP impurity B has maximum UV absorption at 200-205 nm.

[0024] In some embodiments of the present invention, the topiramate EP impurity D has maximum UV absorption at 190 nm.

[0025] In some embodiments of the present invention, the volume ratio of acetonitrile to water in the acetonitrile aqueous solution is 1:(2-3).

[0026] In some preferred embodiments of the present invention, the volume ratio of acetonitrile to water in the acetonitrile aqueous solution is 1:(2-2.5).

[0027] In some embodiments of the present invention, the volume ratio of topiramate oral liquid formulation to acetonitrile aqueous solution in the test solution is 1:(8-12).

[0028] In some preferred embodiments of the present invention, the volume ratio of topiramate oral liquid formulation to acetonitrile aqueous solution in the test sample solution is 1:(9-11).

[0029] In some embodiments of the present invention, the concentrations of topiramate EP impurities B and D in the reference solution are 4-6 μg / mL, respectively.

[0030] In some preferred embodiments of the present invention, the concentrations of topiramate EP impurities B and D in the reference solution are 4.5-5.5 μg / mL, respectively.

[0031] In some embodiments of the present invention, the concentration of the potassium dihydrogen phosphate buffer in the mobile phases A and B is 8-12 mmol / L, and the pH is 2.0-2.5.

[0032] In some preferred embodiments of the present invention, the concentration of the potassium dihydrogen phosphate buffer in the mobile phases A and B is 9-11 mmol / L, and the pH is 2.1-2.5.

[0033] In some embodiments of the invention, the pH of the potassium dihydrogen phosphate buffer is adjusted using phosphoric acid.

[0034] In some embodiments of the present invention, the chromatographic column includes Phenomenex. Omega 5μm PSC18 The dimensions are 250*4.6mm.

[0035] In some embodiments of the present invention, the chromatographic conditions further include at least one of the following: column temperature 30-40℃; flow rate 0.8-1.2 mL / min; injection volume 80-120 μL.

[0036] In some preferred embodiments of the present invention, the chromatographic conditions further include at least one of the following: column temperature 33-35℃; flow rate 0.9-1.1 mL / min; injection volume 90-110 μL.

[0037] In some embodiments of the present invention, the retention time of the topiramate EP impurity B is 31.9 ± 0.5 min.

[0038] In some embodiments of the present invention, the retention time of the topiramate EP impurity D is 38.4 ± 0.5 min.

[0039] The basic principles of this invention are explained as follows:

[0040] 1) This invention, through studying the ultraviolet absorption characteristics of topiramate EP impurities B and D, discovered that topiramate EP impurity B...

[0041] The maximum UV absorption is at 200-205 nm, and the maximum UV absorption of topiramate EP impurity D is at 190 nm. When the UV detector is selected at a wavelength of 190 nm, the common absorption of EP impurities B and D can be taken into account. Moreover, at the same concentration, the UV absorption intensity of EP impurity D is weaker than that of EP impurity B. Selecting 190 nm can ensure that EP impurity D has sufficient detection sensitivity. Therefore, both impurities can be detected at 190 nm at the same time, avoiding the complexity of wavelength-separated detection.

[0042] 2) 190nm belongs to the "end absorption" region of the ultraviolet detector, where there is often compound absorption interference. Moreover, the noise at 190nm is slightly higher than that at longer wavelengths. Therefore, this invention optimizes chromatographic conditions (including column type, mobile phase composition, gradient elution program, etc.) to ensure the separation and signal-to-noise ratio of EP impurities B and D, improves the specificity and sensitivity of the method, and enables baseline separation of topiramate EP impurities B and D from the excipient peaks. Combined with the external standard method to calculate the content, the qualitative and quantitative analysis of topiramate EP impurities B and D in topiramate oral liquid formulations can be achieved.

[0043] Compared with the prior art, the beneficial effects of the present invention are:

[0044] 1) The method for detecting impurities in topiramate oral liquid preparations provided by the present invention, by using an ultraviolet detector and a terminal absorption wavelength of 190 nm, as well as a suitable chromatographic column, a suitable mobile phase system and gradient elution program, enables topiramate EP impurities B and D to avoid interference from a large number of excipient peaks in topiramate oral liquid preparations while having a certain response value. This makes the method have both good specificity and sensitivity, avoiding the problems of topiramate EP impurities B and D being difficult to locate or easily interfered with by excipients in general detectors (such as differential detectors), as well as the problem of insufficient detector sensitivity that fails to meet the detection requirements.

[0045] 2) The method for detecting impurities in topiramate oral liquid preparations provided by the present invention only requires the use of a conventional high performance liquid chromatograph and ultraviolet detector. The instrument cost is low and the method pretreatment is simple and convenient. Only a simple dissolution operation is required for the topiramate oral solution. There is no need for complex pretreatment such as extraction or salting out.

[0046] 3) The method for detecting impurities in topiramate oral liquid preparations provided by the present invention is not affected by blank solvents and formulation excipients, has good linearity, high detection accuracy, good repeatability and strong practicality. Attached Figure Description

[0047] Figure 1 The HPLC chromatogram of the blank solvent in Example 1;

[0048] Figure 2 This is the HPLC chromatogram of the mixed reference solution of topiramate EP impurities B and D in Example 1;

[0049] Figure 3 The HPLC chromatogram of the test solution in Example 1;

[0050] Figure 4 This is the HPLC chromatogram of the spiked test solution in Example 1;

[0051] Figure 5 The peak area-concentration linear regression curve of topiramate EP impurity B in Example 2;

[0052] Figure 6 The peak area-concentration linear regression curve of topiramate EP impurity D in Example 2;

[0053] Figure 7 The HPLC chromatogram of the test solution in Comparative Example 1;

[0054] Figure 8 The image shows the HPLC chromatogram of the spiked test solution in Comparative Example 2. Detailed Implementation

[0055] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0056] Example 1

[0057] This embodiment verifies the chromatographic conditions, specificity, and injection precision of the method for detecting impurities in topiramate oral liquid formulations. The steps are as follows:

[0058] Preparation of blank solvent:

[0059] Acetonitrile and water were mixed at a volume ratio of 1:2 to obtain a blank solvent;

[0060] Preparation of a mixed reference solution of impurities B and D in topiramate EP:

[0061] Topiramate EP Impurity B Reference Stock Solution: Take about 12.5 mg of topiramate EP impurity B standard and place it in a 50 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to dissolve and dilute to 50 mL. Shake well.

[0062] Topiramate EP Impurity D Reference Stock Solution: Take about 12.5 mg of topiramate EP impurity D standard and place it in a 50 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to dissolve and dilute to 50 mL. Shake well.

[0063] Take 10 mL each of the topiramate EP impurity B reference stock solution and the topiramate EP impurity D reference stock solution and place them in a 100 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 100 mL. Shake well to obtain a mixed reference solution of topiramate EP impurities B and D.

[0064] Preparation of the test solution:

[0065] Take about 1 mL of the self-prepared sample of topiramate oral solution and place it in a 10 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to dissolve and dilute to 10 mL. Shake well to obtain the test solution.

[0066] Preparation of spiked test solution:

[0067] Take about 1 mL of the self-prepared sample of topiramate oral solution and place it in a 10 mL volumetric flask. Add 2 mL of the mixed reference solution of topiramate EP impurities B and D, and then add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to make up to 10 mL. Shake well to obtain the spiked test solution.

[0068] High-performance liquid chromatography-ultraviolet detection (HPLC-UV detection) was used, referring to Chapter 0512 of the 2020 edition of the Chinese Pharmacopoeia, Part IV, for the analysis of blank solvent, mixed reference solution of topiramate EP impurities B and D, test solution, and spiked test solution. Chromatograms were recorded, and the chromatographic conditions were as follows:

[0069] Detector: Detection wavelength is 190nm;

[0070] Chromatographic column: Phenomenex octadecylsilane-bonded silica gel packed column Omega 5μm PS C18 The dimensions are 250*4.6mm;

[0071] Mobile phase A: Potassium dihydrogen phosphate buffer (10 mmol / L, pH adjusted to 2.3 with phosphate) and acetonitrile at a volume ratio of 85:15;

[0072] Mobile phase B: Potassium dihydrogen phosphate buffer (10 mmol / L, pH adjusted to 2.3 with phosphate) and acetonitrile at a volume ratio of 20:80;

[0073] Column temperature: 35℃;

[0074] Flow rate: 1 mL / min;

[0075] Injection volume: 100 μL;

[0076] Gradient elution procedure:

[0077] Time (min) Mobile phase A (%) Mobile phase B (%) 0 100 0 10 100 0 50 0 100 60 0 100 60.1 100 0 75 100 0

[0078] Figure 1 The HPLC chromatogram of the blank solvent in Example 1 is shown below. Figure 1 It can be seen that the blank solvent has no interfering peak at 190 nm and the baseline is stable, which can rule out the influence of the blank solvent on the detection of impurities B and D in topiramate EP.

[0079] Figure 2 This is the HPLC chromatogram of the mixed reference solution of topiramate EP impurities B and D in Example 1, from... Figure 2 The retention times and peak shapes of impurities B and D in topiramate EP could be determined. The characteristic peaks of the impurities did not overlap with those of the excipients, verifying the specificity of the chromatographic conditions.

[0080] Figure 3 The HPLC chromatogram of the test solution in Example 1 is shown below. Figure 3 The initial contents of impurities B and D in topiramate EP in the test sample can be determined, and the position of the excipient peak can be determined.

[0081] Figure 4 The HPLC chromatogram of the spiked test solution in Example 1 is shown below. Figure 4The method specificity can be verified, and it can be demonstrated that the B and D peaks of topiramate EP impurities are baseline separated from the excipient peaks.

[0082] Table 1. Injection precision results of the reference solution in Example 1, repeated injections six times.

[0083]

[0084] Table 1 shows the injection precision results of the reference solution in Example 1 after 6 repeated injections. As shown in Table 1, the retention time range of topiramate EP impurity B in 6 injections was 0.013 min, with an RSD of 0.1%, and the retention time range of topiramate EP impurity D in 6 injections was 0.021 min, with an RSD of 0.1%. The retention times of both impurities showed almost no fluctuation, indicating that the chromatographic system was highly stable. The peak area RSD of topiramate EP impurity B in 6 injections was 0.7%, which meets the requirements for trace analysis, and the peak area RSD of topiramate EP impurity D in 6 injections was 1.2%, which also meets the pharmacopoeia requirement (RSD ≤ 2%).

[0085] Figure 1-4 As shown in Table 1, the method for detecting impurities in topiramate oral liquid preparations provided by this invention can be used to directly determine the content of topiramate EP impurities B and D in topiramate oral solution without the need for complex pretreatment. There is no interference from excipients, EP impurities B and D are completely separated, the chromatographic system has good stability, and the method has high precision and reliability.

[0086] Example 2

[0087] This embodiment verifies the linear range of the method for detecting impurities in topiramate oral liquid formulations. The steps are as follows:

[0088] A stock solution of topiramate EP impurity B, a stock solution of topiramate EP impurity D, and a mixed stock solution of topiramate EP impurities B and D were prepared according to the method in Example 1. Linear solutions L1-L6 were then prepared using the mixed stock solution of topiramate EP impurities B and D.

[0089] Linear solution L1: Take 1 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 10 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 10 mL. Shake well.

[0090] Linear solution L2: Take 3 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 20 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 20 mL. Shake well.

[0091] Linear solution L3: Take 2 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 10 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 10 mL. Shake well.

[0092] Linear solution L4: Take 5 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 20 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 20 mL. Shake well.

[0093] Linear solution L5: Take 3 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 10 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 10 mL. Shake well.

[0094] Linear solution L6: Take 1 mL each of topiramate EP impurity B reference stock solution and topiramate EP impurity D reference stock solution and place them in a 25 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 25 mL. Shake well.

[0095] High performance liquid chromatography-ultraviolet detection was used to detect linear solutions L1-L6 according to the Chinese Pharmacopoeia 2020 edition, Part IV, General Chapter 0512. The peak areas of topiramate EP impurities B and D in the chromatograms were recorded, and the peak areas were used to perform linear regression on the actual concentrations.

[0096] Figure 5 This is the peak area-concentration linear regression curve for impurity B in topiramate EP in Example 2. Figure 6 Table 2 shows the peak area-concentration linear regression curve for topiramate EP impurity D in Example 2, and the linear results for topiramate EP impurities B and D in Example 2. Figure 5 , Figure 6 As shown in Table 2, the detection concentration of EP impurity B in topiramate exhibits good linearity in the range of 2.532-10.128 μg / mL, and the detection concentration of EP impurity D in topiramate exhibits good linearity in the range of 2.493-9.973 μg / mL. This indicates that the method provided by this invention has good linearity and quantitative accuracy at a detection wavelength of 190 nm when determining the content of EP impurities B and D in topiramate oral liquid formulations.

[0097] Table 2. Linearity results for topiramate EP impurities B and D in Example 2.

[0098]

[0099] Example 3

[0100] This embodiment verifies the repeatability of the method for detecting impurities in topiramate oral liquid formulations. The steps are as follows:

[0101] Topiramate EP impurity B reference stock solution, topiramate EP impurity D reference stock solution and reference solution were prepared according to the method in Example 1. Six test solutions were prepared in parallel according to the method in Example 1. Linear solutions L1-L6 were prepared according to the method in Example 2.

[0102] High-performance liquid chromatography-ultraviolet detection was used, and linear solutions L1-L6 and the test solution were injected and detected according to the Chinese Pharmacopoeia 2020 edition, Part IV, General Chapter 0512. The peak areas of topiramate EP impurities B and D in the chromatograms were recorded. Linear regression was performed on the peak areas against the actual concentrations, and the contents of topiramate EP impurities B and D in the test sample were calculated from the linear regression curves.

[0103] Table 3. Repeatability test results of impurities B and D in topiramate EP in Example 3.

[0104]

[0105]

[0106] Table 3 shows the repeatability test results of impurities B and D in topiramate EP in Example 3. As can be seen from Table 3, the average content of impurity B in topiramate EP in the 6 parallel samples was 0.2005%, with an RSD of 1.6%, and the average content of impurity D in topiramate EP was 0.1983%, with an RSD of 2.0%. The RSDs of both samples meet the pharmacopoeia requirement of ≤2%, indicating that the method provided by the present invention is simple to operate, has good repeatability of the test results, and has high precision.

[0107] Example 4

[0108] This embodiment verifies the accuracy of the method for detecting impurities in topiramate oral liquid formulations. The steps are as follows:

[0109] Topiramate EP impurity B reference stock solution, topiramate EP impurity D reference stock solution, and mixed reference solution of topiramate EP impurities B and D were prepared according to the method in Example 1.

[0110] Reference solution: Take 2 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 10 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 10 mL. Shake well.

[0111] 50% concentration accuracy test solution: Take about 1 mL of the self-developed sample of topiramate oral solution and place it in a 10 mL volumetric flask. Add 1 mL of the mixed reference solution of topiramate EP impurities B and D, and then add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to make up to 10 mL. Shake well and prepare 3 parallel portions.

[0112] 100% concentration accuracy test solution: Take about 1 mL of the self-developed sample of topiramate oral solution and place it in a 10 mL volumetric flask. Add 2 mL of the mixed reference solution of topiramate EP impurities B and D, and then add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to make up to 10 mL. Shake well and prepare 3 parallel portions.

[0113] 150% concentration accuracy test solution: Take about 1 mL of the self-developed sample of topiramate oral solution and place it in a 10 mL volumetric flask. Add 3 mL of the mixed reference solution of topiramate EP impurities B and D, and then add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to make up to 10 mL. Shake well and prepare 3 parallel portions.

[0114] High-performance liquid chromatography-ultraviolet detection was used, and the reference solution, 50% accuracy test solution, 100% accuracy test solution and 150% accuracy test solution were injected and detected according to the Chinese Pharmacopoeia 2020 edition, Part IV, General Chapter 0512. The peak areas of topiramate EP impurities B and D in the chromatograms were recorded, and the recoveries of topiramate EP impurities B and D in the test samples were calculated.

[0115] Table 4 shows the accuracy results for the detection of impurities B and D in topiramate EP in Example 4. As shown in Table 4, the recovery rate of topiramate EP impurity B ranged from 100.16% to 103.71%, with an average of 101.6% and an RSD of 1.1%. The recovery rate of topiramate EP impurity D ranged from 96.46% to 103.50%, with an average of 99.7% and an RSD of 2.2%. The spiked recoveries of both impurities were within the pharmacopoeia-required limits (90%-108%), with no outliers, indicating high accuracy and good stability of the method. This example verified the accuracy within the actual content range of 50%-150%, demonstrating that the method has high accuracy at different concentration levels.

[0116] Table 4. Accuracy results of topiramate EP impurity B and D detection in Example 4.

[0117]

[0118] Example 5

[0119] This embodiment verifies the solution stability of the method for detecting impurities in topiramate oral liquid formulations. The steps are as follows:

[0120] Topiramate EP impurity B reference stock solution, topiramate EP impurity D reference stock solution, and mixed reference solution of topiramate EP impurities B and D were prepared according to the method in Example 1.

[0121] Reference solution: Take 2 mL of the mixed reference solution of topiramate EP impurities B and D and place it in a 10 mL volumetric flask. Add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) and dilute to 10 mL. Shake well.

[0122] Test solution: Take about 1 mL of the self-developed sample of topiramate oral solution and place it in a 10 mL volumetric flask. Add 2 mL of the mixed reference solution of topiramate EP impurities B and D, and then add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to make up to 10 mL. Shake well.

[0123] Place the reference solution and the test solution in a sample pan at 15℃, take 100 μL of each, and use high performance liquid chromatography-ultraviolet detection method. According to the Chinese Pharmacopoeia 2020 edition, Part IV, General Chapter 0512, the samples were injected and detected at the specified time. The peak areas of topiramate EP impurities B and D in the chromatogram were recorded, and the change rate of impurity peak area was calculated.

[0124] Table 5 shows the stability results of the control solution in Example 5.

[0125]

[0126]

[0127] Table 6 shows the stability results of the test solution in Example 5.

[0128]

[0129] Table 5 shows the stability results of the reference solution in Example 5. As can be seen from Table 5, the peak area change rate of topiramate EP impurity B in the reference solution ranges from -1.17% to +1.09%, and the peak area change rate of topiramate EP impurity D ranges from -4.64% to +0.06%, both less than 10%, which meets the GMP analytical method validation requirements and shows excellent stability. Overall, the stability of the reference solution is good within 60 hours at 15°C.

[0130] Table 6 shows the stability results of the test solution in Example 5. As can be seen from Table 6, the peak area fluctuation range of topiramate EP impurity B in the test solution is +0.10% to +1.47%, and the peak area fluctuation range of topiramate EP impurity D is -2.20% to +0.34%, both less than 10%, which meets the GMP analytical method validation requirements and is consistent with the trend of the reference solution. Overall, the stability of the test solution is also good within 60 hours at 15°C.

[0131] Example 6

[0132] This embodiment verifies the sensitivity of the method for detecting impurities in topiramate oral liquid formulations. The steps are as follows:

[0133] Take an appropriate amount of the mixed reference solution of impurities B and D in topiramate EP, add acetonitrile aqueous solution (acetonitrile:water = 1:2, v / v) to dilute to a suitable concentration, inject the sample for determination, and record the chromatogram. When the signal-to-noise ratio is 10:1, it is the limit of quantitation (LOQ), and when the signal-to-noise ratio is 3:1, it is the limit of detection (LDQ).

[0134] Table 7. Limits of Quantitation (LOQ) Results of Detection Methods for Impurities in Topiramate Oral Liquid Formulation

[0135]

[0136] Table 8. Detection limits of methods for detecting impurities in topiramate oral liquid formulations.

[0137]

[0138] Table 7 shows the limit of quantitation (LOQ) results of the method for detecting impurities in topiramate oral liquid formulations, and Table 8 shows the limit of detection (LOD) results of the method for detecting impurities in topiramate oral liquid formulations. As can be seen from Tables 7 and 8, the method for detecting impurities in topiramate oral liquid formulations provided by this invention has a limit of quantitation (LOQ) of 0.1013 μg / mL and a limit of detection (LOD) of 0.0304 μg / mL for topiramate EP impurity B, and a limit of quantitation (LOQ) of 1.9945 μg / mL and a LOD of detection (LOD) of 0.5984 μg / mL for topiramate EP impurity D. The method has high sensitivity and is suitable for trace detection of EP impurities B and D.

[0139] Example 7

[0140] This embodiment verifies the robustness of the method for detecting impurities in topiramate oral liquid formulations, and the steps are as follows:

[0141] The tolerance of minor variations in chromatographic conditions to the determination of topiramate EP impurities B and D in the spiked test solution (prepared according to Example 1) was assessed by changing column temperature, flow rate, mobile phase ratio, pH value, and chromatographic column.

[0142] Table 9 Robustness of Topiramate EP Impurity B Detection

[0143]

[0144] Table 10 Robustness of Topiramate EP Impurity D Detection

[0145]

[0146] Table 9 shows the robustness of the detection of impurity B in topiramate EP, and Table 10 shows the robustness of the detection of impurity D in topiramate EP. As can be seen from Tables 9 and 10, the method for detecting impurities in topiramate oral liquid preparations provided by this invention can separate topiramate EP impurities B and D from the baseline when the column temperature is 30-40℃, the flow rate is 0.9-1.1mL / min, the pH value is in the range of 2.1-2.5, and different serial number chromatographic columns are used. Moreover, the detection results are stable, indicating that the method has strong robustness.

[0147] Comparative Example 1

[0148] The only difference between this comparative example and Example 1 is that the gradient elution procedure is changed as follows:

[0149] Time (min) Mobile phase A (%) Mobile phase B (%) 0 100 0 5 100 0 35 0 100 45 0 100 45.1 100 0 60 100 0

[0150] High performance liquid chromatography-ultraviolet detection method was used, referring to the Chinese Pharmacopoeia 2020 edition, Part IV, General Chapter 0512, to inject and detect the mixed reference solution and test solution of topiramate EP impurities B and D that are exactly the same as those in Example 1, and the chromatograms were recorded.

[0151] Figure 7 The HPLC chromatogram of the test solution in Comparative Example 1 shows that, based on the peak positioning of the mixed reference solution of topiramate EP impurities B and D, under the chromatographic conditions of this comparative example, the retention time of the topiramate EP impurity B peak is 25.343 min, while... Figure 7 The chromatogram of the test solution shows that, under these chromatographic conditions, there is a peak of excipient at 25.048 min, which is similar to the retention time of impurity B in EP and will interfere with the elution of impurity B. If the test solution contains degradation products of impurity B, baseline separation between impurity B and adjacent excipient peaks cannot be achieved, which will seriously affect the quantitative accuracy of impurity B.

[0152] Comparative Example 2

[0153] The difference between this comparative example and Example 1 is that a Waters Xbridge C18 5μm 4.6*250mm column was used instead of a Phenomenex column. Omega 5μm PS C18 250*4.6mm.

[0154] The stock solutions of topiramate EP impurity B, topiramate EP impurity D, and a mixed reference solution of topiramate EP impurities B and D, as well as the spiked test solution, were prepared according to the method in Example 1.

[0155] High performance liquid chromatography-ultraviolet detection method was used to detect the mixed reference solution of impurities B and D of topiramate EP, as well as the spiked test solution, according to the Chinese Pharmacopoeia 2020 edition, Part IV, General Chapter 0512. Chromatograms were recorded.

[0156] Figure 8 The HPLC chromatogram of the spiked test solution in Comparative Example 2 is shown below. Figure 8 It can be seen that under the chromatographic conditions of this comparative example, the peak of impurity B in topiramate EP could not be baseline separated from the peak of the excipient, and the excipient seriously interfered with the determination of impurity B.

[0157] It is evident that the method for detecting impurities in topiramate oral liquid formulations provided by this invention requires specific chromatographic conditions to separate topiramate EP impurities B and D from the excipient peak baseline, thereby avoiding interference from excipients and ensuring that the separation and detection of EP impurities B and D have good specificity and quantitative accuracy.

Claims

1. A method for detecting impurities in topiramate oral liquid formulations, characterized in that, This includes the simultaneous detection of impurities B and D in topiramate EP using high performance liquid chromatography (HPLC); wherein the HPLC method employs an ultraviolet (UV) detector for detection.

2. The detection method according to claim 1, characterized in that, The detection method specifically includes the following steps: Preparation of the test solution: Take topiramate oral liquid preparation and mix it with acetonitrile aqueous solution to obtain the test solution; Preparation of reference solution: Take the standards of impurities B and D of topiramate EP, mix them with aqueous acetonitrile solution to obtain the reference solution; The test solution and the reference solution were injected into a high-performance liquid chromatograph, the chromatograms were recorded, and the contents of impurities B and D in topiramate EP were calculated using the external standard method. Chromatographic conditions include: Detector: Detection wavelength is 190±5nm; Column: Octadecylsilane-bonded silica gel packed column; Mobile phase A: Potassium dihydrogen phosphate buffer and acetonitrile are mixed at a volume ratio of (80-85):(15-20); Mobile phase B: Potassium dihydrogen phosphate buffer and acetonitrile are mixed at a volume ratio of (15-20):(80-85); Gradient elution program: 0-10 min, 0% A → 100% A; 10-50 min, 100% A → 0% A; 60.1-75 min, 100% A.

3. The detection method according to claim 2, characterized in that, In the acetonitrile aqueous solution, the volume ratio of acetonitrile to water is 1:(2-3).

4. The detection method according to claim 3, characterized in that, In the test solution, the volume ratio of topiramate oral liquid formulation to acetonitrile aqueous solution is 1:(8-12).

5. The detection method according to claim 3, characterized in that, In the reference solution, the concentrations of topiramate EP impurities B and D were 4-6 μg / mL, respectively.

6. The detection method according to claim 2, characterized in that, In the mobile phases A and B, the concentration of the potassium dihydrogen phosphate buffer solution is 8-12 mmol / L, and the pH is 2.0-2.

5.

7. The detection method according to claim 2, characterized in that, The chromatographic column includes Phenomenex. Omega 5μm PS C18 The dimensions are 250*4.6mm.

8. The detection method according to claim 2, characterized in that, The chromatographic conditions also include at least one of the following: column temperature 30-40℃; flow rate 0.8-1.2 mL / min; injection volume 80-120 μL.

9. The detection method according to claim 8, characterized in that, The retention time of the topiramate EP impurity B was 31.9 ± 0.5 min.

10. The detection method according to claim 8, characterized in that, The retention time of the topiramate EP impurity D was 38.4 ± 0.5 min.

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