Method for detecting impurity content of cilnidipine optical isomer

Abstract

The present invention provides a cilnidipine optical isomer impurity content detection method, which comprises: detecting cilnidipine optical isomer impurities by using a high performance liquid chromatography to obtain a liquid chromatogram, and calculating according to the liquid chromatogram to obtain the cilnidipine optical isomer impurity content, wherein a mobile phase used in the high performance liquid chromatography comprises methanol and water; a chromatographic column used in the high performance liquid chromatography is selected from Formes Speedcore PFP (Polyfluoropropylene). The method is high in detection efficiency and accuracy, good in impurity and principal component peak shape and capable of achieving baseline separation.

Description

Technical Field

[0001] The invention relates to the technical field of drug analysis, and in particular to a method for detecting the impurity content of cilnidipine optical isomers. Background Art

[0002] Cilnidipine, chemically known as 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)-3,5-pyridinedicarboxylic acid-2-methoxyethyl ester (E) cinnamyl alcohol, belongs to the 1,4-dihydropyridine calcium antagonist, which was developed by Fujirebio Company of Japan and launched on the market in 1996. This product is a new type of calcium channel antagonist with strong lipophilicity, which can bind to the dihydropyridine site of the L-type calcium channel on the membrane of vascular smooth muscle cells, inhibit the influx of calcium ions, and inhibit the release of intracellular calcium ions, thereby relaxing and dilating vascular smooth muscle, playing a long-term hypotensive effect, and the hypotensive effect is better than nifedipine; it can also inhibit the release of norepinephrine from sympathetic nerve endings and sympathetic nerve activity by inhibiting the transmembrane influx of calcium ions through the N-type calcium channel on the membrane of sympathetic nerve cells.

[0003] The optical isomer of cilnidipine (Z-cilnidipine) impurity is one of the main degradation impurities of cilnidipine. Since the retention time of this impurity is almost the same as the retention time of the main peak of cilnidipine in the related substance methods included in the existing pharmacopoeias JP18 and ChP2020, it is difficult to effectively separate it under general chromatographic conditions and chromatographic columns, making it impossible to examine the exact content of this impurity.

[0004] Therefore, it is necessary to study and develop a method for effectively detecting the impurity content of the optical isomer of cilnidipine (Z-cilnidipine). Summary of the invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for detecting the content of impurities of optical isomers of cilnidipine. The method has high detection efficiency and high accuracy, and can effectively and accurately detect the content of impurities of optical isomers of cilnidipine (Z-cilnidipine).

[0006] The present invention provides a method for detecting the impurity content of cilnidipine optical isomers (Z-cilnidipine), comprising: using high performance liquid chromatography to detect the impurities of cilnidipine optical isomers to obtain a liquid chromatogram, and calculating the content of the impurities of cilnidipine optical isomers (Z-cilnidipine) according to the liquid chromatogram;

[0007] Wherein, the mobile phase used in the high performance liquid chromatography comprises methanol and water;

[0008] The chromatographic column used in the high performance liquid chromatography is selected from Fortis Speedcore PFP. PFP represents pentafluorophenyl stationary phase.

[0009] The present invention finds that the optical isomer of cilnidipine (Z-cilnidipine) is consistent with cilnidipine in ultraviolet absorption, and it is difficult to achieve effective separation using ordinary chromatographic conditions. Therefore, the best chromatographic conditions are screened and optimized from different aspects, such as the selection of organic phase and the selection of chromatographic column.

[0010] In some embodiments, the organic phases used in the HPLC include methanol, ethanol, n-propanol and acetonitrile. On a Fortis Speedcore PFP, 4.6 mm×150 mm, 2.6 μm chromatographic column, the mobile phase of the present invention preferably uses methanol as the organic phase.

[0011] In some embodiments, the mobile phase is a mixed solvent of methanol and water, and the volume ratio of methanol to water is 85:15 to 75:25, such as 85:15, 80:20, 75:25 or any value therebetween.

[0012] In some embodiments, the mobile phase is a mixed solvent of methanol and water, and the volume ratio of methanol to water is 80:20.

[0013] In some embodiments, the HPLC column is a Fortis Speedcore PFP, 4.6 mm×150 mm, 2.6 μm column.

[0014] In some embodiments, the flow rate of the mobile phase in the chromatographic column is 0.4 mL / min to 0.6 mL / min, such as 0.4 mL / min, 0.45 mL / min, 0.5 mL / min, 0.55 mL / min, 0.6 mL / min or any value therebetween.

[0015] In some embodiments, the high performance liquid chromatography uses the mobile phase for isocratic elution. In some specific embodiments, the elution time is 30 to 40 min, for example, 30 min, 32 min, 34 min, 36 min, 38 min, 40 min or any value therebetween.

[0016] In some specific embodiments, the elution temperature is 20-30°C, for example, 20°C, 22°C, 24°C, 26°C, 28°C, 30°C or any value therebetween.

[0017] In some embodiments, the detector used in the high performance liquid chromatography is an ultraviolet detector.

[0018] In some embodiments, the detection wavelength of the detector is 240 nm.

[0019] In some specific embodiments, the method comprises the steps of:

[0020] (1) preparing a Z-cilnidipine impurity reference solution;

[0021] (2) Prepare the test solution;

[0022] (3) using a mobile phase for isocratic elution, and detecting the cilnidipine optical isomer impurity reference solution and the test solution by high performance liquid chromatography to obtain a liquid chromatogram;

[0023] (4) Calculating the content of the Z-cilnidipine impurity according to the liquid chromatogram obtained in step (3).

[0024] In some embodiments, the method of preparing a cilnidipine optical isomer (impurity A) reference solution comprises: dissolving and diluting the cilnidipine optical isomer (impurity A) with a mobile phase.

[0025] In some embodiments, the mobile phase comprises methanol and water.

[0026] In some embodiments, in the mobile phase, the volume ratio of methanol to water is 85:15 to 75:25, such as 85:15, 80:20, 75:25 or any value therebetween.

[0027] In some embodiments, the volume ratio of methanol to water in the mobile phase is 80:20.

[0028] In some embodiments, the dissolving is performed by ultrasound.

[0029] In some embodiments, the concentration of the cilnidipine optical isomer (impurity A) reference solution is 0.1-1 μg / mL, for example, 0.1 μg / mL, 0.2 μg / mL, 0.3 μg / mL, 0.4 μg / mL, 0.5 μg / mL, 0.6 μg / mL, 0.7 μg / mL, 0.8 μg / mL, 0.9 μg / mL, 1 μg / mL or any value therebetween.

[0030] In some embodiments, the concentration of the cilnidipine optical isomer (impurity A) reference solution is 0.5 μg / mL.

[0031] In some embodiments, the calculation formula for the content of the cilnidipine optical isomer impurity is:

[0032]

[0033] Wherein: H% represents the content of impurities of the optical isomer of cilnidipine (Z-cilnidipine);

[0034] A 样 Represents the peak area of ​​the optical isomer of cilnidipine (Z-cilnidipine) impurity in the test solution, the unit is mAU·min;

[0035] A 对 Represents the peak area of ​​the impurity reference solution of the optical isomer of cilnidipine (Z-cilnidipine), in units of

[0036] mAU·min;

[0037] C 对 Represents the concentration of the impurity reference solution of the optical isomer of cilnidipine (Z-cilnidipine), in units of

[0038] μg / mL;

[0039] C 样 Represents the concentration of cilnidipine sample in the test solution, in μg / mL.

[0040] In some embodiments, the concentration of the cilnidipine optical isomer impurity is between 3 ng / mL and 5000 ng / mL, for example, 100 ng / mL, 500 ng / mL, 1000 ng / mL, 2000 ng / mL, 3000 ng / mL, 4000 ng / mL, 5000 ng / mL or any value therebetween.

[0041] In some embodiments, the concentration of the cilnidipine optical isomer impurity is 0.0006% to 1.0% of the test solution, for example, 0.01%, 0.05%, 0.1%, 0.5%, 0.8%, 1% or any value therebetween.

[0042] In some embodiments, the method detects the minimum amount of the cilnidipine optical isomer impurity reaching 0.0075 ng.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. The method of the present invention can achieve effective separation of cilnidipine and cilnidipine optical isomer (Z-cilnidipine) impurities, with good peak shape and capable of achieving baseline separation;

[0045] 2. The method of the present invention has high analytical sensitivity, accurate and reliable results, and is simple and quick, and can be used for the analysis and detection of the impurity content of the optical isomer of cilnidipine (Z-cilnidipine) in cilnidipine;

[0046] 3. The method of the present invention uses an ultraviolet detector with high sensitivity, and can detect the minimum amount of cilnidipine optical isomer (Z-cilnidipine) impurities reaching 0.0075 ng (detection limit);

[0047] 4. In the method of the present invention, when the concentration of the impurity of the optical isomer of cilnidipine (Z-cilnidipine) is 3 ng / mL to 5000 ng / mL, which is equivalent to 0.0006% to 1.0% of the concentration of the test solution, the linear relationship is good and the content of the impurity of the optical isomer of cilnidipine (Z-cilnidipine) can be accurately detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the blank solvent spectrum in Example 1.

[0049] Figure 2 This is the specificity map in Example 1.

[0050] Figure 3 This is the system suitability spectrum in Example 1.

[0051] Figure 4 This is the quantitative limit spectrum of the optical isomer of cilnidipine (Z-cilnidipine) in Example 2.

[0052] Figure 5 This is the detection limit spectrum of the optical isomer of cilnidipine (Z-cilnidipine) in Example 2.

[0053] Figure 6 This is the repetitive spectrum in Example 3.

[0054] Figure 7 This is the solution stability spectrum obtained by injecting the test solution at room temperature for 0 hours in Example 4.

[0055] Figure 8 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 3 hours.

[0056] Fig. 9 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 6 hours.

[0057] Fig.10 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 9 hours.

[0058] Fig.11 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 12 hours.

[0059] Fig.12 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 18 hours.

[0060] Fig.13 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 24 hours.

[0061] Fig.14 This is the solution stability spectrum obtained by injecting the test solution in Example 4 after it was placed at room temperature for 30 hours.

[0062] Fig.15 This is the system suitability spectrum in Comparative Example 1.

[0063] Fig.16 This is the system suitability spectrum in Comparative Example 2.

[0064] Fig.17 This is the system suitability spectrum in Comparative Example 3.

[0065] Fig.18 This is the system suitability spectrum in Comparative Example 4. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings. The specific embodiments and drawings described herein are only used to explain the present invention and are not intended to constitute any limitation to the present invention.

[0067] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0068] Unless otherwise defined, the technical terms used in the following examples have the same meanings as those generally understood by those skilled in the art to which the present invention belongs. The reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the raw materials, instruments and equipment used in the following examples, etc., can all be purchased on the market or can be obtained by existing methods; the reagent amounts, unless otherwise specified, are the reagent amounts used in conventional experimental operations; the experimental methods, unless otherwise specified, are all conventional methods.

[0069] Chromatography Column Fortis Speedcore PFP

[0070] In the present application, the calculation formula for the content of cilnidipine optical isomer impurities is:

[0071]

[0072] Wherein: H% represents the content of impurities of the optical isomer of cilnidipine (Z-cilnidipine);

[0073] A 样 Represents the peak area of ​​the optical isomer of cilnidipine (Z-cilnidipine) impurity in the test solution, the unit is mAU·min;

[0074] A 对 Represents the peak area of ​​the impurity reference solution of the optical isomer of cilnidipine (Z-cilnidipine), in units of

[0075] mAU·min;

[0076] C 对 Represents the concentration of the impurity reference solution of the optical isomer of cilnidipine (Z-cilnidipine), in units of

[0077] μg / mL;

[0078] C 样 Represents the concentration of cilnidipine sample in the test solution, in μg / mL.

[0079] The chromatographic conditions used in the following embodiments of the present invention are:

[0080] High performance liquid chromatograph: The brand model is Agilent 1260.

[0081] Column: Fortis Speedcore PFP, 4.6 mm × 150 mm, 2.6 μm.

[0082] Mobile phase: a mixed solvent of methanol and water, with a volume ratio of 80:20.

[0083] Elution mode: isocratic elution.

[0084] Detector: UV detector.

[0085] Detection wavelength: 240nm.

[0086] Flow rate: 0.5mL / min.

[0087] Column temperature: 25℃.

[0088] Injection volume: 5 μL.

[0089] Solvent: Mobile phase.

[0090] Example 1 Specificity and system suitability of the HPLC (high performance liquid chromatography) method for determining the impurity content of the optical isomer of cilnidipine (Z-cilnidipine)

[0091] 1. Prepare the mixed impurity reference stock solution of cilnidipine: accurately weigh 12.5 mg each of the reference substances of cilnidipine optical isomer (Z-cilnidipine) (impurity A), impurity B, impurity C, impurity D, impurity E, impurity G and impurity H, add mobile phase to ultrasonically dissolve and dilute to 25 mL; accurately measure 1 mL and place it in a 100 mL volumetric flask, add mobile phase to dilute to the scale, shake well, and use it as the mixed impurity reference stock solution.

[0092] 2. Prepare the mixed impurity reference solution of cilnidipine: accurately measure 10 mL of the above mixed impurity reference stock solution into a 100 mL volumetric flask, add the mobile phase to dilute to the scale, and shake well.

[0093] 3. Prepare specific solution: weigh 25 mg of cilnidipine test sample and place it in a 50 mL volumetric flask, add the mixed impurity reference solution and ultrasonically dissolve and dilute to the scale, and shake well.

[0094] 4. Prepare the reference solution of Z-cilnidipine (Impurity A): Take an appropriate amount of impurity A reference substance, dissolve it ultrasonically in the mobile phase and dilute it to a solution containing 0.5 μg of impurity A per 1 mL as the reference solution.

[0095] 5. Prepare system suitability solution: Take 12.5 mg of cilnidipine reference substance, weigh accurately, dissolve and dilute to 25 mL with reference substance solution, shake well, and use as system suitability solution.

[0096] 6. Inject the blank solvent (mobile phase), specificity solution and system suitability solution in sequence, and detect them under the set liquid chromatography conditions to conduct specificity and system suitability experiments.

[0097] like Figure 1-2 As shown, in the specificity test, the blank solution has no interference, the optical isomer of cilnidipine (Z-cilnidipine) (impurity A) and the main component can be completely separated, the separation degree is greater than 2.0, and it does not interfere with the sample detection.

[0098] like Figure 3 As shown, in the system suitability solution, the RSDs of the peak areas of the optical isomer of cilnidipine (Z-cilnidipine) (impurity A) and cilnidipine were both less than 2.0%, meeting the verification requirements. The specific results are shown in Table 1 below.

[0099] Table 1 Cilnidipine optical isomer (Z-cilnidipine) (impurity A) and cilnidipine system suitability test results

[0100]

[0101] This shows that the method has good specificity and system applicability.

[0102] Example 2 HPLC (High Performance Liquid Chromatography) Determination of Impurity Content of Z-cilnidipine Optical Isomers Quantitative Limit and Detection Limit

[0103] The chromatographic conditions were the same as those in Example 1.

[0104] The reference solution of the optical isomer of cilnidipine (Z-cilnidipine) (impurity A) prepared in Example 1 was diluted stepwise with the mobile phase and injected. When the signal-to-noise ratio was 10:1, the quantitative limit of the optical isomer of cilnidipine (Z-cilnidipine) (impurity A) was established (e.g. Figure 4 The detection limit of Z-cilnidipine (impurity A) was established when the signal-to-noise ratio was 3:1. Figure 5 The detection limit is 0.0075 ng.

[0105] It can be seen that this method has high sensitivity and good accuracy.

[0106] Example 3 Repeatability of the method for determining the impurity content of the optical isomer of cilnidipine (Z-cilnidipine) by HPLC (high performance liquid chromatography).

[0107] The chromatographic conditions were the same as those in Example 1.

[0108] The cilnidipine optical isomer (Z-cilnidipine) reference solution is the same as the cilnidipine optical isomer (Z-cilnidipine) (impurity A) reference solution in Example 1.

[0109] Test solution: Take 25 mg of cilnidipine test sample, accurately weigh it, put it in a 50 mL volumetric flask, dissolve it with mobile phase and dilute it to the scale, shake well, and prepare 6 portions in parallel using the same method.

[0110] Accurately measure 5 μL of the Z-cilnidipine reference solution and the test solution, inject them into the liquid chromatograph, and record the chromatogram (such as Figure 6As shown in the figure, the results of the impurity content of the optical isomer of cilnidipine (Z-cilnidipine) in the 6 test solutions were consistent, with a range of 0.003%, indicating that the method has good repeatability.

[0111] Example 4 Solution Stability of the Method for Determining the Impurity Content of the Optical Isomer of Cilnidipine (Z-cilnidipine) by HPLC (High Performance Liquid Chromatography)

[0112] The chromatographic conditions were the same as those in Example 1.

[0113] Take 25 mg of cilnidipine test sample, accurately weigh it, put it in a 50 mL volumetric flask, dissolve it with mobile phase and dilute it to the scale, shake it well, and use it as the test solution.

[0114] The test solution was placed at room temperature for 30 hours, and the sample was injected at 0h, 3h, 6h, 9h, 12h, 18h, 24h, and 30h, and the chromatograms were recorded (respectively as Figure 7 , Figure 8 , Fig. 9 , Fig.10 , Fig.11 , Fig.12 , Fig.13 , Fig.14 The change of the impurity peak area of ​​the optical isomer of cilnidipine (Z-cilnidipine) was investigated and the RSD value was calculated.

[0115] The results showed that after standing at room temperature for 30 hours, the RSD of the impurity peak area of ​​the optical isomer of cilnidipine (Z-cilnidipine) was 3.15%, indicating that the solution was stable within 30 hours under the conditions of this method.

[0116] Comparative Example 1

[0117] The difference from Example 1 is that the chromatographic column is a Hypersil C18 chromatographic column (4.6 mm×150 mm, 5 μm), and the other chromatographic conditions are the same as those in Example 1.

[0118] Preparation of Z-cilnidipine (Impurity A) reference solution: Take an appropriate amount of impurity A reference solution, dissolve it ultrasonically with mobile phase and dilute it to a solution containing 0.5 μg of impurity A per 1 mL as the reference solution.

[0119] Preparation of system suitability solution: Take 12.5 mg of cilnidipine reference substance, accurately weigh it, dissolve it with reference substance solution and dilute it to 25 mL, shake well, and use it as system suitability solution.

[0120] The system suitability solution was injected and tested under the set liquid chromatography conditions to conduct a system suitability experiment.

[0121] like Fig.15 As shown, the impurity A reference substance cannot be effectively separated after the main peak of cilnidipine.

[0122] Comparative Example 2

[0123] The difference from Example 1 is that the mobile phase is acetonitrile and water (volume ratio is 80:20), and the other chromatographic conditions are the same as those in Example 1.

[0124] Preparation of Z-cilnidipine (Impurity A) reference solution: Take an appropriate amount of impurity A reference solution, dissolve it ultrasonically with mobile phase and dilute it to a solution containing 0.5 μg of impurity A per 1 mL as the reference solution.

[0125] Preparation of system suitability solution: Take 12.5 mg of cilnidipine reference substance, accurately weigh it, dissolve it with reference substance solution and dilute it to 25 mL, shake well, and use it as system suitability solution.

[0126] The system suitability solution was injected and tested under the set liquid chromatography conditions to conduct a system suitability experiment.

[0127] like Fig.16 As shown, the impurity A reference substance cannot be effectively separated after the main peak of cilnidipine.

[0128] Comparative Example 3

[0129] The difference from Example 1 is that the mobile phase is ethanol and water (volume ratio is 80:20), and the other chromatographic conditions are the same as those in Example 1.

[0130] Preparation of Z-cilnidipine (Impurity A) reference solution: Take an appropriate amount of impurity A reference solution, dissolve it ultrasonically with mobile phase and dilute it to a solution containing 0.5 μg of impurity A per 1 mL as the reference solution.

[0131] Preparation of system suitability solution: Take 12.5 mg of cilnidipine reference substance, accurately weigh it, dissolve it with reference substance solution and dilute it to 25 mL, shake well, and use it as system suitability solution.

[0132] The system suitability solution was injected and tested under the set liquid chromatography conditions to conduct a system suitability experiment.

[0133] like Fig.17 As shown, the impurity A reference substance cannot be effectively separated after the main peak of cilnidipine.

[0134] Comparative Example 4

[0135] The difference from Example 1 is that the mobile phase is n-propanol and water (volume ratio is 80:20), and the other chromatographic conditions are the same as those in Example 1.

[0136] Preparation of Z-cilnidipine (Impurity A) reference solution: Take an appropriate amount of impurity A reference solution, dissolve it ultrasonically with mobile phase and dilute it to a solution containing 0.5 μg of impurity A per 1 mL as the reference solution.

[0137] Preparation of system suitability solution: Take 12.5 mg of cilnidipine reference substance, accurately weigh it, dissolve it with reference substance solution and dilute it to 25 mL, shake well, and use it as system suitability solution.

[0138] The system suitability solution was injected and tested under the set liquid chromatography conditions to conduct a system suitability experiment.

[0139] like Fig.18 As shown, the impurity A reference substance cannot be effectively separated after the main peak of cilnidipine.

[0140] The chromatographic conditions of Comparative Examples 1-4 above cannot effectively separate impurity A and the main peak of cilnidipine.

[0141] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for detecting the impurity content of the optical isomers of cilnidipine, comprising: Using high performance liquid chromatography to detect the optical isomer impurities of cilnidipine to obtain a liquid chromatogram, and calculating the content of the optical isomer impurities of cilnidipine according to the liquid chromatogram; Wherein, the mobile phase used in the high performance liquid chromatography comprises methanol and water; The chromatographic column used in the high performance liquid chromatography is selected from Fortis Speedcore PFP.

2. The method according to claim 1, characterized in that In the mobile phase, the volume ratio of methanol to water is 85:15 to 75:25; Preferably, in the mobile phase, the volume ratio of methanol to water is 80:

20.

3. The method according to claim 1 or 2, characterized in that: The chromatographic column of the high performance liquid chromatography is FortisSpeedcore PFP, 4.6 mm×150 mm, 2.6 μm; preferably, the flow rate of the mobile phase in the chromatographic column is 0.4 mL / min to 0.6 mL / min.

4. The method according to any one of claims 1 to 3, characterized in that: The high performance liquid chromatography method uses the mobile phase for isocratic elution. Preferably, the elution time is 30 to 40 minutes, and / or the elution temperature is 20 to 30°C.

5. The method according to any one of claims 1 to 4, characterized in that: The detector used in the high performance liquid chromatography is an ultraviolet detector. Preferably, the detection wavelength of the detector is 240 nm.

6. The method according to any one of claims 1 to 5, characterized in that: The steps include: (1) Prepare a cilnidipine optical isomer impurity reference solution, (2) Prepare the test solution; (3) using a mobile phase for isocratic elution, and detecting the cilnidipine optical isomer impurity reference solution and the test solution by high performance liquid chromatography to obtain a liquid chromatogram; (4) calculating the content of the optical isomer impurity of cilnidipine according to the liquid chromatogram obtained in step (3).

7. The method according to claim 6, characterized in that The concentration of cilnidipine in the test solution is 0.3-1.0 mg / mL, preferably 0.5 mg / mL.

8. The method according to claim 6 or 7, characterized in that: The calculation formula for the content of the cilnidipine optical isomer impurity is: Wherein: H% represents the content of cilnidipine optical isomer impurities; A 样 Represents the peak area of ​​the optical isomer impurities of cilnidipine in the test solution, the unit is mAU·min; A 对 Represents the peak area of ​​the impurity reference solution of the optical isomer of cilnidipine, the unit is mAU·min; C 对 Represents the concentration of the cilnidipine optical isomer impurity reference solution, in μg / mL; C 样 Represents the concentration of cilnidipine sample in the test solution, in μg / mL.

9. The method according to any one of claims 1 to 8, characterized in that: The impurity concentration of the optical isomers of cilnidipine is between 3 ng / mL and 5000 ng / mL.

10. The method according to any one of claims 1 to 8, characterized in that: The method can detect the minimum amount of the cilnidipine optical isomer impurity to be 0.0075 ng.

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