Method for detecting impurity components in rafenasin solution for inhalation

Abstract

The invention discloses a method for detecting impurity components in a rafenasin solution for inhalation, and relates to the technical field of medicine detection.The method comprises the following steps that firstly, a mobile phase A is prepared, and the mobile phase A is pretreated; analyzing and detecting the rafenasin aerosol inhalation solution by adopting a high performance liquid chromatography; chromatographic conditions of the high performance liquid chromatography are as follows: a chromatographic column takes octadecylsilane chemically bonded silica as a filler; the mobile phase A is a phosphate buffer solution, and the mobile phase B is acetonitrile; performing gradient elution; the column temperature is 30 DEG C, the flow rate is 1.0 mL / min, and the sample size is 50 mu L; according to the method for detecting the impurity components in the rafenasin solution for inhalation, by optimizing chromatographic conditions and carefully selecting and proportioning the composition of the mobile phase, the stability and repeatability in the chromatographic process are ensured, meanwhile, the sample preparation and analysis process is simplified, high-sensitivity detection and effective separation of the impurity components are achieved, and the detection accuracy is improved. The sensitivity and the accuracy of a detection result are improved.

Description

Technical Field

[0001] The invention relates to a drug detection technology, and in particular to a method for detecting impurity components in a refenacin solution for inhalation. Background Art

[0002] Revenacin is a long-acting anticholinergic bronchodilator, mainly used for the maintenance treatment of patients with chronic obstructive pulmonary disease (COPD). It dilates the bronchi by inhibiting smooth muscle muscarinic M3 receptors, reducing the frequency and severity of acute attacks of the disease caused by increased cholinergic bronchial contraction mediated by muscarinic receptors to parasympathetic ganglia and airway smooth muscle.

[0003] Testing impurities in revenacin solution for inhalation is of great significance for ensuring drug safety, controlling the content of impurities that may pose a risk to patient health, reducing drug side effects, improving drug quality, and maintaining therapeutic effects. In addition, impurity testing also provides a scientific basis for drug research and development and production process improvements, thereby ensuring patient drug safety and improving overall quality of life.

[0004] However, since the impurities in the refenacin solution for inhalation may be similar to the main components in chemical properties, it is difficult to effectively separate them during the chromatographic process. The current detection methods are not effective in detecting and separating impurities in the refenacin solution for inhalation, thereby affecting the accuracy of impurity detection in the refenacin solution for inhalation. Summary of the invention

[0005] The purpose of the present invention is to provide a method for detecting impurity components in a refenacin solution for inhalation, so as to solve the problem that the detection and separation effects of impurities in the refenacin solution for inhalation in the prior art are poor.

[0006] In order to achieve the above object, the present invention provides the following technical solution: a method for detecting impurities in a refenacin solution for inhalation, comprising the following steps:

[0007] S1, first prepare mobile phase A, and pretreat mobile phase A;

[0008] S2. The refenacin nebulized inhalation solution was analyzed and detected by high performance liquid chromatography; the chromatographic conditions of the high performance liquid chromatography were as follows: the chromatographic column was filled with octadecylsilane bonded silica gel; the mobile phase A was phosphate buffer, and the mobile phase B was acetonitrile; the gradient elution was performed; the column temperature was 30°C, the flow rate was 1.0 mL / min, and the injection volume was 50 μL.

[0009] Furthermore, the impurity components are

[0010] Further, in volume percentage, the gradient elution is as follows:

[0011] 0-20min, mobile phase A 90%, mobile phase B 10%;

[0012] 20-30 min, mobile phase A 60%, mobile phase B 40%;

[0013] 30-35 min, mobile phase A 30%, mobile phase B 70%;

[0014] 35-37 min, mobile phase A 30%, mobile phase B 70%;

[0015] 37-50min, mobile phase A 90%, mobile phase B 10%.

[0016] Furthermore, the chromatographic column is YMC-Tri art C18, 4.6 mm×250 mm, 5 μm.

[0017] Furthermore, the mobile phase A is a diammonium phosphate solution, and the preparation steps of the diammonium phosphate solution are as follows: weigh 3.45 g of diammonium phosphate, add 1000 ml of water to dissolve it, and adjust the pH value to 2.9 with phosphoric acid to obtain the diammonium phosphate solution.

[0018] Furthermore, in the chromatographic conditions described in S2, the detection wavelength is 230 nm.

[0019] Furthermore, the pretreatment in S1 includes pH adjustment, filtration and degassing.

[0020] Furthermore, the pH adjustment is to slowly add a phosphoric acid solution into the mobile phase A solution to adjust the pH value to a target range of 2.8-3.0.

[0021] Furthermore, the filtration is filtering the mobile phase A solution through a 0.22 micron filter membrane.

[0022] Furthermore, the degassing is to degas the mobile phase A solution by ultrasound or a degasser to remove dissolved gas in the solution.

[0023] Compared with the prior art, the present invention provides a method for detecting impurity components in a refenacin solution for inhalation, which optimizes chromatographic conditions for impurity components that may exist in the refenacin solution for inhalation, thereby achieving high-sensitivity detection and effective separation of the impurity components;

[0024] By carefully selecting and proportioning the composition of the mobile phase, the stability and repeatability of the chromatographic process are ensured, while the sample preparation and analysis process are simplified; this simplification not only reduces the experimental cost, but also improves the convenience of operation, allowing experimenters to quickly perform sample analysis without the need for a complicated mobile phase preparation process, thus improving experimental efficiency;

[0025] By adjusting the chromatographic conditions, effective separation between refenacin and its degradation products was achieved. This optimization not only improved the resolution, but also reduced the possibility of peak overlap, thereby improving the accuracy and reliability of the detection; by precisely controlling the experimental conditions and optimizing the detection parameters, this method can accurately identify and quantify the degradation products in the refenacin solution;

[0026] In summary, the newly developed method for detecting related substances in refenasin solution for inhalation has the characteristics of simple mobile phase, convenient operation, good separation and accuracy, which not only improves the sensitivity and separation of the test results, but also provides a scientific basis for the safe use and effective supervision of drugs. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0028] Figure 1 A schematic diagram of the overall detection method flow provided by an embodiment of the present invention;

[0029] Figure 2 A quantitative limit detection result diagram of the detection method provided in an embodiment of the present invention;

[0030] Figure 3 This is a graph of the detection limit detection results of the detection method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] Embodiment 1:

[0033] See also Figure 1 , a method for detecting impurities in a refenacin solution for inhalation, comprising the following steps:

[0034] S1. First, prepare mobile phase A and pre-treat mobile phase A; pre-treatment includes pH adjustment, filtration and degassing; pH adjustment includes slowly adding phosphoric acid solution to the mobile phase A solution to adjust the pH value to the target range of 2.8-3.0; filtration includes filtering the mobile phase A solution through a 0.22 micron filter membrane; degassing includes degassing the mobile phase A solution through ultrasound or a degasser to remove dissolved gas in the solution;

[0035] S2. The refenacin atomized inhalation solution was analyzed and detected by high performance liquid chromatography; the chromatographic conditions of the high performance liquid chromatography were as follows: the chromatographic column was filled with octadecylsilane bonded silica gel; the mobile phase A was phosphate buffer, and the mobile phase B was acetonitrile; the gradient elution was performed; the column temperature was 30°C, the flow rate was 1.0 mL / min, the injection volume was 50 μL, and the detection wavelength was 230 nm;

[0036] The impurity components are

[0037] In volume percentage, the gradient elution is as follows:

[0038] 0-20min, mobile phase A 90%, mobile phase B 10%;

[0039] 20-30 min, mobile phase A 60%, mobile phase B 40%;

[0040] 30-35 min, mobile phase A 30%, mobile phase B 70%;

[0041] 35-37 min, mobile phase A 30%, mobile phase B 70%;

[0042] 37-50min, mobile phase A 90%, mobile phase B 10%.

[0043] The chromatographic column is YMC-Tri art C18, 4.6 mm × 250 mm, 5 μm.

[0044] Mobile phase A is a diammonium phosphate solution. The preparation steps of the diammonium phosphate solution are as follows: weigh 3.45 g of diammonium phosphate, add 1000 ml of water to dissolve it, and adjust the pH value to 2.9 with phosphoric acid to obtain the diammonium phosphate solution.

[0045] The specific implementation method is that the impurity components include

[0046] Testing for these impurities is critical to ensuring the quality and safety of revenacin inhalation solution.

[0047] Phosphoric acid solution is slowly added to the mobile phase A solution to adjust the pH value to 2.8-3.0. pH adjustment is an important step in chromatographic analysis because it directly affects the charge state and solubility of the compounds in the sample. In the present technical scheme, phosphoric acid solution is selected as a pH adjuster, which can quickly and effectively adjust the pH value of the mobile phase A solution. At the same time, they have a high degree of ionization in the solution and have little effect on chromatographic analysis.

[0048] When adjusting the pH value, phosphoric acid solution should be added slowly and the pH value of mobile phase A solution should be continuously monitored until it reaches the target range of 2.8-3.0; this process requires the use of an accurate pH meter and ensure that it is accurately calibrated; in addition, when adding phosphoric acid solution, avoid local overconcentration to avoid causing local pH changes in the solution.

[0049] Accurate control of pH value is crucial to ensure the stability and repeatability of chromatographic analysis. Deviation of pH value may lead to degradation or conversion of refenacin, affecting the separation of chromatographic peaks and the accuracy of peak area. Therefore, accurate control of pH value is the key to ensure the reliability of analytical results.

[0050] Filtration of the mobile phase A solution through a 0.22 micron filter is a process that utilizes a physical barrier (the filter) to remove solid particles suspended in a liquid. In chromatography, the purpose of filtration is to ensure that the sample does not contain any particulate matter that could clog the column, which is critical to maintaining the integrity of the column and extending its life.

[0051] The 0.22-micron filter was chosen to ensure that it would capture tiny particles that could affect chromatographic analysis; the 0.22-micron pore size effectively removes bacteria and most particulates while allowing small molecules in the mobile phase A solution to pass through.

[0052] In actual operation, it is necessary to ensure that the filter membrane is sterile and uncontaminated before use; the filter membrane should be installed under sterile conditions and the filter device should be kept clean; during the filtration process, excessive pressure should be avoided to avoid damaging the filter membrane or causing adsorption or denaturation of components in the solution when passing through the filter membrane.

[0053] Degas the mobile phase A solution by ultrasound or a degasser to remove dissolved gases in the mobile phase A solution, because dissolved gases may form bubbles in the chromatographic system and affect the signal stability of the detector and the shape of the chromatographic peak.

[0054] Ultrasonic degassing and degasser degassing are two commonly used degassing methods. Ultrasonic degassing uses the cavitation effect of ultrasound to break the dissolved state of gas in the solution, while the degasser promotes the release of gas through vacuum and heating. During ultrasonic degassing, the appropriate ultrasonic power and time should be selected to avoid thermal degradation or damage to the compounds in the solution; in this scheme, the ultrasonic power is 20% to 40% of the maximum output power of the equipment, and the ultrasonic time is 5-15 minutes. When the degasser is degassed, it is necessary to set the appropriate temperature and vacuum degree according to the properties of the solution. In this scheme, the temperature is 30℃-50℃ and the vacuum degree is 0.01MPa-0.1MPa (absolute pressure). The effect of degassing directly affects the stability and repeatability of chromatographic analysis. Insufficient degassing may lead to the formation of bubbles, affecting the signal of the detector, while excessive degassing may cause volatilization or degradation of compounds in the solution.

[0055] The pretreatment step is key to ensuring the accuracy and repeatability of chromatographic analysis. Each step of pH adjustment, filtration and degassing has its own specific operating details and parameter requirements, which need to be optimized according to the properties of the solution and the requirements of the chromatographic system. By precisely controlling these parameters, the variability in the sample processing process can be minimized, thereby improving the quality and reliability of chromatographic analysis. In actual operation, each step needs to be strictly controlled and monitored to ensure the best effect of pretreatment and lay a solid foundation for subsequent chromatographic analysis.

[0056] S2. The nebulized inhalation solution of refenacin was analyzed and detected by high performance liquid chromatography; the chromatographic conditions of the high performance liquid chromatography were as follows: the chromatographic column was filled with octadecylsilane bonded silica gel; the mobile phase A was phosphate buffer, and the mobile phase B was acetonitrile; the gradient elution was performed; the column temperature was 30°C, the flow rate was 1.0 mL / min, and the injection volume was 50 μL; and the detection wavelength was 230 nm.

[0057] The influence of the selection of chromatographic conditions on the analysis results: The selection of chromatographic conditions is a key step in high performance liquid chromatography (HPLC) analysis, which directly affects the separation effect, detection sensitivity and analysis time. In this technical scheme, specific chromatographic conditions are selected to achieve effective separation of refenacin and its degradation impurities. The selection of chromatographic columns is based on the chemical and physical properties of their fillers. Octadecylsilane bonded silica gel (ODS) is a commonly used reverse phase chromatography filler, which is widely used due to its good hydrophobicity and stability; ODS filler is suitable for a variety of analytical tasks, especially for the separation of hydrophobic compounds.

[0058] The performance of a chromatographic column is affected by many factors, including the particle size, pore size, chemical stability, and physical strength of the filler. The 5μm particle size used in the YMC-Tri art C18 column provides good separation efficiency and lower column pressure, and it has high performance and durability and is suitable for a variety of analytical conditions.

[0059] Mobile phase A is phosphate buffer and mobile phase B is acetonitrile. This combination provides a good separation effect because they form a contrast in polarity, which helps to achieve effective separation of compounds of different polarities during chromatography; phosphate buffer provides a stable pH environment, while acetonitrile, as an organic solvent, can adjust the hydrophobicity of the mobile phase; the buffering capacity of mobile phase A is essential for maintaining a stable pH environment, and ammonium dihydrogen phosphate solution is a commonly used buffer because it has good buffering capacity over a wide pH range; when preparing mobile phase A, it is necessary to accurately weigh ammonium dihydrogen phosphate and ensure that it is completely dissolved. The use of phosphoric acid to adjust the pH value to 2.9 is to simulate the actual use conditions of the refenacin inhalation solution and ensure the accuracy of the chromatographic analysis.

[0060] The detection wavelength directly affects the sensitivity and selectivity of the detection. At a wavelength of 230nm, refenasin and its degradation impurities have good ultraviolet absorption, which helps to improve the sensitivity and accuracy of the detection. Choosing 230nm as the detection wavelength can ensure that refenasin and its degradation impurities have good ultraviolet absorption, thereby improving the sensitivity and accuracy of the detection.

[0061] The gradient elution of HPLC is as follows, in volume percentage:

[0062] 0-20min, mobile phase A 90%, mobile phase B 10%;

[0063] 20-30 min, mobile phase A 60%, mobile phase B 40%;

[0064] 30-35 min, mobile phase A 30%, mobile phase B 70%;

[0065] 35-37 min, mobile phase A 30%, mobile phase B 70%;

[0066] 37-50min, mobile phase A 90%, mobile phase B 10%.

[0067] Gradient elution achieves separation of compounds of different polarities at different time points by gradually changing the composition of the mobile phase during the analysis. This method is particularly suitable for separating complex samples with a wide range of polarities. Gradient elution can improve the flexibility and efficiency of chromatographic analysis because it allows compounds with large differences in polarity to be separated in the same analysis. In addition, gradient elution can also reduce the interaction between the sample and the chromatographic column, reduce column pressure, and improve the symmetry of the chromatographic peak; it can optimize the separation effect at different time points, which is particularly important for the analysis of complex samples.

[0068] The selection of chromatographic conditions, gradient elution, chromatographic column selection, preparation of mobile phase A and detection wavelength selection in the high performance liquid chromatography analysis and detection (S2) are key factors to ensure the accuracy and repeatability of the detection of related substances in refenasin inhalation solution; by optimizing and precisely controlling these parameters, effective separation and accurate detection of refenasin and its degradation impurities can be achieved, ensuring the accuracy and repeatability of the detection results, thereby providing strong data support for the quality control of refenasin inhalation solution.

[0069] Embodiment 2:

[0070] This embodiment provides a technical solution based on the first embodiment: detecting the precision of a method for detecting impurities in a refenacin solution for inhalation.

[0071] (I) Experimental instruments, reagents and reference substances

[0072] (1) The instruments used are high performance liquid chromatograph (with UV detector or DAD detector), electronic balance and pH meter;

[0073] (2) The experimental reagents are acetonitrile, diammonium phosphate and phosphoric acid;

[0074] (3) Reference substances: Impurity LN03 reference substance, Impurity LN05-12 reference substance, Impurity LNSM02 reference substance and Impurity LN05-T reference substance.

[0075] (II) Chromatographic conditions

[0076] The chromatographic column is filled with octadecylsilane bonded silica gel (such as a chromatographic column of YMC-Triart C18, 4.6 mm × 250 mm, 5 μm or a chromatographic column of equivalent performance); the mobile phase A is phosphate buffer (the preparation steps of the diammonium phosphate solution are as follows: weigh 3.45 g of diammonium phosphate, add 1000 ml of water to dissolve it, and adjust the pH value to 2.9 with phosphoric acid), and the mobile phase B is acetonitrile; gradient elution; column temperature is 30°C, flow rate is 1.0 mL / min, injection volume is 50 μL; detection wavelength is 230 nm;

[0077] In volume percentage, the gradient elution is as follows:

[0078] 0-20min, mobile phase A 90%, mobile phase B 10%;

[0079] 20-30 min, mobile phase A 60%, mobile phase B 40%;

[0080] 30-35 min, mobile phase A 30%, mobile phase B 70%;

[0081] 35-37 min, mobile phase A 30%, mobile phase B 70%;

[0082] 37-50min, mobile phase A 90%, mobile phase B 10%.

[0083] (III) Experiment 1: Repeatability test (experimenter A)

[0084] Diluent: Mobile phase A-Mobile phase B (90:10)

[0085] Mixed impurity stock solution: Take appropriate amount of each impurity reference substance, weigh accurately, add appropriate amount of diluent to dissolve and dilute to make a mixed solution containing 5.8 μg of LN03, LN05-12, LNSM02 and LN05-T per 1 ml.

[0086] Test solution: Take 2 ml of the impurity mixed stock solution and place it in 6 different 20 ml volumetric flasks. Dissolve it with the inhalation refenacin solution and dilute it to the scale to obtain the test solution.

[0087] Control solution: Take 6 portions of the test solution (1 ml each), place them in 6 different 100 ml volumetric flasks, and dilute to the mark with diluent.

[0088] The test solution and the control solution were measured using the above chromatographic conditions, the peak area of ​​each impurity was recorded, and the content of each impurity was obtained using the following formula.

[0089]

[0090] Where:

[0091] A V is the peak area of ​​impurities in the test solution;

[0092] As is the area of ​​the refenacin peak in the control solution;

[0093] V is the dilution factor of the control solution;

[0094] Test 2: Intermediate precision test (experimenter B)

[0095] Experimenter B conducted the experiment on different dates, using different instruments and different batches of chromatographic columns according to the same method as experimenter A. The results of the two experiments are shown in the following table:

[0096]

[0097] As mentioned above, the repeatability and precision of this method are good.

[0098] Embodiment three:

[0099] See also Figure 2-Figure 3 This embodiment provides a technical solution based on the first embodiment: the sensitivity of a detection method for impurity components in a refenacin solution for inhalation is detected:

[0100] (I) Experimental instruments, reagents and reference substances

[0101] (1) The instruments used are high performance liquid chromatograph (with UV detector or DAD detector), electronic balance and pH meter;

[0102] (2) The experimental reagents are acetonitrile, diammonium phosphate and phosphoric acid;

[0103] (3) The reference substances are refenacin reference substance, impurity LN03 reference substance, impurity LN05-12 reference substance, impurity LNSM02 reference substance and impurity LN05-T reference substance;

[0104] (II) Chromatographic conditions

[0105] The chromatographic column is filled with octadecylsilane bonded silica gel (such as a chromatographic column of YMC-Triart C18, 4.6 mm × 250 mm, 5 μm or a chromatographic column of equivalent performance); the mobile phase A is phosphate buffer (the preparation steps of the diammonium phosphate solution are as follows: weigh 3.45 g of diammonium phosphate, add 1000 ml of water to dissolve it, and adjust the pH value to 2.9 with phosphoric acid), and the mobile phase B is acetonitrile; gradient elution; column temperature is 30°C, flow rate is 1.0 mL / min, injection volume is 50 μL; detection wavelength is 230 nm;

[0106] In volume percentage, the gradient elution is as follows:

[0107] 0-20min, mobile phase A 90%, mobile phase B 10%;

[0108] 20-30 min, mobile phase A 60%, mobile phase B 40%;

[0109] 30-35 min, mobile phase A 30%, mobile phase B 70%;

[0110] 35-37 min, mobile phase A 30%, mobile phase B 70%;

[0111] 37-50min, mobile phase A 90%, mobile phase B 10%.

[0112] (III) Solution preparation and impurity component detection

[0113] Diluent: Mobile phase A-Mobile phase B (90:10)

[0114] Mixed reference substance stock solution: Take appropriate amount of each reference substance, weigh accurately, add appropriate amount of diluent to dissolve and dilute to make a mixed solution containing 58 μg of each of LN03, revenacin, LN05-12, LNSM02 and LN05-T per 1 ml.

[0115] Quantitative limit solution: Take the mixed reference stock solution, dilute it step by step with diluent and then test it. When the ratio of the response value of each peak to the noise is about 10, the reference concentration is the quantitative limit concentration.

[0116] Detection limit solution: Take the mixed reference stock solution, dilute it step by step with diluent, and then test it. When the ratio of the response value of each peak to the noise is about 3, the reference concentration is the detection limit concentration.

[0117] The above chromatographic conditions were used to measure each quantitative limit solution and detection limit solution, and the signal-to-noise ratio of each impurity peak and the main peak was recorded. The quantitative limit concentration was about 0.006μg / ml, and the percentage relative to the concentration of the test solution was 0.010%; the detection limit concentration was about 0.002μg / ml, and the percentage relative to the concentration of the test solution was 0.003%, indicating that the detection sensitivity of this method is high. The quantitative limit and detection limit spectra are shown in Figure 2 and Figure 3 .

[0118] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for detecting impurities in a refenacin solution for inhalation, characterized in that: The steps include: S1, first prepare mobile phase A, and pretreat mobile phase A; S2. The refenacin nebulized inhalation solution was analyzed and detected by high performance liquid chromatography; the chromatographic conditions of the high performance liquid chromatography were as follows: the chromatographic column was filled with octadecylsilane bonded silica gel; the mobile phase A was phosphate buffer, and the mobile phase B was acetonitrile; the gradient elution was performed; the column temperature was 30°C, the flow rate was 1.0 mL / min, and the injection volume was 50 μL.

2. The method for detecting impurities in a revenacin solution for inhalation according to claim 1, characterized in that: The impurity components are 3. The method for detecting impurities in a revenacin solution for inhalation according to claim 1, characterized in that: In volume percentage, the gradient elution is as follows: 0-20min, mobile phase A 90%, mobile phase B 10%; 20-30 min, mobile phase A 60%, mobile phase B 40%; 30-35 min, mobile phase A 30%, mobile phase B 70%; 35-37 min, mobile phase A 30%, mobile phase B 70%; 37-50min, mobile phase A 90%, mobile phase B 10%.

4. The method for detecting impurities in a revenacin solution for inhalation according to claim 1, characterized in that: The chromatographic column is YMC-Tri art C18, 4.6 mm×250 mm, 5 μm.

5. The method for detecting impurities in a revenacin solution for inhalation according to claim 1, characterized in that: The mobile phase A is a diammonium phosphate solution. The preparation steps of the diammonium phosphate solution are as follows: weigh 3.45 g of diammonium phosphate, add 1000 ml of water to dissolve it, and adjust the pH value to 2.9 with phosphoric acid to obtain the diammonium phosphate solution.

6. The method for detecting impurities in a revenacin solution for inhalation according to claim 1, characterized in that: In the chromatographic conditions described in S2, the detection wavelength is 230 nm.

7. The method for detecting impurities in a revenacin solution for inhalation according to claim 1, characterized in that: The pretreatment described in S1 is pH adjustment, filtration and degassing.

8. The method for detecting impurities in a revenacin solution for inhalation according to claim 7, characterized in that: The pH adjustment is to slowly add phosphoric acid solution into the mobile phase A solution to adjust the pH value to the target range of 2.8-3.

0.

9. The method for detecting impurities in a revenacin solution for inhalation according to claim 7, characterized in that: The filtration is to filter the mobile phase A solution through a 0.22 micron filter membrane.

10. The method for detecting impurities in a revenacin solution for inhalation according to claim 7, characterized in that: The degassing is to degas the mobile phase A solution by ultrasound or a degasser to remove dissolved gas in the solution.

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