Method for determining residual quantity of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography

Abstract

The invention discloses a method for determining residual quantity of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography, which comprises the following steps: weighing pentafluoropentanethiol, diluting with a diluent, and preparing a reference solution; weighing a fulvestrant raw material medicine, diluting the fulvestrant raw material medicine with a diluent, and preparing a test solution; the test solution and the reference solution are detected by liquid chromatography, and the conditions of liquid chromatography detection are as follows: a chromatographic column takes octadecylsilane bonded hybrid silica gel particles as a stationary phase, a trifluoroacetic acid aqueous solution as a mobile phase A and a methanol solution as a mobile phase B for gradient elution; and calculating the residual quantity of the pentafluoropentyl mercaptan in the fulvestrant bulk drug by adopting an external standard method. According to the method disclosed by the invention, the concentration range of the pentafluoropentyl mercaptan is 3.2 mu g / mL-21.3 mu g / mL, the linear correlation coefficient R is 0.9992, and the linearity is good; the detection limit of the pentafluoropentyl mercaptan is 1.28 mu g / mL, and the sensitivity is high; the standard addition recovery rate RSD of a sample after 6 times of parallel determination is 1.70%, the standard addition recovery rate RSD of a sample after 12 times of parallel determination is 2.64%, and the repeatability is good.

Description

Technical Field

[0001] The present invention relates to the technical field of pharmaceutical detection, and in particular to a method for determining the residual amount of pentafluoropentanethiol in a fulvestrant raw material drug by liquid chromatography. Background Art

[0002] Fulvestrant is a new class of estrogen receptor antagonists - estrogen receptor downregulators for the treatment of breast cancer. It is used to treat metastatic advanced breast cancer in postmenopausal women who have failed to respond to anti-estrogen therapy, whose disease has progressed, or whose breast cancer is hormone receptor-positive.

[0003] Pentafluoropentanethiol, also known as 4,4,5,5,5-pentafluoropentane-1-thiol (CAS No. 148757-88-4), is an important pharmaceutical intermediate. As a key starting material in the synthesis of fulvestrant, pentafluoropentanethiol provides the primary functional groups and main structure. With a molecular weight of 194.166, a boiling point of 113.2±40.0°C at 760 mmHg, and an oil-water distribution coefficient (LogP) of 2.30, pentafluoropentanethiol is a hydrophobic small molecule.

[0004] Currently, no national pharmacopoeia includes a method for determining pentafluoropentanethiol. Most existing detection methods use the area normalization method to detect the purity of chemical products or pharmaceutical intermediates after production to ensure factory quality, which is not suitable for accurate quantification. There is also no relevant literature on the detection method of pentafluoropentanethiol in fulvestrant raw materials. Since pentafluoropentanethiol is a thiol compound with a strong odor and the compound itself contains five fluorine atoms, it has a potentially toxic structure. Therefore, it is very necessary to develop a simple and accurate quantitative method for detecting the residual amount of pentafluoropentanethiol, which will help improve the safety of medication and provide a basis for the quality control strategy of related drugs. Summary of the Invention

[0005] The object of the present invention is to provide a method for determining the residual amount of pentafluoropentanethiol in fulvestrant raw materials by liquid chromatography, so as to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solution: a method for determining the residual amount of pentafluoropentanethiol in fulvestrant raw materials by liquid chromatography, comprising the following steps:

[0007] Weigh pentafluoropentanethiol and dilute it with diluent to prepare a reference solution;

[0008] Weigh the fulvestrant bulk drug and dilute it with diluent to prepare the test solution;

[0009] The test solution and the reference solution were detected by liquid chromatography. The liquid chromatography detection conditions were as follows: the chromatographic column used octadecylsilane bonded hybrid silica gel particles as the stationary phase, trifluoroacetic acid aqueous solution as the mobile phase A, and methanol solution as the mobile phase B for gradient elution;

[0010] The external standard method was used to calculate the residual amount of pentafluoropentanethiol in the fulvestrant raw material.

[0011] Furthermore, the chromatographic column is a Waters Xterra MS C18 column with a specification of 4.6 mm*250 mm and 5 μm.

[0012] Furthermore, the column temperature of the chromatographic column is 28° C. to 35° C., the injection volume is 50 μL, and the flow rate is 0.95 to 1.1 mL / min.

[0013] Furthermore, the detector selected for detection is an ultraviolet detector with a detection wavelength of 210 nm.

[0014] Furthermore, the diluent is methanol.

[0015] Furthermore, 100 mg of fulvestrant API was weighed, dissolved in methanol and diluted to 10 mL to prepare a test solution with a concentration of 10 mg / mL.

[0016] Furthermore, 50 mg of pentafluoropentanethiol was weighed, dissolved in methanol and diluted in sequence to prepare a stock solution with a concentration of 1 mg / mL, a reference substance stock solution of 0.1 mg / mL and a reference substance solution of 0.01 mg / mL.

[0017] Furthermore, the reference substance stock solution was further diluted with methanol to prepare a linear solution with a concentration ratio of 30% to 200%, the linear solution with a concentration ratio of 30% was taken as the quantitative limit solution, 0.4 mL of the quantitative limit solution was added to 0.6 mL of methanol solution to prepare a detection limit solution, and the reference substance stock solution was further diluted with methanol to prepare a spiked solution with a concentration ratio of 80% to 150%.

[0018] Furthermore, the mobile phase A is a trifluoroacetic acid aqueous solution with a concentration of 0.1%, and the mobile phase B is a methanol solution with a concentration of 100%.

[0019] Furthermore, the conditions of the gradient elution are:

[0020] The first gradient elution time was 0 min, with mobile phase A accounting for 80% and mobile phase B accounting for 20%;

[0021] The second gradient elution time was 20 min, with mobile phase A accounting for 20% and mobile phase B accounting for 80%;

[0022] The first gradient elution time was 40 min, with mobile phase A accounting for 0% and mobile phase B accounting for 100%;

[0023] The first gradient elution time was 41 min, with mobile phase A accounting for 80% and mobile phase B accounting for 20%;

[0024] The first gradient elution time was 50 min, with mobile phase A accounting for 80% and mobile phase B accounting for 20%.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention uses octadecylsilane bonded hybrid silica gel particles as the stationary phase. The chromatographic column is mature and easy to obtain, the experimental cost is low, and it can tolerate a mobile phase with a wide pH range and adapt to a mobile phase with a low pH value, thereby avoiding hydrolysis of the bonded phase of the chromatographic column under acidic conditions and extending the life of the chromatographic column. Trifluoroacetic acid aqueous solution is used as mobile phase A to inhibit the dissociation of thiol groups and enhance reverse phase retention. As an ion pair reagent, it improves peak shape and solves the problem of tailing of polar substances. Methanol solution is used as mobile phase B to reduce the elution intensity of the organic phase, extend the retention time of pentafluoropentanethiol, and avoid overlap with the solvent peak. Through the synergistic effect of methanol and trifluoroacetic acid, effective retention and trace detection of highly polar thiol compounds are achieved. Moreover, the methanol and trifluoroacetic acid aqueous solution system is simple to operate and has low preparation difficulty. The method has strong properties, high sensitivity, good repeatability, and can accurately and quickly determine the residual amount of pentafluoropentanethiol in the fulvestrant raw material drug.

[0027] 2. It has been verified that the linear correlation coefficient R of this method is 0.9992 in the concentration range of 3.2μg / mL to 21.3μg / mL for pentafluoropentanethiol, indicating good linearity; the detection limit of pentafluoropentanethiol is 1.28μg / mL, indicating high sensitivity; the RSD of the spiked recovery rate of 6 parallel measurements of samples is 1.70%, and the RSD of the spiked recovery rate of 12 samples is 2.64%, indicating good repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The chromatogram is detected by automatic sampling of gas chromatograph;

[0029] Figure 2 The chromatogram is detected by gas chromatograph headspace injection;

[0030] Figure 3 The chromatogram is detected when acetonitrile:methanol:phosphoric acid = 700:300:1 is used as mobile phase B;

[0031] Figure 4 This is the chromatogram of 1 mg / ml pentafluoropentanethiol injected into an Agilent Poroshell EC C18 with 0.1% phosphoric acid in water.

[0032] Figure 5 This is the chromatogram of 1 mg / ml pentafluoropentanethiol injected into an Agilent Poroshell EC C18 sample with 0.05% trifluoroacetic acid in water.

[0033] Figure 6 This is the chromatogram of 1 mg / ml pentafluoropentanethiol injected into a Waters Xterra MS C18 column with 0.1% trifluoroacetic acid in water.

[0034] Figure 7 Is the chromatogram of the blank solution of the present invention;

[0035] Figure 8 is a chromatogram of the reference solution of the present invention;

[0036] Figure 9 It is a chromatogram of the test solution of the present invention;

[0037] Figure 10 The chromatogram is a 100% test sample spiked solution of the present invention;

[0038] Figure 11 It is a linear relationship diagram of the present invention;

[0039] Figure 12 This is the chromatogram of the present invention when the flow rate is 0.95 mL / min. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] This embodiment provides a method for determining the residual amount of pentafluoropentanethiol in a fulvestrant bulk drug by liquid chromatography, comprising the following steps:

[0042] S1: Weigh pentafluoropentanethiol and dilute it with diluent to prepare a reference solution;

[0043] S2: Weigh the fulvestrant bulk drug substance and dilute it with the diluent to prepare the test solution;

[0044] S3: The test solution and the reference solution were tested by liquid chromatography, and the liquid chromatography test conditions were as follows: the chromatographic column used octadecylsilane bonded hybrid silica gel particles as the stationary phase, trifluoroacetic acid aqueous solution as the mobile phase A, and methanol solution as the mobile phase B for gradient elution;

[0045] S4: The external standard method was used to calculate the residual amount of pentafluoropentanethiol in the fulvestrant raw material.

[0046] The drug was weighed using a Sartorius Secura 225D-1CN electronic balance. Since the detection target was pentafluoropentanethiol, which is soluble in alcohols, and the sample matrix fulvestrant to be detected was soluble in methanol, methanol was selected as the diluent in this example.

[0047] Example 1: Preparation of solution

[0048] Blank solution (diluent): 100% methanol

[0049] Test solution: Weigh 100 mg of fulvestrant API as the test sample, accurately weigh it, place it in a 10 mL volumetric flask, add methanol to dissolve it, and dilute it to the scale line. Shake well to prepare a test solution with a concentration of 10 mg / mL.

[0050] Reference solution: Weigh 50 mg of pentafluoropentanethiol as a reference substance, dissolve it in methanol and dilute it to 50 mL to prepare a stock solution with a concentration of 1 mg / mL. Take 1 mL of the stock solution and dilute it to 10 mL with methanol to prepare a reference stock solution with a concentration of 0.1 mg / mL. Take 1 mL of the reference stock solution and dilute it to 10 mL with methanol to prepare a reference solution with a concentration of 0.01 mg / mL.

[0051] Linearity solution: Further dilute the reference substance stock solution with methanol to prepare a linearity solution.

[0052] Prepare the linear solutions according to Table 1 below:

[0053] Table 1: Linear solution configuration table

[0054]

[0055] Quantitation limit solution: directly take the linear solution with a concentration of 30% as the quantitation limit solution.

[0056] Detection limit solution: Take 0.4 mL of quantification limit solution and add 0.6 mL of methanol solution. Shake well to obtain the detection limit solution.

[0057] Spiking solution: The reference sample stock solution was further diluted with methanol to prepare the spiking solution.

[0058] Prepare the spiked solutions according to Table 2 below:

[0059] Table 2: Spiking solution configuration table

[0060]

[0061] Test Example 1: Gas Phase Automatic Sampling Detection

[0062] Considering that pentafluoropentanethiol is a typical small molecule compound with a relatively low boiling point and molecular weight, a gas chromatograph with FID detection and automatic sampling was used for detection. When using this detection method, although the system suitability, specificity, linearity and quantification limit tests were normal, the boiling point of the test substance fulvestrant was about 580°C, which is a high-boiling-point substance. In gas phase detection, the boiling point of the test substance cannot be higher than 400°C. Therefore, due to the interference of the high-boiling-point test substance, the baseline fluctuated greatly, and the repeatability and recovery rate could not meet expectations. Figure 1 shown.

[0063] Test Example 2: Gas Phase Headspace Sampling Detection

[0064] To avoid substandard recovery rates due to interference from high-boiling-point test samples, headspace injection was used for detection, considering that the boiling point of pentafluoropentanethiol is only 113°C. However, after injection, it was found that the peak of pentafluoropentanethiol fluctuated, not only was it impossible to reproduce, but the recovery rate was also extremely abnormal. After consulting relevant information and performing corresponding analysis, it was found that pentafluoropentanethiol, a thiol compound, is relatively active. When using headspace injection, it is easily adsorbed on the tubing of the headspace sampler, resulting in its detected peak area fluctuating and disproportionate. As shown in Figure 2, from top to bottom are the control solution, 50% test sample spiked solution, 100% test sample spiked solution, and 150% test sample spiked solution.

[0065] Test Example 3: Liquid Chromatography

[0066] The reference solution and the test solution were detected by liquid chromatography. The high performance liquid chromatograph used was Waters W2695, equipped with a diode array detector and a 100 μL autosampler. Acetonitrile was preferably used as the mobile phase of the liquid chromatograph because acetonitrile has lower back pressure and cutoff wavelength and stronger elution ability. However, when acetonitrile was used as the mobile phase to detect pentafluoropentanethiol, the detection effect was poor. Acetonitrile: methanol: phosphoric acid with a ratio of 700:300:1 was used as mobile phase B for testing. As a result, when a 1 mg / mL pentafluoropentanethiol solution was injected, the pentafluoropentanethiol peak was bifurcated, as shown in FIG. Figure 3 As shown, methanol is used as mobile phase B in this embodiment;

[0067] The test was conducted using an Agilent Poroshell 120EC C18 column, with a 0.1% phosphoric acid aqueous solution as mobile phase A. When the pentafluoropentanethiol reference solution was injected at a volume of 50 μL, the peak shape of the pentafluoropentanethiol peak was poor, with a tailing factor of only about 0.6. The poor tailing factor could not guarantee repeatability, and the response value of pentafluoropentanethiol was insufficient at injection volumes of 30 μL or less. Figure 4As shown in the figure, using 0.05% trifluoroacetic acid aqueous solution as mobile phase A, after injecting 1 mg / mL pentafluoropentanethiol, it was found that its tailing factor was about 0.78, which was still not good. In addition, the elution time of pentafluoropentanethiol on the Agilent Poroshell 120EC C18 column was too early, which may cause interference. Figure 5 As shown;

[0068] In this embodiment, a 0.1% trifluoroacetic acid aqueous solution was used as mobile phase A, and a Waters XterraMS C18 column was selected. After injecting 1 mg / mL pentafluoropentanethiol solution, the tailing factor was about 1.1, which is relatively ideal. Figure 6 shown.

[0069] Pentafluoropentanethiol was scanned at all wavelengths using diode array detection, and its optimal detection wavelength was determined to be around 200nm. Theoretically, a detector wavelength of 200nm is more appropriate, but because the mobile phase used is methanol and the mobile phase modifier is trifluoroacetic acid, both have UV cutoff wavelengths of 205nm. If the detector wavelength is set to 200nm, trace amounts of pentafluoropentanethiol will be affected by the mobile phase and will not be detected. Moreover, when the detector wavelength is lower than the mobile phase cutoff wavelength, the baseline noise will also be relatively large. To ensure the reliability of the method, while ensuring that the sensitivity meets the requirements, the final detection wavelength is selected as 210nm;

[0070] Considering that the mobile phase A used is a 0.1% trifluoroacetic acid aqueous solution with a pH of about 2.0, the pH range of ordinary octadecylsilane bonded high-purity silica gel chromatographic columns (C18 columns) is generally 2.0-8.0. This mobile phase pH value is close to or exceeds the service limit of ordinary high-purity silica gel chromatographic columns. If forced to use, it may cause hydrolysis of the chromatographic column bonded phase, thereby shortening the chromatographic column life and increasing the detection cost. Therefore, the preferred chromatographic column is an octadecylsilane chromatographic column (C18 column) using hybrid particles. It can tolerate mobile phases with a wide pH range and can adapt to the low pH mobile phase in the method. A more mature product on the market is selected: Waters' Xterra MS C18 4.6*250mm, 5μm high-performance liquid chromatography column. The chromatographic column is mature and easy to obtain, the experimental cost is low, the instrument structure is simple and mature, and it is easy to operate.

[0071] In summary, the detection conditions of liquid chromatography are shown in Table 3 below:

[0072] Table 3: Liquid chromatography detection conditions

[0073]

[0074] Example 2: System suitability testing

[0075] Step S3 was repeated to inject the reference solution 5 times and then reinject the reference solution once. The results are shown in Table 4 below:

[0076] Table 4: Test data of reference solution

[0077]

[0078] Example 3: Specificity detection

[0079] The blank solution methanol, the reference solution, the test solution and the test solution spiked were injected once each, and the retention time of pentafluoropentanethiol was detected. The results are shown in Table 5 below, and a chromatogram was obtained. Figures 7 to 10 As shown;

[0080] Table 5 Test data of blank solution, reference solution, test solution and spiked solution

[0081]

[0082]

[0083] Example 4: Linearity Detection

[0084] Each linear solution was injected once, and the test results are shown in Table 6 below, and a linear relationship diagram was obtained. Figure 11 As shown;

[0085] Table 6 Detection data of linear solution

[0086]

[0087] Example 5: Detection limit detection

[0088] The detection limit solution was injected once, and the results are shown in Table 7:

[0089] Table 7 Detection data of detection limit solution

[0090]

[0091] Example 6: Quantitation Limit Detection

[0092] The quantification limit solution was injected 6 times, and the results are shown in Table 8:

[0093] Table 8 Detection data of quantitative limit solution

[0094]

[0095]

[0096] Example 7: Accuracy detection

[0097] Each spiked solution was injected once, and the results are shown in Table 9:

[0098] Table 9 Test data of spiked solution

[0099]

[0100] Example 8: Repeatability detection

[0101] Each spiked solution was injected once (the 1st to 3rd spiked solutions were shared with the 100% accuracy solution). The results are shown in Table 10:

[0102] Table 10 Test data of spiked solution

[0103]

[0104] Example 9: Intermediate Precision Testing

[0105] Different people, at different times, using different instruments and different chromatographic columns, reconfigured the solutions and conducted the experiment: each spiked solution was injected once, and the obtained results were combined with the repeatability to calculate the RSD. The results are shown in Table 11:

[0106] Table 11 Detection data of spiked solution

[0107]

[0108]

[0109] Example 10: Solution stability test

[0110] The reference solution was injected at different time points, and the rate of change of the peak area of ​​pentafluoropentanethiol was calculated. The results are shown in Table 12:

[0111] Table 12 Test data of reference solution

[0112]

[0113] Example 11: Durability Testing

[0114] Adjust the chromatographic conditions as follows:

[0115]

[0116] Then, for each condition, a blank solution was injected until the system was equilibrated, the reference solution was injected five times, the test solution was injected once, the test solution spiked once, and the reference solution was injected back once at the end of the sequence. The results are shown in Table 13:

[0117] Table 13 Test data of blank solution, reference solution, test solution and spiked solution

[0118]

[0119] When the flow rate change test was performed at 0.9 mL / min, the average peak area of ​​pentafluoropentanethiol in the reference sample was 53162 after five injections, and the peak area of ​​pentafluoropentanethiol in the spiked solution of the test sample was 35861. The recovery rate was about 67.4%, which failed to meet the expected requirements. Figure 12 As shown. System suitability was checked. The RSD of the peak area of ​​the reference solution for five injections was 1.31%, which is normal. The peak area of ​​the back-injection was 52706, which is also normal, indicating that the system suitability meets the requirements. It was speculated that the flow rate change was too drastic, so the flow rate was adjusted from 0.9 mL / min to 0.95 mL / min. The durability flow rate change test was re-performed, and the test result passed, confirming the hypothesis. This shows that although the method can be reproducible within the tested flow rate range, it is still sensitive to flow rate changes and requires attention.

[0120] As shown in Tables 4-13, the detection method of the present invention has strong specificity, high sensitivity, good precision, excellent stability, and strong durability. It uses a single-point external standard method to calculate the residual amount of pentafluoropentanethiol in the test sample by the peak area ratio of the reference solution to the test solution, and can accurately detect the residual amount of pentafluoropentanethiol in the fulvestrant raw material. The calculation formula is as follows:

[0121]

[0122] Wherein, As represents the peak area of ​​pentafluoropentanethiol in the test solution; Ar represents the average peak area of ​​pentafluoropentanethiol in the reference solution after 5 injections; Cr represents the concentration of pentafluoropentanethiol in the reference solution, mg / mL; Cs represents the concentration of the sample in the test solution, mg / mL; P represents the purity of pentafluoropentanethiol, %.

[0123] The present invention uses octadecylsilane bonded hybrid silica gel particles as a stationary phase. The chromatographic column is mature and easily available, with low experimental cost. It can tolerate mobile phases in a wide pH range and is adaptable to low pH mobile phases. Hydrolysis of the bonded phase of the chromatographic column under acidic conditions is avoided, thereby extending the life of the chromatographic column. Trifluoroacetic acid aqueous solution is used as mobile phase A to inhibit thiol group dissociation and enhance reverse phase retention. As an ion pair reagent, it improves peak shape and solves the problem of tailing of polar substances. Methanol solution is used as mobile phase B to reduce the elution intensity of the organic phase, extend the retention time of pentafluoropentanethiol, and avoid overlap with solvent peaks. Through the synergistic effect of methanol and trifluoroacetic acid, effective retention and trace detection of highly polar fluorinated compounds are achieved. Moreover, the methanol and trifluoroacetic acid aqueous solution system is simple to operate and has low preparation difficulty. The method has strong properties, high sensitivity, and good repeatability, and can accurately and quickly determine the residual amount of pentafluoropentanethiol in the fulvestrant raw material drug. The invention discloses a gradient elution procedure; it has been verified that the concentration range of pentafluoropentanethiol in the method is 3.2 μg / mL-21.3 μg / mL, the linear correlation coefficient R is 0.9992, and the linearity is good; the detection limit of pentafluoropentanethiol is 1.28 μg / mL, and the sensitivity is high; the RSD of the spiked recovery rate of 6 parallel measurements of samples is 1.70%, and the RSD of the spiked recovery rate of 12 samples is 2.64%, and the repeatability is good.

[0124] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the residual amount of pentafluoropentanethiol in fulvestrant raw materials by liquid chromatography, characterized in that: The following steps are involved: Weigh pentafluoropentanethiol and dilute it with diluent to prepare a reference solution; Weigh the fulvestrant bulk drug substance and dilute it with the diluent to prepare the test solution; The test solution and the reference solution were detected by liquid chromatography. The liquid chromatography detection conditions were as follows: the chromatographic column used octadecylsilane bonded hybrid silica gel particles as the stationary phase, trifluoroacetic acid aqueous solution as the mobile phase A, and methanol solution as the mobile phase B for gradient elution; The external standard method was used to calculate the residual amount of pentafluoropentanethiol in the fulvestrant raw material.

2. The method for determining the residual amount of pentafluoropentanethiol in the fulvestrant bulk drug by liquid chromatography according to claim 1, characterized in that: The chromatographic column used was a Waters Xterra MS C18 column with a specification of 4.6 mm*250 mm and 5 μm.

3. The method for determining the residual amount of pentafluoropentanethiol in the fulvestrant bulk drug by liquid chromatography according to claim 1 or 2, characterized in that: The column temperature of the chromatographic column is 28° C. to 35° C., the injection volume is 50 μL, and the flow rate is 0.95 to 1.1 mL / min.

4. The method for determining the residual amount of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography according to claim 1, characterized in that: The detection was performed using a high performance liquid chromatograph equipped with an ultraviolet detector at a detection wavelength of 210 nm.

5. The method for determining the residual amount of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography according to claim 1, characterized in that: The diluent is methanol.

6. The method for determining the residual amount of pentafluoropentanethiol in the fulvestrant bulk drug by liquid chromatography according to claim 5, characterized in that: Weigh 100 mg of fulvestrant API, dissolve it in methanol and dilute it to 10 mL to prepare a test solution with a concentration of 10 mg / mL.

7. The method for determining the residual amount of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography according to claim 5, characterized in that: Weigh 50 mg of pentafluoropentanethiol, dissolve it in methanol and dilute it in sequence to prepare a 1 mg / mL stock solution, a 0.1 mg / mL reference substance stock solution and a 0.01 mg / mL reference substance solution.

8. The method for determining the residual amount of pentafluoropentanethiol in the fulvestrant bulk drug by liquid chromatography according to claim 7, characterized in that: The reference substance stock solution was further diluted with methanol to prepare a linear solution with a concentration of 30% to 200%; the linear solution with a concentration of 30% was taken as the quantification limit solution; 0.4 mL of the quantification limit solution was added to 0.6 mL of methanol solution to prepare the detection limit solution; the reference substance stock solution was further diluted with methanol to prepare a spiked solution with a concentration of 80% to 150%.

9. The method for determining the residual amount of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography according to claim 1, characterized in that: The mobile phase A is a trifluoroacetic acid aqueous solution with a concentration of 0.1%, and the mobile phase B is a methanol solution with a concentration of 100%.

10. The method for determining the residual amount of pentafluoropentanethiol in fulvestrant bulk drug by liquid chromatography according to claim 1 or 9, characterized in that: The conditions of the gradient elution are: The first gradient elution time was 0 min, with mobile phase A accounting for 80% and mobile phase B accounting for 20%; The second gradient elution time was 20 min, with mobile phase A accounting for 20% and mobile phase B accounting for 80%; The first gradient elution time was 40 min, with mobile phase A accounting for 0% and mobile phase B accounting for 100%; The first gradient elution time was 41 min, with mobile phase A accounting for 80% and mobile phase B accounting for 20%; The first gradient elution time was 50 min, with mobile phase A accounting for 80% and mobile phase B accounting for 20%.

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