A method for optimizing tablet dissolution profile and in vivo bioequivalence
By optimizing the formulation and dissolution detection method of indobufen tablets, the problem of inconsistent dissolution curves was solved, achieving similar dissolution of the drug in different media and consistency of in vivo efficacy, thus improving the accuracy and comparability of test results.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- BEIJING SUN-NOVO PHARM RES CO LTD
- Filing Date
- 2024-12-30
- Publication Date
- 2026-06-30
AI Technical Summary
In the existing technology, the dissolution detection methods for indobufen tablets vary, and different types of lactose and microcrystalline cellulose on the market affect the dissolution process, resulting in inconsistent dissolution curve results. There is a lack of unified or standardized dissolution curve standards, which affects the consistency of drug quality control and clinical efficacy.
The formulation of indobufen tablets was optimized by selecting lactose with a median particle size of 38–60 μm and a bulk density of 0.55–0.68 g/ml, and microcrystalline cellulose with a median particle size of 20–40 μm and a bulk density of 0.30–0.40 g/ml. The basket dissolution method was adopted, and the dissolution medium was controlled at a temperature of 37±1℃, a pH of 4.5–7.6, and a rotation speed of 75–100 rpm. A standardized dissolution curve detection method was established by combining UV detection.
This study achieved similarity in the dissolution curves of indobufen tablets in different media, ensuring the consistency of the drug's in vivo efficacy and improving the accuracy and comparability of test results.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of pharmaceutical formulation analysis technology, and particularly relates to a method for optimizing tablet dissolution profiles and in vivo bioequivalence. Background Technology
[0002] Indobufen is a racemic mixture developed by Farmitalia Carlo Erba Pharmacia (acquired by Pfizer) in 1970. It is an antiplatelet drug and was first launched in Italy in August 1984. It is available in tablet form, 0.2g in strength, and marketed under the brand name IBUSTRIN. It is used to prevent coronary artery bypass graft occlusion after transplantation and to treat intermittent claudication caused by peripheral arterial occlusive disease.
[0003] Although the standard dissolution testing conditions for indobufen tablets refer to the first method (basket method) in the new drug approval standard, existing technologies employ various dissolution testing methods. For example, patent CN117919230A discloses an indobufen drug composition and its preparation method, which uses the first method (basket method) of "0931 Dissolution and Release Determination Method" in the General Chapter IV of the 2020 edition of the Chinese Pharmacopoeia and the standards issued by the State Pharmacopoeia Bureau to determine dissolution. CN118340732A discloses an indobufen tablet composition, its preparation method, and its application, which uses the dissolution method of the General Chapter IV of the 2020 edition of the Chinese Pharmacopoeia: the slurry method. CN107281149B discloses an indobufen drug composition and its quality control method, which uses the second method (slurry method) of Section "0931 Dissolution and Release Determination Method" in the General Chapter IV of the 2015 edition of the Chinese Pharmacopoeia to determine dissolution.
[0004] Meanwhile, the inventors discovered that different types of lactose and microcrystalline cellulose available commercially can significantly affect the disintegration state of indobufen tablets during dissolution, thus impacting dissolution profile results and bioequivalence. Furthermore, no unified or standardized dissolution profile standard has been established for this formulation, with each company developing its own testing methods based on its specific needs. Therefore, to ensure consistent drug quality control and clinical efficacy, there is an urgent need for systematic optimization and standardization of the dissolution profile of indobufen tablets. This will help improve the accuracy and comparability of test results, further promoting the research and clinical application of this type of drug. Summary of the Invention
[0005] In view of this, the present invention aims to develop a method for optimizing the dissolution profile and in vivo bioequivalence of indobufen tablets, so as to provide a reference for the standardization and normalization of the dissolution profile of indobufen tablets.
[0006] To achieve the above technical objectives, the present invention adopts the following technical solution: A method for optimizing the dissolution curve and in vivo bioequivalence of indobufen tablets, wherein the indobufen tablets comprise, by weight, 180-220 parts indobufen, 200-250 parts lactose, 40-60 parts microcrystalline cellulose, 10-20 parts povidone, 20-40 parts sodium carboxymethyl starch, 1-10 parts sodium dodecyl sulfate, and 1-10 parts magnesium stearate; preferably, indobufen 1 90-210 parts, lactose 200-220 parts, microcrystalline cellulose 50-60 parts, povidone 10-20 parts, sodium carboxymethyl starch 20-35 parts, sodium dodecyl sulfate 3-8 parts, magnesium stearate 3-8 parts; more preferably, indobufen 200 parts, lactose 200-220 parts, microcrystalline cellulose 50-60 parts, povidone 10-20 parts, sodium carboxymethyl starch 30-35 parts, sodium dodecyl sulfate 5-8 parts, magnesium stearate 5-8 parts.
[0007] The median particle size of the lactose is 38–60 μm, for example, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm, 46 μm, 47 μm, 48 μm, 49 μm, 50 μm, 51 μm, 52 μm, 53 μm, 54 μm, 55 μm, 56 μm, 57 μm, 58 μm, 59 μm or 60 μm, but is not limited to the listed values; other unlisted values within this range are also applicable. The bulk density is 0.55 to 0.68 g / ml, for example 0.55 g / ml, 0.56 g / ml, 0.57 g / ml, 0.58 g / ml, 0.59 g / ml, 0.60 g / ml, 0.61 g / ml, 0.62 g / ml, 0.63 g / ml, 0.64 g / ml, 0.65 g / ml, 0.66 g / ml, 0.67 g / ml or 0.68 g / ml, but is not limited to the listed values; other unlisted values within this range also apply.
[0008] Basket dissolution is used, and the controlled conditions include: a temperature of 37±1℃, a pH of 4.5 to 7.6 in the dissolution medium, and purified water. The pH of the dissolution medium can be pH 4.5, pH 5, pH 6, pH 6.4, pH 6.8, pH 7.2, pH 7.5, or pH 7.6, but is not limited to the listed values. Other unlisted values within this range are also applicable.
[0009] The speed range is 75 to 100 rpm, such as 75 rpm, 80 rpm, 85 rpm, 90 rpm, 95 rpm or 100 rpm, but is not limited to the listed values. Other unlisted values within this range also apply.
[0010] Further, the median particle size of the microcrystalline cellulose is 20–100 μm, and the bulk density is 0.20–0.40 g / ml, preferably 20–40 μm, and the bulk density is 0.30–0.40 g / ml. The median particle size of the microcrystalline cellulose can be 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, or 40 μm, but is not limited to the listed values; other unlisted values within this range are also applicable.
[0011] The bulk density of the microcrystalline cellulose may be 0.30 g / ml, 0.31 g / ml, 0.32 g / ml, 0.33 g / ml, 0.34 g / ml, 0.35 g / ml, 0.36 g / ml, 0.37 g / ml, 0.38 g / ml, 0.39 g / ml or 0.40 g / ml, but is not limited to the listed values. Other unlisted values within this range are also applicable.
[0012] Furthermore, the basket dissolution process includes: placing one indobufen tablet into 1000 mL of dissolution medium, and then taking samples at fixed points for UV detection. The "UV detection" mentioned in this invention refers to ultraviolet-visible spectrophotometry, a method for measuring the absorbance of substances in the wavelength range of 190–800 nm, used for identification, impurity inspection, and quantitative determination.
[0013] Furthermore, the fixed-point sampling time points are 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, and 60 min.
[0014] Furthermore, the dissolution medium is selected from one of purified water, an acidic solution with pH 4.5, a weakly acidic solution with pH 6.4 and pH 7.6.
[0015] Furthermore, the acidic solution with pH 4.5 includes acetate buffer, phosphate buffer, or citrate buffer.
[0016] Furthermore, the weakly acidic solutions with pH 6.4 and pH 7.6 include acetate buffer, phosphate buffer, or citrate buffer.
[0017] Furthermore, the weakly acidic solutions at pH 6.4 and pH 7.6 are phosphate buffer solutions at pH 6.4 and pH 7.6.
[0018] Furthermore, the rotational speed is 75 rpm or 100 rpm.
[0019] Furthermore, the rotational speed is 75 rpm.
[0020] This invention selects lactose with a median particle size of 38–60 μm and a bulk density of 0.55–0.68 g / ml, and microcrystalline cellulose with a median particle size of 20–40 μm and a bulk density of 0.30–0.40 g / ml as excipients. Combined with an optimized dissolution detection method, it can ensure that the dissolution curves of the self-made sample and the reference preparation are similar in multiple media, and ensure that the in vivo efficacy is consistent with that of the reference preparation. Attached Figure Description
[0021] Figure 1 This is a comparison of the dissolution curves of the reference formulation at 75 rpm in different media.
[0022] Figure 2 This is a comparison of the dissolution curves of the reference formulation at 100 rpm in different media.
[0023] Figure 3 A comparison of dissolution curves at 75 rpm for lactose type testing.
[0024] Figure 4 A comparison of dissolution curves at 100 rpm for lactose grades.
[0025] Figure 5 A comparison of dissolution curves at 75 rpm for different types of microcrystalline cellulose.
[0026] Figure 6 A comparison of dissolution curves at 100 rpm for different types of microcrystalline cellulose.
[0027] Figure 7 This is a comparison of the dissolution curves of the self-made sample T3 in three media. Detailed Implementation
[0028] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.
[0029] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.
[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.
[0031] Table 1 Sample Specification Information
[0032]
[0033] Example 1: Composition and preparation method of indobufen tablets:
[0034] Indobufen tablets are oral solid dosage forms. This product is a plain tablet. The active ingredient in the formulation is indobufen, and the excipients are lactose, microcrystalline cellulose, sodium carboxymethyl starch, povidone, sodium lauryl sulfate, and magnesium stearate. The composition of the unit dosage form, the role of each component in the formulation, and the implementation standards are shown in Table 2.
[0035] Table 2. Formulation of Indobufen Tablet Unit Dosage
[0036] Element Dosage (mg) effect Implementation Standards Indobufen 200 Active ingredients Enterprise Internal Control Standards lactose 210.2 filler Enterprise Internal Control Standards microcrystalline cellulose 52.6 filler Enterprise Internal Control Standards Povidone 15.6 adhesives Enterprise Internal Control Standards Sodium carboxymethyl starch 31.2 Disintegrant Enterprise Internal Control Standards Purified water 140 wetting agent ChP 2020 Edition, Part Two Sodium dodecyl sulfate 5.2 Cosolvent Enterprise Internal Control Standards magnesium stearate 5.2 lubricant Enterprise Internal Control Standards
[0037] The preparation method of indobufen tablets is shown in Table 3:
[0038] Table 3 Preparation methods
[0039]
[0040] Example 2 Selection of dissolution method for reference formulation
[0041] The dissolution methods for indobufen tablets, as published in the standards for the approval of new drugs, are shown in Table 4.
[0042] Table 4. Dissolution conditions for indobufen tablets as published in the standards for new drug approval.
[0043]
[0044]
[0045] Based on Table 4, the dissolution of the reference formulation in purified water, pH 4.5 medium (pH 4.5 acetate buffer), pH 6.4 medium (pH 6.4 phosphate buffer), and pH 7.6 medium (pH 7.6 phosphate buffer) was further investigated. Data at 75 rpm and 100 rpm under basket method conditions were compared, and summarized in Tables 5-6, and refer to [reference needed]. Figures 1-2 :
[0046] Table 5 Dissolution curves of the reference formulation at 75 rpm in different media.
[0047]
[0048] Table 6 Dissolution curves of the reference formulation at 100 rpm in different media.
[0049]
[0050]
[0051] According to Tables 5-6 and Figures 1-2 The results show that: at 75 rpm, complete dissolution was not achieved in purified water and pH 4.5 medium; dissolution exceeded 85% in pH 7.6 medium after 10 minutes, indicating extremely rapid dissolution; and the dissolution curve in pH 6.4 medium was flatter and more discriminative. At 100 rpm, complete dissolution was still not achieved in purified water and pH 4.5 medium; dissolution exceeded 85% in pH 6.4 medium after 15 minutes, indicating extremely rapid dissolution; and dissolution exceeded 85% in pH 7.6 medium after 10 minutes, also indicating extremely rapid dissolution. In summary, using the basket method at 75 rpm and 100 rpm, and using purified water, pH 4.5 acetate buffer, pH 6.4 phosphate buffer, and pH 7.6 phosphate buffer for reference formulation dissolution curve testing is feasible, with pH 6.4 phosphate buffer showing better results.
[0052] Example 3
[0053] Three batches of indobufen tablets, T1, T2, and T3, were prepared according to the composition and method of Example 1. The lactose type was investigated; the lactose type and formulation information are shown in Table 7, and the particle size analysis results for different lactose types are shown in Table 8.
[0054] Table 7 Summary of prescriptions for lactose type investigation
[0055]
[0056] The data unit is mg.
[0057] Table 8 Summary of Lactose Granule Type Investigation Results
[0058]
[0059]
[0060] Note: The intelligent powder property tester manufactured by Dandong Better Instruments Co., Ltd., model BT-1001, was used to test the angle of repose, tapped density, loose packing density, and particle size distribution in automatic mode.
[0061] Three types of lactose were dissolved at 75 rpm and 100 rpm in a pH 6.4 phosphate buffer solution, and in vitro dissolution curves were studied. The results are shown in Tables 9 and 10. Figures 3-4 As shown.
[0062] Table 9. Results of Lactose Type Evaluation at 75 rpm Dissolution Curve
[0063]
[0064] Note: When f2 ≥ 50, it indicates that the dissolution curves are similar. The larger the f2, the better.
[0065] Table 10 Results of Lactose Type Dissolution Curves at 100 rpm
[0066]
[0067] Note: When the dissolution rate of both the reference (R) and the self-made (T) is >85% after 15 min, there is no need to calculate f2, and the dissolution curves are directly determined to be similar.
[0068] Through Tables 9-10 and Figures 3-4 The results show that the ability to distinguish lactose types varies at different speeds, with the strongest differentiation at 75 rpm and no differentiation at 100 rpm.
[0069] Example 4
[0070] Nine batches of indobufen tablets (T3 to T11) were prepared according to the composition and method of Example 1. The microcrystalline cellulose type was investigated; the microcrystalline cellulose type and formulation information are shown in Table 11, and the particle size analysis results for different microcrystalline celluloses are shown in Table 12.
[0071] Table 11 Summary of Microcrystalline Cellulose Types and Formulas
[0072]
[0073] The data unit is mg.
[0074] Table 12 Summary of the Investigation Results of Microcrystalline Cellulose Particle Sizes
[0075]
[0076] Note: The intelligent powder property tester manufactured by Dandong Better Instruments Co., Ltd., model BT-1001, was used to test the angle of repose, tapped density, loose packing density, and particle size distribution in automatic mode.
[0077] Nine types of microcrystalline cellulose were subjected to in vitro dissolution curve studies at 75 rpm and 100 rpm in a pH 6.4 phosphate buffer solution. The results are shown in Tables 13-14. Figures 5-6 As shown.
[0078] Table 13 Results of Dissolution Curves of Microcrystalline Cellulose Types at 75 rpm
[0079]
[0080] Note: When f2 ≥ 50, it indicates that the dissolution curves are similar. The larger the f2, the better. n = 5.
[0081] Table 14 Results of Dissolution Curves of Microcrystalline Cellulose Types at 100 rpm
[0082]
[0083] Note: When the dissolution rate of both the reference (R) and the self-made (T) solution is >85% at 15 min, there is no need to calculate f2; the dissolution curves are directly determined to be similar. A f2 ≥ 50 indicates similar dissolution curves. A larger f2 is better. n = 5.
[0084] Through Tables 13-14 and Figures 5-6 The results show that the ability to distinguish lactose types varies at different speeds, with the strongest differentiation at 75 rpm and no differentiation at 100 rpm.
[0085] Table 15 further compares the dissolution results of the T3 self-made sample and the reference preparation in three media: purified water, pH 4.5 acetate buffer, and pH 7.6 phosphate buffer, and combines them with... Figure 7 As shown.
[0086] Table 15 shows the dissolution curves of the self-made T3 sample in three media.
[0087]
[0088]
[0089] Note: When f2 ≥ 50, it indicates that the dissolution curves are similar. The larger the f2, the better. When the dissolution rate of both the reference (R) and the self-made (T) is > 85% after 15 min, there is no need to calculate f2, and the dissolution curves are directly determined to be similar.
[0090] It is evident that the dissolution profiles of the T3 sample and the reference formulation are very similar in the three media at 75 rpm.
[0091] Example 5 Bioequivalence Study
[0092] T3 sample was selected for a pharmacokinetic endpoint bioequivalence study. Ten subjects were enrolled in both fasting and postprandial settings. A single-center, randomized, open-label, single-dose, two-sequence, two-period, crossover trial design was used. The final results showed that T3 sample and R met the in vivo bioequivalence (C). max With AUC last A 90% confidence interval satisfying 80.00% to 125.00% is sufficient to prove equivalence.
[0093] Table 14 Results of the bioequivalence study of T3 and R fasting
[0094]
[0095] Table 15 Results of the T3 vs. R postprandial bioequivalence study
[0096]
[0097] In summary, through the series of studies conducted in this invention, the following conclusions can be drawn:
[0098] (1) Using 125M lactose, the T1 sample has many particles of 425-1000μm, small angle of repose, and good fluidity. In pH 6.4 medium, the dissolution curves are similar to those of the reference preparation at 75rpm and 100rpm.
[0099] (2) The T2 sample using 150M lactose has more particles of 150-250μm, a larger angle of repose, and slightly poorer fluidity. In pH 6.4 medium, the dissolution curves at 75rpm and 100rpm are similar to those of the reference preparation.
[0100] (3) The T4 sample using PH101 microcrystalline cellulose has more particles of 45-75μm, a larger angle of repose, and slightly poorer flowability. In pH 6.4 medium at 100rpm, the dissolution curve is similar to that of the reference preparation. In pH 6.4 medium at 75rpm, f2 < 50 does not meet the requirement that the dissolution curve is similar to that of the reference preparation.
[0101] (4) The T5 sample using PH102 microcrystalline cellulose has a large number of particles of 45-75μm, a small angle of repose, and good flowability. In pH 6.4 medium at 100rpm, the dissolution curve is similar to that of the reference preparation. In pH 6.4 medium at 75rpm, f2 is less than 50, which does not meet the requirement that the dissolution curve is similar to that of the reference preparation.
[0102] (5) The T6 sample using PH200 microcrystalline cellulose has more particles of 45-75μm, a larger angle of repose, and slightly poorer flowability. In pH6.4 medium, under conditions of 75rpm and 100rpm, f2 is less than 50, which does not meet the dissolution curve requirements similar to the reference preparation.
[0103] (6) Use The T7 sample of 101 microcrystalline cellulose has a large number of particles of 150-250 μm, a small angle of repose, and good flowability. In pH 6.4 medium, under conditions of 75 rpm and 100 rpm, f2 < 50, which does not meet the dissolution curve requirements and is similar to the reference formulation.
[0104] (7) Use The T8 sample of 102 microcrystalline cellulose had many particles in the 0-45 μm range, a large angle of repose, and slightly poor flowability. In pH 6.4 medium, under conditions of 75 rpm and 100 rpm, f2 was less than 50, which did not meet the dissolution curve requirements similar to the reference formulation.
[0105] (8) Use The T9 sample of 25 microcrystalline cellulose had many particles of 45-75 μm, a large angle of repose, and slightly poor flowability. In pH 6.4 medium, under conditions of 75 rpm and 100 rpm, f2 was less than 50, which did not meet the dissolution curve requirements similar to the reference formulation.
[0106] (9) Use The T10 sample of 50 microcrystalline cellulose had many particles of 45-75 μm, a large angle of repose, and slightly poor flowability. In pH 6.4 medium, under conditions of 75 rpm and 100 rpm, f2 was less than 50, which did not meet the dissolution curve requirements similar to the reference formulation.
[0107] (10) Use The T11 sample of 200 microcrystalline cellulose had many particles of 45-75 μm, a large angle of repose, and slightly poor flowability. In pH 6.4 medium, under conditions of 75 rpm and 100 rpm, f2 was less than 50, which did not meet the dissolution curve requirements similar to the reference formulation.
[0108] (11) Use 200M lactose and The T3 sample of 105 microcrystalline cellulose had numerous particles in the 0–45 μm range, a large angle of repose, and poor flowability. Its dissolution profiles at 75 rpm and 100 rpm in pH 6.4 medium were similar to the reference formulation. Furthermore, its dissolution profiles at 75 rpm in purified water, pH 4.5, and pH 7.6 mediums were also similar to the reference formulation.
[0109] (12) 200M lactose and The T3 sample of 105 microcrystalline cellulose was finally compared with the reference formulation in an in vivo bioequivalence study. The results showed that it was equivalent and met the requirements for consistent in vivo efficacy.
[0110] Therefore, indobufen tablets can be made from lactose with a median particle size of 38–60 μm and a bulk density of 0.55–0.68 g / mL, preferably lactose with a median particle size of 38 μm and a bulk density of 0.55 g / mL; and microcrystalline cellulose with a median particle size of 20–40 μm and a bulk density of 0.30–0.40 g / mL. By employing specific dissolution detection methods, the dissolution curves of the self-made sample and the reference formulation can be similar in multiple media, and the in vivo efficacy of the self-made sample can be guaranteed to be consistent with that of the reference formulation.
[0111] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.
Claims
1. A method for determining the dissolution profile and in vivo bioequivalence of a tablet, wherein the tablet comprises, by weight, 180-220 parts indobufen, 200-250 parts lactose, 40-60 parts microcrystalline cellulose, 10-20 parts povidone, 20-40 parts sodium carboxymethyl starch, 1-10 parts sodium dodecyl sulfate, and 1-10 parts magnesium stearate; characterized in that... The lactose has a median particle size of 38–60 μm and a bulk density of 0.55–0.68 g / ml; it is dissolved using a basket dissolution method, with controlled conditions including: a temperature of 37±1℃, a pH of 4.5–7.6 in the dissolution medium and purified water, and a rotation speed of 75–100 rpm.
2. The method according to claim 1, characterized in that, The microcrystalline cellulose has a median particle size of 20–100 μm and a bulk density of 0.20–0.40 g / ml, preferably a median particle size of 20–40 μm and a bulk density of 0.30–0.40 g / ml.
3. The method according to claim 2, characterized in that, The basket dissolution process includes: placing one indobufen tablet into 1000 mL of dissolution medium, and then taking samples at fixed points for UV detection.
4. The method according to claim 3, characterized in that, The fixed-point sampling time points are 5 min, 10 min, 15 min, 20 min, 30 min, 45 min, and 60 min.
5. The method according to claim 1, characterized in that, The dissolution medium is selected from one of purified water, an acidic solution with pH 4.5, a weakly acidic solution with pH 6.4 and pH 7.
6.
6. The method according to claim 5, characterized in that, The acidic solution with pH 4.5 includes acetate buffer, phosphate buffer, or citrate buffer.
7. The method according to claim 6, characterized in that, The weakly acidic solutions with pH 6.4 and pH 7.6 include acetate buffer, phosphate buffer, or citrate buffer.
8. The method according to claim 6, characterized in that, The weakly acidic solutions with pH 6.4 and pH 7.6 are pH 6.4 and pH 7.6 phosphate buffer solutions.
9. The method according to any one of claims 1 to 8, characterized in that, The rotational speed is 75 rpm or 100 rpm.
10. The method according to claim 9, characterized in that, The rotational speed is 75 rpm.