Method for measuring substituent group content in cellulose ether by using nuclear magnetic resonance technology

Abstract

The invention discloses a method for measuring substituent group content in cellulose ether by using a nuclear magnetic resonance technology. The invention provides a method for determining the substituent group content in cellulose ether, which comprises the following steps: carrying out hydrolysis reaction on cellulose ether and deuterated acid, and mixing with heavy water to obtain a test sample; carrying out 1HNMR detection on the test sample; carrying out 1HNMR detection to obtain the substitution degree of a substituent group to be detected; and calculating the content of substituent groups according to a formula W substituent group = mA / mB. The method provided by the invention is simple to operate, quick, efficient, good in reproducibility and strong in universality, does not need a reference substance and an internal standard substance, and is good in flexibility, low in cost and more environment-friendly compared with a traditional method.

Description

Technical Field

[0001] The invention relates to a method for determining the substituent content in cellulose ether by utilizing nuclear magnetic resonance technology. Background Art

[0002] Cellulose ether is a high-molecular compound with an ether structure made from cellulose. In the pharmaceutical field, cellulose ether is an important pharmaceutical excipient. The degree of substitution of cellulose ether is significantly correlated with its functional properties. It is widely used in the fields of tablet coating, suspending agents, plant capsules, sustained-release preparations, etc.

[0003] The 2020 edition of the Chinese Pharmacopoeia, Part IV, General Chapter 0712, Methods for Determination of Methoxy, Ethoxy, and Hydroxypropoxy Groups, includes gas chromatography and volumetric methods for determining the degree of substitution in cellulose ethers. Both methods require derivatization pretreatment, which is complex and tedious. Furthermore, derivatization reactions can be prone to incomplete reactions or side reactions, leading to uncertainty in test results. Furthermore, the volumetric method is limited to methoxy and hydroxypropoxy groups, making it less universally applicable.

[0004] The quantitative nuclear magnetic resonance method (QNMR) in the 2020 edition of the Chinese Pharmacopoeia, 0441, has the advantages of rapid and accurate analysis, strong specificity, simple operation, and good repeatability. It has been well applied in the test of the degree of substitution of cellulose ethers and has development potential. Low molecular weight and low viscosity cellulose ethers are dissolved in traditional NMR solvents (such as DMSO-d6, CDCl3, D2O, CD3OD) and then quickly tested for the degree of substitution, such as the ethyl cellulose CDCl3 solvent system. In addition, scientists have developed a variety of new solvent systems, such as alkali / urea aqueous solution systems, to quickly dissolve cellulose at low temperatures and test the degree of substitution.

[0005] However, cellulose ether compounds have a wide molecular weight distribution, and different grades exhibit significant variations in solubility and functional viscosity. For example, hydropropyl methylcellulose K100M PH DC1 has a molecular weight of 1,000,000 and a viscosity of 140,000 mPa·s, while K100LV PH PRM2 has a molecular weight of 164,000 and a viscosity of only 100 mPa·s. The difficulty in selecting NMR solvents for high-viscosity cellulose ethers limits their practical applications. Summary of the Invention

[0006] The present invention aims to overcome the shortcomings of existing techniques for testing high-viscosity cellulose ethers, such as the limited availability and generalizability of existing methods. The method provides a method for determining the substituent content in cellulose ethers using nuclear magnetic resonance technology. This method is simple, rapid, efficient, reproducible, and universally applicable. It requires no reference substances or internal standards, offering greater flexibility, lower cost, and improved environmental friendliness compared to traditional methods.

[0007] The present invention solves the above technical problems through the following technical solutions.

[0008] The present invention provides a method for determining the substituent content in cellulose ether, comprising the following steps:

[0009] The cellulose ether is hydrolyzed with a deuterated acid and then mixed with heavy water to obtain a test sample;

[0010] The test product will be 1 HNMR detection; passed 1 The degree of substitution of the substituent to be tested is obtained by HNMR detection; the content of the substituent to be tested is calculated by the following formula:

[0011]

[0012] Among them, m A is the relative mass of the substituent to be measured; m B It is the sum of the relative masses of the anhydrous glucose group and all the substituent groups to be measured; the degree of substitution is the molar ratio of the substituent group to be measured to the anhydrous glucose group.

[0013] In some embodiments, the cellulose ether is a high-viscosity or low-viscosity cellulose ether, such as hypromellose, hydroxyethyl cellulose, hydroxypropyl cellulose, or hypromellose phthalate, preferably hypromellose.

[0014] In some embodiments, the cellulose ether has a viscosity of 80-300000 mPa.s, for example, a viscosity (mPa.s) of 2700-5040, 7500-14000, 80-120, 200-300, 562-1050, 1125-2100, 2700-5040, 13500-25200, 26250-49000, 75000-140000, 150000-280000, 2700-5040, 13500-25200, or 75000-140000.

[0015] In some embodiments, the viscosity of the hypromellose is 414 mPa·s.

[0016] In some embodiments, the weight average molecular weight of the cellulose ether is 100,000-1,200,000.

[0017] In some embodiments, in the test sample, the mass volume ratio of the cellulose ether to the test sample is 10 mg / mL-50 mg / mL, preferably 10 mg / mL-38 mg / mL.

[0018] In some embodiments, in the cellulose ether, the substituent to be detected is, for example, a methoxy group, a hydroxypropoxy group, a hydroxyethyl group, a hydroxypropyl group, or a phthaloyl group.

[0019] In some embodiments, the deuterated acid is deuterated sulfuric acid, deuterated hydrochloric acid, or deuterated perchloric acid, preferably deuterated sulfuric acid.

[0020] In some embodiments, the deuterated acid is used in the form of a deuterated acid deuterated aqueous solution, wherein the concentration of the deuterated acid is 10%-30%, preferably 20%-30%, most preferably 20%, where the percentage is the mass percentage of the deuterated acid in the deuterated acid deuterated aqueous solution.

[0021] In some embodiments, the mass volume ratio of the cellulose ether to the deuterated acid heavy aqueous solution is 50 mg / mL-150 mg / mL.

[0022] In some embodiments, the reaction temperature of the hydrolysis reaction is 45°C-50°C, preferably 50°C.

[0023] In some embodiments, the hydrolysis reaction is heated in a water bath.

[0024] In some embodiments, the reaction time of the hydrolysis reaction is 20 min-40 min.

[0025] In some embodiments, the heavy water mixing step produces a solution; preferably, the volume ratio of the heavy water to the deuterated acid heavy water solution is (2-5):1, preferably 3:1.

[0026] In some embodiments, the amount of the deuterated acid heavy aqueous solution is 100 μL-300 μL, preferably 200 μL.

[0027] In some embodiments, the sampling amount of the cellulose ether is 1-50 mg, preferably 10-30 mg.

[0028] In some embodiments, the determination method comprises the following steps: mixing cellulose ether with 20% deuterated sulfuric acid heavy water solution, heating in a 50°C water bath for 20-40 minutes, adding heavy water solution to mix into a clear and transparent solution, and transferring to a nuclear magnetic resonance tube for determination.

[0029] In some embodiments, the 1 The hydrogen spectrum detected by HNMR does not produce any miscellaneous peaks between 5 and 6 ppm.

[0030] In some embodiments, the 1 HNMR detection was performed using a 600 MHz nuclear magnetic resonance spectrometer.

[0031] In some embodiments, the 1The HNMR test was carried out using the zg30 pulse sequence at a probe temperature of 298K.

[0032] In some embodiments, the 1 The key instrument parameters for HNMR testing meet one or more of the following conditions:

[0033] (1) RF center O1P: 6.2ppm;

[0034] (2) Spectral width SWH: 19.8ppm;

[0035] (3) Relaxation delay time D1: 5-60s, for example, 10s;

[0036] (4) Sampling time AQ: 2.75s;

[0037] (5) Gain RG: 9.8;

[0038] (6) Number of sampling points TD: 64k;

[0039] (7) Sampling number NS ≥ 128, for example 256;

[0040] (8) Number of empty sweeps DS: 2;

[0041] (9) The test time is 50 minutes.

[0042] In some embodiments, when the cellulose ether is hypromellose, the content of each substituent therein is calculated by the following formula:

[0043]

[0044] Wherein, DS is the degree of substitution of each substituent in the hypromellose, and its calculation formula is as follows:

[0045]

[0046]

[0047] Wherein, I1 is the integral of H at position 1 in the hydrogen spectrum of Formula I, I2 is the integral of H at positions 2-9 in the hydrogen spectrum of Formula I, I3 is the integral of H at position 10 in the hydrogen spectrum of Formula I, A2 is the number of protons in the methyl group, and A3 is the number of protons in the methyl group of the hydroxypropyl group; preferably,

[0048] I1 is the integral between 4.70 and 4.25, I2 is the integral between 4.25 and 2.60, and I3 is the integral between 1.40 and 0.90.

[0049] In some embodiments, when the cellulose ether is hypromellose, the methoxy content of the hypromellose is 19%-30%, preferably 21%-30%.

[0050] In some embodiments, when the cellulose ether is hypromellose, the content of hydroxypropoxy in the hypromellose is 4%-12%, preferably 6%-10%.

[0051] In some embodiments, when the cellulose ether is hydroxyethyl cellulose, the content of each substituent therein is calculated by the following formula:

[0052]

[0053] Wherein, DS is the degree of substitution of each substituent in the hydroxyethyl cellulose; for example, the degree of substitution of hydroxyethyl is:

[0054]

[0055] Where I1 is the integral value at 4.70-4.15; I2 is the integral value at 4.15-2.75.

[0056] In some embodiments, when the cellulose ether is hydroxyethyl cellulose, the hydroxyethyl content of the hydroxyethyl cellulose is 30%-50%, preferably 35%-45%.

[0057] In some embodiments, when the cellulose ether is hydroxypropyl cellulose, the content of each substituent therein is calculated by the following formula:

[0058] When DS 羟丙基 When it is greater than 3, the hydroxypropoxy content is calculated according to the following formula:

[0059]

[0060] When DS 羟丙基 When it is less than 3, the hydroxypropoxy content is calculated according to the following formula:

[0061]

[0062] Wherein, DS is the degree of substitution of each substituent in the hydroxypropyl cellulose; for example, the degree of substitution of hydroxypropyl is:

[0063]

[0064] Where I1 is the integral value at 4.70-2.60; I2 is the integral value at 1.40-0.90.

[0065] In some embodiments, when the cellulose ether is hydroxypropyl cellulose, the hydroxypropyl content in the hydroxypropyl cellulose is 70%-90%, preferably 78%-85%.

[0066] In some embodiments, when the cellulose ether is hypromellose phthalate, the content of each substituent therein is calculated by the following formula:

[0067]

[0068] Wherein, DS is the degree of substitution of each substituent in the hydroxypropyl methylcellulose phthalate; for example, the degree of substitution of each substituent is:

[0069]

[0070] Where I1 is the integral value at 7.80-7.40; I2 is the integral value at 4.70-4.15; I3 is the integral value at 4.15-2.60; I4 is the integral value at 1.40-0.90.

[0071] In some embodiments, when the cellulose ether is hypromellose phthalate, the phthalate content of the hypromellose phthalate is 20%-40%, preferably 25%-35%.

[0072] In the present invention, the DS substitution degree refers to the molar ratio of each substituent group to anhydroglucose groups.

[0073] In the present invention, anhydrous glucose groups refer to the monomeric glucose that constitutes cellulose.

[0074] The positive progress effect of the present invention is:

[0075] (1) The detection method provided by the present invention adopts a hydrolysis method for pretreatment and a nuclear magnetic resonance relative quantitative method for testing, which has good reproducibility, is simple to prepare, fast and efficient, and can achieve high-throughput analysis; the method is applicable to different types of cellulose ethers, has a wide range of applicability, and has strong popularity.

[0076] (2) The detection method provided by the present invention has strong selectivity and can be used for pretreatment with different acidic reagents. A suitable, safe and economical acidic reagent can be selected according to the test conditions. This method does not require reference substances and internal standards. Compared with traditional methods, this method has good flexibility, low cost and is more environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0077] Figure 1 Hydroxypropyl cellulose 1 HNMR spectrum;

[0078] Figure 2 Hydroxyethyl cellulose 1 HNMR spectrum;

[0079] Figure 3Hydroxypropyl methylcellulose phthalate 1 HNMR spectrum;

[0080] Figure 4 The hypromellose of Example 4 1 H-NMR spectrum. DETAILED DESCRIPTION

[0081] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples.

[0082] Example 1:

[0083] ①Instruments and reagents

[0084] Bruker 600MHz NMR spectrometer, equipped with AVANCE NEO cabinet and PABBO dual-resonance broadband probe; Mettler Toledo XP205 100,000 electronic balance.

[0085] Heavy water (D2O, 99.8% D, Shanghai Adamas Reagent Co., Ltd.), deuterated sulfuric acid (D2SO4, 99.5% D, Shanghai Adamas Reagent Co., Ltd.), hypromellose (Anhui Shanhe Pharmaceutical Excipients Co., Ltd., batch number 230814), hydroxypropyl cellulose (Anhui Shanhe Pharmaceutical Excipients Co., Ltd., batch number 230503), hydroxyethyl cellulose (Anhui Shanhe Pharmaceutical Excipients Co., Ltd., batch number W2081), and hypromellose phthalate (Anhui Shanhe Pharmaceutical Excipients Co., Ltd., batch number 230601).

[0086] ② Preparation of test solution

[0087] Weigh 10-30 mg of cellulose ether into a centrifuge tube, add 200 μL of 20% D2SO4-deuterated water solution, and stir until a paste forms. Heat in a 50°C water bath for 20-40 minutes until the sample becomes a viscous liquid. Add 600 μL of deuterated water solution and mix until a clear solution forms. Once dissolved and clear, transfer the solution to an NMR tube for analysis.

[0088] ③Test conditions

[0089] The zg30 pulse sequence was used for testing at a probe temperature of 298 K. Key instrument parameters include RF center O1P: 6.2 ppm, spectral width SWH: 19.8 ppm, relaxation delay time D1: 10 s, sampling time AQ: 2.75 s, gain RG: 9.8, sampling points TD: 64 k, sampling times NS: 256, and empty sweep times DS: 2.

[0090] ④Precision experiment

[0091] Weigh 30 mg of HPMC (lot number 230814) and prepare six test samples according to method ②. The assay was performed according to conditions in ③. After adjusting the baseline and phase, integration was performed and the methoxy and hydroxypropoxy content was calculated. The results showed that the average methoxy content of the six samples was 28.7% with an RSD of 0.47%, and the average hydroxypropoxy content was 8.9% with an RSD of 0.35%. This demonstrates good precision of the method.

[0092] ⑤Stability test

[0093] Take a random sample from step 4 and test it according to the conditions in step 2 at 12, 24, 48, and 72 hours. Compare the results with the initial test results. The absolute difference from the 0-hour test result should be no greater than 1.0%. The stability results are shown in Table 1, indicating that the sample solution is stable within 72 hours.

[0094] Table 1 Solution stability of Hydroxypropyl Methylcellulose

[0095] Time / h Methoxy content Hydroxypropoxy content 0 28.5％ 9.0％ 12 28.1％ 9.0％ 24 28.6％ 9.0％ 48 28.7％ 9.0％ 72 28.2％ 9.0％

[0096] ⑥Durability test

[0097] Take a random sample from step ④ and change the temperature and relaxation time. Compare the results with the initial test conditions. The absolute difference between the results should be no greater than 1.0%. The durability results are shown in Table 2. The results show that the sample has good durability.

[0098] Table 2 Method robustness of Hydroxypropyl Methylcellulose

[0099] Probe temperature / K Relaxation time / s Methoxy content Hydroxypropoxy content 298 10 28.5％ 9.0％ 300 10 28.6％ 9.0％ 296 10 28.6％ 9.1％ 298 12 28.5％ 9.0％ 298 8 28.4％ 9.0％

[0100] 7. Scope

[0101] In this experiment, the concentration range of the sample (hydroxypropyl methylcellulose) is 10 mg / mL to 30 mg / mL. In order to verify the validity of the interval within this range, two test solutions of low concentration -20% (8 mg / mL) and high concentration +20% (36 mg / mL) were prepared and compared with the results of the initial concentration. The difference in the absolute value of the determination results should be no more than 1.0%, and the signal-to-noise ratio (S / N) of the low concentration test solution should be no less than 250. The test results are shown in Table 3, which show that the nuclear magnetic resonance content determination method of hydropropyl methylcellulose is applicable to the concentration range of 10 mg / mL to 30 mg / mL.

[0102] Table 3 Concentration range of Hydroxypropyl Methylcellulose

[0103] Concentration (mg / mL) Methoxy content Hydroxypropoxy content 10 28.5％ 9.0％ 8 27.9％ 9.1％ 36 28.6％ 9.1％

[0104] ⑧Accuracy of Hydroxypropyl Methylcellulose

[0105] Take a sample of HPMC and prepare the test solution according to the method in ②. Perform the determination according to the conditions in ③. After adjusting the baseline and phase, integrate and calculate the methoxy and hydroxypropoxy contents. Compare them with the manufacturer's CoA results. The determination results are shown in Table 4.

[0106] Table 4 Accuracy of Hydroxypropyl Methylcellulose

[0107]

[0108] Comparison with the manufacturer's CoA results showed that this method has good accuracy and is suitable for the determination of HPMC.

[0109] ⑨Scope of application of this method

[0110] This method is applicable to all cellulose ethers.

[0111] Take hydroxypropyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methylcellulose phthalate respectively, prepare the test solution according to the method in ②, and measure according to the conditions in ③. After adjusting the baseline and phase, integrate and calculate the content of the corresponding substituent, and compare with the manufacturer's CoA results. The nuclear magnetic resonance results (H spectrum see Figure 1-3 ) are consistent with CoA.

[0112] Table 5 Accuracy of three cellulose ethers (hydroxypropyl cellulose, hydroxyethyl cellulose, and hypromellose phthalate)

[0113]

[0114] Example 2: Sample pretreatment conditions

[0115] 1. Screening of sulfuric acid concentration

[0116] The present invention uses sulfuric acid of different concentrations to hydrolyze cellulose ether under different conditions. Taking hypromellose as an example, the results are as follows:

[0117] Table 6 Reaction phenomena at room temperature with different sulfuric acid concentrations

[0118]

[0119]

[0120] Table 7 Water bath reaction phenomena at different sulfuric acid concentrations

[0121]

[0122] The results in Tables 6 and 7 show that under high concentration sulfuric acid conditions, the hydrolysis reaction is rapid at room temperature, and finally sugar carbonization occurs, completely destroying the cellulose ether structure and making it impossible to conduct effective testing;

[0123] Under low-concentration sulfuric acid (less than 50%) conditions, no reaction was observed during hydrolysis of cellulose ether at room temperature. However, increasing the temperature resulted in the same hydrolysis reaction as under high-concentration sulfuric acid conditions. Considering safety risks, low-concentration sulfuric acid is beneficial for laboratory safety. Therefore, low-concentration sulfuric acid and cellulose ether were allowed to react in a water bath for a certain period of time to achieve the desired hydrolysis. Finally, a sulfuric acid concentration of 20% to 30% was selected for the heating reaction in a water bath.

[0124] 2. Selection of water bath temperature and water bath time

[0125] Taking Hydroxypropyl Methylcellulose as an example: the judgment basis is that there is no impurity peak between 5-6ppm (small molecule glucose products produced by excessive reaction)

[0126] When selecting the water bath temperature and reaction time, the principle is to avoid excessive hydrolysis (when small molecular glucose products appear in the hydrolysis products, the calculation results will be inaccurate), observe the sample dissolution phenomenon and the appearance of the solution, and use the reaction endpoint as the basis for judgment.

[0127] Experiments showed that the sample dissolved rapidly after a 5-minute reaction in a 60°C water bath, and a distinct small molecule peak appeared between 5 and 6 ppm in the H-NMR spectrum. The short reaction time (only 5 minutes) was not conducive to the operation and quenching of the reaction, making accurate experimental control difficult.

[0128] The sample dissolved slowly in a 40°C water bath and began to soften after 60 minutes, resulting in low experimental efficiency.

[0129] The reaction was carried out in a water bath at 50°C, the sample dissolution time was moderate, and no obvious impurity peaks were observed at 5-6 ppm in the H-NMR spectrum.

[0130] The final reaction temperature was determined to be 50°C and the reaction time was 20 to 40 minutes. At 50 minutes, the hydrolysis reaction would produce an impurity peak at 5-5.5 ppm.

[0131] In summary, a better experimental protocol is: add 200 μl of 20% D2SO4-deuterated water solution to 10-30 mg of HPMC and stir until it forms a paste. Heat in a 50°C water bath for 20-40 minutes until the sample becomes a viscous liquid. Add 600 μl of deuterated water solution and mix until a clear, transparent solution forms. (Note: Different cellulose ethers have different molecular weights; the reaction time and temperature should be adjusted based on the above criteria.)

[0132] Example 3: Instrument detection parameter selection

[0133] 1. Relaxation delay time

[0134] Using a nuclear magnetic resonance spectrometer to measure the relaxation time (T1) of the free induction decay signal after the nuclear spin flip of the sample, the T1 values ​​for HPMC, hydroxyethyl cellulose, hydroxypropyl cellulose, and HPMC phthalate were 1.65s, 0.88s, 1.45s, and 1.26s, respectively. When the pulse excitation interval is 5 times the T1, the longitudinal magnetization vector can be recovered by 99.3%, meeting the requirements of qNMR. Therefore, a pulse excitation interval (D1) of 10s can meet the quantitative requirements.

[0135] 2. Number of scans

[0136] 1 The H NMR signal-to-noise ratio (S / N) must meet 250, and the number of scans NS = 256. When the concentration of cellulose ether is above 10 mg / mL, the S / N ratio is greater than 250, which meets the quantitative requirements. Moreover, the testing time for each sample at this number of scans is about 50 minutes, which has good application value.

[0137] Example 4: Spectrum Integration

[0138] After data acquisition, data processing was performed using topspin 4.0.5 software, with automatic baseline calibration and manual phase correction. Trimethylphenoxysilane (TMSP) in the selected solvent was marked as 0 ppm, 4.80-4.15 ppm was integrated as 1, and 4.15-2.70 ppm and 1.20-0.90 ppm were integrated separately. Figure 4 shown.

[0139] Example 5: Signal Peak Analysis

[0140] Table 8 Hydrogen spectrum signal peak attribution of Hydroxypropyl Methylcellulose

[0141]

[0142] Chemical shift / ppm Attribution serial number 0.00 Tetramethylsilane 1.40-0.90 10 <![CDATA[I3]]> ～2.5 Deuterated dimethyl sulfoxide Dimethyl sulfoxide-d5 4.25-2.60 2、3、4、5、6、7、8、9 <![CDATA[I2]]> 4.70-4.25 1 <![CDATA[I1]]> ～15 trifluoroacetic acid

[0143] Example 6: Calculation of Substituent Content

[0144] Degree of substitution calculation formula:

[0145] The degree of substitution of methoxy and hydroxypropoxy in HPMC is defined as the average value of methyl or hydroxypropyl groups in each anhydrous glucose unit, that is, the degree of substitution of methoxy and hydroxypropoxy is the molar ratio of methoxy or hydroxypropoxy groups to anhydrous glucose groups. The following formula can be inferred: Degree of substitution DS = M A / M B , M A is the molar concentration of methoxy or hydroxypropyl, M B is the molar concentration of anhydrous glucose groups. According to the hydrogen spectrum analysis in Table 8, the formula can be obtained:

[0146]

[0147] Wherein I1 is the integral at 4.70-4.25, I2 is the integral at 4.25-2.60, I3 is the integral at 1.40-0.90, A2 is the number of protons of the methyl group, and A3 is the number of protons of the methyl group in the hydroxypropyl group.

[0148] Content calculation formula:

[0149] The content of methoxy and hydroxypropoxy can be converted by the degree of substitution, the substituent content W = m A / m B , m A is the relative mass of methoxy or hydroxypropyl, m B is the sum of the relative masses of the anhydrous glucose group and the substituent group, and the formula is:

[0150]

[0151] The relative molecular weight of methoxy is 31.03, and the relative molecular weight of hydroxypropoxy is 75.09. Three hydroxyl groups in the glucose group will be replaced, so the composition of their relative molecular weight is 112.16+17.00×3 (three hydroxyl groups), where m 甲氧基 =DS 甲氧基 ×31.03m 羟丙氧基 =DS 羟丙氧基 ×75.09,m 无水葡萄 Sugar group = 1 × 112.16 + (3-DS hydroxypropoxy-DS methoxy) × 17:

[0152]

[0153] After simplification, we can get:

[0154]

[0155] Hydroxyethyl cellulose:

[0156] The hydroxyethyl substitution degree was calculated by direct comparison method as follows:

[0157]

[0158] Where I1 is the integral value at 4.70-4.15; I2 is the integral value at 4.15-2.75.

[0159] Calculate the hydroxyethyl content according to the following formula:

[0160]

[0161] Hydroxypropyl cellulose:

[0162] The hydroxypropyl substitution degree was calculated by direct comparison method as follows:

[0163]

[0164] Where I1 is the integral value at 4.70-2.60; I2 is the integral value at 1.40-0.90.

[0165] When DS 羟丙基 When it is greater than 3, the hydroxypropoxy content is calculated according to the following formula:

[0166]

[0167] When DS 羟丙基 When it is less than 3, the hydroxypropoxy content is calculated according to the following formula:

[0168]

[0169] Hydroxypropyl methylcellulose phthalate:

[0170] The degree of substitution of each substituent was calculated by direct comparison method as follows:

[0171]

[0172] Where I1 is the integral value at 7.80-7.40; I2 is the integral value at 4.70-4.15; I3 is the integral value at 4.15-2.60; I4 is the integral value at 1.40-0.90.

[0173] The content of each substituent is calculated according to the following formula:

[0174]

[0175] Example 7: Sample viscosity

[0176] The relative molecular mass range of commercially available hydroxypropyl cellulose is mainly 50,000 to 1.25 million. Domestically available hydroxypropyl methylcellulose (HPMC) has various viscosity grades to choose from, mainly 3, 5, 15, 30, 50, 100, 4,000, 10,000, 15,000, and 100,000 mPa·s. The scope of application of this patented method can be used for cellulose ethers of all viscosities.

[0177] Table 9 Conventional HPMC available in the domestic market

[0178] model Weight average molecular weight concentration(%) Indicated viscosity (mPa.s) E4M Pharm1 400,000 2 2700-5040 E10M Pharm1 746,000 2 7500-14000 K100LV PH PRM2 164,000 2 80-120 K250PH PRM2 200,000 2 200-300 K750PH PRM2 250,000 2 562-1050 K1500PH PRM2 300,000 2 1125-2100 K4M Pharm1 400,000 2 2700-5040 K15M Pharm1 575,000 2 13500-25200 K35M Pharm1 675,000 2 26250-49000 K100M Pharm1 1,000,000 2 75000-140000 K200M Pharm1 1,200,000 2 150000-280000 K4M PH DC1 400,000 2 2700-5040 K15M PH DC1 575,000 2 13500-25200 K100M PH DC1 1,000,000 2 75000-140000

[0179] Example 8: Sample concentration

[0180] 1For accurate quantification by H NMR, the signal-to-noise ratio (S / N) must be greater than 100. As the sample concentration increases, the dissolution rate of the test solution slows down and the viscosity increases, affecting the normal NMR scanning.

[0181] In the experiment with hypromellose (batch number 20210104, viscosity 414 mPa·s), the signal-to-noise ratio reached 300-400 at a concentration of 10 mg / mL, so 10 mg / mL was selected as the lowest test concentration. When the concentration was greater than 40 mg / mL, the viscosity increased significantly and the fluidity deteriorated, so 40 mg / mL was selected as the highest test concentration for this variety.

[0182] Example 9: Reagent Selection

[0183] This method was developed mainly using deuterated sulfuric acid heavy water solvent. After the method was improved, acidic reagents such as hydrochloric acid, perchloric acid, formic acid, acetic acid, trifluoroacetic acid, and nitric acid were tried for testing. The tests found that hydrochloric acid and perchloric acid had the same effect, while other acids were less effective. However, considering that hydrochloric acid and perchloric acid are prone to overflowing harmful gases, low-concentration sulfuric acid is preferred for the experiment for safety reasons, while hydrochloric acid and perchloric acid are used as backup options.

[0184] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A method for determining the substituent content in cellulose ether, characterized in that: It includes the following steps: The cellulose ether is hydrolyzed with a deuterated acid and then mixed with heavy water to obtain a test sample; The test product will be 1 HNMR detection; passed 1 The degree of substitution of the substituent to be tested is obtained by HNMR detection; the content of the substituent to be tested is calculated by the following formula: Among them, m A is the relative mass of the substituent to be measured; m B It is the sum of the relative masses of the anhydrous glucose group and all the substituent groups to be measured; the degree of substitution is the molar ratio of the substituent group to be measured to the anhydrous glucose group.

2. The assay method according to claim 1, wherein The determination method satisfies one or more of the following conditions: (1) The deuterated acid is used in the form of a deuterated acid heavy aqueous solution; (2) The cellulose ether is a high-viscosity cellulose ether.

3. The assay method according to claim 2, wherein The determination method satisfies one or more of the following conditions: (1) The cellulose ether is hydroxypropyl methylcellulose, hydroxyethyl cellulose, hydroxypropyl cellulose or hydroxypropyl methylcellulose phthalate; (2) The viscosity of the cellulose ether is 80-300000 mPa.s; (3) the weight average molecular weight of the cellulose ether is 100,000-1,200,000; (4) The cellulose ether sampling amount is 1-50 mg; (5) The deuterated acid is deuterated sulfuric acid, deuterated hydrochloric acid or deuterated perchloric acid; (6) In the deuterated acid heavy aqueous solution, the concentration of the deuterated acid is 10%-30%, where the percentage is the mass percentage of the deuterated acid in the deuterated acid heavy aqueous solution; (7) The volume ratio of the heavy water to the deuterated acid heavy water solution is (2-5):1; (8) In the test sample, the mass volume ratio of the cellulose ether to the test sample is 10 mg / mL-50 mg / mL; (9) The mass volume ratio of the cellulose ether to the deuterated acid heavy aqueous solution is 50 mg / mL-150 mg / mL; (10) The amount of the deuterated acid heavy aqueous solution is 100 μL-300 μL; (11) The reaction temperature of the hydrolysis reaction is 45°C-50°C; (12) The hydrolysis reaction is heated in a water bath; (13) The reaction time of the hydrolysis reaction is 20 min-40 min; (14) 1 The hydrogen spectrum detected by HNMR does not produce any stray peaks between 5 and 6 ppm; (15) 1 HNMR detection was performed using a 600 MHz nuclear magnetic resonance spectrometer; (16) 1 HNMR detection was performed using the zg30 pulse sequence at a probe temperature of 298K. (17) The substituent to be tested is methoxy, hydroxypropoxy, hydroxyethyl, hydroxypropyl or phthaloyl.

4. The assay method according to claim 3, wherein The determination method satisfies one or more of the following conditions: (1) The cellulose ether is hypromellose; (2) The cellulose ether sampling amount is 10-30 mg; (3) The deuterated acid is deuterated sulfuric acid; (4) In the deuterated acid heavy water solution, the concentration of the deuterated acid is 20%-30%, where the percentage is the mass percentage of the deuterated acid to the solution; (5) the volume ratio of the heavy water to the deuterated acid heavy water solution is 3:1; (6) In the test sample, the mass volume ratio of the cellulose ether to the test sample is 10 mg / mL-38 mg / mL; (7) The amount of the deuterated acid heavy aqueous solution is 200 μL; (8) The reaction temperature of the hydrolysis reaction is 50°C.

5. The assay method according to claim 3, wherein The determination method satisfies one or more of the following conditions: (1) In the deuterated acid heavy water solution, the concentration of the deuterated acid is 20%, where the percentage is the mass percentage of the deuterated acid to the solution; (2) The viscosity of the hydropropyl methylcellulose is 414 mPa·s.

6. The assay method according to claim 3, wherein The determination method comprises the following steps: mixing cellulose ether with 20% deuterated sulfuric acid heavy water solution, heating in a 50° C. water bath for 20-40 minutes, adding the heavy water solution to mix into a clear and transparent solution, and transferring the mixture to a nuclear magnetic tube for determination.

7. The assay method according to claim 3, wherein described 1 The key instrument parameters for HNMR testing meet one or more of the following conditions: (1) RF center O1P: 6.2ppm; (2) Spectral width SWH: 19.8ppm; (3) Relaxation delay time D1: 5-60s, for example, 10s; (4) Sampling time AQ: 2.75s; (5) Gain RG: 9.8; (6) Number of sampling points TD: 64k; (7) Sampling number NS ≥ 128, for example 256; (8) Number of empty sweeps DS: 2; (9) The test time is 50 minutes.

8. The assay method according to claim 1, wherein The determination method is any of the following: (1) When the cellulose ether is hypromellose, the content of each substituent therein is calculated by the following formula: Wherein, DS is the degree of substitution of each substituent in the hypromellose, and its calculation formula is as follows: Wherein, I1 is the integral of H at position 1 in the hydrogen spectrum of Formula I, I2 is the integral of H at positions 2-9 in the hydrogen spectrum of Formula I, I3 is the integral of H at position 10 in the hydrogen spectrum of Formula I, A2 is the number of protons in the methyl group, and A3 is the number of protons in the methyl group of the hydroxypropyl group; preferably, I1 is the integral between 4.70 and 4.25, I2 is the integral between 4.25 and 2.60, and I3 is the integral between 1.40 and 0.90; (2) When the cellulose ether is hydroxyethyl cellulose, the content of each substituent therein is calculated by the following formula: Wherein, DS is the degree of substitution of each substituent in the hydroxyethyl cellulose; for example, the degree of substitution of hydroxyethyl is: Where I1 is the integral value at 4.70-4.15; I2 is the integral value at 4.15-2.75; (3) When the cellulose ether is hydroxypropyl cellulose, the content of each substituent therein is calculated by the following formula: When DS 羟丙基 When it is greater than 3, the hydroxypropoxy content is calculated according to the following formula: When DS 羟丙基 When it is less than 3, the hydroxypropoxy content is calculated according to the following formula: Wherein, DS is the degree of substitution of each substituent in the hydroxypropyl cellulose; for example, the degree of substitution of hydroxypropyl is: Where I1 is the integral value at 4.70-2.60; I2 is the integral value at 1.40-0.90; (4) When the cellulose ether is hydroxypropyl methylcellulose phthalate, the content of each substituent therein is calculated by the following formula: Wherein, DS is the degree of substitution of each substituent in the hydroxypropyl methylcellulose phthalate; for example, the degree of substitution of each substituent is: Where I1 is the integral value at 7.80-7.40; I2 is the integral value at 4.70-4.15; I3 is the integral value at 4.15-2.60; I4 is the integral value at 1.40-0.

90.

9. The assay method according to claim 7, wherein The determination method satisfies one or both of the following conditions: (1) When the cellulose ether is hypromellose, the methoxy content of the hypromellose is 19%-30%; (2) When the cellulose ether is hypromellose, the hydroxypropoxy content of the hypromellose is 4%-12%; (3) When the cellulose ether is hydroxyethyl cellulose, the hydroxyethyl content of the hydroxyethyl cellulose is 30%-50%; (4) When the cellulose ether is hydroxypropyl cellulose, the hydroxypropyl content of the hydroxypropyl cellulose is 70%-90%; (5) When the cellulose ether is hypromellose phthalate, the phthalate group content of the hypromellose phthalate is 20%-40%.

10. The measuring method according to claim 9, wherein The determination method satisfies one or both of the following conditions: (1) When the cellulose ether is hypromellose, the methoxy content of the hypromellose is 21%-30%; (2) When the cellulose ether is hypromellose, the hydroxypropoxy content of the hypromellose is 6%-10%; (3) When the cellulose ether is hydroxyethyl cellulose, the hydroxyethyl content of the hydroxyethyl cellulose is 35%-45%; (4) When the cellulose ether is hydroxypropyl cellulose, the hydroxypropyl content of the hydroxypropyl cellulose is 78%-85%; (5) When the cellulose ether is hypromellose phthalate, the phthalate group content of the hypromellose phthalate is 25%-35%.

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