A method for detecting calcium / magnesium stearate content in a preparation by ion chromatography

Abstract

The present application relates to the field of pharmaceutical excipient detection, in particular to a method for quantitatively detecting calcium stearate and magnesium stearate in preparations by ion chromatography. The present application draws the standard curves of calcium / magnesium ions and excipients calcium stearate / magnesium stearate respectively, obtains the slope ratio of the two, obtains the conversion coefficient of the content of calcium / magnesium ions in calcium stearate / magnesium stearate, so as to accurately detect the content of calcium stearate or magnesium stearate in preparations. The detection method has high sensitivity, strong specificity, high precision, strong accuracy, simple and fast operation, wide applicability, low detection cost, realizes the quantitative detection of common excipients calcium stearate / magnesium stearate in preparations, thereby effectively guiding the self-prepared preparations to be consistent with the reference preparation prescription.

Description

Technical Field

[0001] This invention relates to a method for detecting the calcium / magnesium stearate content in a pharmaceutical preparation by ion chromatography, and relates to the field of pharmaceutical excipient detection technology. Background Technology

[0002] Calcium stearate / magnesium, mainly calcium stearate / magnesium (C 36 H 70 O4X) and calcium / magnesium palmitate (C 32 H 62 A mixture of O4X (where X represents Ca or Mg).

[0003] Calcium stearate is a white powder, insoluble in water, cold ethanol, and ether, soluble in hot benzene, toluene, and turpentine, and slightly soluble in hot ethanol and ether. It slowly decomposes when heated to 400℃, is flammable, and decomposes in strong acids into stearic acid and the corresponding calcium salt. It is hygroscopic. It is mainly used as a stabilizer, lubricant, paint smoothing agent, and lubricant for pencil leads.

[0004] Magnesium stearate is a white, non-gritty powder that has a slippery feel upon contact with skin. It is insoluble in water, ethanol, or ether and is primarily used as a lubricant, anti-adhesion agent, and gliding agent. It is particularly suitable for granulation of oily and extract-based drugs, producing granules with excellent flowability and compressibility. It is used as a gliding agent in direct compression. It can also be used as a filter aid, clarifying agent, and effervescent agent, as well as a suspending agent and thickener in liquid preparations.

[0005] Due to its wide application and important role in pharmaceutical formulations, pharmaceutical research institutions usually need to determine its dosage when developing generic drugs to facilitate formulation and process development.

[0006] Because this product is a mixture, the existing method (Chinese Pharmacopoeia 2020 Edition, Part IV) is to determine the concentration of calcium or magnesium in pure excipient magnesium stearate / calcium by complexometric titration. However, this method suffers from large matrix interference and poor specificity in the case of multi-component formulation samples, and cannot quantitatively detect the content of magnesium stearate / calcium.

[0007] According to relevant literature, gas chromatography can be used to determine the ratio and total content of stearic acid and palmitic acid in magnesium stearate / calcium stearate excipients. This method uses an extraction-derivation-extraction sample pretreatment method, which is complicated and risky. When the sample composition is complex, extraction is difficult and prone to large systematic errors, resulting in inaccurate detection results.

[0008] Alternatively, Raman spectroscopy can be used for quantitative detection, but the instruments used in this method are not commonly used and are expensive, making it difficult to popularize.

[0009] Another method uses inductively coupled plasma mass spectrometry (ICP-MS). After digestion, calcium and magnesium elements are obtained, and their concentrations are then determined using ICP-MS. The molecular weight is then used to calculate the magnesium stearate / calcium content. However, this method uses expensive ICP-MS instruments, has limited availability, poor applicability, and requires expensive standard materials, resulting in high detection costs.

[0010] Based on this, the present invention provides a method for quantitatively detecting calcium stearate / magnesium as an excipient in a formulation by ion chromatography. Summary of the Invention

[0011] To overcome the challenge of accurately quantifying the pharmaceutical excipients calcium / magnesium stearate in existing technologies, this invention provides a method for the quantitative detection of calcium / magnesium stearate in pharmaceutical preparations using ion chromatography (IC). By digesting the sample to eliminate the influence of organic components such as lactose, soluble starch, dextrin, sodium carboxymethyl cellulose, polyethylene glycol, povidone K30, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, polyvinylpyrrolidone, microcrystalline cellulose, and film-coating premixes, the problem of matrix interference in multi-component formulations is solved, significantly improving the detection specificity.

[0012] Traditionally, after sample digestion, the acid removal step usually involves reserving 1-2 ml of digestate for dissolving various elements to prevent precipitation or volatilization, which could lead to incomplete transfer and systematic errors. However, digestate is typically a strong acid and / or a strong oxidizing agent, which can damage the ion chromatography column. Furthermore, it disrupts the microenvironment of the mobile phase within the column after injection, resulting in abnormal peak elution of the target analytes. To address this issue, we adjusted the acid removal process. Because calcium and magnesium ions have high boiling points and do not volatilize at the acid removal temperature, all digestate is evaporated to dryness during the acid removal process. We then experimented with different reconstitution methods and ultimately determined that a 6 mmol / L nitric acid aqueous solution is used as the reconstitution solvent, dissolved by shaking in a water bath at 60℃–80℃.

[0013] Most published calculation methods use the molar mass ratio of calcium / magnesium ions to calcium / magnesium stearate or the molar mass ratio of carboxyl groups to calcium / magnesium stearate for conversion. However, calcium / magnesium stearate is a mixture with a molecular weight range, making it impossible to accurately calculate the conversion factor using molecular weight alone. This invention utilizes standard curves plotted on ion chromatography using standard solutions of calcium / magnesium elements at different concentrations and calcium / magnesium stearate solutions, respectively, to obtain the slope ratio of the two curves, which serves as the conversion factor between calcium / magnesium ions and calcium / magnesium stearate. Formulation process development is a long-term process involving multiple tests of calcium / magnesium stearate excipients. Using the method of this invention, only the conversion factor needs to be pre-determined; all subsequent tests can omit the step of plotting the standard curve for the magnesium / calcium stearate solution. The standard curve can be directly plotted using the calcium / magnesium element standard solution, and the content of calcium / magnesium stearate or magnesium stearate excipient can be calculated using the conversion factor. This avoids the cumbersome process of multiple digestion, acid removal, and resolution of calcium / magnesium stearate excipients. Furthermore, compared to other methods that use a single component to calculate the conversion factor, this invention can more accurately determine the content of calcium / magnesium stearate in the excipients.

[0014] The present invention adopts the following technical solution:

[0015] A method for quantitatively determining calcium stearate / magnesium in a formulation by ion chromatography includes the following steps:

[0016] 1. Digestion conditions: Microwave power 1500W. Temperature increased from 25℃ to 130℃ over 20 minutes, maintained at 130℃ for 5 minutes; temperature increased from 130℃ to 185℃ over 20 minutes, maintained at 185℃ for 20 minutes. Fan speed was set to level 1 during microwave digestion. After digestion, cooling was performed at level 3 fan speed for 30 minutes.

[0017] 2. Acid removal-resolution treatment: After digestion, remove the acid from the sample at 120℃~170℃ for 1~3 hours until the acid is completely removed. Then add an appropriate amount of 6mmol / L nitric acid solution and shake in a water bath at 60℃~80℃ until the sample in the digestion tube is dissolved. Then cool to room temperature.

[0018] 3. Ion chromatography conditions: The detector is a conductivity detector; the column is a cation analysis column; the flow rate is 0.3-0.7 ml / min; the injection volume is 10 μl; the column temperature is 25-40℃; and the mobile phase is 3-10 mmol / L nitric acid solution.

[0019] 4. Plot a standard curve of calcium / magnesium concentration versus target peak response: Accurately measure different volumes of calcium / magnesium standard solution, dilute with water to the specified concentration, and prepare a standard curve solution for calcium / magnesium. Inject 10 μl of the solution into an ion chromatograph and determine the peak area of ​​calcium / magnesium ions.

[0020] Standard curve 1 was plotted with calcium / magnesium concentration on the x-axis and peak area of ​​calcium / magnesium ions on the y-axis, and the slope k1 of the curve was obtained. The concentration range of the calcium / magnesium standard curve solution was 0.25 μg / ml to 2.00 μg / ml.

[0021] 5. Plot the standard curve for calcium stearate / magnesium stearate solution: Accurately weigh an appropriate amount of the excipients calcium stearate / magnesium stearate, place it in a digestion tube, add the digesting agent, and perform digestion and acid removal-resolution treatment according to steps 1 and 2. Transfer the solution in the digestion tube to a volumetric flask, dilute with water to the mark, and shake well to obtain a calcium stearate / magnesium stearate stock solution. Then, accurately transfer appropriate volumes of this stock solution and dilute with water to the specified concentration to prepare a linear solution of calcium stearate / magnesium stearate.

[0022] Take 10 μl and inject it into an ion chromatograph to determine the peak area of ​​calcium / magnesium ions. Plot a standard curve 2 with the concentration of calcium / magnesium stearate on the x-axis and the peak area of ​​calcium / magnesium ions on the y-axis. Obtain the slope k2 of the curve. The concentration range of the linear solution of calcium stearate is 3.8 μg / ml to 30.6 μg / ml, and the concentration range of the linear solution of magnesium stearate is 6.1 μg / ml to 49.4 μg / ml.

[0023] Then, using the formula: conversion factor = k1 / k2, we can obtain the conversion factor for the content of calcium / magnesium ions in calcium / magnesium stearate.

[0024] 6. Sample Testing: Take an appropriate amount of the test sample (for liquid preparations, weigh directly; for solid preparations, grind into a fine powder and weigh), accurately weigh it, place it in a digestion tube, add the digesting agent, and perform digestion and acid removal-resolution treatment according to steps 1 and 2. After digestion, transfer the solution in the digestion tube to a volumetric flask, dilute with water to the mark, and shake well. Take 10 μl and inject it into an ion chromatograph, and record the peak area A of calcium / magnesium ions. 供 .

[0025] To eliminate the influence of other excipients or active pharmaceutical ingredients containing calcium / magnesium on the detection of calcium / magnesium stearate content, a negative control (containing no calcium / magnesium stearate, with other components prepared and mixed according to the formulation of the test sample) was used. Following the same detection procedure as the test sample, the peak area A of calcium / magnesium ions in the blank sample solution was measured. 空 .

[0026] (A) 供 -A 空 Substituting into the equation of standard curve 1 in step 4, we obtain the concentration C of calcium / magnesium.

[0027] 7. Calculation: The content of calcium stearate / magnesium stearate in the sample = C × conversion factor × dilution factor / sample weight × 100%.

[0028] The volume of the digesting agent mentioned in steps 5 and 6 shall not exceed 1 / 3 of the volume of the digestion tube; the preferred volume of the digesting agent is 4 to 8 ml, and the optimal volume is 6 ml.

[0029] The digesting agent is selected from one or more of concentrated nitric acid, concentrated hydrochloric acid, hydrofluoric acid, and hydrogen peroxide; the preferred digesting agent is 68 wt% concentrated nitric acid.

[0030] In steps 5 and 6, the amount of sample to be digested should not exceed 250 mg.

[0031] Preferably, the acid removal conditions in step 2 are acid removal at 150°C for 2 hours.

[0032] Preferably, the flow rate in step 3 is 0.5 ml / min; the column temperature is 30 °C; and the mobile phase is 6 mmol / L nitric acid solution.

[0033] Compared with the prior art, the advantages of the present invention are as follows:

[0034] The detection method of this invention has high sensitivity, strong specificity, high precision, high accuracy, and is simple and fast to operate. In addition, the method has wide applicability and low detection cost. It realizes the quantitative detection of calcium stearate / magnesium, a commonly used excipient in formulations, thereby effectively guiding self-made formulations to achieve consistency with reference formulations. Attached Figure Description

[0035] Figures 1-3 The ion chromatogram of the blank sample in Example 3;

[0036] Figures 4-8 This is the ion chromatogram of the calcium and magnesium mixed standard solution in Example 4;

[0037] Figures 9-13 This is the ion chromatogram of the linear mixed solution of calcium stearate and magnesium stearate in Example 4. Detailed Implementation

[0038] The applicant will further describe the present invention below with reference to the embodiments and accompanying drawings, but the scope of protection of the present invention is not limited to these embodiments. Those skilled in the art should understand that equivalent substitutions or corresponding improvements made to the technical features of the present invention still fall within the scope of protection of the present invention.

[0039] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; the water used is ultrapure water; and the materials and reagents used are commercially available unless otherwise specified.

[0040] Unless otherwise specified, the nitric acid used in the following examples is 68 wt%, the hydrochloric acid is 37 wt%, and the hydrogen peroxide is 30 wt%.

[0041] The magnesium and calcium single-element standard solutions used in the following examples were both sourced from the National Nonferrous Metals and Electronic Materials Analysis and Testing Center, with batch numbers 222008-3 and 228018-1, respectively, and a concentration of 1 mg / ml.

[0042] The microwave digestion system used in the following examples is a Milestone ETHOS UP microwave digestion system, the ion chromatography system is a Metrohm Eco ion chromatograph, and the acid removal system is a LabTech VB48 UP acid removal system. Example 1: Establishment of Analytical Method 1 (Digesterone Selection)

[0043] Digestion conditions: Microwave power 1500W. Temperature increased from 25℃ to 130℃ over 20 minutes, maintained at 130℃ for 5 minutes; then increased from 130℃ to 185℃ over 20 minutes, maintained at 185℃ for 20 minutes. Fan speed was level 1 during microwave digestion. After digestion, cooling was performed at level 3 fan speed for 30 minutes.

[0044] Under these digestion conditions, nitric acid, hydrochloric acid-nitric acid (3:1, v / v), and hydrogen peroxide-nitric acid (1:2, v / v) were selected as digesting agents. Formulation 1 (containing common excipients such as microcrystalline cellulose, lactose, and starch, with components shown in Table 2), Formulation 2 (containing conventional excipients such as hydroxypropyl cellulose, low-substituted hydroxypropyl cellulose, lactose, and sodium lauryl sulfate, with components shown in Table 2), and Formulation 3 (containing conventional excipients such as corn starch, lactose, glycerol, croscarmellose sodium, microcrystalline cellulose, and copovidone, with components shown in Table 2) were used for digestion tests. The volume of the digesting agent was 6 ml. The visual observation results of the test samples under different sample volumes are shown in Table 1.

[0045] Table 1

[0046]

[0047]

[0048] Table 2

[0049]

[0050] The above observations show that nitric acid alone promotes better digestion than a mixture of nitric acid and hydrochloric acid or nitric acid and hydrogen peroxide. However, excessive sample volume can also lead to incomplete digestion. It is recommended that the sample weight not exceed 250 mg.

[0051] In summary, microwave digestion can solve the problem of sample insolubility and also eliminate interference from other excipients.

[0052] Example 2: Establishment of Analytical Methods 2 (Selection of Acid Removal-Resolution Method)

[0053] Chromatographic conditions:

[0054] Detector: Conductivity detector; Column: Cation analysis column (Metrosep C6, size: 4.0×250mm); Flow rate: 0.5ml / min; Injection volume: 10μl; Column temperature: 30℃; Mobile phase: 6mmol / L nitric acid solution; Run time: 20min.

[0055] Weigh 178.29 mg of formulation 1 from Table 2, 61.32 mg of formulation 2 from Table 2, and 90.89 mg of formulation 3 from Table 2, and place them in different digestion tubes. Add 6 ml of nitric acid to each tube and digest according to the digestion conditions in Example 1. After digestion, discard the digested sample and place it in an acid-removing apparatus. Remove the acid at 150°C until approximately 1 ml of nitric acid remains. Transfer the sample to a 25 ml volumetric flask, dilute with water to the mark, and mix well. Inject 10 μl into an ion chromatograph and detect under the chromatographic conditions described above. No peak should be observed in the sample solution. Adding an organic or inorganic base to the sample solution for neutralization may not achieve the desired neutralization effect if the amount added is too small, or may interfere with the target peak if the amount added is too large.

[0056] Therefore, the reconstitution method was investigated: 177.69 mg of formulation 1 from Table 2, 62.12 mg of formulation 2 from Table 2, and 91.25 mg of formulation 3 from Table 2 were weighed and placed in different digestion tubes. 6 ml of nitric acid was added to each tube, and digestion was carried out according to the digestion conditions in Example 1. After digestion, the digested samples were discarded and placed in an acid-removing apparatus at 150°C until all acid was removed (acid removal time was 2 hours). 6 ml of 6 mmol / L nitric acid solution was added to dissolve the sample, and the solution was transferred to a 25 ml volumetric flask, diluted to the mark with water, and shaken well. 10 μl of the solution was injected into an ion chromatograph, and detection was performed under the chromatographic conditions described above. The sample solution showed normal peak elution.

[0057] The relationship between the amount of digesting agent and the acid removal time was investigated, and it was found that when the volume of digesting agent was 4-8 ml, the acid removal time was 1-3 h.

[0058] In summary, after the acid removal process is completed, a reconstitution process needs to be added to reduce the acid concentration in the solution, thereby solving the problem of the sample solution not producing peaks when the acid concentration is too high.

[0059] Example 3: Specificity Experiment

[0060] Blank sample detection: Weigh 178.61 mg of negative control 1 (preparation 1 in Table 3), 61.47 mg of negative control 2 (preparation 2 in Table 3), and 86.1 mg of negative control 3 (preparation 3 in Table 3) into three digestion tubes, add 6 ml of nitric acid to each, and place them in a microwave digester. After digestion under the conditions described in Example 1, remove the digestion tubes and place them in an acid removal apparatus for acid removal-resolution treatment (after acid removal at 150°C for 2 hours, add 6 ml of 6 mmol / L nitric acid solution, and shake in an 80°C water bath until the sample in the digestion tube dissolves). After resolution, cool the solution to room temperature and transfer it to a 25 ml volumetric flask, then dilute with water to the mark. Detect ion chromatography under the chromatographic conditions described in Example 2 (see Example 2). Figures 1-3 Record the peak areas of calcium and magnesium.

[0061] Table 3

[0062]

[0063]

[0064] Figure 1 , 2 The chromatograms of negative controls 1, 2, and 3 are shown in order. Figures 1-3 It can be seen that after the sample is processed by the sample pretreatment method of the present invention, the detection of the target element (calcium or magnesium) in the obtained ion chromatogram is not interfered with, and the method has good specificity.

[0065] Example 4: Plotting Standard Curves and Calculating Conversion Factors

[0066] 1. Plotting the standard curves for calcium and magnesium elements

[0067] Figure 4-8 The following are ion chromatograms of mixed standard solutions of calcium and magnesium with concentrations of 0.25, 0.50, 1.00, 1.50, and 2.00 μg / ml, respectively. Linear standard solutions: Accurately measure 25 μl, 50 μl, 100 μl, 150 μl, and 200 μl of calcium single-element standard solution (concentration: 1 mg / ml) and magnesium single-element standard solution (concentration: 1 mg / ml), respectively, and place them in the same volumetric flask. Dilute with water according to Table 4 below to prepare a series of mixed standard solutions.

[0068] Table 4

[0069] linear concentration Transfer volume μl Fixed volume (ml) Concentration μg / ml 25％ 25 100 0.25 50％ 50 100 0.50 100％ 100 100 1.00 150％ 150 100 1.50 200％ 200 100 2.00

[0070] Take the above series of mixed standard solutions and perform ion chromatography under the chromatographic conditions described in Example 2. Record the peak areas of the chromatographic peaks with retention times of 9.0 min (magnesium ions) and 12.0 min (calcium ions). The concentration is calculated as the labeled concentration of the calcium or magnesium single-element standard solution divided by the dilution factor of the standard solution. A standard curve is plotted with concentration on the x-axis and the peak area of ​​the corresponding ion's characteristic peak on the y-axis, as shown in Table 5 below.

[0071] Table 5

[0072]

[0073] 2. Plotting the standard curves for calcium stearate and magnesium stearate

[0074] Figures 9-13 Ion chromatograms of linear mixed solutions of calcium stearate and magnesium stearate at concentrations of 25%, 50%, 100%, 150%, and 200%, respectively. Preparation of the calcium stearate-magnesium stearate stock solution: 191.04 mg of calcium stearate excipient and 308.34 mg of magnesium stearate excipient were accurately weighed and placed in different digestion tubes. After digestion and acid removal-resolution treatment according to the method in Example 3, the solutions were transferred to the same 50 ml volumetric flask, diluted to the mark with water, and shaken well. 50 μl, 100 μl, 200 μl, 300 μl, and 400 μl of this calcium stearate-magnesium stearate stock solution were accurately measured and diluted with water according to Table 6 below to prepare linear mixed solutions.

[0075] Table 6

[0076] linear concentration Transfer volume μl Fixed volume (ml) 25％ 50 50 50％ 100 50 100％ 200 50 150％ 300 50 200％ 400 50

[0077] Take the above linear mixed solution and perform ion chromatography under the chromatographic conditions described in Example 2. Record the peak areas of the chromatographic peaks with retention times of 9.0 min (magnesium ions) and 12.0 min (calcium ions). The concentration is calculated as the sample weight of calcium stearate or magnesium stearate divided by the dilution factor. Plot a standard curve with concentration on the x-axis and the peak area of ​​the corresponding ion's characteristic peak on the y-axis, as shown in Table 7 below.

[0078] Table 7

[0079]

[0080]

[0081] According to the formula: Conversion factor = K 镁或钙 / K 硬脂酸镁或硬脂酸钙 The conversion factor for magnesium to magnesium stearate was calculated to be 23.4, and the conversion factor for calcium to calcium stearate was 14.2, where K... 镁 K 钙K represents the slope of the standard curve equations for magnesium and calcium, respectively. 硬脂酸镁 K 硬脂酸钙 These are the slopes of the standard curve equations for magnesium stearate and calcium stearate, respectively.

[0082] Example 5: Accuracy Test

[0083] Linear standard solutions: A series of mixed standard solutions were prepared according to the method for plotting standard curve 1 in Example 4.

[0084] Accuracy solutions for calcium stearate (Formulation 1): Approximately 178 mg of negative control 1 (Formulation 1 in Table 3) was accurately weighed, and approximately 0.2 mg, 0.4 mg, and 0.6 mg of calcium stearate excipients were added to each. These were placed in separate digestion tubes, and 6 ml of nitric acid was added to each. After digestion and acid removal-resolution treatment according to the method in Example 3, the solutions were transferred to 25 ml volumetric flasks, diluted to the mark with water, and shaken well to prepare 50%, 100%, and 150% spiking solutions, respectively. Three replicates were prepared for each concentration level.

[0085] Magnesium stearate (Formulation 2) accuracy solution: Accurately weigh approximately 62 mg of negative control 2 (Formulation 2 in Table 3), add approximately 0.3 mg, 0.6 mg, and 0.9 mg of magnesium stearate excipient, respectively, and place them in separate digestion tubes. Add 6 ml of nitric acid to each tube, and digest and remove acid and reconstitute according to the method in Example 3. Transfer the solutions to 25 ml volumetric flasks, dilute with water to the mark, and shake well to prepare 50%, 100%, and 150% spiking solutions, respectively. Prepare three parallel solutions for each concentration level.

[0086] Magnesium stearate (Formulation 3) accuracy solution: Accurately weigh approximately 90 mg of negative control 3 (Formulation 3 in Table 3), add approximately 0.3 mg, 0.6 mg, and 0.9 mg of magnesium stearate excipient, respectively, and place them in separate digestion tubes. Add 6 ml of nitric acid to each tube, and digest and remove acid and reconstitute according to the method in Example 3. Transfer the solutions to 25 ml volumetric flasks, dilute with water to the mark, and shake well to prepare 50%, 100%, and 150% spiking solutions, respectively. Prepare three parallel solutions for each concentration level.

[0087] Take the above linear standard solution and each accuracy solution, and detect ion chromatography according to the chromatographic conditions in Example 2. Record the peak areas of the chromatographic peaks with retention times of 9.0 min (magnesium ion) and 12.0 min (calcium ion).

[0088] A standard curve was plotted with the concentration of calcium / magnesium ions in the linear standard solution on the x-axis and the peak area of ​​the corresponding ion's characteristic peak on the y-axis, as shown in Table 8 below:

[0089] Table 8

[0090]

[0091] The measured amount was calculated using the following two methods: (1) Conversion factor method: Substitute the peak area of ​​the characteristic peak of each accuracy solution into the standard curve equation in Table 8 to obtain the concentration of calcium / magnesium. Then, according to the formula: Measured amount = concentration * dilution factor * conversion factor, where the conversion factor for calcium stearate is 14.2 and the conversion factor for magnesium stearate is 23.4 (see Example 4); (2) Direct calculation method: Substitute the peak area of ​​the characteristic peak of each accuracy solution into the standard curve equation in Table 8 to obtain the concentration of calcium / magnesium. Then, according to the formula: Measured amount = concentration * dilution factor * molecular weight (硬脂酸钙 / 镁) / molecular weight (钙 / 镁) Finally, the recovery rate of the accuracy solution is calculated using the formula: Recovery rate = Measured amount / Added amount * 100%.

[0092] The accuracy results are as follows:

[0093] Table 9

[0094]

[0095] Table 10

[0096]

[0097]

[0098] Table 11

[0099]

[0100] The data above show that the average recoveries of calcium stearate / magnesium in formulations 1, 2, and 3, calculated using the conversion factor method, are 99.0%, 98.8%, and 99.4%, respectively. However, when the calcium stearate / magnesium excipients are treated as single substances, the average recoveries of calcium stearate / magnesium in formulations 1, 2, and 3, determined using the direct calculation method, are 105.8%, 103.9%, and 104.6%, respectively. According to the requirements for accuracy of quantitative analytical methods in the 2020 edition of the Chinese Pharmacopoeia, Volume IV, 9101 Validation Guidelines, the recovery rate should be in the range of 98.0% to 102.0%. Directly using the molecular weight conversion of a single component results in an overall high recovery rate, exceeding the accuracy requirement range. Therefore, the conversion factor method of this invention provides higher accuracy.

[0101] Example 6: Sample Detection Repeatability

[0102] Preparation of test solutions: Take 20 tablets of each of the three formulations in Table 2, grind them into fine powder, and then accurately weigh approximately 178 mg (Formulation 1), 61 mg (Formulation 2), and 91 mg (Formulation 3) of the sample powder respectively. Place them in their respective digestion tubes, add 6 ml of nitric acid, and digest and undergo acid removal-resolution treatment according to the method in Example 3. After digestion, transfer the solutions to 25 ml volumetric flasks, dilute with water to the mark, and shake well. Prepare 6 parallel solutions. The actual sample weights are shown in Table 12.

[0103] Take the above-mentioned test solutions and perform ion chromatography under the chromatographic conditions in Example 2. Record the peak areas of the chromatographic peaks with retention times of 9.0 min (magnesium ions) and 12.0 min (calcium ions). Substitute these values ​​into the equation of standard curve 1 in Example 4 to obtain the concentration of calcium / magnesium. Then calculate the content of calcium / magnesium stearate according to the following formula: Content = Concentration * Dilution factor * Conversion factor / Sample weight. Calculate the content of calcium / magnesium stearate in the sample. Then calculate the relative deviation according to the formula: Relative deviation = (Measured content - Prescription amount) / Prescription amount. The prescription amount is shown in Table 2. The results are as follows:

[0104] Table 12 Calculation Table for Repeatable Samples

[0105]

[0106] The data in the table above show that the RSDs of the contents of the six samples of preparations 1, 2, and 3 were 3.75%, 2.07%, and 0.70%, respectively, indicating that the method has good repeatability. The average relative deviation between the measured content and the amount added in the prescription was less than 3.0% (when the content is low, the relative deviation between it and the amount added in the prescription is generally required to be less than 5.0%), indicating that the method has good accuracy.

[0107] Example 7: Method Robustness

[0108] Linear standard solutions: A series of mixed standard solutions were prepared according to the method for plotting standard curve 1 in Example 4.

[0109] Preparation of test solution: Accurately weigh 178.25 mg and 173.2 mg (Formulation 1), 61.56 mg and 62.55 mg (Formulation 2), and 91.55 mg and 91.35 mg (Formulation 3) of the sample fine powder of formulations 1, 2 and 3 in Example 6, respectively, place them in the digestion tubes, add 6 ml of nitric acid, digest and remove acid and reconstitute according to the method of Example 3, transfer to 25 ml volumetric flasks, dilute with water to the mark, and shake well.

[0110] Take the above-mentioned linear standard solutions and test solutions, and after making slight changes to the chromatographic conditions in Example 2 (details of the changes are shown in Table 13), perform ion chromatography and record the peak areas of magnesium and calcium ions. Plot a standard curve with the concentration of calcium / magnesium ions in the linear standard solutions as the x-axis and the peak area of ​​the corresponding characteristic peaks as the y-axis. Substitute the peak areas of calcium / magnesium in the test solution into the standard curve equation to obtain the concentration of calcium / magnesium. Then calculate the content of calcium / magnesium stearate according to the following formula: Content = Concentration * Dilution factor * Conversion factor / Sample weight, calculate the content of calcium / magnesium stearate in the sample; then calculate the recovery rate according to the formula: Recovery rate = Measured amount after chromatographic condition change / Measured amount by conventional method. The measured amount by conventional method refers to the sample repeatability results in Example 6. The detection results are as follows:

[0111] Table 13 Statistical Table of Durability Results

[0112]

[0113] As shown in the table above, when the ion chromatography conditions (flow rate, column temperature, and acid concentration in the mobile phase) change slightly, compared with the results detected under conventional conditions, the recovery rates of calcium stearate in formulation 1 are 99.5%–101.4%, magnesium stearate in formulation 2 are 99.6%–100.5%, and magnesium stearate in formulation 3 are 99.4%–100.3%. All recovery rates are within the range of 98.0%–102.0%, indicating that the method has good robustness.

Claims

1. A method for detecting the calcium / magnesium stearate content in a formulation by ion chromatography, characterized in that, Includes the following steps: 1) Plotting the standard curves for calcium / magnesium: Accurately measure different volumes of calcium / magnesium standard solutions, place them in volumetric flasks, dilute with water to the mark, shake well, and prepare the standard curve solutions for calcium / magnesium; inject each standard curve solution into an ion chromatograph and determine the peak areas of calcium / magnesium ions. Plot a standard curve 1 with the concentration of calcium / magnesium elements on the x-axis and the peak area of ​​calcium / magnesium ions on the y-axis, and obtain the slope k1 of the curve. The concentration range of the calcium / magnesium element standard curve solution is 0.25~2.00μg / ml. 2) Plotting the standard curve of calcium stearate / magnesium: Accurately weigh the excipients calcium stearate / magnesium, place them in a digestion tube, add 68wt% concentrated nitric acid, and perform digestion and acid removal-resolution treatment. Transfer the solution in the digestion tube to a volumetric flask, dilute with water to the mark, and shake well to prepare a calcium stearate / magnesium stock solution. Then, accurately transfer different volumes of this calcium stearate / magnesium stock solution to a volumetric flask, dilute with water to the mark, and prepare a linear solution of calcium stearate / magnesium. Each linear solution was injected into an ion chromatograph, and the peak area of ​​calcium / magnesium ions was measured. A standard curve 2 was plotted with the concentration of calcium / magnesium stearate as the abscissa and the peak area of ​​calcium / magnesium ions as the ordinate. The slope k2 of the curve was obtained. The concentration range of the linear calcium stearate solution was 3.8~30.6μg / ml, and the concentration range of the linear magnesium stearate solution was 6.1~49.4μg / ml. Then, according to the formula: conversion factor = k1 / k2, the conversion factor of calcium / magnesium ion content in calcium / magnesium stearate can be obtained; 3) Sample testing: Take the test sample, weigh it accurately, place it in a digestion tube, add 68wt% concentrated nitric acid, digest and remove acid-redissolve it, then transfer the solution in the digestion tube to a volumetric flask, dilute it with water to the mark, shake well, and use it as the test sample solution. Take the test solution, inject it into the ion chromatograph, and record the peak areas of calcium / magnesium ions. ; Take a negative control and, following the same detection procedure as the test sample, measure the peak area of ​​calcium / magnesium ions in the blank sample solution. ; The negative control is: free of calcium / magnesium stearate, and other components are prepared and mixed according to the formula of the test sample; Will Substituting into the standard curve equation 1 of step 1), we obtain the concentration C of calcium / magnesium. 4) Calculation: The content of calcium stearate / magnesium stearate in the sample = C × conversion factor × dilution factor of the test solution / sample weight × 100%; In steps 2) and 3), the procedure for acid removal and resolution is as follows: after digestion, remove the acid from the sample at 120℃~170℃ for 1~3 hours until the acid is completely removed, then add 6mmol / L nitric acid solution, shake in a water bath at 60℃~80℃ until the sample in the digestion tube is dissolved, and then cool to room temperature. The formulation is selected from one of formulation 1, formulation 2, and formulation 3; The components of formulation 1 are methylcobalamin, microcrystalline cellulose, spray lactose, corn starch and calcium stearate; The components of formulation 2 are celecoxib, hydroxypropyl cellulose, low-substituted hydroxypropyl cellulose, lactose, sodium lauryl sulfate, and magnesium stearate; The components of formulation 3 are citalopram hydrobromide, corn starch, lactose, glycerin, croscarmellose sodium, microcrystalline cellulose, copovidone, magnesium stearate, hydroxypropyl methylcellulose, polyethylene glycol, and titanium dioxide.

2. The method according to claim 1, characterized in that, In steps 2) and 3), the digestion procedure is as follows: microwave power 1500W; 20 min, temperature rises from 25℃ to 130℃, maintains 130℃ for 5 min; 20 min, temperature rises from 130℃ to 185℃, maintains 185℃ for 20 min; during microwave digestion, the fan speed is level 1; after digestion, cool for 30 min at level 3 fan speed.

3. The method according to claim 1, characterized in that, In steps 1), 2), and 3), the detection conditions for the ion chromatograph are as follows: the detector is a conductivity detector; the chromatographic column is a cation analysis column; the flow rate is 0.3~0.7 ml / min; the injection volume is 10 μl; the column temperature is 25~40℃; and the mobile phase is 3~10 mmol / L nitric acid solution.

4. The method according to claim 1, characterized in that, In steps 2) and 3), the procedure for acid removal and resolution is as follows: after digestion, remove the acid from the sample at 150°C for 2 hours until the acid is completely removed, then add 6 ml of 6 mmol / L nitric acid solution, and shake in a water bath at 60°C~80°C until the sample in the digestion tube is dissolved, and then cool to room temperature.

5. The method according to claim 3, characterized in that, In steps 1), 2), and 3), the detection conditions of the ion chromatograph are as follows: the detector is a conductivity detector; the chromatographic column is a cation analysis column; the flow rate is 0.5 ml / min; the injection volume is 10 μl; the column temperature is 30℃; and the mobile phase is 6 mmol / L nitric acid solution.

6. The method according to claim 1, characterized in that, The volume of concentrated nitric acid in steps 2) and 3) is 4-8 ml.

7. The method according to claim 6, characterized in that, The volume of concentrated nitric acid in steps 2) and 3) is 6 ml.

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