Atomic absorption detection method for sodium content in ceftizoxime sodium for coping with complex organic matrix influence

Abstract

The invention provides a method for detecting sodium content in ceftizoxime sodium by atomic absorption spectrometry. Aiming at the problems of ionization and background interference of complex matrixes such as thiazole rings and oximido groups in ceftizoxime sodium molecules in a flame atomization process, the method comprises the following steps: adding a proper amount of nitric acid in a first-step dissolution process of a test sample, centrifuging after ceftizoxime is separated out, taking supernate, and carrying out second-step dilution; most interference caused by a ceftizoxime complex organic matrix is eliminated, and an alkali metal ionization inhibitor (preferably cesium chloride) with a specific concentration is also introduced into a detection system and is matched with a nitric acid medium to achieve a synergistic effect, so that matrix interference is effectively eliminated. The concentration interval of the reference substance series solution is limited to be 60%-120% of the target detection concentration, the absorbance of the test solution is measured at the characteristic absorption wavelength of the sodium element, and the sodium content is calculated. Experiments prove that the correlation coefficient r of the method is greater than or equal to 0.998, the absolute value ratio of y intercept is less than or equal to 2.0%, and the method has extremely high specificity, accuracy and durability. The method is simple and convenient to operate and stable in result, and the quality control level of the ceftizoxime sodium is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of drug quality control technology, specifically to a method for detecting the sodium content in cefazolin sodium. Background Technology

[0002] Cefazolin sodium, chemically named (6R,7R)-7-[2-(2-aminothiazo-4-yl)-2-(methoxyimino)acetamido]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-en-2-carboxylic acid sodium salt, is mainly used to treat lower respiratory tract infections, urinary tract infections, abdominal infections, pelvic infections, sepsis, skin and soft tissue infections, bone and joint infections, meningitis caused by Streptococcus pneumoniae or Haemophilus influenzae, and uncomplicated gonorrhea caused by susceptible bacteria. Because cefazolin has poor water solubility, preparing it as a sodium salt improves its water solubility. During treatment, this drug is a hidden source of sodium ions, requiring accurate measurement to prevent adverse consequences from sodium overdose or underdose. Insufficient sodium content may indicate incomplete salt formation of cefazolin, affecting the absorption rate and distribution of the drug; excessive sodium content may pose serious clinical safety risks to patients. Therefore, sodium ion content is a key quality attribute affecting the safety and efficacy of drugs.

[0003] A review of existing methods reveals that common methods for detecting sodium in compounds include atomic absorption spectrophotometry, ion chromatography, inductively coupled plasma atomic emission spectrometry (ICP-AES), and ICP-AES mass spectrometry. However, atomic absorption spectrophotometry offers the greatest advantage in terms of operational convenience and detection cost. Due to the presence of thiazole rings, oxime groups, and sulfur- and nitrogen-containing heterocyclic structures in the cefazolin sodium molecule, molecular absorption background is easily generated during flame atomization, altering the atomization and ionization equilibrium of sodium. This results in a poor linear relationship between sodium absorbance and concentration under conventional atomic absorption spectrometry conditions, and the measurement results are highly sensitive to changes in detection conditions. Existing conventional sodium determination methods cannot simultaneously meet the requirements of specificity, accuracy, repeatability, and robustness for pharmaceutical quality control. Therefore, there is an urgent need to establish a sodium content detection method that can effectively eliminate ionization and background interference during atomic absorption spectrometry, while ensuring accurate and stable results, taking into account the complex matrix characteristics of cefazolin sodium.

[0004] Therefore, the technical problem to be solved by the present invention is:

[0005] How to effectively eliminate ionization and background interference caused by the unique matrix of cefazolin sodium in the atomic absorption spectrophotometric determination system, and achieve accurate and stable determination of sodium content within a limited detection parameter window. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides an atomic absorption spectrometry method for detecting sodium content in cefazolin sodium, which addresses the influence of complex organic matrices. This method comprises the following steps:

[0007] (1) A mixed solution containing nitric acid and an alkali metal ionization inhibitor is used as a blank solution, wherein the alkali metal ionization inhibitor is a cesium salt, preferably cesium chloride;

[0008] (2) Using sodium chloride as the sodium source reference standard, a series of reference standard solutions were prepared under the same matrix conditions as the blank solution, and the concentration range of the series of reference standard solutions was limited to 60% to 120% of the target detection concentration;

[0009] (3) The preferred method for processing the test sample is to dissolve the cefazolin sodium sample in an appropriate amount of water, add acid to allow the cefazolin to precipitate effectively, centrifuge to collect the supernatant, and dilute it under the same conditions as the blank solution to prepare the test sample solution.

[0010] (4) Detect sodium at the characteristic absorption wavelength (preferably 589.0 nm) using a flame atomization atomic absorption spectrophotometer. Establish a standard curve using a series of reference solutions and calculate the sodium content in the test solution based on the standard curve. The method described herein must meet the following system suitability conditions: in the series of reference solutions, the absorbance value and concentration should be linear, with a correlation coefficient r ≥ 0.998, and the y-intercept (the ratio of the absolute value of the linear intercept to the response value at 100% concentration) should not be greater than 2.0%; the absorbance value of the blank solution should be within ±2.0% of the absorbance value of the 100% linear solution.

[0011] Compared with the prior art, the present invention has at least the following beneficial effects:

[0012] (1) The present invention eliminates most of the interference caused by the complex organic matrix of cefazolin by adding an appropriate amount of nitric acid during the first dissolution process of the test sample, and centrifuging the supernatant after cefazolin precipitates for a second dilution.

[0013] (2) This invention introduces cesium salts within a specific concentration range as ionization inhibitors into the detection system, which work synergistically with nitric acid media to effectively eliminate the interference of the complex organic matrix of cefazolin sodium on the sodium atomization and ionization process, thus significantly improving the detection specificity.

[0014] (3) This invention clearly defines the linear range of sodium content determination for cefazolin sodium samples as 60% to 120%, avoiding the linear deviation and intercept abnormality problems that occur under conventional wide linear range conditions, thereby significantly improving the detection accuracy and repeatability.

[0015] (4) Within the parameter window, the method of the present invention has good robustness to changes in the amount of ionization inhibition and acidic medium added, and can meet the requirements for method robustness in drug quality control.

[0016] (5) The method of the present invention does not require complex digestion of the sample, is simple to operate, has good repeatability and stable results, and is suitable for quality control and detection of sodium content in cefazolin sodium raw material and its preparations. Attached Figure Description

[0017] Figure 1 Linear graph of the reference solution of the present invention. Detailed Implementation

[0018] To gain a better understanding of the technical solution and beneficial effects of the present invention, the present invention will be further described in detail below with reference to the embodiments.

[0019] Example 1: In this example, the sodium content in cefazolin sodium was determined by the following steps.

[0020] (1) Preparation of cesium chloride solution: Weigh 0.8g of cesium chloride, place it in a 100ml volumetric flask, add water to dissolve and dilute to the mark, shake well, and the solution is ready.

[0021] (2) Preparation of blank solution: Accurately measure 2 ml of nitric acid, place it in a 100 ml volumetric flask, accurately add 10 ml of cesium chloride solution, dilute with water to the mark, and shake well to obtain the blank solution.

[0022] (3) Preparation of sodium chloride stock solution: Take 19 mg of sodium chloride that has been dried at 105℃ for 2 h, weigh it accurately, put it in a 100 ml volumetric flask, add water to dissolve and dilute to the mark, shake well, accurately measure 5 ml, put it in a 100 ml volumetric flask, add water to dilute to the mark, shake well, and the solution is ready.

[0023] (4) Preparation of reference solution series: Accurately measure 3 ml, 4 ml, 4.5 ml, 5 ml and 6 ml of sodium chloride stock solution and put them into 50 ml volumetric flasks respectively. Then add 1 ml of nitric acid and 5 ml of cesium chloride solution into the above volumetric flasks respectively, dilute with water to the mark, and shake well to obtain the solution.

[0024] (5) Preparation of test solution: Weigh 0.07g of this product, place it in a 200ml volumetric flask, add 10ml of water to dissolve it, add 2ml of nitric acid, let it stand for 10min, dilute with water to the mark, shake well, centrifuge at 8000rpm for 10min, accurately measure 1ml of supernatant, place it in a 50ml volumetric flask, accurately add 5ml of cesium chloride solution and 1ml of nitric acid, dilute with water to the mark, shake well, and the test solution is obtained.

[0025] (6) Detection conditions: The light source is a sodium hollow cathode lamp, the nebulizer is an acetylene-air flame with an air-acetylene flow rate of 10:2.5 (unit: L / min), the absorption wavelength is 589.0 nm, and the slit width is 0.2. Blank solution, reference solution series, and test solution are injected into the atomic absorption spectrometer to obtain the measured value C (μg / ml). Calculated according to the standard curve method and based on anhydrous content, the sodium content of this product should be 5.4%–6.0%.

[0026] System suitability requirements: In the reference solution series, the absorbance value should be linear with the concentration, with a correlation coefficient r ≥ 0.998, and the y-intercept (the ratio of the absolute value of the linear intercept to the response value at 100% concentration) should not be greater than 2.0%; the absorbance value of the blank solution should be within ±2.0% of the absorbance value of the 100% linear solution.

[0027] The formula for calculating sodium content is as follows:

[0028]

[0029] In the formula:

[0030] C: The sodium concentration in the test solution was measured, in μg / ml;

[0031] V 供试品 : Dilution factor of the test solution, in ml;

[0032] M: Sample weight, g.

[0033] Example 2: Methodological Investigation Results

[0034] (1) Examination of method specificity, system applicability, and linearity.

[0035] We need to examine whether the blank solution interferes with the detection of sodium and the linearity of the reference solution series.

[0036] Cesium chloride solution, blank solution, sodium chloride stock solution and reference solution were prepared according to Example 1.

[0037] Take blank solution and reference solution series, inject them under the specified conditions, and record the chromatograms.

[0038] Table of Specificity and System Suitability Study Results for Sodium Content Determination in Cefazolin Sodium

[0039]

[0040] Based on the results of the specificity and system suitability analysis, the absorbance values ​​of the reference solution series are linearly related to the concentration, with the linear equation being y = 0.73401x + 0.00252. The correlation coefficient r is 0.999568, which is greater than 0.998. The y-intercept (the ratio of the absolute value of the linear intercept to the response value at 100% concentration) is 0.88%, which is less than 2%, indicating a good linear relationship. The absorbance value of the reagent blank solution accounts for -0.11% of the absorbance value of the 100% linear solution, which is less than 2.0%, indicating good specificity and system suitability.

[0041] (2) Examination of injection precision

[0042] ① Prepare cesium chloride solution, blank solution, and sodium chloride stock solution according to Example 1.

[0043] ②Preparation of 100% concentration level reference solution: Accurately measure 5 ml of sodium chloride stock solution and place it in a 50 ml volumetric flask. Then add 1 ml of nitric acid and 5 ml of cesium chloride solution to the same volumetric flask, dilute with water to the mark, and shake well.

[0044] Take blank solution and 100% concentration level control solution, inject them under the specified conditions, and record the spectrum.

[0045] Table of Precision Results of Injection of 100% Concentration Level Sodium Chloride Reference Solution

[0046]

[0047] Based on the results of the sample injection precision measurement, after 5 consecutive measurements, the RSD of the absorbance value was 0.30%, which is less than 1%, indicating good sample injection precision.

[0048] (3) Method accuracy assessment

[0049] Based on the results of the examination of method specificity, system applicability, linearity, and injection precision, it can be seen that the method has strong specificity, good linearity, and high injection precision. Therefore, its accuracy will be examined below.

[0050] ① Prepare a series of solutions including cesium chloride solution, blank solution, sodium chloride stock solution and reference standard according to Example 1.

[0051] ②Preparation of 90% accuracy solution: Accurately measure 4.5 ml of sodium chloride stock solution and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride and 1 ml of nitric acid. Dilute with water to the mark and shake well. Prepare 3 parallel batches.

[0052] ③Preparation of 100% accuracy stock solution: Accurately measure 5 ml of sodium chloride stock solution and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride and 1 ml of nitric acid, dilute with water to the mark, and shake well. Prepare 3 parallel batches.

[0053] ④ Preparation of 110% accuracy solution: Accurately measure 5.5 ml of sodium chloride stock solution and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride and 1 ml of nitric acid. Dilute with water to the mark and shake well. Prepare 3 parallel portions.

[0054] Take blank solution, reference solution series, and accuracy solution, inject them for determination, and record the spectrum.

[0055] Results of the accuracy study on sodium content detection in cefazolin sodium

[0056]

[0057] Sodium recovery rates were all in the range of 99% to 103%, with RSD less than 2.0%, proving that the method is highly accurate.

[0058] (4) Examination of method repeatability

[0059] ① Prepare a series of solutions including cesium chloride solution, blank solution, sodium chloride stock solution and reference standard according to Example 1.

[0060] ② Preparation of the test solution: Weigh 0.07 g of this product and place it in a 200 ml volumetric flask. Add 10 ml of water to dissolve it, then add 2 ml of nitric acid. Let it stand for 10 min, then dilute with water to the mark. Shake well and centrifuge at 8000 rpm for 10 min. Accurately measure 1 ml of the supernatant and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride solution and 1 ml of nitric acid. Dilute with water to the mark and shake well. Prepare 6 parallel solutions.

[0061] Take blank solution, reference solution series, and test solution, inject them under the specified conditions, and record the chromatogram.

[0062] Results of repeatability study of sodium content detection in cefazolin sodium

[0063]

[0064] Six samples were repeatedly tested, and the sodium content was found to be within the range of 5.66% to 5.68%, with an RSD of less than 0.2%. This demonstrates that the method has good repeatability.

[0065] (5) Examination of method durability

[0066] ① Preparation of cesium chloride solution: Weigh 0.8g of cesium chloride, place it in a 100ml volumetric flask, add water to dissolve and dilute to the mark, shake well, and the solution is ready.

[0067] ②Preparation of blank solution: Accurately measure 2 ml of nitric acid and place it in a 100 ml volumetric flask. Accurately add 10 ml of cesium chloride solution, dilute with water to the mark, and shake well to obtain the blank solution.

[0068] ③Preparation of sodium chloride stock solution: Accurately weigh 19 mg of sodium chloride that has been dried at 105℃ for 2 h, place it in a 100 ml volumetric flask, add water to dissolve and dilute to the mark, shake well, accurately measure 5 ml, place it in a 100 ml volumetric flask, add water to dilute to the mark, shake well, and the solution is ready.

[0069] ④ Preparation of reference solution series: Accurately measure 3 ml, 4 ml, 4.5 ml, 5 ml and 6 ml of sodium chloride stock solution and place them in 50 ml volumetric flasks respectively. Then add 1 ml of nitric acid and 5 ml of cesium chloride solution to the above volumetric flasks respectively, dilute with water to the mark, and shake well to obtain the solution.

[0070] ⑤ Test sample stock solution: Weigh 0.07g of this product, place it in a 200ml volumetric flask, add 10ml of water to dissolve it, add 2ml of nitric acid, let it stand for 10min, dilute with water to the mark, shake well, centrifuge at 8000rpm for 10min, and take the supernatant as the test sample stock solution.

[0071] ⑥ Test solution: Accurately measure 1 ml of the test solution stock solution and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride solution and 1 ml of nitric acid. Dilute with water to the mark and shake well. Prepare two parallel solutions.

[0072] ⑦ Test solution (4.5 ml cesium chloride): Accurately measure 1 ml of the test solution and place it in a 50 ml volumetric flask. Accurately add 4.5 ml of cesium chloride solution and 1 ml of nitric acid. Dilute with water to the mark and shake well.

[0073] ⑧ Test solution (5.5 ml cesium chloride): Accurately measure 1 ml of the test solution and place it in a 50 ml volumetric flask. Accurately add 5.5 ml of cesium chloride solution and 1 ml of nitric acid. Dilute with water to the mark and shake well.

[0074] ⑨ Test solution (0.9 ml nitric acid): Accurately measure 1 ml of the test solution and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride solution and 0.9 ml of nitric acid. Dilute with water to the mark and shake well.

[0075] ⑩ Test solution (1.1 ml nitric acid): Accurately measure 1 ml of the test solution and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride solution and 1.1 ml of nitric acid. Dilute with water to the mark and shake well.

[0076] The effects of changes in the amount of cesium chloride and nitric acid added on the detection results were investigated separately. After each change in conditions, blank solution, reference solution series, and test solution were injected and measured, and the spectra were recorded.

[0077] Summary table of sodium content measured under various conditions

[0078]

[0079] By adjusting the amounts of cesium chloride and nitric acid added, the sodium content was measured to be between 5.67% and 5.76%, and the RSD was less than 2.0% compared with normal conditions. This demonstrates that the method is robust to the addition amounts of nitric acid and cesium chloride.

[0080] Example 3: Investigation of different cesium salts

[0081] Replace 0.8% cesium chloride with 0.93% cesium nitrate or 0.86% cesium sulfate. The preparation, detection conditions and calculation methods for the remaining samples are the same as those under "Example 1".

[0082] Comparison of linear detection results for different cesium salts

[0083]

[0084] The above linear determination results all meet the requirement of a correlation coefficient greater than 0.998, the ratio of the absolute value of the y-intercept to the response value at 100% concentration point is not greater than 2.0%, and the ratio of the blank to the 100% linear response value is within ±2.0%. The sodium content in cefazolin sodium was determined using the above linear determination method, and the results are as follows:

[0085] Test results of the sample:

[0086]

[0087] Comparing the test results of the three cesium salts, all were within the required range, but the RSD and fluctuation of the cesium chloride test result were the smallest, so cesium chloride was preferred.

[0088] Example 4: Investigation of different cesium chloride concentrations

[0089] Because cesium chloride can provide a large number of electrons, it effectively suppresses the ionization of sodium in an air-acetylene flame. In order to achieve the effect of suppressing ionization, the reported concentration range of cesium chloride in the atomic absorption spectrometry determination methods for other cephalosporin sodium salts varies greatly in the prior art, such as 3 mg / ml and 8 mg / ml. Therefore, the concentration of cesium chloride is studied in this invention.

[0090] Replace 0.8% cesium chloride (0.8 mg / ml) with 0.4% cesium chloride (0.4 mg / ml) or 8% cesium chloride (8 mg / ml). The preparation, detection conditions and calculation methods for the remaining samples are the same as those under "Example 1".

[0091] Comparison of detection results for a series of cesium chloride reference solutions of different concentrations

[0092]

[0093] The study investigated different concentrations of cesium chloride and found that when the concentration of cesium chloride was low, its linear correlation coefficient was less than 0.999 and the intercept ratio was greater than 1%. When the concentration of cesium chloride was high, its absorbance was relatively low, less than 0.12 at the target concentration, which may introduce a relatively large detection error. Therefore, 0.8% cesium chloride is more suitable.

[0094] Example 5: Investigating the effect of not adding acid in the first dilution of the test sample

[0095] (1) Prepare a series of solutions of cesium chloride, blank solution, sodium chloride stock solution and reference standard according to “Example 1”.

[0096] (2) First step: dilute and acidify the test solution: Weigh 0.07 g of this product and place it in a 200 ml volumetric flask. Add 10 ml of water to dissolve it, then add 2 ml of nitric acid. Let it stand for 10 min, then dilute with water to the mark. Shake well and centrifuge at 8000 rpm for 10 min. Accurately measure 1 ml of the supernatant and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride solution and 1 ml of nitric acid. Dilute with water to the mark and shake well. Prepare 6 parallel portions.

[0097] (3) First step of diluting the test solution without acid: Weigh 0.07g of this product and place it in a 200ml volumetric flask. Dissolve and dilute to the mark with water, shake well, accurately measure 1ml and place it in a 50ml volumetric flask. Accurately add 5ml of cesium chloride solution and 1ml of nitric acid, dilute to the mark with water, and shake well. Prepare 6 parallel portions.

[0098] The detection conditions and calculation methods are the same as those under "Example 1".

[0099] Results of two different sample treatment methods:

[0100]

[0101] In the pretreatment of the test sample, if no acid is added during the first dilution step, the measured result fluctuates within the range of 5.64% to 5.86%, and the measured RSD value is 1.57%. Compared with the measured result with acid, the data deviates far from the central theoretical value (5.67%), and the data fluctuation range is also larger.

[0102] Comparative Example 1: Without cesium chloride

[0103] (1) Preparation of blank solution: Accurately measure 2 ml of nitric acid, place it in a 100 ml volumetric flask, dilute with water to the mark, and shake well to obtain the blank solution.

[0104] (2) Preparation of sodium chloride stock solution: Take 19 mg of sodium chloride that has been dried at 105℃ for 2 h, weigh it accurately, put it in a 100 ml volumetric flask, add water to dissolve and dilute to the mark, shake well, accurately measure 5 ml, put it in a 100 ml volumetric flask, add water to dilute to the mark, shake well, and the solution is ready.

[0105] (3) Preparation of reference solution series: Accurately measure 3 ml, 4 ml, 4.5 ml, 5 ml and 6 ml of sodium chloride stock solution and put them into 50 ml volumetric flasks respectively. Then add 1 ml of nitric acid to each of the above volumetric flasks, dilute with water to the mark, and shake well to obtain the solution.

[0106] Detection conditions: Same as the specific detection conditions and calculation formulas in Example 1.

[0107] Take blank solution and reference solution series, and inject them according to the specified conditions.

[0108] The reference standard series solutions were tested under the above conditions, and the results are as follows:

[0109]

[0110] Without the addition of cesium chloride, the correlation coefficient of its linear curve is 0.9872, which does not meet the requirements for linearity.

[0111] Comparative Example 2: Potassium chloride as an ionization inhibitor

[0112] In existing technologies, potassium chloride is used as an ionization inhibitor. Referring to the method in the literature, we used 0.5% potassium chloride as an ionization inhibitor to prepare the reference and test solutions for determination.

[0113] (1) Preparation of 0.5% potassium chloride solution: Weigh 5g of potassium chloride, add 1000ml of water, dissolve, and shake well to obtain the solution.

[0114] (2) Preparation of blank solution: Accurately measure 2 ml of nitric acid, place it in a 100 ml volumetric flask, add 0.5% potassium chloride solution to dilute to the mark, shake well, and the blank solution is obtained.

[0115] (3) Preparation of sodium chloride stock solution: Weigh 19 mg of sodium chloride that has been dried at 105℃ for 2 h accurately, place it in a 100 ml volumetric flask, add 0.5% potassium chloride solution to dissolve and dilute to the mark, shake well, accurately measure 5 ml, place it in a 100 ml volumetric flask, add 0.5% potassium chloride solution to dilute to the mark, shake well, and the solution is ready.

[0116] (4) Preparation of reference solution series: Accurately measure 3 ml, 4 ml, 4.5 ml, 5 ml and 6 ml of sodium chloride stock solution and put them into 50 ml volumetric flasks respectively. Then add 1 ml of nitric acid to each of the above volumetric flasks, add 0.5% potassium chloride solution to dilute to the mark, shake well and the solution is ready.

[0117] (5) Preparation of test solution: Weigh 0.07g of this product and place it in a 200ml volumetric flask. Add 10ml of 0.5% potassium chloride solution to dissolve it. Add 2ml of nitric acid and let it stand for 10min. Dilute with water to the mark and shake well. Centrifuge at 8000rpm for 10min. Accurately measure 1ml of the supernatant and place it in a 50ml volumetric flask. Accurately add 1ml of nitric acid and dilute with 0.5% potassium chloride solution to the mark. Shake well to obtain the test solution.

[0118] Detection conditions: Same as the specific detection conditions and calculation formulas in Example 1.

[0119] Take blank solution, reference solution series, and test solution, and inject them according to the specified conditions.

[0120] The sodium content in the test sample was determined using the above conditions, and the results are as follows:

[0121] Based on the above results, potassium chloride was added as an ionization inhibitor and matrix interference eliminator as required by the literature. However, the measured sample results showed large fluctuations and poor stability.

[0122] Comparative Example 3: The linear range is too wide

[0123] (1) Preparation of cesium chloride solution: Weigh 0.8g of cesium chloride, place it in a 100ml volumetric flask, add water to dissolve and dilute to the mark, shake well, and the solution is ready.

[0124] (2) Preparation of blank solution: Accurately measure 2 ml of nitric acid, place it in a 100 ml volumetric flask, accurately add 10 ml of cesium chloride solution, dilute with water to the mark, and shake well to obtain the blank solution.

[0125] (3) Preparation of sodium chloride stock solution: Take 19 mg of sodium chloride that has been dried at 105℃ for 2 h, weigh it accurately, put it in a 100 ml volumetric flask, add water to dissolve and dilute to the mark, shake well, accurately measure 5 ml, put it in a 100 ml volumetric flask, add water to dilute to the mark, shake well, and the solution is ready.

[0126] (4) Preparation of reference solution series: Accurately measure 1 ml, 2.5 ml, 5 ml, 7.5 ml and 10 ml of sodium chloride stock solution and place them in 50 ml volumetric flasks respectively. Then add 1 ml of nitric acid and 5 ml of cesium chloride solution to the above volumetric flasks respectively, dilute with water to the mark, and shake well to obtain the solution.

[0127] Detection conditions: Same as the specific detection conditions in Example 1.

[0128] Take blank solution and reference solution series, and inject them according to the specified conditions.

[0129] The measured linear equation results are as follows:

[0130]

[0131] Based on the above results, it can be seen that when the linear range is too wide (20% to 200% of the target value), the correlation coefficient of the measured linear equation is poor, and the ratio of the absolute value of the linear intercept to the response value at the 100% concentration point cannot meet the requirements for content determination.

[0132] Comparative Example 4: Measurement at 330.3 nm

[0133] (1) Preparation of cesium chloride solution: Weigh 0.8g of cesium chloride, place it in a 100ml volumetric flask, add water to dissolve and dilute to the mark, shake well, and the solution is ready.

[0134] (2) Preparation of blank solution: Accurately measure 2 ml of nitric acid, place it in a 100 ml volumetric flask, accurately add 10 ml of cesium chloride solution, dilute with water to the mark, and shake well to obtain the blank solution.

[0135] (3) Preparation of reference solution: Weigh 10mg, 20mg, 30mg, 40mg and 50mg of sodium chloride that have been dried at 105℃ for 2h accurately, place them in a 100ml volumetric flask, add 2ml of nitric acid and 10ml of cesium chloride solution accurately, dilute with water to the mark, shake well, and the solution is ready.

[0136] (4) Preparation of test solution: Weigh 0.13g of this product and place it in a 100ml volumetric flask. Accurately add 2ml of nitric acid and 10ml of cesium chloride solution. Dilute with water to the mark, shake well, and centrifuge an appropriate amount at 8000rpm for 10min. Take the supernatant to obtain the test solution. Prepare 3 parallel solutions.

[0137] Detection conditions: The light source was a sodium hollow cathode lamp; the nebulizer was an acetylene-air flame with an air-acetylene flow rate of 10:2.5 (L / min); the absorption wavelength was 330.3 nm; and the slit width was 0.7 mm. Blank solution, reference solution, and test solution were injected into the atomic absorption spectrometer. The sodium content was calculated.

[0138] Take blank solution, reference solution series, and test solution, inject them under the specified conditions, and record the data.

[0139] The sodium content in the test sample was determined using the above conditions, and the results are as follows:

[0140]

[0141] Based on the above results, the signal value of sodium at 330.3 nm is much lower than that at 589.0 nm, and the measured result is slightly lower, with slightly larger fluctuations in the data.

[0142] Comparative Example 5: Without nitric acid

[0143] In existing atomic absorption spectrometry methods for other sodium salts, although potassium chloride or cesium chloride are used as ionization inhibitors, nitric acid is not added. Therefore, we also studied the method of not adding nitric acid when measuring the sodium content in cefazolin sodium.

[0144] (1) Preparation of cesium chloride solution: Weigh 0.8g of cesium chloride, place it in a 100ml volumetric flask, add water to dissolve and dilute to the mark, shake well, and the solution is ready.

[0145] (2) Preparation of blank solution: Accurately measure 10 ml of cesium chloride solution, place it in a 100 ml volumetric flask, dilute with water to the mark, and shake well to obtain the blank solution.

[0146] (3) Preparation of sodium chloride stock solution: Take 19 mg of sodium chloride that has been dried at 105℃ for 2 h, weigh it accurately, put it in a 100 ml volumetric flask, add water to dissolve and dilute to the mark, shake well, accurately measure 5 ml, put it in a 100 ml volumetric flask, add water to dilute to the mark, shake well, and the solution is ready.

[0147] (4) Preparation of reference solution series: Accurately measure 3 ml, 4 ml, 4.5 ml, 5 ml and 6 ml of sodium chloride stock solution and put them into 50 ml volumetric flasks respectively. Then add 5 ml of cesium chloride solution to each of the above volumetric flasks, dilute with water to the mark, and shake well to obtain the solution.

[0148] (5) Preparation of the test solution: Weigh 0.07 g of this product and place it in a 200 ml volumetric flask. Add 10 ml of water to dissolve it, then add 2 ml of nitric acid. Let it stand for 10 min, then dilute with water to the mark. Shake well and centrifuge at 8000 rpm for 10 min. Accurately measure 1 ml of the supernatant and place it in a 50 ml volumetric flask. Accurately add 5 ml of cesium chloride solution, dilute with water to the mark, and shake well. Prepare 6 parallel solutions.

[0149] Detection conditions: Same as the specific detection conditions in Example 1.

[0150] Take blank solution, reference solution series, and test solution, inject them under the specified conditions, and record the data.

[0151] The sodium content in the test sample was determined using the above conditions, and the results are as follows:

[0152]

[0153] The reference solution series and the test solution were tested without nitric acid. Although the average value of the 6 data points met the detection requirements and was within the theoretical range, the RSD was greater than 2%, indicating large data fluctuations. Furthermore, the data could not meet the relevant requirements for the detection of sodium content in cefazolin sodium.

[0154] In summary, based on the results of this invention and comparative examples, it is evident that by adding a certain amount of acid during the initial dissolution and dilution process of the test sample, followed by the addition of cesium chloride and nitric acid during subsequent detection, the complex molecular structure of cefazolin sodium can effectively mitigate matrix interference. Furthermore, the selected series of reference solutions exhibit reasonable concentrations and good linearity, and the detection wavelength demonstrates high sensitivity and accuracy, enabling accurate and stable determination of sodium content in cefazolin sodium.

Claims

1. An atomic absorption spectrometry method for detecting sodium content in cefazolin sodium to address the influence of complex organic matrices, characterized in that, The determination was performed using atomic absorption spectrophotometry under detection conditions containing an ionization suppression system. The method includes the following steps: (1) Prepare a blank solution, wherein the blank solution contains nitric acid and an alkali metal ionization inhibitor, wherein the alkali metal ionization inhibitor is a cesium salt; (2) Using sodium chloride as a reference standard, a series of reference standard solutions were prepared under the same matrix conditions as the blank solution, and the concentration range of the series of reference standard solutions was limited to 60% to 120% of the target detection concentration; (3) The preferred method for processing the test sample is to dissolve the cefazolin sodium sample in an appropriate amount of water, add acid to allow the cefazolin to precipitate effectively, centrifuge to collect the supernatant, and dilute it under the same conditions as the blank solution to prepare the test sample solution. (4) The absorbance of the reference series solutions and the test solution was measured at a wavelength of 589.0 nm using a flame atomization atomic absorption spectrophotometer to establish a standard curve and calculate the sodium content in the test sample. The method shall meet the following system suitability conditions: the absorbance and concentration of the reference series solutions are linearly related, the linear regression correlation coefficient r ≥ 0.998, and the absolute value of the y-intercept of the linear regression equation is not greater than 2.0% relative to the response value at the 100% concentration point.

2. The method for detecting sodium content in cefazolin sodium as described in claim 1, characterized in that, The cesium salt is one or more of cesium chloride, cesium nitrate, or cesium sulfate, preferably cesium chloride.

3. The method for detecting sodium content in cefazolin sodium as described in claim 2, characterized in that, In the preparation of the solution, the concentration of cesium chloride in the solution is 0.075% to 0.085% (w / v), preferably 0.08% (w / v).

4. The method for detecting sodium content in cefazolin sodium as described in claim 1, characterized in that, In the preparation of the solution, the concentration of nitric acid in the solution is 1.8% to 2.2% (v / v), preferably 2% (v / v).

5. The method as described in claim 1, characterized in that, The reference standard is sodium chloride, and the range of the series concentrations is related to the concentration of sodium element from 0.224 μg / ml to 0.449 μg / ml (60% to 120%).

6. The method as described in claim 1, characterized in that, The characteristic wavelength of sodium is preferably 589.0 nm, and the light source is a sodium hollow cathode lamp.

7. The method as described in claim 1, characterized in that, The slit width during testing is 0.

2.

8. The method as described in claim 1, characterized in that, The number of data reads at the characteristic wavelength of sodium is 3 to 9, preferably 6.

9. The method as described in claim 1, characterized in that, The air-acetylene ratio is 4:1, the air flow rate is 10 L / min, and the acetylene flow rate is 2.5 L / min.

10. The method as described in claim 1, characterized in that, In step (1), the preparation method of the test sample is as follows: Weigh 0.07g of the sample, place it in a 200ml volumetric flask, add 10ml of water to dissolve it, add 2ml of nitric acid, let it stand for 10min, dilute it with water to the mark, shake it well, centrifuge it at 8000rpm for 10min, accurately measure an appropriate amount of the supernatant, and dilute it to the required concentration with an aqueous solution containing 0.075% to 0.085% cesium chloride (w / v) and 1.8% to 2.2% (v / v) nitric acid.

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