ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometer) detection method for carbomer content in cyclosporine eye drops

Abstract

The invention relates to the technical field of pharmaceutical analysis, in particular to an ICP-OES (Inductively Coupled Plasma-Optical Emission Spectrometry) detection method for the content of carbomer in cyclosporine eye drops. The method comprises the following steps: fully dissociating carboxylic acid groups of carbomer under alkaline conditions, carrying out metering reaction on the carboxylic acid groups and added calcium ions, detecting the content of residual calcium elements in a solution after the reaction through ICP-OES (Inductively Coupled Plasma Optical Emission Spectrometry), and carrying out back calculation by combining with a metering relationship between the calcium ions and carbomer, so as to obtain the content of carbomer in the cyclosporine eye drops. Compared with an existing titration method, the method is easy and convenient to operate, high in detection efficiency and good in repeatability and accuracy, can effectively adapt to complex matrix systems such as cyclosporine eye drops and the like, and has good industrial application value.

Description

Technical Field

[0001] This invention relates to the field of pharmaceutical analysis technology, and in particular to an ICP-OES method for detecting carbomer content in cyclosporine eye drops. Background Technology

[0002] Carbomer is a type of high-molecular-weight thickener based on cross-linked acrylic acid, commonly used in pharmaceutical formulations such as eye drops and gels to adjust viscosity, improve adhesion, and influence formulation stability. Accurate detection of carbomer content in formulations is crucial for product quality control.

[0003] Currently, the commonly used method for detecting carbomer content in formulations is titration. For example, Chinese patent CN 107328766A discloses a method for determining the carbomer content in a gel containing carbomer. This method requires the use of reagents such as EDTA titrant, and the detection is completed by manually controlling the titration process and observing the titration endpoint. This type of detection method has the following drawbacks: (1) The titration method has a complex operation process and requires high professional skills and experience from the operators. It is easy for human judgment errors to lead to inaccurate test results. (2) The detection cycle is long, which cannot meet the needs of rapid detection of batch samples and the efficiency is low; (3) The titration process requires the use of a variety of chemical reagents, which consumes a large amount of reagents and may generate waste liquid pollution, resulting in poor environmental performance; (4) The titration process is easily affected by the sample matrix, resulting in poor repeatability.

[0004] Therefore, there is an urgent need for a carbomer content detection method that is easy to operate, fast to detect, accurate to provide results, and environmentally friendly. Summary of the Invention

[0005] To address the problems of complex operation, low detection efficiency, large result error, and poor environmental friendliness in existing titration methods for detecting carbomer content, the present invention aims to provide an ICP-OES method for detecting carbomer content in cyclosporine eye drops, achieving rapid, accurate, and efficient determination of carbomer content in cyclosporine eye drops.

[0006] To achieve the above and other related objectives, this invention provides an ICP-OES method for detecting carbomer content in cyclosporine eye drops, comprising the following steps: (1) Solution preparation: Prepare a diluent of nitric acid and purified water for diluting samples and standard solutions; Using the diluent as a blank, the calcium standard solution was diluted to obtain a series of linear calcium standard solutions with concentrations covering the required detection range; Sodium hydroxide solution and calcium chloride solution were prepared separately to provide an alkaline environment for the reaction system and to act as a reaction reagent. (2) Preparation of blank solution: Add the sodium hydroxide solution and calcium chloride solution of the specified volume to the container, add purified water to make up the volume, and after shaking and centrifugation, take the supernatant and make up the volume with diluent to obtain a blank solution; (3) Preparation of test solution: Weigh the cyclosporine eye drop sample, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2), add purified water to make up the volume, and after shaking and centrifugation, take the supernatant and make up the volume with diluent to obtain the test solution; (4) Preparation of reference standards and spiking solutions: Weigh a known amount of carbomer reference standard, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2), add purified water to make up to volume, and after shaking and centrifugation, take the supernatant and make up to volume with diluent to obtain the reference standard solution; A spiked solution can be obtained by adding calcium standard solution to the reference solution or the test solution; (5) ICP-OES testing: The linear standard solution, blank solution, test solution, reference solution, and spiked solution were tested using an ICP-OES instrument, and the measured values ​​of calcium in each solution were recorded. A standard curve was plotted based on the test results of the linear solution, and the linear regression equation was determined. (6) Calculation of carbomer content: The carbomer content is calculated using the following formula: Content % (g / g) = [(Amount of added Ca - Amount of detected Ca) / M Ca2+ ]×2×72 / (M 样品 (×1000)×100%; in: The amount of Ca added and the amount of Ca detected are both calcium element content by mass. The difference between them represents the mass of calcium element consumed by the carbomer during the reaction, in mg. M Ca2+ This represents the molar mass number of calcium atoms, specifically 40.08 g / mol. 72 is the molecular weight of the carbomer monomer, in g / mol; M 样品 The sample weight is in grams.

[0007] Compared with titration, the ICP-OES detection method of the present invention has the following advantages: 1. Simple operation: No complicated titration operation or endpoint judgment is required. The analysis can be completed through solution preparation and instrument detection, which reduces the dependence on the operator's experience. 2. High efficiency in testing: The entire testing process is short, enabling rapid testing of batch samples and significantly improving testing efficiency; 3. Accurate results: Thanks to the high sensitivity and stability of the ICP-OES instrument, human error is reduced, resulting in better accuracy and repeatability of the test results; 4. Environmentally friendly and energy-saving: The amount of reagent used is more reasonable, reducing the generation of waste liquid, and its environmental friendliness is better than that of traditional titration methods.

[0008] As a preferred embodiment of step (1), nitric acid and purified water are mixed at a volume ratio of 1:49 to prepare a diluent.

[0009] As a preferred embodiment of step (1), the concentration of the sodium hydroxide solution is 0.1 mol / L; and the concentration of the calcium chloride solution is 0.5%.

[0010] As a preferred embodiment of step (1), the concentration of the calcium standard solution is 1000 μg / mL.

[0011] As a preferred option for step (1), the concentration gradient of the linear standard solution can be flexibly adjusted according to the detection range to ensure coverage of the calcium detection range corresponding to carbomer in the test sample.

[0012] As a preferred embodiment of steps (2), (3), and (4), the shaking and centrifugation treatment includes ultrasonic shaking for 2 to 10 minutes, followed by centrifugation at 3000 to 10000 r / min for 5 to 15 minutes.

[0013] As a preferred embodiment of step (3), weigh the cyclosporine eye drop sample, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2) and mix them together, and add a carbomer network disruptor, which is ethanol, isopropanol or a mixture of both. Then add purified water to make up the volume, shake at 40℃±2℃ for a period of time, centrifuge and take the supernatant, and make up the volume with diluent to obtain the test solution.

[0014] As a preferred embodiment of step (4), weigh a known amount of carbomer reference standard, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2) and mix them together, and add a carbomer network disruptor, which is ethanol, isopropanol or a mixture of both. Then add purified water to make up the volume, shake at 40℃±2℃ for a period of time, centrifuge and take the supernatant, and make up the volume with diluent to obtain the test solution.

[0015] Furthermore, the carbomer network disruptor is preferably a mixture of ethanol and isopropanol, with a volume ratio of ethanol to isopropanol of 1:1 to 1:5. The amount of the carbomer network disruptor added is 20% to 60% of the volume of the cyclosporine eye drop sample or carbomer reference standard.

[0016] By adding trace amounts of ethanol and / or isopropanol, swelling promotes the dispersion of carbomer and exposure of carboxylic acid groups, enhancing its affinity for Ca. 2+ The reaction rate was accelerated by temperature control (approximately 40°C) and ultrasonic-assisted treatment, causing the carbomer structure to expand rapidly, ensuring that the cross-linking points of the carbomer were effectively destroyed, and increasing the degree of calcium ion complexation.

[0017] As a preferred embodiment of step (5), the detection parameters of the ICP-OES instrument include: RF power of 1150W; detection mode of radial mode; sample injection method of automatic injection; solution rinsing time of 60s; and solution lifting time of 80s.

[0018] As a preferred method for step (5), the wavelength for detecting calcium is 393.366 nm.

[0019] As a preferred option for step (5), the signal intensity of calcium element at wavelengths of 393.366 nm and 396.847 nm is recorded, and the matrix interference is corrected by calculating the ratio of the two signal intensities to obtain the accurate calcium content.

[0020] As described above, the ICP-OES method for detecting carbomer content in cyclosporine eye drops of the present invention has the following beneficial effects: 1. This invention utilizes the reaction between carbomer and calcium chloride under alkaline conditions. The remaining calcium content in the solution after the reaction is detected using an ICP-OES instrument, and the carbomer content is calculated based on the stoichiometric relationship, achieving accurate detection of carbomer content in cyclosporine eye drops. This invention, based on ICP-OES technology combined with a chemical reaction for carbomer content detection, integrates instrumental analysis with chemical reaction, breaking through the traditional titration method detection mode.

[0021] 2. This invention optimizes the solution preparation system, including the diluent ratio, auxiliary solution concentration and dosage, and sample processing procedures, ensuring the accuracy and repeatability of the detection results. Furthermore, during the preparation of the test sample and reference standard, the use of a carbomer network disruptor and ultrasonic-assisted treatment ensures the complete reaction between carbomer and calcium ions, reducing errors caused by cross-linking structures.

[0022] 3. This invention clarifies the ICP-OES instrument parameters adapted to this detection method, enabling rapid and efficient detection of carbomer content in cyclosporine eye drops. Furthermore, it integrates a multi-wavelength ratio method into the ICP-OES detection process, using signal intensity detection at wavelengths of 393.366 nm and 396.847 nm to calculate the ratio, thereby correcting for matrix interference and improving the accuracy and stability of the results. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0024] Reagents and materials: Reference standards: calcium standard solution (concentration 1000 μg / mL), carbomer A (batch number 0000054519).

[0025] Test sample: Cyclosporine eye drops (II), samples from different batches are identified by their corresponding numbers.

[0026] Instruments: ICP-OES instrument (model iCAP PRO XP), electronic balance, high-speed centrifuge, constant temperature incubator shaker, ultrapure water system, pipette, etc.

[0027] Reagents: nitric acid, sodium hydroxide, anhydrous calcium chloride, ethanol, isopropanol, and purified water, wherein nitric acid and purified water are mixed in a specific ratio to form a diluent.

[0028] Consumables: 50mL, 15mL centrifuge tubes, etc.

[0029] Example 1 This embodiment provides an ICP-OES method for detecting carbomer content in cyclosporine eye drops, including the following steps: (1) Solution preparation: Nitric acid and purified water are mixed at a volume ratio of 1:49 to prepare a diluent for diluting samples and standard solutions. Using the diluent as a blank (L-BLK), the calcium standard solution (concentration 1000 μg / mL) was diluted to obtain a series of linear standard solutions (L-1 to L-5) with concentration ranges covering the required detection range; Prepare 0.1 mol / L sodium hydroxide solution and 0.5% calcium chloride solution respectively as alkaline environment providers and reaction reagents for the reaction system; (2) Preparation of blank solution: Add a set volume of 0.1 mol / L sodium hydroxide solution and 0.5% calcium chloride solution to the container, add purified water to make up the volume, and after shaking and centrifugation, take the supernatant and make up the volume with diluent to obtain a blank solution. (3) Preparation of test solution: Weigh the cyclosporine eye drop sample, add the same volume of 0.1 mol / L sodium hydroxide solution and 0.5% calcium chloride solution as in step (2), add purified water to make up the volume, take the supernatant after shaking and centrifugation, and make up the volume with diluent to obtain the test solution. Prepare multiple samples in parallel. (4) Preparation of reference standards and spiking solutions: Weigh out the set mass of carbomer A reference standard, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2), add purified water to make up to volume, and after shaking and centrifugation, take the supernatant and make up to volume with diluent to obtain the reference standard solution; A spiked solution can be obtained by adding a predetermined volume of calcium standard solution to the test sample solution, and multiple samples can be prepared in parallel. (5) ICP-OES testing: The linear standard solution, blank solution, test solution, reference solution, and spiked solution were tested using an ICP-OES instrument, and the measured values ​​of calcium in each solution were recorded. A standard curve was plotted based on the test results of the linear solution, and the linear regression equation was determined. The instrument parameters are as follows:

[0030] (6) Calculation of carbomer content: The carbomer content is calculated using the following formula: Content % (g / g) = [(Amount of added Ca - Amount of detected Ca) / M Ca2+ ]×2×72 / (M 样品 (×1000)×100%; in: The amount of Ca added and the amount of Ca detected are both calcium element content by mass. The difference between them represents the mass of calcium element consumed by the carbomer during the reaction, in mg. M Ca2+ This represents the molar mass number of calcium atoms, specifically 40.08 g / mol. 72 is the molecular weight of the carbomer monomer, in g / mol; M 样品 The sample weight is in grams.

[0031] The test results are shown in Tables 1 and 2. Table 1 shows the test results of cyclosporine eye drops under unspiked conditions, where "Measured Value" is the concentration of residual calcium in the solution after the reaction, and "Measured Carbomer A" is the carbomer mass calculated based on the amount of calcium consumed. The results indicate that the method of the present invention has good repeatability. Table 2 shows the results of the spiked recovery test. The recovery rates of each spiked sample are concentrated, indicating that the method of the present invention has good accuracy and can effectively overcome the influence of the complex matrix of cyclosporine eye drops on the determination of carbomer content.

[0032]

[0033] Example 2 This embodiment provides an ICP-OES method for detecting carbomer content in cyclosporine eye drops, including the following steps: (1) Solution preparation: Nitric acid and purified water are mixed at a volume ratio of 1:49 to prepare a diluent for diluting samples and standard solutions. Using the diluent as a blank (L-BLK), the calcium standard solution (concentration 1000 μg / mL) was diluted to obtain a series of linear standard solutions (L-1 to L-5) with concentration ranges covering the required detection range; Prepare 0.1 mol / L sodium hydroxide solution and 0.5% calcium chloride solution respectively as alkaline environment providers and reaction reagents for the reaction system; (2) Preparation of blank solution: Add 2 mL of 0.1 mol / L sodium hydroxide solution and 2 mL of 0.5% calcium chloride solution to the container, add purified water to make up to 15 mL, shake and centrifuge, take the supernatant, and make up to 50 mL with diluent to obtain a blank solution. (3) Preparation of test solution: Weigh 1.000g of cyclosporine eye drops sample, add the same volume of 0.1mol / L sodium hydroxide solution and 0.5% calcium chloride solution as in step (2), add a mixed solvent of ethanol and isopropanol in a volume ratio of 1:3 as a carbomer network disruptor, the volume of which is 50% of the sample volume, add purified water to make up to 15mL, place the resulting solution at 40℃ and shake for 20min, and then perform ultrasonic assisted treatment for 8min, followed by centrifugation at 8000r / min for 10min, take the supernatant, and make up to 50mL with diluent as the test solution; (4) Preparation of reference standards and spiking solutions: Weigh 0.020 g of carbomer A reference standard, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2), add a mixed solvent of ethanol and isopropanol in a volume ratio of 1:3 as a carbomer network disruptor, the volume of which is 50% of the sample volume, add purified water to make up to 15 mL, place the resulting solution at 40 °C and shake for 20 min, and then perform ultrasonic assisted treatment for 8 min, followed by centrifugation at 8000 r / min for 10 min, take the supernatant, and make up to 50 mL with diluent to obtain the reference standard solution; A spiked solution can be obtained by adding a predetermined volume of calcium standard solution to the test sample solution, and multiple samples can be prepared in parallel. (5) ICP-OES testing: The linear standard solution, blank solution, test solution, reference solution, and spiked solution were detected using an ICP-OES instrument. Simultaneously, the signal intensity of calcium at wavelengths of 393.366 nm and 396.847 nm was recorded. Matrix interference was corrected by calculating the ratio of these two signal intensities to obtain the corrected calcium content. A standard curve was plotted based on the detection results of the linear solution to determine the linear regression equation. The instrument parameters are as follows:

[0034] (6) Calculation of carbomer content: The carbomer content is calculated using the following formula: Content % (g / g) = [(Amount of added Ca - Amount of detected Ca) / M Ca2+ ]×2×72 / (M 样品 (×1000)×100%; in: The amount of Ca added and the amount of Ca detected are both calcium element content by mass. The difference between them represents the mass of calcium element consumed by the carbomer during the reaction, in mg. M Ca2+ This represents the molar mass number of calcium atoms, specifically 40.08 g / mol. 72 is the molecular weight of the carbomer monomer, in g / mol; M 样品 The sample weight is in grams.

[0035] The results show that, compared with single-wavelength detection, the multi-wavelength ratio method has higher detection stability and accuracy in eye drop matrices containing oil phase and surfactant.

[0036] In summary, this invention fully dissociates the carboxylic acid groups of carbomer under alkaline conditions, allowing them to undergo a stoichiometric reaction with added calcium ions. The remaining calcium content in the solution after the reaction is detected by ICP-OES, and the carbomer content in cyclosporine eye drops is calculated by combining the stoichiometric relationship between calcium ions and carbomer. Compared with existing titration methods, this invention is simple to operate, has high detection efficiency, good repeatability and accuracy, and can effectively adapt to complex matrix systems such as cyclosporine eye drops, possessing significant industrial application value. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial utilization value.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An ICP-OES method for detecting carbomer content in cyclosporine eye drops, characterized in that, Includes the following steps: (1) Solution preparation: Prepare a diluent for nitric acid and purified water; Using the diluent as a blank, the calcium standard solution was diluted to obtain a series of linear calcium standard solutions of different concentrations. Prepare sodium hydroxide solution and calcium chloride solution separately; (2) Preparation of blank solution: Add the sodium hydroxide solution and calcium chloride solution of the specified volume to the container, add purified water to make up the volume, and after shaking and centrifugation, take the supernatant and make up the volume with diluent to obtain a blank solution; (3) Preparation of test solution: Weigh the cyclosporine eye drop sample, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2), add purified water to make up the volume, and after shaking and centrifugation, take the supernatant and make up the volume with diluent to obtain the test solution; (4) Preparation of reference standards and spiking solutions: Weigh a known amount of carbomer reference standard, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2), add purified water to make up to volume, and after shaking and centrifugation, take the supernatant and make up to volume with diluent to obtain the reference standard solution; A spiked solution can be obtained by adding calcium standard solution to the reference solution or the test solution; (5) ICP-OES testing: The linear standard solution, blank solution, test solution, reference solution and spiked solution were detected by ICP-OES instrument, and the measured value of calcium in each solution was recorded. A standard curve was plotted based on the test results of the linear solution to determine the linear regression equation; (6) Calculation of carbomer content: The carbomer content is calculated using the following formula: Content % (g / g) = [(Amount of added Ca - Amount of detected Ca) / M Ca2+ ]×2×72 / (M 样品 (×1000)×100%; in: The amount of Ca added and the amount of Ca detected are both calcium element content by mass. The difference between them represents the mass of calcium element consumed by the carbomer during the reaction, in mg. M Ca2+ The molar mass number of calcium atoms is expressed in g / mol. 72 is the molecular weight of the carbomer monomer, in g / mol; M 样品 The sample weight is in grams.

2. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, Nitric acid and purified water were mixed at a volume ratio of 1:49 to prepare a diluent; the concentration of sodium hydroxide solution was 0.1 mol / L; the concentration of calcium chloride solution was 0.5%; and the concentration of calcium standard solution was 1000 μg / mL.

3. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, In step (2) or (3) or (4), the shaking and centrifugation treatment includes ultrasonic shaking for 2 to 10 minutes, followed by centrifugation at 3000 to 10000 r / min for 5 to 15 minutes.

4. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, In step (3), weigh the cyclosporine eye drop sample, add the same volume of sodium hydroxide solution and calcium chloride solution as in step (2) and mix them together, and add a carbomer network disruptor, which is ethanol, isopropanol or a mixture of both. Then add purified water to make up the volume, shake at 40℃±2℃ for a period of time, centrifuge and take the supernatant, and make up the volume with diluent to obtain the test solution.

5. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, In step (4), a known amount of carbomer reference standard is weighed, and mixed with the same volume of sodium hydroxide solution and calcium chloride solution as in step (2). A carbomer network disruptor, which is ethanol, isopropanol, or a mixture of both, is added. Then purified water is added to make up the volume, and the mixture is shaken at 40℃±2℃ for a period of time. After centrifugation, the supernatant is taken and diluted with a diluent to obtain the test solution.

6. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 5 or 6, characterized in that, The carbomer network disruptor is preferably a mixture of ethanol and isopropanol, with the volume ratio of ethanol or isopropanol being 1:1 to 1:

5.

7. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 5 or 6, characterized in that, The amount of the carbomer network disruptor added is 20% to 60% of the volume of the cyclosporine eye drop sample or carbomer reference standard.

8. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, In step (5), the detection parameters of the ICP-OES instrument include: RF power of 1150W; detection mode of radial mode; sample injection method of automatic injection; solution rinsing time of 60s; and solution lifting time of 80s.

9. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, In step (5), the wavelength for detecting calcium is 393.366 nm.

10. The ICP-OES method for detecting carbomer content in cyclosporine eye drops according to claim 1, characterized in that, In step (5), the signal intensity of calcium element at wavelengths of 393.366 nm and 396.847 nm is recorded, and the matrix interference is corrected by calculating the ratio of the two signal intensities to obtain the accurate calcium content.

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