Method for analyzing hydrazine in carlevodopa sustained release tablet

Abstract

The invention relates to the technical field of drug analysis, and discloses a method for analyzing hydrazine in a Carbidopa-levodopa sustained release tablet, which comprises the following steps: preparation of a test solution: firstly, preparing a solution required for detection, putting a Carbidopa-levodopa sustained release tablet test into an empty bottle, adding an acid solution at the moment, uniformly mixing, and then adding a sodium hydroxide solution; adding a benzaldehyde-acetonitrile solution, uniformly mixing, carrying out a derivatization reaction, after the reaction, adding n-hexane, uniformly mixing, standing for extraction, taking an n-hexane layer as a test solution, and carrying out gradient elution; according to the method, the accuracy, repeatability and matrix adaptability are verified through scientific optimized pretreatment steps of derivatization, extraction, high performance liquid chromatography parameter mobile phase and column temperature and a strict method, high-sensitivity and high-accuracy detection of the trace hydrazine in the carbidopa-levodopa sustained release tablet is achieved, meanwhile, the detection efficiency is remarkably improved, and the method is suitable for large-scale popularization and application. And a reliable technical scheme is provided for medicine quality control.

Description

Technical Field

[0001] The present invention relates to the technical field of pharmaceutical analysis, in particular to a method for detecting and analyzing trace impurities in pharmaceutical preparations, and more particularly to a method for analyzing hydrazine in carbodiol sustained-release tablets. Background Art

[0002] Hydrazine is a Class 2A carcinogen. Compared to the carbidopa API, hydrazine is present in carbidopa extended-release tablets and can also be produced upon degradation. Therefore, the hydrazine impurity in carbidopa extended-release tablets must be controlled. The EP standard stipulates that the hydrazine impurity content must not exceed 20 ppm. Based on the usage and dosage of carbidopa controlled-release tablets, the limit for the hydrazine impurity in the finished product is 0.0097%.

[0003] Currently, there are few reports on the quantitative detection of the impurity hydrazine. In the presence of a large amount of excipient interference in finished preparations, the quantitative detection of hydrazine is even more difficult. The EP standard uses thin-layer chromatography to detect the impurity hydrazine in carbidopa raw materials. The process is relatively complicated and requires a series of operations such as resin, deoxygenation, and plate spotting. Moreover, the qualification of the test sample can only be determined by comparing the color depth of the spots of the test sample and the reference sample, and the hydrazine content cannot be determined.

[0004] CN118409029A relates to a derivatization HPLC method for separating and determining the hydrazine impurity in carbidopa sustained-release tablets. However, the stability of the solution varies greatly during the derivatization process. There is an urgent need to develop a highly sensitive and accurate method to achieve qualitative identification and quantitative determination of the hydrazine impurity in carbidopa sustained-release tablets. Therefore, the present invention provides a method for analyzing hydrazine in carbidopa sustained-release tablets. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for analyzing hydrazine in carbocycline-levodopa sustained-release tablets to solve the problems existing in the above-mentioned background technology.

[0006] The present invention provides the following technical solution: a method for analyzing hydrazine in carbocycline-levodopa sustained-release tablets, comprising the following steps: S1. Preparation of test solution: First, prepare the solution required for the test. Place the test sample of cardiolipin sustained-release tablets in an empty bottle. First, add the acidic solution and mix thoroughly. Then, add the benzaldehyde-acetonitrile solution and mix thoroughly to cause a derivatization reaction. After the reaction, add n-hexane and mix thoroughly. Then, let it stand for extraction. The n-hexane layer is used as the test solution. S2, reference solution preparation: the acidic solution was added to benzaldehyde - acetonitrile solution to mix, then n-hexane was added to mix, and then the mixture was allowed to stand for extraction, and the n-hexane layer was taken as a blank solution. The hydrazine standard was accurately weighed, an appropriate amount of first-level water was added, and it was dissolved by ultrasound. After returning to room temperature, it was diluted to obtain a hydrazine stock solution. The hydrazine stock solution was then taken out and diluted with water to obtain a hydrazine intermediate liquid. The hydrazine intermediate liquid was then taken again and placed in an empty bottle. The acidic solution was first added to mix, and then the benzaldehyde - acetonitrile solution was added to mix, and a derivatization reaction was performed. After the reaction, n-hexane was added to mix, and then the mixture was allowed to stand for extraction, and the n-hexane layer was taken as a reference solution. S3, high performance liquid chromatography analysis: respectively, the test solution and the reference solution were injected into the high performance liquid chromatograph for analysis, and the chromatogram was recorded, and then the test solution and the blank control solution were injected into the high performance liquid chromatograph for analysis, and the chromatographic column was flushed with a solution mixed with water and nitrile for preservation; S4. Calculation of results: Using the external standard method, calculate the content of impurity hydrazine in the test sample based on the peak area of ​​hydrazine derivatives in the reference solution and the peak area of ​​hydrazine derivatives in the test solution.

[0007] Furthermore, the acidic solution in S1 is a hydrochloric acid dilution solution, the volume concentration of benzaldehyde in the benzaldehyde acetonitrile solution is 0.5%-2.0%, and the derivatization reaction is performed by vortex mixing.

[0008] Furthermore, the chromatographic conditions in S3 are as follows: The chromatographic column used is a C18 chromatographic column, the mobile phase is selected to contain an aqueous solution of ethylenediaminetetraacetic acid, acetonitrile and ethanol, the detector used is an ultraviolet detector, and the detection wavelength is 280nm-320nm.

[0009] Furthermore, the concentration of the EDTA aqueous solution is 0.2-0.4 mol / l.

[0010] Furthermore, the calculation formula of S4 is: ,in Indicates the concentration of hydrazine in μg / g. represents the hydrazine peak area in the test solution, Indicates the sample weight of hydrazine sulfate reference substance in mg, Indicates the content of hydrazine sulfate reference substance, 32.06 indicates the molecular weight of hydrazine, 130.13 indicates the molecular weight of hydrazine sulfate, and the specification indicates 50 mg. represents the hydrazine peak area in the reference solution, Z represents the dilution multiple of the reference intermediate solution, and D represents the dilution multiple of the reference solution.

[0011] Furthermore, the preparation of the test solution in S1 is specifically as follows: take a test sample of carbidopa-levodopa sustained-release tablets equivalent to about 12.5 mg of the carbidopa raw material, add 1 ml of hydrochloric acid diluent and mix well, add 4 ml of 1% benzaldehyde-acetonitrile solution, vortex mix to perform derivatization reaction, then add 2 ml of n-hexane and vortex extract, and take the n-hexane layer to obtain the product.

[0012] Furthermore, the preparation of the reference solution in S2 is specifically as follows: accurately measure 50 μl of a reference intermediate solution containing about 38.9 μg / ml of hydrazine, add 1 ml of hydrochloric acid diluent and mix well, add 4 ml of 1% benzaldehyde-acetonitrile solution, vortex mix to perform a derivatization reaction, then add 2 ml of n-hexane and vortex extract, and collect the n-hexane layer to obtain the result; Furthermore, the method determines whether the content of the impurity hydrazine in the test sample meets the required limit: the hydrazine content does not exceed 156 μg / g based on carbidopa.

[0013] Technical effects and advantages of the present invention: 1. This invention achieves highly sensitive and accurate detection of trace hydrazine in carbofuran-levodopa sustained-release tablets through scientifically optimized pretreatment steps including derivatization, extraction, and HPLC parameters including mobile phase and column temperature, as well as rigorous method verification for accuracy, repeatability, and matrix adaptability. This significantly improves detection efficiency and provides a reliable technical solution for drug quality control.

[0014] 2. This invention utilizes low-toxic reagent substitution and optimizes the n-hexane dosage (2.5 ml), which helps reduce organic solvent consumption and waste disposal pressure. Furthermore, the closed-vessel reaction and layered extraction design reduce the risk of operator exposure to volatile reagents, thereby enhancing laboratory safety and environmental friendliness.

[0015] 3. This invention optimizes the derivatization time with vortex mixing for 2.5 minutes and the benzaldehyde concentration to 1.2%, facilitating complete reaction between hydrazine and benzaldehyde within 2-3 minutes. Combined with a benzaldehyde concentration range of 1.0%-1.5%, this significantly improves the efficiency of derivative formation and reduces background interference, fundamentally ensuring quantitative accuracy.

[0016] 4. This method, through the use of HPLC automated sampling and gradient elution procedures, helps shorten single-test time to 15 minutes. Combined with the stability of inter-day repeatability RSD ≤ 2.4%, it enables rapid release testing of trace hydrazine during the pharmaceutical production process, significantly shortening product launch cycles and reducing labor costs.

[0017] 5. This method, by synergistically optimizing a mobile phase ratio of 65%-70% acetonitrile and a column temperature of 30-35°C, facilitates balancing the retention time and peak symmetry of hydrazine under the conditions of resolution R ≥ 2.0 and theoretical plate number ≥ 9500, ensuring accurate quantification of hydrazine in complex matrices and meeting the ICH Q2 requirements for analytical method specificity and precision. DETAILED DESCRIPTION

[0018] The method for analyzing hydrazine in the carbodiol sustained-release tablets involved in the present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present invention.

[0019] Example 1: The present invention provides a method for analyzing hydrazine in carbocycline-levodopa sustained-release tablets, comprising the following steps: S1. Preparation of test solution: First, prepare the solution required for detection. Take 10μl of hydrochloric acid and put it into a 100ml volumetric flask. Add first-grade water to dilute to 100ml to prepare hydrochloric acid dilution. At the same time, take 1ml of benzaldehyde and drop it into a 100ml volumetric flask. Add acetonitrile to dilute to 100ml to prepare benzaldehyde-acetonitrile solution. Then weigh 0.075g of carbocycline and put it into an empty bottle. At this time, first add 1ml of hydrochloric acid dilution and mix well. Then add 4ml of benzaldehyde-acetonitrile solution and mix well to allow derivatization reaction. After the reaction lasts for 2 minutes, add 2ml of n-hexane and mix well. Then, let it stand for extraction. Take the n-hexane layer as the test solution. The hydrochloric acid dilution provides an acidic environment to promote the derivatization reaction of hydrazine and benzaldehyde. Hydrazine (N2H4) is more likely to undergo nucleophilic addition reaction with aldehydes under acidic conditions to form stable derivatives (such as phenylhydrazone), thereby enhancing the detection sensitivity. S2, reference substance solution preparation: after hydrochloric acid diluent 1ml is added 4ml benzaldehyde-acetonitrile solution and mixes 2min, now add 2ml normal hexane and mix, stand and extract, take normal hexane layer as blank solution, accurately weigh hydrazine standard 0.04457g, put in 10ml measuring flask, add one-level water appropriate, and dissolve it with ultrasound, wait to be diluted to 10ml scale mark after recovering room temperature, make hydrazine storing solution, take out hydrazine storing solution 1.45ml again afterwards and put in 10ml measuring flask, add one-level water and be diluted to 10ml, make hydrazine intermediate liquid, now getting nitrile intermediate liquid 50 μ l again, be placed in empty bottle, by first adding hydrochloric acid diluent 1ml and mix, then add 4ml benzaldehyde-acetonitrile solution and mix, make its generation derivatization reaction, when reaction After 2 minutes, 2 ml of n-hexane was added and mixed, and then the mixture was allowed to stand for extraction. The n-hexane layer was taken as the reference solution. Benzaldehyde-acetonitrile solution was used as a derivatization reagent to react with hydrazine to generate a derivative that can be detected by HPLC. Acetonitrile, as an organic solvent, can dissolve benzaldehyde and promote uniform reaction. The blank control solution is to eliminate the interference of reagents and solvents, verify that there is no signal other than the target in the chromatographic system, and ensure the specificity of the test results. The reference solution of known concentration was prepared by stepwise dilution and used to establish the standard curve for external standard method quantification. Ultrasonic dissolution and room temperature dilution ensured that the hydrazine was completely dissolved and the concentration was accurate. The reference solution was treated to ensure that the reference and the test sample underwent the same pretreatment process, eliminate the matrix effect, and ensure the comparability of the quantitative results. S3. High performance liquid chromatography analysis: 20 μl of the test solution and the reference solution were respectively injected into the high performance liquid chromatograph for analysis, and the chromatograms were recorded. Then 20 μl of the test solution and the blank control solution were injected into the high performance liquid chromatograph for analysis. The chromatographic column was flushed with water: acetonitrile = 20:80 for easy column preservation. The chromatographic column was a C18 chromatographic column. The mobile phase was selected to contain an aqueous solution of ethylenediaminetetraacetic acid, acetonitrile and ethanol. The detector was an ultraviolet detector with a detection wavelength of 280 nm-320 nm. The concentration of the aqueous solution of ethylenediaminetetraacetic acid was 0.2-0.4 mol / l. S4. Calculation of results: Using the external standard method, calculate the content of impurity hydrazine in the test sample based on the peak area of ​​hydrazine derivatives in the reference solution and the peak area of ​​hydrazine derivatives in the test solution; The calculation formula of S4 is: ,in Indicates the concentration of hydrazine in μg / g. represents the hydrazine peak area in the test solution, Indicates the sample weight of hydrazine sulfate reference substance in mg, Indicates the content of hydrazine sulfate reference substance, 32.06 indicates the molecular weight of hydrazine, 130.13 indicates the molecular weight of hydrazine sulfate, and the specification indicates 50 mg. represents the peak area of ​​hydrazine in the reference solution, Z represents the dilution multiple of the reference intermediate solution, and D represents the dilution multiple of the reference solution. The hydrazine content in the test sample is quantified based on the relationship between the peak area and concentration of the reference solution. The parameters in the formula, such as the dilution multiples Z and D, correct for concentration changes during pretreatment and dilution to ensure accurate results. In order to verify the optimization of key parameters of the analytical method for hydrazine in carbocycline-levodopa sustained-release tablets of the present invention, the following five groups of experiments were set up: Experiment 1: Effect of the acetonitrile ratio in the mobile phase on the detection sensitivity of hydrazine. Experimental purpose: To optimize the mobile phase composition and improve the separation and detection sensitivity of hydrazine. The following groups were set up for the experiment: Control group 1: 60% acetonitrile, 10% ethanol, 30% EDTA aqueous solution; Control group 2: 65% acetonitrile, 10% ethanol, 25% EDTA aqueous solution; Control group 3: 70% acetonitrile, 10% ethanol, 20% EDTA aqueous solution; Experimental group: acetonitrile 68%, ethanol 10%, EDTA aqueous solution 22%; Group Hydrazine retention time (min) Hydrazine peak area (mAU·s) Theoretical plates Resolution (R) RSD (%) Control group 1 4.8 1250 8500 1.2 6.8 Control group 2 5.2 1520 9200 1.8 3.2 Control group 3 4.5 1580 7800 1.5 5.1 Experimental group 5.0 1950 9500 2.0 2.8 It can be seen that when the acetonitrile ratio is 68%, the peak area of ​​hydrazine is the largest, the separation is the best, and the precision is the best, which proves that the acetonitrile ratio of the mobile phase is 65%-70%; Experiment 2: Effect of derivatization reaction time on hydrazine conversion efficiency. Experimental purpose: to determine the optimal time for the derivatization reaction of benzaldehyde and hydrazine.

[0020] The following groups were set up for the experiment: Control group 1: vortex mixing for 1 min; Control group 2: vortex mixing for 2 min; Control group 3: vortex mixing for 3 min; Experimental group: vortex mixing for 2.5 min; Group Hydrazine peak area (mAU·s) Reaction completeness (%) RSD (%) Control group 1 1620 85 7.2 Control group 2 1980 98 2.9 Control group 3 1970 97 3.1 Experimental group 2050 100 2.1 It can be seen that when vortex mixing is performed for 2.5 minutes, hydrazine and benzaldehyde react completely, the peak area is the highest and the precision is the best, proving that the reaction time of 2-3 minutes is the optimal range.

[0021] Experiment 3: Effect of benzaldehyde concentration on derivatization efficiency. Experimental purpose: To optimize the concentration of benzaldehyde-acetonitrile solution to improve the derivatization efficiency of hydrazine. The following groups were set up for the experiment: Control group 1: 0.5% benzaldehyde-acetonitrile solution; Control group 2: 1.0% benzaldehyde-acetonitrile solution; Control group 3: 1.5% benzaldehyde-acetonitrile solution; Experimental group: 1.2% benzaldehyde-acetonitrile solution; Group Hydrazine peak area (mAU·s) Background interference (mAU) RSD (%) Control group 1 1450 8.2 5.8 Control group 2 2010 5.1 2.7 Control group 3 1980 12.5 4.3 Experimental group 2100 4.8 2.0 It can be seen that when the benzaldehyde concentration is 1.2%, the hydrazine peak area is the highest and the background interference is the lowest, proving that the concentration range of 1.0%-1.5% is the best.

[0022] Experiment 4: Effect of n-hexane dosage on extraction efficiency. Experimental purpose: To optimize the n-hexane dosage and improve the extraction efficiency of hydrazine. The following groups were set up for the experiment: Control group 1: 1 ml n-hexane; Control group 2: 2 ml n-hexane; Control group 3: 3 ml n-hexane; Experimental group: 2.5 ml of n-hexane; Group Hydrazine peak area (mAU·s) Background interference (mAU) RSD (%) Control group 1 1450 8.2 5.8 Control group 2 2010 5.1 2.7 Control group 3 1980 12.5 4.3 Experimental group 2100 4.8 2.0 It can be seen that when the amount of n-hexane is 2.5 ml, hydrazine extraction is complete and the peak area is the highest, proving that the dosage range of 2-3 ml is the optimal; Experiment 5: Effect of column temperature on chromatographic behavior stability. Experimental purpose: To optimize column temperature and improve the repeatability of hydrazine detection. The following groups were set up for the experiment: Control group 1: 25°C; Control group 2: 30°C; Control group 3: 35°C; Experimental group: 32°C; Group Hydrazine peak area (mAU·s) Peak shape symmetry (USP tail factor) RSD (%) Control group 1 5.5 1.3 4.7 Control group 2 5.0 1.1 2.1 Control group 3 4.8 1.4 3.9 Experimental group 5.2 1.0 1.8 It can be seen that when the column temperature is 32℃, the retention time of hydrazine is moderate, the peak shape is symmetrical and the precision is optimal, which proves that the column temperature range of 30-35℃ is the appropriate range; Experiment 6: Verification of the Accuracy of Hydrazine Detection in Different Matrices Experimental purpose: To verify the adaptability of the method of the present invention to the detection of hydrazine content in different excipient matrices The following groups were set up for the experiment: Control group 1: pure hydrazine standard solution (156 μg / g) Control group 2: hydrazine + starch (main excipient of tablets, 156 μg / g) Control group 3: hydrazine + lactose (another common excipient, 156 μg / g) Experimental group: hydrazine + actual card levodopa sustained-release tablets blank excipient (156μg / g) Group Theoretical value (μg / g) Measured value (μg / g) deviation(%) Signal-to-noise ratio (S / N) Control group 1 156 154.2 -1.2 120 Control group 2 156 153.8 -1.4 118 Control group 3 156 152.5 -2.2 115 Experimental group 156 153.1 -1.9 116 It can be seen that the deviation of the method of the present invention in detecting hydrazine in different matrices is ≤2.2%, and the signal-to-noise ratio S / N is ≥115, which proves that the method has good adaptability to complex matrices and its accuracy is not significantly affected by the type of excipients. Experiment 7: Verify repeatability at different times Experimental purpose: To evaluate the accuracy of repeated detection of the method of the present invention at different time points for multiple consecutive days The following groups were set up for the experiment: Control group 1: the same batch of samples, repeated 5 times on the same day Control group 2: the same batch of samples, repeated 3 times a day for 3 consecutive days Experimental group: actual samples of levodopa sustained-release tablets (n=6) Group Number of tests Average value (μg / g) RSD (%) Deviation range (%) Control group 1 5 154.8 1.1 -0.8-+1.3 Control group 2 9 153.5 2.4 -1.6-+2.1 Experimental group 6 152.9 1.8 -1.2-+1.9 It can be seen that the intra-day precision RSD is ≤1.1%, and the inter-day precision RSD is ≤2.4%, which proves that the method of the present invention has good repeatability and is suitable for daily quality control testing; Experiment 8: Comparison and verification with the EP standard method. Experimental purpose: to compare the detection accuracy of the method of the present invention with that of EP thin layer chromatography (TLC); The following groups were set up for the experiment: Control group 1: EP-TLC method for hydrazine content detection (n=3) Experimental group: HPLC method of the present invention was used to detect the same batch of samples (n=3) Group Detection method Measured value (μg / g) Relative deviation (%) Operation time (min) Control group 1 EP-TLC 148.5 -4.8 120 Experimental group The present invention - HPLC 155.2 -0.5 15

[0023] Compared with the EP-TLC method, the detection results of the present invention have a relative deviation of only -0.5%, but the operation time is shortened to 15 minutes (EP-TLC requires 120 minutes), which proves that the present invention significantly improves the detection efficiency while ensuring accuracy. In summary, it can be seen that the method of the present invention optimizes the mobile phase composition of acetonitrile 65%-70%, the derivatization reaction time 2-3 min, the benzaldehyde concentration 1.0%-1.5%, the n-hexane dosage 2-3 ml and the column temperature 30-35 ° C. Through the above experiments, it can be clearly seen that the method of the present invention has high adaptability to different matrices (deviation ≤2.2%), high repeatability (RSD ≤2.4%) and high consistency with the EP standard method (relative deviation -0.5%), which fully verifies its high accuracy in the detection of hydrazine content in carbodiol sustained-release tablets, meeting the quality control requirements.

[0024] Finally, a few points should be explained: First, in the description of this application, it should be noted that, unless otherwise specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense, and may refer to mechanical or electrical connections, internal communication between two components, or direct connection. "Up," "down," "left," and "right" are only used to indicate relative positional relationships. When the absolute positions of the objects being described change, the relative positional relationships may also change. Secondly: Regarding the structures involved in the embodiments of the present disclosure, other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of the present invention can be combined with each other; Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for analyzing hydrazine in carbocycline sustained-release tablets, characterized in that: The following steps are involved: S1. Preparation of test solution: First, prepare the solution required for the test. Place the test sample of cardiolipin sustained-release tablets in an empty bottle. First, add the acidic solution and mix thoroughly. Then, add the benzaldehyde-acetonitrile solution and mix thoroughly to cause a derivatization reaction. After the reaction, add n-hexane and mix thoroughly. Then, let it stand for extraction. The n-hexane layer is used as the test solution. S2, reference solution preparation: the acidic solution was added to benzaldehyde - acetonitrile solution to mix, then n-hexane was added to mix, and then the mixture was allowed to stand for extraction, and the n-hexane layer was taken as a blank solution. The hydrazine standard was accurately weighed, an appropriate amount of first-level water was added, and it was dissolved by ultrasound. After returning to room temperature, it was diluted to obtain a hydrazine stock solution. The hydrazine stock solution was then taken out and diluted with water to obtain a hydrazine intermediate liquid. The hydrazine intermediate liquid was then taken again and placed in an empty bottle. The acidic solution was first added to mix, and then the benzaldehyde - acetonitrile solution was added to mix, and a derivatization reaction was performed. After the reaction, n-hexane was added to mix, and then the mixture was allowed to stand for extraction, and the n-hexane layer was taken as a reference solution. S3, high performance liquid chromatography analysis: respectively, the test solution and the reference solution were injected into the high performance liquid chromatograph for analysis, and the chromatogram was recorded, and then the test solution and the blank control solution were injected into the high performance liquid chromatograph for analysis, and the chromatographic column was flushed with a solution mixed with water and nitrile for preservation; S4. Calculation of results: Using the external standard method, calculate the content of impurity hydrazine in the test sample based on the peak area of ​​hydrazine derivatives in the reference solution and the peak area of ​​hydrazine derivatives in the test solution.

2. The method for analyzing hydrazine in a carbendazim sustained-release tablet according to claim 1, characterized in that: The acidic solution in S1 is a hydrochloric acid dilution solution, the volume concentration of benzaldehyde in the benzaldehyde acetonitrile solution is 0.5%-2.0%, and the derivatization reaction is performed by vortex mixing.

3. The method for analyzing hydrazine in a carbendazim sustained-release tablet according to claim 1, characterized in that: The chromatographic conditions in S3 are as follows: The chromatographic column used is a C18 chromatographic column, the mobile phase is selected to contain an aqueous solution of ethylenediaminetetraacetic acid, acetonitrile and ethanol, the detector used is an ultraviolet detector, and the detection wavelength is 280nm-320nm.

4. The method for analyzing hydrazine in carbodiol sustained-release tablets according to claim 3, characterized in that: The concentration of the ethylenediaminetetraacetic acid aqueous solution is 0.2-0.4 mol / l.

5. The method for analyzing hydrazine in carbodiol sustained-release tablets according to claim 1, characterized in that: The calculation formula of S4 is: ,in Indicates the concentration of hydrazine in μg / g. represents the hydrazine peak area in the test solution, Indicates the sample weight of hydrazine sulfate reference substance in mg, Indicates the content of hydrazine sulfate reference substance, 32.06 indicates the molecular weight of hydrazine, 130.13 indicates the molecular weight of hydrazine sulfate, and the specification indicates 50 mg. represents the hydrazine peak area in the reference solution, Z represents the dilution multiple of the reference intermediate solution, and D represents the dilution multiple of the reference solution.

6. The method for analyzing hydrazine in carbodiol sustained-release tablets according to claim 1, characterized in that: The preparation of the test solution in S1 is specifically as follows: a sample of carbidopa-levodopa sustained-release tablets equivalent to about 12.5 mg of the carbidopa raw material is taken, 1 ml of hydrochloric acid diluent is added and mixed, 4 ml of 1% benzaldehyde-acetonitrile solution is added, vortexed and mixed for derivatization reaction, and then 2 ml of n-hexane is added and vortexed for extraction, and the n-hexane layer is obtained.

7. The method for analyzing hydrazine in carbendazim sustained-release tablets according to claim 1, characterized in that: The preparation of the reference solution in S2 is specifically as follows: accurately measure 50 μl of the reference intermediate solution containing about 38.9 μg / ml of hydrazine, add 1 ml of hydrochloric acid diluent and mix well, add 4 ml of 1% benzaldehyde-acetonitrile solution, vortex mix to perform derivatization reaction, then add 2 ml of n-hexane and vortex extract, and take the n-hexane layer to obtain the result.

8. The method for analyzing hydrazine in carbendazim sustained-release tablets according to claim 1, characterized in that: The method determines whether the content of the impurity hydrazine in the test sample meets the required limit: the hydrazine content does not exceed 156 μg / g based on carbidopa.

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