CN113325091B

CN113325091B - Method for measuring methyl iodide residue in crude drug for treating epilepsy

Info

Publication number: CN113325091B
Application number: CN202110406224.2A
Authority: CN
Inventors: 徐东; 荆玉琳; 任娜; 付亚冰; 许惠
Original assignee: Zibo High And New Technology Industry Development Districk Biomedicine Research Institute; Shandong University
Current assignee: Zibo High And New Technology Industry Development Districk Biomedicine Research Institute; Shandong University
Priority date: 2021-04-15
Filing date: 2021-04-15
Publication date: 2022-08-09
Anticipated expiration: 2041-04-15
Also published as: CN113325091A

Abstract

The invention relates to the technical field of analysis and detection, and particularly relates to a method for determining methyl iodide residue in a crude drug for treating epilepsy. The method for determining the methyl iodide residue in the crude drug for treating epilepsy comprises the steps of detecting by gas chromatography, carrying out headspace gas phase analysis, calculating the content of methyl iodide in a sample by using an external standard point method, wherein methyl iodide is used as a reference substance, 1, 4-dioxane is used as a diluent, and the content of methyl iodide in the sample is calculated by using an external standard point method. The method for measuring the methyl iodide residue solves the technical problem that a medicament for treating epilepsy, namely the methyl iodide, is insoluble, ensures the stability of the methyl iodide in the detection process, and has the advantages of low detection limit of the methyl iodide, high sensitivity, good repeatability and high response.

Description

Method for measuring methyl iodide residue in crude drug for treating epilepsy

Technical Field

The invention relates to the technical field of analysis and detection, and particularly relates to a method for determining methyl iodide residue in a crude drug for treating epilepsy.

Background

Epilepsy is a chronic brain disease which is characterized by recurrent epileptic seizures, patients have irregular seizures, can have unconscious seizures suddenly, can have clinical symptoms such as convulsion, spasm, syncope, two eyes straightening and staring, and has the characteristics of paroxysmal, transient, repetitive and stereotypy.

Clobazam (frisure) is a drug for the treatment of epilepsy and has anxiolytic and anticonvulsant effects, and the ED50, which is resistant to electrical shock, is smaller than diazepam and larger than phenobarbital and sodium valproate. The clobazam is suitable for treating intractable epilepsy which is ineffective to other antiepileptic drugs, can be used independently, and can also be used as adjuvant therapy. Has better effect on the systemic attack secondary to the complex partial attack and Lennox-Gas-laut syndrome.

Methyl iodide is needed in the synthesis of clobazam, is very sensitive to the central nervous system, and can cause instability and hallucinations of limbs when a small amount of methyl iodide crosses the blood brain barrier and enters the brain stem, thereby causing serious damage to the nervous system of people. Therefore, the methyl iodide residue in the medicine needs to be detected, but the detection limit of the existing analysis and detection method cannot meet the requirement due to the solubility problem of the clobazam and the instability of the methyl iodide.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for measuring the residual methyl iodide in a crude drug for treating epilepsy, which solves the technical problem that the drug for treating epilepsy is difficult to dissolve in clobazam, ensures the stability of methyl iodide in the detection process, and has the advantages of low detection limit of methyl iodide, high sensitivity, good repeatability and high response.

The method for determining the methyl iodide residue in the crude drug for treating epilepsy comprises the steps of detecting by gas chromatography, carrying out headspace gas phase analysis, calculating the content of methyl iodide in a sample by using an external standard point method, wherein methyl iodide is used as a reference substance, 1, 4-dioxane is used as a diluent, and the content of methyl iodide in the sample is calculated by using an external standard point method.

Specifically, the method for determining the methyl iodide residue in the crude drug for treating epilepsy comprises the following steps:

(1) preparing a blank solution: taking the diluent 1, 4-dioxane as a blank solution;

(2) preparation of standard solutions: preparing a methyl iodide solution with the concentration of 0.185 mu g/mL as a standard solution by taking the diluent 1, 4-dioxane as a solvent and a reference substance methyl iodide as a solute;

(3) preparing a sample solution: preparing a sample solution with the concentration of 5g/L by using diluent 1, 4-dioxane as a solvent, adding 2mL of the sample solution with the concentration of 5g/L into a 20mL headspace bottle, and sealing to obtain a sample test solution;

(4) and (3) detection: and (3) injecting a sample solution in a headspace of a gas chromatograph, and calculating the content of the iodomethane in the sample by using an external standard one-point method.

Preferably, the diluent, blank solution, standard solution and sample solution can be prepared as follows:

diluting liquid: 1, 4-dioxane.

Blank solution: and (4) diluting the solution.

Standard solution:

(1) preparation of a control stock solution: accurately weighing 40mg of methyl iodide, placing the methyl iodide in a 20mL measuring flask with a proper amount of solvent, diluting the methyl iodide to a scale with 1, 4-dioxane, and shaking up to obtain the methyl iodide. The concentration was 2 mg/mL.

(2) Preparation of a control intermediate stock solution: measuring 50 μ L of reference stock solution, placing in a 100mL measuring flask, diluting with 1, 4-dioxane to scale, and shaking. The concentration was 1. mu.g/mL.

(3) Preparation of control solutions (100% limit concentration): measuring 3.7mL of the intermediate stock solution of the reference substance, placing in a 20mL measuring flask, diluting with 1, 4-dioxane to scale, and shaking. The concentration was 0.185. mu.g/mL.

Sample solution: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, shaken by 1, 4-dioxane and dissolved, and diluted to the scale mark. 2mL of the solution is precisely measured, placed in a 20mL headspace bottle and sealed.

The gas phase conditions were:

a chromatographic column: DB-624: 30 m.times.0.320 mm.times.1.8 μm;

sample inlet temperature: 110-130 ℃;

flow rate: 1.0-1.5 mL/min;

carrier gas: nitrogen gas;

the split ratio is as follows: 10: 1;

detector temperature: 290 ℃ and 300 ℃;

sample introduction amount: 1.0 mL;

operating time: 20-25 min;

temperature rising procedure: maintaining at 40 deg.C for 5-8min, heating to 180 deg.C at 50 deg.C/min, and maintaining for 3-8 min;

headspace conditions: furnace temperature: 55-65 ℃; and (3) quantitative ring: 110 ℃; transmission line: 115 ℃ is carried out; the balance time is as follows: 30-35 min; sample introduction time: 1.0 min; GC cycle time: 21 min;

the quantitative method comprises the following steps: and (4) an external standard one-point method.

Preferably, the column is of sequence number USF0376861H or USF 372642H.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, 1, 4-dioxane is used as a diluent, and compared with solvents such as ethanol, methanol, dichloromethane, toluene, N-methylpyrrolidone, N-dimethylformamide and the like, the technical problem that the clobazam is difficult to dissolve is solved, and methyl iodide does not react with the 1, 4-dioxane under the detection condition, so that the detection precision is ensured;

(2) the invention ensures the stability of the methyl iodide in the detection process by selecting proper diluent, injection port temperature and temperature rise program, and has the advantages of low detection limit of the methyl iodide, high sensitivity, good repeatability and high response.

Drawings

FIG. 1 is a detection spectrum of the applicability of the system of example 1, in which the detection spectra of the components numbered 1 to 6 are shown in the sequence from bottom to top;

FIG. 2 is a specificity detection map of example 2, in which the detection maps of the components with the sequence numbers 1-4 are shown from top to bottom;

FIG. 3 is a detection limit spectrum of example 3, in which the detection limits of the components numbered 1 to 3 are arranged in this order from bottom to top;

FIG. 4 is a quantitative limit detection spectrum of example 3, in which detection spectra of components numbered 1 to 6 are shown in order from bottom to top;

FIG. 5 is a linear range detection spectrum of example 4, in which the detection spectra of the components numbered 1 to 6 are shown in order from bottom to top;

FIG. 6 is a linear range diagram of example 4;

FIG. 7 is a repetitive detection pattern of example 5, in which the detection patterns of the components numbered 1 to 6 are arranged in order from bottom to top;

FIG. 8 is a middle precision detection spectrum of example 5, in which the detection spectra of the components numbered 1 to 6 are shown in order from bottom to top;

FIG. 9 is an accuracy detection map of example 6, in which the detection maps of the components numbered 1 to 11 are arranged from top to bottom;

FIG. 10 is a detection map of the headspace furnace temperature of 58 ℃ in example 8;

FIG. 11 is a detection map of the headspace furnace temperature of 62 ℃ in example 8;

FIG. 12 is a detection spectrum of a column model USF372642H in example 8;

FIG. 13 is a detection map at a flow rate of 1.4mL/min in example 8;

FIG. 14 is a detection map of example 8 in which the detector temperature is 290 ℃;

FIG. 15 is a graph showing the detection of the residual amount of methyl iodide in the crude drug for epilepsy therapy of example 9.

Detailed Description

The present invention is further described below with reference to examples.

The raw materials used in the examples were as follows:

methyl iodide, AR grade, manufacturer: chemical of nine tripods;

1, 4-dioxane, AR grade, manufacturer: mclin.

The apparatus used in the examples is as follows:

gas chromatograph: model 7890A, and manufacturer agent.

Unless otherwise specified, the detection conditions in the examples are as follows:

a chromatographic column: DB-624: 30 m.times.0.320 mm.times.1.8 μm; SN: USF 0376861H;

sample inlet temperature: 120 ℃;

flow rate: 1.5 mL/min;

carrier gas: nitrogen gas;

the split ratio is as follows: 10: 1;

detector temperature: 300 ℃;

sample introduction amount: 1.0 mL;

operating time: 22 min;

temperature rising procedure: maintaining at 40 deg.C for 6min, heating to 180 deg.C at 50 deg.C/min, and maintaining for 4 min;

headspace conditions: furnace temperature: 60 ℃; and (3) quantitative ring: 110 ℃; transmission line: 115 ℃ is carried out; and (3) balancing time: 30 min; sample introduction time: 1.0 min; GC cycle time: 21 min;

Example 1

And (3) testing the applicability of the system:

carrying out system applicability investigation before the sequence, wherein the blank solution has no interference peak or interference meeting the requirement; the system suitability was determined in 6 consecutive replicates.

(1) Acceptance criteria

The relative standard deviation RSD percent of the iodomethane peak area in the chromatogram obtained 6 times is less than or equal to 15.0 percent.

The recovery rate of the methyl iodide in the quality control solution is 80-120%.

(2) Solution preparation

1) Preparation of a methyl iodide reference stock solution: accurately weighing about 40mg of methyl iodide, placing the methyl iodide in a 20mL measuring flask, diluting the methyl iodide to a scale with 1, 4-dioxane, and shaking up to obtain the methyl iodide with the concentration of 2 mg/mL.

2) Preparation of a control intermediate stock solution: taking 50 μ L of the stock solution of the reference substance, precisely measuring, placing in a 100mL measuring flask, diluting with 1, 4-dioxane to scale, and shaking to obtain the final product with concentration of 1 μ g/mL.

3) Preparation of a methyl iodide control solution (100% limit concentration): taking 3.7mL of the intermediate stock solution of the reference substance, precisely measuring, placing in a 20mL measuring flask, diluting with 1, 4-dioxane to scale, and shaking up to obtain the final product with the concentration of 0.185 μ g/mL.

(3) The detection profile is shown in FIG. 1, and the results are shown in Table 1.

TABLE 1 System suitability test results

Example 2

Specificity test:

(1) acceptance criteria

1) No significant interference peak is generated near the position of the target peak in the blank solution; if an interference peak exists, the interference to the methyl iodide peak is less than or equal to 5 percent of the area of the control peak.

2) The peak positions of the components are positioned, and the separation degree of the iodomethane peak and the adjacent peak in the standard solution is more than or equal to 1.5.

(2) Solution preparation

1) Blank solution: precisely measuring 2mL of 1, 4-dioxane, placing in a 20mL headspace bottle, and sealing to obtain the final product.

2) Methyl iodide control solution: precisely measuring 3.7mL of the intermediate stock solution of the reference substance, placing in a 20mL measuring flask, diluting with 1, 4-dioxane to scale, shaking, precisely measuring 2mL of the solution, placing in a 20mL headspace flask, and sealing.

3) Test solution: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, dissolved by 1, 4-dioxane and diluted to the scale. 2mL of the solution is precisely measured, placed in a 20mL headspace bottle and sealed.

4) 100% spiked solution: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, dissolved with a 100% limit iodomethane standard solution, and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

(3) The detection profile is shown in FIG. 2, and the results are shown in Table 2.

TABLE 2 results of the specificity test

Example 3

Testing detection limit and quantification limit:

(1) acceptance criteria

The quantitative limiting solution (10% limiting concentration) is continuously injected for 6 times, the RSD% value of the peak area is less than or equal to 25%, and the signal-to-noise ratio is more than or equal to 10: 1.

And continuously injecting the detection limiting solution for 3 times, and recording the signal-to-noise ratio of each needle, wherein the signal-to-noise ratio is more than or equal to 3: 1.

(2) Solution preparation

1) Preparation of a quantitative limiting solution: measuring 0.37mL of the reference intermediate stock solution, placing the reference intermediate stock solution in a 20mL measuring flask, diluting the reference intermediate stock solution to a scale mark by using 1, 4-dioxane, and shaking up. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

2) Preparation of detection limiting solution: taking 2mL of quantitative limiting solution, precisely measuring, placing in a 10mL measuring flask, diluting to scale with 1, 4-dioxane, and shaking up. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

(3) The detection profiles are shown in FIGS. 3 to 4, and the results are shown in tables 3 to 4.

TABLE 3 detection Limit test results

TABLE 4 quantitative Limit precision test results

Example 4

Linear range test:

(1) linear range: the component to be measured is 0.0187 mu g/mL-0.3739 mu g/mL (corresponding to 10% -200% of the limit concentration).

(2) Acceptance criteria: within a specified linear range, the correlation coefficient r is more than or equal to 0.99.

(3) Preparation of solutions

2) Preparation of a control intermediate stock solution: precisely measuring 50 μ L of iodomethane reference substance stock solution, placing in a 100mL measuring flask, diluting with 1, 4-dioxane to scale, and shaking.

3) Preparation of standard curve working solution: with the above control intermediate stock solutions, linear standard solutions (LOQ, 20%, 50%, 100%, 150%, 200%) having not less than 5 points were prepared, respectively, as shown in table 5:

TABLE 5 Linear solution preparation Table

(4) The detection profile is shown in FIG. 5, the linear range is shown in FIG. 6, and the results are shown in Table 6.

TABLE 6 Linear results for each concentration level

Example 5

And (3) precision test:

a: repeatability test

(1) Acceptance criteria

The RSD percent of the content of the methyl iodide in 6 parts of solution is less than or equal to 20.0 percent.

(2) Solution preparation:

6 portions of 100% standard sample solution are prepared and injected continuously for 6 times. The preparation method comprises the following steps: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, shaken with a 100% limited iodomethane standard solution, dissolved and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

(3) The detection profile is shown in FIG. 7, and the results are shown in Table 7.

TABLE 7 results of the repeatability tests

Calculating the formula:

b: intermediate precision test

(1) Acceptance criteria

1) The RSD percent of the content of the methyl iodide in 6 parts of solution is less than or equal to 20.0 percent.

2) The RSD percent of the content of the methyl iodide in 12 parts of solution is less than or equal to 25.0 percent.

(2) Solution preparation

At different times, 6 portions of sample solutions were prepared by different experimenters and injected 6 times in succession.

(3) The detection profile is shown in FIG. 8, and the results are shown in Table 8.

TABLE 8 results of intermediate precision test

Example 6

And (3) accuracy test:

(1) acceptance criteria

The average recovery rate of each concentration is 80-120%.

(2) Solution preparation

1) Preparation of blank test solution: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, shaken by 1, 4-dioxane solution, dissolved and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product. 2 portions of the product are prepared by the same method.

2) Preparation of a labeled sample: preparing accuracy solutions of 50%, 100% and 150% respectively with reference stock solution of methyl iodide.

Accuracy test-blank: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, dissolved by 1, 4-dioxane solution and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product. 2 portions of the product are prepared by the same method.

Accuracy test-50%: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, dissolved by using a 50% limited iodomethane standard solution, and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product. 3 parts of the compound is prepared by the same method.

Accuracy test-100%: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, dissolved by a 100% limited iodomethane standard solution, and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product. 3 parts of the compound is prepared by the same method.

Accuracy test-150%: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, dissolved by using a 150% limit methyl iodide standard solution, and diluted to the scale mark. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product. 3 parts of the compound is prepared by the same method.

(3) The detection profile is shown in FIG. 9, and the results are shown in Table 9.

TABLE 9 accuracy test results

Example 7

And (3) solution stability test:

(1) acceptance criteria

And (3) respectively placing the 100% limit methyl iodide control solution and the 100% standard sample solution at room temperature for a certain time, and then injecting a sample for detection, wherein the change of the content of methyl iodide is less than or equal to 20.0% compared with 0 hour.

(2) Solution preparation:

1) preparation of a control solution of methyl iodide (100% limit concentration): precisely measuring 3.7mL of the intermediate stock solution of the reference substance, placing in a 20mL measuring flask, diluting with 1, 4-dioxane to scale, shaking, precisely measuring 2mL of the solution, placing in a 20mL headspace flask, and sealing.

2) Preparation of 100% spiked samples: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, shaken with a 100% limit iodomethane standard solution, dissolved and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

(3) The test results are shown in table 10:

TABLE 10 control solution stability test results

Time	Content of methyl iodide (. mu.g/mL)
		24h standard solution	0.181 (calculated system applicability)
0h standard solution	0.187 (calculated system suitability)
		Rate of change%	-3.2
Test results	Rate of change of iodomethane content<20.0%, meeting the acceptance standard.

TABLE 11100% spiked sample solution stability test results

Time	Content of methyl iodide (. mu.g/mL)
		24h 100% labelling sample solution	0.187 (calculated system suitability)
0h 100% labelling sample solution	0.222 (calculated system applicability)
		Rate of change%	-18.7
Test results	Rate of change of iodomethane content<20.0%, meeting the acceptance standard.

Example 8

Method durability test:

(1) acceptance criteria:

the determination conditions are changed, the difference value of the detection results meets the requirement (the relative deviation is less than or equal to 20 percent), the separation degree of the component to be detected and the adjacent peak is more than or equal to 1.5, and the durability is good.

(2) Solution preparation:

1) preparing a reference substance solution: precisely measuring 3.7mL of the intermediate stock solution of the reference substance, placing in a 20mL measuring flask, diluting with 1, 4-dioxane to scale, shaking, precisely measuring 2mL of the solution, placing in a 20mL headspace flask, and sealing.

2) Preparing a sample solution: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, shaken with a 100% limited iodomethane standard solution, dissolved and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

(3) The assay conditions were changed:

1) the headspace furnace temperature was changed, and the other conditions were unchanged.

2) The chromatographic column (same brand, same specification and different serial numbers) is changed, and other conditions are not changed. Chromatographic column 1 sequence number: USF0376861H, column 2 serial No.: USF 372642H.

3) The flow rate was changed to 1.4mL/min, and other conditions were unchanged. (pending according to the particular case)

4) The detector temperature was changed to 290 ℃ and other conditions were unchanged. (pending according to the particular case)

(4) The detection profiles are shown in FIGS. 10 to 14, wherein the detection profiles with the changed measurement conditions are shown in FIG. 7 No. 6, and the results are shown in Table 12.

TABLE 12 determination of Condition Change test results

Example 9

And (3) sample determination:

preparing a test sample: about 50mg of the test sample is precisely weighed, placed in a 10mL measuring flask, shaken by 1, 4-dioxane solution, dissolved and diluted to the scale. Precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain the product.

Sample detection: the Wott Empower3 workstation is adopted for data acquisition and data processing, and the concentration of the test sample is calculated by adopting automatic integration processing if no special sample exists. The injection sequence is shown in Table 13.

TABLE 13 exemplary sample introduction sequence Listing

Sample name	Number of sample introduction needles
		Blank solution	1～2
Control solution	6
		Blank solution	1
Sample solution	1
		Control solution	1

The sample detection profile is shown in fig. 15, and the sample detection results are shown in table 14, wherein:

the calculation is carried out according to an external standard one-point method and the RSD percent is less than or equal to 15 percent by calculating the peak area of the solution in the system applicability test.

TABLE 14 determination of methyl iodide residue in crude drug for epilepsy treatment

Claims

1. A method for measuring methyl iodide residue in a crude drug for treating epilepsy is characterized by comprising the following steps: detecting by gas chromatography, performing headspace gas phase analysis, calculating the content of methyl iodide in the sample by an external standard one-point method by using methyl iodide as a reference substance and 1, 4-dioxane as a diluent;

the gas phase conditions were:

a chromatographic column: DB-624: 30 m.times.0.320 mm.times.1.8 μm;

sample inlet temperature: 110-130 ℃;

flow rate: 1.0-1.5 mL/min;

carrier gas: nitrogen gas;

the split ratio is as follows: 10: 1;

detector temperature: 290 ℃ and 300 ℃;

sample introduction amount: 1.0 mL;

operating time: 20-25 min;

the quantitative method comprises the following steps: and (4) external standard one-point method.

2. The method for determining the residual methyl iodide in the crude drug for treating epilepsy according to claim 1, wherein the method comprises the following steps: the method comprises the following steps:

(4) and (3) detection: and (3) introducing a sample solution into a headspace of a gas chromatograph, and calculating the content of the methyl iodide in the sample by using an external standard point method.

3. The method for determining the residual methyl iodide in the crude drug for treating epilepsy according to claim 1 or 2, wherein: headspace conditions:

furnace temperature: 55-65 ℃;

and (3) quantitative ring: 110 ℃;

transmission line: 115 ℃ is carried out;

the balance time is as follows: 30-35 min;

sample introduction time: 1.0 min;

GC cycle time: and 21 min.

4. The method for determining the residual methyl iodide in the crude drug for treating epilepsy according to claim 1, wherein the method comprises the following steps: the column is of sequence number USF0376861H or USF 372642H.

5. The method for determining the residual methyl iodide in the crude drug for treating epilepsy according to claim 2, wherein the method comprises the following steps: the standard solution was prepared as follows:

(1) preparation of a control stock solution: taking about 40mg of methyl iodide, accurately weighing, placing into a 20mL measuring flask with a proper amount of solvent, diluting to scale with 1, 4-dioxane, and shaking uniformly to obtain the product with the concentration of 2 mg/mL;

(2) preparation of a control intermediate stock solution: measuring 50 μ L of reference stock solution, placing in a 100mL measuring flask, diluting with 1, 4-dioxane to scale, and shaking to obtain the final product with concentration of 1 μ g/mL;

(3) preparation of 100% Limit concentration control solutions: measuring 3.7mL of the intermediate stock solution of the reference substance, placing the intermediate stock solution in a 20mL measuring flask, diluting the intermediate stock solution to a scale with 1, 4-dioxane, and shaking up to obtain the standard solution with the concentration of 0.185 mu g/mL.

6. The method for determining the residual methyl iodide in the crude drug for treating epilepsy according to claim 2, wherein the method comprises the following steps: the sample solution was prepared as follows:

taking about 50mg of a test sample, precisely weighing, placing the test sample in a 10mL measuring flask, shaking the test sample by using 1, 4-dioxane, dissolving the test sample, and diluting the test sample to a scale mark; and precisely measuring 2mL of the solution, placing the solution in a 20mL headspace bottle, and sealing to obtain a sample solution.