Method for determining residual quantity of methyl iodide in riociguat raw material medicine by adopting GC (Gas Chromatography)

Abstract

The invention relates to the technical field of gas chromatographic analysis, in particular to a method for determining the residual quantity of methyl iodide in a riociguat raw material by adopting GC (Gas Chromatography), which comprises the following steps: treating a sample by adopting a capillary column taking polyethylene glycol as a stationary liquid and adopting a mode of taking an organic solvent to dissolve the riociguat raw material and then adding water, so as to determine the residual quantity of methyl iodide in the riociguat raw material. A hydrogen flame ionization detector is adopted to determine the residual quantity of iodomethane in the riociguat bulk drug. The method has the following beneficial effects that the sample solubility is good, the recovery rate is high, the specificity is good, the sensitivity is high, the accuracy is good, the durability is good, and the stability indication capability is good.

Description

Technical Field

[0001] The present invention relates to the technical field of gas chromatography analysis, and in particular to a method for determining the residual amount of methyl iodide in a riociguat raw material drug by using GC. Background Art

[0002] Riociguat, referred to as ROCG, is a compound developed by Bayer Pharmaceuticals in Germany that can stimulate soluble guanylate cyclase (sGC). sGC regulates vasodilation in multiple vascular beds by acting on cGMP and can be used to treat cardiovascular diseases and / or sexual dysfunction. Currently, the oral tablet developed by Bayer Pharmaceuticals for the treatment of pulmonary arterial hypertension (PAH) has been approved by the FDA under the trade name Adempas.

[0003] In the prior art, the preparation of riociguat requires the use of methyl iodide, which is an impurity in riociguat, so it is necessary to determine the residual amount of methyl iodide in the riociguat raw material. The commonly used detection methods in the prior art are as follows.

[0004] Solvent: N,N-dimethylformamide-water (1:1).

[0005] Test solution: Take about 200 mg of the product, weigh accurately, place in an empty bottle, add 2 ml of solvent, seal, and shake to dissolve.

[0006] Reference solution: Take an appropriate amount of methyl iodide and dilute it to make a solution containing about 10 μg of methyl iodide per 1 ml, transfer 2 ml to a headspace bottle and seal it. Prepare 2 copies in parallel.

[0007] Chromatographic conditions: capillary column (HP-INNOWAX 30m×0.32mm, 0.5μm or chromatographic column with equivalent performance) with polyethylene glycol (PEG) (or similar polarity) as the stationary phase; the starting temperature is 40℃, maintained for 10 minutes, and then increased to 220℃ at a rate of 30℃ per minute and maintained for 5 minutes; the injection port temperature is 220℃; the detector is a hydrogen flame ionization detector (FID), and the detector temperature is 260℃; the carrier gas is nitrogen; the split ratio is 10:1; the headspace equilibrium temperature is 80℃, and the equilibrium time is 30 minutes.

[0008] In the existing detection methods, the samples cannot be dissolved, and there are problems such as low recovery rate and instability of the reference solution at room temperature, which need to be solved urgently. Summary of the invention

[0009] The object of the present invention is to provide a method for determining the amount of methyl iodide residue in riociguat raw materials by GC, which has the characteristics of good accuracy and good stability indication ability.

[0010] The above technical objectives of the present invention are achieved through the following technical solutions: a method for determining the residual amount of methyl iodide in riociguat raw materials by GC, using a capillary column with polyethylene glycol as a stationary liquid, treating the sample by pipetting an organic solvent to dissolve the riociguat raw materials and then adding water, and using a hydrogen flame ionization detector (FID) to determine the residual amount of methyl iodide in the riociguat raw materials.

[0011] Preferably, the organic solvent is N,N-dimethylformamide.

[0012] Preferably, the ratio of organic solvent to water is 9:1.

[0013] Preferably, the amount of organic solvent used is 1.8 ml, and the amount of water used is 0.2 ml.

[0014] Preferably, the reference solution: contains 10 μg of iodomethane per 1 ml and is stored at 2-8°C; the test solution: take 200 mg of the product, accurately weigh it, place it in a 20 ml headspace bottle, add 1.8 ml of N,N-dimethylformamide, shake to dissolve, then add 0.2 ml of water, seal, shake well, and store at 2-8°C.

[0015] Preferably, the chromatographic conditions include:

[0016] Chromatographic column: capillary column with polyethylene glycol as stationary liquid;

[0017] Carrier gas: nitrogen;

[0018] Injection pressure: 30Kpa;

[0019] Split ratio: 10:1;

[0020] Inlet temperature: 220°C;

[0021] Detector temperature: 260°C;

[0022] Heating program: initial temperature 40°C, maintain for 10 minutes, then increase the temperature to 220°C at a rate of 30°C per minute, maintain for 5 minutes;

[0023] Headspace equilibration time: 30min;

[0024] Headspace equilibrium temperature: 80°C.

[0025] Preferably, the specification parameters of the chromatographic column are DB-WAX 30m×0.32mm 0.5μm.

[0026] Preferably, the preparation of the reference solution comprises:

[0027] Reference substance stock solution①: Take 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric flask, add solvent to dilute to the mark, shake well, prepare 2 portions in parallel, and store at 2-8°C;

[0028] Reference substance stock solution ②: Accurately measure 1 ml of reference substance stock solution ①, place in a 100 ml volumetric flask, add solvent to dilute to the mark, shake well, prepare 2 portions in parallel, and store at 2-8°C;

[0029] Reference substance solution: Measure 1.8 ml of reference substance stock solution ② and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well. This is the reference substance solution. Each 1 ml of the solution contains 10 μg. Store at 2-8°C.

[0030] Preferably, prepare the test sample spike solution:

[0031] Take 200 mg of this product, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of reference substance stock solution ②, shake to dissolve, then add 0.2 ml of water, place in the same 20 ml headspace bottle, seal, shake well, and use this as the test sample spike solution.

[0032] In summary, the present invention has the following beneficial effects:

[0033] The method has good sample solubility, high recovery rate, good specificity, high sensitivity, good accuracy, good durability and good stability indication ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a chromatogram of a blank solvent of the present invention;

[0035] Figure 2 is a chromatogram of the methyl iodide positioning solution of the present invention;

[0036] Figure 3 is a chromatogram of the test solution of the present invention;

[0037] Figure 4 It is the test sample spiked solution of the present invention;

[0038] Figure 5 is the linear graph of methyl iodide of Example 1 of the present invention;

[0039] Figure 6 is a linear graph of methyl iodide content in Comparative Example 1;

[0040] Figure 7 is the stability overlay of the reference solution in Example 1 (0h, 3h, 9h);

[0041] Figure 8 It is an overlay chart of the stability of the reference solution in Comparative Example 1 (0h, 9h, 24h). DETAILED DESCRIPTION

[0042] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0043] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0044] Example 1: A method for determining the amount of methyl iodide residue in the Riociguat API by GC, wherein the chromatographic conditions and sample preparation steps are as follows.

[0045] (1) Chromatographic conditions:

[0046] Chromatographic column: capillary column with polyethylene glycol (PEG) (DB-WAX-30m×0.32mm 0.5μm or similar polarity) as stationary liquid;

[0047] Carrier gas: nitrogen;

[0048] Injection pressure: 30Kpa;

[0049] Split ratio: 10:1;

[0050] Inlet temperature: 220°C;

[0051] Detector (FID) temperature: 260°C;

[0052] Heating program: initial temperature 40°C, maintain for 10 minutes, then increase the temperature to 220°C at a rate of 30°C per minute, maintain for 5 minutes;

[0053] Headspace equilibration time: 30min;

[0054] Headspace equilibrium temperature: 80°C.

[0055] (2) Sample preparation:

[0056] Solvent: The solvent used in this embodiment is an organic solvent, specifically N,N-dimethylformamide;

[0057] Blank solution: Pipette 1.8 ml of N,N-dimethylformamide and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well to obtain;

[0058] Reference substance stock solution ①: Take about 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric flask, add solvent to dilute to the mark, shake well; prepare 2 portions in parallel (store at 2-8°C);

[0059] Reference substance stock solution ②: Accurately measure 1 ml of reference substance stock solution ①, place in a 100 ml volumetric flask, add solvent to dilute to the mark, shake well; prepare 2 portions in parallel and store at 2-8°C;

[0060] Reference solution: Measure 1.8 ml of reference stock solution ② and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well. This is the reference solution, with each ml containing about 10 μg of solution (stored at 2-8°C);

[0061] Test solution: Take about 200 mg of the product, weigh accurately, put it into a 20 ml headspace bottle, add 1.8 ml of N, N-dimethylformamide, shake to dissolve, then add 0.2 ml of water, seal, shake well, and use as the test solution;

[0062] Test sample spike solution: Take about 200 mg of this product, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of reference sample stock solution ②, shake to dissolve, then add 0.2 ml of water, place in the same 20 ml headspace bottle, seal, shake well, and use as the test sample spike solution.

[0063] The water used in the above operation in this embodiment is ultrapure water.

[0064] The chromatograms of the blank solvent, methyl iodide positioning solution, test solution, and test solution spiked with the sample 1 were measured as follows: Figures 1 to 4 shown.

[0065] Comparative Example 1: The existing technology described in the background technology was used to determine the residual amount of methyl iodide in the Riociguat API, and the chromatographic conditions and sample preparation steps were as follows.

[0066] (1) Chromatographic conditions:

[0067] A capillary column (HP-INNOWAX 30m×0.32mm, 0.5μm or a chromatographic column with equivalent performance) with polyethylene glycol (PEG) (or a substance with similar polarity) as the stationary phase; the starting temperature is 40°C, maintained for 10 minutes, and then increased to 220°C at a rate of 30°C per minute and maintained for 5 minutes; the injection port temperature is 220°C; the detector is a hydrogen flame ionization detector (FID), and the detector temperature is 260°C; the carrier gas is nitrogen; the split ratio is 10:1; the headspace equilibrium temperature is 80°C, and the equilibrium time is 30 minutes.

[0068] (2) Sample preparation:

[0069] Solvent: N,N-dimethylformamide-water (1:1);

[0070] Test solution: Take about 200 mg of the product, weigh accurately, add 2 ml of solvent accurately into an empty bottle, seal, and shake to dissolve;

[0071] Reference solution: Take an appropriate amount of methyl iodide and dilute it to make a solution containing about 10 μg of methyl iodide per 1 ml, transfer 2 ml to a headspace bottle and seal it. Prepare 2 copies in parallel.

[0072] Example 2: Specificity and systematic experiment.

[0073] The chromatographic conditions, solvents, blank solution, reference solution (locating solution), test solution, and test spiked solution are as described in Example 1.

[0074] The results are as follows:

[0075]

[0076] From the data in the above table, it can be seen that the solvent and the riociguat raw material have no interference with the determination of methyl iodide, and the specificity of the present invention is good; the reference solution was measured 6 times continuously, and the RSD of the main peak retention time and peak area were less than 2.0%, and the system applicability of the present invention is good.

[0077] Example 3: Quantitation limit and detection limit experiments.

[0078] The chromatographic conditions, solvents, blank solution, and reference solution (positioning solution) are as described in Example 1.

[0079] Quantitative limit solution: dilute the reference solution step by step and prepare the quantitative limit solution according to S / N ≥ 10. Perform 6 injections in succession to examine the precision of the quantitative limit (store at 2-8℃).

[0080] Detection limit solution: dilute the quantitative limit solution step by step to prepare the detection limit solution (store at 2-8°C) according to S / N ≥ 3.

[0081] The results are as follows:

[0082]

[0083] The S / N of the detection limit solution of iodomethane is greater than 3, and the S / N of the quantitative limit solution is greater than 10, both of which are less than 0.005% of the concentration of the test sample. The present invention has high sensitivity.

[0084] Example 4: Linearity and range experiments.

[0085] For the linearity and range experiments, the chromatographic conditions, solvents and blank solutions were as described in Example 1.

[0086] Linear stock solution ①: Take about 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric bottle, add solvent to dilute to the scale, shake well (store at 2-8°C)

[0087] Linear stock solution ① is prepared into a series of linear stock solutions ② according to the following table: (stored at 2-8°C).

[0088] name Measure the volume of linear stock solution①(ml) Volume of measuring flask (ml) Equivalent to limit percentage (%) LOQ / / / L1 0.5 100 50 L2 0.8 100 80 L3 1.0 100 100 L4 1.5 100 150

[0089] Linear solution: Accurately pipette 1.8 ml of each concentration of linear stock solution and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well (store at 2-8°C).

[0090] The results are as follows:

[0091]

[0092] The linear equation of iodomethane in the concentration range of 4.7336 μg / ml to 17.7510 μg / ml is y=906.9412x+25.4715, r=0.9984.

[0093] The linearity and range experiments of Comparative Example 1, the chromatographic conditions, solvents, and blank solutions were the same as those described in Comparative Example 1.

[0094] Linear stock solution ①: Take about 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric flask, add solvent to dilute to the scale, and shake well.

[0095] Linear stock solution ① is prepared into a series of linear stock solutions ② according to the following table:

[0096] name Measure the volume of linear stock solution① (ml) Volume of measuring flask (ml) Equivalent to limit percentage (%) LOQ / / / L1 0.2 100 20 L2 0.5 100 50 L3 0.8 100 80 L4 1.0 100 100 L5 1.5 100 150

[0097] Linear solution: Accurately pipette 1.8 ml of each concentration of linear stock solution ② and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well.

[0098] The results are as follows:

[0099]

[0100] The linear equation of iodomethane in the concentration range of 0.5056 μg / ml to 16.8919 μg / ml is y=2582.8943x+1220.4174, r=0.9928.

[0101] Example 5: Recovery rate experiment.

[0102] The recovery rate experiment, chromatographic conditions, solvents, and blank solution were as described in Example 1.

[0103] Reference substance stock solution①: Take about 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric flask, add solvent to dilute to the scale, and shake well; prepare 2 portions in parallel (store at 2-8°C).

[0104] Reference substance stock solution ②: Accurately measure 1 ml of reference substance stock solution ① and place it in a 100 ml volumetric flask. Add solvent to dilute to the mark and shake well. Prepare 2 portions in parallel (store at 2-8°C).

[0105] Reference solution: Measure 1.8 ml of reference stock solution ② and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well as the reference solution (each 1 ml contains about 10 μg of solution) (store at 2-8°C)

[0106] Iodomethane stock solution: Take the first reference stock solution① (stored at 2-8℃).

[0107] Accuracy stock solution ①: Accurately measure 0.5 ml of iodomethane stock solution, place it in a 100 ml volumetric flask, add solvent to dilute to the scale, and shake well (each 1 ml contains about 5 μg of solution) (store at 2-8°C).

[0108] Accuracy stock solution ②: Accurately measure 1.5 ml of iodomethane stock solution, place it in a 100 ml volumetric flask, add solvent to dilute to the scale, and shake well (each 1 ml contains approximately 15 μg of solution) (store at 2-8°C).

[0109] Accuracy stock solution ③: Accurately measure 1.0 ml of iodomethane stock solution, place it in a 100 ml volumetric flask, add solvent to dilute to the scale, and shake well (each 1 ml contains approximately 10 μg of solution) (store at 2-8°C).

[0110] 50% recovery solution: Take about 200 mg of riociguat test sample, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of accuracy stock solution ①, shake to dissolve, then add 0.2 ml of water, seal, shake well, as 50% recovery solution. Prepare 3 portions in parallel (store at 2-8°C).

[0111] 100% recovery solution: Take about 200 mg of the riociguat test sample, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of accuracy stock solution ③, shake to dissolve, then add 0.2 ml of water, seal, shake well, and use as 100% recovery solution. Prepare 3 portions in parallel (store at 2-8°C).

[0112] 150% recovery solution: Take about 200 mg of riociguat test sample, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of accuracy stock solution ②, shake to dissolve, then add 0.2 ml of water, seal, shake well, and use as 150% recovery solution. Prepare 3 portions in parallel (store at 2-8°C).

[0113] The results are as follows:

[0114]

[0115]

[0116] The recovery rate of iodomethane was between 82% and 89%, with an average recovery rate of 85% and an RSD of 2.87%.

[0117] The recovery rate experiment of Comparative Example 1, the chromatographic conditions, solvent, and blank solution were the same as those described in Comparative Example 1.

[0118] Reference substance stock solution①: Take about 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric flask, add solvent to dilute to the scale, shake well; prepare 2 portions in parallel.

[0119] Reference substance stock solution ②: Accurately measure 1 ml of reference substance stock solution ① and place it in a 100 ml volumetric flask. Add solvent to dilute to the mark and shake well. Prepare 2 portions in parallel.

[0120] Reference substance solution: Measure 1.8 ml of reference substance stock solution ② and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well to prepare the reference substance solution (each 1 ml contains approximately 10 μg of solution).

[0121] Iodomethane stock solution: Take the first reference stock solution①.

[0122] Accuracy stock solution ①: Accurately measure 0.5 ml of iodomethane stock solution, place it in a 100 ml volumetric flask, add solvent to dilute to the scale, and shake well (each 1 ml contains approximately 5 μg of solution).

[0123] Accuracy stock solution ②: Accurately measure 1.5 ml of iodomethane stock solution, place it in a 100 ml volumetric flask, add solvent to dilute to the scale, and shake well (each 1 ml contains approximately 15 μg of solution).

[0124] Accuracy stock solution ③: Accurately measure 1.0 ml of iodomethane stock solution, place it in a 100 ml volumetric flask, add solvent to dilute to the scale, and shake well (each 1 ml contains approximately 10 μg of solution).

[0125] 50% recovery solution: Take about 200 mg of the Riociguat test sample, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of accuracy stock solution ①, shake to dissolve, then add 0.2 ml of water, seal, shake well, and use as the 50% recovery solution. Prepare 3 copies in parallel.

[0126] 100% recovery solution: Take about 200 mg of the Riociguat test sample, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of accuracy stock solution ③, shake to dissolve, then add 0.2 ml of water, seal, shake well, and use as the 100% recovery solution. Prepare 3 copies in parallel.

[0127] 150% recovery solution: Take about 200 mg of Riociguat test sample, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of accuracy stock solution ②, shake to dissolve, then add 0.2 ml of water, seal, shake well, and use as 150% recovery solution. Prepare 3 copies in parallel.

[0128] The results are as follows:

[0129]

[0130] The recovery rates of samples with 50% iodomethane concentration were all less than 70%, which did not meet the experimental requirements.

[0131] Example 6: Stability experiment.

[0132] Stability test, chromatographic conditions, solvent, blank solution, reference solution are as described in Example 1, the stability overlay (0h, 3h, 9h) of the reference solution is as shown Figure 7 shown.

[0133] The results are as follows:

[0134]

[0135] The reference solution is stable for 9 hours at 2-8°C.

[0136] In the stability experiment of Comparative Example 1, the chromatographic conditions, solvent, blank solution and reference solution were as described in Comparative Example 1, and the stability overlay (0h, 9h, 24h) of the obtained reference solution was as follows: Figure 8 shown.

[0137] The results are as follows:

[0138]

[0139] The reference solution is not stable at room temperature.

[0140] Example 7: Precision experiment.

[0141] For the precision experiment, the chromatographic conditions, solvents, blank solution, reference solution, and test sample spiked solution were as described in Example 1.

[0142] The results are as follows:

[0143]

[0144] The average repeatability of 6 samples was 0.0095%, and the RSD was 1.98%; the average intermediate precision of 12 samples was 0.0092%, and the RSD was 3.46%.

[0145] Example 8: Durability test.

[0146] For the durability experiment, the chromatographic conditions, solvents, blank solution, reference solution, and test sample spiked solution were as described in Example 1.

[0147] The changed chromatographic parameters are shown in the following table:

[0148] Chromatographic parameters Proposed conditions Range of change Injection pressure 30Kpa ±2Kpa Column temperature 40℃ ±2℃ Inlet temperature 220℃ ±5℃ Detector temperature 260℃ ±5℃

[0149] The results are as follows:

[0150]

[0151]

[0152] In the case of a single factor change of some chromatographic parameters, the method is still applicable to the detection of iodomethane residues in Riociguat API. The detection result of iodomethane residues is not greatly affected, the method has good durability, and changing the chromatographic conditions within an appropriate range does not affect the analytical purpose of the method of the present invention.

[0153] Example 9: Data analysis.

[0154] The detection methods of Comparative Example 1 and Example 1 are compared, and the specific results are shown in the following table:

[0155]

[0156] Through the above comparative analysis, it can be seen that compared with Comparative Example 1, the analytical method described in Example 1 has the advantages of good solubility, good reproducibility, high accuracy, good stability indication ability, etc. in determining the residual amount of iodomethane in the raw material drug of Riocil.

Claims

1. A method for determining the residual amount of methyl iodide in Riociguat API by GC, characterized in that: A capillary column with polyethylene glycol as the stationary phase was used. The sample was treated by pipetting an organic solvent to dissolve the Riociguat API and then adding water. A hydrogen flame ionization detector was used to determine the residual amount of methyl iodide in the Riociguat API.

2. The method for determining the residual amount of methyl iodide in the riociguat raw material drug by GC according to claim 1, characterized in that: The organic solvent is N,N-dimethylformamide.

3. The method for determining the residual amount of methyl iodide in the Riociguat API by GC according to claim 1, characterized in that: The ratio of organic solvent to water is 9:

1.

4. The method for determining the residual amount of methyl iodide in the riociguat raw material drug by GC according to claim 3, characterized in that: The amount of organic solvent used was 1.8 ml, and the amount of water used was 0.2 ml.

5. The method for determining the residual amount of methyl iodide in the Riociguat API by GC according to claim 4, characterized in that: Reference solution: Each ml contains 10 μg of iodomethane, stored at 2-8°C; Test solution: Take 200 mg of the product, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of N,N-dimethylformamide, shake to dissolve, then add 0.2 ml of water, seal, shake well, and store at 2-8 °C.

6. The method for determining the residual amount of methyl iodide in the riociguat raw material drug by GC according to claim 1, characterized in that: The chromatographic conditions included the following: Chromatographic column: capillary column with polyethylene glycol as stationary liquid; Carrier gas: nitrogen; Injection pressure: 30Kpa; Split ratio: 10:1; Inlet temperature: 220°C; Detector temperature: 260°C; Heating program: initial temperature 40°C, maintain for 10 minutes, then increase the temperature to 220°C at a rate of 30°C per minute, maintain for 5 minutes; Headspace equilibration time: 30 min; Headspace equilibrium temperature: 80°C.

7. The method for determining the residual amount of methyl iodide in the riociguat raw material drug by GC according to claim 6, characterized in that: The specification parameters of the chromatographic column are DB-WAX 30m×0.32mm 0.5μm.

8. The method for determining the residual amount of methyl iodide in the riociguat raw material drug by GC according to claim 6, characterized in that: The preparation of the reference solution includes: Reference substance stock solution①: Take 22 mg of methyl iodide, weigh accurately, place in a 20 ml volumetric flask, add solvent to dilute to the mark, shake well, prepare 2 portions in parallel, and store at 2-8°C; Reference substance stock solution ②: Accurately measure 1 ml of reference substance stock solution ①, place in a 100 ml volumetric flask, add solvent to dilute to the mark, shake well, prepare 2 portions in parallel, and store at 2-8°C; Reference substance solution: Measure 1.8 ml of reference substance stock solution ② and 0.2 ml of water into a 20 ml headspace bottle, seal, and shake well. This is the reference substance solution. Each 1 ml of the solution contains 10 μg. Store at 2-8°C.

9. The method for determining the residual amount of methyl iodide in the riociguat raw material drug by GC according to claim 8, characterized in that: Prepare the test sample spike solution: Take 200 mg of this product, weigh accurately, place in a 20 ml headspace bottle, add 1.8 ml of reference substance stock solution ②, shake to dissolve, then add 0.2 ml of water, place in the same 20 ml headspace bottle, seal, shake well, and use this as the test sample spike solution.

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