A detection method for nitromethane in hydroxylamine hydrochloride based on gas chromatography

Abstract

The present invention belongs to the field of analytical chemistry, relates to gas chromatography, and specifically relates to a method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography. A sample of hydroxylamine hydrochloride to be tested is added to a solvent to obtain a test solution, and the test solution is injected by headspace injection for gas chromatography analysis; wherein, the solvent is water containing sodium chloride and N,N-dimethylformamide, and the mass-volume ratio of sodium chloride to water is 4.0-6.0:100, g / mL; the volume ratio of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and the aqueous sodium chloride solution is 4.0-6.0:100. The detection method provided by the present invention has the characteristics of strong specificity, high sensitivity, high accuracy, etc., and is simple, convenient, and efficient to operate.

Description

Technical Field

[0001] The present invention belongs to the field of analytical chemistry, relates to gas chromatography, and specifically relates to a method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and it is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Azilsartan is an angiotensin II receptor antagonist, which is clinically used to treat hypertension. Hydroxylamine hydrochloride is the starting material for synthesizing azilsartan raw materials; and nitromethane is the starting material for synthesizing hydroxylamine hydrochloride. Nitromethane is a class 2B carcinogen and is harmful to the human body. During the actual production process, the residual amount of nitromethane in the raw drug should be strictly controlled within the specified range to ensure the safety of subsequent preparation production and subsequent drug use.

[0004] According to the research and understanding of the inventor, during the current detection of nitromethane by gas chromatography, solvents such as water and dimethyl sulfoxide are generally used for dissolution, and then gas chromatography detection is carried out. However, the inventor has found that when using these methods to detect nitromethane in hydroxylamine hydrochloride, there are problems such as poor solubility and high recovery rate. Summary of the Invention

[0005] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography. The detection method provided by the present invention has the characteristics of strong specificity, high sensitivity, high accuracy, etc., and is simple, convenient and efficient to operate.

[0006] In order to achieve the above purpose, the technical solution of the present invention is as follows:

[0007] On the one hand, a method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography, adding a sample of the hydroxylamine hydrochloride to be detected into a solvent to dissolve to obtain a test solution, and using the headspace injection method to inject the test solution for gas chromatography analysis;

[0008] Wherein, the solvent is water containing sodium chloride and N,N-dimethylformamide, the mass-volume ratio of sodium chloride to water is 4.0 - 6.0:100, g / mL; the ratio of the volume of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and the sodium chloride aqueous solution is 4.0 - 6.0:100.

[0009] The detection object of the present invention is nitromethane in hydroxylamine hydrochloride. Hydroxylamine hydrochloride is an inorganic substance, and nitromethane is an organic substance. If the existing solvents for detecting nitromethane (such as water, dimethyl sulfoxide, etc.) are used, there is a problem that hydroxylamine hydrochloride and nitromethane cannot be dissolved simultaneously. To solve this problem, the present invention first uses N,N-dimethylformamide as a solvent. However, due to the different compositions of the reference solution and the test solution, when nitromethane undergoes headspace analysis, its partition coefficient between the gas and liquid phases is different, resulting in a quantitative error.

[0010] Since the main component in the detection object of the present invention is hydroxylamine hydrochloride, the present invention uses water as the main component of the solvent. Since nitromethane has poor solubility in water and good solubility in N,N-dimethylformamide, considering using N,N-dimethylformamide as the solvent, hydroxylamine hydrochloride belongs to inorganic compounds. For the test solution with a large concentration in the headspace injection method, matrix effects may be introduced. Because of its good water solubility, to eliminate matrix effects, during the solvent research, a certain amount of inorganic salts is considered to be added to water. However, there are various inorganic salts, such as sodium chloride, dipotassium hydrogen phosphate, etc. Experiments of the present invention show that when sodium chloride is added, the recovery rate is better and the detection of nitromethane in hydroxylamine hydrochloride is more accurate.

[0011] On the other hand, a quality control method for producing hydroxylamine hydrochloride uses the above-mentioned method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography to detect the content of nitromethane in the produced hydroxylamine hydrochloride.

[0012] In the third aspect, a detection kit is used for gas chromatography detection of nitromethane in hydroxylamine hydrochloride by the headspace injection method; it includes sodium chloride, N,N-dimethylformamide, and water. The mass-volume ratio of sodium chloride to water is 4.0 - 6.0:100, g / mL; after sodium chloride and water are made into an aqueous sodium chloride solution, the volume ratio of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and the aqueous sodium chloride solution is 4.0 - 6.0:100.

[0013] The beneficial effects of the present invention are as follows:

[0014] By adding N,N-dimethylformamide and sodium chloride to water, the present invention can not only reduce the quantitative error caused by the different distribution coefficients of nitromethane between the gas and liquid phases, but also eliminate the basic influence. Experiments have shown that the method for gas chromatography detection of nitromethane in hydroxylamine hydrochloride provided by the present invention, using water containing sodium chloride and N,N-dimethylformamide as the solvent, does not interfere with the inspection of nitromethane for both the solvent and the test sample. The recovery rate ranges from 103.52% to 104.60%, the detection limit is as low as 0.1414 μg / ml (0.00014%), the relative standard deviation (RSD) of the peak area is 1.50% for the quantitative limit solution injected continuously for 6 times, and nitromethane has a good linear relationship in the concentration range of 0.4712 μg / ml to 7.8525 μg / ml, with a correlation coefficient of 0.9999. It has the characteristics of strong specificity, high sensitivity, and high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings forming a part of this invention are used to provide a further understanding of the invention. The schematic embodiments and descriptions thereof of the invention are used to explain the invention and do not unduly limit the invention.

[0016] Figure 1 It is the chromatogram of the nitromethane reference solution in the embodiment of the present invention;

[0017] Figure 2 It is the chromatogram of the quantitative limit solution in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] In view of the problems of poor solubility and high recovery rate when the existing gas chromatography method is used to detect nitromethane in hydroxylamine hydrochloride, the present invention proposes a detection method for nitromethane in hydroxylamine hydrochloride based on gas chromatography.

[0021] In a typical embodiment of the present invention, a method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography is provided. A test sample of hydroxylamine hydrochloride is added to a solvent to dissolve and obtain a test solution, and the test solution is injected by headspace injection for gas chromatography analysis.

[0022] Among them, the solvent is water containing sodium chloride and N,N-dimethylformamide. The mass-volume ratio of sodium chloride to water is 4.0 - 6.0:100, g / mL; the ratio of the volume of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and sodium chloride aqueous solution is 4.0 - 6.0:100.

[0023] In some embodiments, in the headspace injection method, the equilibrium temperature of the headspace vial is 75 - 85 °C. Specifically, the equilibrium time of the headspace vial is 20 - 40 minutes.

[0024] In some embodiments, in the gas chromatography analysis, the detector used is a flame ionization detector (FID). Specifically, the temperature of the detector is 240 - 260 °C.

[0025] In some embodiments, in the gas chromatography analysis, the chromatographic column used is a capillary column, and the stationary phase in the capillary column is 5.5 - 6.5% (mass percentage) cyanopropylphenyl - 94.5 - 94.5% (mass percentage) dimethylpolysiloxane as the stationary phase.

[0026] In some embodiments, in the gas chromatography analysis, column temperature: the initial temperature is 35 - 45 °C, maintained for 11 - 13 minutes, and then heated at a heating rate of 8 - 12 °C per minute to 170 - 190 °C, and maintained for 13 - 15 minutes.

[0027] In some embodiments, in the gas chromatography analysis, the inlet temperature is 150 - 250 °C, preferably 180 - 220 °C.

[0028] In some embodiments, in the gas chromatography analysis, split ratio: 4.5 - 5.5:1.

[0029] In another embodiment of the present invention, a quality control method for producing hydroxylamine hydrochloride is provided. The content of nitromethane in the produced hydroxylamine hydrochloride is detected by using the above method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography.

[0030] The third embodiment of the present invention provides a detection kit for gas chromatography detection of nitromethane in hydroxylamine hydrochloride by headspace injection method; it includes sodium chloride, N,N-dimethylformamide and water, and the mass-volume ratio of sodium chloride to water is 4.0 - 6.0:100, g / mL; after preparing an aqueous sodium chloride solution from sodium chloride and water, the volume ratio of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and the aqueous sodium chloride solution is 4.0 - 6.0:100.

[0031] In some embodiments, it further includes a nitromethane reference substance.

[0032] In some embodiments, it further includes a hydroxylamine hydrochloride reference substance.

[0033] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0034] In the following examples, during the method exploration process, if not specifically stated, the test sample solution (main component: 400 mg / ml), the reference substance solution (nitromethane concentration: 20 μg / ml), and the 100% recovery solution (main component: 400 mg / ml, nitromethane concentration: 20 μg / ml).

[0035] Example 1:

[0036] Instrument: Agilent GC 7820A, Agilent Technologies Co., Ltd.;

[0037] Chromatographic column: A capillary column with 6% cyanopropylphenyl - 94% dimethylpolysiloxane as the stationary phase was used as the chromatographic column (DB-624, 0.53 mm × 30 m, 3 μm, Agilent Technologies Co., Ltd.);

[0038] Column temperature: The initial temperature was 40°C, maintained for 12 minutes, then heated at a rate of 10°C per minute to 180°C, and maintained for 14 minutes;

[0039] Detector: Flame ionization detector (FID);

[0040] Detector temperature: 250°C;

[0041] Injector temperature: 200°C;

[0042] Flow rate: 2.0 ml / min;

[0043] Split ratio: 5:1;

[0044] Hydrogen flow rate: 30 ml / min;

[0045] Air flow rate: 300 ml / min;

[0046] Nitrogen flow rate: 30 ml / min;

[0047] Running time: 40 minutes;

[0048] Headspace vial equilibration temperature: 100 °C;

[0049] Headspace vial equilibration time: 30 minutes;

[0050] Solvent: N,N-dimethylformamide. The test results are shown in Table 1.

[0051] Table 1 Gas Chromatography Detection Results with N,N-dimethylformamide as Solvent

[0052]

[0053] The test results show that nitromethane was not detected in the test solution, and the average recovery rate of nitromethane in the 100% recovery solution was 318.77%, with a high recovery rate. The solvent of this detection method was studied.

[0054] Example 2

[0055] Instrument: Agilent GC 7820A, Agilent Technologies;

[0056] Chromatographic column: A capillary column with 6% cyanopropylphenyl-94% dimethylpolysiloxane as the stationary phase (DB-624, 0.53 mm × 30 m, 3 μm, Agilent Technologies);

[0057] Column temperature: The initial temperature was 40 °C, maintained for 12 minutes, then heated at a rate of 10 °C per minute to 180 °C and maintained for 14 minutes;

[0058] Detector: Flame ionization detector (FID);

[0059] Detector temperature: 250 °C;

[0060] Injector temperature: 200 °C;

[0061] Flow rate: 2.0 ml / min;

[0062] Split ratio: 5:1;

[0063] Hydrogen flow rate: 30 ml / min;

[0064] Air flow rate: 300 ml / min;

[0065] Nitrogen flow rate: 30 ml / min;

[0066] Running time: 40 minutes;

[0067] Headspace vial equilibration temperature: 80 °C;

[0068] Headspace vial equilibration time: 30 minutes;

[0069] Solvent: 5% DMF solution / aqueous solution containing 5% sodium chloride and 5% DMF / aqueous solution containing 5% dipotassium hydrogen phosphate and 5% DMF. The test results are shown in Table 2.

[0070] Table 2 Test results of gas chromatography detection with different solvents

[0071]

[0072] In summary, the method with the aqueous solution containing 5% sodium chloride and 5% DMF as the solvent has the highest accuracy, and this solvent is determined as the final solvent. There are significant differences in the response values of nitromethane in different solvents. According to the response values of the proposed solvents, the concentration of the reference solution is adjusted to 5 μg / ml, and the concentration of the test solution is 100 mg / ml.

[0073] The finally determined method is as follows:

[0074] Instrument: Agilent GC 7820A, Agilent Technologies;

[0075] Chromatographic column: A capillary column with 6% cyanopropylphenyl - 94% dimethylpolysiloxane as the stationary phase (DB - 624, 0.53 mm × 30 m, 3 μm, Agilent Technologies);

[0076] Column temperature: The initial temperature is 40 °C, maintained for 12 minutes, then heated at a rate of 10 °C per minute to 180 °C and maintained for 14 minutes;

[0077] Detector: Flame ionization detector (FID);

[0078] Detector temperature: 250 °C;

[0079] Injector temperature: 200 °C;

[0080] Flow rate: 2.0 ml / min;

[0081] Split ratio: 5:1;

[0082] Hydrogen flow rate: 30 ml / min;

[0083] Air flow rate: 300 ml / min;

[0084] Nitrogen flow rate: 30 ml / min;

[0085] Run time: 40 minutes;

[0086] Headspace vial equilibration temperature: 80 °C;

[0087] Headspace vial equilibration time: 30 minutes;

[0088] Solution preparation:

[0089] Solvent: Take 5 g of sodium chloride, dissolve it in 100 ml of water, shake well. Take 95 ml of the above solution, add 5 ml of N,N-dimethylformamide, and shake well.

[0090] Stock solution of reference substance: Take about 0.02 g of nitromethane, accurately weigh it, place it in a 100-ml volumetric flask, dilute it to the mark with the solvent, and shake well. As the stock solution of reference substance, accurately measure 5 ml and place it in a 20-ml headspace vial, seal it, and use it as the nitromethane peak positioning solution.

[0091] Reference solution: Accurately measure 2.5 ml of the stock solution of reference substance, place it in a 100-ml volumetric flask, dilute it to the mark with the solvent, shake well. Accurately measure 5 ml and place it in a 20-ml headspace vial, seal it, and shake well to obtain the reference solution.

[0092] Test solution: Take about 0.5 g of hydroxylamine hydrochloride, accurately weigh it, place it in a 20-ml headspace vial, add 5 ml of the solvent to dissolve it, and seal it.

[0093] Determination method: Inject the test solution and the reference solution into the headspace sampler respectively, and record the chromatogram.

[0094] Limit: Calculated by the external standard method based on the peak area, the content of nitromethane shall not exceed 0.005%.

[0095] Calculation formula:

[0096]

[0097] As is the peak area of the test solution;

[0098] Ar is the peak area of the reference solution;

[0099] Ws is the weighed amount of the test sample, g;

[0100] Wr is the weighed amount of the reference substance, g.

[0101] The methodological study of the above method is as follows:

[0102] 1. Specificity

[0103] 100% recovery solution: Take about 0.5 g of hydroxylamine hydrochloride, accurately weigh it, place it in a 20-ml headspace vial, accurately add 5 ml of the reference solution to dissolve it, seal it, and shake well to obtain the 100% recovery solution. (Prepare three portions in the same way);

[0104] Take the solvent, nitromethane peak location solution, test solution, reference solution, and 100% recovery solution, inject them into the gas chromatograph, and record the chromatogram. The test results are shown in Tables 3 - 4.

[0105] Table 3 Results of Nitromethane Peak Location Test in Hydroxylamine Hydrochloride

[0106]

[0107] Table 2 Results of Specificity Recovery Test for Nitromethane Inspection in Hydroxylamine Hydrochloride

[0108]

[0109] The test results show that neither the solvent nor the test sample interferes with the inspection of nitromethane, and the recovery rate ranges from 103.52% to 104.60%.

[0110] 2. System Suitability Test

[0111] Take about 0.02 g of nitromethane, accurately weigh it, place it in a 100 - ml volumetric flask, dilute it to the mark with the solvent, shake well, and use it as the reference stock solution. Accurately measure 2.5 ml of the reference stock solution, place it in a 100 - ml volumetric flask, dilute it to the mark with the solvent, shake well, accurately measure 5 ml, place it in a 20 - ml headspace vial, seal it, and shake well to obtain the reference solution. Take the reference solution and inject it into the headspace sampler 5 times, record the chromatogram, and the test results are shown in Figure 1 , Table 3.

[0112] Table 4 Results of System Suitability Test for Nitromethane Inspection in Hydroxylamine Hydrochloride

[0113]

[0114] The test results show that when the reference solution is injected continuously 5 times, the RSD of the retention time of nitromethane is 0.03%; the RSD of the peak area is 1.02%, indicating good system suitability.

[0115] 3. Quantitation Limit and Detection Limit

[0116] Take an appropriate amount of nitromethane, accurately weigh it, and dilute it with the solvent to prepare a series of concentration solutions. When the signal - to - noise ratio (S / N) ≈ 10, it is the quantitation limit, and when S / N ≈ 3, it is the detection limit. Take the quantitation limit solution and inject it continuously 6 times.

[0117] The chromatogram is as shown in Figure 2 . The test results are shown in Tables 5 - 6.

[0118] Table 5 Results of Quantitation Limit and Detection Limit Tests for Nitromethane Inspection in Hydroxylamine Hydrochloride

[0119]

[0120] Table 6 Results of Repeatability Test for Quantitation Limit of Nitromethane in Hydroxylamine Hydrochloride

[0121]

[0122] The test results show that this method can accurately quantify nitromethane. For the detection limit concentration solution, the signal-to-noise ratio S / N ≈ 3, and for the quantitation limit concentration solution, the signal-to-noise ratio S / N ≈ 10. The quantitation limit solution was injected continuously for 6 times, and the RSD of the peak area was 1.50%. The quantitation limit and detection limit of the method are good.

[0123] 4. Linear Relationship and Range Test

[0124] Take 0.02 g of nitromethane, weigh it accurately, place it in a 100 ml volumetric flask, dissolve it with the solvent and dilute it to the mark, shake well, and use it as the stock solution of the reference substance. Respectively take 2.5 ml, 4 ml, 5 ml, 6 ml, and 7.5 ml of the stock solution of the reference substance and place them in 200 ml volumetric flasks, dilute them to the mark with the solvent, shake well, and use them as the linear test series concentration solutions of 50%, 80%, 100%, 120%, and 150% respectively. Take 5 ml each of the quantitation limit solution and the above linear test series concentration solutions, place them in 20 ml headspace vials, seal them, and perform headspace injection, and inject them into the gas chromatograph respectively, and record the chromatograms. Each concentration is injected 3 times. The test results are shown in Table 7.

[0125] Table 7 Results of Linear Relationship and Range Test for Nitromethane in Hydroxylamine Hydrochloride

[0126]

[0127] The test results show that nitromethane has a good linear relationship in the concentration range of 0.4712 μg / ml to 7.8525 μg / ml, the correlation coefficient is 0.9999, and the ratio of the intercept to the 100% response value is 0.76%, indicating a good linear relationship.

[0128] 5. Inspection

[0129] Using the above method, nitromethane in hydroxylamine hydrochloride was inspected, and the test results are shown in Table 8.

[0130] Table 8 Test Results of Nitromethane in Hydroxylamine Hydrochloride

[0131]

[0132] The test results show that nitromethane was not detected in this batch of hydroxylamine hydrochloride.

[0133] In summary, the method provided in Example 2 for detecting nitromethane in hydroxylamine hydrochloride has good sensitivity, specificity and accuracy, and is simple and efficient to operate.

[0134] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography, characterized in that, adding a hydroxylamine hydrochloride sample to be tested into a solvent to dissolve and obtain a test solution, and using headspace injection to inject the test solution for gas chromatography analysis; wherein, the solvent is water containing sodium chloride and N,N-dimethylformamide, the mass-volume ratio of sodium chloride to water is 4.0 - 6.0:100, g / mL; the volume ratio of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and sodium chloride aqueous solution is 4.0 - 6.0:100; in the headspace injection method, the equilibrium temperature of the headspace vial is 75 - 85 °C; in gas chromatography analysis, the detector used is a flame ionization detector; in gas chromatography analysis, the chromatographic column used is a capillary column, and the stationary phase in the capillary column is 5.5 - 6.5% cyanopropylphenyl - 94.5 - 94.5% dimethylpolysiloxane as the stationary phase; in gas chromatography analysis, column temperature: the initial temperature is 35 - 45 °C, maintained for 11 - 13 minutes, and then heated at a heating rate of 8 - 12 °C per minute to 170 - 190 °C, and maintained for 13 - 15 minutes; in gas chromatography analysis, the inlet temperature is 150 - 250 °C; in gas chromatography analysis, split ratio: 4.5 - 5.5:

1.

2. The method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography according to claim 1, characterized in that, in the headspace injection method, the equilibrium time of the headspace vial is 20 - 40 minutes.

3. The method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography according to claim 1, characterized in that, in gas chromatography analysis, the temperature of the detector is 240 - 260 °C.

4. The method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography according to claim 1, characterized in that, in gas chromatography analysis, the inlet temperature is 180 - 220 °C.

5. A quality control method for producing hydroxylamine hydrochloride, characterized in that, using the method for detecting nitromethane in hydroxylamine hydrochloride based on gas chromatography according to any one of claims 1 - 4 to detect the content of nitromethane in the produced hydroxylamine hydrochloride.

6. A detection kit, characterized in that, the detection kit is used for gas chromatography detection of nitromethane in hydroxylamine hydrochloride by headspace injection; it includes sodium chloride, N,N-dimethylformamide and water, the mass-volume ratio of sodium chloride to water is 4.0 - 6.0:100, g / mL; after preparing sodium chloride aqueous solution with sodium chloride and water, the volume ratio of N,N-dimethylformamide to the sum of the volumes of N,N-dimethylformamide and sodium chloride aqueous solution is 4.0 - 6.0:

100.

7. The detection kit according to claim 6, characterized in that, it further includes a nitromethane reference substance; or, it further includes a hydroxylamine hydrochloride reference substance.

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