Method for measuring chromatographic purity of m-nitrotrifluoromethyl benzene and by-products by GC (gas chromatography) method

Abstract

The invention relates to the technical field of m-nitro-trifluoromethyl benzene detection, and discloses a method for determining chromatographic purity of m-nitro-trifluoromethyl benzene and by-products by GC (gas chromatography), which comprises the following steps: dissolving a substance to be detected by acetonitrile to obtain a solution to be detected with the concentration of the substance to be detected being 20-100mg / mL, and performing GC determination on the solution to be detected to obtain the chromatographic purity of the m-nitro-trifluoromethyl benzene and the by-products of the m-nitro-trifluoromethyl benzene and the by-products of the m-nitro-trifluoromethyl benzene. The content of each substance in the to-be-detected substance is obtained; during GC determination, dimethyl polysiloxane is used as a capillary chromatographic column of a stationary phase; n2 is used as carrier gas, H2 is used as fuel gas, and air is used as combustion-supporting gas; the method can be used for simultaneously detecting the raw material trifluorotoluene and the by-products o-nitro trifluoromethyl benzene and 1-nitro-4-trifluoromethyl benzene, and has the advantages of good separation degree, convenience in operation, short running time and accurate detection result.

Description

Technical Field

[0001] The invention relates to the technical field of m-nitrotrifluoromethylbenzene detection, and in particular to a method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and a by-product by using a GC method. Background Art

[0002] m-Nitrotrifluoromethylbenzene has the following structural formula:

[0003]

[0004] The existing synthetic route is:

[0005]

[0006] The reaction uses trifluorotoluene as a raw material, and the resulting product also contains o-nitrotrifluoromethylbenzene and 1-nitro-4-trifluoromethylbenzene as by-products.

[0007] m-nitrobenzotrifluoride (NTF) is an important organic chemical raw material, which is widely used in the fields of medicine, pesticides and other fine chemicals.

[0008] In order to ensure that the purity of the produced m-nitrotrifluoromethylbenzene meets the requirements for use as a raw material for fine chemicals such as medicines and pesticides, it is necessary to accurately test the purity of the produced m-nitrotrifluoromethylbenzene so as to grade the products for use and avoid waste.

[0009] However, the existing detection method for the purity of m-nitrotrifluoromethylbenzene is a gas chromatography detection method or a liquid chromatography detection method. The m-nitrotrifluoromethylbenzene compound has one nitro group and three fluorine atoms, and the raw materials and by-products of m-nitrotrifluoromethylbenzene also have similar structures. This is not conducive to the effective separation of various material components in the gas chromatography capillary column system. The existing detection method cannot obtain accurate results, and impurities cannot be effectively removed during the production process, resulting in the purity of the exported products not meeting the downstream use requirements, and the performance of the product is unstable, affecting the quality and use effect of the final product.

[0010] Therefore, we continue to develop a method for effectively detecting the content of m-nitrotrifluoromethylbenzene in the product.

[0011] The GC detection method is gas chromatography, which is a chromatography method using gas as the mobile phase. It is mainly used to detect volatile organic compounds, such as hydrocarbon compounds, alkanes, cycloalkanes, aromatic hydrocarbons, olefins, etc. It is also used to detect pollutants and contaminants in air, water and soil, such as volatile organic compounds (VOCs), pesticides, herbicides, industrial chemicals, etc. It is also used to analyze chemical substances in petroleum samples, such as hydrocarbon compounds, and monitor pollutants in the production process, such as sulfur dioxide, nitrogen oxides, etc. This method has not been used to detect the content of intermediate nitrotrifluoromethylbenzene in the reaction product. Summary of the invention

[0012] The invention provides a method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its byproducts by GC method. The method can accurately detect the purity of m-nitrotrifluoromethylbenzene prepared by reaction with trifluorotoluene as a raw material, and the detection result is accurate, so as to solve the above problems.

[0013] The scheme of the present invention is:

[0014] A method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method comprises the following steps:

[0015] 1) dissolving the substance to be detected by a solvent to prepare a test solution having a concentration of 20 to 100 mg / mL of the substance to be detected;

[0016] 2) subjecting the test solution to GC determination;

[0017] 3) After obtaining the peak areas of m-nitrotrifluoromethylbenzene and by-products according to the obtained spectrum, the purity of the m-nitrotrifluoromethylbenzene and by-products to be measured is obtained by using the peak area percentage method;

[0018] The GC method uses dimethylpolysiloxane as a capillary chromatographic column with a stationary phase; N2 as a carrier gas, H2 as a fuel gas, and air as a combustion-supporting gas;

[0019] The substance to be tested is the reaction solution obtained by the following reaction:

[0020]

[0021] The separation degree of any two adjacent peaks is calculated according to the GC spectrum obtained by GC method. When the separation degree R of any two adjacent peaks corresponding to the substance is ≥1.5, the corresponding peak area of ​​the substance is calculated as the purity of the substance;

[0022] The separation degree of any two adjacent substances

[0023] where t R,2 ,t R,1 are the retention times of the two component peaks, W 1 / 2,1 , W 1 / 2,2are the chromatographic half-peak widths of the two component peaks respectively.

[0024] As a preferred technical solution, the test solution in 2) is subjected to GC determination:

[0025] The temperature program of the chromatographic column was to maintain the temperature at 80°C for 1 min, then increase the temperature from 80°C to 150°C at a heating rate of 15°C / min, and finally increase the temperature from 150°C to 250°C at a heating rate of 30°C / min, and maintain the temperature for 3.5 min to complete the sample measurement.

[0026] As a preferred technical solution, the chromatographic column used in the GC determination in 2) is a DB-1 gas chromatography column, wherein DB-1, Agilent 122-1022, 25m×250μm×0.25μm.

[0027] As a preferred technical solution, the total running time of the heating program is 12.5 minutes.

[0028] As a preferred technical solution, the front detector used in the GC determination in 2) is a FID detector.

[0029] As a preferred technical solution, the column flow rate in the GC determination condition 2) is 1.0 mL / min.

[0030] As a preferred technical solution, in the 2) GC method determination conditions, the tail gas is N2; and the heater is 250°C.

[0031] As a preferred technical solution, in the 2) GC determination conditions, the H2 flow rate is 40 mL / min; the air flow rate is 400 mL / min; the tail gas flow rate is 25 mL / min; the split ratio is 30:1; and the injection volume of the test solution is 1 μL.

[0032] When the method provided in the present application is used to measure the analyte, the separation degree of any two adjacent substances in the obtained spectrum meets the requirement, indicating that the method can achieve effective separation of the substances in the reactants obtained by the above reaction, thereby obtaining reliable purity values ​​of each substance in the substance.

[0033] As a preferred technical solution, the analyte is obtained by mixing trifluorotoluene with sulfuric acid and nitric acid and stirring the mixture at 0-5°C for 2 hours.

[0034] Advantages of the present invention:

[0035] 1) The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC provided in the present application can simultaneously detect the raw material trifluorotoluene, the by-products o-nitrotrifluoromethylbenzene and 1-nitro-4-trifluoromethylbenzene, and has good separation, convenient operation, short running time, and accurate detection results.

[0036] 2) The GC method provided in the present application for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products uses a capillary chromatographic column with dimethylpolysiloxane as the stationary phase and N2 as the carrier gas for a gradient temperature increase program to separate and determine m-nitrotrifluoromethylbenzene and its by-products in a capillary chromatographic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the gas chromatogram of the standard product m-nitrotrifluoromethylbenzene in Example 1 of the present invention;

[0038] Figure 2 The gas chromatogram of the intermediate nitrotrifluoromethylbenzene reaction liquid in Example 2 of the present invention; the figure contains a mixed gas chromatogram of m-nitrotrifluoromethylbenzene, trifluorotoluene, o-nitrotrifluoromethylbenzene and 1-nitro-4-trifluoromethylbenzene;

[0039] Figure 3 For the present invention Figure 2 Partially enlarged chromatogram after adjusting the peak height;

[0040] Figure 4 This is a gas chromatogram of the reaction of trifluorotoluene with sulfuric acid and nitric acid in Example 3 of the present invention. DETAILED DESCRIPTION

[0041] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0042] Embodiment 1:

[0043] 1. Prepare the test solution: accurately weigh the test sample, place it in a volumetric flask, dissolve it in acetonitrile and dilute it to the scale, prepare a test solution with a concentration of 20-100 mg / mL, shake well, and the injection volume of the test solution is 1 μL.

[0044] 2. Carry out the gradient heating procedure according to the table below:

[0045]

[0046] The chromatographic detection was carried out under the following conditions:

[0047] Chromatographic conditions:

[0048] Chromatographic system: American Agilent 8860 gas chromatography system and workstation;

[0049] Chromatographic column Capillary column with dimethylpolysiloxane as stationary phase: DB-1, Agilent 122-1022, 25m×250μm×0.25μm;

[0050] Front detector: FID detector;

[0051] Flow rate: 1.0 mL / min;

[0052] Make-up gas: N2;

[0053] Heater: 250℃;

[0054] H2 flow rate: 40mL / min;

[0055] Air flow rate: 400mL / min;

[0056] Make-up gas flow rate: 25mL / min;

[0057] Split ratio: 30:1;

[0058] The injection volume of the test solution was 1 μL.

[0059] N2 is used as carrier gas, H2 is used as fuel gas, and air is used as auxiliary gas.

[0060] The above test was carried out using a standard substance of m-nitrotrifluoromethylbenzene, and the results obtained were as follows: Figure 1 shown.

[0061] As can be seen from the figure, the standard product of m-nitrotrifluoromethylbenzene contains 1-nitro-4-trifluoromethylbenzene as an impurity. 1-nitro-4-trifluoromethylbenzene is an impurity that is difficult to remove in the production of m-nitrotrifluoromethyl products. Figure 1 It can be seen that another compound peak (peak 1) appears next to the main peak (peak 2) and is relatively close to the main peak.

[0062] To determine the separation of any two substances, the separation R value can be used:

[0063] Separation

[0064] where t R,2 ,t R,1 are the retention times of the two component peaks, W 1 / 2,1 , W 1 / 2,2 are the chromatographic half-peak widths of the two component peaks, and the specific data can be found in Figure 1 .

[0065] As can be seen from the above formula, the greater the difference in retention time between the two peaks (i.e. the farther the distance between the two peaks), the smaller the width of the two peaks (i.e. the narrower the two peaks), the greater the separation, and the better the separation of the two adjacent components.

[0066] When R = 0.8, the separation degree of the two groups can reach 89%; when R = 1, the maximum separation degree is 98%; when R = 1.5, the separation degree can reach 99.7%. Therefore, for m-nitrotrifluoromethylbenzene, R ≥ 1.5 is selected as the sign of complete separation of two adjacent peaks.

[0067] Figure 1 The results showed that the chromatographic peaks of 1-nitro-4-trifluoromethylbenzene (3.927 min) and m-nitrotrifluoromethane (4.078 min) were close, and the calculated separation R1 was 3.43, indicating that the two peaks could be separated. The purity of m-nitrotrifluoromethane obtained by the peak area percentage method of gas chromatograph was 98.72%.

[0068] Embodiment 2:

[0069] The difference from Example 1 is that the test sample is the reaction solution of m-nitrotrifluoromethylbenzene.

[0070] The method for obtaining the reaction solution of m-nitrotrifluoromethylbenzene is as follows: trifluorotoluene is mixed with sulfuric acid and nitric acid, and the mixture is stirred and reacted at 0°C for 2 hours to obtain the solution.

[0071] The reaction that occurs is:

[0072]

[0073] The results of the sample injection test under the chromatographic conditions of Example 1 are as follows: Figure 2 As shown, Figure 2 The results showed that the retention time of m-nitrotrifluoromethylbenzene in the test sample was 4.045min, which could be effectively separated from the raw material trifluorotoluene with a retention time of 1.993min and the by-product o-nitrotrifluoromethylbenzene with a retention time of 4.402min.

[0074] The separation degree R of m-nitrotrifluoromethylbenzene and trifluorotoluene is 66.52.

[0075] The separation degree R of m-nitrotrifluoromethylbenzene and o-nitrotrifluoromethylbenzene is 13.70.

[0076] The retention time of 1-nitro-4-trifluoromethylbenzene is 3.921 min, and the chromatographic peak is close to that of m-nitrotrifluoromethylbenzene.

[0077] Figure 2 The results showed that the chromatographic peaks of 1-nitro-4-trifluoromethylbenzene (3.921min) and m-nitrotrifluoromethane product (4.045min) in the reaction solution were close, and the separation degree R2 of the two components was calculated to be 4.09, indicating that the peaks of the two substances can be separated;

[0078] Figure 3 for Figure 2 Chromatogram after adjusting the peak height. Figure 3 It can be clearly seen that the m-nitrotrifluoromethylbenzene in the reaction solution is separated from the raw material trifluorotoluene, the byproducts o-nitrotrifluoromethylbenzene and 1-nitro-4-trifluoromethylbenzene. This shows that this method can accurately detect the content of each substance in the reaction solution and can effectively realize the effective detection of the product.

[0079] Embodiment 3:

[0080] The difference from Example 2 is that the test substance is obtained by mixing trifluorotoluene with sulfuric acid and nitric acid and stirring the mixture at 5°C for 2 hours. Figure 4 As shown, Figure 4 The results showed that 89.60% of m-nitrotrifluoromethylbenzene (retention time: 3.992 min) had been generated, accompanied by 2.94% of 1-nitro-4-trifluoromethylbenzene (retention time: 3.871 min) and 7.46% of o-nitrotrifluoromethylbenzene (retention time: 4.344 min).

[0081] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC, characterized in that: The following steps are involved: 1) dissolving the substance to be detected by a solvent to prepare a test solution having a concentration of 20 to 100 mg / mL of the substance to be detected; 2) subjecting the test solution to GC determination; 3) After obtaining the peak areas of m-nitrotrifluoromethylbenzene and by-products according to the obtained spectrum, the purity of the m-nitrotrifluoromethylbenzene and by-products to be measured is obtained by using the peak area percentage method; The GC method uses dimethylpolysiloxane as a capillary chromatographic column with a stationary phase; N2 as a carrier gas, H2 as a fuel gas, and air as a combustion-supporting gas; The separation degree of any two adjacent peaks is calculated according to the GC spectrum obtained by GC method. When the separation degree R of any two adjacent peaks corresponding to the substance is ≥1.5, the corresponding peak area of ​​the substance is calculated as the purity of the substance; The separation degree of any two adjacent substances where t R,2 ,t R,1 are the retention times of the two component peaks, W 1 / 2,1 , W 1 / 2,2 are the chromatographic half-peak widths of the two component peaks respectively.

2. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method according to claim 1, characterized in that: The test solution in 2) is subjected to GC determination: The temperature program of the chromatographic column was to maintain the temperature at 80°C for 1 min, then increase the temperature from 80°C to 150°C at a heating rate of 15°C / min, and finally increase the temperature from 150°C to 250°C at a heating rate of 30°C / min, and maintain the temperature for 3.5 min to complete the sample measurement.

3. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 1, characterized in that: The chromatographic column used in the GC method determination in 2) is a DB-1 gas chromatographic column.

4. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 3, characterized in that: The total running time of the heating program is 12.5 min.

5. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 1, characterized in that: The front detector used in the GC method determination in 2) is a FID detector.

6. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 1, characterized in that: The column flow rate in the GC determination condition 2) is 1.0 mL / min.

7. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 1, characterized in that: In the 2) GC method measurement conditions, the tail gas is N2 and the heater is 250°C.

8. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 1, characterized in that: In the 2) GC determination conditions, the H2 flow rate is 40 mL / min; the air flow rate is 400 mL / min; the tail gas flow rate is 25 mL / min; the split ratio is 30:1; and the injection volume of the test solution is 1 μL.

9. The method for determining the chromatographic purity of m-nitrotrifluoromethylbenzene and its by-products by GC method as claimed in claim 1, characterized in that: The substance to be tested is obtained by mixing trifluorotoluene, sulfuric acid and nitric acid, and stirring the mixture at 0-5°C for 2 hours.

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