A method for analyzing the content of 2-cyano-N,N-dimethylacetamide and its application

Abstract

The present invention relates to the technical field of chemical detection and analysis, and specifically to a method for analyzing the content of 2-cyano-N,N-dimethylacetamide and its application. The method comprises the following steps: (1) using dibutyl phthalate as an internal standard, dissolving and diluting a sample to be tested and a standard with methanol to obtain a sample solution and a standard solution, respectively; (2) subjecting the sample solution and the standard solution to gas chromatography analysis, using a hydrogen flame ionization detector, with a hydrogen:nitrogen:air ratio of 30-40:30-40:300-400, an initial column temperature of 80-120°C, a column head pressure of 20-40KPa, an injection volume of 0.5-2μL, and a split ratio of 5:1-20:1, to calculate the content of 2-cyano-N,N-dimethylacetamide in the sample to be tested. The method has good peak shape and good separation on gas chromatography, strong specificity and good precision, and is particularly suitable for quality control of pesticide intermediates and organic synthesis raw materials, thereby meeting the production requirements of high-quality pesticides and other chemical products.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical detection and analysis, and in particular to a method for analyzing the content of 2-cyano-N,N-dimethylacetamide and an application thereof. Background Art

[0002] Nicosulfuron belongs to the neonicotinoid pesticide, with the molecular formula C 15 H 18 N6O6S is typically used as a post-emergence herbicide to protect corn crops from weeds. 2-Cyano-N,N-dimethylacetamide is an important intermediate in the synthesis of nicosulfuron and can also be used as a starting material for the synthesis of biologically active 2-aminothiophene derivatives. Currently, common synthetic routes for 2-Cyano-N,N-dimethylacetamide include the methyl cyanoacetate transesterification method, the chloropropiolate nitrile method, and the cyanoacetamide methylation method.

[0003] The quality of intermediates directly impacts the quality of the final product. Intermediates are a crucial step in in-process control, and their analysis helps ensure yield and final product purity. Secondly, toxic impurities may be introduced into the final product through intermediates, necessitating their analysis and control. Thirdly, intermediates may also affect other indicators of the final product, such as appearance or optical rotation. Therefore, effectively characterizing the quality of intermediates, especially critical intermediates, is crucial.

[0004] After reviewing relevant domestic and international literature, no clear method for detecting 2-cyano-N,N-dimethylacetamide has been found in existing technologies. To better control the production of nicosulfuron and ensure the final quality of the finished product, it is necessary to provide a method for analyzing the content of 2-cyano-N,N-dimethylacetamide. Summary of the Invention

[0005] In response to the technical problem that the prior art lacks a method for analyzing the content of 2-cyano-N,N-dimethylacetamide, the present invention provides a method for analyzing the content of 2-cyano-N,N-dimethylacetamide and an application thereof. The method achieves good peak shape and excellent separation on gas chromatography; the method has strong specificity and good precision, and is particularly suitable for quality control of pesticide intermediates and organic synthesis raw materials, thereby meeting the production requirements of high-quality pesticides and other chemical products.

[0006] In a first aspect, the present invention provides a method for analyzing the content of 2-cyano-N,N-dimethylacetamide, comprising the following steps:

[0007] (1) Using dibutyl phthalate as the internal standard, the sample to be tested and the standard were dissolved and diluted with methanol to obtain the sample solution and the standard solution respectively;

[0008] (2) The sample solution and the standard solution obtained in step (1) were subjected to gas chromatography analysis using a hydrogen flame ionization detector, with a hydrogen:nitrogen:air ratio of 30-40:30-40:300-400, an initial column temperature of 80-120°C, a column head pressure of 20-40 kPa, an injection volume of 0.5-2 μL, and a split ratio of 5:1-20:1. The content of 2-cyano-N,N-dimethylacetamide in the sample to be tested was calculated.

[0009] Furthermore, in step (2), the ratio of hydrogen:nitrogen:air was 30:30:300, the initial column temperature was 100°C, the column head pressure was 30 KPa, the injection volume was 1 μL, and the split ratio was 10:1.

[0010] Furthermore, step (2) uses a cross-linked chromatographic column having a coating of 14% cyanopropyl-phenyl-86% methylpolysiloxane, an inner diameter of 0.18-0.32 mm, a column length of 10-60 m, and a film thickness of 0.15-1 μm.

[0011] Furthermore, step (2) uses an Agilent DB-1701 chromatographic column.

[0012] Furthermore, the Agilent DB-1701 column has an inner diameter of 0.32 mm, a column length of 30 m, and a film thickness of 1 µm.

[0013] Furthermore, in step (2), after the baseline of the instrument is stabilized, several injections of standard sample are continuously injected, and the relative response value of each injection is calculated. After the change in the relative response value of two adjacent injections is less than 1.5%, the samples are injected in the order of standard sample, sample, sample, and standard sample.

[0014] Furthermore, in step (2), the content of 2-cyano-N,N-dimethylacetamide in the sample to be tested is calculated according to the following formula:

[0015] , ;

[0016] Where:

[0017] A s ——The average value of the peak area of ​​2-cyano-N,N-dimethylacetamide in the standard sample;

[0018] A r ——The average value of the peak area of ​​the internal standard dibutyl phthalate in the standard sample;

[0019] m r ——The mass of the internal standard dibutyl phthalate weighed in the standard sample;

[0020] m s ——The mass of 2-cyano-N,N-dimethylacetamide standard sample weighed in the standard sample;

[0021] p i ——The mass fraction of 2-cyano-N,N-dimethylacetamide in the standard sample;

[0022] f——Correction factor of 2-cyano-N,N-dimethylacetamide and dibutyl phthalate in the standard sample;

[0023] X i ——The mass fraction of 2-cyano-N,N-dimethylacetamide in the sample;

[0024] A i ——The average value of the peak area of ​​2-cyano-N,N-dimethylacetamide in the sample;

[0025] m i ——Weigh the mass of the 2-cyano-N,N-dimethylacetamide sample to be tested in the sample;

[0026] m1——the mass of the internal standard dibutyl phthalate weighed in the sample;

[0027] A1——the average peak area of ​​internal standard dibutyl phthalate in the sample;

[0028] f1——Correction factor of 2-cyano-N,N-dimethylacetamide and dibutyl phthalate in the sample.

[0029] In a second aspect, the present invention provides an application of the above-mentioned content analysis method in the quality evaluation of 2-cyano-N,N-dimethylacetamide.

[0030] The beneficial effects of the present invention are:

[0031] The present invention provides a novel method for detecting the mass fraction of 2-cyano-N,N-dimethylacetamide, filling a technical gap in the corresponding field of the prior art. Using methanol as a solvent and dibutyl phthalate as an internal standard, the method can effectively and completely separate 2-cyano-N,N-dimethylacetamide, resulting in a good chromatographic peak shape. By selecting the column temperature, column head pressure, split ratio, and other factors, the reliability of the detection results is ensured, and the integral calculation results are accurate and reproducible. The method is particularly suitable for quality control of technical intermediates and organic synthesis raw materials, plays an important role and has practical significance in ensuring the quality of the final product, and the obtained results are more accurate and timely. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] Figure 1 This is the chromatogram of the standard sample in Example 1.

[0034] Figure 2 This is the sample chromatogram in Example 1.

[0035] Figure 3 This is the linear relationship diagram in Verification Example 2. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0037] Example 1

[0038] The workshop produced 600 kg of the intermediate 2-cyano-N,N-dimethylacetamide and took samples for analysis. The specific steps are as follows:

[0039] (1.1) Preparation of standard stock solution

[0040] Accurately weigh 0.0536 g (accurate to 0.0002 g) of 2-cyano-N,N-dimethylacetamide standard and 0.0517 g (accurate to 0.0002 g) of internal standard dibutyl phthalate into a 10 mL volumetric flask, add 8 mL of methanol, and dissolve under ultrasonic vibration. After cooling to room temperature, dilute to the scale with methanol to obtain the standard stock solution.

[0041] (1.2) Preparation of sample stock solution

[0042] Accurately weigh 0.0528 g (accurate to 0.0002 g) of the sample containing 2-cyano-N,N-dimethylacetamide and 0.0514 g (accurate to 0.0002 g) of the internal standard dibutyl phthalate into a 10 mL volumetric flask, add 8 mL of methanol, and dissolve under ultrasonic vibration. After cooling to room temperature, dilute to the scale with methanol to obtain the sample stock solution.

[0043] (2) Testing and data processing

[0044] An Agilent 8860 gas chromatograph with an FID detector was used. The chromatographic column was a cross-linked column coated with (14% cyanopropyl-phenyl)-methylpolysiloxane (Agilent DB-1701, inner diameter 0.32 mm, column length 30 m, film thickness 1 µm). The hydrogen: nitrogen: air ratio was 30:30:300, the column head pressure was 30 kPa, and the initial column temperature was 100 °C, which was maintained for 10 min.

[0045] After the machine has passed the self-test and the baseline has stabilized under the specified operating conditions, several injections of standard samples are continuously injected and the relative response value of each injection is calculated. When the relative response value of two adjacent injections changes by less than 1.5%, the standard sample, sample, sample, and standard sample are injected in this order. The injection volume is 1μL and the split ratio is 10:1. The chromatogram is shown below. Figure 1 and 2 As shown, Figure 2 The peak at 3.426 min is the internal standard, i.e., dibutyl phthalate, and the peak at 6.209 min is 2-cyano-N,N-dimethylacetamide. The obtained data are shown in Table 1 below:

[0046] Table 1 Gas chromatography test results of standard sample and sample in Example 1

[0047]

[0048] Substituting into the formula:

[0049] , ;

[0050] Calculation shows that the mass fraction of 2-cyano-N,N-dimethylacetamide in the sample to be tested is 97.03%.

[0051] Example 2

[0052] The workshop produced 480 kg of the intermediate 2-cyano-N,N-dimethylacetamide and took samples for analysis. The specific steps are as follows:

[0053] (1.1) Preparation of standard stock solution

[0054] Accurately weigh 0.0515 g (accurate to 0.0002 g) of 2-cyano-N,N-dimethylacetamide standard and 0.0509 g (accurate to 0.0002 g) of internal standard dibutyl phthalate into a 10 mL volumetric flask, add 8 mL of methanol, and dissolve under ultrasonic vibration. After cooling to room temperature, dilute to the scale with methanol to obtain the standard stock solution.

[0055] (1.2) Preparation of sample stock solution

[0056] Accurately weigh 0.0511 g (accurate to 0.0002 g) of the sample to be tested containing 2-cyano-N,N-dimethylacetamide and 0.0523 g (accurate to 0.0002 g) of the internal standard dibutyl phthalate into a 10 mL volumetric flask, add 8 mL of methanol, and dissolve under ultrasonic vibration. After cooling to room temperature, dilute to the scale with methanol to obtain the sample stock solution.

[0057] (2) Testing and data processing

[0058] An Agilent 8860 gas chromatograph with an FID detector was used. The chromatographic column was a cross-linked column coated with (14% cyanopropyl-phenyl)-methylpolysiloxane (Agilent DB-1701, inner diameter 0.32 mm, column length 30 m, film thickness 1 µm). The hydrogen: nitrogen: air ratio was 30:30:300, the column head pressure was 30 kPa, and the initial column temperature was 100 °C, which was maintained for 10 min.

[0059] After the machine self-test passes, under the specified operating conditions, after the instrument baseline is stable, continuously inject several needles of standard sample and calculate the relative response value of each needle. When the relative response value change between two adjacent needles is less than 1.5%, inject the standard sample, sample, sample, and standard sample in this order. The injection volume is 1μL and the split ratio is 10:1. The data obtained are shown in Table 2 below:

[0060] Table 2 Gas chromatography test results of standard sample and sample in Example 2

[0061]

[0062] Substituting into the formula:

[0063] , ;

[0064] Calculation shows that the mass fraction of 2-cyano-N,N-dimethylacetamide in the sample to be tested is 96.81%.

[0065] Verification Example 1 Repeatability Verification

[0066] Take the workshop production sample (same as the sample in Example 2) and process it according to the following method:

[0067] (1.1) Preparation of standard stock solution

[0068] Accurately weigh 0.0522 g (accurate to 0.0002 g) of 2-cyano-N,N-dimethylacetamide standard and 0.0541 g (accurate to 0.0002 g) of internal standard dibutyl phthalate into a 10 mL volumetric flask, add 8 mL of methanol, and dissolve under ultrasonic vibration. After cooling to room temperature, dilute to the scale with methanol to obtain the standard stock solution.

[0069] (1.2) Preparation of sample stock solution

[0070] Accurately weigh 6 portions of the test sample containing 2-cyano-N,N-dimethylacetamide and place them in a 10 mL volumetric flask respectively. Weigh the internal standard dibutyl phthalate and place it in a volumetric flask respectively. Add 8 mL of methanol and dissolve it under ultrasonic vibration. After cooling to room temperature, dilute to the scale with methanol to obtain the sample stock solution.

[0071] (2) Testing and data processing

[0072] An Agilent 8860 gas chromatograph with an FID detector was used. The chromatographic column was a cross-linked column coated with (14% cyanopropyl-phenyl)-methylpolysiloxane (Agilent DB-1701, inner diameter 0.32 mm, column length 30 m, film thickness 1 µm). The hydrogen: nitrogen: air ratio was 30:30:300, the column head pressure was 30 kPa, and the initial column temperature was 100 °C, which was maintained for 10 min.

[0073] After the machine self-test passes, under the specified operating conditions, after the instrument baseline is stable, several needles of standard sample are continuously injected, and the relative response value of each needle is calculated. After the change in the relative response value of two adjacent needles is less than 1.5%, the samples are injected in sequence according to the standard sample, sample, sample, and standard sample. The impurities are completely separated and the peak shape is good. The effective component content of the sample to be tested is calculated. Six samples are tested separately according to the above process. The results are listed in Table 3. It can be seen from the data in Table 3 that the experimental results of this method have good repeatability.

[0074] Table 3 Repeatability verification test results

[0075]

[0076] Verification Example 2: Linear Relationship Verification

[0077] (1) Preparation of sample stock solution

[0078] Accurately weigh 0.0218 g (internal standard 0.0510 g), 0.0315 g (internal standard 0.0525 g), 0.0433 g (internal standard 0.0518 g), 0.0507 g (internal standard 0.0530 g), 0.0609 g (internal standard 0.0536 g), and 0.0708 g (internal standard 0.0516 g) of 2-cyano-N,N-dimethylacetamide samples after bench-scale purification and place them in a 10 mL volumetric flask. Add 8 mL of methanol and ultrasonically shake to dissolve them. After cooling to room temperature, dilute to the scale with methanol to obtain 7 sample stock solutions, in which the concentrations of 2-cyano-N,N-dimethylacetamide were 218 μg / mL, 315 μg / mL, 433 μg / mL, 507 μg / mL, 609 μg / mL, and 708 μg / mL, respectively.

[0079] (2) Testing and data processing

[0080] The method of Example 2 was used for detection. The peak area ratio of 2-cyano-N,N-dimethylacetamide to the internal standard (A) was used for linear regression against the mass ratio of 2-cyano-N,N-dimethylacetamide to the internal standard (M) in the sample. The obtained regression equation was y=0.7279x+0.0027, R 2 =0.9999. It can be seen that 2-cyano-N,N-dimethylacetamide has a good linear relationship in the range of 200~700 μg / mL.

[0081] Verification Example 3: Intermediate Precision Verification

[0082] (1) Preparation of sample stock solution

[0083] Different personnel in different laboratories accurately weighed 6 portions of the test sample containing 2-cyano-N,N-dimethylacetamide (0.05 g (accurate to 0.0002 g) and the internal standard dibutyl phthalate (0.05 g (accurate to 0.0002 g)), placed them in 10 mL volumetric flasks, added 8 mL of methanol and dissolved by ultrasonic oscillation. After cooling to room temperature, the solution was diluted to the mark with methanol to obtain 6 portions of sample stock solution.

[0084] (2) Testing and data processing

[0085] An Agilent 8860 gas chromatograph with an FID detector was used. The chromatographic column was a cross-linked column coated with (14% cyanopropyl-phenyl)-methylpolysiloxane (Agilent DB-1701, inner diameter 0.32 mm, column length 30 m, film thickness 1 µm). The hydrogen: nitrogen: air ratio was 30:30:300, the column head pressure was 30 kPa, and the initial column temperature was 100 °C, which was maintained for 10 min.

[0086] After the machine self-test passes, under the specified operating conditions, after the instrument baseline is stable, several needles of standard sample are continuously injected, and the relative response value of each needle is calculated. After the change in the relative response value of two adjacent needles is less than 1.5%, the samples are injected in sequence according to the standard sample, sample, sample, and standard sample. The impurities are completely separated and the peak shape is good. The effective component content of the sample to be tested is calculated. Six samples are tested separately according to the above process. The results are listed in Table 4. It can be seen from the data in Table 4 that the intermediate precision of the experimental results of this method is good.

[0087] Table 4 Intermediate precision verification test results

[0088]

[0089] Verification Example 4: Stability Verification

[0090] (1) Preparation of sample stock solution

[0091] Accurately weigh 0.0514 g of the sample containing 2-cyano-N,N-dimethylacetamide and 0.0507 g of the internal standard dibutyl phthalate into a 10 mL volumetric flask, add 8 mL of methanol and ultrasonically oscillate to dissolve them. After cooling to room temperature, dilute to the scale with methanol to obtain the sample stock solution.

[0092] (2) Testing and data processing

[0093] Detection was performed at 0, 1, 2, 4, 8, and 24 hours, and scanning was performed at different times according to the method of Example 2. The impurities were completely separated and the peak shape was good. The effective ingredient content of the sample to be tested was calculated. The results are listed in Table 5. It can be seen from the data in Table 5 that the experimental results of this method have good time stability.

[0094] Table 5 Stability verification test results

[0095]

[0096] It can be seen from the above verification examples that the analysis method for the content of 2-cyano-N,N-dimethylacetamide provided by the present invention has high accuracy and good operability, and can be widely applied to the analysis and detection of the content of 2-cyano-N,N-dimethylacetamide.

[0097] Although the present invention has been described in detail with reference to the accompanying drawings and in conjunction with preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be easily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A method for analyzing the content of 2-cyano-N,N-dimethylacetamide, characterized in that: The steps include: (1) Using dibutyl phthalate as the internal standard, the sample to be tested and the standard were dissolved and diluted with methanol to obtain the sample solution and the standard solution respectively; (2) The sample solution and the standard solution obtained in step (1) were subjected to gas chromatography analysis using a cross-linked chromatographic column with a coating of 14% cyanopropyl-phenyl-86% methylpolysiloxane, an inner diameter of 0.18-0.32 mm, a column length of 10-60 m, a film thickness of 0.15-1 μm, a hydrogen flame ionization detector, a hydrogen: nitrogen: air ratio of 30-40:30-40:300-400, an initial column temperature of 80-120°C, maintained for 10 min, a column head pressure of 20-40 KPa, an injection volume of 0.5-2 μL, and a split ratio of 5:1-20:

1. The content of 2-cyano-N,N-dimethylacetamide in the sample to be tested was calculated.

2. The content analysis method according to claim 1, wherein In step (2), the hydrogen: nitrogen: air ratio was 30:30:300, the initial column temperature was 100°C, the column head pressure was 30 kPa, the injection volume was 1 μL, and the split ratio was 10:

1.

3. The content analysis method according to claim 1, wherein Step (2) uses an Agilent DB-1701 chromatographic column.

4. The content analysis method according to claim 3, wherein The Agilent DB-1701 column has an inner diameter of 0.32 mm, a column length of 30 m, and a film thickness of 1 µm.

5. The content analysis method according to claim 1, wherein In step (2), after the instrument baseline is stable, several injections of standard sample are continuously injected, and the relative response value of each injection is calculated. When the change in the relative response value of two adjacent injections is less than 1.5%, the samples are injected in the order of standard sample, sample, sample, and standard sample.

6. The content analysis method according to claim 1, wherein In step (2), the content of 2-cyano-N,N-dimethylacetamide in the sample to be tested is calculated according to the following formula: ， ； Where: A s ——The average value of the peak area of ​​2-cyano-N,N-dimethylacetamide in the standard sample; A r ——The average value of the peak area of ​​the internal standard dibutyl phthalate in the standard sample; m r ——The mass of the internal standard dibutyl phthalate weighed in the standard sample; m s ——The mass of 2-cyano-N,N-dimethylacetamide standard weighed in the standard sample; p i ——The mass fraction of 2-cyano-N,N-dimethylacetamide in the standard sample; f——Correction factor of 2-cyano-N,N-dimethylacetamide and dibutyl phthalate in the standard sample; X i ——The mass fraction of 2-cyano-N,N-dimethylacetamide in the sample; A i ——The average value of the peak area of ​​2-cyano-N,N-dimethylacetamide in the sample; m i ——Weigh the mass of the 2-cyano-N,N-dimethylacetamide sample to be tested in the sample; m1——the mass of the internal standard dibutyl phthalate weighed in the sample; A1——the average peak area of ​​internal standard dibutyl phthalate in the sample; f1——Correction factor of 2-cyano-N,N-dimethylacetamide and dibutyl phthalate in the sample.

7. Use of the content analysis method according to any one of claims 1 to 6 in the quality evaluation of 2-cyano-N,N-dimethylacetamide.

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