Determination method for acidity in dimethylacetamide

Abstract

The invention discloses a method for measuring the acidity of dimethylacetamide, which comprises the following steps: A, preparing solutions, including a series of dimethylacetamide standard solutions with known acidity and a dimethylacetamide sample solution; b, instrument preparation: adopting a gas chromatograph and an FTD detector; c, sample introduction and analysis: precisely absorbing 1 [mu] L of a dimethylacetamide standard solution or a dimethylacetamide sample solution, rapidly injecting the dimethylacetamide standard solution or the dimethylacetamide sample solution into a sample introduction port of a gas chromatograph, after the sample solution enters a chromatographic column, separating each component in the chromatographic column under the driving of carrier gas, and sequentially feeding the separated components into an FTD detector, the FTD is used for converting the concentration signal of each component into an electric signal and recording a chromatogram; the method for determining the acidity in dimethylacetamide not only has the advantages of high sensitivity, high selectivity, rapidness and accuracy through proper chromatographic conditions, diluents and stable instruments, but also effectively improves the safety of researchers.

Description

Technical Field

[0001] This invention relates to the field of acidity determination technology in dimethylacetamide, specifically to a method for determining the acidity in dimethylacetamide. Background Technology

[0002] Acidity is one of the important indicators of dimethylacetamide's quality. Changes in acidity can affect the purity and performance of dimethylacetamide. Measuring acidity can assess whether the product meets quality standards and ensure its stability and reliability in various applications.

[0003] In the production of dimethylacetamide, monitoring acidity helps to promptly identify problems in the production process, such as whether the reaction is complete or whether impurities are generated. This allows for adjustments and optimization of the production process, ensuring consistent product quality. Furthermore, measuring the acidity of dimethylacetamide provides data support for research on related chemical reaction mechanisms. Understanding the impact of acidity on the chemical reactions involving dimethylacetamide contributes to a deeper understanding of the reaction process, providing a basis for developing new synthetic methods or improving existing processes.

[0004] However, existing methods for determining the acidity of dimethylacetamide typically employ non-aqueous acidity titration, which involves titrating a specific volume of sample solution with sodium methoxide and isopropanol standard titration solution under nitrogen protection, using thymol blue as an indicator. This method is not only slow but also requires strict condition control. Furthermore, dimethylacetamide is toxic and irritates the skin, eyes, and respiratory tract. Prolonged use of this method cannot effectively guarantee the safety of researchers. Therefore, we propose a method for determining the acidity of dimethylacetamide. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the existing defects and provide a method for determining the acidity of dimethylacetamide. With appropriate chromatographic conditions, diluents and stable instruments, it has the advantages of high sensitivity, high selectivity, speed and accuracy, and reduces the contact time between researchers and dimethylacetamide, effectively improving the safety of researchers and effectively solving the problems in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for determining the acidity of dimethylacetamide, comprising the following steps: A. Prepare solutions, including a series of dimethylacetamide standard solutions and dimethylacetamide sample solutions with known acidity; B. Instrument preparation: Gas chromatograph with FTD detector is used; C. Injection and Analysis: Accurately pipette 1 μL of dimethylacetamide standard solution or dimethylacetamide sample solution and rapidly inject it into the injection port of the gas chromatograph. After the sample solution enters the chromatographic column, the components are separated in the chromatographic column under the action of the carrier gas. The separated components enter the FTD detector in sequence. The FTD detector converts the concentration signal of each component into an electrical signal and records the chromatogram. The detection conditions of the gas chromatograph are as follows: the chromatographic column is a 60m×0.25mm×1.4μm SH-Rtx-624 capillary column, the injection port temperature is 220°C, the carrier gas is helium, the carrier gas flow rate is 0.75ml / min, the FTD detector temperature is 250°C, and the split ratio is 10:1. The column temperature was increased using a curve. The specific method was as follows: the initial temperature of the column oven was 100℃, held for 2 minutes, the first heating rate was 5℃ / min, the temperature was increased to 130℃ and held for 2 minutes, the second heating rate was 45℃ / min, the temperature was increased to 220℃ and held for 18 minutes.

[0007] Preferably, in step A, the preparation steps of the dimethylacetamide standard solution are as follows: weigh an appropriate amount of acetic acid with known acidity and add it to a certain amount of dimethylacetamide, shake well and set aside. The preparation steps for the dimethylacetamide sample solution are as follows: Weigh an appropriate amount of dimethylacetamide sample, place it in a volumetric flask, dilute it to the mark with chromatographic grade cyclohexane, and shake well for later use.

[0008] Compared with existing technologies, the beneficial effects of this invention are as follows: This method for determining the acidity in dimethylacetamide, through appropriate chromatographic conditions, diluents, and stable instruments, possesses the advantages of high sensitivity, high selectivity, speed, and accuracy; it can detect extremely low levels of acetic acid, exhibiting high accuracy in determining trace amounts of acetic acid in dimethylacetamide, capable of detecting acetic acid at the ppm level or even lower concentrations; secondly, by selecting appropriate chromatographic columns and separation conditions, acetic acid, dimethylacetamide, and other impurities can be effectively separated, avoiding interference from other substances, thereby accurately determining the acetic acid content; furthermore, the analysis speed is relatively fast, and a single analysis can not only determine the acetic acid content but also simultaneously analyze other components in the sample solution, providing more information about the composition of the sample solution; additionally, it reduces the contact time between researchers and dimethylacetamide, effectively improving the safety of researchers. Attached Figure Description

[0009] Figure 1 Chromatogram for determining the acidity of dimethylacetamide using a gas chromatograph; Figure 2 for Figure 1 A table or graph showing detailed information about each chromatographic peak; Figure 3 This is a table showing the temperature program curve and parameters for the column oven. Detailed Implementation

[0010] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] Please see Figures 1-2 This embodiment provides a technical solution: a method for determining the acidity of dimethylacetamide, comprising the following steps: A. Prepare solutions, including a series of dimethylacetamide standard solutions and dimethylacetamide sample solutions with known acidity; wherein the acidity range of the dimethylacetamide standard solutions should cover the possible acidity range of the sample solutions, and the acidity values ​​of each dimethylacetamide standard solution should have a certain gradient in order to plot a standard curve.

[0012] B. Instrument preparation: Use a gas chromatograph with an FTD detector. Simultaneously, check that all components of the gas chromatograph and the FTD detector are functioning correctly, including the gas source, column, and injector. Ensure the instrument is in a stable operating state and that all parameters are set correctly.

[0013] C. Injection and Analysis: Accurately pipette 1 μL of dimethylacetamide standard solution or dimethylacetamide sample solution and rapidly inject it into the gas chromatograph's injection port. After entering the column, the sample solution is carried by the carrier gas, and the components are separated in the column. Due to the different partition coefficients of different components between the stationary and mobile phases, their retention times in the column are also different, thus achieving separation. The separated components sequentially enter the FTD detector, which converts the concentration signals of each component into electrical signals and records the chromatogram. In this process, the injection volume must be accurate and reproducible to effectively ensure the accuracy and precision of the analytical results.

[0014] The detection conditions of the gas chromatograph are as follows: the chromatographic column is a 60m×0.25mm×1.4μm SH-Rtx-624 capillary column, the injection port temperature is 220°C, the carrier gas is helium, the carrier gas flow rate is 0.75ml / min, the FTD detector temperature is 250°C, and the split ratio is 10:1. The column temperature was increased using a curve. The specific method was as follows: initial oven temperature 100℃, hold for 2 minutes; first stage temperature ramp rate 5℃ / min, raise to 130℃ and hold for 2 minutes; second stage temperature ramp rate 45℃ / min, raise to 220℃ and hold for 18 minutes. See Figure 3 for details. In this embodiment, data processing is also included, in which a standard curve for dimethylacetamide is fitted based on the chromatogram of the dimethylacetamide standard solution, with the acidity of the dimethylacetamide standard solution as the abscissa and the corresponding peak area as the ordinate. The peak area of ​​acidic substances is measured from the chromatogram of the dimethylacetamide sample solution, and then the acidity in the dimethylacetamide sample solution is automatically calculated based on the dimethylacetamide standard curve.

[0015] The determination method of this invention, through appropriate chromatographic conditions, diluents, and stable instruments, possesses the advantages of high sensitivity, high selectivity, speed, and accuracy. It can detect extremely low concentrations of acetic acid, exhibiting high accuracy in determining trace amounts of acetic acid in dimethylacetamide, detecting concentrations at the ppm level or even lower. Secondly, by selecting appropriate chromatographic columns and separation conditions, acetic acid, dimethylacetamide, and other impurities can be effectively separated, avoiding interference from other substances and thus accurately determining the acetic acid content. Furthermore, the analysis speed is relatively fast; a single analysis can not only determine the acetic acid content but also simultaneously analyze other components in the sample solution, providing more information about the sample solution's composition. In addition, it reduces the contact time between researchers and dimethylacetamide, effectively improving researcher safety.

[0016] In step A, the preparation steps of the dimethylacetamide standard solution are as follows: weigh an appropriate amount of acetic acid with known acidity and add it to a certain amount of dimethylacetamide, shake well and set aside. The preparation steps for the dimethylacetamide sample solution are as follows: Weigh an appropriate amount of dimethylacetamide sample, place it in a volumetric flask, dilute it to the mark with chromatographic grade cyclohexane, and shake well for later use.

[0017] In this embodiment, acetic acid can be other acidic substances, and chromatographic grade cyclohexane can be other solvents. However, its miscibility with dimethylacetamide and its interference with chromatographic analysis need to be considered. If the sample contains impurities or other interfering substances, pretreatment such as filtration and extraction may be necessary to ensure the purity of the sample and avoid contamination or interference to the chromatographic column and detector.

[0018] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for determining the acidity of dimethylacetamide, characterized in that, It comprises the following steps: A. Preparation of solution, including a series of dimethylacetamide standard solution with known acidity and dimethylacetamide sample solution; B. Instrument preparation, using gas chromatograph, FTD detector; C. Injection and analysis, 1 μL of dimethylacetamide standard solution or dimethylacetamide sample solution is precisely pipetted and quickly injected into the injection port of the gas chromatograph, after the sample solution enters the chromatographic column, each component is separated in the chromatographic column under the driving of the carrier gas, and then enters the FTD detector, the FTD detector converts the concentration signal of each component into an electric signal, and records the chromatogram; The detection conditions of the gas chromatograph are as follows: the chromatographic column is a SH-Rtx-624 capillary column with a size of 60 m*0.25 mm*1.4 μm, the injection port temperature is 220°C, the carrier gas is helium, the carrier gas flow rate is 0.75 ml / min, the FTD detector temperature is 250°C, and the split ratio is 10:1; The temperature of the chromatographic column is curve heating, and the specific method is as follows: the initial temperature of the column oven is 100°C, constant temperature for 2 minutes, the first stage heating speed is 5°C / min, constant temperature at 130°C for 2 minutes, the second stage heating speed is 45°C / min, constant temperature at 220°C for 18 minutes.

2. A method of determining the acidity of dimethylacetamide according to claim 1, characterized in that, In step A, the preparation steps of the dimethylacetamide standard solution are as follows: an appropriate amount of acetic acid with known acidity is weighed and added into a certain amount of dimethylacetamide, and then shaken uniformly for standby use; The preparation steps of the dimethylacetamide sample solution are as follows: an appropriate amount of dimethylacetamide sample is weighed and placed in a volumetric flask, diluted to the scale with chromatographic pure cyclohexane, shaken uniformly for standby use.

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