CN111665312A - Method for detecting content of N-methylimidazole in water phase system - Google Patents

Abstract

The invention discloses a method for detecting N-methylimidazole content in an aqueous phase system, belonging to the technical field of N-methylimidazole content determination, using ethylene glycol as an internal standard substance, and N,N-dimethylformamide as Dilute the solvent, obtain the correction factor through the working curve of ethylene glycol and N-methylimidazole, carry out quantitative analysis to detect the content of N-methylimidazole in the aqueous system, the accuracy is high, the stability is good, the linear range is wide, and the method Simple and fast.

Description

A kind of method for detecting N-methylimidazole content in aqueous system

technical field

The invention relates to the technical field of N-methylimidazole content determination, in particular to a method for detecting the content of N-methylimidazole in an aqueous phase system.

Background technique

N-methylimidazole is a very important fine chemical raw material and intermediate, which has a wide range of uses. N-methylimidazole is mainly used as organic synthesis intermediates, such as ionic liquids, resin curing agents, adhesives, and is also an active ingredient in many pesticides, enzyme inhibitors, pharmaceuticals and fine chemicals. In the synthesis of N-methylimidazole, the rapid and accurate detection of the product content in the aqueous synthesis stock solution is of great significance to the control of the yield.

For the detection of the product in the organic reaction, the traditional method of separating and purifying the product and then detecting it is time-consuming and labor-intensive, and is not suitable for the control of the reaction process in industrial production. The synthetic stock solution can be directly detected by an ultraviolet spectrophotometer or an Abbe refractometer, and then the product content in the stock solution can be calculated according to the standard curve obtained in advance. However, the composition of the actual synthetic stock solution is relatively complex, and there are by-products of the reaction and unreacted raw materials in the system, which will interfere with the detection of the UV spectrophotometer or Abbe refractometer, resulting in large errors in the detection results. It is difficult to accurately obtain the content of N-methylimidazole. By choosing a suitable chromatographic system, gas chromatography can accurately determine the content of various volatile organic components, and it is also a commonly used method to detect the content of products in organic media. However, for the synthesis system of N-methylimidazole containing a large amount of water, the water will seriously interfere with the measurement of the synthetic stock solution in the aqueous phase by gas chromatography, making the gas chromatography method unsuitable for the determination of the content of N-methylimidazole in the aqueous solution.

SUMMARY OF THE INVENTION

In view of the above-mentioned technical problems, the present invention provides a method for detecting the content of N-methylimidazole in an aqueous system, using ethylene glycol as an internal standard substance, N,N-dimethylformamide as a dilution solvent, and using ethylene glycol as a dilution solvent. The calibration factor was obtained from the working curve with N-methylimidazole, and quantitative analysis was carried out to detect the content of N-methylimidazole in the aqueous system.

To achieve the above object, the present invention adopts the following technical solutions:

A method for detecting N-methylimidazole content in an aqueous system, comprising the following steps:

S1. Quantitative method: the internal standard method is used, the internal standard is ethylene glycol, and the sample is dissolved by N,N-dimethylformamide;

S2. Drawing of the working curve: prepare mixed solutions of ethylene glycol and pure N-methylimidazole with different ratios, dilute with N,N-dimethylformamide to make the volume to 50ml, and the injection volume is 0.4μl. Gas chromatograph measures the peak areas of ethylene glycol and pure N-methylimidazole, obtains the peak area ratios under different mass ratios, and draws the working curve to obtain the correction factor;

S3. Detection of the sample to be tested: Accurately weigh 1.8000-2.2000g of the sample to be tested into a 50ml volumetric flask, then add 0.5500-0.6500g of ethylene glycol, and use N,N-dimethylformamide to dilute to the volume. Calculate the peak area ratio of the internal standard substance and the sample from the spectrum obtained by the gas chromatograph, calculate the content according to the correction factor obtained in step S2, inject the sample three times on average, and take the average value.

Preferably, in the step S2, the ratio of ethylene glycol to pure N-methylimidazole is 3:1, 2:1, 1:1, 1:2, 1:3, and the ratios of 3:1, 2 : 1, 1:1, 1:2, 1:3 to add a new ratio in the ratio range.

Preferably, in the step S2, the peak area ratio of ethylene glycol and N-methylimidazole is used as the ordinate and the mass ratio as the abscissa, and a standard working curve is drawn to obtain a correction factor.

Preferably, the ethylene glycol is chromatographically pure.

Preferably, the N,N-dimethylformamide is analytically pure.

The beneficial technical effects of the present invention are as follows: the present invention uses ethylene glycol as the internal standard substance, and N,N-dimethylformamide as the dilution solvent, both of which can be well mixed with the synthetic stock solution of N-methylimidazole; , N-dimethylformamide is used as a dilution solvent to dilute the synthetic stock solution to reduce the influence of the presence of water in the stock solution on the detection results, and to solve the problem that the presence of a large amount of water seriously interferes with the measurement of the aqueous synthetic stock solution by gas chromatography; In gas chromatographic detection, the elution time of ethylene glycol and N,N-dimethylformamide was significantly different from that of N-methylimidazole and other organic components in the synthetic stock solution. The signal peaks on the gas chromatogram did not overlap and did not Due to the interference of other organic components in the synthetic stock solution, the obtained working curve has a good linear relationship in a wide range. Therefore, using ethylene glycol as the internal standard and N,N-dimethylformamide as the dilution solvent, The working curve of ethylene glycol and N-methylimidazole can be obtained, and then the content of N-methylimidazole in the aqueous system can be quantitatively analyzed and detected; the internal standard and dilution solvent are inexpensive and non-toxic, the sample processing is simple, and the accuracy is high. , Good stability, wide linear range, no interference during analysis, simple and fast.

Description of drawings

Fig. 1 is the gas chromatogram of standard solution of the present invention;

Fig. 2 is the working curve diagram of the present invention.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Example 1

A method for detecting N-methylimidazole content in an aqueous system, comprising the following steps:

S1. Quantitative method: the internal standard method is used, the internal standard is chromatographic grade ethylene glycol, and the sample is dissolved by analytically pure N,N-dimethylformamide;

S2. Drawing of working curve: using pure N-methylimidazole as standard sample, the ratios of ethylene glycol:N-methylimidazole are 3:1, 2.5:1, 2:1, 1.5:1, 1: 1, 1:2, 1:3 Weigh N-methylimidazole standard sample and ethylene glycol standard sample, dilute with N,N-dimethylformamide to 50ml, inject 0.4μl, use gas phase The chromatograph measures the peak area of ethylene glycol and pure N-methylimidazole, obtains the peak area ratio of ethylene glycol and pure N-methylimidazole under different mass ratios, and draws the working curve to obtain the correction factor;

The gas chromatogram of the standard solution is shown in Figure 1, wherein the peak at the 2.2min elution time is the ethylene glycol signal peak, and the 2.4min position is the N,N-dimethylformamide signal peak, and the elution time is 3.3min. The N-methylimidazole signal peak and other signal peaks do not overlap, and the peak shape is good; the obtained working curve is shown in Figure 2, wherein the mass and mass ratio of ethylene glycol and N-methylimidazole corresponding to the working curve are the same as The area ratio is shown in Table 1, and the working curve has a good linearity.

Table 1

S3. Detection of the sample to be tested: Accurately weigh 2.1137g of the sample to be tested #1 in a 50ml volumetric flask, add 0.5718g of ethylene glycol, make up to volume with N,N-dimethylformamide, and the injection volume is 0.4 μl, calculate the peak area ratio of the internal standard substance and the sample from the spectrum obtained by the gas chromatograph, calculate its content according to the correction factor obtained in step S2, repeat the detection 3 times to get the average value, and the test results are shown in Table 2 Show.

Example 2

Accurately weigh 2.0983g of sample #2 to be tested into a 50ml volumetric flask, add 0.5704g of ethylene glycol, dilute to volume with N,N-dimethylformamide, and inject according to gas chromatography conditions, the injection volume is 0.4μl , calculate the peak area ratio of the internal standard substance and the sample from the spectrum obtained by the gas chromatograph, calculate the content according to the correction factor obtained in step S2 of Example 1, repeat the detection 3 times to get the average value, and the test results are shown in the table 2 shown.

Example 3

Accurately weigh 2.0762g of sample #3 to be tested into a 50ml volumetric flask, add 0.5889g of ethylene glycol, dilute to volume with N,N-dimethylformamide, and inject according to gas chromatography conditions, the injection volume is 0.4μl , calculate the peak area ratio of the internal standard substance and the sample from the spectrum obtained by the gas chromatograph, calculate the content according to the correction factor obtained in step S2 of Example 1, repeat the detection 3 times to get the average value, and the test results are as shown in the table 2 shown.

Table 2 Test results of actual samples

Methodological investigation:

Take the standard solution of N-methylimidazole with the same concentration and repeat the test 5 times, the results are shown in Table 3 below.

Table 3 Repeatability test results

It can be seen from Table 3 that the relative standard deviation of the peak area ratio of repeated tests is 0.03%, indicating that the correction factor detected by this method has high precision and good reproducibility.

The above are only preferred embodiments of the present invention, and are not intended to limit the present invention. On the basis of the technical solutions of the present invention, those skilled in the art can make various modifications or Variations are still within the scope of the present invention.

Claims (5)

1. A method for detecting the content of N-methylimidazole in an aqueous phase system is characterized by comprising the following steps:

s1, quantitative method: adopting an internal standard method, wherein the internal standard substance adopts ethylene glycol, and the sample is dissolved by adopting N, N-dimethylformamide;

s2, drawing a working curve: respectively preparing mixed solutions of glycol and pure N-methylimidazole with different proportions, diluting with N, N-dimethylformamide to a constant volume of 50ml, wherein the sample injection amount is 0.4 mu l, measuring peak areas of the glycol and the pure N-methylimidazole by using a gas chromatograph to obtain peak area ratios under different mass ratios, and drawing a working curve to obtain a correction factor;

s3, detection of the sample to be detected: accurately weighing 1.8000-2.2000g of sample to be detected in a 50ml volumetric flask, adding 0.5500-0.6500g of ethylene glycol, performing constant volume by using N, N-dimethylformamide, wherein the sample injection amount is 0.4 mu l, calculating the peak area ratio of an internal standard substance and the sample from a spectrogram obtained by a gas chromatograph, calculating the content of the internal standard substance and the sample according to the correction factor obtained in the step S2, performing average sample injection for three times, and taking an average value.

2. The method for detecting the content of N-methylimidazole in the aqueous phase system as claimed in claim 1, wherein in step S2, the ratio of ethylene glycol to pure N-methylimidazole is 3:1, 2:1, 1:2, 1:3, and a new ratio can be added within the range of the ratio of 3:1, 2:1, 1:2, 1: 3.

3. The method according to claim 1, wherein in step S2, a standard working curve is drawn by using a peak area ratio of ethylene glycol to N-methylimidazole as an ordinate and a mass ratio as an abscissa, so as to obtain the calibration factor.

4. The method for detecting the content of N-methylimidazole in an aqueous system as claimed in claim 1, wherein the ethylene glycol is chromatographically pure.

5. The method for detecting the content of N-methylimidazole in an aqueous system as claimed in claim 1, wherein the N, N-dimethylformamide is analytically pure.

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