阅读说明：本技术 一种高效液相色谱法测定硫酸铵中己内酰胺含量的方法 (Method for determining caprolactam content in ammonium sulfate by high performance liquid chromatography ) 是由 陈艳芬 瞿亚平 吴道斌 杨立新 吴望成 张方 于 2019-11-29 设计创作，主要内容包括：一种高效液相色谱法测定硫酸铵中己内酰胺含量的方法,包括以下步骤：步骤一,标准液的配置；步骤二,样品溶液的配置；步骤三,色谱条件的确定；步骤四,样品测定：待仪器的基线稳定后,测定标准溶液和样品溶液,先测定标准溶液,连续注入多针相同溶度的标准溶液直至相邻两针标准溶液面积变化小于1.5％后,测定样品溶液,注入两针相同溶度的样品溶液面积变化小于1.5％后,再注入多针同一溶度的标准溶液至相邻两针标准溶液面积变化小于1.5％,进样完毕,在两次标准溶液注入的中间注入样品溶液；步骤五,高效液相色谱分析,该方法过程简单易操作,最大限度地消除人为误差,稳定性好、准确度高、精密度好。(A method for measuring caprolactam content in ammonium sulfate by high performance liquid chromatography comprises the following steps: step one, preparing standard solution; step two, preparing a sample solution; step three, determining chromatographic conditions; step four, sample determination: after the baseline of the instrument is stable, measuring a standard solution and a sample solution, measuring the standard solution, continuously injecting a plurality of standard solutions with the same solubility until the area change of the standard solutions of two adjacent needles is less than 1.5%, measuring the sample solution, injecting the standard solutions of the same solubility into the two needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, then injecting the standard solutions of the same solubility into the two adjacent needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, and injecting the sample solution into the middle of the two times of injection of the standard solutions after the sample injection is finished; and step five, high performance liquid chromatography analysis, wherein the method is simple in process and easy to operate, human errors are eliminated to the maximum extent, and the method is good in stability, high in accuracy and good in precision.)

1. A method for measuring caprolactam content in ammonium sulfate by high performance liquid chromatography is characterized in that: the method comprises the following steps:

step one, preparing standard solution: weighing 0.1g, 0.2g, 0.3g, 0.5g, 0.8g and 1.0g caprolactam respectively, dissolving with pure water and diluting to 500ml volumetric flask to obtain 1-6^#A standard solution;

step two, preparing a sample solution: weighing 15-25g ammonium sulfate sample in 100ml volumetric flask, dissolving with pure water and diluting to scale to obtain 1-5^#A sample solution;

step three, determining chromatographic conditions: a chromatographic column: ODS-SP column, phi 4.6mm x 250 mm; mobile phase: performing low-pressure elution by combining a mobile phase A and a mobile phase B, wherein the mobile phase A is methanol, and the mobile phase B is a buffer solution; flow rate: 1 ml/min; column temperature: 30 ℃; sample introduction amount: 20 ul;

step four, sample determination: after the baseline of the instrument is stable, measuring a standard solution and a sample solution, measuring the standard solution, continuously injecting a plurality of standard solutions with the same solubility until the area change of the standard solutions of two adjacent needles is less than 1.5%, measuring the sample solution, injecting the standard solutions of the same solubility into the two needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, then injecting the standard solutions of the same solubility into the two adjacent needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, and injecting the sample solution into the middle of the two times of injection of the standard solutions after the sample injection is finished;

step five, high performance liquid chromatography analysis: according to the peak-out retention time, using a standard substance control method to determine the caprolactam in the sample solution; and respectively recording the areas of the standard solution and the sample solution per needle in the fourth step, and quantitatively calculating the content of caprolactam in the sample by using an external standard method.

2. The method for determining caprolactam content in ammonium sulfate by high performance liquid chromatography as claimed in claim 1, wherein: the buffer solution consists of a sodium perchlorate solution and a potassium phosphate solution, and the volume ratio of the sodium perchlorate solution to the potassium phosphate solution is 1: 1.65.

3. the method for determining caprolactam content in ammonium sulfate by high performance liquid chromatography as claimed in claim 2, wherein: the molar concentration of the sodium perchlorate is 85mmol/L, and the concentration of the potassium phosphate solution is 15 mmol/L.

4. The method for determining caprolactam content in ammonium sulfate by high performance liquid chromatography as claimed in claim 1, wherein: the volume ratio of the mobile phase A to the mobile phase B is 1: 4.

5. The method for determining caprolactam content in ammonium sulfate by high performance liquid chromatography as claimed in claim 1, wherein: the mobile phase, sample solution and standard solution were filtered through a 0.45um microporous membrane before entering the column.

Technical Field

The invention belongs to the field of caprolactam detection, and particularly relates to a method for determining caprolactam content in ammonium sulfate by high performance liquid chromatography.

Background

Caprolactam is an important petrochemical product for producing synthetic fibers and engineering plastics, the market demand for caprolactam is rapidly increased along with the rapid development of economic construction in China, the technical route for producing caprolactam at home and abroad mainly comprises a benzene method and a toluene method, the toluene method for producing caprolactam is a method for producing caprolactam by using toluene as a raw material developed by Italian St.I. (SNIA) company in 1960, at present, more methods for producing caprolactam are used for producing caprolactam by using benzene as a raw material, amide oil containing caprolactam, ammonium sulfate and byproducts is generated after oximation and rearrangement reaction of the material, and the amide oil is separated, extracted and refined to obtain pure caprolactam and ammonium sulfate.

The method comprises the steps of extracting and analyzing dichloromethane, evaporating dichloromethane by using a rotary evaporator after extraction is finished, adding a small part of dichloromethane into an internal standard, and analyzing by using gas chromatography, wherein 1-2 bottles of dichloromethane are used for each sample in the whole analysis process.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a method for determining the caprolactam content in ammonium sulfate by high performance liquid chromatography.

The invention adopts the following technical scheme:

a method for measuring caprolactam content in ammonium sulfate by high performance liquid chromatography comprises the following steps:

step one, preparing standard solution: weighing 0.1g, 0.2g, 0.3g, 0.5g, 0.8g and 1.0g caprolactam respectively, dissolving with pure water and diluting to 500ml volumetric flask to obtain 1-6^#A standard solution;

step two, preparing a sample solution: weighing 15-25g ammonium sulfate sampleDissolving in 100ml volumetric flask with pure water and diluting to scale to obtain 1-5^#A sample solution;

step three, determining chromatographic conditions: a chromatographic column: ODS-SP column, phi 4.6mm x 250 mm; mobile phase: performing low-pressure elution by combining a mobile phase A and a mobile phase B, wherein the mobile phase A is methanol, and the mobile phase B is a buffer solution; flow rate: 1 ml/min; column temperature: 30 ℃; sample introduction amount: 20 ul;

step four, sample determination: after the baseline of the instrument is stable, measuring a standard solution and a sample solution, measuring the standard solution, continuously injecting a plurality of standard solutions with the same solubility until the area change of the standard solutions of two adjacent needles is less than 1.5%, measuring the sample solution, injecting the standard solutions of the same solubility into the two needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, then injecting the standard solutions of the same solubility into the two adjacent needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, and injecting the sample solution into the middle of the two times of injection of the standard solutions after the sample injection is finished;

step five, high performance liquid chromatography analysis: according to the peak-out retention time, using a standard substance control method to determine the caprolactam in the sample solution; and respectively recording the areas of the standard solution and the sample solution per needle in the fourth step, and quantitatively calculating the content of caprolactam in the sample by using an external standard method.

Further, the buffer solution is composed of a sodium perchlorate solution and a potassium phosphate solution, and the volume ratio of the sodium perchlorate solution to the potassium phosphate solution is 1: 1.65.

further, the molar concentration of the sodium perchlorate is 85mmol/L, and the concentration of the potassium phosphate solution is 15 mmol/L.

Further, the volume ratio of the mobile phase A to the mobile phase B is 1: 4.

Further, the mobile phase, sample solution and standard solution are filtered through a 0.45um microporous membrane before entering the chromatographic column.

As can be seen from the above description of the present invention, compared with the prior art, the beneficial effects of the present invention are: and qualitatively and quantitatively analyzing the content of caprolactam in the ammonium sulfate product by adopting a standard substance control method and an external standard method. The method has the advantages of simple process, easy operation, high stability, high accuracy, high precision, reduced solvent consumption, improved inspection efficiency, and increased economic benefit of enterprises.

Drawings

FIG. 1 is a standard curve of a standard solution;

FIG. 2 is a standard solution chromatogram;

FIG. 3 is a sample solution chromatogram.

Detailed Description

The invention is further described below by means of specific embodiments.

A method for measuring caprolactam content in ammonium sulfate by high performance liquid chromatography comprises the following steps:

step one, preparing standard solution: weighing 0.1g, 0.2g, 0.3g, 0.5g, 0.8g and 1.0g caprolactam respectively, dissolving with pure water and diluting to 500ml volumetric flask to obtain 1-6^#A standard solution;

step two, preparing a sample solution: weighing 15-25g ammonium sulfate sample in 100ml volumetric flask, dissolving with pure water and diluting to scale to obtain 1-5^#A sample solution;

step three, determining chromatographic conditions: a chromatographic column: ODS-SP column, phi 4.6mm x 250 mm; mobile phase: performing low-pressure elution by combining a mobile phase A and a mobile phase B, wherein the mobile phase A is methanol, and the mobile phase B is a buffer solution; flow rate: 1 ml/min; column temperature: 30 ℃; sample introduction amount: 20 ul;

step four, sample determination: after the baseline of the instrument is stable, measuring a standard solution and a sample solution, measuring the standard solution, continuously injecting a plurality of standard solutions with the same solubility until the area change of the standard solutions of two adjacent needles is less than 1.5%, measuring the sample solution, injecting the standard solutions of the same solubility into the two needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, then injecting the standard solutions of the same solubility into the two adjacent needles until the area change of the standard solutions of the two adjacent needles is less than 1.5%, and injecting the sample solution into the middle of the two times of injection of the standard solutions after the sample injection is finished;

step five, high performance liquid chromatography analysis: according to the peak-out retention time, using a standard substance control method to determine the caprolactam in the sample solution; and respectively recording the areas of the standard solution and the sample solution per needle in the fourth step, and quantitatively calculating the content of caprolactam in the sample by using an external standard method.

Specifically, the volume ratio of the mobile phase A to the mobile phase B is 1:4, the mass concentration of methanol is 90%, the buffer solution is composed of a sodium perchlorate solution and a potassium phosphate solution, and the volume ratio of the perchloric acid solution to the potassium phosphate solution is 1: 1.65, the molar concentration of the sodium perchlorate is 85mmol/L, and the concentration of the potassium phosphate solution is 15 mmol/L.

Further, the mobile phase, sample solution and standard solution were filtered through a 0.45um microporous membrane before being introduced into the column.

And (3) test results:

firstly, preparing a standard solution according to the steps to obtain the following results;

TABLE 1 Standard solution preparation Table

And drawing a standard curve according to the configuration result of the standard solution, as shown in figure 1.

Secondly, the following results can be obtained according to the fourth step:

TABLE 2 relevant data sheet for sample solution testing

Thirdly, the following results can be obtained according to the fifth step:

FIG. 2 is a standard chromatogram in which 12.915 is the peak area of caprolactam; FIG. 3 is a chromatogram of a sample solution, wherein 12.906 is the peak area of caprolactam, and the mass fraction of caprolactam in the sample is quantitatively calculated to be 0.10% by an external standard method.

Test verification

First, precision verification

Are respectively paired with 1^#The standard solution is subjected to l0 times of parallel measurement, the average retention time is 12.913min, the relative standard deviation of the retention time is 0.3457%, the peak area is recorded, and the measurement is calculatedThe relative standard deviation of caprolactam was determined to be 0.3114%, and the results are shown in Table 3:

watch 31^#Data sheet of standard solution

As can be seen from Table 3, the caprolactam content measured by the above method has a small standard deviation and a good precision of the test results.

Second, accuracy verification

The accuracy of caprolactam recovery was shown by the spiked recovery for known concentrations of ammonium sulfate samples, and the results are shown in table 4:

TABLE 4 ammonium sulfate sample standard recovery test data sheet

As can be seen from Table 4, the recovery rate of the spiked sample is 95% -98%, which indicates that the accuracy of the experimental result is high, and the accuracy of the method meets the analysis requirement.

Third, determining detection limit

Under the condition of the method, the lowest detection limit of the method is calculated to be 0.01mg/L by using 3 times of limit noise.

In conclusion, the content of caprolactam in the ammonium sulfate product is qualitatively and quantitatively analyzed by adopting a standard substance control method and an external standard method. The method has the advantages of simple process, easy operation, high stability, high accuracy, high precision, reduced solvent consumption, improved inspection efficiency, and increased economic benefit of enterprises.

The above description is only a preferred embodiment of the present invention, and therefore should not be taken as limiting the scope of the invention, which is defined by the appended claims and their equivalents and modifications within the scope of the description.