Gas chromatography determination method of industrial dimethyl sulfate

Abstract

The invention discloses a gas chromatographic determination method of industrial dimethyl sulfate. A chromatographic column stationary phase used in the method is 5 wt% diphenyl-95 wt% dimethyl polysiloxane; the temperature programming conditions are as follows: the initial column temperature is 55-65 DEG C, and the temperature is kept for 3-6 minutes; raising the temperature to 90-120 DEG C at the temperature raising rate of 8-12 DEG C / min, and keeping the temperature for 2-4 minutes; the temperature is raised to 140-160 DEG C at the temperature raising rate of 8-12 DEG C / min, and the temperature is kept for 2-4 min; the temperature is raised to 190-210 DEG C at the temperature raising rate of 8-12 DEG C / min, and the temperature is kept for 9-12 min. The method provided by the invention realizes rapid detection of dimethyl sulfate, has the advantages of high sensitivity, good precision and accuracy, simple and rapid operation, and more practical determination of the content of industrial dimethyl sulfate.

Description

Technical Field

[0001] The invention relates to a gas chromatography determination method for dimethyl sulfate, which has the characteristics of a gas chromatography qualitative or quantitative determination method for an industrial dimethyl sulfate product and belongs to the technical field of instrument analysis. Background Art

[0002] Dimethyl sulfate is a commonly used methylating agent in industrial production. It can methylate DNA. After methylation, DNA can be degraded at the methylated position. It is a highly toxic substance in the "Catalogue of Hazardous Chemicals (2015 Edition)". It is a colorless or slightly yellow oily flammable liquid with a slight onion smell. It will hydrolyze to produce sulfuric acid and methanol at above 50°C or in an alkaline environment. Dimethyl sulfate is slightly soluble in water, soluble in ethanol, ether, acetone, etc.; it is flammable when exposed to heat, open flames or oxidants.

[0003] my country's HG / T 4001-2008 stipulates that the determination of industrial dimethyl sulfate is a titration method. This method adds a certain amount of potassium hydroxide-ethanol standard solution to the sample. After saponification, the remaining potassium hydroxide-ethanol standard solution is titrated with sulfuric acid standard titration solution, and a reagent blank test is performed at the same time. The total ester content is obtained based on the difference in the volume of the sulfuric acid standard titration solution consumed. The free sulfuric acid in the sample reacts with potassium hydroxide-ethanol to neutralize, and the acid content is converted into dimethyl sulfate content and deducted to obtain the content of dimethyl sulfate. The instrumentation used in the titration method is relatively simple and easy to operate, but the operation error is large, the time is long, and there are safety risks in weighing and titrating dimethyl sulfate, which is easy to cause occupational injuries. Summary of the invention

[0004] In order to solve the shortcomings of the existing titration method for determining dimethyl sulfate, the present invention provides a gas chromatography determination method for industrial dimethyl sulfate, which has the advantages of high safety, fast analysis speed, high sensitivity, small sample size and good result repeatability, and can fully separate dimethyl sulfate from impurities dimethyl ether and methanol, realize qualitative and quantitative analysis of dimethyl sulfate, and greatly improve the detection efficiency of industrial dimethyl sulfate.

[0005] The specific technical solutions of the present invention are as follows:

[0006] The invention discloses a gas chromatography determination method for industrial dimethyl sulfate. The invention carries out qualitative or quantitative determination of dimethyl sulfate by gas chromatography.

[0007] Furthermore, during gas chromatography determination, the stationary phase of the chromatographic column used is 5wt% diphenyl-95wt% dimethylpolysiloxane, such as Elite-5, SE-54, HP-5, DB-5, BP-5 capillary column. The size of the chromatographic column is 30m×0.32mm×0.25μm.

[0008] Furthermore, during gas chromatography determination, programmed temperature rise was adopted, and the temperature rise program was as follows: the initial column temperature was 55-65°C, maintained for 3-6 minutes; the temperature was increased to 90-120°C at a heating rate of 8-12°C / min, maintained for 2-4 minutes; the temperature was increased to 140-160°C at a heating rate of 8-12°C / min, maintained for 2-4 minutes; the temperature was increased to 190-210°C at a heating rate of 8-12°C / min, maintained for 9-12 minutes.

[0009] Preferably, the temperature program is: the initial column temperature is 60°C, maintained for 5 minutes; the temperature is increased to 100°C at a heating rate of 10°C / min, maintained for 3 minutes; the temperature is increased to 150°C at a heating rate of 10°C / min, maintained for 3 minutes; the temperature is increased to 200°C at a heating rate of 10°C / min, maintained for 10 minutes.

[0010] Furthermore, during gas chromatography determination, the detector is a hydrogen flame ionization detector (FID), and the detector temperature is 200-250°C, for example, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C.

[0011] Furthermore, during gas chromatography determination, the carrier is nitrogen or helium, and the carrier gas flow rate is 0.5-2.5 mL / min, for example, 0.5 mL / min, 1.0 mL / min, 1.5 mL / min, 2.0 mL / min, 2.5 mL / min.

[0012] Furthermore, during gas chromatography determination, the split ratio is 50-100:1, for example, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1.

[0013] Furthermore, during gas chromatography measurement, the temperature of the vaporization chamber is 180-220°C, for example, 180°C, 190°C, 200°C, 210°C, 220°C.

[0014] Furthermore, during gas chromatography determination, the injection volume is 0.5-2.0 μL, for example, 0.5 μL, 1.0 μL, 1.5 μL, 2.0 μL.

[0015] Further, the gas chromatography determination comprises the following steps:

[0016] (1) Add different masses of dimethyl ether standard and methanol standard to dimethyl sulfate standard and mix them evenly to obtain a series of standard samples containing dimethyl ether and methanol; at the same time, use dimethyl sulfate standard as blank control sample:

[0017] (2) performing gas chromatography analysis on each standard sample and blank control sample to obtain the retention time and peak area of ​​dimethyl sulfate, dimethyl ether, and methanol;

[0018] (3) drawing a standard curve of dimethyl ether content versus corrected peak area and a standard curve of methanol content versus corrected peak area, wherein the corrected peak area is the peak area of ​​dimethyl ether or methanol in the standard sample minus the peak area of ​​dimethyl ether or methanol in the blank control sample;

[0019] (4) The dimethyl sulfate sample to be tested is subjected to gas chromatography analysis, and the peak areas of dimethyl ether and methanol are substituted into the standard curve of step (3) to obtain the contents of dimethyl ether and methanol, where the content of dimethyl sulfate = 100% - dimethyl ether content - methanol content.

[0020] Furthermore, in step (1), 4 standard samples are prepared, wherein standard sample 1 contains 100 g of dimethyl sulfate standard, 0.2 g of dimethyl ether and 0.2 g of methanol, standard sample 2 contains 100 g of dimethyl sulfate standard, 0.5 g of dimethyl ether and 0.5 g of methanol, standard sample 3 contains 100 g of dimethyl sulfate standard, 0.8 g of dimethyl ether and 0.8 g of methanol, and standard sample 4 contains 100 g of dimethyl sulfate standard, 1.5 g of dimethyl ether and 1.5 g of methanol.

[0021] Furthermore, in step (1), the standard sample is prepared in a pressure-resistant reagent bottle by first adding dimethyl sulfate standard, then adding methanol standard, and finally adding methyl ether standard, and mixing them evenly to obtain the standard sample.

[0022] Furthermore, the dimethyl sulfate standard product used meets the requirements of HG / T 4001-2008, and the dimethyl sulfate content in the standard product is ≥99.7%, and the acidity is ≤0.05%. The dimethyl sulfate standard product can be obtained by vacuum distillation and purification of industrial dimethyl sulfate samples, or can be purchased from the market.

[0023] Furthermore, the dimethyl ether and methanol standards used were of analytical grade.

[0024] Furthermore, the retention time of dimethyl ether is about 3.40 min, the retention time of methanol is about 4.19 min, and the retention time of dimethyl sulfate is about 7.41 min.

[0025] Beneficial effects: The present invention is suitable for the detection of dimethyl sulfate products. Dimethyl sulfate is qualitatively and quantitatively determined by a capillary column and a hydrogen flame ionization detector. Dimethyl sulfate and its impurities can be well separated by selecting gas chromatography conditions. The present invention has the advantages of simple operation, high sensitivity, good precision and accuracy, good result reproducibility, and rapid detection, and is more practical for determining the content of industrial dimethyl sulfate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a gas chromatogram obtained using the chromatographic conditions of the present invention.

[0027] Figure 2 This is a gas chromatogram obtained using an SE-30 column.

[0028] Figure 3 This is a gas chromatogram obtained using a column temperature of 3.

[0029] Figure 4 This is the standard curve of dimethyl ether.

[0030] Figure 5 This is the standard curve of methanol. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is described in detail and completely through embodiments below, so that those skilled in the art can better understand the advantages and features of the present invention and define the protection scope of the present invention more clearly. The embodiments described in the present invention are only part of the embodiments of the present invention. Based on the embodiments in the present invention, all embodiments obtained by ordinary technicians in the field without creative work belong to the protection scope of the present invention.

[0032] Example 1 Chromatographic column screening

[0033] 1. The instrument used in the present invention is a Panno gas chromatograph FID detector, model A60, with good chromatographic performance.

[0034] 2. The standard sample reagents used in the present invention are: dimethyl sulfate standard: high-purity dimethyl sulfate, manufacturer Shandong Kairuiying Material Technology Co., Ltd., dimethyl sulfate content ≥99.7%, acidity ≤0.05%. Dimethyl ether standard: dimethyl ether standard gas, high-purity gas ≥99%, Henan Zhengyuan Special Gas Co., Ltd. Methanol standard: high-grade purity, Tianjin Fuchen Chemical Reagent Co., Ltd.

[0035] 3. The detailed parameters of gas chromatography conditions are shown in Table 1 below:

[0036] Table 1

[0037]

[0038]

[0039] 4. Preparation of standard samples: Accurately weigh 100g of dimethyl sulfate standard in a 100mL pressure-resistant reagent bottle, accurate to 0.0002g, first add 0.2g of methanol standard to the dimethyl sulfate standard, mix well, then add 0.2g of dimethyl ether standard gas, mix well to obtain a standard sample.

[0040] 5. Gas chromatography determination: Take 0.1 microliter of standard sample and use the above gas chromatography conditions to determine. The results show that dimethyl sulfate, dimethyl ether and methanol can be well separated when using the Elite-5 column. Although other columns have peaks, they cannot separate the three well. Therefore, the Elite-5 column is selected as the chromatographic column. The gas chromatogram of the Elite-5 column is as follows: Figure 1 As shown, the gas chromatogram of SE-30 column is as follows Figure 2 shown.

[0041] Example 2 Screening of programmed temperature conditions

[0042] 1. The instrument used in the present invention is a Panno gas chromatograph FID detector, model A60, with good chromatographic performance.

[0043] 2. The standard sample reagents used in the present invention are: dimethyl sulfate standard: high-purity dimethyl sulfate, manufacturer Shandong Kairuiying Material Technology Co., Ltd., dimethyl sulfate content ≥99.7%, acidity ≤0.05%. Dimethyl ether standard: dimethyl ether standard gas, high-purity gas ≥99%, Henan Zhengyuan Special Gas Co., Ltd. Methanol standard: high-grade purity, Tianjin Fuchen Chemical Reagent Co., Ltd.

[0044] 3. The detailed parameters of gas chromatography conditions are shown in Table 2 below:

[0045] Table 2

[0046]

[0047]

[0048] 4. Preparation of standard samples: same as in Example 1.

[0049] 5. Gas chromatography determination: Take 0.1 μl of standard sample and use the above gas chromatography conditions for determination. The results show that the chromatographic separation conditions when using different program temperature rise conditions are shown in Table 3 below. Therefore, the program temperature rise selects the condition of column temperature 4:

[0050] Table 3

[0051]

[0052]

[0053] Among them, the gas chromatogram at column temperature 3 is as follows Figure 3 shown.

[0054] Example 3

[0055] 1. The instrument used in the present invention is a Panno gas chromatograph FID detector, model A60, with good chromatographic performance.

[0056] 2. The standard sample reagents used in the present invention are: dimethyl sulfate standard: high-purity dimethyl sulfate, manufacturer Shandong Kairuiying Material Technology Co., Ltd., dimethyl sulfate content ≥99.7%, acidity ≤0.05%. Dimethyl ether standard: dimethyl ether standard gas, high-purity gas ≥99%, Henan Zhengyuan Special Gas Co., Ltd. Methanol standard: high-grade purity, Tianjin Fuchen Chemical Reagent Co., Ltd.

[0057] 3. The detailed parameters of gas chromatography conditions are shown in Table 4 below:

[0058] Table 4

[0059]

[0060]

[0061] 4. Preparation of standard samples: Accurately weigh 100g of dimethyl sulfate standard in 100mL pressure-resistant reagent bottles, accurate to 0.0002g, first add methanol standard to the dimethyl sulfate standard, mix well, then add dimethyl ether standard gas, mix well to obtain a series of standard samples. The masses of dimethyl ether standard gas and methanol standard in each standard sample are shown in Table 5 below:

[0062] Table 5

[0063] Standard samples a b c d Dimethyl ether standard gas / g 0.2 0.5 0.8 1.5 Methanol standard / g 0.2 0.5 0.8 1.5

[0064] 5. Gas chromatography determination:

[0065] Take 0.1 μl of each standard sample and measure it under the above gas chromatography conditions. Use pure dimethyl sulfate standard as blank control. Subtract the peak area of ​​dimethyl ether or methanol in the blank control from the peak area of ​​dimethyl ether or methanol in the standard sample to obtain the corrected peak area of ​​dimethyl ether or methanol. Draw a standard curve of the corrected peak area of ​​dimethyl ether and methanol and their contents. From the standard curve, obtain the standard equation, where the dimethyl ether standard curve is as follows: Figure 4 The standard curve of methanol is shown in Figure 5 As shown in the figure, it can be seen that the linear relationship is good within the content range of 0.2-1.5% of dimethyl ether and methanol.

[0066] Example 4

[0067] In order to verify the feasibility of the method in Example 3 for the quantitative analysis of dimethyl sulfate, the following precision experiments, detection limit and quantification limit experiments were carried out respectively.

[0068] (1) Precision test

[0069] Take the standard sample a in Example 3, and perform parallel experiments 6 times according to the detection method of Example 3, record the peak area, calculate the precision, and the results are shown in Table 6. The test results show that the RSD of methanol in the precision experiment of this detection method is 3.61%, and the RSD of dimethyl ether is 3.11%, which meets the quantitative detection requirements, and the precision of this detection method is good.

[0070] Table 6

[0071]

[0072] (2) Limit of detection and limit of quantification experiments

[0073] Test method: Weigh approximately 0.1 g of methanol and dimethyl ether standard samples respectively, place in two pressure-resistant bottles containing 100 mL of water, and shake well as standard sample stock solution. Take an appropriate amount of standard sample stock solution, dilute with water to a series of concentration solutions, inject and test, when the signal-to-noise ratio S / N is not less than 3, it is used as the detection limit, when the signal-to-noise ratio S / N is not less than 10, it is used as the quantitative limit. The results are shown in Table 7. The quantitative limit was prepared in duplicate for 6 times, and gas chromatography was performed for detection, the chromatogram was recorded, and the precision of the quantitative limit was observed. The results are shown in Table 8.

[0074] Test results: The detection limit and quantitative limit test results in Table 7 show that the detection limit concentration of methanol in the detection method of this application is 0.5541 mg / L, which is equivalent to a methanol content of 0.0011% that can be detected, and the detection limit concentration of dimethyl ether is 0.4102 mg / L, which is equivalent to a dimethyl ether content of 0.0007% that can be detected. The quantitative limit concentration of methanol is 1.4961 mg / L, which is equivalent to a methanol content of 0.0030% that can be quantitatively detected, and the quantitative limit concentration of dimethyl ether is 1.0255 mg / L, which is equivalent to a dimethyl ether content of 0.0019% that can be quantitatively detected. It shows that the sensitivity of this method to methanol and dimethyl ether meets the detection requirements, proving that the detection method of this application has high sensitivity and meets the detection requirements of the substance. The quantitative limit repeatability test results in Table 8 show that the RSD of the peak area of ​​6 parts of methanol is 1.71%, and the RSD of the peak area of ​​6 parts of dimethyl ether is 2.19%, which meets the requirements, indicating that the quantitative limit repeatability of this method is good.

[0075] Table 7

[0076]

[0077] Table 8

[0078]

[0079]

[0080] Example 4 Actual sample detection

[0081] Dimethyl sulfate product was purchased from the market as a sample to be tested. The sample to be tested was subjected to gas chromatography detection according to the chromatographic conditions in Example 3 to obtain the peak areas of dimethyl ether and methanol. The peak areas were brought into the standard curve of Example 3 to obtain the contents of dimethyl ether and methanol in the sample. The results were as follows:

[0082] Samples to be tested Methanol content Dimethyl ether content Dimethyl sulfate content 1 0.10％ 0.05％ 99.85％ 2 0.13％ 0.04％ 99.83％

[0083] The invention separates dimethyl ether and methanol through a chromatographic column, thereby realizing rapid detection of industrial dimethyl sulfate, having simple operation, high sensitivity, good precision and accuracy, and having better practicability than existing detection methods.

Claims

1. A gas chromatographic determination method for industrial dimethyl sulfate, characterized in that: Dimethyl sulfate was measured by gas chromatography, and the chromatographic conditions included: Chromatographic column: stationary phase is 5wt% diphenyl-95wt% dimethylpolysiloxane; Program temperature conditions: initial column temperature is 55-65℃, maintained for 3-6min; heated to 90-120℃ at a heating rate of 8-12℃ / min, maintained for 2-4min; heated to 140-160℃ at a heating rate of 8-12℃ / min, maintained for 2-4min; heated to 190-210℃ at a heating rate of 8-12℃ / min, maintained for 9-12min.

2. The gas chromatography method according to claim 1, characterized in that: The detector is a hydrogen flame ionization detector; the detector temperature is 200-250°C.

3. The gas chromatography method according to claim 1, characterized in that: The carrier is nitrogen or helium, and the carrier gas flow rate is 0.5-2.5mL / min.

4. The gas chromatography method according to claim 1, characterized in that: The split ratio is 50-100:

1.

5. The gas chromatography method according to claim 1, characterized in that: The temperature of the vaporization chamber is 180-220°C.

6. The gas chromatography determination method according to claim 1, characterized in that: The injection volume is 0.5-2μL.

7. The gas chromatography method according to any one of claims 1 to 6, characterized in that: The following steps are involved: (1) Add different masses of dimethyl ether standard and methanol standard to dimethyl sulfate standard and mix them evenly to obtain a series of standard samples containing dimethyl ether and methanol; at the same time, use pure dimethyl sulfate standard as blank control sample: (2) performing gas chromatography analysis on each standard sample and blank control sample to obtain the retention time and peak area of ​​dimethyl sulfate, dimethyl ether, and methanol; (3) drawing a standard curve of dimethyl ether content versus corrected peak area and a standard curve of methanol content versus corrected peak area, wherein the corrected peak area is the peak area of ​​dimethyl ether or methanol in the standard sample minus the peak area of ​​dimethyl ether or methanol in the blank control sample; (4) The dimethyl sulfate sample to be tested is subjected to gas chromatography analysis, and the peak areas of dimethyl ether and methanol are substituted into the standard curve of step (3) to obtain the contents of dimethyl sulfate, dimethyl ether and methanol.

8. The gas chromatography method according to claim 7, characterized in that: In step (1), 4 standard samples are prepared, wherein standard sample 1 contains 100 g of dimethyl sulfate standard, 0.2 g of dimethyl ether and 0.2 g of methanol, standard sample 2 contains 100 g of dimethyl sulfate standard, 0.5 g of dimethyl ether and 0.5 g of methanol, standard sample 3 contains 100 g of dimethyl sulfate standard, 0.8 g of dimethyl ether and 0.8 g of methanol, and standard sample 4 contains 100 g of dimethyl sulfate standard, 1.5 g of dimethyl ether and 1.5 g of methanol.

Images