Method for detecting methyl methacrylate in air of workplace

Abstract

The invention relates to a method for detecting methyl methacrylate in air of a workplace. The method comprises the steps that a p-aminophenol impregnated activated carbon adsorption tube is used for collecting air in a workplace, gas to be detected is obtained, and the air in the workplace comprises methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid; placing the aminophenol impregnated activated carbon adsorption tube in a solvent desorption bottle, and desorbing the to-be-detected gas by using a mixed solution of dichloromethane and acetonitrile to obtain a to-be-detected solution; and separating the to-be-detected liquid by using a gas chromatographic method, and detecting by using a flame ionization detector to obtain the content of methyl methacrylate in the air of the workplace. The method provided by the invention solves the technical problem of low detection accuracy of the content of methyl methacrylate in the air in the prior art.

Description

Technical Field

[0001] The present application relates to the field of chromatography detection technology, and in particular to a method for detecting methyl methacrylate in workplace air. Background Art

[0002] Methylmethacrylate (MMA), with the structural formula C5H8O2, is a commonly used organic solvent that is irritating to the eyes, nose and throat. Long-term contact can cause dermatitis, anesthesia and systemic toxicity.

[0003] The standard detection methods are thermal desorption-gas chromatography and direct injection-gas chromatography. Thermal desorption requires the use of a thermal desorber, but automatic thermal desorbers are less popular, manual operation is inefficient, and the precision is not high; the direct injection method cannot perform long-term sampling, the sample storage time is short, and the sensitivity is low.

[0004] In some chemical sites, methyl methacrylate will quickly volatilize into the air of the workplace, causing respiratory, skin and eye irritation, nausea and vomiting symptoms to workers, affecting their health. Therefore, it is very important to accurately detect the content of methyl methacrylate in the air of the workplace. Summary of the invention

[0005] The present application provides a method for detecting methyl methacrylate in workplace air, so as to solve the technical problem of low detection accuracy of the existing detection of methyl methacrylate content in air.

[0006] In a first aspect, an embodiment of the present application provides a method for detecting methyl methacrylate in workplace air, the method comprising:

[0007] Using p-aminophenol-impregnated activated carbon adsorption tubes to collect workplace air to obtain a gas to be tested, wherein the workplace air includes methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid;

[0008] The activated carbon adsorption tube impregnated with aminophenol is placed in a solvent desorption bottle, and the gas to be tested is desorbed by a mixed solution of dichloromethane and acetonitrile to obtain a liquid to be tested;

[0009] The liquid to be tested is separated by gas chromatography and detected by flame ionization detector to obtain the content of methyl methacrylate in the air of the workplace.

[0010] Optionally, the specific surface area of ​​the aminophenol-impregnated activated carbon is 1100-1300m 2 / g, the volume of the micropores of the aminophenol-impregnated activated carbon accounts for 80%-95% of the total volume of the micropores and mesopores.

[0011] Optionally, the volume of the mixed solution of dichloromethane and acetonitrile is 80% to 100% of the volume of the adsorption tube.

[0012] Optionally, the method further includes:

[0013] Prepare standard application solutions of methyl methacrylate of different concentrations respectively, perform gas chromatography detection on the standard application solutions of methyl methacrylate and blank control solutions, and draw a standard curve of methyl methacrylate;

[0014] The methyl methacrylate standard curve uses the theoretical concentration value of methyl methacrylate in the methyl methacrylate standard application solution as the abscissa and the peak area as the ordinate.

[0015] Optionally, the gas chromatography column in the gas chromatography method is a 35% diphenyl-65% dimethylpolysiloxane column.

[0016] Optionally, the detection parameters of the gas chromatography method are: initial temperature 55°C, then 22°C

[0017] / min to 160℃, then to 190℃ at 20℃ / min; split ratio: 8:1; carrier gas (nitrogen) flow rate: 1.8mL / min; vaporization chamber temperature: 250℃; detector temperature: 300℃; hydrogen flow rate: 32.0mL / min; air flow rate: 300.0mL / min.

[0018] Optionally, the volume ratio of dichloromethane to acetonitrile is (6-12):1.

[0019] Optionally, the volume ratio of dichloromethane to acetonitrile is (8-10):1.

[0020] Optionally, before separating the liquid to be tested by gas chromatography, the method includes: performing preliminary sample treatment through a C18 SPE column and eluting with an aqueous solution having a mass fraction of 5% methanol.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] According to the method provided in the embodiment of the present application, when the workplace air contains methyl methacrylate and polymethyl methacrylate product esters, since the contents of methyl methacrylate and ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid in the air are not much different, the chromatographic peaks show tailing, thereby affecting the quantitative accuracy; in addition, it also leads to the broadening of the methyl methacrylate peak, reducing the separation degree and detection sensitivity; therefore, the method of the present application uses aminophenol to fully absorb formic acid and butyric acid in the air, which can reduce the influence of a part of formic acid and butyric acid acidic substances on methyl methacrylate, thereby comprehensively improving the detection accuracy of methyl methacrylate in the workplace air.

[0023] The linear relationship of methyl methacrylate measured by this method was good in the range of 180-1850.0 mg / L, with a correlation coefficient of 0.99998 and a minimum detection concentration of 0.4 mg / mL. 3 (Based on the collection of 1.5L air sample), the average desorption efficiency is 97.9% to 99.8%, the sampling efficiency is 99% to 100.0%, and the sample can be stored in a refrigerator at 4°C for 7-10 days. The method of the present application is simple to operate, has high sensitivity, good precision and accuracy, and is suitable for improving the detection accuracy of methyl methacrylate when the air in the workplace includes methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0025] 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 paying any creative labor.

[0026] Figure 1 A schematic flow chart of a method for detecting methyl methacrylate in workplace air provided in an embodiment of the present application.

[0027] Figure 2 A chromatogram of methyl methacrylate in workplace air provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0029] In the workplace of chemical enterprises, such as latex enterprises, methyl methacrylate (MMA) volatilizes into the air, causing respiratory, skin and eye irritation, nausea and vomiting symptoms to workers, affecting human health. The exposure limits of methyl methacrylate in the air may vary from country to country. According to the "Occupational Exposure Limits for Hazardous Factors in the Workplace Part 1: Chemical Hazardous Factors" (GBZ 2.1-2007), the permissible exposure limits for methyl methacrylate (MMA) in the air of the workplace are as follows: Occupational Exposure Limit-Time Weighted Average (PC-TWA): 100mg / m 3 (about 25ppm); occupational exposure limit - short-term exposure (PC-STEL): 150mg / m 3 (about 37.5ppm).

[0030] Generally speaking, the content of methyl methacrylate in the air may be between 2-50ppm. For such a low dose of methyl methacrylate in the air, it is very important to reduce the influence of gas substances in the air on the characteristic peak area of ​​methyl methacrylate when detecting it with a gas chromatograph.

[0031] Generally speaking, when detecting methyl methacrylate in the air, there are also methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid in the air. How to reduce the influence of methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid on the accuracy of the detection results is the key research direction.

[0032] Figure 1 It is shown that the embodiment of the present application provides a method for detecting methyl methacrylate in the air of a workplace.

[0033] like Figure 1 As shown, the present application provides a method for detecting methyl methacrylate in workplace air, and the method includes: steps 100 to 300.

[0034] Step 100, collecting workplace air using an activated carbon adsorption tube impregnated with p-aminophenol to obtain a gas to be tested, wherein the workplace air includes methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid;

[0035] In this embodiment, it is found that due to the presence of organic acids and organic esters in the air, ordinary activated carbon tubes, hydroquinone impregnated activated carbon tube sampling tubes, alkaline silicone tubes, acidic silicone tubes, and ethanol solutions are used to sample methyl methacrylate in the workplace. The experiment found that the aminophenol impregnated activated carbon adsorption tube can retain the methyl methacrylate content to the maximum extent and remove the interference of organic acids on the methyl methacrylate detection results, while other collection tubes affect the accuracy of the detection results of methyl methacrylate in a fixed volume of air.

[0036] The reason is that hydroquinone is a medium polar compound, and its hydroxyl group has a certain symmetry, which can produce hydrogen bonds with MMA molecules, but not as strong as aminophenol. Aminophenol has highly polar amino and hydroxyl groups, which can form stronger hydrogen bonds or other chemical bonds with MMA molecules, and has higher selectivity for polar compounds. Hydroquinone has relatively low selectivity for MMA to polar compounds.

[0037] Step 200, placing the aminophenol-impregnated activated carbon adsorption tube in a solvent desorption bottle, and using a mixed solution of dichloromethane and acetonitrile to desorb the gas to be tested to obtain a liquid to be tested;

[0038] Step 300, using gas chromatography to separate the liquid to be tested, and using a flame ionization detector for detection to obtain the content of methyl methacrylate in the air of the workplace.

[0039] In the embodiments of the present application, the method of the present invention is simple and accurate, can reduce the influence of polymethyl methacrylate product ester in the air on the detection of methyl methacrylate in the air, can simultaneously detect the content of methyl methacrylate and other compounds, is of great significance for monitoring the content of methyl methacrylate in the workplace, and has a low detection limit of 0.05 mg / m 3 .

[0040] In some embodiments, the aminophenol-impregnated activated carbon has a specific surface area of ​​1100-1300 m 2 / g, the volume of the micropores of the aminophenol-impregnated activated carbon accounts for 80-95% of the total volume of the micropores and mesopores.

[0041] In some embodiments, the volume of the mixed solution of dichloromethane and acetonitrile is 80% to 100% of the volume of the adsorption tube.

[0042] In some embodiments, the method further comprises:

[0043] Prepare standard application solutions of methyl methacrylate of different concentrations respectively, perform gas chromatography detection on the standard application solutions of methyl methacrylate and blank control solutions, and draw a standard curve of methyl methacrylate;

[0044] The methyl methacrylate standard curve uses the theoretical concentration value of methyl methacrylate in the methyl methacrylate standard application solution as the abscissa and the peak area as the ordinate.

[0045] In this step, a methyl methacrylate standard curve can be obtained by preparing standard application solutions of methyl methacrylate of different concentrations. In some embodiments, standard application solutions of ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid can be prepared respectively, and the corresponding standard curves can be drawn by gas chromatography detection of the methyl methacrylate standard application solution, ethyl acetate standard application solution, propyl acetate standard application solution, methyl formate standard application solution, ethyl formate standard application solution, formic acid standard application solution and butyric acid standard application solution and a blank control solution.

[0046] In some embodiments, the gas chromatography column in the gas chromatography method is a 35% diphenyl-65% dimethylpolysiloxane column.

[0047] Methyl methacrylate is a polar compound, and generally a strong polar or medium polar stationary phase is selected. In order to reduce the influence of polymethyl methacrylate product ester on the detection of methyl methacrylate content, the present application adopts a polar chromatographic column with a phenyl-bonded dimethylpolysiloxane as the stationary phase, especially a 35% diphenyl-65% dimethylpolysiloxane column, which can further improve the separation effect between the compounds, reduce the tailing of the chromatographic peak, and improve the accuracy of the detection.

[0048] In some embodiments, the detection parameters of gas chromatography are: initial temperature 55°C, then heated to 160°C at 22°C / min, and then heated to 190°C at 20°C / min; split ratio: 8:1; carrier gas (nitrogen) flow rate: 1.8mL / min; vaporization chamber temperature: 250°C; detector temperature 300°C; hydrogen volume: 32.0mL / min; air flow: 300.0mL / min.

[0049] In the examples of the present application, the gas chromatography conditions of the detection method are reasonably controlled to ensure good separation and peak shape between the chromatographic peaks of each substance to be tested and the internal standard, thereby improving the accuracy of the detection. And under the same detection conditions, the content of methyl methacrylate can be accurately detected. In addition, methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid that may be contained in the sample can be detected simultaneously in one injection, shortening the chromatographic peak time required for detection.

[0050] In some embodiments, in order to improve the desorption efficiency, the volume ratio of dichloromethane to acetonitrile is (6-12):1.

[0051] In some embodiments, in order to improve the desorption efficiency and the accuracy of the detection results, the volume ratio of dichloromethane to acetonitrile is (8-10):1.

[0052] In some embodiments, before separating the test liquid by gas chromatography, the method includes: performing preliminary sample treatment by C18 SPE column and eluting with an aqueous solution of 5% methanol by mass. Therefore, in order to remove the interference of ethyl acetate, propyl acetate, methyl formate and ethyl formate, a pretreatment process can be used to separate methyl methacrylate from other ester substances.

[0053] The method of the present invention will be described in detail below with reference to embodiments, comparative examples and experimental data.

[0054] Example 1

[0055] This embodiment provides a method for detecting methyl methacrylate in workplace air, the method comprising the following steps:

[0056] Step 100, using p-aminophenol impregnated activated carbon adsorption tube to collect workplace air to obtain the gas to be tested, wherein the workplace air includes methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid; the specific surface area of ​​the aminophenol impregnated activated carbon is 1200m 2 / g, the volume of the micropores of the aminophenol-impregnated activated carbon accounts for 90% of the total volume of the micropores and mesopores.

[0057] Step 200, placing the aminophenol-impregnated activated carbon adsorption tube in a solvent desorption bottle, and desorbing the gas to be tested using a mixed solution of dichloromethane and acetonitrile to obtain a liquid to be tested; specifically, the volume of the mixed solution of dichloromethane and acetonitrile added is 100% of the volume of the adsorption tube. The volume ratio of dichloromethane to acetonitrile is 10:1. Then, a preliminary sample treatment is performed through a C18 SPE column, and the liquid to be tested is eluted using an aqueous solution with a mass fraction of 5% methanol.

[0058] Step 300, using gas chromatography to separate the liquid to be tested, and using a flame ionization detector to detect, so as to obtain the content of methyl methacrylate in the workplace air. Specifically, the gas chromatography column in the gas chromatography is a 35% diphenyl-65% dimethylpolysiloxane column. The detection parameters of the gas chromatography are: initial temperature 55°C, then heating to 160°C at 22°C / min, and then heating to 190°C at 20°C / min; split ratio: 8:1; carrier gas (nitrogen) flow rate:

[0059] 1.8mL / min; vaporization chamber temperature: 250℃; detector temperature: 300℃; hydrogen flow rate: 32.0mL / min; air flow rate: 300.0mL / min.

[0060] Preparation and determination of standard series VA and MMA mixed standard stock solutions were used to prepare MMA standard series with mass concentrations of 93.6, 187.2, 374.4, 748.8, 1497.6, and 1872.0 mg / L, respectively, as shown in Table 1. Referring to the instrument operating conditions, the gas chromatograph was adjusted to the optimal determination state, and 1.0 μL was injected to determine each standard series, and the standard curve was drawn with the measured peak area versus the corresponding MMA level.

[0061] The sampling volume was converted into the standard sampling volume according to formula (1). The mass concentration of MMA in the air was calculated using formula (2).

[0062] V0=V×293 / (273+t)×P / 101.3 (1)

[0063] In the formula: V0—standard sampling volume, L; V—sampling volume, L; t—temperature of the sampling point, ℃; P—atmospheric pressure at the sampling point, kPa.

[0064] C=(C1+C2)v / V0 (2)

[0065] Where: C—mass concentration of MMA in air, mg / m 3 ; C1, C2—the mass concentration of MMA in the desorption liquid of the front and rear adsorption tubes (minus the sample blank), mg / L; v—the volume of the desorption liquid, mL; V0—the standard sampling volume, L.

[0066] Table 1

[0067]

[0068] Example 2

[0069] The difference between this embodiment and embodiment 1 is that the specific surface area of ​​the aminophenol-impregnated activated carbon is 1100 m 2 / g, the volume ratio of the micropores of the aminophenol-impregnated activated carbon to the total volume of the micropores and mesopores is 85%.

[0070] Example 3

[0071] The difference between this embodiment and embodiment 1 is that the specific surface area of ​​the aminophenol-impregnated activated carbon is 1300 m 2 / g, the volume of the micropores of the aminophenol-impregnated activated carbon accounts for 95% of the total volume of the micropores and mesopores.

[0072] Example 4

[0073] The difference between this embodiment and embodiment 1 is that the volume ratio of the mixed solution of dichloromethane and acetonitrile is different, and the volume ratio of dichloromethane to acetonitrile is 8:1.

[0074] Example 5

[0075] The difference between this embodiment and embodiment 1 is that the volume ratio of the mixed solution of dichloromethane and acetonitrile is different, and the volume ratio of dichloromethane to acetonitrile is 12:1.

[0076] Example 6

[0077] The present embodiment is different from the embodiment 1 in that the step of performing preliminary sample treatment by using a C18 SPE column and eluting the test solution by using an aqueous solution with a mass fraction of 5% methanol is not performed.

[0078] Example 7

[0079] The difference between this embodiment and embodiment 1 is that the detection parameters of the gas chromatography method in this embodiment are as follows: initial temperature 60°C, then heated to 180°C at 22°C / min, and then heated to 190°C at 20°C / min; split ratio: 10:1; carrier gas (nitrogen) flow rate: 2.0mL / min; vaporization chamber temperature: 260°C; detector temperature 300°C; hydrogen flow rate: 30.0mL / min; air flow rate: 300.0mL / min.

[0080] Comparative Example 1-2

[0081] The difference between this comparative example and Example 1 is that the adsorbent in the adsorption tube is different. Comparative Examples 1-2 use: ordinary activated carbon, hydroquinone-impregnated activated carbon in sequence.

[0082] Table 2 Experimental results.

[0083]

[0084] The detection and addition in Table 2 were carried out at room temperature, with 10 parallel experimental groups.

[0085] In summary, it is shown that using p-aminophenol-impregnated activated carbon to collect air to detect the amount of MMA added can retain MMA to the greatest extent for subsequent detection.

[0086] Comparative Example 3

[0087] The difference between this comparative example and Example 1 is that the mixed solution of dichloromethane and acetonitrile is replaced by carbon disulfide.

[0088] Comparative Example 4

[0089] The difference between this comparative example and Example 1 is that the mixed solution of dichloromethane and acetonitrile is replaced by dichloromethane.

[0090] Table 3 Desorption liquid selection experimental results

[0091]

[0092] Comparative Example 5

[0093] The difference between this comparative example and Example 1 is that the 35% diphenyl-65% dimethylpolysiloxane column is replaced by Carboxen-564 carbon molecular sieve.

[0094] Comparison of results

[0095] The gas chromatography detection was performed by the method of the embodiment and the comparative example, and the sample was injected 5 times repeatedly. The results were averaged. The detection results are shown in Table 1. The concentration of methyl methacrylate in the air of the embodiment and the comparative example was 100 mg / L respectively. The above air was resampled and detected by the method of the embodiment and the comparative example. When the method of the embodiment and the comparative example was used for independent detection 50 times, the difference of 1 mg / L from the accurate concentration of 100 mg / L was determined to be accurate. The accuracy results of the above method detection are shown in Table 4.

[0096] Table 4. Examples and Comparative Examples Detection of methyl methacrylate content in workplace air.

[0097]

[0098] As can be seen from Table 4, through the embodiments and comparative examples, it can be known that the method for detecting methyl methacrylate in the air can remove the interference of acids and esters in the air, improve the signal intensity of the methyl methacrylate product during gas chromatography detection, and avoid other substances or methyl methacrylate product content affecting the area of ​​the characteristic peak of the methyl methacrylate product in the chromatogram, thereby affecting the detection result.

[0099] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements.

[0100] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for detecting methyl methacrylate in workplace air, characterized in that: The method comprises: Using p-aminophenol-impregnated activated carbon adsorption tubes to collect workplace air to obtain a gas to be tested, wherein the workplace air includes methyl methacrylate, ethyl acetate, propyl acetate, methyl formate, ethyl formate, formic acid and butyric acid; The activated carbon adsorption tube impregnated with aminophenol is placed in a solvent desorption bottle, and the gas to be tested is desorbed by a mixed solution of dichloromethane and acetonitrile to obtain a liquid to be tested; The liquid to be tested is separated by gas chromatography and detected by flame ionization detector to obtain the content of methyl methacrylate in the air of the workplace.

2. The method according to claim 1, characterized in that The specific surface area of ​​the aminophenol-impregnated activated carbon is 1100-1300 m 2 / g, the volume of the micropores of the aminophenol-impregnated activated carbon accounts for 80%-95% of the total volume of the micropores and mesopores.

3. The method according to claim 1, characterized in that The volume of the mixed solution of dichloromethane and acetonitrile is 80% to 100% of the volume of the adsorption tube.

4. The method according to claim 1, characterized in that: The method further comprises: Prepare standard application solutions of methyl methacrylate of different concentrations respectively, perform gas chromatography detection on the standard application solutions of methyl methacrylate and blank control solutions, and draw a standard curve of methyl methacrylate; The methyl methacrylate standard curve uses the theoretical concentration value of methyl methacrylate in the methyl methacrylate standard application solution as the abscissa and the peak area as the ordinate.

5. The method according to claim 1, characterized in that The gas chromatography column in the gas chromatography method is a 35% diphenyl-65% dimethylpolysiloxane column.

6. The method according to claim 1, characterized in that The detection parameters of the gas chromatography method are as follows: initial temperature 55°C, then heated to 160°C at 22°C / min, and then heated to 190°C at 20°C / min; split ratio: 8:1; carrier gas (nitrogen) flow rate: 1.8mL / min; vaporization chamber temperature: 250°C; detector temperature 300°C; hydrogen flow: 32.0mL / min; air flow: 300.0mL / min.

7. The method according to claim 1, characterized in that The volume ratio of dichloromethane and acetonitrile is (6-12):

1.

8. The method according to claim 1, characterized in that The volume ratio of dichloromethane and acetonitrile is (8-10):

1.

9. The method according to claim 1, characterized in that: Before separating the liquid to be tested by gas chromatography, the method includes: performing preliminary sample treatment through a C18 SPE column and eluting with an aqueous solution with a mass fraction of 5% methanol.

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