A detection method for trace benzene in liquefied petroleum gas and its application

Abstract

The invention belongs to the technical field of liquefied petroleum gas detection, and specifically relates to a detection method and application of trace benzene in liquefied petroleum gas; in the liquefied petroleum gas of the invention, trace benzene is detected by a gas chromatograph, the liquefied petroleum gas is mixed with a solvent, the solvent is n-butanol and / or toluene, the benzene in the liquefied petroleum gas can be transferred to the organic solvent, and then the impurities are eliminated by comparing with the chromatographic peak of the blank solvent, and further a spiked test and a reference substance test are used, so as to accurately detect the content of benzene in the liquefied petroleum gas; the detection method of the invention can detect the content of trace risk substance benzene in the liquefied petroleum gas, is convenient for monitoring the risk component benzene of the propellant in cosmetics, reduces the addition of problematic liquefied petroleum gas as a propellant into cosmetics, and reduces the risk of excessive benzene in cosmetics.

Description

Technical Field

[0001] The invention belongs to the technical field of liquefied petroleum gas detection, and particularly relates to a detection method and application of trace benzene in liquefied petroleum gas. Technical Background

[0002] As more and more aerosol and foam products appear on the market, these products require the pressure of propellants to spray the contents in the form of mist. As an important component of these products, the requirements for propellants are becoming increasingly higher. Due to the high vapor pressure of liquefied petroleum gas (37.8°C), which can reach an average of 0.5-1.0 MPa, its chemical properties are stable, and it has high solubility and is non-corrosive. It can be used as an excellent propellant for aerosol and foam products. The propellants available for aerosol and foam products include fluorocarbons, propane, butane and isobutane. Among them, the foam produced by fluorocarbons is milky. Propane, butane and isobutane can make the foam of the product lighter. However, the use of propane, butane and isobutane has environmental pollution and safety issues (Bernd Ziolkowsky, Wu Jianguo. Aerosol foam agents in modern cosmetics [J]. Daily Chemicals Science, 1987(03):60-63.). Therefore, the quality control of propane or butane is particularly important. On the other hand, when propane, butane, and isobutane in liquefied petroleum gas are used as cosmetic propellants, the trace amounts of the risk substance benzene contained therein will migrate into the inner materials of the cosmetics, and may cause a type of carcinogen benzene to harm the users of the cosmetics.

[0003] However, there is currently no accurate detection method for trace benzene in liquefied petroleum gas, which makes it difficult to accurately control the benzene content in cosmetics. Patent document CN102323369A discloses a gas chromatography method for determining the benzene content in lean and rich oils. However, this patent detects crude benzene raw oil by mixing liquid lean and rich oils with hexadecane, rather than detecting trace benzene in propane or butane gas in liquefied petroleum gas. It is difficult to accurately determine the trace benzene content; CN103018369A discloses a method for determining the benzene content in liquefied petroleum gas by mixing liquid lean and rich oils with hexadecane. A method for detecting solvent residues in gas extraction products is intended to detect the residues of liquefied petroleum gas (LPG) as a subcritical extraction solvent in natural product extracts. The method involves passing n-butane, isobutane, and propane into an oil to be tested that does not contain such substances. After stirring in a constant-temperature water bath, the upper gas and lower liquid layers of the mixture are measured using gas chromatography, thereby analyzing the composition and content of the residual gas in the oil phase. However, this patent only detects the solvent and does not cover the detection of other components contained in the solvent, such as trace amounts of benzene. 104764795A discloses a method for analyzing liquefied natural gas. This method directly performs mass spectrometry and gas chromatography detection after gasification of natural gas. Ultimately, no benzene component in liquefied natural gas is detected. Therefore, this method has extremely low sensitivity for detecting trace amounts of benzene in liquefied petroleum gas or natural gas. In addition, Shi Huijuan proposed a method for detecting the benzene content in coal gas by gas chromatography (Shi Huijuan. Detection of benzene content in coal gas by gas chromatography [J]. China Petroleum and Chemical Standards and Quality, 2019(23):2.). This method is mainly aimed at washing The benzene content in the coal gas before and after the benzene tower is washed is detected by gas chromatography. This detection method adopts an internal standard to measure the gaseous sample of the coal gas, uses an HP-5 capillary column, and the carrier gas is high-purity helium (99.999%) with a flow rate of 20 mL / min, a valve open, a time of 0.5 min, a detector temperature of 250°C, an injection port temperature of 250°C, a heater temperature of 300°C, a hydrogen flow rate of 30 mL / min, an air flow rate of 300 mL / min, a tail blow volume of 25 mL / min, an injection volume of 20 L, and a split ratio of 50:1. Column heating program: initial temperature 80℃, retention 4min, the final detection P value of benzene content in coal gas is 0.218~0.222, P>0.05, the recovery rate after the tower is 94.40~98.33%, RSD is 1.41~2.94%. The accuracy of this method for determining the benzene content in coal gas after the benzene washing tower still needs to be improved; Li Haifang et al. studied the solid phase extraction sampling and gas chromatography-mass spectrometry detection of aromatic impurities in liquefied petroleum gas. They established graphitized carbon GCB as a solid adsorption sampling, which can capture aromatic impurities in liquefied petroleum gas and perform qualitative and quantitative analysis by GC-MS. The recovery rate of this gas chromatography-mass spectrometry method is 92.9~109.0%, and the detection limit is as low as 1.0~6.2μg / m 3The relative standard deviation is 0.6-5.8%, and the standard deviation is 0.8-8.25, which has good accuracy. However, this method uses solid-state adsorption and requires the use of graphitized carbon, which is very expensive. At the same time, the solid-state adsorption device requires the assembly of specific equipment, which is very difficult to operate and not easy to use for routine detection.

[0004] In summary, there is currently no efficient and accurate detection method for the quantitative detection of trace benzene in liquefied petroleum gas. It is urgent to develop an accurate quantitative detection method for trace benzene in liquefied petroleum gas to improve the safety of cosmetics and food. Summary of the Invention

[0005] In response to the above problems in the prior art, the present invention provides a method for detecting trace benzene in liquefied petroleum gas, which can perform efficient and accurate quantitative detection of trace benzene in liquefied petroleum gas in the fields of cosmetics and food.

[0006] The first aspect of the present invention provides a method for detecting trace amounts of benzene in liquefied petroleum gas, comprising the following steps:

[0007] S1. Preparation of test solution

[0008] Transfer the liquefied petroleum gas into a sample bottle containing the solvent, mix well, keep constant temperature, and shake;

[0009] S2. Preparation of reference solution

[0010] Accurately pipette a quantitative amount of the benzene reference standard solution in toluene, dilute it with toluene, and then make up to volume with toluene;

[0011] S3. Gas chromatography detection

[0012] Accurately aspirate the reference solution and the test solution respectively, inject them into the gas chromatograph through the injection port, perform the measurement under the set chromatographic conditions, record the chromatogram, and calculate the benzene content.

[0013] Furthermore, the mass ratio of liquefied petroleum gas to solvent in step S1 is 65-105:5-30.

[0014] Preferably, the mass ratio of the liquefied petroleum gas to the solvent is 80:20.

[0015] Furthermore, the solvent in step S1 is selected from one or a combination of methanol, ethanol, n-butanol, acetone, DMSO, acetonitrile, DMF, acetic acid, isopropanol, pyridine, tetrahydrofuran, methyl formate, methyl ethyl ketone, ethyl acetate, ether, isopropyl ether, n-butyl ether, diphenyl ether, dichloromethane, chloroform, dichloroethane, toluene, carbon tetrachloride, carbon disulfide, cyclohexane, hexane, and kerosene, preferably n-butanol and / or toluene.

[0016] Furthermore, the mass ratio of liquefied petroleum gas to solvent in step S1 is (65-105):(5-30), preferably 80:20.

[0017] Furthermore, the constant temperature in step S1 is 40°C to 55°C, preferably 50°C.

[0018] Furthermore, the constant temperature time in step S1 is not less than 12 hours.

[0019] Furthermore, in the chromatographic conditions set in step S3, the detector temperature is 200-250°C, and the injection port temperature is 200-250°C.

[0020] Furthermore, the pressure of the carrier gas nitrogen in the chromatographic conditions set in step S3 is 0.4-0.5 MPa.

[0021] Furthermore, the temperature program conditions in the chromatographic conditions set in step S3 are: initial temperature 60° C., maintained for 5 minutes, then increased to 150° C. at 20° C. / min, and maintained for 5 minutes.

[0022] The second aspect of the present invention provides the application of the cosmetics in the analysis of ingredients of dosage forms including but not limited to foams, sprays, etc.; the products include daily chemicals, pesticides, auto repair products, etc.

[0023] The third aspect of the present invention provides the application of the method for detecting trace amounts of benzene in liquefied petroleum gas in the analysis of propellant components.

[0024] The liquefied petroleum gas of the present invention can specifically be one or a combination of methane, ethane, ethylene, propane, isobutane, n-butane, neopentane, isopentane, n-pentane, hexane, methylcyclopentane, cyclohexane, heptane, methylcyclohexane and octane components.

[0025] The reagents and solutions used in the detection method of the present invention are as follows:

[0026] Methanol, ethanol, n-butanol, acetone, DMSO, acetonitrile, DMF, acetic acid, isopropanol, pyridine, tetrahydrofuran, methyl formate, methyl ethyl ketone, ethyl acetate, ether, isopropyl ether, n-butyl ether, diphenyl ether, dichloromethane, chloroform, dichloroethane, toluene, carbon tetrachloride, carbon disulfide, cyclohexane, hexane were all of chromatographic grade; water was ultrapure water.

[0027] The gas chromatography equipment used in the detection method of the present invention is a Beirui GC-8890 gas chromatograph, which adopts a hydrogen flame ionization detector; a capillary chromatographic column (Cat No: 1734-4AT.OV-1701 30m×0.32mm×0.5μm), a hydrogen generator, 99.999% bottled nitrogen, compressed air, and a 10μL microinjector.

[0028] The present invention mixes liquefied petroleum gas with an organic solvent, and can transfer benzene in the liquefied petroleum gas into the organic solvent. Since n-butanol (chromatographically pure) or toluene (chromatographically pure) has good solubility, n-butanol (chromatographically pure) and / or toluene (chromatographically pure) are used as solvents to transfer a trace amount of benzene in the propellant into the solvent. Then, impurities are eliminated by detecting blank n-butanol (chromatographically pure) and toluene (chromatographically pure) chromatographic peaks, and spiked tests and reference substance tests are performed to determine the retention time of the target peak benzene, thereby achieving accurate detection of the benzene content in the gas and facilitating monitoring of benzene, a risk component in the propellant.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention mixes liquefied petroleum gas with a solvent, which can maximize the migration of trace benzene in the liquefied petroleum gas into the solvent. The benzene content can be accurately measured by gas chromatography with good sensitivity, accuracy and reproducibility.

[0031] 2. The detection method of the present invention can accurately detect the content of trace benzene in liquefied petroleum gas, avoid the use of liquefied petroleum gas containing the risk substance "benzene" as a propellant in cosmetics, monitor the benzene content in cosmetics, and reduce the harm of cosmetics to the human body.

[0032] 3. The detection method of the present invention has a certain promoting effect on the industry standards for benzene content and detection methods in liquefied petroleum gas and the industry standards for benzene content and detection methods in cosmetics. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the gas chromatogram of the sample before treatment.

[0034] Figure 2 This is the gas chromatogram of benzene detection in sample batch number 20220510001.

[0035] Figure 3 This is the gas chromatogram of benzene detection in sample batch number 20220510002.

[0036] Figure 4 This is the gas chromatogram of benzene detection in sample batch number 20220510003. DETAILED DESCRIPTION

[0037] The experimental methods in the following examples of the present invention, where specific conditions are not specified, are generally carried out under conventional conditions or conditions recommended by the manufacturers. The various commonly used chemical reagents used in the examples are all commercially available products.

[0038] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific embodiments. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0040] Example 1

[0041] The specific steps for detecting trace amounts of benzene in pure butane from liquefied petroleum gas of the present invention are as follows:

[0042] S1. Preparation of test solution

[0043] Accurately weigh 80g of liquefied petroleum gas sample and transfer it to a sample bottle containing 20g of toluene. After mixing, place the sample bottle at a constant temperature of 50℃ for 12h, and shake it every 2h to prepare the test solution. Since the solvent is easily volatile, seal the sample bottle with sealing film after opening it and place it in an ice bath to reduce the evaporation of the solvent and take away the analyte benzene.

[0044] S2. Preparation of reference standard solution

[0045] Accurately pipette the benzene reference standard solution in toluene into a volumetric flask and dilute to volume with toluene to prepare a reference standard solution;

[0046] S3. Gas chromatography detection

[0047] Accurately pipette 1 μl of each reference standard solution and test solution and inject them into the gas chromatograph. The chromatographic conditions are:

[0048] A Beirui GC-8890 gas chromatograph was used with a hydrogen flame ionization detector; a capillary column (Cat No: 1734-4AT.OV-1701 30 m × 0.32 mm × 0.5 μm), a detector temperature of 200°C, an inlet temperature of 200°C, an air pressure of 0.05 MPa, a nitrogen pressure of 0.5 MPa, and a hydrogen pressure of 0.07 MPa.

[0049] The column temperature and heating program conditions were as follows: initial temperature 60 °C, hold for 5 min, then increase to 150 °C at 20 °C / min, hold for 5 min;

[0050] According to the above chromatographic conditions, the butane content in the three batches of liquefied petroleum gas samples (20220510001, 20220510002, and 20220510003) used in the present invention is ≥95%. The specific compositions of the three batches of liquefied petroleum gas samples are shown in Table 1 and the attached Figure 1 As shown:

[0051] Table 1: Composition of liquefied petroleum gas samples

[0052] Liquefied petroleum gas composition content <![CDATA[Methane CH4]]> 0.125％ <![CDATA[Ethane C2H6]]> 0.147％ <![CDATA[Propane C3H8]]> 3.036％ <![CDATA[Propylene C3H6]]> 0％ <![CDATA[Isobutane I-C4H 10 > 30.216％ <![CDATA[n-Butane N-C4H 10 > 66.476％ <![CDATA[Butene C4H8]]> 0％ <![CDATA[trans-2-butene T-2-C4H8]]> 0％ <![CDATA[Maleic C-2-C4H8]]> 0％ <![CDATA[1,3-Butadiene C4H6]]> 0％ <![CDATA[n-Pentane N-C5H 12 > 0％ Sulfur 0.36ppm moisture No free water

[0053] Attachment Figure 1 The peak time, concentration, and peak area in the gas chromatogram are shown in Table 2;

[0054] Table 2

[0055]

[0056]

[0057] The above detection method was used to measure the samples respectively and record the color spectrum. The standard curve (y=0+2.13458X; R 2 =0.99612), and the benzene content P (%) in the liquefied petroleum gas was calculated by the external standard method, and the calculation formula is shown in (1):

[0058]

[0059] The same batch of samples was measured 5 times, and the standard deviation of the results was no more than 5%. The arithmetic mean was taken as the measurement result.

[0060] Test Example 1: Detection Results, Accuracy, and Precision Test of Trace Benzene in Liquefied Petroleum Gas of the Present Invention

[0061] The three batches of liquefied petroleum gas samples in Example 1 were tested according to the detection method of Example 1. The accuracy and precision of the detection method were determined by injecting samples from the same batch five times. The benzene content in the liquefied petroleum gas was calculated according to formula (1) of Example 1. The results are shown in Table 3:

[0062] Table 3: Detection results of trace benzene in liquefied petroleum gas

[0063]

[0064] As shown in Table 3, the detection method of the present invention can detect trace benzene in three batches of liquefied petroleum gas samples, and the content of benzene in the liquefied petroleum gas is about 0.068-0.0803 ppm. The detection method of the present invention has good accuracy and precision, with SD of 0.0017-0.0037 and RSD of 2.521%-4.9%.

[0065] For details, please see the attached Figures 2-4 The gas chromatogram of the 20220510001 batch of samples is as follows: Figure 2 As shown, the retention time of benzene in the sample is 3.0217min; the gas chromatogram of the 20220510002 batch of samples is as follows Figure 3 As shown, the retention time of benzene in the sample is about 3.0633min. The gas chromatogram of the 20220510003 batch of samples is as follows: Figure 4 As shown, the retention time of benzene in the sample is about 3.0617 min.

[0066] Test Example 2: Test for detecting trace amounts of benzene in liquefied petroleum gas according to the present invention

[0067] The benzene content of the liquefied petroleum gas sample of batch number 20220510001 was tested (2 parallel tests) and spiked (6 parallel tests) according to the detection method in Example 1, and the recovery was calculated. The results are shown in Tables 4 and 5.

[0068] Table 4: Detection results of trace benzene content in liquefied petroleum gas

[0069]

[0070] Table 5: Results of spiked test for trace amounts of benzene in liquefied petroleum gas

[0071]

[0072] As can be seen from the above table, the recovery rate of the detection method of the present invention for the spiked detection of trace benzene in liquefied petroleum gas can reach 87.13% to 88.38%.

[0073] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for detecting trace amounts of benzene in liquefied petroleum gas, characterized in that: The detection method comprises the following steps: S1. Preparation of test solution Transfer the liquefied petroleum gas to a sample bottle containing a solvent, mix well, keep the temperature constant, and oscillate, wherein the solvent is n-butanol and / or toluene; S2. Preparation of reference solution Accurately pipette a quantitative amount of the benzene reference standard solution in toluene, dilute it with toluene, and then make up to volume with toluene; S3. Gas chromatography detection The test solution and the reference solution were accurately aspirated respectively, and injected into the gas chromatograph through the injection port, and the measurement was carried out under the set chromatographic conditions, wherein the detector temperature in the chromatographic conditions was 200-250°C, the injection port temperature was 200-250°C, the pressure of the carrier gas nitrogen was 0.4Mpa-0.5Mpa, and the temperature program conditions were: the initial temperature was 60°C, maintained for 5 minutes, then increased to 150°C at 20°C / min, maintained for 5 minutes, the chromatogram was recorded, and the benzene content was calculated; the detector adopted was a hydrogen flame ionization detector; the chromatographic column was a capillary chromatographic column: CatNo: 1734-4AT.OV-170130m×0.32mm×0.5μm.

2. The method for detecting trace benzene in liquefied petroleum gas according to claim 1, characterized in that: The mass ratio of liquefied petroleum gas to solvent in step S1 is 65-105:5-30.

3. The method for detecting trace amounts of benzene in liquefied petroleum gas according to claim 2, characterized in that: The mass ratio of liquefied petroleum gas to solvent in step S1 is 80:

20.

4. The method for detecting trace benzene in liquefied petroleum gas according to claim 1, characterized in that: In step S1, the constant temperature is 40°C to 55°C, and the constant temperature time is not less than 12 hours.

5. Application of the detection method according to any one of claims 1 to 4 in the analysis of the components of spray and foam products.

6. Application of the detection method according to any one of claims 1 to 4 in the analysis of propellant components.

Images