A method for detecting volatile organic compounds in waste gas from a fixed pollution source using a detection device

Abstract

The present invention discloses a device and method for detecting volatile organic compounds in waste gas from fixed pollution sources. After the vacuum bottle is contaminated, the bottle cap can be opened for cleaning, which is convenient, fast and cost-saving. At the same time, long-term sampling can be performed, and it is a reasonable sampling device worthy of selection. At the same time, the invention can detect 117 types of VOCs, adding an effective detection scheme for waste gas from fixed pollution sources with a wide variety of pollutants, high concentrations, and difficult to detect. It is of great significance to improve the monitoring system, strengthen environmental management, protect human health, and standardize the determination method of volatile organic compounds in waste gas from fixed pollution sources. At the same time, it also reduces safety hazards for enterprises and saves resources.

Description

Technical Field

[0001] The present invention relates to the field of volatile organic compound detection, and in particular to a device and method for detecting volatile organic compounds in waste gas from a fixed pollution source. Background Art

[0002] Volatile organic compounds have multiple definitions. The World Health Organization (WHO) defines it as a general term for organic compounds with a melting point below room temperature and a boiling point below 200-260°C under standard atmospheric pressure. VOCs are photochemically active and can cause photochemical smog under certain conditions, affecting human respiratory function and causing symptoms such as chest tightness, nausea, and fatigue. The many toxic, harmful, flammable, and explosive gases they contain can cause a variety of discomfort reactions in the human body, such as irritation to the skin and mucous membranes, anesthesia to the central nervous system, and even carcinogenicity. VOCs are important precursors of secondary organic aerosols (SOA), which can form haze pollution. They are also important precursors of near-ground O3 formation. The photochemical reaction of VOC-NOx will increase the ozone concentration in the atmospheric troposphere and cause a greenhouse effect.

[0003] Data quality is the core of emission reduction, and accurate detection of VOCs is a necessity for current environmental protection work. However, the existing methods for detecting volatile organic compounds in waste gas from fixed pollution sources are still not perfect, and they include few types of volatile organic compounds.

[0004] The collection and pretreatment of samples are crucial in the entire analysis process. If the collected samples cannot truly reflect the overall quality of the object being tested, or if a large amount of the components to be tested are lost during the pretreatment process, accurate analysis results cannot be obtained.

[0005] The sampling of gaseous pollutants is usually divided into direct sampling method and concentrated sampling method. The vacuum bottle sampling specified in the sample collection method listed in the industry standard HJ / T 397-2007 belongs to the direct sampling method. At present, the vacuum bottle technology is becoming more and more mature. It can not only collect large-volume samples, but also has relatively mature quality control measures for leak detection and cleaning of sampling containers. Compared with other sampling, it is easy to operate, has no discrimination effect on target compounds during sample collection, and can collect full-component samples. In addition to sample collection, the focus of VOCs detection technology is also on sample pretreatment. VOCs adopt different pretreatment methods according to the state of the sample. The pretreatment is complicated and has a great impact on the analysis results.

[0006] The target of determination in the environmental standard "Determination of Volatile Organic Compounds in Exhaust Gas from Stationary Pollution Sources by Solid Phase Adsorption-Thermal Desorption / Gas Chromatography-Mass Spectrometry" (HJ 734-2014) is the characteristic species of the electronics industry, which does not include the characteristic emission factors of most industries and the components specified in the emission standards, and cannot represent the actual situation of VOCs in the exhaust pipe. The environmental standard "Determination of VOCs in Exhaust Gas from Stationary Pollution Sources by Gas Chromatography-Mass Spectrometry" (DB 50 / T 679-2016) stipulates that inertized stainless steel tanks are used for sampling, and after being concentrated by a gas cold trap concentrator, they are analyzed by a gas chromatography-mass spectrometer. It is difficult to clean the sampling tank after collecting high-concentration exhaust gas. Because the cost of the sampling tank is very high, it costs a lot to use it to collect exhaust gas from fixed pollution sources. Similarly, if the concentration of volatile organic compounds in fixed pollution sources is too high, it is easy to cause instrument contamination and delay the normal detection process if it is not diluted. In the environmental standard "Sampling Air Bag Method for Volatile Organic Compounds in Exhaust Gas from Stationary Pollution Sources" (HJ 732-2014), the sampling device is an air bag, which can only collect instantaneous samples and is difficult to achieve long-term sampling. In addition, the existing standard cannot meet the needs of environmental supervision because it includes few VOCs emission factors that are the main characteristics of various VOCs emission industries. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention aims to provide a device and method for detecting volatile organic compounds in waste gas from fixed pollution sources.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A device for detecting volatile organic compounds in waste gas from a fixed pollution source comprises a vacuum bottle, a quantitative loop sampling device, a gas cold trap concentrator, a gas chromatograph-mass spectrometer and a data processing system which are connected in sequence; the vacuum bottle is used to collect waste gas from a fixed pollution source; the quantitative loop sampling device is used to perform quantitative loop sampling on the waste gas from the fixed pollution source in the vacuum bottle and inject it into a third-level cold trap of the gas cold trap concentrator for focusing; the gas cold trap concentrator uses a carrier gas to purge the focused waste gas from the fixed pollution source into the gas chromatograph-mass spectrometer; the gas chromatograph-mass spectrometer is used to perform gas chromatography separation on the waste gas from the fixed pollution source, wherein a hydrogen flame ionization detector is used to detect C2-C3 target compounds, a mass spectrometer is used to detect the remaining target compounds, and the detection data is sent to the data processing system for data analysis.

[0010] Furthermore, the volatile organic compounds include 117 kinds, including 57 kinds of volatile organic compounds in PAMS standard gas, 13 kinds of aldehyde and ketone compounds and 47 kinds of volatile organic compounds in TO-15 standard gas.

[0011] Furthermore, the volatile organic compounds include acetylene, ethylene, propylene, n-butene, butadiene, trans-2-butene, cis-2-butene, 1-pentene, 2-methyl-1,3-butadiene, trans-2-pentene, cis-2-pentene, 1-hexene, ethane, propane, isobutane, n-butane, isopentane, n-pentane, 2,2-dimethylbutane, cyclopentane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, methylcyclopentane, 2,4-dimethylpentane, cyclohexane, 2-methylhexane, 2,3-dimethylpentane, 3-methylhexane, 2,2,4- trimethylpentane, n-heptane, methylcyclohexane, 2,3,4-trimethylpentane, 2-methylheptane, 3-methylheptane, n-octane, n-nonane, decane, undecane, dodecane, benzene, toluene, ethylbenzene, m-, p-xylene, styrene, o-xylene, isopropylbenzene, benzaldehyde, n-propylbenzene, 1-ethyl-3-methylbenzene, 1-ethyl-4-methylbenzene, 1,3,5-trimethylbenzene, 1-ethyl-2-methylbenzene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, 1,4-diethylbenzene, 1,3-diethylbenzene, naphthalene, acetaldehyde, acrolein, acetone, propionaldehyde, isopropyl alcohol, methylbenzene acrolein, methyl tert-butyl ether, vinyl acetate, n-butyraldehyde, 2-butanone, ethyl acetate, tetrahydrofuran, crotonaldehyde, valeraldehyde, 1,4-dioxane, methyl methacrylate, 4-methyl-2-pentanone, 2-hexanone, hexanal, m-methylbenzaldehyde, formaldehyde, difluorodichloromethane, chloromethane, 1,1,2,2-tetrafluoro-1,2-dichloroethane, vinyl chloride, bromomethane, chloroethane, trichlorofluoromethane, 1,1-dichloroethylene, dichloromethane, 1,2,2-trifluoro-1,1,2-trichloroethane, trans-1,2-dichloroethylene, 1,1-dichloroethane, cis-1, 2-Dichloroethylene, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, carbon tetrachloride, 1,2-dichloropropane, bromodichloromethane, trichloroethylene, trans-1,3-dichloro-1-propene, cis-1,3-dichloropropene, 1,1,2-trichloroethane, dibromochloromethane, 1,2-dibromoethane, tetrachloroethylene, chlorobenzene, bromoform, 1,1,2,2-tetrachloroethane, chlorotoluene, 1,3-dichlorobenzene, p-dichlorobenzene, o-dichlorobenzene, 1,2,4-trichlorobenzene, 1,1,2,3,4,4-hexachloro-1,3-butadiene, carbon disulfide.

[0012] Furthermore, the quantitative loop sampling device has the functions of automatic quantitative sampling and automatic addition of internal standards, and can realize automatic sampling of samples in vacuum bottles.

[0013] Furthermore, the gas cold trap concentrator has the functions of automatic quantitative sampling and automatic addition of standard gas and internal standard gas, and has three-stage cold traps, and the third-stage cold trap can be cooled to -190°C.

[0014] Furthermore, in the gas chromatograph-mass spectrometer, the gas chromatograph can perform electronic pressure control on the carrier gas, and the column oven has a program temperature rising function; the mass spectrometer has a 70 eV electron bombardment ion source, and has the functions of NIST mass spectrum library, manual / automatic tuning, data acquisition, quantitative analysis and spectrum library retrieval.

[0015] The present invention also provides a method for utilizing the above detection device, the specific process of which is as follows:

[0016] S1. First, clean the vacuum bottle with a vacuum bottle cleaning device, use a cleaned vacuum bottle to collect the waste gas sample of the fixed pollution source, and then use another cleaned vacuum bottle to collect a bottle of internal standard gas;

[0017] S2. The waste gas sample from the fixed pollution source collected in the vacuum bottle is collected through the sample quantitative loop in the quantitative loop injection device, and the corresponding internal standard gas is collected through the internal standard quantitative loop in the quantitative loop injection device, and is focused through the third-stage cold trap of the gas cold trap concentrator;

[0018] S3. Use carrier gas to purge into gas chromatography-mass spectrometry for separation, use hydrogen flame ionization detector to detect C2-C3 target compounds, use mass spectrometry detector to detect other target compounds, and use data processing system to analyze sample data; C2-C3 target compounds are qualitatively determined by retention time and quantitatively determined by external standard method; other target compounds are qualitatively determined by retention time and mass spectrum comparison with standard substances, and quantitatively determined by internal standard method.

[0019] Further, in step S2, the quantitative loop injection device has 10 inlet and outlet positions, and positions 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 are arranged equidistantly in a circle; the operation modes of the quantitative loop injection device and the gas cold trap concentrator are divided into two types, namely, sampling mode and injection mode;

[0020] In sampling mode, the sample flows in through position 1, flows into the sample quantitative loop through position 2, fills the sample quantitative loop and passes through positions 6 and 5 in sequence to discharge excess sample; the internal standard gas enters from position 4, flows into the internal standard quantitative loop through position 3, fills the internal standard quantitative loop and passes through positions 9 and 10 in sequence to discharge excess gas; the carrier gas enters from position 8, and enters the third-level cold trap of the gas cold trap concentrator through position 7 for focusing;

[0021] In the injection mode, the sample enters from position 1 and enters the sample quantitative loop through position 2, and the excess sample is discharged through position 10; the internal standard gas is injected from position 4, and the excess gas is discharged through position 5; the carrier gas enters through position 8, enters the internal standard quantitative loop through position 9, pushes the internal standard gas into positions 3 and 2 in turn, then enters the sample quantitative loop and pushes the sample into positions 6 and 7 in turn, and finally enters the third-stage cold trap of the gas cold trap concentrator for focusing.

[0022] Furthermore, the specific process of drawing the standard curve required for the data processing system to perform analysis is as follows: referring to the process of injecting the exhaust gas sample from the fixed pollution source, 1 mL is drawn from the standard gas series of 0.10 μmol / mol, 0.40 μmol / mol, 0.80 μmol / mol, 1.2 μmol / mol, and 2.00 μmol / mol respectively into the quantitative loop of the quantitative loop injection device, and 0.25 mL of 1.00 μmol / mol internal standard gas is correspondingly drawn, and after being focused by the third-stage cold trap of the gas cold trap concentrator, it is entered into the gas chromatography-mass spectrometer for measurement, and the data processing system draws the standard curve;

[0023] According to the instrument reference conditions, the measurements were carried out from low concentration to high concentration;

[0024] Draw a standard curve with the concentration of C2-C3 target compounds as the horizontal axis and the chromatographic peak response value as the vertical axis;

[0025] For the remaining target compounds, the standard curves were drawn using the average relative response factor method, and the relative response factors were calculated according to formula (1). The average relative response factors of all standard concentration points of the target compounds were calculated according to formula (2);

[0026] (1)

[0027] Where: RRF i Indicates the standard series i Relative response factors of point target compounds; Ai Indicates the standard series i Point target compound quantitative ion response value; A ISi Indicates the standard series i The response value of the internal standard quantifier ion; ρ IS represents the mole fraction of the internal standard in the standard series, nmol / mol; ρ i Indicates the standard series i The mole fraction of the point target compound, nmol / mol;

[0028] Average relative response factors of target compounds Calculate according to formula (2):

[0029] (2)

[0030] Where: represents the average relative response factor of the target compound; RRF i Indicates the standard series i Relative response factors of point target compounds; n Indicates the standard series points;

[0031] The standard curve requires that the relative standard deviation of the relative response factor should be less than or equal to 30%, or the linear standard curve established by the least squares method should have a correlation coefficient greater than or equal to 0.990.

[0032] Furthermore, in step S3, the quantification of the target compounds C2-C3 is performed using an external standard method and is calculated according to formula (5):

[0033] (5)

[0034] Where: ρ x Indicates the concentration of the target compound in the sample, µg / m 3 ; ρ a represents the mole fraction of the target compound obtained from the standard curve, nmol / mol; M represents the molar mass of the target compound, g / mol; 22.4 represents the molar volume of the gas under standard conditions, L / mol; f Indicates the dilution multiple;

[0035] The quantification of the remaining target compounds was performed using the internal standard method and calculated according to formula (6):

[0036] (6)

[0037] Where: ρ x Indicates the concentration of the target compound in the sample, µg / m3; A X Indicates the response value of the quantitative ion of the target compound; A IS Indicates the response value of the internal standard quantification ion; ρ IS Indicates the mole fraction of the internal standard in the sample, nmol / mol; represents the average relative response factor of the target compound; Mrepresents the molar mass of the target compound, g / mol; 22.4 represents the molar volume of the gas under standard conditions, L / mol; f Indicates the dilution factor.

[0038] The beneficial effects of the present invention are:

[0039] The present invention provides a detection device and method for 117 volatile organic compounds in waste gas from fixed pollution sources by sampling with a vacuum bottle sampling quantitative loop. After the vacuum bottle is contaminated, the bottle cap can be opened for cleaning, which is convenient, fast and cost-saving. At the same time, long-term sampling can be performed, and it is a reasonable sampling device worthy of selection. At the same time, the present invention can detect 117 types of VOCs, adding an effective detection scheme for waste gas from fixed pollution sources with a wide variety of pollutants, high concentrations, and difficult to detect. It is of great significance to improve the monitoring system, strengthen environmental management, protect human health, and standardize the determination method of volatile organic compounds in waste gas from fixed pollution sources. At the same time, it also reduces safety hazards for enterprises and saves resources.

[0040] The present invention is applicable to the gas chromatography-mass spectrometry of 117 volatile organic compounds in the waste gas emitted by the stationary pollution sources in an organized and unorganized manner. The 117 volatile organic compounds include 57 volatile organic compounds in PAMS standard gas, 13 aldehyde and ketone compounds and 47 volatile organic compounds in TO-15 standard gas, which basically include the main characteristic VOCs emission factors of various VOCs emission industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a schematic diagram of device connection in Example 1 of the present invention;

[0042] Figure 2 This is a schematic diagram of the operation of the quantitative loop sampling device in the sampling mode in Example 2 of the present invention;

[0043] Figure 3 This is a schematic diagram of the operation of the quantitative loop injection device in the injection mode in Example 2 of the present invention;

[0044] Figure 4 GC-FID chromatograms of the five C2-C3 target compounds at a concentration of 2 ppm in Example 2 of the present invention;

[0045] Figure 5 This is the GC-MS total ion current diagram of the remaining 112 target compounds in Example 2 of the present invention at a concentration point of 2 ppm. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment. Example 1

[0047] This embodiment provides a device for detecting volatile organic compounds in waste gas from a fixed pollution source, such as Figure 1 As shown, it includes a vacuum bottle 1, a quantitative loop sampling device 2, a gas cold trap concentrator 3, a gas chromatograph-mass spectrometer 4 and a data processing system 5 which are connected in sequence; the vacuum bottle 1 is used to collect waste gas from fixed pollution sources, the quantitative loop sampling device 2 is used to perform quantitative loop collection on the waste gas from fixed pollution sources in the vacuum bottle 1 and inject it into the third-level cold trap of the gas cold trap concentrator 3 for focusing, and the gas cold trap concentrator uses a carrier gas to purge the focused waste gas from the fixed pollution sources into the gas chromatograph-mass spectrometer 4; the gas chromatograph-mass spectrometer 4 is used to perform gas chromatography separation on the waste gas from fixed pollution sources, wherein a hydrogen flame ionization detector is used to detect 5 C2-C3 target compounds (acetylene, ethylene, ethane, propylene, propane), and a mass spectrometer is used to detect the remaining target compounds, and the detection data is sent to the data processing system for data analysis.

[0048] In this embodiment, there are 117 target volatile organic compounds to be detected by the above detection device, as shown in Table 1, including 57 volatile organic compounds in PAMS standard gas, 13 aldehyde and ketone compounds and 47 volatile organic compounds in TO-15 standard gas.

[0049] Table 1 117 kinds of volatile organic compound mixed standard gases

[0050]

[0051] In this embodiment, the vacuum bottle 1 is a glass sampling jar with a deactivated inner wall, a volume of 1 L, and a pressure resistance value of >150 kPa. This embodiment uses an Entech Bottle-Vac™ 1L sampling bottle.

[0052] In this embodiment, the vacuum bottle 1 is cleaned by a vacuum bottle cleaning device, and the vacuum bottle cleaning device can draw the vacuum bottle to a vacuum state (<10 Pa). Preferably, the vacuum bottle cleaning device has heating, humidification, and pressurization cleaning functions. This embodiment uses the Entech 3108D fully automatic tank cleaning instrument. The tank cleaning instrument is an independent instrument for cleaning vacuum bottles.

[0053] It should be noted that the quantitative loop sampling device 2 has the functions of automatic quantitative sampling and automatic addition of internal standards, and can realize automatic sampling of samples in vacuum bottles. This embodiment uses Entech 7650-M automatic headspace sampler.

[0054] In this embodiment, the standard gas and the sample share the same sample dosing ring, which is a 1cc dosing ring, and the internal standard gas uses an internal standard dosing ring with a 0.25cc dosing ring. The size of the dosing ring determines the maximum injection volume of the sample. This embodiment uses Entech 1cc dosing ring and Entech 0.25cc dosing ring.

[0055] In this embodiment, the gas cold trap concentrator has the functions of automatic quantitative sampling and automatic addition of standard gas and internal standard gas, and has a three-stage cold trap (the third-stage cold trap can be cooled to -190 ° C). The gas cold trap concentrator and the gas chromatography-mass spectrometry connecting pipeline are both made of inert materials. This embodiment uses Entech 7200 atmospheric pre-concentrator.

[0056] In this embodiment, in the gas chromatograph-mass spectrometer, the gas chromatograph can perform electronic pressure control on the carrier gas, and the column oven has a program temperature rise function; the mass spectrometer has a 70 eV electron impact (EI) ion source, and has functions such as NIST mass spectrum library, manual / automatic tuning, data acquisition, quantitative analysis, and spectrum library retrieval. This embodiment uses an Agilent 8890 / 5977B gas chromatograph-mass spectrometer.

[0057] In the gas chromatography-mass spectrometer, the chromatographic column for GC-FID analysis of C2-C3 target compounds has a quartz capillary column of 30 m×320 µm×0.2 µm, and a stationary phase of styrene-divinylbenzene, or other equivalent capillary columns. This embodiment uses an Agilent HP-PLOT / Q+PT column (30 m×320 µm×20 µm).

[0058] In the gas chromatography-mass spectrometer, the chromatographic column for GC-MS analysis of the remaining target compounds is a quartz capillary column, 60 m×320 µm×1 µm, with a stationary phase of 100% dimethyl polysiloxane, or other equivalent capillary columns. In this embodiment, an Agilent 122-1063 DB-1 column (60 m×250 µm×1 µm) is used.

[0059] In this embodiment, when preparing the standard curve series, the standard working gas needs to be diluted, and the dilution multiple of the gas dilution device can be at least 100 times. In this embodiment, the ENTECH 4700 high-precision diluter is used. The diluter is an independent instrument used to dilute the standard gas into the standard working gas.

[0060] In this embodiment, the carrier gas is helium (purity ≥ 99.999%).

[0061] In this embodiment, liquid nitrogen is used for cooling in the M3 focusing process of the gas cold trap concentrator (7200 M3 focusing, focusing temperature: -190°C, temperature controlled by a low-temperature solenoid valve) and the initial process of the heating program of the gas chromatography-mass spectrometry (5°C maintained for 6 min, temperature controlled by a low-temperature solenoid valve). Example 2

[0062] This embodiment provides a method for utilizing the device described in Embodiment 1, and the specific process is as follows:

[0063] S1. First, clean the vacuum bottle with a vacuum bottle cleaning device, use a cleaned vacuum bottle to collect 2.00 μmol / mol of fixed pollution source exhaust gas sample, and then use another cleaned vacuum bottle to collect a bottle of 1.00 μmol / mol of internal standard gas.

[0064] In this embodiment, the internal standard gas used is a 1.00 μmol / mol 4-component internal standard gas, including bromochloromethane, 1,4-difluorobenzene, chlorobenzene-d5, and 4-bromofluorobenzene.

[0065] S2. 1 mL of the waste gas sample from the fixed pollution source collected in the vacuum bottle is collected through the sample quantitative loop in the quantitative loop injection device, and 0.25 mL of the corresponding internal standard gas is collected through the internal standard quantitative loop in the quantitative loop injection device, and focused through the third-level cold trap of the gas cold trap concentrator.

[0066] In this embodiment, the quantitative loop injection device has 10 inlet and outlet positions, and positions 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 are equidistantly arranged in a circle; the operation modes of the quantitative loop injection device and the gas cold trap concentrator are divided into two types, namely, sampling mode and injection mode, specifically:

[0067] like Figure 2 As shown, in the sampling mode, the sample flows in through position 1, flows into the sample quantitative loop 21 through position 2, fills the sample quantitative loop 21 and passes through positions 6 and 5 in sequence to discharge excess sample; the internal standard gas enters from position 4, flows into the internal standard quantitative loop 22 through position 3, fills the internal standard quantitative loop 22 and passes through positions 9 and 10 in sequence to discharge excess gas; the carrier gas enters from position 8 and enters the third-stage cold trap of the gas cold trap concentrator through position 7 for focusing.

[0068] like Figure 3As shown, in the injection mode, the sample enters from position 1 and enters the sample quantitative loop 21 through position 2, and the excess sample is discharged through position 10; the internal standard gas is injected from position 4, and the excess gas is discharged through position 5; the carrier gas enters through position 8, enters the internal standard quantitative loop 22 through position 9, pushes the internal standard gas to enter positions 3 and 2 in sequence, then enters the sample quantitative loop and pushes the sample to enter positions 6 and 7 in sequence, and finally enters the third-stage cold trap of the gas cold trap concentrator for focusing.

[0069] In this embodiment, the operating parameters of the quantitative loop injection device (7650M) and the gas cold trap concentrator (7200) are:

[0070] Temperature: Heater for 7650M holder: 80 °C; Heater for 7650M transfer line between holder and loop module: 80 °C; Heater for 7650M transfer line between loop module and 7200 M3: 100 °C; Heater for 7650M loop valve: 150 °C; Focusing with 7200 M3, focusing temperature: -190 °C.

[0071] Duration: internal standard flushing: 0.50 min; quantitative loop flushing delay: 0.10 min; quantitative loop flushing: 0.50 min; sample passing through the quantitative loop module to 7200 M3 and focusing: 3.00 min; injection into GC: 1.00 min; quantitative loop baking: 1.00 min.

[0072] S3, use carrier gas to purge into gas chromatography-mass spectrometry for separation, use hydrogen flame ionization detector to detect C2-C3 target compounds, and use mass spectrometry detector to detect other target compounds. C2-C3 target compounds (5 kinds) are qualitatively determined by retention time and quantitatively determined by external standard method; other target compounds (112 kinds) are qualitatively determined by comparison of retention time and mass spectrum with standard substances, and quantitatively determined by internal standard method.

[0073] The reference conditions for the GC-FID analysis of C2-C3 target compounds are:

[0074] Heating program: 5℃ for 6 min, then increase the temperature to 170℃ at a rate of 5℃ / min, and maintain for 5 min; then increase the temperature to 200℃ at a rate of 15℃ / min, and maintain for 10 min. Column flow rate: 1.0 ml / min; Inlet temperature: 100℃.

[0075] Detector temperature: 250°C.

[0076] The reference conditions for the GC-MS analysis of the remaining target compounds are:

[0077] Heating program: 5℃ for 6 min, then increase the temperature to 170℃ at a rate of 5℃ / min, and maintain for 5 min; then increase the temperature to 200℃ at a rate of 15℃ / min, and maintain for 10 min. Column flow rate: 1.0 ml / min; Inlet temperature: 100℃.

[0078] MS transfer line temperature: 250°C. Ion source temperature: 230°C. Scan mode: EI (full scan). Solvent delay time: 8.50 min. Scan range: Segmented scan: starting at 8.50 min, scan range: 25 amu ~ 260 amu. Ionization energy: 70 eV.

[0079] In this embodiment, the specific drawing process of the standard curve is as follows: referring to the process of sampling the waste gas sample from the fixed pollution source, 1 mL is extracted from the standard gas series of 0.10 μmol / mol, 0.40 μmol / mol, 0.80 μmol / mol, 1.2 μmol / mol, and 2.00 μmol / mol into the quantitative loop of the quantitative loop injection device, and 0.25 mL of 1.00 μmol / mol internal standard gas is correspondingly extracted, and after being focused by the third-level cold trap of the gas cold trap concentrator, it enters the gas chromatography-mass spectrometry instrument for measurement, and the data processing system draws the standard curve. According to the instrument reference conditions, the measurement is carried out from low concentration to high concentration in sequence (the standard curve should contain at least 5 concentration points, which does not include 0 point, which can be adjusted according to the actual sample situation). In this embodiment, the standard gas used is 117 kinds of volatile organic compound mixed standard gases, including 57 PAMS components, 13 aldehyde and ketone compound components, and 47 TO-15 components.

[0080] Draw a standard curve with the concentration of C2-C3 target compounds as the horizontal axis and the chromatographic peak response value as the vertical axis.

[0081] The average relative response factor method was used to draw standard curves for the remaining target compounds. The relative response factors were calculated according to formula (1). The average relative response factors of all standard concentration points of the target compounds were calculated according to formula (2).

[0082] (1)

[0083] Where: RRF i Indicates the standard series i Relative response factors of point target compounds; A i Indicates the standard series i Point target compound quantitative ion response value; A ISiIndicates the standard series i The response value of the internal standard quantifier ion; ρ IS represents the mole fraction of the internal standard in the standard series, nmol / mol; ρ i Indicates the standard series i The mole fraction of the target compound, nmol / mol.

[0084] Average relative response factors of target compounds Calculate according to formula (2):

[0085] (2)

[0086] Where: represents the average relative response factor of the target compound; RRF i Indicates the standard series i Relative response factors of point target compounds; n Indicates the standard series points.

[0087] The relative standard deviation (RSD) of the standard curve relative response factor should be less than or equal to 30%, or the correlation coefficient of the linear standard curve established by the least squares method should be greater than or equal to 0.990.

[0088] In this embodiment, the qualitative method of the target compound is:

[0089] The target compounds C2-C3 were qualitatively identified based on relative retention time; the remaining target compounds were qualitatively identified based on relative retention time and comparison of sample and standard mass spectra.

[0090] In this embodiment, the quantitative method of the target compound is:

[0091] The quantification of C2-C3 target compounds was performed using the external standard method and calculated according to formula (5):

[0092] (5)

[0093] Where: ρ X Indicates the concentration of the target compound in the sample, µg / m3; ρ a represents the mole fraction of the target compound obtained from the standard curve, nmol / mol; M represents the molar mass of the target compound, g / mol; 22.4 represents the molar volume of the gas under standard conditions (273.15 K, 101.325 kPa), L / mol; f Indicates the dilution factor.

[0094] The quantification of the remaining target compounds was performed using the internal standard method and calculated according to formula (6).

[0095] (6)

[0096] Where: ρ x Indicates the concentration of the target compound in the sample, µg / m3; A X Indicates the response value of the quantitative ion of the target compound; A IS Indicates the response value of the internal standard quantification ion; ρ IS Indicates the mole fraction of the internal standard in the sample, nmol / mol; represents the average relative response factor of the target compound; M represents the molar mass of the target compound, g / mol; 22.4 represents the molar volume of the gas under standard conditions (273.15 K, 101.325 kPa), L / mol; f Indicates the dilution factor.

[0097] The drawing of standard curve and data processing and analysis of samples are carried out in Figure 1 The data processing system shown is completed, and a spectrum and data analysis system runs in the data processing system.

[0098] In this example, the peak order of the target compound and the quantitative ions and auxiliary ions are shown in Table 2:

[0099] Table 2 Peak order, quantitative ions and auxiliary ions of target compounds

[0100]

[0101] Using the above method, under the specified chromatographic conditions, the GC-FID chromatograms of the five C2-C3 target compounds at a concentration of 2 ppm are shown in Figure 4 The GC-MS total ion currents of the remaining 112 target compounds at 2 ppm concentration are shown in Figure 5 .

[0102] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for detecting volatile organic compounds in waste gas from a fixed pollution source using a detection device, the detection device comprising a vacuum bottle, a quantitative loop injection device, a gas cold trap concentrator, a gas chromatograph-mass spectrometer and a data processing system connected in sequence; the vacuum bottle is used to collect waste gas from a fixed pollution source, the quantitative loop injection device is used to perform quantitative loop collection on the waste gas from the fixed pollution source in the vacuum bottle and inject it into the third-level cold trap of the gas cold trap concentrator for focusing, and the gas cold trap concentrator uses a carrier gas to purge the focused waste gas from the fixed pollution source into the gas chromatograph-mass spectrometer; Features: S1. First, clean the vacuum bottle with a vacuum bottle cleaning device, use a cleaned vacuum bottle to collect the waste gas sample of the fixed pollution source, and then use another cleaned vacuum bottle to collect a bottle of internal standard gas; S2. The waste gas sample from the fixed pollution source collected in the vacuum bottle is collected through the sample quantitative loop in the quantitative loop injection device, and the corresponding internal standard gas is collected through the internal standard quantitative loop in the quantitative loop injection device, and is focused through the third-stage cold trap of the gas cold trap concentrator; S3, using carrier gas to purge into a gas chromatography-mass spectrometer for separation, using a hydrogen flame ionization detector to detect C2-C3 target compounds, using a mass spectrometer to detect the remaining target compounds, and using a data processing system to analyze the sample data; The target compounds C2-C3 were identified qualitatively by retention time and quantified by external standard method; The remaining target compounds were qualitatively identified by comparing retention time and mass spectra with standard substances and quantitatively identified by internal standard method; In step S2, the quantitative loop injection device has 10 inlet and outlet positions, and positions 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 are arranged equidistantly in a circle; the operation modes of the quantitative loop injection device and the gas cold trap concentrator are divided into two types, namely, sampling mode and injection mode; In sampling mode, the sample flows in through position 1, flows into the sample quantitative loop through position 2, fills the sample quantitative loop and passes through positions 6 and 5 in sequence to discharge excess sample; the internal standard gas enters from position 4, flows into the internal standard quantitative loop through position 3, fills the internal standard quantitative loop and passes through positions 9 and 10 in sequence to discharge excess gas; the carrier gas enters from position 8, and enters the third-level cold trap of the gas cold trap concentrator through position 7 for focusing; In the injection mode, the sample enters from position 1 and enters the sample quantitative loop through position 2, and the excess sample is discharged through position 10; the internal standard gas is injected from position 4, and the excess gas is discharged through position 5; the carrier gas enters through position 8, enters the internal standard quantitative loop through position 9, pushes the internal standard gas into positions 3 and 2 in turn, then enters the sample quantitative loop and pushes the sample into positions 6 and 7 in turn, and finally enters the third-stage cold trap of the gas cold trap concentrator for focusing.

2. The method according to claim 1, characterized in that The volatile organic compounds include 117 kinds, including 57 kinds of volatile organic compounds in PAMS standard gas, 13 kinds of aldehyde and ketone compounds and 47 kinds of volatile organic compounds in TO-15 standard gas.

3. The method according to claim 2, characterized in that The volatile organic compounds include acetylene, ethylene, propylene, n-butene, butadiene, trans-2-butene, cis-2-butene, 1-pentene, 2-methyl-1,3-butadiene, trans-2-pentene, cis-2-pentene, 1-hexene, ethane, propane, isobutane, n-butane, isopentane, n-pentane, 2,2-dimethylbutane, cyclopentane, 2,3-dimethylbutane, 2-methylpentane, 3-methylpentane, n-hexane, methylcyclopentane, 2,4-dimethylpentane, cyclohexane, 2-methylhexane, 2,3-dimethylpentane, 3-methylhexane, 2,2,4-trimethylpentane alkane, n-heptane, methylcyclohexane, 2,3,4-trimethylpentane, 2-methylheptane, 3-methylheptane, n-octane, n-nonane, decane, undecane, dodecane, benzene, toluene, ethylbenzene, m-, p-xylene, styrene, o-xylene, isopropylbenzene, benzaldehyde, n-propylbenzene, 1-ethyl-3-methylbenzene, 1-ethyl-4-methylbenzene, 1,3,5-trimethylbenzene, 1-ethyl-2-methylbenzene, 1,2,4-trimethylbenzene, 1,2,3-trimethylbenzene, 1,4-diethylbenzene, 1,3-diethylbenzene, naphthalene, acetaldehyde, acrolein, acetone, propionaldehyde, isopropyl alcohol, methacrylic acid Aldehyde, methyl tert-butyl ether, vinyl acetate, n-butyraldehyde, 2-butanone, ethyl acetate, tetrahydrofuran, crotonaldehyde, valeraldehyde, 1,4-dioxane, methyl methacrylate, 4-methyl-2-pentanone, 2-hexanone, hexanal, m-methylbenzaldehyde, formaldehyde, difluorodichloromethane, chloromethane, 1,1,2,2-tetrafluoro-1,2-dichloroethane, vinyl chloride, bromomethane, chloroethane, chlorotrifluoromethane, 1,1-dichloroethylene, dichloromethane, 1,2,2-trifluoro-1,1,2-trichloroethane, trans-1,2-dichloroethylene, 1,1-dichloroethane, cis-1,2- Dichloroethylene, chloroform, 1,2-dichloroethane, 1,1,1-trichloroethane, carbon tetrachloride, 1,2-dichloropropane, bromodichloromethane, trichloroethylene, trans-1,3-dichloro-1-propylene, cis-1,3-dichloropropylene, 1,1,2-trichloroethane, dibromochloromethane, 1,2-dibromoethane, tetrachloroethylene, chlorobenzene, bromoform, 1,1,2,2-tetrachloroethane, chlorotoluene, 1,3-dichlorobenzene, p-dichlorobenzene, o-dichlorobenzene, 1,2,4-trichlorobenzene, 1,1,2,3,4,4-hexachloro-1,3-butadiene, carbon disulfide.

4. The method according to claim 1, characterized in that: The quantitative loop injection device has the functions of automatic quantitative sampling and automatic addition of internal standards, and can realize automatic injection of samples in vacuum bottles.

5. The method according to claim 1, characterized in that The gas cold trap concentrator has the functions of automatic quantitative sampling and automatic addition of standard gas and internal standard gas. It has three-stage cold trap, and the third stage cold trap can be cooled to -190 ℃.

6. The method according to claim 1, characterized in that In the gas chromatography-mass spectrometry instrument, the gas chromatograph can perform electronic pressure control on the carrier gas, and the column oven has a program temperature rising function; the mass spectrometer has a 70 eV electron bombardment ion source, and has the functions of NIST mass spectrum library, manual / automatic tuning, data acquisition, quantitative analysis and spectrum library retrieval.

7. The method according to claim 1, characterized in that The specific process of drawing the standard curve required for the data processing system to perform analysis is as follows: referring to the process of injecting the exhaust gas sample from the fixed pollution source, 1 mL is drawn from the standard gas series of 0.10 μmol / mol, 0.40 μmol / mol, 0.80 μmol / mol, 1.2 μmol / mol, and 2.00 μmol / mol into the quantitative loop of the quantitative loop injection device, and 0.25 mL of 1.00 μmol / mol internal standard gas is correspondingly drawn, and after being focused by the third-stage cold trap of the gas cold trap concentrator, it is entered into the gas chromatography-mass spectrometry instrument for measurement, and the data processing system draws the standard curve; According to the instrument reference conditions, the measurements were carried out from low concentration to high concentration; Draw a standard curve with the concentration of C2-C3 target compounds as the horizontal axis and the chromatographic peak response value as the vertical axis; For the remaining target compounds, the standard curves were drawn using the average relative response factor method, and the relative response factors were calculated according to formula (1). The average relative response factors of all standard concentration points of the target compounds were calculated according to formula (2); (1) Where: RRF i Indicates the standard series i Relative response factors of point target compounds; A i Indicates the standard series i Point target compound quantitative ion response value; A ISi Indicates the standard series i The response value of the internal standard quantifier ion; ρ IS represents the mole fraction of the internal standard in the standard series, nmol / mol; ρ i Indicates the standard series i The mole fraction of the point target compound, nmol / mol; Average relative response factors of target compounds Calculate according to formula (2): (2) Where: represents the average relative response factor of the target compound; RRF i Indicates the standard series i Relative response factors of point target compounds; n Indicates the standard series points; The standard curve requires that the relative standard deviation of the relative response factor is less than or equal to 30%, or the linear standard curve established by the least squares method has a correlation coefficient greater than or equal to 0.

990.

8. The method according to claim 1, characterized in that In step S3, the quantification of the target compounds C2-C3 is performed using the external standard method, and is calculated according to formula (5): (5) Where: ρ x Indicates the concentration of the target compound in the sample, µg / m 3 ; ρ a represents the mole fraction of the target compound obtained from the standard curve, nmol / mol; M Indicates the molar mass of the target compound, g / mol; 22.4 represents the molar volume of gas under standard conditions, L / mol; f Indicates the dilution multiple; The quantification of the remaining target compounds was performed using the internal standard method and calculated according to formula (6): (6) Where: ρ x Indicates the concentration of the target compound in the sample, µg / m3; A X Indicates the response value of the quantitative ion of the target compound; A IS Indicates the response value of the internal standard quantification ion; ρ IS Indicates the mole fraction of the internal standard in the sample, nmol / mol; represents the average relative response factor of the target compound; M Indicates the molar mass of the target compound, g / mol; 22.4 represents the molar volume of gas under standard conditions, L / mol; f Indicates the dilution factor.

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