High-flow membrane sampling device and method for realizing high-sensitivity mass spectrometry analysis of gases

Abstract

The present invention discloses a large-flow membrane sampling device and a method for using the device for realizing high-sensitivity mass spectrometry analysis of gas, relates to the technical field of mass spectrometer sampling analysis, solves the problem of low membrane enrichment efficiency of existing membrane sampling devices, and improves the analysis sensitivity of the instrument. The specific scheme is as follows: it includes a gas supply mechanism, a membrane enrichment mechanism and a mass spectrometer connected in sequence, two gas outlet joints and one gas inlet joint are provided on the membrane enrichment mechanism, the three joints are arranged in an equilateral triangle and the center of the equilateral triangle coincides with the center of the membrane enrichment mechanism, an enrichment membrane is provided in the membrane enrichment mechanism, the enrichment membrane divides the inner chamber of the membrane enrichment mechanism into an independent sample flow chamber and a sample enrichment chamber, and the sample enrichment chamber is connected to the mass spectrometer through a capillary.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometer sample injection analysis, and in particular to a large-flow membrane sample injection device for realizing high-sensitivity mass spectrometry analysis of gases and a use method thereof. Background Art

[0002] Mass spectrometry is an analytical instrument used for chemical component identification and plays an irreplaceable role in environmental monitoring. Currently, the main sampling methods for online mass spectrometry analysis are capillary injection and membrane injection. Capillary injection is relatively simple, and the injection volume can be controlled based on the length and inner diameter of the capillary. However, this injection method is only suitable when there are few interfering substances in the matrix and the concentration level of the sample molecules is above the detection limit of the mass spectrometer. Membrane injection is a selective injection method that does not require sample pretreatment, has a simple structure, and has the ability to enrich the sample. It is widely used in the detection of volatile organic compounds (VOCs) in the environment.

[0003] The diffusion of VOCs in membranes is based on the dissolution-diffusion-desorption principle. First, when a VOC sample contacts the membrane surface, the organic components in the sample dissolve in varying proportions based on their solubility. Subsequently, the pressure differential across the membrane causes the dissolved organic components to migrate from one side of the membrane to the other, with components with greater solubility typically having a greater diffusion rate. Finally, the organic components that reach the other side of the membrane desorb and vaporize under low pressure.

[0004] When the VOCs sample is in a steady state in the membrane, the transport mechanism of the membrane can be described by Fick's first law:

[0005] I ss =ADS(P s / L)

[0006] Where, I ss is the permeation rate of the sample in the membrane (mol / s), A represents the effective surface area of ​​the membrane (cm 2 ), D represents the diffusion coefficient of the sample in the membrane (cm 2 / s), S is the solubility coefficient of the sample in the membrane (mol / Pa cm 3 )), Ps is the pressure on the sample side of the membrane (Pa), L is the thickness of the membrane (cm), when the thickness of the membrane is constant, the permeation rate of the sample in the membrane is only related to the area of ​​the membrane.

[0007] The existing membrane sampling devices for online gas mass spectrometry all adopt a design with one sampling passage and one sampling passage. When the membrane area is increased to improve sensitivity, the large flow rate of sample always flows along the narrow space from the sampling port to the sampling port on the membrane surface. The sample gas cannot flow evenly across the large membrane surface. The actual utilization area of ​​the membrane is limited and the dead volume is large, which greatly reduces the enrichment efficiency of the membrane and thus reduces the sensitivity of the mass spectrometer. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a large-flow membrane sampling device and a method of use for realizing high-sensitivity mass spectrometry analysis of gases. The membrane enrichment mechanism is provided with two gas outlet connectors and one gas inlet connector. The three connectors are arranged in an equilateral triangle. The sample forms two flow channels in the sample flow chamber and flows more evenly on the surface of the enrichment membrane, thereby increasing the effective enrichment area of ​​the enrichment membrane and the flow rate of the sample on the surface of the enrichment membrane, effectively reducing the dead volume of the sample flow, and solving the problem of low membrane enrichment efficiency of the existing membrane sampling device.

[0009] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0010] In the first aspect, the present invention provides a large-flow membrane sampling device for realizing high-sensitivity mass spectrometry analysis of gas, comprising a gas supply mechanism, a membrane enrichment mechanism and a mass spectrometer connected in sequence, the membrane enrichment mechanism being provided with two gas outlet connectors and one gas inlet connector, the three connectors being arranged in an equilateral triangle and the center of the equilateral triangle coinciding with the center of the membrane enrichment mechanism, an enrichment membrane being provided in the membrane enrichment mechanism, the enrichment membrane dividing the inner chamber of the membrane enrichment mechanism into an independent sample flow chamber and a sample enrichment chamber, the sample enrichment chamber being connected to the mass spectrometer via a capillary.

[0011] As a further implementation method, the gas supply mechanism includes a first gas supply unit for providing sample standard gas and a second gas supply unit for providing purge gas. The first gas supply unit and the second gas supply unit are connected to the gas inlet connector through a gas supply pipe. The gas supply pipe is provided with a flow meter and a first switch valve for controlling the first gas supply unit and a second switch valve for controlling the second gas supply unit.

[0012] As a further implementation, the air outlet connector is connected to the exhaust gas collecting unit via an air outlet pipe.

[0013] As a further implementation method, the membrane enrichment mechanism is composed of a cover plate, an enrichment membrane, a membrane support assembly, a membrane fixing part, and a capillary fixing part arranged in sequence. The air inlet connector and the air outlet connector are installed on the cover plate, the membrane support assembly is located in the membrane fixing part, and the cover plate, membrane fixing part and capillary fixing part are fixed by screws.

[0014] As a further implementation, a boss is provided at the center of the capillary fixture, and a thread is processed on the outer surface of the boss for connection with and sealing the surface of the ionization source cavity of the mass spectrometer.

[0015] As a further implementation, sealing rings are provided between the cover plate, the membrane fixing member and the capillary fixing member, and between the capillary fixing member and the capillary.

[0016] As a further implementation, the membrane support assembly is composed of a nickel metal mesh, a stainless steel metal mesh and an annular gasket arranged in sequence, and the nickel metal mesh is fitted to the central enrichment portion of the enrichment membrane.

[0017] As a further implementation, the area of ​​the enrichment membrane is 500 to 1500 mm 2 .

[0018] As a further implementation, the air inlet connector and the air outlet connector are both quick-connect connector structures, and the ratio of the membrane area of ​​the enrichment membrane to the distance between adjacent connectors is 47.4.

[0019] In a second aspect, the present invention provides a method for using a high-flow membrane sampling device for achieving high-sensitivity mass spectrometry analysis of gases, as follows:

[0020] When analyzing a sample, the first switch valve is opened and the second switch valve is closed. The sample standard gas enters the sample flow chamber through the air inlet pipe and the excess sample standard gas is discharged into the waste gas collection unit through the air outlet pipe. The sample standard gas is enriched on the surface of the enrichment membrane and enters the sample enrichment chamber on the other side of the membrane under the action of the pressure difference, and enters the mass spectrometer through the capillary for analysis;

[0021] When the analysis is finished, the first on-off valve is closed and the second on-off valve is opened to provide a purge gas to the membrane enrichment mechanism for flushing.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) The membrane enrichment mechanism of the present invention is provided with two gas outlet connectors and one gas inlet connector, and the three connectors are arranged in an equilateral triangle. The sample forms two flow channels in the sample flow chamber and flows more evenly on the surface of the enrichment membrane, thereby increasing the effective enrichment area of ​​the enrichment membrane and the flow rate of the sample on the surface of the enrichment membrane, effectively reducing the dead volume of the sample flow, and can be used for direct sampling and analysis of large membrane area and high flow rate gas without sample pretreatment, effectively improving the enrichment efficiency of large area membrane sampling, and significantly improving the instrument analysis sensitivity when used in conjunction with a mass spectrometer.

[0024] (2) The enrichment membrane of the present invention is supported by a membrane support assembly, which can effectively prevent the enrichment membrane from being torn under a large pressure difference. Among them, the nickel metal mesh is used to lift the enrichment membrane and increase the effective enrichment area of ​​the enrichment membrane. The stainless steel metal mesh and the annular gasket are used for the rigid support of the enrichment membrane.

[0025] (3) The introduction of the purge gas of the present invention can flush the air inlet pipe and the enrichment membrane after the analysis is completed, thereby avoiding the adsorption of organic matter on the enrichment membrane and accelerating the flushing of residual samples, effectively reducing the memory effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0027] Figure 1 Schematic diagram of the structure of a high-flow membrane sampling device for realizing high-sensitivity mass spectrometry analysis of gases according to one or more embodiments of the present invention;

[0028] Figure 2 is a schematic diagram of a three-dimensional structure of a membrane enrichment mechanism according to one or more embodiments of the present invention;

[0029] Figure 3 is a schematic diagram of an exploded structure of a membrane enrichment mechanism according to one or more embodiments of the present invention;

[0030] Figures 4(a), 4(b), 4(c), 4(d), 4(e), and 4(f) are schematic diagrams of sample flow paths when the sample inlet and outlet positions of the membrane sampling device are different;

[0031] Figure 5 is a comparative spectrum of ethane signals obtained by increasing the membrane area of ​​the membrane sampling device according to one or more embodiments of the present invention;

[0032] Figure 6 is a comparative spectrum of ethane signals obtained by increasing the ionization source pressure of the membrane sampling device according to one or more embodiments of the present invention;

[0033] Figure 7 Spectra comparing the signals of benzene, toluene, and xylene obtained by direct capillary injection and a membrane injection device according to one or more embodiments of the present invention;

[0034] Figure 8 Spectra comparing ethane signals obtained using a membrane sampling device according to one or more embodiments of the present invention and a conventional one-in-one-out membrane sampling device;

[0035] In the figure: the distances or sizes between parts are exaggerated to show the positions of the parts, and the diagram is for illustration only;

[0036] Among them, 1. gas supply mechanism; 2. membrane enrichment mechanism; 3. first gas supply unit; 4. first switch valve; 5. second switch valve; 6. second gas supply unit; 7. air inlet pipe; 8. flow meter; 9. exhaust gas collection unit; 10. air outlet pipe; 11. quick connector; 12. cover plate; 13. sample flow chamber; 14. enrichment membrane; 15. sample enrichment chamber; 16. nickel metal mesh; 17. stainless steel metal mesh; 18. ring gasket; 19. membrane fixing part; 20. capillary fixing part; 21. first sealing ring; 22. second sealing ring; 23. boss; 24. capillary; 25. mass spectrometer. DETAILED DESCRIPTION

[0037] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0038] As introduced in the background technology, the existing membrane sampling devices for online gas mass spectrometry analysis all adopt a design of one sampling passage and one sampling passage. When the membrane area is increased to improve sensitivity, the large flow rate of sample always flows along the narrow space from the sampling port to the sampling port on the membrane surface. The sampling gas cannot flow evenly on the large area of ​​the membrane surface. The actual utilization area of ​​the membrane is limited and the dead volume is large, which greatly reduces the enrichment efficiency of the membrane and thus reduces the sensitivity of the mass spectrometer. In order to solve the above technical problems, the present invention proposes a large flow rate membrane sampling device and a method of use for realizing high-sensitivity mass spectrometry analysis of gas.

[0039] Example 1

[0040] In a typical embodiment of the present invention, Figures 1-8 As shown, a large-flow membrane sampling device for realizing high-sensitivity mass spectrometry analysis of gas is proposed, comprising a gas supply mechanism 1, a membrane enrichment mechanism 2 and a mass spectrometer 25 connected in sequence, which can separate and enrich volatile organic compounds in the environment, and can be connected to the mass spectrometer 25 to improve the detection sensitivity.

[0041] The gas supply mechanism 1 is mainly used for supplying and discharging sample gas and purge gas. The gas supply mechanism 1 consists of a first gas supply unit 3 , a second gas supply unit 6 , an air inlet pipe 7 , an exhaust gas collecting unit 9 and an air outlet pipe 10 .

[0042] Among them, the first gas supply unit 3 is used to supply the sample standard gas, and the second gas supply unit 6 is used to supply the purge gas. The first gas supply unit 3 and the second gas supply unit 6 are connected to an inlet joint on the membrane enrichment mechanism 2 through an inlet pipe 7 to supply the sample standard gas to the membrane enrichment mechanism 2;

[0043] The membrane enrichment mechanism 2 is further provided with two gas outlet connectors, which are respectively connected to the waste gas collection unit 9 through the gas outlet pipe 10 for collecting and treating the waste gas.

[0044] Two switch valves are installed on the air intake pipe 7, namely the first switch valve 4 and the second switch valve 5. The first switch valve 4 is located on the branch where the first air supply unit 3 is installed, and the second switch valve 5 is located on the branch where the second air supply unit 6 is installed, so as to control the on and off of the corresponding branch.

[0045] A flow meter 8 is also installed on the air intake pipe 7 for online detection of the gas flow in the air intake pipe 7 .

[0046] The air inlet pipe 7 and the air outlet pipe 10 are both polytetrafluoroethylene pipes. The outer diameter of the air inlet pipe 7 and the air outlet pipe 10 is 4 mm, and the inner diameter is 2-3 mm. The purge gas is nitrogen or zero air. The flow rate of the purge gas and the sample standard gas is 500-2000 mL / min.

[0047] The membrane enrichment mechanism 2 is composed of a cover plate 12 , an enrichment membrane 14 , a membrane support assembly, a membrane fixing member 19 , a capillary fixing member 20 , and a capillary 24 .

[0048] Among them, three quick-plug connectors 11 are threadedly installed on the cover plate 12, which are respectively used to connect to the air inlet pipe 7 and the air outlet pipe 10. The three quick-plug connectors 11 are arranged in an equilateral triangle, that is, the three quick-plug connectors 11 are respectively located at a corner of the equilateral triangle, and the center of the equilateral triangle enclosed by the three quick-plug connectors 11 coincides with the center of the cover plate 12. The distance between two adjacent quick-plug connectors 11 is 26.5 mm, that is, the side length of the equilateral triangle is 26.5 mm.

[0049] This embodiment optimizes the design of the sample inlet and outlet on the cover plate 12 (i.e., the position of the quick-connect connector 11), mainly optimizing the number and position of the sample inlet and outlet. The optimized positions of the different sample ports are as follows: Figure 4(a) 、 one Two inlets and two outlets (one inlet and two outlets), the three sample ports are equidistant with a spacing of 26.5 mm; Figure 4(b), two inlets and one outlet, the three sample ports are equidistant with a spacing of 26.5 mm; Figure 4(c) 、 one The three sample ports are coaxially placed, with one inlet and two outlets. The sample inlet is located in the center of the cover plate 12, and the distance from the other two sample ports is 16 mm. Figure 4(d) 、 one There are two inlets and outlets, and the sample ports are equidistant with a spacing of 15 mm; Figure 4(e) 、 one Inlet and outlet, the sample ports are coaxially placed with a spacing of 26.5 mm; Figure 4(f) 、 oneThe inlet and outlet ports are coaxially placed with a spacing of 13 mm.

[0050] The simulation results are shown in Figure 4. The flow rates of the samples on the membrane surface are Figure 4(a): 0.40 m / s; Figure 4(b): 0.29 m / s; Figure 4(c): 0.19 m / s; Figure 4(d): 0.21 m / s; Figure 4(e): 0.25 m / s; Figure 4(f): 0.23 m / s. It can be seen from the above results that the flow rate of the sample on the membrane surface obtained by model a is the highest. At the same time, model a also maximizes the effective utilization area of ​​the membrane. Specifically, when the distance between adjacent joints and the membrane area of ​​the enrichment membrane 14 have a proportional relationship of membrane area / adjacent joint distance = 47.4, the flow rate of the sample on the membrane surface is the highest, and the effective utilization area of ​​the membrane is also the largest. The unit of membrane area is mm 2 , the unit of import and export distance is mm.

[0051] The enrichment membrane 14 is located between the cover plate 12 and the membrane fixing member 19. Both the cover plate 12 and the membrane fixing member 19 contain chambers, which are divided into two independent sample flow chambers 13 and sample enrichment chambers 15 by the enrichment membrane 14. In this embodiment, the depth of the sample flow chamber 13 is 2 mm, and the depth of the sample enrichment chamber 15 is 4 mm.

[0052] The sample enrichment chamber 15 is connected to a mass spectrometer 25 through a capillary 24. The mass spectrometer 25 can be a VOCs cruise monitoring mass spectrometer, a single photon ionization time-of-flight mass spectrometer, or a portable VOCs mass spectrometer.

[0053] A capillary fixing part 20 is installed on the side of the membrane fixing part 19 away from the cover plate 12. A boss 23 is provided at the center of the capillary fixing part 20. A first sealing ring 21 is provided at the position where the membrane fixing part 19 and the capillary fixing part 20 are installed with the capillary 24. A thread is processed on the outer surface of the boss 23 for connecting and sealing with the surface of the ionization source cavity of the mass spectrometer 25. The cover plate 12, the membrane fixing part 19 and the capillary fixing part 20 are all made of stainless steel. The cover plate 12, the membrane fixing part 19 and the capillary fixing part 20 are fixed by screws, and the adjacent components are sealed by a second sealing ring 22.

[0054] The enrichment membrane 14 is made of polydimethylsiloxane with a thickness of 50 μm. The enrichment membrane 14 is squeezed between the cover plate 12 and the membrane fixing member 19 to facilitate the replacement of the enrichment membrane 14. The enrichment membrane 14 is sealed against the cover plate 12 and the membrane fixing member 19. The central enrichment part of the enrichment membrane 14 is supported by a membrane support assembly.

[0055] The membrane support assembly is located in the sample enrichment chamber 15, and the membrane support assembly is composed of a nickel metal mesh 16, a stainless steel metal mesh 17 and an annular gasket 18 arranged in sequence, wherein the nickel metal mesh 16 is fitted with the central enrichment part of the enrichment membrane 14 to lift the enrichment membrane 14, utilize the membrane surface area as much as possible, and increase the effective enrichment area of ​​the enrichment membrane 14; the stainless steel metal mesh 17 has a thickness of 0.2 mm; the annular gasket 18 is made of polytetrafluoroethylene, one side of the annular gasket 18 is tightly fitted with the bottom surface of the groove (chamber) of the membrane fixing part 19, and the other side is tightly fitted with the surface of the stainless steel metal mesh 17. The stainless steel metal mesh 17 and the annular gasket 18 are used for rigid support of the enrichment membrane 14 to prevent the enrichment membrane 14 from being torn under a large pressure difference.

[0056] The outer diameter of the capillary 24 is 1.6 mm, and the inner diameter is 0.5-1.4 mm. The capillary 24 passes through the membrane fixing member 19 and the capillary fixing member 20 in sequence. The capillary 24 is sealed and fixed by squeezing the first sealing ring 21. The first sealing ring 21 and the second sealing ring 22 are both made of fluororubber or nitrile.

[0057] The area of ​​the enrichment membrane 14 is 500 to 1500 mm 2 range, the best is 1256mm 2 , which greatly increases the permeation rate of volatile organic compounds. The membrane support assembly installed behind the enrichment membrane 14 can effectively prevent the enrichment membrane 14 from being torn under a large pressure difference.

[0058] The enrichment performance was optimized and tested using 50ppm ethane. C2H3 + (m / z=27) is the characteristic peak of ethane. According to Fick's first law, when the pressure on the sample side of the enrichment membrane 14 and the thickness of the enrichment membrane 14 are constant, the permeation rate of the sample in the enrichment membrane 14 is only related to the membrane area, such as Figure 5 As shown, the membrane area is increased from 490mm 2 Increased to 1256mm 2 The sensitivity of the instrument is increased by 2 times, and the large membrane area allows for large flow rate injection of samples; on this basis, Figure 6 As shown in Figure 2, increasing the gas pressure in the ionization source from 0.6 Pa to 4.0 Pa increases the sensitivity by another five times.

[0059] The signal intensities of the spectra obtained under capillary injection and membrane injection were compared. The standard gases used were benzene, toluene, and xylene at a concentration of 50 ppb, and the acquisition time was 60 s. Figure 7 The following are comparison spectra of the benzene, toluene, and xylene signals obtained using the membrane sampling device described in this example and direct capillary injection. The results show that the signal intensity of benzene, toluene, and xylene obtained using the membrane sampling device is nearly two orders of magnitude more sensitive than that obtained using direct capillary injection. Figure 8 The signal intensity of the sample spectra obtained by the membrane sampling device in this embodiment and the traditional one-in-one-out membrane sampling device is compared. The standard gas used is ethane with a concentration of 50ppm, the acquisition time is 60s, and C2H3 is selected in the experiment. + (m / z=27) is the characteristic peak of ethane, and the results are as follows Figure 8 As shown, the C2H3 obtained by the membrane injection device + The signal intensity is 1.4 times that of the traditional single-channel membrane injection device.

[0060] To sum up, in the one-inlet and two-outlet membrane sampling device in this embodiment, the sample forms two flow channels in the sample flow chamber 13, and flows more evenly on the surface of the enrichment membrane 14, thereby increasing the effective enrichment area of ​​the enrichment membrane 14 and the flow rate of the sample on the enrichment membrane surface, effectively reducing the dead volume of the sample flow, and can be used for direct sampling and analysis of large membrane area and high flow rate gases without the need for sample pretreatment, effectively improving the enrichment efficiency of large area membrane sampling, and significantly improving the instrument analysis sensitivity when used in conjunction with the mass spectrometer 25.

[0061] Example 2

[0062] In a typical embodiment of the present invention, a method for using a high-flow membrane sampling device for achieving high-sensitivity mass spectrometry analysis of gases is proposed, as follows:

[0063] When analyzing a sample, the first on-off valve 4 is opened and the second on-off valve 5 is closed. The sample standard gas enters the sample flow chamber 13 through the air inlet pipe 7 and the flow meter 8 in sequence. The excess sample standard gas in the sample flow chamber 13 is discharged into the waste gas collection unit 9 through the air outlet pipe 10. The sample standard gas flows evenly in the sample flow chamber 13 of the membrane enrichment mechanism 2, is enriched on the surface of the enrichment membrane 14, and enters the sample enrichment chamber 15 on the other side of the enrichment membrane 14 under the action of the pressure difference, and enters the mass spectrometer 25 through the capillary 24 for analysis.

[0064] When the analysis is finished, the first on-off valve 4 is closed and the second on-off valve 5 is opened to supply purge gas to the membrane enrichment mechanism 2 , and the purge gas is used to flush the air inlet pipe 7 and the enrichment membrane 14 .

[0065] The introduction of the purge gas can flush the air inlet pipe 7 and the enrichment membrane 14 after the analysis is completed, thereby avoiding the adsorption of organic matter on the enrichment membrane 14 and accelerating the flushing of residual samples, effectively reducing the memory effect.

[0066] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A high-flow membrane sampling device for realizing high-sensitivity mass spectrometry analysis of gases, characterized in that: The invention comprises a gas supply mechanism, a membrane enrichment mechanism and a mass spectrometer connected in sequence, wherein the membrane enrichment mechanism is provided with two gas outlet connectors and one gas inlet connector, the three connectors being arranged in an equilateral triangle with the center of the equilateral triangle coinciding with the center of the membrane enrichment mechanism, the membrane enrichment mechanism is provided with an enrichment membrane, the enrichment membrane divides the inner chamber of the membrane enrichment mechanism into an independent sample flow chamber and a sample enrichment chamber, and the sample enrichment chamber is connected to the mass spectrometer via a capillary tube; The three connectors are located on the side of the cover plate facing away from the enrichment membrane; The ratio of membrane area to the distance between adjacent joints is 47.

4.

2. The high-flow membrane sampling device for realizing high-sensitivity mass spectrometry analysis of gas according to claim 1, characterized in that: The gas supply mechanism includes a first gas supply unit for providing sample standard gas and a second gas supply unit for providing purge gas. The first gas supply unit and the second gas supply unit are connected to the gas inlet joint through a gas supply pipe. The gas supply pipe is provided with a flow meter and a first switch valve for controlling the first gas supply unit and a second switch valve for controlling the second gas supply unit.

3. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 1, characterized in that: The air outlet connector is connected to the exhaust gas collecting unit through an air outlet pipe.

4. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 1, characterized in that: The membrane enrichment mechanism consists of a cover plate, an enrichment membrane, a membrane support assembly, a membrane fixing part, and a capillary fixing part arranged in sequence. The air inlet joint and the air outlet joint are installed on the cover plate, the membrane support assembly is located in the membrane fixing part, and the cover plate, membrane fixing part and capillary fixing part are fixed by screws.

5. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 4, characterized in that: A boss is provided at the center of the capillary fixing piece, and a thread is processed on the outer surface of the boss for connecting with and sealing the surface of the ionization source cavity of the mass spectrometer.

6. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 4, characterized in that: Sealing rings are provided between the cover plate, the membrane fixing member and the capillary fixing member, and between the capillary fixing member and the capillary.

7. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 4, characterized in that: The membrane support assembly consists of a nickel metal mesh, a stainless steel metal mesh and an annular gasket which are arranged in sequence. The nickel metal mesh is fitted to the central enrichment part of the enrichment membrane.

8. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 1, characterized in that: The area of ​​the enrichment membrane is 500-1500 mm 2 .

9. The high-flow membrane sampling device for realizing high-sensitivity gas mass spectrometry analysis according to claim 1, characterized in that: The air inlet joint and the air outlet joint are both quick-plug joint structures.

10. A method for using the high-flow membrane sampling device for realizing high-sensitivity mass spectrometry analysis of gas according to any one of claims 1 to 9, characterized in that: The details are as follows: When analyzing a sample, the first switch valve is opened and the second switch valve is closed. The sample standard gas enters the sample flow chamber through the air inlet pipe and the excess sample standard gas is discharged into the waste gas collection unit through the air outlet pipe. The sample standard gas is enriched on the surface of the enrichment membrane and enters the sample enrichment chamber on the other side of the membrane under the action of the pressure difference, and enters the mass spectrometer through the capillary for analysis; When the analysis is finished, the first on-off valve is closed and the second on-off valve is opened to provide a purge gas to the membrane enrichment mechanism for flushing.

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