A corona discharge radical sampling mass spectrometer

Abstract

The application discloses a corona discharge radical sampling mass spectrometer device, and belongs to the field of analytical chemistry instruments. The application comprises a quartz glass tube, a tungsten discharge needle, a discharge gas source, a sampling cone a, a sampling cone b, a vacuum ultraviolet lamp and a time-of-flight mass spectrometer. The tungsten discharge needle is arranged in the quartz glass tube, the quartz glass tube is in a vacuum environment, one end of the quartz glass tube is connected with the discharge gas source, the discharge gas source generates discharge gas, and the discharge gas can enter the quartz glass tube; the other end of the quartz glass tube is connected with one side of the sampling cone a, the other side of the sampling cone a is connected with one side of the sampling cone b, the other side of the sampling cone b is connected with the time-of-flight mass spectrometer, and the vacuum ultraviolet lamp is arranged between the sampling cone a and the sampling cone b. The application adopts a method of vacuum ultraviolet photoionization and capturing of ionized radicals, and has the advantages of simple device, convenient sampling and no fragment production.

Description

Technical Field

[0001] This invention relates to a corona discharge free radical sampling mass spectrometry device, belonging to the field of analytical chemistry instruments. Background Technology

[0002] Free radicals are important intermediates in atmospheric chemical reactions, determining the formation and removal of secondary pollutants in the atmosphere, and are a core component of research on atmospheric oxidizing and compound pollution causes. Free radicals are characterized by low concentration, high reactivity, and a wide variety of types, making their real-time online detection technically challenging. Currently, methods for free radical detection mainly fall into two categories: spectroscopic methods and mass spectrometry. Mass spectrometry offers good versatility, high sensitivity, and fast response; combined with soft ionization techniques such as vacuum ultraviolet photoionization, it enables rapid online sampling of free radicals.

[0003] Wu Zucheng et al. invented a method and apparatus for capturing transient free radicals generated by low-temperature plasma discharge (patent number 200610154447.X). Under an average electric field strength of 4–10 kV / cm, transient gas-phase free radicals generated by low-temperature plasma corona discharge react with a spin trapping agent in solution to form spin adducts. The concentration of the spin trapping agent solution is 0.001–0.1 mol / L, and the reaction time is 1–100 s. After the reaction, 0.1–0.2 mL of the captured solution is placed in a quartz flat sample tube and detected using an electron spin resonance spectrometer. The type of free radical is determined by the characteristic ESR spectral morphology of the spin adduct, and its content is determined by the intensity of the spectral signal. This invention utilizes electron spin trapping technology to rapidly capture various transient gas-phase free radicals generated in low-temperature plasma reactions through spin addition reactions between transient gas-phase free radicals and spin trapping agents. Accurate qualitative and quantitative analysis is then performed using an electron spin resonance spectrometer.

[0004] Huang Wei et al. invented a corona discharge ion source for measuring gaseous sulfuric acid (application number 201611104860.5), which mainly consists of two parts: a reagent ion generation region and an ion molecular reaction chamber. The reagent ion generation region mainly comprises a high-voltage power supply, a tungsten needle, a NaOH filter, a stainless steel tee, a polytetrafluoroethylene tee, a 5L / min mass flow meter, and a 1L / min mass flow meter. The ion molecular reaction chamber mainly consists of an IDP3 pump and a conical stainless steel reaction chamber. Summary of the Invention

[0005] To address the above shortcomings, this invention provides a corona discharge free radical sampling mass spectrometry device. The mass spectrometry device is convenient for sampling, mainly obtains molecular ions, and does not generate debris.

[0006] The device used to solve the technical problem of this invention includes a quartz glass tube, a tungsten discharge needle, a discharge gas source, sampling cone a, sampling cone b, a vacuum ultraviolet lamp, and a time-of-flight mass spectrometer. The tungsten discharge needle is disposed inside the quartz glass tube, which is in a vacuum environment. One end of the quartz glass tube is connected to the discharge gas source, which generates discharge gas that can enter the quartz glass tube. The other end of the quartz glass tube is connected to one side of sampling cone a, the other side of sampling cone a is connected to one side of sampling cone b, and the other side of sampling cone b is connected to the time-of-flight mass spectrometer. The vacuum ultraviolet lamp is positioned between sampling cone a and sampling cone b.

[0007] Optionally, an insulating fixing frame is provided inside the quartz glass tube to fix the tungsten discharge needle, and the tungsten discharge needle coincides with the central axis of the quartz glass tube.

[0008] Optionally, a three-way adapter is provided between the discharge gas source and the quartz glass tube. The three-way adapter has three ports: end a, end b, and end c. End c is connected to one end of gas pipeline b, and the other end of gas pipeline b is connected to the quartz glass tube. End a contains a wire, one end of which is connected to a DC high-voltage power supply, and the other end of which passes through gas pipeline b and is connected to the tungsten discharge needle. End b is connected to the discharge gas source through gas pipeline a.

[0009] Optionally, a mass flow meter is provided on the gas pipeline a to measure the flow rate of the discharge gas entering the gas pipeline a from the discharge gas source, and a pressure sensor is provided on the side of the gas pipeline a between the mass flow meter and the three-way adapter to measure the pressure value inside the gas pipeline a.

[0010] Optionally, a two-way adapter is provided between the gas pipeline b and the quartz glass tube; and an O-ring is provided between the gas pipeline b and the sampling cone a.

[0011] Optionally, the discharge gas source is a volatile organic compound in an inert gas background.

[0012] Preferably, the volatile organic compound is methane.

[0013] Optionally, a silicone sealing gasket is provided inside the a end; the quartz glass tube is made of either polytetrafluoroethylene or stainless steel; both sampling cone a and sampling cone b are made of stainless steel, and sampling cone a is provided with a grounding wire;

[0014] Optionally, both sampling cone a and sampling cone b are sieve-type circular flat plates with a central hole, and the two central holes form an ion channel; the central hole diameter of sampling cone a is 50-500μm; and the central hole diameter of sampling cone b is 1-3mm.

[0015] Optionally, the quartz glass tube is a cylindrical hollow tube with an inner diameter of 2-8 mm; the distance between the tungsten discharge needle and the central hole of the sampling cone a is 0.5-5 mm.

[0016] Optionally, the vacuum ultraviolet lamp is selected from one of low-pressure discharge krypton lamp, deuterium lamp, and argon lamp, and the central axis of the light beam of the vacuum ultraviolet lamp is perpendicular to the ion channel.

[0017] Beneficial effects:

[0018] This invention employs a vacuum ultraviolet photoionization method to capture ionized free radicals. The device is simple, sampling is convenient, and it mainly yields molecular ions without generating fragments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the device of the present invention.

[0020] Figure 2 This is the detection mass spectrum of Example 2.

[0021] As shown in the figure, 1. Discharge gas source, 2. Mass flow meter, 3. Pressure sensor, 4. T-connector, 5. Two-way connector, 6. Quartz glass tube, 7. Tungsten discharge needle, 8. DC high voltage power supply, 9. Sampling cone a, 10. Vacuum ultraviolet lamp, 11. Wire, 12. Gas line a, 13. O-ring, 14. Insulating bracket, 15. Gas line b, 16. Time-of-flight mass spectrometer, 17. Sampling cone b. Detailed Implementation

[0022] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0023] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0024] Example 1

[0025] The apparatus used in this embodiment includes a quartz glass tube 6, a tungsten discharge needle 7, a discharge gas source 1, a sampling cone a9, a sampling cone b17, a vacuum ultraviolet lamp 10, and a time-of-flight mass spectrometer 16. The tungsten discharge needle 7 is disposed inside the quartz glass tube 6, which is a vacuum environment. One end of the quartz glass tube 6 is connected to the discharge gas source 1, which generates discharge gas that can enter the quartz glass tube 6. The other end of the quartz glass tube 6 is connected to one side of the sampling cone a9, and the other side of the sampling cone a9 is connected to one side of the sampling cone b17. The other side of the sampling cone b17 is connected to the time-of-flight mass spectrometer 16. The vacuum ultraviolet lamp 10 is positioned between the sampling cone a9 and the sampling cone b17.

[0026] An insulating fixing bracket 14 is provided inside the quartz glass tube 6 to fix the tungsten discharge needle 7, and the tungsten discharge needle 7 coincides with the central axis of the quartz glass tube 6.

[0027] A three-way adapter 4 is provided between the discharge gas source 1 and the quartz glass tube 6. The three-way adapter 4 has three ports: a, b, and c. The c port is connected to one end of the gas pipeline b15, and the other end of the gas pipeline b15 is connected to the quartz glass tube 6. A wire 11 is provided inside the a port. One end of the wire 11 is connected to the DC high-voltage power supply 8, and the other end of the wire 11 passes through the gas pipeline b15 and is connected to the tungsten discharge needle 7. The b port is connected to the discharge gas source 1 through the gas pipeline a12.

[0028] A mass flow meter 2 is installed on the gas pipeline a12 to measure the flow rate of the discharge gas from the discharge gas source 1 into the gas pipeline a12. A pressure sensor 3 is installed on the side of the gas pipeline a12 between the mass flow meter 2 and the three-way adapter 4 to measure the pressure value inside the gas pipeline a12.

[0029] A two-way adapter 5 is provided between the gas pipeline b15 and the quartz glass tube 6; an O-ring 13 is provided between the gas pipeline b15 and the sampling cone a9.

[0030] The discharge gas source 1 is an inert gas mixed with volatile organic compounds, and the volatile organic compounds are methane.

[0031] The a-end is equipped with a silicone sealing gasket; the quartz glass tube 6 is made of stainless steel; the sampling cone a9 and the sampling cone b17 are both made of stainless steel, and the sampling cone a9 is equipped with a grounding wire.

[0032] Both sampling cones a9 and b17 are sieve-type circular flat plates with a central hole, forming an ion channel; the central hole diameter of sampling cone a9 is 50-500μm; the central hole diameter of sampling cone b17 is 1-3mm.

[0033] The quartz glass tube 6 is a cylindrical hollow tube with an inner diameter of 2-8 mm; the distance between the tungsten discharge needle 7 and the center hole of the sampling cone a9 is 0.5-5 mm.

[0034] The vacuum ultraviolet lamp 10 is an argon lamp, and the central axis of the light beam of the vacuum ultraviolet lamp 10 is perpendicular to the ion channel.

[0035] Example 2

[0036] This embodiment consists of a discharge gas source 1, a mass flow meter 2, a pressure sensor 3, a three-way adapter 4, a two-way adapter 5, a quartz glass tube 6, a tungsten discharge needle 7, a DC high-voltage power supply 8, a sampling cone, a vacuum ultraviolet lamp 10, and a time-of-flight mass spectrometer 16.

[0037] The discharge gas source 1 is a methane gas prepared with helium at a concentration of 5000ppm; the pressure sensor 3 is used to measure the pipeline pressure; the three-way adapter 4a end is sealed with a silicone gasket, and the DC high-voltage power supply 8 passes through the silicone gasket at the three-way adapter 4a end via the wire 11, and is connected to the tungsten discharge needle 7 through the two-way adapter 5 and the inside of the quartz glass tube 6; the gas pipeline material is polytetrafluoroethylene.

[0038] The quartz glass tube 6 is sealed by an O-ring 13; the tungsten discharge needle 7 is fixed to the center of the quartz glass tube 6 by an insulating bracket 14 embedded inside the quartz glass tube 6; the distance between the tungsten discharge needle 7 and the cone hole of the sampling cone a9 is 2 mm; the sampling cone a9 is a sieve-type circular flat stainless steel electrode, grounded by a wire, with a central aperture of 100 μm; the sampling cone b17 is a sieve-type circular flat stainless steel electrode with a central aperture of 2 mm. The vacuum ultraviolet lamp 10 is a low-pressure discharge krypton lamp; the vacuum ultraviolet lamp 10 is placed between the sampling cone a9 and the sampling cone b17.

[0039] Mass spectra of methyl radicals generated by actual discharge photoionization, for example... Figure 2 As shown, no methyl radicals (m / z 15) were detected when corona discharge and vacuum ultraviolet lamp (VUV lamp) were turned on individually. However, when both were turned on simultaneously, the discharge + photoionization detection yielded m / z 15.021564 with a mass accuracy of 5 ppm, which can be identified as methyl radicals.

[0040] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A corona discharge free radical sampling mass spectrometry device, characterized in that, The device includes a quartz glass tube (6), a tungsten discharge needle (7), a discharge gas source (1), a sampling cone a (9), a sampling cone b (17), a vacuum ultraviolet lamp (10), and a time-of-flight mass spectrometer (16). The tungsten discharge needle (7) is disposed inside the quartz glass tube (6), which is a vacuum environment. One end of the quartz glass tube (6) is connected to the discharge gas source (1), which generates discharge gas that can enter the quartz glass tube (6). The other end of the quartz glass tube (6) is connected to one side of the sampling cone a (9), and the other side of the sampling cone a (9) is connected to one side of the sampling cone b (17). The other side of the sampling cone b (17) is connected to the time-of-flight mass spectrometer (16). The vacuum ultraviolet lamp (10) is disposed between the sampling cone a (9) and the sampling cone b (17).

2. The corona discharge free radical sampling mass spectrometry device according to claim 1, characterized in that, An insulating fixing bracket (14) is provided inside the quartz glass tube (6) to fix the tungsten discharge needle (7), and the tungsten discharge needle (7) coincides with the central axis of the quartz glass tube (6).

3. The corona discharge free radical sampling mass spectrometry device according to claim 1, characterized in that, A three-way adapter (4) is provided between the discharge gas source (1) and the quartz glass tube (6). The three-way adapter (4) has three ports: a, b, and c. The c port is connected to one end of the gas pipeline b (15), and the other end of the gas pipeline b (15) is connected to the quartz glass tube (6). A wire (11) is provided inside the a port. One end of the wire (11) is connected to the DC high voltage power supply (8), and the other end of the wire (11) passes through the gas pipeline b (15) and is connected to the tungsten discharge needle (7). The b port is connected to the discharge gas source (1) through the gas pipeline a (12).

4. The corona discharge free radical sampling mass spectrometry device according to claim 3, characterized in that, A mass flow meter (2) is provided on the gas pipeline a (12) to measure the flow rate of the discharge gas source (1) entering the gas pipeline a (12). A pressure sensor (3) is provided on the side of the gas pipeline a (12) between the mass flow meter (2) and the three-way adapter (4) to measure the pressure value in the gas pipeline a (12).

5. The corona discharge free radical sampling mass spectrometry device according to claim 3, characterized in that, A two-way adapter (5) is provided between the gas pipeline b (15) and the quartz glass tube (6); an O-ring (13) is provided between the gas pipeline b (15) and the sampling cone a (9).

6. The corona discharge free radical sampling mass spectrometry device according to claim 3, characterized in that, The a end is provided with a silicone sealing gasket; the quartz glass tube (6) is selected from polytetrafluoroethylene and stainless steel; the sampling cone a (9) and the sampling cone b (17) are both made of stainless steel, and the sampling cone a (9) is provided with a grounding wire.

7. The corona discharge free radical sampling mass spectrometry device according to claim 1, characterized in that, The sampling cones a (9) and b (17) are both scoop-type circular flat plates with a central hole, and the two central holes form an ion channel; the central hole diameter of the sampling cone a (9) is 50-500 μm; the central hole diameter of the sampling cone b (17) is 1-3 mm.

8. The corona discharge free radical sampling mass spectrometry device according to claim 7, characterized in that, The vacuum ultraviolet lamp (10) is selected from one of the following: low-pressure discharge krypton lamp, deuterium lamp, and argon lamp; the central axis of the light source of the vacuum ultraviolet lamp (10) is perpendicular to the ion channel.

9. The corona discharge free radical sampling mass spectrometry device according to claim 1, characterized in that, The quartz glass tube (6) is a cylindrical hollow tube with an inner diameter of 2-8 mm; the distance between the tungsten discharge needle (7) and the center hole of the sampling cone a (9) is 0.5-5 mm.

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