Semi-open all-dielectric barrier discharge low-temperature plasma ionization source device

Abstract

The invention relates to the technical field of low-temperature plasmas, in particular to a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device which comprises a sample tube, a jet tube and an ion area, one end of the sample tube is provided with a sample input end, the other end of the sample tube is a closed end, and the jet tube penetrates through the closed end. A receiving opening is formed in the end, located on the inner side of the cavity of the sample pipe, of the jet pipe, and the other end of the jet pipe is connected with an ion area arranged on the outer side of the jet pipe through an output opening; according to the in-situ ionization device, the technical means of a semi-open structure, filling of a cavity with low-temperature plasma, bidirectional jet flow, directional jet flow paths and the like are combined, and the in-situ ionization device is suitable for in-situ ionization of irregular, low-concentration and difficult-to-volatilize solids; and the ionization efficiency, the signal intensity and the detection sensitivity are obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of low-temperature plasma, in particular to a semi-open full dielectric barrier discharge low-temperature plasma ionization source device. Background Art

[0002] Ion mobility spectrometry (IMS) is based on the difference in the migration speed of ions in neutral gas under the action of electric field to achieve the separation and detection of different ions. Ion mobility spectrometry has the advantages of single spectrum analysis speed at ms level and is suitable for the development of portable instruments. It can be used in conjunction with atmospheric pressure chemical ionization source with high ionization efficiency. The detection limit can be as low as pptv (10–12). It is widely used in the on-site rapid detection of trace explosives and industrial hazardous chemicals. An important step in ion mobility spectrometry measurement is to convert the neutral molecules of the analyte into their ionic form, which can be achieved by using various ionization methods. According to the different ionization methods, the ion mobility spectrometry ionization source has radioactive ionization source, corona discharge ionization source, photoionization source, electrospray ionization source, dielectric barrier discharge ionization source, gas pressure DC glow discharge ionization source, flame ionization, etc. Among them, the traditional dielectric barrier discharge ionization source (DBDI) is an open environmental ionization source used for solid detection. At present, there are two main structures of common dielectric barrier discharge ionization sources, ring-ring discharge and needle-ring discharge. Closed DBDI is mainly used to detect gases and liquids. For solid detection, traditional DBDI is usually an open ionization source. This ionization source design has some obvious disadvantages and limitations, which are mainly reflected in the following aspects:

[0003] 1. Sample dissipation: large sample loss. The open ionization source means that sample molecules are easily diffused into the surrounding environment during the ionization process, resulting in a small amount of sample actually participating in ionization, affecting the ionization efficiency.

[0004] 2. Environmental background interference: (1) Interference from ambient air: open ionization sources are easily interfered by other components in the ambient air (such as water vapor, carbon dioxide, volatile organic compounds, etc.), which may be mis-ionized or react chemically with the target sample to produce interfering ions, affecting the analysis results; (2) Unstable ionization environment: Since the ionization zone is exposed to the air, changes in environmental conditions (such as temperature, humidity, airflow, etc.) will have an unstable effect on the ionization efficiency and ion signal, resulting in poor repeatability of the results;

[0005] 3. Low ion collection efficiency: (1) Difficulty in ion capture: The ions in an open ion source are easily dispersed under the action of the electric field and are difficult to be effectively captured and guided to the ion mobility spectrometer or mass spectrometer, resulting in large signal loss and reduced detection sensitivity; (2) Irregular ion path: The ion flight path in an open ion source is easily affected by environmental factors and may deviate from the predetermined collection direction, causing signal noise and inaccurate detection results. Therefore, in view of the above situation, there is an urgent need to develop a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device to overcome the shortcomings in current practical applications. Summary of the invention

[0006] The object of the present invention is to provide a semi-open full dielectric barrier discharge low-temperature plasma ionization source device to solve the problems raised in the above background technology.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A semi-open all-dielectric barrier discharge low-temperature plasma ionization source device comprises: a sample tube, a jet tube, an ion zone, a first annular electrode, a second annular electrode, a third annular electrode and an air inlet pipe, wherein one end of the sample tube is provided with a sample input end, and the other end is a closed end, the closed end is penetrated by the jet tube, and is used to cooperate with the jet tube to form a semi-open structure for sample introduction and ionization, the jet tube is provided with a receiving port at one end located inside the sample tube cavity, and an output port at the other end, the receiving port and the output port are both connected to the jet tube cavity inside the jet tube, and the output port is also connected to the ion zone arranged outside the jet tube, an air inlet pipe is arranged on the tube wall of the sample tube close to the jet tube, and is used to realize the input of discharge gas, a first annular electrode is arranged around the outer wall of the sample tube away from the jet tube, and the first annular electrode is connected to a ground wire, a second annular electrode is arranged around the outer side of the jet tube, a third annular electrode is arranged around the outer side of the air inlet pipe, and the second annular electrode and the third annular electrode are both connected to a high-voltage power supply.

[0009] As a further solution of the present invention: the first annular electrode, the second annular electrode and the third annular electrode are installed in the discharge area, and the dielectric material covers the electrodes to achieve dielectric barrier discharge.

[0010] As a further solution of the present invention: a closed structure is arranged inside the sample tube cavity.

[0011] As a further solution of the present invention: it also includes: an ion gate and a migration zone, the ion gate is arranged at one end of the ion zone away from the jet tube, and the ion gate is connected to the migration zone.

[0012] As a further solution of the present invention: the migration zone further comprises: a Faraday plate and a shielding grid, a shielding grid is arranged on the inner side of one end of the migration zone away from the ion zone, and a Faraday plate is also arranged on the shielding grid.

[0013] As a further solution of the present invention: the discharge gas is helium.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] When the device is in operation, the sample is placed at the sample input end of the sample tube, and the discharge gas helium is introduced through the air inlet pipe. A voltage is applied between the first annular electrode, the second annular electrode and the third annular electrode through a high-voltage power supply. The electric field is evenly distributed in the cavity through the annular electrodes, causing the discharge gas to undergo dielectric barrier discharge. Due to the design of the discharge gas flow direction and the device structure, plasma jets in two directions are formed inside the structure at the same time. The jets in these two directions exist at the same time and act on different target areas respectively. The generated low-temperature plasma fills the entire cavity together. Under the action of the first annular electrode and the third annular electrode, an ionization jet pointing to the sample surface is formed in the sample tube cavity, and high-energy particles can act on the object to be tested in a concentrated manner to form an efficient ionization effect. At this stage, the ionization jet provides direct plasma contact for the object to be tested, so that the molecules of the object to be tested are ionized into charged ions and other active products. At the same time, under the action of the first annular electrode and the second annular electrode, a transmission jet pointing to the ion region is formed in the jet tube cavity. This transmission jet The flow pushes the ionization products from the discharge zone to the ion zone, and the ionization products are smoothly transmitted to the ion zone. Compared with the DBDI devices in the prior art, the present application mostly adopts a closed or completely open structure. The closed structure has restrictions on the sample size and state and cannot be detected in situ, while the open structure has low ionization and transmission efficiency and is easily disturbed by the environment. By adopting a semi-open structure, while ensuring the stability of the ionization zone, the plasma jet can directly act on the external sample, which significantly improves the convenience and efficiency of detection. At the same time, the semi-open design is effective in isolating part of the impurities and humidity of the outside air, which helps to improve the ionization efficiency and detection sensitivity. The present application also adopts a three-electrode ring bidirectional jet structure, which realizes a bidirectional jet in a single device. The ionization jet can effectively ionize the sample, and the transmission jet stably transmits the ionization product. Under the joint action of the bidirectional jet, the low-temperature plasma fills the entire cavity, effectively preventing ion neutralization, reducing ion loss, and improving signal strength and detection sensitivity. It is particularly suitable for the detection needs of low-concentration samples or solid samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the structure of a semi-open full dielectric barrier discharge low-temperature plasma ionization source device.

[0017] Figure 2 This is a schematic diagram of the three-dimensional structure of a semi-open full dielectric barrier discharge low-temperature plasma ionization source device.

[0018] Figure 3 This is a schematic diagram of the DBDI structure.

[0019] Figure 4 Schematic diagram of DBDI-IMS structure.

[0020] In the figure: 1-sample tube, 2-jet tube, 3-ion zone, 4-high voltage power supply, 5-first annular electrode, 6-second annular electrode, 7-third annular electrode, 8-closed end, 9-inlet pipe, 10-sample input end, 11-receiving port, 12-output port, 13-sample tube cavity, 14-jet tube cavity, 15-ground wire, 16-ion gate, 17-migration zone, 18-Faraday disk, 19-shielding grid. DETAILED DESCRIPTION

[0021] The technical solution of the present application is further described in detail below in conjunction with specific implementation methods.

[0022] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0023] See also Figure 1 , Figure 2 and Figure 3 In one embodiment of the present invention, a semi-open all-dielectric barrier discharge low-temperature plasma ionization source device includes: a sample tube 1, a jet tube 2, an ion region 3, a first annular electrode 5, a second annular electrode 6, a third annular electrode 7 and an air inlet pipe 9. The sample tube 1 is provided with a sample input end 10 at one end and a closed end 8 at the other end. The closed end 8 is penetrated by the jet tube 2 and is used to cooperate with the jet tube 2 to form a semi-open structure for sample introduction and ionization. The jet tube 2 is located at one end inside the sample tube cavity 13 and is provided with a receiving port 11, and the other end is provided with an output port 12. The receiving port 11 The output port 12 is connected to the jet tube cavity 14 inside the jet tube 2, and the output port 12 is also connected to the ion zone 3 arranged on the outside of the jet tube 2. An air inlet pipe 9 is arranged on the tube wall of the sample tube 1 close to the jet tube 2, for realizing the input of discharge gas. A first annular electrode 5 is arranged around the outer wall of the sample tube 1 away from the jet tube 2, and the first annular electrode 5 is connected to the ground wire 15. A second annular electrode 6 is arranged around the outside of the jet tube 2, and a third annular electrode 7 is arranged around the outside of the air inlet pipe 9. The second annular electrode 6 and the third annular electrode 7 are both connected to the high-voltage power supply 4.

[0024] In this embodiment, the first annular electrode 5 is tightly sleeved and fitted on the sample tube 1, and is connected to the ground through the grounding wire 15, the second annular electrode 6 is tightly sleeved and fitted on the jet tube 2, and is connected to the high-voltage power supply 4, and the third annular electrode 7 is tightly sleeved and fitted on the air inlet pipe 9, and is connected to the high-voltage power supply 4. When the device is running, the sample is placed on the sample input end 10 of the sample tube, and the discharge gas helium is introduced through the air inlet pipe 9. A voltage is applied between the first annular electrode 5, the second annular electrode 6 and the third annular electrode 7 through the high-voltage power supply 4. The electric field is evenly distributed in the cavity through the annular electrodes, which causes the discharge gas to generate dielectric barrier discharge. Due to the design of the discharge gas flow direction and the device structure, two directions of plasma jets are formed inside the structure at the same time. The two directions of jets exist at the same time and act on different target areas respectively. The generated low-temperature plasma fills the entire cavity together. Under the action of the first annular electrode 5 and the third annular electrode 7, an ionization jet pointing to the sample surface is formed in the sample tube cavity 13. High-energy particles can act on the object to be tested in a concentrated manner to form an efficient ionization effect. At this stage, the ionization jet provides direct plasma contact for the object to be tested, so that the molecules of the object to be tested are ionized into charged ions and Other active products, at the same time, under the action of the first annular electrode 5 and the second annular electrode 6, a transmission jet pointing to the ion zone 3 is formed in the jet tube cavity 14, and this transmission jet pushes the ionization product from the discharge zone to the ion zone 3, and the ionization product is smoothly transmitted to the ion zone 3. Compared with the DBDI device in the prior art, the present application mostly adopts a closed or completely open structure. The closed structure has restrictions on the sample size and state and cannot be detected in situ, while the open structure has low ionization and transmission efficiency and is easily disturbed by the environment. By adopting a semi-open structure, while ensuring the stability of the ionization zone, the plasma jet can It acts directly on external samples, significantly improving the convenience and efficiency of detection. At the same time, the semi-open design is effective in isolating some impurities and humidity from the outside air, which helps to improve ionization efficiency and detection sensitivity. The application also adopts a three-electrode ring bidirectional jet structure to achieve bidirectional jet in a single device. The ionization jet can effectively ionize the sample, while the transmission jet stably transmits the ionization product. Under the joint action of the two-way jet, the low-temperature plasma fills the entire cavity, effectively preventing ion neutralization, reducing ion loss, and improving signal strength and detection sensitivity. It is particularly suitable for the detection needs of low-concentration samples.

[0025] In one embodiment of the present invention, the first annular electrode 5, the second annular electrode 6 and the third annular electrode 7 are installed in the discharge region, and the dielectric material covers the electrodes to achieve dielectric barrier discharge and ensure stable plasma generation.

[0026] In one embodiment of the present invention, a closed structure is disposed inside the sample tube cavity 13 to isolate impurities and moisture in the external air to avoid interference with the ion generation process.

[0027] In one embodiment of the present invention, the ion gate 16 and the migration zone 17 are also included. The ion gate 16 is arranged at one end of the ion zone 3 away from the jet tube 2 , and the ion gate 3 is connected to the migration zone 17 .

[0028] In one embodiment of the present invention, the migration zone 17 also includes: a Faraday disk 18 and a shielding grid 19. The shielding grid 19 is arranged on the inner side of one end of the migration zone 17 away from the ion zone 3, and the Faraday disk 18 is also arranged on the shielding grid 19. By setting the migration zone 17, the ionization products (including charged ions) are smoothly transmitted to the ion zone 3, and then enter the migration zone 17, and finally form an electrical signal on the Faraday disk 18 for analysis.

[0029] In one embodiment of the present invention, the discharge gas is helium.

[0030] In one embodiment of the present invention, the diameter, length and connection angle of the conduit are controlled by precision machining to achieve a bidirectional jet flow path, thereby ensuring the stability of the airflow direction and the jet path.

[0031] The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device adopts a semi-open structural design. The partially enclosed area effectively shields the interference of humidity and impurities in the outside air on the ionization zone, thereby reducing the generation of noise signals and significantly improving the sensitivity and accuracy of detection. The partially enclosed area isolates the direct contact between the ionization zone and the outside air, reducing the influence of water vapor and other volatile impurities on the ionization process, thereby reducing the generation of interfering ions and improving the clarity and detection reliability of the signal. The directional jet design makes the ion transmission path more regular and the signal transmission more stable. Compared with the fully open structure, the semi-open directional jet significantly improves the signal. The repeatability and stability of the DBDI are particularly outstanding in the detection of low-concentration samples. The design of the directional jet path reduces the fluctuation in the signal transmission process, making the ion transmission more concentrated and efficient, significantly improving the repeatability and sensitivity of the signal, and meeting the needs of high-precision analysis. Compared with the completely closed structure, the semi-open design allows the ionization source to act directly on the sample surface, eliminating the need for sample pretreatment or transfer of the traditional ionization source. The traditional closed DBDI cannot realize in-situ detection of large samples or irregular samples because the sample needs to enter the ionization zone. The semi-open DBDI can directly ionize and analyze the sample on site, improving the convenience and efficiency of detection;

[0032] This device adopts a three-electrode ring bidirectional jet structure design, so that the ionization jet can directly ionize the sample, while the transmission jet quickly transmits the ionization product to the ion detection area. By separating the ionization and transmission paths, the bidirectional jet design significantly improves the efficiency of the ionization and transmission process. The unique structure of the bidirectional jet makes the ionization and product transmission independent of each other, avoiding the instability in the jet direction, ensuring that the ionization product can enter the detection area efficiently and stably, thereby improving the accuracy of detection and the stability of signal transmission. Under the action of the bidirectional jet, the low-temperature plasma fills the entire cavity to form an active ion environment, effectively preventing the ions in the ionization product from neutralizing. This design reduces the loss of ions during the transmission process, thereby improving the detection sensitivity and signal strength. The filling effect of the low-temperature plasma ensures that the ions in the entire cavity remain active during the transmission process, avoiding signal attenuation caused by ion neutralization. This feature makes the device particularly effective in the detection of low-concentration samples and ensures high-quality signal transmission. .

[0033] The above are only preferred embodiments of the present invention. It should be pointed out that, for those skilled in the art, several modifications and improvements can be made without departing from the concept of the present invention. These should also be regarded as the protection scope of the present invention. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A semi-open full dielectric barrier discharge low-temperature plasma ionization source device, characterized in that: include: A sample tube, a jet tube, an ion zone, a first annular electrode, a second annular electrode, a third annular electrode and an air inlet pipe, wherein a sample input end is arranged at one end of the sample tube, and the other end is a closed end, the closed end is penetrated by the jet tube, and is used to cooperate with the jet tube to form a semi-open structure for sample introduction and ionization, the jet tube is provided with a receiving port at one end located inside the sample tube cavity, and an output port is arranged at the other end, the receiving port and the output port are both connected to the jet tube cavity inside the jet tube, and the output port is also connected to the ion zone arranged outside the jet tube, an air inlet pipe is arranged on the tube wall of the sample tube close to the jet tube, for realizing the input of discharge gas, a first annular electrode is arranged around the outer wall of the sample tube away from the jet tube, and the first annular electrode is connected to the ground wire, a second annular electrode is arranged around the outside of the jet tube, a third annular electrode is arranged around the outside of the air inlet pipe, and the second annular electrode and the third annular electrode are both connected to a high-voltage power supply.

2. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that: The first annular electrode, the second annular electrode and the third annular electrode are installed in the discharge area, and the dielectric material covers the electrodes to realize dielectric barrier discharge.

3. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that: A closed structure is arranged inside the sample tube cavity.

4. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that: Also includes: The ion gate and the migration zone, the ion gate is arranged at one end of the ion zone away from the jet tube, and the ion gate is connected to the migration zone.

5. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 4, characterized in that: The migration zone further comprises: a Faraday plate and a shielding grid. A shielding grid is arranged on the inner side of one end of the migration zone away from the ion zone, and a Faraday plate is also arranged on the shielding grid.

6. The semi-open all-dielectric barrier discharge low-temperature plasma ionization source device according to claim 1, characterized in that: The discharge gas is helium.

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