A low-temperature plasma in-situ capture atomizer and its use method

Abstract

This invention discloses a warm plasma in-situ capture atomizer and its usage method, comprising a columnar discharge electrode and a mesh discharge electrode, which are respectively connected to the two poles of a high-voltage discharge power supply. The columnar discharge electrode is externally covered with a first tubular dielectric, and the mesh discharge electrode is internally lined with a second tubular dielectric. A carrier gas inlet is installed on the second tubular dielectric. A discharge cavity is formed between the second tubular dielectric and the columnar discharge electrode or the first tubular dielectric. This device can achieve room temperature in-situ capture and enrichment of elements, and room temperature in-situ release detection. This device is not only simple in structure, but also effectively solves the problem of transmission loss between the capture-release device and the atomic spectroscopy atomizer.

Description

Technical Field

[0001] The present invention relates to a low-temperature plasma atomizer capable of achieving in-situ capture and enrichment of elements at room temperature, and in-situ release and detection at room temperature, and in particular to a low-temperature plasma in-situ capture atomizer and a method of using the same, belonging to the technical field of analysis and detection. Background Art

[0002] Due to the increasing requirements for environmental protection, the detection of elements in samples has now reached the sub-microgram / kilogram level. However, the detection sensitivity of conventional atomic spectroscopy usually cannot meet this requirement, so it is necessary to improve the detection sensitivity through the enrichment-release process.

[0003] The commonly used enrichment-release process can be carried out in either the liquid phase or the gas phase. In comparison, the gas phase process is relatively simple and convenient. However, conventional gas phase enrichment-release often requires the use of high temperatures, which will result in increased energy consumption and complexity of the device. Invention patent 201610141066.1 discloses a gas phase capture and release device and method based on dielectric barrier discharge, which can achieve room temperature capture and release of arsenic (As) at room temperature, and can improve the detection sensitivity by more than 8 times. This patent solves the problem of room temperature capture-release very well, but the device for capture-release in this patent is connected in series to the front end of the atomic spectrometer atomizer, and its structure is still relatively complex; and according to the data given in Example 1, its injection volume increased by more than 10 times, while the enrichment efficiency only increased by 8 times, indicating that significant losses occurred in the process. Considering that there is a significant transmission distance between the capture-release device and the atomic spectrometer atomizer, transmission losses should have occurred. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects in the prior art and provide a low-temperature plasma in-situ capture atomizer and a method for using the same.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a low-temperature plasma in-situ capture atomizer, a structure of which is shown in FIG. Figure 1In the figure, the columnar discharge electrode and the mesh discharge electrode are respectively connected to the two poles of the high-voltage discharge power supply; the outside of the columnar discharge electrode is coated with a first tubular dielectric, and the inside of the mesh discharge electrode is lined with a second tubular dielectric. The second tubular dielectric is equipped with a carrier gas inlet, wherein the first tubular dielectric is not necessary and can be eliminated; a discharge cavity is formed between the second tubular dielectric and the columnar discharge electrode or the first tubular dielectric. During use, gaseous molecules or aerosols containing the element to be measured and a mixed gas containing oxygen are first introduced into the discharge cavity through the carrier gas inlet, and at the same time, a high-voltage discharge power supply is turned on to generate discharge in the discharge cavity to form a low-temperature plasma. At this time, the element to be measured in the mixed gas will be captured on the outer wall of the second tubular dielectric and the inner wall of the first tubular dielectric, thereby achieving capture and enrichment of the element to be measured. Thereafter, the high-voltage discharge power supply is turned off, and an inert gas containing hydrogen is introduced from the carrier gas inlet. After purging for a period of time, the high-voltage discharge power supply is turned on again to generate discharge in the discharge cavity to form a low-temperature plasma. At this time, the captured element to be measured will be released from the outer wall of the second tubular dielectric and the inner wall of the first tubular dielectric, and free atoms and excited-state free atoms of the element to be measured will be formed in the discharge cavity, which can be used for subsequent atomic spectrum detection.

[0007] Preferably, Figure 2 Another structure is shown in the figure, in which a columnar discharge electrode and a mesh discharge electrode are respectively connected to the two poles of a high-voltage discharge power supply; the outside of the columnar discharge electrode is coated with a first tubular dielectric, and the inside of the mesh discharge electrode is lined with a second tubular dielectric, and a carrier gas inlet is installed on the second tubular dielectric, wherein the first tubular dielectric is not necessary and can be omitted; the outside of the mesh discharge electrode is coated with a tubular shielding layer, on which a shielding gas inlet is installed; a discharge cavity is formed between the second tubular dielectric and the columnar discharge electrode or the first tubular dielectric. During use, gaseous molecules or aerosols containing the element to be measured and a mixed gas containing oxygen are first introduced into the discharge cavity through the carrier gas inlet. At the same time, a high-voltage discharge power supply is turned on to generate discharge in the discharge cavity to form a low-temperature plasma. At this time, the element to be measured in the mixed gas will be captured on the outer wall of the second tubular dielectric and the inner wall of the first tubular dielectric, thereby achieving capture and enrichment of the element to be measured. Thereafter, the high-voltage discharge power supply is turned off, and an inert gas containing hydrogen is introduced through the carrier gas inlet. After a period of purging, an inert gas containing or not containing hydrogen is introduced into the shield inlet. At the same time, the high-voltage discharge power supply is turned on again to generate discharge in the discharge cavity to form a low-temperature plasma. At this time, the captured element to be measured will be released from the outer wall of the second tubular dielectric and the inner wall of the first tubular dielectric, forming free atoms and excited-state free atoms of the element to be measured in the discharge cavity. Due to the function of the shield, these free atoms and excited-state free atoms can be transmitted to the tube mouth atomization zone, where they can be used for subsequent atomic spectrum detection.

[0008] The present invention provides a low-temperature plasma in-situ capture atomizer. It has the following beneficial effects:

[0009] 1. The present invention is a low-temperature plasma in-situ capture atomizer, which can achieve in-situ capture and enrichment of elements at room temperature, and in-situ release and detection at room temperature. The device is not only simple in structure, but also can well solve the problem of transmission loss between the capture-release device and the atomic spectrum atomizer.

[0010] 2. The dielectric barrier discharge in the present invention is a low-temperature, normal-pressure, non-thermal equilibrium plasma, which belongs to low-temperature plasma. It has the advantages of simple discharge structure, easy plasma generation, stability at room temperature and pressure, and low energy consumption.

[0011] 3. The DBD low-temperature plasma of the present invention contains electrons with high kinetic energy (1-10 eV), metastable ions, atoms, and molecules. These ions can effectively atomize and ionize the sample particles when they collide with them. DBD low-temperature plasma is an ideal low-temperature atomizer, atmospheric pressure excitation source, and gas chromatography detector.

[0012] 4. Using the dielectric barrier discharge (DBD) principle and structure, the present inventors have developed a small, low-temperature plasma atomizer suitable for atomic fluorescence spectrometry (AFS). They have also studied a method for analyzing trace tellurium (Te) in environmental samples using a hydride generation-low-temperature plasma atomizer-atomic fluorescence spectrometry method. DBD plasma atomizers offer advantages such as compactness and low temperature.

[0013] 5. Plasma, as used herein, refers to a gas mixture containing a certain concentration of anions, cations, free electrons, neutral atoms, and molecules, which is generally neutrally conductive. Plasma, as a light source, is a new type of light source for emission spectroscopy developed in the 1960s. Argon plasma is commonly used for emission spectroscopy. Although a small amount of cations generated by the sample may be present, argon ions and electrons are the primary conductive species. The argon ions formed in the plasma can absorb sufficient energy from the external light source and maintain the temperature at a certain level, allowing further ionization. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0015] Figure 1 It is a structural schematic diagram of the present invention;

[0016] Figure 2It is another structural schematic diagram of the present invention;

[0017] Figure 3 This is one of the structural schematic diagrams of the present invention for atomic emission spectroscopy detection;

[0018] Figure 4 This is the second structural diagram of the present invention for atomic emission spectroscopy detection.

[0019] In the figure: 1. Columnar discharge electrode; 2. Mesh discharge electrode; 31. First tubular dielectric; 32. Second tubular dielectric; 33. Carrier gas inlet; 34. Tubular shielding layer; 35. Shielding gas inlet; 4. Discharge cavity; 5. High-voltage discharge power supply; 61. First lens; 62. Spectrometer; 7. Tube mouth atomization zone; 81. Excitation light source; 82. Second lens; 83. Third lens; 84. Photodetector. DETAILED DESCRIPTION

[0020] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. Example 1

[0021] The columnar discharge electrode 1 and the mesh discharge electrode 2 are respectively connected to the two poles of a high-voltage discharge power supply (5). The outer portion of the columnar discharge electrode 1 is covered with a first tubular dielectric 31. The inner portion of the mesh discharge electrode 2 is lined with a second tubular dielectric 32. The second tubular dielectric 32 is provided with a carrier gas inlet 33. A discharge cavity 4 is formed between the second tubular dielectric 32 and the columnar discharge electrode 1 or the first tubular dielectric 31.

[0022] A method for using a low-temperature plasma in-situ capture atomizer is disclosed. One method is as follows: first, gaseous molecules or aerosols containing an element to be measured and a mixed gas containing oxygen are introduced into a discharge cavity 4 through a carrier gas inlet 33. Simultaneously, a high-voltage discharge power supply 5 is turned on to generate discharge in the discharge cavity 4 to form a low-temperature plasma. At this time, the element to be measured in the mixed gas is captured on the outer wall of the second tubular dielectric 32 and the inner wall of the first tubular dielectric 31, thereby achieving capture and enrichment of the element to be measured. Then, the high-voltage discharge power supply 5 is turned off, and an inert gas containing hydrogen is introduced through the carrier gas inlet 33. After a period of purging, the high-voltage discharge power supply 5 is turned on again to generate discharge in the discharge cavity 4 to form a low-temperature plasma. At this time, the captured element to be measured is released from the outer wall of the second tubular dielectric 32 and the inner wall of the first tubular dielectric 31, forming free atoms and excited-state free atoms of the element to be measured in the discharge cavity 4, which can be used for subsequent atomic spectrum detection.

[0023] A method for using a low-temperature plasma in-situ capture atomizer. Another method is as follows: first, gaseous molecules or aerosols containing an element to be measured and a mixed gas containing oxygen are introduced into a discharge cavity 4 through a carrier gas inlet 33, and at the same time, a high-voltage discharge power supply 5 is turned on to generate discharge in the discharge cavity 4 to form a low-temperature plasma. At this time, the element to be measured in the mixed gas will be captured on the outer wall of the second tubular dielectric 32 and the inner wall of the first tubular dielectric 31, thereby achieving capture and enrichment of the element to be measured; then, the high-voltage discharge power supply 5 is turned off, and an inert gas containing hydrogen is introduced from the carrier gas inlet (33). After a period of purging, an inert gas containing or not containing hydrogen is introduced into the shield inlet, and the high-voltage discharge power supply 5 is turned on again. Discharge occurs in the discharge cavity 4 to form a low-temperature plasma. At this time, the captured elements to be measured will be released from the outer wall of the second tubular dielectric 32 and the inner wall of the first tubular dielectric 31, and free atoms and excited-state free atoms of the elements to be measured will be formed in the discharge cavity 4. Due to the effect of the shield, these free atoms and excited-state free atoms can be transmitted to the tube mouth atomization zone 7, and can be used for subsequent atomic spectrum detection. Example 2

[0024] Will Figure 1 The device is used for atomic emission spectroscopy detection, and its overall device is shown in Figure 3 In the figure, a first lens 61 and a spectrometer 62 are added to the atomizer to detect and quantify the light emitted by excited free atoms of the element to be measured in the discharge cavity 4. This device achieves a detection limit of less than 1 μg / kg for elements such as arsenic (As), lead (Pb), mercury (Hg), cadmium (Cd), selenium (Se), antimony (Sb), tin (Sn), bismuth (Bi), zinc (Zn), tellurium (Te), germanium (Ge), cobalt (Co), nickel (Ni), and chromium (Cr). Example 3

[0025] Will Figure 1 The device is used for atomic emission spectroscopy detection, and its overall device is shown in Figure 4 In the figure, an excitation light source 81, a second lens 82, a third lens 83, and a photodetector 84 are added to the atomizer. Light from the excitation light source 81 is focused by the second lens 82 onto the free atoms in the atomization region 7 at the nozzle, exciting them and causing them to emit atomic fluorescence. The emitted atomic fluorescence is focused by the third lens 83 onto the photodetector 84, forming an atomic fluorescence signal that is used for quantification. This device achieves a detection limit of less than 10 ng / kg for elements such as arsenic (As), lead (Pb), mercury (Hg), cadmium (Cd), selenium (Se), antimony (Sb), tin (Sn), bismuth (Bi), zinc (Zn), tellurium (Te), germanium (Ge), cobalt (Co), nickel (Ni), and chromium (Cr).

[0026] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for using a low-temperature plasma in-situ capture atomizer, characterized in that: The low-temperature plasma in-situ capture atomizer comprises a columnar discharge electrode (1) and a mesh discharge electrode (2), wherein the columnar discharge electrode (1) and the mesh discharge electrode (2) are respectively connected to two poles of a high-voltage discharge power supply (5), the columnar discharge electrode (1) is coated with a first tubular dielectric (31) on the outside, the mesh discharge electrode (2) is lined with a second tubular dielectric (32) on the inside, the second tubular dielectric (32) is provided with a carrier gas inlet (33), and a discharge cavity (4) is formed between the second tubular dielectric (32) and the columnar discharge electrode (1) or the first tubular dielectric (31); the second tubular dielectric (32) is further coated with a tubular shielding layer (34), and the tubular shielding layer (34) is further provided with a shielding gas inlet (35); firstly, a gaseous molecule or aerosol containing an element to be measured is mixed with a gaseous molecule or aerosol containing an element to be measured; and then, a gaseous molecule or aerosol containing an element to be measured is mixed with a gaseous molecule or aerosol containing an element to be measured. A mixed gas of oxygen is introduced into the discharge cavity (4) through a carrier gas inlet (33), and at the same time, a high-voltage discharge power source (5) is turned on to generate discharge in the discharge cavity (4) to form a low-temperature plasma. At this time, the element to be measured in the mixed gas is captured on the outer wall of the second tubular dielectric (32) and the inner wall of the first tubular dielectric (31), thereby achieving capture and enrichment of the element to be measured. Thereafter, the high-voltage discharge power source (5) is turned off, and an inert gas containing hydrogen is introduced from the carrier gas inlet (33). After purging for a period of time, the high-voltage discharge power source (5) is turned on again to generate discharge in the discharge cavity (4) to form a low-temperature plasma. At this time, the captured element to be measured is released from the outer wall of the second tubular dielectric (32) and the inner wall of the first tubular dielectric (31), and forms free atoms and excited-state free atoms of the element to be measured in the discharge cavity (4), which are used for subsequent atomic spectrum detection.

2. The method for using a low-temperature plasma in-situ capture atomizer according to claim 1, characterized in that: Another method is as follows: first, gaseous molecules or aerosols containing the element to be measured and a mixed gas containing oxygen are introduced into the discharge cavity (4) from the carrier gas inlet (33), and at the same time, a high-voltage discharge power supply (5) is turned on to generate discharge in the discharge cavity (4) to form a low-temperature plasma. At this time, the element to be measured in the mixed gas will be captured on the outer wall of the second tubular dielectric (32) and the inner wall of the first tubular dielectric (31), thereby achieving capture and enrichment of the element to be measured; then, the high-voltage discharge power supply (5) is turned off, and an inert gas containing hydrogen is introduced from the carrier gas inlet (33) to purge for a period of time. After that, an inert gas containing or not containing hydrogen is introduced into the inlet of the shield, and the high-voltage discharge power supply (5) is turned on again, so that discharge occurs in the discharge cavity (4) to form a low-temperature plasma. At this time, the captured element to be measured is released from the outer wall of the second tubular dielectric (32) and the inner wall of the first tubular dielectric (31), and free atoms and excited free atoms of the element to be measured are formed in the discharge cavity (4). Due to the effect of the shield, the free atoms and excited free atoms are transmitted to the tube mouth atomization area (7) for subsequent atomic spectrum detection.

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