Gas exchange device in front of sample introduction cone of inductively coupled plasma mass spectrometer

Abstract

The invention discloses a gas exchange device in front of a sample introduction cone of an inductively coupled plasma mass spectrometer, the gas exchange device in front of the sample introduction cone is arranged outside an ICP torch tube in a sleeving manner, and the gas exchange device in front of the sample introduction cone is mounted on a partition plate around the sample introduction cone; the sample injection cone front gas exchange device comprises a porous breathable layer and a shell; an argon inlet is formed in one end, close to the sample introduction cone, of the shell; one end, far away from the sample introduction cone, of a space between the porous breathable layer and the ICP torch tube is opened and is communicated with the atmosphere. According to the invention, the environmental gas components in the space between the ICP torch tube and the mass spectrum interface device are exchanged into the preset clean gas, so that the sample ionization process is not interfered by the environmental air components, a lower noise baseline is obtained, and meanwhile, the generation of environmental component ions such as nitrogen oxide ions which possibly interfere mass spectrum analysis is reduced; the sensitivity of mass spectrometry detection and the environment anti-interference capability are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of inductively coupled plasma mass spectrometry, and in particular relates to a gas exchange device before an injection cone of an inductively coupled plasma mass spectrometer. Background Art

[0002] Inductively coupled plasma mass spectrometry (ICP-MS) is an analytical instrument that combines ICP technology and mass spectrometry. ICP technology uses a high-frequency radio frequency signal with strong power applied to an inductive coil to form a high-temperature plasma inside the coil, and through the propulsion of gas, it ensures the equilibrium and continuous ionization of the plasma; Figure 1 As shown, in ICP-MS, the ICP torch 1 acts as an ion source, and the formed ions pass through the mass spectrometer interface device 2 (MS Interface) and then enter the mass spectrometer 3 for detection.

[0003] The specific structure of the ICP torch 1 is as follows Figure 2 As shown, a water-cooled high-frequency induction coil 14 is installed at the ignition end of a pipeline composed of three concentric quartz tubes. Cooling gas flows tangentially through the outer tube 11, auxiliary gas flows axially through the middle tube 12, and sample gas flows axially through the inner tube 13. During operation, a high-frequency radio frequency signal is applied to the high-frequency induction coil 14, generating a high-frequency alternating magnetic field within the coil. An ignition device (such as a Tesla coil) generates plasma from gas molecules such as argon in the cooling gas. Under the influence of the high-frequency alternating magnetic field, a ring-shaped high-temperature plasma region is formed, which further ionizes the sample gas to form a torch-like plasma flame. The cooling gas is typically argon, nitrogen, or a nitrogen-argon mixture, with an intake rate of 10-20 L / min. This high flow rate maintains and stabilizes the plasma, suppresses its expansion, and keeps it "pinched" within the outer tube. The auxiliary gas is primarily used to prevent flashback and protect the capillary tip of the inner tube 13. The sample gas is axially delivered through the capillary tip and ionized as it passes through the plasma flame. The stability of the plasma flame is affected by factors such as ambient pressure, and the gas flow rate is large. Therefore, even if the formation of the plasma flame does not depend on the composition of the ambient air, the front end of the ICP torch tube usually still needs to maintain an open system to atmospheric pressure to ensure stable gas pressure.

[0004] The mass spectrometer interface device 2 typically includes two coaxially placed conical devices, usually made of nickel or platinum. The conical device at the front (i.e., close to the ICP torch tube 1) is the sampling cone 21; the conical device at the back (i.e., close to the ion lens chamber 31 of the mass spectrometer 3) is the skimmer cone 22. The tops of the sampling cone 21 and the skimmer cone 22 are respectively provided with millimeter-scale circular holes (the former is about 1mm, and the latter is about 0.5mm), and the distance between the two circular holes is about 6-7mm. The sampling cone 21 and the skimmer cone 22 are surrounded by a partition of the interface chamber 23, and the interface chamber 23 is maintained at about 3×10 2 The primary vacuum is about Pa; the ion lens chamber after the skimmer 22 is maintained at 3×10 -2 Pa below the secondary vacuum; through the step-by-step pressure reduction of atmospheric pressure-primary vacuum-secondary vacuum, the plasma gas flow under atmospheric pressure is first diverted at the injection cone 21, and a part of the gas flow enters the interface chamber 23 through the circular hole, and then is intercepted by the intercepting cone 22, enters the secondary vacuum ion lens chamber 31, and finally enters the subsequent analysis device with higher vacuum degree (such as quadrupole analyzer 32 and ion detector 33, etc.).

[0005] In the prior art, due to the unprecedented direct connection between the ignition end of the ICP torch 1 and the injection cone 21 to the atmospheric pressure environment, atmospheric components such as nitrogen and oxygen can also participate in the plasma ionization reaction, forming a large number of nitrogen oxide ions. This has always been a pain point in the field, especially in affecting high-precision mass spectrometry isotope analysis. On the other hand, if the experimental environment air cleanliness is insufficient, the aerosol particulate components in the ambient air will also significantly affect the mass spectrometry signal, resulting in a high background noise. Therefore, how to ensure that the sample ionization process is not interfered with by components in the ambient air while maintaining the stability of the external air pressure of the plasma flame, thereby improving the sensitivity of analytical detection, is an urgent problem to be solved. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to maintain the space from the ignition end of the ICP torch tube 1 to the injection cone 21 connected to the atmosphere, and exchange the ambient gas components in the space between the two with a preset clean gas (such as argon) to improve the sensitivity and anti-interference ability of analysis and detection.

[0007] To achieve the above object, the present invention provides a gas exchange device before the injection cone of an inductively coupled plasma mass spectrometer, the inductively coupled plasma mass spectrometer comprising an ICP torch, a mass spectrometer interface device, and a mass spectrometer, the mass spectrometer interface device having an injection cone, the ICP torch and the injection cone being coaxially arranged, and a partition being arranged around the injection cone;

[0008] The gas exchange device before the injection cone is sleeved on the outside of the ICP torch tube, and the gas exchange device before the injection cone is installed on the partition around the injection cone; the gas exchange device before the injection cone includes a porous gas-permeable layer and an outer shell, the porous gas-permeable layer is arranged in the outer shell, and the space between the porous gas-permeable layer and the outer shell is a ventilation interlayer; the ventilation interlayer is closed at one end close to the injection cone; the outer shell is provided with an argon gas inlet at one end close to the injection cone; the space between the porous gas-permeable layer and the ICP torch tube is open at one end away from the injection cone and is connected to the atmosphere.

[0009] Preferably, the ventilation interlayer opens at an end away from the injection cone.

[0010] Preferably, the ventilation interlayer is closed at the end away from the injection cone, and the housing is provided with an argon outlet at the end away from the injection cone.

[0011] Preferably, the gas exchange device before the injection cone is provided with a transparent observation window, and the porous gas-permeable layer and the shell are respectively provided with transparent windows at positions corresponding to the transparent observation window.

[0012] Preferably, the gas exchange device before the injection cone is provided with a torch position adjustment opening, which is used for allowing the gas supply and power supply pipeline of the ICP torch to extend, and prevents the gas supply and power supply pipeline from colliding with the gas exchange device before the injection cone when the ICP torch is fine-tuned in position; the ventilation interlayer is closed at the edge of the torch position adjustment opening.

[0013] Preferably, the porous gas-permeable layer is one of a gas exchange membrane, porous ceramics or porous quartz.

[0014] On the other hand, the present invention provides an inductively coupled plasma mass spectrometer, comprising an ICP torch, a mass spectrometer interface device, a mass spectrometer, and the aforementioned gas exchange device before the injection cone, wherein the mass spectrometer interface device has an injection cone, the ICP torch and the injection cone are coaxially arranged, a partition is arranged around the injection cone, and a mounting structure corresponding to the gas exchange device before the injection cone is provided on the partition.

[0015] The beneficial effects of the present invention are:

[0016] (1) The gas exchange device before the injection cone of the present invention exchanges the ambient gas in the space between the ICP torch tube and the mass spectrometer interface device with a preset clean gas (such as argon), so that the ambient gas components at one end close to the plasma flame are gradually exchanged with the above-mentioned gas, so that the sample ionization process is not interfered with by the ambient air components, a lower noise baseline is obtained, and the generation of environmental component ions such as nitrogen oxide ions that may interfere with mass spectrometry analysis is reduced, thereby improving the sensitivity of mass spectrometry detection and the environmental anti-interference ability.

[0017] (2) The space between the gas exchange device before the injection cone of the present invention and the ICP matrix tube is connected to the atmosphere at the end away from the plasma flame, and the gas exchange of the porous gas permeable layer produces a uniform and stable airflow, thereby maintaining the plasma flame in an atmospheric pressure environment, and reducing the pressure fluctuations in the environment around the plasma flame caused by factors such as airflow in the external environment, thereby further stabilizing the air pressure environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 It is a structural diagram of an ICP-MS instrument in the prior art;

[0020] Figure 2 It is a structural diagram of an ICP torch in the prior art;

[0021] Figure 3 Schematic diagram of a device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0022] One of the core points of the present invention is to maintain the space between the ignition end of the ICP torch tube 1 and the injection cone 21 connected to the atmosphere, and exchange the ambient gas components in the space between the two with a preset clean gas (such as argon) to improve the sensitivity and anti-interference ability of analysis and detection.

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] like Figure 3 As shown, the ICP-MS instrument disclosed in this embodiment includes an ICP torch 1, a mass spectrometer interface device 2, a mass spectrometer 3, and a pre-injection cone gas exchange device 4. The ICP torch 1 and the injection cone 21 of the mass spectrometer interface device 2 are coaxially arranged; the pre-injection cone gas exchange device 4 is generally cylindrical and is sleeved outside the ICP torch 1. One end of the pre-injection cone gas exchange device 4 is mounted on the partition surrounding the injection cone 21 (i.e., the body shell formed by the mass spectrometer interface device 2 and the mass spectrometer 3). It is used to exchange the ambient gas components between the ICP torch 1 and the injection cone 21 with a preset clean gas (e.g., argon).

[0025] The gas exchange device 4 before the sampling cone includes a porous gas-permeable layer 41 and a shell 42. The porous gas-permeable layer 41 is located in the shell 42. The porous gas-permeable layer 41 is a gas exchange membrane or a porous ceramic, porous quartz or other breathable material. The space between the shell 42 and the porous gas-permeable layer 41 is a ventilation interlayer. The ventilation interlayer is closed at one end (i.e., the right end) close to the sampling cone 21, and the shell 42 is provided with an argon inlet 43 near the end. Argon gas flows to the left after entering the ventilation interlayer from the argon inlet 43, and passes through the porous gas-permeable layer 41 and the gas exchange layer 43. The ambient air inside exchanges gas components; the porous air-permeable layer 41 and the outer shell 42 extend to the left to a position away from the ignition end of the ICP torch tube 1, and the ventilation interlayer can be directly opened to the atmosphere at this end, or a closed interlayer structure can be maintained and an argon outlet 44 can be provided on the outer shell 42; a corresponding mounting structure part (such as a snap-fit structure, etc., not shown in the figure) is provided on the partition of the sampling cone 21, which is used to be fixedly connected to the gas exchange device 4 in front of the sampling cone, so that the area between the ICP torch tube 1 and the sampling cone 21 is separated from the atmospheric environment near this end.

[0026] In a preferred embodiment, a torch position adjustment opening is provided on the gas exchange device 4 before the injection cone, and the gas supply and power supply lines such as the cooling gas / auxiliary gas inlet and the coil connection line of the ICP torch 1 can extend from the inside of the gas exchange device 4 before the injection cone to the outside through the torch position adjustment opening, so that the ICP torch 1 will not collide with the gas exchange device 4 before the injection cone when fine-tuning the relative position with the injection cone 21; the ventilation interlayer is closed at the edge of the torch position adjustment opening. Since this place is far away from the ignition end, the small area of the torch position adjustment opening connected to the atmosphere does not affect the ventilation effect. In some other embodiments, the cooling gas / auxiliary gas inlet and the coil connection line of the ICP torch 1 can also extend from the left end to avoid the position of the gas exchange device 4 before the injection cone.

[0027] In a preferred embodiment, the gas exchange device 4 is provided with a transparent observation window at a position corresponding to the ignition end of the ICP torch tube 1, and the operator can observe the state of the plasma flame from the outside through the transparent observation window; the transparent observation window is provided in such a manner that transparent windows are provided on the outer shell 42 and the porous gas permeable layer 41 at corresponding positions of the transparent observation window.

[0028] During operation, argon gas is introduced from the argon inlet 421, and the argon gas flowing in the ventilation interlayer is exchanged with the air components in the gas exchange device 4 before the sampling cone and outside the ICP torch 1 through the porous gas permeable layer 41, and the air is taken away from the plasma flame. The left end of the space between the gas exchange device 4 before the sampling cone and the ICP torch 1 is open to the atmosphere. Therefore, the ambient gas in the space between the gas exchange device 4 before the sampling cone and the ICP torch 1 is gradually exchanged for clean argon components from the left end to the right end. On the one hand, the process of sample gas ionization is not interfered by the air components, which reduces the generation of interfering ions such as nitrogen oxide ions, and improves the sensitivity of analysis and detection and the environmental anti-interference ability; on the other hand, by connecting to the atmosphere, the ambient air pressure around the plasma flame can be maintained stable at atmospheric pressure, thereby maintaining the stability of the plasma flame.

[0029] Each embodiment in this specification focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other.

[0030] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A gas exchange device before an injection cone of an inductively coupled plasma mass spectrometer, the inductively coupled plasma mass spectrometer comprising an ICP torch, a mass spectrometer interface device, and a mass spectrometer, the mass spectrometer interface device having an injection cone, the ICP torch and the injection cone being coaxially arranged, and a partition being provided around the injection cone, characterized in that: The gas exchange device before the injection cone is sleeved on the outside of the ICP torch tube, and the gas exchange device before the injection cone is installed on the partition around the injection cone; the gas exchange device before the injection cone includes a porous gas-permeable layer and an outer shell, the porous gas-permeable layer is arranged in the outer shell, and the space between the porous gas-permeable layer and the outer shell is a ventilation interlayer; the ventilation interlayer is closed at one end close to the injection cone; the outer shell is provided with an argon gas inlet at one end close to the injection cone; the space between the porous gas-permeable layer and the ICP torch tube is open at one end away from the injection cone and is connected to the atmosphere.

2. The gas exchange device before the injection cone according to claim 1, characterized in that: The ventilation interlayer is opened at one end away from the injection cone.

3. The gas exchange device before the injection cone according to claim 1, characterized in that: The ventilation interlayer is closed at one end away from the injection cone, and the housing is provided with an argon outlet at one end away from the injection cone.

4. The gas exchange device before the injection cone according to claim 1, characterized in that: The gas exchange device before the injection cone is provided with a transparent observation window, and the porous gas-permeable layer and the shell are respectively provided with transparent windows at positions corresponding to the transparent observation window.

5. The gas exchange device before the injection cone according to claim 1, characterized in that: The gas exchange device before the injection cone is provided with a torch position adjustment opening, which is used to allow the gas supply and power supply pipeline of the ICP torch to extend out, and to prevent the gas supply and power supply pipeline from colliding with the gas exchange device before the injection cone when the ICP torch is fine-tuned in position; the ventilation interlayer is closed at the edge of the torch position adjustment opening.

6. The gas exchange device before the injection cone according to claim 1, characterized in that: The porous gas-permeable layer is one of a gas exchange membrane, porous ceramics or porous quartz.

7. An inductively coupled plasma mass spectrometer, characterized in that: The invention comprises an ICP torch, a mass spectrometer interface device, a mass spectrometer and a gas exchange device before the injection cone as described in any one of claims 1 to 6, wherein the mass spectrometer interface device has an injection cone, the ICP torch and the injection cone are coaxially arranged, a partition is arranged around the injection cone, and a mounting structure corresponding to the gas exchange device before the injection cone is provided on the partition.

Images