A sampling tube array vuv photoionization source for mass spectrometry

Abstract

The application discloses a sampling tube array VUV photoionization source for mass spectrometry, comprising a large-flow sampling port, an array VUV light source sampling tube, a VUV light source, an ion transmission cavity, an ion transmission electrode, an ion extraction electrode and a gas suction pump. Since the sensitivity of the VUV photoionization source is closely related to the sample amount and sample utilization, in order to improve the sensitivity of the VUV photoionization source, the sample amount and sample utilization can be increased. The application designs a sampling tube array VUV photoionization source, which combines the VUV light source and the sampling tube in a clever way, so that the sample can be effectively irradiated by the VUV light source during the transmission of the sampling tube, thereby improving the sample utilization and the sample ionization efficiency, and achieving the purpose of VOCs detection sensitivity. In addition, a large-flow sampling port is adopted, so as to improve the accuracy of the sampling concentration. The application can effectively improve the detection sensitivity and accuracy of the mass spectrometer for gas samples, and has a wide application prospect in the technical field of VOCs detection such as rapid atmospheric environment monitoring and industrial process online monitoring.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry analysis technology, and more particularly to a sampling tube array VUV photoionization source for mass spectrometry. Background Technology

[0002] Volatile organic compounds (VOCs) are not only important precursors to PM2.5 and ozone, but most are also biotoxic, posing a threat to human health. However, environmental VOCs are characterized by their wide distribution, diverse types, low concentrations, and rapid spatial and temporal variations, posing new challenges to VOCs monitoring technologies and necessitating the development of ultra-sensitive and rapid monitoring technologies. The mobile mass spectrometry (MMS) technology for VOCs, which has emerged in recent years, can correlate VOCs pollution data with geographical locations, quickly creating regional VOCs pollution maps and enabling differentiated management. The ionization source is the core of mobile mass spectrometry, influencing the sensitivity of the mass spectrometer, the types of detectable compounds, and ion characteristics.

[0003] The soft ionization sources used in mobile mass spectrometry mainly include proton transfer reaction (PTR) ionization sources and vacuum ultraviolet photoionization sources (VUV-PI). Soft ionization technology effectively solves the peak overlap problem caused by the high fragmentation of traditional electron impact ionization (EI) technology, resulting in simple and easily interpretable spectra, making it highly suitable for mobile monitoring of environmental VOCs. However, for mobile monitoring, current mass spectrometry ionization technology still suffers from small sample injection volumes and low utilization rates. Environmental VOCs are characterized by large sample sizes and inexhaustible resources, while current mass spectrometry ionization sources are mainly used for laboratory analysis with limited injection flow rates and ionization spaces. This not only fails to accurately reflect actual VOC concentrations but also hinders the effective utilization of large VOC samples. Therefore, the development of array ionization source designs is needed to meet the high-flow-rate sampling and high-sensitivity requirements of rapid monitoring mass spectrometry.

[0004] Through patent and paper searches, the following patents related to mass spectrometer array ionization sources were found: 1. A patent application filed and disclosed by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences on December 17, 2012, regarding an array-type photoelectric emission ionization source and its application. This technology is used for ion mobility spectrometry. The array-type photoelectric emission ionization source significantly increases light intensity, greatly increasing the number of ions ionized in the ionization region and effectively improving the sensitivity of the ion mobility tube. However, this design, while targeting ion mobility spectrometry, is limited by the volume of the ion mobility spectrum, thus limiting the light intensity enhancement. 2. A patent application filed and disclosed by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences on November 21, 2013, regarding an ionization source based on vacuum ultraviolet light, using a nano-array modification to enhance photoelectron emission. This invention modifies the electrode surface with a nano-gold array, utilizing the surface plasmon resonance effect of the nano-gold array to improve the efficiency of photoelectrons generated by the vacuum ultraviolet lamp, enhancing sensitivity and improving the stability of the ionization source without changing the ultraviolet light intensity. This invention is mainly used for photoelectron or photoelectron-induced ionization and is ineffective for single-photon ionization. In addition, the array ionization design of both patents occurs at the sampling back end, which is not efficient enough for sample utilization and cannot effectively utilize large sample amounts of compounds. Summary of the Invention

[0005] This invention proposes a sampling tube array VUV photoionization source for mass spectrometers, which solves the problem of large sample utilization and improves the instrument's instantaneous sensitivity and measurement accuracy.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] A sampling tube array VUV photoionization source includes a high-flow-rate sampling port, an array of VUV light source sampling tubes, a VUV light source, an ion transport cavity, an ion transport electrode assembly, an ion extraction electrode, and a pump; characterized in that:

[0008] The X direction is to the right, and the Y direction is upward.

[0009] The sample sampling port is funnel-shaped or frustum-shaped with its inner diameter gradually decreasing along the X-direction. Its right port is sealed to the left port of the array VUV light source sampling tube. The array VUV light source sampling tube is a tubular structure with a central through-hole, and has four or more array VUV light windows arranged in an array along the X-direction. Each array VUV light window consists of four cylindrical through-holes on the side wall of the array VUV light source sampling tube, and is symmetrically arranged along the radial direction of the cylindrical array VUV light source sampling tube. The axes of adjacent array VUV light windows are perpendicular to each other in the radial direction. A VUV light source is located on the outside of the light windows away from the array VUV light source sampling tube. The light emitted by the VUV light source enters the array VUV light source sampling tube through the light windows. The VUV light source is located on the outside of the array VUV light source sampling tube, and the light outlet of the VUV light source is sealed to the light window and placed coaxially. It is placed perpendicular to the axis of the array VUV light source sampling tube; the central axis of the sample sampling port is coaxial with the central axis of the array VUV light source sampling tube; the ion transmission cavity is a hollow, sealed circular cavity with an inlet at the middle of its left end, which is coaxial and sealed with the right port of the array VUV light source sampling tube; inside the ion transmission cavity, from left to right along the X direction, there are ion transmission electrode groups and ion extraction electrodes; the ion transmission electrode group consists of three or more flat ion transmission electrodes with circular through holes in the middle, which are parallel to each other, with the through holes in the middle coaxial and spaced apart, and the last ion transmission electrode along the X direction is parallel to the ion extraction electrode, with the through holes in the middle coaxial and spaced apart; the through hole in the middle of the ion extraction electrode is connected to the outside of the ion transmission cavity; the vacuum pump is connected to the ion transmission cavity and is used to remove unionized neutral samples.

[0010] Furthermore, the high-flow-rate sampling port can be made of one or more of the following materials: metal or non-metal, such as stainless steel, aluminum alloy or copper, PEEK, PTFE, or plexiglass. The inner diameter of the high-flow-rate sampling port is 0.1 to 10 mm, and the sample gas flow rate is 0.1 to 10 L / min.

[0011] Furthermore, the diameter of the through hole in the middle of the array VUV light source sampling tube is 2–20 mm; the diameter of the through hole in the middle of the ion transport electrode is 2–20 mm; and the diameter of the through hole in the middle of the ion extraction electrode is 0.2–5 mm.

[0012] Furthermore, along the X direction, different voltages (e.g., V1, V2, V3, etc.) are sequentially applied to each electrode of the ion transport electrode group in descending order of voltage, forming an ion transport electric field with a magnitude of 1 to 100 V / cm.

[0013] Furthermore, the ion extraction electrode is connected to a mass analyzer, which is a time-of-flight mass analyzer, a quadrupole mass analyzer, or an ion trap mass analyzer.

[0014] Furthermore, the VUV light source is a gas discharge lamp, a laser light source, or a synchrotron radiation light source; the internal gas pressure of the ion transmission cavity is 1-1000 Pa.

[0015] This invention cleverly combines a VUV light source and a sampling tube, ensuring that the sample is continuously and effectively irradiated by the VUV light source during transport through the sampling tube. This improves sample utilization and ionization efficiency, thereby enhancing VOCs detection sensitivity. Furthermore, the use of a high-flow-rate inlet improves the accuracy of sampling concentration. This invention effectively enhances the sensitivity and accuracy of mass spectrometers in detecting gaseous samples, and has broad application prospects in VOCs detection technologies such as rapid atmospheric environmental monitoring and online industrial process monitoring. Attached Figure Description

[0016] The accompanying drawings further illustrate the present invention, but the content of the drawings does not constitute any limitation on the present invention.

[0017] Figure 1 This is a schematic diagram of the overall structure of the sampling tube array VUV photoionization source according to one embodiment of the present invention;

[0018] In the figure, 7 represents the sample ions after ionization, and 10 represents the sample molecules that have entered the ionization region. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0022] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0023] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0024] This embodiment provides a sampling tube array VUV photoionization source for a mass spectrometer, comprising a high-flow-rate sampling port 2, an array VUV light source sampling tube 11, a VUV light source 3, an ion transmission chamber 13, an ion transmission electrode group 9, an ion extraction electrode 8, and a vacuum pump 5; characterized in that:

[0025] The X direction is to the right, and the Y direction is upward.

[0026] The sample sampling port 2 is funnel-shaped or frustum-shaped with its inner diameter gradually decreasing along the X direction. Its right port is sealed to the left port of the array VUV light source sampling tube 11. The array VUV light source sampling tube 11 is a tubular structure with a central through hole. Along the X direction, it has four or more array VUV light windows 4. Each array VUV light window 4 consists of four cylindrical through holes on the side wall of the array VUV light source sampling tube 11, and they are symmetrically arranged along the radial direction of the cylindrical array VUV light source sampling tube 11. Along the radial direction, the axes of adjacent array VUV light windows 4 are perpendicular to each other. A VUV light source 3 is located on the outside of the light window away from the array VUV light source sampling tube. The light emitted by the VUV light source 3 enters the array VUV light source sampling tube through the light window. The VUV light source 3 is located outside the array VUV light source sampling tube 11, and the light outlet of the VUV light source 3 is sealed to the light window 4 and placed coaxially. The VUV light source sampling tube 11 is placed vertically along its axis; the central axis of the sample sampling port 2 is coaxial with the central axis of the array VUV light source sampling tube 11; the ion transmission cavity 13 is a hollow, sealed circular cavity with an inlet at the center of its left end, which is coaxially and sealed with the right port of the array VUV light source sampling tube 11; inside the ion transmission cavity 13, from left to right along the X direction, there are ion transmission electrode group 9 and ion extraction electrode 8 arranged sequentially; the ion transmission electrode group 9 consists of three or more flat ion transmission electrodes 12 with circular through holes in the center, which are parallel to each other, with their through holes coaxial and spaced apart, and the last ion transmission electrode 12 along the X direction is parallel to the ion extraction electrode 8, with its through holes coaxial and spaced apart; the through hole in the center of the ion extraction electrode 8 is connected to the outside of the ion transmission cavity 13; the vacuum pump 5 is connected to the ion transmission cavity 13 and is used to remove the unionized neutral sample 6.

[0027] Furthermore, the high-flow-rate sampling port 2 can be made of one or more of the following materials: metal or non-metal, such as stainless steel, aluminum alloy or copper, PEEK, PTFE, or plexiglass. The inner diameter of the high-flow-rate sampling port 2 is 0.1 to 10 mm, and the flow rate of the sample gas 1 is 0.1 to 10 L / min.

[0028] Preferably, the high-flow-rate sampling port 2 is made of stainless steel, with an inner diameter of 0.3 mm and a flow rate of 0.5 L / min, which simultaneously meets the requirements of large injection volume and mass spectrometry vacuum system.

[0029] Furthermore, the diameter of the through hole in the middle of the array VUV light source sampling tube 11 is 2-20 mm; the diameter of the through hole in the middle of the ion transport electrode 12 is 2-20 mm; and the diameter of the through hole in the middle of the ion extraction electrode 8 is 0.2-5 mm.

[0030] Preferably, the diameter of the central hole of the array VUV light source sampling tube 11 is 10 mm to meet the spatial and optical path requirements; the diameter of the central hole of the ion transport electrode 12 is 10 mm to meet the ion transport design; and the diameter of the central hole of the ion extraction electrode 8 is 1 mm to meet the requirements of the next stage differential vacuum.

[0031] Furthermore, along the X direction, different voltages (e.g., V1, V2, V3, etc.) are sequentially applied to each electrode of the ion transport electrode group 9 in descending order of voltage, forming an ion transport electric field with a magnitude of 1 to 100 V / cm.

[0032] Furthermore, the ion extraction electrode 8 is connected to a mass analyzer, which is a time-of-flight mass analyzer, a quadrupole mass analyzer, or an ion trap mass analyzer.

[0033] Furthermore, the VUV light source 3 is a gas discharge lamp light source, a laser light source, or a synchrotron radiation light source; the internal gas pressure of the ion transmission cavity 13 is 1-1000 Pa.

[0034] Preferably, the internal pressure of the ion transmission cavity 13 is 500 Pa.

[0035] In practical operation, sample 1, driven by the vacuum pump 5, enters the array VUV light source sampling tube 11 through the high-flow sampling port 2. During transmission, it is continuously and effectively irradiated by the VUV light source 3 to improve sample utilization and ionization efficiency. Ionized ions in the sampling tube enter the ion transmission chamber 13, and are finally shaped and converged under the influence of an electric field, before being extracted by the extraction electrode 8 to the mass spectrometer. This invention can effectively improve the detection sensitivity and accuracy of mass spectrometers for gas samples, and has broad application prospects in VOCs detection technologies such as rapid atmospheric environment monitoring and online industrial process monitoring.

[0036] The technical principles of the present invention have been described above with reference to specific embodiments. These descriptions are merely for explaining the principles of the invention and should not be construed as limiting the scope of protection of the invention in any way. Based on this explanation, those skilled in the art can readily conceive of other specific embodiments of the invention without inventive effort, and these equivalent variations or substitutions are all included within the scope defined by the claims of this application.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A sampling tube array VUV photoionization source, comprising a high-flow-rate sampling port (2), an array VUV light source sampling tube (11), a VUV light source (3), an ion transmission chamber (13), an ion transmission electrode group (9), an ion extraction electrode (8), and a vacuum pump (5); characterized in that: The X direction is to the right, and the Y direction is upward. The high-flow-rate sample sampling port (2) is horn-shaped or frustum-shaped and its inner diameter gradually decreases along the X direction. Its right port is sealed to the left port of the array VUV light source sampling tube (11). The array VUV light source sampling tube (11) is a tubular structure with a central through hole. Along the X direction, it is arrayed with more than 4 sets of array VUV light windows (4). Each set of array VUV light windows (4) consists of 4 cylindrical through holes set on the side wall of the array VUV light source sampling tube (11). The sample tube (11) is centrally symmetrically arranged in the radial direction. Along the radial direction, the axes of adjacent array VUV light windows (4) are arranged perpendicular to each other. A VUV light source (3) is provided on the outside of the light window away from the array VUV light source sampling tube. The light emitted by the VUV light source (3) enters the array VUV light source sampling tube through the light window. The VUV light source (3) is placed outside the array VUV light source sampling tube (11), and the light outlet of the VUV light source (3) is sealed and connected to the light window (4) and placed coaxially. The sample tube (11) is placed vertically along its axis; the central axis of the high-flow-rate sample sampling port (2) is coaxial with the central axis of the array VUV light source sampling tube (11); the ion transmission cavity (13) is a hollow, sealed circular cavity with an inlet at the middle of its left end, which is coaxially and sealed with the right port of the array VUV light source sampling tube (11); inside the ion transmission cavity (13), from left to right along the X direction, there are ion transmission electrode groups (9) and ion extraction electrodes (8); the ion transmission electrode groups (9) It consists of three or more flat ion transport electrodes (12) with circular through holes in the middle. The ion transport electrodes (12) are parallel to each other, with the through holes in the middle coaxial and spaced apart. The last ion transport electrode (12) along the X direction is parallel to the ion extraction electrode (8), with the through holes in the middle coaxial and spaced apart. The through hole in the middle of the ion extraction electrode (8) is connected to the outside of the ion transport cavity (13). The vacuum pump (5) is connected to the ion transport cavity (13) and is used to remove the unionized neutral sample (6).

2. The photoionization source according to claim 1, characterized in that: The high-flow sampling port (2) is made of one or more of metal or non-metal materials, with an inner diameter of 0.1 to 10 mm and a flow rate of 0.1 to 10 L / min for the sample gas (1).

3. The photoionization source according to claim 1, characterized in that: The diameter of the through hole in the middle of the array VUV light source sampling tube (11) is 2-20 mm; the diameter of the through hole in the middle of the ion transport electrode (12) is 2-20 mm; and the diameter of the through hole in the middle of the ion extraction electrode (8) is 0.2-5 mm.

4. The photoionization source according to claim 1, characterized in that: Along the X direction, different voltages are applied sequentially to each electrode of the ion transport electrode group (9) in order from high to low voltage, forming an ion transport electric field with a magnitude of 1 to 100 V / cm.

5. The photoionization source according to claim 1, characterized in that: The ion extraction electrode (8) is connected to a mass analyzer, which is a time-of-flight mass analyzer, a quadrupole mass analyzer, or an ion trap mass analyzer.

6. The photoionization source according to claim 1, characterized in that: The VUV light source (3) is a gas discharge lamp light source, a laser light source or a synchrotron radiation light source; the internal pressure of the ion transmission cavity (13) is 1 to 1000 Pa.

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