A high-coverage polarity-switching ionization source

Abstract

This invention discloses a high-coverage polarity-switching ionization source for mass spectrometry, comprising a VUV light source, an ion source cavity, a repulsion electrode, an extraction electrode, a transport electrode, a focusing electrode, an extraction electrode, an upper evacuation line, a flow meter, an evacuation pump, an auxiliary gas source, an auxiliary gas inlet tube, a lower evacuation line, a clean air source, a make-up gas line, a sample inlet tube, and a two-way valve. Since different polarity ion sources can cover the ionization of more compounds, and the product ions of the same compound will differ under different polarity conditions, this is more helpful for compound qualitative analysis. Therefore, this invention designs a high-coverage polarity-switching ionization source, cleverly combining flow control and voltage control to facilitate switching between positive and negative ionization sources. This invention can effectively improve the coverage and accuracy of photoionization mass spectrometry in detecting complex samples, and has broad application prospects in VOCs detection technology fields such as atmospheric environmental monitoring, factory emission monitoring, and online industrial process monitoring.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry analysis technology, and in particular to a high-coverage polarity-switching ionization source for mass spectrometry analysis. Background Technology

[0002] The ionization source is the core component of a mass spectrometer, used to ionize neutral samples. It is the primary step in mass spectrometry analysis, affecting the detection sensitivity, analyzable compound range, stability, and accuracy of the entire system. Volatile organic compounds (VOCs) are widely present in the environment. Due to their volatility and high toxicity, VOCs in the atmosphere and water have a serious impact on the ecological environment and human health, making their detection and pollution monitoring crucial. However, VOCs are diverse in type and properties, making high-coverage, high-sensitivity, and high-accuracy measurement extremely difficult. Using a bipolar ionization source capable of analyzing both positive and negative polarities offers a practical solution to improve the coverage and accuracy of VOC measurements.

[0003] Currently, the ionization sources commonly used in VOCs analysis include chemical ionization sources and photoionization sources. Photoionization (PI) is the process by which sample molecules absorb photons, causing them to lose electrons when their energy reaches or exceeds their own ionization energy. Typically, the energy of the photons absorbed by the molecules is greater than the ionization energy threshold but less than the dissociation energy threshold, resulting in fewer product fragments and a high molecular ion yield. Subsequently, researchers combined photoionization and chemical ionization sources to develop photochemical ionization methods, improving the detection range of photoionization sources and enhancing their versatility to some extent. However, research on positive-negative switching bipolar mass spectrometry photoionization sources for VOCs detection is still scarce.

[0004] Through patent and paper searches, the following patents related to polarity-switching ionization sources for mass spectrometers were found: 1. A multi-mode ionization source and its application were applied for and disclosed by the Institute of Chemistry, Chinese Academy of Sciences on March 3, 2016. This multi-mode ionization source can switch between two ionization modes: electrospray ionization and plasma ionization. 2. A corona discharge-electrospray ionization source device was applied for and disclosed by Guangzhou Hexin Instrument Co., Ltd. on December 27, 2018. This device can simultaneously realize or switch between low-temperature plasma ionization source and electrospray ionization source. 3. A corona discharge-electrospray ionization source device was applied for and disclosed by Xiamen Medical College on October 10, 2020. This device integrates electrospray ionization source and atmospheric pressure chemical ionization ionization source into the same device, and the two functions can be quickly switched by adjusting the parameters. However, all three patents are atmospheric pressure ionization sources, mostly used for liquid or solid compounds, and are difficult to use for VOCs analysis. 4. Beijing Beifen Instrument Technology Co., Ltd. applied for and disclosed a bipolar controllable pulsed corona discharge ionization source and its ion mobility spectrometer on November 30, 2017. This patent utilizes a simple bipolar controllable high-voltage pulsed corona discharge structure to simultaneously generate positive and negative ions under atmospheric pressure. This patent is mainly used for atmospheric pressure ionization and can also be used for gas detection, but the discharge method has stability issues. In summary, all currently reported methods for high-coverage polarity switching ionization sources still have room for improvement, and there is no truly effective bipolar ionization source for VOCs detection. Summary of the Invention

[0005] This invention proposes a high-coverage polarity-switching ionization source for mass spectrometers to solve the problems of high coverage and accuracy in VOCs measurement.

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

[0007] A high-coverage polarity-switching ionization source includes a VUV light source, an ion source cavity, an upper suction line, a first flow meter, a second flow meter, a third flow meter, an upper suction pump, a lower suction pump, an auxiliary gas source, an auxiliary gas inlet pipe, a lower suction line, a clean air source, a make-up gas line, a sample inlet pipe, and a two-way valve; characterized in that:

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

[0009] The ion source cavity is a hollow, sealed cavity. Inside the ion source cavity, from left to right along the X-direction, are arranged a repulsion electrode, an extraction electrode, a transport electrode, a converging electrode, and an extraction electrode. Each of these electrodes is a flat plate structure with a central through-hole, and they are parallel, with their central holes coaxial and spaced apart. The central through-hole of the extraction electrode connects to the outside of the ion source cavity. The VUV light source is located on the left side of the ion source cavity, and its emission port is located inside the ion source cavity. One opening of the upper suction pipe passes through the upper wall of the ion source cavity from the outside and extends into the cavity, reaching between the repulsion and extraction electrodes. The other opening of the upper suction pipe is connected to the upper suction pump via a first flow meter. One opening of the auxiliary gas inlet pipe passes through the upper wall of the ion source cavity from the outside. The auxiliary gas inlet tube enters the ion source cavity and extends between the extraction electrode and the transfer electrode. The other opening of the auxiliary gas inlet tube is connected to the auxiliary gas source via a second flow meter. The lower suction line enters the ion source cavity from the outside, passes through the upper wall of the ion source cavity, and extends between the transfer electrode and the converging electrode. The other opening of the lower suction line is connected to the lower suction pump via a third flow meter. The make-up gas line enters the ion source cavity from the outside, passes through the lower wall of the ion source cavity, and extends between the transfer electrode and the converging electrode. The other opening of the make-up gas line is connected to a clean air source via a two-way valve. The sample inlet tube enters the ion source cavity from the outside, passes through the lower wall of the ion source cavity, and extends between the extraction electrode and the transfer electrode. The sample can enter the ion source cavity through the sample inlet tube.

[0010] Furthermore, the upper suction line, auxiliary gas inlet tube, lower suction line, make-up gas line, and sample inlet tube 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, plexiglass, etc., with an inner diameter of 0.1 to 2 mm and a flow rate of 0.1 to 3 L / min.

[0011] Furthermore, the diameter of the through hole in the middle of the repulsion electrode, extraction electrode, transport electrode, and convergence electrode is 2–20 mm; the diameter of the through hole in the middle of the lead-out electrode is 0.2–5 mm.

[0012] Furthermore, along the X direction, an ion transport electric field with a magnitude of 1 to 100 V / cm is formed on each electrode—repulsion electrode, extraction electrode, transport electrode, convergence electrode, and extraction electrode—in descending order of voltage (e.g., applying different voltages V1, V2, V3, etc. in sequence).

[0013] Furthermore, the lead-out 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 light source, a laser light source, or a synchrotron radiation light source.

[0015] This invention designs a high-coverage polarity-switching ionization source, which cleverly combines flow control and voltage control to facilitate switching between positive and negative ionization sources. This invention can effectively improve the coverage and accuracy of photoionization mass spectrometry in detecting complex samples, and has broad application prospects in VOCs detection technologies such as atmospheric environmental monitoring, factory emission 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 a high-coverage polarity-switching ionization source according to one embodiment of the present invention. Detailed Implementation

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] This embodiment of a high-coverage polarity-switching ionization source for a mass spectrometer includes a VUV light source 1, an ion source cavity 2, an upper suction line 4, a first flow meter 3, a second flow meter 7, a third flow meter 11, an upper suction pump 5, a lower suction pump 9, an auxiliary gas source 6, an auxiliary gas inlet pipe 8, a lower suction line 10, a clean air source 16, a make-up gas line 14, a sample inlet pipe 19, and a two-way valve 15; its characteristic is that:

[0024] The X direction is to the right, and the Y direction is upward.

[0025] The ion source cavity 2 is a hollow, sealed cavity. Inside the ion source cavity 2, from left to right along the X direction, are arranged a repulsion electrode 21, an extraction electrode 20, a transport electrode 17, a convergence electrode 13, and an extraction electrode 12. The repulsion electrode 21, extraction electrode 20, transport electrode 17, convergence electrode 13, and extraction electrode 12 are all flat plate structures with through holes in the center. They are parallel, with their central holes coaxial and spaced apart. The through hole in the center of the extraction electrode 12 communicates with the outside of the ion source cavity 2. The V... The UV light source 1 is placed on the left side of the ion source cavity 2, and the light outlet of the VUV light source 1 is located inside the ion source cavity 2. One opening of the upper suction pipe 4 passes through the upper wall of the ion source cavity 2 from the outside and enters the interior of the ion source cavity 2, extending between the repulsion electrode 21 and the extraction electrode 20. The other opening of the upper suction pipe 4 is connected to the upper suction pump 5 through the first flow meter 3. One opening of the auxiliary gas inlet pipe 8 passes through the upper wall of the ion source cavity 2 from the outside and enters the ion source cavity 2. The auxiliary gas inlet tube 8 extends into the ion source cavity 2, between the extraction electrode 20 and the transfer electrode 17. The other open end of the auxiliary gas inlet tube 8 is connected to the auxiliary gas source 6 via a second flow meter 7. One open end of the lower suction line 10 passes through the upper wall of the ion source cavity 2 from the outside of the ion source cavity 2 and enters the interior of the ion source cavity 2, extending between the transfer electrode 17 and the converging electrode 13. The other open end of the lower suction line 10 is connected to the lower suction pump 9 via a third flow meter 11. One open end of the replenishment gas line 14 is connected to the ion source cavity 2 by the auxiliary gas inlet tube 8. The outside of the source cavity 2 passes through the lower wall of the ion source cavity 2 and enters the interior of the ion source cavity 2, extending between the transmission electrode 17 and the converging electrode 13. The other open end of the gas supply line 14 is connected to the clean air source 16 through a two-way valve 15. One open end of the sample injection tube 19 passes through the lower wall of the ion source cavity 2 and enters the interior of the ion source cavity 2, extending between the extraction electrode 20 and the transmission electrode 17. The sample 18 can enter the ion source cavity 2 through the sample injection tube 19.

[0026] Furthermore, the upper suction line 4, the auxiliary gas inlet line 8, the lower suction line 10, the make-up gas line 14, and the sample inlet line 19 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, plexiglass, etc., with an inner diameter of 0.1 to 2 mm and a flow rate of 0.1 to 3 L / min.

[0027] Preferably, the upper suction line 4, the auxiliary gas inlet line 8, the lower suction line 10, the make-up gas line 14, and the sample inlet line 19 are made of PTFE material with an inner diameter of 1.5 mm.

[0028] Furthermore, the diameter of the through hole in the middle of the repulsion electrode 21, extraction electrode 20, transfer electrode 17 and convergence electrode 13 is 2 to 20 mm; the diameter of the through hole in the middle of the lead-out electrode 12 is 0.2 to 5 mm.

[0029] Preferably, the diameter of the central aperture of the repulsion electrode 21, extraction electrode 20, transfer electrode 17 and convergence electrode 13 is 10 mm; the diameter of the central aperture of the lead-out electrode 12 is 1 mm.

[0030] Furthermore, along the X direction, an ion transport electric field with a magnitude of 1 to 100 V / cm is formed on each electrode—repulsion electrode 21, extraction electrode 20, transport electrode 17, convergence electrode 13, and extraction electrode 12—in descending order of voltage (e.g., applying different voltages V1, V2, V3, etc. in sequence).

[0031] Preferably, along the X direction, different voltages of 3000V, 2300V, 1600V, 900V, and 100V are sequentially applied to the repulsion electrode 21, extraction electrode 20, transport electrode 17, convergence electrode 13, and extraction electrode 12 in descending order of voltage. In positive ion mode, different voltages of -3000V, -2300V, -1600V, -900V, and -100V are sequentially applied. In negative ion mode, different voltages of -3000V, -2300V, -1600V, -900V, and -100V are sequentially applied.

[0032] Furthermore, the lead-out electrode 12 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 1 is a gas discharge lamp light source, a laser light source, or a synchrotron radiation light source.

[0034] The specific workflow is as follows: In positive ion mode, different voltages of 3000V, 2300V, 1600V, 900V, and 100V are sequentially applied to the repulsion electrode 21, extraction electrode 20, transport electrode 17, convergence electrode 13, and extraction electrode 12. The lower suction pump 9 is turned on, and the pumping speed is controlled by the third flow meter 11. The sample 18 enters the ionization region under negative pressure and is ionized by the VUV light source 1. Finally, the ionization source is extracted under the dual action of airflow and voltage. If chemical ionization is required, the auxiliary gas source 6 is turned on, and the flow rate of the auxiliary gas source is controlled by the second flow meter 7 to chemically ionize the sample. Negative ion mode: Different voltages of -3000V, -2300V, -1600V, -900V, and -100V are sequentially applied to the repulsion electrode 21, extraction electrode 20, transmission electrode 17, convergence electrode 13, and extraction electrode 12. The upper air pump 5 is turned on, and the pumping speed is controlled by the first flow meter 3. The sample 18 enters the ionization zone under negative pressure. At the same time, the auxiliary gas source 6 is turned on, and the flow rate of the auxiliary gas source is controlled by the second flow meter 7. Under the action of the airflow, the sample 18 and the auxiliary gas are blown toward the VUV light source 1, generating negative ion ionization. Finally, the generated negative ions 22 are extracted from the ionization source under the action of the electric field.

[0035] 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.

[0036] 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 high-coverage polarity-switching ionization source, comprising a VUV light source (1), an ion source cavity (2), an upper suction line (4), a first flow meter (3), a second flow meter (7), a third flow meter (11), an upper suction pump (5), a lower suction pump (9), an auxiliary gas source (6), an auxiliary gas inlet pipe (8), a lower suction line (10), a clean air source (16), a make-up gas line (14), a sample inlet pipe (19), and a two-way valve (15); characterized in that: The X direction is to the right, and the Y direction is upward. The ion source cavity (2) is a hollow, sealed cavity. Inside the ion source cavity (2), from left to right along the X direction, are arranged a repulsion electrode (21), an extraction electrode (20), a transport electrode (17), a convergence electrode (13), and an extraction electrode (12). The repulsion electrode (21), extraction electrode (20), transport electrode (17), convergence electrode (13), and extraction electrode (12) are all flat plate structures with through holes in the center. They are parallel, with their central holes coaxial and spaced apart. The through hole in the center of the extraction electrode (12) is connected to the outside of the ion source cavity (2). The VUV light... The source (1) is placed on the left side of the ion source cavity (2), and the light outlet of the VUV light source (1) is located inside the ion source cavity (2); one opening of the upper suction pipe (4) passes through the upper wall of the ion source cavity (2) from the outside of the ion source cavity (2) and enters the interior of the ion source cavity (2), extending between the repulsion electrode (21) and the extraction electrode (20); the other opening of the upper suction pipe (4) is connected to the upper suction pump (5) through the first flow meter (3); one opening of the auxiliary gas injection pipe (8) passes through the upper wall of the ion source cavity (2) from the outside of the ion source cavity (2) and enters the ion source cavity. (2) Inside, and extends between the extraction electrode (20) and the transmission electrode (17), the other opening of the auxiliary gas injection tube (8) is connected to the auxiliary gas source (6) through the second flow meter (7); one opening of the lower gas extraction tube (10) passes through the upper wall of the ion source cavity (2) from the outside of the ion source cavity (2) and enters the interior of the ion source cavity (2), and extends between the transmission electrode (17) and the converging electrode (13), the other opening of the lower gas extraction tube (10) is connected to the lower gas extraction pump (9) through the third flow meter (11); one opening of the gas replenishment tube (14) is from the ion source cavity The body (2) passes through the lower wall of the ion source cavity (2) and enters the interior of the ion source cavity (2), extending between the transmission electrode (17) and the convergence electrode (13). The other opening of the gas supply line (14) is connected to the clean air source (16) through a two-way valve (15). One opening of the sample injection tube (19) passes through the lower wall of the ion source cavity (2) and enters the interior of the ion source cavity (2), extending between the extraction electrode (20) and the transmission electrode (17). The sample (18) can enter the ion source cavity (2) through the sample injection tube (19).

2. The ionization source according to claim 1, characterized in that: The upper suction line (4), the auxiliary gas inlet line (8), the lower suction line (10), the supplementary gas line (14), and the sample inlet line (19) are made of one or more of metal or non-metal materials, with an inner diameter of 0.1~2 mm and a flow rate of 0.1~3 L / min.

3. The ionization source according to claim 1, characterized in that: The diameter of the through hole in the middle of the repulsion electrode (21), extraction electrode (20), transport electrode (17) and convergence electrode (13) is 2~20mm; the diameter of the through hole in the middle of the lead-out electrode (12) is 0.2~5mm.

4. The ionization source according to claim 1, characterized in that: Along the X direction, an ion transport electric field with a magnitude of 1~100 V / cm is formed on each of the repulsion electrode (21), extraction electrode (20), transport electrode (17), convergence electrode (13) and extraction electrode (12) in order of voltage from high to low.

5. The ionization source according to claim 1, characterized in that: The lead-out electrode (12) 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 ionization source according to claim 1, characterized in that: The VUV light source (1) is a gas discharge lamp light source, a laser light source, or a synchrotron radiation light source.

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