Broad-spectrum mass spectrum ionization source based on low-voltage glow discharge

Abstract

The invention discloses a broad-spectrum mass spectrum ionization source based on low-voltage glow discharge. The broad-spectrum mass spectrum ionization source comprises a sample introduction module, a low-voltage glow discharge adjustable module and an energy regulation and ionization module. Wherein the sample injection module is provided with a heating control assembly, and samples in different forms are controllably vaporized; the low-voltage glow discharge adjustable module comprises a high-voltage electrode and a low-voltage electrode and realizes continuous and accurate regulation and control of plasma energy; the energy regulation and ionization module comprises an energy regulation and control area formed by utilizing controllable direct-current voltage difference between a low-voltage electrode and a downstream ion funnel, kinetic energy and internal energy of ions can be regulated and controlled by regulating voltage, and continuous switching of collision induced ionization in the ion funnel between a soft ionization mode and a hard ionization mode is achieved. And the quasi-molecular ion peak is rapidly and accurately measured, so that the reliability of qualitative analysis is remarkably improved. The invention provides an effective technical solution for high-flux and high-coverage mass spectrometry of small molecular substances in a complex matrix.

Description

Technical Field

[0001] This invention belongs to the field of mass spectrometry ionization technology and analytical instrument technology, specifically relating to a broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge. Background Technology

[0002] The analytical capabilities of mass spectrometry fundamentally depend on the ionization methods employed. Despite continuous advancements in ionization techniques in recent years, existing ionization sources still exhibit significant limitations in terms of spectral breadth and energy tunability.

[0003] In terms of spectral breadth, the analytical range of common ionization sources is still limited by the physicochemical properties of the samples. For example, electrospray ionization (ESI) responds well to polar compounds but is difficult to effectively ionize nonpolar or weakly polar small molecules; atmospheric pressure chemical ionization (APCI) can cover some moderately polar substances, but its ionization process is easily affected by the ambient atmosphere and matrix, and its stability and reproducibility often face challenges.

[0004] In terms of functionality and energy tunability, most existing ionization sources are designed with fixed modes, making it difficult to flexibly adjust the "soft" or "hard" degree of ionization. Soft ionization techniques (such as ESI and MALDI) can preserve complete molecular ion information, but lack fragment signals sufficient for inferring molecular structure; hard ionization techniques (such as electron impact ionization, EI) can provide rich fragment spectra, but often lead to the disappearance of molecular ion peaks, making it impossible to directly obtain molecular weight information. Under the current technological system, continuous, tunable, and precise control of ionization energy within a single ionization source has not yet been achieved, thus making it impossible to dynamically adjust the degree of fragmentation according to analytical needs. This significantly limits the application efficiency and information depth of mass spectrometry in rapid screening, in-situ analysis, and multi-dimensional analysis of complex systems. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge. It has the advantages of flexible and adjustable ionization mode, wide analysis range, high sensitivity, and good repeatability. It solves the technical problem that existing ionization technologies cannot simultaneously achieve broad-spectrum ionization and precise control of molecular fragmentation. It provides a brand-new solution for realizing comprehensive analysis of polar to nonpolar substances and flexible switching between soft and hard ionization modes.

[0006] The technical solution adopted by this invention to solve its technical problem is: providing a broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge, including...

[0007] The sample injection module is equipped with a heating control component;

[0008] A low-voltage glow discharge adjustable module is used to generate plasma; the plasma contains primary ions with kinetic energy.

[0009] An energy regulation and ionization module includes an ion funnel, wherein an energy regulation region with a voltage difference is formed between the ion funnel and the ion outlet of a low-voltage glow discharge module.

[0010] In a preferred embodiment of the present invention, the sample injection module includes a sample injection tube; the heating control component is disposed at the outlet end of the sample injection tube and includes a heating sleeve.

[0011] In a preferred embodiment of the present invention, the low-voltage glow discharge adjustable module includes a sleeve-type low-voltage electrode and a porous high-voltage electrode, which are arranged opposite to each other to form a sealed discharge chamber.

[0012] In a preferred embodiment of the present invention, the ion outlet is disposed at the end of the sleeve-type low-pressure electrode.

[0013] In a preferred embodiment of the present invention, the porous high-voltage electrode is connected to an inert gas inlet pipe, and the edges of the porous high-voltage electrode have a rounded corner structure.

[0014] In a preferred embodiment of the present invention, the inert gas includes helium, neon or argon, and the primary ions with kinetic energy include the corresponding atomic ions of the inert gas, He⁺, Ne⁺ or Ar⁺.

[0015] In a preferred embodiment of the present invention, an ionization chamber is further included. The sample introduction module and the low-pressure glow discharge adjustable module are connected to the ionization chamber. The ion funnel is disposed in the ionization chamber and is located downstream of the sleeve-type low-pressure electrode.

[0016] In a preferred embodiment of the present invention, the energy control zone controls the kinetic energy and internal energy of ions by adjusting the DC voltage difference between the sleeve-type low-pressure electrode and the first electrode plate of the ion funnel.

[0017] In a preferred embodiment of the present invention, when primary ions via the energy control region collide with the sample molecules in the ion funnel, they selectively generate complete quasi-molecular ion peaks or characteristic fragment ions.

[0018] In a preferred embodiment of the present invention, the sample range includes polar and nonpolar small molecule compounds.

[0019] Compared with the prior art, this technical solution has the following advantages:

[0020] 1. The ionization source of this invention can achieve broad-spectrum ionization of substances ranging from strongly polar to nonpolar without switching operating modes, covering various compounds such as water, alcohols, benzene series compounds, and alkanes. In particular, for molecules such as alkanes that are prone to uncontrollable fragmentation during traditional ionization processes, this invention can achieve continuous and controllable adjustment of the ionization process and fragmentation degree of the target substance by precisely controlling the ionization energy, thereby effectively obtaining its quasi-molecular ion peak and characteristic fragment information;

[0021] 2. This invention adds a heating control component to the sample introduction module, enabling controllable heating of various types of introduced samples. The heating jacket can provide a heating temperature of no less than 500°C, and its high temperature effectively and rapidly converts samples with different volatility characteristics (including high-boiling-point liquids, solids, and viscous samples) into a gaseous state. This ensures that a broad spectrum of samples, including non-volatile substances, can stably diffuse into the subsequent ionization region in gaseous form, providing an ideal gas-phase reaction medium for the subsequent ionization process, thereby significantly expanding the sample applicability and analytical capabilities of the device.

[0022] 3. This invention employs a low-pressure glow discharge adjustable module, which is advantageous for utilizing a low-pressure environment. On the one hand, it effectively eliminates interference from complex components in the air, obtaining a relatively clean mass spectrometry background; on the other hand, it significantly enhances the electric field's control over particle energy and reaction pathways, successfully achieving broad-spectrum and controllable ionization of compounds from polar to nonpolar.

[0023] 4. The present invention sets up an energy control zone at the front end of the sample reaction zone, and uses the adjustable DC voltage difference between the low-voltage glow discharge adjustable module and the ion funnel plate to realize the control of ion kinetic energy and internal energy.

[0024] 5. This invention employs an ion funnel as the core sample reaction zone. This design fully utilizes the ion funnel's ability to operate stably at relatively high pressures (around 100 Pa), allowing the reaction zone to maintain a pressure environment higher than that of traditional high-vacuum zones. This significantly increases the collision frequency between sample molecules and primary ions, thereby ensuring efficient and complete gas-phase charge transfer reactions. Simultaneously, the ion funnel's radio frequency electric field effectively confines the product ions generated in the reaction within its axial channel, achieving efficient focusing and directional transport of ions while completing the reaction, effectively avoiding radial diffusion losses. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the ionization source structure for an example.

[0026] Figure label:

[0027] Inert gas inlet pipe (1); stainless steel connecting and sealing assembly (2, 3); fixing and wiring plate (4); pre-stage inlet chamber (5); extraction port (6); PEEK connecting and sealing assembly (7, 8); PEEK insulation components (9, 10, 13); porous high-voltage electrode (11); sleeve-type low-voltage electrode (12); copper electrode (14); ion funnel (15); ionization chamber body (16); lens plate (17); aluminum plate connected to the subsequent stage (18); sample injection tube (19); heating sleeve (20). Detailed Implementation

[0028] The technical solution of the present invention will be described below with reference to the accompanying drawings and embodiments:

[0029] Example

[0030] This embodiment discloses a broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge, comprising an ionization chamber connected to a sample introduction module and a low-voltage glow discharge adjustable module. An ion funnel 15 is located within the ionization chamber, with an ion optical lens plate 17 positioned at its rear end. Furthermore, the ionization chamber body 16 also includes necessary copper electrodes 14 and their PEEK insulating components 13, an aluminum plate 18 for connection to subsequent stages, and insulation or sealing devices between other components.

[0031] The sample introduction module includes a sample introduction tube 19, which is a stainless steel tube with an inner diameter of 0.5 mm, an outer diameter of 3 mm, and a length of 20 cm. Its inlet end is placed in the atmospheric environment, and its outlet end extends to the energy control region, that is, the low-pressure region between the ion outlet of the low-pressure glow discharge adjustable module and the subsequent ion funnel 15, which is used to directly transfer the sample to be tested from the atmospheric pressure environment to the target ionization region. The sample introduction module is equipped with a heating control component, which is a heating sleeve 20 fitted at the outlet end of the sample introduction tube 19. Its inner diameter is 3mm, outer diameter is 5mm, and length is 5mm. Through active heating, it provides an adjustable vaporization temperature for the sample flowing through it, and performs precise temperature management of the flow path to regulate the physical state and transport dynamics of the sample. For liquid samples, it provides controllable vaporization energy to efficiently and stably convert liquid samples into vapor and promote the initial transport of vapor. For gaseous samples, it can adjust the temperature, volumetric flow rate, and molecular diffusion rate of the gas to optimize its transport and diffusion process, thereby ensuring that the sample can diffuse instantaneously and uniformly after entering the low-pressure chamber.

[0032] The adjustable low-pressure glow discharge module includes a sleeve-type low-pressure electrode 12 and a porous high-pressure electrode 11, which are arranged opposite each other and together form a sealed discharge chamber. The main body of the discharge chamber is placed into the ionization chamber via PEEK insulating components 9 and 10. The porous high-pressure electrode 11 is connected to an inert gas (such as argon) inlet pipe 1. The inert gas inlet pipe 1 enters the pre-stage inlet chamber containing the evacuation port through stainless steel connecting sealing components 2 and 3 on the fixing and wiring plate, and is then introduced into the discharge chamber between the porous high-pressure electrode 11 and the sleeve-type low-pressure electrode 12 through PEEK connecting sealing components 7 and 8. A DC voltage is applied between the two electrodes to form a glow discharge, generating a large number of primary ions. The porous high-pressure electrode 11 has 32 uniformly distributed small holes with a diameter of 1 mm. Its porous structure is used to promote uniform diffusion of gas in the discharge area, thereby ensuring uniform glow discharge distribution between the two electrodes and forming a stable and uniform glow discharge plasma region. Furthermore, the edges of the high-voltage electrode are rounded to enhance the concentration of the electric field intensity along the electrode axis, effectively suppressing discharge phenomena in unexpected directions and improving the stability and controllability of the system discharge. The sleeve-type low-voltage electrode 12 has a 3mm diameter ion outlet at its end (top center position in the diagram), which can efficiently extract the generated primary ion beam from the plasma while maintaining the stability of the discharge region and directionally accelerate it to the subsequent energy control region.

[0033] The energy regulation and ionization module includes an ion funnel 15. An energy regulation region with a voltage difference is formed between the ion funnel 15 and the ion outlet of the low-voltage glow discharge module. By adjusting the DC voltage difference between the sleeve-type low-voltage electrode 12 and the foremost electrode plate of the ion funnel 15, primary ions with different energies can be obtained, achieving precise control over the kinetic and internal energy of the ions. Furthermore, gaseous sample molecules undergo charge transfer reactions within the energy regulation region and can further undergo collision-induced dissociation inside the ion funnel 15. When the voltage difference increases, the electric field strength increases accordingly, causing the ions drawn from the low-voltage electrode to gain higher kinetic energy, resulting in more violent collision-induced dissociation as they fly towards the ion funnel 15, generating more fragment ions; conversely, reducing the voltage difference achieves gentler ionization. In this way, the system achieves continuous and seamless switching from soft ionization mode to hard ionization mode. The ion funnel 15 consists of 20 PCB electrode sheets arranged sequentially along the ion transport direction. Each PCB electrode sheet has a central perforated hole to form an ion transport channel, and the diameter of the perforated hole decreases equally along the ion transport direction from 21.5 mm to 2.5 mm. A lens base is located at the end of the ion funnel 15, and the center of the lens base has a 1 mm diameter through hole for collecting and transporting ions to the subsequent analysis device.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 therein. Such 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 broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge, characterized in that: include The sample injection module is equipped with a heating control component; A low-voltage glow discharge adjustable module is used to generate plasma; the plasma contains primary ions with kinetic energy. An energy regulation and ionization module includes an ion funnel, wherein an energy regulation region with a voltage difference is formed between the ion funnel and the ion outlet of a low-voltage glow discharge module.

2. The broadband mass spectrometry ionization source based on low-voltage glow discharge according to claim 1, characterized in that: The sample injection module includes a sample injection tube; the heating control component is located at the outlet end of the sample injection tube and includes a heating sleeve.

3. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 1, characterized in that: The adjustable low-voltage glow discharge module includes a sleeve-type low-voltage electrode and a porous high-voltage electrode, which are arranged opposite each other to form a sealed discharge chamber.

4. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 3, characterized in that: The ion outlet is located at the end of the sleeve-type low-pressure electrode.

5. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 3, characterized in that: The porous high-voltage electrode is connected to an inert gas inlet pipe, and the edges of the porous high-voltage electrode have a rounded corner structure.

6. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 5, characterized in that: The inert gas includes helium, neon, or argon, and the primary ions with kinetic energy include the corresponding atomic ions of the inert gas, He⁺, Ne⁺, or Ar⁺.

7. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 1, characterized in that: It also includes an ionization chamber, the sample introduction module and the low-pressure glow discharge adjustable module are connected to the ionization chamber, and the ion funnel is disposed in the ionization chamber and located downstream of the sleeve-type low-pressure electrode.

8. A broad-spectrum mass ionization source based on low-voltage glow discharge according to claim 1, characterized in that: The energy regulation zone controls the kinetic and internal energy of ions by adjusting the DC voltage difference between the sleeve-type low-pressure electrode and the first electrode plate of the ion funnel.

9. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 8, characterized in that: When primary ions in the energy control region collide with the molecules of the sample to be tested in the ion funnel, they selectively generate complete quasi-molecular ion peaks or characteristic fragment ions.

10. A broad-spectrum mass spectrometry ionization source based on low-voltage glow discharge according to claim 1, characterized in that: The sample range includes polar and nonpolar small molecule compounds.

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