Three-dimensional laser post-ionization-secondary neutron particle mass spectrometer

Abstract

The invention discloses a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer which comprises a vacuum pool, a sample introduction system, a primary ion emission system, a three-dimensional laser post-ionization system, an ion optical system, a time-of-flight mass spectrometer, an observation system and a computer control system. By adjusting the wavelength, the frequency and the energy value of the laser, resonance between the energy of laser photons and the electron energy level of target molecules can be realized to realize selective ionization of substances, and the method has extremely high element, nuclide and molecule selectivity, can provide the sensitivity of an instrument, and can be used for mass spectrometry. The device can be applied to single-cell imaging analysis test of lipid, metabolites, small-molecule drugs and part of elements with the molecular weight smaller than 1000 Da, the problems of space metabolome small-molecule metabolite test and ultrahigh spatial resolution imaging are solved, and the device can be independently used as an SIMS when laser post-ionization is not used.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometers, and more specifically to a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer. Background Art

[0002] Spatial metabolomics technology is an emerging research technology that integrates mass spectrometry imaging and metabolomics. It can obtain the structure, content and spatial distribution information of endogenous metabolite molecules in biological tissues, which is of great significance for revealing the related mechanisms of metabolites in biological tissues. It has great potential in many fields such as disease diagnosis, drug development, and plant metabolism research. In 2022, it was listed as one of the seven most noteworthy technologies by Nature. At present, the mass spectrometry imaging technology used in spatial metabolomics is divided into secondary ion mass spectrometry (SIMS) technology, desorption electrospray ionization mass spectrometry imaging (DESI-MSI) technology, laser sputtering-electrospray ionization mass spectrometry imaging (LA-ESI-MSI) technology and matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) technology according to different ion sources.

[0003] The existing technology has the following main problems: 1. DESI-MSI does not require complicated sample pretreatment, matrix, and is convenient for the expansion of liquid and gas samples, but the spatial resolution is low and the signal is easily disturbed by the external environment; 2. LAESI-MSI sample preparation is simple and does not require a matrix, but requires aqueous and relatively stable samples and has low spatial resolution; 3. MALDI-MSI technology requires matrix assistance and sample pretreatment. It can detect thousands of molecules without targeting and can provide spatial distribution maps of molecules such as proteins and lipids in tissues. However, the matrix severely inhibits the detection of small molecule metabolites and cannot measure small molecule metabolism. The spatial resolution is low and the sensitivity needs to be improved. 4. SIMS has nanometer-level spatial resolution, but in fact, about 99% of the particles produced in the primary ion sputtering process are neutral particles, of which secondary ions account for only a small part of the total sputtering products (about 0.01% to 1%). The sputtering components dominated by neutral particles lead to the overall low ionization efficiency and low sensitivity of SIMS and TOF-SIMS.

[0004] 5. The sputtering yield of SIMS secondary ions is seriously affected by the different chemical environments on the sample surface (matrix effect). The secondary ion yield of the same element in different matrices and the secondary ion yield of different elements in the same matrix often vary by several orders of magnitude. This makes SIMS difficult to quantify accurately; 6. At present, some studies use secondary neutral particles generated by primary ion sputtering, that is, the method of ionizing secondary neutral particles is adopted, including electron gas ionization, electron beam ionization and other means. The sputtered neutrons will diffuse into a growing plume as the distance increases. It is difficult to cover them, and the efficiency of electron gas and electron beam ionization is less than 1%, which is still low; Therefore, it is necessary to invent a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer to solve the above problems. Summary of the invention

[0005] In order to overcome the above defects of the prior art, the present invention provides a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer to solve the problems of low spatial resolution and low sensitivity of the prior art mentioned in the above background technology.

[0006] In order to achieve the above-mentioned purpose, the present invention provides the following technical solutions: a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer, comprising a vacuum pool, a sample introduction system, a primary ion emission system, a three-dimensional laser post-ionization system, an ion optical system, a time-of-flight mass spectrometer, an observation system and a computer control system, wherein the vacuum pool comprises a moving table, a freezing pool, a sample holder, and a multi-stage vacuum pump group, the sample introduction system comprises a push rod, a sample tube, a high vacuum gate valve and a pre-vacuum chamber, the primary ion emission system comprises an ion source and an ion lens barrel, and the three-dimensional laser post-ionization system comprises a laser source, an optical path system, a galvanometer, a field mirror and a particle cloud.

[0007] As a further description of the above technical solution, the vacuum pool is made of stainless steel, and the interconnections are sealed with flanges with knife edges and copper gaskets. The mobile platform is installed at the bottom of the vacuum pool, the freezing pool is installed on the mobile platform, the sample holder is fixedly installed on the freezing pool, and the vacuum pump group is a combination of a mechanical pump + a turbomolecular pump + an ion pump; As a further description of the above technical solution, the ion source is selected from one or more of a gas discharge source, a liquid metal ion gun, and a surface ionization source; As a further description of the above technical solution, the optical path system includes a reflector, an attenuator, a beam expander and a beam shaping system for adjusting the laser beam emitted by the laser source to a desired beam; As a further description of the above technical solution, the galvanometer refers to a three-axis galvanometer system or a two-axis galvanometer system, the three-axis galvanometer system mainly includes a moving lens, a focusing lens, an X-axis galvanometer and a Y-axis galvanometer, and the two-axis galvanometer system mainly includes an X-axis galvanometer and a Y-axis galvanometer; As a further description of the above technical solution, the laser source is a tunable laser with a wavelength range of 325nm-2500nm, and the scanning speed of the galvanometer is greater than 30m / s; As a further description of the above technical solution, the ion optical system is used to transmit secondary ions generated by laser ionization of neutral particles to a mass detector, and the time-of-flight mass spectrometer includes a field-free drift tube and an ion detector, which is used to separate ions according to their flight time and flight speed; As a further description of the above technical solution, the observation system consists of a camera, a lens barrel and an objective lens, which are used to observe sample-related conditions. The computer control system consists of an industrial computer, communication modules of various components, pressure sensors and position sensors, which collect and process information data and issue control instructions to control the coordinated work of various components.

[0008] Compared with the prior art, the present invention has the following beneficial effects: The present invention can achieve nanometer-level spatial resolution. Through the three-dimensional galvanometer system, the laser beam can be accurately positioned in the X-axis and Y-axis, and high-speed and precise focusing can be achieved in the Z-axis, truly realizing the three-dimensional laser ionization of sample ions and neutral particle clouds that will be generated during the sputtering process of the primary ionization source, greatly improving the accuracy and efficiency of laser ionization, and the ionization laser can basically cover the neutral particle cloud team, greatly improving the efficiency of laser ionization.

[0009] 2. The efficiency of three-dimensional laser ionization used in the present invention is at least several orders of magnitude higher than the secondary ion yield of SIMS ion beams that stably bombard sputtered particles on samples. It is also much higher than the secondary ion yield of secondary neutral particle mass spectrometers that use electron gas ionization, electron beam ionization and traditional laser ionization. Moreover, since the sputtering process and the ionization process are separated, the signal intensity is not affected by the matrix effect and can be accurately quantified (including oxide samples).

[0010] 3. The present invention adopts a tunable laser, which can adjust the wavelength, frequency and energy value of the laser to make the energy of the laser photon resonate with the electronic energy level of the target molecule to achieve selective ionization of the substance. This method has extremely high element, nuclide and molecular selectivity, can provide instrument sensitivity, and can be applied to single-cell imaging analysis and testing of lipids, metabolites, small molecule drugs and some elements with a molecular weight of less than 1000Da, solve the problems of spatial metabolomics small molecule metabolite testing and ultra-high spatial resolution imaging, and can be used alone as SIMS when laser post-ionization is not used. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0012] Figure 1 A system structure diagram of a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer provided by the present invention.

[0013] Description of reference numerals: Vacuum cell; 11. Moving stage; 12. Freezing cell; 13. Sample holder; 14. Multi-stage vacuum pump group; 2. Sample introduction system; 3. Primary ion emission system; 31. Ion gun; 32. Ion column; 4. Three-dimensional laser post-ionization system; 41. Laser source; 42. Optical path system; 421. Reflector; 422. Attenuator; 423. Beam expander; 424. Beam shaping system; 43. Galvanometer; 44. Field mirror; 45. Particle cloud; 5. Observation system; 6. Ion optical system; 7. Time-of-flight mass spectrometer; 71. Field-free drift tube; 72. Ion detector. DETAILED DESCRIPTION

[0014] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are 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 creative work are within the scope of protection of the present invention.

[0015] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0016] See attached Figure 1A three-dimensional laser post-ionization-secondary neutron particle mass spectrometer of this embodiment includes a vacuum cell 1, a sample introduction system 2, a primary ion emission system 3, a three-dimensional laser post-ionization system 4, an ion optical system 6, a time-of-flight mass spectrometer 7, an observation system 5 and a computer control system.

[0017] Vacuum pool 1: Made of stainless steel, the interconnections are sealed with flanges with knife edges and copper gaskets, and are fully sealed, comprising a moving platform 11, a freezing pool 12, a sample holder 13, and a multi-stage vacuum pump group 14, wherein the vacuum pump group is preferably a combination of a mechanical pump + a turbomolecular pump + an ion pump; the moving platform 11 is a nano vacuum moving platform 11, which can be selected as a three-axis or a five-axis, with a resolution of less than or equal to 10nm and a repeatability accuracy of less than or equal to 300nm; the freezing pool 12 can cool biological tissue samples to 0 degrees Celsius to -40 degrees Celsius to make them solid samples; the sample holder 13 is installed on the freezing pool 12 for placing and fixing samples.

[0018] Sample introduction system 2: It is composed of a push rod, a sample tube, a high vacuum gate valve and a pre-vacuum chamber, etc., and is used to transfer the sample into the vacuum pool 1.

[0019] The primary ion emission system 3 is mainly composed of an ion source or ion gun 31 and an ion column 32. Ion source: mainly produces primary ions, and can select gas discharge sources O2+, O-, N2+, Ar+, or liquid metal ion gun 31LMIG as ion PI source, such as Au and Bi ion sources, surface ionization sources Cs+, Rb+; ion column 32, used to accelerate primary ions and focus them on the sample.

[0020] The three-dimensional laser post-ionization system 4 includes a laser source 41, an optical path system 42, a galvanometer 43, a field lens 44 and a particle cloud 45. The laser adopts a tunable laser with a wavelength range of 325nm-2500nm and high output stability. The optical path system 42 is composed of a reflector 421, an attenuator 422, a beam expander 423, a beam shaping system 424, etc., which is used to adjust the laser beam. The galvanometer 43 can be a three-axis galvanometer system including a moving lens, a focusing lens, an X-axis galvanometer and a Y-axis galvanometer, etc. The scanning speed is close to or exceeds 30m / s, and the particle cloud 45 can be scanned in three dimensions at high speed, or it can be a two-axis galvanometer system including an X-axis galvanometer and a Y-axis galvanometer for two-dimensional plane scanning. The field lens 44 is used to focus the laser beam on the sample particle cloud 45, and the laser ionizes the neutral particles.

[0021] Ion Optics 6 Ion Lens: Transmits secondary ions produced by laser ionization of neutral particles to the mass detector.

[0022] Time-of-flight mass spectrometer 7: Secondary ions are extracted into the field-free drift tube 71 and arrive at the ion detector 72 along a predetermined flight path. Since the speed of a given ion is inversely proportional to its mass, its flight time will be different accordingly. Heavier ions will arrive at the ion detector 72 later than lighter ions and will be separated in the field-free drift tube 71 according to their speed.

[0023] The observation system 5 is mainly composed of a camera, a lens barrel and an objective lens, etc., and is used to observe the sample position, sample state and the conditions in the vacuum cell 1 during analysis.

[0024] Computer control system: It is composed of industrial computers, communication modules of various components, pressure sensors, position sensors, etc., and is used for information data collection, processing and control of the coordinated work of various components.

[0025] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A three-dimensional laser post-ionization-secondary neutron particle mass spectrometer, characterized in that: The invention comprises a vacuum pool (1), a sample introduction system (2), a primary ion emission system (3), a three-dimensional laser post-ionization system (4), an ion optical system (6), a time-of-flight mass spectrometer (7), an observation system (5) and a computer control system. The vacuum pool (1) comprises a moving table (11), a freezing pool (12), a sample holder (13) and a multi-stage vacuum pump group (14). The sample introduction system (2) comprises a push rod, a sample tube, a high vacuum gate valve and a pre-vacuum chamber. The primary ion emission system (3) comprises an ion source and an ion lens barrel (32). The three-dimensional laser post-ionization system (4) comprises a laser source (41), an optical path system (42), a galvanometer (43), a field lens (44) and a particle cloud (45).

2. A three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 1, characterized in that: The vacuum pool (1) is made of stainless steel, and the interconnected parts are sealed with flanges with knife edges and copper gaskets. The movable platform (11) is installed at the bottom of the vacuum pool (1), the freezing pool (12) is installed on the movable platform (11), and the sample holder (13) is fixedly installed on the freezing pool (12). The vacuum pump group is a combination of a mechanical pump + a turbomolecular pump + an ion pump.

3. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 2, characterized in that: The ion source is selected from one or more of a gas discharge source, a liquid metal ion gun (31), and a surface ionization source.

4. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 3, characterized in that: The optical path system (42) comprises a reflector (421), an attenuator (422), a beam expander (423) and a beam shaping system (424), and is used to adjust the laser beam emitted by the laser source (41) to a required beam.

5. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 4, characterized in that: The galvanometer (43) refers to a three-axis galvanometer system or a two-axis galvanometer system. The three-axis galvanometer system mainly includes a moving lens, a focusing lens, an X-axis galvanometer and a Y-axis galvanometer. The two-axis galvanometer system mainly includes an X-axis galvanometer and a Y-axis galvanometer.

6. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 5, characterized in that: The laser source (41) is a tunable laser with a wavelength range of 325 nm to 2500 nm, and the scanning speed of the galvanometer (43) is greater than 30 m / s.

7. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 6, characterized in that: The ion optical system (6) is used to transmit secondary ions generated by laser ionization of neutral particles, and the time-of-flight mass spectrometer (7) comprises a field-free drift tube (71) and an ion detector (72) for separating ions according to their flight time and flight speed.

8. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 7, characterized in that: The observation system (5) is composed of a camera, a lens barrel and an objective lens, and is used to observe the relevant conditions of the sample. The computer control system is composed of an industrial computer, communication modules of various components, a pressure sensor and a position sensor, and is used to collect and process information data and issue control instructions to control the coordinated work of various components.

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