A three-dimensional laser post-ionization-secondary neutron particle mass spectrometer

Abstract

The present invention discloses a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer, which includes a vacuum chamber, 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 using a tunable laser, the present invention can achieve selective ionization of substances by adjusting the wavelength, frequency and energy value of the laser to make the energy of the laser photons resonate with the electronic energy level of the target molecule. This method has extremely high element, nuclide and molecular selectivity, can provide the sensitivity of the instrument, and can be applied to single-cell imaging analysis and testing of lipids, metabolites, small molecule drugs with molecular weights less than 1000 Da and some elements, solve the problems of small molecule metabolite testing in spatial metabolomics and ultra-high spatial resolution imaging. When not using laser post-ionization, it can be used alone as SIMS.

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 information on the structure, content, and spatial distribution of endogenous metabolite molecules in biological tissues, which is of great significance for revealing the mechanisms related to 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 promising technologies by "Nature". At present, the mass spectrometry imaging technologies applied in spatial metabolomics are divided into secondary ion mass spectrometry imaging (SIMS) technology, desorption electrospray ionization mass spectrometry imaging (DESI-MSI) technology, laser ablation electrospray ionization mass spectrometry imaging (LA-ESI-MSI) technology, and matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) according to different ion sources.

[0003] The following are the main existing problems:

[0004] 1. DESI-MSI does not require complex sample pretreatment, does not require a matrix, and is convenient for the extension of liquid and gas samples, but has low spatial resolution and the signal is easily interfered by the external environment;

[0005] 2. LAESI-MSI has simple sample preparation and does not require a matrix, but requires a water-containing and relatively stable sample and has low spatial resolution;

[0006] 3. MALDI-MSI technology requires matrix assistance and requires sample pretreatment. It can detect thousands of molecules without a target and can provide spatial distribution maps of molecules such as proteins and lipids in tissues. The matrix severely inhibits the detection of small molecule metabolites, and small molecule metabolism cannot be measured. The spatial resolution is relatively low and the sensitivity needs to be improved;

[0007] 4. SIMS has a nanoscale spatial resolution. However, in fact, about 99% of the particles generated during the primary ion sputtering process are neutral particles, and only a very small part of the total sputtering products are secondary ions (about 0.01% - 1%). The sputtering composition mainly composed of neutral particles leads to the problems of low ionization efficiency and low sensitivity of SIMS and TOF - SIMS as a whole.

[0008] 5. The sputtering yield of SIMS secondary ions is severely affected by different chemical environments on the sample surface (matrix effect). The secondary ion yields of the same element in different matrices and the secondary ion yields of different elements in the same matrix often vary by several orders of magnitude. This makes it difficult for SIMS to accurately quantify;

[0009] 6. Currently, some studies utilize the secondary neutral particles generated by primary ion sputtering, that is, by ionizing the secondary neutral particles. The means include electron gas ionization, electron beam ionization, etc. The sputtered neutrons will diffuse into an ever - increasing plume as the distance increases, and it is difficult to cover them. Moreover, the ionization efficiencies of both electron gas and electron beam are lower than 1%, and the efficiency is still low;

[0010] 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

[0011] In order to overcome the above - mentioned 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 relatively low spatial resolution and low sensitivity in the prior art as described in the above - mentioned background technology.

[0012] To achieve the above purpose, the present invention provides the following technical solution: A three - dimensional laser post - ionization - secondary neutron particle mass spectrometer, comprising a vacuum chamber, 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. The vacuum chamber includes a moving stage, a cryogenic chamber, a sample holder, and a multi - stage vacuum pump group. The sample introduction system consists of a push rod, a sample tube, a high - vacuum gate valve, and a pre - evacuation chamber. The primary ion emission system includes an ion source and an ion lens barrel. The three - dimensional laser post - ionization system includes a laser source, an optical path system, a galvanometer scanner, a field lens, and a particle cloud.

[0013] As a further description of the above - mentioned technical solution, the vacuum chamber is made of stainless steel, and the joints are sealed with flanges with knife edges and copper gaskets. The moving stage is installed at the bottom of the vacuum chamber, the cryogenic chamber is installed on the moving stage, the sample holder is fixedly installed on the cryogenic chamber, and the vacuum pump group is a combination of a mechanical pump + a turbo molecular pump + an ion pump;

[0014] 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;

[0015] 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 the required beam;

[0016] 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. The two-axis galvanometer system mainly includes an X-axis galvanometer and a Y-axis galvanometer;

[0017] As a further description of the above technical solution, the laser source is a tunable laser with a wavelength range of 325 nm - 2500 nm, and the scanning speed of the galvanometer is greater than 30 m / s;

[0018] As a further description of the above technical solution, the ion optical system is used to transmit the secondary ions generated by laser ionization of neutral particles to the mass detector. The time-of-flight mass spectrometer includes a field-free drift tube and an ion detector for separating ions according to the ion flight time and flight speed;

[0019] As a further description of the above technical solution, the observation system is composed of a camera, a lens barrel, and an objective lens for observing the relevant conditions of the sample. The computer control system is composed of an industrial control computer, communication modules for each component, a pressure sensor, and a position sensor to collect, process information data, and issue control instructions to control the coordinated work of each component.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] The present invention can achieve a spatial resolution of the nanometer level. Through the three-dimensional galvanometer system, the laser beam can be accurately positioned on the X-axis and Y-axis, and high-speed and accurate focusing can be achieved on the Z-axis, truly realizing three-dimensional laser ionization of the sample ions and neutral particle clouds 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.

[0022] 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 stable bombardment and sputtering particles of the SIMS ion beam on the sample, and is also much higher than the secondary ion yields of those secondary neutral particle mass spectrometers using 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).

[0023] 3. By adopting a tunable laser, the present invention can adjust the wavelength, frequency and energy value of the laser to achieve the selective ionization of substances through the resonance of the energy of laser photons with the electronic energy levels of target molecules. This method has extremely high element, nuclide and molecular selectivity, can improve the sensitivity of the instrument, and can be applied to the single-cell imaging analysis and testing of lipids, metabolites, small molecule drugs with molecular weight less than 1000 Da and some elements, solving the problems of small molecule metabolite testing in spatial metabolomics and ultra-high spatial resolution imaging. When laser post-ionization is not used, it can be used alone as SIMS. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a system structure diagram of a three-dimensional laser post-ionization-secondary neutron particle mass spectrometer provided by the present invention.

[0026] Description of the reference numerals:

[0027] Vacuum chamber; 11, mobile stage; 12, cryogenic cell; 13, sample holder; 14, multi-stage vacuum pump set; 2, sample introduction system; 3, primary ion emission system; 31, ion gun; 32, ion lens barrel; 4, three-dimensional laser post-ionization system; 41, laser source; 42, optical path system; 421, mirror; 422, attenuator; 423, beam expander; 424, beam shaping system; 43, galvanometer; 44, field lens; 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 OF THE EMBODIMENTS

[0028] The following specific embodiments illustrate the implementation manners of the present invention. Those skilled in this technology can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0029] In order to enable those skilled in the art of this technology to better understand the solution of this application, the following will further describe this application in detail with reference to the drawings and specific implementation manners.

[0030] Refer to the attached Figure 1, A three-dimensional laser post-ionization-secondary neutron particle mass spectrometer of this embodiment includes a vacuum chamber 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.

[0031] Vacuum chamber 1: Made of stainless steel, the joints are sealed with flanges with knife edges and copper gaskets, and it is a fully sealed design. It includes a mobile stage 11, a cryogenic cell 12, a sample holder 13, and a multi-stage vacuum pump group 14. The vacuum pump group preferably combines a mechanical pump, a turbomolecular pump, and an ion pump; the mobile stage 11 is a nano-vacuum mobile stage 11, which can be three-axis or five-axis, with a resolution less than or equal to 10 nm and a repeat positioning accuracy less than or equal to 300 nm; the cryogenic cell 12 can cool biological tissue samples to 0 °C to -40 °C to make them solid samples; the sample holder 13 is installed on the cryogenic cell 12 for placing and fixing samples.

[0032] Sample introduction system 2: Consists of a push rod, a sample tube, a high-vacuum gate valve, a pre-pumping vacuum chamber, etc., and is used to transfer the sample into the vacuum chamber 1.

[0033] The primary ion emission system 3 mainly consists of an ion source or ion gun 31 and an ion lens barrel 32. Ion source: Mainly generates primary ions. Gas discharge sources O2+, O-, N2+, Ar+ can be selected, or a liquid metal ion gun 31 LMIG can be used as the ion PI source, such as Au and Bi ion sources, and surface ionization sources Cs+, Rb+; the ion lens barrel 32 is used to accelerate the primary ions and focus them on the sample.

[0034] 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 uses a tunable laser with a wavelength range of 325 nm - 2500 nm and has high output stability. The optical path system 42 consists of a mirror 421, an attenuator 422, a beam expander 423, a beam shaping system 424, etc., and 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., with a scanning speed close to or exceeding 30 m / s, and can perform three-dimensional high-speed scanning on the particle cloud 45, or 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 onto the sample particle cloud 45 to ionize neutral particles with the laser.

[0035] Ion optical system 6 Ion lens: Transfers the secondary ions generated by laser ionization of neutral particles to the mass detector.

[0036] Time-of-flight mass spectrometer 7: Secondary ions are extracted into the field-free drift tube 71 and reach the ion detector 72 along a predefined flight path. Since the velocity of a given ion is inversely proportional to its mass, its flight time will be correspondingly different. Heavier ions will reach the ion detector 72 later than lighter ions, and they are separated in the field-free drift tube 71 according to their velocities.

[0037] The observation system 5 mainly consists of a camera, a lens barrel, an objective lens, etc., and is used to observe the sample position, the sample state, and the conditions inside the vacuum chamber 1 during analysis.

[0038] Computer control system: It consists of an industrial control computer, communication modules for each component, pressure sensors, position sensors, etc., and is used to collect, process information data, and control the coordinated operation of each component.

[0039] Finally: The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A three-dimensional laser postionization-secondary neutron particle mass spectrometer, characterized by: 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 stage (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 column (32). The three-dimensional laser post-ionization system (4) comprises a laser source (41), an optical path system (42), a galvanometer (43), a field mirror (44) and a particle cloud (45). The optical path system (42) includes 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 desired beam; 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, and the two-axis galvanometer system mainly includes an X-axis galvanometer and a Y-axis galvanometer; the laser source (41) is a tunable laser with a wavelength range of 325nm to 2500nm, and the scanning speed of the galvanometer (43) is greater than 30m / s; By using a tunable laser, the wavelength, frequency and energy value of the laser are adjusted to resonate the energy of the laser photons with the electronic energy level of the target molecule to achieve selective ionization of the substance.

2. The 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 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) includes a field-free drift tube (71) and an ion detector (72) for separating ions according to their flight time and flight speed.

5. The three-dimensional laser post-ionization-secondary neutron particle mass spectrometer according to claim 4, 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, pressure sensors and position sensors, 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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