Analytical instrument based on combination of glow discharge and quadrupole mass spectrometry

Abstract

The invention relates to the technical field of mass spectrometers, and discloses an analytical instrument based on glow discharge and quadrupole mass spectrometry combination, which comprises an ion source, an ion transmission system and an ion separator, wherein the ion source is a glow discharge ion source; the ion separator is a quadrupole rod mass analyzer, and the quadrupole rod mass analyzer comprises four electrodes which are arranged in parallel. Compared with an existing analytical instrument, the glow discharge ion source can directly analyze a solid sample without being pretreated into a solution, and compared with an inductively coupled plasma source, the glow discharge ion source is small in matrix effect and especially suitable for high-salt and high-carbon samples; the quadrupole rod mass analyzer is simple in structure, small in size, low in cost, especially suitable for commercialized popularization and high in scanning speed.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry, specifically to an analytical instrument based on the combined use of glow discharge and quadrupole mass spectrometry. Background Technology

[0002] A mass spectrometer is an instrument that analyzes the composition of a sample by measuring the mass-to-charge ratio (m / z) of ions. Its core working principle can be divided into five key steps: sample ionization, ion transport, ion separation, ion detection, and data analysis. Sample ionization is the step of converting neutral molecules into charged ions (positive or negative ions). The choice of ionization technique directly affects the analyte range, sensitivity, and spectral quality. Currently, there are five common methods: electron impact ionization, electrospray ionization, matrix-assisted laser desorption / ionization, inductively coupled plasma, and glow discharge ionization.

[0003] The ion transport system connects the ion source and the mass analyzer, effectively eliminating neutral particles by altering the ion trajectory. Its performance directly determines crucial parameters of the mass spectrometer, such as sensitivity and detection limit. Currently, the ion transport systems used in mainstream MS products each have unique designs and characteristics, essentially achieving electric field deflection to separate charged particles from neutral molecules.

[0004] Currently, ion lens systems in use are mainly divided into three types: photon baffle lenses, off-axis deflection lenses, and 90° deflection lenses. Photon baffle lenses suffer significant ion loss due to their operation. Off-axis lenses, compared to photon baffle lenses, can greatly improve the efficiency of ion passage, but are prone to capacitance effects, affecting the accuracy of results. Furthermore, off-axis lenses often require the removal of impurity particles through holes or grids on the electrodes, resulting in a complex internal design and difficult cleaning and maintenance of components. 90° deflection lenses utilize the characteristic that impurity particles fly in a straight line unaffected by an electric field to filter them out. The extraction lens uses a conical design and applies negative pressure, improving the space charge behind the interface while accelerating cation extraction. To avoid the negative pressure of the extraction lens affecting the ion beam shape, an entrance lens is added at the deflection lens inlet for secondary adjustment of the ion beam shape. Similarly, to prevent excessive action of the electrodes on the ions in the deflection lens, hollow cylindrical lenses are added before and after the electrodes to accelerate and focus the ions, shortening the interaction time of the deflection electrodes to achieve the desired deflection effect.

[0005] Ion separation is the core of mass spectrometry analysis, mainly using physical methods to separate ions with different mass-to-charge ratios (m / z). The core component is the mass analyzer, and several commonly used techniques include: quadrupole, time-of-flight, ion trap, orbital trap, and magnetic sector mass analyzer.

[0006] Current instruments generally use inductively coupled plasma (ICP) combined with a quadrupole mass analyzer. The advantages are small size, low maintenance cost, and fast analysis speed. The disadvantage is that in the ICP ion source, the plasma gas and matrix components easily form polyatomic ion interference (such as ArO₂). + ArCl + This affects the determination of low mass number elements (such as Fe, As, and Se). High salt content or organic matrices may inhibit the signal (such as Na). + K + Interference) requires dilution or matrix matching for optimization.

[0007] Some instruments combine glow discharge ion sources with magnetic sector mass spectrometers. These instruments can perform direct solid-state analysis without complex pretreatment. The glow discharge ion source can directly sputter solid samples (bulk, powder, or coating) without acid digestion or dissolution, reducing contamination and loss. GD-MS exhibits less matrix effect, making it particularly suitable for high-salt and high-carbon samples. However, its disadvantages include slower analysis speed. Magnetic sector mass spectrometry typically uses sequential scanning, resulting in longer analysis times compared to quadrupole or TOF-MS (potentially several minutes to tens of minutes for a single sample). The equipment is also expensive and complex to maintain. High-resolution magnetic mass spectrometers are costly (typically several million RMB) and require a high-vacuum system and liquid nitrogen-cooled superconducting magnets (for some models), leading to high maintenance costs. Summary of the Invention

[0008] In view of the above-mentioned shortcomings of the existing technology, the present invention provides an analytical instrument based on glow discharge and quadrupole mass spectrometry.

[0009] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an analytical instrument based on glow discharge and quadrupole mass spectrometry, including an ion source, an ion transport system, and an ion separator; The ion source is a glow discharge ion source; The ion separator is a quadrupole mass analyzer, which includes four parallel electrodes.

[0010] Furthermore, it also includes an analytical vacuum chamber, wherein the ion separator is disposed within the analytical vacuum chamber, and the electrodes of the ion separator are arranged along the longitudinal direction of the analytical vacuum chamber; The ion source is configured on one side of the analytical vacuum chamber, and one end of the ion source can be connected to the analytical vacuum chamber. The ion emission direction of the ion source is set along the transverse direction of the analytical vacuum chamber. The ion transport system is located between the ion source and the ion separator. Ions that escape laterally along the analytical vacuum chamber are redirected by the ion transport system and then enter the ion separator for screening.

[0011] Furthermore, the ion source includes: The primary vacuum chamber is located on one side of the analytical vacuum chamber, and the primary vacuum chamber and the analytical vacuum chamber are interconnected. The chamber door is rotatably mounted on one side of the primary vacuum chamber. The sample stage is connected to the side of the chamber door facing the primary vacuum chamber; The anode disk, located in the primary vacuum chamber, is used to form a discharge circuit with the sample placed on the sample stage; The ion sampling cone is positioned on the side of the anode disk away from the sample stage.

[0012] Furthermore, a sliding hole is provided on one side of the primary vacuum chamber, and a sliding valve is slidably disposed in the sliding hole. The sliding valve is driven to move along the sliding hole and can cut off the communication between the primary vacuum chamber and the analytical vacuum chamber.

[0013] Furthermore, a linear mechanism is provided at the bottom of the sample stage. In the working state, the linear mechanism pushes the sample stage toward the anode disk. With the door open, the sample stage is arranged parallel to the workbench surface.

[0014] Furthermore, the anode plate includes an anode cylinder, a cylinder base, and a water-cooling plate; The water cooling plate has a built-in water circuit, and the cooling water circulates in the water circuit to remove heat during operation. The cylindrical base is located inside the water-cooling plate; The anode tube is located inside the tube base, and an ion jet outlet is provided on the side of the anode tube facing the primary vacuum chamber.

[0015] Furthermore, the cylindrical base includes a first insulating layer and a first conductor layer; The first insulating layer is the layer that contacts the sample at the base of the cylinder, and it is made of alumina ceramic; The first conductor layer is disposed on the side of the first insulating layer away from the sample, and the first conductor layer is in contact with the water cooling plate; Furthermore, an air supply groove is provided on the top of the first insulating layer, and the air supply groove is tangent to the inner cavity of the cylinder base.

[0016] Furthermore, the anode cylinder includes a second insulating layer and a second conductor layer, the second conductor layer being disposed inside the second insulating layer; The cavity at the center of the cylindrical base is a conical cavity, and the outer wall of the second insulating layer is a corresponding conical cylinder; Furthermore, the thickness of the second insulating layer and the second conductor layer are the same as the thickness of the first conductor layer.

[0017] Furthermore, the ion transport system includes an accelerating lens and a deflecting lens group; The accelerating lens is disposed in the primary vacuum chamber, and the interior of the accelerating lens is hollow. The end of the accelerating lens facing the anode disk has a tapered structure with a hole. The deflecting lens group is installed in the analytical vacuum chamber.

[0018] Furthermore, the deflecting lens group includes a focusing lens, a front deflecting lens, an L-shaped frame, and a rear deflecting lens; The L-shaped frame is fixedly installed in the analytical vacuum chamber; Both the front deflecting lens and the rear deflecting lens are hollow cylindrical structures, and the front deflecting lens and the rear deflecting lens are respectively set at both ends of the L-shaped frame, with the axes of the front deflecting lens and the rear deflecting lens being perpendicular to each other. The focusing lens has a hollow cylindrical structure. Both the focusing lens and the accelerating lens are coaxially arranged with the front deflecting lens, and the focusing lens is located on the side of the front deflecting lens facing the accelerating lens.

[0019] The technical solution provided by this invention has the following advantages compared with the prior art: Compared to existing analytical instruments, the glow discharge ion source of this invention can directly analyze solid samples without pretreatment into solutions. Compared to inductively coupled plasma sources, it exhibits less matrix effect, making it particularly suitable for high-salt and high-carbon samples. The quadrupole mass analyzer has a simple structure, small size, and low cost, making it especially suitable for commercial application. It offers fast scanning speed; by rapidly adjusting the radio frequency (RF) and direct current (DC) voltages, it can complete full-mass range scanning in milliseconds, making it suitable for high-throughput analysis. It is easy to maintain, highly stable, and requires no superconducting magnets (such as FT-ICR) or complex optical systems (such as TOF), resulting in minimal daily maintenance. It is suitable for industrial, clinical, and routine laboratory use, and has relatively low vacuum requirements (typically 10). -5 -10 -6 Torr is easier to operate than magnetic mass spectrometry or Orbitrap; the 90° deflection ion transport system can effectively eliminate electrons, photons and neutral particles, greatly improving ion transport efficiency and enhancing the analytical sensitivity and signal-to-noise ratio of the mass spectrometer. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0021] Figure 1 This is a schematic diagram of the analytical instrument structure based on glow discharge and quadrupole mass spectrometry as described in an embodiment of the present invention; Figure 2This is a schematic diagram of the structure of the ion source described in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of the anode disk described in an embodiment of the present invention; Figure 4 This is a schematic diagram of the anode disk from another perspective, as described in an embodiment of the present invention. Figure 5 for Figure 4 A cross-sectional view of section AA in the middle; Figure 6 This is a schematic diagram of the assembly of the ion sampling cone and the cylinder base as described in an embodiment of the present invention; Figure 7 This is a schematic diagram from another perspective of the assembly of the ion sampling cone and the cylindrical base as described in an embodiment of the present invention; Figure 8 for Figure 7 A cross-sectional view of section BB in the middle section; Figure 9 This is a schematic diagram of the assembly of the ion transport system described in an embodiment of the present invention; Figure 10 This is a schematic diagram of the ion transport system described in an embodiment of the present invention; Figure 11 This is a schematic diagram of the ion transport system described in an embodiment of the present invention from another perspective. Figure 12 This is a schematic diagram of the ion transport system described in an embodiment of the present invention from another perspective. Figure 13 This is a schematic diagram of the ion transport system described in an embodiment of the present invention from another perspective. Figure 14 for Figure 13 A cross-sectional view of section CC; Figure 15 This is a schematic diagram of the screening of the ion transport system described in an embodiment of the present invention; Figure 16 This is a COMSOL simulation diagram of the ion transport system described in an embodiment of the present invention.

[0022] The labels in the diagram represent: 100, ion source; 110, primary vacuum chamber; 111, sliding hole; 112, mechanical pump interface; 120, chamber door; 121, glow discharge chamber; 130, sample stage; 140, anode plate; 141, water-cooled plate; 142, cylinder base; 1421, first insulating layer; 14211, gas supply tank; 1422, first conductor layer; 143, anode cylinder; 1431, second insulating layer; 1432, second conductor layer; 150, ion sampling cone; 160, linear mechanism; 170, slide valve; 200. Ion transport system; 210. Accelerating lens; 220. Deflecting lens group; 221. Focusing lens; 222. Front deflecting lens; 223. L-shaped frame; 224. Rear deflecting lens; 225. Deflecting shaft; 226. Insulating shaft; 227. Insulating fixing block; 300. Ion separator; 400. Analytical vacuum chamber; 500. Signal detector. Detailed Implementation

[0023] 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] The present invention will be further described below with reference to embodiments.

[0025] Please see Figures 1-16 This invention provides a technical solution: an analytical instrument based on glow discharge and quadrupole mass spectrometry, comprising an ion source 100, an ion transport system 200, an ion separator 300, and an analytical vacuum chamber 400. The ion source 100 is a glow discharge ion source; the ion separator 300 is a quadrupole mass analyzer, which includes four parallel electrodes fixedly mounted in the analytical vacuum chamber by a ceramic support.

[0026] The ion separator 300 is installed inside the analytical vacuum chamber 400, so as to... Figure 1 The analytical vacuum chamber 400 shown is longitudinal in length, and transverse in the same horizontal plane. The electrodes of the ion separator 300 are arranged longitudinally along the analytical vacuum chamber 400. The ion source 100 is disposed on one side of the analytical vacuum chamber 400, and one end of the ion source 100 can communicate with the analytical vacuum chamber 400. The ion escape direction of the ion source 100 is arranged transversely along the analytical vacuum chamber 400. The ion transport system 200 is disposed between the ion source 100 and the ion separator 300. Ions that escape laterally along the analytical vacuum chamber 400 and enter the analytical vacuum chamber 400 are redirected by the ion transport system 200 and then enter the ion separator 300 for screening. A signal detector 500 is also provided in the analytical vacuum chamber for detecting ions screened by the ion separator 300. The signal detector 500 is an electron multiplier.

[0027] A mechanical pump is installed on one side of the ion source 100 to provide a vacuum environment for glow discharge; a molecular pump is installed on one side of the analytical vacuum chamber 400 to provide a vacuum environment for the detection process.

[0028] In the above technical solution, a glow discharge ion source is used as the ion source 100, a 90° ion deflection lens group is used as the ion transmission system 200, a quadrupole mass analyzer is used as the ion separator 300 to screen ions, and finally an electron multiplier is used as the signal detector 500. At the same time, mechanical pumps and molecular pumps provide the corresponding vacuum environment for glow discharge, ion transmission, and detection. A cooling water circulation system provides cooling for the glow discharge ion source, and a gas module provides argon gas for the glow discharge ion source. At the same time, corresponding control circuits are set for the glow discharge ion source, ion transmission system, ion separator, signal detector, and gas module. A main control circuit integrates the control circuits of all components and communicates with the host computer.

[0029] In the technical solution of this application, the glow discharge ion source can directly analyze samples with almost no pretreatment, avoiding contamination and dilution. It is suitable for analyzing ultra-low content impurities in solids, especially elements such as C, N, O, and S that cannot be analyzed by ICP.

[0030] In a specific example, the ion source 100 includes: a primary vacuum chamber 110 disposed on one side of the analytical vacuum chamber 400, and the primary vacuum chamber 110 and the analytical vacuum chamber 400 are communicative; a chamber door 120 rotatably disposed on one side of the primary vacuum chamber 110; a sample stage 130 connected to the side of the chamber door facing the primary vacuum chamber 110; an anode disk 140 disposed within the primary vacuum chamber 110 for forming a discharge circuit with the sample placed on the sample stage 130; and an ion sampling cone 150 disposed on the side of the anode disk 140 away from the sample stage.

[0031] In addition, a linear mechanism 160 is provided at the bottom of the sample stage 130. In the working state, the linear mechanism 160 pushes the sample stage 130 toward the anode disk 140; in the open state, the sample stage is arranged parallel to the workbench surface. The workbench surface is the working surface on which the analytical instrument is placed. For example, if the analytical instrument (mainly the analytical vacuum chamber) is placed on a table, then the workbench surface is the table surface.

[0032] In a specific example, a sliding hole 111 is provided on one side of the primary vacuum chamber 110, and a slide valve 170 is slidably disposed in the sliding hole 111. The slide valve 170 is driven to move along the sliding hole 111 to cut off the communication between the primary vacuum chamber 110 and the analytical vacuum chamber 400.

[0033] In the aforementioned technical solution, the sample stage 130 and the chamber door 120 are integrated together, employing a downward-flipping opening mechanism. After the chamber door 120 is opened, the sample stage 130 is parallel to the workbench surface, facilitating sample placement. A linear mechanism 160 is provided at the bottom of the sample stage 130. In a specific example of this application, the linear mechanism 160 is a small piston cylinder, and a ceramic insulating gasket is placed between the linear mechanism and the chamber door 120. After the chamber door 120 is closed, gas in the small piston cylinder pushes the piston out, pressing the sample against the anode disk 140. During actual operation, the sample stage 130 uses a magnet to attract a sample holder, embedding the sample in the sample holder to prevent it from falling out when the door is closed. This sample placement structure design facilitates operation and reduces contamination caused by complex operations during sample placement.

[0034] A glow discharge chamber 121 is located inside the chamber door 120, corresponding to the anode disk 140. A linear mechanism 160 is installed inside the glow discharge chamber 121. A negative high-voltage power supply line is provided on the sample stage 130, leading out of the glow discharge chamber 121 through a sealed through-plate interface. An argon gas driving pipe (not shown in the figure) is located at the bottom of the sample stage 130 inside the chamber door 120. The argon gas driving pipe is connected to an external gas module, filling the glow discharge chamber 121 with argon gas. The chamber door 120 is surrounded by a sealing strip, which can seal the entire glow discharge chamber 121 when closed. A mechanical pump interface 112 is provided on one side of the primary vacuum chamber 110. Through this mechanical pump interface 112, an external mechanical pump is connected, which can maintain the pressure inside the glow discharge chamber 121 at 100 Pa.

[0035] It should be noted that, in one specific embodiment of this application, the anode plate 140 consists of three rings with different structures: a water-cooling plate 141, a cylinder base 142, and an anode cylinder 143. The water-cooling plate 141, located on the outermost ring, is a copper disc with a chrome-plated surface to increase hardness and corrosion resistance. The side of the water-cooling plate 141 that contacts the chamber door 120 is polished to ensure a perfect fit with the sealing ring of the chamber door 120, guaranteeing a tight seal. The water-cooling plate 141 has internal water channels; during operation, cooling water circulates within these channels to remove heat.

[0036] The inner ring of the water-cooling plate 141 is provided with threads and a flat surface. The cylindrical base 142 is fixed to the inner ring of the water-cooling plate by the threads and pressed against the flat surface for better heat exchange. Furthermore, the cylindrical base 142 includes a first insulating layer 1421 and a first conductor layer 1422. The first insulating layer 1421, which is the layer in contact with the sample, is made of alumina ceramic. The thickness of the first insulating layer 1421 allows for the setting of the distance between the sample and the anode cylinder 143. Alumina ceramic has high hardness, effectively resisting wear during contact with metal samples, resulting in a long service life. It also has high temperature resistance; during glow discharge, the electrode temperature can reach up to 1000℃ for a short time, and alumina ceramic can withstand temperatures up to 1600℃, adapting to the high-temperature environment during glow discharge. The insulation performance of alumina ceramic reaches >10. 15 Ω·cm can easily ensure insulation between the anode (anode cylinder 143) and the cathode (sample), guaranteeing that the discharge range is limited to the area between the anode cylinder 143 and the sample.

[0037] The first conductor layer 1422 is disposed on the side of the first insulating layer 1421 away from the sample, and the first conductor layer 1422 is in contact with the water-cooling plate 141; and a gas supply groove 14211 is disposed on the top of the first insulating layer 1421, the gas supply groove 14211 being tangential to the receiving cavity of the anode cylinder 143. The gas supply groove 14211 can form a stable spiral airflow within the anode cylinder 143, which can fully mix the excited ions with argon gas and uniformly enter the primary vacuum chamber 110, ensuring the continuity and stability of ion sampling. At the same time, the swirling gas can throw large, incompletely excited, high-mass particles onto the inner wall of the anode cylinder 143, playing a preliminary role in particle screening, ensuring the cleanliness of the sampled ions, and extending the service life of the sampling cone. The above technical solution uses a swirling argon gas channel, which can screen out sputtered particles that are too light or too heavy, ensuring that only particles of appropriate size enter the ionization stage.

[0038] The anode cylinder 143 includes a second insulating layer 1431 and a second conductor layer 1432, with the second conductor layer 1432 disposed inside the second insulating layer 1431. The accommodating cavity at the center of the cylinder base 142 is a conical cavity, and the outer wall of the second insulating layer 1431 is a corresponding conical cylinder. The conical surface fit can achieve automatic centering, and the radial positioning accuracy can reach 0.01mm. At the same time, it can adapt to thermal deformation, so that the relative position of the anode cylinder 143 will not change due to temperature changes during operation. There is no wear between the anode cylinder 143 and the cylinder base 142, and the long-term stability is good.

[0039] The thicknesses of the second insulating layer 1431 and the second conductor layer 1432 along the ion flow escape direction are the same as the thickness of the first conductor layer 1422. That is, in the working state, the sample placed on the sample stage 130 is pressed against one side of the cylinder base 142 by the push of the linear mechanism 160, so that a discharge gap is formed between the sample and the anode cylinder 143.

[0040] The second insulating layer 1431 is a conical cylinder made of alumina, which fits tightly with the cylinder base 142. After installation, it separates the sample from the first insulating layer 1421, creating an open electrical gap between the sample (glow discharge cathode) and the anode, within which glow discharge occurs. The second conductor layer 1432 inside the anode cylinder 143 is a copper cylinder, closed on the side near the primary vacuum chamber 110, leaving only a small-diameter through hole. After installation, the copper second conductor layer 1432 is connected to the cylinder base 142 and the water-cooling plate 141, and finally grounded. During operation, glow discharge occurs at the sample-oriented end face of the anode cylinder 143, and the generated plasma is drawn into the primary vacuum chamber 110. Since the pressure in glow chamber 121 is 100 Pa and the pressure in primary vacuum chamber 110 is about 2 Pa, the pressure ratio between the two chambers is 0.02, which is far lower than the critical pressure ratio of supersonic jet (about 0.528). Therefore, a supersonic ion jet will be generated at the outlet of anode cylinder 143, providing conditions for subsequent sampling by ion sampling cone 150.

[0041] The second insulating layer 1431 provided in the anode cylinder 143 can concentrate the glow discharge phenomenon between the central copper second conductor layer 1432 and the sample, concentrating the energy and better exciting the sample into a charged ion state.

[0042] In the above technical solution, the analytical instrument based on glow discharge and quadrupole mass spectrometry first prepares the vacuum environment in the analytical vacuum chamber 400 by a molecular pump. At this time, the slide valve 170 cuts off the connection between the analytical vacuum chamber 400 and the primary vacuum chamber 110, thus maintaining the vacuum environment in the analytical vacuum chamber 400 and avoiding the need to re-evacuate to a high vacuum each time, thereby improving analytical efficiency. Then, the chamber door 120 is opened, the sample is placed in the sample holder on one side of the sample stage 130, and the door is closed. At this time, the linear mechanism 160 pushes the sample out and presses it against the anode disk 140. Then, the primary vacuum chamber 110 is evacuated by a mechanical pump, and the glow discharge chamber 121 is filled with argon gas through the gas module. After glow discharge ignition, the slide valve 170 is moved to connect the primary vacuum chamber 110 and the analytical vacuum chamber 400 for analysis.

[0043] Specifically, the ion transport system 200 includes an accelerating lens 210 and a deflecting lens group 220. The accelerating lens 210 is disposed in the primary vacuum chamber 110, and the deflecting lens group 220 is disposed in the analytical vacuum chamber 400. The accelerating lens 210 is hollow inside, and the end of the accelerating lens 210 facing the anode disk has a conical perforated structure. This structure can effectively collect ions. The accelerating lens 210 is located at a distance from the deflecting lens group 220 near the primary vacuum chamber 110, and the accelerating lens 210 and the ion sampling cone 150 of the mass spectrometer are coaxially aligned. This structure can remove neutral gas while maximizing the extraction of ions to be detected. By applying a negative voltage to form an extraction electric field, this electric field can direct spatially dispersed ions, ensuring that ions enter the subsequent deflecting lens group 220 to the maximum extent and reducing ion transport loss.

[0044] The majority of cations in the plasma are generated by energy excitation during glow discharge, and therefore carry only one positive charge. Assuming the ions deflect along a predetermined trajectory, the electric field strength is related to their initial kinetic energy. The initial kinetic energy of the ions is determined by the thermodynamic temperature of the plasma at the time of excitation. However, after passing through the ion sampling cone 150, the ions are further focused and accelerated by the electric field from the accelerating lens 210. The work done on the ions during the entire motion of the accelerating lens 210 is divided into two parts: the electric field does positive work on the ions in the first half of the acceleration lens 210 motion and negative work in the second half. Throughout the process, the ions accelerate first and then decelerate, converting the potential energy received during the motion into kinetic energy. The energy gained by the ions can be derived from the following formula: ; In the formula: q is the charge number of the ion, U is the voltage applied by the accelerating lens 210, and the supersonic jet formed by the plasma ionized by the glow discharge at the interface of the ion sampling cone 150 has an initial velocity, the kinetic energy formula of which is: ; Where E k Let m be the kinetic energy of the gas flow, v be the mass of the ion, and v be the gas flow velocity. Based on the above kinetic energy formula, the kinetic energy range of the ions entering the ion transport system from the ion sampling cone 150 interface is calculated to be 0.19 eV to 6.53 eV. Furthermore, considering the overall potential of the plasma, extracting cations requires overcoming the plasma potential energy; therefore, the initial kinetic energy of the ions is corrected as follows: ; Where E k0 V represents the initial kinetic energy of the corrected ion flow, e is the amount of positive charge, and V is the initial kinetic energy of the ion flow. pThe plasma potential is given. Different elements require different amounts of energy to be extracted. For heavy elements such as uranium, the required voltage is between 11.8V and 14.4V. Therefore, the corrected maximum kinetic energy is about 20eV. To ensure the stable extraction of cations, the minimum voltage of the accelerating lens can be calculated from the formula as -20V.

[0045] In addition, the deflecting lens group 220 includes a focusing lens 221, a front deflecting lens 222, an L-shaped frame 223, and a rear deflecting lens 224; the L-shaped frame 223 is fixedly installed in the analytical vacuum chamber 400; the front deflecting lens 222 and the rear deflecting lens 224 are both hollow cylindrical structures, and the front deflecting lens 222 and the rear deflecting lens 224 are respectively installed at both ends of the L-shaped frame, and the axes of the front deflecting lens 222 and the rear deflecting lens 224 are perpendicular to each other; the focusing lens 221 is a hollow cylindrical structure, and the focusing lens 221, the accelerating lens 210, and the front deflecting lens 222 are coaxially arranged, and the focusing lens 221 is located on the side of the front deflecting lens 222 facing the accelerating lens 210.

[0046] The focusing lens 221 is a cylindrical hollow structure, coaxially mounted with the front deflecting lens 222 and the accelerating lens 210, and a negative DC voltage is applied to the focusing lens 221; its core function is to further focus the ion beam transmitted through the accelerating lens 210 and optimize the ion beam shape to adapt to subsequent detection requirements.

[0047] The L-shaped frame 223 in the above technical solution has a 90° L-shaped structure with circular intersecting through holes inside. Ions to be tested can be deflected by 90° and enter the subsequent mass analyzer to meet subsequent detection requirements. Neutral particles are discharged through the through holes, reducing background noise. The deflection lens group 220 also includes a deflection shaft 225. The front deflection lens 222, deflection shaft 225, and rear deflection lens 224 are installed inside the L-shaped frame 223 and are electrically insulated from it. The front deflection lens 222 and rear deflection lens 224 are hollow cylindrical structures, which can deflect and focus ions. The deflection shaft 225... 25 is mounted on the L-shaped frame 223 via an insulating shaft 226 and an insulating fixing block 227. The deflection shaft 225 is a cylinder with an internal hole. It is mounted on the L-shaped frame 223 via the insulating shaft 226 and the insulating fixing block 227. The insulating shaft 226 and the insulating fixing block 227 are made of polytetrafluoroethylene. Their main function is to fix the deflection shaft 225 and insulate it from the L-shaped frame 223. The front deflection lens 222, the deflection shaft 225 and the rear deflection lens 224 are electrically connected and are all set with the same voltage, which is -200V to -350V. By controlling the DC voltage, the ions are controlled to achieve a 90° deflection.

[0048] In an electrostatic field, the deflection radius of ions is proportional to the kinetic energy per unit charge. Therefore, all ions with the same initial position, direction, and kinetic energy per unit charge should have the same trajectory in an electrostatic field. The ionization mechanism of plasma determines that all cations in it carry a positive charge, and the high ionization temperature determines that thermal energy is the main source of the kinetic energy of discrete ions. At the same temperature, the kinetic energy of different ions should remain basically the same. Therefore, in an ideal state, the ion transport system should have the same deflection effect on ions with different mass-to-charge ratios. To this end, this invention adjusts the voltage range and finds the optimal parameters.

[0049] According to the electrostatic field principle of deflecting lenses, the centripetal force on ions moving in an electrostatic field is equal to the electric force exerted on them by the electrostatic field. The relationship between the electric field strength and the deflection radius can be expressed as: ; Where E is the electric field strength, e is the positive charge, r is the distance between charged particles, m is the ion mass, and v is the airflow velocity; The relationship between the voltage and kinetic energy of the deflecting lens is as follows: ; Where E is the deflection lens voltage, i.e., the electric field strength, q is the charge number of the ion, and U is the voltage applied to the accelerating lens. k0 Let e ​​be the initial kinetic energy of the corrected ion flow, e be the amount of positive charge, and r be the distance between charged particles.

[0050] It can be seen that the strength of the deflection electric field is related to the initial kinetic energy of the ions and the voltage applied by the accelerating lens. The types of ions contained in the sample are mostly not unique, which leads to a deviation in ion kinetic energy. The focusing and accelerating effect provided by the accelerating lens can reduce the difference in kinetic energy between different ions. Since this system is designed as a 90° deflection ion transport system, for the same type of ion, the smaller the kinetic energy, the easier it is to be attracted by the front deflection lens and thus deviate from the ideal trajectory. The greater the kinetic energy, the higher the voltage required for deflection. From the above formula, the optimal voltage for the lowest kinetic energy ions to achieve the ideal trajectory deflection is approximately -250V.

[0051] The entire ion transport system consists of metal components. During the transport process, the ion beam generates a weak current, which in turn generates an electric field of unpredictable magnitude on the metal conductor, altering the preset shape of the electrostatic field. Therefore, in order to eliminate this interference factor, all components except the accelerating lens, the front deflecting lens, and the rear deflecting lens are grounded to form a stable electrostatic field.

[0052] In the above technical solution, an ion deflection and transmission system is composed of an accelerating lens and a deflecting lens group. This system can focus positively charged ions across the entire mass number range and efficiently input them into the deflecting lens group. A specific voltage is applied to the deflecting lens group, which greatly improves the ion transmission efficiency. This negative electric field accelerates positive ions while repelling electrons. Neutral ions and photons are not affected by the deflecting lens and may continue to transmit through.

[0053] In the technical solution of this application, COMSOL simulation was performed on ion deflection transport to optimize the electric field of the ion transport system and ensure ion transport efficiency. The simulation results for using an accelerating lens of -80V, a focusing lens of -35V, and a deflection voltage of -350V are as follows: Figure 16 As shown, ions passing through the ion sampling cone 150 interface are captured, focused, and accelerated by the electric field generated by the accelerating lens. During the process of passing through the accelerating lens and reaching the focusing lens, the ion beam diverges again. When the diverged ion beam passes through the low-voltage electric field of the focusing lens, it is refocused into a more ideally shaped ion beam to improve the success rate of subsequent deflection. Ions moving in a straight line after entering the front deflection lens are captured by the high-voltage electric field formed by the front deflection lens. At this time, the electric field force within the deflection lens electric field domain between the front and rear deflection lenses provides the centripetal force for the ions to move in a circular motion. Furthermore, a focusing lens with the same voltage as the front deflection lens is located on the front deflection lens side to accelerate the ions, shortening their residence time during deflection and ensuring that the deflection angle does not exceed 90°. After being ejected from the transmission system, the ions enter the collision cell or quadrupole mass analyzer for further analysis, thus completing the ion transmission process.

[0054] 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 of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. An analytical instrument based on glow discharge coupled with quadrupole mass spectrometry, characterized in that, This includes ion sources, ion transport systems, and ion separators; The ion source is a glow discharge ion source; The ion separator is a quadrupole mass analyzer, which includes four parallel electrodes.

2. The analytical instrument based on glow discharge and quadrupole mass spectrometry as described in claim 1, characterized in that, It also includes an analytical vacuum chamber, wherein the ion separator is disposed within the analytical vacuum chamber and the electrodes of the ion separator are arranged along the longitudinal direction of the analytical vacuum chamber; The ion source is configured on one side of the analytical vacuum chamber, and one end of the ion source can be connected to the analytical vacuum chamber. The ion emission direction of the ion source is set along the transverse direction of the analytical vacuum chamber. The ion transport system is located between the ion source and the ion separator. Ions that escape laterally along the analytical vacuum chamber are redirected by the ion transport system and then enter the ion separator for screening.

3. The analytical instrument based on glow discharge and quadrupole mass spectrometry as described in claim 2, characterized in that, The ion source includes: The primary vacuum chamber is located on one side of the analytical vacuum chamber, and the primary vacuum chamber and the analytical vacuum chamber are interconnected. The chamber door is rotatably mounted on one side of the primary vacuum chamber. The sample stage is connected to the side of the chamber door facing the primary vacuum chamber; The anode disk, located in the primary vacuum chamber, is used to form a discharge circuit with the sample placed on the sample stage; The ion sampling cone is positioned on the side of the anode disk away from the sample stage.

4. The analytical instrument based on glow discharge and quadrupole mass spectrometry as described in claim 3, characterized in that, A sliding hole is provided on one side of the primary vacuum chamber, and a sliding valve is slidably disposed in the sliding hole. The sliding valve is driven to move along the sliding hole and can cut off the connection between the primary vacuum chamber and the analytical vacuum chamber.

5. The analytical instrument based on glow discharge and quadrupole mass spectrometry as described in claim 3, characterized in that, A linear mechanism is provided at the bottom of the sample stage. In operation, the linear mechanism pushes the sample stage toward the anode disk. With the door open, the sample stage is arranged parallel to the workbench surface.

6. The analytical instrument based on glow discharge coupled with quadrupole mass spectrometry according to claim 3, characterized in that, The anode plate includes an anode cylinder, a cylinder base, and a water-cooling plate; The water cooling plate has a built-in water circuit, and the cooling water circulates in the water circuit to remove heat during operation. The cylindrical base is located inside the water-cooling plate; The anode tube is located inside the tube base, and an ion jet outlet is provided on the side of the anode tube facing the primary vacuum chamber.

7. The analytical instrument based on glow discharge coupled with quadrupole mass spectrometry according to claim 6, characterized in that, The cylindrical base includes a first insulating layer and a first conductor layer; The first insulating layer is the layer that contacts the sample at the base of the cylinder, and it is made of alumina ceramic; The first conductor layer is disposed on the side of the first insulating layer away from the sample, and the first conductor layer is in contact with the water cooling plate; Furthermore, an air supply groove is provided on the top of the first insulating layer, and the air supply groove is tangent to the inner cavity of the cylinder base.

8. The analytical instrument based on glow discharge coupled with quadrupole mass spectrometry according to claim 7, characterized in that, The anode cylinder includes a second insulating layer and a second conductor layer, with the second conductor layer disposed inside the second insulating layer; The cavity at the center of the cylindrical base is a conical cavity, and the outer wall of the second insulating layer is a corresponding conical cylinder; Furthermore, the thickness of the second insulating layer and the second conductor layer are the same as the thickness of the first conductor layer.

9. The analytical instrument based on glow discharge coupled with quadrupole mass spectrometry according to claim 3, characterized in that, The ion transport system includes an accelerating lens and a deflecting lens group; The accelerating lens is disposed in the primary vacuum chamber, and the interior of the accelerating lens is hollow. The end of the accelerating lens facing the anode disk has a tapered structure with a hole. The deflecting lens group is installed in the analytical vacuum chamber.

10. The analytical instrument based on glow discharge and quadrupole mass spectrometry as described in claim 9, characterized in that, The deflecting lens group includes a focusing lens, a front deflecting lens, an L-shaped frame, and a rear deflecting lens; The L-shaped frame is fixedly installed in the analytical vacuum chamber; Both the front deflecting lens and the rear deflecting lens are hollow cylindrical structures, and the front deflecting lens and the rear deflecting lens are respectively set at both ends of the L-shaped frame, with the axes of the front deflecting lens and the rear deflecting lens being perpendicular to each other. The focusing lens has a hollow cylindrical structure. Both the focusing lens and the accelerating lens are coaxially arranged with the front deflecting lens, and the focusing lens is located on the side of the front deflecting lens facing the accelerating lens.

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