Ion trap mass spectrum device and method capable of switching internal and external ion sources

Abstract

The invention discloses an ion trap mass spectrometry device and method capable of switching internal and external ion sources, and the device comprises an ion source cavity, the exterior of the ion source cavity is provided with a heating module, the side wall of the ion source cavity is provided with a sample introduction hole, and the sample introduction hole is internally provided with a chromatographic column I; the electron beam generation system is arranged at the front side position of the ion source cavity; the insulation connecting piece is communicated with the ion source cavity, and a lens I, a lens II and a lens III are sequentially arranged in the insulation connecting piece in the sample injection direction; a signal acquisition system; wherein a chromatographic column II is arranged on the ion trap. The two ionization modes inside and outside the trap are integrated, and different detection requirements can be flexibly met by switching the sample introduction path of the chromatographic column and regulating and controlling the voltage parameters of the lens I, the lens II and the lens III.

Description

Technical Field

[0001] This invention relates to the field of ionization source technology for mass spectrometers, and in particular to an ion trap mass spectrometry device and method with switchable internal and external ion sources. Background Technology

[0002] Mass spectrometry is one of the core technologies of modern analytical chemistry, widely used in environmental monitoring, food safety, drug development, life sciences, and many other fields. Ion trap mass spectrometers, with their unique ion capture capabilities and powerful multi-stage mass spectrometry functions, have become an important tool for analyzing complex mixtures. Among them, gas chromatography-ion trap mass spectrometry (GC-MS) combines the high separation capabilities of gas chromatography with the excellent qualitative capabilities of ion trap mass spectrometry, showing broad application prospects.

[0003] Ionization is the crucial first step in mass spectrometry analysis. Based on the relationship between the ionization location and the mass analyzer, existing technologies are mainly divided into two categories: one is external ionization (external ion source), where the sample is ionized in an ion source independent of the ion trap, and the ions are injected into the ion trap via a transmission element. Its advantages are good spectral reproducibility, comparability with standard spectral libraries, strong instrument stability, and resistance to contamination, but it has the disadvantages of large ion transmission loss and limited sensitivity; the other is internal ionization (internal ion source), where the sample is directly introduced into the ion trap for ionization. It has the advantages of high ion utilization efficiency, strong multi-stage mass spectrometry analysis capability, and compact instrument structure, but the ionization conditions are different from those of the standard source, and the spectrum cannot match the standard spectral library, which restricts its application in screening unknown substances.

[0004] Currently, there are no mass spectrometry devices that are compatible with both internal and external ion source modes, either domestically or internationally. Single-mode ionization sources suffer from insufficient sensitivity or limited qualitative capabilities, making it difficult to simultaneously meet the needs of high-sensitivity detection of known substances and accurate qualitative identification of unknown substances. There is an urgent need for a technical solution that can switch ionization modes to fill this gap. Summary of the Invention

[0005] The purpose of this invention is to provide an ion trap mass spectrometry device and method with switchable internal and external ion sources to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: The present invention provides an ion trap mass spectrometer with switchable internal and external ion sources, comprising: An ion source chamber is provided, a heating module is installed on the outside of the ion source chamber, and an injection port is opened on the side wall of the ion source chamber, and a chromatographic column I is installed in the injection port; An electron beam generating system is installed at the front side of the ion source cavity to generate an initial electron beam; An insulating connector is provided, which is connected to the ion source cavity. Lens I, lens II, and lens III are arranged sequentially along the sample introduction direction within the insulating connector. Lens I is used for initial focusing, lens II is used to constrain electron beam divergence, and lens III is used to collimate the electron beam and guide it to the center of the ion trap. The signal acquisition system is used to receive the initial electrons generated by the collision of the detected ions in the ion trap and convert the originally weak ion detection signal into a strong electrical signal that can be recognized and recorded by the instrument. The ion trap is equipped with a chromatographic column II.

[0007] According to the ion trap mass spectrometry device with switchable internal and external ion sources provided by the present invention, the electron beam generation system includes filament assembly I, filament assembly II, tungsten filament, and filament repulsion electrode. Filament assembly I, tungsten filament, and filament assembly II are connected in series. Filament assembly I and filament assembly II are fixed on the front side of the ion source cavity by a fixing member. The filament repulsion electrode is installed on filament assembly I and filament assembly II and is used to control the on / off state of filament assembly I and filament assembly II.

[0008] According to the ion trap mass spectrometer with switchable internal and external ion sources provided by the present invention, the fixing component includes a perforated insulating cover plate, a metal plate and a heat insulation plate. The heat insulation plate is fixed on the ion source cavity, the metal plate is mounted on the heat insulation plate, the insulating cover plate is mounted on the metal plate, and the filament assembly I and the filament assembly II are both fixed on the insulating cover plate.

[0009] According to the ion trap mass spectrometry device with switchable internal and external ion sources provided by the present invention, the signal acquisition system includes a multiplier and a dynamo electrode. The dynamo electrode is used to receive the initial electrons generated by the collision of the detected ions in the ion trap and emit more secondary electrons to achieve preliminary amplification of the electronic signal. The multiplier receives the secondary electrons output by the dynamo electrode and amplifies the weak electronic signal, converting the originally weak ion detection signal into a strong electrical signal that can be recognized and recorded by the instrument.

[0010] According to the ion trap mass spectrometry device with switchable internal and external ion sources provided by the present invention, the ion trap includes a front cover end, a rear cover end, and an annular electrode disposed between the front cover end and the rear cover end, wherein the front cover end is in communication with the insulating connector.

[0011] According to the ion trap mass spectrometer with switchable internal and external ion sources provided by the present invention, the tungsten filament voltage is -70V.

[0012] According to the ion trap mass spectrometry device with switchable internal and external ion sources provided by the present invention, lens I, lens II and lens III are respectively connected to interface I, interface II and interface III.

[0013] A method for operating an ion trap mass spectrometer with switchable internal and external ion sources includes an internal ion source operating mode and an external ion source operating mode. The internal ion source operating mode includes the following steps: Step 1: Start the electron beam generation system and introduce the gas sample to be tested into the system through the chromatographic column II installed on the ion trap; Step 2: Set the electrostatic potential parameters through the voltage control module. The bias voltage of the electron beam generation system is set to -70V. Lens I is given a positive bias voltage of +45V to +55V, lens II is given a negative bias voltage of -25V to -35V, and lens III is given a positive bias voltage of +45V to +55V to construct an efficient electron transport path. Step 3: The electron beam is directly injected into the ion trap through an optimized path, and the neutral analyte molecules in the trap are ionized by electron bombardment. Step 4: Switch the system to the mass spectrometry analysis stage, cut off the gas sample introduction, raise the potential of lens I to +200V, and at the same time set the potentials of lens II and lens III to zero to block the electron beam from continuing to enter the ion trap. Step 5: The signal acquisition system receives the initial electrons generated by the collision of the detected ions in the ion trap, converts the originally weak ion detection signal into a strong electrical signal that can be recognized and recorded by the instrument, and outputs it. The external ion source operating mode includes the following steps: Step 1: Start the electron beam generation system. The sample gas is introduced into the ionization region outside the ion trap through the chromatographic column I in the sample inlet of the ion source chamber side wall. Step 2: Set the working parameters through the high-precision digital control voltage module. The voltage of the electron beam generating system is -70V. Lens I is subjected to a negative bias voltage of -220V to -180V. The voltage of lens II is -5V to -10V. The voltage of lens III is set to -160V to -140V, forming a specific potential field range for electron collision ionization. Step 3: Electrons emitted by the electron beam generation system gain high kinetic energy under the action of a strong electric field and collide with gas molecules in the ionization region, causing the gas molecules to ionize and form positively charged ions. The ions enter the lens system for focusing and transmission under the subsequent electric field gradient. Step 4: Stop the carrier gas supply to interrupt the ionization process, and then simultaneously reduce the potentials of lens II and lens III to zero to eliminate the residual electric field in the ionization region; Step 5: The signal acquisition system receives the initial electrons generated by the collision of the detected ions in the ion trap, converts the originally weak ion detection signal into a strong electrical signal that can be recognized and recorded by the instrument, and outputs it.

[0014] The present invention discloses the following technical effects: This invention integrates both in-trap and out-of-trap ionization modes, allowing for flexible adaptation to different detection needs by switching the column injection path and adjusting the voltage parameters of lenses I, II, and III. The in-trap ion source mode reduces ion transport loss and significantly improves the detection sensitivity of known targets; the out-of-trap ion source mode generates abundant fragment ion information, enhancing the qualitative ability of unknown substances, effectively solving the pain point of traditional single-mode mass spectrometers in balancing sensitivity and qualitative performance.

[0015] This invention utilizes insulated connectors to precisely arrange lens groups, combined with a stable electron supply from the electron beam generation system, and voltage configuration optimized by SIMION software to construct an efficient electron transport and ion focusing path. A heating module ensures a stable ion source chamber environment, and the dual-injection design of columns I and II, along with voltage blocking technology, avoids interference during the analysis phase, significantly improving ionization efficiency and detection signal accuracy, providing reliable assurance for the analysis of complex matrix samples.

[0016] This invention features a compact structure and high functional integration, making it suitable for rapid detection scenarios using small mass spectrometers. It meets qualitative needs such as environmental pollutant screening and unknown substance screening, while also enabling highly sensitive quantitative detection of known targets. Mode switching can be completed without changing the ion source, making it convenient to operate and significantly expanding the application scenarios of mass spectrometers, enhancing their adaptability and practicality in various analytical tasks. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the ion trap mass spectrometer device (internal ion source working mode) with switchable internal and external ion sources according to the present invention. Figure 2 This is a schematic diagram of the ion trap mass spectrometer device (external ion source working mode) with switchable internal and external ion sources according to the present invention. Figure 3 Simulation of the internal ion source working mode of this invention Figure I ; Figure 4 Simulation of the external ion source working mode of this invention Figure I ; Figure 5 Simulation of the internal ion source working mode of this invention Figure II ; Figure 6 Simulation of the external ion source working mode of this invention Figure II .

[0019] The components are as follows: 1. Filament assembly I; 2. Perforated insulating cover; 3. Metal plate; 4. Heat insulation plate; 5. Ion source chamber; 6. Chromatographic column I; 7. Filament assembly II; 8. Filament repulsion electrode; 9. Tungsten filament; 10. Heating module; 11. Interface I; 12. Interface II; 13. Interface III; 14. Lens I; 15. Lens II; 16. Lens III; 17. Insulating connector; 18. Front cover end; 19. Ring electrode; 20. Rear cover end; 21. Chromatographic column II; 22. Multiplier; 23. Derma-electrode. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Reference Figures 1-4 This invention provides an ion trap mass spectrometer with switchable internal and external ion sources, comprising: Ion source chamber 5, heating module 10 is installed on the outside of ion source chamber 5, and sample inlet is opened on the side wall of ion source chamber 5, and chromatographic column I 6 is installed in the sample inlet; An electron beam generating system is installed at the front side of the ion source cavity 5 to generate an initial electron beam; An insulating connector 17 is connected to the ion source cavity 5. Lenses I 14, II 15 and III 16 are arranged sequentially along the sample introduction direction inside the insulating connector. Lens I 14 is used for preliminary focusing, lens II 15 is used to constrain electron beam divergence, and lens III 16 is used to collimate the electron beam and guide it to the center of the ion trap. The signal acquisition system is used to receive the initial electrons generated by the collision of the detected ions in the ion trap and convert the originally weak ion detection signal into a strong electrical signal that can be recognized and recorded by the instrument. The ion trap is equipped with a chromatographic column II21.

[0023] The scheme is further optimized. The electron beam generation system includes filament assembly I1, filament assembly II7, tungsten filament 9, and filament repulsion electrode 8. Filament assembly I1, tungsten filament 9, and filament assembly II7 are connected in series. Filament assembly I1 and filament assembly II7 are fixed to the front side of the ion source cavity 5 by a fixing component. The filament repulsion electrode 8 is installed on filament assembly I1 and filament assembly II7 and is used to control the on and off of filament assembly I1 and filament assembly II7.

[0024] The design is further optimized. The fixing components include a perforated insulating cover plate 2, a metal plate 3, and a heat insulation plate 4. The heat insulation plate 4 is fixed on the ion source cavity 5, the metal plate 3 is installed on the heat insulation plate 4, the insulating cover plate is installed on the metal plate 3, and the filament assembly I1 and filament assembly II7 are both fixed on the insulating cover plate.

[0025] Further optimization of the scheme: the signal acquisition system includes a multiplier 22 and a tandem electrode 23. The tandem electrode 23 is used to receive the initial electrons generated by the collision of the detected ions in the ion trap and emit more secondary electrons to achieve preliminary amplification of the electronic signal. The multiplier 22 receives the secondary electrons output by the tandem electrode 23 and amplifies the weak electronic signal, converting the originally weak ion detection signal into a strong electrical signal that can be recognized and recorded by the instrument.

[0026] The ion trap is further optimized by including a front cover end 18, a rear cover end 20, and an annular electrode 19 disposed between the front cover end 18 and the rear cover end 20. The front cover end 18 is connected to the insulating connector 17.

[0027] The scheme was further optimized, and the voltage of tungsten wire 9 was -70V.

[0028] The scheme was further optimized so that lens I14, lens II15 and lens III16 are connected to interface I11, interface II12 and interface III13 respectively.

[0029] A method for operating an ion trap mass spectrometer with switchable internal and external ion sources, including an internal ion source operating mode and an external ion source operating mode. The internal ion source operating mode includes the following steps: The gas sample to be tested is introduced into the system through the chromatographic column II21 of the ion trap. Simultaneously, the filament repulsion electrode 8 triggers a control signal, causing the series-connected filament assemblies I1 and II7 to conduct, driving the tungsten filament 9 (filament voltage fixed at -70V) to emit the initial electron beam. In the fixture, the heat insulation plate 4 isolates the heat conduction of the ion source cavity 5, preventing temperature interference in the electron beam generation system; the metal plate 3 and the perforated insulating cover plate 2 work together to fix the filament assemblies I1 and II7, ensuring a stable electron emission path and laying the foundation for subsequent electron focusing.

[0030] Electron beam focusing and in-trap ionization: Lenses I 14, II 15, and III 16 are connected to preset voltages via interfaces I 11, II 12, and III 13, respectively. Lens I 14 is given a positive bias of +45V to +55V for initial electron focusing; lens II 15 is given a negative bias of -25V to -35V to constrain electron beam divergence; and lens III 16 is given a positive bias of +45V to +55V to collimate the electron beam. The optimized electron beam passes through insulating connector 17 and precisely enters the ion trap front cover end 18, which is connected to the connector. It ultimately reaches the interior of the ion trap, which consists of the front cover end 18, the rear cover end 20, and the annular electrode 19. Electron bombardment directly ionizes the neutral analyte molecules within the trap, effectively reducing losses during ion transport. SimION simulation software is used. Figure 3 .

[0031] Interference blocking during the analysis phase: After entering the mass spectrometry analysis phase, the system cuts off the gas sample introduction. Through interface I11, the potential of lens I14 is raised to +200V to form a high-voltage barrier. Simultaneously, through interfaces II12 and III, the potentials of lenses II15 and III are returned to zero, completely blocking the electron beam from entering the ion trap. This ensures that only ionized ions within the trap participate in mass analysis, avoiding interference from subsequent ionization events on the detection signal. Simion simulation software is used as follows: Figure 5 It can be observed that electrons cannot enter the ion trap after the voltage is changed.

[0032] Signal amplification and output: The detected ions in the ion trap collide to generate initial electrons. After receiving the initial electrons, the damper 23 in the signal acquisition system emits more secondary electrons to complete the initial signal amplification. The multiplier 22 receives the secondary electrons output by the damper 23 and further amplifies the weak electronic signal, ultimately converting the originally weak ion detection signal into a strong electrical signal that the instrument can recognize and record.

[0033] The operating mode of an external ion source includes the following steps: The sample gas is introduced directly into the ionization region outside the ion trap through the chromatographic column I6 in the sample inlet port on the side wall of the ion source chamber 5. The filament repulsion electrode 8 emits a conduction signal, causing the filament assembly I1 and filament assembly II7 to work in series, driving the tungsten filament 9 (filament voltage -70V) to emit an electron beam. The heat insulation plate 4, metal plate 3, and perforated insulating cover plate 2 of the fixing components together ensure the structural stability and constant temperature of the electron beam generation system, avoiding the influence of external factors on the stability of electron kinetic energy.

[0034] Electron acceleration and external ionization: Specific voltages are applied to the lens assembly via interfaces I11, II12, and III13. Lens I14 is connected to a relatively high negative bias voltage of -220V to -180V to accelerate electrons and enhance their kinetic energy; lens II15 is connected to -5V to -10V to form a weak focusing field; lens III16 is connected to -160V to -140V, working in conjunction with lens I14 to construct a specific potential field range for electron collision ionization. Electrons emitted by tungsten filament 9 gain sufficient kinetic energy in this strong electric field, colliding with sample gas molecules in the ionization region, causing the molecules to ionize into positively charged ions. These ions, driven by the electric field gradient, enter the lens system to complete focusing and transmission. SimION simulation software is used. Figure 4 .

[0035] Environmental purification during the analysis phase: Upon entering the analysis phase, the system first stops the carrier gas supply, interrupting the ionization process. Then, through interfaces II12 and III13, the potentials of lenses II15 and III16 are controlled to zero, eliminating residual electric fields in the ionization region and ensuring the termination of all ionization events. Simultaneously, the front cover 18 and rear cover 20 of the ion trap, along with the annular electrode 19, form a stable internal space, providing a pure starting environment for subsequent ion introduction and mass analysis, avoiding interference from residual ions or electric fields with the detection results. SimION simulation software is used. Figure 6 It can be observed that neither electrons nor ions can enter the ion trap after the voltage is changed.

[0036] Signal amplification and recognition: After the ions transmitted through the lens enter the ion trap, the initial electrons generated by the impact are captured by the darad 23. The darad 23 achieves preliminary signal amplification by emitting secondary electrons. The multiplier 22 receives the secondary electrons and performs secondary amplification, converting the weak ion detection signal into a strong electrical signal, which is finally recognized and recorded by the instrument. The rich fragment ion information can provide key basis for the qualitative analysis of unknown substances.

[0037] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0038] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An ion-trap mass-spectrometry device with switchable internal and external ion sources, characterized in that It comprises: An ion source cavity (5) is externally provided with a heating module (10), and a sample inlet hole is formed in the side wall of the ion source cavity (5), and a chromatographic column I (6) is installed in the sample inlet hole; An electron beam generating system is installed at the front side of the ion source cavity (5) to generate an initial electron beam; An insulating connecting piece (17) is in communication with the ion source cavity (5), and a lens I (14), a lens II (15) and a lens III (16) are arranged in the insulating connecting piece (17) in sequence in the sample inlet direction, the lens I (14) is used for preliminary focusing, the lens II (15) is used for restraining electron beam divergence, and the lens III (16) is used for collimating and guiding the electron beam to the center of the ion trap; A signal acquisition system is used for receiving the initial electrons generated by the detected ions in the ion trap, and converting the originally weak ion detection signal into a strong electric signal that can be recognized and recorded by the instrument; Wherein, the ion trap is provided with a chromatographic column II (21).

2. The switchable internal and external ion source ion trap mass spectrometer of claim 1, wherein, The electron beam generating system comprises a filament assembly I (1), a filament assembly II (7), a tungsten filament (9) and a filament repeller (8), the filament assembly I (1), the tungsten filament (9) and the filament assembly II (7) are connected in sequence, the filament assembly I (1) and the filament assembly II (7) are fixed on the front side of the ion source cavity (5) through a fixing piece, and the filament repeller (8) is installed on the filament assembly I (1) and the filament assembly II (7) to control the on-off of the filament assembly I (1) and the filament assembly II (7).

3. The switchable internal and external ion source ion trap mass spectrometer of claim 2, wherein, The fixing piece comprises a hole insulating cover plate (2), a metal plate (3) and a heat insulation plate (4), the heat insulation plate (4) is fixed on the ion source cavity (5), the metal plate (3) is installed on the heat insulation plate (4), the insulating cover plate is installed on the metal plate (3), and the filament assembly I (1) and the filament assembly II (7) are fixed on the insulating cover plate.

4. The switchable internal and external ion source ion trap mass spectrometer of claim 1, wherein, The signal acquisition system comprises a multiplier (22) and a repeller (23), the repeller (23) is used for receiving the initial electrons generated by the detected ions in the ion trap and emitting more secondary electrons to realize preliminary amplification of the electronic signal, and the multiplier (22) receives the secondary electrons output by the repeller (23) and amplifies the weak electronic signal, so as to convert the originally weak ion detection signal into a strong electric signal that can be recognized and recorded by the instrument.

5. The switchable internal and external ion source ion trap mass spectrometer of claim 1, wherein, The ion trap comprises a front cover end (18), a rear cover end (20) and an annular electrode (19) arranged between the front cover end (18) and the rear cover end (20), and the front cover end (18) is in communication with the insulating connecting piece (17).

6. The switchable internal and external ion source ion trap mass spectrometer of claim 2, wherein, The voltage of the tungsten filament (9) is generally-70V.

7. The switchable internal and external ion source ion trap mass spectrometer of claim 1, wherein, The lens I (14), the lens II (15) and the lens III (16) are connected with an interface I (11), an interface II (12) and an interface III (13) respectively.

8. A method of operating an ion trap mass spectrometer device with switchable internal and external ion sources, based on the ion trap mass spectrometer device with switchable internal and external ion sources according to any one of claims 1 to 7, characterized in that It comprises an internal ion source working mode and an external ion source working mode, and the internal ion source working mode comprises the following steps: Step one: start the electron beam generating system, and introduce the gas sample to be tested into the system through the chromatographic column II (21) arranged on the ion trap; Step two: set the electrostatic potential parameters through the voltage control module, wherein the bias voltage of the electron beam generating system is set to -70 V, the lens I (14) applies a positive bias voltage of +45 V to +55 V, the lens II (15) applies a negative bias voltage of -25 V to -35 V, and the lens III (16) applies a positive bias voltage of +45 V to +55 V, thereby constructing an efficient electron transmission path; Step three: the electron beam is directly injected into the ion trap through the optimized path, and the neutral molecules to be tested in the ion trap are ionized through electron bombardment; Step four: switch the system to the mass spectrometry analysis stage, cut off the gas sampling, raise the potential of the lens I (14) to -200 V, and at the same time, set the potentials of the lens II (15) and the lens III (16) to zero, thereby blocking the electron beam from continuing to enter the ion trap; Step five: the signal acquisition system receives the initial electrons generated by the detected ions in the ion trap, converts the originally weak ion detection signal into a strong electric signal that can be recognized and recorded by the instrument, and outputs the signal. The external ion source working mode comprises the following steps: Step one: start the electron beam generating system, and introduce the sample gas into the ionization zone outside the ion trap through the chromatographic column I (6) in the sidewall sampling hole of the ion source cavity (5); Step two: set the working parameters through the high-precision digital control voltage module, wherein the voltage of the electron beam generating system is -70 V, the lens I (14) applies a negative bias voltage of -220 V to -180 V, the voltage of the lens II (15) is -5 V to -10 V, and the voltage of the lens III (16) is set to -160 V to -140 V, thereby forming a specific potential field interval for electron impact ionization; Step three: the electrons emitted by the electron beam generating system obtain high kinetic energy under the action of the strong electric field, collide with the gas molecules in the ionization zone, ionize the gas molecules to form positively charged ions, and the ions are driven into the lens system for focusing and transmission under the action of the subsequent electric field gradient; Step four: stop the carrier gas supply to interrupt the ionization process, and then set the potentials of the lens II (15) and the lens III (16) to zero at the same time, thereby eliminating the residual electric field in the ionization zone; Step five: the signal acquisition system receives the initial electrons generated by the detected ions in the ion trap, converts the originally weak ion detection signal into a strong electric signal that can be recognized and recorded by the instrument, and outputs the signal.

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