Portable photoionization mass spectrometer

Abstract

The application discloses a portable photoelectric ion mass spectrometer device, which comprises a vacuum unit, a sampling unit, a UV light unit and a detector. The vacuum unit comprises a vacuum cavity, and a vacuum device is arranged on one side of the vacuum cavity. The ion trap mass analyzer and the detector are arranged in the vacuum cavity. The sampling unit is arranged at the bottom of the vacuum cavity, one end of the sampling unit is communicated with the inside of the ion trap mass analyzer, and a control assembly is arranged on the sampling unit. The UV light unit comprises a vacuum UV light generator and a vacuum UV light controller. The vacuum UV light generator is fixedly connected to the side of the vacuum cavity, and the vacuum UV light generator is arranged correspondingly to the ion trap mass analyzer. The vacuum UV light controller is electrically connected to the vacuum UV light generator. The application utilizes the sampling unit to transmit the non-ionized sample molecules into the vacuum unit, and then directly ionizes and analyzes through the vacuum UV light, without the ion transmission process, so that the ion loss in the transmission process is avoided, and the stability and reliability of the analysis are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of portable mass spectrometry, and in particular to portable photoionization mass spectrometry devices. Background Technology

[0002] With the continuous development of mass spectrometry technology, the demand for portable mass spectrometers for rapid on-site detection is increasing. Currently, portable mass spectrometers have significant research value in various fields and are being increasingly adopted in areas such as food safety, public safety, chemical warfare agent detection, clinical diagnosis, and drug detection. Compared to large laboratory mass spectrometers, they are smaller, lighter, consume less power, allow for rapid on-site detection, and are highly portable. A portable mass spectrometer consists of an atmospheric pressure ion source, an atmospheric interface, an ion transmission device, a mass analyzer, and an electron multiplier.

[0003] Atmospheric pressure ion sources can ionize untreated complex analytes under atmospheric pressure, and then introduce the ions into the vacuum of a mass analyzer for mass analysis. The application of atmospheric pressure ion sources enables portable mass spectrometers to perform rapid in-situ analysis of complex samples. Discontinuous atmospheric interfaces can introduce ions from an atmospheric pressure environment into a vacuum environment while maintaining the vacuum level required for mass analyzer operation. This allows atmospheric pressure ion sources to be integrated into portable mass spectrometers; therefore, the combination of an atmospheric pressure ion source and a discontinuous atmospheric interface is widely used in portable mass spectrometry technology.

[0004] However, this technology has a major drawback: the ion implantation duty cycle during the process of ions generated under atmospheric pressure entering the vacuum environment through discontinuous atmospheric flow is only 1%, resulting in poor stability and analysis speed of the analytical method and low ion transmission efficiency. This is precisely the key challenge that portable mass spectrometry aims to address. Summary of the Invention

[0005] The purpose of this invention is to provide a portable photoionization mass spectrometry device 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 a portable photoionization mass spectrometry device, comprising:

[0007] A vacuum unit includes a vacuum chamber, on one side of which a vacuum device is provided; an ion trap mass analyzer and a detector are provided inside the vacuum chamber; the detector is provided correspondingly to the ion trap mass analyzer.

[0008] A sample introduction unit is disposed at the bottom of the vacuum chamber, one end of which is connected to the interior of the ion trap, and a control component is provided on the sample introduction unit;

[0009] The ultraviolet light unit includes a vacuum ultraviolet light generator and a vacuum ultraviolet light controller. The vacuum ultraviolet light generator is fixedly connected to the side of the vacuum cavity and is correspondingly arranged with the ion trap mass analyzer. The vacuum ultraviolet light controller is electrically connected to the vacuum ultraviolet light generator.

[0010] According to the portable photoionization mass spectrometry device provided by the present invention, the vacuum device includes a micro turbomolecular pump, which is fixedly connected to one side of the vacuum chamber and is correspondingly arranged with the ion trap mass analyzer.

[0011] According to the portable photoionization mass spectrometry device provided by the present invention, the ion trap mass analyzer is provided with a through hole, and the vacuum ultraviolet light generator and the micro turbomolecular pump are respectively arranged corresponding to the ion trap mass analyzer.

[0012] According to the portable photoionization mass spectrometer provided by the present invention, the sample introduction unit includes a first sample introduction tube and a second sample introduction tube. The first sample introduction tube is vertically fixedly connected to the side wall of the vacuum chamber, and one end of the first sample introduction tube extends into the ion trap mass analyzer. The control component and the second sample introduction tube are both located outside the vacuum chamber.

[0013] According to the portable photoionization mass spectrometry device provided by the present invention, the control component includes a pulse valve, and the first sample inlet tube and the second sample inlet tube are connected through the pulse valve. The pulse valve is used to control the on / off state of the first sample inlet tube and the second sample inlet tube.

[0014] According to the portable photoionization mass spectrometer provided by the present invention, molecules are sequentially introduced into the ion trap mass analyzer through the first sample inlet tube and the second sample inlet tube to form an ion source.

[0015] According to the portable photoionization mass spectrometer provided by the present invention, a carrier gas inlet is provided on the outer wall of the vacuum chamber, and the carrier gas inlet is fixedly connected to the ion trap mass analyzer.

[0016] The present invention discloses the following technical effects:

[0017] 1. The photoionization mass spectrometry device of this invention provides stable and reliable analysis. This invention utilizes the sample introduction unit to transport unionized sample molecules into the vacuum unit, where they are then directly ionized and analyzed by a vacuum ultraviolet lamp in the ion trap mass analysis unit. This eliminates the need for ion transport, thus preventing ion loss during transport. Furthermore, the vacuum unit is free from interference from other components, significantly improving the stability and reliability of the analysis.

[0018] 2. This invention avoids the use of redundant components, and the unit layout is compact and reasonable, which improves the portability of the instrument.

[0019] 3. Ionization occurs within the ion trap mass analysis unit; ions are generated and immediately captured without the need for transport. This device is suitable for any ion trap apparatus.

[0020] 4. During ionization, the mass analyzer operates in a low vacuum environment, significantly increasing the number of ions generated. During scanning, it operates in a high vacuum environment to ensure stable operation of the mass analyzer.

[0021] 5. The vacuum UV lamp is controlled by a high-voltage pulse power supply. Turn off the UV lamp during analysis to ensure that the analysis is not disturbed.

[0022] 6. The sample introduction unit can be used in conjunction with conventional atmospheric pressure ionization sources (such as electrospray ionization sources, atmospheric pressure chemical ionization sources, etc.) to form a multi-ionization source system. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the structure of the portable photoionization mass spectrometry device of the present invention;

[0025] Figure 2 This is a schematic diagram of the structure of the portable photoionization mass spectrometry device (three-dimensional ion trap) of the present invention;

[0026] Figure 3 This is a timing diagram of the operation of the portable photoionization mass spectrometer of the present invention;

[0027] Figure 4 This is the mass spectrum of the sample gas in full-range scanning mode in Example 2 of the present invention;

[0028] Figure 5 This is the mass spectrum of the selected ion detection mode in Embodiment 2 of the present invention;

[0029] Figure 6 This is a mass spectrum in the second-order mass spectrometry mode of Embodiment 2 of the present invention.

[0030] The components include: 1. Vacuum unit; 2. Sample introduction unit; 3. Ultraviolet light unit; 101. Vacuum chamber; 102. Vacuum device; 103. Ion trap mass analyzer; 104. Detector; 201. Control component; 202. First sample introduction tube; 203. Second sample introduction tube; 301. Vacuum ultraviolet light generator; 302. Vacuum ultraviolet light controller; 4. Carrier gas inlet; 5. Three-dimensional ion trap; 6. Ring electrode; 7. Front cover electrode; 8. Rear cover electrode; 9. Vacuum ultraviolet lamp; 10. High-voltage pulse power supply; 11. Electron multiplier. Detailed Implementation

[0031] 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.

[0032] 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.

[0033] Example 1:

[0034] Reference Figure 1-3 The present invention provides a portable photoionization mass spectrometry device, comprising:

[0035] Vacuum unit 1, the vacuum unit 1 includes a vacuum chamber 101, a vacuum device 102 is provided on one side of the vacuum chamber 101; an ion trap mass analyzer 103 and a detector 104 are provided inside the vacuum chamber 101; the detector 104 is provided correspondingly to the ion trap mass analyzer 103.

[0036] Sample introduction unit 2 is disposed at the bottom of the vacuum chamber 101. One end of the sample introduction unit 2 is connected to the inside of the ion trap mass analyzer 103. A control component 201 is disposed on the sample introduction unit 2.

[0037] The ultraviolet light unit 3 includes a vacuum ultraviolet light generator 301 and a vacuum ultraviolet light controller 302. The vacuum ultraviolet light generator 301 is fixedly connected to the side of the vacuum cavity 101 and is correspondingly arranged with the ion trap mass analyzer 103. The vacuum ultraviolet light controller 302 is electrically connected to the vacuum ultraviolet light generator 301.

[0038] This invention utilizes the sample introduction unit 2 to transport unionized sample molecules into the vacuum unit 1, where they are then directly ionized and analyzed by a vacuum ultraviolet lamp 99 in the ion trap mass analysis unit. This eliminates the need for ion transport, thus preventing ion loss during transport. Furthermore, the vacuum unit 1 is free from interference from other devices, significantly improving the stability and reliability of the analysis.

[0039] In a further optimized design, the vacuum device 102 includes a micro turbomolecular pump, which is fixedly connected to one side of the vacuum chamber 101 and is configured correspondingly to the ion trap mass analyzer 103.

[0040] In a further optimized design, the ion trap mass analyzer 103 is provided with a through hole, and the vacuum ultraviolet light generator 301 and the micro turbomolecular pump are respectively set to correspond to the ion trap mass analyzer 103.

[0041] In a further optimized scheme, the sample introduction unit 2 includes a first sample introduction tube 202 and a second sample introduction tube 203. The first sample introduction tube 202 is vertically fixedly connected to the side wall of the vacuum chamber 101, and one end of the first sample introduction tube 202 extends into the ion trap mass analyzer 103. The control component 201 and the second sample introduction tube 203 are both located outside the vacuum chamber 101.

[0042] In a further optimized scheme, the control component 201 includes a pulse valve, through which the first injection tube 202 and the second injection tube 203 are connected, and the pulse valve is used to control the on / off state of the first injection tube 202 and the second injection tube 203.

[0043] In a further optimized scheme, molecules sequentially pass through the first sample inlet tube 202 and the second sample inlet tube 203 into the ion trap mass analyzer 103 to form an ion source.

[0044] In a further optimized design, a carrier gas inlet 4 is provided on the outer wall of the vacuum chamber 101, and the carrier gas inlet 4 is fixedly connected to the ion trap mass analyzer 103.

[0045] Reference manual attached Figure 2 ,

[0046] In this embodiment, an ion trap selection three-dimensional ion trap 5 is used. The three-dimensional ion trap 5 includes a ring electrode 6 and a front cover end electrode 7 and a rear cover end electrode 8 respectively disposed at both ends of the ring electrode 6. The sample injection unit 2 is inserted into the ring electrode 6. The front cover end electrode 7 and the rear cover end electrode 8 are respectively provided with through holes for corresponding to the vacuum ultraviolet light generator 301 and the detector 104. The vacuum ultraviolet light generator 301 selects the vacuum ultraviolet lamp 9. The vacuum ultraviolet light controller 302 selects the high voltage pulse power supply 10, and the detector 104 selects the electron multiplier 11.

[0047] Specific work process:

[0048] The electron multiplier 11 and the three-dimensional ion trap 5 are placed in a vacuum chamber 101, and the vacuum level is maintained at 5 × 10⁻⁶ by the turbomolecular pump. -5 Torr. The light window of the vacuum ultraviolet lamp 9 is in contact with the vacuum chamber 101 through an O-ring seal. The vacuum ultraviolet lamp 9, the small hole of the cap electrode of the three-dimensional ion trap 5, and the electron multiplier 11 are on the same axis. The carrier gas inlet 4 is introduced into the gap between the ring electrode 6 and the rear cap electrode 8 of the three-dimensional ion trap 5 by a capillary tube. The first sample inlet tube 202 extends into the gap between the ring electrode 6 and the rear cap electrode, and the rear end is connected to the second sample inlet tube 203.

[0049] The photoionization mass spectrometry (PMS) device operates in four stages: ionization and cooling, selected ion monitoring (SIM), collision-induced dissociation (CID), and scanning. It can perform full-range scanning, selected ion monitoring (SIM), secondary mass spectrometry (MS2), and multi-stage mass spectrometry (MSn) modes. The ionization and cooling stage time T1 < 300 ms, the ion monitoring stage time T2 < 10 ms, the collision-induced dissociation stage time T3 < 100 ms, and the scanning stage time T4 < 50 ms. The entire cycle time is less than 0.5 s, enabling rapid monitoring and analysis of target analytes.

[0050] Ionization and Cooling Stage: The clamp valve opens (opening time approximately 2–6 ms), connecting the atmospheric pressure environment with the vacuum environment. Under the influence of the pressure difference, the sample is introduced into the vacuum chamber 101 in molecular form, causing the gas pressure inside the vacuum chamber 101 to rapidly rise to a sub-atmospheric pressure environment close to 1 Torr. Simultaneously, the high-voltage pulse power supply 10 is turned on, and the vacuum ultraviolet lamp 9 is activated. Photons pass through the electrode 7 at the front cover of the ion trap and enter the ion trap to form a photon beam ionization region. Sample molecules passing through the ionization region are ionized and immediately stored in the ion trap. After the clamp valve closes, the unionized sample gas is expelled from the vacuum environment by the action of a micro-turbomolecular pump, and the vacuum level gradually increases. When the vacuum level returns to 5 × 10⁻⁶, the vacuum level gradually increases. -5 This phase ends when Torr stabilizes;

[0051] Ion selection stage: The stored waveform inverse Fourier transform technology is used to output an AC waveform that does not contain the intrinsic frequency of the ion to be detected, thereby popping other ions in the ion trap out of resonance and achieving isolation between target ions and non-target ions.

[0052] Collision-induced dissociation stage: Based on resonant excitation dissociation technology, a smaller excitation voltage is selected so that the target ion can be driven to fragment but the kinetic energy obtained is insufficient to eject the ion. The target ion is resonantly excited and absorbs the energy of the driving radio frequency electric field to gain kinetic energy, and collides with the background gas in the trap to produce fragment ions.

[0053] Scanning phase: The basic operation of ion trap mass spectrometry is to scan the ion trap in order of mass-to-charge ratio and detect it by electron multiplier 118. At the beginning of this phase, the vacuum ultraviolet lamp 9 must be kept off to prevent photons from entering the multiplier and generating photocurrent that would cause signal interference.

[0054] Full Scan mode: consists of 1 to 4 stages, with T2=0, T3=0, and the cycle is T1+T4;

[0055] Select Ion Detection Mode (SIM): Consists of 1→2→4 stages, with T3=0 and the cycle being T1+T2+T4;

[0056] Secondary mass spectrometry mode (MS2): consists of stages 1→2→3→4, with a period of T1+T2+T3+T4;

[0057] Multi-level mass spectrometry mode (MSn): by The phase consists of a period of T1+(T2+T3)×(n-1)+T4;

[0058] Example 2:

[0059] refer to Figure 4-6 The present invention uses 5×10 -6 The detection performance of this device was tested using mol / mol benzene (molecular weight 78, with N2 as the filling gas) as the sample gas.

[0060] Figure 4 The mass spectrum of the sample gas in full scan mode contains contamination peaks with mass-to-charge ratios of 95 and 131. For accurate characterization, secondary mass spectrometry analysis of the target peak 78 is required.

[0061] Figure 5 To select the mass spectrum for ion detection mode (SIM), ions stored in the ion trap are resonantly ejected by an AC signal that does not contain a mass-to-charge ratio of 78. This isolates non-target ions from target ions, facilitating further secondary mass spectrometry analysis of the target ions.

[0062] Figure 6 The mass spectrum is in MS2 mode, showing fragment peaks at 53, 52, 51, and 39, which are consistent with the EI library of benzene, achieving accurate characterization.

[0063] 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.

[0064] 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. A portable photoionization mass spectrometer, characterized in that, include: A vacuum unit (1) includes a vacuum chamber (101) and a vacuum device (102) is provided on one side of the vacuum chamber (101); an ion trap mass analyzer (103) and a detector (104) are provided inside the vacuum chamber (101); the detector (104) is provided corresponding to the ion trap mass analyzer (103); The sample introduction unit (2) is located at the bottom of the vacuum chamber (101). One end of the sample introduction unit (2) is connected to the inside of the ion trap mass analyzer (103). A control component (201) is provided on the sample introduction unit (2). The ultraviolet light unit (3) includes a vacuum ultraviolet light generator (301) and a vacuum ultraviolet light controller (302). The vacuum ultraviolet light generator (301) is fixedly connected to the side of the vacuum cavity (101), and the vacuum ultraviolet light generator (301) is correspondingly arranged with the ion trap mass analyzer (103). The vacuum ultraviolet light controller (302) is electrically connected to the vacuum ultraviolet light generator (301). The vacuum device (102) includes a micro turbomolecular pump, which is fixedly connected to one side of the vacuum chamber (101) and is correspondingly arranged with the ion trap mass analyzer (103); The ion trap mass analyzer (103) is provided with a through hole, and the vacuum ultraviolet light generator (301) and the micro turbomolecular pump are respectively set to correspond to the ion trap mass analyzer (103); The sample introduction unit (2) includes a first sample introduction tube (202) and a second sample introduction tube (203). The first sample introduction tube (202) is vertically fixed to the side wall of the vacuum chamber (101), and one end of the first sample introduction tube (202) extends into the ion trap mass analyzer (103). The control component (201) and the second sample introduction tube (203) are both located outside the vacuum chamber (101). The ion trap is a three-dimensional ion trap (5), which includes a ring electrode (6) and a ring electrode (6). The sample injection unit (2) of the front cover end electrode (7) and the rear cover end electrode (8) set at both ends of the ring electrode (6) is inserted into the ring electrode (6). The front cover end electrode (7) and the rear cover end electrode (8) are respectively provided with through holes for corresponding to the vacuum ultraviolet light generator (301) and the detector (104); the vacuum ultraviolet light generator (301) selects the vacuum ultraviolet lamp (9); the vacuum ultraviolet light controller (302) selects the high voltage pulse power supply (10), and the detector (104) selects the electron multiplier (11); The photoionization mass spectrometry device operates in four stages: ionization and cooling, ion selection, collision-induced dissociation, and scanning. It can perform full-range scanning, selected ion detection, secondary mass spectrometry, and multi-stage mass spectrometry scanning modes. The ionization and cooling stage time T1 is less than 300 ms, the ion selection stage time T2 is less than 10 ms, the collision-induced dissociation stage time T3 is less than 100 ms, and the scanning stage time T4 is less than 50 ms. The entire cycle time is less than 0.5 s, enabling rapid monitoring and analysis of target analytes. Ionization and Cooling Stage: The clamp valve is opened, and the atmospheric pressure is connected to the vacuum environment. Under the action of the pressure difference, the sample is sent into the vacuum chamber (101) in the form of molecules, which causes the gas pressure in the vacuum chamber (101) to rise rapidly to a sub-atmospheric pressure environment close to 1 Torr. At the same time, the high-voltage pulse power supply (10) is turned on and the vacuum ultraviolet lamp (9) is turned on. Photons pass through the electrode (7) at the front cover of the ion trap and enter the ion trap to form a photon beam ionization region. After the sample molecules pass through the ionization region, they are ionized and immediately stored in the ion trap. After the clamp valve is closed, the unionized sample gas is discharged from the vacuum environment under the action of the micro turbomolecular pump. The vacuum degree gradually rises. When the vacuum degree returns to 5×10-5 Torr and stabilizes, this stage ends. Ion selection stage: The stored waveform inverse Fourier transform technology is used to output an AC waveform that does not contain the intrinsic frequency of the ion to be detected, thereby popping other ions in the ion trap out of resonance and achieving isolation between target ions and non-target ions. Collision-induced dissociation stage: Based on resonant excitation dissociation technology, a smaller excitation voltage is selected so that the target ion can be driven to fragment but the kinetic energy obtained is insufficient to eject the ion. The target ion is resonantly excited and absorbs the energy of the driving radio frequency electric field to gain kinetic energy, and collides with the background gas in the trap to produce fragment ions. Scanning phase: The basic operation of ion trap mass spectrometry is to scan the ion trap in order of mass-to-charge ratio and detect it by the electron multiplier (118). At the beginning of this phase, the vacuum ultraviolet lamp (9) must be kept off to prevent photons from entering the multiplier and generating photocurrent to form signal interference. Full-range scan mode: consists of 1→4 stages, with T2=0, T3=0, and the period is T1+T4; Select ion detection mode: consisting of 1→2→4 stages, set T3=0, and the cycle is T1+T2+T4; Secondary mass spectrometry mode: consists of 1→2→3→4 stages, with a period of T1+T2+T3+T4; Multi-stage mass spectrometry mode: consists of 1→(2↔3)n-1→4 stages, with a period of T1+(T2+T3)×(n-1)+T4.

2. The portable photoionization mass spectrometer according to claim 1, characterized in that: The control component (201) includes a pulse valve, through which the first injection tube (202) and the second injection tube (203) are connected. The pulse valve is used to control the opening and closing of the first injection tube (202) and the second injection tube (203).

3. The portable photoionization mass spectrometry device according to claim 2, characterized in that: Molecules pass sequentially through the first injection tube (202) and the second injection tube (203) into the ion trap mass analyzer (103) to form an ion source.

4. The portable photoionization mass spectrometer according to claim 1, characterized in that: A carrier gas inlet (4) is provided on the outer wall of the vacuum chamber (101), and the carrier gas inlet (4) is fixedly connected to the ion trap mass analyzer (103).

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