Photoionization source integrated with filamentous ion guider

Abstract

The invention relates to the technical field of mass spectrometry instruments, in particular to a photoionization source integrated with a filamentous ion guider. Comprising an ionization source cavity, a vacuum ultraviolet lamp, a repulsion electrode and a filamentous ion guider, wherein the vacuum ultraviolet lamp, the repulsion electrode and the filamentous ion guider are arranged in the ionization source cavity from top to bottom; an ion output port is formed in the bottom of the ionization source cavity; photons emitted by the vacuum ultraviolet lamp sequentially pass through the repulsion electrode and the filamentous ion guider and then are output from the ion output port. The filamentous ion guider comprises a support frame and a plurality of filamentous electrodes which are arranged on the support frame at intervals along the circumferential direction; the plurality of filamentous electrodes are enclosed to form a conical ion focusing transmission channel of which the inner diameter is gradually reduced along the photon emitting direction; dC voltage is applied to the repulsion electrode, and radio frequency voltage is applied to the wire electrode. According to the invention, the surface area of collision between photons and the electrode is greatly reduced, so that the photoelectron yield is reduced, complex side reactions are avoided, and the purity of single-photon ionization is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mass spectrometry instruments, in particular to a photoionization source integrated with a filament ion guide. BACKGROUND

[0002] As a soft ionization technology, photoionization source directly excites or ionizes target molecules by vacuum ultraviolet light (VUV), has the core advantages of less fragmentation and high proportion of molecular ion peaks, and is particularly suitable for high specificity analysis of volatile organic compounds (VOCs). In recent years, its application in the fields of environmental monitoring, biomedicine and public safety has rapidly expanded, and it has become an indispensable key ionization method in mass spectrometry analysis.

[0003] To meet the needs of trace analysis, researchers have improved the sensitivity of photoionization sources by methods such as gas pressure regulation, increasing light flux, developing photoionization modes, and radio frequency ion guide technology. However, although the introduction of radio frequency field can significantly improve sensitivity, it will also increase the complexity of the ionization process. Experimental studies have shown that the radio frequency electric field can accelerate the photoelectrons (produced by the interaction of photons and the surface of metal electrodes) in the ionization region, leading to photoelectron ionization and other example molecule side reactions, thereby damaging the detection specificity of the target analyte and severely restricting the reliability of photoionization sources in complex matrix sample analysis. SUMMARY

[0004] To solve the above problems, the present application provides a photoionization source integrated with a filament ion guide to solve the core contradiction between sensitivity and specificity in traditional photoionization sources.

[0005] To achieve the above objectives, the technical scheme adopted by the present application is as follows:

[0006] The present application provides a photoionization source integrated with a filament ion guide, which comprises an ionization source cavity, a vacuum ultraviolet lamp, a repelling electrode and a filament ion guide arranged in the ionization source cavity from top to bottom, and an ion output port provided at the bottom of the ionization source cavity; the photons emitted by the vacuum ultraviolet lamp pass through the repelling electrode and the filament ion guide in turn and are output by the ion output port, and the filament ion guide has a tapered ion focusing transmission channel with a gradually decreasing inner diameter along the direction of photon emission.

[0007] The filament ion guide comprises a support frame and a plurality of filament electrodes arranged on the support frame in a circumferential direction, and the plurality of filament electrodes enclose the tapered ion focusing transmission channel; a direct current voltage is applied to the repelling electrode, and a radio frequency voltage is applied to the filament electrodes.

[0008] The filament electrodes are made of conductive metal wires, the diameter of the filament electrodes is 0.1-0.5mm, the number of the filament electrodes is 8-16, and the filament electrodes are symmetrically distributed in pairs.

[0009] The support frame includes a top fixing plate and a bottom fixing plate arranged above and below and at least three support columns connected between the top fixing plate and the bottom fixing plate;

[0010] The top fixing plate and the bottom fixing plate are both circular plate structures with a central hole, and are both provided with a mounting hole group for mounting the wire-shaped electrode.

[0011] The top fixing plate, bottom fixing plate and support column are all made of insulating materials; the center hole diameters of the top fixing plate and the bottom fixing plate are 4-10mm and 2-8mm respectively, and the thickness is 3-6mm; the diameter of the support column is 2-5mm and the length is 20-80mm.

[0012] The pole piece material of the repelling electrode is a conductive metal or a flat plate with a conductive metal layer plated on the surface.

[0013] The repelling electrode is a circular flat plate structure with a central hole, and has a thickness of 3-7 mm and a central hole diameter of 4-10 mm.

[0014] The DC voltage applied to the repelling electrode is 10-20V; the RF frequency applied to the filament electrode is 0.5-5MHz, the RF peak-to-peak value is 10-500V, and the RF peak-to-peak amplitudes of any two adjacent filament electrodes are equal and the phases are opposite.

[0015] The ionization source cavity is a closed cylindrical structure, and the left and right side walls of the ionization source cavity are respectively provided with an injection port and a vacuum pumping port;

[0016] The injection port is provided with an injection capillary, the outlet of the injection capillary is located in the area between the repeller electrode and the filamentary ion guide, and the inlet of the injection capillary is located in the external environment;

[0017] The vacuum pumping port is connected to a vacuum pump through a needle valve, and the air pressure in the ionization source cavity is 1-1000Pa.

[0018] The material of the injection capillary is stainless steel, quartz or polyetheretherketone, the inner diameter of the injection capillary is 50-500 μm, and the length is 10-60 cm.

[0019] The advantages and beneficial effects of the present invention are as follows: the present invention uses filament electrodes to replace traditional flat or rod-shaped electrodes, greatly reducing the surface area of ​​photon collision with the electrode, thereby reducing the photoelectron yield, avoiding the occurrence of complex side reactions, and ensuring the purity of single-photon ionization; in addition, by applying radio frequency voltage to the filament electrode, a dynamic focusing electric field is formed, which realizes efficient confinement and transmission of ions, and significantly improves the sensitivity of the ionization source. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic structural diagram of a photoionization source with an integrated filamentary ion guide according to the present invention;

[0021] Figure 2 It is a structural schematic diagram of the top fixing plate in the present invention.

[0022] In the figure: 1. ionization source chamber; 2. vacuum ultraviolet lamp; 3. repeller electrode; 4. top fixing plate; 401. electrode groove; 402. filament electrode fixing hole; 5. bottom fixing plate; 6. support column; 7. filament electrode; 8. needle valve; 9. vacuum pump; 10. injection capillary. DETAILED DESCRIPTION

[0023] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0024] See also Figure 1 and Figure 2 As shown, the present invention provides a photoionization source with an integrated filamentary ion guide, comprising an ionization source cavity 1 and a vacuum ultraviolet lamp 2, a repeller electrode 3 and a filamentary ion guide arranged from top to bottom in the ionization source cavity 1. An ion output port is provided at the bottom of the ionization source cavity 1; photons emitted by the vacuum ultraviolet lamp 2 pass through the repeller electrode 3 and the filamentary ion guide in sequence and are then output from the ion output port. The filamentary ion guide has a tapered ion focusing transmission channel with an inner diameter that gradually decreases along the photon emission direction.

[0025] See also Figure 1 As shown, in the embodiment of the present invention, the ionization source chamber 1 is a sealed cylindrical structure, with a sample inlet and a vacuum pump port provided on the left and right side walls, respectively. The sample inlet is provided with a sample injection capillary 10, the outlet of which is located between the repeller electrode 3 and the top fixing plate 4 of the filamentary ion guide, and the inlet of which is located in the external environment. The vacuum pump port is connected to a vacuum pump 9 via a needle valve 8. The air pressure within the ionization source chamber 1 is 1-1000 Pa, which is jointly regulated by the needle valve 8 and the vacuum pump 9 connected to the vacuum pump port.

[0026] Furthermore, the material of the injection capillary 10 is stainless steel, quartz, or polyetheretherketone, etc., and the inner diameter of the injection capillary 10 is 50-500 μm and the length is 10-60 cm.

[0027] See also Figure 1 As shown, in an embodiment of the present invention, the filamentary ion guide includes a support frame and a plurality of filamentary electrodes 7 arranged on the support frame at intervals along the circumferential direction, and the plurality of filamentary electrodes 7 enclose a conical ion focusing transmission channel; a DC voltage is applied to the repelling electrode 3, and a radio frequency voltage is applied to the filamentary electrode 7.

[0028] In the embodiment of the present invention, the wire electrode 7 is made of a thin wire of a conductive metal (such as tungsten or stainless steel). The wire electrode 7 has a diameter of 0.1-0.5 mm and is 8-16 in number, distributed symmetrically in an even number. The pole piece of the repelling electrode 3 is made of a conductive metal (such as stainless steel) or a flat plate coated with a conductive metal layer.

[0029] Furthermore, the repelling electrode 3 is a circular flat plate with a central hole, having a thickness of 3-7 mm and a diameter of 4-10 mm. A DC voltage of 10-20 V is applied to the repelling electrode 3. The radio frequency applied to the filamentary electrodes 7 is 0.5-5 MHz, with a peak-to-peak RF voltage of 10-500 V. The peak-to-peak RF amplitudes of any two adjacent filamentary electrodes 7 are equal and opposite in phase.

[0030] See also Figure 1 As shown, in an embodiment of the present invention, the support frame includes a top fixing plate 4 and a bottom fixing plate 5 arranged upper and lower and at least three support columns 6 connected between the top fixing plate 4 and the bottom fixing plate 5; the top fixing plate 4 and the bottom fixing plate 5 are both circular plate structures with a center hole, the center hole radius of the bottom fixing plate 5 is smaller than the center hole radius of the top fixing plate 4, and the top fixing plate 4 and the bottom fixing plate 5 are both provided with a mounting hole group for mounting the wire electrode 7, and the support columns 6 are parallel to the center axes of the top fixing plate 4 and the bottom fixing plate 5.

[0031] Furthermore, the top fixing plate 4, bottom fixing plate 5, and support column 6 are all made of insulating materials such as ceramic or polyetheretherketone. The circular light window, repeller electrode 3, top fixing plate 4, bottom fixing plate 5, and ion output port of the vacuum ultraviolet lamp 1 are all coaxial. The center hole diameters of the top fixing plate 4 and bottom fixing plate 5 are 4-10 mm and 2-8 mm, respectively, and the thickness of each is 3-6 mm. The support column 6 has a diameter of 2-5 mm and a length of 20-80 mm.

[0032] The filamentary electrodes 7 are multiple thin wire electrodes evenly distributed around the central holes of the top fixing plate 4 and the bottom fixing plate 5, with their two ends respectively fixed to the corresponding mounting positions of the top fixing plate 4 and the bottom fixing plate 5, forming a conical ion focusing transmission channel with an inner diameter gradually shrinking along the photon emission direction.

[0033] Specifically, both the top fixing plate 4 and the bottom fixing plate 5 are provided with a mounting hole group for fixing the wire electrode 7. The mounting hole group includes a plurality of electrode grooves 401 and a plurality of wire electrode fixing holes 402 evenly distributed around the central hole of the fixing plate. The plurality of wire electrode fixing holes 402 surround the outer sides of the plurality of electrode grooves 401. The two ends of the wire electrode 7 pass through the electrode grooves 401 of the top fixing plate 4 and the bottom fixing plate 5 respectively and are fixed to the wire electrode fixing holes 402 by bolts, so that the wire electrode 7 is tightened. Figure 2 shown.

[0034] In an embodiment of the present invention, the vacuum ultraviolet lamp 2 is a low-pressure inert gas discharge lamp, such as a krypton (Kr) discharge lamp, a deuterium (D2) discharge lamp, or a xenon (Xe) discharge lamp. The vacuum ultraviolet lamp 2 is fixed to a side of the ionization source chamber 1, away from the ion output port. The circular light window of the vacuum ultraviolet lamp 2 faces the ion output port. A repeller electrode 3 and a filamentary ion guide are sequentially positioned along the photon emission direction of the vacuum ultraviolet lamp 2. The ion output port of the ionization source chamber 1 is connected to an external mass analyzer, which can be a time-of-flight mass analyzer, a quadrupole mass analyzer, an ion trap mass analyzer, or the like.

[0035] Preferably, the repeller electrode 3 has a thickness of 5 mm and a center hole diameter of 8 mm; the diameter of the wire electrodes 7 is 0.4 mm, and there are 8 of them, which are evenly symmetrically distributed; the pole piece material of the repeller electrode 3 is a stainless steel flat plate; and the material of the wire electrodes 7 is a silver-plated metal wire. The top fixing plate 4, the bottom fixing plate 5, and the support column 6 are made of polyetheretherketone; the center hole diameters of the top fixing plate 4 and the bottom fixing plate 5 are 7 mm and 3 mm, respectively, and the thickness is 5 mm; the diameter of the support column 6 is 4 mm and the length is 50 mm. A DC voltage of 20 V is applied to the repeller electrode 3; an RF voltage of 2 MHz and a peak-to-peak RF voltage of 60 V is applied to the wire electrodes 7. The peak-to-peak RF amplitudes of any adjacent wire electrodes 7 are equal and the phases are opposite. The injection capillary 10 is made of stainless steel, with an inner diameter of 250 μm and a length of 50 cm. The vacuum ultraviolet lamp 2 is a low-pressure krypton (Kr) discharge lamp, and the ion output port of the ionization source cavity 1 is connected to an external mass analyzer, which is a time-of-flight mass analyzer. The gas pressure in the ionization source cavity 1 is 450 Pa.

[0036] In an embodiment of the present invention, the filamentary ion guide is composed of a plurality of filamentary electrodes 7 uniformly distributed around a circumference, the inner diameter of which gradually decreases along the light emission direction of the vacuum ultraviolet lamp 2 to form a conical focusing channel. By applying a radio frequency voltage to the filamentary electrode 7, a dynamic focusing electric field is formed, which achieves efficient confinement and transmission of ions, significantly improving the sensitivity of the ionization source; in addition, the fine wire structure of the filamentary electrode 7 greatly reduces the contact area between the electrode surface and the photons, inhibiting photon-electrode collisions from a physical level, reducing the photoelectron yield, and effectively avoiding complex side reactions caused by photoelectron acceleration in the radio frequency field, thereby ensuring the purity of the single-photon ionization process. The present invention solves the problem of the inability to reconcile the sensitivity of the photoionization source with the purity of the signal through the synergistic effect of structural innovation and electrical regulation, and can be widely used in the analysis of trace substances in the fields of environmental monitoring, biomedicine, etc.

[0037] The above description is only an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modification, equivalent replacement, improvement, expansion, etc. made within the spirit and principle of the present invention are included in the scope of protection of the present invention.

Claims

1. A photoionization source with an integrated filamentary ion guide, characterized in that: The invention comprises an ionization source cavity (1), a vacuum ultraviolet lamp (2), a repeller electrode (3) and a filamentary ion guide arranged in the ionization source cavity (1) from top to bottom, wherein an ion output port is provided at the bottom of the ionization source cavity (1); photons emitted by the vacuum ultraviolet lamp (2) pass through the repeller electrode (3) and the filamentary ion guide in sequence and are then output from the ion output port; the filamentary ion guide has a tapered ion focusing transmission channel with an inner diameter that gradually decreases along the photon emission direction.

2. The photoionization source with integrated filamentary ion guide according to claim 1, characterized in that: The filamentary ion guide comprises a support frame and a plurality of filamentary electrodes (7) arranged on the support frame at intervals along the circumferential direction, wherein the plurality of filamentary electrodes (7) enclose the conical ion focusing transmission channel; a direct current voltage is applied to the repelling electrode (3), and a radio frequency voltage is applied to the filamentary electrode (7).

3. The photoionization source integrated with a filamentary ion guide according to claim 2, characterized in that: The material of the wire-shaped electrodes (7) is a conductive metal thin wire; the diameter of the wire-shaped electrodes (7) is 0.1-0.5 mm, the number of the wire-shaped electrodes (7) is 8-16, and they are symmetrically distributed in an even number.

4. The photoionization source with integrated filamentary ion guide according to claim 2, characterized in that: The support frame comprises a top fixing plate (4) and a bottom fixing plate (5) arranged above and below, and at least three supporting columns (6) connected between the top fixing plate (4) and the bottom fixing plate (5); The top fixing plate (4) and the bottom fixing plate (5) are both circular plate structures with a central hole, and both the top fixing plate (4) and the bottom fixing plate (5) are provided with a mounting hole group for mounting the wire-shaped electrode (7).

5. The photoionization source integrated with a filamentary ion guide according to claim 4, characterized in that: The top fixing plate (4), the bottom fixing plate (5) and the support column (6) are all made of insulating materials; the center hole diameters of the top fixing plate (4) and the bottom fixing plate (5) are 4-10 mm and 2-8 mm respectively, and the thicknesses of both are 3-6 mm; the diameter of the support column (6) is 2-5 mm, and the length is 20-80 mm.

6. The photoionization source integrated with a filamentary ion guide according to claim 2, characterized in that: The pole piece material of the repelling electrode (3) is a conductive metal or a flat plate with a conductive metal layer plated on its surface.

7. The photoionization source integrated with a filamentary ion guide according to claim 6, characterized in that: The repelling electrode (3) is a circular flat plate structure with a central hole, a thickness of 3-7 mm, and a central hole diameter of 4-10 mm.

8. The photoionization source integrated with a filamentary ion guide according to claim 2, characterized in that: The DC voltage applied to the repelling electrode (3) is 10-20V; the radio frequency applied to the filamentary electrode (7) is 0.5-5MHz, the radio frequency peak-to-peak value is 10-500V, and the radio frequency peak-to-peak values ​​of any two adjacent filamentary electrodes (7) are equal in amplitude and opposite in phase.

9. The photoionization source integrated with a filamentary ion guide according to claim 1, characterized in that: The ionization source cavity (1) is a closed cylindrical structure, and the left and right side walls of the ionization source cavity (1) are respectively provided with an injection port and a vacuum pumping port; The injection port is provided with an injection capillary (10), the outlet of the injection capillary (10) is located in the area between the repeller electrode (3) and the filamentary ion guide, and the inlet of the injection capillary (10) is located in the external environment; The vacuum pumping port is connected to a vacuum pump (9) via a needle valve (8), and the air pressure in the ionization source cavity (1) is 1-1000 Pa.

10. The photoionization source integrated with a filamentary ion guide according to claim 9, characterized in that: The material of the sampling capillary (10) is stainless steel, quartz or polyetheretherketone, and the inner diameter of the sampling capillary (10) is 50-500 μm and the length is 10-60 cm.

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