An electrospray photoionization composite ionization source

Abstract

The present invention relates to the technical field of mass spectrometers, and in particular to an electrospray photoionization composite ionization source. It includes a vacuum ionization source cavity, an ion transmission system, an ion extraction electrode, a sensing electrode and a spray capillary array group, wherein the interior of the vacuum ionization source cavity is provided with a spray capillary array group, an ion transmission system and an ion extraction electrode from left to right in sequence, and the sensing electrode is arranged on the outside of the spray capillary array group, and is used to apply voltage to the sample, and the sample is sprayed and ionized to obtain ions; the ion transmission system includes a plurality of transmission electrodes arranged at intervals, and each transmission electrode is provided with a miniature ultraviolet light source, and non-polar neutral molecules that are not sprayed and ionized by the sensing electrode are ionized under the irradiation of the miniature ultraviolet light source, and the ions are output by the ion extraction electrode. The present invention improves the detection sample flux, combines the pulse-induced electrode application method and the miniature ultraviolet light source, and improves the ionization efficiency, ion utilization rate and ionization coverage.

Description

Technical Field

[0001] The present invention relates to the technical field of mass spectrometers, and particularly to an electrospray photoionization composite ionization source. Background Art

[0002] Ionization is the primary step in mass spectrometry. Currently, the most commonly used ion source in commercial mass spectrometers is the electrospray ionization source (ESI), which has been widely used in fields such as biology, pharmacy, and environmental analysis. The spray droplets of traditional atmospheric pressure electrospray ionization sources (ESI) are relatively large, and the ionization efficiency is low. Although the ionization efficiency of nanoelectrospray (nESI) is high, the throughput is small, and ions are generated at atmospheric pressure, resulting in relatively serious transmission losses, which greatly affect the detection sensitivity. In addition, ESI-type ionization sources respond well to polar compounds, but poorly to non-polar or weakly polar compounds. Therefore, it is envisaged whether ESI ionization can be achieved in a vacuum in an array manner and combined with ultraviolet photoionization ingeniously to improve the detection sensitivity of non-polar compounds and broaden the application range of the entire ion source.

[0003] Through patent and literature searches, the relevant patents involving photoionization and electrospray are as follows: On June 5, 2020, Purple Spectrum Eddy (Suzhou) Technology Co., Ltd. applied for and disclosed an electrospray extraction vacuum ultraviolet photoionization composite ionization source, which includes a vacuum ionization source cavity, a mass spectrometry inlet electrode, a mass analyzer, and an extraction reagent syringe, an extraction spray tube, and a sample transfer tube for introducing sample gas placed outside the vacuum ionization source cavity. Inside the vacuum ionization source cavity, an initial ion receiving electrode group, a vacuum ultraviolet lamp, an ion converging and transmitting electrode group, and a differential ion outlet electrode are sequentially arranged at intervals from left to right. However, in this technology, electrospray ionization is carried out at atmospheric pressure, and the transmission and ionization efficiencies are relatively low. The irradiation area of the vacuum ultraviolet light source is small, and the photoionization efficiency is also limited. On November 2, 2016, Shimadzu Corporation applied for and disclosed a non-contact DC induction electrospray ionization device and ionization method. The electrospray ion source and other desorption / ionization devices (such as laser desorption ion sources) are placed in the same vacuum cavity, and the sample molecules in the vacuum cavity are independently or jointly acted on. The ions generated by ionization are sent into the ion analyzer through an ion focusing device for analysis. This invention is mainly used for laser imaging analysis, and traditional electrospray ionization is adopted, with low ionization efficiency. In addition, there is no effective collection design for the ions generated by ionization. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide an electrospray photoionization composite ionization source to improve the detection sensitivity and ionizable range of electrospray ionization mass spectrometry.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] The present invention provides an electrospray photoionization composite ionization source, which includes a vacuum ionization source cavity, an ion transmission system, an ion extraction electrode, an induction electrode, and a spray capillary array group. Inside the vacuum ionization source cavity, the spray capillary array group, the ion transmission system, and the ion extraction electrode are sequentially arranged from left to right. The induction electrode is arranged outside the spray capillary array group and is used to apply a voltage to the sample in the spray capillary array group, so that the sample is induced to spray and ionized to obtain ions. The ion transmission system includes a plurality of transmission electrodes arranged at intervals in sequence from left to right. Each transmission electrode is provided with a micro ultraviolet light source. The plurality of transmission electrodes are used to focus and transmit ions. Non-polar neutral molecules that are not induced to spray and ionized by the induction electrode are ionized under the irradiation of the micro ultraviolet light source, and the ions are output by the ion extraction electrode.

[0007] The transmission electrode has a cube structure with a cylindrical through hole Ⅰ in the middle. Cylindrical through holes Ⅱ communicating with the cylindrical through hole Ⅰ are provided on four side walls of the cube structure, and each cylindrical through hole Ⅱ is embedded with one of the micro ultraviolet light sources.

[0008] The diameter of the cylindrical through hole Ⅰ in the middle of the transmission electrode is 2 - 50 mm, and the diameters of the cylindrical through holes Ⅰ of the plurality of transmission electrodes decrease sequentially from left to right. DC voltages are sequentially applied to the transmission electrodes from left to right to form an ion transmission electric field with a magnitude of 1 - 50 V / cm in the axial direction of the ion transmission system.

[0009] The micro ultraviolet light source is a micro discharge light source or an LED light source, and the wavelength range of the emitted photons is 100 - 500 nm.

[0010] The ion extraction electrode has a flat plate structure with a frustum-shaped through hole in the middle, and the diameter of the through hole is 0.1 - 2 mm. The right side of the ion extraction electrode is connected to a mass spectrometer.

[0011] The spray capillary array group is composed of two or more capillaries. The left end of the spray capillary array group is sealed and fixed by a sealing sleeve, and an inlet is provided at the left end of the sealing sleeve.

[0012] The spray capillary array group is composed of quartz capillaries, and the inner diameter of the quartz capillary is 5 - 530 μm.

[0013] The inlet of the sealing sleeve is connected to a micro-injection pump through a sampling pipeline. The sample in the micro-injection pump is injected into the sealing sleeve through the sampling pipeline and then transferred to the spray capillary array group. The flow rate of the micro-injection pump is 0.01 - 10 μL / min.

[0014] The induction electrode is of a rectangular flat plate structure and is arranged below the spray capillary array group in the vacuum ionization source cavity; the induction electrode is connected to an induction power supply outside the vacuum ionization source cavity through a wire.

[0015] The frequency of the induction voltage output by the induction power supply is 10 - 2000 Hz, and the amplitude is 1000 - 4000 V; the vacuum ionization source cavity is connected to a vacuum pump to control the internal air pressure to be 100 - 10000 Pa.

[0016] The advantages and beneficial effects of the present invention are as follows: An electrospray photoionization composite ionization source provided by the present invention improves the detection sample throughput through an array capillary group, utilizes the vacuum environment to improve the desolvation efficiency, and cleverly combines the pulse-induced electrode application method and a micro ultraviolet light source, ultimately achieving the improvement of the ionization efficiency, ion utilization rate, and ionization coverage of the composite ionization source. The present invention can be used as a highly sensitive general mass spectrometry ionization technology and has broad application prospects in the fields of biology, pharmacy, environmental analysis, etc. Brief Description of the Drawings

[0017] The drawings further illustrate the present invention, but the content in the drawings does not constitute any limitation to the present invention.

[0018] Figure 1 It is a schematic diagram of the overall structure of an electrospray photoionization composite ionization source of the present invention;

[0019] In the figure: 1 is a micro-injection pump, 2 is a sampling pipeline, 3 is a sealing sleeve, 4 is a vacuum ionization source cavity, 5 is an induction power supply, 6 is an ion, 7 is a micro ultraviolet light source, 8 is a transfer electrode, 9 is an ion extraction electrode, 10 is an ion transfer system, 11 is an induction electrode, and 12 is a spray capillary array group. Detailed Embodiments

[0020] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The description of at least one exemplary embodiment below is actually only illustrative and in no way restrictive of the present invention and its application or use. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by orientation words such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal" and "top, bottom", etc. is usually based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description. Without contrary instructions, these orientation words do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the protection scope of the present invention: the orientation words "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0023] As Figure 1 shown, an electrospray photoionization composite ionization source provided by the present invention includes a vacuum ionization source cavity 4, an ion transmission system 10, an ion extraction electrode 9, an induction electrode 11, and a spray capillary array group 12. Among them, a spray capillary array group 12, an ion transmission system 10, and an ion extraction electrode 9 are sequentially arranged from left to right inside the vacuum ionization source cavity 4. The induction electrode 11 is arranged outside the spray capillary array group 12. The induction electrode 11 is used to apply a voltage to the sample in the spray capillary array group 12, so that the sample is induced to spray and ionized to obtain ions 6; the ion transmission system 10 includes a plurality of transmission electrodes 8 arranged at intervals in sequence from left to right. A micro ultraviolet light source 7 is provided on each transmission electrode 8. The plurality of transmission electrodes 8 are used to focus and transmit ions 6. Non-polar neutral molecules that are not induced to spray and ionized by the induction electrode 11 are ionized under the irradiation of the micro ultraviolet light source 7. The ions 6 are output by the ion extraction electrode 9.

[0024] In an embodiment of the present invention, the transmission electrode 8 is a cube structure with a cylindrical through hole Ⅰ in the middle. Cylindrical through holes Ⅱ communicating with the cylindrical through hole Ⅰ are provided on the four side walls of the cube structure. A micro ultraviolet light source 7 is embedded in each cylindrical through hole Ⅱ. That is to say, each transmission electrode 8 is provided with four identical micro ultraviolet light sources 7. The light emission direction of the micro ultraviolet light source 7 irradiates the inside of the cylindrical through hole Ⅰ.

[0025] Specifically, the ion transmission system 10 is composed of three or more transmission electrodes 8. The diameter of the cylindrical through hole Ⅰ in the middle of the transmission electrode 8 is 2 - 50 mm, and the diameters of the cylindrical through holes Ⅰ in the middle of the plurality of transmission electrodes 8 decrease sequentially from left to right; DC voltages are applied to the transmission electrodes 8 in sequence from left to right to form an ion transmission electric field with a magnitude of 1 - 50 V / cm in the axial direction of the ion transmission system 10.

[0026] In an embodiment of the present invention, the micro ultraviolet light source 7 is a micro discharge light source or an LED light source, and the wavelength range of the emitted photons is 100 - 500 nm.

[0027] In an embodiment of the present invention, the ion extraction electrode 9 is a flat plate structure with a frustum-shaped through hole in the middle, and the diameter of the through hole is 0.1 - 2 mm; the right side of the ion extraction electrode 9 is connected to a mass spectrometer, and the mass spectrometer is a time-of-flight mass spectrometer, a quadrupole mass spectrometer, a magnetic mass spectrometer, an ion trap mass spectrometer, an electrostatic trap mass spectrometer, or various tandem mass spectrometers.

[0028] In an embodiment of the present invention, the spray capillary array group 12 is composed of two or more identical capillaries. The left end of the spray capillary array group 12 is sealed and fixed by a sealing sleeve 3, and an inlet is provided at the left end of the sealing sleeve 3.

[0029] Specifically, the spray capillary array group 12 is composed of quartz capillaries, and the inner diameter of the quartz capillaries is 5 - 530 μm.

[0030] Furthermore, the inlet of the sealing sleeve 3 is connected to the micro-injection pump 1 through the sampling pipeline 2; the sample in the micro-injection pump 1 is injected into the sealing sleeve 3 through the sampling pipeline 2 and then transferred to the spray capillary array group 12. The flow rate of the micro-injection pump 1 is 0.01 - 10 μL / min. The right end of the spray capillary array group 12 enters the vacuum ionization source cavity 4 from the outside along the X direction and the outer wall surface is hermetically connected to the vacuum ionization source cavity 4.

[0031] Specifically, the induction electrode 11 is a rectangular flat plate structure and is arranged below the spray capillary array group 12 in the vacuum ionization source cavity 4; the induction electrode 11 is connected to the induction power supply 5 outside the vacuum ionization source cavity 4 through a wire.

[0032] Furthermore, the frequency of the induction voltage output by the induction power supply 5 is 10 - 2000 Hz, and the amplitude is 1000 - 4000 V; the vacuum ionization source cavity 4 is connected to a vacuum pump to control the internal air pressure to be 100 - 10000 Pa.

[0033] An electrospray photoionization composite ionization source provided in this embodiment, such as Figure 1As shown in the figure, with the right direction as the X direction and the upward direction as the Y direction, the vacuum ionization source cavity 4 is a hollow closed cavity structure. Preferably, the flow rate of the micro-injection pump 1 is 0.1 μL / min, the spray capillary array group 12 is composed of 10 quartz capillaries, and the inner diameter of the quartz capillaries is 20 μm. The diameter of the through hole 1 of the electrode plate in the transfer electrode 8 is 35 mm, and it decreases uniformly from left to right; a DC voltage is applied to the transfer electrode 8 from left to right in sequence, forming an ion transfer electric field with a magnitude of about 10 V / cm in the axial direction of the ion transfer system 10. The induction voltage frequency output by the induction power supply 5 connected to the induction electrode 11 is 50 Hz, and the amplitude is 2000 V. The ion extraction electrode 9 has a through hole diameter of 1 mm; the through hole of the ion extraction electrode 9 is connected to the mass spectrometer on its right side, and the mass spectrometer is a high-resolution electrostatic trap mass spectrometer, with more accurate qualitative analysis. The micro ultraviolet light source 7 uses an LED light source, and the wavelength range of the emitted photons is 110 nm. The vacuum ionization source cavity 4 is connected to a vacuum pump to control the internal air pressure to 200 Pa.

[0034] During specific operation, first, the micro-injection pump 1 injects the sample into the sealing sleeve 3 at a certain speed and transports it to the spray capillary array group 12; then, the induction power supply 5 applies an induction voltage to the induction electrode 11 below the spray capillary array group 12, and the sample in the spray capillary array group 12 forms spray droplets under the induction voltage; the spray droplets can be efficiently desolvated in the vacuum environment of the vacuum ionization source cavity 4, thereby obtaining a high ionization efficiency; the ions 6 generated after desolvation gradually converge to the center of the ion transfer system 10 under the action of the ion transfer system 10. At the same time, some non-polar neutral molecules that are not inductively spray ionized are ionized under the irradiation of multiple groups of micro ultraviolet light sources 7 arranged on the transfer electrode 8, and finally, together with the ions generated by inductive spraying, they efficiently pass through the ion outlet electrode 9 and enter the mass spectrometer for analysis. The present invention can effectively improve the detection sensitivity and ionizable range of the electrospray ionization source, and has broad application prospects in the fields of biology, pharmacy, environmental analysis, etc.

[0035] The spray droplets of the traditional atmospheric pressure electrospray ionization source (ESI) are relatively large, and the ionization efficiency is low. Although the ionization efficiency of nanoelectrospray (nESI) is high, the throughput is small, and the ions are all generated under atmospheric pressure, resulting in relatively serious transmission losses, which greatly affect the detection sensitivity. In addition, ESI-type ionization sources have a better response to polar compounds, while the response to non-polar or weakly polar compounds is poor. A kind of electrospray photoionization composite ionization technology disclosed by the present invention improves the detection sample throughput through an array capillary group, uses a vacuum environment to improve the desolvation efficiency, and ingeniously combines a pulse-induced electrode application method and a micro ultraviolet light source, finally achieving the improvement of the ionization efficiency, ion utilization rate, and ionization coverage of the composite ionization source. The present invention can effectively improve the detection sensitivity and ionizable range of the electrospray ionization source, and has broad application prospects in the fields of biology, pharmacy, environmental analysis, etc.

[0036] The technical principles of the present invention are described above in combination with specific embodiments. These descriptions are only for explaining the principles of the present invention and cannot be interpreted in any way as limiting the scope of protection of the present invention. Based on the explanations here, technicians in this field can think of other specific implementations of the present invention without creative work, and these equivalent variations or substitutions are all included in the scope defined by the claims of this application.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electrospray photoionization composite ionization source, characterized in that: The invention comprises a vacuum ionization source chamber (4), an ion transmission system (10), an ion extraction electrode (9), a sensing electrode (11) and a spray capillary array group (12), wherein the inside of the vacuum ionization source chamber (4) is provided with a spray capillary array group (12), an ion transmission system (10) and an ion extraction electrode (9) in sequence from left to right, the sensing electrode (11) is arranged outside the spray capillary array group (12), and the sensing electrode (11) is used to apply a voltage to a sample in the spray capillary array group (12), so that the sample is sprayed and ionized to obtain ions (6); the ion transmission system (10) comprises a plurality of transmission electrodes (8) arranged in sequence from left to right, each transmission electrode (8) is provided with a miniature ultraviolet light source (7), and the plurality of transmission electrodes (8) are used to focus and transmit ions (6); non-polar neutral molecules that are not sprayed and ionized by the sensing electrode (11) are ionized under the irradiation of the miniature ultraviolet light source (7), and the ions (6) are output by the ion extraction electrode (9).

2. The electrospray photoionization composite ionization source according to claim 1, characterized in that: The transmission electrode (8) is a cubic structure with a cylindrical through hole I in the middle, and cylindrical through holes II communicating with the cylindrical through hole I are provided on the four side walls of the cubic structure, and a micro ultraviolet light source (7) is embedded in each cylindrical through hole II.

3. The electrospray photoionization composite ionization source according to claim 2, characterized in that: The diameter of the cylindrical through hole I in the middle of the transmission electrode (8) is 2 to 50 mm, and the diameters of the cylindrical through holes I of the transmission electrodes (8) decrease from left to right. A direct current voltage is applied to the transmission electrodes (8) from left to right, forming an ion transmission electric field with a magnitude of 1 to 50 V / cm in the axial direction of the ion transmission system (10).

4. The electrospray photoionization composite ionization source according to claim 1, characterized in that: The micro ultraviolet light source (7) is a micro discharge light source or an LED light source, and the wavelength range of the emitted photons is 100 to 500 nm.

5. The electrospray photoionization composite ionization source according to claim 1, characterized in that: The ion extraction electrode (9) is a flat plate structure with a truncated cone-shaped through hole in the middle, and the diameter of the through hole is 0.1-2 mm; the right side of the ion extraction electrode (9) is connected to a mass spectrometer.

6. The electrospray photoionization composite ionization source according to claim 1, characterized in that: The spray capillary array group (12) is composed of two or more capillaries. The left end of the spray capillary array group (12) is sealed by a sealing sleeve (3), and an inlet is provided at the left end of the sealing sleeve (3).

7. The electrospray photoionization composite ionization source according to claim 6, characterized in that: The spray capillary array group (12) is composed of quartz capillaries, and the inner diameter of the quartz capillaries is 5 to 530 um.

8. The electrospray photoionization composite ionization source according to claim 6, characterized in that: The inlet of the sealing sleeve (3) is connected to the microinjection pump (1) via an injection pipeline (2); the sample in the microinjection pump (1) is injected into the sealing sleeve (3) via the injection pipeline (2) and transmitted to the spray capillary array group (12); the flow rate of the microinjection pump (1) is 0.01 to 10 μL / min.

9. The electrospray photoionization composite ionization source according to claim 1, characterized in that: The induction electrode (11) is a rectangular flat plate structure and is arranged below the spray capillary array group (12) in the vacuum ionization source cavity (4); the induction electrode (11) is connected to an induction power supply (5) outside the vacuum ionization source cavity (4) via a wire.

10. The electrospray photoionization composite ionization source according to claim 1, characterized in that: The induction voltage output by the induction power supply (5) has a frequency of 10 to 2000 Hz and an amplitude of 1000 to 4000 V. The vacuum ionization source cavity (4) is connected to a vacuum pump to control the internal air pressure to be 100 to 10000 Pa.

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