CN110648897A - An ion molecule reaction tube with a quadrupole funnel structure and its ion focusing method - Google Patents

Abstract

The invention relates to an ion molecule reaction tube with a quadrupole funnel structure and an ion focusing method thereof. The reaction tube comprises an ionization source, an electrode in front of the tube, a plurality of reaction tube electrodes and an ion outlet electrode; the ionization source is connected with the electrode in front of the tube. The described tube front electrode, the multi-piece reaction tube electrode and the ion outlet electrode are all connected in turn by resistance; the inner diameter of the described multi-piece reaction tube electrode gradually shrinks from the ion inlet end to the ion outlet end, forming a funnel shape; The center of the front electrode of the tube and the center of the ion exit electrode are respectively provided with small holes for ion entry and ion extraction; the multi-piece reaction tube electrodes are vertically cut into four small electrodes in the radial direction to form a quadrupole structure, and the opposite two are formed. Each small electrode is connected by a wire, and two adjacent small electrodes are connected by an inductance. The ion focusing method is to form a more efficient focusing and guiding electric field in a new quadrupole funnel structure reaction tube, and the product ions can be efficiently focused and guided. The invention has important value for improving the sensitivity of chemical ionization and photoionization detection instruments.

Description

An ion molecule reaction tube with a quadrupole funnel structure and its ion focusing method

technical field

The invention belongs to the field of analysis and detection, and in particular relates to an ion molecule reaction tube with a quadrupole funnel structure and an ion focusing method thereof.

Background technique

Proton transfer reaction mass spectrometry is a newly developed chemical ionization mass spectrometry technology based on the principle of ion-molecule reaction, including core components such as ion source, reaction tube, transition cavity and mass detector. It usually prepares the parent ion H ₃ O ⁺ of the ion-molecular reaction through a water vapor discharge ion source, and then introduces the parent ion H ₃ O ⁺ into the reaction tube through the small hole between the ion source and the reaction tube. It is determined that volatile organic compounds M can react with H ₃ O ⁺ ion-molecularly and be ionized into MH ⁺ . MH ⁺ can finally be detected by mass spectrometry to obtain molecular weight information and concentration information. Due to the advantages of high sensitivity, fast response, soft ionization, and no need for calibration, this technology has attracted more and more attention in the field of volatile organic compound monitoring and analysis in recent years.

Although proton transfer mass spectrometry is already the most sensitive chemical ionization mass spectrometry technology for the detection of volatile organic compounds, the technology itself still has room for further improvement, such as the off-axis diffusion of precursor ions and product ions in the reaction tube, resulting in can not be completely guided into the transition cavity and the mass spectrometer cavity, thus affecting the detection sensitivity, so Wang Yujie et al. The funnel concept is introduced into the reaction tube, which improves the detection sensitivity. The ion funnel is a funnel-shaped potential formed inside the electrode by applying a radio frequency voltage to a disc electrode with a gradually reduced inner diameter, thereby reducing the diffusion of ions and improving the efficiency of ion transmission. The inventor Shen Chengyin and others also proposed to add a primary ion funnel between the ion source and the reaction tube in the early stage to form a double-focusing ion funnel structure of the ion source and the reaction tube, which can further improve the efficiency of introducing parent ions into the reaction tube and improve the detection of organic substances. sensitivity. These techniques can improve the detection sensitivity of proton transfer reaction mass spectrometry to a certain extent, but for the monitoring of ultra-low concentrations of characteristic organics, higher sensitivity proton transfer reaction mass spectrometry is still a long-term demand now and even in the future.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is to provide an ion molecule reaction tube with a quadrupole funnel structure and an ion focusing method thereof in response to the research needs of ultra-low concentration characteristic organic matter monitoring. This ion molecule reaction tube is composed of multiple quadrupole sheet electrodes with a gradually decreasing inner diameter, and the interior is funnel-shaped. The parent ions and the product ions generated by the reaction can react to the ions under the combined action of the radio frequency electric field and the DC electric field in the reaction tube. The central hole of the exit electrode converges and leads out. On the one hand, the loss of ions is further reduced, and on the other hand, the reaction time is prolonged, and more product ions are generated, thereby realizing the highly sensitive detection of organic substances by the mass spectrometer detector.

The technical solution of the present invention:

An ion molecule reaction tube with a quadrupole funnel structure, comprising an ion source (1), a front electrode (2), a multi-piece reaction tube electrode (3), and an ion outlet electrode (4); the ion source (1) Connected with the front electrode (2) of the tube; the front electrode (2), the multi-piece reaction tube electrode (3) and the ion outlet electrode (4) are all connected in turn through resistance elements; the multi-piece reaction tube The inner diameter of the central hole of the electrode (3) is gradually reduced from the ion inlet end to the ion outlet end, forming a funnel shape; the center of the front electrode (2) of the tube is respectively provided with a small hole for ions to enter, and the center of the ion outlet electrode (4) A small hole for ion extraction is provided; the multi-piece reaction tube electrode (3) is vertically cut into four small electrodes in a fan shape in the radial direction to form a quadrupole structure, and the two opposite first small electrodes (5) Connected by wires, two opposite second small electrodes (6) are also connected by wires, and adjacent first small electrodes (5) and second small electrodes (6) are connected by inductance.

The multiple pieces of reaction tube electrodes (3) are separated by insulating sealing gaskets to form a reaction tube cavity, or the reaction tube cavity is formed by placing the whole into the sealed cavity; the pressure in the reaction tube cavity is 10Pa～1000Pa .

The diameter of the ion extraction hole in the center of the ion outlet electrode (4) is 0.1 mm to 5 mm.

The present invention also provides an ion focusing method for an ion molecule reaction tube with a quadrupole funnel structure. The steps are as follows:

By applying a DC voltage between the front electrode (2) and the ion outlet electrode (4), a uniform electric field is formed in the reaction tube through the resistance partial pressure between each electrode in the reaction tube electrode (3);

By applying radio frequency voltages with opposite polarities to the adjacent first small electrodes (5), the second and the small electrodes (6) in each piece of reaction tube electrodes (3), an ion focusing electric field is formed in the reaction tube; The parent ions generated by the source and the product ions generated by the reaction between the parent ions and the test, or the product ions directly generated by photoionization can migrate to the ion exit electrode (4) under the guidance of a uniform electric field, and move toward the ion exit electrode (4) under the action of the ion focusing electric field. Axial focusing is finally drawn out through the central small hole of the ion exit electrode (4), so as to realize efficient focusing and guiding of ions.

The difference and advantage of the present invention compared with the prior art are:

(1) In proton transfer reaction mass spectrometry, a certain reaction pressure is required in the reaction tube to efficiently generate ion-molecule reactions, while the mass spectrometer cavity requires low air pressure for the mass spectrometer device to work safely, so the end of the reaction tube can only pass through the current-limiting orifice Guide ions, which also causes the precursor ions and product ions in the reaction tube to not easily exit the reaction tube through the small holes. This will reduce the intensity of the ion signal detected by the mass spectrometer, impairing the detection sensitivity. The invention adopts the quadrupole funnel structure as the ion molecule reaction tube, realizes the efficient focusing of ions, and realizes the focusing and guiding of the parent ions and product ions in the reaction tube; at the same time, the ions oscillate under the action of the radio frequency electric field, which prolongs the reaction time of the ion molecules. Time, improve the generation efficiency of product ions, and the comprehensive effect is to improve the detection sensitivity, and realize the highly sensitive detection of chemical ionization mass spectrometry similar to proton transfer reaction mass spectrometry. The invention mainly includes an ion source, a tube front electrode, a multi-piece reaction tube electrode, an ion outlet electrode and the like. The multi-piece reaction tube electrodes not only form a funnel-shaped reaction tube structure with a gradually decreasing inner diameter, but also each piece of reaction tube electrode is vertically cut into four small electrodes in the radial direction to form a quadrupole structure, and the two opposite small electrodes pass through the wire. When connected, the two adjacent small electrodes are connected by inductance, and the connection mode of the ion molecule reaction tube of this quadrupole funnel structure is different from that of the prior art.

(2) The innovation of the present invention is that each electrode of a conventional funnel-shaped reaction tube is equally divided into four small electrodes to form a quadrupole structure, two opposite small electrodes are connected by wires, and two adjacent small electrodes are connected by wires. The electrodes are connected by an inductance. Positive and negative radio frequency voltages are respectively applied to the two small electrodes connected by each group of inductors, and positive and negative radio frequency voltages are also respectively applied to the electrodes connected in sequence through the resistance. In this way, the radio frequency voltage forms a focusing electric field in the funnel-shaped reaction tube to avoid the loss of ions hitting the wall; the direct current voltage forms an ion guiding electric field, which leads the ions out of the ion exit electrode. Compared with the existing conventional direct current reaction tube and funnel-shaped reaction tube, the biggest advantage of the present invention is that more parent ions and product ions can fly out of the reaction tube and be detected by the back-end mass spectrometer, and the reaction tube can be extended at the same time. The reaction time of the ionic molecules is, therefore, more sensitive for the detection of volatile organic compounds.

Description of drawings

Fig. 1 is the schematic diagram of the ion molecule reaction tube of a kind of quadrupole funnel structure of the present invention;

FIG. 2 is a schematic diagram of the quadrupole structure of each electrode in the plurality of reaction tube electrodes 3 of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Thus, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present invention.

As shown in FIG. 1, an ion molecule reaction tube with a quadrupole funnel structure according to an embodiment of the present invention includes: an ion source 1, a tube front electrode 2, a multi-piece reaction tube electrode 3, and an ion outlet electrode 4; The source 1 is connected with the front electrode 2 of the tube; the front electrode 2 of the tube, the multi-piece reaction tube electrode 3 and the ion outlet electrode 4 are all connected in turn by resistance elements; the distance between the centers of the multi-piece reaction tube electrodes 3 is from The inner diameter of the ion inlet end is gradually reduced towards the ion outlet end, forming a funnel shape; the distance between the adjacent electrodes of the multi-piece reaction tube electrodes 3 can be between 0.5mm and 10mm, and the number of electrodes is determined according to the length of the reaction tube, generally 5 between 50 pieces; the front electrode 2 of the tube is provided with a small hole for ion entry, and the outlet electrode 4 is provided with a small hole for ion extraction; as shown in FIG. 2 , each electrode of the multi-piece reaction tube electrode 3 The shape is a polygonal shape such as a round cake or a quadrilateral, and is vertically evenly divided into four small electrodes in a fan shape in the radial direction. The first small electrode 5 is connected through a wire, the two opposite second small electrodes 6 are also connected through a wire, and the adjacent first small electrodes 5 and the second small electrodes 6 are connected through an inductance; the multi-piece reaction tube The electrodes 3 may be separated by insulating sealing gaskets to form the reaction tube cavity, or the reaction tube cavity may be formed by placing the whole into the sealed cavity.

The method of the present invention is realized as follows: by applying a DC voltage between the front electrode 2 of the tube and the ion outlet electrode 4, and dividing the voltage by the resistive elements between each electrode in the reaction tube electrode 3, a uniform electric field is formed in the reaction tube; The adjacent first small electrodes 5 and second small electrodes 6 in each electrode of the tube are applied with radio frequency voltages with opposite polarities, thereby forming an ion focusing electric field in the reaction tube; the parent ions and parent ions generated by the discharge ion source are the same as those to be measured. The product ions generated by the reaction, or the product ions directly generated by photoionization, can migrate to the direction of the ion exit electrode 4 under the guidance of a uniform electric field, focus on the axis under the action of the ion focusing electric field, and finally pass through the center of the ion exit electrode 4 Small holes are drawn out, enabling efficient focused guidance of the ions. Through the focusing and guidance of the ion molecule reaction tube of the quadrupole funnel structure, the efficient transmission of the parent ion and the product ion is realized, so as to realize the high-sensitivity detection of the mass spectrometry instrument.

The direction of the uniform electric field is related to the polarity requirements of the guided ions. If the positive ions are guided to migrate towards the outlet electrode 4, the uniform electric field direction should point from the front electrode 2 to the ion outlet electrode 4; if the negative ions are guided to the outlet electrode 4 direction migration, the uniform electric field direction should be directed from the ion exit electrode 4 to the front electrode 2 direction of the tube. That is, the method of the present invention can be used for both positive and negative ion focusing guidance.

In order to obtain the highly sensitive detection effect of chemical ionization, the air pressure in the reaction tube chamber can be set in the range of 10Pa～1000Pa; according to different vacuum system configurations, the diameter of the ion extraction hole in the center of the ion outlet electrode 4 is 0.1mm ~5mm; the effective electric field range formed by the RF electric field and the DC electric field in the source drift tube and the reaction tube should be in the range of 10V/cm~700V/cm; the front electrode 2 of the tube or the ion exit electrode 4 is provided with an injection port , the analyte can be introduced into the reaction tube.

During specific implementation, the ion source 1 can be a discharge ion source that generates parent ions, an ultraviolet lamp ionization source, or a collective ionization source that can be individually switched and controlled to select any one of them; when the ion source 1 is When the UV lamp ionization source is used, the object to be tested in the reaction tube will be directly ionized into product ions, and the product ions will focus and move forward in the ion molecule reaction tube of the quadrupole funnel structure, and finally be led out of the ion outlet electrode 4; if it is a collective ionization source, Then it can selectively ionize molecules of different properties, and more species can be detected; according to the needs of ion detection, the ion molecule reaction tube can be combined with quadrupole mass spectrometry, time-of-flight mass spectrometry, ion trap mass spectrometry, Fourier transform ion cyclotron resonance Detectors such as mass spectrometry or magnetic mass spectrometry are connected to form a highly sensitive mass spectrometry detection system.

The parts of the present invention that are not described in detail in the specification belong to the well-known technology in the art.

The above description is only a part of the specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Any person familiar with the art within the technical scope disclosed by the present invention can easily think of changes or substitutions. Included in the protection scope of the present invention.

Claims (7)

1. an ion molecule reaction tube of a quadrupole funnel structure, characterized in that: comprising an ion source (1), a front electrode (2), a multi-piece reaction tube electrode (3), an ion outlet electrode (4); the described The ion source (1) is connected to the front electrode (2) of the tube; the front electrode (2), the multi-piece reaction tube electrode (3) and the ion outlet electrode (4) are all connected in turn by resistance elements; The center hole of the multi-piece reaction tube electrode (3) gradually shrinks from the ion inlet end to the ion outlet end, forming a funnel shape; The center of the outlet electrode (4) is provided with a small hole for ion extraction; the multi-piece reaction tube electrode (3) is vertically cut into four small electrodes in a fan shape in the radial direction to form a quadrupole structure, and the two opposite A small electrode (5) is connected through a wire, two opposite second small electrodes (6) are also connected through a wire, and adjacent first small electrodes (5) and second small electrodes (6) are connected through an inductance. 2. The ion molecule reaction tube of a quadrupole funnel structure according to claim 1, characterized in that: the electrodes (3) of the multiple reaction tubes are separated by insulating sealing gaskets to form a reaction tube cavity The reaction tube cavity is formed by placing the whole into the sealed cavity; the air pressure in the reaction tube cavity is 10Pa to 1000Pa. 3 . The ion molecule reaction tube with a quadrupole funnel structure according to claim 1 , wherein the diameter of the ion extraction hole in the center of the ion outlet electrode ( 4 ) is 0.1 mm to 5 mm. 4 . 4 . The ion molecule reaction tube with a quadrupole funnel structure according to claim 1 , wherein the ion source ( 1 ) is a discharge ion source for generating parent ions. 5 . 5 . The ion molecule reaction tube with a quadrupole funnel structure according to claim 1 , wherein the ion source ( 1 ) is an ultraviolet lamp ionization source. 6 . 6 . The ion molecule reaction tube with a quadrupole funnel structure according to claim 1 , wherein the ion source ( 1 ) is a collective ion source that has a single switch control to select any ion source for use. 7 . 7. An ion focusing method for an ion molecule reaction tube of a quadrupole funnel structure, characterized in that the steps are as follows: A DC voltage is applied between the front electrode (2) of the tube and the ion outlet electrode (4), and a uniform electric field is formed in the reaction tube through the resistance partial pressure between each electrode in the reaction tube electrode (3); By applying radio frequency voltages with opposite polarities to the adjacent first small electrodes (5) and second small electrodes (6) in each piece of reaction tube electrode (3), an ion focusing electric field is formed in the reaction tube; The parent ions generated by the source and the product ions generated by the reaction between the parent ions and the test object, or the product ions directly generated by photoionization, migrate to the direction of the ion exit electrode (4) under the guidance of the uniform electric field, and move to the axis under the action of the ion focusing electric field. The center is focused and finally drawn out through the center hole of the ion exit electrode (4), so as to realize the efficient focusing and guidance of the ions.

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