CN211788914U - Soft focusing ionizer with shielding net electrode - Google Patents

Abstract

The utility model relates to a soft focusing ionizer for shielding mesh electrodes, which comprises an ionization source, an inlet electrode, a plurality of ring electrodes, a plurality of shielding mesh electrodes, an ion exit electrode and a DC power supply; The left side of the opening is closed by the conductive mesh, and the right side is open; the opening diameter of the right side of the multi-piece shielding mesh electrode gradually decreases from large to large, forming a funnel shape; the inlet electrode, the multi-piece ring electrode, The plurality of shielding mesh electrodes and the ion outlet electrodes are separated by insulating sealing gaskets to form a hollow ionizer cavity; the ion focusing method of the utility model is formed in a soft focusing ionizer of a shielding mesh electrode. The electric field is gradually guided by soft focusing, and the product ions can be efficiently focused and guided and maintain the soft ionization effect of the low electric field. It has high ion transmission efficiency and soft ionization effect, and no additional RF power supply is required. In terms of volume, power, weight, cost, etc. have more advantages.

Description

A soft-focusing ionizer with shielded mesh electrodes

technical field

The utility model belongs to the field of analysis and detection, in particular to a soft focus ionizer for shielding mesh electrodes.

Background technique

Since the standard detection method of volatile organic compounds (VOCs) is still a slow chromatography technique or olfactory sniffer, due to problems such as poor timeliness and subjectivity, environmental protection departments are in urgent need of efficient, objective, sensitive, and feasible On-site investigation of VOCs pollution source monitoring technologies and methods and even instruments. Proton transfer reaction mass spectrometry (PTR-MS) technology is especially suitable for fast and highly sensitive detection of low-concentration gases due to its fast response, low detection limit, self-quantitative measurement and soft ionization. Therefore, the inventor team developed a mobile proton transfer reaction mass spectrometry (M-PTR-MS) based on the principle of PTR-MS. The mass spectrometer has low power, small size and light weight, and can be easily It is installed on the environmental monitoring vehicle to "test while walking" to carry out rapid investigation of urban VOCs pollution sources. It has been adopted by environmental protection departments and environmental protection enterprises in many provinces and cities across the country. However, in the early stage, according to the needs of vehicle navigation, M-PTR-MS gave priority to volume and power, while the M-PTR-MS with a miniaturized and low-power design had limited sensitivity and was suitable for second-level navigation monitoring of ppbv-level VOCs. Sensitive pptv level VOCs monitoring requires more than ten seconds. Therefore, further improving the sensitivity of M-PTR-MS mass spectrometry can increase the speed of navigation, and can obtain the distribution characteristics of pptv-level low-concentration VOCs in urban areas in a shorter time.

The classic PTR-MS ionizer uses a DC voltage to obtain a uniform electric field to guide the ions. However, under the condition of uniform electric field, the ions cannot pass through the small holes of the vacuum differential due to the collision and diffusion of ions, which limits the improvement of the sensitivity of PTR-MS. In recent years, researchers have been trying to develop ion focusing techniques for PTR-MS ionizers, and have achieved certain results. Cost, etc., are not suitable for use in M-PTR-MS designed for miniaturization and low power.

Utility model content

The technology of the utility model solves the problem: aiming at the limited sensitivity of M-PTR-MS, a soft focus ionizer for shielding mesh electrodes is provided. This ionizer is composed of a shielding mesh electrode unit with a gradually decreasing inner diameter. The shielding mesh is on the left side of the central opening of the shielding mesh electrode unit, and the right side is open. Under the action of the electrostatic field of this ionizer, the ion can be softly focused and extracted to the central small hole of the ion exit electrode. The generation of fragment ions is avoided while reducing the ion loss, thereby realizing the highly sensitive detection of organic compounds by the mass spectrometer.

The technical solution of the utility model is as follows: a soft focusing ionizer for shielding mesh electrodes, comprising an ionization source, an inlet electrode, a plurality of circular electrodes, a plurality of shielding mesh electrodes, an ion exit electrode and a DC power supply; The source, inlet electrode, multi-piece ring electrode, multi-piece shielding mesh electrode, and ion outlet electrode are assembled concentrically from left to right;

The two poles of the DC power supply are respectively connected to both ends of the inlet electrode and the ion outlet electrode;

The inlet electrodes, the multi-piece ring electrodes, the multi-piece shielding mesh electrodes, and the ion outlet electrodes are sequentially connected by resistors;

The shielding mesh electrode has an opening in the center, a conductive mesh is arranged on the left side of the opening to shield the electric field before and after the isolation conductive mesh, and the right side is open; Large and gradually reduced, combined to form a funnel-shaped opening;

The center of the entrance electrode is provided with a first hole, and the center of the ion exit electrode is provided with a second hole for ion extraction. The insulating sealing gaskets are separated to form a hollow ionizer cavity, or the ionizer cavity is formed by being integrated into another sealed cavity.

Further, the two poles of the DC power supply are respectively connected to both ends of the inlet electrode and the outlet electrode, specifically:

When used for positive ions, the positive electrode of the DC power supply is connected to the inlet electrode, and the negative electrode is connected to the ion outlet electrode; or, when used for negative ions, the negative electrode of the DC power supply is connected to the inlet electrode, and the positive electrode is connected to the ion outlet electrode.

Further, the hole in the center of the shielding mesh electrode is a cylindrical hole, a cone-shaped hole, a spherical hole or a square hole.

Further, the diameter of the second ion extraction hole in the center of the ion outlet electrode is 0.1 mm˜5 mm.

Further, the diameter of the first hole in the center of the inlet electrode is 0.1 mm to 25 mm.

Further, the ionization source is a discharge ion source, a photoionization source, an electron bombardment ionization source or an electrospray ionization source.

Further, the air pressure in the ionizer chamber is 10Pa-1000Pa.

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

(1) In conventional proton transfer reaction mass spectrometry, the ions are guided by a uniform electric field in the ionizer, and the collision and diffusion of ions will cause the ions to fail to pass through the small holes of vacuum differential, which limits the improvement of the sensitivity of PTR-MS. In the prior art, the ionizer instrument is large in size, high in power and cost, and requires a complex electrode structure and an additional radio frequency power supply, which makes the implementation of the technical method more complicated and high cost. Adding radio frequency power not only increases power consumption Power, volume and weight will also increase, which is not suitable for M-PTR-MS with miniaturized, low-power design. The utility model adopts a soft-focusing ionizer with a shielded mesh electrode, which realizes high-efficiency soft-focusing of ions, improves detection sensitivity, and realizes high-sensitivity detection of chemical ionization mass spectrometry and photoionization mass spectrometry similar to proton transfer reaction mass spectrometry. The utility model mainly includes an ionization source, an inlet electrode, a multi-piece ring electrode, a multi-piece shielding mesh electrode, an ion outlet electrode and a DC power supply. There is an opening in the center of the shielding mesh electrode, the left side of the opening is closed by the conductive mesh, and the right side is open. The inlet electrode, the multi-piece annular electrode, the multi-piece shielding mesh electrode and the ion outlet electrode are connected in turn by resistors. The connection mode of the soft-focusing ionizer with the shielded mesh electrode is different from that in the prior art.

(2) The innovation of the present utility model lies in that an ion focusing component is formed by combining a new type of shielding mesh electrode unit. This new type of shielding mesh electrode has an opening in the center, the left side of the opening is closed by the conductive mesh, and the right side is open. , the opening diameter on the right side of the multi-piece shielding mesh electrode gradually decreases from large to form a funnel shape. The inlet electrode, the multi-piece annular electrode, the multi-piece shielding mesh electrode and the ion outlet electrode are connected in turn by resistors. Under the condition of conventional DC power electrostatic field, a multi-level focusing electric field is formed to achieve gradual soft focusing, avoiding the loss of ions hitting the wall, and pulling more ions out of the ion exit electrode. Compared with the existing conventional DC voltage ionizer, the utility model has higher ion transmission efficiency and the same soft ionization effect; The utility model does not require a radio frequency power supply, and has advantages in terms of volume, power, weight, and cost. The biggest advantage of the utility model is that the focusing effect is good, the soft ionization is not destroyed, the cost is low, and the volume, power and weight of the instrument are not increased. .

Description of drawings

1 is a schematic diagram of a soft-focusing ionizer of a shielded mesh electrode of the present invention;

FIG. 2 is a preliminary test comparison result of a soft-focusing ionizer with a shielded mesh electrode of the present invention.

Detailed ways

The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all 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. Accordingly, 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 , a soft focusing ionizer with a shielded mesh electrode according to an embodiment of the present invention includes an ionization source 1, an inlet electrode 2, a plurality of ring electrodes 3, a plurality of shielded mesh electrodes 4, and an ion exit electrode. 5 and the DC power supply 6; the described ionization source 1, the inlet electrode 2, the multi-piece ring electrodes 3, the multi-piece shielding mesh electrodes 4, and the ion outlet electrodes 5 are assembled concentrically from left to right; when used for positive ions, The positive electrode of the DC power supply 6 is connected with the inlet electrode 2, and the negative electrode is connected with the ion outlet electrode 5; or, when used for negative ions, the negative electrode of the DC power supply 6 is connected with the inlet electrode 2, and the positive electrode is connected with the ion outlet electrode 5; The entrance electrode 2, the multi-piece annular electrode 3, the multi-piece shielding mesh electrode 4, and the ion exit electrode 5 are connected with each other by resistors in turn; the shielding mesh electrode 4 has an opening in the center, and the left side of the opening is provided with a The conductive mesh is used to shield the electric field before and after the isolation of the conductive mesh, and the right side is open; the right opening of the shielding mesh electrode 4 is a spherical hole, and a plurality of shielding mesh electrodes 4 whose spherical apertures gradually decrease from large are combined to form a funnel shape. The center of the entrance electrode 2 is provided with a first hole, and the center of the ion exit electrode 5 is provided with a second hole for ion extraction; 4. The ion outlet electrodes 5 are separated by insulating sealing gaskets to form a hollow ionizer cavity 7, or the ionizer cavity 7 is formed by placing the whole into a sealed large cavity; the ionizer cavity 7 is formed as described above. The distance between adjacent electrodes can be between 0.5mm and 10mm, and the number of shielding mesh electrodes 4 is determined according to the length of the reaction tube and the need for focusing effect;

According to the preferred embodiment of the present invention, one to several pieces of shielding mesh electrodes 4 may be selected at the end of the ionizer 7 , or all of the shielding mesh electrodes 4 may be used instead of the ring electrodes 3 .

The soft-focusing ionization soft-focusing method of the shielding mesh electrode of the utility model comprises the following specific steps:

The DC power source 6 applies a DC voltage on the inlet electrode 2 and the ion outlet electrode 5, and the resistance divides the voltage into the multi-piece ring electrode 3 and the multi-piece shielding mesh electrode 4, forming an electrostatic field between the electrodes, wherein the multi-piece circular ring Electrode 3 forms a uniform electrostatic field, and multiple shielding mesh electrodes 4 form a focused electrostatic field; if the ionization source 1 is a discharge ion source, the parent ions enter the ionizer cavity 7 through the first hole in the center of the entrance electrode 2, and react through ion molecules. The principle is to ionize the test substance; if the ionization source 1 is a photoionization source, the photons enter the ionizer cavity 7 through the first hole in the center of the entrance electrode 2, and the test substance is ionized by the photoionization principle; The ion beam in the cavity 7 is first guided by the uniform electric field between the multiple ring electrodes 3, collides with the carrier gas, the ions diffuse, and the beam diameter becomes larger, and then is gradually focused and guided by the focusing electric field between the multiple shielding mesh electrodes 4 , the diameter of the ion beam is gradually reduced, and finally the second hole of the ion exit electrode 3 is guided out, so as to realize the efficient focusing and guidance of the ions.

The polarity of the DC power supply is related to the polarity requirements of the guided ions. If the positive ions are guided to migrate toward the ion outlet electrode 5, the positive electrode of the DC power supply should be connected to the inlet electrode 2, and the negative electrode should be connected to the ion outlet electrode 5; The negative ions migrate towards the ion outlet electrode 5 , the negative electrode of the DC power supply should be connected to the inlet electrode 2 , and the positive electrode should be connected to the ion outlet electrode 5 . That is, the method of the present invention can be used for both positive ion and negative ion focusing guidance.

In order to obtain chemical ionization or photoionization highly sensitive focusing detection effect, the hole in the center of the shielding mesh electrode 4 can be a cylindrical hole, a cone-shaped hole, a spherical hole, a square hole, etc.; the ionizer cavity 7 The inner air pressure is 10Pa～1000Pa; the diameter of the second ion extraction hole in the center of the ion outlet electrode 5 is 0.1mm～5mm; the diameter of the first hole in the center of the inlet electrode 2 is 0.1mm～25mm; the inner diameter of the ionizer 7 The formed effective electric field should be in the range of 10V/cm-700V/cm; the inlet electrode 2 or the ion outlet electrode 5 is provided with a sample inlet, which can introduce the analyte into the ionizer 7 .

The ionization source 1 can be a discharge ion source, a photoionization source, an electron bombardment ionization source, or an electrospray ionization source.

During specific implementation, the ionization source 1 can be a discharge ion source for generating parent ions, a photoionization source or an electrospray ion source, etc., or a collective ionization source that can be individually switched and controlled to select any one of them; When the ionization source 1 is a photoionization source, the object to be tested will be directly ionized into product ions in the ionizer cavity 7, and the product ions will focus and move forward under the action of the electric field in the ionizer cavity 7, and finally be led out of the ion exit electrode 5; If it is a collective ionization source, it can selectively ionize molecules of different properties, and more species can be detected; according to the needs of ion detection, the ionizer can be combined with quadrupole mass spectrometry, time-of-flight mass spectrometry, ion trap mass spectrometry, Fourier transform ion cyclotron resonance mass spectrometry or magnetic mass spectrometry and other detectors are connected to form a highly sensitive mass spectrometry detection system.

Fig. 2 shows the preliminary test comparison result of a soft-focusing ionizer of a shielded mesh electrode of the present invention, the solid line is the experimental result of the traditional annular electrode ionizer, and the dotted line is the shielded mesh electrode ionizer of the present invention. According to the preliminary test results of the chemist, the bending line indicates the increase in sensitivity. The preliminary results show that this method can increase the sensitivity by at least three to five times. Further optimization of the structure and experimental parameters may increase the sensitivity by more than ten times.

The part that is not described in detail in the description of the present utility model belongs to the well-known technology in the art.

The above 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 can easily think of changes or substitutions within the technical scope disclosed by the present invention. , should be covered within the protection scope of the present invention.

Claims (7)

1. A soft focus ionizer for shielding mesh electrodes, characterized in that: comprising an ionization source (1), an inlet electrode (2), a plurality of circular electrodes (3), a plurality of shielding mesh electrodes (4), an ion An outlet electrode (5) and a DC power supply (6); the ionization source (1), the inlet electrode (2), the multi-piece annular electrode (3), the multi-piece shielding mesh electrode (4), the ion outlet electrode (5) ) are assembled concentrically from left to right; The two poles of the DC power supply (6) are respectively connected to both ends of the inlet electrode (2) and the ion outlet electrode (5); The inlet electrode (2), the multi-piece annular electrode (3), the multi-piece shielding mesh electrode (4), and the ion outlet electrode (5) are sequentially connected by resistance; The shielding mesh electrode (4) has an opening in the center, a conductive mesh is arranged on the left side of the opening to shield the electric field before and after the isolation conductive mesh, and the right side is open; The aperture diameter of the opening on the right side is gradually reduced from large to large, and the combination forms a funnel-shaped opening; A first hole is arranged in the center of the inlet electrode (2), and a second hole for ion extraction is arranged in the center of the ion outlet electrode (5); the inlet electrode (2), the plurality of ring electrodes (3), The plurality of shielding mesh electrodes (4) and the ion outlet electrodes (5) are separated by insulating sealing gaskets to form a hollow ionizer cavity (7), or an ionizer is formed by placing the whole into another sealed cavity cavity (7). 2. The soft-focusing ionizer of a shielded mesh electrode according to claim 1, wherein the two poles of the DC power supply (6) are respectively connected to the inlet electrode (2) and the ion outlet electrode (5) Both ends, specifically: When used for positive ions, the positive electrode of the DC power supply (6) is connected to the inlet electrode (2), and the negative electrode is connected to the ion outlet electrode (5); or, when used for negative ions, the negative electrode of the DC power supply (6) is connected to The inlet electrode (2) is connected, and the positive electrode and the ion outlet electrode (5) are connected. 3. The soft-focusing ionizer for shielding mesh electrodes according to claim 1, characterized in that: the openings in the center of the shielding mesh electrodes (4) are cylindrical holes, conical-cylindrical holes, spherical holes or square hole. 4 . The soft-focusing ionizer for shielding mesh electrodes according to claim 1 , wherein the diameter of the second ion extraction hole in the center of the ion exit electrode ( 5 ) is 0.1 mm to 5 mm. 5 . 5 . The soft-focusing ionizer for shielding mesh electrodes according to claim 1 , wherein the diameter of the first hole in the center of the inlet electrode ( 2 ) is 0.1 mm to 25 mm. 6 . 6. The soft focus ionizer of a shielded mesh electrode according to claim 1, wherein the ionization source (1) is a discharge ion source, a photoionization source, an electron bombardment ionization source or an electrospray source of ion. 7 . The soft-focusing ionizer for shielding mesh electrodes according to claim 1 , wherein the air pressure in the ionizer cavity ( 7 ) is 10 Pa to 1000 Pa. 8 .

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