CN113793796A - Corona discharge type ionization source component and ion mobility spectrometer - Google Patents
Corona discharge type ionization source component and ion mobility spectrometer Download PDFInfo
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- CN113793796A CN113793796A CN202010482345.0A CN202010482345A CN113793796A CN 113793796 A CN113793796 A CN 113793796A CN 202010482345 A CN202010482345 A CN 202010482345A CN 113793796 A CN113793796 A CN 113793796A
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Abstract
The present disclosure provides an ionization source assembly and a detection apparatus of a corona discharge type. The corona discharge type ionization source assembly (100) defines an ionization region (101) and includes: a first electrode (120); a second electrode (130) positioned opposite the first electrode, the first and second electrodes being constructed and arranged to generate a corona field therebetween when a voltage is applied to ionize sample molecules into the ionization region (101) to produce product ions; a first conductive member (140) for supplying power to the first electrode; and a second conductive member (150) for supplying power to the second electrode, at least one of the first and second conductive members being provided with an exhaust channel extending to a position proximate to the first or second electrode and opening into the ionization region such that corona off-gases generated during ionization of sample molecules are at least partially expelled from the ionization region through the exhaust channel into the external environment.
Description
Technical Field
Embodiments of the present disclosure relate generally to the field of detection, and more particularly, to a corona discharge ionization source assembly and an ion mobility spectrometer including the same.
Background
The analytical instrument based on the Ion Mobility Spectrometry (IMS) has the advantages of high sensitivity, quick response and the like, and can be widely applied to the occasions of chemical warfare agents and industrial toxic and harmful gas detection, drug and explosive detection, container fumigant detection, customs smuggling inspection, animal, plant and food inspection and quarantine, gas leakage monitoring of chemical parks, fire fighting inspection and the like. Most of traditional ion migration products adopt radioactive sources to generate reactive ions, but the radioactive sources have high risk and can pose potential threats to human health. The corona discharge ionization source can replace a radioactive source to ionize target molecules to generate product ions, and has the advantages of high ion yield, no radioactivity, strong applicability and the like.
Corona discharge sources have the common disadvantages of rapid wear and short life, frequent replacement of parts, and increased difficulty in instrument design. The conventional corona discharge ionization source needs large power, needs regular cleaning and has complex cleaning process.
Disclosure of Invention
The present disclosure is directed to overcoming at least one of the above-mentioned and other problems and disadvantages of the prior art.
According to one aspect of the present disclosure, there is provided an ionization source assembly of corona discharge type defining an ionization region and comprising:
a first electrode;
a second electrode positioned opposite the first electrode, the first and second electrodes constructed and arranged to generate a corona field therebetween when a voltage is applied to ionize sample molecules into the ionization region to produce product ions;
a first conductive member for supplying power to the first electrode; and
a second electrically conductive member for supplying power to the second electrode, at least one of the first and second electrically conductive members being provided with an exhaust channel extending to a position close to the first or second electrode and opening into the ionization region, such that corona off-gases generated during ionization of sample molecules are at least partially expelled from the ionization region through the exhaust channel into the external environment.
In some embodiments, the corona discharge type ionization source assembly further comprises an insulative body defining a cavity therein, the first and second electrodes being mounted within the cavity such that the ionization region is defined within the cavity, the cavity having an opening communicating with the ionization region and open to the exterior.
In some embodiments, the insulator body has a generally cylindrical structure defining an outer profile of the ionization source assembly, the cavity being formed proximate an end of the cylindrical structure, the cylindrical structure being configured such that the end is adapted for insertion within an ion mobility tube to position the cavity and first and second electrodes mounted therein within the ion mobility tube.
In some embodiments, the first electrode comprises a needle electrode and the second electrode defines a flared opening in communication with the ionization region and an exterior of the ionization source assembly, a flared end of the opening facing outwardly of the ionization source assembly, and a flared end of the opening positioned proximate to the tip to generate a corona discharge between the flared end and the tip when a voltage is applied.
In some embodiments, the needle electrode is removably mounted within the cavity and is movable in the direction of its axis to adjust the distance between the tip and the second electrode.
In some embodiments, the second electrode includes two discharge plates arranged in a substantially "eight" shape, each of which is positioned obliquely with respect to an axial direction of the needle electrode such that one end of the discharge plate is fixed to the insulating body away from the other discharge plate and the other end is directed toward the tip of the needle electrode in proximity to the other discharge plate.
In some embodiments, the first conductive member includes a first end positioned within the cavity and a second end positioned outside of the insulative body, the exhaust passage includes a gas passage extending within the first conductive member from the second end to the first end, and the needle electrode is inserted through the first end of the first conductive member such that a tip of the needle electrode is exposed in the ionization region.
In some embodiments, the first conductive member is inserted through the insulative body to electrically connect to a first electrode located within the cavity; and/or the second conductive member is inserted through the insulative body to electrically connect to a second electrode located within the cavity.
In some embodiments, the corona discharge ionization source assembly further comprises a third electrode as a focusing electrode positioned within the chamber opposite the second electrode to cooperate with at least one of the first and second electrodes when a voltage is applied to focus product ions generated by ionizing sample molecules.
In some embodiments, the third electrode is electrically connected to the first conductive member.
According to another aspect of the present disclosure, there is also provided a detection apparatus comprising a corona discharge type ionization source assembly as described in any one of the embodiments in the present disclosure.
In some embodiments, the detection apparatus comprises an ion mobility spectrometer comprising an ion mobility tube defining an ionization region and an ion mobility region therein, wherein the corona discharge type ionization source assembly is positioned at least partially in the ionization region proximate a first end of the ion mobility tube to ionize sample molecules entering the ion mobility tube to produce product ions, a drift electrode disposed within the ion mobility region and configured to produce an electric field pull for causing the product ions to migrate through the ion mobility region toward a detector disposed within the ion mobility tube proximate an opposite second end of the ion mobility tube to receive the product ions migrating through the ion mobility region to produce an electrical signal, and a detector.
In some embodiments, the corona discharge ionization source assembly is positioned to allow corona off-gas generated during ionization of sample molecules to be expelled from the ionization region at least partially through the exhaust channel and out of the ion transfer tube.
In some embodiments, the ion transfer tube is provided with a mounting aperture through which the corona discharge type ionization source assembly is partially inserted for positioning in the ionization section.
In some embodiments, the detection apparatus further comprises a carrier gas input via which carrier gas carrying sample enters the ion transfer tube, and the corona discharge ionization source assembly is arranged to allow carrier gas carrying sample to enter the ionization region from a side of the corona discharge ionization source assembly facing away from the carrier gas input.
In some embodiments, the detection apparatus further comprises a power supply circuit for supplying a voltage to the first and second electrodes to create a voltage difference for corona discharge at the first and second electrodes.
In some embodiments, the voltage difference is in a range of 500 volts to 10000 volts.
In some embodiments, a power supply circuit includes: a voltage source; a first output terminal for outputting a first voltage from the voltage source to the first conductive member; a second output terminal for outputting a second voltage from the voltage source to the second conductive member; and a filter sub-circuit located between the voltage source and the first output terminal or the second output terminal.
In some embodiments, the power supply circuit further comprises a voltage sensing sub-circuit for sensing the voltage at the first output terminal and/or the second output terminal.
Other objects and advantages of the present disclosure will become apparent from the following detailed description of the disclosure, which proceeds with reference to the accompanying drawings, and may assist in a comprehensive understanding of the disclosure.
Drawings
The features and advantages of the present disclosure may be more clearly understood by reference to the accompanying drawings, which are illustrative and not intended to limit the disclosure in any way, and in which:
fig. 1 is a schematic diagram showing the arrangement of a detection apparatus according to an exemplary embodiment of the present disclosure;
fig. 2A is a schematic diagram illustrating an arrangement of corona discharge ionization source assemblies according to one exemplary embodiment of the present disclosure;
fig. 2B is a schematic view illustrating a structure of an insulating body of a corona discharge type ionization source assembly according to an exemplary embodiment of the present disclosure;
fig. 2C is a schematic diagram illustrating an arrangement of electrodes of a corona discharge ionization source assembly according to an exemplary embodiment of the present disclosure;
fig. 3A is a front view illustrating a corona discharge type ionization source assembly according to an exemplary embodiment of the present disclosure;
fig. 3B is a side view illustrating a corona discharge type ionization source assembly according to an exemplary embodiment of the present disclosure; and
fig. 4 is a schematic diagram showing the arrangement of a power supply circuit of a detection apparatus according to an exemplary embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present disclosure will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present disclosure, and it is obvious that the described embodiments are only a part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments disclosed herein without making any creative effort, shall fall within the protection scope of the present disclosure.
Furthermore, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are shown in schematic form in order to simplify the drawing.
Fig. 1 illustrates an arrangement of a detection apparatus according to an exemplary embodiment of the present disclosure, in which a corona discharge type ionization source assembly 100 according to an embodiment of the present disclosure is installed. Detection apparatus according to embodiments of the present disclosure may include any instrument that ionizes and analyzes a substance using an ionization source, such as an Ion Mobility Spectrometer (IMS), a mass spectrometer, a multi-capillary chromatography column and a combined ion mobility (MCC-IMS) apparatus, and the like, which may be, for example, a mobile analysis instrument. Hereinafter, an ion mobility spectrometer will be described as an example.
As shown in fig. 1, the ion mobility spectrometer includes an ion mobility tube 11, which includes, for example, a housing formed of a material (e.g., ceramic) having high melting point, high hardness, high wear resistance, oxidation resistance, and the like, and defines an ionization section I and an ion mobility region M inside the ion mobility tube. The ion mobility spectrometer also includes an ionization source assembly 100 of the corona discharge type positioned at least partially in the ionization region I proximate a first end (right end in the figure) of the ion mobility tube 11 to ionize sample molecules entering the ion mobility tube 11 to produce product ions. The product ions move in a controlled manner through the ion transfer region to a detector 16 disposed at an opposite second end (left end in the figure) of the ion transfer tube 11, the detector 16 receiving the product ions to generate an electrical signal that can be indicative of a property of the sample, such as mobility, species, concentration, etc. As an example, the detector may comprise a faraday disk. An external data acquisition and processing device (not shown) is electrically connected to the detector to receive the electrical signals that can be used by the ion mobility spectrometer to perform analysis and detection of the sample.
To effect the migration of the product ions, the ion mobility spectrometer also includes a drift electrode 15 disposed in the ion mobility region M that generates an electric field to provide a pulling force for urging the product ions to migrate through the ion mobility region M towards the detector. Illustratively, the drift electrode 16 may comprise coaxial rings arranged at equal intervals. Furthermore, the ion mobility spectrometer may further comprise an ion gate 13 disposed between the ionization region I and the ion mobility region M, the voltage applied across the ion gate forming a periodically varying forward or reverse electric field that forms an "on" or "off" state of the ion gate such that the ion gate forms an ion trap, thereby enabling or disabling the passage of product ions in the ionization region I into the ion mobility region M through the ion gate in a controlled manner, e.g. pulsed manner.
As shown in fig. 1, the ion mobility spectrometer may further include a carrier gas input 1102, a mobility gas input 1103, and an exhaust 1104, which may illustratively include a conduit or port form. A carrier gas input 1102 may direct a sample-carrying carrier gas into the ion mobility tube 11 at a first end of the ion mobility tube 11, the carrier gas flowing into the ionization source assembly 100 such that the sample carried therein enters an ionization region of the ionization source assembly 100. In some examples, the sample carrier gas, after entering ion mobility tube 11 in the first direction (from right to left in fig. 1), flows around ionization source assembly 100 (as indicated by the curved arrows on both sides of ionization source assembly 100 in fig. 1) to the side of ionization source assembly 100 facing away from carrier gas input device 1102, from which it enters ionization source assembly 100 via an opening (as will be described below), i.e., the sample carrier gas does not enter ionization source assembly 100 directly in the first direction from the front of ionization source assembly 100, such that direct impact of the sample carrier gas on product ions already formed in ionization source assembly 100 or instability of the ion generation process can be avoided. A migration gas input 1103 may introduce a migration gas into the ion transfer tube 11 at a second end of the ion transfer tube 11, the migration gas flowing within the ion transfer tube 11 in a second direction (left to right in fig. 1) generally opposite the first direction to purge species or exhaust gas within the ion transfer tube other than product ions away from the detector, the purged species or exhaust gas being discharged from the exhaust 1104 under the influence of the migration gas flow.
In an embodiment of the present disclosure, corona gas (which includes various substances such as nitride, oxide, etc. generated during ionization) generated by the ionization source assembly 100 while ionizing sample molecules may be discharged to the outside through an exhaust channel provided in the ionization source assembly itself, as shown in fig. 1, which will be described in detail below. Therefore, the self-cleaning effect of the ionization source component can be realized, the accumulation of substances contained in the corona gas on the discharge electrode is reduced or eliminated, the service life and the ionization performance of the electrode are improved, the problem that the corona voltage needs to be increased due to the accumulation of the substances on the electrode can be further avoided, and the design of the low-voltage ionization source can be realized. Illustratively, in embodiments of the present disclosure, the voltage difference for corona discharge between the first electrode and the second electrode may be in the range of 500 volts to 10000 volts, with a low voltage difference significantly lower than the corona onset voltage of conventional ionization sources.
Fig. 2A to 3B schematically illustrate the structure of a corona discharge type ionization source assembly 100 according to an exemplary embodiment of the present disclosure. As shown, ionization source assembly 100 includes first and second electrodes 120, 130 positioned in opposition and defining an ionization region 101 within the interior of ionization source assembly 100, e.g., at least between first and second electrodes 120, 130, between which first and second electrodes 120, 130 can generate an electric field (also referred to as a corona field) for corona discharge when a suitable voltage is applied or a suitable voltage difference exists therebetween for ionizing sample molecules entering ionization region 101 to produce product ions. The ionization region 101 opens into, for example, the interior of the ion transfer tube so that the product ions produced can enter the interior of the ion transfer tube. Furthermore, ionization source assembly 100 further comprises a first conductive member 140 and a second conductive member 150, first conductive member 140 being electrically connected to first electrode 120 to receive a first voltage from a power supply circuit, e.g., through power supply terminal 104, and supply it to first electrode 120; the second conductive member 150 is electrically connected to the second electrode 130 to supply a second voltage from the power circuit to the second electrode 130, thereby generating an electric field for ionizing sample molecules between the two electrodes.
Illustratively, the corona ionization source assembly can meet the performance requirements of both positive and negative ionization sources: when the positive mode is used, a positive voltage is applied to the first electrode and the second electrode, and the voltage of the second electrode is higher than that of the first electrode; when the negative mode is used, negative voltage is applied to both the first electrode and the second electrode, and the voltage of the first electrode is higher than that of the second electrode.
Corona gases are generated during the ionization of sample molecules and contain various substances such as nitrides, oxides, etc. which if not discharged in time, deposit or accumulate on the electrodes, which if not cleaned in time, reduce the useful life of the electrodes and require increased voltages to be applied to the electrodes for corona initiation. In an embodiment of the present disclosure, no separate exhaust means need to be additionally provided, but rather an exhaust channel is provided in the electrically conductive member supplying the electrodes, which exhaust channel extends to a position close to the electrodes and opens into the ionization region, so that corona exhaust gases generated during ionization of the sample molecules are at least partially discharged from the ionization region through the exhaust channel into the external environment. Since such an exhaust passage is provided in the conductive member adjacent to and connected to the electrode, corona gas generated by the discharge ionization of the electrode is easily and stably discharged through the exhaust passage, and substances such as nitride or oxide generated by the ionization are not or rarely concentrated in the ionization region and adhere to the electrode.
In an exemplary embodiment, the ionization source assembly may be configured as a separate component for removable or replaceable mounting to the detection apparatus, such as at least partially in the ion mobility tube. As an example, as shown in fig. 2A-2B and 3A-3B, the ionization source assembly 100 further includes an insulating body 110, the insulating body 110 defining a cavity 111 therein, and a first electrode 120 and a second electrode 130 mounted within the cavity 111 to form one integral component. Accordingly, ionization region 101 is defined within chamber 111, chamber 111 having an opening 1111 in communication with ionization region 101 and opening to an exterior of the ionization source assembly (e.g., to the interior of the ion mobility tube), such that a sample carrier gas entering the ion mobility tube and carrying a sample can enter ionization region 101 of ionization source assembly 100 through opening 1111, while product ions generated by ionizing the sample within ionization source assembly 100 can exit the ionization source assembly through opening 1111 under the influence of an electric field, e.g., enter the interior space of the ion mobility tube, e.g., be captured by an ion gate or moved through the ion mobility region to a bottom detector. As an example, the insulating body may be made of engineering plastic (e.g., PEEK) having excellent properties of high temperature resistance, self-lubrication, easy processing, high mechanical strength, low outgassing rate in a high temperature state, and the like.
In the illustrated embodiment, insulating body 110 has, overall, a substantially cylindrical structure defining the outer contour of ionization source assembly 100, chamber 111 being formed near one end of the cylindrical structure; accordingly, the ionization source assembly 100 is also generally cylindrical in structure as a whole. Such a columnar structure is adapted to be at least partially inserted into ion transfer tube 11, for example, with mounting hole 1101 provided at the tube wall near the first end of ion transfer tube 11, and columnar ionization source assembly 100 is inserted through mounting hole 1101 to be positioned at least partially within ion transfer tube 11, thereby positioning chamber 111 and first and second electrodes 120 and 130 mounted in chamber 111 within ion transfer tube 11, in ionization section I.
As shown, the other end of the insulator body 110 is provided with a flange or laterally extending mounting plate 112 adapted to abut or be mounted on the outer wall surface of the ion transfer tube 11. In addition, as shown in fig. 2A-2B and 3A-3B, a sealing ring 106 may be fitted over the insulator body 110 adjacent to the flange or laterally extending mounting plate 112 to provide a seal between the insulator body 110 and the wall of the ion transfer tube 11 at the mounting hole 1101.
According to an embodiment of the present disclosure, since the ionization source assembly is formed as a separate kit, it may be detachably or replaceably mounted to the detection apparatus, such as at least partially in the ion transfer tube, so that portability, ease of assembly and maintenance of the detection apparatus may be achieved. The ionization source assembly designed by the present disclosure can be realized by a very small size, for example, the outline size can be as small as 66.5mm × 30mm × 14.8mm, and the ionization source assembly can be directly placed in a transfer tube for working, and has the advantages of simple installation, convenient operation, strong stability and strong practicability.
In the illustrated embodiment, the first electrode 120 is a needle electrode, which may also be referred to as a corona needle; the tip 121 of the needle electrode is positioned, for example, to point toward a central region between the ends of the second electrode 130. As the needle electrode, a tungsten needle, a tungsten alloy needle, an iridium alloy needle, or other inert metal and alloy needles thereof can be used. The surface of the needle may be gold plated to improve the surface finish of the needle, reduce its adhesion, not easily enrich the sample oxide layer, and increase its lifetime.
The needle-shaped first electrode 120 may be detachably installed in the cavity 111 and may be movable in the axial direction thereof to adjust the distance between the tip 121 and the second electrode 130, so that the corona voltage may be adjusted as desired. For example, as shown in fig. 2A and 3B, the first electrode 120 is mounted in the cavity 111 by the mount 170, the mount 170 may be screwed to the insulating body 110 on the side opposite to the opening 1111 of the cavity 111, the first electrode 120 may be translated in the axial direction thereof by screwing or rotating the mount 170, which may adjust the distance between the tip 121 and the second electrode 130 to a suitable range for corona generation, and the first electrode may be conveniently mounted, detached, or replaced. By way of example, the length of the needle electrode may range from 5mm to 7mm, and the radius of curvature of the tip 121 may range from 5um to 300 umm.
As shown in fig. 1, 2A, 3A, and 3B, the second electrode 130 is positioned such that the first electrode 120 is closer to the ion transfer region, and is installed in the chamber 111 near the opening 1111. For example, a pressure plate 103 may be provided, the pressure plate 103 being mounted to the insulating body 110 at the opening 1111 by the fastener 105, the pressure plate 103 pressing against the second electrode 130 to secure the second electrode 130 in the cavity 111. The pressure plate may be made of the same material as the insulating body. Illustratively, the second electrode may be made of gold-plated stainless steel, which enhances electrical conductivity, optimizes electric field distribution, and simultaneously increases surface finish, reduces adhesion, and improves wear resistance.
In an exemplary embodiment of the present disclosure, second electrode 130 defines a flared opening in communication with ionization region 101 and the exterior of the ionization source assembly, the flared end of the opening facing out of the ionization source assembly, such as toward the ion transfer region of the ion transfer tube, the flared end of the opening being positioned proximate tip 121 of first electrode 120, e.g., the flared end of the flared opening is formed around tip 121 to create a corona discharge between the flared end and tip 121 when a voltage is applied. For example, the second electrode 130 is in a symmetrical structure with respect to the axis of the first electrode 120.
In some examples, the second electrode 130 may include two discharge plates arranged in a substantially "eight" shape, each of which is positioned obliquely with respect to the axial direction of the needle electrode 120 such that one end of the discharge plate is fixed to the insulating body 110 away from the other discharge plate and the other end is directed toward the tip 121 of the needle electrode in close proximity to the other discharge plate. The structure of the second electrode is not limited thereto, and in other examples, may take the form of a plate electrode having a central hole, or may take the form of a horn-shaped or tapered electrode.
The first conductive member 140 is inserted through the insulating body 111 to be electrically connected to the first electrode 120 located within the cavity 111; and/or, the second conductive member 150 is inserted through the insulating body 110 to be electrically connected to the second electrode 130 located within the cavity 111. For example, as shown in fig. 2A and 2B, the insulating body 110 is provided therein with a through hole 114 and/or a through hole 115, and the through hole 114 and/or the through hole 115 may extend longitudinally along the insulating body; the first conductive member 140 is inserted and mounted in the through hole 114, and the second conductive member 150 is inserted and mounted in the through hole 115.
In the illustrated embodiment, the first conductive member 140 includes a first end 141 positioned within the cavity 111 and a second end 142 positioned outside the insulative body 110, and the exhaust passage includes a gas passage 143 extending within the first conductive member 140 from the second end 142 to the first end 141, which leads to the ionization region 101. In other embodiments, an exhaust passage may also be provided in the second conductive member. For example, the first and/or second conductive members may illustratively take the form of hollow conductive rods; the first conductive member and/or the second conductive member may be made of a material having good conductive properties, such as stainless steel.
The first electrode 120 is connected or mounted to the first end 141 of the first conductive member 140 to enable electrical and/or mechanical connection of the first electrode 120 to the first conductive member 140. For example, a needle-shaped first electrode 120 is inserted through the first end portion 141 such that its tip 121 is exposed in the ionization region 101. The second electrode 130 may be electrically and/or mechanically connected to an end of the second conductive member 150 located within the cavity 111.
In an exemplary embodiment, as shown in fig. 2A and 2C, the ionization source assembly 100 can further include a third electrode 160 as a focusing electrode that can be positioned within the chamber 111 opposite the second electrode 130 to cooperate with the first electrode 120 and/or the second electrode 130 to focus product ions generated by ionizing sample molecules when a voltage is applied, which can optimize the electric field distribution within the ionization source and increase the passage rate of the product ions. For example, the third electrode may be electrically connected with the first conductive member, i.e. the third electrode may be at the same potential as the first electrode. The third electrode may be made of a material having good conductive properties, such as stainless steel.
In the illustrated embodiment, the third electrode 160 may take the form of a pedestal disposed within the cavity 111 having a recess facing the second electrode 120, e.g., with a protruding edge that substantially circumferentially surrounds a free end (such as the aforementioned flared end) of the second electrode. The needle-shaped first electrode 120 may be positioned in the base such that its tip 121 is located substantially in the space defined by the free end of the second electrode 130 (e.g., the aforementioned flared end) and the recess of the third electrode 160. By the positioning of the base, the first electrode can be firmly held within the cavity 111. Illustratively, the first end portion 141 of the first conductive member 140 may be inserted or seated in the third electrode 160 as a base. To this end, a gas channel 163 leading to the ionization region 101, which communicates with the gas channel 143 in the first conductive member 140, may also be provided in the base.
Fig. 4 shows an arrangement of a power supply circuit of a detection device for providing a voltage difference for corona discharge between a first electrode and a second electrode of a power supply assembly according to an exemplary embodiment of the present disclosure. As shown, the power circuit includes a voltage source 01 that outputs a first voltage to the first electrode 120 via a first output terminal VSG1 (and via a first conductive member) and a second voltage to the second electrode 130 via a second output terminal VSG2 (and via a second conductive member). The voltage source 01 may comprise a direct voltage source DC and an adjustable voltage source S connected to the direct voltage source DC via an LC circuit, which adjustable voltage source S may provide a pulsed or continuous source voltage. A filter sub-circuit 02, which can effectively remove the generation of the spike and other sudden change signals, may be disposed between the voltage source 01 and the first output terminal VSG1 or the second output terminal VSG 2. The filter sub-circuit may include an RC filter circuit and an RL filter circuit, as desired. The power supply circuit may further comprise a voltage sensing sub-circuit 03 for sensing the voltage at the first output terminal VSG1 and/or the second output terminal VSG2, for example the voltage at the first output terminal VSG1 and/or the second output terminal VSG2 may be telemetered in a resistive voltage division manner, so that the stability of the voltage supplied to the electrodes of the power supply assembly can be monitored in real time.
Although embodiments of the present disclosure have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.
Claims (19)
1. An ionization source assembly (100) of the corona discharge type defining an ionization region (101) and comprising:
a first electrode (120);
a second electrode (130) positioned opposite the first electrode, the first and second electrodes being constructed and arranged to generate a corona field therebetween when a voltage is applied to ionize sample molecules into the ionization region (101) to produce product ions;
a first conductive member (140) for supplying power to the first electrode; and
a second conductive member (150) for supplying power to the second electrode, at least one of the first and second conductive members being provided with an exhaust channel extending to a position proximate to the first or second electrode and opening into the ionization region such that corona off-gases generated during ionization of sample molecules are at least partially expelled from the ionization region through the exhaust channel into the external environment.
2. The assembly of claim 1, further comprising an insulative body (110) defining a cavity (111) therein, said first and second electrodes being mounted within said cavity such that said ionization region is defined within said cavity, said cavity having an opening (1111) communicating with said ionization region and opening to the exterior.
3. The assembly of claim 2, wherein said insulative body has a generally cylindrical structure defining an outer profile of said assembly, said cavity being formed proximate one end of the cylindrical structure,
the columnar structure is configured such that the end is adapted to be inserted into an ion transfer tube (11) to position the cavity and first and second electrodes mounted in the cavity in the ion transfer tube.
4. The corona discharge type ionization source assembly of claim 2, wherein
The first electrode comprises a needle-like electrode,
the second electrode defines a flared opening communicating with the ionization region and an exterior of the ionization source assembly, the flared end of the opening facing outwardly of the ionization source assembly, the flared end of the opening being positioned proximate the tip to generate a corona discharge between the flared end and the tip when a voltage is applied.
5. The assembly of claim 4, wherein said needle electrode is removably mounted within said chamber and movable in the direction of its axis to adjust the distance between said tip and said second electrode.
6. The corona discharge type ionization source assembly of claim 4, wherein the second electrode includes two discharge plates arranged in a generally "eight" shape, each discharge plate being positioned obliquely with respect to an axial direction of the needle electrode such that one end of the discharge plate is fixed to the insulating body away from the other discharge plate and the other end is directed toward a tip of the needle electrode in proximity to the other discharge plate.
7. The corona discharge type ionization source assembly of claim 4, wherein
The first conductive member including a first end (141) positioned within the cavity and a second end (142) positioned outside of the insulative body, the vent passage including a gas passage extending within the first conductive member from the second end to the first end,
the needle electrode is inserted through the first end of the first conductive member such that a tip of the needle electrode is exposed in the ionization region.
8. The corona discharge type ionization source assembly of any one of claims 2-7,
the first conductive member is inserted through the insulative body to electrically connect to a first electrode located within the cavity; and/or
The second conductive member is inserted through the insulative body to electrically connect to a second electrode located within the cavity.
9. The corona discharge type ionization source assembly of any one of claims 2-7, further comprising a third electrode (160) as a focusing electrode positioned within the chamber opposite the second electrode to cooperate with at least one of the first and second electrodes when a voltage is applied to focus product ions generated by ionizing sample molecules.
10. The corona discharge type ionization source assembly of claim 9, wherein the third electrode is in electrical connection with the first conductive member.
11. A detection apparatus comprising the corona discharge ionization source assembly of any one of claims 1-10.
12. A detection apparatus according to claim 11, comprising an ion mobility spectrometer comprising an ion mobility tube (11) within which the ionization region (I) and the ion mobility region (M) are defined, a drift electrode (15) and a detector (16), wherein
The corona discharge type ionization source assembly being positioned at least partially in the ionization section proximate the first end of the ion mobility tube to ionize sample molecules entering the ion mobility tube to produce product ions,
the drift electrode disposed within the ion transfer region and configured to generate an electric field pull for causing the product ions to migrate through the ion transfer region towards a detector,
the detector is disposed within the ion transfer tube proximate an opposite second end of the ion transfer tube to receive product ions that migrate through the ion transfer region to generate an electrical signal.
13. The detection apparatus of claim 12, wherein the corona discharge ionization source assembly is positioned to allow corona exhaust gas generated during ionization of sample molecules to be expelled from the ionization region at least partially through the exhaust channel and out of the ion transfer tube.
14. The detection apparatus of claim 12, wherein the ion transfer tube is provided with a mounting aperture (1101) through which the corona discharge type ionization source assembly is partially inserted for positioning in the ionization section.
15. The detection apparatus according to any one of claims 12-14, further comprising a carrier gas input (1102) via which a carrier gas carrying the sample enters the ion transfer tube, and
the corona discharge ionization source assembly is arranged to allow carrier gas carrying sample to enter the ionization region (101) from a side of the corona discharge ionization source assembly facing away from the carrier gas input.
16. The detection apparatus according to any one of claims 11-14, further comprising a power supply circuit for supplying a voltage to the first and second electrodes to create a voltage difference for corona discharge at the first and second electrodes.
17. The detection device of claim 16, wherein the voltage difference is in a range of 500 volts to 10000 volts.
18. The detection apparatus of claim 16, wherein the power circuit comprises:
a voltage source (01);
a first output terminal (VSG1) for outputting a first voltage from a voltage source to a first conductive member;
a second output terminal (VSG2) for outputting a second voltage from the voltage source to the second conductive member; and
a filter sub-circuit (02) between the voltage source and the first output terminal or the second output terminal.
19. The detection device according to claim 18, wherein the power supply circuit further comprises a voltage sensing subcircuit (03) for sensing the voltage at the first output terminal and/or the second output terminal.
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