CN111105984A - Nested Faraday cylinder-based high-field asymmetric waveform ion mobility spectrometer - Google Patents
Nested Faraday cylinder-based high-field asymmetric waveform ion mobility spectrometer Download PDFInfo
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- CN111105984A CN111105984A CN201911356855.7A CN201911356855A CN111105984A CN 111105984 A CN111105984 A CN 111105984A CN 201911356855 A CN201911356855 A CN 201911356855A CN 111105984 A CN111105984 A CN 111105984A
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- 238000001514 detection method Methods 0.000 claims abstract description 30
- 238000013508 migration Methods 0.000 claims abstract description 8
- 230000005012 migration Effects 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 3
- 239000004020 conductor Substances 0.000 abstract 1
- 150000002500 ions Chemical class 0.000 description 41
- 230000037230 mobility Effects 0.000 description 32
- 230000005684 electric field Effects 0.000 description 19
- 239000007789 gas Substances 0.000 description 9
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 5
- 238000001228 spectrum Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 238000000926 separation method Methods 0.000 description 4
- 239000012159 carrier gas Substances 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 230000002093 peripheral effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000000766 differential mobility spectroscopy Methods 0.000 description 1
- 238000001871 ion mobility spectroscopy Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/26—Mass spectrometers or separator tubes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/022—Circuit arrangements, e.g. for generating deviation currents or voltages ; Components associated with high voltage supply
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J49/00—Particle spectrometers or separator tubes
- H01J49/02—Details
- H01J49/06—Electron- or ion-optical arrangements
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Abstract
A nested Faraday-cylinder-based high-field asymmetric waveform ion mobility spectrometer comprises an ion source, a migration region and a detection region; wherein the detection zone consists of two parts: one part is a sensitive electrode which is used as a sensitive element and is directly connected with a weak current detection circuit, the other part is a deflection electrode, a direct current source is used for providing voltage, and the two parts are both made of conductive materials. The length of the sensitive electrode is less than or equal to that of the deflection electrode, the periphery of the deflection electrode is closed and nested outside the sensitive electrode, and a gap for air flow to pass through is reserved between the deflection electrode and the sensitive electrode. The high-field asymmetric waveform ion mobility spectrometer provided by the invention can greatly reduce the interference of the outside and the voltage applied on the deflection electrode on the sensitive electrode, obviously improve the signal-to-noise ratio of the instrument, has good shielding effect, and is simple in structure and easy to integrate.
Description
Technical Field
The invention relates to a high-field asymmetric waveform ion mobility spectrometer, in particular to a high-field asymmetric waveform ion mobility spectrometer with a Faraday cylinder as a detection part, and belongs to the technical field of biochemical substance online detection technology and equipment.
Background
The high-field asymmetric waveform ion mobility spectrometer is a biochemical substance on-line detection technology developed gradually in the nineties of the twentieth century, and the basic principle is that the ion mobility is irrelevant to the electric field strength under the condition of a low electric field, and when the electric field strength is more than 10000V/cm, the ion mobility changes nonlinearly along with the electric field strength. The relationship between the mobility of ions at high field and the electric field strength can be expressed as follows:
K＝K0[1+α1(E/N)2+α2(E/N)4+…]，
wherein K is the mobility of the ions in a high electric field, K0For the mobility of ions at low electric field, E is the electric field strength, N is the gas molecular density, α1、α2Is the ion mobility decomposition coefficient. Order:
α(E)＝[α1(E/N)2+α2(E/N)4+…]the relationship between the mobility of the ions under the high field and the electric field strength can be changed to K ═ K0[1+α(E)]According to the different rule of ion mobility changing with the electric field intensity, it can be divided into three types of ions A, B and C, when α (E/N) > 0, K > K0Ions belonging to type A, K increases with increasing electric field intensity E, and K < K when α (E/N) < 00Ions belonging to type C, K decreasing with increasing E, ions belonging to type B, K ≈ K, when α (E/N) ≈ 00. Namely 10000V cm at the electric field intensity-1In the above, the mobilities of the ions exhibit different nonlinear variation trends, which enables ions having the same or similar ion mobilities under low electric field strength to be separated under high electric field strength. Here, the electric field satisfying the ion separation condition is a separation electric field, and a voltage applied to the electrode to form such an electric field is called a separation voltage and is usually supplied by using an asymmetric high-voltage high-frequency radio frequency power supply (RF power supply). While applying a Compensation Voltage (CV) to the electrodes to compensate for the ion deflection caused by the separation voltage to cause a certain amount of ion deflectionA particular ion passes through the mobility zone to the detection zone.
In recent years, with the development of high-field asymmetric waveform ion mobility spectrometers, the detection part of the ion mobility spectrometer mainly adopts two parallel opposite polar plates to form a detector, one side of the detector is used as a sensitive electrode of a faraday cage, and the other side of the detector is used for applying a deflection voltage, as shown in fig. 1. However, the faraday cage in the form of parallel plates is difficult to electromagnetically shield the sensitive electrode, the applied deflection voltage also affects the sensitive electrode, and the dispersed electric field between the two parallel plates can cause charged particles to be lost before entering the detection part. Therefore, a large amount of noise signals are superposed into a spectrum of the high-field asymmetric waveform ion mobility spectrometer, and simultaneously, a baseline of the spectrum is also lifted along with the increase of the deflection voltage.
Disclosure of Invention
The invention aims to provide a high-field asymmetric waveform ion mobility spectrometer based on a nested Faraday cylinder, aiming at overcoming the defects and shortcomings of the prior art and solving the problems that the shielding of a sensitive electrode is difficult and the interference of a deflection electrode on the sensitive electrode is difficult in the high-field asymmetric waveform ion mobility spectrometer based on a flat-plate detector.
In order to solve the problems, the technical scheme of the invention is as follows:
a nested Faraday-cylinder-based high-field asymmetric waveform ion mobility spectrometer comprises an ion source, a migration area and a detection area; the detection area comprises a Faraday cylinder, a direct current source and a weak current detection circuit; the method is characterized in that: the Faraday cylinder adopts a nested structure and comprises a sensitive electrode and a deflection electrode nested at the periphery of the sensitive electrode, the periphery of the deflection electrode is closed, and a gap for air flow to pass through is reserved between the deflection electrode and the sensitive electrode; the direct current power supply is electrically connected with the deflection electrode, and the sensitive electrode is directly connected with the weak current detection circuit.
Among the above-mentioned technical scheme, its characterized in that: the gap between the deflecting electrode and the sensitive electrode is larger than zero and less than or equal to 5 cm.
The invention is also characterized in that: the length of the sensitive electrode along the flowing direction of the sample gas is less than or equal to the length of the deflecting electrode in the flowing direction. Preferably, the length of the sensitive electrode along the flowing direction of the sample gas is more than zero and less than or equal to 10 cm.
Preferably, the nested structure of the Faraday cage is a cuboid sleeve, a cylinder sleeve or a sphere sleeve.
Compared with the prior art, the Faraday rotator has the advantages that ① the Faraday rotator is nested outside the sensitive electrode and the periphery of the Faraday rotator is closed, the peripheral deflecting electrode plays a role in applying a deflecting voltage and also plays a role in electromagnetically shielding the sensitive electrode, so that the interference of the outside and the deflecting voltage on the sensitive electrode is reduced, the signal-to-noise ratio of an output signal of an instrument is greatly improved, ② the length of the Faraday rotator in the invention is less than or equal to that of the peripheral deflecting electrode, the sensitive electrode can be effectively protected, meanwhile, the influence of a dispersed electric field on the periphery of a Faraday rotator on charged particles is avoided, and ion loss is reduced.
Drawings
Fig. 1 is a schematic structural diagram of a high-field asymmetric waveform ion mobility spectrometer in the prior art.
Fig. 2 is a schematic diagram of the structural principle of the nested faraday cage of the present invention.
Fig. 3 is a schematic structural diagram of an embodiment of the present invention.
Fig. 4(a) and 4(b) are graphs comparing experimental results of the application of the conventional flat-type detection region and the nested faraday cage detection region provided by the present invention in a high-field asymmetric waveform ion mobility spectrometer, respectively.
In the figure: 1-sample gas; 2-a source of ions; 3-a migration zone; 4-upper electrode 1 in the migration zone; 5-a migration zone lower electrode 2; 6-radio frequency power supply; 7-a superimposing circuit; 8-compensation voltage; 9-ground electrode; 10-a detection zone; 11-a deflection pole; 12-a sensitive electrode; 13-weak current detection circuit; 14-a direct current source; 15-flat plate type Faraday cage.
Detailed Description
The present invention is further described below in conjunction with the drawings and examples so that those skilled in the art can fully understand and implement the present invention.
Fig. 3 is a schematic structural diagram of a nested faraday cup-based high-field asymmetric waveform ion mobility spectrometer, which includes an ion source 2, a mobility region 3, and a detection region, where the detection region includes a sensitive electrode 12, a deflection electrode 11, a direct current source 14, and a weak current detection circuit 13; a voltage is applied to the deflection electrode 11 using a dc power supply. The sensitive electrode 12 is directly connected with the weak current detection circuit 13; the periphery of the deflection electrode is sealed and nested at the periphery of the sensitive electrode, and the deflection electrode can not only provide electromagnetic shielding protection for the sensitive electrode, but also provide deflection voltage; a gap for air flow to pass through is reserved between the deflecting electrode and the sensitive electrode; the gap is typically greater than zero and less than or equal to 5 cm.
Fig. 2 is a schematic structural diagram of an embodiment of the faraday cage according to the present invention, wherein the length of the sensitive electrode along the sample gas flowing direction is smaller than or equal to the length of the deflecting electrode along the sample gas flowing direction, and the length of the sensitive electrode along the sample gas flowing direction is greater than zero and less than or equal to 10cm in a general case. The nested structure of the Faraday cylinder can be a cuboid sleeve type, a cylinder sleeve type or a sphere sleeve type. The sensitive electrode 12 is directly connected to the weak current detection circuit, and the voltage on the deflection electrode is provided by a direct current power supply.
The invention effectively solves the problem of difficult shielding of the sensitive electrode in the flat plate type detection part, and simultaneously solves the influence of the deflection voltage on the deflection electrode on the baseline of the high-field asymmetric waveform ion mobility spectrogram.
Example 1:
experiments were performed in a high-field asymmetric waveform ion mobility spectrometer using the existing flat panel detection zone application, as shown in fig. 1. The distance between the two polar plates in the migration area is 1.5 mm. The experiment was carried out with ethyl acetate as a gas sample for the experiment, a concentration of 109ppm, 99.999% nitrogen as a carrier gas, and a 10.6eV ultraviolet lamp as an ionization source, with no RF voltage applied and only a Compensation Voltage (CV) applied, and the ion mobility spectrum was as shown in fig. 4(a) when the deflection voltages were 1.5V, 9V, and 18V, respectively.
The nested Faraday cup provided by the invention is applied to a high-field asymmetric waveform ion mobility spectrometer for experiments, and is shown in figure 3. The distance between the two polar plates in the migration area is 1.5 mm. The experiment was carried out with ethyl acetate as a gas sample for the experiment, a concentration of 109ppm, 99.999% nitrogen as a carrier gas, and a 10.6eV ultraviolet lamp as an ionization source, with no RF voltage applied and only a Compensation Voltage (CV) applied, and the ion mobility spectrum was as shown in fig. 4(b) when the deflection voltages were 1.5V, 9V, and 18V, respectively.
Through comparison, the noise of the high-field asymmetric waveform ion mobility spectrometry applying the flat-plate Faraday cup is about 2pA, and meanwhile, the spectrogram baseline can be improved along with the increase of the deflection voltage; the noise of the high-field asymmetric waveform ion mobility spectrum of the Faraday cup is about 0.2pA, and the spectrogram base line cannot be improved along with the increase of the deflection voltage. The invention can effectively improve the signal-to-noise ratio of the ion mobility spectrometry, shield the interference of the outside on the sensitive electrode and the interference of the deflection voltage applied on the deflection electrode on the sensitive electrode, simultaneously, the shield electrode and the deflection electrode of the detection area have a structure, simplify the detection area in the high-field asymmetric waveform ion mobility spectrometer and is easy to process and integrate.
Claims (5)
1. A nested Faraday-cylinder-based high-field asymmetric waveform ion mobility spectrometer comprises an ion source (2), a migration region (3) and a detection region (10); the detection area comprises a Faraday cylinder, a direct current source (14) and a weak current detection circuit (13); the method is characterized in that: the Faraday cage adopts a nested structure and comprises a sensitive electrode (12) and a deflecting electrode (11) nested at the periphery of the sensitive electrode, wherein the deflecting electrode is closed at the periphery, and a gap for air flow to pass through is reserved between the deflecting electrode and the sensitive electrode; the direct current power supply (14) is electrically connected with the deflection electrode (11), and the sensitive electrode (12) is directly connected with the weak current detection circuit (13).
2. The nested faraday cup-based high-field asymmetric waveform ion mobility spectrometer of claim 1, wherein: the gap between the deflecting electrode (11) and the sensitive electrode (12) is larger than zero and less than or equal to 5 cm.
3. A nested faraday cup based high field asymmetric waveform ion mobility spectrometer according to claim 1 or 2, wherein: the length of the sensitive electrode (12) along the flowing direction of the sample gas is less than or equal to the length of the deflecting electrode (11) in the flowing direction.
4. The nested faraday cup-based high-field asymmetric waveform ion mobility spectrometer of claim 3, wherein: the length of the sensitive electrode (12) along the flowing direction of the sample gas is more than zero and less than or equal to 10 cm.
5. The nested faraday cup-based high-field asymmetric waveform ion mobility spectrometer of claim 1, wherein: the nested structure of the Faraday cylinder is a cuboid sleeve type, a cylinder sleeve type or a sphere sleeve type.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111933511A (en) * | 2020-07-30 | 2020-11-13 | 清华大学 | High-field asymmetric waveform ion mobility spectrometer |
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| JPH0251836A (en) * | 1988-08-12 | 1990-02-21 | Nec Kyushu Ltd | Ion implanter |
| US5124658A (en) * | 1988-06-13 | 1992-06-23 | Adler Richard J | Nested high voltage generator/particle accelerator |
| CN101599407A (en) * | 2009-03-20 | 2009-12-09 | 清华大学 | A kind of array type microfaraday cage |
| CN103871820A (en) * | 2012-12-10 | 2014-06-18 | 株式会社岛津制作所 | Ion mobility analyzer and combination unit thereof and ion mobility analysis method |
| CN110221339A (en) * | 2018-10-26 | 2019-09-10 | 新瑞阳光粒子医疗装备(无锡)有限公司 | A kind of beam intensity detection device and particle accelerator |
| CN211295036U (en) * | 2019-12-25 | 2020-08-18 | 清华大学 | Nested Faraday cylinder-based high-field asymmetric waveform ion mobility spectrometer |
-
2019
- 2019-12-25 CN CN201911356855.7A patent/CN111105984A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5124658A (en) * | 1988-06-13 | 1992-06-23 | Adler Richard J | Nested high voltage generator/particle accelerator |
| JPH0251836A (en) * | 1988-08-12 | 1990-02-21 | Nec Kyushu Ltd | Ion implanter |
| CN101599407A (en) * | 2009-03-20 | 2009-12-09 | 清华大学 | A kind of array type microfaraday cage |
| CN103871820A (en) * | 2012-12-10 | 2014-06-18 | 株式会社岛津制作所 | Ion mobility analyzer and combination unit thereof and ion mobility analysis method |
| CN110221339A (en) * | 2018-10-26 | 2019-09-10 | 新瑞阳光粒子医疗装备(无锡)有限公司 | A kind of beam intensity detection device and particle accelerator |
| CN211295036U (en) * | 2019-12-25 | 2020-08-18 | 清华大学 | Nested Faraday cylinder-based high-field asymmetric waveform ion mobility spectrometer |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111933511A (en) * | 2020-07-30 | 2020-11-13 | 清华大学 | High-field asymmetric waveform ion mobility spectrometer |
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