CN212934550U - High-field asymmetric waveform ion mobility spectrometer - Google Patents
High-field asymmetric waveform ion mobility spectrometer Download PDFInfo
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- CN212934550U CN212934550U CN202021553116.5U CN202021553116U CN212934550U CN 212934550 U CN212934550 U CN 212934550U CN 202021553116 U CN202021553116 U CN 202021553116U CN 212934550 U CN212934550 U CN 212934550U
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- 238000013508 migration Methods 0.000 claims abstract description 74
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- 238000009828 non-uniform distribution Methods 0.000 abstract 1
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- 238000010586 diagram Methods 0.000 description 8
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- 230000009286 beneficial effect Effects 0.000 description 1
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- 230000003247 decreasing effect Effects 0.000 description 1
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Abstract
A high-field asymmetric waveform ion mobility spectrometer comprises an ion source, a migration region and a detection region; the migration zone comprises an electrode pair consisting of two upper and lower electrodes, wherein one electrode is a grid-type flat electrode, and the other electrode is a metal flat electrode. The application of an asymmetric waveform voltage to the electrode pair generates an asymmetric waveform electric field with spatially non-uniform distribution in the transition region. Under such an electric field, a tendency of movement of a specific ion toward the central plane of the migration region is generated in the migration region, that is, focusing of the ion in the migration region is generated. The ion focusing in the migration zone reduces the diffusion loss of ions in the migration zone, thereby improving the passing efficiency of the ions in the migration zone. This kind of ion mobility spectrometer can improve the sensitivity of instrument, under the same condition, the utility model discloses a signal strength that ion mobility spectrometer measured compares with the signal strength of current flat asymmetric waveform ion mobility spectrometer and has showing the improvement.
Description
Technical Field
The utility model relates to a high-field asymmetric waveform ion mobility spectrometer belongs to a plate high-field asymmetric waveform ion mobility spectrometer very much, belongs to biochemical substance on-line measuring technique and equipment technical field.
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, K0Is the mobility of the ions in a 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 laws of ion mobility varying with the electric field intensity, three types of ions, a, B and C, can be classified. When alpha (E/N) > 0, K > K0Ions belonging to type a, K increasing with increasing electric field strength E; when alpha (E/N) < 0, K < K0Ions belonging to type C, K decreasing with increasing E; when alpha (E/N) ≈ 0, it belongs to ions of type B, K ≈ K0. 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). A Compensation Voltage (CV) is applied to the electrodes to compensate for the ion deflection caused by the separation voltage, thereby allowing a particular ion to pass through the mobility region to the detection region.
The high-field asymmetric waveform ion mobility spectrometer can be divided into a flat-plate type high-field asymmetric waveform ion mobility spectrometer and a cylindrical type high-field asymmetric waveform ion mobility spectrometer according to the geometric characteristics of a migration region of the high-field asymmetric waveform ion mobility spectrometer. The electrodes in the migration region of the flat-plate type high-field asymmetric waveform ion mobility spectrometer are applied with separation voltage by two parallel electrodes, and the electrodes in the migration region of the cylindrical type high-field asymmetric waveform ion mobility spectrometer are applied with separation voltage by two concentric cylindrical electrodes. Due to the spatial non-uniformity of the electric field distribution in the migration region of the cylindrical high-field asymmetric waveform ion mobility spectrometer, when specific ions pass through the migration region, the specific ions tend to move towards the axial plane in the migration region, namely, the ions in the migration region are focused. The ion focusing in the migration zone can effectively improve the passing rate of ions in the migration zone, thereby improving the detected ion strength and improving the sensitivity of the instrument.
The flat-plate type migration zone is widely applied due to the advantages of simple and convenient process, high processing precision, easy miniaturization and the like. However, because the upper electrode and the lower electrode used in the migration region of the conventional flat-plate type high-field asymmetric waveform ion mobility spectrometer are both electrodes formed by metal flat plates, the internal electric field is uniformly distributed, so that the cylindrical migration region of the ion focusing usually has higher sensitivity than that of the flat-plate type migration region with the same specification because the cylindrical migration region of the ion focusing does not have the ion focusing capability in the migration region of the cylindrical high-field asymmetric waveform ion mobility spectrometer. Although the prior art introduces the ion focusing function into the flat-plate type high-field asymmetric waveform ion mobility spectrometer, for example, a focusing region is added before the migration region, so that ions are focused before the migration region is carried out, because ions cannot be continuously focused in the migration region, the improvement effect of the methods on the ion throughput in the migration region is limited. So far, ion focusing inside the migration region of a flat-plate type high-field asymmetric waveform ion mobility spectrometer has not been realized.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a flat asymmetric waveform ion mobility spectrometer in high field to the not enough and defect that prior art exists to solve the problem that flat asymmetric waveform ion mobility spectrometer in high field can't realize the ion focusing in the migration district inside.
In order to solve the above problem, the technical scheme of the utility model is as follows:
a flat-plate type high-field asymmetric waveform ion mobility spectrometer comprises an ion source, a migration region, a detection region, a radio frequency power supply, a superposition circuit, a compensation voltage, a weak current detection circuit and a direct current source; the migration area comprises a flat plate electrode pair consisting of an upper electrode and a lower electrode; the detection area contains Faraday cylinder sensitive pole and Faraday cylinder deflection pole, its characterized in that: the upper electrode is a grid type flat electrode, and the lower electrode is a metal flat electrode; or the upper electrode is a metal flat plate electrode, and the lower electrode is a grid type flat plate electrode.
Among the above-mentioned technical scheme, its characterized in that: the metal stripe direction of the grid type flat plate electrode is parallel to the air flow direction.
Preferably, the metal width of the grid-type flat electrode is in the range of 0.1mm to 1mm, and the width of the gap between the metals is in the range of 0.1mm to 1 mm.
Compared with the prior art, the utility model, have following advantage and outstanding technological effect: firstly, the utility model can realize the ion focusing which can not be realized in the prior art in the migration region of the flat-plate type high-field asymmetric waveform ion mobility spectrometer, so that the diffusion loss of ions in the flat-plate type migration region is reduced, and the passing efficiency of the ions in the flat-plate type migration region is improved; the utility model can reduce the equivalent load of the electrode in the migration area of the flat high-field asymmetric waveform ion mobility spectrometer, thereby reducing the power consumption of the radio frequency power supply; third the utility model discloses can make the contact area of the asymmetric waveform ion mobility spectrometer migration zone inner electrode in flat high field and ion reduce to further reduce the diffusion loss of ion, improve the efficiency of passing through of ion in flat migration zone, improve signal strength.
Drawings
Fig. 1 is a schematic structural diagram of a flat-plate type high-field asymmetric waveform ion mobility spectrometer in the prior art.
Fig. 2 is a schematic structural diagram of an embodiment of the present invention, wherein the upper electrode is a grid-type flat electrode.
Fig. 3 is a schematic structural diagram of another embodiment of the present invention, wherein the lower electrode is a grid-type flat electrode.
Fig. 4 is a schematic structural diagram of the grid-type plate electrode of the present invention, wherein H is the width of the metal stripe of the grid-type plate electrode, and H is the width of the gap between the metal stripes of the grid-type plate electrode.
Fig. 5 is a comparison graph of experimental results of the grid-type flat electrode migration area applied to the flat-type high-field asymmetric waveform ion mobility spectrometer.
In the figure: 1-sample gas; 2-a source of ions; 3-a migration zone; 4-an upper electrode; 5-a lower electrode; 6-radio frequency power supply; 7-a superimposing circuit; 8-compensation voltage; 9-detection area; 10-faraday cup sensitive electrode; 11-faraday cup deflection pole; 12-weak current detection circuit; 13-a direct current source; 14-grid type flat plate electrodes; 15-grid type flat plate electrode metal stripes; 16-gaps of metal stripes of grid type flat plate electrodes.
Detailed Description
The present invention is further described with reference to the following drawings and examples so that those skilled in the art can fully understand and implement the invention.
Fig. 1 is a schematic structural diagram of a flat-plate high-field asymmetric waveform ion mobility spectrometer in the prior art, which includes an ion source 2, a migration region 3, a detection region 9, a radio frequency power supply 6, a superposition circuit 7, a compensation voltage 8, a weak current detection circuit 12 and a direct current source 13; the migration area comprises a flat electrode pair consisting of an upper electrode 4 and a lower electrode 5; the detection area 9 contains a Faraday cylinder sensitive electrode 10 and a Faraday cylinder deflection electrode 11; the upper electrode 4 and the lower electrode 5 are both metal flat plate electrodes.
Fig. 2 is a schematic diagram of an embodiment of a high-field asymmetric waveform ion mobility spectrometer provided by the present invention. The ion mobility spectrometer is different from the traditional flat-plate high-field asymmetric waveform ion mobility spectrometer in that: the upper electrode in the migration zone 3 is a grid-type flat electrode 14, and the lower electrode 5 is a metal flat electrode.
Fig. 3 is a schematic diagram of another embodiment of a high-field asymmetric waveform ion mobility spectrometer provided by the present invention. The ion mobility spectrometer is different from the traditional flat-plate high-field asymmetric waveform ion mobility spectrometer in that: the upper electrode 4 in the migration region 3 is a metal flat plate electrode, and the lower electrode is a grid-type flat plate electrode 14. In this case, the RF voltage waveform for generating the focus is opposite in polarity to the RF voltage waveform for generating the focus in the embodiment shown in FIG. 2.
Fig. 4 is the utility model provides a flat-plate type high-field asymmetric ion mobility spectrometer's grid type flat plate electrode schematic diagram, grid type flat plate electrode comprises the clearance 16 of grid type flat plate electrode metal stripe 15 and grid type flat plate electrode metal stripe, and the direction of metal stripe is on a parallel with the air current direction. The width H of the grid type metal stripes ranges from 0.1mm to 1mm, and the width H of gaps among the grid type metal stripes ranges from 0.1mm to 1 mm.
Fig. 5 is a comparison graph of experimental results of the grid-type flat electrode migration area applied to the flat-type high-field asymmetric waveform ion mobility spectrometer. The curves in the figure show the variation of ion signal intensity at different compensation voltages. Wherein the solid line is the signal intensity of the migration region using the gate type flat plate electrode, and the dotted line is the signal intensity of the migration region using the existing flat plate.
The principle of using the present invention to produce ion focusing in the migration zone is briefly described as follows. Taking the structure shown in fig. 2 as an example, when an asymmetric waveform is applied, an electric field with a nonuniform spatial distribution is formed inside the transition region 3 due to the combined action of the gate-type plate electrode 14 and the metal plate electrode. Similar to the focusing phenomenon of specific ions caused by the non-uniformity of the electric field inside the cylindrical migration region, the present invention also forms a balance region inside the migration region 3, when the specific ions are far away from the balance region, the specific ions will have a net motion close to the balance region within a period of the rf voltage, and the focusing of the ions inside the migration region is generated in a macroscopic view. Under the action of the focusing, the ions tend to move towards a focal plane inside the migration zone, and the ion loss caused by the impact of ion diffusion on the electrodes of the migration zone is partially counteracted, so that the passing rate of the ions in the migration zone is improved.
The utility model discloses effectively solved the inside unable ion focusing's of realizing problem in the prior art in plate migration district, formed the inside inhomogeneous electric field in migration district through the grid type flat plate electrode who uses one side for specific ion can produce the focus effect in the migration district, improves the efficiency that these ions pass through the migration district, effectively improves the signal strength of the asymmetric waveform ion mobility spectrometer in plate high field, promotes the sensitivity of instrument.
Example 1:
experiments were performed using existing flat plate type mobility regions in a high field asymmetric waveform ion mobility spectrometer, as shown in fig. 1. The distance between the two electrodes in the migration zone is 0.3 mm. The sample gas used in the experiment was ethanol sample gas with a concentration of 107ppm (carrier gas was 99.999% nitrogen), and a 10.6eV UV lamp was used as the ionization source. A series of spectrograms are obtained by changing the amplitude of the radio frequency voltage, and the spectrograms are subjected to Gaussian fitting to obtain the heights of spectral peaks under different compensation voltages, namely signal intensity. Thus, the relationship between the signal intensity and the compensation voltage using the conventional flat-plate type transition region is obtained.
Use the utility model provides a grid type flat plate electrode migration zone uses and experiments in the asymmetric waveform ion mobility spectrometer in flat high field, as shown in figure 2. The distance between the two electrodes in the migration zone is 0.3 mm. The gas sample used in the experiment is ethanol, the concentration is 107ppm, the carrier gas is 99.999% nitrogen, the 10.6eV ultraviolet lamp is used as an ionization source, the experiment and data processing are carried out by using the same method, and the relationship between the signal intensity of the grid type flat plate electrode migration area and the compensation voltage is obtained and used.
Fig. 5 is a graph plotting the two signal intensity-compensation voltage relationships under the same coordinate system for comparison. By comparison, the signal intensity of the migration region using the gate type flat plate electrode is higher than that of the migration region using the existing flat plate electrode under the same conditions. When the radio frequency voltage is not large, the focusing effect of ions in the migration region is not obvious, the compensation voltage corresponding to the ion spectrum peak position is small, and the signal intensity difference between the grid type flat plate electrode migration region and the existing flat plate migration region is not large; when the radio frequency voltage is increased, the focusing effect of ions in the migration area is obvious, the corresponding compensation voltage is increased, the signal intensity of the migration area using the grid type flat plate electrode is obviously improved compared with the signal intensity of the migration area using the existing flat plate, and when the difference is the largest, the signal intensity of the migration area using the grid type flat plate electrode is about 20 times of the signal intensity of the migration area using the existing flat plate.
It can be seen from the above embodiments that the use of the grid-type flat plate electrode migration region provided by the utility model can significantly improve the signal intensity of the flat-plate high-field asymmetric waveform ion mobility spectrometer, which is beneficial to increasing the sensitivity of the instrument; and the structure is simple, and the integration is easy.
Claims (3)
1. A high-field asymmetric waveform ion mobility spectrometer comprises an ion source (2), a migration region (3), a detection region (9), a radio frequency power supply (6), a superposition circuit (7), a compensation voltage (8), a weak current detection circuit (12) and a direct current source (13); the migration area comprises a flat electrode pair consisting of an upper electrode (4) and a lower electrode (5); the detection area (9) contains Faraday cylinder sensitive electrode (10) and Faraday cylinder deflection electrode (11), and is characterized in that: the upper electrode is a grid type flat electrode (14), and the lower electrode (5) is a metal flat electrode; or the upper electrode (4) is a metal flat plate electrode, and the lower electrode is a grid type flat plate electrode (14).
2. A high-field asymmetric-waveform ion mobility spectrometer as claimed in claim 1, wherein: the direction of the metal stripes in the grid type flat plate electrode is parallel to the direction of the gas flow.
3. A high-field asymmetric-waveform ion mobility spectrometer according to claim 1 or 2, wherein: the width of the metal stripes of the grid type flat plate electrode is within the range of 0.1 mm-1 mm, and the width of the gaps among the metal stripes is within the range of 0.1 mm-1 mm.
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