RU2444007C1 - Apparatus for simultaneous separation of positive and negative ions - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: apparatus for separating positive and negative ions has two coaxial and/or concentric electrodes between which there is cavity which is blown with a stream of drift gas containing a mixture of said ions, a source of slowly varying compensating voltage and variable voltage with periodically asymmetric polarity, connected to electrodes. The apparatus also includes a coaxial and/or concentric electrode which forms with one of the electrodes an extra cavity which is blown with a stream of drift gas containing a mixture of said ions, wherein the source of variable voltage with periodically asymmetric polarity is connected to the electrode between the other two electrodes.

EFFECT: simultaneous separation of positive and negative ions widens the range of detected substances and also increases selectivity and specificity of analysis.

3 cl, 2 dwg

Description

The invention relates to gas analysis and can be used to solve the problems of separation of positive and negative ions in gases, for example, ions of explosive or narcotic substances in air.

A device for the simultaneous separation of positive and negative ions, including a gas-filled cavity bounded by an electrode system, voltage sources connected to the electrode system and providing a uniform electric field inside the cavity, two shutters in the middle of the cavity, located perpendicular to the axis of the cavity and at a certain distance from friend, two sources of pulse voltage connected to the gates, and the first source provides pulse input of positive ions into one olovinu cavity, and the second - negative ions in the second half cavity [US patents: №4445038, 24.04.1984; No. 7259369, 08.21.2007].

The main disadvantage of this technical solution is the inefficient use of ions, since only a fraction of the ions injected by the input pulse from the continuous stream gets into separation. The consequence of this is the low sensitivity and high detection limit of analytical devices that use these technical solutions.

Known devices for the simultaneous separation of positive and negative ions, including two plane-parallel electrodes located at some distance from each other and forming a cavity blown by a stream of drift gas containing a mixture of these ions, sources of slowly varying compensating voltage and alternating periodic asymmetric polarity voltage connected to electrodes [US patents: No. 7005632, 02/28/2006; No. 7129482, 10.31.2006; No. 7339164, 03/04/2008; No. 7619214, 11/17/2009].

The main disadvantage of these technical solutions is the high degree of ion recombination at the electrodes due to diffusion spreading. As a result, low sensitivity and high detection limit of the analytical device.

This disadvantage is deprived of the known device for separating either positive or negative ions, including two coaxial cylindrical electrodes of different diameters, between which an annular cavity is formed, blown by a flow of drift gas containing a mixture of these ions, sources of slowly varying compensating voltage, and alternating periodic voltage-asymmetric connected to the electrodes [RF patent No. 2293977, publ. 02/20/2007].

A device for separating either positive or negative ions is also known, including two coaxial cylindrical electrodes of different diameters with concentric spherical ends, between which a cavity is formed, blown by a flow of drift gas containing a mixture of these ions, sources of slowly varying compensating voltage and alternating periodic voltage-asymmetric polarity connected to the electrodes [US patent No. 6504149, 01/07/2003].

The main disadvantage of these technical solutions is the impossibility of simultaneously registering positive and negative ions. The result is a limited list of simultaneously separated ions of substances and low selectivity and specificity of the analysis, since some substances can form both positive and negative ions.

Closest to the proposed device is the separation of either positive or negative ions, including two coaxially located internal and external electrodes, between which a cavity is formed, blown by a stream of drift gas containing a mixture of these ions, sources of slowly varying compensating voltage and alternating periodic asymmetric voltage polarity connected to the electrodes [RF patent No. 2265832, publ. 12/10/2005].

The main disadvantage of this technical solution is the impossibility of simultaneously registering positive and negative ions. And as mentioned above, the result of this is a limited list of simultaneously separated ions of substances and low selectivity and specificity of the analysis.

This drawback is due to the fact that when using coaxial cylindrical or concentric spherical electrodes, an electric field having a spatial gradient is formed inside the cavity. In such a field, for example, negative ions, whose mobility increases with increasing electric field strength, are focused and transported in the drift gas flow for registration, while positive ions, whose mobility also increase with increasing electric field strength, are defocused and recombined on the electrodes . All this leads to the fact that it is impossible to simultaneously detect (for example, microimpurities of explosives, which can form both negative ions (2,4,6-trinitrotoluene, hexogen) and positive (triacetone triperoxide, hexamethylene triperoxide) diamine). To register ions of different signs, it is necessary to switch the polarity of the asymmetric voltage.

An object of the present invention is to provide a device for the simultaneous separation of positive and negative ions.

The specified technical problem is solved in that in a device for separating positive and negative ions, comprising two coaxially and / or concentrically located electrodes, between which a cavity is formed, blown by a stream of drift gas containing a mixture of these ions, sources of slowly varying compensating voltage and variable periodic asymmetric according to the polarity, the voltage connected to the electrodes according to the invention is additionally introduced coaxially and / or concentrically ny electrode, forming one of the electrodes of the additional cavity which is blown a stream of drift gas containing a mixture of these ions, the source of alternating periodic asymmetrical voltage of the polarity connected to the electrode disposed between two other electrodes.

Additionally introduced a source of slowly changing compensating voltage connected to the specified electrode.

Electrodes are bodies of revolution or their segments.

The location of the electrodes and the connection of voltage sources to them is carried out in such a way that conditions are created in the first cavity for efficient separation and transportation of ions of one sign for registration, while ions of another sign diffuse to the electrodes, and vice versa in the second cavity.

The advantages of the present invention will be described in detail below with reference to the accompanying figures, where:

figure 1 shows one embodiment of the proposed device;

figure 2 shows the positive and negative spectra of vapors of metaphos in air, recorded simultaneously.

A device for simultaneous separation of positive and negative ions contains cylindrical electrodes 1, 2, 3, located coaxially with respect to the axis of symmetry and forming cavities 4 and 5, blown by the drift gas flow, a source of alternating periodic asymmetric polarity voltage 6 connected to the central electrode 2, sources slowly varying compensating voltage 7 and 8, connected respectively to the external 1 and internal 3 electrodes. Other examples of electrode geometry can be concentrically arranged spheres, coaxially arranged cylindrical electrodes with hemispherical ends spaced concentrically relative to each other, and any other electrodes made, for example, in the form of bodies of revolution or their segments, arranged coaxially and / or concentrically relative to each other . In addition, for ion separation, either one slowly varying compensating voltage source connected to the central electrode 2 or two such sources connected to any two electrodes can be used.

Ions of different types differ from each other in charge sign (positive or negative), the type of dependence of mobility on electric field strength (increase or decrease in mobility with increasing field), and the degree of dependence of mobility on field strength. When a potential difference is applied to nonplanar coaxially and / or concentrically located opposite electrodes (for example, cylindrical, spherical, conical, etc.) between which a cavity is formed, an electric field with a spatial gradient arises inside the cavity. Under the action of a superposition of electric fields (slowly changing and variable periodic asymmetric in polarity) having a spatial gradient, ions of different types, with a certain sign of charge and a certain type of mobility dependence, will be separated by the degree of mobility dependence on field strength and focus in those areas of space, where the effect of the indicated field superposition for these types of ions is compensated. A slow change in the compensating voltage allows in the drift gas stream to transport for registration sequentially, according to a change in the degree of mobility dependence, all types of ions with a certain charge sign and a certain type of dependence. Ions of a different sign, whose mobility decreases with increasing field, will also be separated and focused, while ions of a different sign, whose mobility increases with increasing field, and ions of the same sign, whose mobility decreases with increasing field, will be defocused and recombined by electrodes. Registration of such ions is possible only when the polarity of the alternating periodic asymmetric voltage changes.

As follows from the foregoing, in order to separate all types of ions at the same time, it is necessary to form another cavity in which the polarity of the alternating periodic asymmetric field is opposite to the polarity of the field in the first cavity. This can be realized by introducing an additional coaxial and / or concentric electrode into the device. Figure 1 shows one of the variants of such a device containing three coaxial cylindrical electrodes 1, 2 and 3, forming cavities 4 and 5, blown by the flow of drift gas, a source of alternating periodic asymmetrical polarity voltage 6 connected to the Central electrode 2, and sources slowly varying compensating voltages 7 and 8, connected respectively to electrodes 1 and 3. To simplify, the figure shows the trajectories of ions of different signs, but with the same type of dependence of mobility on tension Olya. In the cavity 4, positive ions are separated and focused, the mobility of which increases with increasing field, and similar negative ions are defocused. In cavity 5, on the contrary, negative ions, whose mobility increases with increasing field, are separated and focused, and similar positive ions are defocused. A slow change in the compensating voltages of sources 7 and 8 allows all types of positive ions to be sequentially transported from the cavity 4 to the registration from the cavity 4 for registration from the cavity 4 and all types of negative ions from the cavity 5.

The simultaneous separation of positive and negative ions allows you to expand the list of registered substances, in addition, to increase the selectivity and specificity of the analysis. Figure 2 shows the positive and negative spectra of vapors of metaphos in the air, recorded simultaneously. As can be seen from the figure, ionic peaks of this substance are observed in both spectra, which significantly increases the selectivity and specificity of the analysis.

The implementation of the proposed technical solution is a simple technical task. For this, it is necessary to introduce an additional electrode into the prototype device and organize the transportation of ions for registration from the formed cavity.

Claims (3)

1. A device for separating positive and negative ions, comprising two coaxially and / or concentrically arranged electrodes, between which a cavity is formed, blown by a flow of drift gas containing a mixture of these ions, sources of slowly varying compensating voltage and alternating periodic voltage-asymmetric polarity connected to electrodes, characterized in that it is additionally introduced coaxially and / or concentrically located electrode forming with one of the electrodes an additional cavity, which is blown by the flow of drift gas containing a mixture of these ions, the source of alternating periodic asymmetrical polarity of voltage connected to the electrode located between two other electrodes. 2. The device according to claim 1, characterized in that an additionally introduced source of slowly varying compensating voltage connected to an additionally introduced electrode. 3. The device according to claim 1, characterized in that the electrodes are bodies of revolution or their segments.

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