WO2017154073A1 - Ion gate and ion mobility spectrometer - Google Patents

Abstract

In the present invention, to prevent an ion gate known as a BN gate from shorting during use in a high-temperature environment because of grid loosening resulting from differences in the amounts of thermal expansion of a substrate and electrode, a substrate that forms a pair of comb electrodes 21, 22 is made to be a structure in which both ends of two insulating substrates 11, 12 are connected with a space therebetween by connection members 13, 14. The space surrounded by these four members is made to be an opening 15 for ion passage. Each of the linear electrodes A of the comb electrodes 21, 22 crosses over the two insulating substrates 11, 12 and has both ends fixed thereto. The two connection members 13, 14 are formed from a material having the same coefficient of thermal expansion as the coefficient of thermal expansion of the linear electrode A.

Description

Ion gate and ion mobility analyzer

The present invention relates to an ion gate that allows or blocks passage of charged particles such as ions by controlling the voltage applied to an electrode, and an ion mobility analyzer using the ion gate.

For example, in ion mobility analyzers (IMS) and time-of-flight mass spectrometers (TOFMS), in order to measure ion drift time and flight time, introduction of ions taken from the sample into the drift region or flight space is required. Only within a very short time width, it is guided to the drift region or flight space as packet-like ions.

In order to realize this, an ion gate is called between an ion source that extracts ions from a sample and a drift tube that forms a drift region, or between a ion source and a TOF tube that also forms a free flight space. Devices are placed. Conventionally known ion gates include a BN gate (Bradbury-Nielsen gate) and a Tyndall gate (Tyndall-Powell gate). Each of these has a structure in which grid-like electrodes (grids) are arranged at appropriate intervals so that different voltages can be applied to adjacent electrodes.

As illustrated in the schematic perspective view of FIG. 3, the BN gate is formed by connecting one end portions of a plurality of linear electrodes A parallel to each other on the surface of a single insulating substrate 31 by connection electrodes B. The pair of comb-shaped electrodes 32 and 33 are formed so that each linear electrode A of one comb-shaped electrode 32 is positioned between each linear electrode A of the other comb-shaped electrode 33, and the insulating substrate 31 includes a linear electrode. Corresponding to the formation position of the group, it has a structure in which an opening 34 for passing ions is formed, and as a whole, ions are formed by grid-like electrodes (grids) that can apply different potentials to linear electrodes adjacent to each other A gate having a structure covering the passage opening is obtained (see, for example, Non-Patent Document 1 or Patent Document 1).

Here, each of the comb-shaped electrodes 32 and 33 uses a thin film patterned by etching (see Patent Document 1), or a wire is wound around the substrate 31 to fix a required portion by adhesion or the like, and a wire is removed by removing unnecessary portions. There is also a method of forming the connection electrode portion B by forming the electrode group A and separately fixing a wire to a required portion.

On the other hand, the Tyndall gate forms a grid on each of the two insulating substrates, and superimposes these substrates via an insulating sheet (such as a mica sheet), and each substrate has a grid formed on each. Align and fix so that the linear electrodes of each grid are alternately positioned in parallel with each other without overlapping, and openings for passing ions on each substrate corresponding to the positions where the grid electrodes are formed It is the structure which formed.

In the ion gate as described above, if the adjacent linear electrodes have the same potential, the ions pass through the grid, and if different potentials are applied to the adjacent linear electrodes, the ion trajectory is generated by the electric field generated between the adjacent grids. The ions are substantially shielded without being bent and put into a drift tube or a TOF tube provided at a later stage.

In addition, since the Tyndall gate has a three-dimensional structure, it is not easy to manufacture and the transmittance of ions is not good. In recent years, BN gates are mainly used.

International Publication No. WO03 / 065763 Pamphlet

T. Brunner and 11 others, A large Bradbury Nielsen ion gate with flexible wire spacing based on photo-etched stainless steel grids and its characterization applying symmetric and asymmetric potentials, 「International Journal of Mass Spectrometry 309 (2012)

By the way, the ion gate as described above may be exposed to high temperature depending on the apparatus to which it is applied.

For example, in an ion mobility analyzer, molecular ions extracted from a sample are allowed to pass through a very short time width by an ion gate, guided into a drift tube in a packet shape, and an accelerating electric field formed there. Accelerated. A diffusion gas flows in the drift tube in the direction opposite to the acceleration direction of the ions, and the ions travel through the drift tube and reach the detector while colliding with molecules of the diffusion gas. In this flight process, ions are separated in time according to the ion mobility depending on their size, three-dimensional structure, charge, etc., and the drift time required to reach the detector is information representing the ion mobility. .

In such an ion mobility analyzer, if there are water vapor or fine droplets of a solvent that is not sufficiently vaporized in the drift tube, the ions to be measured come into contact with them and the drift time is accurate. There is a possibility that it cannot be measured. Therefore, in this type of apparatus, the drift tube is generally heated to a high temperature of about several hundreds of degrees Celsius at the time of analysis in order to eliminate water vapor and fine droplets of solvent from the drift tube as much as possible. ing.

Here, in this type of apparatus, since the ion gate is disposed adjacent to the drift tube, the temperature of the ion gate rises to a temperature equivalent to the heating temperature of the drift tube, and operation at a high temperature is possible. Forced. When an ion gate as illustrated in FIG. 3 is placed in a high temperature environment, the electrode is pulled or loosened due to the difference in thermal expansion coefficient between the substrate material and the electrode material.

For example, in FIG. 3, the material of the pair of comb-shaped electrodes 32 and 33 constituting the grid is SUS304 (Japanese Industrial Standard), and the material of the substrate 31 is ceramic (alumina). Consider a case where the environmental temperature is raised from 20 ° C. (room temperature) to 150 ° C. when the length between the fixed ends is 40 mm and the distance between adjacent linear electrodes A is 0.5 mm.

The thermal expansion coefficient of SUS304 is about 18 × 10 ⁻⁶ (/ ° C.), and each linear electrode A having a fixed end length of 40 mm is 40 (mm) × 130 (° C.) × 18 × 10 ^{−6 in the} longitudinal direction. (/ ° C) ≈ 0.9 mm. On the other hand, the thermal expansion coefficient of the ceramic substrate 31 is about 8 × 10 ⁻⁶ (/ ° C.), and the distance 40 mm between the portions fixing both ends of the linear electrode A is 40 (mm) × 130 (° C. ) × 8 × 10 ⁻⁶ (/ ° C.) ≈elongated by 0.5 mm. The linear electrode A extends more than the ceramic substrate 31. However, since both ends of the linear electrode A are fixed to the substrate 31, the extension in the longitudinal direction is limited. Therefore, the linear electrode A is slackened in a direction orthogonal to the longitudinal direction. This slack induces a short circuit between adjacent linear electrodes A as described below.

FIG. 4 is an explanatory diagram corresponding to a plan view obtained by simplifying the ion gate of FIG. FIG. 4A schematically shows the state at room temperature, and FIG. 4B schematically shows the state at the time of temperature rise.

In the state at room temperature shown in (A), the length l between the fixed ends of the linear electrodes A constituting the grid with respect to the substrate 31 is equal to the distance L between the fixed portions of the linear electrodes A on the substrate 31 and is linear. There is no slack in the electrode A. When the temperature rises, these extend by amounts corresponding to the respective thermal expansion coefficients, and become l + Δl and L + ΔL, respectively. In the combination of SUS304 and alumina described above, the thermal expansion amount of the linear electrode A made of SUS304 is large, and both ends are constrained, so that it is slackened in the direction perpendicular to the longitudinal direction. Thus, the maximum amount Δx protruding in the direction orthogonal to the longitudinal direction based on the slack can be calculated by the following equation: Δx = {(l + Δl) ² − (L + ΔL) ² } ^1/2 / 2

As shown in FIG. 4A, when the distance between the adjacent linear electrodes A is d, when Δx exceeds d, these electrodes may come into contact with each other and short-circuit. When Δx is calculated by applying the above-mentioned combination of materials (SUS304 and alumina), the length between fixed ends of the linear electrode A (40 mm), and the temperature increase amount (130 ° C.), 1.0 mm is obtained. Since the distance d between the linear electrodes in a practically used BN gate is about 0.1 to 0.5 mm, the adjacent linear electrodes A come into contact with each other in the above setting to cause an electrical short circuit. .

This problem can be alleviated by shortening the grid length (the length of the linear electrode A) and widening the interval between adjacent linear electrodes. For example, if the grid length is 20 mm and the distance between the linear electrodes is 0.5 mm, Δx is halved to 0.5 mm, which is equal to the distance between the linear electrodes, but the linear electrodes still contact each other. Fear remains.

In the first place, in this type of ion gate, if the interval between the linear electrodes is widened, the ability to deflect ions is weakened, and the function as the ion gate is deteriorated. Further, when the length of the linear electrode is shortened, the opening of the ion gate is accordingly reduced, and the gate transmittance of ions is lowered, which affects the sensitivity.

As described above, in the conventional BN gate that operates in a high temperature environment, the gap between the linear electrodes constituting the grid is increased to improve the gate function, and the opening of the ion gate is increased. Thus, there has been a limit to improving the ion transmittance and increasing the sensitivity.

In addition, in an ion mobility analyzer equipped with a conventional BN gate, even if an attempt is made to increase the heating temperature of the drift tube in order to more surely remove water vapor or fine droplets of solvent from the drift tube, This cannot be realized due to the problem of electrical shorting of the gate.

The present invention has been made in view of such circumstances, and even in an ion gate operated at a high temperature, the gate opening diameter can be made larger than in the prior art. Providing an ion gate that can improve the gate function with a close spacing, and the drift tube heating temperature is higher than before, so that water vapor and fine solvent droplets in the drift region can be obtained. It is an object of the present invention to provide an ion mobility analyzer capable of more reliably eliminating analysis of ions and thereby improving analysis reliability.

In order to solve the above-described problem, the ion gate of the present invention includes a pair of comb electrodes in which one end of each of a plurality of linear electrode groups parallel to each other is connected by a connecting electrode portion. Each linear electrode is formed on the substrate so as to be positioned between the linear electrodes of the other comb electrode, and the substrate has an ion passage opening at a position corresponding to the position where the linear electrode group is formed. In an ion gate that allows or blocks the passage of ions through the opening by controlling the voltage applied to the pair of comb electrodes,
The substrate is composed of two insulating substrates and two connecting members that connect each of the insulating substrates with predetermined intervals at both ends thereof, and the two insulating substrates and the two insulating substrates. A portion surrounded by the connecting member forms an opening for passing ions, and both ends of each linear electrode of the pair of comb-shaped electrodes are fixed to both insulating substrates facing each other through the opening. With
Each of the connecting members is characterized by being formed of a material having a thermal expansion coefficient substantially equal to that of each linear electrode.

Here, in the present invention, each of the connecting members can be formed of the same material as each of the linear electrodes, and it is particularly preferable that both of them are made of stainless steel.

On the other hand, the ion mobility analyzer of the present invention introduces ions taken from a sample into a drift tube through an ion gate, and allows the ions to pass through a predetermined atmosphere while being accelerated by a predetermined electric field. In the ion mobility analyzer for analyzing a sample from the required time, the ion gate of the present invention described above is used as the ion gate.

The present invention is called a BN gate in which a grid is formed by combining a pair of comb-shaped electrodes capable of applying different voltages on the same plane of a substrate on which an ion passage opening is formed to cover the opening. In the ion gate, it is intended to solve the problem by making the thermal expansion coefficient of the substrate in the longitudinal direction of each linear electrode constituting the grid (a pair of comb electrodes) substantially equal to that of the linear electrode. is there.

In other words, in the present invention, a substrate on which an ion passage opening and an electrode for opening and closing the opening with respect to ions are formed as two insulating substrates without being integrated as in the prior art. These are the structures composed of two connecting members that are connected to each other at predetermined intervals at both ends, and the space surrounded by these four members is the ion passage opening. Each linear electrode of each comb-shaped electrode is provided so as to be passed between two insulating substrates, and both ends thereof are fixed to different insulating substrates.

According to the above configuration, the amount of change in the interval between the two insulating substrates when the temperature changes is equal to the amount of change in the length of the connecting member, that is, the amount of change in the interval when the temperature of the two insulating substrates changes. Depends on the coefficient of thermal expansion of the connecting member. Here, since the separation direction of the two insulating substrates coincides with the longitudinal direction of each linear electrode, if the connecting member is formed of a material having a thermal expansion coefficient substantially equal to the thermal expansion coefficient of each linear electrode, The amount of change in the length between the fixed ends of the linear electrodes at the time of change is substantially equal to the amount of change in the length between the same portions on the substrate structure.

Therefore, according to the configuration of the ion gate of the present invention, when the linear electrode expands due to the temperature rise, the connecting member also expands by substantially the same amount at the same time, so that each linear electrode is not pulled or loosened.

According to the present invention, even when the temperature is raised to a high temperature, the linear electrode group constituting the grid is loosened and the adjacent ones come into contact with each other, and the conventional pulling causes deformation or cutting. It is possible to operate at a higher temperature than

In order to increase the amount of ions that pass through the ion gate, it is necessary to lengthen each linear electrode of the grid in order to increase the opening diameter of the gate. However, in the conventional ion gate, as the linear electrode length increases, There is a problem that the amount of slack of the linear electrode increases and the possibility that adjacent ones come into contact with each other increases. However, since the ion gate of the present invention does not have such a problem, the opening diameter of the gate can be easily increased. This makes it easier to improve the sensitivity of the device.

Furthermore, even when operated at high temperatures, the grid linear electrodes are less likely to loosen, so it is possible to easily reduce the spacing between the grid linear electrodes. It will be easier to improve.

According to the ion mobility analyzer using the ion gate of the present invention described above, various problems do not occur in the linear electrodes of the grid even if the operating temperature of the ion gate disposed adjacent to the drift tube is increased. Therefore, the heating temperature of the drift tube can be made higher than before, and this greatly reduces the chance of contact with ions by reliably eliminating water vapor and solvent fine droplets in the drift tube. Thus, a highly reliable ion mobility analyzer with few measurement errors of ion drift time can be obtained.

The top view of embodiment of the ion gate of this invention. The schematic block diagram of the ion mobility analyzer of this invention. The schematic perspective view which shows an example of the conventional ion gate (BN gate). Explanatory drawing of generation | occurrence | production of the slack of the linear electrode of a grid at the time of temperature rising of the conventional ion gate.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a plan view of an ion gate of the present invention.

The substrate structure 1 having an opening 15 for allowing ions to pass through the center is formed by the two insulating substrates 11 and 12 and the two connecting members 13 and 14. Each of the insulating substrates 11 and 12 has a strip shape, and these are connected to each other by rod-shaped connecting members 13 and 14 at predetermined intervals at both ends thereof. A region surrounded by the connecting members 13 and 14 penetrates the substrate structure 1 in the thickness direction to form an opening for passing ions. The connection structure by the connection members 13 and 14 is not particularly limited. For example, both end surfaces of the connection members 13 and 14 are bonded to the insulating substrates 11 and 12 using a rod, or bolts threaded at both ends are used. It can also be fastened to each insulating substrate 11, 12.

A pair of comb electrodes 21 and 22 are formed on the surface of the substrate structure 1. Each comb-shaped electrode 21, 22 has a pattern in which one end portions of a plurality of linear electrodes A parallel to each other are connected to each other by a connection electrode portion B, and each of the linear electrodes of one comb-shaped electrode 21 They are arranged in such a positional relationship that A enters between the linear electrodes A of the other comb-shaped electrode 22. These comb-shaped electrodes 21 and 22 can be applied with voltages independent of each other, and ions are allowed or blocked from passing through the opening 15 by controlling the applied voltage.

Each of the comb-shaped electrodes 21 and 22 is, for example, a thin film patterned by etching, and fixed to the insulating substrates 21 and 22 oppositely arranged on both sides so as to straddle the opening 15 by bonding, or similarly using a wire Similarly, it is fixed to the insulating substrates 21 and 22 by adhesion under the pattern.

More specifically, the one comb-shaped electrode 21 fixes the connection electrode portion B and the base end portion of each linear electrode A connected thereto to the one insulating substrate 11 and the tip of each linear electrode A. The part is fixed to the other insulating substrate 12. Further, the other comb-shaped electrode 22 fixes the connecting electrode portion B and the base end portion of each linear electrode A connected thereto to the other insulating substrate 12, and the distal end portion of each linear electrode A to one side Fix to the insulating substrate 21.

In the above configuration, materials having substantially the same coefficient of thermal expansion are selected as the materials for the connecting members 13 and 14 and the comb-shaped electrodes 21 and 22. In this example, SUS304 is used for all of them. SUS304 is a material suitable both as a material for this type of electrode and as a structural material such as the connecting members 13 and 14. Note that alumina or the like can be suitably used as the material of the insulating substrates 11 and 12.

According to the above embodiment of the present invention, since the coefficient of thermal expansion of SUS304 is 17.3 × 10 ⁻⁶ , the length between the fixed ends of the linear electrodes A of the comb-shaped electrodes 21 and 22 to the insulating substrates 11 and 12 is as follows. When the thickness is 30 mm, when the temperature is increased by 200 ° C., the length between the fixed ends of each linear electrode A is increased by 106 μm. At this time, since the connecting members 13 and 14 are also extended by substantially the same amount and the distance between the insulating substrates 11 and 12 is also extended, the linear electrodes A are not pulled or loosened. In addition, although the dimension to the direction of the board | substrate structure 1 becomes large by expansion | extension of the connection members 13 and 14, this leaves the allowance for the dimension increase at the time of maximum temperature rise in the installation part of the board | substrate structure 1. The main part (substrate structure) of the ion gate is not deformed.

Next, an embodiment of the ion mobility analyzer of the present invention will be described.
FIG. 2 shows a schematic configuration diagram thereof. The feature of this example is mainly in the structure of the ion gate 103, and the basic configuration as an ion mobility analyzer is the same as that of a publicly known one. The explanation is limited.

Now, the ion mobility analyzer of this example includes an ion source 101 that ionizes component molecules in a sample, and a large number of annular rings to form a required electric field for accelerating ions in a drift region D formed inside. A drift electrode group 102 having an electrode E, an ion gate 103 provided at the entrance of the drift region D, and a detector 104 for detecting ions moving in the drift region D are provided. Is provided with a drift tube (not shown).

In the above configuration, the ions extracted from the sample by the ion source 101 are temporarily blocked by the ion gate 103, and the ions are introduced into the drift region D in a packet form by opening the ion gate 103 only momentarily. . In the drift region D, a flow of a neutral diffusion gas DG is formed in the direction opposite to the acceleration direction by the electric field created by the drift electrode group 102. Therefore, the ions move toward the detector 104 by the accelerating electric field while colliding with the gas molecules coming in the drift region D. Ions are temporally separated by ion mobility determined by their size, shape, charge, etc., and ions of different ion mobility reach the detector with a time difference. The ion mobility information based on the detection result of the detector 104 is used for analysis of the component molecules of the sample.

The feature of this embodiment is that the ion gate shown in FIG. 1 is used for the ion gate 103, which makes it possible for the ion mobility analyzer of this embodiment to compare the temperature of the drift tube with that of the prior art. Thus, it is possible to increase the temperature to high temperature, and thus to reliably remove impure particles such as water vapor in the drift region D, thereby improving the reliability of the analysis.

That is, as described above, in this type of analyzer, if water vapor or solvent fine droplets exist in the drift region D, the measurement target ions collide with this, and the measurement result of the drift time is not correct. In order to eliminate such impure particles, the drift tube is heated and the analysis operation is performed. This heating raises the temperature of the adjacent ion gate, and the linear electrodes of the grid are loosely adjacent as described above. Since there is a risk of electrical shorting due to contact between the two, the heating temperature of the drift tube has to be limited. By using the ion gate according to the present invention illustrated in FIG. 1 as the ion gate 103, the problem of the slack of the linear electrode due to the temperature rise is eliminated or greatly reduced. As a result, the analysis can be performed in a state in which impure particles such as water vapor are reduced.

Here, the example in which the ion gate of the present invention is applied to an ion mobility analyzer has been described above. However, the ion gate of the present invention is applied to any other apparatus such as a time-of-flight mass spectrometer (TOFMS). In particular, it can be applied to an apparatus that needs to be operated at a high temperature to exert its effect.

In addition, regarding the ion gate of the present invention, it is preferable that each linear electrode constituting the comb-shaped electrode and the material of the connecting member are metals suitable for any application such as SUS304. Of course, they may be formed of different metals that are close to each other, or may be a metal and a non-metal whose thermal expansion coefficient is close to that of the metal.

DESCRIPTION OF SYMBOLS 1 Substrate structure 11, 12 Insulating substrate 13, 14 Connection member 15 Opening part 21, 22 Comb electrode A Linear electrode B Connection electrode 101 Ion source 102 Drift electrode group 103 Ion gate 104 Detector D Drift region E Toroidal electrode

Claims (4)

A pair of comb-shaped electrodes formed by connecting one end portions of a plurality of linear electrode groups parallel to each other with a connecting electrode portion, and each linear electrode of one comb-shaped electrode is between each linear electrode of the other comb-shaped electrode An opening for passing ions is formed on the substrate at a position corresponding to the position where the linear electrode group is formed, and the voltage applied to the pair of comb-shaped electrodes is controlled by the substrate. In an ion gate that allows or blocks the passage of ions through the opening,
The substrate is composed of two insulating substrates and two connecting members that connect each of the insulating substrates with predetermined intervals at both ends thereof, and the two insulating substrates and the two insulating substrates. A portion surrounded by the connecting member forms an opening for passing ions, and both ends of each linear electrode of the pair of comb-shaped electrodes are fixed to both insulating substrates facing each other through the opening. With
The ion gate, wherein each of the connecting members is formed of a material having a thermal expansion coefficient substantially equal to that of each linear electrode. 2. The ion gate according to claim 1, wherein each of the connecting members is made of the same material as each of the linear electrodes. 3. The ion gate according to claim 2, wherein each of the connecting members and each of the linear electrodes are made of stainless steel. Ion migration that introduces ions taken from the sample into the drift tube via an ion gate, accelerates them by a predetermined electric field, passes through a predetermined atmosphere for a fixed distance, and analyzes the sample from the required time In the mobility analyzer, the ion gate according to any one of claims 1 to 3 is used as the ion gate.

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