Ion guide and mass spectrometer

Abstract

To provide an ion guide and a mass spectrometer, capable of achieving both of a high-ion fetching efficiency and a high-ion convergence efficiency.SOLUTION: In an ion guide, an ion is directed from an inlet side to an outlet side, and the ion progresses in an inner space. The ion guide comprises a plurality of plate-like electrodes, and the plurality of plate-like electrodes is laminated to a lamination direction orthogonal to a progressing direction where the ion is progressed with an interval. At least two of the plurality of plate-like electrodes are an inclination plate-like electrode having an inclination surface inclined to the progressing direction to a part faced to the inner surface. Each inclination plate-like electrode includes an inclination start point that the inclination surface is started at an end surface on the inlet side. At least two inclination plate-like electrodes adjacent to the lamination direction have a different position of the inclination start point in a direction orthogonal to both of the progressing direction and the lamination direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to an ion guide and a mass spectrometer, and relates to, for example, an ion guide and a mass spectrometer capable of achieving both high ion capture efficiency and high ion focusing efficiency. [Background technology]

[0002] In a mass spectrometer, ions generated in an ion source are transported to a mass analysis section by an ion transport section. Mass analysis devices using atmospheric pressure ionization transport ions generated under atmospheric pressure to a mass analysis section in a vacuum, so they generally have a differential pumping system configuration in which the vacuum chamber is divided into multiple sections. In this case, the ion transport section is often placed in a differential pumping chamber with a low degree of vacuum and high pressure on the upstream side. To achieve high sensitivity in a mass analysis device, the ion transport section is required to have high ion capture efficiency and high ion focusing efficiency.

[0003] A typical ion transport section uses an ion guide system that focuses ions using a radio frequency electric field formed by applying a radio frequency voltage. Ion guides include the ion funnel system, which has ring-shaped electrodes stacked in the ion transport direction, and the multipole ion guide system, which is made up of multiple rod electrodes.

[0004] In Patent Document 1, a multipole is constructed using electrodes with a trapezoidal cross section, thereby realizing an ion guide of about 12-fold. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Pat. No. 1,047,5633 Summary of the Invention [Problem to be solved by the invention]

[0006] In the ion funnel method, ring-shaped electrodes are stacked in the ion transport direction, so ions are likely to collide with the electrode surface, and the electrodes may be easily contaminated. On the other hand, in the multipole ion guide method, the ion capture efficiency generally increases with the number of electrodes (number of multipoles). In Patent Document 1, trapezoidal electrodes are arranged radially, so it is considered difficult to increase the number of electrodes by further finer arrangement. In other words, there are considered to be issues in further improving the ion capture efficiency.

[0007] The present invention has been made to solve the above problems, and has an object to provide an ion guide and a mass spectrometer that can achieve both high ion capture efficiency and high ion focusing efficiency. [Means for solving the problem]

[0008] An example of an ion guide according to the present invention is An ion guide in which ions travel through an internal space from an inlet side to an outlet side, The ion guide comprises a plurality of plate electrodes; The plurality of plate-shaped electrodes are stacked at intervals in a stacking direction perpendicular to the direction in which the ions travel, At least two of the plurality of plate electrodes are inclined plate electrodes having an inclined surface inclined with respect to the traveling direction in a portion facing the internal space, Each of the inclined plate electrodes has an inclination starting point at which the inclined surface starts on the end surface on the inlet side, At least two of the inclined plate electrodes adjacent to each other in the stacking direction have different positions of the inclination start points in a direction perpendicular to both the moving direction and the stacking direction.

[0009] An example of a mass spectrometer according to the present invention comprises an ion guide as described above. Effect of the Invention

[0010] The ion guide and mass spectrometer according to the present invention can achieve both high ion capture efficiency and high ion focusing efficiency. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a configuration diagram of a mass spectrometer according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the configuration of the ion guide of the first embodiment (as viewed from the Z direction). [Diagram 3] FIG. 2 is a diagram showing the configuration of the ion guide of the first embodiment (as viewed from the Z direction). [Figure 4] FIG. 2 is a diagram showing the configuration of the ion guide of the first embodiment (as viewed from the X direction). [Diagram 5] FIG. 2 is an explanatory diagram of the plate electrode of the first embodiment (viewed from the X direction). [Figure 6] FIG. 2 is a configuration diagram (perspective view) of the ion guide according to the first embodiment. [Figure 7] FIG. 2 is a configuration diagram (perspective view) of the ion guide according to the first embodiment. [Figure 8] FIG. 13 is a diagram showing the configuration of an ion guide according to a second embodiment (as viewed from the Z direction). [Figure 9] FIG. 11 is a diagram showing the configuration of an ion guide according to a third embodiment (as viewed from the Z direction). [Figure 10] FIG. 11 is a diagram showing the configuration of an ion guide according to a third embodiment (as viewed from the X direction). [Figure 11] FIG. 13 is a diagram showing the configuration of an ion guide according to a fourth embodiment (as viewed from the Z direction). [Figure 12] FIG. 13 is a diagram showing the configuration of an ion guide according to a fifth embodiment (as viewed from the Z direction). [Figure 13] FIG. 13 is a diagram showing the configuration of an ion guide according to a sixth embodiment (as viewed from the Z direction). [Figure 14] FIG. 13 is a diagram showing the configuration of an ion guide according to a seventh embodiment (as viewed from the Z direction). [Figure 15] FIG. 13 is a diagram showing the configuration of an ion guide according to an eighth embodiment (as viewed from the Z direction). [Figure 16] FIG. 13 is a diagram showing the configuration of an ion guide according to a ninth embodiment (as viewed from the Z direction). [Figure 17] FIG. 23 is a diagram showing the configuration of an ion guide according to a tenth embodiment (as viewed from the Z direction). [Figure 18] FIG. 23 is a diagram showing the configuration of an ion guide according to an eleventh embodiment (as viewed from the Z direction). [Figure 19] FIG. 23 is an explanatory diagram of a plate electrode of Example 12 (viewed from the X direction). [Figure 20] FIG. 23 is an explanatory diagram of a plate electrode of Example 13 (viewed from the X direction). [Figure 21] FIG. 23 is an explanatory diagram (perspective view) of a plate electrode of Example 14. [Figure 22] FIG. 23 is a diagram showing the configuration of an ion guide according to a fifteenth embodiment (as viewed from the Z direction). [Diagram 23] FIG. 23 is a diagram showing the configuration of an ion guide according to a sixteenth embodiment (as viewed from the Z direction). [Figure 24] FIG. 21 is a diagram showing the configuration of an ion guide according to a seventeenth embodiment (as viewed from the Y direction). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. (Example 1) (upper and lower opposite phases) In the first embodiment, a configuration of an ion guide and a mass spectrometer in which radio frequency voltages of opposite phases are applied between opposing plate electrodes will be described.

[0013] The configuration of the mass spectrometer of this embodiment is shown in Figure 1. The mass spectrometer 1 mainly comprises an ion source 2 and a vacuum vessel 4 having a mass analysis section 3 therein. The ion source 2 mainly comprises an ion generation section 5 and an ion source chamber 6.

[0014] Ions generated in the ion source 2 are introduced into the vacuum chamber 4 through a hole 8 in the introduction electrode 7, and are analyzed in the mass analysis section 3. Various voltages are applied to the ion source 2 and the mass analysis section 3 by a power supply 9. The timing of voltage application by the power supply 9 and the voltage value are controlled by a control section 10.

[0015] The ion source 2 can use various ionization methods, such as electrospray (ESI), atmospheric pressure chemical ionization (APCI), and atmospheric pressure photoionization (APPI). When ionizing a sample solution, many droplets are sprayed in addition to ions, so the inside of the ion source chamber 6 is often evacuated to remove unnecessary droplets. For example, in the case of the ESI method, in order to reduce unnecessary droplets, it is common to promote vaporization of the solution and improve ionization efficiency by combining electrostatic spraying by applying a high voltage from the power supply 9 and gas spraying.

[0016] Although it depends on the flow rate of the sample solution (generally in the range of nL / min to mL / min), the gas flow rate is around 0.5 to 10 L / min, and inert gases such as nitrogen or argon are typically used.

[0017] To further improve ionization efficiency, it is common to use a method in which the space into which the ions or droplets are sprayed is heated with a heating gas (up to about 800°C). The flow rate of the heating gas is about 0.5 to 50 L / min, and inert gases such as nitrogen and argon are generally used.

[0018] The inside of the vacuum vessel 4 may be divided into a plurality of vacuum chambers 11, 12, and 13 as shown in Fig. 1. In that case, the vacuum chambers 11, 12, and 13 are connected to each other through small-diameter holes 14 and 15. The hole 8 in the introduction electrode 7 and these holes 14 and 15 are paths for ions, and a voltage may be applied to each member having a hole. In that case, it is preferable to insulate the vacuum vessel 4 and other housing parts via an insulator (not shown) or the like.

[0019] The diameter of holes 8, 14, 15 is generally a few mm or less (for example, 10 mm or less). Vacuum chambers 11, 12, 13 are evacuated by vacuum pumps 16, 17, 18, respectively, and generally maintained at several hundred to several thousand Pa (for example, 100 to 10,000 Pa), several Pa (for example, 1 to 10 Pa), and 0.1 Pa or less, respectively.

[0020] The mass spectrometer 1 includes an ion guide 19. The ion guide 19 is installed in a vacuum chamber 11. The vacuum chamber 12 includes an ion transport section 20 that focuses and transmits ions in the same manner as the ion guide 19. The ion transport section 20 may be a multipole ion guide, an electrostatic lens, an ion funnel, or the like.

[0021] A high frequency voltage, a direct current voltage, an alternating current voltage, or a combination of these voltages is applied from a power source 9 to the ion guide 19 and the ion transport section 20. The number of vacuum chambers may be more or less than three (FIG. 1). For example, another vacuum chamber may be provided between the vacuum chambers 11 and 12, and this may be kept at about several hundred Pa (for example, 100 to 1000 Pa), in which another ion transport section, etc. may be disposed.

[0022] The mass analysis section 3 includes an ion analysis section 21 and a detector 22. The ion analysis section 21, which separates and dissociates ions, may use an ion trap, a quadrupole filter electrode, a collision cell, a time-of-flight mass spectrometer (TOF), or a combination of these. Ions that have passed through the ion analysis section 21 are detected by the detector 22. The detector 22 may use an electron multiplier, a multichannel plate (MCP), or the like.

[0023] The ions detected by the detector 22 are converted into electric signals, etc., and information such as the mass and intensity of the ions can be analyzed in detail by the control unit 10. The control unit 10 also includes an input / output unit and memory for receiving instructions from the user and controlling the voltage, etc., and also has software required for power supply operation, etc. The voltage supplied from the power supply 9 to the mass analysis unit 3 can be a radio frequency voltage, a direct current voltage, an alternating current voltage, or a combination of these.

[0024] In the configuration of FIG. 1, a counter electrode 23 is disposed in front of the introduction electrode 7. By flowing gas between the introduction electrode 7 and the counter electrode 23 and spraying it from the hole 24 of the counter electrode 23, it is possible to prevent noise components such as excess droplets sprayed by the ion source 2 from entering the hole 8 of the introduction electrode 7. The gas flow rate is about 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used. The diameter of the hole 24 of the counter electrode 23 is generally several mm or less (for example, 10 mm or less), and the applied voltage is generally a maximum of about ± several kV (for example, an amplitude of 10 kV or less).

[0025] The ion guide 19 of this embodiment will be described in detail with reference to Figures 2 to 7. Figures 2 and 3 are views of the ion guide 19 as seen from the ion inlet direction (the left side of Figure 1), and Figure 4 is a cross-sectional view taken along the line AA in Figure 2. Figures 2 and 3 are views showing the same configuration, but in order to prevent the figures from becoming too complicated, the symbols shown have been made to be as clear as possible.

[0026] The ion guide 19 of this embodiment includes a plurality of plate electrodes 25. The plurality of plate electrodes 25 are stacked at intervals in a stacking direction (X direction) perpendicular to the ion traveling direction (Z direction). In this embodiment, the perpendicular angle is ideally 90 degrees, but does not need to be strictly 90 degrees in consideration of the accuracy of parts and assembly. For example, from the viewpoint of efficient ion transport, the "stacking direction (X direction) perpendicular to the ion traveling direction (Z direction)" is preferably a direction that forms an angle within a range of 75 degrees to 105 degrees with respect to the Z direction, more preferably a direction that forms an angle within a range of 80 degrees to 100 degrees with respect to the Z direction, and even more preferably a direction that forms an angle within a range of 85 degrees to 95 degrees with respect to the Z direction, as shown in FIG. 6.

[0027] Both the thickness of the plate electrodes 25 and the lamination interval between the plate electrodes 25 are preferably several mm or less (for example, 10 mm or less). The ion guide 19 of this embodiment is composed of a total of 28 plate electrodes 25, 25-1 to 25-28.

[0028] The stacked plate electrodes 25 form an internal space 29 of the ion guide 19. Ions travel through the internal space 29 from the inlet side (negative side in the Z direction) of the ion guide 19 to the outlet side (positive side in the Z direction).

[0029] The definition of the "propagation direction of ions" representing the Z direction can be appropriately determined by those skilled in the art. For example, if an ion (particularly an ion reaching the detector 22; its trajectory may be calculated statistically) propagates in the same direction immediately before entering the internal space 29 of the ion guide 19, while propagating through the internal space 29, and immediately after escaping from the internal space 29, that direction is the propagating direction of the ion.

[0030] On the other hand, if the direction of travel of the ion is different (not strictly parallel) immediately before entering the internal space 29, while traveling through the internal space 29, and immediately after escaping from the internal space 29, it is possible to define any one of these as the direction of travel of the ion (whichever direction is defined as the direction of travel, the effect of this embodiment can be obtained at least partially).

[0031] Alternatively, for example, the direction connecting the center of hole 8 in introduction electrode 7 and the center of hole 14 may be defined as the traveling direction of ions.

[0032] An AC voltage (e.g., a high-frequency voltage) and a DC voltage are applied to the plate electrodes 25-1 to 25-28 by the power source 9. In particular, the power source 9 is capable of applying high-frequency voltages of opposite phases between adjacent plate electrodes 25 in the stacking direction. That is, a high-frequency voltage of the same phase is applied to every other electrode, and a high-frequency voltage of opposite phase is applied to adjacent plate electrodes therebetween. For simplicity, the phases are indicated by plus (+) and minus (-) in FIG. 2.

[0033] The ion guide 19 of this embodiment is characterized in that high frequency voltages of opposite phases are applied between the plate electrodes facing each other above and below (Y direction). Note that (+) and (-) may be reversed from the example shown in the figure.

[0034] The high frequency voltage is set to a maximum frequency of about several MHz (for example, 10 MHz or less) and a maximum voltage amplitude of about several kV (for example, 10 kV or less).The DC voltage is set to a maximum of several hundred V (for example, 1 kV or less).

[0035] Another feature of this embodiment is that, as shown in Fig. 5, some of the plate electrodes 25 have an inclined surface 26 inclined with respect to the ion traveling direction (Z direction) in the portion facing the internal space 29. Among the plate electrodes 25, those having the inclined surface 26 (in this embodiment, the plate electrodes 25-2 to 25-13 and 25-16 to 25-27) are particularly called "inclined plate electrodes." At least two of the plate electrodes 25 (in this embodiment, 24 electrodes) are such inclined plate electrodes.

[0036] 5 shows the shape of a plate electrode 25-18 as an example of an inclined plate electrode. An inclined surface 26 is defined by an inclination start point 27 on the entrance side and an inclination end point 28 in the Z direction. That is, each inclined plate electrode has an inclination start point 27 where the inclined surface 26 starts on the end face on the entrance side (negative side in the Z direction). Also, each inclined plate electrode has an inclination end point 28 where the inclined surface 26 ends in a portion facing an internal space 29.

[0037] The plate electrode 25 can be produced by machining a metal plate by milling, punching, laser machining, wire-cut electric discharge machining, or the like.

[0038] A feature of the ion guide 19 of this embodiment is that the position (i.e., Y coordinate) of the inlet side tilt start point 27 in the direction (Y direction) perpendicular to both the ion traveling direction (Z direction) and the stacking direction of the plate electrodes 25 (X direction) is different between adjacent plate electrodes (for simplicity, in FIG. 2, the tilt start point 27 is shown only in the lower left 1 / 4 part). That is, for at least two inclined plate electrodes adjacent to each other in the stacking direction of the plate electrodes 25, the positions of the tilt start points 27 in the direction (Y direction) perpendicular to both the ion traveling direction and the stacking direction of the plate electrodes 25 are different.

[0039] Another feature of the ion guide 19 of this embodiment is that the tilt end points 28 in the Z direction also differ between adjacent plate electrodes (for simplicity, in FIG. 4, the tilt start point 27 and tilt end point 28 are shown only in the portion corresponding to the lower left 1 / 4 portion of FIG. 2). That is, for at least two inclined plate electrodes adjacent in the stacking direction of the plate electrodes 25, the positions of the tilt end points 28 in the ion traveling direction (i.e., the Z coordinate) are different. In this embodiment, the more outer the electrode is in the X direction, the closer the tilt start point 27 is to the X axis and the closer the tilt end point 28 is to the inlet side.

[0040] A plurality of plate-like electrodes 25 form an inscribed shape 30 and an inscribed shape 31 by connecting the inner contact points of the electrodes on the inlet side and outlet side of the internal space 29. In this embodiment, the inscribed shape 30 on the inlet side and the inscribed shape 31 on the outlet side are approximate circles (i.e., shapes that are approximate to a circle, and may be perfect circles).

[0041] The positional relationship between the inclination start point 27 and the inclination end point 28 of each inclined plate electrode is not limited to that shown in this embodiment, and can be modified as desired. If the Y-direction position of the inclination start point 27 of each inclined plate electrode changes according to a monotonically changing function in the broad sense from the outside to the inside in the stacking direction of the plate electrodes 25, the inscribed shape 30 on the entrance side can be formed smoothly. For example, in this embodiment, the Y-direction position of the inclination start point 27 increases monotonically from the plate electrode 25-1 to the plate electrode 25-7.

[0042] The mathematical definition of "broadly monotonic change" will be apparent to those skilled in the art, but includes, for example, broadly monotonic increase and broadly monotonic decrease. Broadly monotonic increase means either increasing or not changing (i.e., not decreasing), and broadly monotonic decrease means either decreasing or not changing (i.e., not increasing).

[0043] In the ion guide 19 of this embodiment, a gap 32 is provided between the plate electrodes facing each other above and below (in the Y direction), so that a total of 28 plate electrodes 25 (the number of plate electrodes that effectively contribute to the formation of a multipole electric field) are inscribed in the inscribed shape 30 (approximate circle) on the entrance side, and a total of 12 plate electrodes 25 (25-5 to 25-10 and 25-19 to 25-24) are inscribed in the inscribed shape 31 (approximate circle) on the exit side.

[0044] By applying a high frequency voltage from the power source 9, a multipole electric field is formed in the internal space 29. In particular, a 28-pole electric field is formed on the entrance side of the internal space 29, and a 12-pole electric field is formed on the exit side. Ions are transported efficiently by such a multipole electric field.

[0045] 6 and 7 show perspective views of the lower left quarter portion of Fig. 2 and Fig. 3. Fig. 6 and Fig. 7 show the same configuration, but in order to prevent the figures from becoming too complicated, the symbols shown have been made to be as minimally overlapping as possible.

[0046] The positions of the inlet-side inclination start point 27 and the Z-direction inclination end point 28 are different and offset between adjacent plate electrodes, so that the inscribed shape gradually becomes smaller from the inscribed shape 30 on the inlet side toward the inscribed shape 31 on the outlet side, forming an internal space 29 that approximates a tapered shape. A total of 24 plate electrodes 25 (25-2 to 25-13 and 25-16 to 25-27), 20 (25-3 to 25-12 and 25-17 to 25-26), and 16 (25-4 to 25-11 and 25-18 to 25-25) are inscribed in the inscribed shapes 34, 35, 36 (approximate circles) at the three Z-direction inclination end points 28, respectively.

[0047] That is, the inclined surface 26 of the plate electrode 25 gradually narrows the internal space 29 along the ion travel direction. In addition, the gap between the plate electrodes facing each other above and below (Y direction) narrows to gap 32, and the electric fields of the four electrodes on the outside are blocked, so that the number of multipoles of the electric field is reduced by four at the end point 28 of the inclination in the Z direction. That is, the number of plate electrodes that effectively contribute to the formation of the multipole electric field and the number of multipoles of the multipole electric field are smaller on the exit side than on the entrance side. As a result, the number of multipoles can be reduced stepwise from the entrance side to the exit side of the ion guide 19, from the 28-pole electric field to the 24-pole electric field to the 20-pole electric field to the 16-pole electric field to the 12-pole electric field. In addition, the area of ​​the inscribed shape of the plate electrodes that form the multipole electric field is smaller on the exit side than on the entrance side. This makes it possible to further increase the convergence efficiency of the ions.

[0048] With this configuration, the ion capture efficiency can be increased by increasing the number of quadrupoles on the inlet side, and the ion convergence efficiency (generally higher as the number of quadrupoles is smaller) can be gradually increased by gradually decreasing the number of quadrupoles, thereby improving the ion transmittance in the ion guide 19. Note that the plate electrodes 25 may include electrodes that are not inclined plate electrodes (i.e., electrodes that do not have the inclined surface 26; for example, 25-1, 25-14, 25-15, 25-18, etc.).

[0049] The configurations of the ion guide 19 and mass spectrometer 1 according to the first embodiment described above make it possible to achieve both high ion capture efficiency and high ion focusing efficiency.

[0050] The ion guide 19 can be disposed in another vacuum chamber such as the vacuum chamber 12 other than the vacuum chamber 11 described above. For example, instead of the ion transport section 20, an ion guide having the same or similar configuration as the ion guide 19 may be used.

[0051] (Example 2) (upper and lower phases) In the second embodiment, a configuration of an ion guide in which radio frequency voltages of the same phase are applied between opposing plate electrodes will be described.

[0052] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 8. For simplicity, the description of parts common to the first embodiment may be omitted. This embodiment is characterized in that high-frequency voltages of the same phase are applied between the plate electrodes facing each other above and below (Y direction). Note that (+) and (-) may be reversed from the example shown in the figure.

[0053] When applying high frequency voltages of opposite phases between the upper and lower opposing plate electrodes 25 as in Example 1, the electric field in the internal space 29 may be disturbed near the position where the number of quadrupoles decreases in the Z direction due to the influence of a multipole electric field (quadrupole electric field) formed between the plate electrodes 25 constituting the internal space 29 and the plate electrodes 25 on the outside of the internal space 29. On the other hand, in the configuration in which high frequency voltages of the same phase are applied between the upper and lower opposing plate electrodes 25 as in this embodiment, a multipole electric field is not formed on the outside, which has the advantage of reducing disturbance of the electric field.

[0054] In the configuration of Fig. 8, the plate electrodes 25-1 and 25-15 are in phase (same potential) with each other, and the plate electrodes 25-14 and 25-28 are in phase (same potential) with each other and are regarded as one electrode, so the number of pupoles is different even though the configuration has the same number of electrodes as Fig. 2. For example, from the entrance side to the exit side of the ion guide 19, the number of pupoles is 26-pole electric field → 22-pole electric field → 18-pole electric field → 14-pole electric field → 10-pole electric field, which is two less for each field compared to Example 1.

[0055] The configuration of the embodiment 2 described above provides the same effects as those of the embodiment 1. In particular, it is effective in reducing electric field disturbances in the quadrupole number reduction portion.

[0056] (Example 3) (Top and bottom single plate) In the third embodiment, an ion guide configuration in which a radio frequency voltage of the same phase is applied between opposing plate electrodes, including a configuration in which the opposing plate electrodes are formed as an integrated part, will be described.

[0057] The ion guide 19 of this embodiment will be described in detail with reference to Figs. 9 and 10. For simplicity, explanations of parts common to the previous embodiment may be omitted. This embodiment is characterized in that high-frequency voltages of the same phase are applied between plate electrodes facing each other above and below (Y direction), and some of the facing electrodes are constructed as integrated parts (25-1 to 25-4, 25-11 to 25-14). Note that (+) and (-) may be reversed from the example shown in the figure.

[0058] In this embodiment, the number of plate electrodes 25 is 20 in total (25-1 to 25-20), which makes it possible to reduce the number of parts compared to the second embodiment, and also makes it possible to obtain substantially the same effects as the second embodiment.

[0059] The configuration of the embodiment 3 described above also provides the same effects as those of the embodiments 1 and 2. In particular, it is effective in reducing costs by reducing the number of parts.

[0060] (Example 4) (Inscribed shape is square) In the fourth embodiment, a configuration in which the inscribed shape of the ion guide is a square will be described.

[0061] The ion guide 19 of this embodiment will be described in detail with reference to Fig. 11. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment is characterized in that the inscribed shapes 30 and 31 are approximated to squares.

[0062] In a configuration in which the inscribed shapes 30 and 31 are approximately circular as described in each of the above-mentioned embodiments (for example, FIG. 3), the distance in the Y direction between adjacent pairs of plate-like electrodes on the electrode surfaces that form the internal space 29 (more precisely, the edges that form the inscribed shape of each plate-like electrode 25, which appear, for example, as the points that form the inscribed shapes 30 and 31) tends to be wider the further out in the X direction the electrode pairs are.

[0063] In adjacent plate-like electrode pairs, when the distance between the electrode surfaces that form the electric field becomes wider (for example, on the outer side in the X direction), the electric field becomes relatively weaker than in areas where the distance between the electrode surfaces is narrower (for example, on the inner side in the X direction), and the overall multipole electric field becomes distorted. In contrast, if the inscribed shapes 30 and 31 are square as shown in Figure 11, it is possible to make the distance between the electrode surfaces in adjacent plate-like electrode pairs almost constant, and a highly symmetrical multipole electric field can be formed.

[0064] The configuration of the above-described embodiment 4 also provides the same effects as those of embodiment 1. It is particularly effective in forming a highly symmetric multipole electric field.

[0065] In the fourth embodiment, the inscribed shapes 30 and 31 are squares, but as a modified example, they may be rhombuses, ordinary rectangles, or other polygons.

[0066] (Example 5) (Inscribed shape is ellipse) In the fifth embodiment, a configuration in which the inscribed shape of the ion guide is an ellipse will be described.

[0067] The ion guide 19 of this embodiment will be described in detail with reference to Fig. 12. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment is characterized in that the inscribed shapes 30 and 31 are approximated to an ellipse, and similarly to the fourth embodiment, the distance (Y direction) between the electrode surfaces that form the electric field with the adjacent plate electrodes can be narrowed even for electrodes located further outward in the X direction, and the electric field can be prevented from being locally weakened.

[0068] The configuration of the embodiment 5 described above can provide the same effects as those of the embodiment 1. In particular, it is effective in preventing the electric field from being locally weakened.

[0069] (Example 6) (Eccentricity) In the sixth embodiment, a configuration in which the center of gravity positions on the entrance side and the exit side of the ion guide are offset will be described.

[0070] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 13. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment is characterized in that the centers of gravity of the inscribed shapes are eccentric between the inscribed shape 30 on the entrance side and the inscribed shape 31 on the exit side. In the example of FIG. 13, the center of gravity of the inscribed shape 31 on the exit side is eccentric to the exit center of gravity position 37 (positive side of the Y direction from the X axis) relative to the center of gravity position (on the X axis) of the inscribed shape 30 on the entrance side.

[0071] In this embodiment, since both the inscribed shape 30 and the inscribed shape 31 are circular, the center of gravity is the center of the circle.

[0072] In this embodiment, the Z axis (the traveling direction of the ions) can be, for example, the direction in which the ions traveled immediately before entering the internal space.

[0073] Generally, if liquid droplets other than ions flow into the vacuum due to insufficient vaporization in the ion source 2, this not only becomes a source of noise but also leads to deterioration of the detector 22 and contamination of the ion analysis section 21, so it is desirable to remove these as early as possible.

[0074] Since droplets other than ions are not affected by the electric field, they tend to go straight when they flow into the vacuum with the airflow. Therefore, if the center of gravity of the inscribed shape 30 on the inlet side and the inscribed shape 31 on the outlet side of the ion guide 19 are eccentric as in this embodiment, contaminants such as droplets go straight, and only ions affected by the electric field are deflected toward the outlet center of gravity position 37. By aligning the outlet center of gravity position 37 with the center position of the hole 14 (see FIG. 1) in the subsequent stage, droplets can be eliminated and only ions can be introduced into the subsequent ion transport section 20. This makes it possible to prevent deterioration of the detector 22 and contamination of the ion analysis section 21.

[0075] The configuration of the embodiment 6 described above also provides the same effects as those of the embodiment 1. It is particularly effective in achieving a highly robust mass spectrometer.

[0076] (Example 7) (The spacing between the upper and lower electrodes is misaligned) In the seventh embodiment, a configuration of an ion guide in which the space between opposing plate electrodes is shifted in the Y direction will be described.

[0077] The ion guide 19 of this embodiment will be described in detail with reference to Fig. 14. For simplicity, the description of parts common to the first embodiment may be omitted. This embodiment is characterized in that the position of the gap 32 between the plate electrodes facing each other above and below (Y direction) is shifted in the Y direction between adjacent electrodes.

[0078] By shifting the Y-direction position of the gap 32 between the electrodes, even in a configuration in which high-frequency voltages of opposite phases are applied above and below as in Example 1, it is possible to reduce the influence of the multipole electric field (quadrupole electric field) formed between the outer plate electrode near the position where the number of quadrupoles is reduced.

[0079] The above-described configuration of the seventh embodiment also provides the same effects as those of the first embodiment, and is particularly effective in reducing electric field disturbances in the portion where the number of quadrupoles is reduced.

[0080] (Example 8) (Lamination direction: two directions) In the eighth embodiment, a configuration of an ion guide having plate electrodes stacked in multiple directions will be described.

[0081] The ion guide 19 of this embodiment will be described in detail with reference to Fig. 15. For simplicity, the description of parts common to the first embodiment may be omitted.

[0082] In the ion guide 19 of the present embodiment, the basic configuration in which a plurality of plate electrodes 25 are stacked at intervals in a stacking direction perpendicular to the ion traveling direction (Z direction) is the same as in the first embodiment.

[0083] A difference from the first embodiment is that the present embodiment has two stacking directions (the X direction and the Y direction in the example of FIG. 15). That is, the present embodiment includes a plate electrode group 25a stacked in the X direction and a plate electrode group 25b stacked in the Y direction.

[0084] By stacking in two directions, it is possible to reduce the change in the electrode surface distance between adjacent plate electrodes, as in Example 4 (Figure 11), and a highly symmetric multipole electric field can be formed.

[0085] The configuration of the above-described embodiment 8 also provides the same effects as those of embodiment 1. It is particularly effective in forming a highly symmetric multipole electric field.

[0086] (Example 9) (Upper and lower electrodes are misaligned) In the ninth embodiment, a configuration of an ion guide in which the positions of upper and lower plate electrodes are shifted will be described.

[0087] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 16. For simplicity, the description of parts common to the first embodiment may be omitted. This embodiment is characterized in that the X-direction positions of the plate electrodes 25 are shifted between the top and bottom (Y direction). For example, the X-direction positions of each plate electrode are different between the plate electrode group 25c on the positive side of the Y direction and the plate electrode group 25d on the negative side of the Y direction.

[0088] In this configuration, similarly to the seventh embodiment (FIG. 14), even in a configuration in which high-frequency voltages of opposite phases are applied above and below, it is possible to reduce the influence of the multipole electric field (quadrupole electric field) formed between the outer electrode and the position where the number of quadrupoles is reduced.

[0089] The above-described configuration of the ninth embodiment also provides the same effects as those of the first embodiment, and is particularly effective in reducing electric field disturbances in the quadrupole number reduction portion.

[0090] (Example 10) (Different plate thickness) In Example 10, an ion guide configuration including plate electrodes of different thicknesses is described. The ion guide 19 of this embodiment will be described in detail with reference to Fig. 17. For simplicity, the description of parts common to the previous embodiment may be omitted.

[0091] This embodiment is characterized in that the thickness of the plate electrode 25 differs between the inside and outside in the X direction. In the example of Fig. 17, the thickness T2 of the outer plate electrode 25 is thinner than the thickness T1 of the inner plate electrode 25.

[0092] This allows the layers to be denser toward the outside, so that, similarly to Example 5, even for plate electrodes located further out in the X direction, the electrode surface distance (distance in the Y direction) that forms the electric field between adjacent plate electrodes can be narrowed, preventing the electric field from being weakened locally.

[0093] It is sufficient if there is at least one combination in which the thickness of the plate electrodes 25 is different between the inside and outside. Also, the thickness may decrease stepwise or monotonically from the inside to the outside, or all the plate electrodes 25 may have different thicknesses.

[0094] The configuration of the embodiment 10 described above can provide the same effects as those of the embodiment 1. In particular, it is effective in preventing the electric field from being locally weakened.

[0095] (Example 11) (Different stacking gaps) In the eleventh embodiment, a configuration of an ion guide having different stacking intervals of plate electrodes will be described.

[0096] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 18. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment is characterized in that the lamination intervals of the plate electrodes 25 are different between the inside and outside in the X direction. In the example of FIG. 18, the lamination interval G2 of the outer plate electrodes 25 is narrower than the lamination interval G1 of the inner plate electrodes 25, and the laminations become denser especially toward the outside.

[0097] As a result, as in the tenth embodiment, in the electrodes located further outward in the X direction, the distance between the electrode surfaces that form the electric field between adjacent plate electrodes can be narrowed, thereby preventing the electric field from being weakened locally.

[0098] It is sufficient if there is at least one combination in which the lamination intervals of the plate electrodes 25 are different between the inside and the outside. The lamination intervals may be decreased stepwise or monotonically from the inside to the outside, or the plate electrodes 25 may all be laminated at different intervals. In some cases, it may be more effective to use this in combination with the configuration of the plate electrodes 25 of Example 10 in which the plate thickness is not constant (Example 10, FIG. 17).

[0099] The above-described configuration of the eleventh embodiment can provide the same effects as those of the first embodiment, particularly the effect of preventing the electric field from being locally weakened.

[0100] (Example 12) (Inclined surface is curved) In the twelfth embodiment, a configuration of an ion guide in which the inclined surface of a plate electrode is a curved surface will be described.

[0101] The ion guide 19 of this embodiment will be described in detail with reference to Fig. 19. For simplicity, the description of parts common to the above-mentioned embodiments may be omitted. In the above-mentioned embodiments, the inclined surface 26 of the plate electrode 25 is flat, whereas this embodiment is characterized in that the inclined surface 26 is curved (for example, the cross section of the inclined surface 26 viewed from the direction shown in Fig. 19 is curved).

[0102] This makes it possible to make the change in the multipole electric field in the vicinity of the position where the number of multipoles decreases gentler, thereby reducing the disturbance of the electric field in this vicinity.

[0103] The shape of the inclined surface 26 is not limited to the planar shape described above or the curved shape of this embodiment, but may include a planar portion perpendicular or parallel to the ion traveling direction (Z direction), may be a composite shape including an inclined plane, a curved surface, and a plane perpendicular or parallel to the Z direction, or may be a shape that changes in stages, and various shapes can be used.

[0104] The above-described configuration of the embodiment 12 provides the same effects as those of the embodiment 1. In particular, it has the effect of reducing local disturbances in the electric field.

[0105] (Example 13) (Reduction in surface area of ​​plate-shaped electrodes) In the thirteenth embodiment, a configuration of an ion guide capable of reducing the surface area of ​​a plate electrode will be described.

[0106] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 20. For simplicity, explanations of parts common to the above-mentioned embodiments may be omitted. As explained in the above-mentioned embodiments, when metal plate electrodes 25 are stacked closely together, the electric capacitance between the plate electrodes becomes large, making it difficult to manufacture the power supply 9 for applying the high frequency voltage. The electric capacitance is proportional to the proximity area and inversely proportional to the proximity distance.

[0107] In this embodiment, the surface area of ​​the plate electrode 25 is reduced by the holes 38 cut out (for example, over as wide an area as possible) in the plate electrode 25, thereby realizing a reduction in the capacitance. The holes 38 are formed, for example, as holes penetrating the plate electrode 25 in the stacking direction.

[0108] The above-described configuration of the thirteenth embodiment provides the same effects as those of the first embodiment, particularly the effect of suppressing the electric capacitance between the electrodes.

[0109] (Example 14) (Insulator and Conductor Layer) In the fourteenth embodiment, a configuration of an ion guide made of a plate electrode having a conductor layer on the surface of an insulating base material will be described.

[0110] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 21. For simplicity, the description of parts common to the above-mentioned embodiments may be omitted. The plate electrode 25 described in the above-mentioned embodiments may be entirely made of metal, whereas the plate electrode 25 of this embodiment is characterized in that it has a conductor layer 39 (hatched portion in FIG. 21) on the surface of the insulator 25e, which is the base material. That is, the plate electrode 25 includes the insulator 25e and the conductor layer 39 formed on a part of the surface of the insulator 25e.

[0111] The insulator 25e may be made of ceramic or plastic, and the conductor layer 39 may be made of a metal. Methods for forming the conductor layer 39 on the surface of the insulator 25e include vapor deposition, plating, and adhesion.

[0112] In the plate electrode 25 of this embodiment, the surface area of ​​the metal conductor layer 39 can be made very small, so that the electric capacitance between the electrodes can be reduced in the same manner as in the thirteenth embodiment.

[0113] It is preferable to form the conductor layer 39 on the electrode surface of the plate electrode 25 (a surface facing the internal space 29 and perpendicular to the stacking direction, including the inclined surface 26), but by further forming it on the adjacent surfaces (areas that may be hit by ions) as shown in Figure 21, charging up of the insulator 25e can be prevented.

[0114] The above-described configuration of the embodiment 14 also provides the same effects as those of the embodiment 1. In particular, it has the effect of suppressing the electric capacitance between the electrodes.

[0115] (Example 15) (Multiple DC Voltages) In the fifteenth embodiment, a configuration of an ion guide in which different DC voltages are applied to the inside and outside of a plate electrode will be described.

[0116] The ion guide 19 of this embodiment will be described in detail with reference to Fig. 22. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment has a feature in which different DC voltages are applied to the inner and outer plate electrodes 25 in the X direction.

[0117] For example, for negative ions, by making the outer DC voltage V2 higher than the inner DC voltage V1, it is expected that the ions will be collected toward the center on the X-axis. Note that it is sufficient if there is at least one combination in which the DC voltages on the inside and outside are different. It is also possible to apply different DC voltages to the plate electrodes 25, such as increasing the voltage stepwise or monotonically from the inside to the outside.

[0118] The configuration of the embodiment 15 described above also provides the same effects as those of the embodiment 1. In particular, it has the effect of focusing ions at the center of the ion guide.

[0119] In addition to or instead of making the DC voltage different in the X direction as in Example 15, the DC voltage may be made different in the up and down direction (Y direction). This makes it possible to deflect ions in the Y direction, and is particularly effective as an auxiliary function when deflecting ions as in Example 6.

[0120] (Example 16) (Airflow cover) In the sixteenth embodiment, a configuration of an ion guide having a cover for suppressing outflow of air currents on the outer side of a plate electrode will be described.

[0121] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 23. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment is characterized by having a cover 40 that suppresses the outflow of airflow on the outer side of the plate electrode 25 in the X direction. This makes it possible to suppress the outflow of excessive airflow from the ion guide 19, and as a result, it is possible to prevent ions from riding on the airflow and flowing out of the ion guide 19, leading to high sensitivity.

[0122] The cover 40 may be formed as an integral part with the outermost plate electrode 25. Although an example in which the cover 40 is provided in the X direction is shown in Fig. 23, the cover 40 may be provided on the outside in the Y direction, or may be provided in both the X and Y directions.

[0123] The configuration of the above-described embodiment 16 also provides the same effects as those of embodiment 1. It is particularly effective in increasing sensitivity.

[0124] (Example 17) (Diagonal arrangement) In the seventeenth embodiment, a configuration in which the lamination direction of the plate electrodes is inclined with respect to the X direction will be described.

[0125] The ion guide 19 of this embodiment will be described in detail with reference to FIG. 24. For simplicity, the description of parts common to the previous embodiment may be omitted. This embodiment is characterized in that the lamination direction of the plate electrodes 25 is inclined by θ [degrees] (however, θ≠0) with respect to the X direction. In other words, the plate electrodes 25 are laminated in a direction that forms an angle of 90-θ [degrees] with respect to the Z direction.

[0126] When θ>0, the entrance side of the internal space becomes wider, and when θ<0, the exit side of the internal space becomes wider. Under the condition of θ>0, the entrance side becomes wider, which is expected to expand the ion introduction area and improve the introduction efficiency into the ion guide 19. On the other hand, under the condition of θ<0, the exit side becomes wider, which is expected to reduce collisions of ions and airflow with the plate electrode 25 and reduce ion loss due to collisions.

[0127] If the absolute value of θ is too large, the distance between the plate electrodes 25 at the center will be too great and the electric field will be weak, so it is desirable to keep it within the range of -15≦θ≦15 (i.e., stacking in a direction that forms an angle within the range of 75 degrees to 105 degrees with respect to the Z direction), more desirable to keep it within the range of -10≦θ≦10 (i.e., stacking in a direction that forms an angle within the range of 80 degrees to 100 degrees with respect to the Z direction), and even more desirable to keep it within the range of -5≦θ≦5 (i.e., stacking in a direction that forms an angle within the range of 85 degrees to 95 degrees with respect to the Z direction).

[0128] The configuration of the embodiment 17 described above also provides the same effects as those of the embodiment 1. In particular, there is an effect of improving the ion introduction efficiency or reducing the ion loss due to collision.

[0129] The ion guide of the present invention is not limited to those according to the above-mentioned embodiments 1 to 17. For example, in addition to the inscribed shapes described above, various shapes (for example, a circular inlet side and a square outlet side, etc.) can be realized according to the inclined surface of the plate-shaped electrode. Therefore, it is possible to deal with ion guides with inscribed shapes of various patterns.

[0130] The same effects can be obtained with the device configurations of the embodiments described above in which the characteristic elements of each device configuration are combined.

[0131] The ion guide with stacked plate electrodes can be modularized by using spacer parts that can maintain the stacking interval and pin parts that determine the positional relationship between the plate electrodes, and then fixing means such as screws. It can also be assembled using an assembly jig. It can also be fixed by directly attaching the plate electrodes to base parts (holders, etc.) or electric circuit boards (for applying high-frequency voltages or direct current voltages) by welding or adhesive. In addition to the method of assembling plate electrodes with inclined surfaces formed in advance, it is also possible to assemble without inclined parts and then post-machine the tapered shape inside the ion guide by wire-cut electric discharge machining or die electric discharge machining. [Explanation of symbols]

[0132] 1...Mass spectrometer 2…Ion source 3...Mass spectrometry section 4...Vacuum container 5…Ion generation section 6…Ion source chamber 7...Introduction electrode 8…hole 9…Power supply 10...Control section 11~13…Vacuum chamber 14~15…holes 16~18…Vacuum pump 19…Ion Guide 20…Ion transport section 21…Ion analysis section 22…Detector 23...Counter electrode 24…holes 25…Plate electrode 25a to 25d: Plate-shaped electrode group 25e…Insulator 26…Slope surface 27…Slope starting point 28…Slope end point 29…Interior space 30~31…Inscribed shape 32…interval 34~36…Inscribed shape 37…Exit center position 38…hole 39...Conductor layer 40…Cover

Claims

1. An ion guide in which ions travel through an internal space from an inlet side to an outlet side, The ion guide comprises a plurality of plate electrodes; The plurality of plate-shaped electrodes are stacked at intervals in a stacking direction perpendicular to the direction in which the ions travel, At least two of the plurality of plate electrodes are inclined plate electrodes having an inclined surface inclined with respect to the traveling direction on a portion facing the internal space, Each of the inclined plate electrodes has an inclination starting point at which the inclined surface starts on the end surface on the inlet side, For at least two of the inclined plate electrodes adjacent to each other in the stacking direction, the positions of the inclination start points in a direction perpendicular to both the moving direction and the stacking direction are different.

1. An ion guide comprising:

2. 2. The ion guide of claim 1, Each of the inclined plate electrodes has an inclination end point where the inclined surface ends in a portion facing the internal space, For at least two of the inclined plate electrodes adjacent to each other in the stacking direction, the positions of the inclination end points in the traveling direction are different.

1. An ion guide comprising:

3. 2. The ion guide of claim 1, a power source capable of applying high-frequency voltages of opposite phases between the plate electrodes adjacent to each other in the stacking direction; A multipole electric field is formed in the internal space by applying the high frequency voltage from the power source.

1. An ion guide comprising:

4. 4. The ion guide of claim 3, the number of the plate electrodes effectively contributing to the formation of the multipole electric field and the number of multipoles of the multipole electric field are smaller on the outlet side than on the inlet side; 1. An ion guide comprising:

5. 4. The ion guide of claim 3, an area of ​​an inscribed shape of the plate-like electrodes forming the multipole electric field is smaller on the outlet side than on the inlet side; 1. An ion guide comprising:

6. 4. The ion guide of claim 3, the center of gravity of the inscribed shape of the plate-like electrode forming the multipole electric field is eccentric between the inlet side and the outlet side; 1. An ion guide comprising:

7. 2. The ion guide of claim 1, Each of the plate electrodes includes an insulator and a conductor layer formed on a portion of a surface of the insulator.

1. An ion guide comprising:

8. 2. The ion guide of claim 1, From the outer side to the inner side in the stacking direction, the position of the inclination start point of each of the inclined plate electrodes changes according to a monotonically changing function in a broad sense.

1. An ion guide comprising:

9. 2. The ion guide of claim 1, The lamination direction perpendicular to the traveling direction is a direction that forms an angle with respect to the traveling direction within a range of 75 degrees to 105 degrees.

1. An ion guide comprising:

10. A mass spectrometer comprising an ion guide according to claim 1.

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