Ion guide and mass spectrometer

Abstract

To improve the robustness of an ion guide.SOLUTION: An ion guide is configured by arranging a plurality of columnar rod electrodes 20 in a circular shape, and is characterized in that a concave cutout portion 21 and a convex portion 26 are provided on the side of each rod electrode 20, and the cutout portion 21 of one rod electrode 20 and the convex portion 26 of another rod electrode 20 are fitted together in a non-contact state. It is also characterized in that the rod electrodes 20 are arranged such that the inscribed circle of the rod electrode 20 on an entrance side is larger than the inscribed circle of the rod electrode 20 on an exit side.SELECTED DRAWING: Figure 3A

Description

[Technical field]

[0001] The present invention relates to the art of ion guides and mass spectrometers. [Background technology]

[0002] In a mass spectrometer, ions generated in an ion source are transported to a mass analyzer via an ion transport section. Mass spectrometers using atmospheric pressure ionization transport ions generated under atmospheric pressure to a mass analyzer in a vacuum, so they are generally configured as devices with a differential pumping system 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 upstream of the mass analyzer. To achieve high sensitivity in a mass analyzer, 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. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Pat. No. 1,047,5633 [Non-patent literature]

[0005] [Non-Patent Document 1] “Conical octopole ion guide: Design, focusing, and its application to the deposition of low energetic clusters”, REVIEW OF SCIENTIFIC INSTRUMENTS, 77, 013302, 2006 Summary of the Invention [Problem to be solved by the invention]

[0006] A multipole ion guide (hereinafter referred to as an ion guide) is supported in a vacuum chamber by a holder made of an insulating material. In addition to ions, droplets are introduced into the ion guide, and it is preferable that the droplets are discharged from the ion guide. At this time, the droplets are discharged to the outside through gaps between the rod electrodes constituting the ion guide, and at this time, some of the discharged droplets adhere to the inside of the holder, contaminating the inside of the holder. Then, the voltage that can be applied to the rod electrodes decreases, and even if the same voltage value as before the contamination is applied to the rod electrodes, there is a high possibility that discharge due to the adhered droplets will occur inside the holder. As a result, there is a risk of the analytical performance and stability of the mass spectrometer being deteriorated.

[0007] Patent Document 1 and Non-Patent Document 1 describe that the ion capture efficiency is improved by increasing the number of rod electrodes (number of quadrupoles). Patent Document 1 and Non-Patent Document 1 also describe that the rod electrodes are arranged obliquely along the longitudinal direction of the rod electrodes, so that the internal space of the ion guide is gradually narrowed toward the ion exit side. In this way, the technology described in Patent Document 1 and Non-Patent Document 1 aims to improve the ion focusing efficiency.

[0008] However, these techniques do not disclose any configuration for preventing the inside of the holder from being contaminated by droplets.

[0009] The present invention has been made in view of the above background, and an object of the present invention is to improve the robustness of an ion guide. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the present invention provides an ion guide configured by arranging a plurality of cylindrical rod electrodes in a circular shape, characterized in that a concave portion and a convex portion are provided on a side surface of each of the rod electrodes, and the concave portion of one of the rod electrodes and the convex portion of another of the rod electrodes are fitted together in a non-contact state. Other solutions will be described in the embodiments as appropriate. Effect of the Invention

[0011] According to the present invention, the robustness of the ion guide can be improved. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram showing a configuration of a mass spectrometer used in a first embodiment. [Diagram 2] FIG. 1 shows the configuration of an ion guide equipped with 12 cylindrical rod electrodes. [Figure 3A] FIG. 1 is a diagram (part 1) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 3B] FIG. 2 is a diagram (part 2) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 4] 1A to 1C are a top view, a cross-sectional view, and an arrow view of one of the rod electrodes according to the present embodiment. [Diagram 5] FIG. 2 is a perspective view showing four of the twelve rod electrodes that make up the ion guide. [Figure 6] FIG. 11 is a diagram relating to the gap between adjacent rod electrodes. [Figure 7] FIG. 1 is a diagram (part 1) showing an example of an ion guide provided with a holder. [Figure 8] FIG. 2 is a diagram (part 2) showing an example of an ion guide provided with a holder. [Figure 9] FIG. 4 is a diagram showing another explanation of the features of the ion guide according to the first embodiment. [Figure 10]FIG. 13 shows an ion guide according to a second embodiment. [Figure 11] FIG. 13 shows an ion guide according to a third embodiment. [Figure 12] FIG. 1 shows an ion guide according to a first modified example. [Figure 13A] FIG. 3 is a diagram (part 3) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 13B] FIG. 4 is a diagram (part 4) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 14] FIG. 13 is a diagram showing an ion guide according to a second modified example. [Figure 15A] FIG. 5 is a diagram (part 5) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 15B] FIG. 6 is a diagram (part 6) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 16] FIG. 13 shows an ion guide according to a third modified example. [Figure 17A] FIG. 7 is a diagram (part 7) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 17B] FIG. 8 is a diagram showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 18] FIG. 13 is a diagram showing the configuration of an ion guide according to a fourth embodiment. [Figure 19A] FIG. 9 is a diagram (part 9) showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 19B] FIG. 10 is a diagram showing only one rod electrode among the rod electrodes that make up the ion guide. [Figure 20] FIG. 2 is a perspective view showing two of the four rod electrodes that constitute the ion guide. [Figure 21] FIG. 13 is a diagram showing the configuration of a dodecapole ion guide in which twelve cylindrical rod electrodes are arranged in parallel according to a fifth embodiment. [Figure 22]FIG. 3 is a diagram showing an example of an ion guide provided with a holder (part 3). [Diagram 23] FIG. 13 is a cross-sectional view showing an ion guide according to a sixth embodiment. [Figure 24] FIG. 1 illustrates common features. [Diagram 25] FIG. 2 is a partial enlarged view of a rod electrode that constitutes an ion guide. [Figure 26] FIG. 1 is a diagram (part 1) showing the configuration of an ion guide according to a comparative example. [Figure 27] FIG. 4 is a diagram showing the configuration of an ion guide provided with a holder. [Figure 28] FIG. 2 is a diagram (part 2) showing the configuration of an ion guide according to a comparative example. [Figure 29] FIG. 5 is a diagram showing the configuration of an ion guide provided with a holder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Next, a mode for carrying out the present invention (referred to as an "embodiment") will be described in detail with reference to the drawings as appropriate.

[0014] [First embodiment] In the first embodiment, a 12-pole ion guide 200 configured with 12 rod electrodes 20 (see FIG. 2) provided with a cutout portion 21 that is a recess having a concave and arcuate shape is used in the mass spectrometer 1.

[0015] (Mass spectrometer 1) FIG. 1 is a diagram showing the configuration of a mass spectrometer 1 used in the first embodiment. The mass spectrometer 1 mainly comprises an ion source 100, an ion guide 200, an ion transport device 300, and a mass analysis section 400. The ion guide 200, the ion transport device 300, and the mass analysis section 400 are provided inside a vacuum vessel 130. In Fig. 1, the dashed lines indicate voltage control lines, and the dashed lines indicate control lines through which information is transmitted.

[0016] The ion source 100 is mainly composed of an ion generator 110, an ion source chamber 120, etc. The ion source 100 can use various ionization methods such as electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), etc. The ion generator 110 generates ions from an introduced sample solution Q and sprays the generated ions into the ion source chamber 120.

[0017] When the sample solution Q is ionized and sprayed, many droplets are sprayed in addition to the ions. Therefore, the inside of the ion source chamber 120 is evacuated (symbol E) to remove unnecessary droplets. For example, in the case of the ESI method, electrostatic spraying and spraying of gas in the ion generator 110 are used in combination to reduce unnecessary droplets. This promotes vaporization of the sample solution Q and improves ionization efficiency. The electrostatic spraying is performed by applying a high voltage to the ion generator 110 by the power supply 500. Although it depends on the flow rate of the sample solution Q, the flow rate of the sprayed gas is about 0.5 to 10 L / min. In general, an inert gas such as nitrogen or argon is used as the gas used in the ion generator 110. Incidentally, the flow rate of the sample solution Q is generally in the range of about nL (nanoliter) / min to mL (milliliter) / min. In order to further improve the ionization efficiency, a method is also common in which the internal space of the ion generating device 110, where the ions or droplets are sprayed, is heated with a heating gas (up to about 800°C) or the like. The flow rate of the heating gas is about 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used.

[0018] In addition, in the configuration of FIG. 1, a counter electrode 121 having a hole H1 is disposed in front of the introduction electrode 122. Gas G is introduced from the hole H11 into a space provided between the introduction electrode 122 and the counter electrode 121. This allows the gas G to be introduced between the introduction electrode 122 and the counter electrode 121. As a result, it is possible to prevent noise components such as excess droplets sprayed by the ion source 100 from being introduced into the hole H2 of the introduction electrode 122. The flow rate of the gas G is about 0.5 to 50 L / min, and an inert gas such as nitrogen or argon is generally used. Note that a voltage is also applied to the counter electrode 121 and the introduction electrode 122 by the power source 500, but control lines for the voltage applied to the counter electrode 121 and the introduction electrode 122 are omitted in FIG. 1.

[0019] The ions introduced into the ion source chamber 120 are introduced into a hole H2 provided in the introduction electrode 122 through a hole H1 provided in the counter electrode 121. At this time, the ions move in the direction of the ion generator 110 → the ion source chamber 120 → the hole H1 → the hole H2 due to the electric field generated between the ion generator 110 and the introduction electrode 122. Generally, the diameters of the hole H1 provided in the counter electrode 121 and the hole H2 provided in the introduction electrode 122 are about several mm or less, and the voltage applied to the counter electrode 121 is about ±several kV at maximum. The polarities of the voltages applied to the counter electrode 121 and the introduction electrode 122 are the same.

[0020] The ions are then introduced from hole H2 provided in introduction electrode 122 through ion guide 200 and ion transport device 300 into mass analysis section 400, where they are analyzed. Various voltages are applied to ion source 100 (ion generator 110), ion guide 200, ion transport device 300, and mass analysis section 400 by power supply 500. The timing and voltage value of voltage application by power supply 500 are controlled by control device 600.

[0021] (Ion guide 200, ion transport device 300) As shown in FIG. 1, the inside of the vacuum vessel 130 may be divided into a plurality of vacuum chambers V1 to V3. The vacuum chambers V1 and V2 are electrically connected to each other through a small-diameter hole H3. The vacuum chambers V2 and V3 are electrically connected to each other through a small-diameter hole H4. The holes H2 and the holes H3 and H4 provided in the introduction electrode 122 are paths for ions. A voltage may be applied to the member having the holes H3 and H4. When a voltage is applied to the member having the holes H3 and H4 (and the hole H2), the housing part such as the vacuum vessel 130 and the member having the holes H3 and H4 (and the hole H2) are insulated via an insulator (not shown) or the like. The holes H3 and H4 are generally several mm or less in size.

[0022] The vacuum chambers V1 to V3 are evacuated by vacuum pumps P1 to P3, respectively. As a result, the vacuum chamber V1 is generally maintained at several hundreds to several thousands Pa, the vacuum chamber V2 at several Pa, and the vacuum chamber V3 at 0.1 Pa or less. The vacuum chamber V1 is provided with an ion guide 200 that transmits ions while converging them. The vacuum chamber V2 is provided with an ion transport device 300 that transmits ions while converging them in the same manner as the ion guide 200. The ion transport device 300 may be provided with a multipole ion guide 200, an electrostatic lens, an ion funnel, or the like. A high-frequency voltage, a direct current voltage, an alternating current voltage, or a combination of these voltages is applied from a power source 500 to the ion guide 200 and the ion transport device 300. The number of vacuum chambers V1 to V3 may be more or less than the number shown in FIG. 1. For example, another vacuum chamber maintained at several hundred Pa may be provided between vacuum chamber V1 and vacuum chamber V2, and an ion transport device 300 other than the ion transport device 300 shown in FIG. 1 may be disposed in this vacuum chamber.

[0023] (Mass spectrometry department 400) The mass analysis section 400 is composed of an ion separation device 401, a detection device 402, and the like. The ion separation device 401, which separates and dissociates ions, can be an ion trap, a quadrupole filter electrode, a collision cell, a time-of-flight mass spectrometer (TOF), or a combination thereof. The ions that have passed through the ion separation device 401 are detected by the detection device 402. The detection device 402 can be an electron multiplier tube, a multichannel plate (MCP), or the like. The ions detected by the detection device 402 are converted into an electric signal, and the information on the mass and intensity of the ions can be analyzed in detail by the control device 600. The control device 600 also includes an input / output unit and a memory (not shown) for receiving instructions input from a user and controlling voltages, and also includes software required for operating the power source 500. The voltage supplied from the power source 500 to the mass analysis section 400 can be a high-frequency voltage, a direct current voltage, an alternating current voltage, or a combination thereof.

[0024] In this embodiment, the longitudinal direction of the ion guide 200 is defined as the X-axis, and axes that are perpendicular to the X-axis, pass through the center C of the ion guide 200, and are perpendicular to each other are defined as the Y-axis and Z-axis. In particular, the direction from the ion source 100 to the mass analysis unit 400 is defined as the X-axis, the direction perpendicular to the X-axis and upward of the mass spectrometer 1 is defined as the Z-axis, and the direction perpendicular to the X-axis and Z-axis is defined as the Y-axis.

[0025] (Ion guide 200) (12-pole cylindrical rod electrode 20) Next, the ion guide 200 according to this embodiment will be described in detail with reference to FIGS. 2 is a diagram showing the configuration of an ion guide 200 including 12 (12-pole) cylindrical rod electrodes 20 (20-1 to 20-12). In the following description, an ion guide 200 having n rod electrodes 20 will be referred to as an n-pole ion guide 200. For simplicity, only the rod electrodes 20 are shown in FIG. In FIG. 2, the left diagram Z1 is a view seen from the ion inlet side. In this embodiment, the ion inlet side (or simply the inlet side) is the side of the ion source 100 shown in FIG. 1. Also, the center diagram Z2 in FIG. 2 is a view seen from the side of the ion guide 200. In addition, for simplicity, only the rod electrodes 20-1 and 20-7 are shown in the center diagram Z2 in FIG. 2. Also, the right diagram Z3 in FIG. 2 is a view seen from the ion outlet side (the right side in FIG. 1). In this embodiment, the ion outlet side (or simply the outlet side) is the side of the mass analysis section 400 shown in FIG. 1. 2, a plurality of rod electrodes 20 (20-1 to 20-12) having a columnar shape are arranged in a circle (annularly arranged) with respect to the center C of the ion guide 200. Each rod electrode 20 is arranged to have an angle "θ" in the longitudinal direction. The angle "θ" will be described later.

[0026] 3A and 3B are diagrams showing only one rod electrode 20 (20-1) among the rod electrodes 20 constituting the ion guide 200 shown in Fig. 2. Fig. 3A is a diagram showing the rod electrode 20 from the ion inlet side, and Fig. 3B is a diagram showing the rod electrode 20 from the ion outlet side.

[0027] As shown in FIG. 3A and FIG. 3B, the rod electrode 20 according to this embodiment is characterized in that the cylindrical rod electrode 20 has a cutout 21, which is a concave and arc-shaped recess, on its side. In addition, a protrusion 26 is provided on the side opposite to the side of the rod electrode 20 on which the cutout 21 is provided. In this way, the cutout 21 (concave) and the protrusion 26 are provided on the side of the rod electrode 20. In FIG. 3A, the shape without the cutout 21 is shown by a dashed line. In this way, the rod electrodes 20-1 to 20-12 having the cutout 21 are arranged at an angle "θ" with respect to the X-axis as shown in FIG. 2, which is a feature of this embodiment. That is, the ion guide 200 according to this embodiment is configured so that the mass spectrometer 1 side (exit side) is reduced in diameter. Incidentally, "θ" is preferably about 10° or less.

[0028] In addition, in order to avoid complication, reference numerals of the notch 21 and the protrusion 26 are omitted in Fig. 2. As shown in Fig. 2 to Fig. 3B, the notch 21 of a certain rod electrode 20 and the protrusion 26 of another rod electrode 20 are fitted together in a non-contact state.

[0029] Fig. 4 shows a top view, a cross-sectional view, and an arrow view of one of the rod electrodes 20 according to this embodiment. When the direction in which the notch 21 is provided is the upper side of the paper of the rod electrode 20, the upper drawing Z4 of Fig. 4 is a view (top view) of the rod electrode 20 seen from above. Moreover, the lower right drawing Z5 of Fig. 4 is an AA cross-sectional view of the rod electrode 20. And the lower left drawing Z6 of Fig. 4 is a view (view of the arrow B) of the rod electrode 20 seen from the arrow B (inclined direction of α°) of the ion guide 200. As shown in FIG. 4, the rod electrode 20 is characterized in that a concave cutout 21 is formed in the shape of a circular arc with a radius of "RC" over the entire length of a cylinder with a diameter (φ) of "D" and a length of "L". The cutout 21 is formed in a state of being inclined at a predetermined angle "α°" with respect to the longitudinal direction of the rod electrode 20 (provided at a predetermined angle). As a result, the cutout 21 is shallow on the entrance side and deep on the exit side. In this way, the thickness of the rod electrode 20 can be changed on the entrance side and the exit side. Even if the twelve rod electrodes 20 are arranged inclined at an angle "θ" with respect to the X-axis as shown in FIG. 2, the ion guide 200 can be assembled without the rod electrodes 20 coming into contact with each other. In other words, even if the rod electrodes 20 are arranged in an inclined manner, the cutout 21 of one rod electrode 20 and the protrusion 26 of another rod electrode can be kept in a non-contact engagement state. It is desirable for "D" to be approximately 10 mm or less, for "L" to be approximately 100 to 300 mm, and for "α°" to be approximately 5° or less.

[0030] 4, in this embodiment, the cutout 21 is formed in the shape of a circular arc with a constant radius "RC" over the entire length of the rod electrode 20. However, as long as a certain amount of gap can be secured without adjacent rod electrodes 20 coming into contact with each other, the shape of the cutout 21 is not important, and as will be described later, the shape of the cutout 21 does not need to be the same over the entire length. The ridge line 22 resulting from the formation of the cutout 21 may be chamfered or arc-chamfered for the purpose of preventing discharge, etc.

[0031] 2, the size of the gap between adjacent rod electrodes 20 depends on the applied voltage value, but is preferably about 0.1 mm to 5 mm. The width of the gap may be configured to be substantially the same from the entrance side to the exit side. Alternatively, the size of the gap may vary from the entrance side to the exit side. This also applies to the embodiments and modifications described below.

[0032] FIG. 5 is a perspective view showing four rod electrodes 20-6 to 20-9 out of the twelve rod electrodes 20 constituting the ion guide 200. The features of the rod electrodes 20 shown in FIGS. 2 to 4 realize an ion guide 200 in which the radius of the inscribed circle gradually decreases from the inscribed circle 23 of the rod electrode 20 on the entrance side to the inscribed circle 24 of the rod electrode 20 on the exit side. That is, the rod electrodes 20 are arranged at an angle "θ" (see FIG. 2) so that the inscribed circle 23 of the rod electrode 20 on the entrance side is larger than the inscribed circle 24 of the rod electrode 20 on the exit side. This makes it possible to gradually narrow the internal space of the ion guide 200 toward the exit side. In this way, by gradually narrowing the internal space of the ion guide 200, the focusing force of the multipole electric field can be gradually strengthened toward the exit side, and ions can be gradually focused near the center C. In addition, during analysis, it becomes possible to exhaust the airflow containing droplets that cause noise from the gaps of the rod electrodes 20 (i.e., to discharge the droplets from the gaps of the rod electrodes 20). In other words, the efficiency of separating the airflow containing droplets from the ions can be improved.

[0033] Next, with reference to FIG. 6, the gap between adjacent rod electrodes 20 will be described. FIG. 6 is a diagram relating to the gap between adjacent rod electrodes 20. As shown in FIG. For simplicity, only the rod electrodes 20-1 and 20-2 are shown in FIG. 6. The dashed-dotted line S connects the centers GC1 to GCn of the rod gaps GA1 to GAn at the same distances "R1" to "Rn" (the respective arcs shown by the dashed lines in FIG. 6) from the center C of the ion guide 200. The ion guide 200 according to this embodiment is characterized in that the dashed-dotted line S is not a straight line. This relationship may exist over the entire length of each rod electrode 20, or may exist in a part of the rod electrode 20 in the longitudinal direction.

[0034] 7 and 8 show an example of an ion guide 200 provided with a holder 210. FIG. A left view Z11 in Fig. 7 is a view of the ion guide 200 in which the holder 210 is provided, viewed from the inlet side. A right view Z12 in Fig. 7 is a side view of the ion guide 200 in which the holder 210 is provided. Fig. 8 is an enlarged view of the rod electrodes 20-1 to 20-2. In Figs. 7 and 8, the same components as those in Figs. 2 to 6 are denoted by the same reference numerals, and the description thereof will be omitted. In the actual ion guide 200, as shown in FIG. 7, the twelve rod electrodes 20 (20-1 to 20-12) are held by the holders 210 (210a, 210b) made of an insulating material, that is, made of an insulating material. As shown in FIG. 7, the holders 210 (210a, 210b) have a shape that contacts each of the rod electrodes 20 and are made of an insulating material. The holders 210 may have any shape as long as they can support the rod electrodes 20. As described above, in the ion guide 200 according to this embodiment, each of the rod electrodes 20-1 to 20-12 is arranged at an incline with respect to the X-axis. Therefore, the holders 210a and 210b made of an insulating material have different inner diameters. That is, the inner diameter of the holder 210a arranged on the entrance side is larger than the inner diameter of the holder 210b arranged on the exit side. As described above, the rod electrodes 20-1 to 20-12 having the concave cutouts 21 (see FIG. 3A, FIG. 3B, etc.) are arranged in a tilted state with respect to the X-axis. In this way, as shown in FIG. 8, when the ion guide 200 is viewed from the inlet side, the contact parts 211a and 211b (the dashed line parts in the left drawing Z11 of FIG. 7) are not visible. The contact parts 211a and 211b are parts where the holder 210 (210a, 210) and the rod electrode 20 are in contact. The contact part 211a is the part where the holder 210a is in contact with the rod electrode 20. Similarly, the contact part 211b is the part where the holder 210b is in contact with the rod electrode 20.

[0035] Since each rod electrode 20 is held by the holder 210, the ion guide 200 can be installed in the vacuum chamber V1 (see FIG. 1) without the rod electrodes 20 being dispersed.

[0036] In particular, as shown in FIG. 8, when the ion guide 200 is viewed from the inlet side, the insulating creeping parts 212a and 212b are invisible. The insulating creeping part 212a is a part of the contact part 211a that corresponds to the gap of the rod electrode 20. Similarly, the insulating creeping part 212b is a part of the contact part 211b that corresponds to the gap of the rod electrode 20. By configuring the insulating creeping parts 212a and 212b to be invisible when the ion guide 200 is viewed from the inlet side, it is possible to improve robustness by preventing contamination. In reality, the contact parts 211a and 211b (and the insulating creeping parts 212a and 212b) have width, but in FIG. 8, they are shown as lines.

[0037] FIG. 9 is a diagram showing another explanation of the features of the ion guide 200 according to the first embodiment. For simplicity, only rod electrodes 20-1 to 20-2 are shown in Fig. 9. A center GC of the rod gap GA at a certain distance "R" (a circular arc shown by a dashed line in Fig. 9) from the center C of the ion guide 200 (see Fig. 2) and a line GL connecting the center C are defined. This embodiment is characterized in that the shapes of adjacent rod electrodes 20 (rod electrodes 20-1 and 20-2 in the example shown in Fig. 9) are asymmetrical with respect to the line GL in the vicinity of the line GL. This relationship may exist over the entire length of the rod electrode 20, or may exist in a part of the longitudinal direction.

[0038] As shown in the first embodiment, the notch 21 of one rod electrode 20 and the protrusion 26 of another rod electrode 20 are fitted together in a non-contact state. In the ion guide 200 having such a configuration, the droplets discharged from the inside of the ion guide 200 to the outside are blocked by the protrusion 26 of the rod electrode 20. This makes it difficult for the droplets to reach the insulating creeping portion 212a.

[0039] The above-described configuration of the ion guide 200 according to this embodiment can prevent the insulating surface portions 212a and 212b of the holder 210 from being contaminated by droplets. This can improve the robustness of the ion guide 200. Furthermore, the improved robustness of the ion guide 200 can increase the diameters of the holes H1 and H2 (see FIG. 1) to increase the amount of ions introduced. This can improve the analytical sensitivity of the mass spectrometer 1 (see FIG. 1).

[0040] The ion guide 200 according to this embodiment can be arranged in other vacuum chambers, such as vacuum chamber V2, in addition to the vacuum chamber V1 shown in FIG.

[0041] Next, modified examples of the ion guide 200 of this embodiment will be described with reference to FIGS.

[0042] [Second embodiment] (Cylindrical rod electrode 20a and octapole ion guide 200a) Next, a second embodiment will be described with reference to FIG. FIG. 10 shows an ion guide 200a according to the second embodiment. In Fig. 10, for simplicity, only the differences from the ion guide 200 shown in Figs. 2 to 9 are explained. In Fig. 10, only the rod electrode 20a is shown for simplicity. The left diagram Z21 in Fig. 10 is a view from the ion inlet direction. Moreover, the center diagram Z22 in Fig. 10 is a view from the side. In the center diagram Z22 in Fig. 10, for simplicity, only the rod electrodes 20a-1 and 20a-5 are shown. And the right diagram Z23 in Fig. 10 is a view from the ion outlet side. FIG. 10 shows an ion guide 200a in which eight (octupole) cylindrical rod electrodes 20a having concave and arcuate cutouts 21 are arranged in a circle around the center C. The structure of each rod electrode 20a is the same as that of the rod electrode 20 shown in the first embodiment. In the ion guide 200a shown in FIG. 10, the cutout 21 of one rod electrode 20a is engaged with the convex portion 26 of another rod electrode 20a in a non-contact state. That is, the ion guide 200a shown in FIG. 10 is different from the configuration of the ion guide 200 shown in FIG. 2 to FIG. 9 in that it is provided with eight cylindrical rod electrodes 20a-1 to 20a-8 (octupole). The basic effect of the ion guide 200a shown in FIG. 10 is the same as that of the example shown in FIG. 2 to FIG. 9, but the ion focusing efficiency of the octupole tends to be higher than that of the dodecapole.

[0043] [Third embodiment] (Cylindrical rod electrode 20b and hexapole ion guide 200b) Next, a third embodiment will be described with reference to FIG. FIG. 11 is a diagram showing a third embodiment of an ion guide 200b. In FIG. 11, for simplicity, only the differences from the ion guide 200 shown in FIG. 2 to FIG. 9 are described. Also, for simplicity, only the rod electrode 20b is shown in FIG. 11. The left diagram Z31 in FIG. 11 is a view from the ion inlet side. The center diagram Z32 in FIG. 11 is a view from the side. Note that, for simplicity, only the rod electrodes 20b-1 and 20b-4 are shown in the center diagram Z32 in FIG. 11. Also, the right diagram Z33 in FIG. 11 is a view from the ion outlet side. FIG. 11 shows an ion guide 200b in which six (hexapole) cylindrical rod electrodes 20b having concave and arcuate cutouts 21 are arranged in a circle around the center C. The structure of each rod electrode 20b is the same as that of the rod electrode 20 shown in the first embodiment. In the ion guide 200b shown in FIG. 11, the cutout 21 of a rod electrode 20b and the convex portion 26 of another rod electrode 20b are engaged in a non-contact state. That is, the ion guide 200b shown in FIG. 11 is different from the ion guide 200 shown in FIG. 2 to FIG. 9 in that it includes six cylindrical rod electrodes 20b-1 to 20b-6 (hexapole). The basic effect of the ion guide 200b is the same as that of the ion guide 200 shown in FIG. 2 to FIG. 9 and the ion guide 200a shown in FIG. 10, but the ion focusing efficiency of the hexapole tends to be higher than that of the octapole.

[0044] Next, modifications of the first embodiment (and the second and third embodiments) will be described with reference to FIGS. 12 to 17B.

[0045] [First Modification] (Approximately long cylindrical dodecapole ion guide 200c) Next, a first modified example will be described with reference to FIG. 12, FIG. 13A and FIG. 13B. FIG. 12 is a diagram showing a first modified ion guide 200c. In FIG. 12, for simplicity, only the differences from the ion guide 200 shown in FIG. 2 to FIG. 9 are described. Also, for simplicity, only the rod electrode 20c is shown in FIG. 12. The left diagram Z41 in FIG. 12 is a view from the ion inlet side direction (the left side in FIG. 1). Also, the center diagram Z42 in FIG. 12 is a view from the side. In addition, in the center diagram Z42 in FIG. 12, only the rod electrodes 20c-1 and 20c-7 are shown for simplicity. And the right diagram Z43 in FIG. 12 is a view from the ion outlet side. The ion guide 200c shown in FIG. 12 has twelve rod electrodes 20c (20c-1 to 20c-12) each having a substantially oval cylindrical shape (cross-sectional shape being substantially oval) arranged in a circle with respect to the center C.

[0046] 13A and 13B are diagrams showing only one rod electrode 20c-1 of the rod electrodes 20c constituting the ion guide 200c. FIG. 13A is a diagram showing the rod electrode 20c-1 seen from the entrance side, and FIG. 13B is a diagram showing the rod electrode 20c-1 seen from the exit side. The rod electrode 20c of the first modification is characterized in that a concave and arcuate cutout portion 21 is provided in the substantially elongated cylindrical rod electrode 20c (rod electrode 20c-1 in FIG. 13A and FIG. 13B). A convex portion 26 is provided on the side opposite to the side of the rod electrode 20c on which the cutout portion 21 is provided. In FIG. 13A, the shape of the rod electrode 200c without the cutout portion 21 is shown by a dashed line. The basic effect of the ion guide 200c according to the first modification is the same as that of the ion guide 200 shown in FIG. 2 to FIG. 9.

[0047] In addition, in order to avoid complication, reference numerals of the cutout portion 21 and the protrusion portion 26 are omitted in Fig. 12. As shown in Fig. 12 to Fig. 13B, the cutout portion 21 of a rod electrode 20c and the protrusion portion 26 of another rod electrode 20c are fitted together in a non-contact state.

[0048] [Second Modification] (12-pole ion guide 200d having a V-shaped notch 21) Next, a second modified example will be described with reference to FIGS. 14, 15A and 15B. FIG. 14 is a diagram showing a second modified ion guide 200d. For simplicity, only the differences from the ion guide 200 shown in Figures 2 to 9 will be described in Figure 14. Also, for simplicity, only the rod electrode 20d is shown in Figure 14. The left diagram Z51 in Fig. 14 is a view from the ion inlet side. The center diagram Z52 in Fig. 14 is a view from the side. For simplicity, only the rod electrodes 20d-1 and 20d-7 are shown in the center diagram Z52 in Fig. 14. And the right diagram Z53 in Fig. 14 is a view from the ion outlet side. 14 shows the configuration of a dodecapole ion guide 200d that is configured with cylindrical rod electrodes 20d (20d-1 to 20d-12). For simplicity, only the rod electrodes 20d are shown in FIG.

[0049] 15A and 15B are diagrams showing only one rod electrode 20d-1 of the rod electrodes 20d constituting the ion guide 200d. Fig. 15A is a diagram showing the rod electrode 20d-1 as viewed from the entrance side. Fig. 15B is a diagram showing the rod electrode 20d-1 as viewed from the exit side. As shown in FIG. 14, each rod electrode 20d is arranged in a circle with respect to the center C. The rod electrode 20d of the second modification shown in FIG. 14 to FIG. 15B (rod electrode 20d-1 in FIG. 15A and FIG. 15B) is characterized in that a concave V-shaped notch 21 is provided in the cylindrical rod electrode 20d. A convex portion 26 is provided on the side opposite to the side of the rod electrode 20d on which the notch 21 is provided. In FIG. 14A, the shape of the rod electrode 20d without the notch 21 is shown by a dashed line. The basic effect of the ion guide 200d is similar to that of the ion guide 200 shown in FIG. 2 to FIG. 9.

[0050] In addition, in order to avoid complication, reference numerals of the cutout portion 21 and the protrusion portion 26 are omitted in Fig. 14. As shown in Fig. 14 to Fig. 15B, the cutout portion 21 of a rod electrode 20d and the protrusion portion 26 of another rod electrode 20d are fitted together in a non-contact state.

[0051] [Third Modification] (12-pole ion guide 200e having a V-shaped notch 21 and a rectangular rod electrode 20e) Next, a third modified example will be described with reference to FIGS. 16, 17A and 17B. FIG. 16 is a diagram showing a third modified ion guide 200e. For simplicity, only the differences from the ion guide 200 shown in Figures 2 to 9 will be described in Figure 16. Also, for simplicity, only the rod electrode 20e is shown in Figure 16. The left diagram Z61 in Fig. 16 is a view from the ion inlet side. The center diagram Z62 in Fig. 16 is a view of the ion guide 200e from the side. For simplicity, only the rod electrodes 20e-1 and 20e-7 are shown in the center diagram Z62 in Fig. 16. The right diagram Z63 in Fig. 16 is a view of the ion guide 200e from the ion outlet side. FIG. 16 shows a dodecapole ion guide 200e that is configured with twelve rectangular rod electrodes 20e (20e-1 to 20e-12).

[0052] 17A and 17B are diagrams showing only one rod electrode 20e-1 among the rod electrodes 20e constituting the ion guide 200e. Fig. 17A is a diagram showing the rod electrode 20e-1 as seen from the entrance side, and Fig. 17B is a diagram showing the rod electrode 20e-1 as seen from the exit side. As shown in FIG. 16, each rod electrode 20e is arranged in a circle with respect to the center C. The rod electrode 20e of the third modification shown in FIG. 16 to FIG. 17B (rod electrode 20e-1 in FIG. 17A and FIG. 17B) is characterized in that a concave V-shaped notch 21 is provided in the rod electrode 20e having a rectangular column shape. A convex portion 26 is provided on the side opposite to the side of the rod electrode 20e on which the notch 21 is provided. In FIG. 17A, the shape of the rod electrode 20e without the notch 21 is shown by a dashed line. The basic effect of the ion guide 200e is similar to that of the ion guide 200 shown in FIG. 2 to FIG. 9.

[0053] In addition, in order to avoid complication, reference numerals of the cutout portion 21 and the protrusion portion 26 are omitted in Fig. 16. As shown in Fig. 16 to Fig. 17B, the cutout portion 21 of a rod electrode 20e and the protrusion portion 26 of another rod electrode 20e are fitted together in a non-contact state.

[0054] [Fourth embodiment] (notch 21 is provided midway) Next, a fourth embodiment will be described with reference to FIGS. In the fourth embodiment, a configuration of a quadrupole ion guide 200f constituted by cylindrical rod electrodes 20f in which a concave, arc-shaped cutout portion 21 is provided midway in the longitudinal direction will be described. FIG. 18 is a diagram showing the configuration of an ion guide 200f according to the fourth embodiment. In FIG. 18, for simplicity, only the differences from the ion guide 200 shown in FIG. 2 to FIG. 9 are described. Also, for simplicity, only the rod electrodes 20f are shown in FIG. 18. The left diagram Z71 in FIG. 18 is a view of the ion guide 200f from the ion inlet side. Also, the center diagram Z72 in FIG. 18 is a view of the ion guide 200f from the side. Note that, in the center diagram Z72 in FIG. 18, only the rod electrodes 20f-1 and 20f-3 are shown for simplicity. And the right diagram Z73 is a view of the ion guide 200f from the ion outlet side. 18 shows the configuration of a quadrupole ion guide 200f in which four cylindrical rod electrodes 20f (20f-1 to 20f-4) are arranged in a circle about a center C. As shown in Fig. 18, in the ion guide 200f, a concave-shaped and arc-shaped cutout portion 21 is provided in the rod electrode 20f from the middle in the longitudinal direction.

[0055] 19A and 19B are diagrams showing only one rod electrode 20f-1 among the rod electrodes 20f constituting the ion guide 200f. FIG. 19A is a diagram showing the rod electrode 20f-1 from the entrance side. FIG. 19B is a diagram showing the rod electrode 20f-1 from the exit side. Thus, the rod electrode 20f of the fourth embodiment (the rod electrode 20f-1 in the example shown in FIG. 19A and FIG. 19B) is characterized in that the rod electrode 20f is provided with a concave-shaped and arc-shaped cutout portion 21 from the middle of the longitudinal direction. Also, a protrusion 26 is provided on the side surface of the rod electrode 20f opposite to the side surface on which the cutout portion 21 is provided.

[0056] FIG. 20 is a perspective view showing two rod electrodes 20f-3 and 20f-4 out of the four rod electrodes 20f constituting the ion guide 200f. 2 to 9, the radius of the inscribed circle gradually decreases from the inscribed circle 23f of the rod electrode 20f on the entrance side to the inscribed circle 24f of the rod electrode 20f on the exit side. In the fourth embodiment, the notch 21 is provided from a starting point 25 provided midway along the longitudinal direction of the rod electrode 20f toward the exit side. That is, in the rod electrode 20f, the notch 21 is provided from midway along the rod electrode 20f toward the ion exit side (the direction of the inscribed circle 24f) with respect to the longitudinal direction of the rod electrode 20f.

[0057] In addition, in order to avoid complication, reference numerals of the cutout portion 21 and the protrusion portion 26 are omitted in Fig. 18. As shown in Fig. 18 to Fig. 20, the cutout portion 21 of a rod electrode 20f and the protrusion portion 26 of another rod electrode 20f are fitted together in a non-contact state.

[0058] In the rod electrode 20f, the holder 210 (see FIG. 7) is not placed in a portion where the notch 21 is not provided. Therefore, in the portion where the notch 21 is not provided, contamination of the insulating creeping portions 212a, 212b does not occur.

[0059] The basic effect of the ion guide 200f is the same as that of the ion guide 200, but the quadrupole tends to have a higher ion focusing efficiency than the hexapole of the third embodiment. In particular, in a configuration in which the number of rod electrodes 20f (number of quadrupoles) is small, it is possible to have a sufficient gap between adjacent rod electrodes 20f on the inlet side even if the inlet does not have the notch 21. Therefore, it is acceptable to form the notch 21 from the middle of the longitudinal direction of the rod electrode 20f as in the fourth embodiment.

[0060] Furthermore, according to the fourth embodiment, compared to the ion guides 200, 200a to 200e, it is possible to reduce the portion to be cut for the notch 21. This allows the cost to be reduced.

[0061] Fifth embodiment (example in which rod electrodes 20g are arranged in parallel) With reference to FIG. 21, the ion guide 200g of the fifth embodiment will be described in detail. FIG. 21 is a diagram showing the configuration of a 12-pole ion guide 200g in which 12 cylindrical rod electrodes 20g (20g-1 to 20g-12) are arranged parallel to the longitudinal direction. In FIG. 21, for simplicity, only the differences from the ion guide 200 are described. In FIG. 21, the left diagram Z81 shows the ion guide 200g from the ion inlet side. Also, in the center diagram Z82 of FIG. 21, only the rod electrodes 20g-1 and 20g-7 are shown for simplicity. Also, the center diagram Z82 of FIG. 21 shows the ion guide 200g from the side. And the right diagram Z83 of FIG. 21 shows the ion guide 200g from the ion outlet side. In the ion guide 200g shown in Fig. 21, cylindrical rod electrodes 20g-1 to 20g-12 each having a concave and arcuate cutout 21 are arranged in parallel. Therefore, the left diagram Z81 and the right diagram Z83 in Fig. 21 show a state in which the electrodes are simply inverted with respect to the Z axis. The rod electrodes 20g are arranged in a circle with respect to the center C.

[0062] 21, a protrusion 26 is provided on a side surface of the rod electrode 20g opposite to the side surface on which the notch 21 is provided. The notch 21 of one rod electrode 20g and the protrusion 26 of another rod electrode 20g are fitted together in a non-contact state.

[0063] The ion guide 200g shown in the fifth embodiment has the same features as those of the ion guide 200, as shown in Fig. 6 and Fig. 9. The feature shown in Fig. 6 is that the dashed dotted line S connecting the centers GC1 to GCn of the rod gaps GA1 to GAn at the same distances R1 to Rn from the center C is not in a straight line. Also, a line GL connecting the center GC of the rod gap GA at a predetermined distance "R" from the center C of the ion guide 200g and the center C is defined. The feature shown in Fig. 9 is that the shape of the rod electrode 20g is asymmetrical with respect to the line GL in the vicinity of the line GL.

[0064] FIG. 22 shows an example of an ion guide 200g provided with a holder 210c. A left diagram Z91 in Fig. 22 is a diagram of the ion guide 200g in which the holder 210c is provided, as viewed from the inlet side, and a right diagram Z92 in Fig. 22 is a side view of the ion guide 200g in which the holder 210c is provided. 22, an actual ion guide 200g may have an insulating holder 210c to hold the 12 rod electrodes 20g (20g-1 to 20g-12). In the fifth embodiment, since the rod electrodes 20g (20g-1 to 20g-12) are arranged parallel to the X-axis, the inlet and outlet holders 210c may have the same shape as shown in FIG.

[0065] The ion guide 200g has the same effects as the ion guide 200 shown in Figures 2 to 9. In addition, since the rod electrodes 20g are not installed at an angle, the ion guide 200g can be installed more easily than the ion guides 200, 200a to 200f.

[0066] Sixth embodiment (ion guide 200h in which notches 21 are provided on both side surfaces of rod electrode 20h) FIG. 23 is a cross-sectional view showing an ion guide 200h according to the sixth embodiment. In FIG. 23, for simplicity, only the differences from ion guide 200 are described. In the examples so far, a configuration is shown in which the notch 21 is provided on one of the rod electrodes 20, 20a to 20g in the vicinity of the gap formed between the adjacent rod electrodes 20, 20a to 20g. That is, in the examples so far, the notch 21 is provided only on one side surface of the rod electrodes 20, 20a to 20g. In contrast to these, the ion guide 200h shown in the sixth embodiment is composed of rod electrodes 20h (20h-1 to 20h-12). In addition, the rod electrodes 20h are provided with concave and arc-shaped notches 21 on the side surfaces of both rod electrodes 20h in the vicinity of the gap formed between the adjacent rod electrodes 20h. The ion guide 200h is composed of 12 rod electrodes (12-pole) and cylindrical rod electrodes 20h. That is, in the sixth embodiment, the notch 21 is provided on both side surfaces of each of the rod electrodes 20h constituting the ion guide 200h. In addition, when the cutout portion 21 is provided on both sides, this means that the cutout portion 21 and the protrusion portion 26 are provided on one side of the rod electrode 20h, and the cutout portion 21 and the protrusion portion 26 are also provided on the other side.

[0067] In the example shown in FIG. 23, an ion guide 200h in which 12 (12-pole) cylindrical rod electrodes 20h (20h-1 to 20h-12) are arranged in a circle around the center C is shown. FIG. 23 is a cross-sectional view of the ion guide 200h in the YZ plane (see FIG. 1 and FIG. 5). As described above, in the adjacent portions adjacent to the gaps of the rod electrodes 20h, the rod electrodes 20h located on both sides of the gaps of the rod electrodes 20h are provided with arc-shaped notches 21. That is, in the ion guide 200h shown in FIG. 23, the notches 21 and the protrusions 26 are provided on both side surfaces of the rod electrodes 20h. The notches 21 of a certain rod electrode 20h and the protrusions 26 of another rod electrode 20h are fitted together in a non-contact state.

[0068] As for the ion guides 200, 200a to 200h of the respective examples described above, the above-mentioned effects can also be obtained by combining the characteristic elements of each of the ion guides 200, 200a to 200h.

[0069] In the following, the ion guide 200 represents the ion guides 200 and 200 to 200h, and the rod electrode 20 represents the rod electrodes 20 and 20a to 20h. Depending on the number of rod electrodes 20 (number of quadrupoles), there is a tendency for different performances to be exhibited, such as ion capture efficiency (higher with a larger number of quadrupoles) and ion focusing efficiency (higher with a smaller number of quadrupoles). However, since the optimal configuration of the ion guide 200 may differ depending on the target sample, the configuration of any number of quadrupoles is very important. Note that the ion guide 200 may be configured with a number of rods other than the quadrupole, hexapole, octapole, and dodecapole shown in the above examples. However, the number of rod electrodes 20 is limited to an even number. This is because voltages of opposite phases are applied to adjacent rod electrodes 20.

[0070] In addition, the ion guide 200 composed of a plurality of rod electrodes 20 may be mounted, for example, by screwing an insulating holder 210 and the rod electrodes 20 together. Alternatively, a fixing means such as gluing the holder 210 and the rod electrodes 20 together may be used. Furthermore, a part such as a pin that determines the positional relationship between the holder 210 and the rod electrodes 20 may be used.

[0071] The rod electrode 20 may have a shape other than the cylinder, rectangular column, and approximately elongated cylinder shown in the above examples (e.g., a hexagonal column, etc.). In addition, various methods can be used to process the cutout portion 21. For example, there are cutting processing (including processing using a multi-axis processing machine, etc.), electric discharge processing (including wire cut electric discharge processing, etc.), casting, a three-dimensional printer, plastic molding processing (adding a metal layer to the surface), etc.

[0072] [Common Features] FIG. 24 is a diagram showing a feature common to the examples described so far (especially the cylindrical rod electrode 20). In FIG. 24, the diameter of the rod electrode 20 (the maximum diameter in the direction where the notch 21 (see FIG. 3A and FIG. 3B, etc.) is not provided) is defined as "D", and the center distance between adjacent rod electrodes 20 is defined as "P". As shown in FIG. 24, the ion guide 200 is characterized by the relationship D>P. That is, since "D" is larger than "P", as shown in FIG. 24, there is an overlapping portion (shaded portion DL) of each rod electrode 20. The overlapping portion (shaded portion DL) is used as the notch 21, and a gap is provided between each rod electrode 20, which is a feature of this embodiment. This relationship may be held over the entire length of the rod electrode 20, or may be held in a part of the longitudinal direction as shown in FIG. 18 to FIG. 20.

[0073] [Summary of effects] Next, with reference to FIG. 25, the effects of the ion guides 200, 200 to 200h shown in FIGS. 2 to 23 will be summarized. In FIG. 25, reference will be mainly made to the ion guide 200 as a representative of the ion guides 200, 200 to 200h. FIG. 25 is a partial enlarged view of the rod electrodes 20-1 and 20-2 out of the rod electrodes 20 that constitute the ion guide 200. As shown in FIG. In the ion guide 200 of this embodiment, the notch 21 of one rod electrode 20 and the protrusion 26 of another rod electrode 20 are fitted together in a non-contact state. In the ion guide 200 having such a configuration, a configuration in which the contact portion 211a and the insulating creeping surface portion 212a are not visible from the center C can be realized. The angle between each of the straight lines L1 and L2 connecting the center C and both ends of the range of the insulating creeping surface portion 212a is defined as "β". An obstacle (i.e., the rod electrode 20-1) exists within the range of "β". Therefore, the feature of this embodiment is that the insulating creeping surface portion 212a is not visible from the center C.

[0074] 2, the rod electrode 20 is arranged at an angle, so that the insulating creeping portions 212a, 212b (see FIG. 8) are not visible when the ion guide 200 is viewed from the inlet side. In this embodiment, in addition to the rod electrode 20 arranged at an angle as shown in FIG. 2, etc., an ion guide 200g in which rod electrodes 20g are arranged in parallel as shown in FIG. 21, etc., can also be used.

[0075] Also, even in a configuration in which the rod electrodes 20g are arranged in parallel as in the ion guide 200g, a configuration in which the insulating creeping portion 212a (FIG. 25) is not visible from the center C can be realized as shown in FIG. 25. In other words, with such a configuration, droplets discharged from the inside of the ion guide 200g to the outside are blocked by the convex portion 26 of the rod electrode 20. This makes it difficult for the droplets to reach the insulating creeping portion 212a. Therefore, it is possible to suppress contamination of the insulating creeping portion 212a with droplets or the like. This improves the robustness of the ion guide 200g as well as the ion guide 200, and improves long-term analytical performance and stability.

[0076] [Comparative Example] Next, a comparative example of this embodiment will be described with reference to FIGS. Fig. 26 is a diagram showing the configuration of an ion guide 200j according to a comparative example. The left diagram Z101 in Fig. 26 shows the ion guide 200j seen from the ion inlet side, and the right diagram Z102 shows a cross-sectional view of the ion guide 200j on the Z axis. In Fig. 26, only the rod electrode 20j is shown for simplicity. FIG. 26 shows a multipole (quadrupole in the example shown in FIG. 26) ion guide 200j that is configured with cylindrical rod electrodes 20j (20j-1 to 20j-4). Moreover, Fig. 27 is a diagram showing the configuration of an ion guide 200j provided with a holder 210. A left diagram Z111 in Fig. 27 shows the ion guide 200j seen from the ion inlet side, and a right diagram Z112 shows a cross-sectional view of the ion guide 200j on the Z axis.

[0077] In Fig. 26, it is necessary to apply high frequency voltages of opposite phases to adjacent rod electrodes 20j. For this reason, as shown in Fig. 27, the rod electrodes 20j are often held by an insulating holder 210. In the YZ plane, a line SA is defined as a line connecting the centers GC1 to GCn of the rod gaps GA1 to GAn at the same distances "R1" to "Rn" (the circles shown by the dashed lines in Fig. 26) from the center C of the ion guide 200j. The characteristic of the ion guide 200j having a multipole as shown in Fig. 26 is that the line SA is a straight line.

[0078] In addition, in the configuration of the ion guide 200j shown in FIG. 26, the rod electrodes 20j are arranged in parallel along the X-axis direction. Therefore, the relationship that the line SA connecting the centers GC1 to GCn of the rod gaps GA1 to GAn is a straight line is constant over the longitudinal direction of the rod electrodes 20j. In this configuration, as shown in the left diagram Z111 of FIG. 27, when the ion guide 200j is viewed from the inlet side, the insulating surface portion 212 of the holder 103 is visible due to the rod gaps GA1 to GAn. Ions and droplets generated in the ion source 100 (see FIG. 1) are introduced into the ion guide 200j. The ion guide 200j has a role of discharging droplets that become a noise factor during analysis from the rod gaps GA1 to GAn (see FIG. 26) and the like, and converging only ions near the center C by the multipole electric field. In other words, the ion guide 200j has a role of separating the airflow containing the droplets from the ions.

[0079] For this reason, as shown in FIG. 27, in a configuration in which the insulating creeping portion 212 of the holder 210 is visible from the rod gaps GA1 to GAn (see FIG. 26), the insulating creeping portion 212 is highly likely to be contaminated by liquid droplets. The insulating creeping portion 212, which is intended to insulate the adjacent rod electrodes 20j, is contaminated by liquid droplets, and the insulating performance deteriorates. Accordingly, the voltage value that can be applied to the rod electrode 20j decreases. As a result, even if the same voltage value as before the contamination is applied to the rod electrode 20j, there is a high possibility that discharge or the like will occur at the insulating creeping portion 212. As a result, there is a risk of degradation of analytical performance and stability.

[0080] Fig. 28 is a diagram showing the configuration of an ion guide 200k according to a comparative example. The left diagram Z121 in Fig. 28 shows the ion guide 200k seen from the ion inlet side, and the right diagram Z122 shows a cross-sectional view of the ion guide 200k on the Z axis. In Fig. 28, only the rod electrode 20k is shown for simplicity. As shown in FIG. 28, the rod electrodes 20k constituting the ion guide 200k have a rectangular columnar shape.

[0081] Moreover, Fig. 29 is a diagram showing the configuration of an ion guide 200k provided with a holder 210. A left diagram Z131 in Fig. 29 shows the ion guide 200k seen from the ion inlet side, and a right diagram Z132 shows a cross-sectional view of the ion guide 200k on the Z axis. 28 and 29, the same components as those in FIGS. 26 and 27 are denoted by the same reference numerals and the description thereof will be omitted. An ion guide 200k configured with rectangular rod electrodes 20k (20k-1 to 20k-4) as shown in FIGS. 28 and 29 has the same features and problems as the ion guide 200j shown in FIGS.

[0082] In order to increase the sensitivity of the mass spectrometer 1, there are techniques for increasing the number of rod electrodes 20j, 20k (number of quadrupoles) and improving the ion capture efficiency, as in Non-Patent Document 1 and Patent Document 1. In addition, in these techniques, the rod electrodes 20j, 20k are arranged obliquely (tilted) along the longitudinal direction of the rod electrodes 20j, 20k. In other words, the internal space of the ion guide 200k is gradually narrowed toward the outlet side. In this way, the ion convergence efficiency is improved. However, in these techniques, as in the above-mentioned problem, the line SA connecting the centers GC1 to GCn of the rod gaps GA1 to GAn shown in FIG. 26 and FIG. 28 remains in a straight line. Therefore, it is considered that the problem of contamination of the holder 210 cannot be solved. In addition, in order to increase the sensitivity, the diameter of the hole H2 (see FIG. 1) of the introduction electrode 122 (see FIG. 1) may be increased to increase the amount of ions introduced from the atmosphere. In such a case, the amount of droplets introduced into the ion guides 200j, 200k also increases. Therefore, the problem of contamination of the holder 210 may become even more pronounced.

[0083] As described above, according to the ion guides 200, 200a to 200h shown in this embodiment, it is possible to prevent such contamination of the holder 210 (the insulating surface portions 212a, 212b).

[0084] The present invention is not limited to the above-described embodiment, and includes various modified examples. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and is not necessarily limited to all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0085] The control device 600 and the like may be realized in part or in whole by hardware, for example, by designing them as an integrated circuit. The above-mentioned configurations, functions, and the like may be realized in software by a processor such as a CPU interpreting and executing a program that realizes each function. Information such as the program, table, and file that realizes each function can be stored in a memory, a recording device such as an SSD (Solid State Drive), or a recording medium such as an IC (Integrated Circuit) card, an SD (Secure Digital) card, or a DVD (Digital Versatile Disc), in addition to being stored in an HD (Hard Disk).

[0086] In addition, in this embodiment, the control lines and information lines are those that are considered necessary for the explanation, and not all control lines and information lines in the product are necessarily shown. In reality, it can be considered that almost all components are connected to each other. [Explanation of symbols]

[0087] 1 Mass spectrometer 20, 20a~20h, 20-1~20-12, 20a-1~20a-8, 20b-1~20b-6, 20c-1~20c-12, 20e-1~20e-12, 20f-1~20f-4, 20h-2~20h-12, 20g-1~20g-12 Rod electrode 21 Notch (recess) 23 Inscribed circle (inscribed circle of rod electrode at inlet side) 23f Inscribed Circle 24 Inscribed circle (inscribed circle of rod electrode at the outlet side) 24f Inscribed Circle 26 Convex 200,200a~200h Ion Guide 210,210a~210c Holder 211a,211b Contact part 212, 212a, 212b Insulating surface part 300 Ion Transport Device C center

Claims

1. An ion guide including a plurality of cylindrical rod electrodes arranged in a circle, A recess and a protrusion are provided on a side surface of each of the rod electrodes, The recess of one of the rod electrodes and the protrusion of another of the rod electrodes are fitted together in a non-contact state.

1. An ion guide comprising:

2. The rod electrode is arranged so that the inscribed circle of the rod electrode on the entrance side is larger than the inscribed circle of the rod electrode on the exit side, and the recess is provided at a predetermined angle with respect to the longitudinal direction of the rod electrode.

2. An ion guide as claimed in claim 1.

3. The recess is provided from the middle of the rod electrode toward the ion outlet side in the longitudinal direction of the rod electrode.

3. An ion guide as claimed in claim 2.

4. The recess and the protrusion are provided on both side surfaces of the rod electrode.

2. An ion guide as claimed in claim 1.

5. The rod electrodes include The rod electrodes are held by a holder having a shape that contacts each of the rod electrodes and is made of an insulating material.

2. An ion guide as claimed in claim 1.

6. 12 of the rod electrodes 2. The ion guide of claim 1, comprising:

7. Eight of the rod electrodes 2. The ion guide of claim 1, comprising:

8. Six of the rod electrodes 2. The ion guide of claim 1, comprising:

9. The rod electrode has a cylindrical shape.

2. The ion guide of claim 1, further comprising:

10. The recess has an arcuate shape.

2. The ion guide of claim 1, further comprising:

11. A mass spectrometer including an ion guide configured by arranging a plurality of cylindrical rod electrodes in a circle, The ion guide comprises: A recess and a protrusion are provided on a side surface of each of the rod electrodes, The recess of one of the rod electrodes and the protrusion of another of the rod electrodes are fitted together in a non-contact state. A mass spectrometer comprising:

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