Ion guide, and mass spectrometer equipped therewith

Abstract

This design enables the creation of an ion guide with a wide m / z range of ions that can pass through it, a simple structure, and strong resistance to contamination. [Solution] This disclosure proposes an ion guide into which ions are introduced and which are focused and ejected, comprising a multipole electrode for forming a multipole electric field and an axial electric field electrode for forming an axial electric field, wherein the cross-sectional area of ​​at least one of the multipole electrode or the axial electric field electrode perpendicular to the central axis of the ion guide changes from the inlet to the outlet of the ion guide.

Description

Technical Field

[0001] The present disclosure relates to an ion guide and a mass spectrometer equipped with the same.

Background Art

[0002] Ion guides are widely used to transport ions within mass spectrometers. In particular, for ion guides used in collision cells of tandem mass spectrometers, it is necessary to generate an axial electric field on the central axis to prevent crosstalk. Regarding the axial electric field, for example, Patent Document 1 discloses generating an axial electric field that accelerates ions in a multipole ion guide configured with parallel rod electrodes of a multipole (such as a quadrupole). Further, for example, Patent Document 2 discloses generating an axial electric field by inserting a resistor electrode to which a high-frequency voltage is applied into the gap between multipole electrodes to which a high-frequency electrode is applied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, ion guides that apply an axial electric field by tilting a pair of rod electrodes, as shown in Patent Document 1, have the problem that the m / z range of ions that can pass through the ion guide becomes narrow. Also, ion guides that insert electrodes into the gap between rod electrodes, as shown in Patent Document 2, have the problem that the ion guide structure is complex, the spacing between electrodes is narrow, and the surface area of ​​the electrodes is small, so the electrodes are easily contaminated by impurities such as neutral droplets introduced into the ion guide, which degrades performance. Furthermore, the ion guide shown in Patent Document 2 has a complex structure, the spacing between electrodes is narrow, and the surface area of ​​the electrodes that form the axial electric field is small. Therefore, there is also the problem that the electrode surface is easily contaminated by impurities such as neutral droplets introduced into the ion guide, which degrades performance. In light of these circumstances, this disclosure proposes a technology for realizing an ion guide that has a wide m / z range of ions that can pass through it, a simple structure, and is resistant to contamination. [Means for solving the problem]

[0005] To solve the above problems, this disclosure proposes an ion guide into which ions are introduced and which are focused and ejected, comprising a multipole electrode for forming a multipole electric field and an axial electric field electrode for forming an axial electric field, wherein the cross-sectional area perpendicular to the central axis of the ion guide of at least one of the multipole electrode or the axial electric field electrode changes from the inlet to the outlet of the ion guide.

[0006] Further features relating to this disclosure will become apparent from the description herein and the accompanying drawings. Furthermore, aspects of this disclosure are achieved and realized through elements and various combinations of elements and the modes of the claims described herein and the accompanying claims. The description herein is merely illustrative and does not limit in any way the claims or applications of this disclosure. [Effects of the Invention]

[0007] The technology disclosed herein makes it possible to realize an ion guide with a simple structure, strong resistance to contamination, and a wide permeable mass range, as well as a mass spectrometer equipped therewith. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view showing a schematic configuration example of a mass spectrometer 10 equipped with a curved ion guide 20 according to the first embodiment. [Figure 2A] This figure shows an example of the external configuration of the ion guide 20 according to the first embodiment. [Figure 2B] This figure shows an example of a cross-sectional configuration of the ion guide 20 according to the first embodiment, along the central axis 23. [Figure 2C] This figure shows an example of the cross-sectional configuration of the inlet 1A and outlet 1B of the ion guide 20 according to the first embodiment. [Figure 3] This figure shows an example configuration of the ion guide power supply 300 used in each embodiment. [Figure 4] This figure shows the pseudopotentials of the ry plane at the inlet 1A and outlet 1B of the ion guide 20 according to the first embodiment. [Figure 5] This figure shows the DC potential in the xz plane including the central axis 23 of the ion guide 20 according to the first embodiment. [Figure 6] This figure shows the potential on the central axis 23 of the ion guide 20 according to the first embodiment (a function of θ in Figures 2 and 5). [Figure 7] This figure shows the DC potential in the yr plane at the inlet 1A and outlet 1B of the ion guide 20 according to the first embodiment. [Figure 8] This figure shows the distribution of transmission times for 200 ions under the conditions of potential differences of 6V, 3V, 1.5V, and 1V between the axial field electrode 22 and the multipole electrode 21. [Figure 9] This figure shows the transmittance of ions in the range of m / z 150 to m / z 4000 under conditions where the potential difference between the axial field electrode 22 and the multipole electrode 21 is 3V and 6V. [Figure 10]This is a diagram showing a schematic configuration example of an ion guide 201 according to the second embodiment. [Figure 11] This shows a schematic configuration example of an ion guide 202 according to the third embodiment. [Figure 12] This is a diagram showing a configuration example of an ion guide 203 according to the fourth embodiment. [Figure 13] This is a diagram showing a configuration example of an ion guide 204 according to the fifth embodiment. [Mode for Carrying Out the Invention]

[0009] The present embodiment discloses realizing an ion guide that has a wide m / z range of ions capable of passing through the ion guide, a simple structure, and high resistance to contamination, by changing at least one of the cross-sectional area of the multipole electrode relative to the central axis (the area of the plane perpendicular to the ion traveling direction) or the cross-sectional area of the axial electric field electrode relative to the central axis from the inlet to the outlet of the ion guide in the ion guide.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be denoted by the same reference numerals. Note that although the accompanying drawings show specific embodiments and implementation examples conforming to the principles of the present disclosure, these are for the purpose of understanding the present disclosure and are by no means intended to be used to interpret the present disclosure in a limited manner.

[0011] Although the present embodiment is described in sufficient detail to enable a person skilled in the art to implement the present disclosure, it should be understood that other implementations and forms are possible, and changes to the configuration and structure and replacement of various elements are possible without departing from the scope and spirit of the technical idea of the present disclosure. Therefore, the following description should not be construed as being limited thereto.

[0012] (1) First Embodiment <Configuration Example of Mass Spectrometer 10> FIG. 1 is a cross-sectional view showing a schematic configuration example of a mass spectrometer 10 including a curved ion guide 20 according to the first embodiment.

[0013] For example, the mass spectrometer 10 includes an ion source 101, a first differential pumping section 102 including an ion guide 121 for ion transport as necessary, a vacuum pump 131 that evacuates the first differential pumping section 102 to create a vacuum, a second differential pumping section 103 including an ion guide (curved ion guide) 20, a vacuum pump 132 that evacuates the second differential pumping section 103 to create a vacuum, an ion guide power supply 300 that applies a voltage to the ion guide, a mass spectrometry chamber 104 having a mass filter 125, a collision cell 126, and a detector 127, and a vacuum pump 133 that evacuates the mass spectrometry chamber 104 to create a vacuum.

[0014] As the ion source 101, an electrospray ion source, an atmospheric pressure chemical ion source, an atmospheric pressure photoionization source, an atmospheric pressure matrix-assisted laser desorption / ionization source, or the like can be used.

[0015] Ions generated by the ion source 101 pass through the small hole 111 provided in the first differential pumping section 102 together with the air flow, and are introduced into the first differential pumping section 102 (vacuum chamber). The ions that have passed through the differential pumping section 102 pass through the small hole 112 provided in the connection portion (wall) between the first differential pumping section 102 and the second differential pumping section 103, and are introduced into the ion guide 20 according to the technique of the present disclosure.

[0016] A voltage is applied to the ion guide 20 by the ion guide power supply 300. In addition, the operating pressure of the ion guide 20 is 1000 Pa to 10 -3 Pa or so. In particular, at 1000 Pa to 0.1 Pa, the kinetic energy of ions is cooled by collision with neutral gas molecules, so that ions can be efficiently focused. The ions ejected from the ion guide 20 pass through the small hole 113 provided in the connection portion (wall) between the second differential pumping section 103 and the mass spectrometry chamber 104, and are introduced into the mass spectrometry chamber 104.

[0017] If the mass spectrometer 10 is, for example, a tandem mass spectrometer, then in the mass spectrometry chamber 104, a specific m / z precursor ion is selected by the mass filter 125 and dissociated in the collision cell 126. The fragment ions generated in the collision cell 126 are detected by the detector 127. An electron multiplier tube or the like can be used as the detector 127. Alternatively, the ion guide 20 can be used as the collision cell 126.

[0018] <Example configuration of Ion Guide 20> Figure 2 shows an example of the configuration of an ion guide according to the first embodiment. Figure 2A shows an example of the external configuration of the ion guide 20. Figure 2B shows an example of the cross-sectional configuration of the ion guide 20 along the central axis 23. Figure 2C shows an example of the cross-sectional configuration of the inlet 1A and outlet 1B of the ion guide 20.

[0019] As shown in Figure 2A, the ion guide 20 has a curved shape (curved ion guide) and is equipped with two plate-shaped multipole electrodes 21 on the top and two on the bottom, and two axial field electrodes 22 on the top and two on the bottom, sandwiched between the upper and lower multipole electrodes. Ions enter from the inlet 1A and accelerated ions exit from the outlet 1B.

[0020] Furthermore, the ion guide 20 is configured such that its central axis 23 is a quarter-circle arc with an ion guide arc center 29. As can be seen from Figure 2A, the cross-section of the inlet 1A of the ion guide 20 is on the x-axis, and the cross-section of the outlet 1B is on the z-axis. In this case, if we let θ be the angle between the radius r of the quarter-circle arc and the x-axis when the radius r is moved along the central axis 23, then the length of the axial field electrode 22 in the direction of distance r (r-axis direction) from the arc center in the cross-section perpendicular to the ion guide central axis 23 changes as a function of angle θ from the arc center 29 of the ion guide 20. In other words, the axial field electrode 22 is configured such that its cross-sectional area increases from the inlet 1A to the outlet 1B. Figure 2B also shows that the size of the axial field electrode 22 (on the xz plane) decreases from the inlet 1A to the outlet 1B.

[0021] The potential formed by the axial field electrode 22 on the central axis (ion guide central axis) 23 of the ion guide 20 depends on the area of ​​the axial field electrode 22 visible from the ion guide central axis 23. Therefore, an axial field is formed on the ion guide central axis 23 corresponding to the potential difference between the potential of the multipole electrode 21 and the potential of the axial field electrode 22. In Figure 2C, the signs "+" and "-" indicate the phase of the RF voltage applied from the ion guide power supply 300 to the multipole electrode 21 and the axial field electrode 22. RF voltages of the same phase and frequency are applied to electrodes with the same sign. To generate a multipole field that confines ions, an RF voltage in opposite phase to that of the adjacent multipole electrode 21 is applied to the multipole electrode 21. Similarly, an RF voltage of the same phase and approximately the same amplitude as that of the adjacent multipole electrode 21 is applied to the axial field electrode 22. By applying voltages in this way, a potential difference in RF voltage does not occur between the multipole electrode 21 and the axial field electrode 22, where the distance between the electrodes is narrow, thus preventing discharge. Furthermore, different offset DC voltages are applied to the set (pair) of multipole electrodes 21 and the set (pair) of axial field electrodes 22. Ions pass through the central axis 23 of the ion guide 20, but the area of ​​the cross-section of the axial field electrodes 22 perpendicular to the central axis 23, as seen from the central axis 23, changes with distance along the central axis 23. As a result, the intensity of the DC voltage on the axial field electrodes 22 received by ions along the central axis 23 changes. This causes the ions to be accelerated.

[0022] <Example configuration of the Ion Guide Power Supply 300> Figure 3 shows examples of the configuration of the ion guide power supply 300 used in each embodiment. Two types of configuration examples of the ion guide power supply 300 are shown in Figure 3.

[0023] In each configuration example, the ion guide power supply 300 comprises an axial field electrode DC power supply 301, a multipole electrode DC power supply 302, and an RF power supply 303, supplying DC voltage to the multipole electrode 21 and the axial field electrode 22 from either the axial field electrode DC power supply 301 or the multipole electrode DC power supply 302. The RF power supply 303 includes an AC power supply and multiple coils, and uses each coil to apply RF voltages with the same phase and amplitude to the multipole electrode 21 and the axial field electrode 22.

[0024] <Simulated potential> Figure 4 shows the pseudopotentials in the ry plane at the inlet 1A and outlet 1B of the ion guide 20. In Figure 4, the pseudopotentials were measured with an ion m / z of 600 and an RF voltage amplitude of 300V0-peak.

[0025] An RF voltage of nearly the same amplitude and in phase with the adjacent multipole electrode 21 is applied to the axial field electrode 22, and the poles of the multipole are formed by the pair of the multipole electrode 21 and the adjacent axial field electrode 22. Therefore, the axial field electrode 22 does not obstruct the multipole electrode 21, making it less likely to cause pseudopotential strain.

[0026] At the ion guide inlet 1A, the length of the axial field electrode 22 in the r-axis direction is shorter (the electrode width is smaller) and the distance from the ion guide central axis 23 is greater compared to the ion guide outlet 1B, resulting in a shallower pseudopotential. Therefore, the pseudopotential becomes funnel-shaped, deepening as it approaches the ion guide outlet 1B. This allows for efficient convergence of the ion distribution.

[0027] In the mass spectrometer 10, charged droplets and neutral impurities are introduced into the vacuum chamber along with ions, causing contamination inside the instrument. In this respect, ions, being less affected by the electric field than large charged droplets and neutral impurities, travel in a straight line along the z-axis in Figure 2 from the pore 112 just before the inlet 1A of the ion guide 20. On the other hand, ions introduced from the inlet 1A of the ion guide 20 are focused near the minimum point of the pseudopotential on the central axis 23, move along the central axis 23, and are discharged from the outlet 1B of the ion guide 20.

[0028] In the ion guide 20 of Figure 2, since the inlet 1A lies on the xy plane and the outlet 1B lies on the yz plane, charged droplets and neutral impurities travel straight in the z-axis direction from the inlet 1A of the ion guide 20 and are excluded from the ion guide 20, while only ions pass through the ion guide 20. This makes it possible to reduce noise.

[0029] Charged droplets and neutral impurities introduced from the fine pore 112 spread over a range of approximately several millimeters and travel straight in the z-axis direction as shown in Figure 2. On the other hand, in the ion guide 20, no electrodes are present in the range through which charged droplets and neutral impurities pass on the front side (z-axis direction) of the inlet 1A, and a wide gap (space) is formed. For this reason, the ion guide 20 has a low possibility that neutral impurities and charged droplets collide with the electrodes (the multipole electrode 21 and the axial electric field electrode 22) to contaminate the electrodes, and is also resistant to contamination.

[0030] <State of DC potential> Figure 5 is a diagram showing the DC potential on the xz plane including the central axis 23 of the ion guide 20. Figure 6 is a diagram showing the potential on the central axis 23 of the ion guide 20 (as a function of θ in Figure 2 and Figure 5). Note that the DC potential is calculated with the potential difference between the axial electric field electrode 22 and the multipole electrode 21 set to 10 V.

[0031] As can be seen from Figure 5, the DC potential on the xz plane is dense near the inlet 1A and sparse near the outlet 1B, so that it is highest at the inlet 1A of the ion guide 20 and gradually decreases toward the outlet 1B of the ion guide 20. Further, as can be seen from Figure 6, the potential decreases substantially proportionally to the angle θ from the curve center along the central axis 23 of the ion guide 20. The potential on this central axis 23 makes it possible to always accelerate ions at a constant acceleration.

[0032] Figure 7 shows the DC potential in the yr plane at the inlet 1A and outlet 1B of the ion guide 20. As can be seen in Figure 7, the potential at the inlet 1A of the ion guide 20 includes components of higher-order multipole systems such as octupoles in addition to the quadrupole. Therefore, due to the effect of higher-order terms, it becomes possible to efficiently transmit ions over a wide m / z range compared to when a quadrupole DC potential is applied. On the other hand, at the outlet 1B of the ion guide 20, the multipole electrodes are covered by the axial field electrode, so the DC potential in the yr plane is almost uniform. Therefore, the spatial distribution of ions does not spread out due to the DC potential, and the spatial distribution of ions can be converged.

[0033] <Distribution of ion permeation time: Simulation results> To verify the technical effectiveness of the ion guide 20, the transmission time was confirmed through simulation. Figure 8 shows the distribution of transmission times for 200 ions under the conditions of potential differences of 6V, 3V, 1.5V, and 1V between the axial field electrode 22 and the multipole electrode 21. Table 1 shows the parameter values ​​other than the potential difference between the axial field electrode 22 and the multipole electrode 21.

[0034] [Table 1]

[0035] As can be seen from Figure 8, the larger the potential difference between the axial field electrode 22 and the multipole electrode 21, the shorter the transmission time and the narrower the full width at half maximum of the time distribution. In other words, according to this simulation, the transmission time becomes 1 ms or less when the potential difference between the axial field electrode 22 and the multipole electrode 21 is 3V or more, and the shortest transmission time occurs when the potential difference is 6V.

[0036] Based on the above, the ion guide 20 allows for shorter transmission times and avoidance of signal crosstalk by accelerating ions with the electric field formed on the central axis 23.

[0037] <Ion m / z range: Simulation results> To verify the technical effectiveness of the ion guide 20, the m / z range of ions that can stably pass through the ion guide 20 was confirmed through simulation. The lower limit of the m / z range of ions that can stably pass through the ion guide 20 is determined by the low mass cut-off value (LMCO), which is the lower limit of the stability region of the Matthew equation. For example, when using a quadrupole electrode, the LMCO for monovalent ions is given by the following equation (1).

[0038]

number

[0039] Here, V is the RF voltage amplitude, m is the ion mass, and q is the ion mass. LMCO ∫ is the q-value of the Matthew equation in the LMCO, e is the elementary charge, Ω is the RF voltage frequency, and r0 is the radius of the inscribed circle of the quadrupole. From this equation (1), it can be seen that the lower limit of the m / z of ions that can stably pass through the ion guide 20 increases as the RF voltage amplitude increases. On the other hand, the upper limit of the m / z of ions that can pass through the ion guide is determined by the relationship between the pseudopotential (Ψ) of a monovalent ion shown in equation (2) and the effect of ion exclusion by the DC potential.

[0040]

number

[0041] Here, E represents the electric field. From equation (1), it can be seen that the pseudopotential is inversely proportional to the ion's m / z, so ions with a high m / z have a low pseudopotential and are excluded by the DC potential. Also, the higher the RF voltage amplitude, the higher the pseudopotential, so the upper limit of the m / z of ions that can be transmitted increases.

[0042] Figure 9 shows the transmittance of ions in the range of m / z 150 to m / z 4000 under conditions where the potential difference between the axial field electrode 22 and the multipole electrode 21 is 3V and 6V. When the potential difference between the axial field electrode 22 and the multipole electrode 21 is 3V, an average transmittance of 97% was obtained for ions in the range of m / z 175 to m / z 2500, i.e., LMCO to LMCO × 14.3. When the potential difference between the axial field electrode 22 and the multipole electrode 21 is 6V, an average transmittance of 97% was obtained for ions in the range of m / z 175 to m / z 1500, i.e., LMCO to LMCO × 8.6.

[0043] As described above, the ion guide 20 according to this embodiment can transmit ions in a wide m / z range. Furthermore, since both the multipole electrode 21 and the axial field electrode 22 are plate-shaped electrodes, the ion guide 20 according to this embodiment offers flexibility in its configuration from the viewpoint of ease of manufacturing, and can accommodate half-circle arcs and more complex channel shapes with the same design concept. Therefore, it can be flexibly implemented in the future according to the footprint (base area) and shape of the mass spectrometer 10.

[0044] (2) Second embodiment Figure 10 shows a schematic example of the ion guide 201 according to the second embodiment. The ion guide 201 has a linear shape and comprises a multipole electrode 21 and an axial field electrode 22. The length of the axial field electrode 22 that forms the axial field is shorter in the x-direction at the inlet 10A (smaller cross-sectional area of ​​the electrode) and longer at the outlet 10B (larger cross-sectional area of ​​the electrode). The configuration of the ion guide 201 in the radial cross-section, pseudopotential, DC potential, and potential on the central axis 23 are the same as in the first embodiment. Since the ion guide 201 has a linear shape, it can be implemented more simply and inexpensively compared to the ion guide 20 according to the first embodiment. On the other hand, since the direction in which ions enter the ion guide 201 and the direction in which ions exit the ion guide 201 are the same, the effect of reducing noise is smaller compared to the first embodiment.

[0045] (3) Third Embodiment Figure 11 shows a schematic configuration example of the ion guide 202 according to the third embodiment. In the ion guide 202, the multipole electrode 21 and the axial field electrode 22 are located in the same xz plane. That is, in the first and second embodiments, the ion guide 20 or 201 is constructed by arranging the multipole electrode 21 and the axial field electrode 22 to overlap spatially in the z-axis direction (see Figures 2A and B, and Figure 10), but in the third embodiment, the ion guide 202 is constructed using four substantially rectangular flat plate electrodes (one pair each, top and bottom) formed by bonding the trapezoidal or triangular multipole electrode 21 and the trapezoidal or triangular axial field electrode 22 together at their sides (by joining the short side (vertex) side and the long side (base) side). Alternatively, the ion guide 202 may be constructed using four substantially rectangular flat plate electrodes (one pair each, top and bottom) arranged with their sides facing each other, without bonding them together.

[0046] Referring to Figure 11, in the ion guide 202, the length of the multipole electrode 21 in the x-direction (electrode width in the x-direction) is longer at the inlet 11A of the ion guide 202 and shorter at the outlet 11B. Similarly, the length of the axial field electrode 22 in the x-direction (electrode width in the x-direction) is shorter at the inlet 11A of the ion guide 202 and longer at the outlet 11B. This electrode configuration forms an axial field.

[0047] In the ion guide 202 according to the third embodiment, the multipole electrode 21 and the axial field electrode 22 are in the same plane (xz plane), so the distance between the electrodes in the y-axis direction is wider compared to the ion guide 20 according to the first embodiment. As a result, incident charged droplets and neutral contaminants are less likely to collide with the electrodes, and the ion guide 202 has the characteristic of being resistant to contamination. On the other hand, the depth of the pseudopotential along the central axis 23 is constant, and the efficiency of ion focusing is relatively low (compared to the first embodiment).

[0048] (4) Fourth Embodiment Figure 12 shows an example of the configuration of the ion guide 203 according to the fourth embodiment. The ion guide 203 is configured such that the width of the axial field electrode 22 in the r-axis direction (xz plane) is constant, and the width of the multipole electrode 21 in the r-axis direction (xz plane) changes according to its position on the central axis of the ion guide.

[0049] The potential formed by the multipolar electrode 21 on the central axis 23 of the ion guide 203 depends on the area of ​​the multipolar electrode 21 visible from the central axis 23 of the ion guide 203. Therefore, an axial electric field is formed on the central axis 23 of the ion guide 203, corresponding to the potential difference between the multipolar electrode 21 and the axial electric field electrode 22.

[0050] (5) Fifth embodiment Figure 13 shows an example of the configuration of the ion guide 204 according to the fifth embodiment. In addition to the components of the ion guide 20 according to the first embodiment, the ion guide 204 is equipped with a second multipole electrode (an additional multipole electrode) located closer to the central axis 23 than the axial field electrode 22. The same voltage is applied to the first multipole electrode 22 and the second multipole electrode 28.

[0051] Although the ion guide 204 has a slightly more complex configuration compared to the ion guide 20 of the first embodiment, the DC potential of the inlet 13A of the ion guide 204 approaches that of a higher-order multipole. Therefore, the ion guide 204 has the advantage of having a wider m / z range for the ions it transmits than the ion guide 20 of the first embodiment.

[0052] (6) Summary of Embodiments The characteristic of each embodiment can be summarized as follows: In the ion guide according to this disclosure, the cross-sectional area perpendicular to the central axis of at least one of the ion guides (20, and 201 to 204) of the multipole electrode 21 or the axial field electrode 22 changes from the inlet (1A, 10A, 11A, 12A, 13A) to the outlet (1B, 10B, 11B, 12B, 13B) of the ion guide.

[0053] (i) According to the first embodiment, the cross-sectional area of ​​the axial field electrode 22 perpendicular to the central axis 23 of the ion guide changes (increases) from the inlet 1A to the outlet 1B of the ion guide 20. This makes it possible to create a funnel-shaped potential where the pseudopotential deepens as you approach the ion guide outlet 1B, and efficiently converge the ion distribution. Also, as shown in Figure 2C, the multipole electrode 21 and the axial field electrode 22 are each installed as two pairs of plate-shaped electrodes. Furthermore, the shapes of both the multipole electrode and the axial field electrode are arc-shaped from the inlet to the outlet (curved electrodes). Specifically, since the inlet 1A is in the xy plane and the outlet 1B is in the yz plane, charged droplets and neutral impurities travel in a straight line in the z-axis direction from the inlet 1A of the ion guide 20 and are removed from the ion guide 20, and only ions pass through the ion guide 20. This makes it possible to reduce noise. Then, the ion guide power supply 300 applies an RF voltage with the same phase and amplitude to the multipolar electrode 21, and applies different DC voltages so that a potential difference is created between the multipolar electrode 21 and the axial field electrode 22. By applying voltages in this way, a potential difference of RF voltage is not generated between the multipolar electrode 21 and the axial field electrode 22, where the distance between the electrodes is narrow, and thus discharge can be prevented.

[0054] Furthermore, as can be seen from Figure 6, the potential decreases along the central axis 23 of the ion guide 20 in approximately proportion to the angle θ from the center of curvature. This potential along the central axis 23 allows ions to be accelerated at a constant acceleration. On the other hand, since the outlet 1B of the ion guide 20 is covered by the axial field electrode, the DC potential in the yr plane becomes almost uniform. Therefore, the ions do not spread out in spatial distribution due to the DC potential, and the spatial distribution of ions can be converged. In this way, by using the ion guide 20, ions in a wide m / z range can be transmitted.

[0055] (ii) In the second embodiment, similar to the first embodiment, the cross-sectional area of ​​the axial field electrode 22 perpendicular to the central axis 23 of the ion guide increases from the inlet 10A to the outlet 10B of the ion guide 201, and the shapes of both the multipole electrode 21 and the axial field electrode 22 are linear. The same technical effects as in the first embodiment can be expected when using the ion guide 201 according to the second embodiment (the voltage application is the same as in the first embodiment).

[0056] (iii) According to the third embodiment, the plate-shaped axial field electrode 22 is configured such that the cross-sectional area perpendicular to the central axis 23 increases from the inlet 11A to the outlet 11B, and the plate-shaped multipole electrode 21 is configured such that the same cross-sectional area decreases from the inlet 11A to the outlet 11B (see Figure 11). The axial field electrode 22 and the multipole electrode 21 are arranged on the same plane with their respective sides facing each other (either attached side by side or arranged in parallel in the same plane (xz plane)). Even in this way, the same technical effects as in the first embodiment can be expected (the voltage application is the same as in the first embodiment).

[0057] (iv) According to the fourth embodiment, the axial field electrode 22 is configured such that the cross-sectional area perpendicular to the central axis 23 of the ion guide is the same from the inlet 12A to the outlet 12B, and the multipole electrode 21 is configured such that the same cross-sectional area increases from the inlet 12A to the outlet 12B (see Figure 12). In this way, by configuring the multipole electrode 21 to be relatively larger than the axial field electrode 22 (configured so that the multipole electrode 21 covers the axial field electrode 22), the same technical effects as in the first embodiment can be expected (voltage application is the same as in the first embodiment).

[0058] (v) According to the fifth embodiment, the cross-sectional area of ​​the ion guide perpendicular to the central axis 23 of the axial field electrode 22, which is positioned closer to the central axis 23 than the multipole electrode 21, increases from the inlet 1A to the outlet 1B of the ion guide 20, and the multipole electrode 21 is positioned to cover the axial field electrode 22 (the configuration up to this point is the same as in the first embodiment). Furthermore, an additional multipole electrode 28 is provided at a position closer to the central axis 23 than the axial field electrode 22. This makes it possible to further widen the m / z range of the transmitted ions.

[0059] (vi) The above descriptions of each embodiment are merely illustrative and do not limit the technology of this disclosure, and various modifications are possible. The descriptions of each embodiment are detailed in order to explain the technology of this disclosure in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described. Furthermore, 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. Furthermore, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations. [Explanation of Symbols]

[0060] 20, 201, 202, 203, 204 Ion Guide 21 Multipole electrode 22-axis field electrode 23. Central axis of the ion guide 28. Second multipolar electrode (additional multipolar electrode) 29 Center of the arc of the central axis of the ion guide 101 Ion source 102 First differential exhaust section 103 Second differential exhaust section 104 Mass spectrometry room 111, 112, 113 pores 121 Ion guide (for ion transport) 125 Mass Filter 126 Collision Cells 131, 132, 133 Vacuum pumps 300 Ion Guide Power Supply 301 Axis field electrode DC power supply 302 Multipole electrode DC power supply 303 RF power supply

Claims

[Claim 1] An ion guide into which ions are introduced and which ions are focused and ejected, It has a multipole electrode for forming a multipole electric field and an axial electric field electrode for forming an axial electric field, The adjacent multipole electrodes and the axial field electrode are configured to function as poles of a single multipole, The multipole electrode and the axial field electrode are subjected to an RF voltage of approximately the same amplitude and a DC voltage of a different amplitude, respectively. Aeon Guide.

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