Quality analysis device

Abstract

The present invention relates to a mass spectrometer. An ion guide (20) disposed in a first intermediate vacuum chamber comprises six rod electrodes (211-216) and a voltage generating unit. In order to make the six rod electrodes (211-216) have a sextupole configuration on the incident side of ions and the four rod electrodes (211, 214, 215, 216) have a quadrupole configuration, two rod electrodes (211, 214) are arranged tilted relative to the Z axis in such a manner as to approach the central axis (201) as the ions travel in the transport direction. The voltage generating unit applies high-frequency voltages ±Vcosωt of mutually reversed phases to adjacent rod electrodes around the central axis (201) relative to the six rod electrodes (211-216), applies a direct current voltage U1 for good ion passage to the four rod electrodes (211, 214, 215, 216), and applies a direct current voltage U2 different from U1 to the other two rod electrodes (212, 213).

Description

Technical Field

[0001] The present invention relates to a mass analysis device. Background Art

[0002] In a mass spectrometer, an ion transport optical system is used to transport ions generated by an ion source to a mass spectrometer. The performance of the ion transport optical system greatly affects the performance of the mass spectrometer itself, such as the ion detection sensitivity and the stability of the detection signal.

[0003] In a mass spectrometer using an atmospheric pressure ion source such as an electrospray ionization (ESI) ion source, a plurality of rooms separated by partition walls and having different degrees of vacuum are provided between an ion source having a substantially atmospheric pressure atmosphere and a high vacuum chamber having a mass spectrometer and maintained in a high vacuum atmosphere. Usually, each of the plurality of rooms is provided with an ion transport optical system. The ion transport optical system has the following functions: that is, it receives ions sent from the preceding stage, constrains and transports the ions, and transmits them to the succeeding stage.

[0004] In most cases, the ion transport optical system installed in a room with a relatively low vacuum degree is a high-frequency ion guide that uses the cooling effect of ions caused by the collision between ions and residual gas. High-frequency ion guides mainly use the pseudo potential generated by the high-frequency electric field to confine ions in a specified space and transport ions. There are roughly two types according to their structure.

[0005] One type of high-frequency ion guide is a multipole ion guide in which four, six, or eight (or more) rod electrodes are arranged to surround the ion optical axis (see Patent Document 1, etc.). In the multipole ion guide, a phase-reversed high-frequency voltage is applied to adjacent rod electrodes around the ion optical axis, thereby generating a pseudopotential in the space surrounded by the rod electrodes, thereby confining and transporting ions.

[0006] Another type of high-frequency ion guide is an ion funnel in which a plurality of electrodes, such as a disk-shaped electrode with a central opening and surrounding ions, are stacked in the ion transport direction (see Patent Document 2, etc.). In the ion funnel, a phase-reversed high-frequency voltage is applied to adjacent electrodes in the ion transport direction, thereby forming a pseudopotential near each electrode that reflects ions, thereby confining and transporting ions.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2008 / 136040

[0010] Patent Document 2: U.S. Patent No. 6107628 Summary of the invention

[0011] Technical problem to be solved by the invention

[0012] In order to improve the analytical sensitivity in a mass spectrometer, especially a mass spectrometer using an atmospheric pressure ion source, it is very important to improve the ion transport efficiency in the ion transport optical system. However, both a multipole ion guide and an ion funnel have the following technical problems.

[0013] The ion confinement ability and ion convergence ability of a multipole ion guide depend on the number of rod electrodes. Generally, the more rod electrodes there are, the higher the ion confinement ability is, while the fewer rod electrodes there are, the higher the ion convergence ability is. Therefore, there is a problem that if one of the ion confinement ability and the ion convergence ability is given priority, the other will be sacrificed, and it is difficult to improve the overall ion transport efficiency by improving both the confinement ability and the convergence ability.

[0014] On the other hand, the ion confinement capability of the ion funnel is relatively high, but the effect of the electric field that converges the ions near the central axis (ion optical axis) of the ion funnel is relatively small. Therefore, in general, in order to converge the ions, the opening diameter of the electrode is gradually reduced along the ion transport direction. However, the electrode with a reduced opening diameter is easily contaminated by ions and neutral particles. In particular, since the intervals between adjacent electrodes in the ion transport direction need to be set extremely narrow in the ion funnel, it is difficult for neutral particles that enter the ion passage space to pass through the gaps between the electrodes and they are easily collided with the electrodes. Therefore, there is a technical problem that it is easy to produce the above-mentioned pollution, and the electric field is easily disturbed due to pollution, resulting in reduced performance.

[0015] An object of the present invention is to provide a mass spectrometer capable of improving ion transport efficiency and thus improving analysis sensitivity by solving the above-mentioned technical problems of conventional multipole ion guides and ion funnels.

[0016] Solutions for solving the above technical problems

[0017] A mass spectrometer according to one aspect of the present invention, which has been developed to solve the above-mentioned technical problems, is a mass spectrometer having an ion transport optical system for transporting ions to be analyzed.

[0018] The ion transport optical system comprises:

[0019] The N-rod electrodes have an even number of 6 or more that are arranged as a whole to extend in the ion transport direction;

[0020] A voltage generating unit applies a predetermined voltage to each of the N rod electrodes.

[0021] At least two of the four rod electrodes are tilted relative to the central axis in such a manner that they approach the central axis of the N-pole configuration or the quadrupole configuration as they travel in the ion transport direction, so that the N rod electrodes are in the N-pole configuration on the ion incident side and four of the N rod electrodes are in the quadrupole configuration on the ion emission side.

[0022] The voltage generating unit is constructed so as to apply high-frequency voltages with reversed phases to adjacent rod electrodes around the ion light axis relative to the N rod electrodes, apply a first DC voltage to the four rod electrodes that form a quadrupole configuration on the ion emission side, and apply a second DC voltage different from the first DC voltage to the (N-4) rod electrodes other than the four rod electrodes among the N rod electrodes.

[0023] In order to solve the above-mentioned technical problems, another aspect of the present invention is a mass spectrometer having an ion transport optical system for transporting ions to be analyzed.

[0024] The ion transport optical system comprises:

[0025] The N-rod electrodes have an even number of 6 or more that are arranged as a whole to extend in the ion transport direction;

[0026] A voltage generating unit applies a predetermined voltage to each of the N rod electrodes.

[0027] The shape of at least two of the four rod electrodes is set so that at least a portion of the rod electrodes extending in the ion transport direction is bent in a manner close to the central axis of the N-pole configuration or the quadrupole configuration, so that the N rod electrodes are in the N-pole configuration on the ion incident side and the four rod electrodes in the N rod electrodes are in the quadrupole configuration on the ion emission side.

[0028] The voltage generating unit is constructed so as to apply high-frequency voltages with reversed phases to adjacent rod electrodes around the ion light axis relative to the N rod electrodes, apply a first DC voltage to the four rod electrodes configured as a quadrupole on the ion emission side, and apply a second DC voltage different from the first DC voltage to the (N-4) rod electrodes other than the four rod electrodes among the N rod electrodes.

[0029] Effects of the Invention

[0030] In the ion transport optical system of the mass spectrometer of the present invention, the incident ions can be efficiently captured by utilizing the higher ion confinement effect on the ion incident side, and the ions can be reduced to a thin diameter and sent to the subsequent stage by utilizing the higher ion convergence effect on the ion emission side. Therefore, according to the mass spectrometer of the present invention, the amount of ions for mass analysis can be increased by achieving a higher ion transport efficiency in the ion transport optical system. As a result, the analysis sensitivity can be improved.

[0031] Furthermore, in the ion transport optical system of the mass spectrometer of the present invention, electrode contamination such as that in an ion funnel is unlikely to occur. Therefore, the mass spectrometer of the present invention can also suppress performance degradation due to electrode contamination of the ion transport optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the configuration of a mass spectrometer according to one embodiment of the present invention.

[0033] Figure 2 This is a plan view of a first ion guide in the mass spectrometer of the present embodiment as viewed from the ion incident side.

[0034] Figure 3 This is a plan view of a first ion guide in the mass spectrometer according to the present embodiment as viewed from above.

[0035] Figure 4 It is a perspective view of a first ion guide in the mass spectrometer according to the present embodiment.

[0036] Figure 5 It is a diagram showing the results of simulation of the trajectory of ions passing through the first ion guide in the mass spectrometer according to the present embodiment.

[0037] Figure 6 This is a plan view of the ion guide according to the first modification example as viewed from the ion incident side.

[0038] Figure 7 This is a perspective view of an ion guide according to a first modified example.

[0039] Figure 8 This is a plan view of the ion guide according to the second modification example as viewed from the ion incident side.

[0040] Fig. 9 It is a perspective view of an ion guide according to a second modified example.

[0041] Fig.10 It is a diagram showing the results of simulation of the orbits of ions passing through the ion guide according to the second modification.

[0042] Fig.11 This is a top view of an ion guide according to still another modified example as viewed from above.

[0043] Fig.12 This is a top view of an ion guide according to still another modified example as viewed from above. DETAILED DESCRIPTION

[0044] A mass spectrometer according to an embodiment of the present invention will be described with reference to the drawings.

[0045] In addition, each drawing used in the following description is schematic, and the ratio of the size of each component does not reflect the actual device. In addition, it is of course that components that are not necessary for the description are appropriately omitted.

[0046] <Configuration of the device according to the present embodiment>

[0047] Figure 1 2 is a schematic diagram of the mass spectrometer of the present embodiment. The mass spectrometer of the present embodiment is a single quadrupole mass spectrometer having a multi-stage differential exhaust system.

[0048] The chamber 1 is provided with an ionization chamber 2 having an atmosphere of substantially atmospheric pressure, a high vacuum chamber 5 having the highest vacuum degree (i.e., the lowest pressure), a first intermediate vacuum chamber 3 and a second intermediate vacuum chamber 4 between which the vacuum degree gradually increases. Although omitted in the figure, the first intermediate vacuum chamber 3 is evacuated by a rotary pump, and the second intermediate vacuum chamber 4 and the high vacuum chamber 5 are evacuated by a combination of a rotary pump and a turbomolecular pump.

[0049] The ionization chamber 2 is provided with an ESI sprayer 6 for performing electrospray ionization. The ionization chamber 2 is connected to the first intermediate vacuum chamber 3 through a heating capillary 7 having a small diameter. A first ion guide 20 is arranged in the first intermediate vacuum chamber 3, and a predetermined voltage is applied to the first ion guide 20 from a first ion guide voltage generator 13. The first intermediate vacuum chamber 3 and the second intermediate vacuum chamber 4 are connected through an ion passage hole 9 formed at the top of a skimmer 8. A second ion guide 10 is arranged in the second intermediate vacuum chamber 4, and a predetermined voltage is applied to the second ion guide 10 from a second ion guide voltage generator 14. A quadrupole mass filter 11 and an ion detector 12 are arranged in the high vacuum chamber 5. A predetermined voltage is applied to the quadrupole mass filter 11 from a mass filter voltage generator 15. The voltages generated by the first ion guide voltage generator 13, the second ion guide voltage generator 14, and the mass filter voltage generator 15 are controlled by a control unit 16.

[0050] Here, in order to easily understand the arrangement and mutual positional relationship of the components arranged in the chamber 1, as shown in FIG. Figure 1As shown in , three axes X, Y, and Z are determined. The Z axis is the direction of the ion optical axis in almost the entire ion path except for the interior of the first ion guide 20, and the X axis and the Y axis are axes that are orthogonal to each other and to the Z axis. The X axis, the Y axis, and the Z axis do not necessarily have to indicate the up, down, right, and left directions of the device, but for ease of explanation, the Y axis direction is set to indicate the up and down direction of the device. Thus, in the device of this embodiment, the ESI sprayer 6 is configured to spray the sample solution downward, but this is only an example and can be appropriately changed.

[0051] <Description of the schematic operation of the device according to the present embodiment>

[0052] The analysis operation in the mass spectrometer of this embodiment is as follows.

[0053] The sample liquid containing the target component is supplied to the ESI sprayer 6. The sample liquid is given a biased charge at the front end of the ESI sprayer 6 and sprayed in an atmosphere of approximately atmospheric pressure. The sprayed sample droplets collide with the atmosphere and become fine, and in the process of evaporation of the solvent in the droplets, ions derived from the sample components are generated. The various ions generated are sucked into the heated capillary 7 together with the atmosphere and sent to the first intermediate vacuum chamber 3. The ions entering the first intermediate vacuum chamber 3 are captured and converged by the electric field formed by the voltage applied from the first ion guide voltage generating unit 13 to the first ion guide 20. In addition, the ions converged to a small diameter are sent to the second intermediate vacuum chamber 4 through the ion passage hole 9.

[0054] In addition, the central axis of the outlet of the heating capillary 7 and the central axis of the ion passage hole 9 are not located on a straight line, but a so-called off-axis structure is adopted. This is to exclude the unionized sample component molecules and active neutral particles sent to the first intermediate vacuum chamber 3 together with the ions in the first intermediate vacuum chamber 3 so that they are not sent to the second intermediate vacuum chamber 4.

[0055] The ions entering the second intermediate vacuum chamber 4 are captured and converged by the electric field formed by the voltage applied from the second ion guide voltage generator 14 to the second ion guide 10, and are sent to the high vacuum chamber 5. Various ions originating from the sample entering the high vacuum chamber 5 are introduced into the quadrupole mass filter 11. Among the various ions, only ions having a specific mass-to-charge ratio corresponding to the voltage applied from the mass filter voltage generator 15 to the quadrupole mass filter 11 pass through the quadrupole mass filter 11 and reach the ion detector 12. The ion detector 12 generates and outputs an ion intensity signal corresponding to the number of ions arriving. For example, the mass filter voltage generator 15 applies a voltage corresponding to the mass-to-charge ratio of the ions of the target sample component to the quadrupole mass filter 11. In this way, the influence of ions originating from inclusions and the like can be excluded, and the intensity signal of the ions of the target sample component can be obtained.

[0056] <Detailed Configuration and Operation of First Ion Guide 20 >

[0057] In the mass spectrometer of the present embodiment, the first ion guide 20 disposed in the first intermediate vacuum chamber 3 guides the ions sent into the first intermediate vacuum chamber 3 through the heated capillary 7 to the ion passage hole 9 of the skive 8 as described above. Next, the configuration and operation of the first ion guide 20 will be described in detail.

[0058] Figure 2 This is a plan view of the first ion guide 20 as viewed from the ion incident side. Figure 3 This is a plan view of the first ion guide 20 as seen from above. Figure 4 It is a perspective view of the first ion guide 20 .

[0059] The first ion guide 20 includes six elongated cylindrical rod electrodes 211 to 216. Figure 2 As shown, on the incident side of the ion (at Figure 1 The end surface of the ion transport device 200 is the left side, and the six rod electrodes 211 to 216 are arranged at the vertices of a regular hexagon 203 centered on the first central axis 201 parallel to the Z axis. Four rod electrodes 212, 213, 215, and 216 among the six rod electrodes 211 to 216 are arranged parallel to the Z axis. On the other hand, two rod electrodes 211 and 214 among the six rod electrodes 211 to 216 are not parallel to the other four rod electrodes 212, 213, 215, and 216, i.e., the Z axis, and are all arranged in a tilted manner approaching the first central axis 201 as they move toward the ion transport direction (refer to Figure 3 ).

[0060] As described above, by arranging the two rod electrodes 211 and 214 in an inclined manner with respect to the Z axis, the ion emission side (at the Figure 1 In the end face (right side), the four rod electrodes 211, 214, 215, 216 are arranged at the vertices of a rectangle 204 centered on the second central axis 202 parallel to the Z axis. The rectangle 204 is not strictly a square, but can be regarded as a roughly square. Therefore, the four rod electrodes 211, 214, 215, 216 are substantially arranged in a quadrupole configuration on the end face on the ion ejection side.

[0061] That is, the six rod electrodes 211 to 216 in the first ion guide 20 are arranged in a sextupole configuration on the ion incident side and in a quadrupole configuration on the ion emission side. Although the first central axis 201, the center of the sextupole configuration, and the second central axis 202, the center of the quadrupole configuration, are parallel to each other, they are not located on a straight line.

[0062] The voltage applied to each rod electrode 211 to 216 from the first ion guide voltage generating unit 13 is as follows: Figure 2 As described in . That is, high-frequency voltages +Vcosωt or -Vcosωt of the same amplitude with opposite phases are applied to any two adjacent rod electrodes around the first central axis 201. Thus, +Vcosωt and -Vcosωt are applied alternately in the circumferential direction around the first central axis 201. Furthermore, in addition to the above-mentioned high-frequency voltage, a DC voltage U1 for efficiently transporting ions inside the first ion guide 20 is applied to the four rod electrodes 211, 214, 215, and 216. On the other hand, a DC voltage U2 higher than the DC voltage U1 (larger on the positive polarity side) is applied to the other two rod electrodes 212 and 213 when the polarity of the ion to be analyzed is positive, and a DC voltage U2 lower than the DC voltage U1 (larger on the negative polarity side) is applied when the polarity of the ion to be analyzed is negative.

[0063] In addition, the DC voltage U1 applied to the four rod electrodes 211, 214, 215, and 216 is generally the same, but it is not necessarily required to be completely the same. The same applies to the DC voltage U2. In addition, this also applies to the modified examples described later.

[0064] A multipolar high-frequency electric field having the function of confining ions is formed in the space surrounded by the six rod electrodes 211 to 216 by applying a high-frequency voltage +Vcosωt or -Vcosωt to each rod electrode 211 to 216. The multipolar high-frequency electric field is a sextupole high-frequency electric field centered on the first central axis 201 near the ion entrance, and a quadrupole high-frequency electric field centered on the second central axis 202 near the ion exit. The state of the electric field between the ion entrance and exit gradually changes from a sextupole high-frequency electric field to a quadrupole high-frequency electric field.

[0065] On the other hand, the voltage difference between the DC voltage U1 and the DC voltage U2 applied to the six rod electrodes 211 to 216 forms an electric field that acts to squeeze the ions distributed around the first central axis 201 toward the second central axis 202, that is, to deflect the orbits of the ions. That is, one of the effects of the DC electric field formed by the DC voltage applied to the six rod electrodes 211 to 216 is to deflect the ions being transported.

[0066] In addition, the DC potential on the first central axis 201 near the entrance of the space surrounded by the six rod electrodes 211 to 216 depends on the DC voltage U1 and the DC voltage U2, while the DC potential on the second central axis 202 near the exit mainly depends only on the DC voltage U1. In the case where the polarity of the ion to be analyzed is positive, since the DC voltage U2 is higher than U1, the DC potential on the first central axis 201 near the entrance becomes higher than the DC potential on the second central axis 202 near the exit. Therefore, if the potential distribution on the optical axis of the ions transported in the space surrounded by the six rod electrodes 211 to 216 is considered, the distribution is generally decreasing from the entrance to the exit. In other words, this is an accelerating electric field that accelerates the ions of positive polarity, so the ions entering the above space are given kinetic energy toward the exit. That is, another effect of the DC electric field formed by the DC voltage applied to the six rod electrodes 211 to 216 is the effect of accelerating the ions being transported.

[0067] Thus, in the space surrounded by the six rod electrodes 211 to 216, the ions incident roughly along the Z-axis direction are captured by the sextupole high-frequency electric field, and as they travel along the Z-axis direction, they are deflected as a whole in the direction close to the rod electrodes 215 and 216. In addition, since the ions are given kinetic energy while traveling, even if they lose energy due to contact with residual gas on the way, for example, they travel smoothly toward the exit without being delayed. Furthermore, as the ions approach the exit of the first ion guide 20, they are captured by the quadrupole high-frequency electric field formed by the four rod electrodes 211, 214, 215, and 216 in a quadrupole configuration, and converge near the second central axis 202, becoming a thin-diameter ion stream and being ejected. The central axis of the exit of the heating capillary 7 that feeds ions to the first ion guide 20 is almost consistent with the first central axis 201, and the central axis of the ion passage hole 9 that feeds ions from the first ion guide 20 to the subsequent stage is almost consistent with the second central axis 202. Therefore, the first ion guide 20 is an off-axis ion optical system in which the incident axis and the emission axis of ions are offset from each other.

[0068] On the ion incident side of the first ion guide 20, the ions are captured by the sextupole high-frequency electric field. The gas sent from the ionization chamber 2 with an atmosphere of approximately atmospheric pressure to the first intermediate vacuum chamber 3 becomes a supersonic free jet when it is discharged from the outlet of the small diameter of the heating capillary 7. Therefore, a characteristic barrel shock is generated in the supersonic free jet, and the ions riding on the gas are diffused to a large extent in the radial direction. In contrast, since the sextupole high-frequency electric field has a stronger confinement effect on the ions than the quadrupole high-frequency electric field (in other words, the ion reception rate is good), the ions in the diffused state can be well captured and taken into the internal space. Therefore, even if the ions are diffused in the radial direction, the loss of ions on the incident side of the first ion guide 20 can be suppressed.

[0069] As described above, the ions efficiently taken into the internal space converge near the second central axis 202 as they travel in the internal space of the first ion guide 20. Although the confinement effect of the ions on the quadrupole high-frequency electric field on the outlet side is relatively low compared to the sextuple high-frequency electric field on the inlet side, on the other hand, the effect on the convergence of the ions is stronger. Therefore, the ions converge well near the second central axis 202. Then, the ion flow reduced to a small diameter is ejected from the first ion guide 20, efficiently passes through the ion passage hole 9, and is sent to the second intermediate vacuum chamber 4. As a result, the loss caused by the collision of ions with the wall surface around the ion passage hole 9 can also be suppressed on the ejection side of the first ion guide 20.

[0070] Furthermore, since kinetic energy is imparted to the ions during transport, it is possible to prevent the ions that have lost energy due to collision with the residual gas from escaping. Thus, the ion passing efficiency in the internal space of the first ion guide 20 is also improved.

[0071] Furthermore, since the first ion guide 20 is an off-axis optical system as described above, even when neutral particles such as unionized sample molecules and active neutral particles are incident together with ions, such neutral particles are not deflected and thus do not reach the ion passage hole 9. Thus, it is also possible to prevent neutral particles from being sent to the subsequent stage.

[0072] Figure 5 1 is a diagram showing the results of computer simulation of the trajectory of ions passing through the first ion guide 20. Here, the gas pressure is assumed to be 100 Pa. It is known that this gas pressure is a very general value as the gas pressure in the intermediate vacuum chamber adjacent to the ionization chamber, and the above-mentioned supersonic free jet is formed under this gas pressure condition. In the simulation, the diffusion of ions caused by the supersonic free jet is also taken into account. In addition, Figure 5 In order to facilitate observation of ion orbits, the three rod electrodes 211 , 212 , and 216 on the front side are not shown, and only the three rod electrodes 213 , 214 , and 215 on the other side are shown.

[0073] like Figure 5 As shown, it can be seen that the ions diffused and incident at the entrance side of the first ion guide 20 are well captured and guided to the internal space. In addition, it can be seen that the ions are gradually deflected and transported downward, and fully converge near the exit and are ejected as a thin ion stream. In this way, it can be understood from the simulation results that in the first ion guide 20 of the mass spectrometer of the present embodiment, the ions are efficiently transported, that is, transported with less loss. As a result, since more ions are introduced into the quadrupole mass filter 11, high analytical sensitivity can be achieved.

[0074] In addition, as described above, the rectangle 204 in which the four rod electrodes 211, 214, 215, and 216 are arranged on the end face on the ion emission side is not strictly a square, but the four rod electrodes 211, 214, 215, and 216 can be arranged at the vertices of the square on the end face on the ion emission side by slightly tilting the two rod electrodes 215 and 216 relative to the Z axis and slightly increasing the tilt of the two rod electrodes 211 and 214. According to such a configuration, the convergence of ions near the exit of the first ion guide 20 becomes better. In addition, in order to adjust the off-axis amount, the exit side of the four rod electrodes 211, 214, 215, and 216 can be tilted toward the -Y axis direction ( Figure 2 The second center axis 202 is further away from the first center axis 201 by adjusting the tilt or the like in the downward direction.

[0075] The first ion guide 20 in the above-mentioned embodiment includes 6 rod electrodes and is configured as a sextupole on the ion incident side, but the number of rod electrodes can be an even number greater than 6. Although the ability to confine ions at the entrance of the ion guide becomes higher as the number of rod electrodes increases, the degree of improvement in the confinement ability is small even if the number of rod electrodes is increased to a certain extent. In addition, the more the number of rod electrodes, the more complicated the structure of the ion guide becomes, and the lower the installability and maintainability. Considering such a situation, in terms of practicality, the number of rod electrodes is preferably about 6, 8, 10 or 12. As a modified example, the following describes the case where the number of rod electrodes is set to 8 and the case where the number of rod electrodes is set to 12.

[0076] <First Modification of Ion Guide>

[0077] Figure 6 This is a top view of the ion guide 30 of the first modification example as viewed from the ion incident side. Figure 7 is a perspective view of the ion guide 30 .

[0078] The ion guide 30 includes eight elongated cylindrical rod electrodes 311 to 318. Figure 6 As shown, on the end surface on the incident side of ions, eight rod electrodes 311 to 318 are arranged at the vertices of a regular octagon 303 centered on the central axis (ion optical axis) 301. Four rod electrodes 312, 313, 316, and 317 of the eight rod electrodes 311 to 318 are arranged parallel to the Z axis. On the other hand, the other four rod electrodes 311, 314, 315, and 318 of the eight rod electrodes 311 to 318 are not parallel to the Z axis, and are all arranged tilted in a manner that they approach the Y axis on the XZ plane and passing through the central axis 301 as they move toward the transport direction of ions (as a whole, they approach the central axis 301).

[0079] As described above, by arranging the four rod electrodes 311, 314, 315, and 318 to be tilted relative to the Z axis, the four rod electrodes 311, 314, 315, and 318 are arranged at the vertices of the rectangle 304 centered on the central axis 301 on the end surface on the ion emission side, and the other rod electrodes are located outside the space surrounded by the four rod electrodes 311, 314, 315, and 318. In this case, the rectangle 304 is a square. Therefore, the eight rod electrodes 311 to 318 in the ion guide 30 are arranged in an octopole configuration on the ion incident side and in a quadrupole configuration on the ion emission side.

[0080] In this case, unlike the configuration of the first ion guide 20 in the above-mentioned embodiment, the central axis 301 is the same in the octupole configuration and the quadrupole configuration, and it is not an off-axis optical system. Figure 1 In the case of the first ion guide 20 in the embodiment, the position of the heating capillary 7 or the skive 8 is changed so that the central axis of the outlet of the heating capillary 7 and the central axis of the ion passage hole 9 of the skive 8 are aligned. This also applies to the case of using the ion guide of the second modified example described later.

[0081] The voltage applied to each rod electrode 311 to 318 is as follows: Figure 6 As described in , high-frequency voltages +Vcosωt or -Vcosωt of the same amplitude with opposite phases are applied to two adjacent rod electrodes around the central axis 301. In addition to the above-mentioned high-frequency voltage, a DC voltage U1 for efficiently transporting ions inside the ion guide 30 is applied to the four rod electrodes 311, 314, 315, and 318 forming a quadrupole on the ion emission side. On the other hand, a DC voltage U2 higher than the DC voltage U1 is applied to the other four rod electrodes 312, 313, 316, and 317 when the polarity of the ion to be analyzed is positive, and a DC voltage U2 lower than the DC voltage U1 is applied when the polarity of the ion to be analyzed is negative.

[0082] As a result, an octopole high-frequency electric field with a strong ion confinement effect is formed at the entrance of the ion guide 30, and the ions introduced into the first intermediate vacuum chamber are efficiently captured and taken into the internal space of the ion guide 30. The taken-in ions are mainly pushed into the space surrounded by the other four rod electrodes 311, 314, 315, and 318 by the DC electric field formed by the DC voltage applied to the four rod electrodes 312, 313, 316, and 317. In this case, since the ion optical axes on the entrance side and the exit side are in a straight line, the electric field that substantially deflects the ions does not play a role, but it has a role as an accelerating electric field that accelerates the ions toward the exit (gives kinetic energy). And, as the ions approach the exit, the quadrupole high-frequency electric field formed by the space surrounded by the four rod electrodes 311, 314, 315, and 318 converges near the central axis 301, and becomes a thin-diameter ion stream and is ejected.

[0083] In this way, the ion guide 30 can also achieve a higher ion transport efficiency.

[0084] In addition, as in the first variant and the following second variant, when there is no need to deflect the ions during transport, the DC voltage U2 may not be higher than the DC voltage U1 (when the ions are of positive polarity). When the ions to be analyzed are of positive polarity and the DC voltage U2 is lower than the DC voltage U1, it is obvious from the above description that the DC potential on the central axis near the entrance of the ion guide becomes lower than the DC potential on the central axis near the exit. That is, if the potential distribution on the optical axis of the ions transported in the space surrounded by a plurality of rod electrodes is taken into account, the distribution is generally increasing from the entrance toward the exit. Since this is a deceleration electric field that decelerates the ions of positive polarity, the ions entering the above space gradually lose kinetic energy as they move toward the exit. That is, the effect of the DC electric field formed by the DC voltage applied to the plurality of rod electrodes is to decelerate the ions being transported.

[0085] For example, Figure 1 In the structure of the mass spectrometer shown, due to the pressure difference between the two ends of the heating capillary 7, the opening diameter of the heating capillary 7, etc., when the flow rate of the atmosphere flowing from the ionization chamber 2 into the first intermediate vacuum chamber 3 is large, the initial kinetic energy of the ions introduced into the first intermediate vacuum chamber 3 is sometimes too large to be captured by the high-frequency electric field. In such a case, it is possible to form a deceleration electric field in advance in the internal space of the ion guide instead of forming an accelerating electric field toward the exit, and actively reduce the kinetic energy of the ions by the action of the deceleration electric field. In this way, the ions can be well captured by the high-frequency electric field, converged and guided to the exit.

[0086] In this way, the magnitude relationship between the DC voltage U1 and the DC voltage U2 can be appropriately changed according to how the ions incident on the ion guide are to be controlled.

[0087] <Second Modification of Ion Guide>

[0088] Figure 8 This is a top view of the ion guide 40 of the second modified example as viewed from the ion incidence side. Fig. 9 is a perspective view of the ion guide 40. Further, Fig.10 This is a diagram showing the results of computer simulation of the orbits of ions passing through the ion guide 40 .

[0089] The ion guide 40 includes 12 elongated cylindrical rod electrodes 411 to 422. Figure 8 As shown, on the end surface on the incident side of ions, 12 rod electrodes 411 to 422 are arranged at the vertices of a regular dodecagon 403 centered on the central axis (ion optical axis) 401. Eight rod electrodes 412, 413, 415, 416, 418, 419, 421, and 422 of the 12 rod electrodes 411 to 422 are arranged parallel to the Z axis. On the other hand, the other four rod electrodes 411, 414, 417, and 420 of the 12 rod electrodes 411 to 422 are not parallel to the Z axis, and are all arranged in a tilted manner to approach the central axis 401 as they move toward the ion transport direction.

[0090] As described above, by arranging the four rod electrodes 411, 414, 417, 420 at an inclination relative to the Z axis, the four rod electrodes 411, 414, 417, 420 are arranged at the vertices of the square 404 centered on the central axis 401 on the end surface on the ion emission side, and the other rod electrodes are located outside the space surrounded by the four rod electrodes 411, 414, 417, 420. Therefore, the 12 rod electrodes 411 to 422 in the ion guide 40 are arranged in a dodecapole configuration on the ion incident side and in a quadrupole configuration on the ion emission side. In this case, it is not an off-axis optical system either.

[0091] The voltage applied to each rod electrode 411-420 is as follows: Figure 8As described in , high-frequency voltages +Vcosωt or -Vcosωt of the same amplitude with opposite phases are applied to two adjacent rod electrodes around the central axis 401. In addition to the above-mentioned high-frequency voltage, a DC voltage U1 for efficiently transporting ions inside the ion guide 40 is applied to the four rod electrodes 411, 414, 417, and 420 forming a quadrupole on the ion emission side. On the other hand, a DC voltage U2 higher than the DC voltage U1 is applied to the other eight rod electrodes 412, 413, 415, 416, 418, 419, 421, and 422 when the polarity of the ion to be analyzed is positive, and a DC voltage U2 lower than the DC voltage U1 is applied when the polarity of the ion to be analyzed is negative.

[0092] As a result, a dodecapole high frequency electric field having a stronger ion confinement effect than the octupole high frequency electric field is formed at the entrance of the ion guide 40, and the ions introduced into the first intermediate vacuum chamber are efficiently captured and taken into the internal space of the ion guide 40. The taken-in ions are gradually pushed into the space surrounded by the other four rod electrodes 411, 414, 417, and 420 mainly through the DC electric field formed by the DC voltage applied to the eight rod electrodes 412, 413, 415, 416, 418, 419, 421, and 422. In this case, since the ion optical axes on the entrance side and the exit side are also on the same straight line, the electric field that substantially deflects the ions does not work, but it has the function of an accelerating electric field that accelerates the ions toward the exit (gives kinetic energy). Furthermore, as the ions approach the exit, they converge near the central axis 401 due to the quadrupole high-frequency electric field formed by the space surrounded by the four rod electrodes 411 , 414 , 417 , and 420 , and are ejected as a thin-diameter ion stream.

[0093] Depend on Fig.10 The simulation results of the ion trajectory shown in the figure also show that the ions diffused and incident at the entrance side of the ion guide 40 are well captured and guided to the internal space. In addition, it can be seen that the ions converge near the central axis 401 as they travel, and fully converge near the exit and are ejected as a thin ion stream. In this way, a high ion transport efficiency can also be achieved in the ion guide 40.

[0094] <Another modification of the ion guide>

[0095] In the above-mentioned embodiment and each modification, the lengths of the 6, 8 or 12 rod electrodes included in the first ion guide 20 or the ion guides 30 and 40 are substantially the same. However, except for the 4 rod electrodes forming a quadrupole configuration on the end surface on the ion ejection side, the other rod electrodes, for example Figure 2 to Figure 4The two rod electrodes 212 and 213 in the first ion guide 20 shown do not necessarily need to extend to the ion ejection end face. This is because the rod electrodes 212 and 213 do not contribute to the formation of the quadrupole high-frequency electric field near the ion exit, and the ion deflection effect caused by the DC electric field is not required near the ion exit. From this point of view, the other rod electrodes except the four rod electrodes in the quadrupole configuration at the ion ejection side end face only need to exist in the area between the spaces surrounded by the four rod electrodes in the quadrupole configuration so that the ions initially diffused in the relatively large internal space can reliably enter.

[0096] Fig.11 This is a top view of an ion guide showing an example of a structure in which a portion of a rod electrode is shorter than other rod electrodes, as seen from above. Figure 3 It is relatively obvious that in this example, the length of two rod electrodes 212 and 213 among the six rod electrodes 211 to 216 is L2, which is shorter than the length L1 of the other four rod electrodes 211, 214, 215, and 216. As long as the ions incident on the ion guide 20 are sufficiently deflected within the length L2 and enter the high-frequency electric field formed by the four rod electrodes 211, 214, 215, and 216, substantially the same effect as the case where the length of the two rod electrodes 212 and 213 is L1 can be obtained. This is also true in the case where the number of rod electrodes is other than 6.

[0097] In addition, in the above-mentioned embodiments and various modifications, the rod electrodes included in the ion guides 20, 30, and 40 are linear, and a portion of the rod electrodes are arranged tilted relative to the Z axis. However, it is also possible to use a rod electrode that is curved at least partially in the middle of its extension direction instead of a linear shape. Fig.12 This is a plan view of an ion guide 50 according to a modified example using curved rod electrodes as viewed from above.

[0098] and Figure 3 It is relatively obvious that in this example, among the six rod electrodes 511 to 516, two rod electrodes 511 and 514 are bent. In such a configuration, since it is also possible to realize a hexapole configuration at the entrance of the ion guide 50 and a quadrupole configuration at the exit, it is possible to obtain an effect almost equivalent to that of the ion guide in the above-mentioned embodiment in terms of ion transport efficiency. In addition, the bent shape referred to here is not necessarily limited to a shape in which a portion of the extension direction of the rod electrode is bent, and also includes a shape in which a portion of the extension direction of the rod electrode (not limited to one portion) is bent at a specified angle.

[0099] In addition, in the description of the above-mentioned embodiments and modified examples, the polarity of the ions to be analyzed is set to positive, but in the case where the polarity of the ions to be analyzed is negative, it is obvious that the problem can be solved by appropriately changing the DC voltage applied to each rod electrode included in the ion guide and the DC voltage applied to other parts.

[0100] <Mass Spectrometer of Another Embodiment>

[0101] In the mass spectrometer of the above embodiment, the first ion guide 20 is arranged in the first intermediate vacuum chamber 3. However, the first ion guide 20 or the ion guides of the above modifications may be arranged in the second intermediate vacuum chamber 4 having a lower gas pressure than the first intermediate vacuum chamber 3 but a higher gas pressure than the high vacuum chamber 5. That is, the first ion guide 20 or the ion guides of the above modifications may be used as Figure 1 The second ion guide 10 in the embodiment of the present invention.

[0102] In addition, it is also possible to configure a mass spectrometer that performs ionization at atmospheric pressure or a pressure close to atmospheric pressure in a triple quadrupole mass spectrometer, a quadrupole-time of flight mass spectrometer, a Fourier transform ion cyclotron resonance mass spectrometer, etc., and transports the ions to a mass separator disposed in a high vacuum atmosphere via one or more intermediate vacuum chambers, instead of a single quadrupole mass spectrometer, and arranges the first ion guide 20 or the ion guides of the above-mentioned modifications inside these intermediate vacuum chambers. In addition, the ion source is not limited to the ESI ion source, but can be replaced by an ion source based on various ionization methods such as atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), probe electrospray ionization (PESI), and direct analysis in real time (DART). That is, the ion source and the mass separator are not limited to those described above, but various types or methods can be used.

[0103] In addition, the first ion guide 20 or the ion guides of the above-mentioned modifications may not be arranged inside the intermediate vacuum chamber, but the first ion guide 20 or the ion guides of the above-mentioned modifications may be arranged inside a pool into which various gases such as collision gas and reaction gas are introduced from the outside so as to perform various operations on ions using the gases.

[0104] Specifically, for example, a triple quadrupole mass spectrometer and a quadrupole-time-of-flight mass spectrometer have a collision cell that causes ions to dissociate by collision induced dissociation (CID), and the first ion guide 20 or the ion guides of the above-mentioned modifications may be arranged inside the collision cell. In addition, an inductively coupled plasma (ICP) mass spectrometer generally has a collision cell or a reaction cell to eliminate interfering ions and molecules, and the first ion guide 20 or the ion guides of the above-mentioned modifications may be arranged inside the collision cell or the reaction cell.

[0105] The above-described embodiment and modified examples are merely examples of the present invention, and modifications, additions, and corrections appropriately made within the scope of the gist of the present invention are also intended to be included in the scope of the claims of the present invention.

[0106] Various embodiments of the present invention have been described above with reference to the drawings. Finally, various aspects of the present invention will be described.

[0107] A mass spectrometer according to a first aspect of the present invention is a mass spectrometer having an ion transport optical system for transporting ions to be analyzed.

[0108] The ion transport optical system (20, 13) comprises:

[0109] N rod electrodes (211 to 216) having an even number of 6 or more rods arranged as a whole to extend in the ion transport direction;

[0110] A voltage generating unit (13) applies a predetermined voltage to each of the N rod electrodes (211 to 216).

[0111] At least two of the four rod electrodes (211, 214, 215, 216) are arranged tilted relative to the central axis (201, 202) in such a manner that they approach the central axis (201, 202) of the N-pole configuration or the quadrupole configuration as they travel in the ion transport direction, so that the N rod electrodes (211-216) are arranged in an N-pole configuration on the ion incident side, and four of the N rod electrodes (211, 214, 215, 216) are arranged in a quadrupole configuration on the ion emission side.

[0112] The voltage generating unit (13) is capable of applying high-frequency voltages with reversed phases to adjacent rod electrodes around the ion light axis relative to the N rod electrodes (211-216), applying a first DC voltage to the four rod electrodes (211, 214, 215, 216) configured as a quadrupole on the ion emission side, and applying a second DC voltage different from the first DC voltage to the (N-4) rod electrodes (212, 213) other than the four rod electrodes among the N rod electrodes (211-216).

[0113] According to the mass spectrometer of the first scheme, although the convergence effect of ions on the incident side of the ion transport optical system is relatively weak, the ion confinement effect is strong, so the introduced ions can be captured with less loss. On the other hand, although the confinement effect of ions on the ejection side of the ion transport optical system is relatively weak, the ion confinement effect is strong, so the ions can be reduced to a thin diameter and sent out. Thus, even in the case where ions are diffused and introduced due to a supersonic free jet, for example, ions can be efficiently collected and transported to the subsequent stage through a thin ion passage hole. As a result, the amount of ions for mass analysis can be increased, improving the analysis sensitivity.

[0114] A mass spectrometer according to a second aspect of the present invention is a mass spectrometer having an ion transport optical system for transporting ions to be analyzed.

[0115] The ion transport optical system (50, 13) comprises:

[0116] N rod electrodes (511 to 516) having an even number of 6 or more arranged as a whole to extend in the ion transport direction;

[0117] A voltage generating unit (13) applies a predetermined voltage to each of the N rod electrodes.

[0118] The shape of at least two of the four rod electrodes (511, 514) is set so that at least a portion of the rod electrodes extending in the ion transport direction is bent in a manner close to the central axis (501, 502) of the N-pole configuration or the quadrupole configuration, so that the N rod electrodes (511-516) are in the N-pole configuration on the ion incident side, and four of the N rod electrodes (511-516) are in the quadrupole configuration on the ion emission side.

[0119] The voltage generating unit can apply high-frequency voltages with reversed phases to adjacent rod electrodes around the ion light axis relative to the N rod electrodes (511~516), and apply a first DC voltage to the four rod electrodes (511, 514, 515, 516) configured as a quadrupole on the ion emission side, and apply a second DC voltage different from the first DC voltage to the (N-4) rod electrodes (512, 513) other than the four rod electrodes among the N rod electrodes (511~516).

[0120] The mass spectrometer according to the second embodiment can achieve the same effect as the mass spectrometer according to the first embodiment. That is, even when ions are diffused and introduced by a supersonic free jet, the ions can be efficiently collected and transported to the subsequent stage through a small ion passage hole. Thus, the amount of ions for mass analysis can be increased, and the analysis sensitivity can be improved.

[0121] A mass spectrometer according to a third aspect of the present invention is the mass spectrometer according to the first or second aspect, wherein

[0122] The voltage generating unit (13) applies the second DC voltage having a voltage value greater than the first DC voltage to the (N-4) rod electrodes.

[0123] According to the mass spectrometer of the third scheme, for example, for positive polarity ions, the DC potential on the central axis of the space surrounded by N rod electrodes and near the entrance of the ions becomes higher than the DC potential on the central axis of the space surrounded by four rod electrodes and near the exit of the ions. That is, since a potential distribution that decreases from the entrance side of the ions toward the exit side is formed in the space surrounded by the rod electrodes, the ions are accelerated. Thus, even if the ions lose kinetic energy due to collisions with residual gas, etc., kinetic energy can be given to the ions so that they are smoothly guided to the exit, thereby improving the ion transport efficiency.

[0124] A mass spectrometer according to a fourth aspect of the present invention is, in the mass spectrometer according to the third aspect,

[0125] The central axis of the N-pole arrangement is parallel to the central axis of the quadrupole arrangement and is not located on a straight line,

[0126] The ion transport optical system deflects ions midway in a direction orthogonal to the two central axes according to a difference between the first DC voltage and the second DC voltage.

[0127] According to the mass spectrometer of the fourth scheme, not only can ions be efficiently transported, but also the ion optical axis can be deviated by the action of the electric field during the transport. As a result, neutral particles such as sample component molecules and active neutral particles that enter the space surrounded by the rod electrode together with the ions are separated from the ions during the transport in the space, and only ions with such neutral particles removed are ejected from the outlet. As a result, the situation where neutral particles are transported to the subsequent stage together with the ions can be reduced.

[0128] A mass spectrometer according to a fifth aspect of the present invention is the mass spectrometer according to the first or second aspect, wherein a central axis (301) of the N-pole arrangement and a central axis (301) of the quadrupole arrangement are located on a straight line.

[0129] According to the mass spectrometer of the fifth scheme, since the central axis of the configuration of the N-pole on the ion incident side in the ion transport optical system and the central axis of the configuration of the quadrupole on the ion ejection side are on a straight line, the loss of ions when passing through the ion transport optical system is less, and the incident ions can be efficiently converged and ejected.

[0130] A mass spectrometer according to a sixth aspect of the present invention is the mass spectrometer according to the first or second aspect, wherein N is an even number in the range of 6-12.

[0131] According to the mass spectrometer of the sixth aspect, it is possible to achieve a high enough ion transport efficiency for practical use while avoiding the structure of the rod electrodes of the ion transport optical system becoming too complicated.

[0132] A mass spectrometer according to a seventh aspect of the present invention is, in the mass spectrometer according to the sixth aspect,

[0133] There is one or more intermediate vacuum chambers (3, 4) between an ionization chamber (2) for ionizing sample components in an atmospheric pressure atmosphere and a high vacuum chamber (5) equipped with a mass separation section (11) and maintained in a high vacuum atmosphere, and the N rod electrodes (211 to 216) are arranged in the intermediate vacuum chamber (3) of the next stage of the ionization chamber (2).

[0134] According to the mass spectrometer of the seventh embodiment, ions derived from sample components generated in the ionization chamber and sent to the intermediate vacuum chamber of the next stage can be efficiently sent to the next intermediate vacuum chamber or high vacuum chamber, that is, while suppressing the loss of ions. Thus, the amount of ions for mass analysis can be increased, achieving high analytical sensitivity.

[0135] A mass spectrometer according to an eighth aspect of the present invention is, in the mass spectrometer according to the sixth aspect,

[0136] There are two or more intermediate vacuum chambers (3, 4) between an ionization chamber (2) for ionizing sample components in an atmospheric pressure atmosphere and a high vacuum chamber (5) equipped with a mass separation section (11) and maintained in a high vacuum atmosphere, and the N rod electrodes (211 to 216) are arranged in the intermediate vacuum chambers (4) at the lower two stages of the ionization chamber (2).

[0137] According to the mass spectrometer of the eighth aspect, ions originating from sample components that are sent from the previous intermediate vacuum chamber to the next intermediate vacuum chamber can be efficiently sent to the next intermediate vacuum chamber or high vacuum chamber, i.e., while suppressing the loss of ions. Thus, the amount of ions for mass analysis can be increased, achieving high analytical sensitivity.

[0138] A mass spectrometer according to a ninth aspect of the present invention is, in the mass spectrometer according to the sixth aspect,

[0139] A collision cell is provided for dissociating ions by contacting them with a predetermined gas, and the N-rod electrodes are arranged in the collision cell.

[0140] According to the mass spectrometer of the ninth embodiment, it is possible to suppress the loss of ions introduced into the collision cell and to dissociate them efficiently. In addition, product ions and the like generated by dissociating the ions can be efficiently discharged from the collision cell, i.e., while suppressing the loss of ions, and thus transported to, for example, a subsequent mass separator. Thus, the amount of ions for mass analysis can be increased in a triple quadrupole mass spectrometer and a quadrupole-time-of-flight mass spectrometer, thereby achieving high analytical sensitivity.

[0141] A mass spectrometer according to a tenth aspect of the present invention is, in the mass spectrometer according to the sixth aspect,

[0142] A reaction cell is provided for reacting ions with a predetermined gas, and the N-rod electrodes are arranged in the reaction cell.

[0143] The mass spectrometer according to the tenth scheme can suppress the loss of ions introduced into the reaction cell and make the undesired neutral particles introduced together with the ions of the analysis object react with the gas efficiently. Thus, in the ICP mass spectrometer, the neutral particles and interfering ions not needed for the analysis can be well removed, and on the other hand, the ions of the analysis object can be efficiently transported to the subsequent stage for mass analysis. As a result, interference can be eliminated and high analytical sensitivity can be achieved.

[0144] Description of Reference Numerals

[0145] 1 Chamber

[0146] 2 Ionization chamber

[0147] 3. The first intermediate vacuum chamber

[0148] 4 Second intermediate vacuum chamber

[0149] 5 High vacuum chamber

[0150] 6 ESI sprayer

[0151] 7 Heating the capillary

[0152] 8 cone body

[0153] 9 Ions pass through the pore

[0154] 10. Second ion guide

[0155] 11 Quadrupole mass filter

[0156] 12 Ion detector

[0157] 13. First ion guide voltage generating unit

[0158] 14. Second ion guide voltage generating unit

[0159] 15 Mass filter voltage generator

[0160] 16 Control Unit

[0161] 20, 30, 40, 50 1st ion guide (ion guide)

[0162] 201, 501 1st Central Axis

[0163] 202, 502 Second Central Axis

[0164] 203 regular hexagon

[0165] 204, 304 Rectangle

[0166] 211~216、311~318、411~422、511~516 Rod electrode 301、401 Center axis

[0167] 303 regular octagon

[0168] 304 Rectangle

[0169] 403 regular dodecagon

[0170] 404 square.

Claims

1. A mass spectrometer having an ion transport optical system for transporting ions to be analyzed, characterized in that: The ion transport optical system comprises: The N-rod electrodes have an even number of 6 or more that are arranged as a whole to extend in the ion transport direction; A voltage generating unit applies a predetermined voltage to each of the N rod electrodes. At least two of the four rod electrodes are tilted relative to the central axis in such a manner that they approach the central axis of the N-pole configuration or the quadrupole configuration as they travel in the ion transport direction, so that the N rod electrodes are in the N-pole configuration on the ion incident side and the four rod electrodes in the quadrupole configuration on the ion emission side. The voltage generating unit is capable of applying high-frequency voltages with mutually reversed phases to adjacent rod electrodes around the ion optical axis relative to the N rod electrodes, applying a first DC voltage to the four rod electrodes configured as a quadrupole on the ion emission side, and applying a second DC voltage different from the first DC voltage to N-4 rod electrodes other than the four rod electrodes among the N rod electrodes. The voltage generating unit applies the second DC voltage having a voltage value greater than the first DC voltage to the N-4 rod electrodes. The voltage generating unit is configured to form an N-pole high-frequency electric field on the incident side of the ions and to form a quadrupole high-frequency electric field on the ejection side of the ions.

2. The mass spectrometer according to claim 1, wherein: The central axis of the N-pole arrangement is parallel to the central axis of the quadrupole arrangement and is not located on a straight line, The ion transport optical system deflects ions in a direction orthogonal to two central axes in the middle of the ion transport according to the difference between the first DC voltage and the second DC voltage.

3. The mass spectrometer according to claim 1, wherein: The central axis of the arrangement of the N-pole and the central axis of the arrangement of the quadrupole are located on a straight line.

4. The mass spectrometer according to claim 1, wherein: The N number of rod electrodes is an even number ranging from 6 to 12.

5. The mass spectrometer according to claim 4, wherein: There is one or more intermediate vacuum chambers between an ionization chamber for ionizing sample components in an atmospheric pressure atmosphere and a high vacuum chamber provided with a mass separation unit and maintained in a high vacuum atmosphere. The N-rod electrodes are arranged in an intermediate vacuum chamber of the next stage of the ionization chamber.

6. The mass spectrometer according to claim 4, wherein: There are two or more intermediate vacuum chambers between an ionization chamber for ionizing sample components in an atmospheric pressure atmosphere and a high vacuum chamber provided with a mass separation unit and maintained in a high vacuum atmosphere. The N-rod electrodes are arranged in the intermediate vacuum chambers of the lower two stages of the ionization chamber.

7. The mass spectrometer according to claim 4, wherein: It has a collision cell that dissociates ions by contacting them with a specified gas. The N rod electrodes are arranged in the collision cell.

8. The mass spectrometer according to claim 4, wherein: A reaction cell is provided to react ions with a predetermined gas. The N-rod electrodes are arranged in the reaction cell.

9. A mass spectrometer having an ion transport optical system for transporting ions to be analyzed, characterized in that: The ion transport optical system comprises: The N-rod electrodes have an even number of 6 or more that are arranged as a whole to extend in the ion transport direction; A voltage generating unit applies a predetermined voltage to each of the N rod electrodes. The shape of at least two of the four rod electrodes is set so that at least a portion of the rod electrodes extending in the ion transport direction is bent in a manner close to the central axis of the N-pole configuration or the quadrupole configuration, so that the N rod electrodes are in the N-pole configuration on the ion incident side and the four rod electrodes in the quadrupole configuration on the ion emission side. The voltage generating unit is capable of applying high-frequency voltages with mutually reversed phases to adjacent rod electrodes around the ion optical axis relative to the N rod electrodes, applying a first DC voltage to the four rod electrodes configured as a quadrupole on the ion emission side, and applying a second DC voltage different from the first DC voltage to N-4 rod electrodes other than the four rod electrodes among the N rod electrodes. The voltage generating unit applies the second DC voltage having a voltage value greater than the first DC voltage to the N-4 rod electrodes. The voltage generating unit is configured to form an N-pole high-frequency electric field on the incident side of the ions and to form a quadrupole high-frequency electric field on the ejection side of the ions.

10. The mass spectrometer according to claim 9, wherein: The central axis of the N-pole arrangement is parallel to the central axis of the quadrupole arrangement and is not located on a straight line, The ion transport optical system deflects ions midway in a direction orthogonal to a central axis of the arrangement of the N-pole and a central axis of the arrangement of the quadrupole, according to a difference between the first DC voltage and the second DC voltage.

11. The mass spectrometer according to claim 9, wherein: The central axis of the arrangement of the N-pole and the central axis of the arrangement of the quadrupole are located on a straight line.

12. The mass spectrometer according to claim 9, wherein: The N number of rod electrodes is an even number ranging from 6 to 12.

13. The mass spectrometer according to claim 12, wherein: There is one or more intermediate vacuum chambers between an ionization chamber for ionizing sample components in an atmospheric pressure atmosphere and a high vacuum chamber provided with a mass separation unit and maintained in a high vacuum atmosphere. The N-rod electrodes are arranged in an intermediate vacuum chamber of the next stage of the ionization chamber.

14. The mass spectrometer according to claim 12, wherein: There are two or more intermediate vacuum chambers between an ionization chamber for ionizing sample components in an atmospheric pressure atmosphere and a high vacuum chamber provided with a mass separation unit and maintained in a high vacuum atmosphere. The N-rod electrodes are arranged in the intermediate vacuum chambers of the lower two stages of the ionization chamber.

15. The mass spectrometer according to claim 12, wherein: It has a collision cell that dissociates ions by contacting them with a specified gas. The N rod electrodes are arranged in the collision cell.

16. The mass spectrometer according to claim 12, wherein: A reaction cell is provided to react ions with a predetermined gas. The N-rod electrodes are arranged in the reaction cell.

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