Mass spectroscope

Abstract

To improve a fetching efficiency of an ion into an ion introduction part.SOLUTION: A mass spectroscope contains: an ion source containing a probe for spraying a liquid sample into an ionization chamber; an ion introduction part transmitting an ion toward a vacuum chamber from the ionization chamber; a reflection electrode that is arranged at a position opposite to an introduction port of the ion introduction part while nipping a spray flow; a first focus electrode that is arranged at a position that is opposite to the reflection electrode while nipping the spray flow; a second focus electrode that is arranged at a position opposite to the reflection electrode while nipping the spray flow, and focuses the ion focusing by the first focus electrode toward the introduction port; and a voltage application part that applies a voltage to each electrode. The voltage application part applies the voltage to each electrode so as to form a magnetic field where the ion in the spray flow is directed to the first focus electrode, is directed to the second focus electrode from the first focus electrode, and is directed to the introduction port from the second focus electrode.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a mass spectrometer, and more particularly to a mass spectrometer that generates ions by atmospheric pressure ionization and separates and detects the generated ions according to their mass-to-charge ratios. [Background technology]

[0002] As a method for ionizing compounds in a liquid sample in a mass spectrometer, atmospheric pressure ionization methods such as electrospray ionization, atmospheric pressure chemical ionization, and atmospheric pressure photoionization are known. In a mass spectrometer using an ion source based on atmospheric pressure ionization, it is necessary to introduce ions generated in an ionization chamber that is in an atmosphere of approximately atmospheric pressure into a vacuum chamber that is maintained in a vacuum atmosphere. In order to improve the analytical sensitivity of such an analyzer, it is particularly important to increase the amount of ions generated in the ionization chamber and to improve the efficiency of introducing ions from the ionization chamber into the vacuum chamber.

[0003] Japanese Patent No. 6593548 (Patent Document 1) discloses a mass spectrometer in which, in order to improve the efficiency of introducing ions from the ionization chamber into the vacuum chamber, a reflector electrode and a focusing electrode are arranged in the ionization chamber on either side of the spray flow ejected from the ionization probe, and the inlet end of a heated capillary that introduces ions into the vacuum chamber is inserted into the opening of the focusing electrode. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6593548 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the mass spectrometer disclosed in Patent Document 1, a reflection electric field that reflects and deflects ions is formed in the space between the reflection electrode and the focusing electrode, and a focusing electric field that focuses ions to the inlet end is formed near the inlet end, thereby increasing the efficiency of introducing ions from the ionization chamber to the vacuum chamber.

[0006] When ions are taken in from the ion introduction part, which is a heated capillary, the efficiency of taking in the ions can be increased by focusing the ions at the end of the ion introduction part to the same extent as the diameter of the inlet. The efficiency of taking in the ions can also be increased by widening the diameter of the inlet, but widening the diameter of the inlet requires improving the performance of the vacuum pump and increases the risk of failure, as impurities other than ions are transported from the inlet into the vacuum chamber. For this reason, it was necessary to focus the ions more at the end of the ion introduction part.

[0007] The present disclosure has been made to solve such problems, and an object of the disclosure is to improve the efficiency of ion uptake into an iontophoresis portion. [Means for solving the problem]

[0008] The mass spectrometer of the present disclosure is a mass spectrometer that generates ions by atmospheric pressure ionization and separates and detects the generated ions according to their mass-to-charge ratios. The mass spectrometer includes an ion source including a probe that sprays a liquid sample into an ionization chamber that is in an atmospheric pressure environment, an ion introduction unit that sends ions in the sample droplets sprayed from the probe from the ionization chamber toward a vacuum chamber in a direction intersecting the direction of spraying the liquid sample from the probe, a reflecting electrode that is disposed at a position facing the inlet of the ion introduction unit across the spray flow of the sample droplets from the probe, a first focusing electrode that is disposed at a position facing the reflecting electrode across the spray flow of the sample droplets from the probe and collects ions reflected or deflected by the reflecting electrode, a second focusing electrode that is disposed at a position facing the reflecting electrode across the spray flow of the sample droplets from the probe and focuses the ions focused by the first focusing electrode toward the inlet, and a voltage application unit that applies voltages to each electrode. The voltage application unit applies a voltage to each electrode so that an electric field is formed in which ions in the spray stream of sample droplets from the probe are directed toward the first focusing electrode, from the first focusing electrode to the second focusing electrode, and from the second focusing electrode to the inlet. Effect of the Invention

[0009] According to the present disclosure, in a mass spectrometer, by disposing a second focusing electrode in addition to a first focusing electrode and forming an electric field from the second focusing electrode to the inlet, ions can be focused further toward the center of the inlet compared to a case where only the first focusing electrode is disposed, and therefore the efficiency of taking in ions into the ion introduction section can be improved. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic diagram showing the overall configuration of a mass spectrometer according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration inside an ionization chamber according to the first embodiment. [Diagram 3] FIG. 11 is a schematic diagram showing a schematic configuration inside an ionization chamber according to a second embodiment. [Figure 4]FIG. 11 is a diagram showing the results of a simulation of ion trajectories in an ionization chamber according to the second embodiment. [Diagram 5] FIG. 13 is a diagram showing the simulation results of the second embodiment and the comparative example, showing the ion arrival positions at the inlet. [Figure 6] FIG. 4 is a schematic diagram showing a schematic configuration inside an ionization chamber according to a comparative example. [Figure 7] FIG. 11 is a schematic diagram showing a schematic configuration inside an ionization chamber according to a third embodiment. [Figure 8] FIG. 13 is a diagram showing the results of a simulation of ion trajectories in an ionization chamber according to the third embodiment. [Figure 9] FIG. 13 is a diagram showing the simulation results of the third embodiment and a comparative example, showing the ion arrival positions at the inlet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference characters and their description will not be repeated.

[0012] [First Example] (Overall configuration of mass spectrometer) 1 is a schematic diagram showing the overall configuration of a mass spectrometer according to Example 1. The mass spectrometer 100 is configured as a multi-stage differential pumping system in which two chambers, a first intermediate vacuum chamber 2 and a second intermediate vacuum chamber 3, are provided between an ionization chamber 1, which is in a substantially atmospheric pressure atmosphere, and an analysis chamber 4, which is in a high vacuum atmosphere evacuated by a high-performance vacuum pump (not shown).

[0013] An ion source including a probe 5 for electrospray ionization (ESI) is disposed in the ionization chamber 1. The ion source is not limited to an ESI ion source, and may be an ion source for other atmospheric pressure ionization methods such as an atmospheric pressure chemical ionization (APCI) ion source or an atmospheric pressure photo ionization (APPI) ion source.

[0014] A liquid sample containing sample components is sprayed from the probe 5 while being electrically charged into the ionization chamber 1. The droplets sprayed from the tip of the probe 5 break down into small particles upon contact with the surrounding air, and the sample components are ionized in the process of the solvent evaporating from the droplets.

[0015] The ionization chamber 1 and the first intermediate vacuum chamber 2 are connected by a cylindrical ion introduction section 9. The ion introduction section 9 is, for example, a heated capillary. There is a pressure difference between both open ends of the ion introduction section 9. This pressure difference creates a gas flow that flows from the ionization chamber 1 through the ion introduction section 9 to the first intermediate vacuum chamber 2. Ions derived from the sample components generated in the ionization chamber 1 are sucked into the ion introduction section 9 by riding on the gas flow generated mainly by the pressure difference, and are sent into the first intermediate vacuum chamber 2 together with the gas flow.

[0016] A multipole ion guide 10 is provided in the first intermediate vacuum chamber 2, surrounding an ion optical axis L, which is the axis of a cylindrical ion introduction section 9. A skimmer 11 having a small diameter orifice is provided in the wall separating the first intermediate vacuum chamber 2 and the second intermediate vacuum chamber 3. Ions sent into the first intermediate vacuum chamber 2 are focused near the orifice of the skimmer 11 by the action of the electric field formed by the ion guide 10, and are sent into the second intermediate vacuum chamber 3 through the skimmer 11.

[0017] A multipole (e.g., octapole) type ion guide 12 is provided in the second intermediate vacuum chamber 3 so as to surround the ion optical axis L. The ions sent into the second intermediate vacuum chamber 3 are focused by the action of a radio frequency (RF) electric field formed by the ion guide 12 and sent into the analysis chamber 4.

[0018] In the analysis chamber 4, a quadrupole mass filter 13 is disposed surrounding the ion optical axis L, and an ion detector 14 is disposed on the ion optical axis L. The ions sent into the analysis chamber 4 are introduced into a space in the longitudinal direction (direction of the ion optical axis L) of the quadrupole mass filter 13, and only ions having a specific mass-to-charge ratio pass through the quadrupole mass filter 13 and reach the ion detector 14 due to the action of an electric field formed by an RF voltage and a direct current (DC) voltage applied to the quadrupole mass filter 13. The ion detector 14 generates a detection signal according to the amount of ions that have reached it, and transmits the detection signal to a data processing device (not shown).

[0019] As described above, in mass spectrometer 100, ions derived from sample components generated in ionization chamber 1 pass through first intermediate vacuum chamber 2 and second intermediate vacuum chamber 3 and are detected in analysis chamber 4. Therefore, by minimizing loss of ions generated in ionization chamber 1 while ultimately allowing a larger number of ions to enter ion detector 14, highly sensitive analysis can be achieved.

[0020] (Schematic configuration of ion source) 2 is a schematic diagram showing a schematic configuration inside the ionization chamber according to Example 1. In the following, the blowing direction along the central axis of the spray from the probe 5 is defined as the Z-axis direction, the ion sucking direction along the central axis of the ion introduction part 9 perpendicular to the Z-axis direction is defined as the X-axis direction, and the direction perpendicular to the X-axis and Z-axis directions is defined as the Y-axis direction.

[0021] An auxiliary electrode 31, a reflecting electrode 32, a first focusing electrode 33, and a second focusing electrode 34 are arranged in the ionization chamber 1. The mass spectrometer 100 includes a control unit 20 that controls the entire mass spectrometer 100, a nozzle power supply unit 21 that applies a voltage to the probe 5, a reflecting electrode power supply unit 22 that applies a voltage to the reflecting electrode 32, a first focusing electrode power supply unit 23 that applies a voltage to the first focusing electrode 33, and a second focusing electrode power supply unit 24 that applies a voltage to the second focusing electrode 34.

[0022] The auxiliary electrode 31 is disposed at a position facing the tip of the probe 5. The auxiliary electrode 31 is a flat electrode in which an opening 31a is formed. The auxiliary electrode 31 is disposed so that the flat surface of the auxiliary electrode 31 is parallel to the XY plane. The auxiliary electrode 31 is also disposed so that the tip of the probe 5 is located within the opening 31a when the auxiliary electrode 31 is viewed from the Z-axis direction in plan, so that the spray of sample droplets from the probe 5 passes through the circular opening 31a.

[0023] The reflecting electrode 32 is disposed at a position opposite to the inlet 9a, which is the inlet end of the ion introduction unit 9, across the spray flow of sample droplets from the probe 5. The reflecting electrode 32 is a flat electrode, and the flat surface is disposed parallel to the YZ plane.

[0024] The first focusing electrode 33 is disposed at a position facing the reflecting electrode 32 across the spray flow of sample droplets from the probe 5. The first focusing electrode 33 is disposed so as to surround a central axis C that is parallel to the X-axis, which is the ion intake direction, and passes through the center of the inlet 9a. For example, the first focusing electrode 33 is a flat electrode in which a circular opening that becomes the first transmission path 33a is formed. The flat surface of the first focusing electrode 33 is disposed parallel to the YZ plane. The first focusing electrode 33 is also disposed so that the central axis C coincides with the central axis of the first transmission path 33a. That is, the first focusing electrode 33 forms the first transmission path 33a. The method of forming the first transmission path 33a by the first focusing electrode 33 is not limited to the method of providing an opening in the first focusing electrode 33.

[0025] The second focusing electrode 34 is disposed at a position facing the reflecting electrode 32 across the spray flow of sample droplets from the probe 5. The second focusing electrode 34 is disposed so as to surround a central axis C that is parallel to the X-axis, which is the ion intake direction, and passes through the center of the inlet 9a, forming a second transmission path 34a. The second focusing electrode 34 is, for example, an ion funnel-type or ion guide-type electrode to which an RF voltage is applied, or a cylindrical electrode to which a DC voltage is applied. An example in which the second focusing electrode 34 is an electrode to which an RF voltage is applied and an example in which the second focusing electrode 34 is an electrode to which a DC voltage is applied will be described later.

[0026] The first focusing electrode 33, the second focusing electrode 34, and the ion introduction section 9 are arranged such that, when the inlet 9a is viewed from the reflecting electrode 32 in a plan view, the inner edge of the second transmission path 34a is located below the inner edge of the first transmission path 33a, and the inlet 9a is located below the inner edge of the second transmission path 34a. For example, the minimum diameter of the first transmission path 33a formed by the first focusing electrode 33 is equal to or larger than the maximum diameter of the second transmission path 34a formed by the second focusing electrode 34. Also, the minimum diameter of the second transmission path 34a is equal to or larger than the diameter of the inlet 9a.

[0027] The control unit 20 controls the entire mass spectrometer 100 and controls the voltages generated by each power supply unit. Although not shown, the control unit 20 has as its main components a CPU (Central Processing Unit) which is a processor, a storage unit which stores programs and data, and a communication I / F (Interface). The components are connected to each other by a data bus.

[0028] The storage unit includes a ROM (Read Only Memory), a RAM (Random Access Memory), and a HDD (Hard Disk Drive). The ROM stores programs executed by the CPU. The RAM temporarily stores data generated by the execution of programs in the CPU and data input via the communication I / F. The RAM can function as a temporary data memory used as a working area. The HDD is a non-volatile storage device. Also, a semiconductor storage device such as a flash memory may be adopted instead of the HDD.

[0029] The program stored in the ROM may be stored in a storage medium and distributed as a program product, or the program may be provided by an information provider as a so-called downloadable program product via the Internet or the like.

[0030] The storage medium is not limited to DVD-ROM (Digital Versatile Disk Read Only Memory), CD-ROM (compact disc read-only memory), FD (Flexible Disk), and hard disk, but may be a medium that carries a program in a fixed manner, such as a magnetic tape, a cassette tape, an optical disk (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), an optical card, a mask ROM, an EPROM (Electronically Programmable Read-Only Memory), an EEPROM (Electronically Erasable Programmable Read-Only Memory), a flash ROM, or other semiconductor memory. The recording medium is a non-transitory medium that allows a computer to read a program, etc.

[0031] The probe 5 includes a capillary 50 through which a liquid sample passes, a neprise gas tube 52 arranged to surround the capillary 50, and a heating gas tube 54 arranged to surround the neprise gas tube 52. The nozzle power supply unit 21 applies a voltage to the capillary 50 to impart an electric charge to the liquid sample sprayed from the probe 5. A DC voltage of up to several kV is applied from the nozzle power supply unit 21 to the capillary 50.

[0032] The charged liquid sample is atomized into fine droplets with the aid of the neprise gas ejected from the neprise gas tube 52. The high-temperature heating gas ejected from the heating gas tube 54 promotes the evaporation of the solvent from the droplets. The flow rate of the neprise gas is 0.5 L / min or more and 3 L / min or less. The flow rate of the heating gas is 3 L / min or more and 20 L / min or less.

[0033] A liquid sample is sprayed from the probe 5 while a voltage is applied from the nozzle power supply unit 21 to the capillary 50 (probe 5), so that the positively or negatively charged liquid sample is sprayed in the Z-axis direction from the probe 5. The charged mist of liquid sample passes through the opening 31a of the auxiliary electrode 31 along the gas flow together with the nebulizing gas, and is sent to the space sandwiched between the reflecting electrode 32 and the first focusing electrode 33.

[0034] The control unit 20 controls the reflective electrode power supply unit 22, the first focusing electrode power supply unit 23 and the second focusing electrode power supply unit 24 so that ions in the gas flow (spray flow) sent to the space sandwiched between the reflective electrode 32 and the first focusing electrode 33 form an electric field that flows toward the first focusing electrode 33, from the first focusing electrode 33 to the second focusing electrode 34, and from the second focusing electrode 34 to the inlet 9a.

[0035] For example, when the liquid sample is sprayed from the probe 5 so as to be positively charged, the voltage V1 applied to the reflection electrode 32, the voltage V2 applied to the first focusing electrode 33, the voltage V3 applied to the second focusing electrode 34, and the voltage V4 applied to the ion introduction unit 9 are set such that the voltage V1 is greater than the voltage V2, the voltage V2 is greater than the voltage V3, and the voltage V3 is greater than the voltage V4. That is, the voltages applied to the respective electrodes are set such that the relationship of the voltages V1 to V4 is V1 > V2 > V3 > V4. In the present embodiment, the conductive wall 31b electrically connected to the auxiliary electrode 31 and the ion introduction unit 9 is grounded, and its potential is, for example, 0V. That is, V4 is 0V. In the present embodiment, since the auxiliary electrode 31 is grounded, the electric fields in the spaces on both sides of the auxiliary electrode 31 (the space on the probe 5 side and the space on the reflection electrode 32 side) hardly affect each other.

[0036] In the following description, it is assumed that the ions to be measured are positive ions. However, when the ions to be measured are negative ions, voltages of opposite polarities are applied to the respective electrodes. In this case, the voltages V1 to V4 are set such that the voltage V1 is smaller than the voltage V2, the voltage V2 is smaller than the voltage V3, and the voltage V3 is smaller than the voltage V4. That is, the voltages applied to the respective electrodes are set such that the relationship of the voltages V1 to V4 is V1 < V2 < V3 < V4.

[0037] By setting each voltage as described above, a reflection electric field that induces positive ions in the direction from the reflection electrode 32 to the first focusing electrode 33 is formed in the space sandwiched between the reflection electrode 32 and the first focusing electrode 33 through which the charged mist-like liquid sample is sent.

[0038] Since V2>V3 is set, a focusing electric field that guides positive ions from the inner edge of the first transmission path 33a in the central axis direction (the direction of the central axis C) of the second transmission path 34a is also formed. In addition, since the potential difference |V1-V3| between the reflecting electrode 32 and the second focusing electrode 34 is larger than the potential difference |V1-V2| between the reflecting electrode 32 and the first focusing electrode 33, a reflecting electric field that more strongly guides ions from the reflecting electrode 32 toward the second focusing electrode 34 is formed.

[0039] Since V3>V4 is set, a focused electric field that induces positive ions from the inner edge of the second transmission path 34a toward the center of the introduction port 9a (the direction of the central axis C) is also formed. In addition, since the potential difference |V1-V4| between the reflecting electrode 32 and the ion introduction section 9 is larger than the potential difference |V1-V3| between the reflecting electrode 32 and the reflecting electrode 32, a reflected electric field that induces ions more strongly from the reflecting electrode 32 toward the ion introduction section 9 is formed.

[0040] Positively charged ions and non-ionized minute charged droplets in the spray flow that have passed through the opening 31a of the auxiliary electrode 31 are guided toward the first focusing electrode 33 by the action of the reflected electric field and are separated from the spray flow (gas flow). The separated charged droplets are focused to the periphery of the inlet 9a by the focusing electric field that runs from the inner edge of the first transmission path 33a to the central axis of the second transmission path 34a, i.e., toward the center of the inlet 9a.

[0041] Furthermore, in this embodiment, a second focusing electrode 34 is provided in addition to the first focusing electrode 33, and a focusing electric field is formed from the inner edge of the second transmission path 34a toward the center of the inlet 9a, so that the separated and focused charged droplets, etc. can be further focused toward the center of the inlet 9a, thereby further improving the efficiency of ion introduction into the ion introduction section 9 and achieving high sensitivity of the mass spectrometer 100.

[0042] [Second Example] 3 is a schematic diagram showing a schematic configuration inside an ionization chamber according to the second embodiment. The mass spectrometer according to the second embodiment differs from the mass spectrometer according to the first embodiment in that it includes an RF electrode 342 as the second focusing electrode 34, and includes a high frequency power supply unit 242 and a DC power supply unit 244 as the second focusing electrode power supply unit 24. In the following, of the configuration inside the ionization chamber 1a according to the second embodiment, the configuration different from the configuration inside the ionization chamber 1 according to the first embodiment will be described, and a description of the common configuration will be omitted.

[0043] The first focusing electrode 33, the RF electrode 342, and the ion introduction section 9 are arranged in this order from the reflecting electrode 32 side along the central axis C. That is, the RF electrode 342 is arranged between the first focusing electrode 33 and the ion introduction section 9. Since the first focusing electrode 33, the RF electrode 342, and the ion introduction section 9 are not positioned overlapping with each other, installation of each component is easy.

[0044] The RF electrode 342 is an ion funnel type electrode having a plurality of ring-shaped electrodes 344 arranged at equal intervals along the central axis C. The RF electrode 342 may be a multipole ion guide type electrode made up of an even number of rod electrodes (usually four or eight) that are arranged at equal angular intervals around the ion optical axis and extend in the direction of the central axis C. In the second embodiment, the RF electrode 342, which is the second focusing electrode 34, can be said to be an electrode group made up of a plurality of electrodes.

[0045] The opening of the multiple ring-shaped electrodes 344 is smaller as it is closer to the ion introduction section 9. Ions pass through the second transmission path 342a, which is a truncated cone-shaped space surrounded by the ring-shaped electrodes 344. The inner diameter of the ring-shaped electrode 344 that is closest to the first focusing electrode 33 among the multiple ring-shaped electrodes 344 is equal to or smaller than the minimum diameter of the first transmission path 33a of the first focusing electrode 33. The inner diameter of the ring-shaped electrode 344 with the smallest inner diameter among the multiple ring-shaped electrodes 344 is equal to or larger than the diameter of the introduction port 9a. That is, when the introduction port 9a is viewed from the reflecting electrode 32 in a plan view, the first focusing electrode 33, the RF electrode 342 (the multiple ring-shaped electrodes 344), and the ion introduction section 9 are arranged so that the inner edge of the second transmission path 342a is located below the inner edge of the first transmission path 33a, and the introduction port 9a is located below the inner edge of the second transmission path 342a.

[0046] RF voltages with mutually opposite phases are applied to two ring-shaped electrodes 344 adjacent in the X-axis direction by the high frequency power supply unit 242. As a result, an RF electric field that focuses ions in the second transmission path 342a, which is a truncated cone-shaped space surrounded by the ring-shaped electrodes 344, is formed.

[0047] In addition, a DC voltage that changes stepwise in the X-axis direction is applied to each of the multiple ring-shaped electrodes 344 by the DC power supply unit 244 so as to form a DC potential gradient that accelerates the ions focused by the first focusing electrode 33 toward the inlet 9a.

[0048] A DC voltage is applied to the reflecting electrode 32 and the first focusing electrode 33. For example, when the liquid sample is sprayed from the probe 5 so as to be positively charged, the voltage V1 applied to the reflecting electrode 32, the voltage V2 applied to the first focusing electrode 33, the DC voltage V31 applied to the ring-shaped electrode 344 arranged closest to the first focusing electrode 33, the DC voltage V32 applied to the ring-shaped electrode 344 arranged closest to the inlet 9a, and the voltage V4 applied to the iontophoresis section 9 are set so that the voltage V1 is greater than the voltage V2, the voltage V2 is greater than the voltage V31, the voltage V31 is greater than the voltage V32, and the voltage V32 is greater than the voltage V4. That is, the DC voltages applied to the electrodes are set so that the relationship between the voltages V1, V2, V31, V32, and V4 is V1>V2>V31>V32>V4.

[0049] As a result, in the space between the reflecting electrode 32 and the first focusing electrode 33, into which the charged atomized liquid sample is delivered, an electric field is formed from the reflecting electrode 32 to the first focusing electrode 33, from the first focusing electrode 33 to the RF electrode 342, and from the RF electrode 342 to the inlet 9a. Furthermore, by applying an RF voltage to the RF electrode 342 by the high frequency power supply unit 242, an RF electric field is formed in the second transmission path 342a, and a substantial potential barrier that restrains ions is formed around the central axis C. As a result, the ions can be focused toward the central axis C.

[0050] In the second transmission path 342a, an RF electric field that focuses ions toward the central axis C and a DC potential gradient that accelerates ions toward the inlet 9a are formed, so that ions sent into the second transmission path 342a are sent toward the inlet 9a while being focused toward the central axis C.

[0051] As described above, in the mass spectrometer of the second embodiment, an RF electric field is formed, which is a focusing electric field that focuses toward the central axis C. This RF electric field can further focus the charged droplets, etc. that have been separated from the spray flow and focused, toward the center of the inlet 9a, thereby further improving the efficiency of ion intake into the ion introduction section 9 and achieving high sensitivity of the mass spectrometer.

[0052] Fig. 4 is a diagram showing a simulation result of an ion trajectory in an ionization chamber according to Example 2. Fig. 5 is a diagram showing a simulation result of Example 2 and a comparative example showing an ion arrival position at an inlet. Fig. 6 is a schematic diagram showing a schematic configuration in an ionization chamber according to a comparative example.

[0053] In the second embodiment, 20 ring electrodes 344 were arranged as the RF electrodes 342, the frequency of the RF voltage applied from the high frequency power supply unit 242 to each ring electrode 344 was 0.6 MHz, the amplitude was 1 kV, the voltage V1 applied to the reflector 32 was 4 kV, the voltage V2 applied to the first focusing electrode 33 was 1 kV, and the DC voltage V31 applied to the ring electrode 344 arranged closest to the first focusing electrode 33 was 952.5 V, and the voltage applied to the ring electrode 344 closer to the ion introduction portion 9 was lower so that the potential difference between the adjacent ring electrodes 344 was 47.5 V, and the simulation results shown in Figs. 4 and 5 were obtained. The voltage V4 applied to the ion introduction portion 9 was 0 V.

[0054] As shown in FIG. 4, all ions are separated from the gas flow and almost all ions can be focused towards the inlet 9a.

[0055] In addition, Fig. 5 shows the ion arrival position in the introduction port 9a, and the circular frame in Fig. 5 shows the inner edge of the introduction port 9a. Fig. 5 shows the simulation results in the comparative example together with the simulation results in the second embodiment.

[0056] 6, the mass spectrometer according to the comparative example differs from the mass spectrometer according to the second embodiment in that the RF electrode 342, which is the second focusing electrode 34, is not disposed in the ionization chamber 1x, that the second focusing electrode power supply unit 24 is not provided with the high frequency power supply unit 242 and the DC power supply unit 244, and that the first focusing electrode 33 is disposed so as to surround the ion introduction unit 9 in the ionization chamber 1x. In the comparative example, the voltage applied to the reflecting electrode 32 was set to 5 kV, and the voltage applied to the first focusing electrode was set to 2.5 kV, and the simulation results shown in FIG. 5 were obtained. The voltage applied to the ion introduction unit 9 was 0 V.

[0057] 5, in the mass spectrometer according to the second embodiment, by providing the RF electrode 342 which is the second focusing electrode, it is possible to improve the focusing of ions to the center of the inlet 9a, compared to a mass spectrometer according to a comparative example which does not have the RF electrode 342 which is the second focusing electrode. As a result, it is possible to improve the efficiency of taking in ions into the ion introduction section 9, thereby realizing high sensitivity of the mass spectrometer.

[0058] [Ion source according to the third embodiment] 7 is a schematic diagram showing a schematic configuration inside an ionization chamber according to Example 3. The mass spectrometer according to Example 3 differs from the mass spectrometer according to Example 1 in that it includes a DC electrode 346 as second focusing electrode 34 and a DC power supply unit 246 as second focusing electrode power supply unit 24. In the following, of the configuration inside ionization chamber 1b according to Example 3, configurations that differ from the configuration inside ionization chamber 1 according to Example 1 will be described, and descriptions of common configurations will be omitted.

[0059] The DC electrode 346 is a cylindrical electrode, and is disposed so that its axis is located on the central axis C. The length of the DC electrode 346 in the direction of the central axis C is longer than that of the first focusing electrode 33, and shorter than that of the ion introduction section 9. This forms an area where the components do not overlap, making it easier to install the components.

[0060] The inner diameter of the cylinder of the DC electrode 346 is smaller than that of the first focusing electrode 33 and larger than that of the ion introduction section 9. The DC electrode 346 is disposed in the first transmission path 33a of the first focusing electrode 33. That is, the first focusing electrode 33 is disposed so as to surround the DC electrode 346. The ion introduction section 9 is disposed in the second transmission path 346a formed by the DC electrode 346. That is, the DC electrode 346 is disposed so as to surround the ion introduction section 9.

[0061] As a result, when the inlet 9a is viewed in a planar view from the reflecting electrode 32, the first focusing electrode 33, the DC electrode 346 and the ion introduction section 9 are positioned so that the inner edge of the second transmission path 346a is located inside the inner edge of the first transmission path 33a, and the inlet 9a is located inside the inner edge of the second transmission path 346a.

[0062] A DC voltage is applied to the reflecting electrode 32, the first focusing electrode 33, and the DC electrode 346. For example, when the liquid sample is sprayed from the probe 5 so as to be positively charged, the voltage V1 applied to the reflecting electrode 32, the voltage V2 applied to the first focusing electrode 33, the voltage V33 applied to the DC electrode 346, and the voltage V4 applied to the iontophoresis section 9 are set so that the voltage V1 is greater than the voltage V2, the voltage V2 is greater than the voltage V33, and the voltage V33 is greater than the voltage V4. That is, the DC voltages applied to the electrodes are set so that the relationship between the voltages V1, V2, V33, and V4 is V1>V2>V33>V4.

[0063] As a result, in the space sandwiched between the reflecting electrode 32 and the first focusing electrode 33, through which the charged mist of liquid sample is delivered, an electric field is formed that flows from the reflecting electrode 32 to the first focusing electrode 33, from the first focusing electrode 33 to the DC electrode 346, and from the DC electrode 346 to the inlet 9a.

[0064] In the third embodiment, by providing the DC electrode 346, a focusing electric field is formed from the inner edge of the second transmission path 346a toward the center of the inlet 9a, and this focusing electric field can further focus the separated and focused charged droplets, etc., toward the center of the inlet 9a, thereby further improving the efficiency of ion introduction into the ion introduction section 9 and achieving high sensitivity of the mass spectrometer. In addition, by using a DC voltage, the circuit design and grounding can be made easier than when an RC voltage is used.

[0065] Fig. 8 is a diagram showing a simulation result of an ion trajectory in an ionization chamber according to Example 3. Fig. 9 is a diagram showing a simulation result of Example 3 and a comparative example showing ion arrival positions at an inlet.

[0066] In the third embodiment, the voltage V1 applied to the reflective electrode 32 was set to 4 kV, the voltage V2 applied to the first focusing electrode 33 was set to 2 kV, and the voltage C33 applied to the DC electrode 346 was set to 0.9 kV, and the simulation results shown in Figures 8 and 9 were obtained.

[0067] As shown in FIG. 8, all ions are separated from the gas flow, and almost all ions can be focused towards the inlet 9a.

[0068] 9 shows the ion arrival position in the inlet 9a, and the circular frame in FIG. 9 shows the inner edge of the inlet 9a. In FIG. 9, the simulation result in the comparative example is shown together with the simulation result in the third embodiment. The mass spectrometer in the comparative example is the same as the mass spectrometer described with reference to FIG. 6, and is different from the mass spectrometer in the third embodiment in that it does not include the DC electrode 346 which is the second focusing electrode 34 and the DC power supply unit 246 which is the second focusing electrode power supply unit 24. In the comparative example, the voltage applied to the reflecting electrode 32 was 5 kV, and the voltage applied to the first focusing electrode was 2.5 kV, and the simulation result shown in FIG. 9 was obtained. The voltage applied to the ion introduction unit 9 was 0 V.

[0069] 9, in the mass spectrometer according to the third embodiment, by providing the DC electrode 346 which is the second focusing electrode, it is possible to improve the focusing in the Z-axis direction compared to the mass spectrometer according to the comparative example which does not have the DC electrode 346 which is the second focusing electrode. As a result, it is possible to improve the efficiency of taking in ions into the ion introduction portion 9, thereby realizing high sensitivity of the mass spectrometer.

[0070] [Aspects] It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

[0071] (Item 1) A mass spectrometer according to one embodiment generates ions by atmospheric pressure ionization and separates and detects the generated ions according to their mass-to-charge ratios. The mass spectrometer includes an ion source including a probe that sprays a liquid sample into an ionization chamber that is in an atmospheric pressure environment, an ion introduction unit that sends ions in the sample droplets sprayed from the probe from the ionization chamber toward the vacuum chamber in a direction intersecting the direction in which the liquid sample is sprayed from the probe, a reflecting electrode that is disposed at a position facing the inlet of the ion introduction unit across the spray flow of sample droplets from the probe, a first focusing electrode that is disposed at a position facing the reflecting electrode across the spray flow of sample droplets from the probe and collects ions reflected or deflected by the reflecting electrode, a second focusing electrode that is disposed at a position facing the reflecting electrode across the spray flow of sample droplets from the probe and focuses the ions focused by the first focusing electrode toward the inlet, and a voltage application unit that applies a voltage to the electrodes. The voltage application unit applies a voltage to each electrode so that an electric field is formed in which ions in the spray stream of sample droplets from the probe are directed toward the first focusing electrode, from the first focusing electrode to the second focusing electrode, and from the second focusing electrode to the inlet.

[0072] According to the mass spectrometer described in paragraph 1, by providing a second focusing electrode in addition to the first focusing electrode and forming an electric field from the second focusing electrode to the inlet, ions can be focused further toward the center of the inlet compared to the case where only the first focusing electrode is provided, and therefore the efficiency of taking in ions into the ion introduction section can be improved.

[0073] (Item 2) In the mass spectrometer described in item 1, a first transmission path is formed by the first focusing electrode. A second transmission path is formed by the second focusing electrode. The first focusing electrode, the second focusing electrode, and the ion introduction section are arranged such that, when the inlet is viewed in a plan view from the reflecting electrode, the inner edge of the second transmission path is located below the inner edge of the first transmission path, and the inlet is located below the inner edge of the second transmission path.

[0074] According to the mass spectrometer described in item 2, the ions can be further focused toward the center of the inlet, and the efficiency of taking in the ions into the ion introduction section can be improved.

[0075] (Item 3) In the mass spectrometer according to item 1 or 2, the voltage application unit includes a radio frequency voltage application unit that applies a radio frequency voltage to the second focusing electrode. The radio frequency voltage application unit applies a radio frequency voltage to the second focusing electrode so as to form a radio frequency electric field that focuses the ions focused by the first focusing electrode from the second focusing electrode toward the center of the inlet.

[0076] According to the mass spectrometer described in item 3, the ions can be further focused toward the center of the inlet by the high frequency electric field, and the efficiency of taking in the ions into the ion introduction section can be further improved.

[0077] (Item 4) In the mass spectrometer according to item 3, the second focusing electrode is disposed between the first focusing electrode and the inlet of the ion introduction section.

[0078] According to the mass spectrometer described in item 4, the first focusing electrode, the second focusing electrode, and the ion introduction portion are not positioned to overlap, which makes it easy to install each component.

[0079] (Item 5) In the mass spectrometer according to item 3 or 4, the second focusing electrode is an ion funnel type or a multipole ion guide type electrode.

[0080] (Item 6) In the mass spectrometer according to item 1 or 2, the voltage application unit includes a DC voltage application unit that applies a DC voltage to the second focusing electrode.

[0081] According to the mass spectrometer described in paragraph 6, by applying a DC voltage, an electric field can be formed from the second focusing electrode toward the inlet, and the ions can be further focused toward the center of the inlet, thereby improving the efficiency of taking in the ions into the ion introduction section. In addition, by using a DC voltage, it is possible to simplify the design and grounding of the circuit compared to the case where a high frequency voltage is used.

[0082] The embodiments disclosed herein are also intended to be combined as appropriate within the scope of technical inconsistency. The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims, not the description of the above embodiments, and is intended to include all modifications within the scope and meaning equivalent to the claims. [Explanation of symbols]

[0083] 1,1a,1b,1x ionization chamber, 2 first intermediate vacuum chamber, 3 second intermediate vacuum chamber, 4 analysis chamber, 5 probe, 9 ion introduction section, 9a introduction port, 10,12 ion guide, 11 skimmer, 13 mass filter, 14 ion detector, 20 control section, 21 nozzle power supply section, 22 reflector electrode power supply section, 23 first focusing electrode power supply section, 24 second focusing electrode power supply section, 31 auxiliary electrode, 31a opening, 31b wall, 32 reflector electrode, 33 first focusing electrode, 33a first transmission path, 34 second focusing electrode, 34a, 342a, 346a second transmission path, 52 nebulizer gas tube, 54 nozzle, 100 mass analyzer, 242 high frequency power supply section, 244, 246 DC power supply section, 342 RF electrode, 342a ion transmission space, 344 Ring electrodes, 346 DC electrodes.

Claims

1. A mass spectrometer that generates ions by atmospheric pressure ionization and detects the generated ions by separating them according to their mass-to-charge ratio, an ion source including a probe for spraying a liquid sample into an ionization chamber in an atmospheric pressure environment; an ion introduction section that introduces ions in the sample droplets sprayed from the probe from the ionization chamber toward a vacuum chamber in a direction intersecting a direction in which the liquid sample is sprayed from the probe; a reflecting electrode disposed at a position facing the inlet of the ion introduction unit across the spray of sample droplets from the probe; a first focusing electrode disposed at a position facing the reflecting electrode across the spray of sample droplets from the probe, the first focusing electrode collecting ions reflected or deflected by the reflecting electrode; a second focusing electrode that is disposed at a position facing the reflecting electrode across the spray of sample droplets from the probe and focuses the ions focused by the first focusing electrode toward the inlet; a voltage application unit that applies voltage to each electrode so as to form an electric field in which ions in a spray of sample droplets from the probe are directed toward the first focusing electrode, from the first focusing electrode to the second focusing electrode, and from the second focusing electrode to the inlet.

2. a first focusing electrode defines a first transmission path; a second focusing electrode forms a second transmission path; 2. The mass spectrometer according to claim 1, wherein the first focusing electrode, the second focusing electrode, and the ion introduction section are arranged such that, when the inlet is viewed in a plan view from the reflective electrode, an inner edge of the second transmission path is located below the inside of an inner edge of the first transmission path, and the inlet is located below the inside of the inner edge of the second transmission path.

3. the voltage application unit includes a radio frequency voltage application unit that applies a radio frequency voltage to the second focusing electrode, 3. The mass spectrometer according to claim 1, wherein the radio frequency voltage application unit applies a radio frequency voltage to the second focusing electrode so as to form a radio frequency electric field that focuses the ions focused by the first focusing electrode from the second focusing electrode toward a center of the inlet.

4. The mass spectrometer according to claim 3 , wherein the second focusing electrode is disposed between the first focusing electrode and an inlet of the ion introduction section.

5. The mass spectrometer according to claim 3 , wherein the second focusing electrode is an ion funnel type or a multipole ion guide type electrode.

6. The mass spectrometer according to claim 1 , wherein the voltage application unit includes a DC voltage application unit that applies a DC voltage to the second focusing electrode.

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