Mass spectrometer

Abstract

The mass spectrometer includes: an ion source including a probe that sprays a liquid sample into an ionization chamber; an ion introduction unit that transports ions from the ionization chamber to the vacuum chamber; a reflective electrode disposed at a position facing the introduction port of the ion introduction unit across the spray flow; a first focusing electrode disposed at a position facing the reflective electrode with the spray stream therebetween; a second focusing electrode disposed at a position facing the reflective electrode with the spray stream therebetween, the second focusing electrode focusing the ions focused by the first focusing electrode toward the guide port; and a voltage applying unit that applies a voltage to each electrode. The voltage applying unit applies a voltage to each electrode so as to form an electric field that causes ions in the spray stream to face the first focusing electrode, from the first focusing electrode to the second focusing electrode, and from the second focusing electrode to the introduction port.

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, separates the generated ions according to their mass-to-charge ratio, and performs detection. Background Art

[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 the atmospheric pressure ionization method, it is necessary to introduce ions generated in an ionization chamber with a substantially atmospheric pressure atmosphere into a vacuum chamber maintained at a vacuum atmosphere. In such an analysis device, in order to improve the analysis sensitivity, 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 Gazette No. 6593548 discloses a mass spectrometer, which is configured such that a reflecting electrode and a focusing electrode are arranged in the ionization chamber in such a manner as to sandwich a spray stream ejected from an ionization probe in order to improve the efficiency of introducing ions from an ionization chamber into a vacuum chamber, and an inlet end of a heating capillary for introducing ions into the vacuum chamber is inserted into the opening of the focusing electrode. Summary of the invention

[0004] According to the mass spectrometer disclosed in Japanese Patent Gazette No. 6593548, 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 at the entrance end is formed near the entrance end, thereby improving the efficiency of ion introduction from the ionization chamber to the vacuum chamber.

[0005] When ions are introduced from the heated capillary, i.e., the ion introduction part, the ion introduction efficiency can be improved by focusing the ions at the end of the ion introduction part to the same degree as the diameter of the introduction port. The ion introduction efficiency can also be improved by enlarging the diameter of the introduction port, but if the diameter of the introduction port is enlarged, the performance of the vacuum pump needs to be improved, and the risk of failures such as impurities other than ions being transported from the introduction port to the vacuum chamber also increases. Therefore, the ions need to be further focused at the end of the ion introduction part.

[0006] The present disclosure has been made to solve such technical problems, and an object of the present disclosure is to improve the efficiency of taking ions into an ion introduction unit.

[0007] The mass spectrometer disclosed in the present invention generates ions by atmospheric pressure ionization, separates the generated ions according to mass-to-charge ratio, and detects them. The mass spectrometer includes: an ion source, including a probe for spraying a liquid sample into an ionization chamber of an atmospheric pressure atmosphere; an ion introduction unit, which transports ions in sample droplets sprayed from the probe from the ionization chamber toward a vacuum chamber in a direction intersecting the spray direction of the liquid sample from the probe; a reflection electrode, which is arranged at a position opposite to the introduction port of the ion introduction unit while sandwiching the spray flow of the sample droplets from the probe; a first focusing electrode, which is arranged at a position opposite to the reflection electrode while sandwiching the spray flow of the sample droplets from the probe, and collects ions reflected or deflected by the reflection electrode; a second focusing electrode, which is arranged at a position opposite to the reflection electrode while sandwiching the spray flow of the sample droplets from the probe, and focuses the ions focused by the first focusing electrode toward the introduction port; and a voltage application unit, which applies voltage to each electrode. The voltage applying unit applies voltage to each electrode to form an electric field that directs ions in the spray flow of sample droplets from the probe toward the first focusing electrode, from the first focusing electrode to the second focusing electrode, and from the second focusing electrode to the introduction port.

[0008] The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 It is a schematic diagram showing the overall structure of the mass spectrometer according to the first embodiment.

[0010] Figure 2 This is a schematic diagram showing the schematic structure of the ionization chamber of the first embodiment.

[0011] Figure 3 This is a schematic diagram showing the schematic structure of the ionization chamber of the second embodiment.

[0012] Figure 4 This is a diagram showing the simulation results of ion orbits in the ionization chamber of the second embodiment.

[0013] Figure 5 It is a diagram showing the simulation results of the second embodiment and the comparative example showing the ion arrival position at the introduction port.

[0014] Figure 6 It is a schematic diagram showing a schematic structure inside an ionization chamber of a comparative example.

[0015] Figure 7 This is a schematic diagram showing the schematic structure of the ionization chamber of the third embodiment.

[0016] Figure 8 This is a diagram showing the simulation results of ion orbits in the ionization chamber of the third embodiment.

[0017] Fig. 9 It is a diagram showing the simulation results of the third embodiment and the comparative example showing the ion arrival position at the introduction port. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0019] [First embodiment]

[0020] (Overall Structure of Mass Analyzer)

[0021] Figure 1 1 is a schematic diagram showing the overall structure of a mass spectrometer according to the first embodiment. The mass spectrometer 100 is a structure having a multi-stage differential exhaust system in which a first intermediate vacuum chamber 2 and a second intermediate vacuum chamber 3 are provided between an ionization chamber 1 having an atmosphere of substantially atmospheric pressure and an analysis chamber 4 having a high vacuum atmosphere which is evacuated by a high-performance vacuum pump (not shown).

[0022] An ion source including a probe 5 for electrospray ionization (ESI) is arranged in the ionization chamber 1. The ion source is not limited to the ESI ion source, but may be an ion source for atmospheric pressure chemical ionization (APCI) or an ion source for other atmospheric pressure ionization methods such as atmospheric pressure photoionization (APPI).

[0023] In the ionization chamber 1, the liquid sample containing the sample components is sprayed while being charged from the probe 5. The droplets sprayed from the tip of the probe 5 become finer when in contact with the surrounding air, and the sample components are ionized in the process of evaporation of the solvent from the droplets.

[0024] The ionization chamber 1 is connected to the first intermediate vacuum chamber 2 through a cylindrical ion introduction section 9. The ion introduction section 9 is, for example, a heated capillary. There is a pressure difference between the two open ends of the ion introduction section 9. Due to the pressure difference, an airflow is formed from the ionization chamber 1 to the first intermediate vacuum chamber 2 through the ion introduction section 9. The ions derived from the sample components generated in the ionization chamber 1 are mainly sucked into the ion introduction section 9 by the flow of the airflow generated by the pressure difference, and are transported to the first intermediate vacuum chamber 2 together with the airflow.

[0025] A multipole ion guide 10 is provided in the first intermediate vacuum chamber 2 so as to surround the ion optical axis L, which is the axis of the cylindrical ion introduction section 9. A taper 11 having a small-diameter throttle hole is provided on a wall separating the first intermediate vacuum chamber 2 from the second intermediate vacuum chamber 3. The ions transported into the first intermediate vacuum chamber 2 are focused near the throttle hole of the taper 11 by the action of the electric field formed by the ion guide 10, and are transported into the second intermediate vacuum chamber 3 through the taper 11.

[0026] A multipole (e.g., octupole) type ion guide 12 is provided in the second intermediate vacuum chamber 3 and is arranged to surround the ion optical axis L. The ions transported into the second intermediate vacuum chamber 3 are focused by the high frequency (RF) electric field formed by the ion guide 12 and transported into the analysis chamber 4.

[0027] A quadrupole mass filter 13 arranged around the ion optical axis L and an ion detector 14 arranged on the ion optical axis L are provided in the analysis chamber 4. The ions transported into the analysis chamber 4 are introduced into the space in the long axis direction (the direction of the ion optical axis L) of the quadrupole mass filter 13, and through the action of the electric field formed by the RF voltage and the direct current (DC) voltage applied to the quadrupole mass filter 13, only ions with a specific mass-to-charge ratio pass through the quadrupole mass filter 13 and reach the ion detector 14. The ion detector 14 generates a detection signal corresponding to the amount of ions that have arrived, and sends the detection signal to a data processing device (not shown).

[0028] As described above, in the mass spectrometer 100, ions derived from sample components generated in the ionization chamber 1 pass through the first intermediate vacuum chamber 2 and the second intermediate vacuum chamber 3 and are detected in the analysis chamber 4. Therefore, by maximally suppressing the loss of ions generated in the ionization chamber 1 and ultimately allowing more ions to enter the ion detector 14, high-sensitivity analysis can be achieved.

[0029] (Schematic structure of ion source)

[0030] Figure 2 This is a schematic diagram showing the general structure of the ionization chamber of the first embodiment. Hereinafter, the blowing direction along the central axis of the spray flow from the probe 5 is set as the Z-axis direction, the ion suction direction along the central axis of the ion introduction part 9 orthogonal thereto is set as the X-axis direction, and the direction orthogonal to the X-axis direction and the Z-axis direction is set as the Y-axis direction.

[0031] An auxiliary electrode 31, a reflection 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 for controlling the mass spectrometer 100 as a whole; a nozzle power supply unit 21 for applying a voltage to the probe 5; a reflection electrode power supply unit 22 for applying a voltage to the reflection electrode 32; a first focusing electrode power supply unit 23 for applying a voltage to the first focusing electrode 33; and a second focusing electrode power supply unit 24 for applying a voltage to the second focusing electrode 34.

[0032] The auxiliary electrode 31 is arranged at a position opposite to the tip of the probe 5. The auxiliary electrode 31 is a flat electrode formed with an opening 31a. The auxiliary electrode 31 is arranged so that the flat surface of the auxiliary electrode 31 is parallel to the XY plane. In addition, the auxiliary electrode 31 is arranged so that the tip of the probe 5 is located in the opening 31a when the auxiliary electrode 31 is viewed from the Z-axis direction, so that the spray flow of the sample droplet from the probe 5 passes through the circular opening 31a.

[0033] The reflection electrode 32 is disposed at a position facing the introduction port 9a, which is the entrance end of the ion introduction unit 9, across the spray flow of the sample droplets from the probe 5. The reflection electrode 32 is a flat plate-shaped electrode, and the flat plate surface is disposed parallel to the YZ plane.

[0034] The first focusing electrode 33 is arranged at a position opposite to the reflecting electrode 32 sandwiching the spray flow of the sample droplets from the probe 5. The first focusing electrode 33 is arranged in a manner to surround a central axis C which is parallel to the X-axis, the direction of ion intake, and passes through the center of the introduction port 9a. For example, the first focusing electrode 33 is a flat plate-shaped electrode formed with a circular opening forming the first through passage 33a. The flat surface of the first focusing electrode 33 is arranged parallel to the YZ plane. In addition, the first focusing electrode 33 is arranged in a manner such that the central axis C coincides with the central axis of the first through passage 33a. That is, the first through passage 33a is formed by the first focusing electrode 33. In addition, the method of forming the first through passage 33a by the first focusing electrode 33 is not limited to the method of providing an opening in the first focusing electrode 33.

[0035] The second focusing electrode 34 is arranged at a position opposite to the reflection electrode 32, sandwiching the spray flow of the sample droplets from the probe 5. The second focusing electrode 34 is arranged in a manner to surround the central axis C which is parallel to the X-axis, the direction of ion inhalation, and passes through the center of the introduction port 9a, forming a second passing passage 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 embodiment in which the second focusing electrode 34 is an electrode to which an RF voltage is applied and an embodiment in which the second focusing electrode 34 is an electrode to which a DC voltage is applied will be described later.

[0036] When the introduction port 9a is viewed from the reflection electrode 32, the first focusing electrode 33, the second focusing electrode 34, and the ion introduction unit 9 are arranged so that the inner edge of the second passage 34a is located below the inner edge of the first passage 33a and the introduction port 9a is located below the inner edge of the second passage 34a. For example, the minimum diameter of the first passage 33a formed by the first focusing electrode 33 is equal to or larger than the maximum diameter of the second passage 34a formed by the second focusing electrode 34. In addition, the minimum diameter of the second passage 34a is equal to or larger than the diameter of the introduction port 9a.

[0037] The control unit 20 controls the entire mass spectrometer 100 and controls the voltage generated in each power supply unit. Although not shown in the figure, the control unit 20 has a CPU (Central Processing Unit) as a processor, a storage unit for storing programs and data, and a communication I / F (Interface) as main components. Each component is connected to each other through a data bus.

[0038] The storage unit includes ROM (Read On Memory), RAM (Random Access Memory) and HDD (Hard Disk Drive). ROM stores programs executed by the CPU. RAM temporarily stores data generated by executing programs in the CPU and data input via the communication I / F. RAM can function as a temporary data storage used as a work area. HDD is a non-volatile storage device. In addition, a semiconductor storage device such as a flash memory can be used instead of the HDD.

[0039] The program stored in the ROM may be stored in a storage medium and distributed as a program product. Alternatively, the program may be provided by an information provider as a program product that can be downloaded via the Internet or the like.

[0040] The storage medium is not limited to DVD-ROM (Digital Versatile Disc Read On Memory), CD-ROM (compact disc read-on memory), FD (Flexible Disk), and hard disk, but may also be a medium that fixedly carries the program, such as a magnetic tape, a cassette, an optical disc (MO (Magnetic Optical Disc) / MD (Mini Disc) / DVD (Digital Versatile Disc)), an optical card, a mask ROM, an EPROM (Electronic Programmable Read-Only Memory), an EEPROM (Electronic Erasable Programmable Read-Only Memory), a flash ROM, and other semiconductor memories. In addition, the recording medium is a non-transitory medium in which a computer can read a program or the like.

[0041] The probe 5 includes a capillary 50 through which the liquid sample passes, a nebulizing gas tube 52 disposed so as to surround the capillary 50, and a heating gas tube 54 disposed so as to surround the nebulizing gas tube 52. The nozzle power supply unit 21 applies a voltage to the capillary 50 for imparting electric charge to the liquid sample sprayed from the probe 5. A DC voltage of a maximum of several kV is applied to the capillary 50 from the nozzle power supply unit 21.

[0042] The liquid sample given an electric charge is assisted by the atomizing gas ejected from the atomizing gas pipe 52, and becomes fine droplets and is sprayed. In addition, the high-temperature heating gas ejected from the heating gas pipe 54 promotes the vaporization of the solvent from the droplets. The flow rate of the atomizing gas is 0.5 L / min or more and 3 L / min or less. In addition, the heating gas is 3 L / min or more and 20 L / min or less.

[0043] By applying voltage from the nozzle power supply unit 21 to the capillary 50 (probe 5) and spraying the liquid sample from the probe 5, the positively or negatively charged liquid sample is sprayed toward the Z-axis direction from the probe 5. The charged mist liquid sample passes through the opening 31a of the auxiliary electrode 31 along the airflow together with the atomizing gas, and is transported to the space sandwiched by the reflection electrode 32 and the first focusing electrode 33.

[0044] The control unit 20 controls the reflecting electrode power supply unit 22, the first focusing electrode power supply unit 23 and the second focusing electrode power supply unit 24 to form an electric field that causes ions in the air flow (spray flow) transported to the space sandwiched by the reflecting electrode 32 and the first focusing electrode 33 to flow 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.

[0045] For example, when the liquid sample is sprayed from the probe 5 in a positively charged state, 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 part 9 are set so 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 electrodes are set so that the relationship between the voltages V1 to V4 is V1>V2>V3>V4. In addition, in the present embodiment, the auxiliary electrode 31 and the conductive wall 31b electrically connected to the ion introduction part 9 are grounded, and the potential thereof is, for example, 0V. That is, V4 is 0V. In the present embodiment, the auxiliary electrode 31 is grounded, so 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) are hardly affected by each other.

[0046] 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 electrodes. In this case, the voltages V1 to V4 are set so 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 electrodes are set so that the relationship between the voltages V1 to V4 is V1<V2<V3<V4.

[0047] By setting the voltages as described above, a reflection electric field that guides positive ions in a direction from the reflection electrode 32 toward the first focusing electrode 33 is formed in a space sandwiched between the reflection electrode 32 and the first focusing electrode 33 where the charged mist liquid sample is transported.

[0048] Since V2>V3 is set, a focusing electric field is formed that guides positive ions from the inner edge of the first passage 33a to the central axis direction of the second passage 34a (the direction of the central axis C). In addition, the potential difference |V1-V3| between the reflection electrode 32 and the second focusing electrode 34 is greater than the potential difference |V1-V2| between the reflection electrode 32 and the first focusing electrode 33, so a reflection electric field that guides ions from the reflection electrode 32 toward the second focusing electrode 34 is formed more strongly.

[0049] Since V3>V4 is set, a focusing electric field is formed to guide positive ions from the inner edge of the second through passage 34a to the center direction of the guide port 9a (the direction of the central axis C). In addition, the potential difference |V1-V4| between the reflection electrode 32 and the ion introduction part 9 is greater than the potential difference |V1-V3| between the reflection electrode 32 and the second focusing electrode 34, so a reflection electric field is formed to guide ions from the reflection electrode 32 toward the ion introduction part 9 more strongly.

[0050] The positively charged ions and the unionized tiny 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 reflected electric field and separated from the spray flow (air flow). The separated charged droplets are focused to the periphery of the introduction port 9a by the focusing electric field from the inner edge of the first through passage 33a toward the central axis of the second through passage 34a, that is, toward the center of the introduction port 9a.

[0051] Furthermore, in this embodiment, in addition to the first focusing electrode 33, a second focusing electrode 34 is also configured to form a focusing electric field from the inner edge of the second through passage 34a toward the center of the inlet 9a, thereby enabling the separated and focused charged droplets to 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.

[0052] [Second embodiment]

[0053] Figure 3 Schematic diagram showing the schematic structure of the ionization chamber of the second embodiment. The mass spectrometer of the second embodiment differs from the mass spectrometer of the first embodiment in that an RF electrode 342 is provided as the second focusing electrode 34, and a high frequency power supply unit 242 and a DC power supply unit 244 are provided as the second focusing electrode power supply unit 24. The following describes the structure of the ionization chamber 1a of the second embodiment that is different from the structure of the ionization chamber 1 of the first embodiment, and omits the description of the common structure.

[0054] The first focusing electrode 33, the RF electrode 342, and the ion introduction part 9 are arranged in order from the reflection 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 part 9. Since the positions of the first focusing electrode 33, the RF electrode 342, and the ion introduction part 9 do not overlap with each other, it is easy to arrange the components.

[0055] The RF electrode 342 is an ion funnel type electrode having a plurality of annular electrodes 344 arranged at equal intervals along the central axis C. Alternatively, the RF electrode 342 may be an electrode of a multipole ion guide type composed of an even number of rod electrodes (usually 4 or 8) arranged at equal angles around the ion optical axis and extending in the direction of the central axis C. In the second embodiment, the RF electrode 342 as the second focusing electrode 34 may also be an electrode group composed of a plurality of electrodes.

[0056] The openings of the plurality of annular electrodes 344 become smaller as they are closer to the ion introduction unit 9. Ions pass through the second passage 342a, which is a truncated cone-shaped space surrounded by the annular electrodes 344. The inner diameter of the annular electrode 344 closest to the first focusing electrode 33 among the plurality of annular electrodes 344 is less than the minimum diameter of the first passage 33a of the first focusing electrode 33. In addition, the inner diameter of the annular electrode 344 with the smallest inner diameter among the plurality of annular electrodes 344 is greater than the diameter of the introduction port 9a. That is, the first focusing electrode 33, the RF electrode 342 (the plurality of annular electrodes 344), and the ion introduction unit 9 are arranged so that, when the introduction port 9a is viewed from the reflection electrode 32, the inner edge of the second passage 342a is located below the inner side of the inner edge of the first passage 33a, and the introduction port 9a is located below the inner side of the inner edge of the second passage 342a.

[0057] The high frequency power supply unit 242 applies RF voltages of opposite phases to two adjacent annular electrodes 344 in the X-axis direction, thereby forming an RF electric field that focuses ions in the second passage 342a, which is a truncated cone-shaped space surrounded by the annular electrodes 344.

[0058] Furthermore, a DC voltage that changes stepwise in the X-axis direction is applied by the DC power supply unit 244 to each of the plurality of annular electrodes 344 to form a DC potential gradient that accelerates the ions focused by the first focusing electrode 33 toward the inlet 9 a .

[0059] A DC voltage is applied to the reflection electrode 32 and the first focusing electrode 33. For example, when the liquid sample is sprayed from the probe 5 in a manner that the liquid sample is positively charged, the voltage V1 applied to the reflection electrode 32, the voltage V2 applied to the first focusing electrode 33, the DC voltage V31 applied to the annular electrode 344 disposed closest to the first focusing electrode 33, the DC voltage V32 applied to the annular electrode 344 disposed closest to the introduction port 9a, 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 V31, the voltage V31 is greater than the voltage V32, and the voltage V32 is greater than the voltage V4. That is, the DC voltage applied to each electrode is set so that the relationship between the voltages V1, V2, V31, V32, and V4 is V1>V2>V31>V32>V4.

[0060] Thus, in the space sandwiched between the reflection electrode 32 and the first focusing electrode 33, where the charged mist liquid sample is transported, an electric field is formed from the reflection electrode 32 toward the first focusing electrode 33, from the first focusing electrode 33 toward the RF electrode 342, and from the RF electrode 342 toward the introduction port 9a. Furthermore, by applying an RF voltage to the RF electrode 342 from the high-frequency power supply unit 242, an RF electric field is formed in the second passing path 342a, and a substantial potential barrier for confining ions is formed around the central axis C. Thus, the ions can be focused toward the central axis C.

[0061] An RF electric field that focuses ions toward the central axis C and a DC potential gradient that accelerates ions toward the guide inlet 9a are formed in the second passing passage 342a. Therefore, ions transported into the second passing passage 342a are focused toward the central axis C and transported toward the guide inlet 9a.

[0062] As described above, in the mass spectrometer of the second embodiment, a focusing electric field, i.e., an RF electric field, is formed that focuses toward the central axis C. Through this RF electric field, charged droplets separated and focused from the spray flow can be further focused toward the center of the inlet port 9a, thereby further improving the efficiency of ion introduction into the ion introduction section 9 and achieving high sensitivity of the mass spectrometer.

[0063] Figure 4 This is a diagram showing the simulation results of ion orbits in the ionization chamber of the second embodiment. Figure 5 It is a diagram showing the simulation results of the second embodiment and the comparative example showing the ion arrival position at the introduction port. Figure 6 It is a schematic diagram showing a schematic structure inside an ionization chamber of a comparative example.

[0064] In the second embodiment, 20 annular electrodes 344 are arranged as RF electrodes 342, the frequency of the RF voltage applied from the high-frequency power supply unit 242 to each annular electrode 344 is set to 0.6 MHz, the amplitude is set to 1 kV, the voltage V1 applied to the reflection electrode 32 is set to 4 kV, the voltage V2 applied to the first focusing electrode 33 is set to 1 kV, the DC voltage V31 applied to the annular electrode 344 arranged closest to the first focusing electrode 33 is set to 952.5 V, and the voltage applied to the annular electrode 344 close to the ion introduction unit 9 is reduced in such a way that the potential difference between adjacent annular electrodes 344 becomes 47.5 V, thereby obtaining Figure 4 and Figure 5 The simulation results are shown. In addition, the voltage V4 applied to the ion introduction part 9 is 0V.

[0065] like Figure 4 As shown, all ions can be separated from the airflow, and almost all ions can be focused toward the introduction port 9a.

[0066] In addition, Figure 5 In FIG. 1 , the ion arrival position at the inlet 9a is shown. Figure 5 The circular frame in FIG. 9 shows the inner edge of the introduction port 9a. Figure 5 , the simulation results in the comparative example are shown together with the simulation results in the second embodiment.

[0067] Reference Figure 6 The mass spectrometer of the comparative example is compared with the mass spectrometer of the second embodiment. The differences are: the RF electrode 342 as the second focusing electrode 34 is not arranged in the ionization chamber 1x; the high frequency power supply unit 242 and the DC power supply unit 244 as the second focusing electrode power supply unit 24 are not provided; and the first focusing electrode 33 is arranged in the ionization chamber 1x in a manner of surrounding the ion introduction unit 9. In the comparative example, the voltage applied to the reflection electrode 32 is set to 5 kV, and the voltage applied to the first focusing electrode is set to 2.5 kV, and the obtained Figure 5 The simulation results are shown. In addition, the voltage applied to the ion introduction part 9 is 0V.

[0068] Reference Figure 5 In the mass spectrometer of the second embodiment, by providing the RF electrode 342 as the second focusing electrode, the focusing property at the center of the ion guide inlet 9a can be improved compared with the mass spectrometer of the comparative example which does not provide the RF electrode 342 as the second focusing electrode. As a result, the efficiency of taking ions into the ion introduction part 9 can be improved, so that the sensitivity of the mass spectrometer can be increased.

[0069] [Ion Source of the Third Embodiment]

[0070] Figure 7 Schematic diagram showing the schematic structure of the ionization chamber of the third embodiment. The mass spectrometer of the third embodiment differs from the mass spectrometer of the first embodiment in that a DC electrode 346 is provided as the second focusing electrode 34 and a DC power supply unit 246 is provided as the second focusing electrode power supply unit 24. The following describes the structure of the ionization chamber 1b of the third embodiment that is different from the structure of the ionization chamber 1 of the first embodiment, and omits the description of the common structure.

[0071] The DC electrode 346 is a cylindrical electrode, and is arranged so that its axis is located on the central axis C. The DC electrode 346 is longer than the first focusing electrode 33 in the direction of the central axis C, and is shorter than the ion introduction unit 9. This forms a region where components do not overlap, so that the arrangement of each component becomes easy.

[0072] The DC electrode 346 has an inner diameter smaller than the first focusing electrode 33 and larger than the ion introduction unit 9. The DC electrode 346 is disposed in the first through passage 33a of the first focusing electrode 33. That is, the first focusing electrode 33 is disposed so as to surround the DC electrode 346. In addition, the ion introduction unit 9 is disposed in the second through passage 346a formed by the DC electrode 346. That is, the DC electrode 346 is disposed so as to surround the ion introduction unit 9.

[0073] Thus, the first focusing electrode 33, the DC electrode 346 and the ion introduction part 9 are configured so that when looking down at the introduction port 9a from the reflection electrode 32, the inner edge of the second through passage 346a is located on the inner side of the inner edge of the first through passage 33a, and the introduction port 9a is located on the inner side of the inner edge of the second through passage 346a.

[0074] A DC voltage is applied to the reflection electrode 32, the first focusing electrode 33, and the DC electrode 346. For example, when the liquid sample is sprayed from the probe 5 in a manner that the liquid sample is positively charged, the voltage V1 applied to the reflection 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 ion introduction unit 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 voltage applied to each electrode is set so that the relationship between the voltages V1, V2, V33, and V4 is V1>V2>V33>V4.

[0075] As a result, in the space sandwiched between the reflecting electrode 32 and the first focusing electrode 33 where the charged mist liquid sample is transported, an electric field is formed from the reflecting electrode 32 toward the first focusing electrode 33, from the first focusing electrode 33 toward the DC electrode 346, and from the DC electrode 346 toward the inlet 9a.

[0076] In the third embodiment, by providing a DC electrode 346, a focusing electric field is formed from the inner edge of the second through passage 346a toward the center of the introduction port 9a. By this focusing electric field, the separated and focused charged droplets can be focused further toward the center of the introduction port 9a, and the efficiency of ion introduction into the ion introduction unit 9 can be further improved, and the sensitivity of the mass spectrometer can be increased. In addition, by using a DC voltage, circuit design and grounding can be easily performed compared to the case of using an RC voltage.

[0077] Figure 8 This is a diagram showing the simulation results of ion orbits in the ionization chamber of the third embodiment. Fig. 9 It is a diagram showing the simulation results of the third embodiment and the comparative example showing the ion arrival position at the introduction port.

[0078] In the third embodiment, the voltage V1 applied to the reflective electrode 32 is set to 4 kV, the voltage V2 applied to the first focusing electrode 33 is set to 2 kV, and the voltage V33 applied to the DC electrode 346 is set to 0.9 kV, and the Figure 8 and Fig. 9 The simulation results are shown.

[0079] like Figure 8 As shown, all ions can be separated from the gas flow, and almost all ions can be focused toward the introduction port 9a.

[0080] In addition, Fig. 9 The ion arrival position at the inlet 9a is shown in FIG. Fig. 9 The circular frame in FIG. 9 shows the inner edge of the introduction port 9a. Fig. 9 , the simulation results in the comparative example are shown together with the simulation results in the third embodiment. Figure 6 The mass spectrometer described above is the same as that of the mass spectrometer of the third embodiment. The mass spectrometer of the comparative example is compared with the mass spectrometer of the third embodiment. The difference is that the DC electrode 346 as the second focusing electrode 34 and the DC power supply unit 246 as the second focusing electrode power supply unit 24 are not provided. In the comparative example, the voltage applied to the reflection electrode 32 is set to 5 kV, and the voltage applied to the first focusing electrode is set to 2.5 kV, and the result is Fig. 9 The simulation results are shown. In addition, the voltage applied to the ion introduction part 9 is 0V.

[0081] Reference Fig. 9 In the mass spectrometer of the third embodiment, by providing the DC electrode 346 as the second focusing electrode, the focusing property in the Z-axis direction can be improved compared with the mass spectrometer of the comparative example which does not provide the DC electrode 346 as the second focusing electrode. As a result, the efficiency of taking ions into the ion introduction part 9 can be improved, so that the sensitivity of the mass spectrometer can be increased.

[0082] [plan]

[0083] Those skilled in the art can understand that the above embodiments are specific examples of the following schemes.

[0084] (Item 1) A mass spectrometer of one scheme is a mass spectrometer that generates ions by atmospheric pressure ionization, separates the generated ions according to mass-to-charge ratio, and detects them. The mass spectrometer includes: an ion source, including a probe that sprays a liquid sample into an ionization chamber of an atmospheric pressure atmosphere; an ion introduction unit that transports ions in sample droplets sprayed from the probe from the ionization chamber toward a vacuum chamber in a direction intersecting the spray direction of the liquid sample from the probe; a reflection electrode that is disposed at a position opposite to the introduction port 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 opposite to the reflection electrode across the spray flow of the sample droplets from the probe, and collects ions reflected or deflected by the reflection electrode; a second focusing electrode that is disposed at a position opposite to the reflection electrode across the spray flow of the sample droplets from the probe, and focuses the ions focused by the first focusing electrode toward the introduction port; and a voltage application unit that applies a voltage to the electrodes. The voltage applying unit may apply voltage to each electrode to form an electric field that directs ions in the spray flow of sample droplets from the probe toward the first focusing electrode, from the first focusing electrode toward the second focusing electrode, and from the second focusing electrode toward the introduction port.

[0085] According to the mass spectrometer described in the first item, the second focusing electrode is arranged in addition to the first focusing electrode, and an electric field is formed from the second focusing electrode toward the introduction port, thereby being able to focus ions further toward the center of the introduction port compared to the case where only the first focusing electrode is arranged. Therefore, the efficiency of ion introduction into the ion introduction unit can be improved.

[0086] (Item 2) In the mass spectrometer described in Item 1, the first passing passage is formed by the first focusing electrode. The second passing passage is formed by the second focusing electrode. The first focusing electrode, the second focusing electrode, and the ion introduction part may be arranged so that when the introduction port is viewed from the reflection electrode, the inner edge of the second passing passage is located below the inner side of the inner edge of the first passing passage, and the introduction port is located below the inner side of the inner edge of the second passing passage.

[0087] According to the mass spectrometer described in the second aspect, the ions can be focused further toward the center of the introduction port, and the efficiency of taking ions into the ion introduction unit can be improved.

[0088] (Item 3) In the mass spectrometer described in Item 1 or Item 2, the voltage applying unit includes a high-frequency voltage applying unit that applies a high-frequency voltage to the second focusing electrode. The high-frequency voltage applying unit may apply the high-frequency voltage to the second focusing electrode to form a high-frequency electric field that focuses the ions focused by the first focusing electrode from the second focusing electrode toward the center of the introduction port.

[0089] According to the mass spectrometer described in Item 3, the ions can be focused further toward the center of the introduction port by the high-frequency electric field, and the efficiency of taking ions into the ion introduction part can be further improved.

[0090] (Item 4) In the mass spectrometer described in Item 3, the second focusing electrode may be arranged between the first focusing electrode and the introduction port of the ion introduction part.

[0091] According to the mass spectrometer described in Item 4, since the positions of the first focusing electrode, the second focusing electrode, and the ion introduction unit do not overlap, the arrangement of the components becomes easy.

[0092] (Item 5) In the mass spectrometer described in Item 3 or 4, the second focusing electrode may be an ion funnel type or a multipole ion guide type electrode.

[0093] (Item 6) In the mass spectrometer described in Item 1 or Item 2, the voltage application unit may include a DC voltage application unit that applies a DC voltage to the second focusing electrode.

[0094] According to the mass spectrometer described in Item 6, by applying a DC voltage, an electric field can be formed from the second focusing electrode toward the introduction port, and the ions can be focused further toward the center of the introduction port, thereby improving the efficiency of ion introduction into the ion introduction unit. In addition, by using a DC voltage, circuit design and grounding can be performed more easily than when using a high-frequency voltage.

[0095] Although the embodiments of the present invention have been described, the embodiments disclosed this time should be considered to be illustrative in all aspects and not restrictive. The scope of the present invention is indicated by the claims, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

Claims

1. A mass spectrometer that generates ions by atmospheric pressure ionization, separates the generated ions according to their mass-to-charge ratio, and performs detection, characterized in that: have: An ion source including a probe for spraying a liquid sample into an ionization chamber of an atmospheric pressure atmosphere; an ion introduction section that transports ions in sample droplets sprayed from the probe from the ionization chamber toward the vacuum chamber in a direction intersecting the spray direction of the liquid sample from the probe; a reflection electrode disposed at a position facing the introduction port of the ion introduction section across the spray flow of the sample droplets from the probe; a first focusing electrode disposed at a position facing the reflecting electrode across the spray flow of the sample droplets from the probe, and collecting ions reflected or deflected by the reflecting electrode; a second focusing electrode disposed at a position facing the reflecting electrode across the spray flow of the sample droplets from the probe, and focusing the ions focused by the first focusing electrode toward the introduction port; The voltage applying unit applies voltage to each electrode to form an electric field that directs ions in the spray flow of sample droplets from the probe toward the first focusing electrode, from the first focusing electrode toward the second focusing electrode, and from the second focusing electrode toward the introduction port.

2. The mass spectrometer according to claim 1, wherein: The first focusing electrode forms a first passing path, The second focusing electrode forms a second passing path, The first focusing electrode, the second focusing electrode and the ion introduction part are configured so that when the introduction port is viewed from the reflecting electrode, the inner edge of the second passing passage is located below the inner side of the inner edge of the first passing passage, and the introduction port is located below the inner side of the inner edge of the second passing passage.

3. The mass spectrometer according to claim 1, wherein: The voltage applying unit includes a high-frequency voltage applying unit for applying a high-frequency voltage to the second focusing electrode. The high-frequency voltage applying unit applies a high-frequency voltage to the second focusing electrode to form a high-frequency electric field for focusing the ions focused by the first focusing electrode from the second focusing electrode toward the center of the introduction port.

4. The mass spectrometer according to claim 3, wherein: The second focusing electrode is disposed between the first focusing electrode and an introduction port 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 applying section includes a DC voltage applying section that applies a DC voltage to the second focusing electrode.

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