Mass spectrometer

Abstract

To obtain more information with one mass analysis.SOLUTION: A control unit performs mass analysis of the sample components while switching the analysis mode between a first analysis mode in which ions are detected under a first polarity mode and a multimode, and a second analysis mode in which ions are detected under a second polarity mode and a single mode.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a mass spectrometer that generates a group of product ions from precursor ions derived from sample components and performs mass analysis on the generated product ions. [Background technology]

[0002] Mass spectrometry is widely used to identify polymer compounds and analyze their structures by dissociating ions (precursor ions) derived from sample components one or more times to generate fragment ions (product ions), which are then separated and detected according to their mass-to-charge ratio.

[0003] As a fragmentation method for generating a group of product ions from precursor ions, collision induced dissociation (CID) is known, in which excited precursor ions are caused to collide with a predetermined gas to induce dissociation.

[0004] Furthermore, Patent Documents 1 and 2 disclose a fragmentation method in which precursor ions derived from sample components having hydrocarbon chains are irradiated with oxidizing radicals, thereby selectively dissociating the precursor ions at the positions of unsaturated bonds contained in the hydrocarbon chains. Hereinafter, the fragmentation method in which precursor ions are selectively dissociated at the positions of unsaturated bonds contained in the hydrocarbon chains by irradiating radicals is also referred to as OAD (Oxygen Attachment Dissociation).

[0005] Patent Document 3 discloses a mass spectrometry method that generates a group of product ions from a precursor ion using both CID and OAD fragmentation methods, thereby obtaining more information useful for structural analysis of a compound in a single mass analysis. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2018 / 186286 [Patent Document 2] International Publication No. 2019 / 155725 [Patent Document 3] International Publication No. 2021 / 028341 Summary of the Invention [Problem to be solved by the invention]

[0007] Lipids are one of the most representative polymer compounds, and it is known that their properties change depending on the length of the hydrocarbon chain and the position of the unsaturated bond within the hydrocarbon chain. Therefore, in analyzing lipids, it is effective to generate and detect product ions that are useful for estimating the length of the hydrocarbon chain and the position of the unsaturated bond within the hydrocarbon chain.

[0008] Furthermore, one type of lipid is a phospholipid, which has a basic structure in which two types of fatty acids and a polar group containing phosphate are bound to glycerol. Patent Document 3 discloses a method for estimating the structure of a phospholipid based on the product ion spectrum obtained by using a phospholipid as a sample component and generating product ions using both CID and OAD fragmentation methods and performing mass analysis.

[0009] Specifically, Patent Document 3 discloses a method for estimating the structure of a phospholipid by extracting candidate structures that a phospholipid can adopt based on the exact mass of a precursor ion and the conditions of the basic structure of the phospholipid, simulating the product ion spectrum that can be adopted for each extracted candidate, and comparing the measured product ion spectrum with the simulation results. According to this estimation method, narrowing down the candidate structures reduces the processing load required for estimation and improves estimation accuracy, so it is necessary to obtain more information useful for structural analysis of compounds. However, in order to obtain more information useful for structural analysis of compounds, more analyses must be performed, which poses challenges such as increased analysis time and increased sample consumption.

[0010] The present disclosure has solved this problem, and one of its objectives is to obtain more information in a single mass analysis. [Means for solving the problem]

[0011] The mass spectrometer disclosed herein generates product ions from precursor ions derived from sample components having hydrocarbon chains and performs mass analysis on the product ions. The mass spectrometer includes a reaction chamber into which the precursor ions are introduced, electrodes disposed within the reaction chamber, an inlet unit that introduces collision gas and radicals into the reaction chamber as substances for fragmenting the precursor ions, a mass separator that separates ions including the product ions generated in the reaction chamber according to their mass-to-charge ratios, a detector that detects ions mass-separated by the mass separator, a power supply unit that applies voltages to the electrodes and the mass separator, and a controller. The controller is switchable between a multi-mode in which the power supply unit is controlled to apply a predetermined first voltage to the electrodes while the collision gas and radicals are introduced into the reaction chamber, and a single-mode in which the power supply unit is controlled to apply a predetermined second voltage to the electrodes while the collision gas is introduced into the reaction chamber. The control unit is switchable between a first polarity mode in which the power supply unit is controlled to apply a third voltage to the mass separation unit for mass separation of ions of a first polarity, and a second polarity mode in which the power supply unit is controlled to apply a fourth voltage to the mass separation unit for mass separation of ions of a second polarity opposite to the first polarity. The control unit performs mass analysis of sample components while switching the analysis mode between a first analysis mode in which ions are detected in the first polarity mode and multimode, and a second analysis mode in which ions are detected in the second polarity mode and singlemode. [Effects of the Invention]

[0012] According to the present disclosure, mass analysis is performed while switching between the first analysis mode and the second analysis mode, so that analysis results obtained in the first analysis mode and analysis results obtained in the second analysis mode can be obtained in a single mass analysis, and more information can be obtained in a single mass analysis. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram of a mass spectrometer according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram of an introduction section. [Figure 3] FIG. 1 is a diagram schematically illustrating the relationship between the voltage value applied to the ion guide and the abundance of product ions. [Figure 4] 1 is a flowchart showing an example of an analysis flow when analyzing lipids. [Figure 5] This is an MS / MS spectrum obtained by performing CID-MS / MS analysis in negative ion mode on [M+HCOO] − (m / z=826.5604) obtained at the first time. [Figure 6] This is an MS / MS spectrum obtained by performing CID-MS / MS analysis in negative ion mode on [M+HCOO] − (m / z=826.5604) obtained at the second time. [Figure 7] This is an MS / MS spectrum obtained by performing Multi-MS / MS analysis in positive ion mode on [M+H]+ (m / z=782.5695) obtained at the first time. [Figure 8] This is an MS / MS spectrum obtained by performing Multi-MS / MS analysis in positive ion mode on [M+H]+ (m / z=782.5695) obtained at the second time. [Figure 9] FIG. 1 shows the basic structure of phosphatidylcholine. [Figure 10] FIG. 1 shows the predicted structure of PC(36:4). DETAILED DESCRIPTION OF THE INVENTION

[0014] 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 numerals, and description thereof will not be repeated.

[0015] [Overall configuration of mass spectrometer] FIG. 1 is a schematic diagram of a mass spectrometer according to a first embodiment. The mass spectrometer 100 is a quadrupole (Q)-time-of-flight (TOF) mass spectrometer. Although the mass spectrometer 100 will be described below as a Q-TOF mass spectrometer, any mass spectrometer capable of performing mass analysis on ions obtained by fragmenting selected ions from ions obtained by ionizing a sample may be used. For example, the mass spectrometer 100 may be a tandem mass spectrometer, such as a tandem quadrupole (QQ) or tandem flight (TOF-TOF) mass spectrometer, or may be a hybrid mass spectrometer, such as an ion trap (IT)-TOF mass spectrometer, a Q-ion cyclotron resonance (ICR) mass spectrometer, or a Q-Fourier transform mass spectrometer.

[0016] The mass spectrometer 100 includes a measurement unit 2 that ionizes a sample, separates the ions according to their mass-to-charge ratio, and measures each ion, a power supply unit 4 that applies voltage to each electrode provided in the measurement unit 2, and a control unit 6 that controls the measurement unit 2 and the power supply unit 4.

[0017] The measurement unit 2 includes an ionization chamber 200, which is under a substantially atmospheric pressure atmosphere, and a vacuum chamber 20, the interior of which is divided into four sections. The vacuum chamber 20 is divided into a first intermediate chamber 201, a second intermediate chamber 202, a first analysis chamber 203, and a second analysis chamber 204, and each chamber is evacuated to a vacuum by a vacuum pump (not shown) so that the degree of vacuum increases in that order.

[0018] An electrospray ionization (ESI) source 21 is disposed in the ionization chamber 200. The ESI source 21 ionizes compounds in the sample liquid by spraying the sample liquid while imparting an electric charge to the sample liquid. However, the method for ionizing compounds is not limited to this, and other ion sources such as an atmospheric pressure chemical ion source may also be used. Furthermore, an ion source that ionizes a gas sample or a solid sample instead of a liquid sample may also be used.

[0019] As an example, a liquid chromatograph is connected to the mass spectrometer 100, and the eluate from the liquid chromatograph is continuously introduced into the ESI source 21. Alternatively, a liquid sample may be continuously introduced into the ESI source 21 by flow injection analysis. Alternatively, a sample may be intermittently introduced into the mass spectrometer 100.

[0020] The ionization chamber 200 and the first intermediate chamber 201 are connected by a desolvation tube 22. Ions derived from sample components and fine charged droplets generated in the ionization chamber 200 are drawn into the desolvation tube 22 and sent to the first intermediate chamber 201 mainly due to the pressure difference between the ionization chamber 200 and the first intermediate chamber 201. The desolvation tube 22 is, for example, a heated capillary, and when the charged droplets pass through the inside of the desolvation tube 22, evaporation of the solvent in the droplets progresses, promoting the generation of ions.

[0021] A multipole ion guide 23 is disposed in the first intermediate chamber 201. The ions sent to the first intermediate chamber 201 are converged by the ion guide 23 to the vicinity of the ion optical axis C1, and are sent to the second intermediate chamber 202 through an opening at the top of the skimmer 24.

[0022] A multipole ion guide 25 is disposed in the second intermediate chamber 202. The ions sent to the second intermediate chamber 202 are sent from the second intermediate chamber 202 to the first analysis chamber 203 by the ion guide 25.

[0023] The first analysis chamber 203 contains a quadrupole mass filter 26 that selects specific ions as precursor ions from ions derived from the sample components, a reaction chamber 27 into which the precursor ions selected by the quadrupole mass filter 26 are introduced, an ion guide 28 that is an electrode disposed within the reaction chamber 27, and part of a transfer electrode 29 that transports ions emitted from the reaction chamber 27. The quadrupole mass filter 26 corresponds to an example of an "ion selector" according to the present disclosure. Note that the ion selector that selects precursor ions is not limited to the quadrupole mass filter 26 and may be, for example, a TOF or IT.

[0024] The measurement unit 2 includes an introduction unit 40 that introduces into the reaction chamber 27 a substance for causing fragmentation of precursor ions introduced into the reaction chamber 27. The configuration of the introduction unit 40 will be described later with reference to FIG. 2. Hydroxy radicals made from water vapor as a raw material and water vapor are continuously or intermittently introduced from the introduction unit 40 into the reaction chamber 27. Note that an inert gas such as argon may also be introduced into the reaction chamber 27 from the introduction unit 40.

[0025] When the precursor ions introduced into the reaction chamber 27 collide with water vapor, they are dissociated by collision-induced dissociation (CID), generating one or more product ions. Hereinafter, the one or more product ions generated by CID are also referred to as the "first product ion group." Furthermore, the precursor ions introduced into the reaction chamber 27 react with hydroxyl radicals, selectively dissociating at the positions of unsaturated bonds in the hydrocarbon chain, generating one or more product ions. Hereinafter, a fragmentation method in which precursor ions are selectively dissociated at the positions of unsaturated bonds in the hydrocarbon chain by irradiating the precursor ions with radicals is referred to as "OAD (Oxygen Attachment Dissociation)." Hereinafter, the one or more product ions generated by OAD are also referred to as the "second product ion group."

[0026] The first group of product ions and / or the second group of product ions generated in the reaction chamber 27 are sent to the transfer electrode 29 .

[0027] The ions emitted from the reaction chamber 27 are converged by the transfer electrode 29 to form a highly parallel ion flow, which is sent to the second analysis chamber 204. A detection unit is disposed in the second analysis chamber 204, which detects the ions sent to the second analysis chamber 204 according to their mass-to-charge ratio. The detection unit includes a mass separation unit that separates the ions, including the product ions generated in the reaction chamber 27, according to their mass-to-charge ratio, and a detector 35 that detects each ion separated by the mass separation unit.

[0028] More specifically, the second analysis chamber 204 is equipped with an orthogonal acceleration electrode 30, an acceleration electrode 31, a flight tube 32, a reflectron 33, a back plate 34, and a detector 35. The highly parallel ion flow that has been sent to the second analysis chamber 204 is emitted by the orthogonal acceleration electrode 30 in a direction that is approximately perpendicular to the direction of the incident ion flow.

[0029] The ions are emitted from the orthogonal acceleration electrode 30 in pulses, i.e., as a single ion packet. The ions emitted from the orthogonal acceleration electrode 30 are further accelerated by the acceleration electrode 31 and introduced into the flight space within the flight tube 32. The flight tube 32, reflectron 33, and backplate 34 create an electric field within the flight space that causes the ions to turn back along a path as shown by C2 in FIG. 1. As a result, the ions turn back and fly again within the flight tube 32, reaching the detector 35. The detector 35 outputs an ion intensity signal corresponding to the amount of incident ions and the time at which the ions reach the detector 35 to the control unit 6.

[0030] The ions sent to the second analysis chamber 204 are given a certain amount of kinetic energy by the orthogonal acceleration electrode 30 and introduced into the flight space. Because ions with smaller mass-to-charge ratios are accelerated faster by the orthogonal acceleration electrode 30, the arrival time at the detector 35 varies depending on the mass-to-charge ratio of the ions, and the ions are separated according to their mass-to-charge ratio. In other words, the mass separation unit that separates ions according to their mass-to-charge ratio includes at least the orthogonal acceleration electrode 30, acceleration electrode 31, flight tube 32, and backplate 34, which are arranged in the second analysis chamber 204.

[0031] The power supply unit 4 applies predetermined voltages to the orthogonal acceleration electrode 30, the acceleration electrode 31, the flight tube 32, the back plate 34, the ion guides 23, 25, 28, the transfer electrode 29, and the quadrupole mass filter 26, respectively.

[0032] In accordance with instructions from the control unit 6, the power supply unit 4 applies a negative or positive voltage to each electrode, including the quadrupole mass filter 26, the orthogonal acceleration electrode 30, the acceleration electrode 31, the flight tube 32, and the back plate 34. For example, when performing mass analysis on positive ions from the ions derived from the sample components, the power supply unit 4 applies a negative voltage to each electrode. On the other hand, when performing mass analysis on negative ions from the ions derived from the sample components, the power supply unit 4 applies a positive voltage to each electrode.

[0033] In the following, the mode in which a negative voltage is applied to each electrode to perform mass analysis on positive ions may be referred to as the "positive ion mode," and the mode in which a positive voltage is applied to each electrode to perform mass analysis on negative ions may be referred to as the "negative ion mode." That is, the power supply unit 4 switches between the positive ion mode and the negative ion mode in accordance with instructions from the control unit 6.

[0034] The control unit 6 controls the measurement unit 2 and the power supply unit 4. The control unit 6 further has a function of processing measurement results such as ion intensity signals sent from the detector .

[0035] The control unit 6 includes a processor 61, a memory 62, an input / output I / F 63, a display 64, and an input device 65, and is typically a computer.

[0036] The processor 61 is typically an arithmetic processing unit such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor 61 controls the operation of the control unit 6 by reading and executing programs stored in the memory 62. The programs include a program that, when executed by a computer, causes the computer to control the measurement unit 2 and the power supply unit 4.

[0037] The memory 62 is realized by a storage device such as a ROM (Read Only Memory), a RAM (Random Access Memory), and an HDD (Hard Disk Drive). The ROM can store programs executed by the processor 61. The RAM can temporarily store data used during execution of a program by the processor 61, and can function as a temporary data memory used as a work area. The HDD is a non-volatile storage device. In addition to or instead of the HDD, a semiconductor storage device such as a flash memory may be used. The programs and / or data may be stored in an external storage device accessible by the processor 61.

[0038] The input / output I / F 63 is an interface for exchanging various types of data between the processor 61 and an external device connected to the input / output I / F 63. The external device includes a display 64, an input device 65, the measurement unit 2, and the power supply unit 4. The display 64 displays, for example, an image for accepting input from the input device 65 and processing results of the processor 61, such as analysis results. The input device 65 is typically composed of a touch panel, a keyboard, a mouse, etc. The input device 65 accepts input operations by the user to the processor 61.

[0039] [Analysis performed in a mass spectrometer] The control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform MS (mass spectrometry) analysis and MS / MS analysis. MS analysis is an analytical method in which a sample is ionized in the ionization chamber 200, and the ions generated are separated and detected according to their mass-to-charge ratio without fragmenting. MS / MS analysis is an analytical method in which specific precursor ions are selected using the quadrupole mass filter 26, product ions are generated from the selected precursor ions in the reaction chamber 27, and the generated product ions are separated and detected according to their mass-to-charge ratio.

[0040] The control unit 6 can perform MS analysis by applying a radio frequency voltage to the quadrupole mass filter 26 and the ion guide 28 to transport ions, while controlling the measurement unit 2 and the power supply unit 4 so as not to introduce substances that cause fragmentation into the reaction chamber 27.

[0041] The control unit 6 can perform MS / MS analysis by applying a predetermined voltage, which is a DC voltage superimposed on an RF voltage, to the quadrupole mass filter 26 and controlling the measurement unit 2 and power supply unit 4 so that fragmentation occurs within the reaction chamber 27.

[0042] The control unit 6 can perform various MS / MS analyses using different fragmentation methods to generate product ions from precursor ions by changing the substance introduced from the inlet unit 40 into the reaction chamber 27 and the voltage applied to the ion guide 28. Specifically, the control unit 6 can perform CID and OAD. The control unit 6 can control the measurement unit 2 and power supply unit 4 between a multimode in which CID and OAD are performed simultaneously, and a single mode in which either CID or OAD is performed.

[0043] As described above, the control unit 6 can perform mass analysis by switching between a "positive ion mode" in which mass analysis is performed on positive ions and a "negative ion mode" in which mass analysis is performed on negative ions.

[0044] That is, by changing the polarity and fragmentation method of the ions to be analyzed, the mass spectrometer 100 can provide multiple types of analysis modes for MS / MS analysis. Specifically, the mass spectrometer 100 can provide six types of analysis modes: (1) positive ion mode and multimode, (2) negative ion mode and multimode, (3) positive ion mode and single mode with CID only, (4) positive ion mode and single mode with OAD only, (5) negative ion mode and single mode with CID only, and (6) negative ion mode and single mode with OAD only.

[0045] [Outline of the introduction] 2 is a schematic diagram of the introduction section. The introduction section 40 includes a radical generation chamber 42, a high-frequency plasma source 44, a water vapor supply section 46, and an argon supply section 48. Although not shown, the introduction section 40 further includes a vacuum pump that evacuates the radical generation chamber 42.

[0046] The radical generating chamber 42 is configured, for example, by a glass torch, and has a needle electrode connected to a high-frequency plasma source 44 disposed therein.

[0047] The high-frequency plasma source 44 supplies microwaves to generate a vacuum discharge in the radical generation chamber 42. When microwaves are supplied from the high-frequency plasma source 44 to the needle electrode, a vacuum discharge occurs in the radical generation chamber 42. In other words, the high-frequency plasma source 44 and the needle electrode are an example of a vacuum discharge unit that generates a vacuum discharge in the radical generation chamber 42.

[0048] The water vapor supply unit 46 supplies water vapor to the radical generation chamber 42 and the reaction chamber 27. The argon supply unit 48 supplies argon gas to the reaction chamber 27.

[0049] The radical generation chamber 42 communicates with the reaction chamber 27. The radical generation chamber 42 and the water vapor supply unit 46 are connected by a flow path 41. A valve B1 is provided on the flow path 41. The water vapor supply unit 46 is also connected to a flow path 43 that is connected to the reaction chamber 27 without passing through the radical generation chamber 42. A valve B2 is provided on the flow path 43.

[0050] When microwaves are supplied to the needle electrode while water vapor is being supplied from the water vapor supply unit 46 to the radical generation chamber 42, a vacuum discharge occurs in the radical generation chamber 42, and hydroxyl radicals are generated from the water vapor. The generated hydroxyl radicals are introduced from the radical generation chamber 42 into the reaction chamber 27. On the other hand, if microwaves are not supplied to the needle electrode, no hydroxyl radicals are generated and are not introduced into the reaction chamber 27. Therefore, the control unit 6 can switch between introducing and stopping the introduction of hydroxyl radicals into the reaction chamber 27 by controlling the high-frequency plasma source 44.

[0051] The water vapor supply unit 46 is connected to a flow path 43 that is connected to the reaction chamber 27 without passing through the radical generation chamber 42. Therefore, the control unit 6 can switch between introducing and stopping the introduction of water vapor into the reaction chamber 27 by controlling the valve B2.

[0052] A flow path 45, which is connected to the reaction chamber 27, is connected to the argon supply unit 48. A valve B3 is provided on the flow path 45. The control unit 6 can switch between introducing and stopping the introduction of argon gas into the reaction chamber 27 by controlling the valve B3.

[0053] Water vapor is one type of collision gas used in CID, and hydroxyl radicals are one type of radical used in OAD.

[0054] With valves B1 and B2 open, control unit 6 supplies microwaves from high-frequency plasma source 44 to the needle electrode, thereby introducing hydroxyl radicals and water vapor into reaction chamber 27. On the other hand, with valves B1 and B2 open, control unit 6 stops the supply of microwaves from high-frequency plasma source 44 to the needle electrode, thereby introducing water vapor into reaction chamber 27 without introducing hydroxyl radicals.

[0055] In this way, by selecting water vapor as the collision gas and hydroxyl radicals made from water vapor as the radicals, the substances introduced into reaction chamber 27 can be easily controlled simply by controlling high-frequency plasma source 44. Furthermore, by selecting water vapor as the collision gas and hydroxyl radicals made from water vapor as the radicals, a common supply source can be used for the two types of substances, simplifying the device configuration.

[0056] In the present embodiment, the introduction unit 40 includes the argon supply unit 48, but it is not necessarily required to include the argon supply unit 48. Furthermore, the mass spectrometer 100 may use argon gas as the collision gas.

[0057] In this embodiment, introduction unit 40 is provided with separate flow paths for supplying water vapor and hydroxyl radicals. The configuration of introduction unit 40 is not limited to the configuration shown in Fig. 2. It is sufficient for introduction unit 40 to be able to introduce collision gas and radicals into reaction chamber 27 and create a situation in which both collision gas and radicals are present in reaction chamber 27.

[0058] For example, introduction unit 40 may not be equipped with flow path 43 and valve B2. In this case, introduction unit 40 may introduce hydroxy radicals or water vapor into reaction chamber 27 by switching between starting and stopping the supply of microwaves from high-frequency plasma source 44 while continuing to supply water vapor to radical generation chamber 42. For example, introduction unit 40 can introduce both hydroxy radicals and water vapor into reaction chamber 27 by alternately introducing hydroxy radicals and water vapor into reaction chamber 27.

[0059] [Relationship between voltage applied to ion guide and fragmentation] This section explains how the progress of each fragmentation changes when the voltage applied to the ion guide 28 is changed when CID and OAD are occurring in the reaction chamber 27. Figure 3 is a diagram showing a schematic diagram of the relationship between the voltage value applied to the ion guide and the abundance of product ions. The solid line L1 in Figure 3 indicates the abundance of the first product ion group generated by CID. The dashed line L2 in Figure 3 indicates the abundance of the second product ion group generated by OAD.

[0060] When a voltage is applied to the ion guide 28, energy is imparted to the precursor ions introduced into the reaction chamber 27. By imparting energy to the precursor ions, the collision energy when the precursor ions collide with the collision gas is increased, and fragmentation by CID progresses. Therefore, as shown in Figure 3, increasing the voltage applied to the ion guide 28 increases the abundance of the first group of product ions generated by CID.

[0061] On the other hand, because the CID and OAD compete with each other, as the fragmentation by the CID progresses, the fragmentation by the OAD slows down. Therefore, as shown in Figure 3, increasing the voltage applied to the ion guide 28 decreases the abundance of the second product ions generated by the OAD.

[0062] For these reasons, it has been thought that it is difficult to carry out both CID and OAD fragmentation in one reaction chamber 27.

[0063] The present inventors have found that by adjusting the voltage value applied to the ion guide 28, it is possible to proceed with both CID and OAD fragmentation within one reaction chamber 27.

[0064] The voltage value is determined by the balance between the peak intensity (detection intensity) of the first product ion group generated by the CID and the peak intensity of the second product ion group generated by the OAD. Generally, fragmentation by the OAD is less likely to occur than fragmentation by the CID. Therefore, the voltage value is set low enough to detect the first product ion group, taking into account the peak intensity of the first product ion group generated by the CID.

[0065] [Analysis flow] Analysis using the mass spectrometer 100 will be described. The mass spectrometer 100 performs MS analysis and MS / MS analysis in positive ion mode, and also performs MS analysis and MS / MS analysis in negative ion mode. The mass spectrometer 100 analyzes eluate continuously introduced from a liquid chromatograph by repeating MS analysis and MS / MS analysis while switching between positive ion mode and negative ion mode until the end of a set analysis time. The following describes the analytical flow when lipids are used as samples to be analyzed, as an example. Figure 4 is a flowchart showing an example of the analytical flow when analyzing lipids.

[0066] In S100, the control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform analysis in positive ion mode. As a result, MS analysis and MS / MS analysis are performed in positive ion mode. S100 includes S102, S104, S106, and S110.

[0067] In S200, the control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform analysis in the negative ion mode. As a result, MS analysis and MS / MS analysis are performed in the negative ion mode. S200 includes S202, S204, S206, and S210.

[0068] The control unit 6 repeats steps S100 and S200 until the set analysis time has elapsed. In this embodiment, the power supply unit 4 is configured to be able to switch polarity at high speed, and the control unit 6 corrects the deviation in the mass-to-charge ratio caused by the fluctuations in the voltage after switching. Therefore, in the mass spectrometer 100, the waiting time for measurement associated with switching between positive ion mode and negative ion mode is one second or less. Note that methods for switching the voltage polarity at high speed and specific correction methods can be methods known to those skilled in the art.

[0069] In S102, the control unit 6 controls the power supply unit 4 so that a negative voltage is applied to each electrode (e.g., the orthogonal acceleration electrode 30, the acceleration electrode 31, the flight tube 32, and the backplate 34) in order to perform MS analysis and MS / MS analysis in positive ion mode.

[0070] In S104, the control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform MS analysis. For example, the control unit 6 controls the power supply unit 4 to apply a radio frequency voltage for transporting ions to the quadrupole mass filter 26 and the ion guide 28. The control unit 6 also controls the measurement unit 2 to stop the supply from each of the water vapor supply unit 46 and the argon supply unit 48, thereby preventing the introduction of substances that cause fragmentation into the reaction chamber 27.

[0071] In S106, the control unit 6 determines precursor ions to be subjected to MS / MS analysis based on the results of the MS analysis obtained in S104. The method for determining precursor ions is not particularly limited, but for example, the control unit 6 determines ions with mass-to-charge ratios having high peak intensities as precursor ions. Note that this method of determining ions with mass-to-charge ratios having high peak intensities as precursor ions and analyzing them is generally referred to as data dependent acquisition (DDA).

[0072] In S110, the control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform a multi-MS / MS analysis. Here, the multi-MS / MS analysis is an MS / MS analysis performed in a multi-mode in which CID and OAD are performed simultaneously. S110 includes S112, S114, S116, and S118.

[0073] In S112, the control unit 6 controls the valves B1 to B3 to start the supply of water vapor and argon gas.

[0074] In S114, the control unit 6 controls the high frequency plasma source 44 so that the supply of microwaves is started.

[0075] In S116, the control unit 6 controls the power supply unit 4 so that a voltage is applied to the quadrupole mass filter 26 such that the precursor ions determined in S106 are introduced into the reaction chamber 27.

[0076] In S118, the control unit 6 controls the power supply unit 4 so that a predetermined first voltage is applied to the ion guide .

[0077] The control unit 6 performs MS / MS analysis in both positive ion mode and multi-mode by performing steps S112 to S118. In the positive ion mode, mass analysis is performed on positive ions, and therefore the precursor ion selected in S106 is also a positive ion. That is, in the multi-MS / MS analysis in S110, positive ions are detected from the first and second product ion groups derived from the positive precursor ion.

[0078] In S202, the control unit 6 controls the power supply unit 4 so that a positive voltage is applied to each electrode (e.g., the orthogonal acceleration electrode 30, the acceleration electrode 31, the flight tube 32, and the back plate 34) in order to perform MS analysis and MS / MS analysis in negative ion mode.

[0079] In S204, the control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform MS analysis. The control method is the same as in S104, and therefore description thereof will not be repeated.

[0080] In S206, the control unit 6 determines the precursor ion to be subjected to MS / MS analysis based on the result of the MS analysis obtained in S204. The method for determining the precursor ion is the same as in S106, and therefore the description will not be repeated.

[0081] In S210, the control unit 6 controls the measurement unit 2 and the power supply unit 4 to perform CID-MS / MS analysis. Here, CID-MS / MS analysis is MS / MS analysis performed in a single mode using only CID. S210 includes S212, S214, S216, and S218.

[0082] In S212, the control unit 6 controls the valves B1 to B3 to start the supply of water vapor and argon gas.

[0083] In S214, the control unit 6 controls the high-frequency plasma source 44 to stop the supply of microwaves. Note that S214 may be performed at any timing after the Multi-MS / MS analysis is performed in S110, and may be performed, for example, between S110 and S202.

[0084] In S216, the control unit 6 controls the power supply unit 4 so that a voltage is applied to the quadrupole mass filter 26 such that the precursor ions determined in S206 are introduced into the reaction chamber 27.

[0085] In S218, the control unit 6 controls the power supply unit 4 so that a predetermined second voltage is applied to the ion guide 28. The second voltage may be set in advance based on, for example, a standard substance or the like.

[0086] The controller 6 performs MS / MS analysis in negative ion mode and single mode using only CID by performing steps S212 to S218. In the negative ion mode, mass analysis is performed on negative ions, and therefore the precursor ions selected in S206 are also negative ions. That is, in the CID-MS / MS analysis in S210, negative ions are detected from the first group of product ions derived from the precursor ions of negative ions.

[0087] 4, the process is set to start in positive ion mode, but it may also be set to start in negative ion mode in S200. Also, CID-MS / MS analysis may be performed in positive ion mode, and Multi-MS / MS analysis may be performed in negative ion mode. The processing order of S112 to S118 and S212 to S218 is not limited to this order.

[0088] [Analysis results] 5 to 8, the mass spectra obtained by performing the analysis shown in Fig. 4 using the mass spectrometer 100 according to this embodiment and the analysis results of the obtained mass spectra will be described. The mass spectra shown in Fig. 5 to 8 are MS / MS spectra obtained by separating an extract extracted from mouse liver by liquid chromatography and subjecting the eluate from the liquid chromatograph to the analytical method shown in Fig. 4.

[0089] The liquid chromatograph used was a Nexera (registered trademark) system (Shimadzu Corporation). The first voltage was set to −35 V and the second voltage to 25 V. This allowed the structure of lipids in the extract extracted from the mouse liver to be estimated.

[0090] In MS analysis in positive ion mode, [M+H] + Two peaks (m / z = 782.5695) were obtained. The retention times of the two peaks were the first and second, respectively. MS analysis in negative ion mode revealed [M+HCOO] -Two peaks (m / z=826.5604) were obtained. The retention times of the two peaks obtained were the first and second, respectively.

[0091] Figure 5 shows the [M+HCOO] obtained at the first time point. - Figure 6 shows the MS / MS spectrum obtained by performing CID-MS / MS analysis in negative ion mode for [M+HCOO] (m / z=826.5604). - (m / z=826.5604) was subjected to CID-MS / MS analysis in negative ion mode.

[0092] Figure 7 shows the [M+H] obtained at the first time. + Figure 8 shows the MS / MS spectrum obtained by performing Multi-MS / MS analysis in positive ion mode on the [M+H] (m / z=782.5695) at the second time point. + (m / z=782.5695) was subjected to Multi-MS / MS analysis in positive ion mode.

[0093] By analyzing the MS / MS spectra shown in Figures 5 and 6, the carbon composition of the hydrocarbon chain in the lipid, including the number of carbon atoms and the number of unsaturated bonds, could be estimated. By analyzing the MS / MS spectra shown in Figures 7 and 8, the polar groups of the lipid and the positions of the double bonds in the hydrocarbon chain could be estimated. The estimation method (analysis method) is well known and will not be described in detail here.

[0094] As a result of the analysis, peaks P1 to P5 in Figures 5 and 6 were estimated to correspond to product ions obtained by CID and to be peaks corresponding to side chains. Furthermore, as a result of the analysis, peaks P1 to P5 were estimated to correspond to hydrocarbon chains (18:3), (18:2), (18:1), (16:0), and (20:4), respectively. The numbers on the left and right in parentheses indicate the number of carbon atoms and the number of double bonds in the hydrocarbon chain.

[0095] As a result of the analysis, it was estimated that peaks P6 and P11 in Figures 7 and 8 correspond to the polar groups of lipids. Furthermore, as a result of the analysis, it was estimated that peaks P7 to P10 and P12 to P15 in Figures 7 and 8 correspond to product ion peaks obtained by dissociation at the positions of unsaturated bonds (C=C bonds) contained in the hydrocarbon chain.

[0096] It is known that the peaks corresponding to the polar groups of lipids are peaks obtained by CID. Furthermore, the peaks of product ions obtained by dissociation at the unsaturated bond (C=C bond) are peaks obtained by OAD. In other words, the mass spectra and analysis results shown in Figures 7 and 8 confirm that both CID and OAD fragmentation can proceed within a single reaction chamber 27.

[0097] From the peaks corresponding to the first product ion group shown in Figures 5 to 8, it was estimated that the extract extracted from mouse liver contained phosphatidylcholine (PC) (36:4). Figure 9 shows the basic structure of phosphatidylcholine. Furthermore, from the peaks obtained by CID, the carbon numbers and double bond numbers of the two hydrocarbon chains (R1, R2) in PC (36:4) were estimated. From the peaks corresponding to the second product ion group shown in Figures 7 and 8, the positions of the double bonds in the hydrocarbon chains R1 and R2 were estimated. Figure 10 shows the estimated structure of PC (36:4). As shown in Figure 10, it was estimated that the extract extracted from mouse liver contained three types of PC (36:4) with different structures.

[0098] As described above, it has become clear that both CID and OAD fragmentation can be promoted by applying a predetermined voltage to the ion guide 28 while introducing radicals and collision gas into one reaction chamber 27. This eliminates the need to perform the two fragmentation methods separately, thereby reducing analysis time and sample consumption.

[0099] Furthermore, by switching the polarity and fragmentation method, multiple types of product ions can be detected in a single mass analysis. Therefore, even in cases where analysis from multiple perspectives is required, such as the structural analysis of polymer compounds, a large amount of information can be obtained in a single mass analysis. As a result, the accuracy of structural analysis estimates can be improved while shortening analysis time and reducing sample consumption.

[0100] The combination of polarity and fragmentation method according to this embodiment is an appropriate combination when the subject of analysis is lipids, and can be selected appropriately depending on the subject of analysis.

[0101] [Aspect] It will be understood by those skilled in the art that the above-described embodiments are specific examples of the following aspects.

[0102] (Item 1) One embodiment of a mass spectrometer generates product ions from precursor ions derived from a sample component having a hydrocarbon chain, and performs mass analysis on the generated product ions. The mass spectrometer includes a reaction chamber into which the precursor ions are introduced, an electrode disposed in the reaction chamber, an inlet unit that introduces collision gas and radicals into the reaction chamber as substances for fragmenting the precursor ions, a mass separator that separates ions including the product ions generated in the reaction chamber according to their mass-to-charge ratios, a detector unit that detects ions mass-separated by the mass separator, a power supply unit that applies voltages to the electrode and the mass separator, and a controller. The controller is switchable between a multi-mode in which the power supply unit is controlled to apply a predetermined first voltage to the electrode while the collision gas and radicals are introduced into the reaction chamber, and a single-mode in which the power supply unit is controlled to apply a predetermined second voltage to the electrode while the collision gas is introduced into the reaction chamber. The control unit is switchable between a first polarity mode in which the power supply unit is controlled to apply a third voltage to the mass separation unit for mass separation of ions of a first polarity, and a second polarity mode in which the power supply unit is controlled to apply a fourth voltage to the mass separation unit for mass separation of ions of a second polarity opposite to the first polarity. The control unit performs mass analysis of sample components while switching the analysis mode between a first analysis mode in which ions are detected in the first polarity mode and multimode, and a second analysis mode in which ions are detected in the second polarity mode and singlemode.

[0103] According to the mass spectrometer described in paragraph 1, mass analysis is performed while switching between the first analysis mode and the second analysis mode, so that analysis results obtained in the first analysis mode and analysis results obtained in the second analysis mode can be obtained in a single mass analysis, and more information can be obtained in a single mass analysis.

[0104] (Item 2) In the mass spectrometer described in item 1, the first voltage is set based on the detection intensities of a group of product ions obtained by colliding precursor ions with a collision gas and a group of product ions obtained by reacting precursor ions with radicals when the collision gas and radicals are introduced into the reaction chamber.

[0105] According to the mass spectrometer described in paragraph 2, it is possible to set a voltage that can detect both product ion groups obtained by colliding precursor ions with a collision gas and product ion groups obtained by reacting precursor ions with radicals.

[0106] (Item 3) In the mass spectrometer described in item 1 or 2, the ions of the first polarity are positive ions and the ions of the second polarity are negative ions. When lipids are the sample components to be analyzed, the control unit performs mass analysis of the sample components while switching the analysis mode between the first analysis mode and the second analysis mode.

[0107] The mass spectrometer described in paragraph 3 can estimate the polar groups of lipids based on the analysis results obtained by mass spectrometry in a first polarity mode on a group of product ions obtained by colliding precursor ions with a collision gas in a first analysis mode. The carbon composition of the hydrocarbon chain in the lipid, including the number of carbon atoms and the number of unsaturated bonds, can be estimated based on the analysis results obtained by mass spectrometry in a second polarity mode on a group of product ions obtained by colliding precursor ions with a collision gas in a second analysis mode. Furthermore, the position of double bonds in the hydrocarbon chain can be estimated based on the analysis results obtained by mass spectrometry in a first polarity mode on a group of product ions obtained by reacting precursor ions with radicals in the first analysis mode. Therefore, even for analyses that require analytical data from various perspectives, such as lipid structural analysis, the necessary analytical data can be obtained in a single analysis, thereby shortening the analysis time and reducing sample consumption.

[0108] The embodiments disclosed herein are intended to be combined as appropriate within the scope of any 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 defined by the claims, not by the description of the above-mentioned embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0109] 2 measurement unit, 4 power supply unit, 6 control unit, 20 vacuum chamber, 21 ESI source, 22 desolvation tube, 23, 25, 28 ion guide, 24 skimmer, 26 quadrupole mass filter, 27 reaction chamber, 29 transfer electrode, 30 orthogonal acceleration electrode, 31 acceleration electrode, 32 flight tube, 33 reflectron, 34 back plate, 35 detector, 40 introduction unit, 41, 43, 45 flow path, 42 radical generation chamber, 44 high frequency plasma source, 46 water vapor supply unit, 48 argon supply unit, 61 processor, 62 memory, 63 input / output I / F, 64 display, 65 input device, 100 mass analyzer, 200 ionization chamber, 201 first intermediate chamber, 202 second intermediate chamber, 203 first analysis chamber, 204 second analysis chamber, B1, B2, B3 valves.

Claims

1. 1. A mass spectrometer that generates product ions from precursor ions derived from a sample component having a hydrocarbon chain and performs mass analysis on the product ions, a reaction chamber into which the precursor ions are introduced; an electrode disposed within the reaction chamber; an introduction unit that introduces a collision gas and radicals into the reaction chamber as substances for causing fragmentation of the precursor ions; a mass separator that separates ions including product ions generated in the reaction chamber according to their mass-to-charge ratios; a detection unit that detects ions mass-separated by the mass separation unit; a power supply unit that applies a voltage to each of the electrodes and the mass separation unit; a control unit; The control unit a multi-mode in which the power supply unit is controlled so that a predetermined first voltage is applied to the electrode while the collision gas and the radicals are introduced into the reaction chamber, and a single mode in which the power supply unit is controlled so that a predetermined second voltage is applied to the electrode while the collision gas is introduced into the reaction chamber; a first polarity mode in which the power supply unit is controlled so that a third voltage for mass-separating ions of a first polarity is applied to the mass separation unit, and a second polarity mode in which the power supply unit is controlled so that a fourth voltage for mass-separating ions of a second polarity opposite to the first polarity is applied to the mass separation unit, A mass spectrometer that performs mass analysis of the sample components while switching between an analysis mode of a first analysis mode in which ions are detected under the first polarity mode and the multimode, and an analysis mode in which ions are detected under the second polarity mode and the single mode.

2. 2. The mass spectrometer according to claim 1, wherein the first voltage is set based on the detection intensities of a group of product ions obtained by collision of the precursor ions with the collision gas and a group of product ions obtained by reaction of the precursor ions with the radicals when the collision gas and the radicals are introduced into the reaction chamber.

3. the group of ions of the first polarity are positive ions; the group of ions of the second polarity are negative ions; The mass spectrometer according to claim 1 or 2, wherein when lipids are the sample components to be analyzed, the control unit performs mass analysis of the sample components while switching the analysis mode between the first analysis mode and the second analysis mode.

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