Ion analysis apparatus

Abstract

To improve ion measurement sensitivity in an apparatus that supplies precursor ions of an analysis target substance and active particles to a reaction chamber to cause a reaction therebetween, thereby generating and analyzing product ions.SOLUTION: An ion analysis apparatus (1) includes: a reaction chamber (132) into which precursor ions generated from an analysis target substance are introduced; an electrode (1331) provided inside the reaction chamber; an active particle generation unit (4) that generates active particles from a predetermined type of material gas; an active particle introduction unit (75) that introduces the active particles generated by the active particle generation unit into the reaction chamber while the precursor ions are introduced into the reaction chamber; and a voltage application unit (5) that applies, to the electrode, a voltage that forms an electric field accelerating product ions generated by a reaction between the precursor ions and the active particles toward an outlet of the reaction chamber while the precursor ions and the active particles are introduced into the reaction chamber.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ion analyzer that generates and measures product ions by reacting precursor ions generated from a substance to be analyzed with active particles such as radicals. [Background technology]

[0002] MS / MS analysis using a mass spectrometer is performed to identify and quantify analytes in samples. In MS / MS analysis, precursor ions generated from the analyte are introduced into a reaction chamber, where they are dissociated to generate product ions, which are then mass-separated and detected.

[0003] One method for dissociating precursor ions involves reacting the precursor ions with radicals (see, for example, Patent Document 1). The technique of dissociating precursor ions by reacting them with oxygen radicals is called OAD (Oxygen Attachment Dissociation). For example, by reacting precursor ions derived from peptides with oxygen radicals, the peptides can be specifically dissociated at the positions where amino acids are bonded (see, for example, Patent Document 2). Furthermore, by reacting precursor ions generated from an analyte having a hydrocarbon chain with oxygen radicals, the peptides can be specifically dissociated at the positions of unsaturated bonds in the hydrocarbon chain (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-191081 [Patent Document 2] International Publication No. 2018 / 186286 [Patent Document 3] International Publication No. 2019 / 155725 [Patent Document 4] International Publication No. 2022 / 059247 [Patent Document 5] US Patent Application Publication No. 6,163,032 Summary of the Invention [Problem to be solved by the invention]

[0005] The reaction chamber is equipped with electrodes for converging precursor ions generated from the analyte and product ions generated by dissociation of the precursor ions along a predetermined ion optical axis while transporting them to a downstream stage. When oxygen radicals are introduced into the reaction chamber and react with the precursor ions, unreacted oxygen radicals adhere to the electrodes arranged inside the reaction chamber, locally oxidizing the surface of the electrode. When a voltage is applied to such an electrode, the oxidized portion charges up. This results in disturbances in the electric field formed inside the reaction chamber, causing ions to scatter instead of being focused inside the reaction chamber and reducing ion transport efficiency, resulting in poor measurement sensitivity.

[0006] Although the reaction between precursor ions and oxygen radicals has been described here, the same problems arise when reacting precursor ions with radicals other than oxygen radicals, and when dissociating precursor ions using other active particles such as ozone or metastable particles.

[0007] The problem to be solved by the present invention is to improve the sensitivity of ion measurement in an apparatus that supplies precursor ions generated from a substance to be analyzed and activated particles to a reaction chamber and reacts the two to generate product ions for analysis. [Means for solving the problem]

[0008] The ion analyzer according to the present invention, which has been made to solve the above problems, is a reaction chamber into which precursor ions generated from an analyte are introduced; an electrode provided inside the reaction chamber; an active particle generating unit that generates active particles from a predetermined type of raw material gas; an active particle introduction unit that introduces active particles generated in the active particle generation unit into the reaction chamber while the precursor ions are being introduced into the reaction chamber; a voltage applying unit that applies to the electrode a voltage that forms an electric field that accelerates product ions generated by the reaction of the precursor ions and the active particles toward an outlet of the reaction chamber while the precursor ions and the active particles are being introduced into the reaction chamber; Equipped with. [Effects of the Invention]

[0009] In the ion analyzer according to the present invention, while precursor ions generated from a substance to be analyzed are being introduced into the reaction chamber, the active particle introduction unit introduces active particles generated in the active particle generation unit into the reaction chamber to react with the precursor ions. This causes the precursor ions to dissociate and generate product ions. Furthermore, while the precursor ions are being introduced into the reaction chamber, the voltage application unit applies a voltage to electrodes provided inside the reaction chamber to form an electric field that accelerates the product ions toward the outlet of the reaction chamber. This allows the product ions to fly quickly within the reaction chamber, preventing ions from scattering without being focused or reducing ion transport efficiency within the reaction chamber, thereby improving measurement sensitivity. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing the configuration of a main part of a mass spectrometer that is an embodiment of an ion analyzer according to the present invention. [Figure 2] 3A and 3B are diagrams illustrating the shape of plate electrodes that constitute the multipole ion guide used in the mass spectrometer of the present embodiment. [Figure 3] FIG. 2 is a diagram illustrating the arrangement of multipole ion guides in a reaction cell of the mass spectrometer of the present embodiment. [Figure 4] 3A and 3B are diagrams for explaining the polarities of radio frequency voltages applied to plate electrodes that constitute the multipole ion guide of the present embodiment. [Figure 5]FIG. 3 is a diagram for explaining the polarity of a DC voltage applied to a plate electrode that constitutes the multipole ion guide of this embodiment. [Figure 6] 10 shows the results of confirming the effect of improving the measurement sensitivity of product ions generated by collision-induced dissociation of precursor ions using the mass spectrometer of this embodiment. [Figure 7] 10 is another result confirming the effect of improving the measurement sensitivity of product ions generated by collision-induced dissociation of precursor ions, when using the mass spectrometer of this embodiment. [Figure 8] 10 shows the results of investigating the relationship between the acceleration voltage and the measured intensity of ions when positive precursor ions are reacted with oxygen radicals to generate product ions in the mass spectrometer of this embodiment. [Figure 9] 10 shows the results of investigating the relationship between the acceleration voltage and the measured intensity of ions when negative precursor ions are reacted with oxygen radicals to generate product ions in the mass spectrometer of this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] A mass spectrometer 1, which is one embodiment of an ion analyzer according to the present invention, will be described below with reference to the drawings. In the drawings used in the following description, the scale of each component has been appropriately changed from the actual ratio to make the configuration of the main components in this embodiment easier to understand.

[0012] <Configuration of Mass Spectrometer 1> 1 shows a schematic configuration of a mass spectrometer 1. The mass spectrometer 1 of this embodiment is a quadrupole time-of-flight (Q-TOF) mass spectrometer equipped with an atmospheric pressure ion source. This mass spectrometer 1 can be used as a liquid chromatograph mass spectrometer by connecting a liquid chromatograph (LC) to the upstream stage.

[0013] The mass spectrometer 1 of this embodiment has an ionization chamber 10 and a vacuum chamber 100. The inside of the ionization chamber 10 is under a substantially atmospheric pressure atmosphere. The inside of the vacuum chamber 100 is divided into multiple compartments (four compartments in this embodiment), which are, in order from the side closest to the ionization chamber 10, a first intermediate vacuum chamber 11, a second intermediate vacuum chamber 12, a first analysis chamber 13, and a second analysis chamber 14. Each of these compartments is evacuated to a vacuum by a vacuum pump (a rotary pump and / or a turbomolecular pump) (not shown), and has a multi-stage differential pumping system configuration in which the degree of vacuum increases sequentially from the ionization chamber 10, which is under a substantially atmospheric pressure atmosphere, to the second analysis chamber 14, which is under a high vacuum atmosphere.

[0014] An electrospray ionization (ESI) probe 101 that applies an electric charge to a liquid sample and sprays it is installed in the ionization chamber 10. A liquid sample containing sample components separated by, for example, an LC column (not shown) is introduced into the ESI probe 101.

[0015] The ionization chamber 10 and the first intermediate vacuum chamber 11 are in communication with each other through a small-diameter desolvation tube 102 heated by a heat source (not shown). The first intermediate vacuum chamber 11 is provided with an ion guide 111, which is made up of a plurality of rod electrodes arranged to surround a predetermined ion optical axis C (the central axis of the ion flight path in terms of the device design), and which focuses ions in the vicinity of the ion optical axis C. An appropriate voltage is applied from a voltage application unit 5 to each of the electrodes constituting the mass spectrometer 1, such as the ion guide 111.

[0016] The first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12 are separated by a skimmer 112 having a small hole at the top. The second intermediate vacuum chamber 12 also has an ion guide 121 arranged therein, which is composed of a plurality of rod electrodes arranged to surround the ion optical axis C and focuses ions in the vicinity of the ion optical axis C.

[0017] In the first analysis chamber 13, a quadrupole mass filter 131 that separates ions according to their mass-to-charge ratio (m / z), a reaction cell 132 equipped with a multipole ion guide 133 therein, and an ion transport electrode 134 that transports ions that have passed through the reaction cell 132 to a subsequent stage are arranged along the ion optical axis C. Three entrance ring electrodes 1321 are arranged at the entrance end of the reaction cell 132, and three exit ring electrodes 1322 are also arranged at the exit end of the reaction cell 132. The entrance ring electrodes 1321 and the exit ring electrodes 1322 are each fixed to the reaction cell 132 via an insulator.

[0018] An opening 1323 is provided in the wall of the reaction cell 132 for inserting the discharge tube 41 of the radical introduction section 4, and a cylindrical tube connecting member 1324 is provided in this opening 1323 so that one end surrounds this opening 1323.

[0019] The radical introducing section 4 may have a configuration similar to that of the radical introducing section described in Patent Document 4, for example. A raw material gas supply source 48 is connected to the discharge tube 41. The raw material gas may be, for example, water vapor that generates oxygen radicals and hydroxyl radicals, oxygen gas that generates oxygen radicals, hydrogen gas that generates hydrogen radicals, nitrogen gas that generates nitrogen radicals, or dry air that generates nitrogen radicals. A valve 40 that adjusts the flow rate of the raw material gas is provided in a flow path connecting the discharge tube 41 and the raw material gas supply source 48. A helical antenna 411 is wound around the outer periphery of the discharge tube 41. When microwaves are supplied to the helical antenna 411 from the microwave power supply 46 while the raw material gas is being supplied from the raw material gas supply source 48 to the inside of the discharge tube 41, the raw material gas is converted into plasma inside the discharge tube 41 and radicals are generated.

[0020] The reaction cell 132 is also connected to a collision-induced dissociation (CID) gas supply source 61. A valve 62 is provided in the flow path connecting the CID gas supply source 61 and the reaction cell 132 to adjust the flow rate of the CID gas (e.g., an inert gas such as argon gas) supplied from the CID gas supply source 61 to the reaction cell 132.

[0021] In the reaction cell 132, a dissociation method (hereinafter referred to as the "radical reaction dissociation method") can be performed, in which precursor ions are dissociated by reacting with radicals such as oxygen radicals supplied from the radical introduction section 4, and a collision-induced dissociation (CID) method can be performed, in which precursor ions are accelerated by imparting energy to them and entering the reaction cell 132, and then colliding with a CID gas to dissociate the precursor ions.

[0022] The quadrupole mass filter 131 has four main rod electrodes 1312. The quadrupole mass filter 131 also has four pre-rod electrodes 1311 on the upstream side of the main rod electrodes 1312 (the ionization chamber 10 side), and four post-rod electrodes 1313 on the downstream side of the main rod electrodes 1312 (the second analysis chamber 14 side).

[0023] The multipole ion guide 133 is composed of eight plate electrodes 1331. As shown in Fig. 2, each plate electrode 1331 has a trapezoidal shape with two parallel sides, one side perpendicular to the other two sides, and one side inclined relative to the other two sides. Note that Fig. 2 corresponds to the A-A' cross section in Fig. 3. Fig. 3 is a view of the interior of the reaction cell 132 as seen from the rear side (the outlet side of the reaction cell 132). As shown in the figure, the eight plate electrodes 1331 are arranged so that one inclined side faces the ion optical axis C and the direction of inclination is opposite between adjacent plate electrodes 1331. In the example of Figure 3, two vertically arranged plate electrodes 1331 and two horizontally arranged plate electrodes 1331 are arranged so that their inclined sides approach the ion optical axis C from the entrance to the exit of the reaction cell 132, and the remaining four plate electrodes 1331 are arranged so that their inclined sides move away from the ion optical axis C from the entrance to the exit of the reaction cell 132.

[0024] The multipole ion guide 133 is originally intended to form an electric field that converges ions flying within the reaction cell 132 near the ion optical axis C. As shown in Fig. 4, two adjacently arranged plate electrodes 1331 are treated as one pair, and a high-frequency voltage is applied from the voltage application unit 5 so that the polarity of the applied voltage to the adjacent pair of plate electrodes 1331 is opposite. This forms a quadrupole electric field inside the reaction cell 132, and the ions are converged near the ion optical axis C by this electric field. Note that Fig. 4 (and Fig. 5, which will be described later) also show the plate electrodes 1331 that constitute the multipole ion guide 133 as seen from the rear side of the reaction cell 132.

[0025] In addition to the above-mentioned radio frequency voltage, a DC voltage (acceleration voltage) for forming an electric field that accelerates ions flying within the reaction cell 132 is also applied from the voltage application unit 5 to the multipole ion guide 133 of this embodiment.

[0026] For example, as described in Patent Document 5, by arranging an even number of electrodes around the ion optical axis C so that the distance from the ion optical axis C gradually changes and the direction of change is opposite between adjacent electrodes and applying DC voltages of opposite polarities between adjacent electrodes, a potential gradient can be formed along the ion optical axis C. In this embodiment, the multipole ion guide 133 having the configuration described above with reference to FIGS. 2 and 3 is used, and as shown in FIG. 5 as an example in which the target ions are positive ions, a DC voltage of the same polarity as the target ions is applied to four plate electrodes 1331 arranged so that one slanted side moves away from the ion optical axis C toward the outlet of the reaction cell 132, and a DC voltage of the opposite polarity to that of the target ions is applied to four plate electrodes 1331 arranged so that one slanted side moves closer to the ion optical axis C toward the outlet of the reaction cell 132, thereby forming a potential gradient that accelerates the target ions from the inlet side to the outlet side of the reaction cell 132.

[0027] When precursor ions are subjected to collision-induced dissociation, an electric field is formed that accelerates the precursor ions (by imparting collision energy) and causes them to enter the reaction cell 132, and the voltage that forms this electric field is applied to the entrance ring electrode 1321 and the exit ring electrode 1322. In other words, the above-mentioned acceleration electric field is applied to the plate electrode 1331 separately from the voltage that is used to impart collision energy to the precursor ions when performing collision-induced dissociation. One feature of the mass spectrometer 1 of this embodiment is that, in both the case of radical reaction dissociation and collision-induced dissociation, the above-mentioned acceleration voltage is applied in addition to the voltage that has conventionally been used.

[0028] The second analysis chamber 14 is equipped with an ion transport electrode 141 for transporting ions incident from the first analysis chamber 13, an orthogonal acceleration unit 142 having a pair of pusher and puller electrodes arranged opposite each other across the ion optical axis C and deflecting the ion flight direction in a direction substantially perpendicular to the direction of flight and sending the ions into the flight space, an acceleration electrode 143 for accelerating the ions sent into the flight space by the orthogonal acceleration unit 142, a reflectron electrode 144 for forming a return trajectory of the ions in the flight space, an ion detector 145, and a flight tube 146 that defines the flight space therein. The ion detector 145 is, for example, an electron multiplier or a multichannel plate.

[0029] The mass spectrometer 1 further includes a control / processing unit 7. The control / processing unit 7 includes a memory unit 71. The memory unit 71 stores a compound database that includes information on analytical conditions (measurement conditions, analysis methods, etc.) for various compounds.

[0030] The memory unit 71 also stores the tuning results of the voltages applied to each electrode in the mass spectrometer 1. In addition to the results of general tuning performed when the mass spectrometer 1 is shipped or installed, the tuning results also include tuning results of the acceleration voltage applied to the plate electrode 1331 to accelerate ions inside the reaction cell 132 for mass analysis in which product ions are generated from precursor ions by radical reactive dissociation and mass analysis in which product ions are generated from precursor ions by collision-induced dissociation. For radical reactive dissociation, tuning results of the acceleration voltage are stored for each combination of the compound to be analyzed and the radical species.

[0031] The control and processing unit 7 has, as its functional blocks, a tuning execution unit 72, an analysis condition setting unit 73, an acceleration voltage setting unit 74, and an analysis execution unit 75. The control and processing unit 7 is configured, for example, by a general-purpose personal computer (PC), and each of the above functional blocks is realized by executing dedicated control and processing software installed in the computer on a processor. An input unit 81 configured, for example, by a mouse and keyboard, and a display unit 82 configured, for example, by a liquid crystal display are connected to the control and processing unit 7.

[0032] <Operation of mass spectrometer 1> Next, the operation of the mass spectrometer 1 of this embodiment will be described. In this mass spectrometer 1, before analyzing a real sample, the acceleration voltage in the reaction cell 132 is tuned and the result is stored in the memory unit 71. The acceleration voltage may be tuned at the time of shipment or installation of the device, or before analyzing a real sample. First, this tuning operation will be described. During tuning, a standard sample containing one or more target compounds may be used, or a real sample containing a substance to be analyzed may be used.

[0033] When the user performs a predetermined input operation to instruct the execution of tuning of the acceleration voltage through the input unit 81, the tuning execution unit 72 displays a screen on the display unit 82 for inputting the name of the compound to be tuned and the dissociation method for dissociating the compound (radical reaction dissociation or collision-induced dissociation). In the case of radical reaction dissociation, the type of radical to be used is also input. The compound name and type of radical can be input, for example, by displaying a list of compounds stored in a compound database on the screen of the display unit 82 and allowing the user to select one of them. Multiple compounds to be tuned may be input.

[0034] When the user inputs the name of the target compound to be tuned and the dissociation method, the tuning execution unit 72 reads the analysis conditions for that compound from the compound database stored in the memory unit 71 and creates a method file describing the measurement conditions. At this time, the acceleration voltage applied to the multipole ion guide 133 in the reaction cell 132 (the acceleration voltage applied to the plate electrode 1331 arranged so as to approach the ion optical axis C toward the outlet of the reaction cell 132) is set to multiple values ​​that differ by a predetermined value (e.g., 0.5 V) within a predetermined range (e.g., 0 V to 5 V), and a method file is created to perform measurements using each set value. If multiple target compounds are input, a method file is created for each of those compounds. Once the method files are created, the tuning execution unit 72 creates a batch file to execute them in order.

[0035] After creating the batch file, when the user loads a sample containing the target compound for tuning and issues a command to execute tuning, the analysis execution unit 75 measures ions of each target compound under multiple measurement conditions with different acceleration voltage values ​​described in the method file. The ions measured here are typically product ions generated from precursor ions by radical reaction dissociation or collision-induced dissociation, but precursor ions may also be measured.

[0036] When measuring the intensity of precursor ions, the quadrupole mass filter 131 allows all ions to pass without selection. Then, in the second analysis chamber 14, the ions are orthogonally accelerated to travel a folded trajectory, and their intensities are detected by the ion detector 145. When measuring the intensity of precursor ions, the radical introduction unit 4 is not operated, and CID gas is not supplied from the CID gas supply source 61. While ions are being introduced into the reaction cell 132, the above-mentioned multiple acceleration voltages are applied individually to the multipole ion guide 133 within the reaction cell 132, and the intensity of ions of the target compound is measured for each acceleration voltage value. This measurement produces a mass spectrum. Since the mass-to-charge ratio of the precursor ions of the target compound is usually known, the height or area of ​​the mass peak of the ion with that mass-to-charge ratio that appears on the mass spectrum can be used as the measured intensity.

[0037] On the other hand, when measuring product ions generated by radical reaction dissociation of precursor ions, radicals are generated from a predetermined type of source gas in the radical introduction unit 4 according to measurement conditions during measurement of the target compound. The generated radicals are introduced into the reaction cell 132 while the precursor ions are being introduced into the reaction cell 132. When precursor ions are subjected to collision-induced dissociation, a predetermined flow rate of CID gas is introduced into the reaction cell 132 from the CID gas supply source 61 while the precursor ions are being introduced into the reaction cell 132. Regardless of the dissociation method used, the acceleration voltage set as described above is applied to the multipole ion guide 133 while the precursor ions of the target compound and radicals or CID gas are being introduced into the reaction cell 132. Then, the intensities of the product ions of the target compound are measured for each of the multiple acceleration voltage values. This measurement results in a product ion spectrum of the target compound for each of the multiple acceleration voltage values. The measured product ion intensity can be the sum of the measured intensities of all product ions or the measured intensities of one or more product ions having a predetermined mass-to-charge ratio.

[0038] When measurements of all target compounds are completed, the tuning execution unit 72 generates information indicating the relationship between the acceleration voltage value and the measured ion intensity for each target compound. As described above, the measured ion intensity may include both the measured intensity of precursor ions and the measured intensities of product ions of the target compound.

[0039] The tuning execution unit 72 then determines the acceleration voltage value at which the measured ion intensity is highest based on the information indicating the relationship between the acceleration voltage value and the measured ion intensity, and stores the determined value in association with the name of the target compound in the storage unit 71. By performing radical reaction dissociation and collision-induced dissociation for each compound recorded in the compound database and executing the above-mentioned processes, the acceleration voltage information for each compound is stored in the storage unit 71.

[0040] As described above, when the information indicating the relationship between the acceleration voltage value and the measured ion intensity for each tuning target compound, dissociation method, and radical species, as well as the acceleration voltage value at which the measured ion intensity is maximized, is stored in the memory unit 71, and the user issues a command to execute an analysis by performing a predetermined input operation through the input unit 81, the analysis condition setting unit 73 first displays a screen on the display unit 82 that prompts the user to input the target compound contained in the actual sample and the dissociation method for the precursor ion of the target compound. This screen may also display, for example, a list of compounds stored in the compound database stored in the memory unit 71, prompting the user to select from the list, and may also prompt the user to select either radical reaction dissociation or collision-induced dissociation. In the case of radical reaction dissociation, the user is also prompted to select the type of radical to be used.

[0041] When the user inputs the compound to be analyzed, the dissociation method of the precursor ion, and the type of radical (in the case of radical reaction dissociation), the analysis condition setting unit 73 reads out the analysis conditions corresponding to the selected compound to be analyzed and the dissociation method of the precursor ion from the compound database. In addition, the acceleration voltage setting unit 74 reads out the tuning results of the acceleration voltage corresponding to the analysis conditions (the acceleration voltage value at which the measured ion intensity is highest) from the memory unit 71 and displays the values ​​on the screen of the display unit 82 together with a graph showing the relationship between the acceleration voltage value and the measured ion intensity.

[0042] Typically, the acceleration voltage value that maximizes the ion measurement intensity is used. However, for example, when there are many target compounds to be analyzed or when the production efficiency of product ions is high, it may be necessary to prioritize measurement efficiency over ion measurement intensity. In such cases, for example, an acceleration voltage value greater than the acceleration voltage value that maximizes the ion measurement intensity can be set to increase the flight speed of the ions within the reaction cell 132. When the user confirms (and changes, if necessary) the acceleration voltage value displayed on the screen of the display unit 82 and performs a predetermined input operation, such as pressing the OK button, the acceleration voltage setting unit 74 determines that acceleration voltage value as the measurement condition, and the analysis condition setting unit 73 creates a method file that describes the measurement conditions, including that acceleration voltage value.

[0043] After creating the method files describing the measurement conditions for all the target compounds, the analytical condition setting unit 73 creates a batch file for executing them continuously.

[0044] After creating the batch file, when the user loads a sample and issues a command to start measurement, the analysis execution unit 75 executes the batch file and sequentially measures the target compounds in the sample. In this measurement, too, if precursor ions are dissociated by radical reaction, radicals are generated from a predetermined type of source gas in accordance with the measurement conditions during the measurement of the target compounds. The generated radicals are then introduced into the reaction cell 132 while the precursor ions are being introduced into the reaction cell 132. In addition, if precursor ions are dissociated by collision-induced dissociation, a predetermined flow rate of CID gas is introduced into the reaction cell 132 from the CID gas supply source 61 while the precursor ions are being introduced into the reaction cell 132. Regardless of the dissociation method used, a set acceleration voltage is applied from the voltage application unit 5 to the multipole ion guide 133 while the precursor ions of the target compounds and radicals or CID gas are being introduced into the reaction cell 132.

[0045] Data output from the ion detector 145 during measurement is sequentially stored in the memory unit 71. After the measurement is completed, a product ion spectrum is created based on the data stored in the memory unit 71, and the target compound is identified and quantified. These processes are the same as those conventionally performed, and therefore a detailed description thereof will be omitted.

[0046] When a measurement is performed in which radicals are introduced into the reaction cell 132 and reacted with precursor ions, unreacted radicals adhere to the plate electrode 1331 and other parts that make up the multipole ion guide 133 of the reaction cell 132. For example, when oxygen radicals adhere, the surface of the plate electrode 1331 is locally oxidized. When a voltage is applied to this plate electrode 1331, the oxidized portion is charged up. As a result, the electric field formed inside the reaction cell 132 is disturbed, causing ions to scatter instead of being focused inside the reaction cell 132, and reducing the ion transport efficiency, resulting in poor measurement sensitivity.

[0047] Even when precursor ions are subjected to collision-induced dissociation, it is possible for analyte compounds or impurities to adhere to the electrode. However, such contamination is limited to the adhesion of substances to the electrode surface. On the other hand, charge buildup caused by, for example, oxygen radicals adhering to the electrode surface and oxidizing it is more severe than charge buildup caused by the adhesion of substances to the electrode surface, significantly reducing the sensitivity of ion measurement. The inventors conducted various tests and found that when radical reaction dissociation was performed and mass spectrometry was performed on precursor ions with collision-induced dissociation in an oxidized electrode surface, the measured intensity of product ions was reduced to approximately half of the measured intensity obtained when the electrode surface was not oxidized.

[0048] These problems are not limited to oxidation of electrode surfaces by oxygen radicals or hydroxyl radicals, but also occur when reducing electrode surfaces by hydrogen radicals or when forming nitrides on electrode surfaces by nitrogen radicals. The same problem also occurs when precursor ions are dissociated using ozone or metastable particles, which are as active as radicals. Metastable particles are atoms (metastable atoms) or molecules (metastable molecules) that are in a long-lived excited state.

[0049] In contrast, in this embodiment, when the radical introducing unit 4 introduces radicals into the reaction cell 132 to react with precursor ions, and when the collision gas is introduced from the CID gas supply source 61 into the reaction cell 132 to dissociate the precursor ions, the voltage applying unit 5 applies an acceleration voltage to the plate electrodes 1331 constituting the multipole ion guide 133 inside the reaction cell 132, forming an electric field that accelerates ions toward the outlet of the reaction cell 132. This allows the precursor ions and product ions to fly quickly inside the reaction cell 132, preventing ions from scattering without being focused inside the reaction cell 132 and reducing ion transport efficiency, thereby improving measurement sensitivity. [Example]

[0050] Here, the results of confirming the effect of applying an acceleration voltage to the plate electrodes 1331 that constitute the multipole ion guide 133 in the mass spectrometer 1 of this embodiment will be described.

[0051] FIG. 6 shows the results of measuring product ions (MRM transition: 609.319>195.06) generated by collision-induced dissociation of precursor ions derived from reserpine with an event time of 200 ms. The intensity (17267) shown on the left is the result of measuring the product ion intensity without using an accelerating voltage when the surface of the plate electrode 1331 was not oxidized. The intensity (21500) shown on the right is the result of measuring the same MRM transition as above after 100 hours of mass analysis using oxygen radicals to dissociate precursor ions through radical reactions in the mass spectrometer 1, i.e., when the surface of the plate electrode 1331 was oxidized, with the accelerating voltage set to 1 V. In conventional methods, the measured intensity of product ions was reduced by half due to surface oxidation of the plate electrode 1331. However, in this embodiment, as can be seen from a comparison of these measured intensities, the measured intensity of product ions is increased by 20% compared to conventional methods.

[0052] Similarly, Figure 7 shows the results of measuring product ions (MRM transition: 609.319>195.06) generated by collision-induced dissociation of precursor ions derived from reserpine with an event time of 200 ms. The intensity (6466) shown on the left is the result of measuring the product ion intensity without using an accelerating voltage, as described above, when the surface of the plate electrode 1331 was not oxidized. Note that this measurement was performed using a different device than the one used to obtain the measurement data shown in Figure 6, so the measured intensity shown on the left of Figure 6 differs from the measured intensity shown on the left of Figure 7. The intensity (10859) shown in the center is the result of measuring the product ion intensity when the surface of the plate electrode 1331 was not oxidized and the accelerating voltage was set to 1 V. The intensity (11500) shown on the right is the result of measuring the same MRM transition as above with the acceleration voltage set to 1 V after 300 hours of mass spectrometry in which precursor ions are subjected to radical reaction dissociation using oxygen radicals in the mass spectrometer 1, i.e., with the surface of the plate electrode 1331 oxidized. The difference between the intensity shown on the left and the intensity shown in the center indicates that the measured ion intensity increases by 68% by setting the acceleration voltage. Furthermore, a comparison of the intensity shown in the center and the intensity shown on the right indicates that the ion measurement sensitivity can be maintained by setting the acceleration voltage, even when the surface of the plate electrode 1331 is oxidized.

[0053] Figure 8 shows the intensity of product ions (MRM transition: 480.3 > 384.1) generated by radical dissociation of a positive precursor ion, a protonated ion of the fatty acid LPE18:1, reacting with an oxygen radical. 400 fmol of LPE18:1 was used for the measurements. An accelerating voltage of 0 V (i.e., no accelerating voltage applied) corresponds to the conventional technique. In addition, a similar measurement was also performed on the precursor ion. Figure 8 shows the relationship between accelerating voltage and ion intensity. When the accelerating voltage was set to 0.5 V, the measured intensity of the positive product ion increased by four times (300% higher) compared to when the accelerating voltage was set to 0 V.

[0054] Figure 9 shows the intensity of product ions (MRM transition: 478.3 > 382.1) generated by radical dissociation of negative precursor ions, which are deprotonated ions of the fatty acid LPE18:1, by reacting them with oxygen radicals. 400 fmol of LPE18:1 was used for the measurements. Again, an accelerating voltage of 0 V (i.e., no accelerating voltage applied) corresponds to the conventional technique. Similar measurements were also performed on the precursor ions. Figure 9 shows the relationship between accelerating voltage and ion intensity. When the accelerating voltage was set to 0.5 V, the measured intensity of the negative product ions was 20% higher than when the accelerating voltage was set to 0 V.

[0055] The above embodiment is merely an example and can be modified as appropriate in accordance with the spirit of the present invention.

[0056] In the above embodiment, radical reaction dissociation, in which the substance to be analyzed is reacted with radicals, is described. However, a similar configuration can also be used when dissociating precursor ions (active particle dissociation) using other active particles such as ozone or metastable particles.

[0057] In the above embodiment, different acceleration voltage values ​​are determined for each compound, each dissociation method, and each radical species by tuning the acceleration voltage. However, this is a preferred example, and other configurations are also possible. For compounds of the same type (e.g., peptides), the relationship between the acceleration voltage value and the measured ion intensity is often similar. Therefore, instead of tuning the acceleration voltage individually for all compounds, the acceleration voltage may be tuned for each type of compound. This allows efficient acquisition of information indicating the relationship between the acceleration voltage value and the measured ion intensity for each compound. Alternatively, for simplicity, a common acceleration voltage for radical reaction dissociation and a common acceleration voltage for collision-induced dissociation may be set for all compounds. The acceleration voltage for radical reaction dissociation may be different for each radical species, or may be common regardless of the radical species.

[0058] In the above embodiment, precursor ions are dissociated in the reaction cell 132 having the shape of a linear ion trap, but other shapes may be used as long as an electric field for accelerating ions can be formed inside the reaction chamber. Also, in the above embodiment, an electric field for accelerating ions is formed by applying a DC voltage to eight plate electrodes 1331, but this electrode shape is just one example, and an electric field for accelerating ions may be formed by applying an acceleration voltage to electrodes of other shapes.

[0059] In the above embodiment, the mass spectrometer is capable of performing both radical reaction dissociation and collision-induced dissociation, but it may also be configured to perform only radical reaction dissociation. Also, in the above embodiment, different acceleration voltage values ​​are set for radical reaction dissociation and collision-induced dissociation, but this is a preferred embodiment and not essential. Furthermore, the same acceleration voltage value may be set for radical reaction dissociation regardless of the radical species.

[0060] In the above embodiment, the mass spectrometer has a configuration known as Q-TOF, which combines a quadrupole mass filter and an orthogonal acceleration time-of-flight mass separator, but the mass spectrometer may have any configuration. Furthermore, the same configuration can be used not only in mass spectrometers but also in other ion analyzers, such as ion mobility spectrometers.

[0061] [Aspect] It will be apparent to those skilled in the art that the above-described exemplary embodiments are examples of the following aspects.

[0062] (Section 1) An ion analyzer according to one aspect of the present invention comprises: a reaction chamber into which precursor ions generated from an analyte are introduced; an electrode provided inside the reaction chamber; an active particle generating unit that generates active particles from a predetermined type of raw material gas; an active particle introduction unit that introduces active particles generated in the active particle generation unit into the reaction chamber while the precursor ions are being introduced into the reaction chamber; a voltage applying unit that applies to the electrode a voltage that forms an electric field that accelerates product ions generated by the reaction of the precursor ions and the active particles toward an outlet of the reaction chamber while the precursor ions and the active particles are being introduced into the reaction chamber; Equipped with.

[0063] In the ion analyzer according to paragraph 1, while precursor ions generated from a substance to be analyzed are being introduced into the reaction chamber, the active particle introduction unit introduces active particles generated in the active particle generation unit into the reaction chamber to react with the precursor ions. This causes the precursor ions to dissociate (active particle dissociation) and generate product ions. Furthermore, while the precursor ions are being introduced into the reaction chamber, the voltage application unit applies a voltage to an electrode provided inside the reaction chamber to form an electric field that accelerates the ions toward the outlet of the reaction chamber. This allows the product ions to fly quickly inside the reaction chamber, preventing ions from scattering without being focused inside the reaction chamber or reducing ion transport efficiency, thereby improving measurement sensitivity.

[0064] (Section 2) The ion analyzer according to paragraph 2 is the ion analyzer according to paragraph 1, further comprising: a memory unit in which a predetermined value for the voltage applied to the electrodes from the voltage application unit is stored for each combination of the substance to be analyzed and the type of active particle; Equipped with The voltage application unit reads a value corresponding to a combination of the target substance and active particles to be analyzed from the values ​​stored in the memory unit, and applies the value to the electrodes. The types of active particles can be classified into, for example, types of radicals, ozone, metastable particles, etc.

[0065] In the ion analyzer according to paragraph 2, an appropriate value of acceleration voltage can be used to improve the measured intensity of ions for each combination of the substance to be analyzed and the type of active particle.

[0066] (Section 3) The ion analyzer according to paragraph 3 is the ion analyzer according to paragraph 1 or 2, further comprising: a collision-induced dissociation gas inlet that introduces a collision-induced dissociation gas into the reaction chamber while the precursor ions are being introduced into the reaction chamber; an analysis condition setting unit that accepts an input to select either active particle reactive dissociation or collision-induced dissociation; an analysis execution unit that, when the analysis condition setting unit receives an input selecting active particle reactive dissociation, introduces active particles from the active particle introduction unit into the reaction chamber, and, when the analysis condition setting unit receives an input selecting collision induced dissociation, introduces collision induced dissociation gas from the collision induced dissociation gas introduction unit into the reaction chamber and executes analysis; Equipped with.

[0067] The ion analyzer according to paragraph 3 can perform mass analysis of product ions generated by dissociating precursor ions using two methods, reactive particle dissociation and collision-induced dissociation, in a single device. In reactive particle dissociation and collision-induced dissociation, precursor ions usually dissociate at different positions, and information on different substructures of the analyte can be obtained from the product ions generated by each dissociation method.

[0068] (Section 4) The ion analyzer according to paragraph 4 is the ion analyzer according to paragraph 3, The voltage application unit applies a voltage to the electrode that forms an electric field that accelerates the ions toward an outlet of the reaction chamber, even while the precursor ions and the collision-induced dissociation gas are being introduced into the reaction chamber.

[0069] In the ion analyzer according to the fourth aspect, the measurement sensitivity of ions can be improved not only when precursor ions of an analyte are subjected to reactive dissociation by activated particles, but also when the precursor ions are subjected to collision-induced dissociation.

[0070] (Section 5) The ion analyzer according to paragraph 5 is the ion analyzer according to any one of paragraphs 1 to 4, further comprising: a tuning execution unit that sets a plurality of different acceleration voltage values, measures the intensity of product ions generated by active particle dissociation of precursor ions of a predetermined target substance using a predetermined target substance and a predetermined type of active particle for each of the plurality of acceleration voltage values, and determines the acceleration voltage value at which the measured intensity of the product ions obtained by the measurement is the highest; Equipped with.

[0071] In the ion analyzer according to paragraph 5, the optimum acceleration voltage value can be automatically determined even for a combination of an analyte and active particles for which the acceleration voltage value has not been set in advance. [Explanation of symbols]

[0072] 1...Mass spectrometer 10...Ionization chamber 100...Vacuum chamber 101...ESI probe 102...Desolvation tube 11...First intermediate vacuum chamber 111...Ion Guide 12...Second intermediate vacuum chamber 121...Ion Guide 13…1st analysis room 131...Quadrupole mass filter 132...Reaction cell 1321...Entrance ring electrode 1322...Exit ring electrode 133...Multipole ion guide 1331...Plate electrode 134...Ion transport electrode 14…Second analysis room 141...Ion transport electrode 142...Orthogonal acceleration section 143...acceleration electrode 144...Reflectron electrode 145...Ion detector 146...Flight tube 4...Radical introduction section 41...discharge tube 411...Helical antenna 46...Microwave power supply 48...Source gas supply source 5...Voltage application section 61...CID gas supply source 7...Control and processing section 71...Storage section 72...Tuning execution unit 73…Analysis condition setting section 74...Acceleration voltage setting section 75...Analysis Execution Department 81...Input section 82...Display section C...Ion optical axis

Claims

1. a reaction chamber into which precursor ions generated from an analyte are introduced; an electrode provided inside the reaction chamber; an active particle generating unit that generates active particles from a predetermined type of raw material gas; a radical introducing unit that introduces active particles generated in the active particle generating unit into the reaction chamber while the precursor ions are being introduced into the reaction chamber; a voltage applying unit that applies to the electrode a voltage that forms an electric field that accelerates product ions generated by the reaction of the precursor ions and the active particles toward an outlet of the reaction chamber while the precursor ions and the active particles are being introduced into the reaction chamber; An ion analyzer comprising:

2. moreover, a memory unit in which a predetermined value for the voltage applied to the electrodes from the voltage application unit is stored for each combination of the substance to be analyzed and the type of active particle; Equipped with The ion analyzer according to claim 1 , wherein the voltage application unit reads out a value corresponding to a combination of an analyte and active particles to be analyzed from the values ​​stored in the memory unit and applies the value to the electrodes.

3. moreover, a collision-induced dissociation gas inlet that introduces a collision-induced dissociation gas into the reaction chamber while the precursor ions are being introduced into the reaction chamber; an analysis condition setting unit that accepts an input to select either active particle reactive dissociation or collision-induced dissociation; an analysis execution unit that, when the analysis condition setting unit receives an input selecting active particle reactive dissociation, introduces active particles from the active particle introduction unit into the reaction chamber, and, when the analysis condition setting unit receives an input selecting collision induced dissociation, introduces collision induced dissociation gas from the collision induced dissociation gas introduction unit into the reaction chamber and executes analysis; The ion analyzer of claim 1 , comprising:

4. 4. The ion analyzing apparatus according to claim 3, wherein the voltage application unit applies to the electrode a voltage that forms an electric field that accelerates the ions toward an outlet of the reaction chamber, even while the precursor ions and the collision induced dissociation gas are being introduced into the reaction chamber.

5. moreover, a tuning execution unit that sets a plurality of different acceleration voltage values, measures the intensity of product ions generated by active particle dissociation of precursor ions of a predetermined target substance using a predetermined target substance and a predetermined type of active particle for each of the plurality of acceleration voltage values, and determines the acceleration voltage value at which the measured intensity of the product ions obtained by the measurement is the highest; The ion analyzer of claim 1 , comprising:

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