Mass analysis method and mass analysis device

Abstract

The present invention relates to a mass analysis method, wherein the mass analysis device (1) used in the method comprises: a first moving mechanism (151) for moving a sample stage (14) in a first direction within a plane parallel to the sample stage (14); and a second moving mechanism (152) for moving the first moving mechanism (151) in a second direction different from the first direction within a plane parallel to the sample stage (14), wherein the irradiation point of an excitation beam is intermittently moved with the first direction as the main moving direction between a plurality of measurement points two-dimensionally arranged in a sample placed on the sample stage (14) (step 4), and mass analysis is performed at each of the plurality of measurement points (step 5).

Description

Technical Field

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

[0002] In order to measure the distribution of target substances in samples such as cells, an imaging mass spectrometer can be used. In the imaging mass spectrometer, in order to measure the distribution of target substances in the target area on the surface of the sample, a plurality of measurement points arranged two-dimensionally in the area are set. Next, the laser is focused on the surface of the sample, and the focusing point is moved sequentially between these multiple measurement points to ionize the substances present at each measurement point and perform mass analysis. This movement is performed intermittently. That is, the movement is stopped at each measurement point, and multiple (e.g., tens to hundreds of times) pulsed laser irradiation is performed. The mass spectrum data of each measurement point is obtained by accumulating the mass spectrum data obtained by the multiple mass analyses. The intensity of the mass peak of the mass-to-charge ratio of the characteristic ion of the target substance is extracted from the mass spectrum data of each measurement point obtained in this way, and an image is created that maps the intensity of the mass peak at each measurement point to the target area, so that the distribution of the target substance in the target area on the surface of the sample can be known (e.g., Patent Document 1).

[0003] In an imaging mass analyzer, light emitted from a laser light source is focused by a focusing lens and irradiated onto the surface of a sample placed on a sample stage. The sample stage is configured to be movable in three directions, for example, two directions in a plane parallel to the surface of the sample stage (xy directions) and a direction perpendicular to the surface (z direction). Movement in the xy directions and movement in the z direction are each performed by an independent moving mechanism. In this case, for example, the sample stage is first fixed to a moving mechanism in the z direction, and the moving mechanism in the z direction is placed on a moving mechanism in the xy direction.

[0004] When measuring multiple measurement points in a two-dimensional configuration, the measurement is generally started from the measurement point located at the end. First, the measurement start point is placed at the irradiation position of the laser, and the pulse laser is repeatedly irradiated a specified number of times and quality analysis is performed. If the quality analysis at the measurement start point is completed, the sample stage is moved in one direction in the two-dimensional configuration, namely the first direction (main moving direction), and the second measurement point is aligned with the irradiation position of the pulse laser and stopped. Next, as with the measurement start point, the pulse laser is irradiated and the quality analysis is repeated a specified number of times. In this way, the sample stage is intermittently moved along the main moving direction. If the quality analysis at the last measurement point in the main moving direction is completed, the sample stage is moved to another direction in the two-dimensional configuration, namely the second direction (secondary moving direction), and the measurement points adjacent to the last measurement point are measured. After that, quality analysis of each measurement point is performed again along the main moving direction.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-068565 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] In recent years, a laser light source has been developed that can focus laser light to a tiny diameter of about 5μm. By using a laser focused to a tiny diameter, imaging quality analysis with higher spatial resolution can be achieved. In addition, a laser light source has been developed that can emit pulsed laser light at a high frequency (repetition frequency of pulsed laser light) of tens of kHz. By using high-frequency pulsed laser light, the time required for quality analysis of each measurement point can be shortened, making it possible to perform imaging quality analysis on larger samples.

[0010] In order to shorten the imaging quality analysis time, the sample stage needs to be moved faster. However, if the acceleration applied to the sample stage is increased to speed up the movement between measurement points, a large vibration will occur when the sample stage is stopped at the next measurement point. If multiple pulse lasers are irradiated while the sample stage is vibrating, the irradiation position will shift each time it is irradiated, resulting in a problem of poor spatial resolution of imaging quality analysis.

[0011] Here, the case where laser light is used as an excitation beam for ionizing a substance on the sample surface is described as an example. However, the same problem as described above also occurs when another type of excitation beam such as electron beam is used.

[0012] The technical problem to be solved by the present invention is to provide a technology capable of maintaining the spatial resolution of imaging mass analysis and increasing the speed of the analysis.

[0013] Solutions for solving the above technical problems

[0014] The present invention completed to solve the above-mentioned technical problems is a mass analysis method, which uses a mass analysis device having a first moving mechanism for moving a sample stage in a first direction in a plane parallel to the sample stage, and a second moving mechanism for moving the first moving mechanism in a second direction different from the first direction in a plane parallel to the sample stage, wherein:

[0015] The sample stage is moved in the first direction by the first moving mechanism, so that the irradiation point of the excitation beam is intermittently moved between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage, with the first direction being the main moving direction, and mass analysis is performed at each of the plurality of measurement points.

[0016] Furthermore, the mass spectrometer of the present invention completed to solve the above-mentioned technical problems comprises:

[0017] A sample table for placing the sample;

[0018] a first moving mechanism for moving the sample stage in a first direction within a plane parallel to the sample stage;

[0019] a second moving mechanism that moves the first moving mechanism in a second direction different from the first direction and in a plane parallel to the sample stage;

[0020] an excitation beam optical system for irradiating the sample stage with an excitation beam;

[0021] The measurement control unit utilizes the first moving mechanism to move the sample stage in the first direction, thereby using the first direction as the main moving direction to intermittently move the irradiation point of the excitation beam between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage, and performing mass analysis at each of the plurality of measurement points.

[0022] Effects of the Invention

[0023] The present invention uses a mass spectrometer to perform mass analysis, wherein the mass spectrometer is provided with: a first moving mechanism that moves a sample stage in a first direction in a plane parallel to the sample stage; and a second moving mechanism that moves the first moving mechanism in a second direction different from the first direction in a plane parallel to the sample stage. In the present invention, between a plurality of measurement points arranged two-dimensionally in a sample placed on the sample stage, the irradiation point of the excitation beam is intermittently moved with the first direction as the main movement direction by using the first moving mechanism, and mass analysis is performed at each of the plurality of measurement points. That is, after performing mass analysis at the measurement start point, the sample stage is moved by using the first moving mechanism, so that the irradiation point of the excitation beam is repeatedly moved to the adjacent measurement point in the main movement direction from the measurement start point and mass analysis is performed. If the mass analysis at the last measurement point in the main movement direction is completed, the sample stage is moved in another direction (the second direction, i.e., the secondary movement direction) in the two-dimensional arrangement, and the measurement point adjacent to the last measurement point is measured. Thereafter, mass analysis of each measurement point is performed again along the main movement direction.

[0024] The second moving mechanism moves both the sample stage and the first moving mechanism, whereas the first moving mechanism moves only the sample stage, so that the load during movement is small, and the vibration generated when the sample stage is stopped when the sample stage is moved in the first direction is smaller than when the sample stage is moved in the second direction. Therefore, even if the acceleration is increased when the sample stage is moved in the first direction, the vibration when the sample stage is stopped can be suppressed to a small value when moving between measurement points, and it is difficult to cause a deviation in the irradiation position of the excitation beam. Therefore, the spatial resolution of the imaging mass analysis can be maintained, and the analysis can be accelerated. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a diagram showing the main components of an imaging mass spectrometer as one embodiment of the mass spectrometer of the present invention.

[0026] Figure 2 1 is a diagram showing a schematic configuration of an ionization unit of the imaging mass spectrometer of this embodiment.

[0027] Figure 3 This is a flowchart of an imaging mass analysis method as one embodiment of the mass analysis method of the present invention.

[0028] Figure 4 This is a graph showing changes in the magnitude of vibrations generated when the sample stage is stopped in a conventional mass spectrometry method.

[0029] Figure 5 This is a graph showing changes in the magnitude of vibration generated when the sample stage is stopped in the mass spectrometry method of this embodiment.

[0030] Figure 6 It is a diagram for explaining the movement order between measurement points in the mass spectrometry method of this embodiment.

[0031] Figure 7 This is a diagram for explaining another example of the movement sequence between measurement points. DETAILED DESCRIPTION

[0032] Hereinafter, an imaging mass spectrometry method and an imaging mass spectrometry apparatus as one embodiment of the mass spectrometry method and the mass spectrometry apparatus of the present invention will be described with reference to the drawings.

[0033] The imaging mass spectrometer 1 of the present embodiment is a device that generates ions and performs mass analysis by using a matrix-assisted laser desorption / ionization (MALDI) method, and generates ions and performs mass analysis at a plurality of measurement points on the surface of a sample placed on a sample stage.

[0034] like Figure 1 As shown in the block diagram, the imaging mass spectrometer 1 is generally composed of an ionization unit 10, a mass spectrometer 20, and a control and processing unit 30. The ionization unit 10 is detachably mounted on the mass spectrometer 20.

[0035] Figure 2 The schematic structure of the ionization unit 10 is shown. The ionization unit 10 includes a laser light source 11, a reflector 12, and a condenser lens 13. The laser light source 11, the reflector 12, and the condenser lens 13 (hereinafter, these are also referred to as "excitation beam optical system") are fixed to the housing 19 directly or indirectly via a holding member (frame).

[0036] The ionization unit 10 also includes a sample stage 14, a stage moving mechanism 15, and a microscope 16. An opening 17 is formed on one side surface of a housing 19. The stage moving mechanism 15 is fixed to the housing 19.

[0037] The sample stage 14 can be moved in three mutually orthogonal directions by the stage moving mechanism 15. The stage moving mechanism 15 comprises: a first linear guide 151 for moving the sample stage 14 in the vertical direction (x direction); a second linear guide 152 for moving the sample stage 14 and the first linear guide 151 in the horizontal direction (y direction); a third linear guide 153 for moving the sample stage 14, the first linear guide 151 and the second linear guide 152 in the horizontal direction (z direction); and a driving source for moving them. The driving source includes, for example, a stepping motor.

[0038] In addition, a microscope 16 for observing the sample placed on the sample stage 14 is provided in the housing 19. The user moves the sample stage 14 to the observation position (the front of the microscope 16), observes the sample surface through the microscope 16, and sets the region of interest of the sample as the target region. In addition, a plurality of measurement points are set in the target region.

[0039] When the imaging mass analyzer is executed, the sample stage 14 is moved so that the target area on the sample surface is located in front of the opening 17 formed on the side of the housing 19. Then, the light emitted from the laser light source 11 and reflected by the reflector 12 is focused by the focusing lens 13 and irradiated to the measurement point in the target area on the sample surface. The ions generated from the sample by the irradiation of the laser are emitted from the opening 17 to the outside of the housing 19.

[0040] The ionization unit 10 is detachably mounted on the mass analysis unit 20. An opening 21 is formed at a position corresponding to the opening 17 of the ionization unit 10 on the side of the housing of the mass analysis unit 20 on which the ionization unit 10 is mounted. The mass analysis unit 20 performs mass analysis on ions incident through the opening 21. The mass analysis unit 20 contains a plasma optical system such as an ion lens for focusing the incident ions, a mass separation unit such as a quadrupole mass filter for separating the ions focused by the ion optical system according to the mass-to-charge ratio, and an ion detector for detecting the ions separated by the mass separation unit.

[0041] The control and processing section 30 controls the operation of the ionization section 10 and the mass analysis section 20, and performs processing such as creating imaging mass analysis data based on the output signal of the ion detector from the mass analysis section 20. In addition to the storage section 31, the control and processing section 30 also includes a measurement control section 321, a measurement point setting section 322, and an imaging mass analysis data creation section 323 as functional modules. The entity of the control and processing section 30 is a general computer, and the functions of the measurement control section 321, the measurement point setting section 322, and the imaging mass analysis data creation section 323 are specifically realized by executing the pre-installed mass analysis software 32 by the processor. In addition, the control and processing section 30 is connected to an input section 40 for the user to perform appropriate input operations and a display section 50 for displaying various information.

[0042] This embodiment is characterized in that, when performing imaging quality analysis, quality analysis of a plurality of measurement points set within a region of interest on a sample surface is performed in an order. Figure 3 The flowchart of the imaging quality analysis process in this embodiment is explained.

[0043] Before performing imaging mass analysis, the user sets a sample on the sample stage 14. The sample is prepared, for example, by coating a matrix material that easily absorbs laser light on a slice cut from a biological sample. Afterwards, if the user performs a prescribed input operation to indicate the start of imaging mass analysis, the measurement control unit 321 activates the stage moving mechanism 15 to move the sample stage 14 to the observation position (the front of the microscope 16). Then, an observation image of the sample surface is obtained through the microscope 16, and the observation image is displayed on the screen of the display unit 50.

[0044] The user confirms the observation image displayed on the screen of the display unit 50, and sets the region of interest, which is the target area for performing imaging quality analysis, on the sample surface. The size of the region of interest can be set to, for example, a 20 mm square at a distance on the surface of the sample. If the user sets the region of interest, the measurement control unit 321 saves the region of interest as a target area in the storage unit 31 together with the observation image of the sample surface.

[0045] When the target area of ​​the sample is saved, the measurement point setting unit 322 displays a screen for setting multiple measurement points in the target area on the display unit 50. In this screen, for example, a column for inputting the interval of the measurement points set in the target area is provided. If the user inputs the interval of the measurement points in this column, multiple measurement points are set in the target area based on the input value (step 1). The input value can be set, for example, to a distance of 5 to 20 μm on the surface of the sample. Specifically, for example, with a predetermined measurement start point (a point at the corner of the rectangular target area) as the starting point, multiple measurement points separated by the distance of the above input value are set two-dimensionally in two directions orthogonal to each other in the target area. In addition, the setting of the measurement points can also be performed by inputting the number of measurement points (for example, the number of measurement points in each of the two directions orthogonal to each other in the target area).

[0046] When a plurality of two-dimensionally arranged measurement points are set in the target area, the measurement control unit 321 operates the stage moving mechanism 15 again to align the measurement start point with the focusing position of the laser light of the excitation beam irradiation system and then stops.

[0047] Next, a pulse laser is irradiated to the measurement start point, so that the ions generated from the measurement start point are taken into the mass analysis unit 20 through the openings 17 and 21, separated according to the mass-to-charge ratio and measured (step 2). The detection signal of the ions obtained in the mass analysis unit 20 is associated with the position information of the measurement start point and stored in the storage unit 31. At the measurement start point, the pulse laser is irradiated once or multiple times, and the ions generated by the irradiation are mass analyzed. For example, the pulse laser is irradiated ten to hundreds of times, and the mass analysis is performed for each irradiation of the pulse laser once or multiple times.

[0048] If the mass analysis at the measurement start point is completed, the measurement control unit 321 confirms whether the mass analysis of the measurement point located at the end of the x direction has been completed. At this point in time, only the mass analysis of the measurement start point has been completed, and there are unmeasured points located in the x direction from the measurement start point ("Yes" in step 3). In this way, if there are unmeasured points adjacent to each other in the x direction, the sample stage 14 is moved in the x direction along the first linear guide 151, and the next measurement point is aligned with the focusing position of the laser and stopped (step 4). Next, similarly to the measurement start point, the pulse laser is irradiated at the measurement point and the mass analysis of the ions generated by the irradiation is performed (step 5), and the detection signal of the ions obtained in the mass analysis unit 20 is associated with the position information of the measurement point and stored in the storage unit 31.

[0049] For the third and subsequent measurement points, as described above, it is determined in turn whether there are any unmeasured points adjacent to the x-direction. If there are any unmeasured points ("yes" in step 3), the sample stage 14 is moved and stopped in the x-direction along the first linear guide (step 4), pulse laser irradiation and mass analysis are performed (step 5), and the detection signal of the ion is associated with the position information of the measurement point and stored in the storage unit 31.

[0050] If the mass analysis of the last measurement point adjacent in the x direction from the measurement start point is completed (that is, there are no unmeasured points adjacent in the x direction. "No" in step 3), the measurement control unit 321 confirms whether there are unmeasured points adjacent in the y direction from the measurement point. Then, if there are unmeasured points adjacent in the y direction ("Yes" in step 6), the sample stage is moved in the y direction along the second linear guide 152, and the measurement points adjacent in the y direction from the last measurement point are aligned with the focusing position of the laser and stopped (step 7). Then, pulse laser irradiation and mass analysis of ions generated by the irradiation are performed at the measurement point (step 8), and the detection signal of the ions obtained in the mass analysis unit 20 is associated with the position information of the measurement point and stored in the storage unit 31.

[0051] Thereafter, the processing of steps 3 to 8 is repeated in the same manner as described above. Next, if there are no unmeasured points in either the x direction or the y direction ("No" in step 3 and "No" in step 6), the measurement is terminated.

[0052] If the mass analysis at all the multiple measurement points is completed, the imaging mass analysis data creation unit 323 reads the detection signal of the ion at each measurement point stored in the storage unit 31, and creates the mass spectrum data of each measurement point (step 9). In the case where multiple mass analyses are performed at each measurement point, the detection signal of the ion is accumulated for each measurement point to create the mass spectrum data. Furthermore, the imaging mass analysis data creation unit 323 creates the imaging mass analysis data by mapping the mass spectrum data of each measurement point to the target area according to the position information of the measurement point (step 10).

[0053] After creating the imaging mass analysis data, if the user inputs the mass-to-charge ratio of the ions, the imaging mass analysis data creation unit 323 reads the detection intensity of the ions of the mass-to-charge ratio at each measurement point, and displays an imaging mass analysis image obtained by mapping the color corresponding to the intensity to the target area (step 11). By inputting the mass-to-charge ratio of the characteristic ions of the substance to be analyzed, the user can know how the substance is distributed on the sample surface.

[0054] In this embodiment, when performing mass analysis on a plurality of measurement points set two-dimensionally in a target area on the surface of a sample, first, the sample stage 14 is repeatedly moved and stopped along the first linear guide 151 that moves only the sample stage 14, and each adjacent measurement point in the x direction is aligned with the focusing position of the laser and mass analysis is performed. When the mass analysis of all adjacent measurement points in the x direction is completed, the sample stage 14 is moved in the y direction along the second linear guide 152. Then, the sample stage 14 is repeatedly moved and stopped again along the first linear guide 151 that moves only the sample stage 14, and each adjacent measurement point in the x direction is aligned with the focusing position of the laser and mass analysis is performed. That is, in this embodiment, between a plurality of measurement points two-dimensionally arranged in a sample placed on the sample stage 14, the irradiation point of the laser is intermittently moved with the movement direction of the sample stage 14, i.e., the x direction, being the main movement direction, of the first linear guide 151, and mass analysis is performed at each of the plurality of measurement points.

[0055] Here, the main moving direction can be defined as a direction in which the number of movements is greater or a direction in which the total moving distance is longer when the sample stage 14 is moved in two directions and the irradiation point of the excitation beam is intermittently moved between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage so as to perform mass analysis at each of the plurality of measurement points. In addition, the main moving direction can also be defined as a direction in which mass analysis is sequentially performed on three or more adjacent measurement points (typically, a direction in which mass analysis is sequentially performed on adjacent measurement points from one end to the other end) when the sample stage 14 is moved in two directions and the irradiation point of the excitation beam is intermittently moved between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage so as to perform mass analysis at each of the plurality of measurement points.

[0056] Since the second linear guide 152 moves both the sample stage 14 and the first linear guide 151, while the first linear guide 151 moves only the sample stage 14, the load during movement is small, and the vibration generated when the sample stage 14 stops when the sample stage 14 is moved in the x direction by the first linear guide is smaller than when the sample stage 14 is moved in the y direction by the second linear guide 152. Therefore, even if the acceleration is increased when the sample stage moves in the x direction, the vibration when the sample stage 14 stops when moving between measurement points can be suppressed to be small, and the irradiation position of the laser is unlikely to be offset.

[0057] In order to suppress the vibration when the sample stage 14 moves in the y direction, the acceleration when the sample stage 14 moves in the y direction can be suppressed to be smaller than that when the sample stage 14 moves in the x direction. Since the number of times the sample stage 14 moves in the y direction is less than the number of times the sample stage 14 moves in the x direction, even if the acceleration when the sample stage 14 moves in the y direction is suppressed to be smaller, the influence on the total execution time of the imaging quality analysis is small. For example, when 100 points × 100 points of measurement points are set in the target area of ​​the sample and the quality analysis is performed as in the above embodiment, the number of times the sample stage 14 moves in the x direction is 9900 times, while the number of times the sample stage 14 moves in the y direction is 100 times, which is less. Assuming that the acceleration when the sample stage 14 moves in the y direction is smaller than the acceleration when the sample stage 14 moves in the x direction, the result is that even if the time for the sample stage 14 to move in the y direction takes 5 times the time for the sample stage 14 to move in the x direction, the movement time of the sample stage 14 in the entire imaging quality analysis is only increased by about 4%. If the number of measurement points arranged in the x direction is large, the above influence is smaller. When the number of measurement points is small, the time required for imaging quality analysis is not too long, so there is no need to consider the movement time of the sample stage 14.

[0058] In order to make the acceleration of the sample stage 14 smaller when it moves in the y direction than when it moves in the x direction, it is sufficient to use different structures in the first linear guide 151 and the second linear guide 152. Alternatively, the same structure may be used in the first linear guide 151 and the second linear guide 152, and different control signals may be sent from the measurement control unit 321 to the two.

[0059] In addition, making the components that generate loads when the sample stage 14 moves lightweight is also an effective means to reduce vibration. In the above embodiment, if such components are made lightweight, the acceleration of the sample stage 14 can be further increased and the vibration of the sample stage 14 can be suppressed. In addition, it is also effective to increase the rigidity of the stage itself. However, these solutions are not necessary in the present invention, and can be appropriately carried out according to needs and considering costs.

[0060] The following describes the results of experiments conducted to confirm the effects obtained by the mass spectrometry method and the mass spectrometry apparatus of this embodiment.

[0061] Figure 4 This is a graph showing the laser displacement meter measuring the magnitude of vibrations generated when the sample stage is moved and stopped using the conventional imaging mass analysis method. Figure 4In the embodiment, the same stage moving mechanism 15 as in the above embodiment is used, and the sample stage 14 is moved with the second linear guide 152 as the main direction of the movement direction of the sample stage 14, that is, the y direction. In the conventional mass spectrometry method like this, after the sample stage stops, until about 50 msec has passed, the maximum vibration of the sample stage position is about ±2 μm. In this way, when a high-speed pulse laser of tens of kHz is irradiated while the sample stage is vibrating, the maximum deviation of the irradiation position of the laser is ±2 μm. That is, the maximum deviation of the irradiation position of the laser is 4 μm, and even if the laser is focused to less than 5 μm, a spatial resolution that matches it cannot be obtained.

[0062] In order to avoid the deterioration of spatial resolution as described above, it was necessary to wait until the vibration of the sample stage weakened, or to slow down the repetition frequency of the pulsed laser, which became a factor that hindered the high-speed imaging mass analysis. In addition, in the previous imaging mass analysis device, among the moving mechanisms that move the sample stage in three directions, there is also a device that uses the direction in which the sample stage is moved by the moving mechanism located at the bottom as the main direction to perform mass analysis. In such a device, when the sample stage is moved and stopped along the main direction, the two moving mechanisms are moved and stopped at the same time (that is, the number of moving mechanisms that move and stop is increased by one compared to the above-mentioned previous example). The load generated when the sample stage is moved and stopped is greater than that in the above-mentioned previous example, and it can be easily inferred that the load generated is greater than that in the above-mentioned previous example. Figure 4 The vibrations shown are greater vibrations.

[0063] Figure 5 This is a graph showing the magnitude of vibrations generated when the sample stage is moved and stopped using the imaging mass analysis method of the above embodiment, measured by a laser displacement meter. Figure 4 As can be seen from the comparison, the magnitude of the vibration generated when the sample stage 14 stops is reduced to about half of the conventional vibration.

[0064] In the above embodiment, the measurement control unit 321 controls the operation of the stage moving mechanism 15 to move the sample stage 14, but the user may also operate the stage moving mechanism 15 to move the sample stage 14.

[0065] In addition, in the above embodiment, if Figure 6 As shown in FIG. 1 , starting from the measurement start point, the measurement points adjacent to the positive direction of the x-axis are moved in sequence to perform quality analysis, and after moving from the measurement point at the end of the x-direction to the measurement point adjacent to the y-direction, the measurement points adjacent to the negative direction of the x-axis are moved in sequence to perform quality analysis, but the order of moving between the measurement points is not limited to this. For example, Figure 7As shown, after performing quality analysis on the measurement points arranged along the x direction from one end to the other end, the measurement point can be moved to a measurement point adjacent to the measurement point on the one end in the y direction, and quality analysis can be performed on the measurement points arranged along the x direction from one end to the other end starting from the measurement point (that is, quality analysis can be performed by moving only along the positive direction of the x axis between a plurality of measurement points located at the same position relative to the y direction). Figure 6 as well as Figure 7 Although an example in which a plurality of measurement points are arranged in a grid pattern is shown, the measurement points may also be arranged in a honeycomb pattern or the like.

[0066] Furthermore, in the above-described embodiment, the ionization section 10 is configured such that the table surface of the sample table 14 is a vertical surface. Alternatively, the ionization section 10 may be configured such that the table surface is a horizontal surface.

[0067] The above embodiment generates ions by the MALDI method and performs mass analysis, but when ions are generated by the LDI (laser desorption ionization) method without using a matrix substance, the same configuration as above can also be used. In addition, in the above embodiment, a laser is used to ionize a substance on the sample surface, but when other types of excitation beams such as electron beams are used, the same configuration as above can also be used.

[0068] [plan]

[0069] Those skilled in the art will appreciate that the above-mentioned multiple exemplary embodiments are specific examples of the following schemes.

[0070] (Item 1)

[0071] One embodiment is a mass spectrometry method using a mass spectrometer having a first moving mechanism for moving a sample stage in a first direction in a plane parallel to the sample stage, and a second moving mechanism for moving the first moving mechanism in a second direction different from the first direction in a plane parallel to the sample stage, wherein:

[0072] The sample stage is moved in the first direction by the first moving mechanism, so that the irradiation point of the excitation beam is intermittently moved between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage, with the first direction being the main moving direction, and mass analysis is performed at each of the plurality of measurement points.

[0073] (Item 2)

[0074] Another mass spectrometer includes:

[0075] A sample table for placing samples;

[0076] a first moving mechanism for moving the sample stage in a first direction within a plane parallel to the sample stage;

[0077] a second moving mechanism that moves the first moving mechanism in a second direction different from the first direction and in a plane parallel to the sample stage;

[0078] an excitation beam optical system for irradiating the sample stage with an excitation beam;

[0079] The measurement control unit utilizes the first moving mechanism to move the sample stage in the first direction, thereby using the first direction as the main moving direction to intermittently move the irradiation point of the excitation beam between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage, and performing mass analysis at each of the plurality of measurement points.

[0080] In the mass spectrometry method described in item 1 and the mass spectrometry device described in item 2, mass spectrometry is performed using a mass spectrometry device, wherein the mass spectrometry device comprises: a first moving mechanism that moves a sample stage in a first direction in a plane parallel to the sample stage; and a second moving mechanism that moves the first moving mechanism in a second direction different from the first direction in a plane parallel to the sample stage. In the mass spectrometry method described in item 1 and the mass spectrometry device described in item 2, the irradiation point of the excitation beam is intermittently moved between a plurality of measurement points two-dimensionally arranged in a sample placed on the sample stage by using the first moving mechanism, thereby using the first direction as a main moving direction, and mass analysis is performed at each of the plurality of measurement points. That is, after performing mass analysis at the measurement start point, the sample stage is moved by using the first moving mechanism, thereby repeatedly moving the irradiation point of the excitation beam to the adjacent measurement point in the main moving direction from the measurement start point and performing mass analysis, and when the mass analysis at the last measurement point in the main moving direction is completed, the sample stage is moved in another direction (secondary moving direction) in the two-dimensional arrangement by using the second moving mechanism, and the measurement point adjacent to the last measurement point is measured. Thereafter, mass analysis is performed again at each measurement point along the main moving direction.

[0081] The second moving mechanism moves both the sample stage and the first moving mechanism, whereas the first moving mechanism moves only the sample stage, so that the load during movement is small, and the vibration generated when the sample stage is stopped when the sample stage is moved in the first direction is smaller than when the sample stage is moved in the second direction. Therefore, even if the acceleration is increased when the sample stage is moved in the first direction, the vibration when the sample stage is stopped can be suppressed to a small value when moving between measurement points, and it is difficult to cause a deviation in the irradiation position of the excitation beam. Therefore, the spatial resolution of the imaging mass analysis can be maintained, and the analysis can be accelerated.

[0082] (Item 3)

[0083] In the mass spectrometer according to item 2,

[0084] The acceleration when the sample stage is moved by the first moving mechanism is greater than the acceleration when the sample stage is moved by the second moving mechanism.

[0085] The object moved by the first moving mechanism is only the sample stage, while the object moved by the second moving mechanism is the sample stage and the first moving mechanism, the latter being heavier. In the mass spectrometer described in item 3, the acceleration when the sample stage is moved in the first direction (main moving direction) by the first moving mechanism is greater than the acceleration when the sample stage is moved in the second direction by the second moving mechanism. Thus, the time required for the sample stage to move in the first direction (main moving direction) can be shortened, and the vibration generated when the sample stage moves in the second direction can be suppressed.

[0086] The number of movements of the sample stage in the second direction is less than the number of movements of the sample stage in the first direction (main movement direction), so even if the acceleration when the sample stage is moved in the second direction is suppressed to be lower than the acceleration when the sample stage is moved in the first direction, the influence on the total execution time of the mass analysis can be suppressed to a small level. In addition, the mass spectrometer described in item 3 can satisfy the above conditions by using different structures in the first moving mechanism and the second moving mechanism, or can satisfy the above conditions by using the same structure in the first moving mechanism and the second moving mechanism and sending different control signals from the measurement control unit to the two.

[0087] (Item 4)

[0088] In the mass spectrometer described in item 2 or 3,

[0089] The excitation beam optical system includes a laser light source that emits laser light and a condenser lens that condenses the laser light emitted from the laser light source.

[0090] In the excitation beam, laser light can be focused into a particularly small diameter. When high spatial resolution mass analysis is performed using laser light focused into a small diameter as in the mass spectrometer described in item 4, the mass spectrometer described in item 2 or 3 can be preferably used.

[0091] (Item 5)

[0092] In the mass spectrometer according to item 4,

[0093] The focusing diameter of the laser light focused by the focusing lens is 5 μm or less.

[0094] The mass spectrometer described in Item 4 can be particularly preferably used in an apparatus that performs high spatial resolution imaging mass analysis using laser light focused to a diameter of 5 μm or less, such as the mass spectrometer described in Item 5.

[0095] (Item 6)

[0096] In the mass spectrometer described in item 4 or 5,

[0097] The sample is a sample in which a matrix substance that absorbs the laser light is mixed.

[0098] Recently, imaging mass spectrometers using matrix-assisted laser desorption ionization (MALDI) have become widely popular. In laser ionization methods represented by MALDI, in order to obtain highly reliable data, laser irradiation and mass analysis are usually performed dozens to hundreds of times at each measurement point, multiple mass spectrum data are obtained for each measurement point, and these data are accumulated, averaged, and processed. In recent years, the high frequency of lasers in the ultraviolet region suitable for MALDI has developed rapidly, and ultraviolet semiconductor lasers that can operate at a high repetition frequency of up to tens of kHz have appeared. In addition, the analysis can also be accelerated in the mass analysis unit, and mass analysis of dozens of measurement points can be performed in 1 second. By using these, the entire sample slice (20 to 30 mm square) can be analyzed with a high spatial resolution of less than 5 μm in a relatively realistic time. That is, as described in item 6, as a device for ionizing a sample using the MALDI method to perform imaging mass analysis, the mass spectrometer described in item 4 or item 5 can be preferably used.

[0099] (Item 7)

[0100] The mass spectrometer according to any one of items 2 to 6 further comprises:

[0101] The third moving mechanism moves the second moving mechanism in a third direction that is not parallel to the sample mounting surface of the sample stage.

[0102] In the mass spectrometer according to item 7, for example, the distance between the excitation beam optical system and the sample stage can be changed, and the distance can be adjusted so that the excitation beam is focused on the surface of the sample placed on the sample stage.

[0103] Description of Reference Numerals

[0104] 1 Imaging quality analysis device

[0105] 10. Ionization section

[0106] 11 Laser light source

[0107] 12. Reflector

[0108] 13 Condenser lens

[0109] 14. Sample table

[0110] 15 mobile units

[0111] 151 No. 1 linear guide

[0112] 152 2nd linear guide

[0113] 153 3rd linear guide

[0114] 16 Microscope

[0115] 17 Opening

[0116] 19 Housing

[0117] 20 Quality Analysis Department

[0118] 21 Opening

[0119] 30 Control and Processing Department

[0120] 31 Storage

[0121] 32 Quality Analysis Software

[0122] 321 Measurement Control Department

[0123] 322 Measuring point setting section

[0124] 323 Imaging Quality Analysis Data Creation Department

[0125] 40 Input section

[0126] 50 Display unit.

Claims

1. A mass spectrometry method using a mass spectrometry device having a first moving mechanism for moving a sample stage in a first direction in a plane parallel to the sample stage, and a second moving mechanism for moving the first moving mechanism in a second direction different from the first direction in a plane parallel to the sample stage, characterized in that: The sample stage is moved in the first direction by the first moving mechanism, so that the irradiation point of the excitation beam is intermittently moved between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage, with the first direction being the main moving direction, and mass analysis is performed at each of the plurality of measurement points. The acceleration when the sample stage is moved by the first moving mechanism is greater than the acceleration when the sample stage is moved by the second moving mechanism.

2. A mass analysis device, characterized in that: have: A sample table for placing samples; a first moving mechanism for moving the sample stage in a first direction within a plane parallel to the sample stage; a second moving mechanism that moves the first moving mechanism in a second direction different from the first direction within a plane parallel to the sample stage; an excitation beam optical system for irradiating the sample stage with an excitation beam; a measurement control unit that moves the sample stage in the first direction by using the first moving mechanism, thereby intermittently moving the irradiation point of the excitation beam between a plurality of measurement points two-dimensionally arranged in the sample placed on the sample stage, using the first direction as a main moving direction, and performing mass analysis at each of the plurality of measurement points; The acceleration when the sample stage is moved by the first moving mechanism is greater than the acceleration when the sample stage is moved by the second moving mechanism.

3. The mass spectrometer according to claim 2, wherein: The excitation beam optical system includes a laser light source that emits laser light and a condenser lens that condenses the laser light emitted from the laser light source.

4. The mass spectrometer according to claim 3, wherein: The focusing diameter of the laser light focused by the focusing lens is 5 μm or less.

5. The mass spectrometer according to claim 3, wherein: The sample is a sample in which a matrix substance that absorbs the laser light is mixed.

6. The mass spectrometer according to claim 2, wherein: Also available: The third moving mechanism moves the second moving mechanism in a third direction that is not parallel to the sample mounting surface of the sample stage.

Images