Probe Electrospray Ionization Mass Spectrometry

Abstract

Under the control of the control unit (25), the probe driving unit (21) causes the probe (6) to descend / rise, thereby extracting the sample (8) at the front end of the probe (6). Afterwards, the high voltage generating unit (20) applies a high voltage whose voltage value increases in a ramp shape to the probe (6). During this period, the mass spectrometer analysis unit at the rear stage of the capillary (10) performs product ion scanning measurements for two stages of probe voltages, and the mass spectrum data obtained by each measurement is stored in the first and second probe voltage corresponding data storage units (301, 302). If the ionization efficiency of the various components contained in the sample (8) is probe voltage dependent, ion peaks originating from different types of components appear in the two mass spectra. As a result, the various components contained in the sample can be roughly separated, and the identification performance based on mass spectrometry and the quantitative performance based on chromatography can be improved.

Description

Technical Field

[0001] The present invention relates to a mass spectrometer equipped with an ion source based on a probe electrospray ionization (PESI) method. Background Art

[0002] As an ionization method for ionizing components in a sample to be measured in a mass spectrometer, various methods have been proposed in the past and put into practical use. As an ionization method for ionizing in an atmospheric pressure environment, the electrospray ionization (ESI) method is well known, and as one of the ionization methods using the ESI, the PESI method has attracted attention in recent years.

[0003] As disclosed in Patent Documents 1 and 2, the PESI ion source includes: a conductive probe having a tip diameter of about several hundred nanometers; a displacement portion that moves at least one of the probe and the sample in order to make the sample adhere to the tip of the probe; and a high voltage generating portion that applies a high voltage to the probe when the tip of the probe has extracted the sample. During measurement, at least one of the probe and the sample is moved by the displacement portion, so that the tip of the probe contacts the sample or slightly penetrates the sample, so that a trace amount of the sample adheres to the tip surface of the probe. Afterwards, the probe is separated from the sample by the displacement portion, and a high voltage is applied to the probe from the high voltage generating portion. As a result, a strong electric field is applied to the sample attached to the tip of the probe, generating an electrospray phenomenon, so that the component molecules in the sample are ionized while being separated.

[0004] In a mass spectrometer using a PESI ion source (hereinafter sometimes referred to as a "PESI mass spectrometer"), troublesome sample pretreatment is omitted, and a liquid sample to be analyzed can be almost directly provided for analysis, so that analysis can be performed simply and quickly. In addition, as disclosed in Non-Patent Document 1, the amount of a specific component in a living experimental animal or the like can also be observed in real time.

[0005] However, in such analysis, since component separation based on liquid chromatography (LC) or the like is not performed, ion peaks originating from a plurality of components contained in the sample appear mixedly on the mass spectrum obtained by the analysis. If peaks originating from a plurality of components are mixed on the mass spectrum, or peaks originating from impurity components are mixed in addition to peaks originating from target components, it is difficult to identify the components by pattern matching, database search, etc.

[0006] One method for improving component identification performance is to enhance the selectivity of ions by performing MS / MS analysis as also implemented in Non-Patent Document 1. However, for example, in a sample derived from an organism, the types of components contained are generally numerous, and there are also many components with similar chemical structures. Therefore, the mass-to-charge ratio of the precursor ion of the target component is often the same as or extremely close to that of the precursor ion derived from an impurity component. In such a case, even on the mass spectrum (product ion spectrum) obtained by MS / MS analysis, it is difficult to distinguish the peak derived from the target component from the peak derived from the impurity component, and the identification accuracy and quantification accuracy of the target component sometimes decrease.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-44110

[0010] Patent Document 2: WO 2016 / 027319

[0011] Non-patent literature

[0012] Non-Patent Document 1: Yumi Hayashi, et al., "Construction of an in vivo real-time monitoring method by PESI / MS / MS", Shimadzu Review, Vol. 74, Nos. 1 and 2, issued on September 20, 2017 Summary of the Invention

[0013] Problem that the invention aims to solve

[0014] The present invention has been completed to solve the above problems, and an object thereof is to provide a PESI mass spectrometry apparatus that can improve, for example, the qualitative performance (identification accuracy) and quantitative performance of a target component by obtaining an analysis result in which a plurality of components contained in a sample are separated to some extent.

[0015] Solutions for solving problems

[0016] The present invention completed in order to solve the above-mentioned problems is a probe electrospray ionization mass spectrometry device, comprising an ion source and a mass spectrometry analysis unit for performing mass spectrometry on ions generated by the ion source, wherein the ion source comprises a conductive probe, a high voltage generating unit and a displacement unit, the high voltage generating unit applies a probe voltage as a high voltage to the probe, the displacement unit moves at least one of the probe and the sample so that the sample adheres to the front end of the probe, the ion source applies the probe voltage to the probe in a state where the displacement unit makes a part of the sample adhere to the front end of the probe and the front end of the probe is separated from the sample, thereby ionizing components in the sample adhered to the probe under atmospheric pressure, and the probe electrospray ionization mass spectrometry device further comprises:

[0017] a) a probe voltage control unit that controls the high voltage generating unit so that the probe voltage applied to the probe changes to a plurality of voltage values;

[0018] b) an analysis control unit that controls the mass spectrometry unit so that mass spectrometry is performed on the same sample in a state where different probe voltages are applied to the probes under the control of the probe voltage control unit to obtain mass spectrometry results; and

[0019] c) an analysis processing unit that identifies a component in the sample or quantifies a target component in the sample based on at least one mass spectrometry result among a plurality of mass spectrometry results obtained at different probe voltages under the control of the analysis control unit.

[0020] In the present invention, the mass spectrometry unit can be any mass spectrometry device that can take in ions generated at approximately atmospheric pressure for mass spectrometry analysis, for example, a single type of quadrupole mass spectrometry device, a triple quadrupole mass spectrometry device that can perform MS / MS analysis, a quadrupole-time of flight (Q-TOF) mass spectrometry device composed of a quadrupole mass filter and a time-of-flight mass separator, etc.

[0021] In the first embodiment of the present invention, after the probe voltage control unit uses the displacement unit to move one or both of the probe and the sample so that the sample is extracted to the front end of the probe, the probe voltage applied to the probe from the high voltage generating unit is changed to a plurality of voltage values. The change in the voltage value at this time can be substantially continuous (slope-shaped) or step-shaped. Then, under the control of the analysis control unit, the mass spectrometry unit performs mass spectrometry on the same sample at different probe voltages, and obtains mass spectrometry results such as mass spectra, respectively. That is, in this case, for one sample extraction, a plurality of mass spectrometry results at different probe voltages are obtained.

[0022] On the other hand, in the second embodiment of the present invention, the probe voltage control unit repeatedly performs the action of extracting the sample to the front end of the probe by moving one or both of the probe and the sample using the displacement unit, and changes the voltage value of the probe voltage applied to the probe from the high voltage generating unit each time the sample is extracted. Then, under the control of the analysis control unit, the mass spectrometry unit performs mass spectrometry on the same sample each time the sample is extracted to obtain the mass spectrometry result. That is, in this case, one mass spectrometry result is obtained for one sample extraction, and multiple mass spectrometry results under different probe voltages are obtained by repeating multiple sample extractions. In the case of any one of the first and second embodiments, multiple mass spectrometry results under different probe voltages are obtained for the same sample.

[0023] The ionization efficiency of various components (compounds) in the PESI ion source depends on the probe voltage to some extent due to the difference in the physical or chemical properties of the components. Therefore, for example, when a probe voltage of a relatively low voltage value is applied to the probe, a certain component A is actively ionized, while another certain component B is hardly ionized at this voltage value, and will not be ionized unless a probe voltage of a voltage value much higher than this voltage value is applied to the probe. In this case, if the sample contains components A and B, the probe voltage is changed between a voltage value suitable for the ionization of component A and a voltage value suitable for the ionization of component B, or within a range of voltage values ​​including these two voltage values. If mass spectrometry is performed in a state where the high voltages of these two voltage values ​​are applied to the probe respectively, a mass spectrometry result related to component A contained in the sample and a mass spectrometry result related to component B can be obtained. That is, instead of obtaining a mass spectrum in which the peaks derived from component A and the peaks derived from component B are mixed together, a mass spectrum in which the peaks are separated to some extent for each component can be obtained.

[0024] Therefore, the analysis processing unit identifies one or more components in the sample based on at least one result of the multiple mass spectrometry analysis results for different probe voltages, or quantifies one or more target components. For example, when component A is the target component and component B is a single impurity component, the target component can be identified based on one mass spectrometry analysis result related to component A among the multiple mass spectrometry analysis results to determine the component. In addition, when both component A and component B are target components, component A and component B can be identified based on the mass spectrometry analysis result related to component A and the mass spectrometry analysis result related to component B, respectively.

[0025] However, it is not possible to completely separate a plurality of components based on the voltage value of the probe voltage. For example, when one mass spectrometry result is a result in which component A and component B are mixed and another mass spectrometry result is a result derived only from component B, it is preferable to obtain a mass spectrometry result that excludes or reduces the influence of component B by subtracting the latter mass spectrometry result from the former mass spectrometry result, and identify component A based on the mass spectrometry result. In this way, a plurality of mass spectrometry results can also be used simultaneously.

[0026] In addition, the mass spectrometry analysis result is not only a mass spectrum, but also a mass chromatogram (extracted ion chromatogram) or a total ion chromatogram. For example, as disclosed in the above-mentioned non-patent document 1, when it is desired to observe the change in the amount (or concentration) of a specific component in a biological sample over time, the area value of the peak in the mass chromatogram or the total ion chromatogram can be obtained, and the quantitative value can be calculated based on the area value. In this case, it is also possible to produce a mass chromatogram or a total ion chromatogram that excludes or reduces the influence of other components, thereby improving the quantitative accuracy.

[0027] Furthermore, as described above, when the voltage value of the probe voltage is changed in a ramp shape and mass spectrometry is performed two or more times during this period, the probe voltage control unit may control the high voltage generating unit so that the slope of the ramp-shaped voltage change changes in multiple stages.

[0028] The change in the slope of the ramp-shaped voltage change means that the voltage change per unit time changes. This makes it possible to adjust the amount of ions from the same component and the type of component provided for mass spectrometry, so that, for example, the sensitivity and resolution of ions in mass spectrometry can be adjusted according to the purpose.

[0029] Effects of the Invention

[0030] According to the PESI mass spectrometer of the present invention, a mass spectrometer analysis result can be obtained by separating a plurality of components contained in a sample to some extent without performing component separation such as chromatography, thereby, for example, being able to separate a target component and an impurity component contained in a sample, thereby improving the identification accuracy and quantitative accuracy of the target component. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of an embodiment of the PESI mass spectrometer involved in the present invention.

[0032] Figure 2 This is an explanatory diagram of the temporal change in the probe voltage when identifying a plurality of components in a sample in the PESI mass spectrometer of this embodiment and the processing operation at that time.

[0033] Figure 3This is a schematic diagram showing an example of the relationship between the probe voltage and the ion intensity of the PESI ion source.

[0034] Figure 4 FIG. 4 is a schematic diagram showing another example of the relationship between the probe voltage and the ion intensity of the PESI ion source.

[0035] Figure 5 FIG. 2 is a diagram showing another example of the change over time of the probe voltage of the PESI mass spectrometer of the present embodiment.

[0036] Figure 6 It is a graph showing the amount of change in probe voltage per unit time.

[0037] Figure 7 FIG. 2 is a diagram showing another example of the change over time of the probe voltage of the PESI mass spectrometer of the present embodiment.

[0038] Figure 8 This is a diagram showing another example of the change over time of the probe voltage of the PESI mass spectrometer of this embodiment. DETAILED DESCRIPTION

[0039] First, an embodiment of the PESI mass spectrometer according to the present invention will be described. Figure 1 It is a schematic structural diagram of the PESI mass spectrometer of this embodiment.

[0040] like Figure 1 As shown, the PESI mass spectrometer has a structure of a multi-stage differential exhaust system, which includes a plurality of (two in this example) intermediate vacuum chambers 2 with a vacuum degree that is gradually increased between an ionization chamber 1 and an analysis chamber 4, wherein the ionization chamber 1 ionizes components contained in a sample in an atmospheric pressure environment, and the analysis chamber 4 performs mass separation and detection of ions in a high vacuum environment.

[0041] A sample 8 to be measured is placed on a sample stage 7 in an ionization chamber 1 arranged in an approximately atmospheric pressure environment. Above the sample 8, a metallic probe 6 held by a probe holder 5 is arranged in a manner extending in the up-down direction (Z-axis direction). The probe holder 5 can be moved in the up-down direction (Z-axis direction) by a probe driving unit 21 including a motor, a reduction mechanism, etc. In addition, the sample stage 7 can be moved in two axial directions, the X-axis and the Y-axis, respectively, by a sample stage driving unit 23. In addition, a high voltage of a maximum of several kV is applied to the probe 6 from a high voltage generating unit 20.

[0042] The ionization chamber 1 is connected to the first intermediate vacuum chamber 2 through a capillary 10 of a small diameter. Due to the pressure difference between the openings at both ends of the capillary 10, the gas in the ionization chamber 1 is introduced into the first intermediate vacuum chamber 2 through the capillary 10. An ion guide 11 is provided in the first intermediate vacuum chamber 2. The ion guide 11 is composed of a plurality of electrode plates arranged around the ion optical axis C along the ion optical axis C. In addition, the first intermediate vacuum chamber 2 is connected to the second intermediate vacuum chamber 3 through a small hole formed on the top of the separator 12. An octopole-type ion guide 13 with eight rod electrodes arranged around the ion optical axis C is provided in the second intermediate vacuum chamber 3. The analysis chamber 4 is also provided with: a front-stage quadrupole mass filter 14 with four rod electrodes arranged around the ion optical axis C; a collision chamber 15 with an ion guide 16 arranged inside; a rear-stage quadrupole mass filter 17 with the same electrode structure as the front-stage quadrupole mass filter 14; and an ion detector 18.

[0043] A collision gas such as argon or helium is continuously or intermittently introduced from the outside into the collision chamber 15. In addition, a voltage generator 24 applies a direct current voltage, a high frequency voltage, or a voltage obtained by superimposing a high frequency voltage on a direct current voltage to the ion guides 11, 13, 16, the quadrupole mass filters 14, 17, the ion detector 18, and the like.

[0044] The detection signal obtained by the ion detector 18 is digitized by the analog-to-digital converter (ADC) 26 and input to the data processing unit 30. The data processing unit 30 includes a first probe voltage corresponding data storage unit 301, a second probe voltage corresponding data storage unit 302, a mass spectrum production unit 303, a chromatogram production unit 304, a qualitative processing unit 305 and a quantitative processing unit 306 as functional blocks. In addition, the control unit 25 performs analysis of the sample 8 by controlling the high voltage generating unit 20, the probe driving unit 21, the sample stage driving unit 23, the voltage generating unit 24, etc. respectively. In addition, the control unit 25 is connected to an input unit 27 and a display unit 28 as a user interface.

[0045] The mass spectrometry operation of the PESI mass spectrometer of this embodiment will be briefly described.

[0046] Assume that the sample 8 is a biological sample such as a biological tissue slice. When the probe 6 is lowered to a predetermined position (at Figure 1 When the probe 6 is moved to the position indicated by the dotted line 6' in the figure, the tip of the probe 6 penetrates the sample 8, and a small amount of the sample is attached to the tip of the probe 6. Then, when the probe 6 is lifted to the predetermined analysis position (in the Figure 1When the probe 6 is at the position indicated by the solid line 6 in FIG. 1 , the high voltage generating unit 20 applies a high voltage to the probe 6. As a result, the electric field is concentrated at the tip of the probe 6, and the components in the sample attached to the tip of the probe 6 are ionized by the electrospray phenomenon.

[0047] The generated ions are sucked into the capillary 10 due to the pressure difference, and are transported to the first intermediate vacuum chamber 2, the second intermediate vacuum chamber 3, and the analysis chamber 4 in sequence under the action of the electric fields formed by the ion guides 11 and 13, respectively. In the analysis chamber 4, the ions are introduced into the front-stage quadrupole mass filter 14, and only the ions (precursor ions) having a mass-to-charge ratio corresponding to the voltage applied to the rod electrodes of the quadrupole mass filter 14 pass through the quadrupole mass filter 14 and are introduced into the collision chamber 15. A collision gas is introduced into the collision chamber 15, and the above ions collide with the collision gas in the collision chamber 15 and are fragmented by collision-induced fragmentation (CID). Various product ions generated by the fragmentation are introduced into the rear-stage quadrupole mass filter 17 after coming out of the collision chamber 15, and only the product ions having a mass-to-charge ratio corresponding to the voltage applied to the rod electrodes of the quadrupole mass filter 17 pass through the rear-stage quadrupole mass filter 17 and reach the ion detector 18. The ion detector 18 generates a detection signal corresponding to the amount of the ions that have arrived.

[0048] For example, the voltage applied to the rod electrodes of the front-stage quadrupole mass filter 14 is set so that only ions with a specific mass-to-charge ratio pass through the quadrupole mass filter 14. At the same time, the voltage applied to the rod electrodes of the rear-stage quadrupole mass filter 17 is scanned so that the mass-to-charge ratio of ions passing through the quadrupole mass filter 17 changes sequentially within a specified range, thereby enabling a detection signal to be obtained for producing a product ion spectrum in a specified mass-to-charge ratio range for a specific precursor ion.

[0049] Next, refer to Figure 2 , Figure 3 The characteristic analysis operation of the PESI mass spectrometer of this embodiment will be described. Figure 2 This is a diagram illustrating the change in probe voltage over time when identifying multiple components in a sample and the processing actions at that time. Figure 3 This is a schematic diagram showing an example of the relationship between the probe voltage and the ion intensity.

[0050] As described above, according to the instruction of the control unit 25, the probe driving unit 21 lowers the lower end of the probe 6 to a predetermined height and then raises it to the analysis position. The height during the descent is adjusted in advance so that the lower end of the probe 6 penetrates the sample 8 to a predetermined depth. Thus, a small amount of sample is attached to the front end of the probe 6, and the probe 6 is placed at the predetermined analysis position in this state. Figure 2 The lowering and ascending actions of the probe 6 are performed during the period indicated by "sample extraction" in FIG.

[0051] When the probe 6 with the sample attached to its front end is placed at the analysis position, the high voltage generating unit 20 applies a high voltage to the probe 6 according to the instruction of the control unit 25. The voltage value of the high voltage is as follows: Figure 2 As shown in FIG. 1 , the voltage increases from V1 to V2 in a ramp shape as time passes. In addition, since the polarity of the ions to be measured is positive, a high voltage of positive polarity is applied to the probe 6. However, if the polarity of the ions to be measured is negative, a high voltage of negative polarity and whose absolute value increases in a ramp shape may be applied to the probe 6. As described above, when a high voltage of a certain voltage value or more is applied to the probe 6, the components in the sample attached to the tip of the probe 6 are ionized by the electrospray phenomenon.

[0052] However, in general, the relationship between the voltage applied to the probe 6 and the ionization efficiency varies depending on the physical or chemical properties (polarity, volatility, etc.) of the components contained in the sample. Here, for the sake of simplicity, it is assumed that the relationship between the probe voltage and the ion intensity (i.e., the ionization efficiency) is as follows: Figure 3 Two components A and B are shown. Component B can generally obtain a high ion intensity at a high probe voltage compared to component A. Currently, Va is selected as the probe voltage at which ions originating from component A are detected with a sufficiently high intensity and ions originating from component B are hardly detected. Conversely, Vb is selected as the probe voltage at which ions originating from component B are detected with a sufficiently high intensity and ions originating from component A are hardly detected.

[0053] Furthermore, the control unit 25 controls the voltage generating unit 24 and the data processing unit 30 so that during the period when the voltage applied to the probe 6 changes from V1 to V2 ( Figure 2 During the "ionization (measurement)" period in the above example), a mass spectrum corresponding to component A is acquired at a timing near the probe voltage Va, and then a mass spectrum corresponding to component B is acquired at a timing near the probe voltage Vb. Specifically, product ion scanning measurements related to one or more pre-set precursor ions are performed respectively. Figure 2 As shown in , data constituting a mass spectrum are obtained at each time point. In the data processing unit 30, the first probe voltage corresponding data storage unit 301 temporarily stores the mass spectrum data obtained when the probe voltage is near Va. On the other hand, the second probe voltage corresponding data storage unit 302 temporarily stores the mass spectrum data obtained when the probe voltage is near Vb. In this way, during the period when the probe voltage changes from V1 to V2, two mass spectrum data for different probe voltages Va and Vb are obtained.

[0054] In addition, the probe voltage actually changes during the execution of a product ion scan measurement, so strictly speaking it is not mass spectrum data for the probe voltages Va and Vb. However, as long as the probe voltage becomes Va and Vb at the beginning, end, and any time during the execution of the product ion scan measurement, the data can be regarded as mass spectrum data for the probe voltages Va and Vb.

[0055] As described above, ions originating from component A are detected under the probe voltage Va, and ions originating from component B are almost not detected. On the other hand, ions originating from component B are detected under the probe voltage Vb, and ions originating from A are almost not detected. Therefore, the mass spectrum data stored in the first probe voltage corresponding data storage unit 301 is substantially the mass spectrum data corresponding to component A, and the mass spectrum data stored in the second probe voltage corresponding data storage unit 302 is substantially the mass spectrum data corresponding to component B. Currently, for example, in the case where components A and B are to be identified at the same time (or whether components A and B exist is to be confirmed), the mass spectrum production unit 303 produces a mass spectrum based on the mass spectrum data respectively stored in the data storage units 301 and 302. Then, the qualitative processing unit 305 identifies each component by library search based on the two mass spectra produced.

[0056] As is known to all, in library search, a library containing standard mass spectra acquired for various components (compounds) is used to evaluate the consistency of the mass spectra in the library with the spectrum patterns of the measured mass spectra to perform component identification. Of course, the method of qualitative processing is not limited to this. For example, in the identification of components such as proteins and peptides, it is preferred to use a database search method using a protein sequence database.

[0057] Furthermore, for example, when one of components A and B is the target component and the other is a simple impurity component and identification of the impurity component is not necessary, only a mass spectrum corresponding to the target component may be prepared and identification processing may be performed.

[0058] In addition, in the above description, Figure 3 As shown in FIG. 1 , it is assumed that the multiple components can be almost completely separated by the probe voltage, but depending on the situation, Figure 4 As shown in FIG. 1 , it is also considered that since component B is ionized in a wide range of probe voltages, it is difficult to completely separate the various components by the probe voltage. Figure 4 In the example shown, ions derived from component B, which is an impurity component, are detected at the probe voltage Vb, and ions derived from component A, which is a target component, are hardly detected. However, at the probe voltage Va, ions derived from component A and ions derived from component B are both detected. In this case, in the mass spectrum for the probe voltage Va, the ion peaks derived from component A and ion peaks derived from component B are mixed together, so it is difficult to directly identify the components by library search or the like.

[0059] Therefore, in such a case, after appropriately adjusting the peak intensity in the mass spectrum for the probe voltage Vb, the mass spectrum for the probe voltage Vb after adjusting the peak intensity is subtracted from the mass spectrum for the probe voltage Va. Thus, regardless of whether each ion peak derived from component B is removed or not removed from the mass spectrum for the probe voltage Va, its peak intensity is greatly reduced. In this way, if a mass spectrum in which ion peaks derived from component A are mainly observed is obtained, the component identification is performed by providing the mass spectrum to the identification process.

[0060] In addition, in the case of a quantitative process based on chromatography rather than a mass spectrometry-based identification process (qualitative process), a chromatogram obtained by separating a plurality of components by a probe voltage can be prepared as described above and quantitative analysis can be performed. Figure 3 Component A and component B are shown to be quantified separately. In this case, since components A and B are known (or the components to be quantified are determined), product ion scanning measurement can be performed, but MRM (multiple reaction monitoring) measurement can also be performed.

[0061] That is, Figure 2 The cycle of sample extraction and ionization (measurement) shown is repeated for a predetermined time, and in each cycle, the ion intensity in the MRM measurement targeting component A under the probe voltage Va and the ion intensity in the MRM measurement targeting component B under the probe voltage Vb are obtained respectively. Then, the chromatogram preparation unit 304 prepares a mass chromatogram for component A and a chromatogram for component B based on these ion intensity data. Even if it is assumed that the transition of the MRM measurement in component A and component B is the same, the two mass chromatograms reflect the intensity of ions originating from component A and the intensity of ions originating from component B, respectively. Therefore, the quantitative processing unit 306 respectively obtains the area values ​​of the peaks observed in the two mass chromatograms, and calculates the amount (concentration) of components A and B based on the area values.

[0062] This makes it possible to improve the quantitative accuracy of the target component, or to separate a plurality of components contained in a sample and perform quantitative analysis with high accuracy.

[0063] In the above embodiment, the scanning speed (ie, the slope of the voltage change) when changing the probe voltage from V1 to V2 (ie, scanning the probe voltage) is fixed, but the scanning speed may be changed in multiple stages. Figure 5 2 is a diagram showing another example of the change in the probe voltage over time. In this example, the scanning speed of the probe voltage from the voltage Va to the voltage Vb is made slower than the scanning speed of the probe voltage from the voltage V1 to the voltage Va. Figure 6(a) and (b) are graphs showing the voltage change amount per unit time t when the scanning speed is fast and when the scanning speed is slow.

[0064] The time required to perform a product ion scan measurement is roughly the same for probe voltages Va and Vb, so when the scan speed is slow, the range of the probe voltage reflected in a product ion scan measurement becomes narrower than when the scan speed is fast. Therefore, in general, if the scan speed is slowed down, the separation accuracy of the components is improved. In addition, if the scan speed is slowed down, the amount of ions generated within the narrow voltage range can be increased, so the detection sensitivity is improved. On the other hand, if the scan speed is slowed down, the time required for one cycle becomes longer, so, for example, the accuracy of grasping the amount of a component that changes in amount over time will be reduced. In this way, depending on the different scan speeds of the probe voltage, differences in separation performance, detection sensitivity, quantification, etc. occur, so it is preferred to appropriately determine the scan speed of the probe voltage according to the purpose.

[0065] In addition, Figure 7 An example of the change in probe voltage over time when the four components contained in the sample are to be separated is shown in FIG. In this example, the scanning speed of the probe voltage is increased in the voltage range of V1 to Va, Vb to Vc, and the scanning speed of the probe voltage is decreased in the voltage range of Va to Vb, Vc to Vd. In this way, by appropriately determining the scanning speed of the probe voltage according to its voltage range, the detection sensitivity and separation performance within the desired voltage range can be improved, and the time required for one cycle can be suppressed to be as short as possible.

[0066] In the above embodiment, measurement at multiple probe voltages is performed for one sample extraction. However, measurement at only one probe voltage (voltage value) may be performed for one sample extraction, and the probe voltage may be changed every time a sample is extracted. Figure 8 2 is a diagram showing an example of a change in the probe voltage over time when such control is performed. In this way, it is possible to obtain a mass spectrum and a mass chromatogram for the probe voltage at multiple stages while shortening the time required for one cycle.

[0067] The above-described embodiments and modifications are merely examples of the present invention, and any appropriate modifications, changes, or additions made within the scope of the gist of the present invention are obviously included in the claims of the present application.

[0068] For example, the PESI mass spectrometer of the above-mentioned embodiment uses a triple quadrupole mass spectrometer as a mass spectrometer, but a single type of quadrupole mass spectrometer that does not perform MS / MS analysis can also be used. In this case, instead of the product ion scanning measurement, a conventional scanning measurement is performed to obtain a mass spectrum. In addition, if quantitative analysis is desired, a SIM (selected ion monitoring) measurement is performed instead of an MRM measurement to produce a mass chromatogram. In addition, a Q-TOF mass spectrometer can also be used instead of a triple quadrupole mass spectrometer.

[0069] Description of Reference Numerals

[0070] 1: ionization chamber; 2: first intermediate vacuum chamber; 3: second intermediate vacuum chamber; 4: analysis chamber; 5: probe holder; 6: probe; 7: sample stand; 8: sample; 10: capillary; 11, 13, 16: ion guide; 12: separator; 14: front quadrupole mass filter; 15: collision chamber; 17: rear quadrupole mass filter; 18: ion detector; 20: high voltage generating unit; 21: probe driving unit; 23: sample stand driving unit; 24: voltage generating unit; 25: control unit; 26: analog-to-digital converter (ADC); 27: input unit; 28: display unit; 30: data processing unit; 301: first probe voltage corresponding data storage unit; 302: second probe voltage corresponding data storage unit; 303: mass spectrum production unit; 304: chromatogram production unit; 305: qualitative processing unit; 306: quantitative processing unit; C: ion optical axis.

Claims

1. A probe electrospray ionization mass spectrometry device, comprising an ion source and a mass spectrometry unit for performing mass spectrometry on ions generated by the ion source, wherein: The ion source includes a conductive probe, a high voltage generating unit, and a displacement unit. The high voltage generating unit applies a probe voltage as a high voltage to the probe. The displacement unit moves at least one of the probe and the sample so that the sample adheres to the front end of the probe. The ion source applies the probe voltage to the probe in a state where a part of the sample adheres to the front end of the probe by the displacement unit and the front end of the probe is separated from the sample, thereby ionizing components in the sample attached to the probe under atmospheric pressure. The probe electrospray ionization mass spectrometry analyzer is characterized in that it further comprises: a) a probe voltage control unit that controls the high voltage generating unit so that the probe voltage applied to the probe changes to a plurality of voltage values; b) an analysis control unit that controls the mass spectrometry unit so that mass spectrometry is performed on the same sample in a state where different probe voltages are applied to the probes under the control of the probe voltage control unit to obtain mass spectrometry results respectively; as well as c) an analysis processing unit that identifies a component in the sample or quantifies a target component in the sample based on at least one mass spectrometry result among a plurality of mass spectrometry results obtained at different probe voltages under the control of the analysis control unit, The probe voltage control unit controls the high voltage generating unit so that the voltage value of the probe voltage changes in a ramp shape, and the slope of the ramp-shaped voltage change changes in a plurality of stages.

2. The probe electrospray ionization mass spectrometry analysis device according to claim 1, characterized in that: After the sample is extracted to the front end of the probe by moving one or both of the probe and the sample using the displacement unit, the probe voltage control unit changes the probe voltage applied to the probe from the high voltage generating unit into a plurality of voltage values. Under the control of the analysis control unit, the mass spectrometry analysis unit performs mass spectrometry analysis on the same sample at different probe voltages.

3. The probe electrospray ionization mass spectrometry analysis device according to claim 1, characterized in that: The probe voltage control unit repeatedly performs the action of extracting the sample to the front end of the probe by moving one or both of the probe and the sample using the displacement unit, and changes the voltage value of the probe voltage applied to the probe from the high voltage generating unit each time the sample is extracted. Under the control of the analysis control unit, the mass spectrometry analysis unit performs mass spectrometry analysis on the same sample each time the sample is extracted.

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