Mass spectrometer and control method thereof

Abstract

If a gas is being supplied from a gas supply unit (19) to a collision cell (11) when a first target ion is to be detected, then before the detection of the first target ion, a controller (22) applies a voltage having a first adjustment voltage value, obtained by adding an adjustment value to a first detection voltage value corresponding to the first target ion, to an electrode positioned on a downstream side of the collision cell (11) in a direction of travel of ions, and during the detection of the first target ion, the controller (22) applies a voltage having the first detection voltage value to the electrode positioned on the downstream side of the collision cell (11) in the direction of travel of ions. The adjustment value is a value having the opposite polarity to the polarity of the first target ion.

Description

[Technical Field]

[0001] The present invention relates to an ICP (Inductively Coupled Plasma) mass spectrometer. [Background technology]

[0002] An ICP mass spectrometer ionizes an element to be detected contained in a liquid sample using plasma, and detects the resulting ions using a detector (see, for example, Japanese Patent Laid-Open Publication No. 10-241625 (Patent Document 1)). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-241625 Summary of the Invention [Problem to be solved by the invention]

[0004] In an ICP mass spectrometer, ions drawn into a vacuum are captured in a chamber maintained under a vacuum atmosphere. The captured ions are accelerated by the electric field generated by the extraction electrode and introduced into a collision cell via a focusing lens. In addition to the ions of the components (elements) being observed, interference ions generated by various factors are also introduced into the chamber. Interference ions include those resulting from gases such as argon used to generate plasma in the ICP ion source, impurities contained in the liquid sample, and additives (such as nitric acid and hydrochloric acid) added to the liquid sample. A collision cell is installed in the ICP mass spectrometer to separate these interference ions from the target ions.

[0005] During analysis, gas (collision gas such as an inert gas, or reaction gas such as hydrogen or ammonia) may be introduced into the collision cell. The various ions introduced into the collision cell repeatedly come into contact with the gas within the collision cell. With each contact, the kinetic energy of the ions decreases. Interfering ions are generally polyatomic ions, and have a larger collision cross section than the elemental ions of interest that have the same mass. Therefore, the interfering ions come into contact with gas more frequently than the elemental ions of interest, and as a result, the kinetic energy of the interfering ions in the collision cell is smaller than the kinetic energy of the ions of the component of interest.

[0006] At the exit of the collision cell, a potential barrier is formed to allow only ions with kinetic energy equal to or greater than a predetermined value to pass through and block ions with kinetic energy less than the predetermined value, thereby separating and removing interfering ions from the ions of the component being observed.

[0007] During analysis, gas may not be introduced into the collision cell. In such cases, it is not possible to expect interference ions to be removed by contact with the gas. This causes interference ions to reach the mass filter, resulting in charge-up of the electrodes that make up the mass filter.

[0008] In other words, in an ICP mass spectrometer, if gas is not introduced into the collision cell during analysis, R When gas was not introduced into the collision cell, more interfering ions were introduced into the mass filter than when gas was introduced. As a result, the charge-up of the electrodes that make up the mass filter was greater when gas was not introduced into the collision cell than when gas was introduced. Therefore, there was a large difference in analytical conditions between when gas was introduced into the collision cell and when it was not.

[0009] The present invention has been devised in view of the above circumstances, and its purpose is to provide a method for analyzing a collision cell in an ICP mass spectrometer in a case where a gas is not introduced into the collision cell and a case where a gas is introduced into the collision cell. RThe object of the present invention is to provide a technique for reducing the difference in analytical conditions between different cases. [Means for solving the problem]

[0010] A mass spectrometer according to one aspect of the present disclosure includes a plasma ion source that ionizes a sample with plasma ions, a mass filter that selectively passes target ions having a specific mass-to-charge ratio from the ionized sample, a detector that detects the target ions, a collision cell disposed between the plasma ion source and the mass filter, a gas supply unit that supplies gas to the collision cell, and a controller that controls the value of the voltage applied to the electrodes, wherein when gas is supplied from the gas supply unit to the collision cell in detecting a first target ion, the controller applies a voltage of a first adjustment voltage value, which is obtained by adding an adjustment value to a first detection voltage value corresponding to the first target ion, to an electrode located downstream of the collision cell in the direction of ion travel before detecting the first target ion, and when detecting the first target ion, applies a voltage of the first detection voltage value to an electrode located downstream of the collision cell in the direction of ion travel, the adjustment value being a value representing a polarity opposite to that of the first target ion.

[0011] In a method for controlling a mass spectrometer according to an aspect of the present disclosure, the mass spectrometer includes a plasma ion source that ionizes a sample with plasma ions, a mass filter that selectively passes ions of interest having a specific mass-to-charge ratio from the ionized sample, a detector that detects the ions of interest, and a collision cell disposed between the plasma ion source and the mass filter. The method includes the steps of: determining whether to supply gas to the collision cell in detecting a first ion of interest; if it is determined that gas should be supplied to the collision cell in detecting the first ion of interest, applying a voltage of a first adjustment voltage value obtained by adding an adjustment value to a first detection voltage value corresponding to the first ion of interest to an electrode located downstream of the collision cell in the direction of ion travel in the mass spectrometer before detecting the first ion of interest; and applying a voltage of the first detection voltage value to the electrode in detecting the first ion of interest, the adjustment value representing a polarity opposite to that of the first ion of interest. [Effects of the Invention]

[0012] According to one aspect of the present disclosure, analysis in an ICP mass spectrometer involves cases where gas is not introduced into a collision cell and cases where gas is introduced. R The difference in analytical conditions between the two cases is small. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram schematically illustrating the configuration of a mass spectrometer according to an embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged view of a portion of the mass spectrometer 100. [Figure 3] FIG. 10 is a diagram showing an example of a set of setting values ​​for each electrode in a gas-free analysis. [Figure 4] 1 shows an example of a set of settings that are used during the period when the ion detector 17 detects ions to be analyzed. [Figure 5] 1 shows an example of a set of setting values ​​that are used for adjustment during periods other than the period when the ion detector 17 is detecting ions that are the subject of analysis. [Figure 6] 1 is a flowchart of a process performed in the mass spectrometer 100 for analyzing a sample. [Figure 7] 7 is a diagram schematically showing the timing of applying a voltage of an adjustment voltage value in the process of FIG. 6. FIG. [Figure 8] 10A and 10B are diagrams for explaining omission of application of a voltage of an adjustment voltage value. [Figure 9] FIG. 10 is a diagram showing the change in the amount of argon ions detected during the analysis of a given sample in a mass spectrometer of a comparative example. [Figure 10] 10A and 10B are diagrams showing the detection results of analyte ions in an analysis with and without gas, respectively. [Figure 11] 10A and 10B are diagrams showing the detection results of analyte ions in an analysis with and without gas, respectively. [Figure 12] FIG. 12 is a diagram showing the maximum rate of change at the start of detection for the detection intensity shown in FIG. 11. [Figure 13] 7 is a flowchart of a modified example of the process of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0015] [Mass spectrometer configuration] Fig. 1 is a diagram showing a schematic configuration of a mass spectrometer according to the present embodiment. The mass spectrometer 100 shown in Fig. 1 is an ICP mass spectrometer.

[0016] The mass spectrometer 100 includes an ionization chamber 1, a first vacuum chamber 2, a second vacuum chamber 3, and a third vacuum chamber 4. The ionization chamber 1 is at approximately atmospheric pressure and is electrically grounded. The first vacuum chamber 2 is configured so that the degree of vacuum increases from the ionization chamber 1 side. The first vacuum chamber 2 is evacuated to a vacuum by a rotary pump. The second vacuum chamber 3 and the third vacuum chamber 4 are evacuated to a vacuum by a rotary pump and a turbomolecular pump.

[0017] An ICP ion source 5 is disposed inside the ionization chamber 1. Note that the configuration of the ICP ion source 5 shown in Fig. 1 is merely an example, and various modifications are possible.

[0018] The ICP ion source 5 includes a plasma torch 51. The plasma torch 51 includes a sample tube through which a liquid sample atomized by a nebulizing gas flows, a plasma gas tube formed around the sample tube, and a cooling gas tube formed around the plasma gas tube.

[0019] An autosampler 52 is provided at the inlet end of the sample tube of the plasma torch 51 to introduce a liquid sample into the plasma torch 51. In addition, although not shown, a nebulizing gas supply source that supplies a nebulizing gas is connected to the sample tube, a plasma gas supply source that supplies a plasma gas (e.g., Ar gas) is connected to the plasma gas tube, and a cooling gas supply source that supplies a cooling gas is connected to the cooling gas tube.

[0020] The first vacuum chamber 2 is formed between a sampling cone 6, which is generally conical, and a skimmer cone 7, which is also generally conical. Both the sampling cone 6 and the skimmer cone 7 have ion passage openings at their tops. The skimmer cone 7 is made of a metal such as Cu or Ni. The first vacuum chamber 2 functions as an interface for sending ions supplied from the ICP ion source 5 to a subsequent stage and for discharging solvent gas and the like.

[0021] Of the three axes (X, Y, Z) shown in FIG. 1, the X axis represents the direction of travel of ions. Arranged within the second vacuum chamber 3, in this order from the skimmer cone 7 side (the side where ions are incident), are a retraction electrode 8, an ion lens 10 for focusing ions, and a collision cell 11. The ion lens 10 includes a front electrode 10A and a rear electrode 10B. The retraction electrode 8 and the ion lens 10 are both disk-shaped electrodes with a substantially circular opening formed therein for allowing ions to pass through. The opening in the retraction electrode 8 is shown as opening 81 in FIG. 2.

[0022] An entrance electrode 12 having an ion passage opening 121 formed therein is disposed on the entrance side of the collision cell 11, and an exit electrode 13 having an ion passage opening 131 formed therein is disposed on the exit side of the collision cell 11. A multipole (e.g., octapole) ion guide 14 including a plurality of rod electrodes arranged parallel to the ion optical axis 18 is disposed inside the collision cell 11. The exit electrode 13 also functions as an electrode for forming an energy barrier.

[0023] An axis bending electrode 15 and an axis bending exit electrode 19A are arranged downstream of the exit electrode 13. The axis bending electrode 15 and the axis bending exit electrode 19A are both disk-shaped electrodes with approximately circular openings for passing ions. The positions of the openings in the axis bending electrode 15 and the axis bending exit electrode 19A change so that they are positioned higher in the Y-axis direction as they approach the third vacuum chamber 4. This causes the axis bending electrode 15 and the axis bending exit electrode 19A to bend the ion optical axis 18. In other words, the location of the ion optical axis 18 in the collision cell 11 is different in the Y-axis direction from the location of the ion optical axis 18 in the quadrupole mass filter 16 in the third vacuum chamber 4 (located higher in FIG. 1).

[0024] A quadrupole mass filter 16 and an ion detector 17 are disposed within the third vacuum chamber 4. The quadrupole mass filter 16 includes a pre-rod electrode 16A and a main rod electrode 16B. An entrance electrode 19B is disposed between the ion detector 17 and the main rod electrode 16B. The entrance electrode 19B is a disk-shaped electrode with a substantially circular opening formed therein for allowing ions to pass through.

[0025] The gas supply unit 19 supplies a collision gas or a reaction gas through a gas supply pipe to the inside of the collision cell 11. The collision gas is He (or another inert gas), and the reaction gas is a reactive gas such as hydrogen or ammonia.

[0026] Voltage generating unit 20 generates voltages to be applied to various components within mass spectrometer 100, but in order to avoid cluttering the drawing, only some of the voltage supply lines are shown in Figure 1. Voltage generating unit 20 includes multiple DC voltage generating units that generate DC voltages of predetermined voltages, and multiple radio frequency voltage generating units that generate radio frequency voltages of predetermined amplitudes and frequencies.

[0027] Under the control of the controller 22, the voltage controller 21 controls the magnitude of the voltage applied from the voltage generating unit 20 to each unit and the timing of application.

[0028] The controller 22 performs overall control of each section within the mass spectrometer 100 in order to perform analysis. The controller 22 also functions as a user interface via an input section 23, a display section 24, etc. The data processing section 25 includes an analog-to-digital (AD) converter that digitizes the detection signal obtained by the ion detector 17, and processes the collected data to create a mass spectrum, etc.

[0029] In one implementation example, controller 22, voltage controller 21, and data processing unit 25 are implemented by a personal computer including a CPU (Central Processing Unit), RAM (Random Access Memory), an external storage device, etc. In one implementation example, control of mass spectrometer 100 can be achieved by the CPU executing a predetermined program that has been installed in advance.

[0030] [An example of the analysis operation of a mass spectrometer] 2 is an enlarged view of a portion of the mass spectrometer 100. An example of the analytical operation of the mass spectrometer 100 will be described below. In the following description, it is assumed that the ions to be detected in the mass spectrometer 100 are positive ions. However, even if the ions to be detected are negative ions, it is clear that an analysis similar to that described below can be performed by appropriately changing the polarity of the voltages applied to the various components.

[0031] Furthermore, in this specification, the positive or negative voltage value applied to each electrode is associated with the polarity of the ion to be detected. More specifically, when the ion to be detected is a positive ion, a positive voltage value (e.g., +1.0 V) is a voltage value that represents the same polarity as the polarity of the ion to be detected, and a negative voltage value (e.g., −1.0 V) is a voltage value that represents the opposite polarity to the polarity of the ion to be detected. On the other hand, when the ion to be detected is a negative ion, a positive voltage value is a voltage value that represents the opposite polarity to the polarity of the ion to be detected, and a negative voltage value is a voltage value that represents the same polarity as the polarity of the ion to be detected.

[0032] In the standby state before the start of analysis, the first vacuum chamber 2, the second vacuum chamber 3, and the third vacuum chamber 4 are each evacuated to a vacuum. When a command to start analysis is given by the user via the input unit 23, or when a command to start analysis is automatically given in accordance with a preset automatic analysis program, the controller 22 starts preparations for analysis.

[0033] In the analysis preparation work, the controller 22 operates the gas supply unit 19 to start supplying a predetermined gas continuously or intermittently into the collision cell 11. The type of gas supplied varies depending on the analysis mode, for example, He gas in the collision mode and H gas in the reaction mode.

[0034] Even after the mass spectrometer 100 starts supplying gas into the collision cell 11, it takes a certain amount of time for the gas to fill the collision cell 11 and stabilize, and until then, substantial analysis cannot be performed. This period is the analysis preparation period.

[0035] In response to an instruction from the controller 22, the voltage controller 21 controls the voltage generator 20 to apply a positive DC voltage of a predetermined voltage value to the pull-in electrode 8 so that a potential barrier higher than the initial energy of the unwanted ions generated in the ICP ion source 5 is formed between the skimmer cone 7 and the pull-in electrode 8. The "undesired ions" are mainly ions derived from the plasma gas used in the ICP ion source 5. When the plasma gas is Ar, the unwanted ions are mainly ions derived from Ar. + , Ar 2+ Since the initial energy of these "undesired ions" is not so large, the voltage applied to the pull-in electrode 8 is generally about + several volts.

[0036] The voltage controller 21 also controls the voltage generating unit 20 under the instruction of the controller 22 so as to apply a positive DC voltage of a predetermined voltage value to the entrance electrode 12 of the collision cell 11. At this time, the voltage applied to the entrance electrode 12 is, for example, about + several tens of volts to +200 volts.

[0037] The voltage controller 21 also controls the voltage generating unit 20 under the direction of the controller 22 so as to apply a high frequency voltage to the ion guide 14 in the collision cell 11 with a larger amplitude than that during normal analysis.

[0038] The voltage controller 21 further controls the voltage generator 20 to continuously or pulse-wise apply a negative DC voltage of a predetermined voltage value larger than that used during normal analysis to the exit electrode 13 of the collision cell 11. At this time, the amplitude value of the radio frequency voltage applied to the ion guide 14 is, for example, 50 V or more, and the DC voltage applied to the exit electrode 13 is, for example, about −100 V (about −10 to −10+ V during normal analysis).

[0039] As described above, a potential barrier is formed near the pull-in electrode 8 by the DC voltage applied to the pull-in electrode 8 due to an electric field of the same polarity as the ions. Ions derived from the plasma gas, etc., generated in the ICP ion source 5 and passing through the ion passage port (opening 61) of the sampling cone 6 and the ion passage port (opening 71) of the skimmer cone 7 and entering the second vacuum chamber 3 are blocked by the potential barrier. As a result, ions are retained in the region 31 between the skimmer cone 7 and the pull-in electrode 8, increasing the ion density.

[0040] The ICP ion source 5 emits not only the above-mentioned ions but also reactive neutral particles derived from the plasma gas and P Plasma gas molecules also try to penetrate into the vacuum region. However, because the ion density in region 31 is high, reactive neutral particles and gas molecules that pass through opening 71 of skimmer cone 7 are likely to come into contact with the ions. The reactive neutral particles and gas molecules that come into contact with the ions change their trajectory, collide with surrounding electrodes, etc., and are annihilated, or are expelled from second vacuum chamber 3 to the outside. This makes it difficult for reactive neutral particles and gas molecules to reach the entrance of collision cell 11, thereby reducing the amount of reactive neutral particles and gas molecules that enter the interior of collision cell 11.

[0041] As described above, an electric field of the same polarity as the ions originating from the plasma gas, etc., is formed in the region 32 between the ion lens 10 and the entrance electrode 12 by the voltage applied to the entrance electrode 12 of the collision cell 11. Therefore, ions that are introduced from the ICP ion source 5 through the first vacuum chamber 2 to the second vacuum chamber 3 and pass through the region 32 are pushed back just before the entrance electrode 12. This makes it possible to further reduce the intrusion of undesired ions originating from the plasma gas, etc., into the collision cell 11.

[0042] Since reactive neutral particles and molecules do not have an electric charge, they are not removed by the action of the electric field formed in region 32. However, as mentioned above, reactive neutral particles and molecules have difficulty passing through region 31, so only a small amount of reactive neutral particles and gas molecules penetrates into the collision cell 11.

[0043] Some ions originating from the plasma gas, etc., may pass through both region 31 and region 32 and enter the collision cell 11. In addition, some reactive neutral particles and molecules originating from the plasma gas, etc., may pass through the above two regions and enter the collision cell 11, where they may come into contact with the gas inside the collision cell 11 and become undesired ions. Ions that have entered from outside and ions generated inside the collision cell 11 lose energy by coming into contact with the gas present inside the collision cell 11 and are captured by the radio frequency electric field formed by the ion guide 14. Because the radio frequency electric field at this time is stronger than that during normal analysis, the ions are focused into a relatively narrow region 33 near the ion optical axis 18.

[0044] As described above, a relatively high voltage of opposite polarity to the ions to be trapped is applied to the exit electrode 13 of the collision cell 11. Therefore, the ions retained in the region 33 are attracted by the strong electric field caused by the voltage applied to the exit electrode 13, and are expelled from the collision cell 11 through the ion passage opening 131 of the exit electrode 13.

[0045] That is, during the analysis preparation period before the execution of an analysis, undesired ions and undesired reactive neutral particles are prevented from entering the collision cell 11 between the ICP ion source 5 and the collision cell 11. On the other hand, undesired ions that have entered the collision cell 11 and undesired ions generated within the collision cell 11 are quickly expelled to the outside of the collision cell 11. In this way, in the mass spectrometer 100, ions are less likely to remain within the collision cell 11 during the analysis preparation period.

[0046] The controller 22 waits until a predetermined waiting time has elapsed so that the collision cell 11 is sufficiently filled with gas supplied from the gas supply unit 19. The gas introduced into the collision cell 11 leaks out from the openings (ion passage openings 121, 131) of the entrance electrode 12 and the exit electrode 13. Therefore, a longer waiting time is better in order to fill the collision cell 11 with gas molecules at as uniform a density as possible. As an example, the waiting time from the start of gas introduction should be 40 seconds or more.

[0047] After a predetermined waiting time has elapsed, the voltage controller 21 controls the voltage generator 20 to apply a negative DC voltage of a predetermined voltage value to the pull-in electrode 8 so as to attract ions. The voltage controller 21 also controls the voltage generator 20 to apply a negative DC voltage of a predetermined voltage value to the entrance electrode 12 of the collision cell 11. The voltage controller 21 also controls the voltage generator 20 to apply a radio frequency voltage of a predetermined amplitude value corresponding to the component to be analyzed (target component) to the ion guide 14 in the collision cell 11. The voltage controller 21 also controls the voltage generator 20 to apply a predetermined voltage for forming a potential barrier to the exit electrode 13 of the collision cell 11.

[0048] Analysis is then performed in mass spectrometer 100. In one implementation, voltage controller 21 sets the voltage applied to quadrupole mass filter 16 so that ions originating from the target component pass through. Then, in mass spectrometer 100, after a time (e.g., several msec) required for the voltages applied to each component to settle has elapsed, the intensity of the ions of the target sample component is detected.

[0049] For example, in collision mode, ions derived from sample components generated by the ICP ion source 5 are introduced into the collision cell 11, which is filled with a collision gas, along with unwanted ions derived from the plasma gas. The introduced ions repeatedly collide with the collision gas, resulting in a loss of energy. Ions with larger collision cross sections have more opportunities to collide with the collision cell, resulting in a greater loss of energy. Typically, the collision cross section of ions derived from the plasma gas is larger than that of ions derived from the target component, resulting in a lower kinetic energy of the ions derived from the plasma gas. Therefore, the ions derived from the plasma gas have a harder time overcoming the potential barrier formed at the exit of the collision cell 11. In this way, unwanted ions derived from the plasma gas, etc., are removed by kinetic energy discrimination, and the ions derived primarily from the sample components are sent to the quadrupole mass filter 16 for analysis.

[0050] As described above, during the analysis preparation period before the start of analysis, almost no ions are present in the collision cell 11. Therefore, when analysis of ions originating from the target component begins, there is almost no space charge effect on the ions residing inside the collision cell 11. Therefore, during analysis, the trajectories of ions originating from the target component (introduced into the collision cell 11) are not affected by the space charge effect. As a result, the ions pass through the collision cell 11 along their normal trajectories and are introduced into the quadrupole mass filter 16. This increases the amount of ions originating from the target component that ultimately reach the ion detector 17, achieving high analytical sensitivity. Furthermore, because the trajectories of ions originating from the sample component are not affected by the space charge effect, drift in ion intensity can be reduced, and the variation in drift due to the type of sample component can also be reduced.

[0051] In the above explanation, the voltages applied to each component were set so that ions would not accumulate in the collision cell 11 throughout the entire analysis preparation period, from when gas supply into the collision cell 11 begins until the collision cell 11 is sufficiently filled with gas and analysis begins. However, it is not necessary to continuously set voltages in this manner throughout the entire analysis preparation period. The basic operation can be the same as described above even in reaction mode instead of collision mode.

[0052] When the target ions are positive ions, a negative voltage is applied to the quadrupole mass filter 16 (each of the pre-rod electrode 16A and the main rod electrode 16B). Specific examples of the applied voltages will be described later with reference to FIGS. 3 to 5.

[0053] [Examples of applied voltage values] (Gas-free analysis) 3 is a diagram showing an example of a set of setting values ​​for each electrode in a gas-free analysis. In the mass spectrometer 100, a gas-free analysis means an analysis that is performed without supplying gas to the collision cell 11. In one implementation example, the set of setting values ​​shown in FIG. 3 is stored in the memory of the controller 22.

[0054] Figure 3 shows three element names (Be, In, Bi) as ion detection targets. Each element name is accompanied by its mass-to-charge ratio.

[0055] Figure 3 shows the combination of setting values ​​for each of the 16 types of electrodes listed below, for each ion (element) to be detected. The unit of each setting value is V (volts). Each of the 16 types of symbols, such as EX, listed in Figure 3 represents the voltage value applied to the following electrodes.

[0056] EX: Retraction electrode 8 L1: Front electrode 10A of ion lens 10 L2: Rear electrode 10B of ion lens 10 L3: entrance electrode 12 of collision cell 11 CCBIAS: bias electrode corresponding to the rod electrode of ion guide 14 CCRF: Reference electrode corresponding to the rod electrode of ion guide 14 L4: Exit electrode 13 of collision cell 11 AC1: Axial bending electrode 15(1) DEF1: Axial bending electrode 15(2) DEF2: Axial bending electrode 15(3) AC2: Axial bending electrode 15(4) AP_P: Axial bending exit electrode 19A PREBIAS: Pre-rod electrode 16A of quadrupole mass filter 16 MAINBIA: Main rod electrode 16B of the quadrupole mass filter 16 AP_D: (Between the ion detector 17 and the main rod electrode 16B) entrance electrode 20B OFFSET: Bias electrode of quadrupole mass filter 16 Of the 16 types, the "axial bending electrode 15(1)," "axial bending electrode 15(2)," "axial bending electrode 15(3)," and "axial bending electrode 15(4)" refer to the four parts that make up the axial bending electrode 15. These are arranged in the X-axis direction as viewed from the ionization chamber 1 side in the order of "axial bending electrode 15(1)," "axial bending electrode 15(2)," "axial bending electrode 15(3)," and "axial bending electrode 15(4)." That is, the "axial bending electrode 15(1)" is located between the collision cell 11 and the "axial bending electrode 15(2)." Furthermore, the "axial bending electrode 15(4)" is located between the "axial bending electrode 15(3)" and the axial bending exit electrode 19A.

[0057] In the example of FIG. 3, different set values ​​are shown for at least some of the electrodes for each ion to be detected.

[0058] (Gas analysis) 4 and 5 each show an example of a set of setting values ​​for each electrode in an analysis with gas. In the mass spectrometer 100, an analysis with gas means an analysis performed with gas supplied to the collision cell 11. The unit of each setting value is V (volts). In one implementation example, the set of setting values ​​shown in each of FIGS. 4 and 5 are stored in the memory of the controller 22.

[0059] 4 shows an example of a set of setting values ​​used during a period when the ion detector 17 is detecting ions to be analyzed. Fig. 5 shows an example of a set of setting values ​​used for adjustment during a period other than the period when the ion detector 17 is detecting ions to be analyzed. As in Fig. 3, Figs. 4 and 5 also show different setting values ​​for each ion to be detected for at least some of the electrodes.

[0060] 4 and 5, the combinations of setting values ​​for the six types of electrodes in the upper row ("EX," "L1," "L2," "L3," "CCBIAS," and "CCRF") and the one type of electrode in the lower row ("OFFSET") are the same, but the combinations of setting values ​​for the nine types of electrodes in the lower row ("L4," "AC1," "DEF1," "DEF2," "AC2," "AP_P," "PREBIAS," "MAINBIA," and "AP_D") are different. More specifically, the absolute values ​​of each setting value shown in FIG. 5 are larger than the absolute values ​​of each setting value shown in FIG. 4.

[0061] In the examples shown in Figures 3 to 5, the three types of ions to be detected are all positive ions (Be + ,In + ,Bi + ) As a result, the set values ​​of the nine types of electrodes in the bottom row shown in FIGS. 4 and 5 are all negative voltage values. The absolute values ​​of the set values ​​of the nine types of electrodes in the bottom row are greater in the values ​​shown in FIG. 5 than in FIG. 4. This means that for the set values ​​of the nine types of electrodes in the bottom row, the values ​​shown in FIG. 5 have been added with a value (negative value) that represents the opposite polarity to the polarity of the target ions to be detected, relative to the values ​​shown in FIG. 4. In the values ​​shown in FIG. 5, the value added to the values ​​shown in FIG. 4 is also referred to as an "adjustment value" in this specification.

[0062] In the example shown in FIGS. 4 and 5, the adjusted voltage values ​​for all of the nine types of electrodes in the bottom row are "-7.0 (V)."

[0063] For example, for "L4" of the element Be, the set value shown in Figure 4 is "-47.7(V)", and the set value shown in Figure 5 is "-54.7(V)". The latter is the value obtained by adding "-7.0(V)" to the former.

[0064] Also, the element Be's " PREBIAS 4 is "-27.9(V)", and the setting value shown in FIG. 5 is "-34.9(V)". The latter is the value obtained by adding "-7.0(V)" to the former.

[0065] [Processing flow] Figure 6 is a flowchart of the processing performed for sample analysis in mass spectrometer 100. The processing shown in Figure 6 is performed, for example, by the CPU executing a given program. The content of the processing shown in Figure 6 will be described below.

[0066] 6, in step S100, mass spectrometer 100 receives an instruction for analysis. In one implementation example, a user inputs the instruction for analysis to input unit 23. Mass spectrometer 100 may receive the instruction for analysis via input unit 23.

[0067] In step S102, the mass spectrometer 100 determines whether the requested analysis is an analysis with or without gas. In one implementation example, the analysis instruction input by the user to the input unit 23 may include a designation of an analysis with or without gas. The mass spectrometer 100 acquires the designation of an analysis with or without gas via the input unit 23.

[0068] If the instructed analysis includes a designation for analysis with gas (YES in step S102), mass spectrometer 100 proceeds to step S114, otherwise (NO in step S102), mass spectrometer 100 proceeds to step S104. That is, if the instructed analysis includes a designation for analysis without gas, mass spectrometer 100 proceeds to step S104.

[0069] In step S104, the mass spectrometer 100 acquires the setting values ​​of each electrode for the ions to be detected in the analysis.

[0070] In analyzing a sample, the mass spectrometer 100 causes the ion detector 17 to acquire detection signals for one or more types of ions. In the process of Fig. 6, the control of steps S104 to S108 is performed for each type of ion to be detected. When detection of two or more types of ions is performed, the control of steps S104 to S108 is repeated the same number of times as the number of types of ions to be detected.

[0071] In one implementation, mass spectrometer 100 obtains settings for the 16 electrodes shown in FIG. 3 for the ions to be detected.

[0072] In step S106, mass spectrometer 100 realizes the set values ​​acquired in step S104, that is, mass spectrometer 100 applies voltages of the acquired set values ​​to the electrodes.

[0073] In step S108, the mass spectrometer 100 controls each element in the mass spectrometer 100 to cause the ion detector 17 to acquire a detection signal of the ions to be detected, thereby performing detection by the ion detector 17 of the ions to be detected.

[0074] In step S110, mass spectrometer 100 determines whether or not any detection using another setting remains for the sample to be analyzed. More specifically, when two or more types of ions are being detected in the ongoing analysis, mass spectrometer 100 determines whether or not any of the two or more types of ions have yet to be selected as the detection target. If there are ions that have yet to be selected as the detection target, mass spectrometer 100 determines that any detection using another setting remains.

[0075] If mass spectrometer 100 determines that detection with other settings remains (YES in step S110), it returns control to step S104; otherwise, it ends the processing of FIG.

[0076] On the other hand, in step S114, the mass spectrometer 100 causes the gas supply unit 19 to supply gas to the collision cell 11.

[0077] In step S116, the mass spectrometer 100 determines whether the above-mentioned "analysis preparation period" has elapsed since the start of gas supply to the collision cell 11. The mass spectrometer 100 repeats the determination in step S116 until it determines that the analysis preparation period has elapsed (NO in step S116), and when it determines that the analysis preparation period has elapsed (YES in step S116), it proceeds to step S118.

[0078] In step S118, the mass spectrometer 100 acquires adjustment voltage values ​​for the 16 types of electrodes shown in Fig. 5 for the ions to be detected. In the analysis with gas, as in the analysis without gas, the mass spectrometer 100 causes the ion detector 17 to acquire detection signals for one or more types of ions. When two or more types of ions are to be detected, the controls of steps S118 to S128 are repeated the number of times corresponding to the number of types of ions to be detected. In step S118, an adjustment voltage value for the ion that is currently being detected is acquired.

[0079] In step S120, mass spectrometer 100 realizes the adjustment voltage values ​​acquired in step S118. That is, mass spectrometer 100 applies the voltages of the acquired adjustment voltage values ​​to the respective electrodes.

[0080] In step S122, the mass spectrometer 100 performs the steps S1 20 After the adjustment voltage value is realized in step S122, the mass spectrometer 100 determines whether the time (adjustment time) set for applying the voltage of the adjustment voltage value to each electrode has elapsed. Mass spectrometer 100 repeats the determination in step S122 until it determines that the adjustment time has elapsed (NO in step S122), and when it determines that the adjustment time has elapsed (YES in step S122), it proceeds to step S124.

[0081] In step S124, mass spectrometer 100 acquires detection setting values ​​for the 16 types of electrodes shown in FIG. 4 for the ions to be detected.

[0082] In step S126, mass spectrometer 100 realizes the detection set values ​​acquired in step S124. That is, mass spectrometer 100 applies the voltage of each acquired detection set value to each electrode.

[0083] In step S128, the mass spectrometer 100 controls each element in the mass spectrometer 100 to cause the ion detector 17 to acquire a detection signal of the ions to be detected, thereby performing detection by the ion detector 17 of the ions to be detected.

[0084] In step S130, mass spectrometer 100 determines whether detection with other settings remains for the sample to be analyzed, as in step S110. If mass spectrometer 100 determines that detection with other settings remains (YES in step S130), it returns control to step S118; otherwise, it ends the processing of FIG.

[0085] [Adjustment voltage value] In the present embodiment described above, the mass spectrometer 100 accepts a designation of either analysis with or without gas as the method of analyzing a sample. When a designation of analysis with gas is accepted, the mass spectrometer 100 realizes an "adjustment voltage value" in step S120 before detecting target ions using the ion detector 17 (step S128). The voltage value realized at each electrode when the ion detector 17 detects target ions is referred to as a "detection voltage value."

[0086] As described with reference to FIGS. 4 and 5, among the 16 types of electrodes, for each of the nine types of electrodes ("L4", "AC1", "DEF1", "DEF2", "AC2", "AP_P", "PREBIAS", "MAINBIA", and "AP_D") located downstream of the collision cell 11 in the direction of ion travel, the target ion is detected as "Be" (Be + ), the "adjustment voltage value" is the value obtained by adding "-7.0 (V)" to the "detection voltage value."

[0087] Here, "-7.0 (V)" is an example of an adjustment value. The adjustment value is a value that represents the polarity opposite to that of the target ion. For example, if the target ion is a positive ion, the adjustment value has a negative value. Note that if the target ion is a negative ion, the adjustment value has a positive value.

[0088] The nine types of electrodes include the pre-rod electrode 16A (PREBIAS) and the main rod electrode 16B (MAINBIA) of the quadrupole mass filter 16. In this sense, each of the pre-rod electrode 16A and the main rod electrode 16B is an example of an electrode to which a voltage of an adjustment voltage value is applied.

[0089] The nine types of electrodes include the exit electrode 13 of the collision cell 11, which is provided between the collision cell 11 and the quadrupole mass filter 16. In this sense, the exit electrode 13 is an example of an electrode to which a voltage of an adjustment voltage value is applied.

[0090] The nine types of electrodes include entrance electrode 20B (AP_D) provided between quadrupole mass filter 16 and ion detector 17. In this sense, entrance electrode 20B is an example of an electrode to which a voltage of an adjustment voltage value is applied.

[0091] The nine types of electrodes described above are provided between the collision cell 11 and the quadrupole mass filter 16, and include axis bending electrodes 15 (AC1, DEF1, DEF2, AC2) and axis bending exit electrode 19A (AP_P) for connecting the ion optical axis in the collision cell 11 and the ion optical axis in the quadrupole mass filter 16 in a given direction (Y-axis direction). In this sense, each of the axis bending electrodes 15 and the exit electrode 19A is an example of an electrode to which a voltage of an adjustment voltage value is applied.

[0092] As described with reference to FIGS. 4 and 5, a "detection voltage value" and an "adjustment voltage value" are set for each electrode and for each target ion.

[0093] For example, for the exit electrode 13 (L4) of the collision cell 11, a detection voltage value and an adjustment voltage value are set for each of three types of target ions. More specifically, for Be ions, a detection voltage value of −47.7 (V) is set, and an adjustment voltage value of −54.7 (V). For In ions, a detection voltage value of −56.6 (V) is set, and an adjustment voltage value of −63.6 (V). For Bi ions, a detection voltage value of −64.4 (V) is set, and an adjustment voltage value of −71.4 (V).

[0094] For the exit electrode 13 (L4) of the collision cell 11, the detection voltage value for each of the three types of target ions is the adjustment voltage value plus "-7.0 (V)." In other words, the adjustment value may be common to multiple types of target ions.

[0095] However, the examples shown in Figures 4 and 5 are merely examples. As the adjustment value, a different voltage value may be set for each type of target ion and / or for each electrode.

[0096] [Start timing of realization of adjustment voltage value] In the process shown in FIG. 6, the mass spectrometer 100 starts supplying gas to the collision cell 11 in step S114, waits for the analysis preparation period to elapse in step S116, and then applies a voltage of an adjustment voltage value to each electrode in step S120.

[0097] The application of the adjustment voltage value is performed to minimize the difference in analysis conditions between analysis with and without gas. More specifically, in analysis with gas, the kinetic energy of interfering ions is reduced by contact with gas in the collision cell 11, which reduces the likelihood of charge-up due to interfering ions occurring in the quadrupole mass filter 16 and other components compared to analysis without gas. Therefore, in analysis with gas, the application of the adjustment voltage value is performed before detection of target ions to bring the amount of charge-up closer to that of analysis without gas. As described above, the application of the adjustment voltage value is initiated after the start of gas supply to the collision cell 11, thereby minimizing the amount of voltage application.

[0098] However, application of the voltage of the adjustment voltage value to each electrode may be started without waiting for the analysis preparation period to elapse, or before the supply of gas to the collision cell 11 is started.

[0099] [Frequency of achieving the adjustment voltage value] In the process shown in Fig. 6, in a gas-present analysis, before each detection of target ions in step S128, a voltage of an adjustment voltage value is applied to each electrode in step S120. That is, the timing of application of voltages of the adjustment voltage value in the process of Fig. 6 is shown in Fig. 7. Fig. 7 is a diagram schematically showing the timing of application of voltages of the adjustment voltage value in the process of Fig. 6.

[0100] In the example of FIG. 7, in the period from time T11 to time T12, each electrode is very In the period from time T12 to T13, the first analysis of the target ions is carried out. In the period from time T13 to T14, the voltages for adjustment are applied to the respective voltages before the second analysis of the target ions. very In the period from time T14 to T15, the second analysis of the target ions is carried out. In the period from time T15 to T16, the voltages for adjustment are applied to the respective voltages before the third analysis of the target ions. veryA voltage of the adjustment voltage value is applied to the analyzer 1. In the period from time T16 to time T17, the third analysis of the target ions is carried out.

[0101] For example, in the analysis of a certain sample, Be ions are detected in the first detection, In ions are detected in the second detection, and Bi ions are detected in the third detection. The first to third detections are performed as an analysis with gas present.

[0102] In addition, when multiple detections are performed consecutively in the gas presence analysis, the application of the voltage of the adjustment voltage value between the detections may be omitted. Fig. 8 is a diagram for explaining the omission of the application of the voltage of the adjustment voltage value.

[0103] In the example of FIG. 8, in the period from time T21 to time T22, each electrode is measured before the first analysis of the target ion. very A voltage of an adjustment voltage value is applied to the target ions. In the period from time T22 to T23, a first analysis of target ions is carried out. In the period from time T23 to T24, a second analysis of target ions is carried out. In the period from time T24 to T25, a third analysis of target ions is carried out.

[0104] [Difference in the amount of charge-up generated between analysis with and without gas] The difference in the amount of charge-up generated between analysis with and without gas will be described with reference to FIGS.

[0105] (detection amount of argon ions) 9 is a graph showing the change in the amount of argon ions detected in the analysis of a given sample in a mass spectrometer of a comparative example. The change shown in FIG. 9 is treated as a comparative example.

[0106] 9, the vertical axis represents the intensity of the detection signal of argon ions (mass-to-charge ratio (m / z)=38) in the ion detector 17. The horizontal axis represents the mass-to-charge ratios targeted by the voltage setting values ​​of the 16 types of electrodes (see FIG. 3, etc.) in the mass spectrometer 100.

[0107] 3 and 4, the set value of the voltage of each electrode changes according to the mass-to-charge ratio of the ions to be detected by mass spectrometer 100. For example, for the PREBIAS electrode in a gas-free analysis (FIG. 3), if the mass-to-charge ratio of the ions to be detected is "9" (Be), the set value is "-14(V)", if the mass-to-charge ratio of the ions to be detected is "115" (In), the set value is "-4(V)", and if the mass-to-charge ratio of the ions to be detected is "209" (Bi), the set value is "-12(V)".

[0108] The graph in Fig. 9 shows the change in the amount of argon ions introduced into the collision cell 11 that reaches the ion detector 17, accompanying changes in the set values ​​of the voltages applied to each electrode. In Fig. 9, line L11 shows the results of an analysis without gas. Line L12 shows the results of an analysis with gas. Note that the analysis with gas in Fig. 9 does not include the application of an adjustment voltage value (step S120).

[0109] 9, the intensity indicated by line L12 does not change significantly even when the mass-to-charge ratio of the target is changed. In other words, in the analysis with gas present, even if the set value of the voltage applied to each electrode is changed, the amount of argon ions reaching the ion detector 17 does not change significantly.

[0110] On the other hand, the intensity indicated by line L11 has a value close to the intensity indicated by line L12 when the mass-to-charge ratio of the target ion is around 209, but is three orders of magnitude larger than the intensity indicated by line L12 in the region where the mass-to-charge ratio is 115 or less. In other words, when the mass-to-charge ratio of the ions to be detected is 115 or less, it can be said that in the analysis without gas, three orders of magnitude more argon ions reach the downstream side of the collision cell 11 than in the analysis with gas.

[0111] (Drift in detection results) 10 is a diagram showing the detection results of ions of the analyte in the analysis with and without gas, respectively. The detection results in FIG. 10 are used as a comparative example.

[0112] FIG. 10 shows the results of the analysis with and without gas for each of the four types of analyte ions (As, Bi, Co, In). The results of the analysis with gas shown in FIG. 10 are the results of the analysis with gas carried out immediately after the analysis without gas carried out separately. The results of the analysis without gas shown in FIG. 10 are the results of the analysis with gas carried out immediately after the analysis with gas shown in FIG. none 10 does not include the application of an adjustment voltage value (step S120).

[0113] In the analysis with gas shown in Figure 10, when the target ion to be detected is "Bi," the change in detection intensity is small over time. However, when the target ion to be detected is "In," the detection intensity increases over time. Furthermore, when the target ion to be detected is "As" or "Co," the detection intensity increases significantly over time, increasing by about 15% from the start of detection to the end of detection.

[0114] In the analysis without gas shown in Figure 10, as in the analysis with gas, when the ion to be detected is "Bi," the change in detection intensity over time is small. However, when the ion to be detected is "In," a drift in detection intensity occurs over time. Furthermore, when the ion to be detected is "As" or "Co," a drift in detection intensity occurs over time, with the detection intensity changing by up to about 15% from the intensity at the start of detection.

[0115] (Improvement in detection results) 11 is a diagram showing the detection results of ions to be analyzed in the analysis with and without gas, respectively. The detection results in FIG. 11 are in accordance with this embodiment.

[0116] 11 shows the results of a no-gas analysis, a gas-containing analysis, and a no-gas analysis performed consecutively for each of nine analyte ions (As, Bi, Cd, Ce, Co, In, Mn, Pb, and Y). The first no-gas analysis is shown as "no-gas analysis (1)," and the second no-gas analysis is shown as "no-gas analysis (2)." That is, the analysis was performed in the following order: no-gas analysis (1), gas-containing analysis, and no-gas analysis (2). The gas-containing analysis in FIG. 11 includes application of an adjustment voltage value (step S120).

[0117] Fig. 12 is a diagram showing the rate of maximum change at the start of detection for the detection intensity shown in Fig. 11. Note that Fig. 12 also shows values ​​for ions (Be) for which data is not shown in Fig. 11. Note that the "*" shown for the value of the Be ion in the analysis with gas means that the ion detector 17 was unable to detect the Be ion in the analysis with gas.

[0118] 12, the maximum value is "1.4%" for Co ions in the analysis (2) without gas. That is, in accordance with the present embodiment, the occurrence of drift in the detection intensity of ions over time from the start of detection is suppressed, even when analysis with and without gas is repeated in mass spectrometer 100, in contrast to the comparative example described with reference to FIGS.

[0119] In this embodiment, in an analysis with gas present, the mass spectrometer 100 applies an adjustment voltage to each electrode before detection, thereby intentionally inducing charge-up. This can prevent drift in the detection results caused by charge-up progressing during detection of target ions in an analysis with gas present. Furthermore, in an analysis with gas, target ions are detected in a state where charge-up has occurred, just as in an analysis without gas, so the difference in analysis conditions between an analysis with gas and an analysis without gas can be reduced.

[0120] [Usage period and voltage application] In the mass spectrometer 100, charge-up in the quadrupole mass filter 16 (the pre-rod electrode 16A and the main rod electrode 16B) and the like is more likely to occur the longer the period of use of the mass spectrometer 100. Therefore, the longer the period of use of the mass spectrometer 100, the shorter the adjustment time (step S122) may be. Furthermore, the longer the period of use of the mass spectrometer 100, the smaller the absolute value of the adjustment voltage may be.

[0121] In one implementation, the usage period of mass spectrometer 100 is written to the memory of controller 22. The memory also stores adjustment voltage values ​​for each electrode corresponding to two or more usage periods. For example, for each electrode, an adjustment voltage value for a usage period of less than five years and an adjustment voltage value for a usage period of five years or more are stored in the memory. The longer the usage period, the smaller the absolute value of the adjustment voltage value may be.

[0122] Fig. 13 is a flowchart of a modified example of the process of Fig. 6. Compared to the process of Fig. 6, the process of Fig. 13 further includes step S117 after step S116.

[0123] If it is determined in step S116 that the analysis preparation period has elapsed, or if it is determined in step S130 that detection with other settings remains, mass spectrometer 100 advances control to step S117.

[0124] In step S117, the mass spectrometer 100 reads the usage period of the mass spectrometer 100 from the memory of the controller 22.

[0125] In step S118, mass spectrometer 100 reads out an adjustment voltage value corresponding to the usage period read out in step S117.

[0126] In another implementation, the memory stores an "adjustment time" corresponding to each of two or more usage periods. The longer the usage period, the shorter the adjustment time may be. In this case, in step S122, the mass spectrometer 100 determines whether the adjustment time corresponding to the usage period read in step S117 has elapsed. If the mass spectrometer 100 determines in step S122 that the adjustment time has elapsed, it proceeds to step S124.

[0127] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0128] (Item 1) A mass spectrometer according to one aspect includes a plasma ion source that ionizes a sample with plasma ions, a mass filter that selectively passes target ions having a specific mass-to-charge ratio from the ionized sample, a detector that detects the target ions, a collision cell provided between the plasma ion source and the mass filter, a gas supply unit that supplies gas to the collision cell, and a controller that controls the value of a voltage applied to an electrode, wherein when gas is supplied from the gas supply unit to the collision cell in detecting a first target ion, the controller applies a voltage of a first adjustment voltage value obtained by adding an adjustment value to a first detection voltage value corresponding to the first target ion to an electrode located downstream of the collision cell in the direction of ion travel before detecting the first target ion, and applies a voltage of the first detection voltage value to an electrode located downstream of the collision cell in the direction of ion travel in detecting the first target ion, wherein the adjustment value may be a value that represents a polarity opposite to that of the first target ion.

[0129] According to the mass spectrometer described in paragraph 1, in the analysis in the mass spectrometer, there are cases where gas is not introduced into the collision cell and cases where gas is introduced. R The difference in analytical conditions between the two cases is small.

[0130] (Item 2) In the mass spectrometer described in item 1, the electrode located downstream of the collision cell in the direction of ion travel may include a rod electrode of the mass filter.

[0131] According to the mass spectrometer described in paragraph 2, the difference in analytical conditions regarding charge-up on the rod electrodes of the mass filter is reduced.

[0132] (Item 3) The mass spectrometer described in item 1 or 2 may further include an exit electrode provided between the collision cell and the mass filter, and the electrode located downstream of the collision cell in the direction of ion travel may include the exit electrode.

[0133] According to the mass spectrometer described in paragraph 3, the difference in analytical conditions regarding charge buildup at the exit electrode provided between the collision cell and the mass filter is reduced.

[0134] (Item 4) The mass spectrometer according to any one of items 1 to 3 may further include an entrance electrode provided between the mass filter and the detector, and the electrode located downstream of the collision cell in the direction of ion travel may include the entrance electrode.

[0135] According to the mass spectrometer described in item 4, a mass filter is provided between the mass filter and the detector. Enter The difference in analytical conditions regarding charge buildup at the electrode is reduced.

[0136] (Item 5) In the mass spectrometer described in any one of Items 1 to 4, the ion optical axis in the mass filter is located at a different position in a given direction from the ion optical axis in the collision cell, and the mass spectrometer further comprises a bending electrode provided between the collision cell and the mass filter for connecting the ion optical axis in the collision cell and the ion optical axis in the mass filter in the given direction, and the electrode located downstream of the collision cell in the ion traveling direction may include the bending electrode.

[0137] According to the mass spectrometer described in item 5, the difference in analytical conditions regarding charge-up at the bent electrode is reduced.

[0138] (Item 6) In the mass spectrometer according to any one of Items 1 to 5, the absolute value of the adjustment value may be smaller as the period of use of the mass spectrometer becomes longer.

[0139] According to the mass spectrometer described in item 6, the minimum voltage value for minimizing the difference in analysis conditions is set as the adjustment voltage value.

[0140] (Item 7) In the mass spectrometer described in any one of Items 1 to 6, the length of time during which the voltage of the first adjustment voltage value is applied to the rod electrodes may be shorter as the period of use of the mass spectrometer is longer.

[0141] According to the mass spectrometer described in item 7, the voltage of the adjustment voltage value is applied for the minimum length of time necessary to reduce the difference in the analysis conditions.

[0142] (Item 8) In the mass spectrometer according to any one of Items 1 to 7, the adjustment value may be common to a plurality of types of target ions.

[0143] According to the mass spectrometer described in item 8, the adjustment value can be easily set. (Item 9) In the mass spectrometer described in any one of Items 1 to 8, application of the voltage of the first adjustment voltage value may be started after the supply of gas to the collision cell is started.

[0144] According to the mass spectrometer described in item 9, the voltage of the adjustment voltage value is applied for the minimum period required.

[0145] (Item 10) In the mass spectrometer described in any one of Items 1 to 9, when detecting a second target ion after detecting the first target ion, the controller may further apply a voltage of the first adjustment voltage value after detecting the first target ion and before detecting the second target ion when gas is supplied to the collision cell in detecting the second target ion.

[0146] According to the mass spectrometer described in paragraph 10, charge-up that occurs in an analysis without gas can be more reliably generated each time detection is performed in an analysis with gas.

[0147] (Item 11) In the mass spectrometer described in any one of Items 1 to 9, when detecting a second target ion after detecting the first target ion, the controller may detect the second target ion without applying a voltage of the first adjustment voltage value after detecting the first target ion, even when gas is supplied to the collision cell in the detection of the second target ion.

[0148] According to the mass spectrometer described in item 11, the voltage applied at the adjustment voltage value is kept to a minimum necessary level.

[0149] (Item 12) In one aspect, a method for controlling a mass spectrometer includes: a plasma ion source that ionizes a sample with plasma ions; a mass filter that selectively passes target ions having a specific mass-to-charge ratio from the ionized sample; a detector that detects the target ions; and a collision cell provided between the plasma ion source and the mass filter. The control method includes the steps of: determining whether to supply gas to the collision cell in detecting a first target ion; and, if it is determined that gas should be supplied to the collision cell in detecting the first target ion, applying a voltage of a first adjustment voltage value, which is obtained by adding an adjustment value to a first detection voltage value corresponding to the first target ion, to an electrode located downstream of the collision cell in the direction of ion travel in the mass spectrometer before detecting the first target ion; and applying a voltage of the first detection voltage value to the electrode in detecting the first target ion. The adjustment value may be a value representing a polarity opposite to that of the first target ion.

[0150] According to the method for controlling a mass spectrometer described in paragraph 12, in an analysis in the mass spectrometer, there are two cases where gas is not introduced into the collision cell and when gas is introduced. R The difference in analytical conditions between the two cases is small.

[0151] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. Furthermore, it is intended that each technique in the embodiments can be implemented alone or, if necessary, in combination with other techniques in the embodiments to the extent possible. [Explanation of symbols]

[0152] 1 ionization chamber, 2 first vacuum chamber, 3 second vacuum chamber, 4 third vacuum chamber, 5 ion source, 6 sampling cone, 7 skimmer cone, 8 lead-in electrode, 10 ion lens, 10A front electrode, 10B rear electrode, 11 collision cell, 12, 19B, 20B entrance electrodes, 13 exit electrode, 14 ion guide, 15 axial bending electrode, 16 mass filter, 16A pre-rod electrode, 16B main rod electrode, 17 ion detector, 18 ion optical axis, 19A axial bending exit electrode, 100 mass analyzer.

Claims

1. a plasma ion source for ionizing a sample with plasma ions; a mass filter that selectively passes target ions having a specific mass-to-charge ratio from the ionized sample; a detector for detecting the target ions; a collision cell disposed between the plasma ion source and the mass filter; a gas supply unit that supplies a gas to the collision cell; a controller that controls the value of the voltage applied to the electrode; When gas is supplied from the gas supply unit to the collision cell in detecting a first target ion, the controller before detecting the first target ion, applying a voltage of a first adjustment voltage value obtained by adding an adjustment value to a first detection voltage value corresponding to the first target ion to an electrode located downstream of the collision cell in the direction of ion travel, In detecting the first target ion, a voltage of the first detection voltage value is applied to an electrode located downstream of the collision cell in the direction of ion travel; A mass spectrometer, wherein the adjustment value is a value representing a polarity opposite to that of the first target ion.

2. 2. The mass spectrometer according to claim 1, wherein the electrode located downstream of the collision cell in the direction of ion travel includes a rod electrode of the mass filter.

3. an exit electrode disposed between the collision cell and the mass filter; The mass spectrometer according to claim 1 , wherein the electrodes located downstream of the collision cell in the direction of ion travel include the exit electrode.

4. an entrance electrode disposed between the mass filter and the detector; The mass spectrometer according to claim 1 , wherein the electrodes located downstream of the collision cell in the direction of ion travel include the entrance electrode.

5. the ion optical axis in the mass filter is located at a different location in a given direction relative to the ion optical axis in the collision cell; a bending electrode provided between the collision cell and the mass filter for connecting an ion optical axis in the collision cell and an ion optical axis in the mass filter in the given direction; The mass spectrometer according to claim 1 , wherein the electrode located downstream of the collision cell in the direction of ion travel includes the curved electrode.

6. The mass spectrometer according to claim 1 , wherein the absolute value of the adjustment value decreases as the period of use of the mass spectrometer increases.

7. 3. The mass spectrometer according to claim 2, wherein the length of time during which the voltage of said first adjustment voltage value is applied to said rod electrodes becomes shorter as the period of use of said mass spectrometer becomes longer.

8. The mass spectrometer according to claim 1 , wherein the adjustment value is common to a plurality of types of target ions.

9. 2. The mass spectrometer according to claim 1, wherein application of the voltage of the first adjustment voltage value is started after supply of gas to the collision cell is started.

10. When detecting a second target ion after detecting the first target ion, when gas is supplied to the collision cell in the detection of the second target ion, the controller further applies a voltage of a second adjustment voltage value obtained by adding a second adjustment value to a second detection voltage value corresponding to the second target ion to an electrode located downstream of the collision cell in the ion traveling direction after the detection of the first target ion and before the detection of the second target ion, The mass spectrometer of claim 1 , wherein the second adjustment value is a value representing a polarity opposite to that of the second target ion.

11. when detecting a second target ion after detecting the first target ion, the controller detects the second target ion without applying a voltage of a second adjustment voltage value obtained by adding a second adjustment value to a second detection voltage value corresponding to the second target ion to an electrode located downstream of the collision cell in the ion traveling direction after detecting the first target ion, even when a gas is supplied to the collision cell in the detection of the second target ion, The mass spectrometer of claim 1 , wherein the second adjustment value is a value representing a polarity opposite to that of the second target ion.

12. A method for controlling a mass spectrometer, comprising: The mass spectrometer is a plasma ion source for ionizing a sample with plasma ions; a mass filter that selectively passes target ions having a specific mass-to-charge ratio from the ionized sample; a detector for detecting the target ions; a collision cell disposed between the plasma ion source and the mass filter; determining whether to supply gas to the collision cell in detecting a first ion of interest; when it is determined that gas is to be supplied to the collision cell in the detection of the first target ion, applying a voltage of a first adjustment voltage value obtained by adding an adjustment value to a first detection voltage value corresponding to the first target ion to an electrode located downstream of the collision cell in the direction of ion travel in the mass spectrometer before the detection of the first target ion; applying a voltage of the first detection voltage value to the electrode in detecting the first target ion; A method for controlling a mass spectrometer, wherein the adjustment value is a value that represents a polarity opposite to that of the first target ion.

Images