Mass spectrometer and display method

Abstract

In the present invention, an ion source generates a first element ion to be measured by ionizing a target element contained in a sample. A separation unit separates an ion generated in an ion source by m / z. A detector detects the separated ion. A control device displays, on a display device, a plurality of second images (Im12-Im15) together with a first image (Im11). The first image (Im 11) includes a spectrum around a first m / z of the first element ion. Each of the second images (Im12-Im15) includes the spectrum around a second m / z of a second element ion, the second element ion constitutes an ion of the same m / z which has the same m / z as the first element ion.

Description

Mass spectrometer and display method

[0001] The present disclosure relates to mass spectrometers and display methods, and more particularly to techniques for displaying spectra.

[0002] ICP mass spectrometers (hereinafter referred to as "ICP-MS") that use an inductively coupled plasma (ICP) ion source as an ion source are known. In ICP-MS, elements contained in a sample are ionized in the ion source, and the ionized elements are separated by mass-to-charge ratio (hereinafter also referred to as "m / z") and then detected by a detector.

[0003] In ICP-MS, a phenomenon called spectral interference easily occurs, in which the signal intensity of an element ion to be measured (hereinafter also referred to as "first element ion") overlaps with the signal intensity of a coexisting ion derived from a coexisting element that coexists with the first element ion in the ion source. Hereinafter, this spectral interference will also be simply referred to as "interference." Various methods have been used to reduce this interference.

[0004] Japanese Patent No. 6636746 (Patent Document 1) discloses a method for reducing the interference by bringing a reactive gas obtained by vaporizing a liquid substance into contact with an ion beam.

[0005] Patent No. 6636746

[0006] However, even if a method for reducing the interference is implemented as in Patent Document 1, it is difficult to know whether the interference has actually been sufficiently eliminated. More specifically, it is difficult to determine whether the signal intensity at the first m / z corresponding to the first element ion consists only of the signal intensity of the first element ion or also includes the signal intensity of coexisting ions.

[0007] Among the coexisting ions, element ions (hereinafter also referred to as "second element ions") that may cause interference include, for example, multiple types of element ions that generate oxides, sulfides, chlorides, hydrides, divalent ions, etc. Typically, a user needs to check whether each of the multiple types of second element ions is present during measurement and / or the magnitude of the corresponding signal intensity. More specifically, a user needs to check the signal intensity of the second m / z corresponding to each of the multiple types of second element ions one by one. However, checking the signal intensities of the multiple types of second m / z one by one is time-consuming for the user.

[0008] A first aspect of the present invention relates to a mass spectrometer including an ion source, a separation unit, a detector, a control device, and a display device. The ion source generates first element ions to be measured by ionizing a target element contained in a sample. The separation unit separates the ions generated by the ion source by m / z. The detector detects the separated ions. The control device displays, on the display device, a first image including a spectrum of the first element ion around a first m / z, and a second image including a spectrum of a second element ion around a second m / z, which constitutes an identical m / z ion having the same m / z as the first element ion.

[0009] Another aspect of the present invention relates to a method for displaying spectra obtained by separating and detecting ions generated in an ion source by m / z, the method comprising the steps of: displaying a first image including a spectrum around a first m / z of a first element ion generated by ionizing a target element contained in a sample; and displaying a plurality of second images including a spectrum around a second m / z of a second element ion that can generate an ion having the same m / z as the first element ion.

[0010] According to the present disclosure, a user can easily determine whether the signal intensity of a first m / z corresponding to a first element ion also includes the signal intensities of each of a plurality of types of second element ions.

[0011] Fig. 1 is a diagram schematically showing an example of the overall configuration of an ICP-MS. Fig. 2 is a diagram showing an overall spectrum. Fig. 3 is a diagram showing a partial spectrum. Fig. 4 is a diagram for explaining interference due to ions of the same m / z. Fig. 5 is a diagram showing a display screen according to a comparative example. Fig. 6 is a diagram showing a display screen according to a comparative example. Fig. 7 is a diagram showing a display screen according to an embodiment. Fig. 8 is a flowchart showing display processing according to an embodiment. Fig. 9 is a diagram showing a display screen according to a modified example.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention 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.

[0013] [1. Overall Configuration of ICP-MS] Figure 1 is a diagram showing a schematic diagram of an example of the overall configuration of an ICP-MS 100. In one embodiment, the ICP-MS 100 ionizes elements in a liquid sample using a plasma gas such as argon (Ar) gas, and then separates and detects the ions according to m / z. The ICP-MS 100 includes an ion source 1, a collision cell / reaction cell 2, an energy barrier-forming electrode 3, a separator 4, a detector 5, a voltage generator 6, a controller 7, and a gas supplier 8. The ICP-MS 100 also includes an ionization chamber 10, a vacuum chamber 11 having a sampling cone 14 formed between the ionization chamber 10 and the vacuum chamber 12, a skimmer 15 formed between the vacuum chamber 11 and the vacuum chamber 12, and a vacuum chamber 13. The ICP-MS 100 further includes a pull-in electrode 16 and an ion lens 17 installed in the vacuum chamber 12.

[0014] The ICP-MS 100 is configured such that the inside of the ionization chamber 10 is an atmospheric pressure atmosphere, and the degree of vacuum increases in the order of vacuum chamber 11, vacuum chamber 12, and vacuum chamber 13 from the ionization chamber 10 side. The ion source 1 is disposed in the ionization chamber 10, the collision cell / reaction cell 2 and the energy barrier forming electrode 3 are disposed in the vacuum chamber 12, and the separation unit 4 and detector 5 are disposed in the vacuum chamber 13.

[0015] The collision cell / reaction cell 2, the separator 4 and the detector 5 are arranged on the optical axis A1 of the ion source 1.

[0016] The ion source 1 ionizes elements contained in a sample using plasma. More specifically, the ion source 1 generates first element ions to be measured by ionizing a target element contained in the sample. When the target element includes multiple isotopes (elements with different mass numbers m), first element ions having different m / z values ​​are generated for each isotope. The ion source 1 includes an autosampler 1a and a plasma torch 1b. Although not shown, the ion source 1 further includes a nebulizer gas supply source, a plasma gas supply source, and a cooling gas supply source for supplying various gases to the plasma torch 1b.

[0017] The autosampler 1a introduces a sample into the plasma torch 1b. In one embodiment, the plasma torch 1b converts argon gas into a plasma state by high-frequency inductive coupling, and the elements in the sample introduced by the autosampler 1a are ionized by the plasma. Specifically, in the argon plasma, the elements in the sample typically become monovalent ions carrying a single charge. However, a small percentage of atoms become divalent ions. Furthermore, a small percentage of atoms recombine in the plasma to form molecules.

[0018] Although not shown, the plasma torch 1b includes a sample tube through which a liquid sample atomized by a nebulizer gas flows, a plasma gas tube formed around the sample tube, and a cooling gas tube formed around the plasma gas tube. In one embodiment, the plasma gas is argon gas.

[0019] The vacuum chamber 11 is formed between the sampling cone 14 and the skimmer 15. The sampling cone 14 and the skimmer 15 each have a substantially conical shape and have an opening at the apex of the cone that is configured to allow particles to pass through.

[0020] The sampling cone 14 is formed so that its opening is positioned on the optical axis A1 that passes through the tip of the plasma torch 1 b. Ions generated by the plasma torch 1 b and particles such as neutral particles generated during the plasma generation process pass through the opening of the sampling cone 14 and are taken into the vacuum chamber 11.

[0021] The skimmer 15 is formed so that its opening is positioned on the optical axis A1. Particles in the vacuum chamber 11 pass through the opening of the skimmer 15 and are taken into the vacuum chamber 12.

[0022] Installed in vacuum chamber 12 are pull-in electrode 16, ion lens 17, collision cell / reaction cell 2, and energy barrier forming electrode 3. Pull-in electrode 16, ion lens 17, and energy barrier forming electrode 3 are each disk-shaped electrodes with approximately circular openings. Pull-in electrode 16, ion lens 17, and energy barrier forming electrode 3 are each disposed in vacuum chamber 12 so that their openings are positioned on optical axis A1.

[0023] The collision cell / reaction cell 2 includes an entrance electrode 21, an exit electrode 22, and an ion guide 23. The entrance electrode 21 and the exit electrode 22 are each a disk-shaped electrode with a substantially circular opening formed therein. The opening formed in the entrance electrode 21 corresponds to the entrance of the collision cell / reaction cell 2, and the opening formed in the exit electrode 22 corresponds to the exit of the collision cell / reaction cell 2.

[0024] The collision cell / reaction cell 2 is disposed in the vacuum chamber 12 so that the opening of the entrance electrode 21, which corresponds to the entrance, and the opening of the exit electrode 22, which corresponds to the exit, are each positioned on the optical axis A1. The ion guide 23 is composed of a plurality of rod electrodes arranged parallel to the optical axis A1.

[0025] Particles in the vacuum chamber 11 pass through the opening of the skimmer 15 , the opening of the pull-in electrode 16 , the opening of the ion lens 17 and the opening of the entrance electrode 21 in this order, and enter the collision cell / reaction cell 2 .

[0026] In addition to the first element ions to be measured, coexisting ions derived from coexisting elements coexisting with the first element ions in the ion source are also captured in the vacuum chamber 12. The coexisting ions include those derived from gases such as Ar gas used to generate plasma in the ion source 1, impurities in the sample, additives in the sample, and the like. Examples of coexisting ions include oxides, sulfides, chlorides, hydrides, and divalent ions. For example, when water is present in the sample, oxides and / or hydrides may be generated in the plasma. Furthermore, for example, when a solid sample is dissolved in an aqueous sulfuric acid solution or an aqueous hydrochloric acid solution, sulfides, chlorides, hydrides, and / or oxides may be generated in the plasma. In this way, coexisting ions derived from elements present in the sample and the environment are captured in the vacuum chamber 12.

[0027] The collision cell / reaction cell 2 is a cell for separating coexisting ions from the first element ions by bringing ions taken in from an inlet of the collision cell / reaction cell 2 into contact with a predetermined gas supplied from a gas supply unit 8. For example, in the collision cell / reaction cell 2, the coexisting ions are decomposed by the predetermined gas.

[0028] The vacuum chamber 13 has an opening formed at a position opposite to the opening of the energy barrier forming electrode 3. In the vacuum chamber 13, the separator 4 and the detector 5 are arranged on the optical axis A1.

[0029] The separator 4 separates the ions generated by the ion source 1 into ions of each m / z. The separator 4 is, for example, a quadrupole mass filter, and includes a pre-rod electrode 41 and a main rod electrode 42. Ions of an m / z corresponding to the voltage applied to the separator 4 pass through the separator 4 and reach the detector 5. Therefore, by changing the voltage of the separator 4, the ions incident on the separator 4 are separated into each m / z.

[0030] The detector 5 detects the ions separated by the separator 4. The detector 5 is, for example, a secondary electron multiplier, and generates a detection signal corresponding to the amount of ions that have reached it, and sends it to the control device 7.

[0031] The control device 7 includes a processor 71 which is a calculation unit, a memory 72 , an input device 73 , and a display device 74 .

[0032] The processor 71 includes, for example, a CPU (Central Processing Unit). The processor 71 reads and executes a program stored in the memory 72 to control the operation of each part of the ICP-MS 100. For example, by executing the program, the processor 71 controls the voltage generating unit 6 to control the voltage applied to each part. Note that while the example in FIG. 1 illustrates a configuration in which there is a single processor 71, the ICP-MS 100 may also be configured to have multiple processors.

[0033] The memory 72 is realized by a non-volatile storage device such as a read-only memory (ROM) or a hard disk. The memory 72 stores programs executed by the processor 71, data used by the processor 71, etc. The programs may be stored in a non-transitory computer-readable medium.

[0034] The input device 73 is typically a mouse, a keyboard, various buttons, a touch panel, etc. The input device 73 receives, through user operation, information necessary for controlling the operation of the ICP-MS 100 and information necessary for the processing performed by the control device 7.

[0035] The display device 74 is typically a liquid crystal monitor or the like, and displays information input by the user via the input device 73, as well as analysis results, analysis conditions, etc. The display device 74 may be configured with a printer and paper, and may display analysis conditions, etc. by printing the analysis results, etc. on paper.

[0036] [2. ICP-MS Spectrum According to the Embodiment] The ICP-MS 100 can perform mass separation of ions within a user-specified m / z range and then detect them with a detector. In one embodiment, the detection results are displayed in a spectral format, with m / z on the horizontal axis and signal intensity on the vertical axis, as shown in Figures 2 and 3. An ICP-MS spectrum is also referred to as a "profile" by those skilled in the art. Herein, a portion of high signal intensity corresponding to a specific m / z is also referred to as a "peak." The ICP-MS spectrum may display waveform peaks, as in the example of Figure 3, or may represent each peak as a bar graph with no width and only height. Figure 2 shows an example of a spectrum within an m / z range specified by a user for analysis. Hereinafter, this "spectrum within an m / z range specified by a user for analysis" will also be referred to as the "overall spectrum." In the example of Figure 2, an overall spectrum from m / z 5 to 260 is shown. Figure 3 shows an example of a partial spectrum, which is a portion of the overall spectrum. In the example of Figure 3, a spectrum around m / z 120 is shown. The user checks the signal intensity of the first element ion by referring to a partial spectrum including a spectrum around the first m / z of the first element ion to be measured. For example, by referring to FIG. 3, the user can check the signal intensity of Sn ＋ The signal intensity of m / z 120 corresponding to the ion can be confirmed. Then, the user can confirm the presence or absence and / or amount of the first element in the sample based on the signal intensity. The first element is an element corresponding to the first element ion. For example, the user can confirm the presence or absence and / or amount of the first element Sn in the sample based on the signal intensity of m / z 120.

[0037] In this specification, the spectrum around the first m / z refers to a partial spectrum including the peak of the first m / z. In one embodiment, the spectrum around the first m / z is displayed so that the first m / z is located at or near the center of the horizontal axis, making the peak of the first m / z easier to observe. In the example of Im91, the peak of the first m / z is underlined to emphasize the first m / z. The spectrum around the first m / z includes an m / z range relatively close to the first m / z but does not include an m / z range relatively far from the first m / z. Preferably, the m / z range included in the spectrum around the first m / z is appropriately adjusted so that the peak of the first m / z is easier to observe. The spectrum around the first m / z is also simply referred to as the "spectrum of the first m / z" or "profile of the first m / z" by those skilled in the art.

[0038] [3. Spectral Interference Due to Coexisting Ions] However, in actual ICP-MS, there is a possibility that coexisting ions (hereinafter also referred to as "same m / z ions") that have the same m / z as the first element ion may exist, causing spectral interference. In this case, the amount of the first element in the sample cannot be measured from the signal intensity of the first m / z peak.

[0039] 4 is a diagram for explaining interference caused by ions with the same m / z. In the example of FIG. 4, the first element ion to be measured is a singly charged iron ion with a mass number of 56. ５６ Fe ＋ In this specification, p A q＋ (p and q are natural numbers) represents a q-valent cation of an atom having the chemical formula A and mass number p. ５６ Fe ＋ The m / z of is m / z = 56 / 1 = 56. On the other hand, as mentioned above, if the sample contains water, oxides may be generated as coexisting ions. Since oxygen has a mass number of 16, an element with a mass number of 40 (for example ４０ When a monovalent ion is formed with Ar, ５６ Fe ＋ In other words, it is a singly charged ion in which argon with a mass number of 40 and oxygen with a mass number of 16 are bonded in a 1:1 ratio. ４０ Ar１６ O ＋ The m / z of is also m / z = (40 + 16) / 1 = 56. ４０ The element ions such as Ar that may cause spectral interference with the first element are called second element ions. As described above, the coexisting ions include oxides derived from the second element ions. ４０ Ar １６ O ＋ When the signal intensity at m / z=56 is ５６ Fe ＋ Strength due to ４０ Ar １６ O ＋ In other words, the peak at m / z=56 contains the intensity of the target molecule. ５６ Fe ＋ and the component corresponding to ４０ Ar １６ O ＋ Therefore, in such a case, the exact amount of iron in the sample cannot be measured by referring to the signal intensity of m / z=56. ４０ Ar １６ O ＋ To accurately measure iron in a sample, it is necessary to find experimental conditions that can eliminate the interference and measure the sample again under those experimental conditions.

[0040] [4. Interference Confirmation Screen for Comparative Example] Existing ICP-MS systems have attempted to physically reduce spectral interference by providing a collision cell / reaction cell 2, but the user must confirm whether spectral interference is actually suppressed. To determine whether or not a first element ion has spectral interference, the user must also confirm the spectrum of the second element ion that constitutes the same m / z ion. In this specification, the presence or absence of interference refers to whether the interference is greater than a predetermined value (described in detail below). More specifically, in this specification, the presence or absence of interference refers to whether or not the influence of the second element ion is sufficiently small in the quantification of the first element in a sample, in other words, whether or not the influence is negligible. Therefore, in this specification, "no interference" includes both cases where there is no actual interference (the amount of interference is zero) and cases where the interference is negligibly small. Examples of cases where the interference is negligibly small include, but are not limited to, the following first and second examples. The first example is a case where the amount of interference (described in detail below) is equal to or less than the magnitude of the variation in signal intensity. The second example is when the amount of interference is a predetermined value (for example, 5% or less of the signal intensity of the first m / z).

[0041] When there is no interference, the signal intensity of the first m / z can be considered to correspond only to the amount of the first element in the sample, and therefore it is possible to convert the signal intensity of the first m / z into the amount of the first element. Furthermore, by utilizing a calibration curve showing the relationship between the signal intensity of the first m / z and the concentration of the first element in the sample, it is possible to determine the concentration of the first element in the sample from the signal intensity of the first m / z. On the other hand, when there is interference, the signal intensity of the first m / z includes a non-negligible amount of intensity due to ions with the same m / z, and therefore the signal intensity of the first m / z cannot be converted into the amount of the first element. Similarly, it is difficult to determine the concentration of the first element from the signal intensity of the first m / z.

[0042] 5 is a diagram showing a display screen according to a comparative example. An image Im9 is displayed on the display screen in FIG. 5. The image Im9 includes an image Im91 and an image Im92.

[0043] Image Im91 shows the spectrum around the first m / z of the first element ion. In the example of FIG. 5, the first element ion has a mass number of 114. １１４ Cd ＋ By referring to image Im91, the user can confirm the signal intensity of the peak at m / z 114, which corresponds to the first element ion.

[0044] Next, a screen for the user to check for the presence or absence of interference in the comparative example will be described. When the user selects list Ly91 in image Im91, image Im93 in FIG. 6 is displayed. In image Im93, the user selects the type of identical m / z ion for which interference is to be checked. The type of identical m / z ion selected in image Im93 is, for example, any of oxide, sulfide, chloride, hydride, and divalent ion.

[0045] When one type of identical m / z ion is selected in image Im93 of Fig. 6 , image Im92 of Fig. 5 is displayed. The second element ion corresponding to image Im92 is, for example, any of an ion of an element that reacts with oxygen to form an oxide, an ion of an element that combines with sulfur to form a sulfide, an ion of an element that reacts with chlorine to form a chloride, an ion of an element that reacts with hydrogen to form a hydride, and an ion of an element that becomes a divalent ion. In one embodiment, when "oxide" is selected in image Im93, the spectrum of the second element ion that constitutes the identical m / z ion of the oxide is displayed in image Im92. More specifically, in image Im92 of Fig. 5 , an oxygen ion having a mass number of 16 is displayed. １６ Bonds with O, １１４ Cd ＋The spectrum around the second m / z of the second element ion constituting the ion with the same m / z as the first element ion is displayed. Here, the second m / z is 114-16=98. Therefore, the spectrum around m / z 98 is displayed in image Im92. In other words, the spectrum of the second element ion with mass number 98 is displayed. The presence or absence of interference can be determined visually by checking the spectrum of the first element ion and the spectrum of the second element ion. More specifically, the presence or absence of interference is determined based on the ratio of the signal intensity of the second element ion that causes the interference to the signal intensity of the first element ion that is subject to the interference. For example, in image Im92, if the ratio of the signal intensity of m / z 98 to the signal intensity of m / z 114 is greater than a predetermined value, the second element ion with atomic weight 98 and the second element ion with atomic weight 98 are displayed. １６ The same m / z ion with O bonded １１４ Cd ＋ Conversely, if the ratio of the signal intensity of m / z 98 to the signal intensity of m / z 114 is smaller than a predetermined value, it is determined that the second element ion with an atomic weight of 98 is interfering with the second element ion. １６ The same m / z ion with O bonded １１４ Cd ＋ A specific method for quantifying interference will be described later.

[0046] Similarly, the user checks the spectrum of the second element ion that constitutes the same m / z ion such as sulfide, chloride, hydride, divalent ion, etc., which may interfere with the spectrum of the first element ion, and determines whether the same m / z ion such as sulfide, chloride, hydride, divalent ion, etc. １１４ Cd ＋ It is determined whether or not there is interference.

[0047] However, as in the comparative example, displaying and checking the spectra of the corresponding second element ions one by one to check whether or not there is interference from the same m / z ions is time-consuming for the user. Furthermore, for the second element ions determined to have interference, estimating the element type from the mass number is also time-consuming for the user. In this specification, the term "element type" refers to element-specific information expressed by the element name (e.g., cadmium) and / or chemical formula (e.g., Cd).

[0048] [5. Interference Confirmation Screen According to the Embodiment] Therefore, the ICP-MS 100 according to the present embodiment displays a screen that allows the presence or absence of interference from multiple types of ions with the same m / z to be confirmed all at once. More specifically, spectra of multiple second element ions corresponding to multiple types of ions with the same m / z are displayed on a single screen. In addition, the type of element that is likely to correspond to each second element ion spectrum is also displayed. This allows the user to quickly and accurately determine the second element ions that interfere with the peak of the first element ion and identify the type of element of the second element ion.

[0049] 7 is a diagram showing a display screen according to the embodiment. An image Im1 is displayed on the display screen in Fig. 7. The image Im1 includes a first image Im11 and a plurality of second images Im12 to Im15.

[0050] The first image Im1 includes a spectrum around the first m / z of the first element ion. In the example of FIG. 7, the first element ion is １１１ Cd ＋ By referring to image Im11, the user can confirm the signal intensity of m / z 111 corresponding to the first element ion.

[0051] The second images Im12 to Im15 include spectra of second element ions around the second m / z, which constitute identical m / z ions having the same m / z as the first element ions. In other words, each second image includes a spectrum around the second peak of the second element ions that may interfere with the first peak of the first element ions. Each of the multiple identical m / z ions is, for example, an oxide, sulfide, chloride, hydride, or divalent ion. As described above, it is possible to comprehensively display spectra of second element ions corresponding to types of identical m / z ions that may occur in sample measurement.

[0052] In the spectra contained in the first image Im1 and the second images Im12 to Im15, the horizontal axis represents m / z and the vertical axis represents signal intensity (kcps). The vertical axis may represent the actual observed absolute signal intensity or the relative intensity obtained by dividing the absolute intensity by a predetermined value. However, it is preferable that the vertical axes of the spectra contained in the first image Im1 and the second images Im12 to Im15 be displayed on a common scale. Specifically, it is preferable that the same vertical axis value in the spectra of the first image Im1 and the second images Im12 to Im15 corresponds to the same absolute intensity. This configuration makes it possible to easily identify second element ions that interfere with first element ions by comparing the spectra of the first image Im1 and the second images Im12 to Im15. In the example of FIG. 7 , the vertical axes of the spectra contained in the first image Im1 and the second images Im12 to Im15 represent relative intensity when the maximum peak in the entire spectrum is set to 1.0.

[0053] In one embodiment, a user selects multiple types of identical m / z ions for which the user wishes to check for interference and registers them in the control device 7. The control device 7 then displays, as the second image, the spectrum of a second element ion corresponding to the type of identical m / z ions for which the user wishes to check for interference. In another embodiment, the type of identical m / z ions for which the user wishes to check for interference may be set in the control device 7 at the time of shipment of the ICP-MS 100, and the control device 7 may display the spectrum of the corresponding second element ion as the second image.

[0054] In the example of FIG. 7, the spectra of four types of second element ions that form oxides, sulfides, chlorides and divalent ions, respectively, are displayed.

[0055] More specifically, in the second image Im12 of FIG. 7, oxygen with mass number 16 １６ Bonds with O, １１１ Cd ＋The spectrum around the second m / z of the second element ion constituting the same m / z ion for the second image Im12 is displayed. Here, the second m / z is 111-16=95. Therefore, the spectrum of the second element ion with mass number 95 is displayed in the second image Im12. In the second image Im12, if the signal intensity of m / z 95 is relatively large compared to the signal intensity of m / z 111, the spectrum of the second element ion with mass number 95 is displayed. １６ The same m / z ion with O bonded １１１ Cd ＋ Conversely, if the signal intensity of m / z 95 is relatively small relative to the signal intensity of m / z 111 in the second image Im12, it can be determined that the second element ion with mass number 95 is interfering with the １６ O-bonded ions of the same m / z １１１ Cd ＋ It can be determined that the interference with the second element ions is sufficiently small and negligible. In other words, the influence of the interference by the second element ions is sufficiently small and negligible. A method for quantifying the influence of the interference by the second element ions will be described later.

[0056] In the second image Im13, sulfur with a mass number of 32 ３２ binds to S, １１１ Cd ＋ The spectrum around the second m / z of the second element ion that constitutes the same m / z ion for the first image Im1 is displayed. Here, the second m / z is 111-32=79. Therefore, the spectrum of the second element ion with mass number 79 is displayed in the second image Im13.

[0057] In the second image Im14, chlorine with a mass number of 35 ３５ It bonds with Cl, １１１ Cd ＋ The spectrum of the second element ion having the same m / z as the first element ion is displayed around the second m / z. Here, the second m / z is 111-35=76. Therefore, the spectrum of the second element ion having the mass number of 76 is displayed in the second image Im14.

[0058] In the second image Im15, １１１ Cd ＋The spectrum of the doubly charged ions that make up the same m / z ion for the second image Im15 is displayed. Here, the second m / z is 111 × 2 = 222. Therefore, the spectrum of the second element ion with mass number 222 is displayed in the second image Im15.

[0059] The user can observe the second images Im12 to Im15 at once by simultaneously displaying the second images Im12 to Im15 on the display device 74. This allows the user to easily identify ions (hereinafter also referred to as "interfering element ions") that are thought to be the cause of spectral interference with the first element ions, among the second element ions corresponding to the second images.

[0060] In one embodiment, the user can determine whether or not an ion is an interfering element ion by referring to the signal intensity of the second m / z in the second images Im12 to Im15. More specifically, the user can quantitatively determine whether or not an ion is an interfering element ion based on the signal intensity of the first element ion, the signal intensity of the second element ion, and the production ratio of ions with the same m / z depending on the type of second element ion. This will be explained in more detail below.

[0061] Identical m / z ions are generated at a predetermined ratio (production ratio) depending on the type of second m / z ion. For example, a predetermined type of second element ion generates an oxide at a predetermined ratio p. Generally, p<<1, e.g., p=0.001. In this case, the signal intensity of the oxide derived from the predetermined second element ion calculated from the signal intensity s2 of the predetermined second element ion is p×s2. In this specification, p×x2 is referred to as the amount of interference of the second element ion with the first element ion. If the amount of interference is less than a predetermined ratio with respect to the signal intensity s1, it is determined that there is no interference, and if it is equal to or greater than the predetermined ratio, it is determined that there is interference.

[0062] Specifically, when the ratio of p × s2 to the signal intensity s1 of the first element ion is equal to or greater than a predetermined value k, and the mathematical formula {(p × s2) / s1}≧k holds, it can be determined that the first element ion is being interfered with by an identical m / z ion derived from the second element ion. In other words, the second element ion is an interfering element ion. On the other hand, when the ratio of p × s2 to the signal intensity s1 of the first element ion is less than a predetermined value k, and the mathematical formula {(p × s2) / s1}<k holds, it can be determined that the first element ion is not being interfered with by an identical m / z ion derived from the second element ion. More precisely, even if the identical m / z ion derived from the second element ion is interfering, the interference is negligibly small. Therefore, the second element ion is determined not to be an interfering element ion.

[0063] The quantitative determination of the interfering element ions may be performed automatically by the processor 71. In this case, the user can be saved the trouble of manually calculating and determining. Naturally, the quantitative determination of the interfering element ions may also be performed manually by the user. Furthermore, users who have extensive experience in determining interference by ICP-MS are accustomed to visually determining the presence or absence of interference by looking at the signal intensity of the first m / z in the first image and the signal intensity of the second m / z in the second image, and such visual determination may be easier than quantitatively determining the interfering element ions. In some cases, the generation ratio does not necessarily need to be an accurate value, but may be an approximate number or an estimate.

[0064] For example, if the signal intensity s1 of the first element ion is 5000 and the signal intensity s2 of the second element ion is 1000, the effect of interference is considered to be negligibly small. The reason for this is explained below. Assuming that the production ratio of ions of the same m / z from the second element ion is 5%, the amount of interference, which is the quotient of the signal intensity S2 and the production ratio, is calculated as 1000 x 0.05 = 50. The amount of interference, 50, is 1% of the signal intensity s1 = 5000. Since this 1% is equal to or less than the signal variation, the interference is determined to be negligibly small.

[0065] On the other hand, when the signal intensity s1 of the first element ion is 75 and the signal intensity s2 of the second element ion is 1000, the influence of interference is considered to be too large to be ignored. The reason for this is explained below. Assuming that the production ratio of identical m / z ions from the second element ion is 5%, the amount of interference, which is the quotient of the signal intensity S2 and the production ratio, is calculated as 1000 x 0.05 = 50. The amount of interference of 50 is approximately 67% of the signal intensity s1 = 75. In this case, the influence of interference is large, and it cannot be said that the first element ion, which is the ion that is originally intended to be measured, is correctly measured.

[0066] By referring to the second images Im12 to Im15, the user can identify which second element ions are causing interference with the first element ions based on the signal intensity of the second element ions and the production ratio of ions with the same m / z depending on the type of second element ion, as described above.

[0067] Before identifying the interfering element ions based on the above-mentioned production ratio, or instead of identifying the interfering element ions based on the above-mentioned production ratio, the user can refer to the signal intensity of the second m / z in the second images Im12 to Im15 and estimate that the second element ions with relatively high signal intensity are interfering element ions.

[0068] Furthermore, each of the second images Im12 to Im15 also displays the type of the corresponding second element ion, which may include, for example, the name and / or chemical formula of the element.

[0069] In one embodiment, the type of second element ion corresponding to each of the second images Im12 to Im15 is determined by the processor 71. For example, the processor 71 displays the type of element ion having a high abundance ratio at the second m / z corresponding to each second image as the type of second element ion corresponding to each second image. As a more specific example, the memory 72 stores a table indicating the type of element ion having a high abundance ratio at each m / z, and the processor 71 determines the type of second element ion corresponding to each of the second images Im12 to Im15 based on the table.

[0070] An example of a method by which the processor 71 displays the type of second element ion corresponding to the second image Im12 will be described below. First, since the second m / z corresponding to the second image Im12 is 95, the processor 71 searches the table stored in the memory 72 for the type of element ion with a high abundance ratio at m / z = 95. Then, the processor 71 displays the type of element ion obtained as a result of the search (Am in the example of FIG. 7 ) as the type of second element ion corresponding to Im12.

[0071] In the example of Fig. 7, the chemical formulas of the second element ions Am, Au, Os, and Rn are displayed corresponding to the second images Im12 to Im15, respectively. This allows the user to determine whether the second element ions corresponding to the second images Im12 to Im15 are Am, Au, Os, and Rn. ＋ , Au ＋ , Os ＋ , Rn ＋ Therefore, the user can easily determine that the second element ion is the second element ion. This eliminates the need to look up the type of element corresponding to the mass number of the second image. This allows the user to quickly identify the type of second element ion that causes spectral interference and to search for an experimental method for removing the second element ion.

[0072] As described above, by referring to the display screen of FIG. 7 , it is possible to display a list of spectra of second element ions that may cause spectral interference with the first element ions being measured. Therefore, it is easy to determine whether or not each second element ion causes spectral interference with the first element ions. Furthermore, it is easy to identify the type of second element ion (e.g., the name and / or chemical formula of the element) that causes spectral interference with the first element ions. Therefore, the user can quickly try conditions that reduce the interference of the second element ions. This shortens the time required to accurately quantify the first element ions with reduced interference from the second element ions.

[0073] [6. Flowchart] Fig. 8 is a flowchart showing a display process according to an embodiment. More specifically, Fig. 8 shows a display process of a spectrum obtained by separating and detecting ions generated in an ion source by m / z. The process of Fig. 8 is performed by the processor 71 of the control device 7.

[0074] In step (hereinafter referred to as "ST") 1, the processor 71 acquires an overall profile. In one embodiment, the processor 71 mass-separates and detects ions within an m / z range specified by the user using the input device 73. Furthermore, the processor 71 creates an overall spectrum based on the signal intensity detected for each m / z.

[0075] In ST2, the processor 71 designates a first element ion to be measured. In one embodiment, the processor 71 designates an element ion (e.g., Cd+) input by the user as the first element ion using the input device 73 as the first element ion to be measured. In another embodiment, the user may input a first element to be measured (e.g., Cd element) using the input device 73, and the processor 71 may designate an element ion (e.g., Cd+) corresponding to the first element as the first element ion to be measured.

[0076] In ST3, the processor 71 specifies multiple types of identical m / z ions for which interference is to be determined. In one embodiment, the processor 71 acquires the type of identical m / z ions for which interference is to be determined, selected by the user using the input device 73, and specifies the type of identical m / z ions for which interference is to be determined, selected by the user. The type of identical m / z ions includes, for example, oxides, sulfides, chlorides, hydrides, or divalent ions.

[0077] In ST4, the processor 71 identifies a plurality of second element ions that constitute identical m / z ions having the same m / z as the first element ions. In one embodiment, the processor 71 identifies second element ions that correspond to the type of identical m / z ions selected in ST3. The second element ions include, for example, ions of elements that react with oxygen to form oxides, ions of elements that combine with sulfur to form sulfides, ions of elements that react with chlorine to form chlorides, ions of elements that react with hydrogen to form hydrides, or ions of elements that become divalent ions.

[0078] In ST5, the processor 71 displays a first image including a spectrum around the first m / z of the first element ion. In one embodiment, the processor 71 displays the image Im11 of FIG.

[0079] In ST6, the processor 71 displays a plurality of second images including spectra around the second m / z of the second element ions, and then ends the processing. In one embodiment, the processor 71 displays images Im12 to Im15 in FIG. 7 on the display device 74.

[0080] 8 may be performed in a different order as long as the effect is not affected. For example, steps ST5 and ST6 may be performed simultaneously. Also, for example, step ST5 may be performed between steps ST3 and ST4.

[0081] [7. Display Screen According to Modification] In the ICP-MS according to the modification, the control device 7 identifies interfering element ions among the second element ions that are considered to be the cause of spectral interference with the first element ions. For example, the control device 7 determines the interfering element ions based on the signal intensity of the second element ions and the production ratio of identical m / z ions according to the type of second element ion. Then, the control device 7 specifically displays a second image corresponding to the interfering element ions.

[0082] 9 is a diagram showing a display screen according to a modified example. An image Im2 is displayed on the display screen in Fig. 9. The image Im2 includes a first image Im21 and a plurality of second images Im22 to Im25.

[0083] FIG. 9 shows an example in which the processor 71 determines whether the amount of interference of each second element ion with respect to the signal intensity of the first element ion is equal to or greater than a predetermined value, and identifies an oxide as an interfering element ion. In this case, the second image Im22 corresponding to the oxide is specifically displayed. The phrase "specifically displaying the second image corresponding to the interfering element ion" refers to displaying the second image in a format different from that of second images not corresponding to interfering element ions. "Specifically displaying the second image corresponding to the interfering element ion" includes framing or coloring the second image corresponding to the interfering element ion. In the example of FIG. 9, the second image Im22 is surrounded by a frame Fr91, making it stand out more than the other second images Im23-25. As described above, framing or coloring the second image corresponding to the interfering element ion emphasizes its difference from the other second images, allowing the user to easily identify the second element ion corresponding to the interfering element ion.

[0084] This configuration saves the user the trouble of identifying interfering element ions. Therefore, when the ICP-MS according to the modified example is used, interfering element ions can be identified more quickly than when the ICP-MS according to the embodiment is used.

[0085] Aspects It will be understood by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0086] (Item 1) A mass spectrometer according to one aspect includes an ion source, a separation unit, a detector, a control device, and a display device. The ion source generates first element ions to be measured by ionizing a target element contained in a sample. The separation unit separates the ions generated by the ion source by m / z. The detector detects the separated ions. The control device displays, on the display device, a first image including a spectrum of the first element ion around a first m / z, and a second image including a spectrum of a second element ion around a second m / z, which constitutes an identical m / z ion having the same m / z as the first element ion.

[0087] The mass spectrometer described in paragraph 1 can display multiple spectra of second element ions that may cause spectral interference with the first element ion being measured, making it easy to determine whether the signal intensity of the first m / z corresponding to the first element ion also includes the signal intensities of multiple types of second element ions.

[0088] (Item 2) In the mass spectrometer described in item 1, each of the plurality of second images also includes an indication of the name and / or chemical formula of the corresponding second element ion.

[0089] According to the mass spectrometer described in paragraph 2, the user can avoid the trouble of finding out the type of element corresponding to the mass number corresponding to the second image.

[0090] (Item 3) In the mass spectrometer according to item 1 or 2, the ions of the same m / z are at least one of oxides, sulfides, chlorides, hydrides, and doubly charged ions.

[0091] According to the mass spectrometer described in the third aspect, it is possible to comprehensively display the spectrum of second element ions corresponding to the type of ions with the same m / z that may occur in the measurement of a sample.

[0092] (Item 4) In the mass spectrometer described in any one of items 1 to 3, the control device identifies interfering element ions among the second element ions that are thought to be the cause of spectral interference with the first element ions, and specifically displays a second image corresponding to the interfering element ions.

[0093] According to the mass spectrometer described in paragraph 4, the user can save the trouble of identifying interfering element ions.

[0094] (Item 5) In the mass spectrometer according to item 4, the specific displaying includes surrounding the second image corresponding to the interfering element ion with a frame or coloring it.

[0095] According to the mass spectrometer described in paragraph 5, the second image corresponding to the interfering element ion can be displayed more emphasized than other second images, so that the user can easily recognize the second element ion corresponding to the interfering element ion.

[0096] (Item 6) A display method according to another aspect is a method for displaying spectra obtained by separating and detecting ions generated in an ion source by m / z. The display method includes the steps of: displaying a first image including a spectrum around a first m / z of a first element ion generated by ionizing a target element contained in a sample; and displaying a plurality of second images including a spectrum around a second m / z of a second element ion that can generate an identical m / z ion having the same m / z as the first element ion.

[0097] According to the display method described in paragraph 6, it is possible to display a plurality of spectra of second element ions that may cause spectral interference with the first element ions to be measured. Therefore, it is possible to easily determine whether or not each second element ion causes spectral interference with the first element ions. As described above, the user can easily determine whether or not there is interference.

[0098] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0099] 1 ion source, 1a autosampler, 1b plasma torch, 2 collision cell / reaction cell, 3 energy barrier forming electrode, 4 separation unit, 5 detector, 6 voltage generation unit, 7 control unit, 10 ionization chamber, 11, 12, 13 vacuum chamber, 14 sampling cone, 15 skimmer, 16 pull-in electrode, 17 ion lens, 21 entrance electrode, 22 exit electrode, 23 ion guide, 41 pre-rod electrode, 42 main rod electrode, 71 processor, 72 memory, 73 input device, 74 display device, A1 optical axis, Ly91 list.

Claims

1. A mass spectrometer comprising: an ion source that generates first element ions to be measured by ionizing a target element contained in a sample; a separation unit that separates the ions generated by the ion source by m / z; a detector that detects the separated ions; a control device; and a display device, wherein the control device displays on the display device a first image that includes a spectrum around a first m / z of the first element ion; and a second image that includes a spectrum around a second m / z of a second element ion that constitutes an identical m / z ion having the same m / z as the first element ion.

2. The mass spectrometer of claim 1, wherein each of the plurality of second images also includes an indication of the name and / or chemical formula of the corresponding second element ion.

3. The mass spectrometer according to claim 1 or 2, wherein each of the same m / z ions is an oxide, sulfide, chloride, hydride or doubly charged ion.

4. The mass spectrometer according to claim 1 or 2, wherein the control device identifies interfering element ions among the second element ions that are thought to be the cause of spectral interference with the first element ions, and specifically displays the second image corresponding to the interfering element ions.

5. The mass spectrometer according to claim 4, wherein the specifically displaying includes surrounding the second image corresponding to the interfering element ion with a frame or coloring it.

6. A method for displaying a spectrum obtained by separating and detecting ions generated in an ion source by m / z, comprising the steps of: displaying a first image including a spectrum around a first m / z of a first element ion generated by ionizing a target element contained in a sample; and displaying a plurality of second images including a spectrum around a second m / z of a second element ion that can generate an identical m / z ion having the same m / z as the first element ion.

Images