Ion source, mass spectroscope with the same, and method for generating ion

Abstract

To provide a mass spectroscope capable of reducing influences of an eluent component used for separating a measurement target substance or a device installation environment and performing a high-sensitivity measurement.SOLUTION: A mass spectroscope comprises: a control unit 400 which receives measurement item information 410 including gradient information; a heating and mixing chamber 110 which ionizes an atomized liquid sample; a charge supply unit 120 which generates species ions and supplies the species ions to the heating and mixing chamber 110; a gas supply unit 500 which supplies gas to the charge supply unit 120 and the heating and mixing chamber 110; and moisture supply units 600 and 640 which supply moisture to the heating and mixing chamber 110. The measurement item information 410 includes composition information on the gas supplied from the gas supply unit 500 to the heating and mixing chamber 110. The control unit 400 controls the moisture supply units 600 and 640 so as to supply the moisture to the heating and mixing chamber 110 on the basis of the measurement item information 410, to analyze ions introduced from the heating and mixing chamber 110.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an ion source, a mass spectrometer including the same, and a method for generating ions. [Background technology]

[0002] A typical analytical device for analyzing liquid samples in mass spectrometry is a liquid chromatograph mass spectrometer. Qualitative and quantitative measurements are performed by ionizing the liquid sample sent from the liquid chromatograph and introducing it into the mass spectrometer. Typical ionization methods include atmospheric pressure ionization (hereinafter APCI method) (Non-Patent Document 1) and electrospray ionization (hereinafter ESI method) (Non-Patent Document 2).

[0003] In the APCI method, the measurement sample is first atomized. Since the measurement sample is continuously delivered from the liquid chromatograph along with the solvent at a rate of several to 1000 μL / min, an airflow-assisted spray using nitrogen gas or the like is often used for atomization. The atomized sample is then vaporized by heating, and the vaporized sample is introduced into a corona discharge generated by a needle-shaped electrode and ionized.

[0004] In the ESI method, the liquid sample is atomized by airflow-assisted spraying, as in the APCI method, and a high voltage is applied to the atomizer to turn the mist into charged droplets. Alternatively, a high voltage is applied to the measurement sample itself to atomize it and turn it into charged droplets. The charged droplets are heated and dried to reduce their size, and the excess charge caused by the reduced size of the charged droplets is ionized by Coulomb repulsion, causing ions to desorb from the droplets.

[0005] In general, it is said that the APCI method has a high ionization efficiency for samples with low to medium polarity, while the ESI method has a high ionization efficiency for samples with medium to high polarity, allowing for measurement with good sensitivity. Therefore, those who use liquid chromatograph mass spectrometers must select the ionization method taking into account the polarity of the substance to be measured.

[0006] Patent Document 1 describes the use of gas obtained from various liquid samples as a reactive gas to eliminate the effects of various interfering ions. Patent Document 1 also describes the use of water vapor as a reactive gas in a multipole electrode ion guide in a mass spectrometer.

[0007] Furthermore, Non-Patent Document 3 describes that when a mixture of water and an organic solvent is ionized, in addition to the ions themselves, molecular ions called cluster ions, which are made up of multiple ions bonded together, may be generated. Cluster ions include molecular ions made up of multiple water molecules bonded together and molecular ions made up of water and an organic solvent ion bonded together.

[0008] Furthermore, Non-Patent Document 4 describes that the Penning ionization method is one of the methods for ionizing a target component using a seed ion gas (particularly a rare gas) and discharge. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2017-15676 A [Non-patent literature]

[0010] [Non-Patent Document 1] “Atmospheric pressure ionization mass spectrometry.Corona discharge ion source for use in a liquid chromatograph-mass spectrometer-computer analytical system”,DICarroll,I.Dzidic,RNStillwell,KDHaegele,and EC Horning,Anal.Chem.,47,2369(1975). [Non-Patent Document 2] “Electrospray ionization for mass spectrometry of large biomolecules” JB Fenn, M Mann, CK Meng, SF Wong, CM Whitehouse, Science, 06 Oct 1989:Vol.246, Issue 4926, pp.64-71. [Non-Patent Document 3] Faraday Discuss.,2005,129,231-245“Phase separation of water-alcohol binary mixtures induced by the microheterogeneity” [Non-Patent Document 4] M. Tsuchiya and H. Kuwabara, Anal. Chem., 56, 14 (1984). Summary of the Invention [Problem to be solved by the invention]

[0011] The ionization method used in measurements using a mass spectrometer connected to a liquid chromatograph is basically selected based on the polarity, molecular weight, molecular structure, etc. of the target substance. In practice, however, measurements are often performed using APCI or ESI, and the ionization method with the highest measurement sensitivity is often selected.

[0012] In addition, the ion source has a high-temperature section for drying the liquid sample, making it difficult to replace the ion source for each target substance separated by liquid chromatography.

[0013] For this reason, when measuring real samples, operators of liquid chromatograph mass spectrometers would group together samples with similar ionization characteristics to the target substance and then subject them to the highly sensitive ionization methods of APCI and ESI for measurement.

[0014] In addition, in mass spectrometers connected to a liquid chromatograph, the measurement sample is often separated into components by the liquid chromatograph and the target substance is measured. One method of using a liquid chromatograph is the gradient measurement method, in which water and organic solvents such as acetonitrile and methanol are mixed and the components are separated while changing the mixing ratio.

[0015] This mixture of water and organic solvent is called the eluent. The organic solvent and mixture ratio used in the eluent change depending on the target substance. Therefore, the composition of the liquid introduced into the mass spectrometer varies and cannot be uniquely determined. On the other hand, when the mixture ratio of organic solvent is high, the ionization efficiency changes due to the influence of atmospheric humidity, and the measurement sensitivity of the mass spectrometer may change.

[0016] As described in Non-Patent Document 3, cluster ions include molecular ions in which multiple water molecules are bonded, and molecular ions in which water and organic solvent ions are bonded.

[0017] When the cluster ions are measured by a mass spectrometer, signals are detected in the low molecular weight region as a complex background.

[0018] APCI, a representative conventional ionization method, ionizes a vaporized sample by introducing it into a corona discharge. ESI ionizes the liquid as it is atomized by applying a high voltage to the atomizer or the liquid sample itself. Both ionization methods ionize the eluent as well as the target substance.

[0019] Therefore, in a mass spectrometer, the signal from the target substance and the signal from the eluent are observed simultaneously. Therefore, when the molecular weight of the target substance to be measured is small, the signal from the cluster ions and the signal from the target substance overlap, which can reduce sensitivity.

[0020] On the other hand, the cluster ions derived from the eluent are involved in charge transfer reactions during ionization, and the amount of ions of the target substance can change depending on the amount of cluster ions (when the amount of cluster ions is large, the amount of ions of the target substance increases, improving the sensitivity of the mass spectrometer).

[0021] An object of the present invention is to provide a liquid chromatograph mass spectrometer that is capable of performing highly sensitive measurements while reducing the effects of the eluent components used in separating a substance to be measured and the environment in which the device is installed (atmospheric effects), an ion source for the mass spectrometer, and a method for generating ions. [Means for solving the problem]

[0022] In order to achieve the above object, the present invention is configured as follows.

[0023] a control unit that receives measurement item information including gradient information; a heated mixing chamber that vaporizes and ionizes an atomized liquid sample; a charge supply unit that generates seed ions from a seed ion gas and supplies the seed ions to the heated mixing chamber; a gas supply unit that supplies gas to the charge supply unit and the heated mixing chamber; and a moisture supply unit that supplies moisture to the heated mixing chamber independently of the liquid sample, and analyzes ions introduced from the heated mixing chamber, wherein the measurement item information includes composition information of the gas supplied from the gas supply unit to the heated mixing chamber, and the control unit controls the moisture supply unit to supply the moisture to the heated mixing chamber based on the measurement item information.

[0024] The ion source of the mass spectrometer also includes a control unit that receives measurement item information including radiant information, a heated mixing chamber that vaporizes and ionizes the atomized liquid sample, a charge supply unit that generates seed ions from a seed ion gas and supplies the seed ions to the heated mixing chamber, a gas supply unit that supplies gas to the charge supply unit and the heated mixing chamber, and a moisture supply unit that supplies moisture to the heated mixing chamber independently of the liquid sample, wherein the measurement item information includes composition information of the gas supplied from the gas supply unit to the heated mixing chamber, and the control unit controls the moisture supply unit to supply the moisture to the heated mixing chamber based on the measurement item information.

[0025] In addition, the method for generating ions includes a first step of atomizing a liquid sample, a second step of supplying the atomized liquid sample to a heated mixing chamber, a third step of supplying a seed ion gas to a charge supply unit to generate seed ions and supplying them to the heated mixing chamber, a fourth step of supplying an auxiliary gas containing moisture to the heated mixing chamber while controlling the flow rate of the moisture, and a fifth step of ionizing a target substance in the heated mixing chamber and introducing it into a mass spectrometer, and the moisture is supplied to the heated mixing chamber based on measurement item information. Effect of the Invention

[0026] According to the present invention, it is possible to provide a liquid chromatograph mass spectrometer that can reduce the influence of the eluent components used in separating a substance to be measured and the environment in which the device is installed (atmospheric influence) and that can perform highly sensitive measurements, an ion source for the mass spectrometer, and a method for generating ions. [Brief description of the drawings]

[0027] [Figure 1] 1 is a configuration diagram of a mass spectrometer according to a first embodiment. [Diagram 2] 4 is an operational flowchart of a method for generating ions to be introduced into the mass spectrometer according to the first embodiment. [Diagram 3] FIG. 11 is a configuration diagram of a mass spectrometer according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. EXAMPLES

[0029] Example 1 FIG. 1 is a configuration diagram of the first embodiment.

[0030] 1, a liquid chromatograph mass spectrometer is a typical analytical device for analyzing liquid samples. The measurement sample is continuously fed by liquid chromatograph 300 at a rate of about several to 1000 μL / min, and fed to atomizer 100.

[0031] The atomizer 100 atomizes a liquid sample. A typical atomizer is a gas-assisted spray, which atomizes the liquid sample by flowing a high-velocity gas around a capillary tube through which the liquid sample flows and bringing the liquid sample into contact with the high-velocity gas at the outlet of the capillary tube. Nitrogen gas or air is generally used as the high-velocity gas. Instead of a gas-assisted spray, an ultrasonic atomizer such as that used in a humidifier may be used.

[0032] In order to vaporize the atomized measurement sample fluid (atomized fluid), the atomized fluid is introduced into the heating and mixing chamber 110. The heating and mixing chamber 110 is itself heated by a heater or the like, and the vaporization of the introduced atomized fluid is promoted by heat transfer from the heating and mixing chamber 110. As other heating methods, the atomized fluid may be heated by generating an electric field of high-frequency heating in the heating and mixing chamber 110, or may be heated by a light source that generates infrared rays.

[0033] The charge supply unit 120 generates seed ions for applying an electric charge to the measurement sample fluid (vaporized fluid) vaporized in the heating and mixing chamber 110. The charge supply unit 120 is set to a more positive pressure (higher pressure) than the heating and mixing chamber 110 so that the vaporized fluid does not flow in. Specifically, a seed ion gas 122 for generating seed ions is supplied to the charge supply unit 120, and a gas flow is generated from the charge supply unit 120 to the heating and mixing chamber 110. As a method of supplying electric charge, a corona discharge is generated in the charge supply unit 120 to generate seed ions.

[0034] As another method of supplying electric charge, seed ions may be generated by rapidly turning on and off a high DC voltage in the electric charge supply unit 120, or by generating an electric field using AC radio frequency (RF) to generate a low-temperature plasma discharge.

[0035] In the heating and mixing chamber 110, the seed ions supplied from the charge supply unit 120 and the target sample gas supplied from the atomizer 100 are mixed to ionize the target substance, and the ions are introduced into the mass spectrometer 150 through the first aperture 140 and detected.

[0036] The seed ion gas 122 is moisture, air, nitrogen, He, Ne, Ar, Xe, or a mixture thereof. These gases are sent to the heating and mixing chamber 110 as the auxiliary gas 130. The seed ion gas 122 has a gas flow rate controlled by a flow rate control unit 510 of a gas supply unit 500, the gas flow rate of which includes a flow rate of 0.

[0037] Similarly to the seed ion gas 122, the flow rate of the auxiliary gas 130 is controlled by the flow rate control unit 520, with the flow rate including zero.

[0038] The seed ion gas 122 and the auxiliary gas 130 are composed of the above-mentioned moisture, air, nitrogen, He, Ar, Xe or a composite gas thereof, and the composite gas is mixed by a mixer 530 .

[0039] The mixing unit 530 has an elemental gas supply source 570, a valve 560 for turning the gas flow On / Off, and an elemental gas control unit 540 having an elemental gas flow rate control unit 550 for controlling the flow rate of the elemental gas. One or more elemental gas control units 540 are provided in the gas supply unit 500, and one or more types of gas are used. For example, when Ar, nitrogen, and He gases are used, three systems are connected.

[0040] The moisture supply unit 640 includes a moisture supply source 670, a valve 660 for turning the moisture flow on and off, and a moisture flow rate control unit 650 for controlling the moisture flow rate. The moisture from the moisture supply unit 640 is mixed with the above-mentioned composite gas by the mixer 530.

[0041] The control unit 400 receives measurement item information 410 instructed by an external input device (not shown) for the above-mentioned seed ion gas 122 and auxiliary gas 130, and the control unit 400 switches the flow path and controls the flow rate. Details will be described below. The measurement item information 410 includes gradient information and other information (described later).

[0042] The above-mentioned atomizer 100, heating and mixing chamber 110, charge supply unit 120, gas supply unit 500, moisture supply unit 640, and control unit 400 form an ion source.

[0043] As mentioned above, in liquid chromatography mass spectrometry, the measurement sample is often separated into components by liquid chromatography to measure the target substance. In component separation by liquid chromatography, if the separation conditions are the same and the substance is the same, the measurement components are separated at the same time (timing). This time is called the retention time.

[0044] Therefore, a measurement sample is introduced into a liquid chromatograph, and the target components are separated at a fixed retention time. Measurement conditions of the mass spectrometer (e.g., observed mass and MSMS conditions) are changed to match the retention time at which the components are separated.

[0045] It is understood that the substance to be measured (target substance) is known in advance by the person who measures it. At least the mass to be measured is known, and in many cases, the molecular structure is also known.

[0046] As described in Non-Patent Document 4, the Penning ionization method is one of the methods for ionizing a target component using a seed ion gas (particularly a rare gas) and discharge.

[0047] In the Penning ionization method, metastable excited species of rare gases produced by discharge undergo multiple reactions, which eventually lead to the ionization of molecules.

[0048] In the ionization of a mass spectrometer, an important point of Penning ionization is that since each of the seed ion gas species has a different internal energy, the energy given to the measurement component can be adjusted by appropriately selecting the seed ion gas.

[0049] For example, metastable excited species generated from He gas have a high internal energy of 19.8 eV and are therefore thought to be capable of ionizing almost any molecule. In addition, Ar gas can selectively ionize molecules with an ionization energy of 11.7 eV or less.

[0050] The internal energy described above has a unique value for each gas type and can be changed by changing the gas type. In addition, the target substance to be measured is also known. Therefore, by selecting and controlling the flow rate of the seed ion gas according to the target substance to be measured, the background signal from the solvent can be reduced and the target substance itself can be ionized.

[0051] When Penning ionization is performed under atmospheric conditions, nitrogen (15.6 eV) and moisture contained in the atmosphere are also ionized at the same time due to the internal energy of the gas species used, and multiple ionization reactions proceed. In particular, when a charge is applied to moisture, cluster ions are likely to be generated due to the properties of water, which may affect the ionization efficiency of the target substance.

[0052] In addition to being supplied from the atmosphere, in mass spectrometers connected to liquid chromatographs, moisture can also be supplied from the eluent used to separate the components of the target substance. When the eluent has a high organic solvent ratio, the effect of moisture supplied from the atmosphere on the ionization efficiency of the target substance can be seen. The amount of moisture (humidity) contained in the atmosphere cannot be controlled, and the organic solvent ratio of the eluent is also determined by the molecular properties of the target component.

[0053] In the above-mentioned liquid chromatographic separation, the separation conditions can be changed by controlling the solvent ratio of the eluent used, and components can be separated in order of molecular weight or polarity.

[0054] When an operator of a liquid chromatograph mass spectrometer is primarily performing quantitative analysis, the operator already knows the molecular weight information of the target substance, and the control unit 400 controls the mass spectrometer 150 to select the ions to be measured according to the values ​​indicated in the measurement item information 410 input at the time of measurement.

[0055] In the above-mentioned liquid chromatographic separation, the organic solvent ratio of the eluent used is controlled to change the separation conditions of the components, and the components are separated in order of molecular weight or polarity. Therefore, the operator knows the organic solvent ratio at the separation time of the target component before the measurement.

[0056] On the other hand, the amount of water (humidity) in the air cannot be controlled.

[0057] Therefore, the operator determines the separation method of the liquid chromatograph, and based on the information on the separation method, controls the amount of water used in the ionization reaction and supplies it to the ion source. For example, it is possible to supply an amount of water that will result in a saturated water vapor amount in the ion source.

[0058] The measurement item information 410 is component information of the eluent for separating the components of the measurement target substance, and the control unit 400 controls the operation of the flow rate control unit 650 of the moisture supply unit 640 during operation of the mass spectrometer 150 based on the organic solvent ratio of the eluent to control the amount of moisture supplied to the heating and mixing chamber 110.

[0059] Instead of the moisture content control method described above, the measurement item information 410 can be the molecular weight of the substance to be measured, and the operation of the flow rate control unit 650 of the moisture supply unit 640 can be controlled based on the molecular weight information to control the amount of moisture supplied to the heating and mixing chamber 110.

[0060] By controlling the amount of moisture in the heating and mixing chamber 110 in the ion source, the ionization reaction proceeding in the ion source can be made constant, and the influence of the atmosphere can also be reduced, thereby making it possible to realize an ion source and mass spectrometer 150 with constant ionization efficiency of the target component and improved measurement stability.

[0061] FIG. 2 is a flowchart showing an operation of a method for generating ions to be introduced into the mass spectrometer 150 in the first embodiment.

[0062] 2, the atomizer 100 atomizes the liquid sample supplied from the liquid chromatograph 300. Then, in step S2, the atomizer 100 supplies the liquid sample atomized by the liquid sample to the heating and mixing chamber 110.

[0063] Next, in step S3, the seed ion gas 122 is supplied from the gas supply unit 500 to the charge supply unit 120, and seed ions are generated and supplied to the heating and mixing chamber 110. Then, in step S4, the auxiliary gas containing moisture is supplied from the gas supply unit 500 to the heating and mixing chamber 110 by controlling the flow rate. In this step S4, the control unit 400 controls the operation of the flow rate control unit 650 of the moisture supply unit 640 based on the organic solvent ratio of the eluent during the operation of the mass spectrometer 150 to control the amount of moisture supplied to the heating and mixing chamber 110. Alternatively, as described above, the control unit 400 controls the amount of moisture supplied to the heating and mixing chamber 110 based on molecular weight information during the measurement of the mass spectrometer 150.

[0064] Next, in step S 5 , the target substance is ionized in the heating and mixing chamber 110 , and the ions are introduced into the mass spectrometer 150 through the first aperture 140 .

[0065] In the first embodiment of the present invention, the amount of charge supplied to the measurement sample is increased by controlling the amount of moisture in the heating and mixing chamber 110, increasing the amount of cluster ions derived from moisture, and bringing the amount of cluster ions to the vicinity of the saturation concentration. By bringing the amount of cluster ions derived from moisture to the vicinity of the saturation concentration, the influence of the environment in which the device is installed can also be reduced.

[0066] In other words, the ionization efficiency of the target substance is improved due to the increase in the amount of charge supplied, and the amount of charge supplied to the measurement sample is constant, so the influence of the device installation environment is reduced and measurement reproducibility can be improved.

[0067] However, since supplying an excessive amount of moisture can cause contamination of the measurement sample in the ion source and condensation when the temperature drops, it is necessary to control the amount of moisture supplied.

[0068] According to the first embodiment of the present invention, it is possible to provide a liquid chromatograph mass spectrometer capable of reducing the influence of the eluent components used in separating a substance to be measured and the environment in which the device is installed (atmospheric influence) and capable of performing highly sensitive measurements, an ion source for the mass spectrometer, and a method for generating ions. In the example shown in FIG. 1, the moisture supply unit 640 is configured to be disposed separately from the gas supply unit 500 , but the moisture supply unit 640 may be disposed inside the gas supply unit 500 .

[0069] Example 2 Next, a second embodiment of the present invention will be described.

[0070] FIG. 3 is a configuration diagram of the second embodiment.

[0071] In the first embodiment shown in FIG. 1, in the second embodiment, moisture is supplied from a moisture supply unit 640 at a controlled flow rate to the heating and mixing chamber 110 via a gas supply unit 500. In the second embodiment, moisture is supplied from a moisture supply unit 640 at a controlled flow rate to the heating and mixing chamber 110 via a gas supply unit 500.

[0072] In contrast, in the second embodiment, moisture with a controlled flow rate is supplied from the moisture supply unit 600 to the heating and mixing chamber 110. In the moisture supply unit 600, the amount of moisture supplied to the heating and mixing chamber 110 is controlled by the control unit 400, similar to the moisture supply unit 640 in the first embodiment.

[0073] In the second embodiment, it is possible to provide a liquid chromatograph mass spectrometer that has the same effect as in the first embodiment, reduces the influence of the eluent components used in separating the measurement target substance and the device installation environment (atmospheric influence) and is capable of performing highly sensitive measurements, an ion source for the mass spectrometer, and a method for generating ions.

[0074] The present invention is not limited to the above-described embodiment, but includes various modified examples. For example, the above-described embodiment has been described in detail to easily explain the present invention, and the present invention is not necessarily limited to the embodiment having all of the described configurations. [Explanation of symbols]

[0075] 100 atomizer, 110 heated mixing chamber, 120 charge supply unit, 122 seed ion gas, 130 auxiliary gas, 140 first pore, 150 mass spectrometer, 300 liquid chromatograph, 400 control unit, 410 measurement item information, 500 gas supply unit, 510, 520 flow rate control unit, 530 gas mixing unit, 540 individual gas control unit, 550 individual gas flow rate control, 560, 660 valve, 570 introduced gases, 600, 640 moisture supply unit, 650 moisture flow rate control unit, 670 moisture supply source

Claims

1. A control unit that receives measurement item information including gradient information, A heating and mixing chamber that vaporizes and ionizes an atomized liquid sample, A charge supply unit that generates species ions from a species ion gas and supplies the species ions to the heating and mixing chamber, A gas supply unit that supplies gas to the charge supply unit and the heating and mixing chamber, A moisture supply unit that supplies moisture to the heating and mixing chamber independently of the liquid sample, Comprising, A mass spectrometer that analyzes ions introduced from the heating and mixing chamber, wherein the measurement item information includes composition information of the gas supplied from the gas supply unit to the heating and mixing chamber, and the control unit controls the moisture supply unit to supply the moisture to the heating and mixing chamber based on the measurement item information. A mass spectrometer characterized by that.

2. In the mass spectrometer according to claim 1, The measurement item information is component information of an eluent for separating components of a measurement target substance, and the control unit controls the amount of moisture supplied from the moisture supply unit to the heating and mixing chamber according to the organic solvent ratio of the eluent. A mass spectrometer characterized by that.

3. In the mass spectrometer according to claim 1, The measurement item information is the molecular weight of the measurement target substance, and the control unit controls the amount of moisture supplied from the moisture supply unit to the heating and mixing chamber based on the information of the molecular weight. A mass spectrometer characterized by that.

4. In the mass spectrometer according to claim 1, The moisture supply unit supplies the moisture to the heating and mixing chamber through the gas supply unit during measurement while the mass spectrometer is operating. A mass spectrometer characterized by that.

5. A control unit that receives measurement item information including gradient information, A heating and mixing chamber that vaporizes and ionizes an atomized liquid sample, A charge supply unit that generates species ions from a species ion gas and supplies the species ions to the heating and mixing chamber, A gas supply unit that supplies gas to the charge supply unit and the heating and mixing chamber, A moisture supply unit that supplies moisture to the heating and mixing chamber independently of the liquid sample, Comprising, The measurement item information includes composition information of the gas supplied from the gas supply unit to the heating and mixing chamber, and the control unit controls the moisture supply unit to supply the moisture to the heating and mixing chamber based on the measurement item information. An ion source characterized by that.

6. A first step of atomizing a liquid sample; A second step of supplying the atomized liquid sample to a heating and mixing chamber; A third step of supplying a seed ion gas to a charge supply unit to generate seed ions and supplying the seed ions to the heating and mixing chamber; A fourth step of supplying an auxiliary gas containing moisture to the heating and mixing chamber while controlling the flow rate of the moisture; A fifth step of ionizing a target substance in the heating and mixing chamber and introducing the ionized target substance into a mass spectrometer; comprising; A method for generating ions, characterized in that the moisture is supplied to the heating and mixing chamber based on measurement item information.

7. In the method for generating ions according to claim 6, the measurement item information is component information of an eluent for separating components of a measurement target substance, and the amount of moisture supplied to the heating and mixing chamber is controlled according to the organic solvent ratio of the eluent. A method for generating ions, characterized by this.

8. In the method for generating ions according to claim 6, the measurement item information is the molecular weight of a measurement target substance, and the amount of moisture supplied to the heating and mixing chamber is controlled based on the information on the molecular weight. A method for generating ions, characterized by this.

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