Gas chromatography mass spectrometer

Abstract

The present invention relates to a gas chromatography mass spectrometer (1), comprising: a gas chromatography section (2) for separating components in a sample gas through a separation chromatography column (12); a mass spectrometer (4) having an ionization section (14) for ionizing components coming out of an outlet (12a) of the separation chromatography column and a detection section (16) for detecting the components ionized by the ionization section; a control section (36) for controlling at least the ionization section, wherein the ionization section (14) comprises: an ion source box (18) having a space inside for ionizing components coming out of the outlet (12a); a heater (28) for adjusting the temperature of the ion source box (18); and a filament (20) arranged outside the ion source box (18) for generating electrons for ionizing the above-mentioned components. The control section (36) is configured to control the output of the heater (28) in association with the amount of heat generated by the filament (20) after applying a voltage to the filament (20), thereby adjusting the temperature of the ion source box (18) to a specified temperature.

Description

Technical Field

[0001] The invention relates to a gas chromatography mass analysis device. Background Art

[0002] A gas chromatograph mass spectrometer is a device comprising the following parts: a gas chromatograph section, which separates the components in a sample gas by means of a separation chromatographic column; and a mass spectrometer section, which ionizes the components separated by the gas chromatograph section and performs analysis using the ratio m / z of the mass m and the charge z of the ionized components (see patent document 1).

[0003] As one of the methods for ionizing the components separated by the gas chromatography part, the EI (Electron Ionization) method is known. The EI method is a method for ionizing by causing thermal electrons to collide with the components from the gas chromatography part. In the ionization part adopting the EI method, a metal box called an ion source box is provided, and a filament and an emission electrode are arranged on the outside of the ion source box with the ion source box clamped therein. If a voltage is applied to the filament, thermal electrons are generated by the filament, and the thermal electrons move toward the emission electrode in a manner of crossing the inside of the ion source box. At this time, the components from the gas chromatography part are ionized by the thermal electrons colliding with the components from the gas chromatography part emitted into the ion source box.

[0004] However, the sample injected into the gas chromatograph contains a solvent, and the solvent component comes out of the gas chromatograph before the component of the analysis object. It is known that if a voltage is applied to the filament during the period when the solvent component from the gas chromatograph is released into the ion source box, the filament will be damaged. Therefore, generally, the voltage is applied to the filament after the release of the solvent component from the gas chromatograph into the ion source box is completed.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-007927 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] The temperature of the ion source box affects the ionization efficiency in the ion source box. Therefore, a heater and a temperature sensor are installed in the ion source box to perform feedback control or the like so that the temperature of the ion source box is maintained at a set temperature.

[0010] When voltage is applied to the filament after the release of the solvent component from the gas chromatograph to the ion source box is completed, the temperature of the ion source box rises due to the heat generated by the filament. Even when the temperature of the ion source box is feedback controlled, the temperature of the ion source box inevitably rises temporarily to a temperature higher than the set temperature, and during this period, there is a problem that the ionization efficiency changes.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the temperature stability of an ion source box.

[0012] Solutions for solving the above technical problems

[0013] The gas chromatography mass spectrometer of the present invention comprises: a gas chromatography section, which generates a sample gas from an injected sample and separates components in the sample gas through a separation chromatographic column; a mass spectrometer section, which has an ionization section for ionizing components coming out of an outlet of the separation chromatographic column of the gas chromatography section, and a detection section for detecting components ionized by the ionization section; a control section, which at least controls the ionization section, wherein the ionization section of the mass spectrometer section comprises: an ion source box, which has a space inside for ionizing components coming out of the outlet of the separation chromatographic column; a heater for adjusting the temperature of the ion source box; a filament, which is arranged on the outside of the ion source box and emits electrons for ionizing components toward the space, wherein the control section is configured to adjust the temperature of the ion source box, which is affected by the heat emitted from the filament, to a specified temperature by controlling the output of the heater in association with the amount of heat generated by the filament after applying a voltage to the filament.

[0014] Here, controlling the output of the heater "in association with the magnitude of heat generation of the filament" includes controlling the output of the heater based on any one of the magnitude of a voltage applied to the filament, the magnitude of a current flowing through the filament, and the magnitude of an emission current.

[0015] Effects of the Invention

[0016] According to the gas chromatograph mass spectrometer of the present invention, after voltage is applied to the filament, the output of the heater is controlled in association with the amount of heat generated by the filament, so that the temperature of the ion source box affected by the heat generated by the filament is adjusted to a specified temperature, thereby improving the temperature stability of the ion source box. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram showing the structure of an embodiment of a gas chromatograph-mass spectrometer.

[0018] Figure 2This is a flowchart showing an example of temperature control of the ion source box during analysis in this embodiment. DETAILED DESCRIPTION

[0019] Hereinafter, embodiments of the gas chromatograph-mass spectrometer according to the present invention will be described with reference to the accompanying drawings.

[0020] like Figure 1 As shown, the gas chromatograph mass spectrometer 1 includes a gas chromatograph 2, a mass spectrometer 4, and a control device 6. The mass spectrometer 4 is composed of an ionization unit 14 and a detection unit 16. The gas chromatograph 2 and the mass spectrometer 4 are housed in a housing (not shown), and at least the mass spectrometer 4 is placed in a vacuum state.

[0021] The gas chromatograph section 2 includes an injector 8, a sample vaporizing section 10, and a separation chromatographic column 12. The injector 8 collects a sample from a sample bottle (not shown) and injects the sample into the sample vaporizing section 10. The sample vaporizing section 10 vaporizes the sample injected by the injector 8 to generate a sample gas, and transports the sample gas to the separation chromatographic column 12 by a carrier gas. In the separation chromatographic column 12, components in the sample gas are separated. An outlet 12a of the separation chromatographic column 12 is arranged in an ion source box 18 of an ionization section 14 described later, and the components separated in the separation chromatographic column 12 are discharged into the space in the ion source box 18.

[0022] The ionization section 14 of the mass spectrometer 4 includes an ion source box 18, a filament 20, an emission electrode 22, an ammeter 23, an ionization power supply 24, a temperature sensor 26, and a heater 28. The ion source box 18 is a metal box that releases the components from the outlet 12a of the separation chromatographic column 12 into the internal space of the ion source box 18. The filament 20 and the emission electrode 22 are arranged in a manner that the ion source box 18 is sandwiched between each other outside the ion source box 18. The ionization power supply 24 is used to apply voltage to the filament 20. The temperature sensor 26 and the heater 28 are installed in the ion source box 18 and are used to adjust the temperature of the ion source box 18.

[0023] The filament 20 is used to generate electrons for ionizing the component molecules emitted from the outlet 12a of the separation chromatographic column 12. The electrons generated by the filament 20 pass through the space in the ion source box 18 toward the emission electrode 22, and collide with the component molecules emitted from the outlet 12a of the separation chromatographic column 12, thereby ionizing the component molecules. The ammeter 23 is used to detect the amount of electrons reaching the emission electrode 22 as an emission current. Generally, the voltage applied to the filament 20 by the ionization power supply 24 is controlled so that the emission current detected by the ammeter 23 is constant at a specified value.

[0024] The detection unit 16 of the mass spectrometer 4 includes an ion lens 30, a quadrupole mass filter 32, and an ion detector 34. The components ionized in the ion source box 18 of the ionization unit 14 are introduced into the quadrupole mass filter 32 through the ion lens 30, and only ions having a mass-to-charge ratio corresponding to the voltage applied to the quadrupole mass filter 32 pass through the quadrupole mass filter 32 and are detected by the ion detector 34.

[0025] The control device 6 is used to control the operation of the gas chromatograph 2 and the mass spectrometer 4, and is implemented by a computer circuit having a CPU (central processing unit) and an information storage device. The control device 6 includes a control unit 36 ​​and a related data storage unit 38. The control unit 36 ​​is a function obtained by executing a program by the CPU, and the related data storage unit 38 is a function implemented by a storage area of ​​a part of the information storage device.

[0026] The control unit 36 ​​is configured to maintain the temperature of the ion source box 18 at a predetermined temperature by controlling the output of the heater 28 in consideration of the influence of the heat generated by the filament 20. In this embodiment, the correlation between the magnitude of the current flowing through the filament 20 and the correction amount of the output of the heater 28 required to eliminate the influence of the filament 20 on the temperature of the ion source box 18 is defined by experiments conducted in advance, and the correlation data is stored in the correlation data storage unit 38.

[0027] use Figure 2 Flowchart and together with Figure 1 The temperature control of the ion source box 18 during analysis by the control unit 36 ​​will be described.

[0028] Before starting analysis, the control unit 36 ​​controls the output of the heater 28 to set the temperature of the ion source box 18 to a set temperature, and controls the ionization power supply 24 so that no voltage is applied to the filament 20. The output of the heater 28 is controlled by adjusting the effective voltage applied to the heater 28.

[0029] When the analysis is started, the control device 6 sends an instruction to the injector 8 to inject the sample, and the injector 8 injects the sample into the sample vaporization chamber 10 (step 101). After the sample is injected, the control unit 36 ​​starts to apply voltage to the filament 20 after a predetermined time has passed (steps 102 and 103). The time from the sample injection to the start of the voltage application to the filament 20 is the time until all the solvent components contained in the injected sample are released from the outlet 12a of the separation chromatographic column 12, and is determined by the internal volume from the sample vaporization chamber 10 to the outlet 12a of the separation chromatographic column 12 and the flow rate of the carrier gas.

[0030] After the voltage starts to be applied to the filament 20, the control unit 36 ​​monitors the magnitude of the current flowing through the filament 20, and uses the magnitude of the current flowing through the filament 20 and the related data stored in the related data storage unit 38 to obtain a correction amount for the temperature control of the ion source box 18 required to eliminate the temperature increase of the ion source box 18 caused by the heat generated by the filament 20 (step 104). Then, the control unit 36 ​​uses the obtained correction amount to correct the control amount (the output of the heater 28) of the temperature control of the ion source box 18 (step 105). In fact, the temperature of the ion source box 18 gradually increases a certain period of time after the voltage starts to be applied to the filament 20. Therefore, the control unit 36 ​​uses the correction amount obtained based on the magnitude of the current flowing through the filament 20 to gradually reduce the effective voltage applied to the heater 28, thereby eliminating the temperature increase of the ion source box 18.

[0031] In addition, since the temperature change of the ion source box 18 is associated with the heat generated by the filament 20, the output of the heater 28 can also be corrected based on the magnitude of the voltage applied to the filament 20 or the magnitude of the emission current associated with the heat generated by the filament 20. In particular, the current flowing through the filament 20 is controlled so that the amount of electrons emitted from the filament 20, that is, the emission current, is constant, and therefore the emission current detected by the ammeter 23 can be used to correct the output of the heater 28. In this case, the correlation data holding unit 38 holds the magnitude of the emission current obtained in advance by the experiment and the correction amount of the temperature control required to eliminate the influence on the ion source box 18.

[0032] According to the experiments conducted by the present inventors, the temperature change of the ion source box 18 after the voltage starts to be applied to the filament 20 has reproducibility. Therefore, by measuring the magnitude of the voltage applied to the filament 20 and the pattern of the temperature change of the ion source box 18 in advance, it is possible to predict how the temperature of the ion source box 18 will change after the voltage is actually applied to the filament 20.

[0033] Generally, in order to maintain the temperature of the ion source box 18 at the set temperature, it is necessary to perform feedback control of the output of the heater 28 based on the signal of the temperature sensor 26. However, if feedback control of the output of the heater 28 based on the signal of the temperature sensor 26 is also performed after the voltage is applied to the filament 20, the temperature of the ion source box 18 shows a behavior of temporarily rising and then returning to the set temperature, and the ionization efficiency will change even temporarily. In contrast, in the gas chromatograph mass spectrometer 1 of this embodiment, it is predicted in advance how the temperature of the ion source box 18 will change after the voltage is applied to the filament 20 of the ionization unit 14, and the output of the heater 28 is reduced before the temperature of the ion source box 18 actually rises. Therefore, compared with the simple feedback control of the output of the heater 28, the temperature stability of the ion source box 18 can be improved.

[0034] When the voltage application to the filament 20 is stopped, the temperature of the ion source box 18 decreases, in contrast to when the voltage application to the filament 20 is started. At this time, as in the case of starting the voltage application to the filament 20, the temperature of the ion source box 18 can be kept constant by predicting the temperature decrease of the ion source box 18 and correcting the output of the heater 28. In this case, the correlation data holding unit 38 holds in advance the correlation between the magnitude of the voltage applied to the filament 20, the magnitude of the current flowing through the filament 20, and the magnitude of the emission current immediately before the voltage application to the filament 20 is stopped, and the output of the heater 28 is corrected using the correlation between the magnitude of the voltage applied to the filament 20, the magnitude of the current flowing through the filament 20, and the magnitude of the emission current immediately before the voltage application is stopped and the correlation held in the correlation data holding unit 38.

[0035] The above-described embodiment is only an example of an embodiment of the present invention. An embodiment of the gas chromatograph-mass spectrometer of the present invention is as follows.

[0036] One embodiment of the gas chromatography mass spectrometer of the present invention comprises: a gas chromatography section, which generates a sample gas from an injected sample and separates components in the sample gas through a separation chromatographic column; a mass spectrometer section, which has an ionization section for ionizing components coming out of an outlet of the separation chromatographic column of the gas chromatography section, and a detection section for detecting components ionized by the ionization section; a control section, which at least controls the ionization section, wherein the ionization section of the mass spectrometer section comprises: an ion source box, which has a space inside for ionizing components coming out of the outlet of the separation chromatographic column; a heater for adjusting the temperature of the ion source box; a filament, which is arranged on the outside of the ion source box and generates electrons for ionizing components coming out of the outlet of the separation chromatographic column, wherein the control section is configured to adjust the temperature of the ion source box, which is affected by the heat emitted from the filament, to a specified temperature by controlling the output of the heater in association with the amount of heat generated by the filament after applying a voltage to the filament.

[0037] In the first aspect of the above-mentioned embodiment, the device comprises:

[0038] A correlation data holding unit holds correlation data on any one of the magnitude of a voltage applied to the filament, the magnitude of a current flowing through the filament, and the amount of electrons emitted from the filament, i.e., an emission current, and a correction amount of the output of the heater required to eliminate the influence of the filament on the temperature of the ion source box,

[0039] The control unit is configured to correct the output of the heater using the correlation data held in the correlation data holding unit to eliminate the influence of the filament on the temperature of the ion source box. According to this scheme, the output of the heater is corrected before the temperature of the ion source box actually changes, so the temperature stability of the ion source box is improved.

[0040] In the second scheme of the above-mentioned embodiment, the control unit is configured to start applying voltage to the filament after the outflow of the solvent from the outlet of the separation chromatographic column ends. According to this scheme, it is possible to prevent the filament from being deteriorated due to the vaporized solvent. In addition, this second scheme can be combined with the above-mentioned first scheme.

[0041] In the second aspect, the control unit may be configured to detect completion of outflow of the solvent from the outlet of the separation column based on an elapsed time after injection of a sample into the gas chromatograph.

[0042] Description of Reference Numerals

[0043] 1Gas chromatography mass analysis device

[0044] 2Gas Chromatography Department

[0045] 4Quality Analysis Department

[0046] 6. Control Device

[0047] 8 Syringes

[0048] 10 Sample Vaporization Chamber

[0049] 12 Separation Column

[0050] 14Ionization unit

[0051] 16. Inspection Department

[0052] 18 ion source box

[0053] 20 filaments

[0054] 22 Emitting electrode

[0055] 23. Ammeter

[0056] 24 ionization power supply

[0057] 26 Temperature Sensor

[0058] 28 Heater

[0059] 30 ion lens

[0060] 32 quadrupole mass filter

[0061] 34 ion detector

[0062] 36 Control Department

[0063] 38 Related data holding unit.

Claims

1. A gas chromatography mass analysis device, characterized in that: have: A gas chromatograph section that generates a sample gas from the injected sample and separates components in the sample gas through a separation chromatographic column; a mass analysis unit having an ionization unit for ionizing a component exiting from an outlet of the separation column of the gas chromatograph unit, and a detection unit for detecting the component ionized by the ionization unit; a control unit for controlling at least the ionization unit, The ionization unit of the mass spectrometry unit includes: an ion source box having a space inside for ionizing the components exiting from the outlet of the separation chromatographic column; A heater, used for adjusting the temperature of the ion source box; A filament is disposed outside the ion source box and generates electrons for ionizing the components exiting the outlet of the separation chromatographic column. The gas chromatography mass spectrometer further comprises: A correlation data holding unit holds correlation data on any one of the magnitude of a voltage applied to the filament, the magnitude of a current flowing through the filament, and the magnitude of an emission current, which is the amount of electrons emitted from the filament, and a correction amount of the output of the heater required to eliminate the influence of the filament on the temperature of the ion source box, The control unit is configured to correct the output of the heater using the correlation data held in the correlation data holding unit so as to eliminate the influence of the filament on the temperature of the ion source box when analysis is started and voltage is started to be applied to the filament.

2. The gas chromatography mass spectrometer according to claim 1, characterized in that: The control unit is configured to start applying a voltage to the filament after outflow of the solvent from the outlet of the separation column ends.

3. The gas chromatography mass spectrometer according to claim 2, characterized in that: The control unit is configured to detect completion of outflow of the solvent from the outlet of the separation column based on an elapsed time after injection of a sample into the gas chromatograph.

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