JP7409492B2 - gas chromatograph mass spectrometer - Google Patents

Description

The present invention relates to gas chromatograph mass spectrometers.

In analysis using a gas chromatograph-mass spectrometer (GC-MS), sensitivity can be increased by efficiently ionizing a sample separated by the gas chromatograph (GC). In GC, helium gas, nitrogen gas, or the like is used as a carrier gas (see Patent Document 1), and is introduced into the ionization chamber together with the sample. In the electron impact ionization method (EI), a sample introduced into an ionization chamber is irradiated with thermionic electrons emitted from a filament placed outside the ionization chamber, and the sample is ionized by reaction with the thermionic electrons. .

Japanese Patent Publication No. 61-225644

Gases containing molecules or atoms with a larger molecular weight than helium, such as nitrogen gas, have a larger molecular size and are more likely to collide with thermoelectrons than helium gas, so when used as a carrier gas, The sensitivity of the analysis may be reduced.

A first aspect of the present invention includes a separation section that separates a sample, a gas supply section that supplies nitrogen gas as a carrier gas to the separation section, and a mass spectrometer section that performs mass analysis of the sample introduced from the separation section. A gas chromatograph mass spectrometer comprising: a filament; and an ionization chamber into which thermionic electrons from the filament and the sample from the separation section are introduced, and electron impact ionization of the sample is performed. and the ratio of the total area (mm ² ) of the openings in the side wall of the ionization chamber in square millimeters to the inner volume of the ionization chamber in cubic millimeters (mm ³ ) is 30. The side wall of the ionization chamber includes a first opening through which the thermoelectrons from the filament pass when entering the ionization chamber, and a first opening through which the thermoelectrons exit from the ionization chamber. a second opening through which the sample is introduced from the separation section; a fourth opening through which the ionized sample passes when exiting from the ionization chamber; and a fifth opening through which the calibration sample is introduced, at least one sixth opening is formed, said sixth opening being configured to discharge carrier gas from said ionization chamber. This invention relates to a gas chromatograph mass spectrometer that is an opening for promoting

According to the present invention, when a gas containing molecules or atoms having a molecular weight larger than that of helium, such as nitrogen gas, is used as a carrier gas, a decrease in analysis sensitivity can be suppressed.

FIG. 1 is a conceptual diagram showing the configuration of a GC-MS according to an embodiment. FIG. 2 is a conceptual diagram showing an ionization section according to one embodiment. FIG. 3 is a conceptual diagram showing the sixth opening. FIG. 4 is a conceptual diagram showing the configuration of an ionization section according to a modification. FIG. 5 is a conceptual diagram showing the configuration of a modified GC-MS. FIG. 6 is a conceptual diagram showing the configuration of an ionization section according to a modification. FIG. 7 is a chromatogram obtained in a comparative example. FIG. 8 is a chromatogram obtained in the example.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

-Embodiment-
FIG. 1 is a conceptual diagram showing the configuration of a gas chromatograph-mass spectrometer (GC-MS) 1 of this embodiment. The GC-MS 1 includes a measurement section 100 and an information processing section 40. The measurement section 100 includes a gas chromatograph (GC) 10, a sample gas introduction tube 20, and a mass spectrometry section 30. The GC 10 includes a carrier gas flow path 11 and a sample introduction section 12. The mass spectrometer 30 includes a vacuum container 31, an exhaust port 32, a vacuum exhaust system 33, an ionization unit 300 that ionizes the sample S to generate ions In, an ion adjustment unit 34, a mass separation unit 35, A detection unit 36 is provided. The ionization section 300 includes an ionization chamber 310, a filament 320, and a trap electrode 330.

The measurement unit 100 separates and detects each component of the sample through two or more separation steps including gas chromatography and mass separation.

The GC 10 functions as a separation unit that separates the sample S introduced into the GC 10 by gas chromatography.

The carrier gas flow path 11 is a flow path for carrier gas, and introduces the carrier gas into the sample introduction section 12 (arrow A1). Although the composition of the carrier gas is not particularly limited, the GC-MS1 can use at least nitrogen as the carrier gas. In the following, nitrogen refers to nitrogen molecules. The sample introduction section 12 includes a sample introduction chamber such as a sample vaporization chamber, and temporarily accommodates a sample injected with a syringe or an injector such as an autosampler (not shown), and vaporizes the sample when the sample is liquid. Then, the sample gas is introduced into a separation column (not shown) (arrow A2).

The GC 10 is equipped with a separation column and separates the sample S in the separation column. When introduced into the separation column, the sample S is in a gas or gaseous state, which is appropriately referred to as a sample gas. The type of separation column is not particularly limited, and any column such as a capillary column can be used. Each component of the sample gas separated in the GC 10 is eluted from the separation column at different times and introduced into the ionization section 300 of the mass spectrometry section 30 through the sample gas introduction tube 20. The sample gas introduction tube 20 may be integrated with the separation column.

The mass spectrometer 30 includes a mass spectrometer, and ionizes the sample S introduced into the ionization section 300, performs mass separation and detection. Ions In originating from the sample S generated in the ionization section 300 move along the ion optical axis Ax1.
Note that the type of mass spectrometer constituting the mass spectrometer 30 is not particularly limited, as long as the ions In originating from the sample S can be detected by mass separation with a desired accuracy. A device including an analyzer can be used.

The vacuum container 31 of the mass spectrometer 30 is equipped with an exhaust port 32 . The exhaust port 32 is connected to a vacuum exhaust system 33 so as to be evacuated. The vacuum evacuation system 33 includes a pump such as a turbo molecular pump that can achieve a low pressure of 10 ⁻² Pa or less, and its auxiliary pump. In FIG. 1, the point where the gas inside the vacuum container 31 is discharged is schematically indicated by an arrow A10.

The ionization section 300 of the mass spectrometry section 30 ionizes the sample S introduced into the ionization section 300 by electron impact ionization (EI). A sample gas introduction tube 20 is connected to the ionization chamber 310 so that the sample gas can be introduced into the ionization chamber. Thermionic electrons emitted from the filament 320 are irradiated onto the sample S introduced into the ionization chamber 310 . In FIG. 1, the flow of the thermoelectrons is schematically shown by arrow A20. The amount of irradiated thermoelectrons is detected by a trap electrode 330 placed on the opposite side of the filament 320 with the ionization chamber 310 in between.

When the molecules contained in the sample S come into contact with the thermoelectrons, the molecules contained in the sample S are ionized and molecular ions are generated. In some cases, molecular ions are cleaved and fragment ions are generated due to the energy of thermal electrons. Ions In originating from the sample S, including molecular ions or fragment ions, are ejected from the ionization chamber 310 by electromagnetic action based on a voltage applied to an electrode placed outside the ionization chamber 310. For example, a voltage with a polarity opposite to that of the ions In to be detected is applied to the ion adjustment section 34, and the ions In are accelerated by an extraction electric field based on the voltage. Alternatively, by applying a voltage of the same polarity as the ions In to an electrode arranged in the ionization chamber, the ions In may be accelerated by an electric field for extrusion based on the voltage.

FIG. 2 is a conceptual diagram showing the configuration of the ionization section 300. The ionization unit 300 includes an ionization chamber 310, a filament 320, a trap electrode 330, and magnets 340a and 340b. The ionization chamber 310 includes a first side wall 311 , a second side wall 312 , a third side wall 313 , a fourth side wall 314 , and a fifth side wall 315 . In addition to this, the ionization chamber 310 includes a sixth side wall, which is a side wall (not shown), disposed at a position facing the fifth side wall 315. In the following, when simply mentioning a side wall, it refers to the first side wall 311, the second side wall 312, the third side wall 313, the fourth side wall 314, the fifth side wall 315, and the sixth side wall without distinction.

In FIG. 2, the Z-axis is set in the direction connecting the filament 320 and the trap electrode 330, the X-axis is set in the direction along the ion optical axis Ax1, and the Y-axis is set perpendicular to the Z-axis and the X-axis. (see coordinate system 9). The first side wall 311 and the second side wall 312 are arranged along the XY plane. The third side wall 313 and the fourth side wall 314 are arranged along the YZ plane. The fifth side wall 315 and the sixth side wall are arranged along the ZX plane.

A first opening 301 and a sixth opening 306 are formed in the first side wall 311 of the ionization chamber 310 . A second opening 302 and a fifth opening 305 are formed in the second side wall 312 . The second side wall 312 is formed at a position facing the first side wall 311 with the ion optical axis Ax1 in between. A third opening 303 is formed in the third side wall 313 . A fourth opening 304 is formed in the fourth side wall 314 .

The side wall of the ionization chamber 310 is made of metal such as stainless steel. The thickness of the side wall of the ionization chamber 310 is not particularly limited as long as there is no problem in manufacturing and analysis, and can be set to several mm, for example. In order to accelerate thermoelectrons, a voltage of +several tens of volts to several hundred volts is applied to the ionization chamber 310 including the first side wall 311 with respect to the filament 320. This voltage is appropriately set from the viewpoint of increasing ionization efficiency.

The ionization chamber 310 can have a rectangular parallelepiped shape, a cylindrical shape, or the like, for example. However, the shape of the ionization chamber 310 is not particularly limited as long as the thermoelectrons emitted from the filament 320 can pass through the first opening 301 and irradiate the sample S, and the ions In obtained by the irradiation can be emitted from the ionization chamber. .

The first opening 301 is an opening through which the thermoelectrons emitted from the filament 320 enter the ionization chamber 310 . The second opening 302 is an opening through which the thermoelectrons emitted from the filament 320 pass when emitted from the ionization chamber 310. The first opening 301 and the second opening 302 are formed with the axis Ax2 as the central axis. It is preferable that the axis Ax2 is substantially perpendicular to the flow of the sample gas from the sample gas introduction tube 20 and the ion optical axis Ax1. Further, it is preferable that the sample gas introduction tube 20 is arranged so that the flow of the sample S discharged from the sample gas introduction tube 20 passes through the intersection of the axis Ax2 and the ion optical axis Ax1. The shapes of the first opening 301 and the second opening 302 are not particularly limited as long as they can perform ionization with desired efficiency. For example, the first opening 301 and the second opening 302 can be circular, oval, square, or rectangular.

The sample gas introduction tube 20 is arranged through the third opening 303. The third opening 303 is an opening through which the sample gas is introduced from the GC 10 into the ionization chamber 310. The ion optical axis Ax1 passes through the fourth opening 304. The fourth opening 304 is an opening through which the sample ionized in the ionization chamber 310 passes when exiting from the ionization chamber 310 .

The fifth opening 305 is an opening through which the calibration sample is introduced into the ionization chamber 310. A calibration sample introduction tube 60 is placed through the fifth opening 305 . The calibration sample introduction tube 60 may not be disposed in the fifth opening 305, and the calibration sample may be introduced into the ionization chamber 310 from outside the ionization chamber 310 by diffusion. The type of calibration sample is not particularly limited, but it may be PFTBA (Perfluorotributylamine), etc., which is used when adjusting each part of the mass spectrometer 30 to increase sensitivity.

The sixth opening 306 is an opening for promoting discharge of the carrier gas from the ionization chamber 310. The sixth opening 306 functions as a nitrogen gas outlet for discharging nitrogen gas. When the molecules of a carrier gas, such as nitrogen gas, are larger than those of helium, thermionic electrons collide with the molecules, reducing the proportion of thermionic electrons that contribute to ionization, resulting in a decrease in ionization efficiency. . This point becomes more noticeable when the residence time in the ionization chamber 310 is longer due to a carrier gas such as nitrogen gas having a larger molecular weight than helium. Ions derived from nitrogen gas may also be detected as noise. For this reason, when nitrogen gas is used as a carrier gas, sensitivity may decrease. By discharging nitrogen gas from the sixth opening 306, it is possible to suppress a decrease in sensitivity.

FIG. 3 is a diagram when the sixth opening 306 is viewed in a direction perpendicular to the first side wall 311, from the positive side to the negative side of the Z-axis in FIG. In this example, the sixth opening 306 is a circular opening in the first side wall 311. The area S6 of the sixth opening 306 is the area of the opening in the side wall of the ionization chamber 310 in square millimeters (mm ² ) with respect to the volume inside the ionization chamber 310 in cubic millimeters (mm ³ ). The total ratio is set to be 1/30 or more. Here, in this embodiment, the total area of the openings in the side wall of the ionization chamber 310 is the first opening 301, the second opening 302, the third opening 303, the fourth opening 304, and the fifth opening. 305 and the area of the sixth opening 306. The area of the opening can be, for example, the minimum value of the area where the opening overlaps a plane parallel to the side wall in which the opening is formed.
Note that the sixth opening 306 can be formed at any position on the side wall of the ionization chamber 310. Further, the shape of the sixth opening 306 is not particularly limited.

The maximum diameter L6 of the sixth opening 306 is preferably less than 20 mm, more preferably 2 mm or more and less than 4 mm, even more preferably 2.5 mm or more and less than 3.5 mm, and even more preferably 3 mm. Here, the maximum diameter L6 of the sixth opening 306 is the length of the longest line segment that is parallel to the side wall in which the sixth opening 306 is formed and connects two points on the inner wall of the sixth opening 306. It can be done. A plurality of sixth openings 306 may be arranged on the side wall of the ionization chamber 310. The lower limit of the maximum diameter L6 of the sixth opening 306 is not particularly limited, and can be, for example, 0.1 mm or more.

Returning to FIG. 2, trap electrode 330 can be any electrode capable of detecting thermoelectrons, but preferably includes a filament. The trap electrode 330 is electrically connected to an ammeter (not shown) or the like, and is configured to be able to measure the amount of thermoelectrons that have reached the trap electrode 330. When the trap electrode 330 is a filament, EI can also be performed using the filament as a thermionic source and the filament 320 as the trap electrode. In this case, it is more preferable that the filament 320 and the trap electrode 330 have the same shape.

Due to the magnetic field generated by magnets 340a and 340b disposed in ionization section 300, thermoelectrons emitted from filament 320 move along a spiral trajectory. This makes it easier for the thermoelectrons to react with the sample S, increasing the efficiency of ionization.

Returning to FIG. 1, the ion adjustment unit 34 of the mass spectrometry unit 30 includes an ion transport system such as an ion guide, and adjusts the flux of ions In by converging it by electromagnetic action. Ions In emitted from the ion adjustment section 34 are introduced into the mass separation section 35.

The mass separator 35 of the mass spectrometer 30 includes a quadrupole mass filter and performs mass separation on the introduced ions In. The mass separator 35 selectively passes ions In based on the value of the mass-to-charge ratio using the voltage applied to the quadrupole mass filter. Ions In obtained by mass separation in the mass separation section 35 enter the detection section 36 .

The detection unit 36 of the mass spectrometry unit 30 includes an ion detector and detects the incident ions In. The detection unit 36 A/D converts the detection signal obtained by detecting the incident ions In using an analog/digital (A/D) converter (not shown), and converts the digitized detection signal into a digital signal. It is output to the information processing section 40 (arrow A20). Hereinafter, data based on a detection signal obtained by detecting ions In by the detection unit 36 will be referred to as measurement data.

The information processing unit 40 includes an information processing device such as a computer, serves as an interface with the user of the GC-MS 1 (hereinafter simply referred to as the "user"), and also performs processing such as communication, storage, and calculation regarding various data. I do. The information processing unit 40 acquires information regarding analysis conditions and the like from the user via an input device such as a mouse, keyboard, or touch panel. The information processing unit 40 includes a control unit including a processing device such as a CPU (Central Processing Unit), and a storage medium such as a memory and a hard disk. The processing device plays a main role in the operation of the GC-MS 1 by reading a program stored in a hard disk or the like into a memory and executing it, controlling the measurement unit 100, processing measurement data, and the like. The method of processing the measurement data is not particularly limited, and may include creating data corresponding to a chromatogram in which the retention time of the ion In detected by the detection unit 36 and the intensity of the detection signal are correlated, or can be identified or quantified. The information processing unit 40 includes a display device such as a display monitor, and displays information obtained through processing by the processing device.
Note that the measuring section 100 and the information processing section 40 may be configured as an integrated device.

In the mass spectrometer 1 of this embodiment, the ratio of the total area of the openings in the side wall of the ionization chamber in square millimeters to the volume inside the ionization chamber 310 in cubic millimeters is 30/30. It is 1 or more. As a result, when nitrogen gas is used as a carrier gas, it is possible to lower the partial pressure of nitrogen gas in the ionization chamber 310 and shorten the residence time of nitrogen, thereby suppressing a decrease in sensitivity due to nitrogen gas. I can do it. Furthermore, the mass spectrometer 1 of this embodiment includes a sixth opening 306 in addition to the first to fifth openings. The sixth opening 306 can be easily processed, and a mass spectrometer 1 that suppresses a decrease in sensitivity can be realized.

The following modifications are also within the scope of the invention and can be combined with the embodiments described above. In the following modified examples, parts having the same structures and functions as those in the above-described embodiment will be referred to with the same reference numerals, and descriptions thereof will be omitted as appropriate.

(Modification 1)
In the embodiment described above, the sixth opening 306 is formed in the side wall of the ionization chamber 310. However, the sixth opening may not be formed in the ionization chamber, and the area of at least one of the first opening, second opening, third opening, fourth opening, and fifth opening may be expanded. .

FIG. 4 is a conceptual diagram showing the configuration of the ionization section 300a of this modification. The ionization section 300a differs from the above-described ionization section 300 in that it includes an ionization chamber 310a instead of the ionization chamber 310. The ionization chamber 310a is different from the above-described ionization unit 300 in that the sixth opening 306 is not provided, the first sidewall 311a is provided instead of the first sidewall 311, and the first opening 301a is provided instead of the first opening 301. It is different from

The first opening 301a has a circular, elliptical, square, or rectangular shape when viewed from a direction perpendicular to the first side wall 311a. The area of the first opening 301a is the sum of the area of the opening in the side wall of the ionization chamber 310a in square millimeters (mm ² ) relative to the inner volume of the ionization chamber 310a in cubic millimeters (mm ³ ). The ratio is set to be 1/30 or more. The GC-MS of this modification can also suppress a decrease in sensitivity when nitrogen gas is used as a carrier gas.

Note that in the case of a configuration in which the trap electrode 330 can be used as a filament and the filament 320 can also be used as a trap electrode, it is preferable to configure the second opening 302 to have the same size as the first opening 301a. . Further, the ratio of the total area of the openings in the side wall of the ionization chamber 310a in square millimeters (mm ² ) to the inner volume of the ionization chamber 310a in cubic millimeters (mm ³ ) is 30%. As long as the number of openings is one or more, the size of any one or more openings may be changed. In addition to changing the size of the first opening 301a as in this modification, the size of at least one of the second opening 302, the third opening 303, the fourth opening 304, and the fifth opening 305 is changed. You may.

(Modification 2)
In the embodiment described above, the area of the opening formed in the side wall of the ionization chamber may be controlled to be changeable.

FIG. 5 is a conceptual diagram showing the configuration of the GC-MS of this modification. GC-MS1 includes a measuring section 100a and an information processing section 40a. The measurement section 100a differs from the measurement section 100 described above in that it includes an ionization section 300b instead of the ionization section 300. The ionization section 300b differs from the above-described ionization section 300 in that it includes an ionization chamber 310b instead of the ionization chamber 310. The information processing section 40a differs from the above-described information processing section 400 in that it includes an aperture control section 400.

FIG. 6 is a conceptual diagram showing the configuration of the ionization section 300b. The ionization chamber 310b differs from the above-described ionization chamber 310 in that instead of the first sidewall 311, it includes a first sidewall 311b on which an opening/closing mechanism 360 is installed. The opening/closing mechanism 360 is configured as an actuator and includes a lid 360a and a drive device 360b. The opening/closing mechanism 360 functions as an opening/closing section that opens and closes the sixth opening 306. The opening/closing mechanism is controlled by an opening control section 400 (FIG. 5). The aperture control section 400 is included in the control section of the information processing section 40a. For example, when the user inputs an input to open or close the sixth opening 306, a control signal is sent from the opening control section 400 to the opening/closing mechanism 360. The drive device 360b opens and closes the sixth opening 306 by moving the lid 360a. By controlling the area of the opening of the ionization chamber 310b in this manner, analysis can be performed under conditions suitable for carrier gases having different molecular weights, such as helium and nitrogen.

Note that the configuration of the opening/closing mechanism 360 is not particularly limited as long as the area of the sixth opening 306 can be changed. Further, at least one of the openings formed in the ionization chamber 310b can be configured to control the area so as to be changeable. An opening/closing mechanism is installed for at least one of the first opening 301, the second opening 302, the third opening 303, the fourth opening 304, the fifth opening 305, and the sixth opening 306. The area can be changed.

(Modification 3)
In the embodiment described above, nitrogen gas can be used as the carrier gas. However, even when GC-MS uses molecules or atoms with a larger molecular weight than helium as a carrier gas, the same effect as described above can be obtained.

(mode)
It will be appreciated by those skilled in the art that the exemplary embodiments or variations described above are specific examples of the following aspects.

(Section 1) A gas chromatograph mass spectrometer according to one aspect is a gas chromatograph mass spectrometer that includes a separation section that separates a sample, and a mass spectrometry section that performs mass spectrometry on the sample introduced from the separation section. The mass spectrometry section includes a filament and an ionization chamber into which the thermoelectrons from the filament and the sample from the separation section are introduced, and the inside of the ionization chamber is expressed in cubic millimeters (mm ³ ). The ratio of the total area (mm ² ) of the openings in the side wall of the ionization chamber in units of square millimeters to the volume of is 1/30 or more. Thereby, when a gas containing molecules or atoms having a molecular weight larger than that of helium, such as nitrogen gas, is used as a carrier gas, a decrease in analysis sensitivity can be suppressed.

(Section 2) In the gas chromatograph mass spectrometer according to another aspect, in the gas chromatograph mass spectrometer according to Item 1, the thermoelectrons from the filament are disposed on the side wall of the ionization chamber. a first opening through which the thermionic electrons pass when entering the ionization chamber; a second opening through which the thermoelectrons pass when exiting from the ionization chamber; and a third opening through which the sample is introduced from the separation section. In addition to a fourth opening through which the ionized sample passes when exiting from the ionization chamber, and a fifth opening through which a calibration sample is introduced, at least one sixth opening An opening may be formed. Thereby, it is possible to easily fabricate an ionization chamber that can suppress a decrease in analysis sensitivity.

(Section 3) In the gas chromatograph mass spectrometer according to another aspect, in the gas chromatograph mass spectrometer according to Section 2, the maximum diameter of the sixth opening can be less than 20 mm. Thereby, it is possible to prevent the adverse effects caused by the opening while suppressing a decrease in analysis sensitivity.

(Section 4) In the gas chromatograph mass spectrometer according to another aspect, the gas chromatograph mass spectrometer according to Section 2 or 3 can be provided with an opening/closing part that opens and closes the sixth opening. Thereby, analysis can be performed under conditions suitable for each carrier gas having a different molecular weight.

(Section 5) In the gas chromatograph mass spectrometer according to another aspect, in the gas chromatograph mass spectrometer according to any one of Items 1 to 3, the opening formed in the ionization chamber is It can include at least one opening/closing section that opens and closes. Thereby, analysis can be performed under conditions more suitable for carrier gases having different molecular weights.

(Section 6) In a gas chromatograph mass spectrometer according to another aspect, in the gas chromatograph mass spectrometer according to any one of Items 1 to 5, the ionization chamber is capable of electron impact ionization. Yes, nitrogen gas can be used as a carrier gas. Thereby, it is possible to more reliably suppress a decrease in analysis sensitivity.

The present invention is not limited to the contents of the above embodiments. Other embodiments considered within the technical spirit of the present invention are also included within the scope of the present invention.

Examples are shown below, but the present invention is not intended to be limited to the following examples.

(Comparative example)
Using GCMS-TQ8040 (Shimadzu Corporation), which is a GC-MS equipped with GC-2010Plus (Shimadzu Corporation) as a GC, a sample containing octafluoronaphthalene was subjected to gas chromatography/mass spectrometry (GC/MS). ).

Conditions for gas chromatography Column: SH-Rxi-5Sil MS (length: 30.0 m, inner diameter: 0.25 mm, film thickness: 0.25 μm) (Shimadzu GLC)
Temperature of sample vaporization chamber: 250℃
Carrier gas control mode: Control the sample injection port pressure to the set value Carrier gas pressure: 21.8kPa
Total flow rate: 50mL/min.
Purge flow rate: 6mL/min.
Injection mode: Splitless column oven temperature: 50°C for the first minute, 40°C/min. The temperature was increased to 200°C at a rate of 15°C/min. The temperature was increased to 250°C at a rate of 250°C, and the temperature was kept at 250°C for 3 minutes.

Mass spectrometry conditions Interface temperature: 250℃
Ion source temperature: 200℃
Measurement mode: Scan Scan range: m/z 200 - 300
Event time: 0.2sec.
Scan speed: 555u/sec.

FIG. 7 is a diagram showing a chromatogram obtained in this comparative example. The chromatogram is a graph in which the horizontal axis shows the retention time and the vertical axis shows the intensity of the detection signal in mass spectrometry of the sample eluted during the retention time. Peak P1 is a peak corresponding to octafluoronaphthalene. The signal/noise ratio (S/N ratio) calculated by quantifying noise using the root mean square (RMS) method using the peak corresponding to octafluoronaphthalene was 78.18.

(Example)
A 3 mm circular hole was made in the side wall of the ionization chamber of GCMS-TQ8040, which is a GC-MS equipped with GC-2010Plus, to create an opening corresponding to the sixth opening described above. Other than that, GC/MS was performed under the same conditions as in the above comparative example. The S/N ratio was calculated in the same manner as in the above comparative example.

FIG. 8 is a diagram showing a chromatogram obtained in this example. Peak P2 is a peak corresponding to octafluoronaphthalene. The S/N ratio was 693.34.

1, 2...GC-MS, 9...Coordinate system, 10...GC, 20...Sample gas introduction tube, 30...Mass spectrometry section, 31...Vacuum container, 33...Evacuation system, 35...Mass separation section, 36...Detection 40, 40a... Information processing section, 100, 100a... Measurement section, 300, 300a, 300b... Ionization section, 301, 301a... First opening, 302... Second opening, 303... Third opening, 304 ...Fourth opening, 305...Fifth opening, 306...Sixth opening, 310, 310a, 310b...Ionization chamber, 311, 311a, 311b...First side wall, 312...Second side wall, 313...Third side wall , 314...Fourth side wall, 315...Fifth side wall, 320...Filament, 330...Trap electrode, 360...Opening/closing mechanism, 400...Aperture control unit, In...Ion, L6...Maximum diameter of the sixth opening, P1, P2 ...Peak corresponding to octafluoronaphthalene, S...sample, S6...area of the sixth opening.

Claims (4)

A gas chromatograph mass spectrometer comprising a separation section that separates a sample, a gas supply section that supplies nitrogen gas as a carrier gas to the separation section, and a mass spectrometry section that performs mass analysis of the sample introduced from the separation section. There it is,
The mass spectrometry section includes a filament and an ionization chamber into which the thermoelectrons from the filament and the sample from the separation section are introduced and electron impact ionization of the sample is performed,
The ratio of the total area (mm ² ) of the openings in the side wall of the ionization chamber in square millimeters to the inner volume of the ionization chamber in cubic millimeters (mm ³ ) is 1/30 or more. and
The side wall of the ionization chamber includes a first opening through which the thermoelectrons from the filament pass when entering the ionization chamber, and a second opening through which the thermoelectrons pass when exiting from the ionization chamber. a third opening through which the sample is introduced from the separation section; a fourth opening through which the ionized sample passes when exiting from the ionization chamber; and a calibration sample through which the sample is introduced. At least one sixth opening is formed in addition to the fifth opening through which the second opening passes when
The sixth opening is an opening for promoting discharge of carrier gas from the ionization chamber . The gas chromatograph mass spectrometer according to claim 1 ,
The gas chromatograph mass spectrometer, wherein the sixth opening has a maximum diameter of less than 20 mm. The gas chromatograph mass spectrometer according to claim 1 or 2 ,
A gas chromatograph mass spectrometer comprising an opening/closing section that opens and closes the sixth opening. The gas chromatograph mass spectrometer according to claim 1 or 2 ,
A gas chromatograph mass spectrometer, comprising an opening/closing section that opens and closes at least one of the openings formed in the ionization chamber.

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