JPH09129175A - Mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ion trap type mass spectrometer capable of stably detecting ions and obtaining a mass spectrum having a high S-N ratio. SOLUTION: Electrons to be ionized in an ion trap 1-6 and ions generated outside the ion trap 1-6 are implanted into the ion trap 1-6 from the position other than an end cap. The ions confined in the ion trap 1-6 are extracted from two opposite end cap electrodes 1-3, 1-5 and fine holes 1-8, 1-11, 1-12 on both sides, and they are detected by ion detection sections 1-13, 1-14 provided in the later stage respectively. The detected data are finally added together.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas chromatograph (G) which is effective for separation and analysis of a mixture.
C) and mass spectrometry (MS) combined equipment, that is, gas chromatograph / mass spectrometry (hereinafter abbreviated as GC / MS), liquid chromatograph (LC) and mass spectrometry (LC). Mass S
pectrometry (MS) coupled device, that is, liquid chromatograph / mass spectrometry (abbreviated as LC / MS hereafter) or capillary electrophoresis (Capillary Electroph)
oresis: CE) using a mass spectrometry as a detector, that is, capillary electrophoresis / mass spectrometry (hereinafter CE /
(MS is abbreviated) and the like, and relates to a device configuration of a device for performing mass analysis by separating a mixed sample existing in a gas phase or a liquid, ionizing it, and introducing it into a mass spectrometer. Further, the present invention relates to a device for performing flow injection analysis in which a solution sample is continuously introduced to perform ionization and mass spectrometry.

[0002]

2. Description of the Related Art At present, in the field of mass spectrometry, a mass spectrometer having an ion trap (hereinafter referred to as an ion trap mass spectrometer = ITMS) is regarded as a promising new analyzer, and GC / MS and LC / MS are promising. Or CE /
It is applied to MS. An example thereof is described in Journal of Mass Spectrometry and Aion Processes, 1991, Vol. 106, page 1. For reference, FIG. 14 shows a typical apparatus configuration of GC / ITMS to which the ion trap mass spectrometer is applied.

The sample to be measured flows out from the gas chromatograph 14-1 and passes through a capillary 14-2, which is an ion trap 14 composed of an end cap electrode 14-3, a ring electrode 14-4, and an end cap electrode 14-5.
-6. Electrons are emitted from the electron gun 14-7 and open in the center of the end cap electrode 14-3.
It is driven into the ion trap through 4-8. The electrons injected into the ion trap ionize the introduced sample molecules by electron impact to generate ions inside the ion trap 14-6.

The ion trap 14-6 is capable of confining ions within a specific mass number range for a predetermined time by a high frequency electric field. Ions trapped for a certain time
By scanning the voltage of the high frequency electric field, (mass number /
Those having a lower valency) were sequentially ejected to the outside, and after being drawn out by the extraction electrode 14-10 through the pore 14-9 opened in the center of the end cap electrode 14-5, they were provided in the subsequent stage of the end cap. Ion detector 14-1
1 is detected.

The signal of the ion thus detected is passed through the control unit 14-14 and the data processing unit 14-1.
2 is transferred. The information obtained is the data processing unit 14
At -12, the monitor unit 14-13 is set as a normal mass spectrum.
Will be displayed. Gas chromatograph 14-1, ion trap 14-6, electron gun 14-7, extraction electrode 14-
10. The ion detector 14-11 is controlled by the controller 14-14. Also, the inside of the device is the exhaust unit 14-15.
Is kept in a vacuum by.

[0006]

In the conventional device as described above, since the shape of the ion trap is spatially symmetric, the ions trapped inside the ion trap ring according to the frequency of the applied high frequency electric field. Draw an orbit that is (ideally) symmetrical with respect to the center of the electrode. Ions moving in a symmetrical orbit with respect to the ring electrode are extracted from the pores of the end cap on one side, and therefore the extraction efficiency differs depending on the position and movement direction of the ions. Stability deteriorates.

An object of the present invention is to provide an ion trap mass spectrometer capable of solving the above problems, capable of stable detection, and capable of obtaining a mass spectrum having a high SN ratio.

[0008]

In the present invention, the ions trapped inside the ion trap are extracted from the pores on the opposite sides of the two facing endcap electrodes, and the ion detector is provided at the subsequent stage of each endcap electrode. To detect the ions. After detection, by adding the obtained data, almost the same effect as double integration can be obtained,
It is possible to obtain a stable mass spectrum with a high SN ratio. In order to achieve this, means for taking in electrons for electron impact ionization inside the ion trap,
Alternatively, as a means for incorporating ions generated by an external ion source into the inside of the ion trap, do not use a hole vacant in the center of the end cap electrode on one side, but use a hole vacant in other places, for example, a ring electrode. .

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an example of a mass spectrometer for realizing the present invention. The sample to be measured flows out from the gas chromatograph 1-1, passes through the capillary 1-2, and the end cap electrodes 1-3,
It is introduced into an ion trap 1-6 composed of a ring electrode 1-4 and an end cap electrode 1-5. The electrons are emitted from the electron gun 1-7 and are injected into the ion trap through the pores 1-8 opened in the ring electrode 1-4.
The acceleration energy of the electrons emitted from the electron gun 1-7 is synchronized with the high frequency voltage applied to the ring electrode 1-4, and the energy of the electrons driven into the ion trap is made constant.

The electrons injected into the ion trap ionize the introduced sample molecules by electron impact, but the ionization energy is constant. The ion trap 1-6 can confine ions within a specific mass number range for a certain period of time by a high frequency electric field. The ions trapped for a certain period of time are ejected to the outside in order from the one with the lowest mass number / valence by scanning the voltage of the high frequency electric field, and the extraction electrodes 1-9 and 1-10 cause the end cap electrode 1 to move. -3, 1-5 After being drawn out through the pores 1-11, 1-12 opened in the center of each, they are detected by the ion detection parts 1-13, 1-14 provided in the subsequent stage of the respective end caps. It

The signal of the ions thus detected is transferred to the data processing section 1-15 through the control section 1-17. The obtained information is 1-1 in this data processing unit.
5 is added, and normally, as a mass spectrum, the monitor unit 1-
16 is displayed. Gas chromatograph 1-1, ion trap 1-6, electron gun 1-7, extraction electrode 1-9,
The control unit 1-17 controls the 1-10 and the ion detection units 1-13 and 1-14. Further, the inside of the apparatus is kept in vacuum by the exhaust unit 1-18.

FIG. 2 is a conceptual diagram showing that the SN ratio of the mass spectrum obtained by the present invention is improved. Conventionally, the measurement was performed only from the detector after the end cap electrode on one side. Therefore, if there is no special measure for the voltage application timing of the extraction electrode, only 50% of the trapped ion amount is detected. Was there. This is almost the same as the amount of ions detected on one side when the measurement is performed from the detectors after the end cap electrodes on both sides according to the present invention. By adding the mass spectra 2-1 and 2-2 by the ions detected on each side, the randomly generated noise portions 2-3 and 2-4 are averaged, and the signal portions 2-5 and 2- 6 is superimposed. The finally obtained mass spectrum 2-7 is about 40
Shows a high SN ratio.

FIG. 3 is a block diagram showing a part of another mass spectrometer for carrying out the present invention. The laser 3-2 is used to ionize the sample molecules introduced into the ion trap 3-1.

FIG. 4 is a diagram showing the time change of the voltage applied to the extraction electrode for carrying out the present invention. In the figure, the time change of the voltage applied to the extraction electrodes on both sides and the time change of the high frequency electric field voltage applied to the ion trap are shown on the same time axis. Ions are confined inside the ion trap for a certain time 4-1 and then the voltage of the high frequency electric field is scanned during the time 4-2. As a result, the ions trapped inside the ion trap can be expelled to the outside in order from the lowest mass number / valence value. The voltage 4-3 applied to the extraction electrodes on both sides is changed at the same frequency as the high frequency electric field. Ions trapped inside the ion trap draw an orbit that is (ideally) symmetric with respect to the center of the ring electrode according to the frequency of the applied high frequency electric field, so that the frequency offset 4-4 is moved,
By adjusting the application timing of the extraction voltage,
Furthermore, highly sensitive detection can be performed.

FIG. 5 is a block diagram showing a part of another mass spectrometer for carrying out the present invention. The sample flows out from the gas chromatograph 5-1 and is introduced into the external ion source 5-3 through the capillary 5-2. The electrons are emitted from the electron gun 5-4 and driven into the external ion source 5-3. The electrons injected into the external ion source ionize the introduced sample molecules by electron impact.

The ions generated by the external ion source 5-3 are emitted from the external ion source by the voltage applied to the repeller electrode 5-5, and pass through the ion trajectory correcting section 5-6,
It is introduced into an ion trap 5-10 composed of an end cap electrode 5-7, a ring electrode 5-8, and an end cap electrode 5-9. At this time, the implantation energy from the external ion source 5-3 is synchronized with the high frequency voltage applied to the ring electrode 5-8 so as to be constant.

A damping gas such as helium is introduced into the ion trap 5-10 from a damping gas introduction section 5-11, and plays a role of stabilizing the ion trajectories inside the ion trap. . After confining the ions, perform the same measurement,
At this time, the external ion source is kept in vacuum by an exhaust unit 5-12 which is different from the exhaust unit 5-13 for exhausting the inside of the apparatus.

FIG. 6 is a constitutional view showing another method for introducing a sample into the external ion source for carrying out the present invention.
By the pores 6-1, 6-2 and the exhaust parts 6-3, 6-4,
Ions are introduced from the atmospheric pressure to the external ion source 6-5 in vacuum. As a result, it is possible to measure impurities in the atmosphere.

FIG. 7 is a block diagram showing another ionization method in an external ion source in vacuum for realizing the present invention. The sample introduced into the external ion source 7-1 is ionized by the laser 7-2. Ions generated in the external ion source 7-1 are emitted from the external ion source by operating the voltage applied to the repeller electrode 7-3.

FIG. 8 is a constitutional view showing another ionization method in an external ion source in a vacuum for realizing the present invention. The reaction substance previously introduced into the external ion source 8-1 is ionized by the electron gun 8-2. Then, the sample is passed through the capillary 8-3 to the external ion source 8
-1, and ionizes the sample molecule by an ion-molecule reaction between the ion of the reactant and the sample molecule. The generated ions are emitted from the external ion source by operating the voltage applied to the repeller electrode 8-3.

FIG. 9 is a block diagram showing a part of another mass spectrometer for carrying out the present invention. The sample flows out of the liquid sending section 9-1, and is sent to the external ion source 9-3 through the capillary 9-2. The ions generated by the external ion source 9-3 are introduced into the mass analysis unit 9-7 through the ion introduction pores 9-5 and the second pores 9-6 of the mass analysis unit heated by the heater 9-4. It The ions introduced into the mass spectrometric section 9-7 are guided to the ion trap through the ion trajectory correction section 9-8. Between 9-5 and 9-6, it is exhausted to about 0.1 to several Torr by a roughing pump.

FIG. 10 is a constitutional view when an electrospray ionization method is adopted as an ionization method in an external ion source under atmospheric pressure in order to realize the present invention. The sample is sent from the liquid sending unit 10-1 through the capillary 10-2 to the stainless thin tube 10-3 at a flow rate of several to several tens of microliters per minute. A high voltage of several kilovolts is applied between the stainless thin tube 10-3 and the ion introduction pore 10-5. The sample is electrostatically sprayed and ionized, and the mass spectrometric analysis unit 10-
4 is introduced.

FIG. 11 is a configuration diagram when the atmospheric pressure chemical ionization method is adopted as the ionization method in the external ion source under the atmospheric pressure in order to realize the present invention. The sample is sent from the liquid sending section 11-1 through the capillary 11-2 to the stainless thin tube 11-3 at a flow rate of several hundred to several thousand microliters per minute. The outlet of the stainless thin tube 11-3 is inserted into the atomizing section 11-4, and the sample is atomized there. The atomized sample is vaporized in the vaporizing section 11-5.
A high voltage of several kilovolts is applied to the needle electrode 11-6, and corona discharge is generated between the needle electrode 11-6 and the ion introduction pore 11-8. The vaporized sample is ionized in this corona discharge region and introduced into the mass spectrometric section 11-9 through the ion introduction pore 11-8.

FIG. 12 is a block diagram showing an ion trajectory correction unit for carrying out the present invention. Ion trajectory correction unit 1
Reference numeral 2-1 includes an Einzel lens 12-3, an ion guide 12-4, and a grid 12-5. The ions 12-2 are converged and orbitally corrected by an electric field and introduced into the ion trap 12-6. .

FIG. 13 is a configuration diagram when ions are deflected in the ion trajectory correction unit for carrying out the present invention. The central axes of the Einzel lens 13-4, the ion guide 13-5, and the grid 13-6, which form the ion trajectory correcting unit 13-1, are deviated, and the ions 13-3 are converged and orbitally corrected by the electric field. Although being introduced into the trap 13-7, the neutral particles or the like 13-2 that cause noise go straight and do not enter the ion trap 13-7.

[0026]

According to the present invention, since it is possible to perform spatially symmetric measurement, it is possible to stably detect the ions confined inside the ion trap. Since the detected data are added together, it is possible to obtain a mass spectrum having a high S / N ratio.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for implementing the present invention.

FIG. 2 is a conceptual diagram showing the effect of the present invention.

FIG. 3 is an apparatus configuration diagram for implementing the present invention.

FIG. 4 is an explanatory diagram showing changes over time in device parameters for carrying out the present invention.

FIG. 5 is a device configuration diagram for carrying out the present invention.

FIG. 6 is a device configuration diagram for carrying out the present invention.

FIG. 7 is a device configuration diagram for carrying out the present invention.

FIG. 8 is a device configuration diagram for carrying out the present invention.

FIG. 9 is a device configuration diagram for carrying out the present invention.

FIG. 10 is a device configuration diagram for carrying out the present invention.

FIG. 11 is a device configuration diagram for carrying out the present invention.

FIG. 12 is a block diagram of an apparatus for carrying out the present invention.

FIG. 13 is a configuration diagram of a device for carrying out the present invention.

FIG. 14 is a configuration diagram of a conventional GC / MS device.

[Explanation of symbols]

1-1 ... Gas chromatograph, 1-2 ... Capillary,
1-3 ... end cap electrode, 1-4 ... ring electrode, 1
-6 ... Ion trap, 1-7 ... Electron gun, 1-8, 1-
11, 1-12 ... Pores, 1-9, 1-10 ... Extraction electrodes, 1-13, 1-14 ... Ion detection section, 1-15 ... Data processing section, 1-16 ... Monitor section, 1 -17 ... control unit,
1-18 ... Exhaust section.

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Hideaki Koizumi 1-280 Higashi Koikeku, Kokubunji, Tokyo Inside Hitachi Central Research Laboratory (72) Inventor Shu Hirabayashi 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Laboratory (72) Inventor Yukiko Hirabayashi 1-280, Higashi Koikekubo, Kokubunji City, Tokyo Central Research Laboratory, Hitachi, Ltd.

Claims (24)

[Claims] 1. A mass spectrometer having an ion trap composed of two facing endcap electrodes and one ring electrode arranged so as to surround a space between the endcap electrodes. From the above, a specific ion is extracted in both opposite directions through the pores at or near the center of the two end cap electrodes. 2. Ions extracted in both directions from the ion trap through the pores in the center of the end cap electrode or in the vicinity of the center are detected by detectors provided at the subsequent stages of the respective end cap electrodes. The mass spectrometer according to claim 1. 3. The mass spectrometer according to claim 2, wherein a mass spectrum of ions detected by a detector provided after the end cap electrode is added and displayed. 4. The mass spectrometer according to claim 1, wherein a gas chromatograph is used as a means for introducing the sample into the ion trap. 5. An electron emitted from an electron gun is used as a means for ionizing a neutral sample inside the ion trap, and the electron is from a location different from the two end cap electrodes facing each other. The mass spectrometer according to any one of claims 1 to 4, wherein the mass spectrometer is incorporated inside the ion trap. 6. Ionization by using electrons emitted from an electron gun as a means for ionizing a neutral sample inside the ion trap, and by synchronizing the emission energy of the electrons with a high frequency applied to a ring electrode. The mass spectrometer according to claim 1, wherein the energy is constant. 7. A laser is used as a means for ionizing a neutral sample inside the ion trap, and the laser is taken in from a place different from the two end cap electrodes facing each other. The mass spectrometer according to claim 1. 8. The mass spectrometer according to claim 1, wherein the voltage applied to extract the ions from the end cap electrode has the same frequency as the high frequency applied to the ring electrode. 9. The neutral particles are ionized by an ion source provided outside the ion trap, and the generated ions are taken into the inside of the ion trap from a place different from the two facing endcap electrodes. The mass spectrometer according to any one of claims 1 to 3, characterized in that. 10. An ion source provided outside the ion trap is used to ionize neutral particles, and the emission energy of the generated ions is synchronized with the high frequency applied to the ring electrode so that the implantation energy into the ion trap is increased. The mass spectrometer according to any one of claims 1 to 3, wherein the mass spectrometer is constant. 11. The mass spectrometer according to claim 8, wherein the ion source is in a vacuum region. 12. The mass spectrometer according to claim 9, wherein a gas chromatograph is used as a means for introducing a sample into the ion source. 13. The mass spectrometer according to claim 9, wherein differential evacuation is used as means for introducing a neutral sample into the ion source. 14. The mass spectrometer according to claim 9, wherein electron impact is used as the ionization means in the ion source. 15. The mass spectrometer according to claim 9, wherein a laser is used as the ionization means in the ion source. 16. The mass spectrometer according to claim 9, wherein an ion-molecule reaction is used as the ionization means in the ion source. 17. The mass spectrometer according to claim 8, wherein the ion source is under atmospheric pressure. 18. The mass spectrometer according to claim 15, wherein an atmospheric pressure chemical ionization method is used as the ionization means in the ion source. 19. The mass spectrometer according to claim 15, wherein an electrospray ionization method is used as the ionization means in the ion source. 20. The mass spectrometer according to claim 15, wherein a liquid chromatograph is used as a means for introducing a sample into the ion source. 21. The mass spectrometer according to claim 15, further comprising a plurality of differential evacuation units for introducing ions generated under the atmospheric pressure into the vacuum region by the ion source. 22. The mass spectrometer according to claim 15, wherein the ion introduction pores for introducing into the vacuum region the ions generated by the ion source under the atmospheric pressure are heated. 23. An ion orbit correction unit for converging and correcting the orbits of the ions generated by the ion source and then guiding the ions into the ion trap unit is provided in the preceding stage of the ion trap. The described mass spectrometer. 24. The mass spectrometer according to claim 20, wherein the ion orbit at the entrance and the ion orbit at the exit of the ion orbit correction unit are not on the same straight line.