Three-dimensional quadrupole mass spectrometer

• US 5,747,800 A
• Filed: 11/13/1996
• Issued: 05/05/1998
• Est. Priority Date: 12/13/1995
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yano, Masayoshi, Mochizuki, Kohei
• Primary Examiner(s): NGUYEN, KIET TUAN
• Application Number:
  US08/749,269
• Time in Patent Office: 538 Days
• Field of Search: 250/292, 250/281, 250/288, 250/288 A, 250/423 R, 250/427
• US Class Current: 250/292
• CPC Class Codes: H01J 27/024 Extraction optics, e.g. grids
• CPC Class Codes: H01J 49/424 Three-dimensional ion traps, i.e. comprising end-cap and ring electrodes
• CPC Class Codes: H01J 49/4265 Controlling the number of trapped ions; preventing space charge effects

Abstract

A three-dimensional quadrupole mass spectrometer is suitable for preventing occurrence of a situation where the mass spectrometry cannot be conducted by an excessive existence of ions in a three-dimensional ion confining space, an amount of ions emitted from an ion source 1 is detected by a first electrode 3 of a lens, an output signal therefrom is inputted to a power supply 17 of a second electrode 4 of the lens and a focusing condition of ions caused by the lens is changed such that an amount of ions existing in the three-dimensional ion confining space does not exceed a certain level.

Claims

1. A three-dimensional quadrupole mass spectrometer comprising:

an ion former for forming ions;

electrodes for forming an electric field in a three-dimensional ion confining space;

a voltage controller for forming a three-dimensional quadrupole electric field in the three-dimensional ion confining space by applying a periodic voltage to the electrodes such that said ions formed by the ion former are confined into the three-dimensional ion confining space, wherein the voltage controller controls the periodic voltage such that said ions having a desired mass/charge ratio are emitted from the three-dimensional ion confining space;

a detector for detecting an estimated amount of said ions existing in the three-dimensional ion confining space by detecting the ions before entering the three-dimensional ion containing space; and

a restrictor to restrict ion density being introduced to the three-dimensional ion confining space.

2. The three-dimensional quadrupole mass spectrometer according to claim 1, wherein the ion former is arranged outside of the three-dimensional ion confining space such that the formed ions are introduced into the three-dimensional ion confining space and the detector is arranged between the ion former and the three-dimensional ion confining space.

3. A three-dimensional quadrupole mass spectrometer comprising:

an ion former for forming ions;

electrodes for forming an electric field in a three-dimensional ion confining space;

a voltage controller for forming a three-dimensional quadrupole electric field by applying a periodic voltage to the electrodes such that said ions formed by the ion former are confined to the three-dimensional ion confining space;

wherein the voltage controller controls the periodic voltage such that said ions having a desired mass/charge ratio are emitted from the three-dimensional ion confining space;

a detector for detecting an estimated amount of said ions by detecting the ions before entering the three-dimensional containing space and generating an electric signal corresponding to the amount of the estimated amount of ions existing in the three-dimensional ion confining space; and

a restrictor restricting the amount of the ions existing in the three-dimensional ion confining space by controlling ion density introduced to the three-dimensional ion confining space such that the amount of the ions does not substantially exceed a predetermined level based on the generated electric signal.

4. The three-dimensional quadrupole mass spectrometer according to claim 3, wherein the ion former is arranged outside of the three-dimensional ion confining space such that the ions formed by the ion former are introduced into the three-dimensional ion confining space, the detector is arranged between the ion former and the three-dimensional ion confining space and said restrictor changes a focusing condition of the ions introduced into the three-dimensional confining space based on the electric signal.

5. The three-dimensional quadrupole mass spectrometer according to claim 4, wherein the focusing condition of the ions is changed such that when the electric signal reaches said predetermined level, the electric signal does not substantially exceed the predetermined level and thereafter, when the electric signal becomes lower than the predetermined level, the changed focusing condition of the ions is recovered to a focusing condition of said ions before the focusing condition has been changed.

6. The three-dimensional quadrupole mass spectrometer according to claim 5, wherein said restrictor includes an electrostatic lens and a power supply for the electrostatic lens, and wherein an output from the power supply can be changed such that the focusing condition of the ions is changed based on the electric signal.

7. The three-dimensional quadrupole mass spectrometer according to claim 3, wherein the ion former is arranged outside of the three-dimensional ion confining space such that the ions formed by the ion former are introduced into the three-dimensional ion confining space, the detector is arranged between the ion former and the three-dimensional ion confining space and said restrictor changes an amount of the ions to be formed by the ion former based on the electric signal.

8. The three-dimensional quadrupole mass spectrometer according to claim 7, wherein the amount of the ions to be formed by the ion former is changed such that when the electric signal reaches the predetermined level, the electric signal does not exceed substantially the predetermined level and thereafter, when the electric signal starts falling from the predetermined level, the changed amount of said ions to be formed is recovered to an amount of said ions to be formed before the amount has been changed.

9. The three-dimensional quadrupole mass spectrometer according to claim 3, wherein the ion former is arranged outside of the three-dimensional ion confining space such that the ions formed by the ion former are introduced into the three-dimensional ion confining space, the detector is arranged between the ion former and the three-dimensional ion confining space and the ion former forms the ions substantially under an atmospheric pressure.

10. The three-dimensional quadrupole mass spectrometer according to claim 9, wherein an ionization under the atmospheric pressure is an ionization by corona discharge using a corona discharge electrode and a position of the corona discharge electrode is changed based on the electric signal.

11. The three-dimensional quadrupole mass spectrometer according to claim 10, wherein the position of the corona discharge electrode is changed such that when the electric signal reaches said predetermined level, the electric signal does not exceed substantially the predetermined level and thereafter, when the electric signal becomes lower than the predetermined level, the changed position of the corona discharge electrode is recovered to a position of the corona discharge electrode before the position has been changed.

12. The three-dimensional quadrupole mass spectrometer according to claim 9, wherein said restrictor changes a focusing condition of the ions introduced into the three-dimensional ion confining space based on the electric signal.

13. The three-dimensional quadrupole mass spectrometer according to claim 12, wherein the focusing condition of the ions is changed such that when the electric signal reaches said predetermined level, the electric signal does not substantially exceed the predetermined level and thereafter, when the electric signal becomes lower than the predetermined level, the changed focusing condition of the ions is recovered to a focusing condition of the ions before the condition has been changed.

14. A three-dimensional quadrupole mass spectrometer comprising:

an ion former for forming ions in a three-dimensional ion confining space;

electrodes for forming an electric field in the three-dimensional ion confining space;

a voltage controller for forming a three-dimensional quadrupole electric field by applying a periodic voltage to the electrodes such that said ions formed by the ion former are confined to the three-dimensional ion confining space;

wherein the voltage controller controls the periodic voltage such that said ions having a desired mass/charge ratio are emitted from the three-dimensional ion confining space;

a detector for detecting an estimated amount of said ions in the three-dimensional confining space by detecting ions emitted from the three-dimensional ion confining space and generating an electric signal corresponding to the amount of the estimated amount of said ions existing in the three-dimensional ion confining region; and

a restrictor restricting the amount of the ions existing in the three-dimensional ion confining space by controlling ion density introduced to the three-dimensional ion confining space such that the amount of the ions does not substantially exceed a predetermined level based on the generated electric signal.

15. The three-dimensional quadrupole mass spectrometer according to claim 14, wherein a sample is introduced into the three-dimensional ion confining space, the ion former forms electrons and causes the electrons to impinge on the introduced sample for ionization and the detector detects the ions existing in the three-dimensional ion confining space by detecting said ions emitted from the three-dimensional ion confining space.

16. The three-dimensional quadrupole mass spectrometer according to claim 15, wherein said restrictor changes an amount of the electrons to be generated or an amount of the sample to be introduced in response to the electric signal.

17. The three-dimensional quadrupole mass spectrometer according to claim 14, wherein an amount of the ions to be formed or an amount of the sample to be introduced is changed such that when the electric signal reaches said predetermined level, the electric signal does not substantially exceed the predetermined level and thereafter, when the electric signal becomes lower than the predetermined level, the changed amount of the ions to be formed or the changed amount of the sample to be introduced is recovered to an amount of the ions to be formed or an amount of the sample to be introduced before the electrical signal reaches the predetermined level.

18. The three-dimensional quadrupole mass spectrometer according to claim 14, wherein the detector includes means for detecting a degree of vacuum of the three-dimensional ion confining space to thereby provide the electric signal and an amount of the sample to be introduced is changed based on the electric signal.

19. The three-dimensional quadrupole mass spectrometer according to claim 18, wherein the amount of the introduced sample is changed such that when the electric signal reaches a predetermined level, the electric signal does not substantially exceed the predetermined level and thereafter, when the electric signal becomes lower than the predetermined level, the changed amount of the sample to be introduced is recovered to an amount of the sample to be introduced before the electrical signal reaches the predetermined level.