JP3758382B2 - Mass spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mass spectrometer used in a gas chromatograph mass spectrometer (GC / MS) and a liquid chromatograph mass spectrometer (LC / MS), and more particularly, a quadrupole filter for ions generated in an ion source. The present invention relates to an ion transport optical system for transporting to a mass separation unit.
[0002]
[Prior art]
FIG. 4 is a diagram showing a basic configuration of a general mass spectrometer. The ion source 10 ionizes sample molecules by using various ionization methods such as an electron impact ionization method and a chemical ionization method, and introduces the ions generated therein to a mass separation unit 11 such as a quadrupole filter to obtain a mass number (mass / mass / The ions are separated for each charge) and then detected by the detector 12. If the ions greatly deviate from the optical axis C from the ion source 10 to the mass separation unit 11, the detection sensitivity and accuracy will be reduced, so that the ions generated from the ion source 10 are mass separated without leakage as much as possible. In order to send to the unit 11, a so-called ion transport optical system is often used.
[0003]
FIG. 5 is a block diagram of a conventional ion transport optical system. A large number of annular (or donut plate-like, flat cylindrical) electrodes 13 are arranged along the ion optical axis C, and a high-frequency voltage whose phase is 180 degrees different from that of the voltage source 14 is applied between the adjacent electrodes 13. . By this voltage, an ion passage 15 having a substantially cylindrical pseudo potential wall is formed inside the electrode 13, so that ions introduced from one end surface side thereof do not protrude from the ion passage 15. To reach the opposite end face.
[0004]
[Problems to be solved by the invention]
However, in the ion transport optical system configured as described above, a large number of electrodes 13 must be fixed at predetermined intervals, and the structure of the holding mechanism for the electrodes 13 becomes complicated. In addition, a voltage must be applied to each electrode 13 and the wiring becomes complicated.
[0005]
The present invention has been made to solve such problems, and an object of the present invention is to provide a mass spectrometer equipped with an ion transport optical system with a simple holding structure and wiring. .
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a mass spectrometer including an ion transport optical system for transporting ions generated in an ion source to a mass separation unit, wherein each of the ion transport optical systems is a spiral. The two electrodes wound in a shape are loosely fitted in the direction of the ion optical axis so that the windings of each electrode are alternately present and separated from each other, and high-frequency voltages with different phases are applied to the two electrodes, respectively. It is characterized by doing.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the ion transport optical system according to the present invention, it is most preferable to apply a high-frequency voltage having a phase difference of 180 degrees to the two electrodes. When such a voltage is applied, an ion passage having a substantially cylindrical potential wall in the direction of the ion optical axis is formed inside the spiral winding of the two electrodes. Therefore, ions introduced into the ion passage from one open end surface of the electrode pass through to the other open end surface of the electrode without diverging outward.
[0008]
【The invention's effect】
In the ion transport optical system according to the present invention, it is only necessary to provide one voltage application point for each electrode, so that wiring becomes very simple. Further, as long as a material having a certain degree of rigidity is used as the electrode, it is not necessary to hold it for each winding. For example, each electrode may be held only at both edge portions. For this reason, the cost can be reduced as compared with the conventional ion transport optical system.
[0009]
【Example】
An embodiment of an ion transport optical system in the mass spectrometer of the present invention will be described with reference to FIGS. FIG. 1 is a perspective view of the ion transport optical system, and FIG. 2 is a side view of the ion transport optical system. In FIG. 1, one of the pair of electrodes shows only both ends.
[0010]
This ion transport optical system has two electrodes (reference numerals 1a and 1b, respectively) formed by spirally winding an elongated metal rod, and the winding of each electrode 1a and 1b is an ion optical axis. They are arranged so as to be alternately spaced apart at a predetermined interval in the C direction. Since each electrode 1a, 1b has high rigidity and hardly bends, as shown in FIG. 2, it is stably fixed by holding appropriate portions of windings at both ends with a holder 2 made of an insulator. be able to. Each electrode 1a, 1b is connected to a voltage source 3 at a predetermined location (one location), and a high-frequency voltage having the same amplitude and the same frequency but having a phase difference of 180 degrees is applied. It is like that.
[0011]
When such a voltage is applied to the electrodes 1a and 1b, the ion passage 4 having a substantially cylindrical pseudo potential wall inside the spiral electrodes 1a and 1b, which is substantially the same as the above-described conventional technique. Is formed. The ions introduced into one end surface of the ion passage 4 proceed so as not to protrude outward from the ion passage 4, reach the other open end surface, and escape. Therefore, by introducing ions generated in the ion source into the ion transport optical system, the ions can be efficiently sent to the subsequent stage (for example, a mass separation unit).
[0012]
The electrodes 1a and 1b may be formed by spirally winding a band-shaped metal plate having a predetermined width instead of a rod.
[0013]
FIG. 3 is a perspective view showing another embodiment of the ion transport optical system according to the present invention. In the above-described embodiment, the windings of the electrodes 1a and 1b are wound in a circle having substantially the same diameter. However, in this embodiment, the diameter of each winding of the electrodes 1a and 1b is gradually increased with respect to the ion traveling direction. It is formed to be smaller.
[0014]
When the above-described high-frequency voltage with reversed phase is applied to the electrodes 1a and 1b having such a shape, the ion passage 4 having a shape obtained by cutting the top of the cone with a circular cross section is formed. That is, ions introduced into one end surface of the ion passage 4 (the end surface on the bottom surface side of the cone) are converged in the vicinity of the ion optical axis C as they travel. Therefore, as shown in FIG. 3, when the skimmer 5 having a small-diameter orifice is arranged at the subsequent stage of the ion transport optical system, the ions can be converged and the orifice can be efficiently passed.
[0015]
In addition, the electric field strength generated between the adjacent turns of the electrodes 1a and 1b increases as the distance between the turns (that is, the pitch) decreases. Therefore, even when the respective windings of the electrodes 1a and 1b are wound to substantially the same diameter as in the embodiment of FIG. 1, the ion passage 4 is formed by gradually narrowing the pitch with respect to the ion traveling direction. It can be made into the shape as shown in.
[0016]
The above-described embodiment is an example, and it is obvious that changes and modifications can be made as appropriate within the scope of the present invention.
[Brief description of the drawings]
FIG. 1 is a perspective view of an embodiment of an ion transport optical system in a mass spectrometer of the present invention.
FIG. 2 is a side view of the embodiment of FIG.
FIG. 3 is a perspective view of another embodiment of the ion transport optical system in the mass spectrometer of the present invention.
FIG. 4 is a basic configuration diagram of a general mass spectrometer.
FIG. 5 is a configuration diagram of a conventional ion transport optical system.
[Explanation of symbols]
1a, 1b ... electrode 2 ... holder 3 ... voltage source 4 ... ion passage

Claims (1)

In a mass spectrometer equipped with an ion transport optical system for transporting ions generated from an ion source to a mass separation unit, the ion transport optical system includes two electrodes wound in a spiral shape in the direction of the ion optical axis. The mass spectrometer is characterized in that windings of each electrode are alternately present and loosely fitted so as to be separated from each other, and high frequency voltages having different phases are applied to the two electrodes.

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