JP2000123780A - Mass spectrometer - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To simplify the configuration of an ion transport optical system. SOLUTION: Two electrodes 1a and 1b each formed by spirally winding a metal conductor bar are arranged in the direction of the ion optical axis C such that their turns are alternately separated by a predetermined distance. Each electrode 1
When high-frequency voltages having phases different from each other by 180 degrees are applied to a and 1b via one feeding point, an ion passage 4 having a substantially cylindrical pseudo potential wall is formed inside the winding. You. Since the electrodes 1a and 1b only need to hold, for example, only the windings at both ends, the holding mechanism is simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer used for a gas chromatograph mass spectrometer (GC / MS) or a liquid chromatograph mass spectrometer (LC / MS). The present invention relates to an ion transport optical system for transporting the extracted ions to a mass separation unit such as a quadrupole filter.

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a basic configuration of a general mass spectrometer. The ion source 10 ionizes the sample molecules by using various ionization methods such as an electron impact ionization method and a chemical ionization method, introduces ions generated there into a mass separation unit 11 such as a quadrupole filter, and outputs a mass number (mass / mass). After the ions are separated for each charge), they are detected by the detector 12. If the ions deviate significantly from the optical axis C from the ion source 10 to the mass separation unit 11, the detection sensitivity and accuracy will be reduced. A so-called ion transport optical system is often used for sending to the section 11.

FIG. 5 is a configuration diagram of a conventional ion transport optical system. A large number of annular (or donut-shaped, flat-cylindrical) electrodes 13 are arranged along the ion optical axis C, and a high-frequency voltage having a phase difference of 180 degrees from a voltage source 14 is applied between adjacent electrodes 13. . Due to 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 thereof do not protrude from the ion passage 15. To reach the opposite end face.

[0004]

However, in the ion transport optical system having the above-mentioned structure, a large number of electrodes 13 must be fixed at predetermined intervals, and the structure of the holding mechanism of the electrodes 13 becomes complicated. In addition, a voltage must be applied to each of the electrodes 13, and the wiring becomes complicated.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a mass spectrometer having an ion transport optical system having a simple holding structure and simple wiring. It is in.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a mass spectrometer having an ion transport optical system for transporting ions generated by an ion source to a mass separation unit. The ion transport optical system is formed by loosely fitting two spirally wound electrodes so that the turns of each electrode are alternately present in the direction of the ion optical axis and are separated from each other. , And high-frequency voltages having different phases are applied to each of them.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In an 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 each of two electrodes. When such a voltage is applied, an ion passage having a substantially cylindrical pseudo-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 face of the electrode pass through to the other open end face of the electrode without diverging outward.

[0008]

According to the ion transport optical system of the present invention,
Since it is sufficient to provide one voltage application point for each electrode, the wiring becomes very simple. If only a material having a certain degree of rigidity is used as the electrode, it is not necessary to hold the material for each winding. For example, it is only necessary to hold the material for each electrode only at both edges. For this reason, the cost can be reduced as compared with the conventional ion transport optical system.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the 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. FIG. 1 shows only one end of one set of electrodes.

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 of the electrodes 1a and 1b. They are arranged so as to alternately exist at predetermined intervals in the direction of the ion optical axis C. Since each of the electrodes 1a and 1b has high rigidity and hardly bends, the electrodes 2a and 1b are stably fixed by holding appropriate portions of the windings at both ends with a holder 2 made of an insulator as shown in FIG. be able to. In addition, 1a and 1b of each electrode are at predetermined locations (each one location).
Are connected to the voltage source 3 so that high-frequency voltages having the same amplitude and the same frequency but differing only in phase from each other by 180 degrees are applied.

When such a voltage is applied to each of the electrodes 1a and 1b, an ion having a substantially cylindrical pseudo potential wall is formed inside the spiral electrodes 1a and 1b, which is substantially the same as that of the prior art. A passage 4 is formed. The ions introduced to one end face of the ion passage 4 proceed so as not to protrude outside from the ion passage 4 and reach another open end face to escape. Therefore, by introducing the ions generated by the ion source into the ion transport optical system, the ions can be efficiently sent to a subsequent stage (for example, a mass separation unit).

The electrodes 1a and 1b may be formed by spirally winding a band-shaped metal plate having a predetermined width instead of a rod.

FIG. 3 is a perspective view showing another embodiment of the ion transport optical system according to the present invention. In the above embodiment, the electrode 1
Although each of the windings a and 1b is wound in a circular shape having substantially the same diameter, in this embodiment, the diameter of each of the windings of the electrodes 1a and 1b is formed so as to gradually decrease in the traveling direction of ions. Have been.

When the high-frequency voltage having the inverted phase as described above is applied to the electrodes 1a and 1b having such a shape, an ion passage 4 having a shape obtained by cutting off the top of the cone with a circular cross section is formed. That is, the ions introduced to one end surface of the ion passage 4 (the end surface on the bottom side of the cone) converge to the vicinity of the ion optical axis C as they proceed. Therefore, as shown in FIG. 3, when the skimmer 5 having a small-diameter orifice is disposed downstream of the ion transport optical system, ions can be converged and efficiently pass through the orifice.

The electric field strength generated between the adjacent turns of the electrodes 1a and 1b increases as the spacing (ie, pitch) between the turns becomes smaller. Therefore, even when the windings of the electrodes 1a and 1b are wound to have substantially the same diameter as in the embodiment of FIG. 1, the pitch of the ion passage 4 can be reduced by gradually narrowing the pitch with respect to the traveling direction of the ions. Can be formed as shown in FIG.

The above embodiment is merely an example, and it is apparent that changes and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a perspective view of one 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)

[Claims] 1. A mass spectrometer provided with an ion transport optical system for transporting ions generated by an ion source to a mass separation unit, wherein the ion transport optical system comprises two spirally wound electrodes. Is formed by loosely fitting so that the turns of each electrode are alternately present in the ion optical axis direction and are separated from each other,
A mass spectrometer characterized by applying high-frequency voltages having different phases to the two electrodes.