JPH0311546A - Mass analyzer for high frequency inductive coupling plasma - Google Patents

Abstract

PURPOSE:To prevent glow electric discharge in an exhaust system section by making up both a nozzle and a skimmer out of an electrical insulating material, and thereby interposing an electrode in a circumferential wail faced to the electromagnetic type mass analyzing system of the skimmer. CONSTITUTION:A nozzle 9 and No.1 skimmer 10 are made up out of an electrical insulating material such as ceramics, rubies and the like, and a conical electrode 22 is concurrently fixed on the circumferential wall on the mass analyzing system 13 side of No.1 skimmer. Voltage roughly equal to the voltage applied to an accelerating electrode 20 is applied to the electrode 22. And when the electrode 22 is brought in line with the ion through hole of No.1 skimmer 10, there thereby exists the electrode 22 in the heart of plasma which flows in a space S2 through No.1 skimmer, electric discharge is easily induced between the electrode 22 and No.2 skimmer 11 via said plasma. This constitution eliminates a member to which high voltage is applied in a surface coming in contact with a space S1 between the nozzle 9 and No.1 skimmer 10, thereby making it possible to prevent glow electric discharge in the exhaust system section of the space S1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an inductively coupled plasma mass spectrometer (ICP-MS) that combines an inductively coupled plasma (ICP) ion source and a mass spectrometer. be.

[Prior Art] Such an ICP-MS has a structure as shown in FIG.

In the figure, 1 is an ICP ion source, and a high frequency coil 2
The torch is composed of a plasma torch 3 made of an electrical insulator such as quartz, and a nebulizer 4 for spraying a sample liquid. Reference numeral 5 designates a sample bottle that stores a sample liquid 6 and is connected to the nebulizer 4 via an introduction tube 7. Although not shown, a shield case kept at ground potential is provided around the outer periphery of the plasma torch 3 to shield two high frequency waves from the high frequency coil.

8 is a cone-shaped nozzle 9 made of a good electrical conductor and a first
12 is a mass spectrometer, and a mass spectrometry system 13 is provided inside.

14 is an oil diffusion pump for maintaining a high vacuum inside the mass spectrometer]-2; 15.16 is the nozzle 9, the first skimmer 10, and the first skimmer 10; This is an oil rotary pump for exhausting the spaces Sl and S2 formed between the second skimmers 10 and 11, respectively, through exhaust pipes 17 and 18.

Reference numeral 19 denotes a group of electrodes for accelerating and converging ions and guiding them to the mass spectrometry system 13.

In this configuration, argon gas is supplied into the plasma torch 3 from a gas supply source not shown, and a sample liquid 6 is introduced in the form of a mist from the nebulizer 4. In this state, when power is applied to the high frequency coil 2 to form a high frequency magnetic field, a plasma P is generated, and sample ions in this plasma are transferred to the nozzle 9. Each skimmer 10.11
It enters into the interface 8 through. Ions that have entered this interface are accelerated and focused by the electrode group 17 and introduced into the sample analysis system 13.

Incidentally, recently, an ICP-MS has been proposed in which a magnetic field type mass spectrometry system is used as the mass spectrometry system 13 to obtain high resolution. When using a magnetic field type mass spectrometry system as described above, it is necessary to give high energy to the sample ions, so an accelerating electrode is installed between the second skimmer 11 and the electrode group 19, as shown by the reference numeral 20 in the figure. For example, ±l on the electrode
While applying a high voltage of about 0 KV, the nozzle 9. 1st
and a second skimmer 10. A similar high voltage must be applied to li as well.

[Problems to be Solved by the Invention] Therefore, as shown in an enlarged sectional view in FIG. 3, the nozzle 9. It is necessary that the housing 21 of the interface 8, which supports the first and second skimmers 10, 11, be made of an electrically insulating material, such as ceramic. Also, exhaust pipe 1
In order to prevent glow discharge occurring between the nozzle 9 or the first skimmer 10 and the oil rotary pump 15 via the
The exhaust pipe 17 is formed of an electrically insulating material such as rubber, and
It is necessary to increase the length of the exhaust pipe. Similarly, exhaust pipe 18
The other side also needs to be devised in the same way. Furthermore, nozzle 9
In order to prevent discharge between the shield case and the nozzle, since the ICP ion source is placed close to each other, it is necessary to install an electrical insulator such as quartz glass on the part of the shield case facing the nozzle. As a result, the structure becomes complicated and large, and this causes an increase in cost.

Therefore, it is an object of the present invention to provide an ICI"MS that can solve these problems.

[Means for Solving the Problem] In order to achieve the above object, the ICP-MS of the present invention ionizes a sample using a high frequency inductively coupled plasma ion source, and directs the generated ions through an interface consisting of a nozzle and a skimmer. In an apparatus to be introduced into a magnetic field type mass spectrometry system, the nozzle and the skimmer are formed of an electrically insulating material, an electrode is provided on the peripheral wall of the skimmer facing the magnetic field type mass spectrometry system, and the electrode is provided with the same ions as the ions. It is characterized by applying a polar high voltage.

Hereinafter, embodiments of the present invention will be explained in detail based on the drawings.

[Example 1] FIG. 1 is an enlarged sectional view of essential parts showing an example of an ICP-MS according to the present invention, and the same reference numerals as in FIGS. 2 and 3 indicate the same components.

This embodiment is different from the conventional examples shown in FIGS. 2 and 3 in that the nozzle 9 and the first skimmer 10 are made of an electrically insulating material such as ceramic or ruby, and the mass spectrometry system of the first skimmer is A cone-shaped electrode 22 is placed on the peripheral wall on the 13 side.
is a fixed point. A voltage comparable to the voltage applied to the accelerating electrode 20 is applied to the electrode 22 . Further, the end of this electrode on the ion passage side is retracted from the edge of the ion passage hole of the first skimmer 10. This is to suppress electrical discharge between the electrode 22 and the second skimmer 11. In other words, if this electrode and the ion passage hole of the first skimmer are aligned, the electrode 22 will be present in the plasma that has flowed into the space S2 through the first skimmer, and the electrode 22 and the second This makes it easier for discharge to occur between the skimmer 11 and the skimmer 11.

Incidentally, since the plasma P (sample ions) enters the interface 8 by a gas flow based on a pressure difference, it is not necessarily necessary to apply a high voltage to the nozzle 9.

In this way, there will be no member to which a high voltage is applied on the surfaces of the nozzle 9 and the first skimmer 10 that are in contact with the space S, thereby preventing the occurrence of glow discharge in the exhaust system of the space S. can do. Therefore, the exhaust pipe can be made of ordinary metal, and
The length of the exhaust pipe can be shortened. Also, the length of the nozzle 9 can be shortened.
Similarly, since it is formed of an electrically insulating material and no high voltage is applied thereto, there is no need to install an electrically insulating material in the portion of the shield case on the ICP ion source 1 side facing the nozzle. As a result, the structure can be simplified and downsized, and
Cost reduction is achieved.

It should be noted that the above description is an example of the present invention, and many modifications can be made in implementing the present invention. For example, in the above embodiment, the first
Although the skimmer and the electrode 22 were prepared separately and fixed together, the present invention is not limited to this; the electrode may be formed directly on the skimmer by vapor deposition.

In addition, in the above embodiment, the interface 8 is formed by two spaces S]-, S2, or only one space S1,
In other words, the same method can be implemented even when the second skimmer 11 is not provided.

[Effects] As detailed above, according to the present invention, there is no need to provide a member (electrode) in the exhaust system of this interface for applying an accelerating potential to ions that have entered the interface. system means can be used. Therefore, the structure can be simplified and downsized, and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of a main part showing an example of an ICP-MS according to the present invention, and FIGS. 2 and 3 are diagrams for explaining a conventional example. 1: ICP ion source 2: High frequency coil 3: Plasma torch 4: Nebulizer 6: Sample liquid 8: Interface 9: Nozzle 10.11: First and second skimmer] 2: Mass spectrometer 13: Mass spectrometry system 15 : Oil rotary pump 17.17: Exhaust pipe 18: Acceleration electrode 22: Electrode 1]: Housing

Claims (1)

[Claims] In an apparatus in which a sample is ionized using a high-frequency inductively coupled plasma ion source and the generated ions are introduced into a magnetic field mass spectrometry system through an interface consisting of a nozzle and a skimmer, the nozzle and skimmer are made of an electrically insulating material. A high frequency inductively coupled plasma mass spectrometer, characterized in that an electrode is provided on a peripheral wall of the skimmer facing the magnetic field type mass spectrometry system, and a high voltage of the same polarity as that of the ions is applied to the electrode.