JP3521218B2 - Metal-insulating ceramic composite sampler and skimmer - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to inductively coupled plasma mass spectrometry (ICP-MS), glow discharge mass spectrometry (GD).
-MS), microwave induction plasma mass spectrometry (MIP)
-MS) and other plasma-based ionization sources, suppress the generation of low-temperature boundary layers that cause sensitivity deterioration and spectral interference, and suppress secondary discharge that causes sputtering and divalent ion generation. It relates to a product for suppressing and directing plasma-generated ions to a mass spectrometer.

[0002]

2. Description of the Related Art Conventionally, a metal sampler or skimmer having a hole at its center has been used to guide ions generated by plasma at atmospheric pressure to a high vacuum mass spectrometer. At this time, the temperature of the plasma becomes high (for example, 5000 to 7000K in ICP), so that almost all the materials are melted and deformed when exposed to the plasma.
Therefore, it was possible to prevent melting and deformation by cooling a part of the sampler and skimmer by utilizing heat conduction. Therefore, metals with high thermal conductivity have been used. Further, it was necessary to be made of metal in order to ground the sampler and skimmer.

[Problems to be Solved by the Invention]

In inductively coupled plasma (ICP),
Not only the induction coil and plasma are inductively coupled,
Since they are also capacitively coupled, the high frequency potential on the coil is transmitted to the plasma. Positive ions flow into the sampler or skimmer when the plasma potential is positive, and electrons flow into the sampler or skimmer when the plasma potential is negative, but the average DC potential (plasma potential) is due to the difference in the moving speed of the ions and electrons. Remains. Since the high-frequency potential transmitted to the plasma reaches 200 V between peaks, arc discharge occurs between the plasma and sampler and between the plasma and skimmer. This discharge is called a secondary discharge, but when the secondary discharge occurs, the following problems occur. 1) The background signal increases due to the light from the discharge, and the detection limit deteriorates. 2) The sampler or skimmer is sputtered and its life is significantly shortened, and the elements forming the sampler or skimmer cannot be analyzed. 3) Since the kinetic energy of ions and the distribution width thereof become large, the resolution and sensitivity of the mass spectrometer are degraded. 4) Doubly charged ions are easily generated, and spectrum interference becomes large.
5) The plasma potential fluctuates each time the ICP conditions are changed,
Since the kinetic energy of ions changes, it is necessary to readjust the ion lens. The problems 1) and 2) above are not only problems of mass spectrometry using plasma as an ion source, but atomic emission analysis using atomic emission in that region by drawing plasma from the sampler into the reduced pressure region. It is also a problem in law.

Further, when the cooled sampler or skimmer is placed in high temperature plasma, the plasma in the region close to the sampler or skimmer is cooled and a low temperature boundary layer is formed. Inside the boundary layer, recombination of ions and electrons, reaction between ions and molecules, etc. occur, which also causes a decrease in sensitivity and spectral interference.

Conventionally, as a method of suppressing the secondary discharge, an intermediate tap method in which the central portion of the induction coil is grounded and half of the coil is positive and the other half is negative to make the subtraction zero, and a side close to the sampler of the coil. A reverse grounding method for grounding the ground has been developed. Also, a multi-layer coil method in which the inner coil shields the high frequency potential of the outer coil and a shield method in which a metal tube called a shield plate is inserted between the coil and the quartz torch to shield the coil are used. However, if it is completely shielded, there are problems that it is difficult to turn on the plasma and the sensitivity of the element having a high ionization potential is lowered. In order to suppress the formation of the boundary layer, a method of increasing the diameter of the orifice of the sampler or the skimmer is adopted, but if it is increased, there are problems that the degree of vacuum is lowered and the apparatus cannot be downsized.
Furthermore, if helium gas is used instead of argon as the plasma gas, the amount of suction becomes too large to suck in air other than helium, so that a reaction between ions and air easily occurs and there is a problem that sensitivity is lowered. It was INDUSTRIAL APPLICABILITY The present invention combines the characteristics of a metal, which is a conductor of good heat and electricity, and the characteristics of a ceramic, which is an electrical insulator and can withstand a higher temperature than a metal, to produce a secondary discharge and generation of a boundary layer. The purpose is to obtain a product that suppresses.

[0006]

In order to achieve the above object, the present invention provides the following inventions . (1) A sampler and a skimmer for guiding ions generated by plasma to a mass spectrometer have a conical shape, and a portion for passing ions formed by the conical shape has an orifice (a central portion) at the top of the conical shape. and the hole) and its tip is formed at an acute angle shape, metal is proximate portions of the orifice and the insulating canceller <br/> made Mick, the other conical portion, characterized in that a metal - insulation Ceramic composite sampler and skimmer. (2) The sampler and skimmer for guiding the ions generated by the plasma to the mass spectrometer have a conical shape, and the part for passing the ions formed by the conical shape has an orifice (center part) at the top of the conical shape. and the hole) and its tip is formed at an acute angle shape, metal, characterized in that the adjacent portions of the orifice was covered with a film made of insulating sera <br/> Mick - insulating <br/> ceramic composite sampler and Skimmer.

[Action]

In the sampler and skimmer constructed as described above, the metal portion comes into contact with the outer peripheral portion of the plasma to establish electrical conduction, thereby grounding the plasma, and having a large heat conductivity. Utilizing it, it works to efficiently transmit low temperature to the insulating ceramic part. Since the insulating ceramic part is an electrical insulator, it does not allow ions or electrons to flow into it even if it is placed in plasma, and thus serves to prevent secondary discharge. Further, since the heat conductivity of the insulating ceramic is smaller than that of metal, the insulating ceramic has a higher temperature than that of a metal, and therefore has a function of suppressing the formation of a boundary layer at a low temperature. Therefore, even if the orifice diameter is reduced, the influence of the boundary layer is less likely to occur. If you can reduce the orifice diameter,
It is possible to reduce the size of the plasma that is the ion source, and the pumps for maintaining the degree of vacuum can be downsized, which is useful for downsizing the plasma mass spectrometer as a whole.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will be described based on examples with reference to the drawings. FIG. 1 is a layout diagram when the metal- insulating ceramic composite sampler and skimmer of the present invention are used in ICP-MS. The sampler 1 and the skimmer 2 of the present invention are mounted on the water-cooled metal plates 3 and 3 ′ and arranged between the quartz torch 5 around which the induction coil 4 is wound and the extraction electrode 6. The sampler 1 and the skimmer 2 each include a metal portion 7 and an insulating ceramic portion 8. Nickel, copper, aluminum, platinum and the like are often used as the metal material of the metal part 7 of the sampler 1 and the skimmer 2, but other metals can also be used as long as they have high thermal conductivity and good electrical conductivity. As the ceramic material of the insulating ceramic portion 8, alumina, zirconia, magnesia or the like having a high heat resistant temperature can be used, but other ceramic materials may be used as long as they have excellent heat resistant temperature and electrical insulation. The metal portion 7 and the insulating ceramic portion 8 are adhered to each other with a ceramic adhesive such as alumina, zirconia, or magnesia. In this case, by reducing the area S1 of the insulating cell <br/> ceramic portion 8 of the sampler 1 of the plasma 9 side, insulating
The metal portion 7 on the outer periphery of the conductive ceramic portion 8 and the plasma 9 are sufficiently contacted with each other so that the ground can be established. On the other hand, by increasing the area S2 of the insulating ceramic portion 8 inside the sampler 1 (on the side of the barrel shock 10), the insulating region is widened to prevent secondary discharge. Even if the secondary discharge occurs, it occurs between the metal part 7 and the barrel shock 10, so that the phenomenon occurs in a region far from the orifice of the sampler 1, and the influence can be removed by the skimmer 2. For the same reason as the sampler 1, by reducing the area S3 of the insulating ceramic part 8 on the barrel shock 10 side of the skimmer 2, the area surrounded by the metal part 7 and the barrel shock 10 on the outer periphery of the insulating ceramic part 8 is reduced. Make sufficient contact so that the ground can be obtained. On the other hand, by increasing the area S4 of the insulating ceramic portion 8 inside the skimmer 2 (on the side opposite to the barrel shock 10), the insulating region is widened to prevent secondary discharge in this portion.

FIG. 2 is a schematic view of another embodiment of the sampler of the present invention, in which a metallic sampler 11 is covered with a film 12 made of an insulating ceramic. After physically polishing the surface layer of a metal sampler that has been used conventionally, or by chemically etching and removing with an acid, etc., apply a ceramic adhesive such as alumina, zirconia, or magnesia, which has a high heat resistance temperature. It is dried, fired, and then polished to be sharpened. For the same reason as above, the coating area S5 on the plasma side of the insulating ceramic film 12 is made small, and the area S6 on the inner side (barrel shock side) is made large. A skimmer is prepared in the same manner. Further, as a coating method, it may be formed with chemical vapor a deposition oxide film or a nitride film having the same insulation and heat resistance and insulating ceramic to the metal surface by a thin film fabrication techniques (CVD) method or the like.

【The invention's effect】

As described above, the metal- insulating ceramic composite sampler and skimmer of the present invention have the characteristics of metal which is a good conductor of heat and electricity, and the heat resistance of metal which is an insulator of electricity. It is possible to suppress the secondary discharge and the generation of the boundary layer, which are major problems in the plasma mass spectrometry, by using the characteristics of the insulating ceramics having high characteristics. This improves analysis sensitivity and resolution,
It has the effect of suppressing interference and extending the life of the sampler and skimmer. Further, since the generation of the boundary layer is suppressed, it is possible to make the orifice of the sampler and the skimmer small, which reduces the plasma that is the ion source,
Further, the pumps for maintaining the degree of vacuum can be downsized, which is useful for downsizing the entire plasma mass spectrometer.

[Brief description of drawings]

FIG. 1 is a diagram showing a metal- insulating ceramic composite sampler and a skimmer of the present invention, and an arrangement when they are used in ICP-MS.

FIG. 2 is a diagram schematically showing another embodiment of the metal- insulating ceramic composite sampler of the present invention.

[Explanation of symbols]

1. Sampler 2. Skimmer 3. Water cooled metal plate 3 '. Water-cooled metal plate 4. Induction coil 5. Quartz torch 6. Extraction electrode 7. Metal part 8. Insulating ceramic part 9. Plasma 10. Barrel shock 11. Metal sampler 12. Insulating ceramic coating 13. Water-cooled metal plate S1. Area S2 of the insulating ceramic portion 8 of the sampler 1 on the plasma side. Area S3 on the barrel shock side of the insulating ceramic part 8 of the sampler 1. Area S4 on the barrel shock side of the insulating ceramic portion 8 of the skimmer 2. An area S5. Of the insulating ceramic portion 8 of the skimmer 2 opposite to the barrel shock. Area S6 of plasma side of insulating ceramic coating 12 Area of the insulating ceramic coating 12 on the barrel shock side

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Claims (2)

(57) [Claims] 1. A sampler and a skimmer for guiding plasma-generated ions to a mass spectrometer are conical, and a portion for passing ions formed by the conical shape is provided.
And an orifice (hole in the center) at the top of the conical, the tip is formed in a sharp angle, absolute proximity portion of the orifice
A metal- insulating ceramic composite sampler and skimmer, characterized in that they are made of edging ceramic and the other part of the conical shape is made of metal. 2. A sampler and a skimmer for guiding ions generated by plasma to a mass spectrometer are conical, and a portion for passing ions formed by the conical shape is provided.
And an orifice (hole in the center) at the top of the conical, the tip is formed in a sharp angle, absolute proximity portion of the orifice
A metal- insulating ceramic composite sampler and skimmer coated with a rimmed ceramic film.