JPH01183050A - Sample introducing device for inductive coupling plasma mass analysis - Google Patents

Abstract

PURPOSE:To make it possible to analyze very small amount of U or Th in a sample at a high sensitivity and a high accuracy, and rapidly, by covering a cuvette surface and the electrode surfaces with an oxide or nitride membrane of a high melting point of metal, and inserting a tube made of a high melting point of metal covered with an oxide or a nitride membrane same as the above coverage in a sample pouring hole of the cuvette. CONSTITUTION:The surface of a cuvette 1 the sample gas is contacted and the surfaces of electrodes 5a and 5b are covered with an oxide or nitride membrane of a high melting point of metal. Moreover, a sample pouring hole 4 is formed in the cuvette 1, to which a tube 3 whose surface is covered with the oxide or the nitride membrane same as the above coverage is inserted. As the high melting point metal oxide, tantalum oxide, tungsten oxide, or zirconium oxide, for example, is used. And as the high melting point metal nitride, tantalum nitride, tungsten nitride, hafnium nitride, or zirconium nitride, for example, is used. The thickness of those membranes is made 0.1 to 10mum practically.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a sample introduction device for inductively coupled plasma mass spectrometry, and particularly relates to a sample introduction device for inductively coupled plasma mass spectrometry.
It relates to a sample introduction device attached to an inductively coupled plasma mass spectrometer for measuring.

(Prior art) If a semiconductor material constituting a dynamic memory contains trace amounts of impurities such as U or Th, the U or Th will spontaneously decay and emit alpha rays, causing soft errors in the memory cell. becomes. In order to miniaturize and highly integrate memories with the aim of increasing speed and capacity, it is important to improve package materials and chip constituent materials to reduce alpha rays. Said U
In order to select a manufacturing method for LSI constituent materials with a low Th content and a material suitable for actual use, it is necessary to develop a simple and highly sensitive analytical device that requires a short measurement time.

Conventional analysis of U and Th is performed by ■inductively coupled plasma emission method,
■Fluorescence method and ■Activation analysis method are adopted. However, methods (1) and (2) have problems in that they lack sensitivity to trace amounts of U and Th, require very complicated chemical pretreatment operations, and require a long analysis time. The method (2) is widely applied to the analysis of U and Th, but it is not practical as an analysis method for quality control because it requires a nuclear reactor.

For this reason, in recent years, attempts have been made to analyze U and Th using inductively coupled plasma mass spectrometry. In this method, a sample in solution is atomized using a nebulizer, introduced into an inductively coupled plasma, and excited and ionized. These ions are mass-separated using a quadrupole mass filter, and the contents of U and Th in the sample are measured. Although this method has higher sensitivity than methods (1) and (2) above, the sample introduction efficiency into the plasma is low and the detection sensitivity is insufficient at 10-12 g, so it is not suitable for very small samples such as semiconductor thin films. It could not be applied in practice.

Therefore, as a method of increasing the efficiency of sample introduction into the plasma and improving the detection sensitivity, an inductively coupled plasma mass spectrometer is attached with a sample introduction device for evaporation. This type of sample introduction device places a sample in solution on a heating element, heats it stepwise by applying current or voltage in an inert gas stream, and evaporates the target components in the sample into a plasma efficiently. It is a good idea to introduce it. As the exothermic substance provided in the sample introduction device, high melting point metals such as graphite, tantalum, and tungsten are generally used. However, when graphite is used as the exothermic substance, when the sample is evaporated, U and Th react with the graphite to form carbides, resulting in a significant decrease in the ionization efficiency of U and Th, and some residual U and Th. A memory effect appears. As a result, there has been a problem in that detection sensitivity and accuracy are significantly deteriorated. On the other hand, when high melting point metals such as tantalum and tungsten are used as exothermic substances, these metals contain a small amount of U and Th as impurities, so this U and Th are detected together with U and Th in the sample. be measured. As a result, there was a problem in that it was difficult to analyze a sample containing less U or Th than the content of U or Th in the high melting point metal.

(Problems to be Solved by the Invention) The present invention has been made in order to solve the above-mentioned conventional problems, and is capable of detecting ultra-trace amounts of U and Th in a sample with high sensitivity and high precision in an inductively coupled plasma mass spectrometer. The purpose of this invention is to provide a sample introduction device that enables quick analysis.

[Structure of the Invention (Means for Solving the Problem) The first invention of the present application is a heating furnace equipped with an electrode made of a good electrical conductor and a cylindrical cuvette made of a pyrogen having a sample injection hole in the center; and a gas control mechanism for flowing an inert gas from one end of the cuvette through the interior and the other end to the plasma torch section of the inductively coupled plasma mass spectrometer and controlling the flow of the inert gas. An inductive coupling characterized in that, in the sample introduction device, the cuvette surface and the electrode surface, which are in contact with heated inert gas or evaporated sample gas, are coated with an oxide film or nitride film of a high melting point metal. This is a sample introduction device for plasma mass spectrometry.

The above electrodes and cuvettes are good electrical conductors and have a rating of 2,600 to 30
Any material that can withstand temperatures of 00°C may be used, such as graphite or tantalum, tungsten,
It is formed from a heat-resistant metal such as rhenium or zirconium.

Examples of the high melting point metal oxide that coats the cuvette surface and electrode surface that are in contact with the heated inert gas and evaporated sample gas include tantalum oxide, tungsten oxide, zirconium oxide, etc. Examples of high melting point metal nitrides that coat the cuvette surface include tantalum nitride, tungsten nitride,
Examples include hafnium nitride, zirconium nitride, titanium nitride, and the like.

The thickness of the above refractory metal oxide film or refractory metal nitride film is determined by the reaction between the vaporized sample and the constituent materials of the electrode and cuvette covered with the protective film, and by the vaporization of impurity vapor in the constituent materials. From the perspective of suppressing contamination into the sample, it is desirable that it be as thick as possible, but in practice it is 0.1 to 10 μm.
And it is sufficient. The coating with such a high melting point metal oxide film or high melting point metal nitride film may be performed by any method such as CVD method, thermal oxidation method, sputter deposition method, coating-baking method, etc., but considering the ease of operation, A coating-baking method is preferred.

Examples of the inert gas include argon or helium, and a small amount of hydrogen may be added to the gas as necessary.

In the second invention of the present application, the cuvette is made of graphite, has a sample injection hole in the cuvette, and has a high melting point surface coated with an oxide film or nitride film of a high melting point metal similar to that described above. A sample introduction device is constructed by inserting a metal tube.

The third invention of the present application provides a heating furnace equipped with an electrode made of a good electrical conductor and a cylindrical cuvette made of a pyrogenic substance having a sample injection hole in the center, and a heating furnace that is provided with a cylindrical cuvette made of a pyrogen having a sample injection hole in the center thereof, In a sample introduction device that includes a gas control mechanism that flows an inert gas into the plasma torch section of an inductively coupled plasma mass spectrometer through a section and a gas control mechanism that controls the flow of the inert gas, heated inert gas, The cuvette surface and the electrode surface, which are in contact with the evaporated sample gas, are coated with a two-layer structure film in which a high melting point metal carbide film and a high melting point metal oxide film or nitride film are laminated in this order. This is a sample introduction device for inductive and coupled plasma mass spectrometry.

The electrodes and cuvettes are made of graphite or a heat-resistant metal such as tantalum, tungsten, rhenium, or zirconium, as described in the first invention of the present application.

Examples of the high melting point metal carbide that coats the cuvette surface and electrode surface that are in contact with the heated inert gas and evaporated sample gas include tantalum carbide, tungsten carbide, hafnium carbide, zirconium carbide, titanium carbide, etc. can be mentioned. Further, as the refractory metal oxide or refractory metal nitride laminated on the refractory metal carbide film, tantalum oxide, tungsten oxide,
Examples include zirconium oxide, tantalum nitride, tungsten nitride, hafnium nitride, zirconium nitride, and titanium carbide.

The high melting point metal carbide film that constitutes the above two-layer structure coating,
The respective thicknesses of the melting point metal oxide film and the high melting point metal nitride film are
It is desirable that these films be as thick as possible from the viewpoint of suppressing the reaction between the constituent materials of the electrodes and cuvettes covered with the vaporized sample and the contamination of impurity vapors from the constituent materials into the vaporized sample. Each of them is 0.1~
It may be 10 μm. Coating with such a two-layer structure film may be performed by any method such as CVD, thermal oxidation, sputter deposition, coating and baking, but the coating and baking method is preferable in view of ease of operation.

Examples of the inert gas include argon or helium, and a small amount of hydrogen may be added to the gas as necessary.

In the invention of Section 4 of the present application, the cuvette is formed of graphite, further has a sample injection hole in the cuvette, and the surface is covered with a film of high melting point metal carbide and high melting point metal oxide film or nitride similar to those described above. A sample introduction device is constructed by inserting a tube made of a high melting point metal coated with a two-layer structure film.

(Function) According to the invention of Section 1 of the present application, the cuvette surface and the electrode surface, which are in contact with the heated inert gas or evaporated sample gas, are coated with an oxide film or nitride film of a high melting point metal. Therefore, when graphite is used as the base material of these cuvettes, etc., it is possible to prevent U and Th in the sample to be analyzed from reacting with the graphite to form carbides. As a result, ionization efficiency can be greatly improved, and
Can eliminate memory effects. On the other hand, when a heat-resistant metal is used as a base material for a cuvette, etc., the barrier effect of the oxide film or nitride film of the high-melting point metal prevents U and Th contained as impurities in the heat-resistant metal from evaporating. can be suppressed. Moreover, by coating the high melting point metal with the oxide film or nitride film, the time to start evaporation of U and Th in the heat-resistant metal can be delayed compared to the time to start evaporation of U and Th in the sample. Therefore, the ion spectrum due to U and Th in the sample and the U and Th in the heat-resistant metal that is the base material
It is possible to temporally separate the ion spectra of Therefore, according to the invention of Section 1 of the present application, ultratrace amounts of U and Th in a sample can be analyzed quickly with high sensitivity and accuracy using an inductively coupled plasma mass spectrometer.

According to the invention of Section 2 of the present application, the cuvette is made of graphite, has a sample injection hole in the cuvette, and has a high melting point metal oxide film or nitride film coated on the surface with the same high melting point metal oxide film or nitride film as described above. By inserting a tube made of a melting point metal, ultra-trace amounts of U and Th in a sample can be analyzed with high sensitivity, accuracy, and speed in the inductively coupled plasma mass spectrometer described above, and the space in the evaporation section of the sample introduction device can be analyzed quickly. can achieve miniaturization. That is, by making the cuvette from a heat-resistant metal and coating its surface with a high-melting-point metal oxide film or nitride film, ultra-trace amounts of U and Th in the sample can be detected with high sensitivity and precision, as described above. Although it can be analyzed,
Since the heat-resistant metal has good thermal conductivity, the space for the evaporation section of the sample introduction device becomes large due to the necessity of heat insulation. For this reason, by forming the cuvette with graphite-13-', which has excellent heat insulation properties, it is possible to reduce the size of the space in the evaporation section of the sample introduction device. In this case, by forming not only the cuvette but also the electrodes from graphite, the -layer can be made smaller. However, if the cuvette is made of graphite, there is a risk that a small amount of graphite will be released even if the surface of the cuvette is coated with an oxide or nitride film of a high melting point metal. If such release of graphite occurs especially in the evaporation space of the sample, U and T in the sample
h reacts with graphite to produce carbide, and U and Th
The ionization efficiency of the ions decreases significantly, and memory effects appear. In other words, the release of graphite that may occur even if the cuvette is made of graphite and its surface is coated with an oxide or nitride film of a high-melting point metal can be avoided if the cuvette is made of a heat-resistant metal and its surface is coated with a similar material. Compared to the release of impurities in heat-resistant metals that may occur even when coated with a oxide or nitride film, the accuracy of analysis is significantly lowered. Therefore, by inserting a high melting point metal tube whose surface is coated with a high melting point metal oxide film or nitride film into the cuvette, and performing evaporation of the sample here, the memory effect can be eliminated and the high It is possible to downsize the evaporation section space of the sample introduction device while maintaining ionization efficiency.

According to the invention of Section 3 of the present application, the cuvette surface and the electrode surface that are in contact with the heated inert gas or the evaporated sample gas are coated with a carbide film of a high melting point metal and an oxide film or a nitride film of a high melting point metal. When graphite is used as the base material for cuvettes, U and T in the sample to be analyzed are covered by a two-layer structure film laminated in this order.
This can prevent h from reacting with graphite to form carbides. As a result, the ionization rate can be greatly improved and the memory effect can be completely eliminated. Furthermore, by coating the cuvette surface and the electrode surface with a high melting point metal oxide film or nitride film via a high melting point metal carbide film, compared to the case where the cuvette surface is directly coated with the oxide film, etc. Adhesion can be significantly improved. On the other hand, when a heat-resistant metal is used as a base material for a cuvette, etc., the presence of a carbide film of a high-melting point metal with excellent gas impermeability provides an even better barrier effect, resulting in U and U contained as impurities in the heat-resistant metal. Evaporation of Th can be effectively suppressed. Furthermore, by coating with the two-layer structure film, the start time of evaporation of U and Th in the heat-resistant metal can be delayed by one hour compared to the start time of evaporation of the sample. The spectrum can be temporally separated from the ion spectrum due to U and Th in the heat-resistant metal that is the base material. In addition, by coating the cuvette surface and electrode surface made of a heat-resistant metal with an oxide film or nitride film of a high melting point metal via a carbide film of a high melting point metal, the oxide film etc. can be directly coated on the cuvette surface. Heat resistance can be significantly improved compared to the case where

Therefore, according to the invention of Section 3 of the present application, ultratrace amounts of U and Th in a sample can be analyzed more sensitively, accurately, and quickly with an inductively coupled plasma mass spectrometer than the invention of Section 1 of the present application.

According to the invention in Section 4 of the present application, the cuvette is formed of graphite, has a sample injection hole in the cuvette, and has a surface covered with a carbide film of a refractory metal similar to that described above and a refractory metal carbide film. By inserting a high-melting point metal tube coated with a two-layer film of oxide or nitride, ultra-trace amounts of U and Th can be detected with high sensitivity in the sample using the inductively coupled plasma mass spectrometer described above. Not only can analysis be performed with high accuracy and speed, but also the space of the evaporation section of the sample introduction device can be reduced in size.

(Embodiments of the Invention) Hereinafter, embodiments of the present invention will be described in detail with reference to FIG.

Example 1 FIG. 1 is a schematic cross-sectional view showing a sample introduction device for inductively coupled plasma mass spectrometry used in this example. 1 in the figure is a cuvette made of pyrogen;
A sample injection hole 2 is opened at the upper center of the sample. A cylindrical tube 3 made of a high melting point metal is inserted into the cuvette 1 so that a sample injection hole 4 opened at the upper center of the tube matches the injection hole 2 of the cuvette 1. The cuvette 1 is surrounded by electrodes 5a and 5b made of a good electrical conductor and divided in a direction perpendicular to the axial direction.
They are in contact with and supported by the inner surface of b. Each of the electrodes 5a
An insulating material layer (not shown) is interposed between the divided surfaces of the s 5b to electrically insulate them. A pipette insertion hole 6 is opened in one electrode 5a. Each of the electrodes 5as and 5b is surrounded by electrode blocks 7a and 7b made of a good electrical conductor and divided in a direction perpendicular to the axial direction, and the outer peripheral surface of each electrode 5a and 5b is surrounded by electrode blocks 7a and 7b, respectively. is in contact with and supported by the inner peripheral surface of the Each electrode block mentioned above? An insulating material layer (not shown) is interposed between the divided surfaces of a and 7b to electrically insulate them. The electrode blocks 7a, 7
b, a cooling water passage 8a for cooling the blocks 7a, 7b.

8b is provided. The electrode blocks 7a, 7b
A quartz pipe 9a serving as a carrier gas outlet and a quartz pipe 9b serving as a carrier gas inlet are respectively inserted in the . Further, a carrier gas external flow path 10 extends from the electrode blocks 7a and 7b to the electrodes 5as and 5b.
a and lOb are respectively drilled, and the quartz pipe 9
Carrier gas internal channels 11a and llb are bored in the electrode blocks 7a and 7b near the insertion portions a and 9b. Quartz pipe 9 as the carrier gas inlet
b and carrier gas internal channels 11a and Ilb are used to flow carrier gas at independent flow rates during the drying and ashing stage and the evaporation stage of the sample in the tube 3. Note that the cuvette 1, tube 3, electrode 5a,
5b, electrode blocks 7a, 7b, etc. constitute a heating furnace.

Further, 12 in the figure is a unitized gas control mechanism. This gas control mechanism 12 includes a first electromagnetic valve 14 disposed on the inert gas inlet 13 side.

This solenoid valve 14 is connected to a pressure regulator 15,
A pressure meter 16 is connected to the regulator 15. These pressure regulator 15 and pressure meter 16 are adjusted to appropriate pressures in advance. Further, the inert gas inlet 13 is provided in the piping section between the solenoid valve 14 and the pressure regulator 15.
The pressure switch 17 is connected to a pressure switch 17 for detecting whether the pressure of the inert gas introduced from the inert gas is sufficient. When the pressure detected by the pressure switch 17 is below a predetermined value, the detection signal is fed back to the power system control section (not shown) of the electrode blocks 7a, 7b, and the cuvette 1 etc. This serves to prevent oxidation caused by heat generation (around 3000°C). On the downstream side of the pressure regulator 15, it is branched into three directions and connected to flow meters 18 to 20 with a flow rate adjustment function. The first flow meter 18 is a carrier gas external flow path 10a of the heating furnace.
5lOb. The second flow meter 19 is connected to the carrier gas internal flow paths 11a and 11b of the heating furnace via a second solenoid valve 21. The third flowmeter 20 is connected via a third electromagnetic valve 22 to a quartz pipe 9b that is a carrier gas inlet of the heating furnace. Note that a fourth piping system connects the heating furnace and the plasma torch (not shown) of the inductively coupled plasma mass spectrometer.
A solenoid valve 23 is provided.

In the first embodiment, the surface of the cuvette 1 is contacted with the heated inert gas or the evaporated sample gas;
It has a structure in which the surface of the tube 3 and the surfaces of the electrodes 5a and 5b are coated with an oxide film or nitride film of a high melting point metal.

Next, the operation of the aforementioned sample introduction device shown in FIG. 1 will be explained.

First, with the second to fourth electromagnetic valves 21 to 23 closed, a sample is dropped into the cylindrical tube 3 through the pipette insertion hole 6 and the sample injection hole 2.4. Next, from the power source, the electrode block 7 is heated according to the heating programming of the control section.
As 7b is energized, and these electrode blocks 7as 7b
A voltage is applied to both ends of the cuvette 1 through the electrodes 5as and 5b to heat the cuvette 1 and the tube 3 to a predetermined temperature, thereby drying the sample 24 in the tube 3.
At the same time, the second and third solenoid valves 21 and 22 are opened to supply inert gas (carrier gas) to the internal flow path 11 of the heating furnace.
aSl■b and a quartz pipe 9b serving as an inlet. As a result, during the drying and ashing stages of the sample 24, water-type gas and coexisting substances are removed from the sample injection hole 4 along with the carrier gas.
．． 2 and pipette insertion hole 6 to the outside of the heating furnace. Next, after plugging the pipette insertion hole 6 and sample injection hole 2.4 with a graphite plug, boron nitride plug, or heat-resistant metal plug (not shown) whose surface is covered with an oxide film or nitride film of a high-melting point metal. The target component in the sample 24 is evaporated by increasing the power supply to the cuvette 1 to generate heat to a higher temperature, and at the same time, the fourth electromagnetic valve 23 is opened to transfer the evaporated target component to the inductively coupled plasma mass spectrometer. plasma)
- introduced into the chamber and excited and ionized. These ions are mass-separated and measured using a quadrupole mass filter, and the concentration of the target component is calculated from the ion intensity using a calibration curve. After the above operations are completed and the cuvette 1 and tube 3 are cooled, the second to fourth electromagnetic valves 21 to 23 are closed, the sample is injected again, and the same operation is repeated to perform measurements.

During the above-described evaporation of the sample, the surface of the cuvette 1, the surface of the tube 3, and the surfaces of the electrodes 5a and 5b, which are in contact with the heated inert gas and the evaporated sample gas, are coated with an oxide film or nitrided film of a high-melting point metal. Cuvette 1 and electrode 5a are coated with a substance film.

When graphite is used as the base material of the tube 5b, it is possible to prevent U and Th in the sample 24 dropped into the tube 3 from reacting with the graphite to form carbide. the result,
Ionization efficiency can be greatly improved and memory effects can be completely eliminated. Therefore, ultra-trace amounts of U and Th in a sample can be analyzed quickly, with high sensitivity and with high precision using an inductively coupled plasma mass spectrometer.

In fact, it was confirmed that by using the sample introduction device for inductively coupled plasma mass spectrometry of Example 1 and conducting the following experiment, it was possible to accurately analyze ultratrace amounts of U and Th in a sample.

Example 1-1 The electrodes 5a and 5b were made of graphite,
As a cuvette, the outer diameter is g muφ, the inner diameter is 61Rmφ,
A cylindrical tube 3 made of graphite with a length of 28 mm and one sample injection hole of 2 mm diameter in the center was used as a cylindrical tube 3 with an outer diameter of 5.5 mm, an inner diameter of 4.5 mm, and a length of 26 mm.
.

Each sample was made of high-purity tantalum and had one 2Hφ sample injection hole in the center. Further, the electrode 5a,
5b, the surfaces of the cuvette 1 and the cylindrical tube 3 that were in contact with the heated inert gas or the evaporated sample gas were coated with a tantalum nitride film about 0.5 μm thick. The tantalum nitride film was coated by applying an organic tantalum compound to the surface of a predetermined member and then firing it in a nitrogen atmosphere.

Comparative Example 1-1 A sample introduction device similar to that of Example 1-1 was assembled, except that the tantalum cylindrical tube was not used and the electrode and cuvette were not coated with a tantalum nitride film.

Comparative Example 1-2 Example 1-2 above except that the electrode, cuvette and tantalum cylindrical tube were not coated with tantalum nitride film.
A sample introduction device similar to 1 was assembled.

Therefore, using the sample introduction device and inductively coupled plasma mass spectrometer of Example 1-1 and Comparative Examples 1-1 and 1-2, the uranium standard solution was 100 pg/mI! sample lOμ
The ionic strength of a 10μ sample of the same standard solution Opg/ax was measured under the following conditions.

Carrier gas in sample introduction device; 4.01! / m
in argon.

Drying in sample introduction device; 150°C, 30 sec.

Ashing in the sample introduction device, 1000°C, 30 sec.

Evaporation in sample introduction device; 2800°C, 7 see
0 Frequency of high frequency power supply in plasma torch; 27.1
2MHz.

High frequency output of high frequency power supply in plasma torch; 1.3
kW.

Cooling gas in plasma torch; 15. ff/min
.

Plasma gas with plasma torch; 0.81! /min
.

As a result of the above, in this Example 1-1, uranium standard solution 100
The ionic strength of the pg/ma sample was 250, and the ionic strength of the same standard solution Opg/Yu sample was 5.

On the other hand, in Comparative Example 1-1, uranium standard solution 100
The ionic strength of the pg/rIli sample is 6, and the same standard solution O
pg/Iti! The ionic strength of the sample was 2, and since the cuvette was made of graphite itself, the uranium turned into carbide and could not be detected.

In addition, in Comparative Example 1-2, the ionic strength of the sample containing the uranium standard solution 1oo H/Pos is 2801, and the ionic strength of the sample containing the same standard solution Opg/Ga is 42. The ionic strength of uranium was measured even in samples with zero standard solution due to contamination with uranium evaporated from the tube.

Example 1-2 The electrodes 5as and 5b were made of graphite,
The cuvette 1 was made of graphite with an outer diameter of 8 amφ, an inner diameter of e mmφ, and a length of 28 mm and a sample injection hole of 2 mmφ in the center, and the cylindrical tube 3 had an outer diameter of 5.5 mmφ, an inner diameter of 4.5 mmφ, and a length of 28 mm. length 26mm
5. Each sample was made of high-purity tungsten and had one sample injection hole of 2 mmφ in the center. Furthermore, the surfaces of the electrodes 5a, 5b, cuvette 1, and cylindrical tube 3 that come in contact with heated inert gas or evaporated sample gas are coated with a tungsten nitride film having a thickness of approximately 0.5 μm. . The tungsten nitride film was coated by applying an organic tungsten compound to the surface of a predetermined member and then firing it in a nitrogen atmosphere.

Comparative Example 1-3 A sample introduction device similar to that of Example 1-2 was assembled, except that the tungsten cylindrical tube was not used and the electrode and cuvette were not coated with a tungsten nitride film.

Comparative Example 1-4 A sample introduction device similar to that of Example 1-2 was assembled, except that the electrode, cuvette, and tungsten cylindrical tube were not coated with a tungsten nitride film.

Therefore, using the sample introduction device and the inductively coupled plasma mass spectrometer of Example 1-2 and Comparative Example 1-3.1-4, the thorium standard solution was 100 pg/rIJ! Sample 1 of
The ionic strength of 10 μ samples of the same standard solution Opg/+1112 was measured under the same conditions as in Example 1-1, except that the ashing conditions were 600° C. and 30 seconds. As a result, in this Example 1-2, thorium standard solution 1
The ionic strength of the sample with 00 pg/m was 240, and the ionic strength of the sample with the same standard solution Opg/ac was 7. On the other hand, in Comparative Example 1-3, the thorium standard solution 1oo p
The ionic strength of the sample in g/mff is 4, and the same standard solution Opg
The ionic strength of the / proof sample was 2, and since the cuvette was made of graphite itself, thorium turned into carbide and could hardly be detected. Moreover, in Comparative Example 1-4, the thorium standard solution was 100 pg/mJ! The ionic strength of the sample is 280, and the same standard solution Opg/mI!
The ionic strength of the sample was 52, and the ionic strength of thorium was measured even in a sample where the standard solution was zero due to the inclusion of thorium evaporated from a tungsten cylindrical tube that was not coated with a tungsten nitride film.

In this way, the sample introduction device of Example 1 can measure uranium and thorium by approximately 100 times compared to normal inductively coupled plasma mass spectrometry, and compared to conventional inductively coupled plasma mass spectrometry using evaporation vaporization. It can be seen that the detection sensitivity of uranium and thorium is improved by about 10 times. In addition, the sample introduction device of Example 1 can also be used in an inductively coupled plasma emission spectrometer, and the detection sensitivity is further improved by approximately 10 times compared to the conventional inductively coupled plasma emission spectrometry method that uses a combination of evaporation and vaporization methods. can be achieved.

Example 2 In the sample introduction device of Example 2, the surface of the cuvette 1, the surface of the tube 3, and the surfaces of the electrodes 5a and 5b, which are in contact with the heated inert gas or the evaporated sample gas, are coated with a high melting point metal. It has a structure in which it is coated with a two-layer film in which a carbide film and a refractory metal oxide film or nitride film are laminated in this order.

According to such a configuration, the surface of the cuvette 1 and the tube 3 that are brought into contact with the heated inert gas and the evaporated sample gas during evaporation of the sample as in Example 1.
Since the surfaces of the cuvette 11 and the surfaces of the electrodes 5a and 5b are coated with a two-layer film consisting of a high melting point metal carbide film and a high melting point metal oxide film or nitride film laminated in this order.
For example, when graphite is used as the base material for the electrodes 5a and 5b, U and T in the sample 24 dropped into the tube 3
This can prevent h from reacting with graphite to form carbides. As a result, the ionization efficiency can be greatly improved and the memory effect can be completely eliminated. Therefore, ultra-trace amounts of U and T in samples in inductively coupled plasma mass spectrometers
h can be analyzed quickly with high sensitivity and accuracy.

In fact, it was confirmed that by using the sample introduction device for inductively coupled plasma mass spectrometry of Example 2 and conducting the following experiment, it was possible to accurately analyze ultratrace amounts of U and Th in a sample.

Example 2-1 The electrodes 5as and 5b were made of graphite,
The cuvette 1 is made of graphite with an outer diameter of 88φ, an inner diameter of e mmφ, and a length of 28 FIm%, and has one sample injection hole of 2 mmφ in the center.
As for outer diameter 5.5mmφ, inner diameter 4.5mmφ, length 28
mm.

High purity with one 2 mmφ sample injection hole in the center.
30 - A material made of tantalum was used. In addition, the electrode 5
a, 5b, the surfaces of the cuvette 1 and the cylindrical tube 3 that come into contact with the heated inert gas or evaporated sample gas are coated with a tantalum carbide film approximately 0.3 μm thick, and further coated with a tantalum carbide film approximately 0.3 μm thick. It was coated with a 0.2 μm tantalum nitride film. The tantalum carbide film was coated by applying an organic tantalum compound to the surface of the specified member and then fired in an argon gas atmosphere, and the tantalum nitride film was coated by applying the organic tantalum compound to the surface of the specified member. After that, it was fired in a nitrogen atmosphere.

Comparative Example 2-1 A sample introduction device similar to that of Example 2-1 was assembled, except that the tantalum cylindrical tube was not used and the electrode and cuvette were not coated with tantalum carbide film and tantalum nitride film. Ta.

Comparative Example 2-2 A sample introduction device similar to that of Example 2-1 was assembled, except that the electrode, cuvette, and tantalum cylindrical tube were not coated with the tantalum carbide film and the tantalum nitride film.

Therefore, using the sample introduction device and the inductively coupled plasma mass spectrometer of Example 2-1 and Comparative Example 2-1.2-2, a sample of 10μ of the uranium standard solution 100'pg/IILll and the same standard solution Opg. The ionic strength of a 10μ sample of /Ini was measured under the same conditions as in Example 1-1. As a result, in this Example 2-1, the uranium standard solution was 1100p/Il! The ionic strength of sample j2 is 250,
The ionic strength of the sample of the same standard solution Opg/Ini was 2. On the other hand, in Comparative Example 2-1, uranium standard solution 1
The ionic strength of the 100 p/m sample is 6, and the same standard solution Op
The ionic strength of the g/ml sample was 2, and since the cuvette was made of graphite itself, the uranium turned into carbide and could hardly be detected. Also,
In Comparative Example 2-2, the ionic strength of the sample containing 100 pg/y of the uranium standard solution was 280, and the ionic strength of the sample containing the same standard solution Opg/y was 42. The ionic strength of uranium was measured even in samples with zero standard solution due to the contamination of uranium vaporized from the sample.

Example 2-2 The electrodes 5a and 5b were made of graphite,
The cuvette 1 was made of graphite with an outer diameter of 8 muφ, an inner diameter of 6 Mφ, a length of 28 mm, and a sample injection hole of 2 mmφ in the center, and a cylindrical tube 3 with an outer diameter of 5.5 mmφ and an inner diameter of 4.5 mm. Each sample was made of high-purity tungsten and had a length of 26 mm and a sample injection hole of 2 mm in the center. Further, the electrode 5
as 5b, the cuvette 1 and the cylindrical tube 3 are coated with a tungsten carbide film with a thickness of about 0.3 μm on the surface of the portion that comes into contact with the heated inert gas or the evaporated sample gas, and is further coated with a tungsten carbide film with a thickness of about 0.3 μm. , coated with a 2 μm tungsten nitride film.

Comparative Example 2-3 A sample introduction device similar to that of Example 2-2 was assembled, except that the tungsten cylindrical tube was not used and the electrode and cuvette were not coated with a tungsten carbide film or a tungsten nitride film.

Comparative Example 2-4 A sample introduction device similar to that of Example 2-2 was assembled, except that the electrode, cuvette, and tungsten cylindrical tube were not coated with a tungsten carbide film or a tungsten nitride film.

Therefore, using the sample introduction device of Example 2-2 and Comparative Example 2-3.2-4 and the inductively coupled plasma mass spectrometer, sample 10 of thorium standard solution 100 pg/ILl was prepared.
The ionic strength of a 10 µl sample of the same standard solution Opg/mz as µ was measured under the same conditions as in Example 1-1 above, except that the incineration conditions were 600°C and 30 sec. As a result, in this Example 2-2, thorium standard solution 100 p
The ionic strength of the sample is 240, and the same standard solution Opg
The ionic strength of the /wLl sample was 2. On the other hand, in Comparative Example 2-3, the thorium standard solution was 1100 p/jl.
lj? The ionic strength of the sample was 4, and the ionic strength of the sample of the same standard solution Opg/bi was 2. Since the cuvette was made of graphite itself, thorium turned into carbide and could hardly be detected. Also, comparative example 2
-4 for Tory 34 = 100 pg/mI of rum standard solution! The ionic strength of the sample is 280, and the same standard solution 01) g/mJ! The ionic strength of the sample was 52, and the ionic strength of thorium was measured even in a sample where the standard solution was zero due to the inclusion of thorium evaporated from a tungsten cylindrical tube that was not coated with a tungsten nitride film.

As described above, the sample introduction device of Example 2 can measure uranium and thorium by approximately 200 times compared to normal inductively coupled plasma mass spectrometry, and compared to conventional inductively coupled plasma mass spectrometry using evaporation vaporization. It can be seen that the detection sensitivity of uranium and thorium is improved by about 20 times. In addition, the sample introduction device of Example 2 can also be used in an inductively coupled plasma emission spectrometer, and has a detection sensitivity that is about 20 times higher than that of the conventional inductively coupled plasma emission spectrometer that uses a combination of evaporation and vaporization methods. improvement can be achieved.

[Effects of the Invention] As detailed above, the present invention provides a sample introduction device that enables an inductively coupled plasma mass spectrometer to analyze an ultra-trace amount of U'PTh in a sample with high sensitivity, high accuracy, and quickly. It is possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of a sample introduction device for inductively coupled plasma mass spectrometry showing one embodiment of the present invention. 1...Cuvette, 2.4...Sample injection hole, 3...
・Cylindrical tube, 5as 5b...electrode, 7a,
7b...electrode block, loas fob...carrier gas internal flow path, lla. 11b... Carrier gas external flow path, 12... Gas control mechanism, 17... Pressure switch, 21-23... Solenoid valve, 24... Sample. Applicant's agent Patent attorney Takehiko Suzue

Claims (4)

[Claims] (1) A heating furnace equipped with a cylindrical cuvette made of a pyrogen having electrodes made of a good electrical conductor and a sample injection hole in the center, and an induction through the inside and the other end of the cuvette from one end of the cuvette. In a sample introduction device consisting of a gas control mechanism that flows an inert gas into the plasma torch section of a coupled plasma mass spectrometer and controls the flow of the inert gas, a heated inert gas or an evaporated sample is used. A sample introduction device for inductively coupled plasma mass spectrometry, characterized in that the cuvette surface and the electrode surface that are in contact with gas are coated with an oxide film or nitride film of a high melting point metal. (2) The cuvette is made of graphite, and the cuvette surface and electrode surface, which are in contact with heated inert gas or evaporated sample gas, are coated with an oxide film or nitride film of a high melting point metal. 2. A tube made of a high melting point metal having a sample injection hole is further inserted into the cuvette, and the surface of the tube is coated with an oxide film or a nitride film of the high melting point metal. Sample introduction device for inductively coupled plasma mass spectrometry. (3) A heating furnace equipped with an electrode made of a good electrical conductor and a cylindrical cuvette made of a heat-generating substance having a sample injection hole in the center, and an induction through the inside and the other end of the cuvette from one end In a sample introduction device consisting of a gas control mechanism that flows an inert gas into the plasma torch section of a coupled plasma mass spectrometer and controls the flow of the inert gas, a heated inert gas or an evaporated sample is used. The cuvette surface and the electrode surface, which are in contact with gas, are coated with a two-layer structure film in which a high melting point metal carbide film and a high melting point metal oxide film or nitride film are laminated in this order. Sample introduction device for inductively coupled plasma mass spectrometry. (4) The cuvette is made of graphite, and the cuvette surface and electrode surface, which are in contact with the heated inert gas and the evaporated sample gas, are covered with a high melting point metal carbide film and a high melting point metal oxide film. A high melting point metal tube having a sample injection hole is inserted into the cuvette, and a high melting point metal carbide is coated on the surface of the tube. 4. The sample introduction device for inductively coupled plasma mass spectrometry according to claim 3, characterized in that the sample introduction device for inductively coupled plasma mass spectrometry is coated with a two-layer structure film in which a film and a refractory metal oxide film or nitride film are laminated in this order.