JP3018909B2 - Laser vaporized particle sampling cell - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for analyzing solid samples such as metals and ceramics quickly and with high accuracy. The present invention relates to a fine particle sample collection cell of a laser vaporization analyzer for introducing into and analyzing an analyzer.

[0002]

2. Description of the Related Art In the material industry, there is an urgent need to quickly obtain highly reliable analysis results in order to maintain and further improve product quality. Laser vaporization analysis technology has been energetically studied as a technology that meets this demand.

In this analysis technique, a solid sample is irradiated with a laser beam to vaporize a part of the solid sample and form fine particles in an inert gas. The inert gas is used as a carrier gas and introduced into an element detector to identify components. Perform quantification. As the element detector, an atomic absorption analyzer, a plasma emission analyzer, or the like is used. In these element detectors, a solution sample is introduced into an excitation flame and the spectrum of an element contained therein is examined. That is, in the past, it was used only for a solution sample, and it took a lot of time to form a solid sample into a solution.

[0004] Sampling in laser vaporization analysis is performed as follows. As shown in FIG.
Is performed by irradiating a solid sample 5 with a laser beam that has a carrier gas introduction part 2 and a discharge part 3 and has passed through a transmission window 4 in a carrier gas atmosphere. Fine particle sampling cell 1 for solid sample 5
The cell is taken in and out by opening the cell at the cell junction 6. The laser beam 10 is emitted from a laser oscillator 11, its direction is directed to a condenser lens 13 by a reflection mirror 12, and the laser beam 10 is condensed by the condenser lens 13 so that the focal point is focused on the sample collection point of the solid sample 5. The transmission window 4 isolates the inside of the fine particle sampling cell 1 from the atmosphere and, at the same time, plays a critical role in transmitting light well and not impairing the light collecting property of the lens.
For this reason, it is made of quartz glass having high light transmittance and having a uniform thickness and a high flatness with emphasis on the parallelism of the front and back surfaces.

[0005] Laser vaporization eliminates the need to convert a solid sample into a solution, and eliminates the time required for solution. However, when the solid sample is large, the time required to cut the sample into small pieces in order to place the sample in a fine particle sample collection cell. Also, the time required for exchanging the sample was required. Furthermore, importantly, there remains a problem that the analysis accuracy is insufficient.

[0006] Stable feeding of an analysis sample to an element detector is indispensable for improvement of analysis accuracy. However, unlike a solution sample in which a sufficient amount of an analysis sample can be prepared, it is difficult to obtain fine particles at the same time. In the case of the transported fine particle sample, the analysis sample cannot be supplied stably unless the fine particles are generated at a stable speed. In addition, the contamination of the carrier gas as well as the contamination of the sample causes a decrease in accuracy.

Conventionally, with respect to the generation speed of fine particles, a fine particle sample collection cell provided with a moving stage for shifting a laser beam irradiation point on a solid sample has been proposed (for example, JP-A-3-118440). In order to prevent the time required for replacement and the accompanying contamination, there has been proposed a particle sampling cell in which the carrier gas tube can be easily replaced (for example, Japanese Patent Application Laid-Open No. Hei 2-227652).

[0008]

However, it is difficult to prevent the fluctuation of the fine particle generation rate only by the movement of the solid sample. In this proposal, there is no countermeasure against the fluctuation of the laser light intensity, and the analysis accuracy is satisfactory. Did not reach. or,
In both of the above proposals, the time required for cutting out the sample in the case of a large solid sample was not shortened at all, and the speed was insufficient.

The present invention has been made to solve these problems. For example, by controlling a carrier gas flow path in a particle sampling cell, fluctuations in laser light intensity are prevented to stabilize the generation speed of particles. Therefore, it is an object of the present invention to improve the analysis accuracy and to further shorten the analysis time by adopting a cell structure capable of handling a large solid sample.

[0010]

An object of the present invention is to provide a fine particle sampling cell used for laser vaporization analysis, which has a carrier gas inlet / outlet, a transmission window, and a carrier gas flow. In a laser vaporized fine particle sample collection cell for collecting a fine particle sample for analysis by irradiating a solid sample located on the opposite side of the transmission window with a laser beam through this transmission window, a carrier gas introduction part is provided on the transmission window side. In addition, it is an essential requirement that the carrier gas discharge unit is provided on the solid sample side and that the carrier gas is a laser vaporized particulate sample collection cell in which a flow path through which the carrier gas flows from the transmission window toward the solid sample is formed .
You.

[0011] Then, the above essential requirement, further, composed of those having a double structure which the cell consists of the inner cylinder and the outer cylinder
The object of the present invention is solved by adding
You. Further, in order to cope with a large solid sample, an apparatus provided with an opening on a surface facing the transmission window is one of the solutions for solving the problems of the present invention.
The effect is exhibited.

Further, as the mode of the above-mentioned opening, an opening having an edge portion made of a sealing material, a bellows tube provided in the opening, and a bellows tube provided in a cylindrical shape with a gap kept therefrom. Some have a double tube structure.

[0013]

When a solid sample is irradiated with a laser beam, vapors and fine particles are scattered from the solid sample and may adhere to the transmission window.

When foreign matter adheres to the transmission window, the laser light is absorbed, reflected, or abnormally refracted by the foreign matter, and the intensity of the laser light applied to the solid sample changes. Fluctuations in the intensity of the laser light lead to fluctuations in the generation rate of the fine particles, leading to a decrease in analysis accuracy.

[0015] If the introduction portion of the carrier gas into the fine particle sample collection cell is provided on the transmission window side and the discharge portion of the carrier gas is provided on the solid sample side, the carrier gas flows from the transmission window toward the solid sample. A flow path is formed, which can prevent vaporized substances and fine particles from adhering to the transmission window. That is, the introduced carrier gas touches the transmission window before containing the vaporized matter and the fine particles, and then contains the vaporized matter and the fine particles around the solid sample and transports them from the discharge part to the outlet. In such a flow of the carrier gas, the transmission window is not contaminated with foreign matter.

The flow of the carrier gas from the transmission window side to the solid sample side in the cell is such that the larger the cross-sectional area of the flow path of the discharge section and the smaller the resistance to the flow, the more evenly the discharge section is distributed around the solid sample. It is hard to be disturbed.

For this purpose, it is one method to provide a plurality of exhaust ports. However, if a cell having a double structure composed of an inner cylinder and an outer cylinder is used, it is easy to increase the cross-sectional area of the discharge passage. It is simple in structure.

Further, the carrier laser beam is slightly absorbed by the fine particles contained in the carrier gas in the fine particle collection cell. If the carrier gas flows out from the periphery of the solid sample without resistance by the double structure, the absorption by the fine particles is further reduced, and the laser beam intensity becomes more stable.

In a fine particle sample collection cell having an opening on the surface facing the transmission window, it is not always necessary to store the solid sample in the cell, and it is possible to cope with a large solid sample that cannot be installed in the cell.

Further, when the solid sample is replaced, it is not necessary to remove the junction of the fine particle sample collection cell and to put the solid sample in and out. This simplifies the operation and eliminates the possibility of exposing the whole cell to the atmosphere. It is possible to save the time required to replace the generated atmosphere with the carrier gas.

In the laser vaporized fine particle sampling cell in which the edge of the opening is formed of a sealing material, the carrier gas does not leak even when applied to a large solid sample having a non-flat sampled surface, and the transport amount of the fine particle sample is stable. I do. At the same time, the flattening grinding of the sampled surface is not required, and the analysis time can be further reduced.

In some cases, such as when a cell for collecting fine particle samples is applied at a production site by remote control, automatic operation, or the like, the opening does not come into full contact with the collection surface. In such a case, the leakage of the carrier gas increases, and the amount of gas introduced into the element detection device fluctuates. Therefore, the temperature of the excitation flame fluctuates, the luminous efficiency changes, and the analysis accuracy may decrease. It is desirable that the change in the amount of the carrier gas be suppressed within 10%.

If a bellows tube is provided in the opening, the bellows tube is elastically deformed and its tip comes into full contact with the sampling surface even if the fine particle sample collection cell is slightly inclined, thereby preventing leakage of the carrier gas.

However, on the other hand, if the bellows tube is severely deformed, the laser beam may be blocked by the bellows tube wall and not irradiated on the sampling surface. In order to avoid this, it is preferable that the opening is formed in a cylindrical shape and a bellows tube is provided at a distance from the opening to form a double tube.

[0025]

【Example】

Embodiment 1 FIG. A fine particle sampling cell having an outer cylinder for a small solid sample was fabricated. The outline is shown in FIG.

FIG. 1A shows a cell having the simplest structure.
The fine particle sample collection cell 1 is provided with a carrier gas inlet 2, a carrier gas outlet 3, and a transmission window 4. The flow path of the carrier gas introduced from the inlet 2 is regulated by the inner surface of the transmission window 4.
It flows toward the solid sample 5. The laser light passes through the transmission window 4 and irradiates the solid sample 5 to vaporize a part thereof to generate fine particles. The fine particle sampling cell 1 has an outer cylinder 7, and a discharge section 3 communicating with the outer cylinder 7 is provided on the solid sample side of the fine particle sampling cell 1. For this reason, the carrier gas heading for the solid sample 5 contains vaporized substances and fine particles from the solid sample 5 in the vicinity of the solid sample 5, and then is discharged from the discharge unit 3 to the outer cylinder 7 and contaminates the transmission window 4. Never.

FIG. 1 (b) is a diagram in which the width of the particle collection cell 1 is narrowed on the solid sample 5 side, and the flow rate of the carrier gas containing the particles is increased so that the particles are removed from the laser beam path more quickly. I will

FIG. 1 (c) uses the outer cylinder 7 also for introducing the carrier gas, and the introduction section 2 is provided in a ring shape. When the solid sample 5 is relatively large and the inside diameter of the particulate sample collection cell 1 is large, the flow of the carrier gas from the transmission window 4 to the solid sample 5 is not easily disturbed.

Embodiment 2 FIG. A fine particle sampling cell suitable for a large sample having an opening on the surface facing the transmission window was manufactured. The outline is shown in FIG.

An opening 8 is provided facing the transmission window 4, and the flow path of the carrier gas in the cell for collecting fine particles is shown in FIG.
It is not different from the one shown in. Since the solid sample 5 can be placed outside the cell, it can be used for a large solid sample that cannot be installed in the cell. In the case of a small sample smaller than the opening, the small sample may be placed on a table, and the opening may be brought into contact with the installation surface while the solid sample is swallowed into the cell.

The opening is circular and has a diameter of about 1 mm. The laser beam is condensed in the vicinity of the opening to a beam diameter of about 100 μm, so that the opening 8 may be small.

FIG. 2B shows a particle sampling cell in which the edge of the opening 8 is formed of a sealing material 9. As the sealing material, a rubber “0” ring was used, but when the solid sample is at a high temperature, an inorganic material such as a ring in which glass fibers are bundled may be used.

Embodiment 3 FIG. A fine particle sampling cell using a bellows tube at the contact portion with the sample sampling surface was fabricated. The outline is shown in FIG.

FIG. 3A shows a bellows tube 21 in the opening 8.
Provided by the elastic deformation of the bellows tube 21,
The leakage of the carrier gas from between the sampling surface was successfully prevented.

FIG. 3 (b) shows a double tube structure.
The amount of deformation of the bellows tube 21 is limited by the cylinder 22. Using a resilient bellows tube having a tip diameter of 20 mm and a spring constant of 10 kg / mm, a gap with the cylinder was made 1 mm, and the position of the tip was made 1 mm ahead of the tip of the cylinder 22. The gap and the position of the tip are factors that determine the amount of deformation of the bellows tube 21.
Excessive restrictions may allow carrier gas to leak.

FIG. 4 shows the relationship between the state of leakage of the carrier gas and the amount of adjustment caused by the deformation of the bellows pipe in a daily operation. The achieved ratio is expressed as a sealing ratio, and the adjustment amount is expressed as an angle that the bellows tube tip surface can cope with. In the figure, a circle indicates an average value, and a line length indicates a range in which the values vary. 90% seal rate if the available angle is less than 2 degrees
, And the amount of deformation is excessively limited.

FIG. 3C shows the bellows tube 21 connected to the cylinder 2.
2 and has a double pipe structure, and the amount of deformation of the bellows pipe 21 is limited by the cylinder 22 as in the case of FIG. In this structure, the generated fine particles do not adhere to the bellows tube.

Embodiment 4 FIG. Using the fine particle sample collection cell shown in FIG. 2 (b), the amount of fine particle samples collected from a large solid steel sample was examined and analyzed to determine the accuracy. Further, the case where a fine particle sample collection cell shown in FIG. 6 which is generally used in the past was used was examined and compared.

The laser oscillator used for sampling the fine particles was a Q-switched pulse YAG laser, and a high frequency inductively coupled plasma emission spectrometer was used for element detection. The laser beam was irradiated while moving the focal point parallel to the surface of the solid sample so that the sampling speed of the fine particles was kept as constant as possible. In addition, in the determination of the elements, correction using the internal standard method of iron was performed so as to eliminate the influence of the variation in the amount of sampled fine particles as much as possible.

The sampling amount of fine particles was 20 times at a time.
The sample was irradiated with a laser beam for seconds and the amount collected was measured. Figure 10 shows the results of this operation performed 10 times in succession and the state of the fluctuation was examined .
It is shown in FIG.

In the figure, the vertical axis represents the amount of sampled fine particles, and the horizontal axis represents the number of times of collection. The results of the examples of the present invention are indicated by ○, and the comparative examples are indicated by ●.

In the embodiment of the present invention, the sampled amount of the fine particles falls within the range of 10 μg to 11 μg and is stable.
In the conventional example, the collection amount of the fine particle sample was reduced from 10 μg every time the collection was performed, and fluctuated to nearly 8 μg.

Regarding the accuracy of the analysis, the relative standard deviation was determined by repeating the analysis 20 times. Table 1 shows the results.

[0044]

[Table 1]

In the table, A is an example of the present invention, and B is a comparative example. In the examples of the present invention, the irradiation intensity of the laser beam does not change, so that the generation amount of the fine particle sample and the representativeness of the sample are stable, and the relative standard deviation is within 2% for all components. It is over 2%.

Further, in the embodiment of the present invention, the time for cutting out the sample is not required, and the time for obtaining the analysis result is greatly reduced. At the same time, since the solid sample was exchanged while the carrier gas was flowing, the inside of the cell was in a pressurized state and was not contaminated by carbon or silicon compounds such as hydrocarbons contained in the atmosphere.

Embodiment 5 FIG. Using the fine particle sample collection cell shown in FIG. 3 (b), a fine particle sample was sampled from a cross section of a steel ingot having a width of 1000 mm and a thickness of 250 mm and analyzed. Laser light irradiation and analysis conditions are the same as those in Example 4. Table 2 shows the results.

[0048]

[Table 2]

As in the case of Example 4, the relative standard deviation was within 2% for all the components, and the analysis values were obtained with good accuracy.

[0050]

As described above, according to the present invention, the inlet and outlet of the carrier gas are provided so that the carrier gas flowing through the cell for collecting fine particles flows from the laser light transmission window toward the solid sample. Therefore, the laser beam intensity does not change without contaminating the transmission window. For this reason, a highly accurate analysis result can be obtained without variation in the amount of sampled fine particles. In addition, by providing an opening in the particle sampling cell, the time required for the solid sample to enter and exit the cell can be saved.
Is, analysis results the time to be obtained is significantly reduced. As described above, the effect of the present invention achieved by combining the speeding up of the laser vaporization analysis and the improvement of the accuracy is great.

[Brief description of the drawings]

FIG. 1 is a schematic view of a particle sampling cell for explaining the present invention.

FIG. 2 is a schematic view of a particle sampling cell having an opening for explaining the present invention.

FIG. 3 is a schematic diagram of a particulate sample collection cell provided with a bellows tube in an opening.

FIG. 4 is a diagram illustrating a relationship between a correctable angle and a seal ratio.

FIG. 5 is a diagram showing the relationship between the number of times of collecting the fine particle sample and the amount of collecting the fine particle sample for comparing the stability of the fine particle sample amount.

FIG. 6 is a conceptual diagram of a laser vaporization analysis sampling section for explaining the relationship between a laser beam and a particle sampling cell.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 particle sampling cell 2 introduction part 3 discharge part 4 transmission window 5 solid sample 6 connection part 7 outer cylinder 8 opening 9 sealing material 10 laser beam 21 bellows tube 22 cylinder

──────────────────────────────────────────────────続 き Continuing on the front page (72) Tadashi Mochizuki, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Takanori Akiyoshi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan (72) Inventor Tetsushi Shiroshiro 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Akiko Sakashita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Yoshihiko Kawai 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Yoshito Iwata 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-5-52722 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01N 1/28 G01N 21/15 G01N 21/31 G01N 21/73

Claims (5)

(57) [Claims] An analysis is performed by irradiating a solid sample located on the opposite side of the transmission window with a laser beam through the transmission window in the flow of the carrier gas. A cell for introducing a carrier gas is provided on the transmission window side, and a carrier gas discharge unit is provided on the solid sample side so that the carrier gas flows from the transmission window through the transmission window. A sample cell for collecting laser vaporized fine particles, characterized in that a flow path toward a sample is formed, and the cell has an outer cylinder and a discharge portion for a carrier gas communicating with the outer cylinder on the solid sample side. 2. The cell for sampling a laser vaporized fine particle according to claim 1, wherein an opening is provided on a surface facing the transmission window. 3. The laser vaporized fine particle sampling cell according to claim 2, wherein the edge of the opening is formed of a sealing material. 4. The laser vaporized fine particle sampling cell according to claim 2, wherein a bellows tube is provided in the opening. 5. The laser vaporized fine particle sampling cell according to claim 2, wherein the opening has a cylindrical shape, and a bellows tube is provided with a gap therebetween to form a double tube structure.