JPH07918Y2 - Sample atomizer for plasma excitation - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to a sample atomization furnace for plasma excitation, and in particular,
The present invention relates to a sample atomization furnace for plasma excitation, which is suitable for directly analyzing a small amount of a solid or solution sample by a plasma analysis method and is capable of efficiently exciting a sample.

[Prior art]

As an analysis method for exciting a sample using plasma as an excitation source, a high-frequency inductively coupled plasma (IC) using electromagnetic induction by a high frequency of about MHz is used.
P), microwave induced plasma utilizing microwave (M
IP), direct current plasma (DCP) using direct current as a discharge power source, etc. Among them, the emission spectroscopic analysis method using ICP as an excitation source is
As a highly sensitive and highly accurate analysis method, it has been put to practical use in a wide range of fields such as steel and environmental measurement. However, the samples that can be introduced into the plasma and analyzed are limited to solutions, gases, or aerosols, and analysis of samples with a small absolute amount (about 5 cm ³ or less) is also difficult with ordinary devices. Therefore, as a method for analyzing solids and minute amounts of solution, a method of inserting a sample into a graphite furnace and directly inserting it into plasma has been reported (EDSalin, G. Horlick: Anal. Chem. Vol. 5).
1, P. 13 (1979) etc.). There are also examples of application to living organisms, environmental samples, etc. (M. Abdullah, K. Fuwa, H. Haraguchi: Spe
ctrochim.Acta, Vol.39B, P.1129 (1984) etc.). However, the atomizer used for these measurements was
With a capacity of 5 to 10 mm ³ , for example, as shown in FIG. 5, the graphite rod 10 has a hole 12 at the tip, so that the heat capacity of the rod portion is too large and the temperature of the sample rapidly rises. However, it is not suitable for exciting a high boiling point metal.
Further, since the amount of sample that can be introduced is small, there is a problem in that there is a large variation in analysis values and the sample is easily affected by segregation. Therefore, the atomization of graphite is made into a cup shape to increase the capacity,
Attempts have also been made to cut the lower part of the atomization part finely to efficiently raise the temperature of the sample (Masao Umemoto, Masaaki Kubota, "Spectroscopic Research," Vol. 35, No. 1, p. 50 (1986)). . However, since the cup portion and the shaft portion are integrally formed, processing is difficult and heat conduction to the shaft portion is large, which is not sufficient to rapidly raise the temperature of only the sample portion.

[Issues to be achieved by the device]

The present invention has been made in order to solve the above-mentioned conventional problems. The heat conduction to the shaft supporting the sample atomization part is small, the sample can be efficiently excited, and the molding process is easy. A sample atomization furnace for plasma excitation is provided.

[Means for achieving the object]

The present invention is a sample atomization furnace for plasma excitation, and a sample atomization part molded of a non-metallic material with excellent thermal conductivity,
The sample atomization part is connected to the supporting / driving part of the analyzer, is separate from the sample atomization part, and has a diameter sufficiently smaller than the outer diameter of the sample atomization part, so that heat conduction can be improved. The above-mentioned object is achieved by providing a small solid shaft portion. Further, in the same plasma-exciting sample atomization furnace as described above, for connecting the sample atomization section to the supporting / driving section of the analyzer, a shaft section which is separate from the sample atomization section,
By molding with a non-heat-conducting material, the above-mentioned object is also achieved.

[Action]

In the present invention, a sample atomization furnace for plasma excitation is connected to a sample atomization section and a shaft section (and a connection section if necessary) for connecting the sample atomization section to a supporting / driving section of an analyzer.
While separating the sample atomization part from a non-metallic material having excellent thermal conductivity (eg, graphite), the shaft part fitted to the sample atomization part is converted into the sample atomization part. The heat conductivity is suppressed by making the diameter sufficiently smaller than the outer diameter of the portion or by molding with a non-heat-conductive material (for example, ceramic). Therefore, the heat conduction to the shaft becomes small, and when it is inserted into the plasma, the sample atomization part and the contained sample are efficiently heated and excited to improve the analysis using the plasma as the excitation source. It can be performed with high sensitivity and high accuracy.

【Example】

Hereinafter, an embodiment of the present invention applied when plasma is formed in a vertical direction will be described in detail with reference to the drawings. In the present embodiment, as shown in FIG. 1, a sample atomization unit 20 and a sample atomization unit 20 for connecting the sample atomization unit 20 to a supporting / driving portion of an analyzer (not shown). An upper end fitted to a hole 20A formed on the bottom surface, a shaft portion 22 which is a separate body from the sample atomization portion 20, and a shaft portion 22 for connecting the shaft portion 22 to an analyzer. Connection part 24 whose lower end is fitted in hole 24A
It consists of and. The sample atomization unit 20 has a plasma temperature of 6,000 to 10,000.
Since the temperature of the atomization part is 0 ° K and the temperature of the atomization part is about 3,000 ° C., and the atomization part is frequently replaced, it is molded with a graphite material such as high-density graphite, glassy carbon, or pyro-coated carbon. It should be noted that a non-metallic material having excellent heat conduction other than graphite can be used for molding. The furnace diameter D of the sample atomizing section 20 can be changed according to the sample amount as long as it is smaller than the innermost tube diameter of the plasma torch.
In order to maintain the plasma stable, 2/3 of the torch tube diameter
The following is desirable. Set the furnace diameter D of the sample atomization unit 20
When the length is 4.5 mm and the furnace length L is 5.5 mm, 50 μl of solution can be injected, and stable plasma can be maintained even when it is inserted into the plasma. Also, using a material with a small hole diameter, the wall thickness is 1 mm.
By making the thickness as follows, it is possible to increase the temperature rising rate in the furnace and prevent the diffusion of the target element through the furnace wall. For the shaft portion 22, it is desirable to use a non-heat conductive material such as heat resistant ceramics. When using a material having a high thermal conductivity like the sample atomization section 20, it is necessary to make the material as thin as possible, and from the viewpoint of strength and the like, the shaft diameter d is preferably 1 to 1.5 mm. . In the embodiment, it is set to 1.5 mm. The length l of the shaft portion 22 is 35 mm in the embodiment. The shape of the connecting portion 24 is changed according to the shape of the atomizing furnace supporting portion of the analyzer, but in the present embodiment, the lower end of the shaft portion 22 is inserted and fitted by a length Z = 4 mm. I am trying to do it. If the device support portion can be directly connected to the shaft portion 22, the connection portion 24 can be omitted. At the time of analysis, the analysis sample is put in the sample atomization section 20, and the shaft section 22 is directly connected to the support section of the analyzer (not shown) through the connection section 24 or inserted into the plasma. A sample is excited by the plasma to perform, for example, emission spectroscopic analysis. When the sample direct insertion method was performed by ICP emission analysis using the sample atomization furnace having the shape shown in FIG. 1 and formed of high-density graphite, the emission signal shown in FIG. 2 was obtained. . 1 μg / each of P, CU, Mn, Sn, Al and Cr is used as the analysis sample.
50 μl of ml (0.1 N HCl) solution is used. FIG. 2 shows that after injecting this solution sample into the atomization part 20 to remove water,
It was obtained by inserting it into the plasma from the bottom of the plasma torch, and the element symbols are entered at the peak positions of each element. On the other hand, an ICP in the case of using a commercially available graphite rod 10 for emission analysis (having a hole 12 with a volume of 50 μl at the tip of the rod) having a shape as shown in FIG.
An example of the luminescence signal is shown in FIG. As is clear from the figure, in the case of this example, the rapid temperature rise of the atomization portion efficiently causes the excitation of each element, the observed emission peak intensity increases, and the waveform becomes sharp. There is. This effect is particularly remarkable in metals such as Cr and Fe that are difficult to atomize (the boiling point of Cr is 2877 ° C and the boiling point of Fe is 2870 ° C). The length l of the shaft portion 22 is 0 mm, 1 mm, 15 m
When it is changed to m and 35 mm, the emission intensity increases like 1: 1, 7: 2 and 3: 2.5, so the axial length l should be 1 mm or more.
Even if it is 5 mm or more, the effect of increasing the excitation efficiency is small. The background equivalent concentration BEC (Background Equivalent Concetratio
n, ICP emission analysis, BEC / (20 to 30) is usually said to be the lower limit of quantification), and repeatability σ are compared between the case of this example and the case of using a commercially available emission analysis graphite rod 10. Then, it becomes as shown in the following Table 1. The number of samples n is 5 in each case. As is clear from Table 1, in this example, BEC
1/2 to 1/8 (sensitivity is 2 to 8 times), and σ
It is clear that the analysis accuracy is greatly improved. In addition, using the sample atomization furnace of Fig. 1, a solid sample (steel)
Fig. 4 shows an example of the luminescence signal when γ is directly excited by ICP. As is clear from the figure, according to the present invention, trace impurities of 0.1% or less in iron matrix can be accurately analyzed, including metals such as Cr that are difficult to atomize. Further, in the graphite sample atomization part 20 of the same capacity as in FIG.
Even when the same operation was performed using a zirconia shaft 22 having a length of 3 mm and a shaft length of 35 mm, a sharp luminescence signal equivalent to that shown in FIG. 2 was obtained, and improvement in atomization efficiency was confirmed.

[Effect of device]

As described above, according to the present invention, the heat transfer in the shaft portion is suppressed as compared with the sample atomization portion, so that the sample can be efficiently excited and the molding process becomes easy. Therefore, a small amount of solid sample or solution sample can be efficiently excited by direct insertion into plasma, and highly sensitive analysis can be performed. Further, since only the atomization part can be easily replaced, there is an excellent effect that the analysis operation can be speeded up and the cost can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the structure of an embodiment of a sample-atomization furnace for plasma excitation according to the present invention, and FIG. 2 is an emission of a solution sample analyzed by ICP emission spectrometry using the above-mentioned embodiment. FIG. 3 is a diagram showing an example of a signal, FIG. 3 is a diagram showing an example of a luminescence signal when a solution sample is analyzed using a commercially available graphite rod for emission analysis, and FIG. ICP
FIG. 5 is a diagram showing an example of a luminescence signal when a fixed steel sample is directly analyzed by an luminescence analysis method, and FIG. 5 is a sectional view showing an example of the shape of a commercially available graphite rod for luminescence analysis. 20 …… Sample atomization part, 22 …… Shaft part, 24 …… Connection part, D…
… Furnace diameter, d… Shaft diameter.

Claims (2)

[Scope of utility model registration request] 1. A sample atomization part formed of a non-metallic material having excellent thermal conductivity, and a separate sample atomization part for connecting the sample atomization part to a supporting / driving part of an analyzer. It is a body and has a solid shaft portion having a small heat conduction by having a diameter sufficiently smaller than the outer diameter of the sample atomization portion, which enables efficient excitation of the sample. A sample atomizer for plasma excitation. 2. A sample atomization part molded of a non-metallic material having excellent heat conduction, and a separate sample atomization part for connecting the sample atomization part to a supporting / driving part of an analyzer. A sample-atomization furnace for plasma excitation, which comprises a body and a shaft formed of a non-heat-conductive material, and enables efficient excitation of the sample.