JPS63210754A - Sample introducing device for icp emission analysis - Google Patents

Abstract

PURPOSE:To prevent the drop of a plasma temp. by inserting a sample introducing bar which is disposed with a sample receiving tray at the top end and a sample heating heater in the lower part of the receiving tray, respectively, into a plasma torch from the lower side thereof in such a manner that said bar can be inserted into and removed from the torch and can be vertically moved. CONSTITUTION:The plasma torch P is constituted of triple pipes; a central pipe 1 for a carrier gas, an intermediate pipe 2 for supplying a gas for forming a plasma flame and a sleeve pipe 3 for supplying a cooling gas. A high-frequency coil 4 for forming the plasma flame 5 is disposed on the outside of the pipe 3. The sample introducing bar 6 provided with the sample receiving tray 7 at the top end is vertically movably inserted into the pipe 1. The bar 6, in the receiving tray 7 of which a sample soln. is dropped, is then inserted into the pipe 1 and the sample is evaporated by a heater 8. The vapor thereof is entrained in the carrier gas and is introduced into the plasma flame 5 so that the sample emits light. Observation of the progress of the sample evaporation with time is thereby permitted without decreasing the plasma temp. and without disturbing the evaporation with time.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an ICP (high frequency inductively coupled plasma) emission spectrometer, and particularly to a sample introduction section in a plasma torch.

In the prior art, sample introduction in ICP analysis is usually carried out as follows. A sample solution is made into a solution, and a sample solution is atomized using a carrier gas using a spray type sample atomizer, and the sample solution is supplied to the plasma flame in the flow of the carrier gas. This method requires a large amount of sample, so when dealing with a small amount of sample in the form of a solution, the direct insert method, in which the sample solution is attached to the tip of a graphite rod and inserted directly into the plasma flame, or the flameless atomic absorption spectrometry method can be used. A method using a graphite sample atomization unit (GFA) such as that used in

C.9 Problems to be Solved by the Invention Although the present invention is directed to the analysis of a trace amount of a solution sample,
In the above-mentioned direct insert method, the graphite rod is inserted directly into the plasma flame, so there is a problem that the temperature of the plasma flame becomes too low (so that it is difficult to sufficiently excite the sample). A graphite furnace is connected to a plasma torch through a carrier gas conduit, a sample solution is dropped into the furnace, and the sample solution is instantaneously heated by electricity, and the evaporated and atomized sample is carried by the carrier gas flow and sent to the plasma torch. The sample atomization section and the volume from the sample atomization section to the plasma torch are large (and when a small amount of sample is atomized, the time course of the sample evaporation phenomenon becomes blurry, and the volume from the previous analysis There is a problem of contamination, where some of the sample remains impregnated on the inner surface of the pipe or in the graphite furnace and mixes into the sample to be analyzed.

The present invention aims to provide a means for introducing a trace amount of a solution sample into a plasma flame without the above-mentioned problems such as lowering the temperature of the plasma flame, difficulty in grasping the time course of sample atomization, and contamination of the previous sample. It is something.

29 Means for Solving Problems A sample tray is placed at the upper end of the tray, and a sample introduction rod with a sample heater placed at the bottom of the tray is placed along the tube axis of the plasma torch.
It was inserted into the plasma torch from below so that it could be inserted and removed and moved in the vertical direction.

E1 Action: Pull out the sample introduction rod from the plasma torch, drop the sample solution into the saucer at the upper end, insert the sample introduction rod into the plasma torch, push the saucer part close to the bottom of the plasma, and energize the heater to release the sample. Evaporate. The evaporated sample is carried by the gas flow inside the torch and immediately enters the plasma flame. Although this device does not insert an object into the plasma flame, it does not lower the temperature of the plasma as in the direct insertion method. In addition, since the sample is evaporated near the bottom of the plasma flame, the time course of sample atomization is transmitted to the plasma flame without any time delay, and the time course of the evaporation phenomenon can be observed without any temporal distortion. It is a part with a very small area compared to the previous model, and although there is no pipe system in the middle, there is no risk of contamination from the previous sample.

Embodiment Figure 1 shows an embodiment of the present invention. P is 3 with plasma torch
It is called a Fassel-type plasma torch, which consists of multiple pipes. A carrier gas is supplied to the center tube l of the triple tube. The intermediate tube 2 is supplied with a plasma flame-forming gas. Cooling gas is supplied to the outermost mantle tube 3. Argon gas is used for all of these gases. A high frequency coil 4 is wound around the outside of the mantle tube 3, and a plasma flame 5 is formed by a high frequency induced electric field formed by this coil. The central tube 3 is made slightly thicker than that of a normal fassel type torch, and a sample introduction rod 6 can be inserted therein. The sample introduction rod 6 is a quartz tube, and a sample tray 7 made of tungsten is removably fitted onto the upper end of the rod. A heater 8 is inserted into the sample introduction rod 6. 9 is a heater power source. The sample introduction rod 6 is inserted into the center tube 1 of the plasma torch, and a backing 10 is interposed between the sample introduction rod 6 and the center tube 1 to prevent the carrier gas from leaking from the lower end of the center tube 1. The sample introduction rod 6 is slidable relative to the backing holder 11, and the backing holder 11 is attached to and detached from the lower end of the central tube 1. Therefore, the sample introduction rod 6 can be slid up and down within the central tube 1, and can be pulled out from the central tube together with the backing holder 11. A threaded groove 12 is provided on the lower outer periphery of the sample introduction rod 6.
is provided, and this thread groove meshes with a gear 14 driven by a motor 13. Therefore, by rotating the motor 13, the sample introduction rod 6 can be moved up and down. Reference numeral 15 denotes a switch for detecting the vertical position of the sample introduction rod 6. When the upward rotation of the sample introduction rod of the motor 13 is stopped at a point where the lower end of the sample introduction rod 6 is separated from the actuator of the switch, the saucer 7 is placed in the plasma. It can be stopped at a height below the bottom surface of the flame 5.

The device described above operates as follows. The sample introduction rod 6 is lowered to disengage the thread groove 12 and the gear 14, and pulled out together with the backing holder 11 downward from the center tube 1 of the plasma torch. Drop a drop of sample solution into the sample tray 7 at the upper end of the sample introduction rod that has been pulled out using a microsyringe, insert the sample introduction rod into the central tube 1 from below, engage the thread groove 12 with the gear 14, and rotate the motor 13 in the correct position. When rotated, the sample introduction rod rises, and when the sample tray 7 reaches a height just below the bottom of the plasma flame, the switch 15 is activated and the motor 13 is stopped. When the heater 8 is now energized, the sample is vaporized and introduced into the plasma flame along with the flow of the carrier gas supplied to the central tube 1. The carrier gas creates an air current that blows upward through the center of the plasma flame, forming a relatively low-temperature tunnel along the center line of the plasma flame, and from there the temperature increases toward the outer periphery. The sample enters the plasma flame along with the flow of carrier gas, diffuses toward the outer periphery, and
It emits light when excited in a high temperature area.

By repeating the above operations, a large number of samples can be analyzed one after another. Since the sample tray 7 is detachable from the sample introduction rod 6, the tray 7 can be replaced for each sample.

According to the present invention, when introducing a small amount of sample, the graphite rod is not inserted directly into the plasma flame, so the temperature of the plasma flame does not decrease, and the sample is vaporized directly under the plasma flame. Because of this, it is possible to observe the time course of the sample evaporation phenomenon without any temporal distortion, and since there is no pipe system for introducing the sample, the sample tray is a very small part, and the entire part can be heated to a uniform temperature. There is no problem of contamination caused by residual samples.

Although the above explanation deals with solution samples, it goes without saying that the apparatus of the present invention can also be applied to small amounts of solid samples.

[Brief explanation of the drawing]

The drawing is a longitudinal sectional side view of a plasma torch according to an embodiment of the present invention. P... Plasma torch, 1... Center tube, 2... Middle tube, 3... Outer tube, 4... High frequency coil, 5...
- Plasma flame, 6... Sample introduction rod, 7... Sample tray, 8... Heater, 9... Heater power supply, 10... Backing, 11... Backing holder, 12...
Screw groove, 13...Motor, 15...Position detection switch.

Claims (1)

[Claims] The sample introduction rod, which has a sample tray attached to the upper end and a sample heater arranged below the tray, can be inserted into and removed from below the plasma torch and moved in the vertical direction along the tube axis of the plasma torch. A sample introduction device for ICP emission analysis characterized by being inserted.