JPH01143935A - Icp emission analyzer - Google Patents

Abstract

PURPOSE:To enable the stable emission analysis of even a slight amt. of hardly volatile sample with high sensitivity by effecting a spark discharge or arc discharge between a sample rod and counter electrode through the plasma formed on a plasma torch. CONSTITUTION:A sample base 5 is removably provided on a central pipe 3 of a plasma torch T. This sample base 5 and the counter electrode 6 disposed above the plasma torch T are connected to both electrodes of a power supply 7 for spark discharge or arc discharge. The sample base 5 is connected to an igniter 8 which generates the corona discharge from the sample base. The spark discharge or arc discharge is effected between the sample rod and the counter electrode 6 through the plasma flame F formed on the plasma torch T. Since the sample is evaporated by the high temp. of the spark discharge or arc discharge, the analysis is possible even with the hardly volatile sample and since the evaporation place of the sample is the central pipe 3 of the plasma torch T, the distance from the evaporation place of the sample to the plasma flame F is short. The evaporated sample is thus effectively sent to the plasma flame F without being stuck to the pipe wall.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an ICP (inductively coupled plasma) emission spectrometer, and particularly to the configuration of a means for introducing a sample into the plasma flame.

B. Conventional Technique 102 In optical emission spectrometry, a sample is usually made into a solution, atomized using a sample atomizer, and then sent into a plasma flame along with a flow of carrier gas. However, this method requires a large amount of sample, so for very small samples, a sample heater using a graphite sample atomization reactor or a boat made of a high-melting point metal such as tungsten is used, and a graphite sample reactor or a sample heater using a boat made of a high-melting point metal such as tungsten can be used. The method used is to turn on electricity, volatilize the sample with the Joule heat generated at that time, and send the volatilized sample to the plasma flame in a carrier gas flow.
Heating using Joule heat does not reach a sufficiently high temperature and cannot be used to analyze difficult-to-volatile samples. In such cases, a method called AG-I PC is used. In this method, the sample and electrode are opposed to each other and spark discharge or arc discharge is performed to evaporate the sample, and the generated sample vapor is conveyed to the plasma torch in the flow of gear gas.

Problems to be Solved by the Invention As mentioned above, when analyzing a trace amount of a non-volatile sample using ICI' emission spectrometry, the 8G-I PC method was conventionally used. Because it is far away from the plasma torch, the sample adheres to the pipe wall along the way, contaminating the gas flow path.''-One sample is lost, which is very small! ! In the case of L samples, the sensitivity decreases, and the sample that evaporated in the pipe re-agglomerates and becomes larger in particle size, and cannot be completely evaporated in the plasma flame, resulting in decreased sensitivity and unstable analytical values. was there. Therefore, the present invention is intended to enable highly sensitive and stable 102 emission analysis even for a trace amount of sample with low volatility.

20 Means for Solving Problems A sample stand is removably inserted into the center tube of the plasma torch, and this sample stand and a counter electrode placed above the plasma torch are connected to both poles of a power source for spark discharge or arc discharge. At the same time, connect the sample stand to a high-voltage power source that generates corona discharge from the sample stand, and create a spark discharge or arc discharge between the sample rod and the counter electrode by penetrating the plasma formed on the plasma torch. I made it happen.

E1 Effect When a sample is attached to the tip of a sample rod and inserted into the center tube of a plasma torch, and a plasma flame is passed through it to cause a spark discharge or arc discharge between the counter electrode and the sample rod, the sample rod The sample at the tip is instantly volatilized by the intensive high temperature of the spark discharge or arc discharge, and the sample vapor is carried by the carrier gas flow into the plasma flame. Since the distance between the sample rod and the counter electrode is large, unless a plasma flame is formed on the plasma torch, spark discharge will not occur unless a special high voltage is applied between the sample rod and the counter electrode. ,
With high frequency, when a high voltage is applied to the sample rod while plasma is being formed, a corona discharge is generated from the sample rod, and filament plasma is extended from the plasma flame. This creates a conductive channel from the counter electrode through the plasma flame filament plasma, resulting in a spark or arc discharge between the counter electrode and the sample rod.

Embodiment Figure 1 shows an embodiment of the present invention. T is for plasma torch,
Mantle tube 1. Intermediate 2. It is a triple tube with a central tube 3, and cooling gas is supplied to the outer tube, plasma forming gas is supplied to the middle tube, and carrier gas is supplied to the central tube. 4 is a high frequency coil that forms a plasma flame. Carrier gas is supplied from the lower side opening of the central tube 3. The lower end of the central tube is open and is closed by the sample stage 5. 6 is a tungsten counter electrode placed above the plasma torch, and 7 is a spark discharge power source, which consists of an AC power source, a step-up transformer T1, a rectifier circuit D, a discharge energy storage capacitor C, etc. One side is the counter electrode 7
and the other end is connected to the sample stage 5. 8 is a Tesla coil used as an igniter and connected to the sample stage 5.

The sample is used by depositing a drop of the solution on the sample stage 5 and drying it. Alternatively, the powder sample may be filled into small holes on the surface of the sample stage 5. Attach the sample stage with the sample attached to the lower end of the central tube 3 of the plasma torch, insert the outer tube l, the middle tube 2. Gas is supplied to each of the central tubes 3 and high frequency power is supplied to the coil 4 to form a plasma flame F. In this state, when a high-pressure high-frequency voltage from the Tesla coil 8 is applied to the sample stage 5, a corona discharge is generated from the sample stage 5, and when the generated ions ride the carrier gas flow and reach the plasma flame F, the plasma flame 7, The filament-shaped plasma extends and reaches the sample stage 5. On the other hand, the capacitor of the spark discharge power supply is in a charged state, and when filament plasma is formed from the plasma flame F toward the sample stage 5, an electric field is concentrated between the counter electrode 6 and the plasma flame F, and the gas between them is The insulation is broken and a spark discharge occurs between the counter electrode and the sample stage 5 at once, and the sample attached to the sample stage 5 is scattered. This sample is sent into the plasma flame F along with the flow of carrier gas.

In the above embodiment, a spark discharge power supply is connected between the sample stage and the counter electrode, but the capacitance of the discharge energy storage capacitor is increased (i.e., a resistance or inductance is inserted between the capacitor and the counter electrode). If this is done, the discharge changes from an instantaneous spark discharge to a sustained arc discharge.Alternatively, an AC arc discharge power source using a leaky transformer such as that used for arc welding may be used.In this case, the filament plasma Arc discharge cannot start even when the sample stage is reached, so either manually insert the counter electrode momentarily into the plasma flame, or connect a separate circuit that applies a high voltage impulse between the sample stage and the counter electrode. The counter electrode 6 may be the coil 4 if the power source for spark or arc discharge is DC.

The shape of the sample is arbitrary, and is not limited to applying a solution and drying it or filling a hole with powder.

A porous material impregnated with a sample solution may be used, and if the sample is conductive, the sample itself may be used as a sample stage.

Effects According to the present invention, since the sample is vaporized by the high temperature of spark discharge or arc discharge, even slightly volatile samples can be analyzed. The distance from the volatilization location to the plasma flame is short (straight), so the volatilized sample is efficiently sent to the plasma flame without adhering to the tube wall, and contamination with the Plasma Dawg sample does not occur, reducing sample loss. hand,
Even trace amounts of samples can be analyzed with high sensitivity.

[Brief explanation of the drawing]

The drawing is a side view of one embodiment of the invention. T...Plasma torch, F...Plasma flame, 1...
- Outer tube, 2... Middle tube, 3... Center tube, 4... Coil, 5... Sample stage, 6... TL pole, 7... TFT source for spark discharge, 8 ...igniter. Agent Patent Attorney Kosuke Agata

Claims (1)

[Claims] A sample stand is removably attached to the center tube of the plasma torch with the sample surface facing, and this sample stand and a counter electrode placed above the plasma torch are connected to both poles of a power source for spark discharge or arc discharge. An ICP emission spectrometer characterized in that a high-voltage power source that generates corona discharge from the sample stage is connected to the sample stage.