JPH0737945B2 - ICP analysis method - Google Patents

Description

The present invention relates to an ICP (high frequency inductively coupled plasma) analyzer and an ICP analysis method for analyzing components of a sample.

(B) Conventional technology An ICP analyzer is a device that introduces a gasified (atomized) sample into a plasma torch to emit light, and spectroscopically measures this light to analyze the sample components. Atomized by the sample atomization chamber, and carrier gas (argon gas)
It is introduced together with the plasma torch. An induction coil is circulated around the plasma torch, and a plasma gas and a cooling gas (usually argon gas are both supplied) to form a plasma flame at the tip of the plasma torch.

By the way, when the plasma flame is turned on, a large amount of electric power is required and a complicated operation such as impedance matching is required. Therefore, when the sample is analyzed intermittently, the state where the plasma is turned on is maintained. In such a case, the amount of gas supplied to the plasma torch and the high-frequency power supplied to the induction coil are kept constant in order to maintain the stability of the plasma and keep the analysis conditions constant.

However, the time required to introduce and analyze one sample is about 10 to 20 seconds, so most of the time is waiting time,
There is a problem that the cost of the expensive argon gas increases and the analysis cost increases.

In order to solve this problem, in the invention of Japanese Patent Application No. 61-61555, a switching valve is provided between the sample atomizing chamber and the plasma torch, and the atomized sample is introduced into the plasma torch only at the time of measurement. At this time, the carrier gas passing through the sample atomization chamber is discharged from the switching valve. In this way, only argon gas is introduced into the plasma torch except during measurement, so the amount of gas required to maintain the minimum ignition plasma and the power supplied to the induction coil can be predicted, and the amount of gas can be reduced. It is possible to reduce the analysis cost by reducing the amount. In addition, the sample atomization chamber is cleaned by the carrier gas except when the analysis is performed, and the sample can be prepared for the next sample introduction.

(C) Problems to be solved In the invention of Japanese Patent Application No. 61-61555 as described above, the switching valve provided between the sample atomizing chamber and the plasma torch is rusted by the atmosphere in the stand and its operating accuracy deteriorates. , There was a problem that it interfered with the analysis. Further, when the airtightness of the switching valve is deteriorated, the plasma becomes unstable or disappears. (The switching valve requires a precise operation and has a complicated structure, and a metal member is also used for the reason of workability.) (D) Means for Solving the Problems In the present invention, the problems of the above-mentioned conventional technology The following methods were taken to solve the problems and issues.

The switching valve provided between the sample atomization chamber and the plasma torch is eliminated, and the carrier gas is turned on / off on the path before being supplied to the sample atomization chamber. Then, the flow rate of the carrier gas is controlled as follows.

During the analysis standby, the amount of gas supplied to the plasma torch and the high frequency power supplied to the induction coil are controlled to maintain the spark plasma and the carrier gas supplied to the sample atomization chamber is shut off. During analysis, increase the amount of gas supplied to the plasma torch and the high frequency power supplied to the induction coil to increase the plasma output, and also supply the carrier gas to the sample atomization chamber to atomize the sample and introduce it into the plasma torch. Measure. After the measurement is completed, the plasma output is kept raised for a while and the carrier gas is supplied to the sample atomizing chamber to clean the sample atomizing chamber. After the cleaning of the sample atomizing chamber is completed, the standby state is restored.

(E) Action Inert argon gas only passes through the carrier gas path before it is supplied to the sample atomization chamber, and the carrier gas can be turned on / off by a valve with a simple structure placed outside the corrosive atmosphere. Therefore, there is no deterioration due to corrosion.

Since the switching valve provided between the sample atomization chamber and the plasma torch is eliminated, the cleaning action of the sample introduction system during the standby time is lost, so the time for the carrier gas to flow from the sample atomization chamber through the plasma torch is extended. In this way, the cleaning action of the sample introduction system is performed. (During this cleaning time, if the gas flow rate or the plasma output is reduced, the plasma may be extinguished by the residual sample gas mixed in the carrier gas, so the output is kept in the increased state.) (F) Example 1 FIG. It is a principal part block diagram of the ICP analyzer which shows one Example of this invention. In the figure, 1 is a cylinder for supplying argon gas, 2 is a plasma torch, 6 and 8 are cooling gas and plasma gas supply pipes supplied to the plasma torch 2, 10 respectively.
Is an induction coil, 12 is a matching box for impedance matching between the high frequency power supply 14 and the induction coil, 16 is a gas controller for controlling the supply amounts of the cooling gas and the plasma gas (the amount of gas supplied to the plasma torch is Control means), 18 is a sample atomization chamber, 20 is a solution sample, 22 is a carrier gas supply pipe, 26 is a valve for turning on / off the carrier gas supplied to the sample atomization chamber, 32
Is a control device (sequence controller) for controlling the operations of the gas controller 16, the high frequency power supply (high frequency power supply means) 14 and the valve 26. (Spectral and measurement units are omitted.) Next, an ICP analysis method (analysis operation sequence) using the apparatus of FIG. 1 will be described. FIG. 2 is a graph showing the amounts of high-frequency power supplied to the induction coil and the gases (cooling gas, plasma gas, carrier gas) supplied to the plasma torch corresponding to the sequence in the analysis, and FIG. In the case of the apparatus shown in FIG. 3, FIG. 3 shows the case of the invention of Japanese Patent Application No. 61-61555.

The ICP analysis method (analysis operation sequence) using the apparatus of FIG. 1 will be described with reference to FIG. 2. (1) During standby, the total amount of cooling gas and plasma gas supplied to the plasma torch is controlled to 6 liters per minute. The flow rate of the carrier gas supplied to the sample atomization chamber 18 is set to zero. (On / off valve 26 is off) At this time, the high frequency power (plasma output) supplied to the induction coil is controlled to about 0.2 kW to maintain the spark plasma.

(2) For analysis, introduce (set) the solution sample 20, increase the total amount of cooling gas and plasma gas supplied to the plasma torch to 13 liters per minute, and increase the high-frequency power supplied to the induction coil to about 1.2 kW. While increasing the plasma output, turn on the valve 26 to supply the carrier gas to the sample atomization chamber (1 liter / min), atomize the sample and introduce it into the plasma torch 2 for measurement (3) Measurement After the end, keep the plasma output in a rising state and supply the carrier gas to the sample atomization chamber 18 to clean the sample atomization chamber for about 10 seconds. (4) After cleaning the sample atomization chamber Return to the state (1).

On the other hand, in the case of the invention of Japanese Patent Application No. 61-61555, the carrier gas is always supplied to the sample atomizing chamber as shown in FIG. 3, the amount of gas supplied to the plasma torch and the induction coil. The high frequency power supplied to is only increased during measurement.

(G) Effect According to the present invention, the consumption of expensive argon gas can be reduced, and the analysis cost can be reduced, and, as in the invention of Japanese Patent Application No. 61-61555, a sample atomization chamber and a plasma torch can be provided. It is possible to solve the problem that the switching valve provided at the position rusts due to the atmosphere in the stand and deteriorates the operation accuracy and hinders the analysis, and the reliability of the analysis is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of the essential parts showing an embodiment of the ICP analysis device of the present invention, and FIG. 2 is a diagram for explaining the analysis method of the present invention,
FIG. 3 is a diagram for explaining a conventional analysis method. 1 …… Argon gas cylinder, 10 …… Induction coil 2 …… Plasma torch, 18 …… Sample atomization chamber 6,8 …… Gas supply pipe, 14 …… High frequency power supply 16 …… Gas controller, 20 …… Sample 22… … Carrier gas supply pipe 26 …… ON / OFF valve 32 …… Control device (sequence controller)

Claims (1)

[Claims] 1. A method of introducing a sample atomized by a sample atomization chamber into a plasma torch to cause it to emit light, and spectroscopically measuring this light to analyze sample components, in the standby state, the amount of gas supplied to the plasma torch and The high-frequency power supplied to the induction coil is controlled to maintain the ignition plasma and the carrier gas supplied to the sample atomization chamber is shut off. During analysis, the amount of gas supplied to the plasma torch and the high-frequency supplied to the induction coil While increasing the electric power to increase the plasma output, a carrier gas is supplied to the sample atomization chamber to atomize the sample and introduce it into the plasma torch for measurement to maintain the increased plasma output and atomize the sample. After supplying the carrier gas to the chamber to clean the sample atomization chamber, after cleaning the sample atomization chamber An ICP analysis method characterized by returning to a standby state.