JPH09159610A - Plasma analyzing device with sample introduction stabilization mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma analyzing device for constantly maintaining the amount of introduced sample containing an atomized gas to a plasma torch regardless of the characteristics of a sample liquid. SOLUTION: A sample liquid 1 is guided to an atomizing nozzle 4 at the edge of a spray chamber 3 via a pipe 2 and is atomized into the chamber 3. The generated mist of the sample liquid 1 is introduced into a plasma flame 10 which is generated by a plasma torch 7 via a pipe 6 and is ionized through a process consisting of vaporizationdesolvent-atomization-excitation-ionization. The generated sample ion is introduced to a mass spectrograph via a sampling corn 11. A pressure sensor 21 for detecting pressure is provided halfway to the pipe 6 and a flow adjusting valve 22 is provided halfway to a pipe 5 for supplying an atomized gas. An operation circuit 23 creates a control signal based on a pressure signal P obtained from the pressure sensor 21 and a gas flow specification signal S and supplies the signal to the flow adjusting circuit 22.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a plasma analyzer such as an inductively coupled plasma mass spectrometer (ICP-MS) or an ICP emission spectrometer, and more particularly to a plasma analyzer provided with a sample introduction stabilizing mechanism. Is.

[0002]

2. Description of the Related Art FIG. 1 shows a standard liquid sample introduction system used when analyzing a liquid sample by ICP-MS. In FIG. 1, a sample liquid 1 is guided to a spray nozzle 4 provided at an end of a spray chamber 3 via a pipe 2 and sprayed into the chamber. In the spray nozzle 4,
A spray gas such as argon is supplied from a gas source (not shown) through the introduction pipe 5.

The mist of the sample liquid sprayed in the spray chamber is taken out from the upper part of the chamber 3 and sent to the plasma torch 7 through the pipe 6. The plasma torch 7 has a multi-tube structure centering on the pipe 6, and the plasma gas 8 and the cooling gas 9 flow from the outside of the pipe 6 toward the open end in the pipe. Then, the plasma frame 10 receives excitation by the high frequency electromagnetic field from the high frequency coil L wound around the outer periphery of the torch near the open end.
Is generated, and the mist of the sample liquid is introduced into the frame 10 through the pipe 6, and is ionized through the steps of vaporization-desolvation-atomization-excitation-ionization. The sample ions thus generated are introduced into a mass spectrometer (not shown) via the sampling cone 11 and mass analyzed. In addition, 12 is an ironing pump for discharging the excess sample liquid which is attached to the inner wall of the spray chamber 3 and accumulated in the chamber.

[0004]

In such a configuration, when the amount of the sample introduced into the plasma flame or the amount of the spray gas changes, the conditions under which the element to be analyzed reacts change, so the amount of generated ions Fluctuates, and as a result, the intensity of the detection signal obtained by mass spectrometry also fluctuates.

Further, when the sample solution contains a solvent having a high volatility such as ammonia or acetic acid and having a relatively high concentration, the whole amount introduced into the plasma is larger than that in the case of the sample solution mainly containing water. The optimum amount of gas introduced into the plasma flame (including the spray gas) changes when the conditions are adjusted with a water-based standard sample solution, which makes it difficult to optimize the measurement conditions.

An object of the present invention is to provide a plasma analyzer which can eliminate the above-mentioned problems.

[0007]

[Means for Solving the Problems] To achieve this object, the present invention comprises atomizing a sample liquid in a spray chamber and introducing the atomized sample liquid into a plasma torch to excite and analyze the sample. In the plasma analyzer described above, a detection means for obtaining a signal corresponding to the flow rate in the flow path from the spray chamber carrying the atomized sample to the plasma torch to the plasma torch is provided, and the detection means is obtained from the detection means. It is characterized in that a control means for controlling the pressure in the spray chamber based on the detection output is provided.

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 shows an IC embodying the present invention.
2 shows a liquid sample introduction system of P-MS, and the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, a pressure sensor 21 that detects the pressure inside the pipe 6 is provided in the middle of the pipe 6 that sends the mist of the sample liquid sprayed in the spray chamber 3 to the plasma torch 7.
Further, a flow rate adjusting valve 22 is provided in the middle of the pipe 5 for supplying the spray gas to the spray nozzle. This flow rate adjustment valve 22
A pressure signal P obtained from the pressure sensor 21 and a gas flow rate designation signal S from a control device (not shown) are supplied to an arithmetic circuit 23 which supplies a control signal to the arithmetic circuit 23. Create a control signal.

In the above structure, the gas flow rate designation signal S is a signal that designates the gas flow rate sent to the plasma torch 7 through the pipe 6. Since this gas flow rate corresponds to the pressure in the pipe 6, the pipe 6 is calculated based on the gas flow rate designation signal S and the pressure signal P from the pressure sensor 21 in the arithmetic circuit 23.
If a control amount for keeping the pressure inside and inside the spray chamber 3 constant is obtained and the obtained control signal is sent to the flow rate adjusting valve 22 to control the flow rate of the atomizing gas passing through the valve 22, feedback is achieved. By control, the pressure in the pipe 6 and the spray chamber 3 can be maintained at a constant value corresponding to the designation signal S. Therefore, the amount introduced into the plasma flame (including the spray gas) is also kept constant.

Since such control is performed, even when the sample liquid using a solvent having high volatility and the sample liquid using a solvent mainly composed of water having low volatility are alternately measured, the volatility is low. In the case of a sample solution that uses a high solvent, it is automatically adjusted to reduce the amount of spray gas, and in the case of a sample solution that uses a water-based solvent, it is automatically adjusted to increase the amount of spray gas. The operator does not have to make adjustments each time.

In the above-described embodiment, the pressure sensor 22 is provided in the middle of the pipe 6 to obtain the pressure in the pipe 6, but the present invention is not limited to this, and the pressure in the spray chamber 3 may be detected. Alternatively, in short, a means for obtaining a signal corresponding to the flow rate of the gas supplied from the spray chamber to the plasma torch may be provided in the flow path from the spray chamber to the plasma torch.

[0012]

As described above in detail, in the present invention, the detection means for obtaining the signal corresponding to the flow rate in the flow path from the spray chamber that carries the atomized sample to the plasma torch to the plasma torch. Since the control means for controlling the pressure in the spray chamber based on the detection output obtained from the detection means is provided, the sample introduction amount including the spray gas to the plasma torch is always maintained regardless of the characteristics of the sample solution. A plasma analyzer that can be maintained constant is realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing a liquid sample introduction system that has been conventionally standardly adopted when analyzing a liquid sample by ICP-MS.

FIG. 2 is a diagram showing a liquid sample introduction system of ICP-MS in which the present invention is implemented.

[Explanation of symbols]

 1: Sample liquid 2, 5, 6: Pipe 3: Spray chamber 4: Spray nozzle 7: Plasma torch 8: Plasma gas 9: Cooling gas 10: Plasma flame L: High frequency coil 11: Sampling cone 21: Pressure sensor 22: Flow rate Regulator valve 23: arithmetic circuit

Claims (2)

[Claims] 1. A plasma analyzer in which a sample liquid is atomized in a spray chamber and the atomized sample liquid is introduced into a plasma torch to excite and analyze the sample, and the atomized sample is carried to the plasma torch. A control means for providing a detection means for obtaining a signal corresponding to a flow rate flowing in the flow path from the spray chamber to the plasma torch and controlling the pressure in the spray chamber based on the detection output obtained from the detection means. A plasma analyzer equipped with a sample introduction stabilization mechanism, characterized in that 2. The detection means is a pressure detection means provided in a flow path connecting the spray chamber and the plasma torch, and the control means supplies the pressure to the spray chamber based on a detection output obtained from the pressure detection means. The plasma analyzer provided with the sample introduction stabilizing mechanism according to claim 1, wherein the flow rate of the atomized gas to be generated is controlled.