JP3274945B2 - Plasma torch and plasma mass spectrometer using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma torch constituting an inductively coupled plasma (hereinafter referred to as "ICP") ion source and an inductively coupled plasma mass spectrometer (hereinafter referred to as "ICP") combining the ion source with a mass spectrometer. -MS.)
About.

[0002]

2. Description of the Related Art An ICP-MS is configured as shown in FIG.

In FIG. 1, reference numeral 1 denotes an ICP ion source, which comprises a plasma torch 3 made of an electric insulator around which a high-frequency induction coil 2 is wound, and a nebulizer 4 for spraying a sample liquid. Reference numeral 5 denotes a high-frequency power supply for applying a high-frequency voltage to the coil 2, and reference numeral 6 denotes a sample bottle that accommodates a sample liquid 7 and is connected to the nebulizer 4 via an introduction pipe 8. Reference numeral 9 denotes a case for shielding high frequency from the coil 2, and this case is connected to the ground side of the high frequency power supply 5.

[0004] Reference numeral 10 denotes an interface composed of a sampling cone 11 and skimmers 12 and 13. Reference numeral 14 denotes a mass spectrometer, in which a mass spectrometry system 15 is provided. Reference numeral 16 denotes an electrode group for accelerating and converging ions and introducing the ions into the mass spectrometry system 15. Reference numeral 17 denotes an oil diffusion pump for maintaining a high vacuum in the mass spectrometer 14, and reference numerals 18 and 19 denote a space A1 between the nozzle 11 and the skimmer 12,
And an oil rotary pump for exhausting a space A2 between the first and second spaces.

In such a configuration, the plasma torch 3
Inside, an argon gas is supplied from a gas supply source (not shown), and a sample liquid 7 is introduced in a nebulized form from a nebulizer 4. In this state, when high-frequency power is applied from the high-frequency power supply 5 to the coil 2 to form a high-frequency magnetic field, a high-frequency inductively coupled plasma (hereinafter, referred to as plasma) P is generated. , Enter the interface 10 through the respective skimmers 12, 13. The ions that have entered the interface are accelerated and converged by the electrode group 16, introduced into the mass spectrometry system 15, and subjected to mass analysis. Either a Q-pole type or a magnetic field type is used as the mass spectrometry system. In the present invention, any of them may be used.

[0006] As a material of the plasma torch, quartz has been widely used in view of electric insulation, heat resistance and acid resistance (excluding hydrofluoric acid). However, when used continuously, the quartz gas torch melts and deforms due to the heat of the plasma gas, and the state of the plasma becomes unstable. Then, the ionization of the sample by the plasma and the efficiency of introduction into the mass spectrometry system decrease, so that the analysis sensitivity and accuracy deteriorate. Further, the high frequency induction coil is easily damaged by the plasma gas. Therefore, the plasma torch must be replaced frequently, and the measurement conditions must be adjusted each time.

As described above, the conventional technology has a problem that the life of the plasma torch is short, and it is difficult to perform highly accurate and sensitive sample analysis.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art. It is an object of the present invention to extend the service life of a plasma torch. Accordingly, an object of the present invention is to provide an inductively coupled plasma mass spectrometer capable of performing sample analysis with high accuracy and high sensitivity for a long period of time.

[0009]

In order to achieve the above object, according to the present invention, a plasma ion source formed under atmospheric pressure, and a sample are ionized using the ion source.
In the apparatus in which the generated ions are introduced into the mass spectrometry system through the sampling cone, the plasma torch has an aluminum content of 2 to 40 ppm by weight, sodium, potassium, lithium, magnesium, calcium,
The content of boron, iron, chromium and copper is 2 weight pp
m or less high-purity quartz.

The aluminum content in quartz is 2 to 40.
It is important to set the weight ppm. When the aluminum content is less than 2 ppm by weight, the heat resistance of the torch is inferior,
If the content exceeds 40 ppm by weight, the thermal conductivity and tensile strength of the torch will be reduced.
This significantly reduces the analysis sensitivity and analysis accuracy of P-MS.

On the other hand, sodium, potassium, lithium,
The content of magnesium, calcium and boron is 2% by weight
pm or less. If the content exceeds 2 ppm by weight, the above elements other than boron have difficulty in the electrical insulation and heat resistance of the torch, and boron causes problems in the heat resistance and tensile strength of the torch. As a result, ICP-MS analysis This results in a situation where the sensitivity and accuracy are reduced.

Further, when the content of iron, chromium and copper exceeds 2 ppm by weight, the tensile strength of the torch is reduced, which impairs the analytical sensitivity and accuracy of ICP-MS.

The method for producing these high-purity quartz glass is as follows:
Any of a gas phase synthesis method using SiCl ₄ as a raw material, an oxyhydrogen gas melting method, an electric melting method, or a combination thereof may be used.

[0014]

The present invention will be described below in detail with reference to examples.
The ppm in Examples and Comparative Examples is ppm by weight. In the example, the inductively coupled plasma mass spectrometer shown in FIG. 1 which is a schematic diagram thereof was used.

(Example 1) As the plasma torch 3, a high-purity quartz glass containing aluminum and sodium, potassium, lithium, magnesium, calcium, boron, iron, chromium and copper as shown in Table 1 was used. .

Using this plasma torch and the inductively coupled plasma mass spectrometer, a europium standard solution 100
For a sample of pg / ml (4% nitric acid), the ionic strength was measured 10 times under the following conditions, the average strength was obtained, and the accuracy (percentage deviation from the average strength) was obtained.

The frequency of the high frequency power supply at the plasma torch;
27.12 MHz.

High frequency output of high frequency power supply in plasma torch; 1.3 KW.

Cooling gas in plasma torch; 15 l /
Minutes.

Plasma gas in a plasma torch; 0.8
1 / min.

As a result, as shown in Table 1, the above sample had an average ionic strength of 3900 and an accuracy of ± 4%.

(Examples 2 and 3) The aluminum content was 3
The experiment was carried out in the same manner as in Example 1 except that a plasma torch made of quartz glass having a content of other elements shown in Table 1 was used. The results are shown in Table 1.

(Comparative Examples 1 and 2) Except that a plasma torch made of quartz glass having an aluminum content of 0.4 ppm or 70 ppm and containing other elements as shown in Table 1 was used. An experiment was performed in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3) The content of sodium was 5 pp
m, and the content of other elements is as shown in Table 1, except that a plasma torch made of quartz glass was used.
An experiment was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4 Magnesium content of 7 p
The experiment was performed in the same manner as in Example 1 except that a plasma torch made of quartz glass having a pm and a content of other elements shown in Table 1 was used. The results are shown in Table 1.

Comparative Example 5 The procedure of Example 1 was repeated except that a plasma torch made of quartz glass having a boron content of 5 ppm and other elements shown in Table 1 was used. Experiments. The results are shown in Table 1.

(Comparative Example 6) Example 1 was repeated except that a plasma torch made of quartz glass having an iron content of 10 ppm and other elements shown in Table 1 was used. The experiment was performed in the same manner. The results are shown in Table 1.

(Comparative Example 7) The content of potassium is 6 ppm
An experiment was conducted in the same manner as in Example 1 except that a plasma torch made of quartz glass having a content of another element shown in Table 1 was used. The results are shown in Table 1.

(Comparative Example 8) The content of lithium is 5 ppm
An experiment was conducted in the same manner as in Example 1 except that a plasma torch made of quartz glass having a content of another element shown in Table 1 was used. The results are shown in Table 1.

Comparative Example 9 A calcium content of 7 pp
m, and the content of other elements is as shown in Table 1, except that a plasma torch made of quartz glass was used.
An experiment was performed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 10 The procedure of Example 1 was repeated except that a plasma torch made of quartz glass having a copper content of 9 ppm and other elements having the contents shown in Table 1 was used. Experiments. The results are shown in Table 1.

(Comparative Example 11) Chromium content is 8 ppm
An experiment was conducted in the same manner as in Example 1 except that a plasma torch made of quartz glass having a content of another element shown in Table 1 was used. The results are shown in Table 1.

[0033]

[Table 1] As is clear from Table 1, in the case of the embodiment using the plasma torch having the element content according to the present invention, a result having high ionic strength and excellent accuracy was obtained.

On the other hand, in the case of the comparative example using a plasma torch having an element content outside the range, the ion intensity was significantly low and the accuracy was poor.

[0035]

By using the plasma torch of the present invention, the ionization of a sample by plasma and the efficiency of introduction into a mass spectrometry system can be improved. The improvement was much better than when using a torch. Further, the present invention can be applied to an inductively coupled plasma optical emission spectrometer, and can analyze trace components with higher accuracy and sensitivity than before.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an inductively coupled plasma mass spectrometer.

[Explanation of symbols]

1: ICP ion source, 2: High frequency induction coil, 3:
Plasma torch, 4 ... Nebulizer, 5 ... High frequency power supply,
6 ... sample bottle, 7 ... sample liquid, 8 ... inlet tube, 9 ...
High frequency shield case, 10 Interface, 1
DESCRIPTION OF SYMBOLS 1 ... Sampling cone, 12, 13 ... Skimmer cone, 14 ... Mass spectrometer, 15 ... Mass spectrometry system, 16
... electrode group, 17 ... oil diffusion pump, 18, 19 ... oil rotary pump

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-18420 (JP, A) JP-A-6-5384 (JP, A) “Application technology of high-purity silica”, supervised by Toshiro Kagami / Ei Hayashi Published by CMC Co., Ltd., March 1, 1991 (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 1/26 G01N 27/62 H01J 27/16 H01J 37/08 H01J 49/10

Claims (2)

(57) [Claims] An aluminum content of 2 to 40 pp by weight
m, sodium, potassium, lithium, magnesium,
A plasma torch comprising high-purity quartz having a content of calcium, boron, iron, chromium and copper of 2 ppm by weight or less. 2. A plasma ion source formed under atmospheric pressure, and an apparatus configured to ionize a sample using the ion source and introduce generated ions into a mass spectrometry system through a sampling cone. The plasma torch constituting the ion source has an aluminum content of 2 to 40 weight pp.
m, sodium, potassium, lithium, magnesium,
An inductively coupled plasma mass spectrometer characterized by being made of high-purity quartz having a content of calcium, boron, iron, chromium and copper of 2 ppm by weight or less.