JPH0843310A - Inductively coupled plasma/mass spectrometer - Google Patents

Abstract

PURPOSE:To prevent recombination of an ion in a plasma with an electron to enhance efficiency of the ion passing through a sampling orifice and improve detecting sensitivity in a detector of mass spectrometer. CONSTITUTION:An electrode 9 connected to a constant voltage power source 11 via a switch 12 is arranged between a plasma torch 2 and a sampling orifice 4, and an electron in a plasma 3 is attracted to the electrode 9 side to prevent recombination of an ion in the plasma with the electron so that the ion can efficiently pass through the sampling orifice without being damaged. The switch 12 is opened at the time of plasma turning-on so as to prevent high frequency power from being applied to the electrode 9 due to inductive coupling at that time. Since the inductive coupling between the plasma 3 and an induction coil becomes strong after the time of plasma turning-on to prevent application of the high frequency power to the electrode 9, the switch 12 is closed to maintain voltage of the electrode 9 at a fixed value, for example, 5-20V.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inductively coupled plasma / mass spectrometer (hereinafter referred to as IC) widely used for environmental analysis such as analysis of impurities in steel and semiconductors or measurement of heavy metals in water.
P / MS).

[0002]

2. Description of the Related Art In a conventional ICP / MS, a solution sample S to be analyzed which has been atomized by a nebulizer 1 is introduced into a plasma 3 generated by an inductively coupled plasma torch 2 and ionized, so that a vacuum degree of Due to the difference, it passes through the sampling orifice 4 and the skimmer 5 from the torch 2 side, is converged by the ion lens 6, and is guided to the mass spectrometer 7 for mass analysis (see FIG. 2).

[0003]

However, the conventional ICP
In MS / MS, the ion is sampling orifice 4
When passing through the skimmer 5, the diameter of the sampling orifice 4 is usually as small as about 1 mm, and the ion loss due to recombination of ionized ions and electrons is not small, so that the ion transmission efficiency is extremely low. Therefore,
In particular, there has been a problem that sufficient detection sensitivity cannot be obtained in trace analysis, which is currently important in ICP / MS.

The present invention has been made in view of the above problems, and prevents loss of ions due to recombination of ions and electrons, improves efficiency of ions that pass through the sampling orifice, and improves detection sensitivity. It is intended to provide ICP / MS.

[0005]

In order to achieve the above object, in the ICP / MS of the present invention, the ions in the plasma generated by the inductively coupled plasma torch are introduced by a sampling orifice, a skimmer and an ion lens. An apparatus for conducting mass analysis by means of means to a mass spectrometer is characterized in that an electrode connected to a constant voltage power source is arranged between the plasma torch and the sampling orifice.

In this case, in order to prevent high frequency power from being applied to the electrodes by inductive coupling during plasma lighting, it is preferable to connect the electrodes and the constant voltage power source through a switch circuit opened during plasma lighting. After the plasma is turned on, the inductive coupling between the plasma and the induction coil becomes strong, and high frequency power is not applied to the electrodes. Therefore, the switch circuit is closed to maintain the electrode voltage at a constant voltage, for example, 5 to 20V.

As the shape of the electrode, various shapes other than the conical shape can be applied.

[0008]

In the ICP / MS constructed as described above, the solution sample to be analyzed atomized by the nebulizer is introduced into the plasma generated by the inductively coupled plasma torch and ionized, and the torch is caused by the difference in the degree of vacuum. From the side, when passing through the sampling orifice and skimmer, being focused by the ion lens and being guided to the mass spectrometer, the electrode arranged between the plasma torch and the sampling orifice attracts electrons in the plasma to the electrode side. To work.
As a result, only ions are present in the plasma, and the loss of ions due to recombination of electrons is prevented.

[0009]

EXAMPLE An ICP / MS of the present invention will be described below with reference to the drawings. In FIGS. 1 and 2, a solution sample S to be analyzed is atomized by a jet of carrier gas such as argon gas in a nebulizer 1. And is supplied to the plasma torch 2 together with the carrier gas.

The plasma torch 2 is provided with an inner carrier gas conduit for guiding the atomized mist of the solution sample to the center of the plasma 3 by the carrier gas, and a plasma gas (for example, argon gas) which is a source of the inductively coupled plasma 3. Coolant gas that cools the supplied intermediate line and torch (eg,
Argon gas) is a triple tube consisting of an outer pipe line through which heat-resistant glass is formed. In addition, an induction coil 8 is arranged on the outer periphery of the tip end portion of the conduit outside the plasma torch 2, and a high-frequency current is caused to flow through the induction coil 8 to cause discharge by an electric field generated by electromagnetic induction due to a time change of the high-frequency magnetic field.

The mist of the solution sample S atomized and introduced into the high temperature argon plasma 3 generated by the plasma torch 2 is excited by thermal energy and ionized,
At the same time, electrons are generated.

The ionized ion to be analyzed passes from the side of the plasma torch 2 through the ion introducing means consisting of the sampling orifice 4 and the skimmer 5 due to the difference in vacuum degree, and is further converged by the ion lens 6 to be quadrupole mass. It is led to the analyzer 7. At this time, the sampling orifice 4
Since the diameter of is small at around 1 mm, the efficiency of the ions passing through the sampling orifice 4 is not always good. Moreover, since the electrons generated at the same time as the ionization recombine with the ionized ions and damage the ions, the efficiency of the ions passing through the sampling orifice 4 further decreases. Therefore, an electrode 9 connected to the constant voltage power source 11 via a switch 12 is arranged between the plasma torch 2 and the sampling orifice 4 to attract the electrons in the plasma 3 to the electrode 9 side and to remove the ions in the plasma. Ions efficiently pass through the sampling orifice 4 without blocking recombination with electrons and damaging the ions.

The switch 12 is opened during plasma lighting in order to prevent high frequency power from being applied to the electrode 9 by inductive coupling during plasma lighting. After the plasma is turned on, the inductive coupling between the plasma and the induction coil becomes strong, and high frequency power is not applied to the electrodes. Therefore, the switch 12 is closed to maintain the voltage of the electrode 9 at a constant voltage, for example, 5 to 20V. The back surface of the electrode 9 is covered with an insulator 9a.

Further, although not shown, a gas ejection nozzle for ejecting an inert gas toward the center of the plasma is arranged between the plasma torch 2 and the sampling orifice 4 to regulate the movement direction of ions in the plasma. If so, the focusing property of the ions is improved, and the efficiency of the ions passing through the sampling orifice 4 is further improved.

The ions introduced into the mass spectrometer 7 are mass-scanned by a known method, and only ions having a desired mass are selected and detected by the detector 10.

[0016]

Since the present invention is configured as described above, the ions in the plasma can pass through the sampling orifice without being recombined with the electrons and impaired, and the detection by the mass spectrometer can be performed. The detection sensitivity in the container is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an embodiment of the present invention.

FIG. 2 is an overall sectional view of an apparatus according to an embodiment of the present invention.

[Explanation of symbols]

1 ... Nebulizer 2 ... Plasma torch 3 ... Plasma 4 ... Sampling orifice 5 ... Skimmer 6 ... Ion lens 7 ... Mass spectrometer 8 ... High frequency induction coil 9 ... Electrode 10 ... Detector 11 ... Constant voltage power supply 12 ... Switch

Claims (1)

[Claims] 1. An apparatus for guiding ions in plasma generated by an inductively coupled plasma torch to a mass spectrometer through an ion introducing means consisting of a sampling orifice, a skimmer and an ion lens, and connecting the constant voltage power source to the mass spectrometer. An inductively coupled plasma / mass spectrometer characterized in that a separate electrode is arranged between the plasma torch and the sampling orifice.