JP2591822B2 - High frequency inductively coupled plasma mass spectrometer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high-frequency inductively coupled plasma (ICP-MS), which is a combination of an inductively coupled plasma (ICP) ion source and a mass spectrometer. is there.

[Prior Art] Such an ICP-MS has a structure as shown in FIG.

In the figure, reference numeral 1 denotes an ICP ion source, and a plasma torch 3 made of an electric insulator such as quartz and wound around a high-frequency induction coil 2.
And a nebulizer 4 for injecting the 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.

Reference numeral 10 denotes an interface including a cone-shaped nozzle 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.

17 is an oil diffusion pump for keeping the inside of the mass spectrometer 14 in a high vacuum, and 18 and 19 are oils for exhausting a space S1 between the nozzle 11 and the skimmer 12 and a space S2 between the skimmers 12 and 13. It is a rotary pump.

In such a configuration, an argon gas is supplied into the plasma torch 3 from a gas supply source (not shown), and the sample liquid 7 is introduced as a mist from the nebulizer 4. In this state, when a high-frequency power is applied from the high-frequency power source 5 to the coil 2 to form a high-frequency magnetic field, a high-frequency induction plasma (hereinafter, referred to as plasma) P is generated. Enter the interface 10 through 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.

By the way, in such an ICP-MS, a high frequency from the coil 2 flows to the nozzle 11 via the plasma P.
Here, when a quadrupole type is used as the mass spectrometry system 15, it is not necessary to apply high energy to the sample ions, and therefore, the nozzle 11 is usually at a ground potential or a potential of several volts. The high frequency power introduced into the high frequency power supply 5 returns to the ground side of the high frequency power supply 5 directly or through a nozzle power supply. Therefore, there is no adverse effect as noise on each power supply of the nozzle 11 and the mass spectrometer 14.

On the other hand, when a magnetic field type mass spectrometry system is used to obtain high resolution, it is necessary to give high energy to sample ions. Therefore, as shown by reference numeral 20 in FIG.
An accelerating electrode is arranged between the skimmer 13 and the electrode group 16, and a high DC voltage of about ± 10 Kv is applied to the accelerating electrode,
The same high DC voltage must be applied to the nozzle 11 by connecting the high voltage power supply 21 thereto. The first and second
A DC high voltage substantially the same as that of the nozzle 11 is also applied to the skimmers 12 and 13 from a high-voltage power supply (not shown).

[Problems to be Solved by the Invention] When a high DC voltage is applied to the nozzle 11 as described above, the input impedance of the output of the high-voltage power supply is generally large, so that it is directly affected by the high frequency introduced into the nozzle,
A stable voltage cannot be maintained and mass spectrometry becomes impossible. Further, the high frequency wave introduced into the nozzle also enters each power supply of the mass spectrometer as a radio wave and causes an abnormality in the control system of the entire mass spectrometer as hum noise.

Accordingly, the present invention has been made in view of such a point, and provides an apparatus capable of preventing an adverse effect of a high frequency introduced into a nozzle with a simple configuration while maintaining a high voltage applied to the nozzle. The purpose is to do that.

[Means for Solving the Problems] To achieve the above object, the high frequency inductively coupled plasma mass spectrometer of the present invention ionizes a sample using a high frequency inductively coupled plasma ion source having a plasma torch,
An apparatus configured to introduce the generated sample ions into the magnetic field type mass spectrometry system through a nozzle to which a high DC voltage is applied to give the sample ions the energy required by the magnetic field type mass spectrometry system. The ground side of the high-frequency induction coil for generating inductively coupled plasma and the nozzle are connected by a capacitor having an impedance lower than that of a power supply for generating a DC high voltage applied to the nozzle with respect to the frequency of the used high frequency. Things.

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment FIG. 1 is an enlarged sectional view of a main part showing an example of an ICP-MS according to the present invention.

This embodiment is characterized in that the capacitor C is connected between the case 9 at the ground potential (the ground side of the coil 2) and the nozzle 11 maintained at a high voltage. Here, when the high frequency is 27 MHz, the capacitor C is 2000
A low impedance type such as ~ 5000pF (withstand voltage of 10Kv or more) is used. In addition, when installing the sensor, the sensor is provided at a position that is not affected by the heat of the plasma P. Further, portions supporting the nozzle and the first and second skimmers are formed of an electrically insulating material 22.

If this is done, the nozzle withstands the pressure of the capacitor C.
The high voltage of 11 can be maintained while the nozzle 11
The high frequency power introduced into the
Capacitor C with low impedance without flowing through
Then, it flows to the case 9 side of the ICP ion source 1 and finally returns to the high frequency power supply 6. Therefore, high frequency power can be prevented from entering the high voltage power supply 21 of the nozzle 11 and each power supply of the mass spectrometer, so that mass analysis in the magnetic field type mass spectrometry system can be performed without any trouble.

The above description is an example of the present invention, and various modifications are conceivable for implementation. For example, when the ICP ion source 1 is moved away from the nozzle 11 at the time of plasma ignition or maintenance and inspection, one of the case 9 and the connection portion between the nozzle 11 and the capacitor C can be manually or automatically detachable. preferable.

[Effects] As described in detail above, according to the present invention, the high voltage applied to the nozzle can be maintained and the adverse effect of the high frequency introduced into the nozzle can be prevented with a simple configuration, so that the mass spectrometer can operate normally. Can be.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a main part showing an example of an ICP-MS according to the present invention, and FIG. 2 is a schematic view showing a configuration of the ICP-MS. 1: ICP ion source 1: High frequency induction coil 3: Plasma torch 4: Nebulizer, 5: High frequency power supply 6: Sample bottle, 7: Sample liquid 9: Case, 11: Nozzle 12: First skimmer, 13: Second skimmer 14: mass spectrometer, 15: mass spectrometry system 21: high voltage power supply, 22: electric insulating material C: capacitor

Claims (1)

(57) [Claims] 1. A high-frequency inductively coupled plasma ion source having a plasma torch is used to ionize a sample, and the generated sample ions are supplied with a DC high voltage for applying energy required by a magnetic field type mass spectrometry system to the sample ions. In an apparatus adapted to be introduced into a magnetic field type mass spectrometry system through an applied nozzle, a ground side of a high frequency induction coil for generating the high frequency inductively coupled plasma and a nozzle are applied to the nozzle with respect to a frequency of a used high frequency. A high frequency inductively coupled plasma mass spectrometer characterized by being connected by a capacitor having an impedance lower than that of a power supply for generating a DC high voltage.