JP2806641B2 - High frequency inductively coupled plasma mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency inductively coupled plasma mass spectrometer (ICP-M) in which a high frequency inductively coupled plasma (ICP) ion source and a mass spectrometer (MS) are coupled.
More particularly, the present invention relates to a high-frequency inductively coupled plasma mass spectrometer using a high-resolution magnetic field type mass spectrometer as MS.

[0002]

2. Description of the Related Art FIG. 2 shows a configuration example of a conventional ICP-MS. In FIG. 2, reference numeral 1 denotes an ICP ion source, which comprises a plasma torch 3 made of an electric insulator such as quartz wound with a high-frequency coil 2 and a nebulizer 4 for spraying a sample liquid. Reference numeral 5 denotes a sample bottle that stores the sample solution 6 and is connected to the nebulizer 4 via the introduction pipe 7. Although not shown, a shield case maintained at the ground potential for shielding the high frequency from the high frequency coil 2 is provided on the outer periphery of the plasma torch 3.

[0003] Reference numeral 8 denotes an interface composed of a sampling cone 9 and a skimmer cone 11 formed of a good electrical conductor. Reference numeral 12 denotes a mass spectrometer.
3 are provided.

[0004] Reference numeral 14 denotes an oil diffusion pump for keeping the inside of the mass spectrometer 12 at a high vacuum, and 15 denotes a sampling cone 9.
This is an oil rotary pump for exhausting a space S1 formed between the pump and the skimmer cone 11 through an exhaust pipe 17.
Further, 19 accelerates and converges the ions to produce the mass spectrometry system 1.
3 is a group of electrodes for leading to No. 3.

In such a configuration, an argon gas is supplied into the plasma torch 3 from a gas supply source (not shown).
Further, the sample liquid 6 is introduced as a mist from the nebulizer 4. In this state, when power is applied to the high-frequency coil 2 to form a high-frequency magnetic field, plasma P is generated. Thus, sample ions in the plasma enter the interface 8 through the sampling cone 9 and the skimmer cone 11. The ions that have entered the interface 8 are accelerated and converged by the electrode group 19 and introduced into the mass spectrometry system 13.

Recently, there has been proposed an ICP-MS in which a magnetic field type mass spectrometry system is used as the mass spectrometry system 13 so as to obtain a high resolution. Since it is necessary to apply high energy to the sample ions, a positive or negative high voltage of about several kV is applied to the sampling cone 9 and the skimmer cone 11 and an accelerating electrode provided between the skimmer cone 11 and the electrode group 19. The ions are accelerated by setting 20 to the ground potential. The sampling cone 9 and the skimmer cone 11 are 7
Since it is exposed to a high temperature of about 000 ° C., it is generally cooled with cooling water to prevent dissolution.

FIG. 3 shows an example of the configuration for this purpose. In FIG. 3, a sampling cone 9 and a skimmer cone 11 made of copper or the like are fixed to a ring-shaped member 30 also made of an electrically conductive material such as copper by a well-known method. 8 are configured. Then, for example, a predetermined positive high voltage of 5 kV is applied to the ring-shaped member 30 by the high-voltage power supply 23 for acceleration voltage. Cooling pipes 25 and 27 for flowing cooling water are formed in the ring-shaped member 30. In the following description, for easy understanding, the cooling pipes 25, 2
It is assumed that 7 communicates inside the ring-shaped member 30. Therefore, the sampling cone 9 and the skimmer cone 11 can be cooled by, for example, connecting a water supply hose to the water supply port I to supply water and connecting a drainage hose to the water discharge port O to drain water.

[0008]

By the way, in the configuration shown in FIG. 3, tap water is usually used as cooling water. However, when the mass spectrometry is actually performed in this manner, a noise indicated by 33 is observed outside the peak 31 indicating the presence of a certain mass number, for example, as shown in FIG. I understood that there was something.
This phenomenon was particularly remarkable when the magnetic field intensity of the mass spectrometry system 13 was vibrated.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a high-frequency inductively coupled plasma mass spectrometer capable of removing noise in the output of a mass spectrometry system.

[0010]

As a result of conducting various experiments on the problem that noise is superimposed on the output waveform as described above, the following has been confirmed. First, the configuration shown in FIG. 5A is a normal use mode, and cooling water supplied from a faucet 36 attached to a tub 35 is supplied by a water supply hose 37.
The cooling water discharged from the water outlet O through the water inlet I of the interface 8 through the drain outlet O is drained into the tub 35 through the drain hose 39. In this configuration, the noise 33 is superimposed on the peak 31 as shown in FIG. On the other hand, when the cooling water that has passed through the drain hose 39 is drained to the electrically insulating container 41 as shown in FIG. 5B, no noise occurs and only the peak indicating the presence of the mass number is generated. confirmed. Further, it was confirmed that an electric current was flowing through the cooling water in the state of FIG. 5A.

From the above, in the state shown in FIG. 5A,
The electric current flowing through the cooling water is, as shown in FIG.
It is considered that the gas flows from the high voltage power supply 23 for acceleration voltage to the ground of the high frequency inductively coupled plasma mass spectrometer shown in FIG.
The ground A of the high-frequency inductively coupled plasma mass spectrometer is connected to the ground of the switchboard 43, and the ground of the switchboard 43 is connected to a ground electrode 45 embedded in the ground. Therefore, it is considered that the current flowing through the cooling water forms a large closed loop as shown by 47 in FIG. 6, and this loop is affected by the external magnetic field, and as a result, the high voltage for the acceleration voltage fluctuates and the output It is considered that noise occurs in the signal. On the other hand, it is understood that if the loop of the current flowing through the cooling water is reduced, the fluctuation of the acceleration voltage due to the external magnetic field can be prevented.

Therefore, in the high frequency inductively coupled plasma mass spectrometer of the present invention, the sample is ionized using the high frequency inductively coupled plasma ion source, and the generated ions are introduced into the magnetic field type mass spectrometer via the interface. In the high frequency inductively coupled plasma mass spectrometer, a positive high voltage is applied to a sampling cone and a skimmer cone of the interface from a high-voltage power supply for acceleration voltage, and a cooling pipe is formed, and the cooling cone is connected to the cooling pipe. The cooling water supply hose and the cooling water drain hose are formed with earth electrodes that contact the cooling water, and each earth electrode is connected to the earth of the high voltage power supply.

[0013]

In the present invention, the ground electrode for contacting the cooling water is formed in the water supply / drain hose, and the ground electrode is connected to the ground of the high voltage power supply for the acceleration voltage.
The loop of the current flowing through the cooling water can be greatly reduced as compared with the conventional case, and as a result, the high-voltage power supply for the acceleration voltage can be stabilized, and the occurrence of noise can be prevented.

[0014]

Embodiments will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of one embodiment of a high frequency inductively coupled plasma mass spectrometer according to the present invention. In FIG. 1, the water supply hose 37 and the drainage hose 39 are formed with electrodes 51 and 53, respectively, which contact the cooling water. This can be done by cutting the hose and connecting both ends to a conductive tubular member such as copper. And these electrodes 51,
Numerals 53 are both connected to the ground A of the high voltage power supply 23 for acceleration voltage.

According to such a configuration, the current flowing through the cooling water does not flow outside the main body of the high-frequency inductively coupled plasma mass spectrometer, but returns to the high-voltage power supply for acceleration voltage 23 in a small loop. Of the stability can be reduced. Actually, when mass spectrometry was performed by the configuration shown in FIG. 1, it was confirmed that noise as shown in FIG. 4 did not occur.

The length of the water supply hose 37 from the electrode 51 to the water supply port I and the length of the drainage hose 39 from the electrode 53 to the water supply port O are set as long as the insulation can be maintained. Therefore, the cooling water may be short in the case of using a water having good electrical insulation such as distilled water, but may be several m in case of using a water having good conductivity such as tap water.
A length of about 10 m is required.

While the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above-described embodiment, the cooling pipes 25 and 27 are connected to each other. However, the cooling water may flow independently and separately.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a high-frequency inductively coupled plasma mass spectrometer according to the present invention.

FIG. 2 is a diagram illustrating a configuration example of an ICP-MS.

FIG. 3 is a diagram illustrating a configuration example of an interface.

FIG. 4 is a diagram for explaining a conventional problem.

FIG. 5 is a diagram for explaining how to supply cooling water.

FIG. 6 is a diagram for explaining a loop of a current flowing through the cooling water.

[Explanation of symbols]

8 Interface, 23 High-voltage power supply for acceleration voltage,
37: Water supply hose, 39: Drain hose, 51, 53: Electrode, A: Ground, I: Water supply port, O: Drain port.

Continuing from the front page (72) Inventor Hiroyasu Ito 16-2 Onogawa, Tsukuba-shi, Ibaraki National Institute for Environmental Studies (72) Inventor Kiichiro Otsuka 3-1-2 Musashino, Akishima-shi, Tokyo Nihon Denshi Co., Ltd. (56) References JP-A-2-15554 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01J 40/00-49/48 H01J 27/00-27/26 G01N 27/62

Claims (1)

(57) [Claims] 1. A high frequency inductively coupled plasma mass spectrometer configured to ionize a sample using a high frequency inductively coupled plasma ion source and to introduce generated ions into a magnetic field type mass spectrometer via an interface. The sampling cone and the skimmer cone are applied with a positive or negative high voltage from a high-voltage power supply for accelerating voltage and formed with a cooling pipe, and a cooling water supply hose and a cooling water drain hose connected to the cooling pipe. , An earth electrode for contacting cooling water is formed, and each earth electrode is connected to the earth of the high voltage power supply.