JPH0654651B2 - High frequency inductively coupled plasma / mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a high frequency inductively coupled plasma / mass spectrometer (Indu) which is a combination of a high frequency inductively coupled plasma and a mass spectrometer.
ctively Coupled plasma-Mass Spectometer, `` ICP
-MS ").

<Prior Art> ICP-MS uses a high-frequency inductively coupled plasma to excite a sample, and guides the generated ions to a mass spectrometer through, for example, an interface consisting of a nozzle and a skimmer, to generate a specific mass of ions. It is configured to analyze the element to be measured and the like in the sample by detecting the amount of ions and measuring the amount of ions accurately. Fig. 3 shows such ICP-MS
FIG. 1 is a diagram for explaining the configuration of a main part of a conventional example, in which 1 is, for example, a plasma torch having a triple tube structure having an outermost chamber 1a, an outer chamber 1b, and an inner chamber 1c, and 2 are wound around the torch 1. A high frequency induction coil, 3 is a high frequency power supply for supplying a high frequency current to the coil 2 through capacitors C ₁ and C ₂ , 4 is high frequency inductively coupled plasma, 5 is a nozzle, and 6 is a skimmer. In this figure, when the high frequency current is passed through the coil 2, a high frequency magnetic field is formed around the coil 2. When electrons or ions are implanted in the argon gas in the plasma torch 1 in the vicinity of the high frequency magnetic field, plasma 4 is instantaneously generated by the action of the high frequency magnetic field, and the plasma has a constant high frequency potential. On the other hand, the plasma 4 and the high frequency induction coil 2 are capacitively coupled, and the plasma 4 has a high frequency potential. On the other hand, since the nozzle 5 and the skimmer 6 are normally grounded and have a ground potential, electric discharge occurs between the tip of the nozzle 5 and the skimmer 6 and the plasma 4. Further, the ions extracted from the plasma 4 into the skimmer 6 lose the ionic characteristics obtained in the plasma 4 due to the influence of such discharge, etc., and ultimately the analytical accuracy of ICP-MS is significantly reduced. I will let you. In order to prevent such a decrease in analysis accuracy, after the high frequency inductively coupled plasma 4 is generated, the shield plate is slid toward the plasma torch 1, and the shield is inserted in the gap formed by the arc prevention tube and the plasma torch. An ICP-MS designed to do so was also devised (see Japanese Patent Application No. 61-243923 (Japanese Patent Laid-Open No. 63-98948)).

<Problems to be Solved by the Invention> However, in the above-mentioned conventional example, there is a major drawback that the more the shield provided between the plasma 4 and the coil 2 is made more strict, the more the plasma 4 is less likely to be generated. It was
In addition, as in the above invention, it is necessary to insert the shield plate after the plasma 4 is generated, because the ICP-MS structure is complicated, and the shield is placed near the plasma 4 which has a high temperature of about 6,000 to 10,000 ° K. The plate also requires a difficult operation to insert, and ultimately has a drawback that the manufacturing cost or the like becomes high and the failure is likely to occur.

The present invention has been made in view of the drawbacks of the conventional example, and an object thereof is an ICP-which can easily generate the plasma 4 while making a shield arranged between the plasma 4 and the coil 2 strict. To provide MS.

<Specific Means for Solving Problems> The feature of the present invention for solving the above problems is that ICP-MS is used.
, A shield plate is disposed between the high frequency induction coil and the plasma torch, the shield plate is connected to the ground potential via an open / close switch, and the high frequency inductively coupled plasma is generated with the switch open to generate the plasma. The rest is that the switch is configured to be closed.

<Example> Hereinafter, the present invention will be described in detail with reference to the drawings. First
FIG. 3 is an explanatory diagram of a main part configuration of an embodiment of the present invention.
The same symbols as those used in the drawings are used with the same meanings, and duplicate explanations are omitted here. Reference numeral 7 is a shield plate disposed outside the plasma torch 1, and a flange portion 7c is provided on one side of the shield plate body 7a and a cut portion 7b is provided over the entire length. Reference numeral 8 is a ground, and 9 is a switch for opening and closing the connection between the shield plate body 7a and the ground 8. In the main part of the embodiment of the present invention having such a configuration, the switch 9 is first opened (OFF). In this state, argon gas is flown into the plasma torch 1. When a high frequency current is supplied to the coil 2, a high frequency magnetic field is formed around the coil 2. When electrons or ions are implanted in the argon gas in the plasma torch 1 near the high frequency magnetic field or ignited by a Tesla coil or the like, plasma 4 is easily and instantly generated by the action of the high frequency magnetic field. The plasma 4 is easily ignited because the switch 9 is open and the capacitive coupling between the coil 2 and the plasma 4 is large. The plasma 4 thus generated has a constant high frequency potential. Then, next, switch 9
When is closed (ON), the shield plate body 7a is connected to the ground 8 and the shield plate 7 as a whole has a ground potential. As a result, the shielding effect of the shield plate 7 is improved, and the capacitive coupling between the coil 2 and the plasma 4 is minimized. Therefore, the ICP-MS whose main structure is shown in FIG.
The shield is strict and the plasma 4 is easily generated. The present invention is not limited to the above-mentioned embodiment, and various modifications can be made. For example, the shield may be connected to a part of the coil 2 at the time of ignition and connected to the ground after ignition. And

FIG. 2 is a diagram for explaining the overall configuration of the embodiment of the present invention. In the figure, the same symbols as those in FIG. 1 and FIG. 3 are used with the same meanings, and duplicate explanations are omitted here. Further, 10a is an argon gas supply source, 10b is a gas regulator, 11 is a tank for storing a sample, 12 is a nebulizer for atomizing the sample into an aerosol sample, 13 is a driving unit including a high frequency power source 3, and 14 is a plasma torch. A housing for housing a fore chamber 1
6 inside 1 torr. A vacuum pump for evacuating by suction until, 17 the center chamber 18 in the example 10 ^-4 tor
A vacuum pump that sucks and exhausts to r. 19, a mass spectrometer detector that is, for example, a quadrupole mass filter, 20 is a vacuum pump that sucks and exhausts the inside of the rear chamber 21, and 22 is a secondary electron multiplier , 23 are arithmetic processing units (for example, microcomputers). In the embodiment of the present invention having such a configuration, the outermost chambers 1a and 1b of the plasma torch 1 are
Is supplied with argon gas from the gas supply source 10a via the gas regulator 10b. There is also a nebulizer 1 in the interior 1c.
The aerosol sample is carried in from 2 by argon gas (supplied through the gas regulator 10b). On the other hand, the coil 2 is supplied with high-frequency energy by the high-frequency power source 3 in the drive unit 13, and a high-frequency magnetic field (not shown) is formed around the coil. Therefore, plasma 4 is generated by the action of the high frequency magnetic field. This plasma 4
The ions inside are extracted into the skimmer 6 through the nozzle 5, and then the mass spectrometer detector 19 detects ions of a specific mass. The detection signal is the secondary electron multiplier 22.
After being amplified by, the signal is sent to the arithmetic processing unit 23, and finally the measured elemental analysis value in the sample and the like are given.

<Effect of the Invention> According to the present invention as described in detail above, the plasma 4
The ICP-MS is realized in which the shield provided between the coil 2 and the coil 2 is made strict and the shield effect is kept good, and the plasma 4 is easily generated to maintain the plasma normally.

[Brief description of drawings]

FIG. 1 is a perspective view of the essential parts of the embodiment of the present invention, FIG. 2 is an overall view of the essential parts of the embodiment of the present invention, and FIG. 3 is an essential part of the prior art. 1 ... Plasma torch, 2 ... High frequency induction coil, 3 ...
… High frequency power source, 4 …… High frequency inductively coupled plasma, 7 ……
Shield plate, 8 ... Ground, 9 ... Switch.

Claims (3)

[Claims] 1. A high frequency energy is supplied to a high frequency induction coil to form a high frequency magnetic field to generate a high frequency inductively coupled plasma, a sample is excited using the plasma to generate ions, and the ions are passed through an interface. In an analyzer that guides and detects a mass spectrometer and analyzes an element to be measured in the sample, a shield plate is placed between the coil and a plasma torch that generates the plasma, and the shield plate is an open / close switch. A high-frequency inductively coupled plasma-mass spectrometer, which is configured to be connected to a ground potential via the switch, generate the plasma with the switch opened, and close the switch after the plasma is generated. 2. The high frequency inductively coupled plasma mass spectrometer according to claim 1, wherein the shield plate has a substantially cylindrical shield plate body. 3. The shield plate according to claim 1 or 2, wherein the shield plate is a shield plate having a flange portion formed at one end and a cut portion provided over the entire length. The described high frequency inductively coupled plasma mass spectrometer.