JP2953010B2 - High frequency inductively coupled plasma mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention supplies high-frequency energy to a high-frequency induction coil to form a high-frequency magnetic field to generate high-frequency inductively coupled plasma, and utilizes the plasma to generate a high-frequency inductively coupled plasma. High frequency inductively coupled plasma mass spectrometer (hereinafter referred to as “ICP
More specifically, the present invention relates to an ICP-MS in which a gate valve has an ion lens function to improve ion transmittance.

<Prior Art> FIG. 2 is a diagram illustrating a general configuration of an ICP-MS. In this figure, an outer chamber 1b and an outermost chamber 1c of a plasma torch 1 are supplied with argon gas from an argon gas supply source 3 via a gas controller 2, and an inner chamber 1a is provided with a solid sample in a sample introduction device 4. Is vaporized by the laser light emitted from the laser light source 5 and then carried in by an argon gas as a carrier gas. When the sample is a liquid, the sample introducing device 4 and the laser light source 5 shown in FIG. 2 are removed, and a nebulizer for atomizing the liquid sample to be introduced and supplying the atomized liquid sample to the inner chamber 1a of the plasma torch 1 is mounted. Also, the sample is often liquid rather than solid.

Further, a high-frequency current is supplied to a high-frequency induction coil 6 wound around the plasma torch 1 by a high-frequency power supply 10, and a high-frequency magnetic field (not shown) is formed around the coil 6. When electrons or ions are implanted in the argon gas in the vicinity of the high-frequency magnetic field in this state, the high-frequency inductively coupled plasma 7 is instantaneously generated by the action of the high-frequency magnetic field.

Further, the inside of the fore-chamber 11 sandwiched between the nozzle 8 and the skimmer 9 is sucked by the vacuum pump 12 to, for example, 1 Torr. Further, in the center chamber 13, an aperture lens 14b, a quadrupole lens 14c, and an aperture
14d is provided, and the inside of the center chamber 13 is sucked to, for example, 10 ^-4 Torr by the first oil diffusion pump 15, and the entrance lens 14e and the quadrupole mass filter 1
The inside of the rear chamber 17 containing 6 is sucked by the second oil diffusion pump 18 to, for example, 10 ^-5 Torr. still,
An extraction electrode 14a is arranged behind the skimmer 9.

In this state, the sample vaporized as described above is introduced into the high frequency inductively coupled plasma, and ionization and light emission are performed. After the ions in the plasma 7 pass through the nozzle 8 and the skimmer 9, the extraction electrode 14a and the ion lens system 14b to
The light is converged through 14 e and introduced into the quadrupole mass filter 16. Of the ions entering the quadrupole mass filter 16, only the ions having the desired mass-to-charge ratio pass and pass through the secondary electron multiplier 19.
Is detected and guided. The detection signal is sent to the signal processing unit 20 and calculated and processed, whereby the analysis value of the element to be measured in the sample is obtained.

On the other hand, FIG. 3 is a partially enlarged view of FIG. 2 and shows a main part of the conventional example. In the figure, reference numeral 21 denotes a housing made of metal and a potential of each of the chambers 11, 13, and 17. The gate valve is maintained at the ground potential as in the case of the first embodiment. The gate valve 21 is provided because of the following necessity. That is, the mass spectrometer part of the ICP-MS and the ion lens system 1
For 4b-14e, it is necessary to operate under high vacuum (vacuum below 10 ^{-4 -10 -6} torr.), And even when not performing analysis, operate the vacuum pump to make the vacuum chamber high vacuum. It is necessary to keep. For this reason, it is necessary to cut off the communication between the fore chamber 11 and the center chamber 13 during non-analysis (for example, at the time of standby) and pass the fore chamber 11 and center chamber 13 during analysis.

<Problems to be solved by the invention> However, in the above conventional example, the extraction electrode 14a
When the interval between the ion lens systems 14b to 14e increases, the tendency of the ion beam to diverge without being able to be kept thin increases,
As a result, the ion transmittance decreases and ultimately ICP-MS
However, there was a disadvantage that the sensitivity as a function was lowered.

Also, once the ion beam diverges, the ion lens system
Even if it is attempted to converge again at 14b to 14e, the number of ions entering the ion lens is greatly reduced.
There is also a disadvantage that the ion transmission efficiency of the whole of 14b to 14e is greatly reduced.

The present invention has been made in view of such a situation, and an object thereof is to provide an ICP-M in which a gate valve is provided with an ion lens function to improve the ion transmittance and improve the analysis sensitivity.
Is to provide S.

<Means for Solving the Problems> In order to achieve such an object, the present invention provides a method in which a sample excited by a plasma torch is extracted from a fore chamber by an extraction electrode, and a sample in a center chamber partitioned by a gate valve. In a high-frequency inductively coupled plasma mass spectrometer that converges with an ion lens system and analyzes the converged sample by a mass filter, the gate valve provided between the fore chamber and the center chamber is connected to the fore chamber and the center. A first insulator and a second insulator that insulate the chamber from the chamber; and a variable voltage power supply that applies a voltage to the gate valve.

<Example> Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view of a main part configuration of an embodiment of the present invention. In the drawing, the same symbols as those in FIG. 3 are used with the same meanings, and redundant description is omitted here. 22a is the center chamber 13
An insulator 22b electrically insulates the gate valve 21 from the fore-chamber 13 and a variable voltage power supply 23 for applying a voltage to the gate valve 21. The fore chamber 11 and the center chamber 13 are electrically connected. Also, insulators 22a, 22
It is desirable that b is mounted near the outer surface so that the inner surface of the chambers 13 and 11 is as hard to see as possible.

In the embodiment of the present invention having such a main part configuration, a variable voltage power supply
The voltage applied from 23 to the gate valve 21 is reduced to zero, the gate valve 21 is closed as shown by the broken line in FIG. 1, and the gate valve 21 plays a role of blocking the communication between the center chamber 13 and the fore chamber 11. .

On the other hand, during analysis, the gate valve is
When a predetermined voltage is applied to the gate 21, the gate valve 21 is opened as shown by the solid line in FIG. 1, and the gate valve 21 functions as an ion lens. For this reason, the distance between the extraction electrode 14a and the ion lens 14b is reduced due to the function of the ICP-MS. Therefore, the number of lenses constituting the ion lens system is increased by one, and the degree of freedom of adjustment of the ion lens system is increased by one, so that the ion lens can be finely adjusted. Therefore, there is no problem that the ICP-MS is slightly increased in size by providing the gate valve 21. The voltage applied to the gate valve 21 from the variable voltage power supply 23 can be controlled manually or by a computer.

Thus, the gate valve 21 functions as an ion lens, and the same effect as when the distance between the extraction electrode 14a and the ion lens 14b is shortened is obtained.Therefore, even if the ion beam passing through the extraction electrode 14a diverges, It can be narrowed down again by the gate valve 21 functioning as a lens. For this reason, the extraction electrode 14a and the ion lens 1
Even when the distance of 4b is large and the ion beam diverges and then converges again, the number of ions entering the ion lens is greatly reduced even when converging again. As a result, the ion transmission efficiency of the entire ion lens systems 14b to 14e is greatly improved.

The operation of the other parts of the embodiment of the present invention is the same as that of the conventional example described in detail with reference to FIG. The present invention is not limited to the above-described embodiment, and various modifications are possible.For example, a plurality of ion lenses may be arranged behind the extraction electrode 14a to further increase the degree of freedom in adjusting the ion lens system. To improve or
The gate valve 21 may be substituted for the ion lens 14b, and the ion lens 14b in FIG. 1 may be removed.

<Effects of the Invention> As described in detail above, the present invention provides a configuration in which a gate valve functions as an ion lens in an ICP-MS to obtain the same effect as a reduction in the distance between the extraction electrode and the ion lens. Therefore, even if the ion beam that has passed through the extraction electrode diverges, it can be narrowed down again by the gate valve that functions as an ion lens. For this reason, the distance between the extraction electrode and the ion lens is large and the ion beam diverges. ICP-MS, which has greatly reduced ion loss and, as a result, has greatly improved the ion transmission efficiency of the entire ion lens system, and ultimately has the function of an ion lens in the gate valve to improve the ion transmittance and improve the analysis sensitivity. Is realized.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a main part of an embodiment of the present invention, FIG. 2 is an explanatory view of a general structure of a high frequency induction plasma mass spectrometer, and FIG. 3 is an explanatory view of a main part of a conventional example. 1 Plasma torch, 6 High frequency induction coil, 7 High frequency inductively coupled plasma, 8 Nozzle, 9 Skimmer, 10 High frequency power supply 11 Fore chamber, 13 Center chamber 14a Extraction electrode, 14b-14e: ion lens system, 16: mass filter, 17: rear chamber, 20: signal processing unit, 21: gate valve, 22a, 22b: insulator, 23: variable voltage Power supply

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01J 49/00-49/48 G01N 27/62

Claims (1)

(57) [Claims] A high frequency induction for extracting a sample excited by a plasma torch from a fore chamber by an extraction electrode, converging with an ion lens system in a center chamber partitioned by a gate valve, and analyzing the converged sample by a mass filter. In the coupled plasma mass spectrometer, a first insulator and a second insulator that insulate the gate valve provided between the fore chamber and the center chamber between the fore chamber and the center chamber are provided. A high-frequency inductively coupled plasma mass spectrometer, comprising: a variable voltage power supply that applies a voltage to the gate valve.