JP3947762B2 - Inductively coupled plasma mass spectrometer and its exhaust control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes an interface chamber and the analyzer chamber continuously provided to the pressure at the time of measurement is different from each other, further, the inductive coupling with a rotary pump for exhausting the interface chamber, and a turbo pump for evacuating the analyzer chamber It relates to a plasma mass spectrometer, in particular, while using a single rotary pump, which can prevent the excessive load on the turbo pump is caused by the gas entering from the rotary pump to the backing line, inductive coupled plasma mass The present invention relates to an analyzer and an exhaust control method thereof .
[0002]
[Prior art]
Recently, an inductively coupled plasma (ICP) mass spectrometer has been proposed in which elemental analysis in solution is performed using ions using inductively coupled plasma used as a light source for emission analysis as an ion source for a mass spectrometer. (See, for example, Japanese Patent Laid-Open No. 62-26757).
[0003]
The vacuum system of the inductively coupled plasma mass spectrometer 10 samples elements ionized by an ionization unit (not shown) under atmospheric pressure and introduces them into a high vacuum ion lens chamber 30 as shown in FIG. A sampling cone 22 for aligning the direction of kinetic energy of ions generated in the ionizer torch 12 and a skimmer cone 24 for passing a part of the ions that have passed through the sampling cone 22. An interface chamber 20, an extraction electrode using an electrostatic ion lens, a focusing lens, a lens group 32 such as an ion lens, and plasma for converging ions passing through the interface chamber 20 and guiding them to the analyzer chamber 40, and plasma Closed to prevent the vacuum from dropping when not lit An ion lens chamber 30 including a valve 34, a quadrupole (referred to as a Q pole) 42 constituting a mass filter for selecting the mass of ions introduced from the ion lens chamber 30, and the Q pole 42 And an analyzer chamber 40 including a detector 44 using a secondary electron multiplier, for example.
[0004]
A first rotary pump (RP) 50 for exhausting the interface chamber is connected to the interface chamber 20 via a pipe 52, and a low vacuum that can be achieved by the rotary pump 50 is obtained.
[0005]
The ion lens chamber 30 and the analyzer chamber 40 are connected to first and second turbo (molecular) pumps (TMP) 60 and 62, respectively, so that a high vacuum required for measurement can be obtained. ing. The backing ports of the turbo pumps 60 and 62 are connected to a second rotary pump (RP) 66 for exhausting the backing line via a piping 64 for the backing line to operate the turbo pumps 60 and 62. The necessary low vacuum is obtained on the back pressure side of the turbo pumps 60 and 62.
[0006]
In the figure, 68 is an opening / closing valve for a backing line provided in the pipe 64 for maintaining the degree of vacuum at the time of factory shipment as much as possible and shortening the start-up time at the customer site.
[0007]
[Problems to be solved by the invention]
In such a conventional vacuum-type inductively coupled plasma mass spectrometer, two rotary pumps and two turbo pumps are required, which occupies a considerable proportion of the mass spectrometer cost. Was.
[0008]
In order to solve such a problem, by connecting the backing port of the turbo pump 62 to the turbo pump 60, the two turbo pumps 60 and 62 are connected in tandem, and only the first rotary pump 50 is It is conceivable to exhaust the backing line of one turbo pump 60. In this case, if the rotary pump 50 is configured to exhaust the backing line of the turbo pump 60 at all times, the inside of the interface chamber 30 is roughed during plasma ignition. At this time, the gas in the low-vacuum ion lens chamber 30 drawn by the rotary pump 50 circulates toward the turbo pump 60, and the backing line pressure rises rapidly, causing a large load on the turbo pump 60. There was a problem of shortening the pump life.
[0009]
The present invention has been made to solve the above-described conventional problems , and prevents a turbo pump from being overloaded with gas entering the backing line from the rotary pump while using a single rotary pump. It is referred to as challenges.
[0011]
[Means for Solving the Problems]
The present invention includes an interface chamber and the analyzer chamber continuously provided to the pressure at the time of measurement is different from each other, further, the inductive coupling with a rotary pump for exhausting the interface chamber, and a turbo pump for evacuating the analyzer chamber In the plasma mass spectrometer, the rotary pump is coupled to a backing port of the interface chamber and the turbo pump via a pipe having an opening / closing valve, and a gate that can be opened and closed between the interface chamber and the analyzer chamber. the valve is provided, further, by providing a means for comparing the pressure of the pressure and the interface chamber backing lines of the turbo pump, it is obtained by solving the previous SL challenges.
[0012]
Further, the means for comparing the pressure of the backing line of the turbo pump and the pressure of the interface chamber is characterized in that both pressures are detected to be substantially the same pressure .
[0013]
The on-off valve on the side coupled to the interface chamber is a variable valve .
[0014]
In the exhaust control method of the inductively coupled plasma mass spectrometer, when the plasma is ignited, the on-off valve on the turbo pump side is temporarily closed and only the on-off valve on the interface side is opened. Opening the gate valve to introduce a portion of the gas from the plasma into the analyzer chamber when the pressure is sufficiently reduced to the interface chamber position, and the turbo pump backing line And opening the on-off valve on the turbo pump side when the pressure becomes substantially the same as the pressure in the interface chamber, and a step of setting to a measurement state .
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
The first embodiment of the present invention is an inductively coupled plasma mass spectrometer similar to the conventional example shown in FIG. 4, and the backing port of the second turbo pump 62 is connected to a backing line pipe 65 as shown in FIG. The first turbo pump 60 is connected to the two turbo pumps 60 and 62 in tandem, and the backing port of the first turbo pump 60 is connected to the rotary pump 50 by the piping 70 for the backing line. The piping 70 can be opened and closed by a backing line opening / closing valve 72, and an interface opening / closing valve 54 is provided on the piping 52 connecting the rotary pump 50 and the interface chamber 20.
[0017]
In this embodiment, when not in use, the interface open / close valve 54 and the gate valve 34 are closed, and only the backing line open / close valve 72 is open, and the downstream side of the gate valve 34 of the ion lens chamber 30 and the analyzer chamber. 40 is evacuated to vacuum.
[0018]
At the time of plasma ignition, if the interface on / off valve 54 is opened with the backing line on / off valve 72 open, the gas in the interface chamber 20 having a low degree of vacuum passes through the pipes 52 and 70 to the first turbo. There is a risk of entering the backing line of the pump 60, applying a large load to the turbo pump 60, and shortening the pump life.
[0019]
Therefore, in the present embodiment, at the time of plasma ignition, the backing line opening / closing valve 72 is first closed, the interface opening / closing valve 54 is opened, and when the pressure in the interface chamber 20 is sufficiently lowered, the gate valve 34 is opened, and the ion lens chamber is opened. The gas is introduced into the downstream side of the 20 gate valve 34 and into the analyzer chamber 40, and when the backing line pressure of the first turbo pump 60 becomes substantially the same as the interface pressure, the interface on-off valve 54 is opened and measurement is performed. Make it ready. In addition, instead of the gate valve, an open / close valve for introducing gas may be provided in a vacuum chamber downstream from the gate valve 34 to open / close it.
[0020]
When the plasma is extinguished after the measurement is completed, first the gate valve 34 is closed, then the interface opening / closing valve 54 is closed, and then the plasma is extinguished.
[0021]
Conventionally, two rotary pumps are required for interface exhaust and turbo pump backing line exhaust. According to the present embodiment, the interface chamber 20 and turbo pumps 60 and 62 have one backing line. The pump can be evacuated by the rotary pump 50 and the turbo pump 60 need not be subjected to an abrupt load. Therefore, the life of the turbo pump 60 is not shortened. Further, it is possible to prevent oil from rising from the turbo pumps 60 and 62 to the ion lens chamber 30 and the analyzer chamber 40 due to a sudden pressure increase in the backing line.
[0022]
In this embodiment, the backing line (pipe 65) of the turbo pump 62 is connected to the turbo pump 60, but it may be directly connected to the backing line (pipe 70) of the turbo pump 60. Alternatively, the ion lens chamber 30 may be connected.
[0023]
Next, a second embodiment of the present invention in which a turbo pump is also shared will be described in detail.
[0024]
This embodiment is a turbo pump with an intermediate port as a second turbo pump for exhausting the analyzer chamber 40 as shown in FIG. 2 in the same rotary pump inductively coupled plasma mass spectrometer as in the first embodiment. By using the pump 80 and connecting the intermediate port 82 of the turbo pump 80 to the downstream side of the gate valve 34 of the ion lens chamber 30 by a pipe 84, the analyzer chamber 40 and the ion lens chamber 30 are connected to the common turbo pump 80. Can be exhausted together.
[0025]
As the turbo pump 80 with an intermediate port, for example, a commercial product (for example, Turbo-V250SF manufactured by Varian) having a configuration as shown in FIG. 3 can be used. In the figure, 86 is a backing port, and 88 is a vent port.
[0026]
In the present embodiment, not only the rotary pump but also the turbo pump can be shared, and the cost can be greatly reduced. A rotary pump for exhausting the backing line of the turbo pump 80 can be provided separately from the rotary pump 50 for exhausting the interface chamber.
[0027]
In the above-described embodiments, a simple on-off valve is used as the interface opening / closing 54. However, the interface opening / closing valve 54 itself may be a variable valve (for example, a needle valve) capable of adjusting pressure, or Alternatively, a separate variable valve may be inserted in series with the on-off valve 54 to enable pressure adjustment of the interface chamber 20.
[0028]
That is, in order to improve the detection limit with hot plasma, it is necessary to lower the pressure of the interface chamber 20, while to reduce the background of molecular ions with cool plasma using a shield torch, the interface Although the pressure in the chamber 20 needs to be increased, when a variable valve is used, the pressure in the interface chamber can be adjusted, and both hot plasma and cool plasma can be easily handled.
[0029]
In each of the above embodiments, the Q pole is used as the mass filter and the secondary electron multiplier is used as the detector. However, the types of the mass filter and the detector are as follows: It is not limited to this.
[0030]
【The invention's effect】
According to the present invention, the cost of these pumps, which occupy a considerable proportion of the cost of the inductively coupled plasma mass spectrometer, can be reduced by using a rotary pump and a turbo pump in common.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a configuration of the second embodiment. FIG. 3 is a turbo pump with an intermediate port used in the second embodiment. FIG. 4 is a cross-sectional view showing the structure of a conventional example.
DESCRIPTION OF SYMBOLS 10 ... Inductively coupled plasma mass spectrometer 20 ... Interface chamber 30 ... Ion lens chamber 34 ... Gate valve 40 ... Analyzer chamber 50 ... Rotary pump (RP)
52, 65, 70, 84 ... piping 54 ... open / close valve for interface 60, 62 ... turbo pump (TMP)
72 ... Opening / closing valve for backing line 80 ... Turbo pump with intermediate port 82 ... Intermediate port

Claims (4)

An interface chamber and analyzer chamber pressure during measurement are different from each other are provided continuously, further, a rotary pump for exhausting the interface chamber, induction and a turbo pump for evacuating the analyzer chamber coupled plasma mass spectrometer In
The rotary pump is coupled to the interface chamber and a backing port of the turbo pump through a pipe having an on-off valve,
A gate valve that can be opened and closed is provided between the interface chamber and the analyzer chamber,
Furthermore, inductive coupled plasma mass spectrometer you comprising means for comparing the pressure of the pressure and the interface chamber backing lines of the turbo pump. 2. The inductively coupled plasma mass spectrometer according to claim 1, wherein the means for comparing the pressure of the backing line of the turbo pump and the pressure of the interface chamber detects that both pressures are substantially equal. . According to claim 1, wherein the on-off valve on the side coupled to the interface chamber, inductive coupled plasma mass spectrometer you characterized in that constituted by a variable valve. In the exhaust control method of the inductively coupled plasma mass spectrometer according to claim 1,
At the time of plasma ignition, temporarily closing the open / close valve on the turbo pump side and opening only the open / close valve on the interface side;
Opening the gate valve to introduce a portion of the gas from the plasma into the analyzer chamber when the pressure is sufficiently reduced to the position of the interface chamber;
When the pressure of the backing line of the turbo pump becomes substantially the same as the pressure of the interface chamber, opening the on-off valve on the turbo pump side to be in a measurement state;
Exhaust control method of the induction coupled plasma mass spectrometer, comprising a.

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