JP2000340168A - Plasma ion source mass spectroscope and ion source position adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reproducibility of a plasma torch fitting position by moving an ionized part based on position information to be the reference of the ionized part, stored in a second storage means, and interval information of measuring time of the ionized part and a mass analysis part stored in a first storage means, to fit the plasma torch to a mass spectroscope. SOLUTION: With respect to a plasma chamber 12, the distance between a plasma torch 21 and a sampling cone is adjusted to be 0 mm, and a space between the center axis of the plasma torch 21 in the Y axis and Z axis directions and the center axis of the sampling cone is adjusted to be 0 mm. A reference origin which is the present position of the plasma chamber 12, the dislocation quantity between the reference origin and an optimum position of the plasma chamber 12, and the optimum parameter value of each part of a device, are stored in a control part 17. When fitting the plasma torch 21 again, the plasma chamber 12 is moved by the stored dislocation quantity on the basis of the position of a new reference origin to lead the plasma torch 21 into an optimum position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma ion source mass spectrometer for ionizing a sample by plasma, and more particularly to improvement of the usability.

[0002]

2. Description of the Related Art Plasma ion source mass spectrometer (ICP)
-MS) is a method in which a plasma is generated by an ion source including a plasma torch made of quartz or the like and a high-frequency induction coil wound around the outer periphery of the plasma torch, and the sample is ionized by introducing the sample into the plasma. The sample is guided to a mass spectrometer for measurement.

[0003] The plasma generated from the ion source is
It is provided so as to be generated toward the sampling cone of the mass spectrometer, and the sample ionized by the plasma is introduced into the mass spectrometer exhausted to a low pressure from the pores provided in the sampling cone. Become.

By the way, the sample is ionized in the plasma. However, the ionization is not performed at the same efficiency everywhere in the plasma flame, but at the position where the ionization is efficiently performed even in the plasma flame. Exists. In a normal measurement, before performing the measurement, an operation of adjusting the position of the ion source is performed so that the efficient position is located at the position of the pores of the sampling cone.

In the conventional plasma ion source mass spectrometer, the ion source is mounted on a moving stage, and the distance between the ion source and the sampling cone is adjusted by adjusting a feed screw and a stepping motor provided on the moving stage. Had been adjusted. As an example of adjusting the position of such an ion source, see, for example, JP-A-9-35681.
There is an official gazette.

In actual measurement, not only the position of the ion source is simply adjusted but also the flow rate of plasma gas, carrier gas, etc.,
It is necessary to adjust a number of set values (parameters) such as an RF output applied to the high-frequency induction coil and a voltage applied to a plurality of ion lenses in the mass spectrometer. In these adjustments, an operator measures the measurement, and changes the setting little by little while observing the result, thereby finding an optimum value.

[0007]

Since the plasma torch of the ion source is contaminated by the passage of the sample, the plasma torch must be cleaned once every several days depending on the frequency of use. Second, the plasma torch must be removed from the ion source. When reattaching this plasma torch, the reference is the high-frequency induction coil, but since this high-frequency induction coil has few flat parts, attach it to the high-frequency induction coil at the same position where it was previously attached. Is difficult, and the possibility of mounting errors is very high. Usually, it is not uncommon for the spacing between the sampling cone and the plasma torch to be shifted by about 1 mm due to the attachment and detachment of the plasma torch. The position of the ion source is set based on a part fixed to the device such as a high-frequency induction coil or a moving stage, but if the mounting position of the plasma torch is different from the state before removal, the position of the ion source itself will be the same as the previous time. Even if they are the same,
The position where the plasma is generated will be different.

For this reason, when the plasma torch is reattached, if the previous measurement conditions are used as it is, the detection accuracy is significantly reduced. Therefore, each time the plasma torch is attached, the optimal ion source is again set. The position was found by the operator himself, and each of the above parameters had to be adjusted again with the movement of the ion source. This adjustment work is very time-consuming, and even an expert in operation of the apparatus requires about one hour for adjustment.

Further, since the torch itself is made of quartz, it is very difficult to manufacture a plurality of torches with completely the same dimensions. For this reason, irrespective of the quality of the method of attaching the torch, individual differences (dimensional errors) also occur in the manufacturing process, and the optimum parameters differ for each torch. Therefore, even when using a different plasma torch, the measurer must optimize the conditions regarding the plasma position while observing the sensitivity, and need to grasp the habit of the torch.

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned problems of the prior art, to improve the reproducibility of the mounting position of the plasma torch, and to measure the mass of the plasma ion source with good reproducibility even when using a plurality of torches. An object of the present invention is to provide an analyzer and a method of adjusting the analyzer.

[0011]

According to the present invention, there is provided an ionization section for ionizing a sample having a plasma torch and a coil wound around the outer periphery of the plasma torch, Means for moving the ionization unit, a sample ionized by the ionization unit is introduced through a member having pores, a mass analysis unit that detects the introduced ionized sample by mass separation, and the ionization unit. In a plasma ion source mass spectrometer including a control unit that controls the mass analysis unit, the control unit includes a first storage unit that stores information on a measurement interval between the ionization unit and the mass analysis unit. And second storage means for storing position information serving as a reference for the ionization unit,
Moving the ionization section based on the position information stored in the second storage means and the interval information stored in the first storage means when the plasma torch is mounted. .

Still further, an ion source for ionizing a sample having a plasma torch and a coil wound around the outer periphery of the plasma torch, means for moving the ion source, and a sample for ionizing the sample ionized by the ion source, Introduced via a member having a mass spectrometer for mass-detecting the ionized sample introduced, and a control unit for controlling the ion source and the mass spectrometer, a plasma ion source mass spectrometer comprising In the ion source position adjusting method,
A step of storing interval information at the time of measurement between the ion source and the mass spectrometry unit; a step of storing position information serving as a reference of the ion source; and Moving the ion source based on the information and the interval information.

[0013]

FIG. 1 is a block diagram showing the overall configuration of a plasma ion source mass spectrometer to which the present invention is applied.

As shown in FIG. 1, a plasma ion source mass spectrometer according to the present invention mainly comprises a sample introduction section 11 for atomizing a sample and a plasma for ionizing a sample introduced from the sample introduction section. Plasma chamber 12 for generating plasma 23, high frequency power supply 1 for generating plasma 23
3, a mass spectrometer 18 for measuring the ionized sample in the plasma chamber 12, control of the entire apparatus and quantitative determination based on the measurement results.
And a control unit 17 for performing qualitative calculation.

Further, the plasma chamber 12 includes a plasma torch 21 made of quartz and a high frequency induction coil 22 wound around the outer periphery of the plasma torch 21. The high frequency induction coil 22 )
Is applied. In addition, the mass spectrometry unit 18 converts the signals extracted from the ion optics system 14 for efficiently introducing ions into the mass spectrometry unit, the mass spectrometer 15 for separating ions for each mass number, and the mass spectrometer 15. And an ion detector 16 for detection.

FIG. 2 shows a detailed view around the plasma chamber 12.

As shown in FIG. 2, the plasma chamber 12
Are mounted on a movable stage that can move independently in three directions (X, Y, Z axes). Here, as the moving direction, the axis connecting the plasma torch 21 and the sampling cone 25 is “X axis”, the horizontal direction is the axis, and the axis perpendicular to the X axis is “Y axis”, and the vertical direction (height direction) is An axis that exists and intersects perpendicularly with the X axis is referred to as a “Z axis”.

The moving stage includes motors 102, 112 and 122, such as a stepping motor, which can move at intervals of about 0.1 mm for moving the X, Y and Z axes, respectively. Operates according to instructions from. Further, the moving stage is provided with position detecting devices 103, 113, and 123 for detecting the amount of movement of each axis.
And position detection plates 104, 114, and 124. As the position detection device, for example, a photocoupler is used,
The amount of movement of each axis can be detected by detecting the reflected light from the position detecting plate.

FIG. 3 and FIG. 4 are views showing a part of the plasma chamber 12 and the ion optical system 14. Ion optical system 14
Is provided with a sampling cone 25 and a skimmer cone 26 which are conical electrodes having pores in the center, and by applying a predetermined voltage to these, the sample ionized by the plasma 23 is put into the mass spectrometer 18. Introduce.

FIG. 3 shows the distance 24 between the plasma torch 21 and the sampling cone 25 in the X-axis direction. Similarly, FIG.
It is shown in the axial direction, and the plasma torch 21
And the horizontal axis or height direction interval 31 between the center axis of the sampling cone 25 and the center axis (position of the pores) of the sampling cone 25.

In the above configuration, the measurer first performs a plasma torch position calibration process at the time of the first measurement (measurement of mounting the plasma torch 21 in the plasma chamber for the first time).

FIG. 7 shows a flowchart of the plasma torch position calibration process.

In FIG. 7, the measurer first enters the control unit 17
A plasma torch position calibration command is selected on a display device such as a CRT included in the device.

Then, the apparatus moves the plasma chamber 12 to a predetermined position (mechanical origin). Here, the mechanical origin is a position set on the moving stage shown in FIG. 2, and is set at a position where the plasma torch 21 does not come into contact with the sampling cone 25 regardless of how the plasma torch 21 is attached.

The torch position adjustment window shown in FIG. 6 is displayed on the display device of the control unit 17 by executing the torch calibration command. The measurer selects the (+) or (-) command on the torch position adjustment window while viewing the positional relationship between the plasma torch 19 and the tip of the sampling cone 25 with respect to the plasma chamber 12 moved to the mechanical origin. Thus, the adjustment is performed so that the distance between the plasma torch 21 and the tip of the sampling cone 25 and the central axis of the plasma torch 21 and the central axis of the sampling cone 25 are not shifted. Specifically, the state is as shown in FIG. That is, FIGS.
Plasma torch 21 and sampling cone 25
The distance 24 between the central axis of the plasma torch 21 and the central axis of the sampling cone 25 (deviation) 31 in the Y-axis / Z-axis direction is adjusted to 0 mm.

The (+) and (-) commands in the torch position adjustment window are such that the position of the plasma chamber 12 is moved by a predetermined interval (for example, 0.1 mm) each time the command is selected. Is set. This operation is not performed on the software side, but a command as shown in a torch position adjustment window is provided as a hardware setting button somewhere in the apparatus main body or in the plasma chamber 12 so that the apparatus alone can adjust the plasma position. May be performed.

In this embodiment, the X-axis is adjusted first, and then the Y-axis and Z-axis are adjusted.

When the adjustment of all the axes is completed, select the "calibration" command in the torch position adjustment window. Thereby, the current position of the plasma chamber 12 is changed to the “reference origin”.
Is stored on a storage device (not shown) such as a hard disk of the control unit 17.

Thereafter, the measurer moves the plasma chamber 12 to find the optimum position of the plasma flame, calculates the “position shift amount (movement amount)” between the position at that time and the reference origin, and Store in the storage device. Furthermore, when the measurement with the attached plasma torch 21 is performed for the first time,
Find the optimal value of the parameter of each part of the device at that position,
It is stored together with the displacement amount.

With the above, the plasma torch position calibration processing is completed.

Thereafter, after the measurement has been performed for a while, the plasma torch 21 is removed for cleaning or the like, and when the plasma torch 21 is attached again, the measurer again performs the plasma torch position calibration process shown in FIG. Since the apparatus stores the amount of positional deviation from the previous reference origin, the apparatus moves the plasma chamber 12 by the stored amount of positional deviation based on the newly calibrated position of the “reference origin”. By doing so, the plasma chamber 12 can be easily guided to the same position as the optimal position of the plasma torch 21 set last time.

Therefore, in the second and subsequent measurements, the positions of the plasma torch 21 and the sampling cone 25 can be kept constant, even if there is an installation error, and the previously set values are used as they are for the parameters of each part of the apparatus. Can also maintain the detection accuracy. Therefore, there is no need to adjust the parameters again.

According to the present invention, when replacing or reattaching the plasma torch 21, the operator can measure the plasma torch 21 with respect to all of the X, Y, and Z axes without worrying about mounting errors. And the tip of the interface (sampling cone 25) is kept constant, and highly accurate measurement can always be performed under the same measurement conditions.

Furthermore, if the calibrated records (date and time, position, etc.) are stored in the storage device of the control unit 17 for the purpose of accuracy control of the device, the history thereof can be monitored.
This is more effective for maintenance management of the device.

Further, since the plasma torch 21 is usually made of quartz, it is very difficult to manufacture it in exactly the same shape, and the size differs slightly depending on the torch.
Therefore, the optimum position and the parameters of each unit of the apparatus are different for each torch. However, in the present invention, the plasma torch 21 used for the first time in the apparatus first sets the optimum position and parameters. Therefore, thereafter, measurement can be performed only by adjusting the reference origin. When a plurality of torches are used in the same device, the controller 17 stores and manages the amount of displacement (movement amount) from the reference origin and the set value of each parameter for each torch, so that As long as the settings are made, the optimum measurement can be performed with only a simple alignment using any plasma torch.

[0036]

According to the present invention, when replacing or reattaching the plasma torch, the positional relationship between the plasma torch and the tip of the interface (sampling cone) can be kept constant without concern for an attachment error. The measurement can be performed in the state of being in a closed position. Thus, highly accurate measurement can always be performed under the same measurement conditions.

Further, even if the plasma torch is reattached, it can be set to the same position as the previous time, so that it is not necessary to set parameters of the respective parts of the apparatus, which had been performed every time in the past. Therefore, the preparation work for the measurement is greatly simplified, and the measurement can be easily performed even by a non-expert.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a plasma ion source mass spectrometer for applying the present invention.

FIG. 2 is a diagram showing details around a plasma chamber.

FIG. 3 is a diagram illustrating an X-axis direction of an interface unit according to the present invention.

FIG. 4 is a diagram showing a Y axis or a Z axis of the interface unit of the present invention.

FIG. 5 is a diagram illustrating a setting state of a reference origin of an interface unit according to the present invention.

FIG. 6 is a diagram showing a torch position adjustment window displayed on a CRT of the control unit.

FIG. 7 is a flowchart illustrating a plasma torch position calibration process of the present invention.

[Explanation of symbols]

11: sample introduction unit, 12: plasma chamber, 13: high frequency power supply unit, 14: ion optical system, 15: mass analysis unit, 16 ...
Detecting unit 17 Control unit 21 Plasma torch 22
High frequency induction coil, 23 Plasma, 24 Distance between tip of sampling cone and high frequency induction coil (X), 25 Sampling cone, 26 Skimmer cone, 27 Rotary pump, 31 Tip of sampling cone and inner tube of plasma torch Distance to center (Y), 41
... Distance (Z) between the tip of the sampling cone and the center of the inner tube of the plasma torch, 101 ... X-axis stage, 102 ... X-axis motor, 103 ... X-axis position detection device, 104 ... X-axis position detection plate, 112 ... Y-axis motor , 113: Y-axis position detection device, 114: Y-axis detection plate, 122: Z-axis motor, 123
... Z-axis position detecting device, 124 ... Z-axis position detecting plate.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hayato Tobe 882 Omo, Oita-shi, Hitachinaka-shi, Ibaraki Inside the measuring instrument division of Hitachi, Ltd. 5C038 GG09 GH02 GH11 GH13 GH15

Claims (9)

[Claims] 1. An ionization section for ionizing a sample having a plasma torch and a coil wound around the outer periphery of the plasma torch, means for moving the ionization section, and a sample ionized by the ionization section having a pore formed therein. Introduced via a member having, a mass spectrometer for mass-detecting the introduced ionized sample and detecting, and a plasma ion source mass spectrometer comprising a controller for controlling the ionization unit and the mass spectrometer, The control unit has a first storage unit that stores interval information at the time of measurement between the ionization unit and the mass analysis unit, and a second storage unit that stores reference position information of the ionization unit. When the plasma torch is attached, based on the position information stored in the second storage means and the interval information stored in the first storage means, Plasma ion source mass spectrometer, characterized in that to move the serial ionization unit. 2. The plasma ion source mass according to claim 1, wherein the position information stored in the second storage means is determined by a distance between the plasma torch and the member having the fine holes. Analysis equipment. 3. The plasma ion source mass spectrometer according to claim 1, wherein the position information stored in said second storage means is updated when said plasma torch is mounted. . 4. The control unit according to claim 1, wherein the control unit has third storage means for storing a high-frequency output value to be applied to the coil, and the third unit stores the high-frequency output value in the coil along with the movement of the ionization unit. A plasma ion source mass spectrometer, which outputs a value stored in a storage means. 5. The plasma ion source mass spectrometer according to claim 1, wherein the information in said first storage means and said third storage means is managed for each of said plasma torches. 6. An ion source for ionizing a sample having a plasma torch and a coil wound around the outer periphery of the plasma torch, means for moving the ion source, and a fine hole for a sample ionized by the ion source. An ion source for a plasma ion source mass spectrometer including a mass spectrometer that is introduced through a member and mass-separates and detects the introduced ionized sample, and a controller that controls the ion source and the mass spectrometer. In the position adjusting method, a step of storing interval information at the time of measurement between the ion source and the mass spectrometer; a step of storing positional information serving as a reference of the ion source; and the mounting of the plasma torch is performed. Moving the ion source based on the position information and the interval information. 7. The ion source position adjusting method according to claim 6, wherein the position information is determined by a distance between the plasma torch and the member having the fine holes. 8. The ion source position adjusting method according to claim 6, wherein the position information is updated when the plasma torch is attached. 9. The method according to claim 6, wherein when the plasma torch is used for measurement for the first time,
A method for adjusting the position of an ion source, comprising: setting and storing a high-frequency output value to be applied to the coil.