WO2023084868A1

WO2023084868A1 - Mass spectrometer

Info

Publication number: WO2023084868A1
Application number: PCT/JP2022/032136
Authority: WO
Inventors: 知義松下
Original assignee: 株式会社島津製作所
Priority date: 2021-11-10
Filing date: 2022-08-26
Publication date: 2023-05-19

Abstract

This mass spectrometer comprises: a plasma ion source that ionizes a sample with plasma; a mass spectrometry unit that performs mass spectrometry on the ionized sample; and a sampling cone. The mass spectrometer also comprises a skimmer cone (7) that is disposed further on the mass spectrometry unit side than the sampling cone. The mass spectrometer further comprises a base for cooling the skimmer cone (7), and a pressing member (91) for fixing at least a portion of the outer edge of the skimmer cone (7) to the base.

Description

Mass spectrometer

The present invention relates to an ICP (Inductively Coupled Plasma) mass spectrometer.

There is a mass spectrometer called an ICP mass spectrometer. An ICP mass spectrometer ionizes an element to be measured contained in a solution sample by plasma, draws the resulting ions into a vacuum through a sampling unit, and performs measurement with a mass spectrometer (for example, Patent Document 1 ). The sampling section includes a conical sampling cone and a skimmer cone. Since the sampling cone and skimmer cone are directly blown with plasma reaching about 7000° C., they need to be made of materials that can withstand high temperatures.

JP-A-10-241625

When metal is used as the material for the skimmer cone, the skimmer cone is machined from a lump of metal. For this reason, the processing cost for manufacturing the skimmer cone is high, which has been a factor in increasing the manufacturing cost of the mass spectrometer as a whole.

The present invention has been devised in view of such circumstances, and its purpose is to provide a technique for reducing the manufacturing cost of mass spectrometers.

A mass spectrometer according to an aspect of the present disclosure includes a plasma ion source that ionizes a sample with plasma, a mass spectrometry unit that performs mass analysis on the ionized sample, and a mass spectrometer that is arranged between the plasma ion source and the mass spectrometer. a sampling unit, wherein the sampling unit includes a sampling cone and a skimmer cone arranged closer to the mass spectrometry unit than the sampling cone; a base for cooling the skimmer cone; a holding member for fixing at least a portion of the outer edge of the skimmer cone to the base.

According to one aspect of the present disclosure, the manufacturing cost of the mass spectrometer is reduced.

It is a figure which shows roughly the structure of the mass spectrometer of this embodiment. 2 is an enlarged view of part of the mass spectrometer 100. FIG. 4 is a perspective view of the unit 9; FIG. 4 is a longitudinal sectional view of the unit 9; FIG. 4 is an exploded perspective view of the unit 9; FIG. 9 is a view showing a cross section near the projection 7X in a state where a pressing member 91 fixes the skimmer cone 7 to the cooling jacket base 92. FIG. 8 is a diagram showing the positional relationship between the skimmer cone 7 and the lead-in electrode 8. FIG.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are denoted by the same reference numerals, and the description thereof will not be repeated.

[Configuration of mass spectrometer]
FIG. 1 is a diagram schematically showing the configuration of the mass spectrometer of this embodiment. The mass spectrometer 100 shown in FIG. 1 is an ICP mass spectrometer.

The mass spectrometer 100 includes an ionization chamber 1, a first vacuum chamber 2, a second vacuum chamber 3, and a third vacuum chamber 4. The ionization chamber 1 is at substantially atmospheric pressure and electrically grounded. The first vacuum chamber 2 is configured such that the degree of vacuum increases in order from the ionization chamber 1 side. The inside of the first vacuum chamber 2 is evacuated by a rotary pump. The insides of the second vacuum chamber 3 and the third vacuum chamber 4 are evacuated by a rotary pump and a turbomolecular pump.

An ICP ion source 5 is arranged inside the ionization chamber 1 . The configuration of the ICP ion source 5 shown in FIG. 1 is merely an example, and various modifications are possible.

The ICP ion source 5 includes a plasma torch 51. The plasma torch 51 includes a sample tube through which the liquid sample atomized by the nebulizing gas flows, a plasma gas tube formed around the sample tube, and a cooling gas tube formed around the plasma gas tube.

An autosampler 52 for introducing a liquid sample into the plasma torch 51 is provided at the inlet end of the sample tube of the plasma torch 51 . In addition, although not shown, the sample tube is connected to a nebulizing gas supply source that supplies nebulizing gas, the plasma gas tube is connected to a plasma gas supply source that supplies plasma gas (for example, Ar gas), and the cooling gas tube is connected to A cooling gas supply is connected to supply a cooling gas.

The first vacuum chamber 2 is formed between a substantially conical sampling cone 6 and a substantially conical skimmer cone 7 . Both the sampling cone 6 and the skimmer cone 7 have ion passage openings at their tops. The skimmer cone 7 is made of metal such as Cu or Ni, for example. The first vacuum chamber 2 functions as an interface for sending ions supplied from the ICP ion source 5 to the subsequent stage and discharging solvent gas and the like.

Of the three axes (X, Y, Z) shown in FIG. 1, the X axis represents the traveling direction of ions.
In the second vacuum chamber 3, a drawing electrode 8, an ion lens 10 for converging ions, a collision cell 11, and an energy barrier forming electrode 15 are arranged in order from the skimmer cone 7 side (the side where ions are incident). It is The drawing electrode 8, the ion lens 10, and the energy barrier forming electrode 15 are all disc-shaped electrodes having a substantially circular opening for passing ions. The opening of the lead-in electrode 8 is shown as opening 81 in FIG.

An entrance electrode 12 having an ion passage aperture 121 is arranged on the entrance side of the collision cell 11 , and an exit electrode 13 similarly having an ion passage aperture 131 formed on the exit side of the collision cell 11 . Inside the collision cell 11, a multipole (for example, octapole) type ion guide 14 including a plurality of rod electrodes arranged parallel to an ion optical axis 18 is arranged.

A quadrupole mass filter 16 including a pre-rod electrode and a main rod electrode, and an ion detector 17 are arranged in the third vacuum chamber 4 .

The gas supply unit 19 supplies collision gas or reaction gas to the interior of the collision cell 11 through the gas supply pipe. The collision gas is He (or another inert gas) and the reaction gas is a reactive gas such as hydrogen or ammonia.

The voltage generating section 20 generates a voltage to be applied to each section in the mass spectrometer 100. In FIG. 1, only some voltage supply lines are drawn to avoid complicating the drawing. ing. The voltage generator 20 includes a plurality of DC voltage generators that generate a DC voltage of a predetermined voltage and a plurality of high frequency voltage generators that generate a high frequency voltage with a predetermined amplitude and a predetermined frequency.

Under the control of the control unit 22, the voltage control unit 21 controls the magnitude of the voltage applied from the voltage generation unit 20 to each unit and the timing of application.

The control unit 22 comprehensively controls each unit in the mass spectrometer 100 in order to perform analysis. The control unit 22 also has a user interface function via the input unit 23, the display unit 24, and the like. The data processing unit 25 includes an analog-to-digital (AD) converter that digitizes the detection signal obtained by the ion detector 17, and processes the collected data to create a mass spectrum.

In one implementation example, the control unit 22, the voltage control unit 21, and the data processing unit 25 are implemented by a personal computer including a CPU (Central Processing Unit), RAM (Random Access Memory), and an external storage device. . Control in the mass spectrometer 100 can be realized by the CPU executing a predetermined program installed in advance.

[Example of analysis operation of mass spectrometer]
FIG. 2 is an enlarged view of a part of the mass spectrometer 100. As shown in FIG. An example of the analysis operation of the mass spectrometer 100 will be described below. In the following description, ions to be analyzed by the mass spectrometer 100 are assumed to be positive ions. It is obvious that even if the ions to be analyzed are negative ions, the same analysis as in the following description can be performed by appropriately changing the polarity of the voltage applied to each part.

In the standby state before starting the analysis, the first vacuum chamber 2, the second vacuum chamber 3, and the third vacuum chamber 4 are each in a state of being evacuated. When the user gives an instruction to start analysis via the input unit 23, or when an instruction to start analysis is automatically given according to a preset automatic analysis program, the control unit 22 starts analysis preparatory work.

In the analysis preparation work, the control unit 22 operates the gas supply unit 19 to start supplying a predetermined gas into the collision cell 11 continuously or intermittently. The type of gas to be supplied differs depending on the analysis mode. For example, He gas is used in the collision mode, and H ₂ gas is used in the reaction mode.

Even if the gas starts to be supplied into the collision cell 11, it takes a certain amount of time for the gas to fill the collision cell 11 and stabilize, and until then, substantial analysis cannot be performed. This period is the analysis preparation period.

In response to the instruction from the control unit 22 , the voltage control unit 21 determines that the potential barrier between the skimmer cone 7 and the pull-in electrode 8 is higher than the initial energy of the unwanted ions generated by the ICP ion source 5 . The voltage generator 20 is controlled so as to apply a positive DC voltage of a predetermined voltage value to the pull-in electrode 8 so as to form a gap between them. "Undesired ions" are mainly ions derived from the plasma gas used in the ICP ion source 5, such as Ar ⁺ and Ar ²⁺ when the plasma gas is Ar. Since the initial energy of the "undesired ions" is not so large, the voltage applied to the pull-in electrode 8 is generally about +several volts.

The voltage control unit 21 also controls the voltage generation unit 20 under the instruction of the control unit 22 so as to apply a positive DC voltage of a predetermined voltage value to the entrance electrode 12 of the collision cell 11 . The voltage applied to the entrance electrode 12 at this time is, for example, about +several tens to two hundred volts.

The voltage control unit 21 also controls the voltage generation unit 20 under the instruction of the control unit 22 so as to apply to the ion guide 14 in the collision cell 11 a high-frequency voltage with a larger amplitude value than during normal analysis. do.

The voltage control unit 21 further controls the voltage generation unit 20 to continuously or pulse-wise apply a negative DC voltage having a predetermined voltage value larger than that during normal analysis to the exit electrode 13 of the collision cell 11. do. At this time, the amplitude value of the high-frequency voltage applied to the ion guide 14 is, for example, 50 V or more, and the DC voltage applied to the exit electrode 13 is, for example, about -100 V (about -10 to -10 and several V during normal analysis).

As described above, due to the DC voltage applied to the drawing electrode 8, a potential barrier is formed in the vicinity of the drawing electrode 8 by an electric field having the same polarity as the ions. Ions derived from the plasma gas or the like generated by the ICP ion source 5 and entered the second vacuum chamber 3 through the ion passage port (opening 61) of the sampling cone 6 and the ion passage port (opening 71) of the skimmer cone 7 are It is blocked by the potential barrier. Therefore, ions stay in the region 31 between the skimmer cone 7 and the drawing electrode 8, and the ion density increases.

From the ICP ion source 5, not only the above ions but also reactive neutral particles derived from the plasma gas and plasma gas molecules try to enter the vacuum region. However, since the ion density in the region 31 is high, reactive neutral particles and gas molecules that have passed through the opening 71 of the skimmer cone 7 are likely to come into contact with ions. Reactive neutral particles and gas molecules that come into contact with the ions change their trajectories, collide with surrounding electrodes or the like and disappear or are discharged from the second vacuum chamber 3 to the outside. Therefore, it is difficult for reactive neutral particles and gas molecules to reach the entrance of the collision cell 11, and the amount of reactive neutral particles and gas molecules entering the interior of the collision cell 11 can be reduced.

As described above, the voltage applied to the entrance electrode 12 of the collision cell 11 forms an electric field having the same polarity as the ions originating from the plasma gas or the like in the region 32 between the ion lens 10 and the entrance electrode 12 . Therefore, ions introduced from the ICP ion source 5 into the second vacuum chamber 3 via the first vacuum chamber 2 and having passed through the region 32 are pushed back before the entrance electrode 12 . As a result, it is possible to further reduce the entry of unwanted ions originating from the plasma gas or the like into the collision cell 11 .

Since the reactive neutral particles and molecules do not have electric charges, they are not removed by the action of the electric field formed in the region 32. However, as described above, the reactive neutral particles and molecules do not pass through the region 31. Therefore, the amount of reactive neutral particles and gas molecules that enter the interior of the collision cell 11 can be reduced.

Some of the ions derived from the plasma gas or the like may pass through both the

regions

31 and 32 and enter the collision cell 11 . Also, some of the reactive neutral particles and molecules originating from the plasma gas or the like pass through the above two regions and enter the collision cell 11, contact the gas within the collision cell 11, and become unwanted ions. Sometimes. Ions entering from the outside and ions generated within the collision cell 11 contact the gas present within the collision cell 11 to reduce their energy and are trapped in the high frequency electric field created by the ion guide 14 . Since the high-frequency electric field at this time is stronger than that during normal analysis, the ions are focused in a relatively narrow region 33 near the ion optical axis 18 .

As described above, the exit electrode 13 of the collision cell 11 is applied with a relatively high voltage having a polarity opposite to that of the ions to be captured. Therefore, the ions staying in the region 33 are attracted by the strong electric field generated by the voltage applied to the exit electrode 13 and are ejected from the collision cell 11 through the ion passage aperture 131 of the exit electrode 13 .

That is, during the analysis preparation period before executing the analysis, between the ICP ion source 5 and the collision cell 11, unwanted ions and unwanted reactive neutral particles are prevented from entering the collision cell 11. be. On the other hand, unwanted ions that have entered the collision cell 11 and unwanted ions generated within the collision cell 11 are rapidly ejected to the outside of the collision cell 11 . Thus, in the mass spectrometer 100, ions are less likely to stay in the collision cell 11 during the analysis preparation period.

The control unit 22 waits until a predetermined waiting time elapses so that the collision cell 11 is sufficiently filled with the gas supplied from the gas supply unit 19 . The gas introduced into the collision cell 11 leaks out through the

openings

121, 131 of the entrance electrode 12 and the exit electrode 13, respectively. For this reason, the longer the waiting time, the better, in order to fill the collision cell 11 with gas molecules with as uniform a density as possible. As an example, it is preferable to set the waiting time from the start of gas introduction to 40 seconds or longer.

After the predetermined waiting time has passed, the voltage control section 21 controls the voltage generating section 20 so as to apply to the drawing electrode 8 a negative DC voltage of a predetermined voltage value that attracts ions. The voltage control unit 21 also controls the voltage generation unit 20 so as to apply a negative DC voltage having a predetermined voltage value to the entrance electrode 12 of the collision cell 11 as well. Further, the voltage control unit 21 controls the voltage generation unit 20 so as to apply to the ion guide 14 in the collision cell 11 a high-frequency voltage having a predetermined amplitude value corresponding to the component to be analyzed (target component). . Further, the voltage control section 21 controls the voltage generation section 20 so as to apply a predetermined voltage for potential barrier formation to the exit electrode 13 of the collision cell 11 .

After that, the mass spectrometer 100 performs analysis. In one implementation, the voltage controller 21 sets the voltage applied to the quadrupole mass filter 16 such that ions originating from the target component pass through. Then, in the mass spectrometer 100, the intensity of the ions of the target sample component is detected after the time (for example, several milliseconds) required for the voltage applied to each part to settle.

For example, in the collision mode, ions derived from sample components generated by the ICP ion source 5 are introduced into the collision cell 11 filled with collision gas together with unwanted ions derived from the plasma gas. The introduced ions repeatedly collide with the collision gas, and their energy is attenuated. Ions with a larger collision cross-section have more opportunities to collide with the collision cell, and their energy is greatly attenuated. Since the collision cross section of ions derived from the plasma gas is generally larger than that of ions derived from the target component, the ions derived from the plasma gas have smaller kinetic energy. Therefore, ions derived from the plasma gas are difficult to overcome the potential barrier formed at the exit of the collision cell 11 . Unnecessary ions derived from the plasma gas or the like are removed by the kinetic energy discrimination method, and ions mainly of sample components can be sent to the quadrupole mass filter 16 for analysis.

As described above, almost no ions exist in the collision cell 11 during the analysis preparation period before the start of analysis. There is little space charge effect for ions residing inside 11 . Therefore, during analysis, the trajectories of ions (introduced into the collision cell 11) originating from the target component are not affected by the space charge effect. As a result, the ions pass through the collision cell 11 following normal trajectories and are introduced into the quadrupole mass filter 16 . As a result, the amount of ions derived from the target component that finally reaches the ion detector 17 is increased, and high analytical sensitivity can be achieved. In addition, since the trajectory of ions originating from the sample component is not affected by the space charge effect, it is possible to reduce the drift of the ion intensity and further reduce the variation in the drift depending on the type of sample component.

Note that in the above description, the collision cell 11 is kept in contact with the collision cell 11 for the entire analysis preparation period from the start of gas supply to the collision cell 11 until the gas sufficiently fills the collision cell 11 and the analysis is started. The voltage applied to each part was set so that ions would not stay inside. However, it is not always necessary to continue such voltage setting throughout the analysis preparation period. Note that the basic operation can be the same as the above even in the reaction mode instead of the collision mode.

[Skimmer cone and surrounding structure]
The structure of the skimmer cone 7 and its neighboring elements will be described with reference to FIGS. The three axes (X, Y, Z) shown in each of FIGS. 3-7 correspond to the three axes shown in FIG.

3 is a perspective view of the unit 9. FIG. Unit 9 includes skimmer cone 7 and pulling electrode 8 . Unit 9 further includes plate 90 and pressing member 91 . The pressing member 91 has a ring shape.

4 is a longitudinal sectional view of the unit 9. FIG. 5 is an exploded perspective view of the unit 9. FIG. As mainly shown in FIG. 4 , a cooling jacket base 92 is arranged between the plate 90 and the lead-in electrode 8 .

The skimmer cone 7 is fixed to the cooling jacket base 92 by pressing the outer edge of the skimmer cone 7 against the cooling jacket base 92 with a pressing member 91 . More specifically, the pressing member 91 fixes the skimmer cone 7 to the cooling jacket base 92 by fixing to the cooling jacket base 92 with

screws

91A and 91B. This allows the skimmer cone 7 to be cooled by the cooling jacket base 92 while maintaining its ability to pass ions through the aperture 71 .

By fixing the outer edge of the skimmer cone 7 to the cooling jacket base 92 by the pressing member 91, the outer diameter of the entire skimmer cone 7 can be made smaller than before. Thereby, the material constituting the skimmer cone 7 can be reduced, and the manufacturing cost of the skimmer cone 7 can be reduced. In addition, since the outer diameter of the skimmer cone 7 is reduced, the processing cost for cutting out the skimmer cone 7 can be suppressed, and the manufacturing cost of the skimmer cone 7 can also be reduced. By reducing the manufacturing cost of the skimmer cone 7, the manufacturing cost of the mass spectrometer 100 as a whole can also be reduced.

The pressing member 91 only needs to fix at least part of the outer edge of the skimmer cone 7 to the cooling jacket base 92 . 5, the skimmer cone 7 can be more reliably fixed to the cooling jacket base 92 by fixing the entire outer edge of the skimmer cone 7 to the cooling jacket base 92 with the pressing member 91. .

As mainly shown in FIG. 5, the surface of the skimmer cone 7 is formed with a convex portion 7X.
FIG. 6 is a cross-sectional view showing the vicinity of the convex portion 7X when the holding member 91 fixes the skimmer cone 7 to the cooling jacket base 92. As shown in FIG.

As shown in FIG. 6, the pressing member 91 has recesses 91X at positions corresponding to the protrusions 7X. The pressing member 91 fixes the skimmer cone 7 to the cooling jacket base 92 with the projection 7X fitted into the recess 91X.

Therefore, it is not necessary to form a screw hole in the skimmer cone 7 for fixing the skimmer cone 7. The shape of the screw hole is difficult to clean and can be degraded by cleaning agents such as nitric acid used during cleaning. By not requiring a screw hole, cleaning of the skimmer cone 7 is facilitated, and destabilization of fixing of the skimmer cone 7 due to deterioration of the screw hole can be avoided. A concave portion may be formed on the skimmer cone 7 side and a convex portion may be formed on the pressing member 91 side.

As shown in FIGS. 5 and 6 (particularly, frames F11 and F12 and frames F21 and F22), the pressing member 91 is in contact with the X-axis and Y-axis surfaces of the skimmer cone 7 . That is, the pressing member 91 is in contact with multiple surfaces of the skimmer cone 7 .

Thereby, the pressing member 91 can contact the skimmer cone 7 over a larger area than the opening 71 of the skimmer cone 7 . Therefore, heat conduction from the skimmer cone 7 to the pressing member 91 is promoted.

Furthermore, as shown in FIGS. 5 and 6 (especially frames F21 and F22), the pressing member 91 is in contact with the surface along the X axis and the surface along the Y axis at the outer edge of the skimmer cone 7 as well. . That is, the outer edge of the skimmer cone 7 has steps, and the outer edge of the pressing member 91 also has steps corresponding to the steps of the skimmer cone 7 .

As a result, the contact area between the skimmer cone 7 and the pressing member 91 increases, and heat conduction from the skimmer cone 7 to the pressing member 91 is promoted.

In the mass spectrometer 100, the pressing member 91 and the skimmer cone can be made of materials having different thermal conductivities. Thereby, the mode of heat transfer from the skimmer cone 7 to the pressing member 91 can be adjusted by selecting each material.

In one implementation, the pressing member 91 is made of a material with higher thermal conductivity than the skimmer cone 7. For example, the pressing member 91 is made of copper and the skimmer cone 7 is made of nickel. As a result, heat transfer from the skimmer cone 7 to the pressing member 91 can be promoted, and the temperature at the tip (opening 71) of the skimmer cone 7 can be reduced. This allows the mass spectrometer 100 to measure a sample that is suitable for lowering the temperature of the opening 71 .

In one implementation, the pressing member 91 is made of a material with a lower thermal conductivity than the skimmer cone 7. For example, the pressing member 91 is made of SUS or brass, and the skimmer cone 7 is made of nickel. Thereby, heat transfer from the skimmer cone 7 to the pressing member 91 is suppressed, and the opening 71 of the skimmer cone 7 can be maintained at a high temperature. Thereby, the mass spectrometer 100 can measure a sample suitable for keeping the temperature of the opening 71 high.

FIG. 7 is a diagram showing the positional relationship between the skimmer cone 7 and the drawing electrode 8. FIG. FIG. 7 shows the positional relationship between the skimmer cone 7 and the lead-in electrode 8 in the YZ plane. The YZ plane is an example of a plane that intersects with the axial directions of the sampling cone 6, the skimmer cone 7, and the lead-in electrode 8. As shown in FIG. The axial directions of the sampling cone 6, the skimmer cone 7, and the drawing electrode 8 mean the main traveling directions of ions.

As shown in FIG. 7, the outer edge of the skimmer cone 7 is positioned outside the opening 81 of the lead-in electrode 8 on the YZ plane. That is, the outer edge of the skimmer cone 7 extends to a position covering the opening 81 of the lead-in electrode 8 . Thereby, discharge from the lead-in electrode 8 can be suppressed by the skimmer cone 7 .

[Aspect]
It will be appreciated by those skilled in the art that the multiple exemplary embodiments described above are specific examples of the following aspects.

(Section 1) A mass spectrometer according to one aspect comprises a plasma ion source that ionizes a sample with plasma, a mass spectrometry section that performs mass analysis on the ionized sample, and a space between the plasma ion source and the mass spectrometry section. a sampling unit arranged in a base for cooling the skimmer cone, the sampling unit including a sampling cone and a skimmer cone arranged closer to the mass spectrometry unit than the sampling cone; and a pressing member for fixing at least part of the outer edge of the skimmer cone to the base.

According to the mass spectrometer according to item 1, the manufacturing cost of the mass spectrometer is reduced.
(Section 2) The mass spectrometer according to Section 1 further includes a pull-in electrode installed closer to the mass spectrometry unit than the skimmer cone, and the pull-in electrode is for allowing the ionized sample to pass through. An opening may be provided, and an outer edge of the skimmer cone may extend to a position covering the opening on a plane intersecting the axial direction of the sampling cone, the skimmer cone, and the lead-in electrode.

According to the mass spectrometer described in item 2, the skimmer cone can suppress discharge from the drawing electrode.

(Section 3) In the mass spectrometer according to

Section

1 or 2, the pressing member may fix the skimmer cone to the base by contacting a plurality of surfaces of the outer edge of the skimmer cone. good.

According to the mass spectrometer described in paragraph 3, heat transfer from the skimmer cone to the base can be promoted.

(Item 4) In the mass spectrometer according to any one of items 1 to 3, a concave portion is formed on one side of the skimmer cone and the pressing member, and the other side of the skimmer cone and the pressing member The skimmer cone may be fixed to the base by forming a convex portion on the side thereof, and fixing the pressing member to the base with the convex portion fitted in the concave portion.

According to the mass spectrometer described in item 4, the skimmer cone can be fixed by the pressing member without forming a screw hole.

(Item 5) In the mass spectrometer according to any one of items 1 to 4, the pressing member and the skimmer cone may be made of materials having different thermal conductivities.

According to the mass spectrometer described in item 5, the mode of heat transfer from the skimmer cone to the pressing member can be adjusted by selecting each material.

(Section 6) In the mass spectrometer according to Section 5, the pressing member may be made of a material having higher thermal conductivity than the skimmer cone.

According to the mass spectrometer described in item 6, the mass spectrometer can measure a sample suitable for lowering the temperature of the opening of the skimmer cone.

(Section 7) In the mass spectrometer according to Section 5, the pressing member may be made of a material having a lower thermal conductivity than the skimmer cone.

According to the mass spectrometer described in item 7, the mass spectrometer can measure a sample that is suitable for maintaining a high temperature at the opening of the skimmer cone.

(Item 8) In the mass spectrometer according to any one of items 1 to 7, the pressing member may fix the entire outer edge of the skimmer cone to the base.

According to the mass spectrometer described in item 8, the skimmer cone can be more reliably fixed by the pressing member.

The embodiments disclosed this time should be considered illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the scope of the claims rather than the description of the above-described embodiments, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims. In addition, it is intended that each technique in the embodiment can be implemented independently or in combination with other techniques in the embodiment as much as possible.

1: ionization chamber, 2: first vacuum chamber, 3: second vacuum chamber, 4: third vacuum chamber, 5: ICP ion source, 6: sampling cone, 7: skimmer cone, 7: convex part, 8: pulling electrode, 9: unit, 10: ion lens, 11 collision cell, 12 entrance electrode, 13 exit electrode, 14 ion guide, 15 energy barrier forming electrode, 16 mass filter, 17 ion detector, 18 ion optical axis, 19 gas supply unit, 20 voltage generation unit, 21 voltage control Part, 31, 32, 33 area, 51 plasma torch, 52 autosampler, 61, 71, 81 opening, 90 plate, 91 pressing member, 91A, 91B screw, 91X recess, 92 cooling jacket base, 100 mass spectrometer, 121, 131 Ion passage openings.

Claims

a plasma ion source that ionizes the sample with plasma;
a mass spectrometer that performs mass spectrometry on the ionized sample;
a sampling unit disposed between the plasma ion source and the mass analysis unit;
The sampling unit
a sampling cone;
a skimmer cone arranged closer to the mass spectrometry unit than the sampling cone;
a base for cooling the skimmer cone;
and a pressing member for fixing at least part of the outer edge of the skimmer cone to the base.
further comprising a pull-in electrode installed closer to the mass spectrometry unit than the skimmer cone;
the drawing electrode has an aperture for passing the ionized sample;
2. The mass spectrometer according to claim 1, wherein an outer edge of said skimmer cone extends to a position covering said opening on a plane intersecting with axial directions of said sampling cone, said skimmer cone, and said pull-in electrode.
The mass spectrometer according to claim 1, wherein the pressing member fixes the skimmer cone to the base by contacting a plurality of surfaces of the outer edge of the skimmer cone.
a concave portion is formed on one side of the skimmer cone and the holding member;
A convex portion is formed on the other side of the skimmer cone and the pressing member,
2. The mass spectrometer according to claim 1, wherein said pressing member is fixed to said base in a state in which said convex portion is fitted in said concave portion, thereby fixing said skimmer cone to said base.
The mass spectrometer according to claim 1, wherein the pressing member and the skimmer cone are made of materials having thermal conductivities different from each other.
The mass spectrometer according to claim 5, wherein the pressing member is made of a material having higher thermal conductivity than the skimmer cone.
The mass spectrometer according to claim 5, wherein the pressing member is made of a material having lower thermal conductivity than the skimmer cone.
The mass spectrometer according to claim 1, wherein the pressing member fixes the entire outer edge of the skimmer cone to the base.