JP5114930B2 - Mass spectrometer ion source - Google Patents

Description

  The present invention relates to heating of an ionization section of an ion source in a mass spectrometer that introduces a gaseous sample and performs ionization.

  The present invention describes an ion source in a mass spectrometer that measures the mass of sample compound molecules, such as a gas chromatograph mass spectrometer (hereinafter referred to as GC / MS).

  In GC / MS, the sample to be analyzed is introduced into the apparatus in a vaporized state, ionized, and ions are separated and measured. However, if the sample is a high boiling point compound, it is adsorbed at the location where the temperature has dropped and the analytical sensitivity is reduced. Arise.

  Since the ion source which is one of the components of the GC / MS has the same influence, the ionization chamber of the ion source is heated and kept warm as a means for preventing adhesion to the walls in the ionization chamber. In order to heat and keep the ionization chamber normally, the heat source is arranged avoiding the filament, repeller electrode, converging lens, and magnet that emit electron beams to ionize the sample gas molecules that are functionally required for the ion source (patented) Reference 1).

  5, 6 and 7 show the structure of the GC / MS ion source. FIG. 5 shows a front view of the ion source. 6 shows a cross-sectional view taken along the line II in FIG. FIG. 7 shows a plan view of FIG.

  In FIG. 5, 15 is a heat source, which is composed of a heater 2, a temperature sensor 3, and a heat block 1 (shown in FIGS. 6 and 7), 9a is a repeller electrode lead terminal, 10 is a filament lead terminal, and 10a is a filament mounting screw. , 26 also serve as a plate for mounting the heat source 15, the repeller electrode 9 and the ionization chamber box 8 (shown in FIG. 6), and these parts are part of the parts constituting the ion source. Reference numeral 13 denotes a sample introduction unit. The ionization chamber box 8 is heated by the heat source 15, and the sample gas from the GC is introduced into the ionization chamber box 8 through the sample introduction unit 13.

  In FIG. 6, electrons radiated from a filament (not shown) arranged outside the ionization chamber box 8 are made to enter the ionization chamber A through the electron incident hole 17 provided in the ionization chamber box 8 in the vertical direction on the paper surface. The sample gas molecules introduced into the ionization chamber A through the sample introduction hole 19 are ionized by the gas chromatograph column 28 connected to the ionization chamber box 8 through the sample introduction unit 13. Two filaments may be provided, and when one is operating, the other functions as an electron trap. The sample ions generated in the ionization chamber A are pushed and converged by the repeller electrode 9 from the ion emission hole 18 provided in the ionization chamber box 8 into the electric field lens space C formed by the lens electrodes 11 and 11a. It is introduced into a mass separation section provided in the vacuum chamber B, mass-separated and detected as an ion signal. Reference numeral 11b denotes a positioning pin for fixing the lens electrodes 11 and 11a. Reference numeral 20 denotes a bolt for fastening and fixing the ionization chamber box 8 and the repeller electrode 9 to the ionization chamber plate 23 by the plate 26, and 20 a is a tap hole for stopping the bolt 20 provided in the ionization chamber plate 23.

  In FIG. 7, as described with reference to FIG. 5, the heat source 15 includes the heat block 1, the heater 2 embedded therein, and the temperature sensor 3, and is fixed to the ionization chamber plate 23. Heat from the heat source 15 is conducted to the ionization chamber box 8 through the ionization chamber plate 23 on which the ionization chamber box 8 is mounted, so that the ionization chamber A is maintained at a predetermined temperature. A spacer 24 serves to hold a filament (not shown) and the magnet 21, and to fix the ionization chamber box 8 and the ionization chamber plate 23, and 12 denotes a base plate of the ion source. The magnet 21 is arranged behind a filament (not shown) arranged outside the ionization chamber box 8 and condenses the electron flow radiated from the filament in the ionization chamber A to interrupt the collision between the sample gas and the electron beam. It works to increase the area and increase ionization efficiency.

However, in the conventional ion source described above, the arrangement of the heat source 15 and the material of the ionization chamber plate 23 that conducts heat in contact with the ionization chamber box 8 and the arrangement of the spacer 24 that supports the ionization chamber plate 23 are also arranged. Depending on the configuration, the efficiency of heating and heat retention of the ionization chamber box 8 and the ionization chamber A is a problem. In addition, when performing maintenance with the equipment stopped, it is necessary to lower the temperature of the ion source in a vacuum in order to avoid deterioration of the surface of the parts material due to atmospheric exposure at high temperatures. There is also a problem that it takes a long time for the temperature to be lowered to about 40 degrees or less, which is a maintainable temperature, depending on the arrangement and configuration.
Japanese Examined Patent Publication No. 6-75390

  The heat source 15 heats and keeps the ionization chamber box 8 through the ionization chamber plate 23 in contact with the heat source, but there is a positional restriction. As shown in FIGS. 5 and 7, the heat source 15 is placed on the opposite side of the sample introduction unit 13. Will be placed. In this configuration, the heat generated from the heat source 15 escapes to the vacuum chamber B through the ionization chamber plate 23, the spacer 24, and the base plate 12. In this case, heat is transferred from the heat source 15 toward the ionization chamber plate 23 and the spacer 24, and a thermal gradient is generated toward the sample introduction unit 13 side. In FIG. 6, the temperature of the ionization chamber box 8 on the sample introduction part 13 side far from the heat source 15 is lowered, and adsorption of the high boiling point component sample occurs on the inner wall of the ionization chamber box 8 on the sample introduction hole 19 side and the inner wall of the sample introduction hole 19. Causes a decrease in analytical sensitivity. Increasing the set temperature so as to compensate for the temperature drop is considered as a countermeasure, but since heat escapes, the temperature of the inner wall of the ionization chamber box 8 does not become uniform, and a temperature difference occurs, and a part that is higher than necessary it can. Therefore, some compounds contact the inner wall and decompose and cannot be analyzed accurately.

  Therefore, there is a problem that the loss of heat conducted from the heat source 15 to the ion source is reduced, the temperature difference is reduced at the portion where the sample contacts, and the temperature difference cannot be maintained uniformly. Further, when maintenance is performed with the apparatus stopped, it is necessary to reduce the temperature of the ion source. However, in a vacuum atmosphere, it takes a long time to decrease to a temperature at which maintenance can be performed.

  In the technique shown in Patent Document 1, the interface block 14 is in contact with the ionization chamber box 8 as shown by the broken line in FIG. 5, and the sample gas molecules pass through the center line of the interface block 14. It is introduced into the ionization chamber from the introduction channel. The interface block 14 is used as a heat source to heat the ionization chamber box. However, there are problems that the ionization chamber cannot be heated and insulated efficiently and the ionization chamber box cannot be heated and insulated independently of the interface block 14. is there.

  The present invention seeks to provide an ion source that solves the above-described problems associated with heating, heat retention and heat dissipation of an ion source of a conventional mass spectrometer.

  In order to solve the above problems, the ion source provided by the present invention is arranged such that the heating source is arranged on the side opposite to the sample introduction part or surrounding the ionization chamber box, and the ionization chamber box and the heating source are directly mounted. The ionization chamber plate is constructed so that the side near the sample introduction part is supported or not supported by a heat insulator, and the side far from the sample introduction part is supported by a heat radiator. This configuration ensures proper heating.

  According to the present invention, the heat distribution from the heating source to the ionization chamber box can be efficiently performed, so that the temperature distribution in the ionization chamber is uniformly maintained at a temperature close to the heat source, and the high-boiling compound sample is sampled in the ionization chamber box Adsorption to the side ionization chamber wall and the sample introduction hole portion can be suppressed. In addition, the inner wall of the ionization chamber is not heated more than necessary, the sample is not decomposed, and the analysis sensitivity is improved. Since the heat source side is fixed with a heat radiating member, when the apparatus is stopped and maintenance is performed, the cooling time of the ion source can be shortened, and the maintenance can be performed quickly.

  The loss on the heat flow rate can be reduced by fixing the sample introduction part side to a structure with less heat dissipation using a material having high heat insulation. Further, by determining the material and structure so that the thermal conductivity of the ionization chamber plate is increased, the amount of temperature decrease with respect to the unit heat flow rate can be reduced.

  Furthermore, the present invention fixes the ionization chamber plate at a site other than the sample introduction part. This configuration further reduces heat loss.

  By not providing a support point on the sample introduction part side, the heat flow to the sample introduction part side is eliminated, so that there is less heat loss than in the first aspect. Further, by determining the material and structure so that the thermal conductivity of the ionization chamber plate is increased, the amount of temperature decrease with respect to the unit heat flow rate can be further reduced. As a result, the temperature of the ionization chamber on the sample introduction portion side becomes closer to the heat source, and the temperature distribution of the ionization chamber wall is improved.

  In the present invention, the shape of the heat source is further configured to surround the ionization chamber box. In other words, the support position of the ionization chamber plate is set to a position outside the heat source that does not affect the temperature decrease of the ionization chamber, and the temperature gradient of the ionization chamber plate in the part in contact with the ionization chamber box is prevented, thereby reducing the temperature of the ionization chamber. Don't make it happen. When the ionization chamber box is surrounded by a heat source and the temperature of the heat source is adjusted in this state, a heat flow is generated toward the support part connected to the vacuum chamber, but the ionization chamber box itself has a heat dissipation path. Is not provided, no heat flow is generated toward the vacuum chamber, and no temperature drop occurs.

The present invention will be described below with reference to examples.
1, 2 and 3 show a first embodiment of the present invention. FIG. 1 is a front view of an ion source, FIG. 2 is a cross-sectional view taken along line I-I, and FIG. 3 is a plan view. As shown in FIG. 2, the structure and arrangement of the ionization chamber box 8 and the plate 26, the filament (not shown), the repeller electrode 9, and the lens electrodes 11 and 11a are the same as those in the prior art. 1 to 4, parts indicated by the same reference numerals as those shown in FIGS. 5 to 7 are the same as the parts shown in FIGS. 5 to 7, and detailed descriptions thereof are omitted.

  In FIG. 1, the heat source 15 includes a heater 2, a temperature sensor 3, and a heat block 1. When the heat block 1 of the heat source 15 is maintained at a constant temperature by a separate temperature control unit, the heat source 15 is fixed to the heat block 1. The upper ionization chamber plate 4 and the lower ionization chamber plate 5 (shown in FIG. 2) are heated to a temperature close to the heat source 15.

  As shown in FIG. 2, the upper ionization chamber plate 4 is in contact with the lower side of the ionization chamber box 8 and the lower ionization chamber plate 5 is fixed in contact with the lower ionization chamber plate 4. The ionization chamber plate 4 is made of a material having a high thermal conductivity, such as an aluminum alloy or a copper alloy, so that heat from the heat source 15 is efficiently transmitted to the ionization chamber box 8 through the ionization chamber plate 4. The lower ionization chamber plate 5 is made of a material having a lower thermal conductivity, such as stainless steel. This is because, as shown in FIG. This is because if a tapped hole 20a for fastening and fixing the repeller electrode 9 with the bolt 20 is provided and a tapped hole is provided in an aluminum alloy or the like, repeated tapping cannot be performed, and the lower plate is made of another material. Reference numeral 27 denotes a plate for positioning the repeller electrode 9.

  If the amount of decrease in temperature is to be minimized, it is desirable that the upper ionization chamber plate 4 and the lower ionization chamber plate 5 are made of a material having high thermal conductivity and integrated. The spacer 6 on the sample introduction part 13 side in FIG. 3 that positions and holds the ionization chamber plate upper 4 and the ionization chamber plate lower 5 has a cross-sectional shape and a length that reduce the amount of heat transfer, compared to the spacer 7 described later. Reducing the heat dissipation. The spacer 7 also serves to hold the filament (not shown) and the magnet 21 and to fix the ionization chamber plate upper 4 and ionization chamber plate lower 5, and the contact area with the ionization chamber plate upper 4 functions to increase the heat radiation amount. It is the maximum without any problem.

  The purpose of increasing the contact area is to finish the cooling in a short time after the temperature adjustment of the heat source 15 is turned off. The amount of heat released through this contact portion is larger than the amount of heat released through the spacer 6 described above. Become bigger. However, since this heat flow does not pass through the vicinity of the ionization chamber box 8 in which no heat radiation flow path is provided and goes directly to the vacuum chamber B, the temperature of the ionization chamber A does not decrease. In addition, the heater 2 uses a heater that has a sufficient margin for the amount of heat released through the spacer 7. As shown in FIGS. 2 and 3, the ionization chamber box 8, filament (not shown), repeller electrode 9, lens electrodes 11, 11a, and magnet 21 are also important positions for fixing the mutual positioning. It is fixed to the base plate 12 so that it can.

  The lower ionization chamber plate 5 holding these components and the spacer 7 are fixed to the base plate 12 with a fitting structure.

  FIG. 4 shows a second embodiment of the present invention. 4 is a front view corresponding to FIG. 3 which is a front view of the first embodiment.

  The difference between the second embodiment and the first embodiment is that the support on the sample introduction part 13 side is not performed as shown in FIG. That is, the spacer 6 in FIG. As a result, the amount of heat escaping through the upper ionization chamber plate 4 and the lower ionization chamber plate 5 around the ionization chamber box 8 becomes very small, and the thermal conductivity of the ionization chamber plate 4 itself is not problematic. For example, it can be made of a material that can ensure strength more than the property, such as stainless steel.

  Accordingly, in the first embodiment, the structure is such that the ionization chamber plate upper 4 and the ionization chamber plate lower 5 are stacked as shown in FIGS. 2 and 3, but in the second embodiment, the single ionization structure is used as shown in FIG. The chamber plate 25 can be used.

  The third embodiment has a structure in which the entire ionization chamber box 8 is heated in the configuration of the first embodiment described above. The point supporting the upper ionization plate 4 and the lower ionization chamber plate 5 is arranged at the same position as the heat source 15 or outside the heat source 15. As in Example 2, the sample introduction part 13 side is not supported. The heat source 15 is integrated with the spacer 7 in the first embodiment and conducts heat up to the sample introduction part 13 side of the ionization chamber box 8.

  As a result, the amount of heat escaping through the upper ionization chamber plate 4 and the lower ionization chamber plate 5 around the ionization chamber box 8 is negligible, and the thermal conductivity of the ionization chamber plate itself is not problematic. Rather than a material that can ensure strength, such as stainless steel. Therefore, also in this embodiment, the upper ionization chamber plate 4 and the lower ionization chamber plate 5 can have a single-sheet structure as in the second embodiment.

  The present invention relates to heating and heat retention of a sample ionization part of a mass spectrometer that ionizes by introducing a gaseous sample, and also relates to a cooling time of an ion source and can be used for a gas chromatograph mass spectrometer or the like. . In the above embodiment, stainless steel is taken as an example of a material having a lower thermal conductivity. However, the material is not limited to this stainless material, and other materials can be used as long as the use conditions are met.

It is a front view which shows the ion source of this invention. It is sectional drawing in the arrow line II of FIG. 1 which shows the ion source of this invention. It is a top view which shows the ion source of this invention. It is a top view which shows the ion source of this invention. It is a front view of the ion source of a prior art example. It is sectional drawing in the arrow line II of FIG. 7 of the ion source of a prior art example. It is a top view of the ion source of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat block 2 Heater 3 Temperature sensor 4 Ionization chamber plate top 5 Ionization chamber plate bottom 6 Spacer 7 Spacer 8 Ionization chamber box 9 Repeller electrode 9a Repeller electrode lead terminal 10 Filament lead terminal 10a Filament mounting screw 11 Lens electrode 11a Lens electrode 11b Positioning Pin 12 Base plate 13 Sample introduction part 14 Interface block 15 Heat source 17 Electron incident hole 18 Ion emission hole 19 Sample introduction hole 20 Bolt 20a Tap hole 21 Magnet 23 Ionization chamber plate 24 Spacer 25 Ionization chamber plate 26 Plate 27 Plate 28 Column 29 Ion Beam A Ionization chamber B Vacuum chamber C Electric lens space

Claims (3)

An ionization chamber box having an ionization chamber inside for ionizing a sample, a sample introduction unit for introducing a sample into the ionization chamber, a heating source for heating the ionization chamber box, and the ionization chamber box and the heating source are mounted. An ionization chamber plate to be mounted; a first spacer fixed to the ion introduction chamber plate and the heating source; and provided on a side closer to the sample introduction portion; the ionization chamber plate and the heat source fixed to the sample; In a mass spectrometer ion source including a second spacer provided on a side far from the introduction unit, the heating source is disposed on the side opposite to the sample introduction unit, and the first spacer is the second spacer. Mass spectrometer ion source characterized in that the heat dissipation is lower than that of the spacer.   An ionization chamber box having an ionization chamber inside for ionizing a sample, a sample introduction unit for introducing a sample into the ionization chamber, a heating source for heating the ionization chamber box, and the ionization chamber box and the heating source are mounted. In a mass spectrometer ion source comprising an ionization chamber plate to be mounted, and a spacer for fixing the ionization chamber plate and the heating source, the heating source is disposed on the side opposite to the sample introduction portion, and the spacer is disposed on the sample A mass spectrometer ion source provided on a side far from the introduction part and not provided on a side near the sample introduction part.   3. The mass spectrometer ion source according to claim 1, wherein the heating source has a structure for heating the entire ionization chamber box. 4.

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