JP4582935B2 - Mass spectrometer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mass spectrometer, and more particularly to a mass spectrometer that analyzes the mass of an adsorbing sample gas with high accuracy.
[0002]
[Prior art]
The most basic method for analyzing gas is mass spectrometry that measures the mass of gas molecules. In mass spectrometry, a sample gas (gas molecule) is ionized, and the sample gas is separated according to each mass by passing an electromagnetic field (electric field or magnetic field or both), and is separated. It is a method of detecting and measuring. Conventionally, an electron impact ionization method has been mainly used as a method for ionizing a sample gas. Since the electron impact ionization method performs ionization by colliding electrons with the sample gas at high speed, there is a problem that gas molecules constituting the sample gas themselves are split (dissociated) by collision energy.
[0003]
There is a chemical ionization method as a method for solving the above problems. In the chemical ionization method, methane gas is ionized by electron bombardment to generate primary ions, the primary ions collide with the sample gas to cause hydrogen adhesion, and the sample gas is ionized. According to the chemical ionization method, surplus energy is large and dissociation cannot be completely eliminated. In addition, there is a problem in that other reactions occur and a plurality of types of ions are generated.
[0004]
An ion attachment ionization method has been developed as a method for ionization by completely suppressing dissociation of gas molecules. This ion attachment ionization method is described by Hodges (Analytical Chemistry vol.48 No.6 P825 (1976)), Bombic (Analytical Chemistry vol.56 No.3 P396 (1984)), Fujii (Analytical Chemistry vol.61). No. 9 P1026 (1986), Chemical Physics Letters vol.191 No.1.2 P162 (1992), JP-A-6-11485).
[0005]
In the above ion attachment ionization method, for example, Li⁺, K⁺, Na⁺Alkali metal etc.saltThe ion emitter containing ion is heated to ionize the alkali metal, and the metal ion is gently attached to the location where the charge of the sample gas molecule is biased to ionize the sample gas. N₂An inert gas such as Ar or Ar is introduced together with the sample gas, and the inert gas and the ionized sample gas collide with each other to quickly take away excess energy from the sample gas ions, thereby stabilizing the sample gas ions. Such an inert gas is called a three-body gas. The ion attachment ionization method is particularly effective for a sample of an organic substance that easily generates dissociation, and is expected to provide a highly accurate analysis of the organic substance sample.
[0006]
Next, a conventional apparatus configuration by the ion attachment ionization method will be described with reference to FIGS. In FIG. 8, 101 is an ionization chamber, 102 is a differential exhaust chamber, 103 is an analysis chamber, 104 is an ion emitter, 105 is a heater, 106 is a repeller, 107 is an ionization region by metal ions, 108 is a first aperture, 109 Is a second aperture, 110 is a mass analyzer, and 111 is a detector. A gas introduction device 112 is attached to the ionization chamber 101, and an exhaust device (not shown) is connected to the exhaust port 102 a of the differential exhaust chamber 102. The gas introduction device 112 includes a sample gas cylinder 121, a sample gas variable flow valve 122, a three-body gas cylinder 123, a three-body gas variable flow valve 124, and a gas introduction pipe 125. The pressure in the ionization chamber 1 is about 100 Pa in total for the three-body gas and the sample gas.
[0007]
Metal ions such as Li from the ion emitter 104 heated by the heater 105⁺Is released. The metal ions move in the direction of the analysis chamber 103 by the electric repulsion by the repeller 106, and in this process, the metal ions adhere to the sample gas and are ionized. An ionization region 107 by metal ions corresponds to a region where metal ions move in the direction of the analysis chamber 103. The ionization region 107 by metal ions functionally corresponds to the ionization region by primary ions in the chemical ionization method. Compared to the ionization region by chemical ionization, the ionization region 107 by ion attachment ionization is localized near the central axis of the ionization chamber 101 because the ion emitter 104 is solid and has a small volume. . The sample gas ionized in the ionization region 107 is transferred to the analysis chamber 103, separated in the analysis chamber 103 by the mass analyzer 110, and detected by the detector 111.
[0008]
Next, FIG. 9 shows another apparatus using the ion attachment ionization method. In FIG. 9, the same elements as those described in FIG. 8 differs from the apparatus shown in FIG. 8 in that the gas introduction device 112 is installed behind the repeller 106A, and the repeller 106A has a mesh shape so that sample gas and the like can pass therethrough. That is. Other configurations and operations are the same as those described with reference to FIG.
[0009]
In the apparatus using ion attachment ionization described above, as shown in FIGS. 8 and 9, the distance from the tip inlet of the gas inlet tube 125 to the center of the ionization region 107 is A, and the inside of the ionization chamber 101 from the tip inlet is shown in FIG. When the representative shortest value of the distance to the wall surface is B, both are provided so as to satisfy the relationship of A> B.
[0010]
[Problems to be solved by the invention]
When analyzing a gas having adsorptivity such as oxygen, water, dibutylsiloxane phthalate and the like using a conventional ion attachment ionization apparatus, there is a problem that an accurate analysis cannot be performed. The reason is that the sample gas having adsorptivity does not stably exist in the ionization region when introduced into the ionization chamber and is adsorbed on the inner wall surface of the ionization chamber.
[0011]
That is, in the conventional ion attachment ionization method, the sample gas must stably realize the original concentration in the gas phase, and for this purpose, the adsorption equilibrium (adsorption speed and desorption speed) are the same on the inner wall surface. Thus, it is necessary to realize a state in which adsorption is not apparently realized. However, in the case of adsorptive gas, once it is adsorbed on the wall surface, it takes a very long time to return to the gas phase again (on the order of minutes or hours), and it takes hours to reach adsorption equilibrium. There are many.
[0012]
Therefore, in the case of an adsorptive gas, if the measurement is performed immediately after the gas is introduced, the value is considerably lower than the original concentration. This is because, since the amount adsorbed on the surface of the inner wall is small, the adsorbing speed is larger than the desorbing speed, and the gas phase sample gas has moved to the inner wall surface. In other words, the inner wall surface functions as a vacuum pump. On the contrary, even if the gas introduction is stopped and the next measurement is started, the sample gas of the previous measurement is measured indefinitely. This is because, since the amount adsorbed on the inner wall surface is large, the desorption rate is higher than the adsorbing rate, and the sample gas adsorbed on the inner wall surface moves to the gas phase.
[0013]
The time until the adsorption equilibrium is reached depends not only on the strength of gas adsorption but also on the wall surface temperature. When the wall surface temperature becomes high, the time during which the gas is adsorbed and stays there (residence time or adsorption time) is shortened, and the time until the adsorption equilibrium is reached is shortened. Note that when the flow rate of the sample gas is small, the decrease in concentration due to adsorption becomes significant, and the time until the adsorption equilibrium is reached becomes long.
[0014]
For this reason, conventionally, a method of measuring while raising the temperature of the gas introduction pipe and the ionization chamber of the sample gas has been adopted. However, depending on the sample gas, the practically possible 200 to 300 ° C. is insufficient, and it cannot often be said that the measurement is necessarily performed in a state where adsorption equilibrium is realized. In addition, in the case of a sample gas that is weak against heat, another problem that the sample gas is decomposed by heat before measurement occurs.
[0015]
An object of the present invention is to solve the above-described problems, and in a mass spectrometer equipped with an ion source for ion attachment ionization, when a gas having adsorptivity is used as a sample gas, the gas is massed with high accuracy. The object is to provide a mass spectrometer capable of analysis.
[0016]
[Means for Solving the Problems]
The mass spectrometer according to the present invention is configured as follows in order to achieve the above-mentioned purpose.
[0017]
  First mass spectrometer (corresponding to claim 1):
  An ionization chamber in which an ionization region for ionizing a sample gas having adsorptivity is formed, and an analysis chamber in which ions of the sample gas ionized in the ionization region are subjected to mass separation by an electromagnetic field,
  The sample gas is introduced into the ionization chamber through the gas introduction tube, and is ionized by attaching the metal ions released from the ion emitter in the ionization region in the ionization chamber to the sample gas, and between the ionization chamber and the analysis chamber. In a mass spectrometer that passes through a provided aperture and is then subjected to mass separation by an electromagnetic field in an analysis room,
  In the ionization chamber,
  An ion emitter that emits metal ions;
  A repeller that is arranged behind the ion emitter with respect to the position of the aperture and moves the metal ions in the direction of the analysis chamber by electric repulsion;
  A gas introduction pipe provided so that a sample gas can be introduced between the aperture and the ion emitter, and
  The gas introduction tube is disposed so as to protrude into the ionization chamber so that the tip introduction port of the gas introduction tube is positioned between the aperture and the ion emitter, and the sample gas is inclined or perpendicular to the horizontal central axis. To be introduced
  The position of the tip inlet of the gas inlet tube is provided so that the distance from the tip inlet to the center of the ionization region is shorter than the typical minimum value of the distance from the tip inlet to the inner wall of the ionization chamber. It is characterized by that.
[0019]
  First2Mass spectrometer (claim)2Is characterized in that, in the above configuration, the pressure of the ionization chamber is set to a value between 10 and 1000 Pa.
[0020]
  First3Mass spectrometer (claim)3In the above configuration, the gas introduction tube is formed of a double reciprocating tube, and the sample gas flows in from the end of one tube, turns back at the tip, flows out from the other tube, and introduces the gas. A part of the sample gas is introduced into the ionization chamber from the leading inlet of the tube.
[0021]
  First4Mass spectrometer (claim)4In the above configuration, the shape of the tip of the gas introduction tube is axisymmetric, and the ionization region is positioned on the tip of the tip.
[0022]
  First5Mass spectrometer (claim)5In the above-described configuration, a desired voltage is applied to the distal end portion of the gas introduction tube, and a potential is set.
[0023]
  First6Mass spectrometer (claim)6In the above configuration, an axially symmetric mesh plate or an apertured plate is provided so that the tip inlet of the gas introduction tube is located outside and the ionization region is located on this axis. It is characterized by that.
[0024]
  First7Mass spectrometer (claim)7In the above configuration, a desired voltage is applied to the mesh plate or the plate with the opening, and the potential is set.
[0025]
[Action]
In order to solve the above-described problems of the present invention, it is necessary to reduce the influence of the inner wall on the concentration in the gas phase state in the ionization chamber. In the following, the above three methods will be examined from this viewpoint.
[0026]
In an apparatus using electron impact ionization, the pressure in the ionization chamber is 10^-2Pa and the mean free path is several tens of centimeters. The “mean free path” is an average value of the length (stroke) that the gas can travel without colliding with other gases. Since the size of the ionization chamber is usually about several centimeters, the sample gas flies around the ionization chamber without colliding with other gases. Therefore, although the gas introduction tube is attached toward the corner of the ionization chamber, the introduced sample gas is uniformly diffused throughout the ionization chamber in an instant (milliseconds or less). Therefore, it can be said that the concentration in the gas phase is governed by the condition of the inner wall. Therefore, even if the gas introduction tube protrudes into the ionization chamber and the leading inlet is located inside the ionization region by electron impact, the degree of this effect hardly changes.
[0027]
In the apparatus using the chemical ionization method, the pressure in the ionization chamber is about 100 Pa and the mean free path is several tens of microns, so that the sample gas always collides with other gases. Since this collision is in a random direction, the sample gas becomes loosely confined, and the speed at which the sample gas moves through the ionization chamber (diffusion speed) becomes very slow. Therefore, if the introduction port at the tip of the gas introduction tube is kept away from the inner wall of the ionization chamber and is located within the ionization region by the primary ions and near the center, the influence of the inner wall on the concentration in the gas phase state can be reduced. it can. That is, the original concentration of the introduced sample gas is considerably realized in the ionization region. However, in this case, the electric field in the ionization region due to the primary ions is disturbed by the influence of the gas introduction tube having a specific potential, and normal ionization cannot be performed. Moreover, since the ionization area | region by a primary ion has extended to the inner wall vicinity of the ionization chamber, the influence of an inner wall will remain considerably. That is, the signal amount finally measured does not indicate the original concentration of the sample gas.
[0028]
In the apparatus using the ion attachment ionization method, as in the chemical ionization method, the pressure in the ionization chamber is about 100 Pa, and the diffusion rate of the sample gas becomes very slow. On the other hand, the ionization region by metal ions is localized near the horizontal axis at the center of the ionization chamber, unlike the chemical ionization method. Therefore, if the introduction port at the tip of the gas introduction tube is positioned near the boundary of the ionization region by metal ions, the influence of the inner wall on the concentration in the gas phase can be greatly reduced without substantially impairing normal ionization. . That is, the signal amount finally measured also indicates the original concentration of the sample gas.
[0029]
As described above, the present invention adopts a novel concept of reducing the influence of the inner wall by confining the sample gas in the space. The conventional idea is to reduce the influence of any ionization described above by reducing the surface area of the inner wall. Therefore, the ionization chamber is often made as small as possible. In practice, however, it is impossible to reduce the surface area of an ionization chamber having a complicated structure by an order of magnitude.
[0030]
On the other hand, according to the present invention, in order to further reduce the contact between the sample gas confined in the space and the inner wall, the idea that the inner wall should be far away is adopted. Therefore, even if the surface area of the inside of the ionization chamber itself is increased, the influence of the inner wall can be reduced by an order of magnitude in order to prevent the sample gas from contacting the inner wall.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. The configuration described in this embodiment is shown schematically to the extent that the present invention can be understood, and the limitations of materials and numerical values are merely examples. Therefore, the present invention is not limited to the following embodiments, and is applied to various forms that can be interpreted from the description of the claims.
[0033]
A first embodiment of the present invention will be described with reference to FIG. In FIG. 1, an ionization chamber 11 is provided at the left end, and an analysis chamber 13 is connected to the ionization chamber 11 via a central differential exhaust chamber 12. A gas introduction device 14 is attached to the ionization chamber 11. A first aperture 15 having a hole 15a formed in the center is provided between the ionization chamber 11 and the differential exhaust chamber 12, and a hole 16a is formed in the center between the differential exhaust chamber 12 and the analysis chamber 13. A second aperture 16 is provided. The exhaust port 12a of the differential exhaust chamber 12 is connected to an exhaust pump (not shown). The analysis chamber 13 is provided with a mass analyzer and a detector set with an electromagnetic field. Illustration of the mass analyzer and the detector is omitted.
[0034]
The ionization chamber 11 is provided with an ion emitter 21 containing an alkali metal salt, a heater (power supply line) 22 for feeding and heating the ion emitter 21, and a repeller 23 disposed behind the ion emitter 21. Yes. In the left region of the ion emitter 21, an ionization region 24 formed by metal ions released from the ion emitter 21 is formed. The ionization region 24 is formed along the horizontal central axis of the ionization chamber 11 and is formed in a relatively narrow region.
[0035]
The gas introduction device 14 includes a sample gas cylinder 31, a three-body gas cylinder 32, a sample gas variable flow valve 33, a three-body gas variable flow valve 34, and a gas introduction pipe 35. The sample gas and the three-body gas supplied from the two cylinders 31 and 32 via the variable flow valves 33 and 34 are mixed and introduced into the ionization region 24 inside the ionization chamber 11 via the gas introduction pipe 35. The Two kinds of gas are blown out from the front end opening of the gas introduction pipe 35 by the blowout jet stream 36. Further, the region shown with the opening at the tip of the gas introduction pipe 35 as a starting point is the sample gas distributed in the ionization chamber 11, and the distribution region substantially coincides with the ionization region 24. The dense density distribution is the ionization region 24 described above, and the thin density distribution indicates the distribution state of the diffused sample gas.
[0036]
Li, which is a metal ion, from the ion emitter 21 heated by the heater 22⁺Is released. The metal ions move toward the analysis chamber 13 by the electric repulsion by the repeller 23. In the course of this movement, the sample gas blows out from the tip of the gas introduction pipe 35 and adheres to the sample gas existing in the ionization region 24, and this sample gas is ionized. Since the ion emitter 21 is solid and has a relatively small volume, the ionization region 24 by metal ions is localized in the vicinity of the central axis of the ionization chamber 11.
[0037]
The pressure in the ionization chamber 11 is set to be about 100 Pa in total of the sample gas and the three-body gas. Therefore, the sample gas always collides with other gases. Since this collision is in a random direction, the sample gas is present in a space that is loosely confined, and the speed at which the sample gas moves through the ionization chamber 11 (diffusion speed) becomes very slow. (For example, 10^-3Seconds).
[0038]
The gas introduction pipe 35 penetrates the wall of the ionization chamber 11 in a linear form, for example, and protrudes into the inside thereof, and the introduction port at the tip is located in the vicinity of the boundary of the ionization region 24 by metal ions. However, the gas introduction pipe 35 is attached obliquely with respect to the axis (horizontal central axis) of the ionization chamber 11 so that the blow-out jet stream 36 does not disturb the flow of metal ions in the ionization region 24 due to metal ions. It is preferable.
[0039]
Regarding the installation position of the gas introduction pipe 35, the distance from the introduction port at the tip of the gas introduction pipe 35 to the center of the ionization region 24 is set to A, and the representative minimum value of the distance from the introduction port to the inner wall surface of the ionization chamber 11 is set. If B, then A <B. Note that even if only a small part of the inner wall surface of the ionization chamber 11 is close to the tip introduction port of the gas introduction pipe 35, there is no significant influence, and in this case, the representative shortest value is meaningful. Here, the “representative shortest value” means the value of the distance of the shortest distance among the inner wall surfaces that affect the ionization chamber. With the above configuration, the influence of the inner wall surface of the ionization chamber 11 on the concentration of the sample gas in the gas phase can be greatly reduced. In addition, since the gas introduction tube 35 does not disturb the electric field of the ionization region 24 due to metal ions, normal ionization is not significantly impaired. As a result, the measured signal quantity indicates the original concentration of the sample gas.
[0040]
Since the arrangement of the gas introduction pipe 35 is configured to satisfy the above conditions in the ion source by ion attachment ionization of the mass spectrometer, the influence of the inner wall surface of the ionization chamber 11 is greatly reduced, and the mass analysis of the gas having adsorptivity is high. Accurate mass spectrometry can be performed.
[0041]
A second embodiment of the present invention will be described with reference to FIG. In FIG. 2, elements that are substantially the same as those described in FIG. In the second embodiment, the gas introduction device 14 described above is separated into two parts, a sample gas introduction device 14A and a three-body gas introduction device 14B, and attached to the ionization chamber 11, respectively.
[0042]
The sample gas introduction device 14 </ b> A is provided in the ionization chamber ceiling above the ionization region 24. The sample gas introduction device 14 </ b> A includes a sample gas cylinder 31, a sample gas variable flow valve 33, and a sample gas gas introduction pipe 41. The gas introduction pipe 41 for the sample gas is disposed so as to penetrate the ceiling portion and to extend substantially straight downward from the ceiling portion. The tip of the sample gas gas introduction pipe 41 is located near the center of the ionization region 24. The distance between the tip of the sample gas introduction pipe 41 and the center of the ionization region 24 is set to A. The distance between the tip of the sample gas gas introduction pipe 41 and the inner wall surface of the ceiling of the ionization chamber 11 is set to B. Reference numeral 42 denotes a blow-out jet flow using a sample gas.
[0043]
The three-body gas introduction device 14 </ b> B is provided on the ionization chamber wall on the left side of the ionization region 24. The three-body gas introduction device 14 </ b> B includes a three-body gas cylinder 32, a three-body gas variable flow valve 34, and a three-body gas gas introduction pipe 43. The three-body gas introduction pipe 43 passes through the left wall and is disposed so as to reach the left side of the repeller 44. The tip of the three-body gas introduction pipe 43 is located on the left side of the repeller 44. Reference numeral 45 denotes a blow-out jet flow using a three-body gas. The repeller 44 has a mesh shape.
[0044]
In the present embodiment, the sample gas and the three-body gas are separately introduced, the sample gas gas introduction pipe 41 is provided in a direction perpendicular to the horizontal central axis of the ionization chamber 11, and the three-body gas gas introduction pipe 43 is provided. It is provided on the shaft. Other configurations are the same as those of the first embodiment.
[0045]
As the gas flow rate, the three-body gas is overwhelmingly larger than the sample gas. Therefore, the influence of the jet jet flow 42 due to the sample gas is small, and the state of the metal ion flow in the ionization region 24 based on the metal ions emitted from the ion emitter 21 is the same as the conventional one. Further, in the second embodiment, since the tip introduction port of the gas introduction pipe 41 for sample gas is closer to the center of the ionization region 24 than in the first embodiment, the value of A / B is smaller. Yes. Therefore, more accurate measurement can be performed.
[0046]
Next, a third embodiment of the present invention will be described with reference to FIG. Also in this embodiment, similarly to the second embodiment, the sample gas introduction device 14A and the three-body gas introduction device 14B are separated and provided in the ionization chamber 11. The sample gas introduction device 14 </ b> A is provided on the ceiling portion of the ionization chamber 11, and the three-body gas introduction device 14 </ b> B is provided on the left wall portion of the ionization chamber 11. 3, elements that are substantially the same as those described in FIG. 2 are given the same reference numerals, and descriptions thereof are omitted.
[0047]
In FIG. 3, a gas introduction pipe 46 is directly provided in the sample gas cylinder 31. The front part of the gas introduction pipe 46 penetrates the ceiling part of the ionization chamber 11 and is disposed at a position slightly protruding into the ionization chamber. A minute hole 46 a is formed at the tip of the gas introduction pipe 46. From the minute hole (or minute aperture) 46 a at the front end of the gas introduction pipe 46, a blow-out jet flow 42 is generated toward the center of the ionization region 24. This jet stream 42 has a relatively long length. Further, an exhaust pipe 48 provided with a variable flow valve 47 is provided on the lower wall of the ionization chamber 11 at a position substantially below the sample gas introduction device 14A. The outlet of the exhaust pipe 48 is connected to the exhaust port 12a.
[0048]
In the present embodiment, the sample gas variable flow valve is not specially provided. Therefore, the inside of the sample gas gas introduction pipe 46 has the same high pressure as the inside of the sample gas cylinder 31. Due to this high pressure, the sample gas passes through the micro holes 46 a and blows out vigorously into the ionization chamber 11. For this reason, the jet stream 42 by the sample gas is longer than the jet stream of the second embodiment. Therefore, the number of times the sample gas collides with another gas (referred to as M) before reaching the center of the ionization region 24 from the inlet at the tip of the gas inlet tube 46 is considerably reduced. In contrast, the number of collisions with other gases (assumed to be N) before reaching the representative minimum value of the distance from the tip inlet to the inner wall surface of the ionization chamber 11 is substantially the same as in the second embodiment. is there. For this reason, in the present embodiment, A> B for lengths A and B, but M <N for M and N for the number of collisions.
[0049]
According to the configuration of the third embodiment, the influence of the inner wall surface on the concentration in the gas phase state in the ionization chamber 11 can be greatly reduced. Since it is further away from the normal ionization, the normal ionization is hardly impaired. Therefore, more accurate measurement can be performed.
[0050]
If M and N are defined more precisely, M is a value obtained by dividing the distance from the tip inlet of the sample gas introduction pipe 46 to the center of the ionization region 14 by the mean free path of the sample gas therebetween, N is a value obtained by dividing the representative shortest value of the distance from the tip inlet of the sample gas introduction tube 46 to the inner wall surface of the ionization chamber 11 by the mean free path of the sample gas during that time.
[0051]
Next, a fourth embodiment of the present invention will be described with reference to FIG. The fourth embodiment is a modification of the third embodiment. In FIG. 4, elements that are substantially the same as the elements described in the above embodiments are assigned the same reference numerals. In this embodiment, the configuration of the sample gas introduction device 14A is partially changed. In this embodiment, the gas introduction pipe 51 attached to the ceiling portion of the ionization chamber 11 is formed as a double reciprocating pipe composed of an outer pipe 51a and an inner pipe 51b. The lower end inlet of the inner tube 51b is provided in the vicinity of the inlet of the outer tube 51a. A micro hole 51 c is formed at the tip of the outer tube 51 a of the gas introduction tube 51. Other configurations are the same as those of the third embodiment.
[0052]
In the present embodiment, the gas introduction pipe 51 for the sample gas is a double reciprocating pipe. Therefore, the sample gas supplied from the sample gas cylinder 31 flows in from the inner tube 51b of the sample gas gas introduction tube 51, and further flows out of the minute hole 51c at the tip of the outer tube 51a. Part of the sample gas exiting from the tip opening of the inner tube 51b is folded and discharged to the outside through the outer tube 51a, and the rest is ionized in the ionization chamber 11 through the micro hole 51c at the tip of the outer tube 51a. Introduced in region 24.
[0053]
According to the configuration of each of the above-described embodiments, only the sample gas that is actually introduced into the ionization chamber 11 flows through the sample gas gas introduction pipe (35, 41, 46). The sample gas flow was relatively very slow. Therefore, it takes a very long time to achieve adsorption equilibrium on the inner wall of the gas introduction pipe, and the amount of sample gas introduced into the ionization chamber 11 itself is likely to deviate from the original value. However, in the case of the present embodiment, the sample gas flows many times as much as the sample gas actually introduced into the ionization chamber 11, so that the flow of the sample gas is fast and the adsorption on the inner wall of the gas introduction pipe 51 is not performed. Achieved in a short time.
[0054]
A fifth embodiment of the present invention will be described with reference to FIG. This embodiment is also a modification of the third embodiment. In FIG. 5, elements that are substantially the same as those described in the above-described embodiments are assigned the same reference numerals. This gas introduction device is configured to be separated into a sample gas introduction device 14A and a three-body gas introduction device 14B. A gas introduction pipe is provided for the sample gas cylinder 31, and the gas introduction pipe 52 is a ring-shaped gas introduction pipe provided in the ionization chamber 11. The ring-shaped gas introduction pipe 52 has a circular ring shape that surrounds the axis around the ionization region 24 inside the ionization chamber 11. The central axis of the ring-shaped gas introduction pipe 52 coincides with the horizontal central axis of the ionization chamber 11. The sample gas cylinder 31 and the ring-shaped gas introduction pipe 52 are connected by an inflow pipe 53. The sample gas discharged from the sample gas cylinder 31 is introduced into the ring-shaped gas introduction pipe 52 via the inflow pipe 53. Further, on the inner peripheral surface of the ring-shaped gas introduction pipe 52, a plurality of gas blowing micro holes 52a for jetting the sample gas to the ionization region 24 are formed in a suitable balance with an appropriate positional relationship. The ring-shaped gas introduction pipe 52 is provided with an outflow pipe 54 for discharging a part of the sample gas supplied from the sample gas cylinder 31 to the outside. The jet gas flow 55 ejected from the minute holes 52a is relatively long. Other configurations are the same as those described in the above-described embodiment.
[0055]
According to the present embodiment, since the ring-shaped gas introduction pipe 52 is provided, the portion facing the ionization region 24 by metal ions is ring-shaped (axial symmetry), so that ionization by metal ions that are originally axially symmetric is performed. The influence of the electric field on the region 24 is very small. Since the sample gas is introduced from the periphery of the ionization region 24, the sample gas is introduced in a well-balanced manner and satisfies the conditions of the third embodiment described with reference to FIG. In addition, in terms of action and effect, it also has the characteristics described in the fourth embodiment.
[0056]
Next, a sixth embodiment of the present invention will be described with reference to FIG. In this embodiment, there is provided a gas introduction device 61 that applies the configuration of the ring-shaped gas introduction pipe according to the fifth embodiment and is formed by combining a sample gas introduction device and a three-body gas introduction device. The gas introduction device 61 is basically the same as that described in the first embodiment. The gas introduction device 61 is disposed above the ionization chamber 11, and the gas introduction pipe 62 is provided inside the ionization chamber 11 through the ceiling by an inflow pipe 63. As the ring-shaped gas introduction pipe 62, a ring-shaped gas introduction pipe having a small diameter is provided around the ionization region 24. A plurality of minute holes 62 a for ejecting the sample gas are formed on the inner peripheral surface of the ring-shaped gas introduction pipe 62. The above-described outflow pipe 54 is not provided in the ring-shaped gas introduction pipe 62. A required voltage is applied to the ring-shaped gas introduction pipe 62 via a wiring 65 by a power source 64, and a required potential is set. Thereby, the ring-shaped gas introduction pipe 62 has a function as a focusing lens. The inflow pipe 63 is provided with an insulating portion 66.
[0057]
In the present embodiment, the gas introduction tube is formed as a ring-shaped tube. This can be considered that the leading end of the introduction tube is formed in a ring shape. The ring-shaped gas introduction pipe 62 is installed closer to the ionization region 24 that is made based on the metal ions emitted from the ion emitter 21. As a result, the sample gas introduction system having the same normal structure as that of the first embodiment can be used. However, although it is axially symmetric based on the ring shape, the influence of the electric field on the ionization region 24 due to metal ions becomes large. Providing positive functions such as effects. The ring-shaped gas introduction pipe 62 also serves as a focusing lens.
[0058]
Further, a seventh embodiment of the present invention will be described with reference to FIG. In this embodiment, the sample gas introduction device 14A and the three-body gas introduction device 14B are separated. The seventh embodiment is a modification of the second embodiment described with reference to FIG. In FIG. 7, elements that are substantially the same as those described in the second embodiment are denoted by the same reference numerals. For example, a cylindrical mesh member 71 is provided at the tip of the gas introduction pipe 41 in the sample gas introduction apparatus 14 </ b> A so as to surround the ionization region 24. The central axis of the cylindrical mesh member 71 coincides with the horizontal central axis of the ionization chamber 11. Cylindrical mesh member 71 is installed such that the distal end inlet of gas inlet tube 41 is disposed outside thereof, and ionization region 24 by metal ions is positioned on the axis thereof. A required voltage is applied to the cylindrical mesh member 41 through a wiring 65 by a power source 64.
[0059]
In the present embodiment, the sample gas ejected from the tip introduction port of the gas introduction tube 41 can pass through the cylindrical mesh member 71 and reach the ionization region 24. Although the electric field is disturbed by the tip inlet of the gas introduction pipe 41 outside the cylindrical mesh member 71, the cylindrical mesh member 71 is installed so as to satisfy the axial symmetry condition. Then, the electric field is axisymmetric. Furthermore, since the required electric potential is set to the cylindrical mesh member 71, the cylindrical mesh member 71 also serves as a focusing lens.
[0060]
Since the mesh member 71 has a large number of small holes (openings), the surface area is smaller than that of a normal (no opening) plate. Therefore, the cylindrical mesh member 71 can reduce the influence of the inner wall surface as compared with the above-described ring-shaped gas introduction pipe, and more accurate measurement is performed.
[0061]
In addition, the board | plate material which has many holes can also be used instead of a mesh member, and the board | plate material which has a hole only near blowing can be used. In the case where it does not also serve as a focusing lens, the potential of the cylindrical mesh member 71 can be kept at the potential of the inner wall of the ionization chamber 11 (normal ground potential).
[0062]
In each of the above embodiments, the pressure of the ionization chamber 11 is preferably 100 Pa. However, the range in which the mean free path in the ionization chamber 11 is sufficiently shorter than the dimensions of the ionization chamber and the confinement effect of the sample gas appears, that is, 1 Pa or more. If it is okay. However, 10 Pa to 1000 Pa is desirable from the request of the ion attachment ionization method. The sample gas is directly introduced from the sample gas cylinder, but the sample itself may be solid or liquid as long as it is gasified by some means and the gas is analyzed. In addition, this apparatus may be connected to another component separation apparatus such as a gas chromatograph or a liquid chromatograph to form a gas chromatograph / mass spectrometer (GC / MS) or a liquid chromatograph / mass spectrometer (LC / MS). it can. The ion emitter is a linear heater with a spherical alkali metal salt attached, but various shapes and structures, such as a thin metal film coated on the heater, a hot plate instead of the heater, etc. Can be.
[0063]
As a metal ion to adhere, Li⁺As an alkali metal ion, K⁺, Na⁺, Rb⁺, Cs⁺Al as other metal ions⁺, Ga⁺, In⁺Etc. can also be used. As the mass analysis mechanism, any of a quadrupole mass spectrometer, an ion trap (three-dimensional) mass spectrometer, a magnetic sector sector mass spectrometer, a TOF (time-of-flight) mass spectrometer, and the like can be used.
[0064]
【The invention's effect】
As is apparent from the above description, according to the present invention, mass spectrometry can be performed with high accuracy even if an adsorptive gas is used as a sample gas in a mass spectrometer using an ion attachment ionization method as an ion source. Can do.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a first embodiment of a mass spectrometer according to the present invention.
FIG. 2 is a schematic configuration diagram of a second embodiment of a mass spectrometer according to the present invention.
FIG. 3 is a schematic configuration diagram of a third embodiment of a mass spectrometer according to the present invention.
FIG. 4 is a schematic configuration diagram of a fourth embodiment of a mass spectrometer according to the present invention.
FIG. 5 is a schematic configuration diagram of a fifth embodiment of a mass spectrometer according to the present invention.
FIG. 6 is a schematic configuration diagram of a sixth embodiment of a mass spectrometer according to the present invention.
FIG. 7 is a schematic configuration diagram of a seventh embodiment of a mass spectrometer according to the present invention.
FIG. 8 is a schematic configuration diagram of a conventional mass spectrometer equipped with an ion source based on ion attachment ionization.
FIG. 9 is a schematic configuration diagram of another conventional mass spectrometer provided with an ion source by an ion attachment ionization method.
[Explanation of symbols]
11 Ionization room
12 Differential exhaust chamber
13 Analysis room
14 Gas introduction device
14A Sample gas introduction device
14B Three-body gas introduction device
21 Ion emitter
22 Heater
23 Repeller
31 Sample gas cylinder
32 Three-body gas cylinder
35 Gas introduction pipe
36 Outlet jet flow

Claims (7)

An ionization chamber in which an ionization region for ionizing a sample gas having adsorptivity is formed, and an analysis chamber in which ions of the sample gas ionized in the ionization region are mass-separated by an electromagnetic field,
Wherein the sample gas is introduced into the ionization chamber through the gas inlet tube, the metal ions emitted from the ion emitter in the ionizing region of the ionization chamber can be attached to the sample gas is ionized, and the ionization chamber In a mass spectrometer that passes through an aperture provided between the analysis chamber and then performs mass separation by an electromagnetic field in the analysis chamber,
In the ionization chamber,
The ion emitter for releasing metal ions;
A repeller that is arranged behind the ion emitter with respect to the position of the aperture and moves metal ions in the direction of the analysis chamber by electric repulsion;
The gas introduction pipe provided so that the sample gas can be introduced between the aperture and the ion emitter, and
The gas introduction tube is disposed so as to protrude into the ionization chamber so that a tip introduction port of the gas introduction tube is located between the aperture and the ion emitter, and the sample gas is disposed on a horizontal central axis. In contrast, it is introduced obliquely or vertically.
The position of the tip inlet of the gas inlet tube is such that the distance from the tip inlet to the center of the ionization region is shorter than the typical minimum value of the distance from the tip inlet to the inner wall of the ionization chamber. The mass spectrometer is provided as described above. Mass spectrometer according to claim 1, characterized in that a value between 10~1000Pa the pressure in the ionization chamber. The gas introduction tube is formed of a double reciprocating tube, and the sample gas flows in from the end of one tube, turns back at the tip, flows out from the other tube, and from the tip introduction port of the gas introduction tube The mass spectrometer according to claim 1 or 2 , wherein a part of the sample gas is introduced into the ionization chamber. The mass according to any one of claims 1 to 3 , wherein a tip shape of the gas introduction tube is axisymmetric, and the ionization region is located on an axis of the tip shape. Analysis equipment. The mass spectrometer according to claim 4, wherein a potential is set at a distal end portion of the gas introduction pipe. An axially symmetric mesh plate or a plate with an opening is provided on the outside so that the tip introduction port of the gas introduction pipe is located and the ionization region is located on the axis. the mass spectrometer according to any one of 1 to 3. The mass spectrometer according to claim 6, wherein an electric potential is set on the mesh plate or the plate with the opening.

Images