阅读说明：本技术 离子化装置和质谱分析装置 (Ionization device and mass spectrometer ) 是由 西口克 于 2018-02-06 设计创作，主要内容包括：一种离子化装置(1)以及具备该离子化装置(1)的质谱分析装置(60),其中,该离子化装置(1)包括：离子化室(10)；试样气体导入口(14),其设于离子化室(10),用于导入试样气体；电子束释放部(11),其用于朝向离子化室(10)释放电子束；电子束通过口(10a、10b),其形成于离子化室(10)的壁面的、供从电子束释放部(11)释放的电子束通过的路径上,该电子束通过口的在该路径的方向上的长度比与该方向正交的截面的宽度长；以及离子出口(10c),其设于离子化室(10),用于将通过照射电子束而生成的试样气体的离子释放。(An ionization device (1) and a mass spectrometer (60) provided with the ionization device (1), wherein the ionization device (1) comprises: an ionization chamber (10); a sample gas inlet (14) provided in the ionization chamber (10) and used for introducing a sample gas; an electron beam discharge section (11) for discharging an electron beam toward the ionization chamber (10); electron beam passage openings (10a, 10b) formed in a path of a wall surface of the ionization chamber (10) through which the electron beam emitted from the electron beam emitting section (11) passes, the length of the electron beam passage opening in the direction of the path being longer than the width of a cross section orthogonal to the direction; and an ion outlet (10c) provided in the ionization chamber (10) and configured to discharge ions of the sample gas generated by the irradiation of the electron beam.)

1. An ionization apparatus, comprising:

a) an ionization chamber;

b) a sample gas inlet provided in the ionization chamber and configured to introduce a sample gas;

c) an electron beam discharge section that discharges an electron beam toward the ionization chamber;

d) an electron beam passage opening formed in a path of the wall surface of the ionization chamber through which the electron beam emitted from the electron beam emitting portion passes, the length of the electron beam passage opening in a direction of the path being longer than a width of a cross section orthogonal to the direction; and

e) and an ion outlet provided in the ionization chamber, for releasing ions of the sample gas generated by irradiation of the electron beam.

2. The ionization apparatus according to claim 1,

the two electron beam passage ports are formed symmetrically with respect to the center of the internal space of the ionization chamber.

3. The ionization apparatus according to claim 1,

a repeller electrode for forming a pushing electric field that pushes ions in a direction toward the ion outlet is also included inside the ionization chamber.

4. A mass spectrometry device characterized in that,

the mass spectrometry device comprises:

the ionization apparatus of claim 1;

a mass separation section for separating ions generated by the ionization device according to a predetermined mass-to-charge ratio; and

a detector for detecting ions exited by the ion separation section.

5. A mass spectrometry apparatus, comprising:

the ionization apparatus of claim 1;

a quadrupole mass filter for separating ions generated by the ionization device according to mass-to-charge ratio; and

a detector for detecting ions separated by the quadrupole mass filter.

6. A mass spectrometry apparatus, comprising:

the ionization apparatus of claim 1;

a front-end quadrupole mass filter for separating ions generated by the ionization device according to mass-to-charge ratio;

an ion dissociation unit for dissociating the ions selected by the front-stage quadrupole mass filter;

a rear stage quadrupole mass filter for separating product ions generated by dissociation in the ion dissociation section according to a mass-to-charge ratio; and

a detector for detecting ions separated by the posterior quadrupole mass filter.

7. A mass spectrometry apparatus, comprising:

the ionization apparatus of claim 1;

a time-of-flight mass separation unit of an orthogonal acceleration system for separating ions generated by the ionization device according to a mass-to-charge ratio; and

a detector for detecting ions exiting from the time-of-flight mass separation section.

8. A mass spectrometry apparatus, comprising:

the ionization apparatus of claim 1;

a quadrupole mass filter for separating ions generated by the ionization device according to mass-to-charge ratio;

an ion dissociation unit for dissociating the ions selected by the quadrupole mass filter;

a time-of-flight mass separation unit of an orthogonal acceleration system for separating product ions generated by dissociation in the ion dissociation unit according to a mass-to-charge ratio; and

a detector for detecting ions exiting from the time-of-flight mass separation section.

9. A mass spectrometry apparatus, comprising:

the ionization apparatus of claim 1;

a double-focusing type mass separation section that separates ions generated by the ionization device according to a mass-to-charge ratio by a sector magnetic field and a sector electric field; and

a detector for detecting ions exited by the dual focusing mass separation section.

Technical Field

The present invention relates to an Ionization apparatus for ionizing a sample gas, and more particularly, to an Ionization apparatus for ionizing a sample gas by an Electron Ionization (EI) method, a Chemical Ionization (CI) method, or a Negative Chemical Ionization (NCI) method. The present invention also relates to a mass spectrometer equipped with such an ionization device.

Background

In a mass spectrometer that ionizes a sample gas and analyzes the sample gas, such as a gas chromatograph-mass spectrometer (GC-MS), an ionizer that ionizes the sample gas by an electron ionization method, a chemical ionization method, or a negative chemical ionization method is used. In the electron ionization method, a sample gas is introduced into an ionization chamber and an electron beam is irradiated to ionize molecules in the sample gas (for example, patent document 1). In the chemical ionization method, a reactive gas is introduced into an ionization chamber together with a sample gas, and molecules in the reactive gas are ionized by irradiating the chamber with an electron beam, and the molecules in the sample gas are ionized by reacting the ions with the molecules in the sample gas. Negative chemical ionization has various ionization mechanisms, such as the generation of negative ions by the trapping of thermal electrons by molecules in the sample gas. The generated ions are transported to a mass separation unit such as a quadrupole mass filter, separated according to the mass-to-charge ratio, and detected.

Fig. 1 shows a schematic configuration of a conventional ionization apparatus 100 for ionizing a sample gas by an electron ionization method. In the ionization apparatus 100, a sample gas is introduced into an ionization chamber 110 disposed in a vacuum-exhausted chamber (not shown) and ionized. The ionization chamber 110 has a box shape formed by combining plate members. Two filaments 111 and 112 are disposed outside the ionization chamber 110 with the ionization chamber 110 interposed therebetween. In use, a predetermined current is supplied to one filament 111 to generate thermionic electrons, which are released toward the other filament 112. Electron beam passing openings 110a and 110b are formed in an electron beam path connecting the filaments 111 and 112 on the wall surface of the ionization chamber 110. An ion outlet 110c is formed in the other wall surface of the ionization chamber 110, and an ion transport optical system 120 for converging ions extracted from the ionization chamber 110 and transporting the ions to a mass separation unit or the like is disposed outside the ion outlet. A repeller electrode 113 is disposed in the ionization chamber 110, and when a dc voltage having the same polarity as that of the ions to be measured is applied to the repeller electrode 113, an electric field is formed in the ionization chamber 110 so as to push the ions toward the ion outlet 110c, thereby releasing the ions from the ionization chamber 110.

Disclosure of Invention

Problems to be solved by the invention

In a mass spectrometer, it is required to improve measurement sensitivity. Since the electron ionization method is a method of generating ions by irradiating molecules in the sample gas present in the ionization chamber 110 with an electron beam, it is conceivable to increase the number density of molecules in the sample gas in the ionization chamber 110 to increase the amount of ions generated in order to increase the measurement sensitivity.

Since the sample gas introduced into the ionization chamber 110 flows out from the electron beam passage openings 110a and 110b or the ion outlet 110c, the number density of molecules in the ionization chamber 110 can be increased by reducing the size of the openings. However, since the incidence amount of the electron beam to the ionization chamber 110 decreases when the electron beam passage openings 110a and 110b are narrowed, the amount of ions generated does not increase as a result even if the number density of molecules of the sample gas in the ionization chamber 110 increases. Further, when the ion outlet 110c is narrowed, the amount of the sample gas flowing out of the ionization chamber 110 is reduced, the number density of molecules in the ionization chamber 110 is increased, and the amount of ions generated is increased, but the amount of ions released from the ionization chamber 110 is reduced, and thus the measurement sensitivity is not improved. That is, even if the electron beam passage openings 110a and 110b or the ion exit 110c are narrowed to increase the number density of molecules in the ionization chamber 110, it is difficult to increase the measurement sensitivity.

Here, the case of using an ionization apparatus using an electron ionization method is described as an example, but the same applies to an ionization apparatus using a chemical ionization method for ionizing a sample gas by using an electron beam as in the electron ionization method, or a negative chemical ionization method.

An object of the present invention is to provide an ionization device capable of improving the measurement sensitivity of ions generated from a sample gas. Further, a mass spectrometer provided with such an ionization device is provided.

Means for solving the problems

An ionization device according to the present invention, which has been made to solve the above problems, includes:

a) an ionization chamber;

b) a sample gas inlet provided in the ionization chamber and configured to introduce a sample gas;

c) an electron beam discharge section that discharges an electron beam toward the ionization chamber;

d) an electron beam passage opening formed in a path of the wall surface of the ionization chamber through which the electron beam emitted from the electron beam emitting portion passes, the length of the electron beam passage opening in a direction of the path being longer than a width of a cross section orthogonal to the direction; and

e) and an ion outlet provided in the ionization chamber, for releasing ions of the sample gas generated by irradiation of the electron beam.

The cross-sectional shape of the electron beam passage opening is, for example, circular, and in this case, the width is defined by a diameter. However, in the present invention, the electron beam passage opening is not limited to a circular shape, and may be an elliptical shape or a polygonal shape. For example, in the case where the electron beam emitting portion has a filament that is long in a direction orthogonal to the emission direction of the electron beam, it is desirable to form the electron beam passage opening in a rectangular or elliptical shape that is long in the direction because the electron beam having a long cross section in the direction is generated. As will be described later, based on the technical idea of reducing the molecular flow conductivity of the electron beam passage opening, when the cross section of the electron beam passage opening is a shape other than a circle (an ellipse, a rectangle, or the like) as described above, the width is defined by the length corresponding to the diameter of a circle having the same cross section.

The ionization device of the present invention has the following features: an electron beam passage opening provided in an ionization chamber of the ionization apparatus has a length in a direction in which an electron beam passes, which is longer than a width of a cross section orthogonal to the direction. An ionization chamber used in a conventional ionization apparatus is formed by combining a plate-shaped member having a thickness of, for example, 1mm or less, and an electron beam passage opening formed in the plate-shaped member having a diameter of, for example, about 3 mm. That is, in the conventional ionization apparatus, the length of the electron beam passage opening formed in the ionization chamber in the direction in which the electron beam passes is shorter than the width of the cross section orthogonal to the direction. In contrast, in the ionization apparatus of the present invention, for example, a plate-shaped member having a thickness of 5mm is used, and an electron beam passage opening having a diameter of about 3mm is formed in the same manner as in the conventional apparatus. This reduces the molecular flow conductivity of the electron beam passage opening as compared with conventional ionization apparatuses, and prevents the sample gas from flowing out of the ionization chamber. As a result, the number density of molecules of the sample gas in the ionization chamber becomes high. In the ionization apparatus of the present invention, the width of the electron beam passage opening formed in the ionization chamber may be the same as that of the conventional one, and the amount of incidence of the electron beam into the ionization chamber is not reduced, so that the amount of ions generated is increased. Further, since the ion outlet is also required to be the same as in the conventional case, the amount of ions released from the ionization chamber is not reduced. Thus, the measurement sensitivity can be improved.

In the ionization apparatus of the present invention, it is preferable that the two electron beam passage openings are formed symmetrically with respect to a center of the internal space of the ionization chamber. In this way, for example, by arranging two filaments, when one of the filaments serving as the electron beam emitting portion is off, the other filament can be operated as the electron beam emitting portion, and the two electron beam passing ports are arranged at equivalent positions, so that even if the filaments are switched, an equivalent structure can be maintained.

The ionization apparatus of the present invention can be suitably used as an ionization section of a mass spectrometer.

ADVANTAGEOUS EFFECTS OF INVENTION

By using the ionization device of the present invention or the mass spectrometer equipped with the ionization device, the measurement sensitivity of ions generated from the sample gas can be improved.

Drawings

Fig. 1 is a schematic configuration diagram of a conventional ionization apparatus.

Fig. 2 is a schematic configuration diagram of an ionization apparatus according to an embodiment of the present invention.

Fig. 3 is a schematic configuration diagram of a quadrupole mass spectrometer according to an embodiment of the present invention.

Fig. 4 is a simulation result of the number density of molecules in the ionization chamber of the ionization apparatus of the present embodiment.

Fig. 5 is a mass chromatogram obtained using a gas chromatograph-mass spectrometer in which the quadrupole mass spectrometer of the present example and a gas chromatograph are combined.

Fig. 6 is an overall configuration diagram of a triple quadrupole mass spectrometer according to another embodiment of the mass spectrometer of the present invention.

Fig. 7 is an overall configuration diagram of a time-of-flight mass spectrometer of an orthogonal acceleration system as still another embodiment of the mass spectrometer of the present invention.

Fig. 8 is an overall configuration diagram of a quadrupole-time-of-flight mass spectrometer according to still another embodiment of the mass spectrometer of the present invention.

Fig. 9 is an overall configuration diagram of an electric-field magnetic-field double-focusing mass spectrometer according to still another embodiment of the mass spectrometer of the present invention.

Detailed Description

An embodiment of an ionization apparatus according to the present invention and a quadrupole mass spectrometer as an embodiment of a mass spectrometer including the ionization apparatus according to the embodiment will be described below with reference to the drawings. Fig. 2 is a main part configuration diagram of an ionization device 1 according to the present embodiment and an ion transport optical system 20 disposed at the subsequent stage thereof, and fig. 3 is a main part configuration diagram of a quadrupole mass spectrometer 60 including the ionization device 1 according to the present embodiment.

The ionization apparatus 1 of the present embodiment ionizes a sample gas introduced into an ionization chamber 10 by an electron ionization method. The ionization chamber 10 has a box shape in which plate-like members are combined. Two filaments 11, 12 having the same shape are arranged outside the ionization chamber 10 with the ionization chamber 10 interposed therebetween, and electron beam passing openings 10a, 10b are formed in an electron beam path from one filament 11 to the other filament 12 on the wall surface of the ionization chamber 10. Further, a sample gas inlet 14 is disposed on the other wall surface of the ionization chamber 10, and the sample gas is introduced into the ionization chamber 10 from the sample gas inlet 14. An ion exit 10c is formed in the other wall surface of the ionization chamber 110, and an ion transport optical system 20 for converging ions extracted from the ionization chamber 10 and transporting the ions to a mass separation unit or the like is disposed outside the ion exit. A repeller electrode 13 is disposed in the ionization chamber 10, and a dc voltage having the same polarity as that of the ions to be measured is applied from a voltage applying unit 15 to the repeller electrode 13, whereby a push electric field is formed in the ionization chamber 10 to push the ions toward the ion outlet 10c, and the ions are released from the ionization chamber 10. In the ionization apparatus 1 of the present embodiment, the two filaments 11 and 12 are disposed symmetrically with respect to the center of the internal space of the ionization chamber 10, and the two electron beam passage openings 10a and 10b are formed symmetrically with respect to the center of the internal space of the ionization chamber 10. In the ionization device 1 of the present embodiment, by disposing the filament 11 and the electron beam passage opening 10a at equivalent positions to the filament 12 and the electron beam passage opening 10b in this manner, when one filament 11 used as an electron beam emitting portion is off, the other filament 12 can be operated as an electron beam emitting portion.

In the ionization apparatus 1 of the present embodiment, plate-shaped members forming the electron beam passage openings 10a and 10b among plate-shaped members constituting the ionization chamber 10 are thicker than plate-shaped members forming other wall surfaces. The ionization device 1 of the present embodiment is characterized in that: the electron beam passage openings 10a and 10b formed in the plate-like members are arranged in the path of the electron beamSpecifically, 2 plate-shaped members having a thickness of 5mm are each formed with a through hole having a cross section of 2mm × mm, and these are used as electron beam passage openings 10a and 10b, and the cross section of the through hole such as 2mm × mm has a shape corresponding to the outer shape of the filaments 11 and 12. in the present embodiment, rectangular openings long in the longitudinal direction of the filaments 11 and 12 are formed, but in the case of using electron beam emitting portions other than the filaments 11 and 12, openings having an appropriate shape corresponding to the outer shape thereof may be used as the electron beam passage openings 10a and 10 b. in the case of the present embodiment, the cross section of the electron beam passage openings 10a and 10b has a shape other than a circular shape, the width of the electron beam passage openings 10a and 10b is defined by a length corresponding to the diameter of a circle having the same cross section area.²I.e. 2 × (8/pi)^1/2(-about 3 mm).

The quadrupole mass spectrometer 60 of the present embodiment is a so-called single quadrupole mass spectrometer, and includes the ionization device 1 and the ion transport optical system 20 shown in fig. 2, which are disposed in the chamber 50 maintained at a predetermined degree of vacuum by a vacuum pump, not shown, and the quadrupole mass filter 30 and the ion detector 40 disposed on the downstream side of the ion transport optical system 20. In fig. 3, the sample gas inlet 14 and the like are not shown, and the ionization apparatus 1 is simplified and shown. Fig. 6 to 9, which will be described later, also illustrate the ionization apparatus 1 in a simplified manner.

In the ionization device 1 included in the quadrupole mass spectrometer 60 of the present embodiment, for example, a sample gas including a sample component separated in time in a column of a gas chromatograph is introduced into the ionization chamber 10 from the sample gas inlet 14. A current is supplied from a power supply not shown to one filament 11 serving as an electron beam emitting portion, thereby heating the filament 11 and generating thermal electrons. Thermal electrons generated by the filament 11 are accelerated toward the other filament 12 by a potential difference between the filament 11 and the other filament 12 to which a predetermined voltage is applied. That is, the electron beam is discharged from one filament 11 as an electron beam discharge portion toward the other filament 12. Molecules in the sample gas introduced into the ionization chamber 10 are ionized by contacting the thermal electrons. The generated ions are released from the ion exit 10c by an electric field formed in the ionization chamber 10 by applying a dc voltage having the same polarity as that of the analysis target from the voltage applying unit 15 to the repeller electrode 13, and are introduced into the ion transport optical system 20.

The ion transport optical system 20 is constituted by a plurality of ring-shaped electrodes. By applying a dc voltage and/or a radio frequency voltage of an appropriate polarity and magnitude to each of the plurality of ring electrodes, ions are converged near the ion optical axis C and are transported to the quadrupole mass filter 30 disposed at the subsequent stage. The quadrupole mass filter 30 consists of 4 rod electrodes. By applying dc voltages and/or high-frequency voltages of appropriate polarity and magnitude to the 4 rod electrodes, ions having a predetermined mass-to-charge ratio are screened from other ions, reach an ion detector 40 disposed at a subsequent stage, and are detected. In the quadrupole mass spectrometer 60 of the present embodiment, MS scan measurement can be performed by scanning the predetermined mass-to-charge ratio, and Selective Ion Monitoring (SIM) measurement can be performed by fixing the predetermined mass-to-charge ratio.

As described above, the ionization device 1 of the present embodiment has a characteristic structure in that the length of the electron beam passage openings 10a and 10b in the direction of the path of the electron beam is longer than the width of the cross section orthogonal to the direction. With respect to this aspect, it will be explained in detail.

In a conventional ionization apparatus, in order to reduce the weight of the apparatus, an ionization chamber is configured by combining thin plate-shaped members (for example, having a thickness of 0.5mm), and two openings having a diameter of, for example, about 3mm are formed in a path of an electron beam, and these openings are used as electron beam passage openings.

In contrast, in the ionization apparatus 1 of the present embodiment, based on the technical idea of increasing the number density of molecules in the ionization chamber 10 and increasing the amount of ions generated to improve the measurement sensitivity, a plate-shaped member having a thickness of 5mm is used for the 2 plate-shaped members facing the filaments 11 and 12, and as described above, through holes having a rectangular cross section of 2mm × 4mm are formed and these are used as the electron beam passage openings 10a and 10 b.

In the case where the ionization apparatus 1 is disposed in the chamber 50 maintained in vacuum like the quadrupole mass spectrometer 60 of the present embodiment, the mean free path of molecules in the ionization chamber 10 is long, and therefore the sample gas flow becomes a molecular flow. The electron beam passage openings 10a and 10b of the ionization apparatus 1 of the present embodiment have a rectangular cross section, but are made approximately circular for ease of explanation. The conductivity of the circular tube in the molecular flow region is proportional to the 3 rd power of the radius of the cross section of the electron beam passage ports 10a and 10b, and inversely proportional to the length of the tube. In the ionization apparatus 1 of the present embodiment, the length (5mm) of the electron beam passage openings 10a and 10b is 10 times the length (0.5mm) of the electron beam passage openings of the conventional ionization apparatus, and therefore the conductivity is suppressed to 1/10. This improves the number density of molecules in the ionization chamber 10 compared to the conventional case.

In addition, considering only the reduction of the conductivity, the method of reducing the inner diameters of the electron beam passage openings is more efficient than the method of lengthening the electron beam passage openings. However, since the incidence amount of the electron beam to the ionization chamber is reduced by reducing the inner diameter of the electron beam passage opening, the amount of ions generated does not increase even if the number density of molecules of the sample gas in the ionization chamber is increased.

Alternatively, it is also considered to increase the number density of molecules in the ionization chamber by increasing the conductivity of the ion outlet or by decreasing the inner diameter. However, in this case, the amount of ions released from the ionization chamber also decreases, and therefore the measurement sensitivity does not increase.

In the ionization apparatus 1 of the present embodiment, the inner diameters of the electron beam passage openings 10a and 10b formed in the ionization chamber 10 are substantially the same as those of the electron beam passage openings of the conventional ionization apparatus, and the amount of incidence of the electron beam into the ionization chamber 10 is not reduced, so that the amount of ions generated is increased. Since the ion outlet 10c is also required as in the conventional case, the amount of ions released from the ionization chamber 10 is not reduced. Therefore, the measurement sensitivity of ions can be improved.

In the ionization apparatus 1 of the present embodiment, the present inventors set the length based on the length of the inner diameter of the electron beam passage openings 10a and 10b as a length that can obtain an effect of increasing the amount of ions generated and improving the measurement sensitivity. This is because the length of the electron beam passage openings 10a and 10b is equal to or greater than the inner diameter thereof, and thus the electron beam passage openings that are openings having substantially no thickness in the conventional ionization apparatus are regarded as tubes having wall surfaces along the traveling direction, such as circular tubes. By forming the electron beam passing openings 10a and 10b so as to satisfy the requirements, the number density of molecules of the sample gas in the ionization chamber 10 can be increased, the amount of ion generation can be increased, and the measurement sensitivity can be improved.

Next, a simulation for confirming the effect obtained by using the ionization device of the present embodiment will be described. In this simulation, the number density of molecules on the path (y-axis) of the electron beam in the ionization chamber was determined for each of the ionization apparatus of this example and the conventional ionization apparatus (comparative example). As described above, since the ionization apparatus of the present embodiment is used in a vacuum environment, the sample gas flows as a molecular stream, and thus the direct simulation Monte Carlo (DSMC: direct simulation Monte Carlo) method is used as a simulation (for example, patent document 2).

In both the ionization device of the present embodiment and the ionization device of the comparative example, the sectional shapes of the electron beam entrance port and the electron beam exit port were set to be rectangles of 2mm × 4mm, and their lengths were set to be 5mm in the present embodiment and 0.5mm in the comparative example. Further, the sample gas flow is introduced from the center of the one side surface parallel to the path of the electron beam, and the point of intersection of the path of the electron beam and the introduction direction of the sample gas flow is the origin.

FIG. 4 shows the results of the simulation, and it is found that the molecular number density of the sample gas in the path of the electron beam in the comparative example is about 2.0 × 10²⁰Per m³In contrast, in the present example, the molecular number density of the sample gas in the path of the electron beam was increased to about 2.5 × 10²⁰Per m³。

In addition, the experimental results for confirming the effects obtained by using the ionization device of the present example will be described. In this experiment, the same standard sample was introduced into each gas chromatograph-mass spectrometer obtained by combining a gas chromatograph in the front stage of each of the quadrupole mass spectrometer having the configuration described with reference to fig. 3 and the quadrupole mass spectrometer having the conventional ionizer (comparative example), and Selective Ion Monitoring (SIM) was performed on a sample component contained in the standard sample and having a retention time of about 3.95 min.

The mass chromatogram obtained from the above experiment is shown in fig. 5. It was found that the detection intensity of ions (arbitrary unit common to the present example and the comparative example) in the mass chromatogram was about 14,000 in the comparative example, whereas the detection intensity of ions was large, about 21,000 in the present example, and the measurement sensitivity of ions was improved by about 5 times compared to the conventional one.

The above embodiments are examples, and can be modified as appropriate according to the spirit of the present invention.

In the above embodiment, the two filaments 11 and 12 are arranged symmetrically with respect to the center of the internal space of the ionization chamber 10, and the two electron beam passage openings 10a and 10b are formed symmetrically with respect to the center of the internal space of the ionization chamber 10. For example, only 1 filament 11 may be disposed, and only 1 ion passage opening 10a may be formed in the wall surface of the ionization chamber 10. With the ionization device of this embodiment, the conductivity of the ion passage opening 10a can be reduced compared to the conventional one, and the number density of molecules in the ionization chamber 10 can be increased compared to the conventional one.

In the above-described embodiments, the case where the sample gas is ionized by the electron ionization method has been described as an example, but the same configuration as described above is also suitably used for an ionization apparatus using a chemical ionization method for ionizing the sample gas by using an electron beam as in the electron ionization method, or a negative chemical ionization method.

In the above-described embodiment, the quadrupole mass spectrometer 60 was described, but the ionization apparatus 1 of the present embodiment can be suitably used in other types of mass spectrometers. Such an example will be described with reference to fig. 6 to 9.

Fig. 6 is an overall configuration diagram of a so-called triple quadrupole mass spectrometer 61 having quadrupole mass filters in front and rear through a collision cell. The triple quadrupole mass spectrometer 61 includes the ionization device 1, the ion transport optical system 20, the front quadrupole mass filter 31, the collision cell (ion dissociation unit) 33 having the multipole ion guide 32 therein, the rear quadrupole mass filter 34, and the ion detector 41 in the vacuum-exhausted chamber 51.

In the triple quadrupole mass spectrometer 61, ions generated in the ionization chamber 10 are introduced into the front quadrupole mass filter 31 via the ion transport optical system 20, and for example, only ions having a predetermined mass-to-charge ratio are introduced into the collision cell 33 as precursor ions by passing through the front quadrupole mass filter 31. A predetermined CID gas such as argon is supplied to the collision cell 33, and the precursor ions come into contact with the CID gas and are cracked by collision-induced dissociation. The various product ions generated by the cracking are introduced into the rear quadrupole mass filter 34, and only the product ions having a predetermined mass-to-charge ratio pass through the rear quadrupole mass filter 34, reach the ion detector 41, and are detected.

In addition to the MS scan measurement and the SIM measurement, the triple quadrupole mass spectrometer 61 can perform product ion scan measurement, precursor ion scan measurement, neutral loss scan measurement, and Multiple Reaction Monitoring (MRM) measurement.

Fig. 7 is an overall configuration diagram of a time-of-flight mass spectrometer 62 of the orthogonal acceleration system. The time-of-flight mass spectrometer 62 of the orthogonal acceleration system includes the ionization device 1, the ion transport optical system 20, the orthogonal acceleration unit 35, a flight space 71 including a reflector 72 in which a plurality of reflection electrodes are arranged, and the ion detector 42, in the interior of the vacuum-exhausted chamber 52.

In this time-of-flight mass spectrometer, ions generated in the ionization chamber 10 are introduced into the orthogonal acceleration unit 35 via the ion transport optical system 20. The orthogonal acceleration unit 35 causes the introduced ions to be pulsed accelerated in a direction substantially orthogonal to the traveling direction thereof at a predetermined timing, and then to be emitted into the flight space 71. The ions fly in the flight space 71, and are reflected at the reflectron 72 to reach the ion detector 42. The ions emitted from the orthogonal acceleration unit 35 have a flight speed corresponding to the mass-to-charge ratio thereof. Therefore, the ions are separated by the mass-to-charge ratio while the ions fly and reach the ion detector 42, and the ions arrive at the ion detector 42 with a time difference and are detected.

Fig. 8 is a diagram showing the entire configuration of a quadrupole-time-of-flight (q-TOF) mass spectrometer 63. The quadrupole-time-of-flight mass spectrometer 63 includes the ionization device 1, the ion transport optical system 20, the front stage quadrupole mass filter 31, the collision cell (ion dissociation unit) 33 having the multipole ion guide 32 therein, the orthogonal acceleration unit 35, the flight space 71 including the reflectron 72 in which a plurality of reflection electrodes are arranged, and the ion detector 43, in the interior of the vacuum-exhausted chamber 53.

In the quadrupole-time-of-flight mass spectrometer 63, ions generated in the ionization chamber 10 are introduced into the front stage quadrupole mass filter 31 via the ion transport optical system 20, and for example, only ions having a predetermined mass-to-charge ratio are introduced into the collision cell 33 as precursor ions by passing through the front stage quadrupole mass filter 31. In the collision cell 33, the precursor ions come into contact with a CID gas such as nitrogen gas, and are cracked by collision-induced dissociation. The product ions generated by the cleavage are introduced into the orthogonal acceleration portion 35. The orthogonal acceleration unit 35 causes the introduced product ions to be pulsed accelerated in a direction substantially orthogonal to the traveling direction thereof at a predetermined timing, and then to be emitted into the flight space 71. The product ions fly in the flight space 71, and are reflected at the reflectron 72 to reach the ion detector 43, thereby being detected.

Fig. 9 is an overall configuration diagram of the magnetic field/electric field double focusing type mass spectrometer 64. The magnetic field-electric field double focusing mass spectrometer 64 includes the ionization device 1, the ion transport optical system 20, an electric field fan 81 for forming a fan-shaped electric field, a magnetic field fan 82 for forming a fan-shaped magnetic field, and the ion detector 44 in the vacuum-exhausted chamber 54.

In the magnetic field-electric field double focusing type mass spectrometer 64, ions generated in the ionization chamber 10 are introduced into the electric field fan 81 via the ion transport optical system 20, and are introduced into the magnetic field fan 82 after correcting imbalance of kinetic energy of the ions by the fan-shaped electric field formed in the electric field fan 81. In the magnetic field sector 82, ions having a predetermined mass-to-charge ratio, for example, are screened from other ions by the sector magnetic field formed in the magnetic field sector 82, and are caused to reach the ion detector 44 and detected. In fig. 9, the ions are configured to pass through the electric field fan 81 and the magnetic field fan 82 in this order, but the ions may also be configured to pass through the magnetic field fan 82 and the electric field fan 81 in this order.

Description of the reference numerals

1 … ionization device; 10 … ionization chamber; 10a, 10b … electron beam passing port; 10c … ion outlet; 11. 12 … filament; 13 … repeller electrodes; 14 … sample gas inlet; 15 … voltage applying part; 20 … ion transport optics; 30 … quadrupole mass filter; 31 … front-stage quadrupole mass filter; a 32 … multipole ion guide; 33 … collision cell; 34 … rear segment quadrupole mass filter; 35 … orthogonal accelerator; 40-44 … ion detector; 50-54 … chambers; a 60 … quadrupole mass spectrometer; 61 … triple quadrupole mass spectrometer; 62 … time-of-flight mass spectrometry; 63 … quadrupole-time-of-flight mass spectrometer; 64 … magnetic field and electric field double focusing mass spectrometer; 71 … flight space; 72 … reflector; 81 … electric field sector; 82 … magnetic field sector.