JP2019021550A - Ionizer and mass spectroscope using the same - Google Patents

Abstract

To provide an ionizer capable of achieving high analytical sensitivity of mass spectroscope by sending out ions, generated in an ionization chamber, to the subsequent stage with a loss as small as possible, and increasing the degree of freedom in the adjustment of characteristics such as the diameter, spread angle, and the like of sent out ions.SOLUTION: An ionization chamber 10 consists of a focus pole 10c where an ion lead-out port 10d is formed, an ionization chamber body 10b constituting other five faces, and an insulating spacer 10e provided in the crevice of them. At the time of positive ion measurement, a voltage higher than that of the ionization chamber body is applied to the focus pole. A voltage lower than that of the ionization chamber body is applied to first and third lens electrodes 21, 23 constituting an ion transport optical system 2, and a voltage higher than that of the ionization chamber body is applied to a second lens electrode 22. With such an arrangement, an electrical field for pulling out the ions generated in the ionization chamber to the ion lead-out port, while focusing, is formed and the impressed voltage to each electrode can be adjusted appropriately.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ionization apparatus for ionizing sample molecules and atoms, and a mass spectrometer using the apparatus, and more specifically, an electron ionization (EI = Electron Ionization) method, a chemical ionization (CI = Chemical Ionization) method. Alternatively, the present invention relates to an ionization apparatus using a negative chemical ionization (NCI) method and a mass spectrometer using the ionization apparatus.

  In a mass spectrometer in a gas chromatograph mass spectrometer (GC-MS), in order to ionize a compound in a sample gas, an electron ionization (EI) method, a chemical ionization (CI) method, or a negative chemical ionization (NCI) method is used. Ionization methods such as are used. The compound in the sample gas introduced into the ionization chamber disposed in the vacuum chamber is ionized by an appropriate ionization method as described above. And the produced | generated ion is conveyed to mass separation parts, such as a quadrupole mass filter, is isolate | separated according to mass-to-charge ratio, and is detected. Therefore, in order to achieve high detection sensitivity in such an apparatus, it is important to improve the efficiency of transporting ions generated in the ionization chamber to the mass separation unit.

  11 and 12 are schematic configuration diagrams of a conventional ionization apparatus using the EI method (see, for example, Patent Document 1 and Non-Patent Document 1). In these ionization apparatuses, a sample gas containing a sample component is introduced into a box-shaped ionization chamber 10 made of a conductive member arranged in a chamber (not shown) maintained in a vacuum atmosphere. The ionization chamber 10 is grounded and has a ground potential (0 V). A filament 11 and a trap electrode 12 are arranged opposite to each other outside the ionization chamber 10, and the thermoelectrons generated by the filament 11 are accelerated and moved to the trap electrode 12 as indicated by a dotted arrow in the drawing. As a result, a thermionic current is formed in the ionization chamber 10. The sample component (compound) in the sample gas supplied into the ionization chamber 10 is ionized by contacting with the thermal electrons.

  In the ionization apparatus shown in FIG. 11, when a plate-like repeller electrode 13 is arranged inside the ionization chamber 10 and the ion to be measured is a positive ion, the repeller electrode 13 has a predetermined positive DC voltage ( + V1) is applied. By applying this voltage to the repeller electrode 13, an extruded electric field having a force to push ions away from the repeller electrode 13 is formed between the repeller electrode 13 and the ion outlet 10 a of the ionization chamber 10. . By the action of this electric field, ions generated in the ionization chamber 10 are pushed in the direction of the ion outlet 10a and are pushed out of the ionization chamber 10 through the ion outlet 10a. An ion transport optical system 201 composed of a plurality of annular electrodes is disposed outside the ion outlet 10a. The ion transport optical system 201 transports the ions while suppressing the spread of ions, for example, a quadrupole mass. It is introduced into a mass separator such as a filter.

  In the ionization apparatus shown in FIG. 11, ions generated in the ionization chamber 10 are taken out to the outside of the ionization chamber 10 only by the pushing electric field generated by the repeller electrode 13. In contrast, in the ionization apparatus shown in FIG. 12, the extraction electrode 200 is disposed outside the ionization chamber 10, and a predetermined DC voltage (-V2) having a polarity opposite to that of the ion to be measured is applied to the extraction electrode 200. Is done. An extraction electric field formed by applying this voltage to the extraction electrode 200 enters the ionization chamber 10 through the ion outlet 10a. The ions generated in the ionization chamber 10 are attracted by this extraction electric field, and are extracted to the outside of the ionization chamber 10 through the ion outlet 10a. Further, a combination of this extraction electric field and an extrusion electric field by the repeller electrode 13 as shown in FIG. 12 is often used.

  In FIG. 12, the extraction electrode 200 is provided between the ion transport optical system 201 and the ionization chamber 10, but the first lens electrode of the plurality of lens electrodes constituting the ion transport optical system 201 serves as the extraction electrode. Although it may be used, the basic operation is substantially the same.

Japanese Patent Laid-Open No. 2006-157523

“Agilent 5977 Series EI Source Selection Guide, Technical Overview”, Agilent Technologies, [online], [Search May 18, 2017], Internet <URL: http://cn.agilent.com /cs/library/technicaloverviews/public/5991-6551EN.pdf>

  In any of the above-described configurations, the electric field generated by the repeller electrode, the electric field extracted by the extraction electrode, or a combination of both electric fields, the ions generated in the ionization chamber are directed to the ion outlet, but the ions are transferred to the ion outlet. The focusing effect is weak or hardly. For this reason, some ions collide with the ionization chamber wall surface and the extraction electrode around the ion outlet and disappear. As a result, the utilization efficiency of the generated ions is lowered, which is one factor that hinders improvement in detection sensitivity.

  Further, in the configuration of the conventional ionization apparatus described above, there is almost no degree of freedom for adjusting the beam characteristics such as the size (diameter) and the divergence angle of the ion beam emitted from the ionization chamber. For this reason, it is difficult to form an ion beam that matches the acceptance characteristics of the ion beam in the subsequent mass separation unit, which may lead to ion loss.

  The present invention has been made to solve these problems, and the object of the present invention is to deliver ions generated in the ionization chamber to the subsequent stage with as little loss as possible. An object of the present invention is to provide an ionization apparatus capable of increasing the degree of freedom in adjusting the beam characteristics of a beam and a mass spectrometer using the apparatus.

  Note that the term “ionization device” sometimes refers only to a component that performs ionization. In this specification, the term “ionization device” refers to a component that forms an ion beam using generated ions, specifically, In the mass spectrometer, an ion transport optical system is included.

The present invention made to solve the above problems is an ionization apparatus for ionizing a sample component contained in a sample gas,
a) a focusing electrode having an ion outlet, and an ionization chamber body which is electrically insulated from the focusing electrode and forms a space substantially separated from the outside together with the focusing electrode. An ionization chamber for ionizing sample components in space and sending the generated ions to the outside through the ion outlet;
b) When the polarity of the ions is positive, a DC voltage whose potential is higher than the potential of the ionization chamber body is applied to the focusing electrode, and when the polarity of the ions is negative, the potential is applied to the focusing electrode. A focusing voltage generator that applies a DC voltage that is lower than the potential of the ionization chamber body;
It is characterized by having.

  The ionization apparatus according to the present invention performs ionization by any one of an electron ionization (EI) method, a chemical ionization (CI) method, and a negative chemical ionization (NCI) method inside the ionization chamber.

  When the ionization method in the ionization apparatus according to the present invention is, for example, the EI method, the sample component in the sample gas introduced into the ionization chamber is ionized by contacting the thermal electrons supplied into the ionization chamber. When the ions to be measured are positive ions, a predetermined DC voltage whose potential is higher than the potential of the ionization chamber body is applied from the focusing voltage application unit to the focusing electrode in which the ion outlet is formed. Generally, since the ionization chamber main body is at a ground potential, a positive DC voltage is applied to the focusing electrode.

  For example, it is generated in the ionization chamber by the action of one or both of the extrusion electric field formed by the repeller electrode disposed in the ionization chamber and the extraction electric field formed by the electrode disposed outside the ion outlet. When ions travel in the direction of the focusing electrode, the electric field formed by the focusing electrode is an electric field that repels the ions, so that the ions gather in the direction of the ion outlet. Thereby, the ions generated in the ionization chamber pass through the ion outlet efficiently without being brought into contact with the focusing electrode itself and are sent out to the outside of the ionization chamber.

In the ionization apparatus according to the present invention, preferably, the focusing electrode and the ionization chamber main body are connected to each other through a spacer made of an insulating member.
In this configuration, the gap between the focusing electrode and the ionization chamber main body is closed by the spacer, and the sealing performance of the ionization chamber is improved. Thereby, ions derived from sample components generated in the ionization chamber and buffer ions at the time of ionization by the CI method are less likely to leak out from the ionization chamber, and ion utilization efficiency and ion generation efficiency can be improved.

  In the ionization apparatus according to the present invention, it is preferable that the ionization chamber further includes a repeller electrode for forming an extruded electric field that pushes ions in the direction of the ion outlet.

  According to this configuration, the sample-derived ions generated in the ionization chamber are pushed in the direction of the ion outlet by the extrusion electric field formed by the repeller electrode. When the repeller electrode is not used, it is necessary to make the extraction electric field formed by the electrode provided outside the ionization chamber reach deep inside the ionization chamber as viewed from the ion outlet. On the other hand, by directing the ions generated in the ionization chamber using the extrusion electric field by the repeller electrode in the direction of the ion outlet, there is no need to forcibly extract ions by the extraction electric field, so the applied voltage to the electrode It becomes easy to adjust.

A first embodiment of the ionization apparatus according to the present invention is as follows.
A first lens electrode having an ion passage opening for guiding ions emitted from the ionization chamber through the ion outlet;
When the polarity of ions is positive, a DC voltage whose potential is lower than the potential of the ionization chamber body is applied to the first lens electrode, and when the polarity of ions is negative, the first lens electrode A lens voltage generator for applying a DC voltage whose potential is higher than the potential of the ionization chamber body;
Is further provided.

  In the configuration of the first embodiment, when the ion to be measured is a positive ion, a DC voltage lower than the potential of the ionization chamber body is applied to the first lens electrode. A negative DC voltage is applied. When the absolute value of the voltage applied to the first lens electrode is made larger than the absolute value of the voltage applied to the focusing electrode, the electric field formed by the first lens electrode is ionized through the ion outlet. Enter the room. With this electric field and the electric field formed by the voltage applied to the focusing electrode described above, ions generated in the ionization chamber can be efficiently extracted outside the ionization chamber through the ion outlet.

In this configuration, the focusing electrode and the first lens electrode can be connected via a spacer made of an insulating member.
According to this configuration, since the gap between the focusing electrode and the first lens electrode is closed by the spacer, the sealing performance of the ionization chamber is improved. Thereby, ions derived from sample components generated in the ionization chamber and buffer ions at the time of ionization by the CI method are less likely to leak out from the ionization chamber, and ion utilization efficiency and ion generation efficiency can be improved.

The ionization apparatus according to the second embodiment of the present invention is
Ions that are emitted from the ionization chamber through the ion outlet and are guided to the subsequent stage, each having at least three lens electrodes having first, second, and third from the ionization chamber side, each having an ion passage opening. Including ion transport optics,
When the polarity of ions is positive, the first and third lens electrodes have the same DC voltage whose potential is lower than the potential of the ionization chamber body, and the potential of the second lens electrode is the ionization chamber body. When a DC voltage that is higher than the potential is applied and the polarity of ions is negative, the same DC voltage that has a potential higher than the potential of the ionization chamber body is applied to the first and third lens electrodes. A lens voltage generator for applying a DC voltage whose potential is lower than the potential of the ionization chamber body to the second lens electrode;
Is further provided.

  Also in the configuration of this embodiment, the electric field formed by the first lens electrode enters the ionization chamber through the ion outlet. Therefore, ions generated in the ionization chamber can be efficiently extracted outside the ionization chamber through the ion outlet by the electric field and the electric field formed by the voltage applied to the focusing electrode.

  At this time, the diameter of the ion beam that passes through the ion outlet mainly depends on the voltage applied to the focusing electrode. Further, a DC voltage is applied to the second lens electrode sandwiched between the first and third lens electrodes constituting the ion transport optical system, with respect to positive ions, the potential of which is higher than the potential of the ionization chamber. . Therefore, the diameter of the ion beam when passing through the ion transport optical system is mainly determined by the relationship between the voltage applied to the first and third lens electrodes and the voltage applied to the second lens electrode. Therefore, by appropriately adjusting the voltage applied to each of these electrodes, the divergence angle of the ion beam sent out from the ion transport optical system can be adjusted as appropriate. It is possible to form an ion beam having an appropriate characteristic that matches the acceptance characteristic of the optical element.

  In general, the voltage applied to each electrode by the voltage generator is such that the ion intensity detected by the ion detector in a device such as a mass spectrometer equipped with this ionization device is at or near the maximum. It is good to adjust to.

Also in the ionization apparatus of the first embodiment, as in the second embodiment, ions that have passed through the ion passage opening of the first lens electrode are guided to the subsequent stage. An ion transport optical system including at least two lens electrodes, the second and third, from the first lens electrode side;
The lens voltage generator applies a DC voltage identical to the DC voltage applied to the first lens electrode to the third lens electrode, and when the ion polarity is positive, the potential is applied to the second lens electrode. A configuration in which a DC voltage that is higher than the potential of the ionization chamber body is applied, and when the polarity of the ions is negative, a DC voltage whose potential is lower than the potential of the ionization chamber body is applied to the second lens electrode. It can be.

The ionization apparatus according to the present invention can be used in various types of mass spectrometers.
A first embodiment of a mass spectrometer according to the present invention includes an ionizer according to the present invention, a quadrupole mass filter that separates ions generated by the ionizer according to a mass-to-charge ratio, and the four And a detector for detecting ions separated by a multipole mass filter. This mass spectrometer is a single type quadrupole mass spectrometer.

  Further, a second embodiment of the mass spectrometer according to the present invention includes an ionizer according to the present invention, a front quadrupole mass filter that separates ions generated by the ionizer according to a mass-to-charge ratio, An ion dissociation part that dissociates ions selected by the front-stage quadrupole mass filter; a rear-stage quadrupole mass filter that separates product ions generated by dissociation in the ion dissociation part according to a mass-to-charge ratio; And a detector for detecting ions separated by the latter-stage quadrupole mass filter. The ion dissociation part is typically a collision cell that dissociates ions by collision-induced dissociation. This mass spectrometer is a triple quadrupole mass spectrometer.

  A third embodiment of the mass spectrometer according to the present invention is a time-of-flight mass that uses the ionization apparatus according to the present invention and a vertical acceleration system that separates ions generated by the ionization apparatus according to a mass-to-charge ratio. A separation unit; and a detector that detects ions separated by the time-of-flight mass separation unit. This mass spectrometer is a time-of-flight mass spectrometer.

  Further, a fourth embodiment of the mass spectrometer according to the present invention includes an ionizer according to the present invention, a quadrupole mass filter that separates ions generated by the ionizer according to a mass-to-charge ratio, An ion dissociation unit that dissociates ions selected by a quadrupole mass filter, and a time-of-flight mass separation unit of a vertical acceleration type that separates product ions generated by dissociation in the ion dissociation unit according to a mass-to-charge ratio And a detector for detecting ions separated by the time-of-flight mass separation unit. Similar to the second embodiment, the ion dissociation part is typically a collision cell that dissociates ions by collision-induced dissociation. This mass spectrometer is a quadrupole-time-of-flight (q-TOF type) mass spectrometer.

  A fifth embodiment of the mass spectrometer according to the present invention includes an ionization apparatus according to the present invention, and a sector magnetic field and a sector electric field that separate ions generated by the ionization apparatus according to a mass-to-charge ratio. And a detector for detecting ions separated by the double-focusing mass separation unit. This mass spectrometer is an electric field magnetic field double focusing type mass spectrometer.

  In any of these mass spectrometers, since the amount of ions used for mass analysis is increased as compared with the prior art, high analytical sensitivity can be realized.

  According to the ionization apparatus according to the present invention, compared with the conventional ionization apparatus, ions derived from the sample components generated in the ionization chamber can be more efficiently taken out from the ionization chamber, and the subsequent ion optics such as a quadrupole mass filter can be obtained. Can be sent to the system. Thereby, in the mass spectrometer using the ionization apparatus according to the present invention, the amount of ions to be subjected to mass analysis can be increased and the analysis sensitivity can be improved.

  Further, according to the ionization apparatus of the present invention, the divergence angle of the ion beam sent out from the ion transport optical system is appropriately adjusted by appropriately adjusting the voltage applied to each lens electrode of the focusing electrode and the ion transport optical system. can do. As a result, an ion beam having an appropriate characteristic matched to the acceptance characteristic of an ion optical element disposed in a subsequent stage such as a quadrupole mass filter can be formed, and the analysis sensitivity can be improved by improving the use efficiency of ions. be able to.

The schematic block diagram of the ionization apparatus by one Example of this invention. The whole block diagram of the quadrupole-type mass spectrometer which is one Example of the mass spectrometer using the ionization apparatus shown in FIG. The figure which shows the simulation result of the ion orbit in the ionization apparatus of a present Example. The figure which shows the experimental result of the difference of the signal strength of the ionizer of a present Example, and the conventional ionizer. The schematic block diagram of the modification of the ionization apparatus by a present Example. The schematic block diagram of another modification of the ionization apparatus by a present Example. The whole block diagram of the triple quadrupole mass spectrometer which is another Example using the ionization apparatus shown in FIG. The whole block diagram of the time-of-flight mass spectrometer which is another Example using the ionization apparatus shown in FIG. The whole block diagram of the quadrupole-time-of-flight mass spectrometer which is another Example using the ionization apparatus shown in FIG. The whole block diagram of the magnetic field electric field double convergence type | mold mass spectrometer which is another Example using the ionization apparatus shown in FIG. The schematic block diagram of the conventional ionization apparatus using an extrusion electric field. The schematic block diagram of the conventional ionization apparatus using both an extraction electric field or an extrusion electric field, and an extraction electric field.

An ionization apparatus which is an embodiment of the present invention and a quadrupole mass spectrometer which is an embodiment of a mass spectrometer using the ionization apparatus will be described with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of an ionization apparatus according to the present embodiment, and FIG. 2 is an overall configuration diagram of a quadrupole mass spectrometer of the present embodiment using the ionization apparatus shown in FIG. In FIG. 1, the same components as those of the conventional ionization apparatus shown in FIGS. 11 and 12 already described are denoted by the same reference numerals.

  As shown in FIG. 1, an ion source 1 in the ionization apparatus of the present embodiment includes an ionization chamber 10 having a substantially rectangular parallelepiped shape, a filament 11, a trap electrode 12, and the like. The ionization chamber 10 is not entirely composed of a single member, but has a conductive ionization chamber main body 10b forming five substantially rectangular parallelepiped surfaces, and a circular ion outlet 10d at the approximate center thereof. A focusing electrode 10c that constitutes one surface of a substantially rectangular parallelepiped and a spacer 10e that is an insulating member such as ceramic filling a gap between the ionization chamber body 10b and the focusing electrode 10c are integrated. Inside the ionization chamber 10, a repeller electrode 13 is disposed opposite to the ion outlet 10d with an ion generation region A centering on the thermoelectron flow interposed therebetween. An ion transport optical system 2 including a first lens electrode 21, a second lens electrode 22, and a third lens electrode 23 is disposed outside the ion outlet 10 d of the ionization chamber 10. These lens electrodes 21, 22, and 23 all have ion passage openings 21a, 22a, and 23a.

  The diameter of the ion passage opening 21a of the first lens electrode 21 is smaller than the diameter of the ion outlet 10d, whereby the extraction electric field formed by the first lens electrode 21 passes through the ion outlet 10d to the inside of the ionization chamber 10. It is easy to get into.

  A predetermined DC voltage (+ V1) is applied to the repeller electrode 13 from the repeller voltage generator 4, and a predetermined DC voltage (+ V2) is applied to the focusing electrode 10c from the focusing voltage generator 5, and the first lens electrode 21 and The same DC voltage (−V 3) is applied to the third lens electrode 23 from the base voltage generator 6, and a predetermined DC voltage (+ V 4) is applied to the second lens electrode 22 from the adjustment voltage generator 7. These voltage generators 4, 5, 6, and 7 are all controlled by the controller 8. The polarity of the voltage described here assumes that the ion to be measured is a positive ion, and when the ion to be measured is a negative ion, the polarity of all applied voltages is The reverse is true.

  As shown in FIG. 2, the quadrupole mass spectrometer of the present embodiment includes an ion source 1 and an ion transport optical system 2 shown in FIG. 1 inside a chamber 100 that is evacuated by a vacuum pump (not shown). And a quadrupole mass filter 101 as a mass separator, and an ion detector 102.

The operation of the ionization apparatus and quadrupole mass spectrometer of the present embodiment will be described.
For example, a sample gas containing sample components temporally separated in a gas chromatograph column is introduced into the ionization chamber 10 through the sample gas introduction pipe 14. A current is supplied to the filament 11 from a power source (not shown), whereby the filament 11 is heated and thermoelectrons are generated. The thermoelectrons are accelerated by the potential difference between the filament 11 and the trap electrode 12 and travel toward the trap electrode 12. That is, an electron flow is formed between the filament 11 and the trap electrode 12. The sample component is ionized in contact with the thermoelectrons. A DC voltage + V1 is applied to the repeller electrode 13 from the repeller voltage generation unit 4, and the electric field generated thereby mainly causes ions (positive ions) generated in the vicinity of the ion generation region A to be directed toward the ion outlet 10d. Has a pushing action.

  Further, a DC voltage -V3 having a polarity opposite to that of ions is applied from the base voltage generator 6 to the first lens electrode 21, and an electric field generated by the voltage is generated in the ionization chamber 10 through the ion outlet 10d. It reaches. This electric field has the effect of attracting ions. On the other hand, a DC voltage + V2 having the same polarity as the ions is applied from the focusing voltage generator 5 to the focusing electrode 10c around the ion outlet 10d. Since the electric field generated by the focusing electrode 10c acts to keep ions away, the electric field and the electric field generated by the first lens electrode 21 are combined to focus the ions in the ionization chamber 10 to the ion outlet 10d. Thus, an electric field having an action of drawing out from the ionization chamber 10 is formed. Ions generated mainly in the vicinity of the ion generation region A are focused on the ion outlet 10d by the extrusion electric field generated by the repeller electrode 13 and the above-described extraction electric field having the focusing action, and are extracted through the ion outlet 10d to be ion transport optics. Sent to system 2.

  In the ion transport optical system 2, a voltage that attracts ions is applied to the first and third lens electrodes 21 and 23, whereas ions are applied to the second lens electrode 22 sandwiched between the lens electrodes 21 and 23. A voltage is applied so as to keep the distance away. Therefore, the ions that have passed through the ion passage opening 21a of the first lens electrode 21 by the action of the extraction electric field are once focused near the ion optical axis by the action of the electric field formed by the second lens electrode 22, and are further accelerated to the first. The three lens electrodes 23 go out through the ion passage openings 23a. At this time, the diameter and divergence angle of the ion beam sent out from the ion transport optical system 2 and the speed thereof are determined by the voltages applied to the focusing electrode 10c and the lens electrodes 21, 22, and 23 (in this case, + V2,- V3, + V4).

  In the quadrupole mass filter 101 arranged in the subsequent stage of the ion transport optical system 2, only ions having a specific mass-to-charge ratio can pass through. However, only ions having a fixed relationship between the displacement from the central axis and the velocity can pass through the quadrupole mass filter 101 with a stable trajectory. Therefore, in order to obtain a high ion transmittance over the entire mass spectrometer, not only a large number of ions are sent out from the ionization chamber 10 but also an ion beam related to displacement and velocity in the ion source 1 and the subsequent ion transport optical system 2. It is important to adjust the characteristics so that the characteristics can be stably passed through the quadrupole mass filter 101. In the ionization apparatus of the present embodiment, as described above, by adjusting the voltage applied to the focusing electrode 10c and the lens electrodes 21, 22, and 23, the diameter and the divergence angle of the ion beam sent out from the ion transport optical system 2 are adjusted. And even its speed can be controlled. Therefore, for example, the quadrupole mass filter ion beam characteristics are adjusted by adjusting each applied voltage so that the ion intensity detected by the ion detector 102 becomes the highest while introducing a standard sample or the like into the ionization chamber 10. do it.

  FIG. 3 is a diagram showing simulation results of ion trajectories between the ionization chamber 10 and the quadrupole mass filter 101 in the quadrupole mass spectrometer of the present embodiment. The trajectory of ions that can reach the inside of the quadrupole mass filter 101 is indicated by a dark line, and the trajectory of ions that have disappeared due to collision with an electrode or the like in the middle is indicated by a light color line. Here, the potential of the ionization chamber 10 is 0V, the potential of the repeller electrode 13 is + 0.5V, the potential of the focusing electrode 10c is + 0.1V, the potentials of the first and third lens electrodes 21 and 23 are −10V, The potential of the two lens electrodes 22 is set to + 2V.

  From FIG. 3, ions starting from the initial position over a wide range (effective range in the figure) in the x direction inside the ionization chamber 10 can reach the inside of the quadrupole mass filter 101 through the ion transport optical system 2. I understand that. This is because the extraction efficiency of ions from the ionization chamber 10 is improved by the action of the electric field formed by the focusing electrode 10 c and the first lens electrode 21, and the quadrupole mass filter 101 has an entrance to the quadrupole mass filter 101. It can be presumed that this is due to the formation of an ion beam having characteristics that match the acceptance characteristics of the polar mass filter 101. These are all the effects of the presence of the focusing electrode 10 c provided on the ion exit side of the ionization chamber 10.

In general, in a conventional ionization apparatus that does not use a focusing electrode, in order to increase the degree of freedom of the characteristics of the ion beam, the lens electrode included in the ion transport optical system has a complicated shape or the number of electrodes is increased. It was necessary to set the voltage applied to each electrode appropriately. On the other hand, in the ionization apparatus according to the present invention, the shape of the focusing electrode and each lens electrode may be simple, and the kind of voltage applied to each electrode may be about the same as the conventional one. Therefore, the cost required for manufacturing the electrode can be suppressed, and the number of voltage generating parts applied to the electrode can be suppressed, and there is an advantage that the mass spectrometer can be highly sensitive while suppressing the cost of the apparatus.
In the simulation shown in FIG. 3, a partition wall having a potential of 0 V and having an ion passage opening is provided behind the third lens electrode 23, which shields the electric field from the subsequent stage. It is not directly related to the passage efficiency.

  FIG. 4 shows experimental results for verifying the effect of the ionization apparatus according to the present invention. The gas chromatograph mass spectrometer (GC-MS) using the conventional ionization apparatus and the GC- using the ionization apparatus of the present embodiment are shown. MS is a comparison of the signal intensity of peaks derived from predetermined components in the total ion chromatogram. From this experimental result, it can be seen that the GC-MS using the ionization apparatus of the present example has a signal strength nearly three times higher than that of the GC-MS using the conventional ionization apparatus. This indicates that the amount of ions reaching the ion detector is increasing, and it has been confirmed from experimental results that high sensitivity of the analysis can be achieved by using the ionization apparatus according to the present invention. It was.

  In the above description, the case of performing ionization by the EI method has been described. However, the ionization apparatus according to the present invention is naturally applicable to an apparatus that performs ionization by the CI method or the NCI method.

  In the ionization apparatus shown in FIG. 1, an insulating spacer 10 e is provided between the ionization chamber body 10 b and the focusing electrode 10 c constituting the ionization chamber 10, thereby improving the sealing performance of the ionization chamber 10. The spacer 10e is not essential. FIG. 5 is a schematic configuration diagram of a modification of the ionization apparatus according to the present invention. In this example, the ionization chamber main body 10b and the focusing electrode 10c are arranged with a predetermined distance therebetween. Since the potential difference between the ionization chamber main body 10b and the focusing electrode 10c is not so large, the interval between them may be small, and only a small amount of ions leak from the gap. Therefore, even with such a configuration, it is possible to achieve substantially the same effect as the ionization apparatus of the above embodiment.

FIG. 6 is a schematic configuration diagram of still another modification of the ionization apparatus according to the present invention.
In this ionization apparatus, not only the insulating spacer 10e is provided between the ionization chamber main body 10b and the focusing electrode 10c constituting the ionization chamber 10, but another separation is provided between the focusing electrode 10c and the first lens electrode 21. An insulating spacer 24 is provided to fill a gap between the focusing electrode 10 c and the first lens electrode 21.

  In this configuration, the first lens electrode 21 can also be regarded as a part of the ionization chamber 10 (that is, the ion source 1), and the ion passage opening 21a of the first lens electrode 21 is a substantial ion outlet. Can be considered. The substantial ion outlet (that is, the ion passage opening 21a) allows the ion beam focused by the previous focusing electrode 10c to pass therethrough, so that the ion ion compared with a conventional ionization apparatus that does not include the focusing electrode. Even if the inner diameter of the passage opening 21a is reduced, good ion transmittance can be achieved. Therefore, as shown in FIG. 6, the gap between the ionization chamber body 10b and the focusing electrode 10c and the gap between the focusing electrode 10c and the first lens electrode 21 are filled with spacers 10e and 24, respectively. By reducing the inner diameter of the ion passage opening 21a, which is a typical ion outlet, there is an advantage that the sealing performance in the ionization chamber 10 is further improved, and the ion utilization efficiency and the generation efficiency can be further improved.

  In the above embodiment, the ionizer according to the present invention is applied to a quadrupole mass spectrometer, but the ionizer according to the present invention can be applied to mass spectrometers of various types and systems. Examples thereof are shown in FIGS.

FIG. 7 is an overall configuration diagram of a triple quadrupole mass spectrometer using the ionization apparatus shown in FIG.
As shown in FIG. 7, inside the chamber 100 to be evacuated, the ion source 1 and the ion transport optical system 2 shown in FIG. 6, the front quadrupole mass filter 110, and the multipole ion guide 112 inside. A collision cell 111, a subsequent quadrupole mass filter 113, and an ion detector 102.

  In this triple quadrupole mass spectrometer, ions generated in the ionization chamber 10 are introduced into the front quadrupole mass filter 110 through the ion transport optical system 2 and, for example, ions having a predetermined mass-to-charge ratio. Only passes through the front quadrupole mass filter 110 and is introduced into the collision cell 111 as precursor ions. A predetermined CID gas such as argon is supplied to the collision cell 111, and the precursor ions come into contact with the CID gas and are cleaved by collision-induced dissociation. Various product ions generated by the cleavage are introduced into the rear quadrupole mass filter 113, and only product ions having a predetermined mass-to-charge ratio pass through the rear quadrupole mass filter 113 and reach the ion detector 102. To do.

  In this triple quadrupole mass spectrometer, similar to the above-described quadrupole mass spectrometer, the characteristics of the ion beam may be adjusted so that ions reach the inside of the previous quadrupole mass filter 110. The conditions of the voltage applied to the focusing electrode 10c and the lens electrodes 21, 22, and 23 may be substantially the same as those of the quadrupole mass spectrometer.

FIG. 8 is an overall configuration diagram of an orthogonal acceleration type time-of-flight quadrupole mass spectrometer using the ionization apparatus shown in FIG.
As shown in FIG. 8, a reflector in which the ion source 1 and the ion transport optical system 2 shown in FIG. 6, the orthogonal acceleration unit 130, and a plurality of reflective electrodes are arranged inside the chamber 100 to be evacuated. A flight space 131 including 132 and an ion detector 133 are arranged.

  In this time-of-flight quadrupole mass spectrometer, ions generated in the ionization chamber 10 are introduced into the orthogonal acceleration unit 130 via the ion transport optical system 2. In the orthogonal acceleration unit 130, the introduced ions are accelerated in a pulse manner in a direction substantially orthogonal to the traveling direction at a predetermined timing, and are introduced into the flight space 131. The ions fly in the flight space 131, are turned back by the reflector 132, and finally reach the ion detector 133. The ions ejected from the orthogonal acceleration unit 130 have a flight speed corresponding to the mass-to-charge ratio. Therefore, until the ions fly and reach the ion detector 133, the ions are separated according to the mass-to-charge ratio, and reach the ion detector 133 with a time difference.

  In this time-of-flight mass spectrometer, if there is an ion at a position away from the ion optical axis in the orthogonal acceleration unit 130 in the radial direction, the initial position of the flight is shifted. It is desirable that they are gathered at a position close to the central axis of the system 2. Therefore, the characteristics may be adjusted so that the diameter of the ion beam emitted from the ion transport optical system 2 is as small as possible and the divergence angle is as small as possible, that is, the ion beam is as parallel as possible. In the ionization apparatus of the present embodiment, since the ion beam diameter and divergence angle can be adjusted flexibly, it is possible to achieve both high mass accuracy, mass resolution, and high analysis sensitivity.

FIG. 9 is an overall configuration diagram of a quadrupole-time-of-flight (q-TOF type) mass spectrometer using the ionization apparatus shown in FIG.
As shown in FIG. 9, the ion source 1 and ion transport optical system 2 shown in FIG. 6, a quadrupole mass filter 110, and a multipole ion guide 112 are provided inside the chamber 100 to be evacuated. A collision cell 111, an orthogonal acceleration unit 130, a flight space 131 including a reflector 132 in which a plurality of reflective electrodes are arranged, and an ion detector 133 are arranged.

  In this q-TOF type mass spectrometer, ions generated in the ionization chamber 10 are introduced into the quadrupole mass filter 110 through the ion transport optical system 2, and only ions having a predetermined mass-to-charge ratio, for example, are introduced. It passes through the front quadrupole mass filter 110 and is introduced into the collision cell 111 as precursor ions. In the collision cell 111, the precursor ion contacts the CID gas and is cleaved by collision-induced dissociation. Various product ions generated by the cleavage are introduced into the orthogonal acceleration unit 130. In the orthogonal acceleration unit 130, the introduced product ions are accelerated in a pulse manner in a direction substantially orthogonal to the traveling direction thereof and are introduced into the flight space 131 at a predetermined timing. Product ions fly in the flight space 131, are turned back by the reflector 132, and finally reach the ion detector 133.

  In this q-TOF mass spectrometer, as in the above-described quadrupole mass spectrometer and triple quadrupole mass spectrometer, the ion beam is transmitted so that ions reach the inside of the quadrupole mass filter 110. Since the characteristics need only be adjusted, the conditions of the voltage applied to the focusing electrode 10c and the lens electrodes 21, 22, and 23 may be substantially the same as those of the quadrupole mass spectrometer.

FIG. 10 is an overall configuration diagram of the magnetic field double-focusing mass spectrometer using the ionization apparatus shown in FIG.
As shown in FIG. 10, inside the chamber 100 to be evacuated, there are an ion source 1 and an ion transport optical system 2 shown in FIG. A sector 121 and an ion detector 122 are arranged. The positions of the electric field sector 120 and the magnetic field sector 121 can be interchanged.

  In this magnetic field electric field double-focusing mass spectrometer, as in the time-of-flight mass spectrometer described above, the characteristics of the ion beam are introduced so that the ion beam having the smallest possible diameter and parallelized is introduced into the electric field sector 120. Can be adjusted.

Further, the ionization apparatus according to the present invention can be used for other apparatuses using ions such as an ion implantation apparatus other than the mass spectrometer.
Each of the above-described embodiments is an example of the present invention, and other than the examples described above, any modifications, changes, and additions within the spirit of the present invention are included in the scope of the claims of the present application. Is clear.

DESCRIPTION OF SYMBOLS 1 ... Ion source 10 ... Ionization chamber 10b ... Ionization chamber main body 10c ... Focusing electrode 10d ... Ion outlet 10e, 24 ... Spacer 11 ... Filament 12 ... Trap electrode 13 ... Repeller electrode 14 ... Sample gas introduction tube 2 ... Ion transport optical system 21, 22, 23 ... lens electrodes 21 a, 22 a, 23 a ... ion passage opening 3 ... focusing electrode 3 a ... ion passage opening 4 ... repeller voltage generation section 5 ... focusing voltage generation section 6 ... base voltage generation section 7 ... adjustment voltage generation section DESCRIPTION OF SYMBOLS 8 ... Control part 9 ... Ionization room A ... Ion production area 100 ... Chamber 101, 110, 113 ... Quadrupole mass filter 102, 122, 133 ... Ion detector 111 ... Collision cell 112 ... Multipole ion guide 120 ... Electric field sector 121 ... Magnetic sector 130 ... Orthogonal acceleration unit 131 ... Flight space 132 ... Reflector

Claims (13)

An ionizer that ionizes sample components contained in a sample gas,
a) a focusing electrode having an ion outlet, and an ionization chamber body which is electrically insulated from the focusing electrode and forms a space substantially separated from the outside together with the focusing electrode. An ionization chamber for ionizing sample components in space and sending the generated ions to the outside through the ion outlet;
b) When the polarity of the ions is positive, a DC voltage whose potential is higher than the potential of the ionization chamber body is applied to the focusing electrode, and when the polarity of the ions is negative, the potential is applied to the focusing electrode. A focusing voltage generator that applies a DC voltage that is lower than the potential of the ionization chamber body;
An ionization apparatus comprising: The ionization apparatus according to claim 1,
An ionization apparatus that performs ionization by electron ionization, chemical ionization, or negative chemical ionization in the ionization chamber. The ionization apparatus according to claim 2,
The ionizing apparatus, wherein the focusing electrode and the ionization chamber body are connected via a spacer made of an insulating member. The ionization apparatus according to any one of claims 1 to 3,
An ionization apparatus, further comprising a repeller electrode for forming a push electric field inside the ionization chamber for pushing ions toward the ion outlet. The ionization apparatus according to any one of claims 1 to 4,
A first lens electrode having an ion passage opening for guiding ions emitted from the ionization chamber through the ion outlet;
When the polarity of ions is positive, a DC voltage whose potential is lower than the potential of the ionization chamber body is applied to the first lens electrode, and when the polarity of ions is negative, the first lens electrode A lens voltage generator for applying a DC voltage whose potential is higher than the potential of the ionization chamber body;
An ionization apparatus characterized by further comprising: The ionization device according to claim 5,
The ionizing apparatus, wherein the focusing electrode and the first lens electrode are connected via a spacer made of an insulating member. The ionization apparatus according to any one of claims 1 to 4,
Ions that are emitted from the ionization chamber through the ion outlet and are guided to the subsequent stage, each having at least three lens electrodes having first, second, and third from the ionization chamber side, each having an ion passage opening. Including ion transport optics,
When the polarity of ions is positive, the first and third lens electrodes have the same DC voltage whose potential is lower than the potential of the ionization chamber body, and the potential of the second lens electrode is the ionization chamber body. When a DC voltage that is higher than the potential is applied and the polarity of ions is negative, the same DC voltage that has a potential higher than the potential of the ionization chamber body is applied to the first and third lens electrodes. A lens voltage generator for applying a DC voltage whose potential is lower than the potential of the ionization chamber body to the second lens electrode;
An ionization apparatus characterized by further comprising: The ionization apparatus according to claim 5 or 6,
Ions that have passed through the ion passage opening of the first lens electrode are guided to the subsequent stage, and each has at least two lens electrodes that are second and third from the first lens electrode side. An ion transport optical system including
The lens voltage generator applies a DC voltage identical to the DC voltage applied to the first lens electrode to the third lens electrode, and when the ion polarity is positive, the potential is applied to the second lens electrode. When a DC voltage that is higher than the potential of the ionization chamber body is applied and the polarity of the ions is negative, a DC voltage whose potential is lower than the potential of the ionization chamber body is applied to the second lens electrode. An ionizer characterized by the above. The ionizer according to any one of claims 1 to 8,
A quadrupole mass filter that separates ions generated by the ionizer according to a mass-to-charge ratio;
A detector for detecting ions separated by the quadrupole mass filter;
A mass spectrometer comprising: The ionizer according to any one of claims 1 to 8,
A pre-quadrupole mass filter that separates ions generated by the ionizer according to a mass-to-charge ratio;
An ion dissociation part for dissociating ions selected by the preceding quadrupole mass filter;
A subsequent quadrupole mass filter that separates product ions generated by dissociation in the ion dissociation part according to a mass-to-charge ratio;
A detector for detecting ions separated by the latter-stage quadrupole mass filter;
A mass spectrometer comprising: The ionizer according to any one of claims 1 to 8,
A time-of-flight mass separation unit of a vertical acceleration system that separates ions generated by the ionization device according to a mass-to-charge ratio;
A detector for detecting ions separated by the time-of-flight mass separator;
A mass spectrometer comprising: The ionizer according to any one of claims 1 to 8,
A quadrupole mass filter that separates ions generated by the ionizer according to a mass-to-charge ratio;
An ion dissociation part for dissociating ions selected by the quadrupole mass filter;
A time-of-flight mass separation unit of a vertical acceleration system that separates product ions generated by dissociation in the ion dissociation unit according to a mass-to-charge ratio;
A detector for detecting ions separated by the time-of-flight mass separator;
A mass spectrometer comprising: The ionizer according to any one of claims 1 to 8,
A double-focusing mass separation unit having a sector magnetic field and a sector electric field for separating ions generated by the ionizer according to a mass-to-charge ratio;
A detector for detecting ions separated by the double-focusing mass separation unit;
A mass spectrometer comprising:

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