Patent Application
20240105437
The present invention relates to a mass spectrometer, and more particularly to a mass spectrometer having a configuration of a multi-stage differential exhaust system.
In a mass spectrometer equipped with an ion source by an atmospheric pressure ionization method such as an electrospray ionization (ESI) method or an atmospheric pressure chemical ionization (APCI) method, a configuration of a multi-stage differential exhaust system is adopted in order to maintain a high degree of vacuum in a high vacuum chamber in which a mass separator such as a quadrupole mass filter is disposed. In a mass spectrometer of a multi-stage differential exhaust system, ions derived from a sample component generated in an ion source are transported to a high vacuum chamber through one or a plurality of intermediate vacuum chambers. In the transport path of the ions, an ion optical element for converging the ions by the action of an electric field, for transporting the ions while trapping the ions, or, in some cases, for accelerating the ions is arranged. The ion optical element herein includes an ion guide, an ion lens, a skimmer (skimmer cone), a deflector, and the like.
In such a mass spectrometer, neutral particles, ions, and the like derived from the sample adhere to the ion optical element at the time of analysis. The longer the device is used, the quality, such as the detection sensitivity or mass accuracy, of the device may deteriorate due to contamination of the ion optical elements. Therefore, a user (operator) or a customer service person periodically or non-periodically performs maintenance work such as taking out the ion optical element from the device main body and cleaning the ion optical element. A conventional general mass spectrometer adopts a structure, for example, in which a lid is provided on an upper portion of a vacuum chamber, and the ion optical element can be removed upward or mounted downward in a state where the lid is opened so that the maintenance work can be easily performed (see Patent Literature 1 and the like).
A liquid chromatograph mass spectrometry (LC-MS) system using the mass spectrometer as described above as a detector of a liquid chromatograph (LC) generally includes a plurality of units such as a liquid feeding unit including a pump which feeds a mobile phase, an injection unit which supplies a sample into the mobile phase, and a column oven unit which houses a column, in addition to the detector unit. A general quadrupole mass spectrometer is considerably larger in size than the above described other units than the detector unit. Therefore, the detector unit that is the quadrupole mass spectrometer is installed separately from the other units, and as a result, the LC-MS system requires a relatively large installation space.
As the field of use of the LC-MS system expands, it has been strongly required to reduce the installation space of the system, and in recent years, a device that is considerably smaller than a conventional general quadrupole mass spectrometer has been developed. For example, in the LC-MS system disclosed in Non Patent Literature 1, the size of a detector unit that is a mass spectrometer is suppressed to the size comparable to other units, and a system configuration in which units including the detector unit are stacked is possible.
The conventional mass spectrometer has the following problems.
In a mass spectrometer having a configuration of a multi-stage differential exhaust system, a plurality of intermediate vacuum chambers are arranged between the ionization chamber and a high vacuum chamber. In each of the intermediate vacuum chamber, ion optical elements such as an ion guide and an ion lens are arranged, and on a partition wall separating these chambers other ion optical elements such as a skimmer cone and a lens electrode are also arranged. When the ion optical element is maintained, it is necessary to detach the ion optical element from the device and attach the ion optical element to the device one by one, and the work is considerably laborious and requires great care.
In addition, since the detector unit that is a mass spectrometer includes a vacuum chamber made of stainless steel or the like, a vacuum pump, and the like, the detector unit has a larger weight than other units constituting the LC-MS system. Therefore, when a plurality of units are stacked, the detector unit is generally placed at the bottom. When maintenance of the ion optical element is to be performed in the LC-MS system having such a configuration, it is necessary to first move another unit placed above the detector unit, which also complicates the maintenance work and elongates the work time.
The present invention has been made to solve at least a part of the above problems, and an object of the present invention is to provide a mass spectrometer capable of reducing time and effort required for maintenance of an ion optical element in the mass spectrometer having a configuration of a multi-stage differential exhaust system.
One aspect of a mass spectrometer according to the present invention made to solve the above problems is a mass spectrometer including a plurality of intermediate vacuum chambers in which a degree of vacuum increases stepwise between an ionization chamber that ionizes a sample component under atmospheric pressure and a high vacuum chamber that performs mass spectrometry of ions generated in the ionization chamber, the mass spectrometer including:
Any forms are included in the first ion guide and the second ion guide as long as the first ion guide and the second ion guide transport ions to the subsequent stage by the action of an electric field including a radio-frequency electric field, a direct-current electric field, or both of them. For example, a plurality of rod electrodes or flat plate electrodes arranged around the ion optical axis can be included, or a plurality of flat plate electrodes arranged in the extending direction of the ion optical axis can be included. In addition, the first partition wall portion and the second partition wall portion can be typically a skimmer cone having a small-diameter ion passage hole at the top, a disk-shaped lens electrode having a small-diameter ion passage hole at the center, or the like.
In the mass spectrometer according to the above aspect of the present invention, a plurality of ion optical elements from a first ion guide for transporting ions introduced into the first intermediate vacuum chamber to a second ion guide for transporting ions introduced into the second intermediate vacuum chamber are substantially integrated as an ion transport unit. By attaching the ion transport unit to the vacuum chamber main body portion, each intermediate vacuum chamber is formed, and the first and second ion guides are arranged at appropriate positions in each intermediate vacuum chamber.
Therefore, according to the mass spectrometer according to the above aspect of the present invention, when maintenance such as cleaning of various ion optical elements disposed in the intermediate vacuum chamber is performed, the ion optical elements are integrally removed from the device as a unit instead of removing each ion optical element one by one from the device. In addition, even when each ion optical element is attached to the device after completion of maintenance, a plurality of ion optical elements can be integrally mounted to the device as a unit. As a result, the operation at the time of performing the maintenance of the ion optical element becomes very simple, and the efficiency of the operation is improved. In addition, since the first holding portion which holds the first ion guide and the first partition wall portion and the second holding portion which holds the second ion guide can be easily separated, the operation of cleaning each ion optical element after the unit including them is detached from the device is also simple, and the operation efficiency is improved.
A mass spectrometer according to an embodiment of the present invention will be described with reference to the accompanying drawings.
This mass spectrometer is a single-type quadrupole mass spectrometer equipped with an ESI ion source.
[Entire Configuration of Mass Spectrometer of Present Embodiment]
Note that, for convenience of description, three axes of an X axis, a Y axis, and a Z axis orthogonal to each other are defined in a space as illustrated in
As illustrated in
As illustrated in
The ionization chamber 22 is provided with an ionization probe 23 which nebulizes a liquid sample while charging the liquid sample, and the ionization chamber 22 and the first intermediate vacuum chamber 11 communicate with each other through the desolvation line 24 having a small diameter. A heater 25 is provided around the desolvation line 24, and the desolvation line 24 is heated to a predetermined temperature by the heater 25.
A first ion guide 14 is disposed inside the first intermediate vacuum chamber 11, and the first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12 communicate with each other through a small hole formed at the top of a skimmer (skimmer cone) 15. A second ion guide 16 is disposed inside the second intermediate vacuum chamber 12, and the second intermediate vacuum chamber 12 and the high vacuum chamber 13 communicate with each other through a small hole formed at the center of a lens electrode 17. Inside the high vacuum chamber 13, a quadrupole mass filter 18 including a pre-rod electrode and a main rod electrode, and an ion detector 19 are disposed.
As illustrated in
[Analysis Operation of Mass Spectrometer of Present Embodiment]
An analysis operation in the mass spectrometer of the present embodiment will be briefly described.
An eluate containing components separated by a column of a liquid chromatograph (LC) (not illustrated) is supplied to the ionization probe 23. A DC high voltage is applied to the tip of the ionization probe 23, and the eluate is nebulized into the ionization chamber 22 at substantially atmospheric pressure while being given a biased charge by an electric field formed by the voltage. In the process of vaporizing the solvent in the nebulized charged droplets, the sample component is ionized. Note that, the sample components may be ionized by an ionization method such as an APCI method or an atmospheric pressure photoionization (APPI) method other than the ESI method.
Ions derived from the sample component generated in the ionization chamber 22 are entrained in a gas flow generated by a pressure difference between both ends of the desolvation line 24, and are sucked into the desolvation line 24 from an ion introduction port 24a. In addition, the charged droplet in which the solvent is not sufficiently vaporized is also sucked into the desolvation line 24, but even in this case, desolvation proceeds in the desolvation line 24 at a high temperature, and ionization is promoted.
The ions thus sent into the first intermediate vacuum chamber 11 through the desolvation line 24 are converged near an orifice 15a formed at the top of the skimmer 15 by the radio-frequency electric field applied to the first ion guide 14. Then, the ions enter the second intermediate vacuum chamber 12 through the orifice 15a. The ions derived from the sample component are transported while being captured by the radio-frequency electric field applied to the second ion guide 16 in the second intermediate vacuum chamber 12, converged by the lens electrode 17 to which a predetermined DC voltage is applied, and introduced into the high vacuum chamber 13 through a small hole 17a at the center thereof. Thereafter, only ions having a specific mass-to-charge ratio corresponding to the voltage applied to the rod electrode of the quadrupole mass filter 18 (voltage obtained by combining the DC voltage and the radio-frequency voltage) pass through the quadrupole mass filter 18, and the other ions diverge on the way. The ion detector 19 detects ions entering through the quadrupole mass filter 18, and outputs a detection signal corresponding to the amount of the ions.
In this manner, in the mass spectrometer of the present embodiment, ions derived from the sample component generated in the ionization chamber 22 located on the most front side as viewed from the operator are introduced into the vacuum chamber 1 located behind the ionization chamber 22, and are sent from the front side to the rear side as a whole. The ions sent to the high vacuum chamber 13 are separated by the quadrupole mass filter 18 according to the mass-to-charge ratio, and then detected by the ion detector 19 in the final stage.
[Detailed Configuration of Ion Optical Element Disposed in Intermediate Vacuum Chamber]
At the time of analysis as described above, droplets in which the solvent is not yet completely vaporized jump into the first intermediate vacuum chamber 11. In addition, neutral particles such as unionized sample component molecules and sample component molecules or solvent molecules generated by recombination of ions also enter the first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12. When such droplets, neutral particles, ions, or the like adhere to the ion guides 14 and 16 or the like and become dirty, the generated electric field is disturbed, and the behavior of the ions becomes unstable or not ideal. In order to avoid this, it is necessary to take out the ion guides 14 and 16 and the like from the device and clean the ion guides. As described below, the mass spectrometer of the present embodiment has a structure in which the ion optical elements such as the ion guides 14 and 16 can be easily taken out from the device.
As illustrated in
When the DL flange 21 is removed, the front face of the vacuum flange 10a forming the front wall of the vacuum chamber 1 is exposed inside the DL flange 21. The vacuum flange 10a is fixed to the vacuum chamber main body portion 10 from the front side by a screw, and when the screw is loosened, the vacuum flange 10a can be removed to the front side. Further, an ion transport unit including the ion optical elements in the first intermediate vacuum chamber 11 and the second intermediate vacuum chamber 12 is pulled forward through the front opening of the vacuum chamber main body portion 10 formed by removing the vacuum flange 10a, so that the ion transport unit can be taken out.
The ion transport unit includes two units of the first unit 30 illustrated in
The first unit 30 includes a first holder 31 having a substantially annular shape, four rod electrodes 14a whose rear ends are fixed to the first holder 31, a plurality of elastic rods 33 whose rear ends are fixed to the first holder 31 and whose longitudinal portions are elastic bodies, an annular pressing ring 32 to which the front ends of the elastic rods 33 are fixed, a skimmer plate 34 attached to the first holder 31, and a circuit board 36 fixed to the first holder 31.
The four rod electrodes 14a constitute a first ion guide 14. In addition, the skimmer 15 is formed on the skimmer plate 34 made of metal. The elastic body of the elastic rod 33 is typically a spring, but is not limited thereto. The elastic rod 33 extends and contracts only in its longitudinal direction, and is attached in parallel to the ion optical axis C.
The second unit 40 includes a second holder 41 having a substantially annular shape, four rod electrodes 16a having a trapezoidal cross section whose rear ends are fixed to the second holder 41, a plurality of elastic rods 42 whose rear ends are fixed to the second holder 41 and a part of which in the longitudinal direction is an elastic body, a lens electrode 17 made of metal attached to the second holder 41, a coupling fitting 46 whose one end is fixed to the second holder 41, a circuit board 45 fixed to the other end of the coupling fitting 46 and the elastic rods (strictly speaking, portions of the elastic rods that do not expand and contract due to elasticity) 42, and an electrical wiring connection portion 47 connected to the circuit board 45. The four rod electrodes 16a constitute the second ion guide 16. Similarly to the elastic rod 33, the elastic rod 42 extends and contracts only in the longitudinal direction thereof, and is attached in parallel to the ion optical axis C.
Both the elastic rod 42 and the elastic rod 33 have a rod portion having rigidity and an elastic portion that expands and contracts. For reasons described later, the elastic portion of the elastic rod 33 in the first unit 30 has a larger elastic force than the elastic portion of the elastic rod 42 in the second unit 40.
In addition, a plurality of cylindrical pins 43 protruding in the longitudinal direction of the elastic rod 42 are provided at the front end portion of the elastic rod 42. On the other hand, pin holes 31a into which the pins 43 are inserted are provided at positions corresponding to the pins 43 on the rear face (face facing the second intermediate vacuum chamber 12 side) of the first holder 31 of the first unit 30. Leaf springs that press the inserted pins 43 are disposed inside the pin holes 31a, and the pins 43 inserted into the pin holes 31a are less likely to come off from the pin holes 31a by the action of the leaf spring.
That is, by sufficiently inserting the pins 43 of the second unit 40 into the pin holes 31a of the first unit 30, the first unit 30 and the second unit 40 are connected to form an ion transport unit. For coupling between the first unit 30 and the second unit 40, a member that requires another tool for attachment and detachment, such as a screw, is not used, and the first unit 30 and the second unit 40 are coupled by simply fitting the pins 43 and the pin holes 31a. Therefore, the first unit 30 and the second unit 40 can be separated relatively easily.
When attaching the ion transport unit in the vacuum chamber 1, as illustrated in
As described above, when the ion transport unit is inserted into the vacuum chamber main body portion 10 as it is, the second holder 41 of the second unit 40 becomes a part of the partition wall separating the second intermediate vacuum chamber 12 and the high vacuum chamber 13 in the vacuum chamber 1, and abuts on a second partition wall portion 10d having a circular opening portion 10e at the substantially center thereof. More specifically, the second holder 41 is provided with a seal member 44 such as an O-ring, the seal member 44 is sandwiched between the second holder 41 and the second partition wall portion 10d, and when the second holder 41 is pressed, the seal member 44 is crushed to seal the gap between the second holder 41 and the second partition wall portion 10d.
At the time when the second holder 41 abuts on the second partition wall portion 10d, the first holder 31 does not yet abut on the first partition wall portion 10b, but when the operator further pushes in the ion transport unit, the elastic portion of the second elastic rod 42 contracts by the force. As described above, since the elastic portion of the first elastic rod 33 has a larger elastic force than the elastic portion of the second elastic rod 42, when the end portion (left end portion in
When the operator further pushes the ion transport unit, the first holder 31 abuts on the first partition wall portion 10b. The first holder 31 is also provided with a seal member 35 such as an O-ring, the seal member 35 is sandwiched between the first holder 31 and the first partition wall portion 10b, and when the first holder 31 is pressed, the seal member 35 is crushed to seal the gap between the first holder 31 and the first partition wall portion 10b. When the operator further pushes the ion transport unit, the elastic portion of the first elastic rod 33 contracts by the force, and the pressing ring 32 is accommodated in the vacuum chamber main body portion 10.
In this state, when the operator fixes the vacuum flange 10a to the vacuum chamber main body portion 10 with a screw, as illustrated in
In the ion transport unit, the center of the small hole 17a of the lens electrode 17, the center axis of the second ion guide 16, the center of the orifice 15a of the skimmer 15, and the center axis of the first ion guide 14 are located on a straight line. In addition, the step formed in the peripheral edge of the opening portion 10c of the second partition wall portion 10d is fitted to the second holder 41, and the step formed in the peripheral edge portion of the opening portion 10c of the first partition wall portion 10b is fitted to the first holder 31. Therefore, when the ion transport unit is appropriately installed in the vacuum chamber main body portion 10 and the vacuum flange 10a is appropriately attached to the vacuum chamber main body portion 10, as illustrated in
In order to take out the ion transport unit from the inside of the vacuum chamber main body portion 10 to the outside, it is only required to take out the ion transport unit in front of the device by a procedure reverse to the above.
In the mass spectrometer of the present embodiment, at the time of analysis, normally, the same radio-frequency voltage +RF1 is applied to the two rod electrodes 14a facing each other across the ion optical axis C among the four rod electrodes 14a constituting the first ion guide 14, and the radio-frequency voltage −RF1 having the same amplitude as the radio-frequency voltage +RF1 and the opposite polarity to the radio-frequency voltage +RF1 is applied to the other two rod electrodes 14a. In addition, the same radio-frequency voltage +RF2 is applied to the two rod electrodes 16a facing each other across the ion optical axis C among the four rod electrodes 16a constituting the second ion guide 16, and the radio-frequency voltage −RF2 having the same amplitude as the radio-frequency voltage +RF2 and the opposite polarity to the radio-frequency voltage +RF2 is applied to the other two rod electrodes 16a. In addition, a predetermined DC voltage is applied to each of the skimmer plate 34 and the lens electrode 17.
The vacuum chamber 1 is at a ground potential (0 V) which is a reference potential, and the skimmer plate 34 is also at the same potential as the vacuum chamber 1. Therefore, as illustrated in
As illustrated in
A predetermined electric wiring pattern 362 is formed on the circuit board 36 attached to the first holder 31 of the first unit 30, and a part thereof is illustrated in
On the other hand, a hole 47a into which the energizing pin 38 is inserted when the first unit 30 and the second unit 40 are appropriately coupled is formed in the electrical wiring connection portion 47 of the second unit 40. The energizing pin 38 inserted into the hole 47a is connected to the electric wiring pattern on the circuit board 45 via the pin receiving portion 471. In the example illustrated in
In addition, the radio-frequency voltages +RF1 and −RF1 sent from the power supply terminal 120 to the circuit board 36 by another energization path are applied to the four rod electrodes 14a via the electric wiring pattern on the circuit board 36. In addition, the radio-frequency voltages +RF2 and −RF2 sent from the power supply terminal 120 to the circuit board 45 may be applied to the four rod electrodes 16a through still another energizing path. Of course, not all the power feeding in the ion transport unit may be performed in the above-described configuration, but only a part thereof may be performed in the above-described configuration.
As described above, when the ion transport unit is mounted at a predetermined position in the vacuum chamber main body portion 10, power is supplied by the contact between the power supply unit provided on the vacuum chamber main body portion 10 side and the power receiving unit provided on the ion transport unit side, so that it is possible to reduce the use of complicated electric wiring, connectors, and the like. In addition, it is possible to reduce the trouble of inserting and removing the connector when attaching and detaching the ion transport unit.
[Modifications]
Note that, the above embodiment is merely an example of the present invention, and it is obvious that modifications, additions, and corrections appropriately made within the scope of the gist of the present invention are included in the claims of the present application.
For example, in the device of the above embodiment, the lens electrode 17 is attached to the second holder 41 which holds the rod electrode 16a of the second ion guide 16, and the lens electrode 17 and the second holder 41 themselves form a part of the partition wall that partitions the second intermediate vacuum chamber 12 and the high vacuum chamber 13, but the partition wall may be formed in advance in the vacuum chamber main body portion 10. That is, the ion optical element (the lens electrode 17 in the present example) provided on the partition wall that partitions the second intermediate vacuum chamber 12 and the high vacuum chamber 13 may not be configured to be drawable forward of the device.
In addition, the form of the ion optical element disposed in each intermediate vacuum chamber or provided on the partition wall separating the adjacent vacuum chambers is not limited to the above-described form, and it is a matter of course that various ion optical elements generally used can be used.
In addition, in the mass spectrometer of the above embodiment, the ion optical axis from the desolvation line 24 to the quadrupole mass filter 18 is straight, but the present invention is not limited thereto, and can also be applied to an ion optical system called axial shift, off-axis, or the like.
In addition, the above embodiment is an example in which the present invention is applied to a single quadrupole mass spectrometer. However, the present invention can also be applied to other mass spectrometers using an atmospheric pressure ion source, specifically, a triple quadrupole mass spectrometer, and the like.
[Various Aspects]
It will be understood by those skilled in the art that the exemplary embodiments described above are specific examples of the following aspects.
(Clause 1) One aspect of a mass spectrometer according to the present invention is a mass spectrometer including a plurality of intermediate vacuum chambers in which a degree of vacuum increases stepwise between an ionization chamber that ionizes a sample component under atmospheric pressure and a high vacuum chamber that performs mass spectrometry of ions generated in the ionization chamber, the mass spectrometer including:
According to the mass spectrometer described in Clause 1, when maintenance such as cleaning of various ion optical elements disposed in the first and second intermediate vacuum chambers is performed, the ion optical elements are integrally removed from the device as a unit instead of removing each ion optical element one by one from the device. In addition, even when each ion optical element is attached to the device after completion of maintenance, a plurality of ion optical elements can be integrally mounted to the device as a unit. As a result, the operation at the time of performing the maintenance of the ion optical element becomes very simple, and the efficiency of the operation is improved. In addition, since the first holding portion which holds the first ion guide and the first partition wall portion and the second holding portion which holds the second ion guide can be easily separated, the operation of cleaning each ion guide after the unit is detached from the device is also simple, and the operation efficiency is improved.
(Clause 2) In the mass spectrometer according to Clause 1,
According to the mass spectrometer described in Clause 2, since the second partition wall portion can also be integrally attached to and detached from the device together with the first ion guide and the second ion guide, the efficiency of the maintenance operation of the ion optical element is further improved.
(Clause 3) In the mass spectrometer according to Clause 1,
According to the mass spectrometer described in Clause 3, the ion transport unit in which the first ion guide and the second ion guide are integrated can be attached to and detached from the front of the mass spectrometer. Therefore, it is not necessary to attach and detach the ion guide or the like from above or from the side of the device, and another device can be stacked and installed above the present device. In addition, the lateral space of the present device may also be narrow. Furthermore, a plurality of vacuum chambers separated by a partition wall can be formed inside the vacuum chamber only by mounting the ion transport unit in the vacuum chamber and closing the front wall portion.
(Clause 4) The mass spectrometer according to Clause 3 may further include:
According to the mass spectrometer described in Clause 4, airtightness of each vacuum chamber formed inside the vacuum chamber is secured.
(Clause 5) The mass spectrometer according to Clause 3 or 4 may further include:
In the mass spectrometer described in Clause 5, when the ion transport unit is inserted into the vacuum chamber from the front of the device, first, the second partition wall portion held by the second holding portion abuts on the second partition wall receiving portion, and the second holding portion is positioned. Then, when a rearward force is applied to the ion transport unit, the second elastic body contracts, the second partition wall portion held by the first holding portion abuts on the second partition wall receiving portion, and the first holding portion is positioned. At this time, adhesion between the second partition wall portion and the second partition wall receiving portion is secured by the biasing force of the second elastic body. When a further rearward force is applied to the ion transport unit, the first elastic body contracts, so that the front wall portion can be mounted to the vacuum chamber main body portion. At this time, adhesion between the first partition wall portion and the first partition wall receiving portion is secured by the biasing force of the first elastic body.
In this manner, according to the mass spectrometer described in Clause 5, it is possible to ensure high airtightness between the vacuum chambers located on the far side of the vacuum chamber, that is, having a relatively high degree of vacuum.
(Clause 6) In the mass spectrometer according to any one of Clauses 3 to 5,
According to the mass spectrometer described in Clause 6, the front wall portion of the vacuum chamber is removed in a state where the ionization chamber is moved to the open position, and the ion transport unit can be attached to and detached from the opening portion of the front face of the vacuum chamber main body portion.
(Clause 7) The mass spectrometer according to any one of Clauses 3 to 6 may further include:
According to the mass spectrometer described in Clause 7, by mounting the ion transport unit inside the vacuum chamber, power can be supplied from the vacuum chamber side to each ion optical element. Accordingly, complicated electric wiring using a connector or the like can be eliminated or reduced.
In addition, when the first holding portion and the second holding portion are connected to each other, the first holding portion and the second holding portion are electrically connected to each other, so that it is possible to receive power supply from the power supply unit of the vacuum chamber only on one side and supply power to the other side.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-215654 | Nov 2019 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2020/030557 | 8/11/2020 | WO |
