WO2022239104A1

WO2022239104A1 - Orthogonal acceleration time-of-flight mass spectrometer

Info

Publication number: WO2022239104A1
Application number: PCT/JP2021/017863
Authority: WO
Inventors: 朋也工藤
Original assignee: 株式会社島津製作所
Priority date: 2021-05-11
Filing date: 2021-05-11
Publication date: 2022-11-17
Also published as: JPWO2022239104A1

Abstract

An embodiment of the mass spectrometer according to the present invention comprises: a vacuum chamber(1) which has an internal space divided into a first vacuum chamber (13) and a second vacuum chamber (14); a transfer electrode (141) which is made from multiple electrode plates arranged across both of the vacuum chambers so as to transfer ions from the first vacuum chamber to the second vacuum chamber, linked together via insulating spacers, and each having an ion-passing hole; an orthogonal acceleration part (142) which is disposed inside the second vacuum chamber and accelerates the ions transferred by the transfer electrode in a direction orthogonal to the incident direction of the ions; a rear-side fixing member (150 to 153, 160, 161) which is for fixing a rear-side electrode plate, that is, an electrode plate positioned inside the second vacuum chamber among the multiple electrode plates, to the vacuum chamber at a position distant in a predetermined direction orthogonal to a central axis of the ion-passing hole of the rear-side electrode plate; and a front-side fixing member which is for positioning a front-side electrode plate, that is, an electrode plate positioned inside the first vacuum chamber among the multiple electrode plates, inside the first vacuum chamber, and which includes a projection part (163) disposed so as to project inward from an inner wall surface of the vacuum chamber and an annular partition wall member (165) which holds the spacer (1415) fixed to the front-side electrode plate and is attached in a slidable manner with respect to the projection part in a direction opposite to the predetermined direction within a predetermined range.

Description

Orthogonal acceleration time-of-flight mass spectrometer

The present invention relates to an orthogonal acceleration time-of-flight mass spectrometer.

Orthogonal Acceleration Time-of-Flight Mass Spectrometer is known as one type of time-of-flight mass spectrometer. Patent Documents 1 and 2 disclose a quadrupole-time-of-flight (Q-TOF) mass spectrometer using an orthogonal acceleration time-of-flight mass spectrometer as a second-stage mass spectrometer. In this type of mass spectrometer, a quadrupole mass filter as a first-stage mass spectrometer and a collision cell are arranged in a first analysis chamber with a relatively high degree of vacuum. An orthogonal acceleration time-of-flight mass spectrometer including an orthogonal accelerator, a flight tube and a detector is located in a second analysis chamber with a high . In order to efficiently transport ions from the first analysis chamber to the second analysis chamber, a transfer electrode is arranged across both analysis chambers.

In the device described in Patent Document 1, the transfer electrode (the rear-stage ion lens in Patent Document 1) has a structure in which four electrode plates are connected in the central axis direction via insulating spacers, and is attached to the collision cell. One electrode plate at the closest position (in the following explanation, the collision cell side is the front and the orthogonal acceleration unit side is the rear) is in the first analysis chamber, and the three electrode plates behind it are in the first analysis chamber. 2 are placed in the analysis chamber. A predetermined voltage is applied to each electrode plate, and a predetermined electric field is formed in the space surrounded by the electrode plates. Ions are guided through this electric field to the orthogonal accelerator. A pulsed electric field is formed in the orthogonal acceleration section to accelerate ions incident through the transfer electrode in a direction substantially orthogonal to the incident direction. The ions accelerated by the orthogonal acceleration section are guided to the flight space in the flight tube, and after flying in the flight space reach the detector and are detected.

In order to improve the analysis performance such as mass accuracy and mass resolution in this type of mass spectrometer, it is important to minimize the position spread (dispersion) and velocity spread in the orthogonal acceleration direction of the ion flow incident on the orthogonal acceleration unit. is. That is, it is important to keep the ion flow incident on the orthogonal acceleration section as thin as possible and parallel to the acceleration electrodes (extrusion electrode and pull-in electrode) of the orthogonal acceleration section. The transfer electrode has a function of shaping the ion flow incident on the orthogonal acceleration section so that it becomes thin and parallel.

WO2019/220554 WO2019/229864

In the mass spectrometer described in Patent Document 1, the electrode plate located at the rearmost position of the transfer electrode (the position closest to the orthogonal acceleration section) is fixed to the base plate via an insulating member, and the orthogonal acceleration section is also fixed to the same base plate. there is Also, the second electrode plate from the front of the transfer electrode is fixed to a partition member separating the first analysis chamber and the second analysis chamber via a seal member.

In this type of mass spectrometer, in order to prevent changes in the flight distance due to thermal expansion of the flight tube, the inside of the second analysis chamber is heated to an appropriate temperature (eg, 42°C) higher than the room temperature of a general room. It is designed to be heated and temperature controlled. When the temperature in the second analysis chamber rises from normal room temperature in this way, the insulating member fixing the rear electrode plate of the transfer electrode thermally expands, displacing the electrode plate in a direction substantially perpendicular to its central axis. There is a risk of The second electrode plate from the front of the transfer electrode is fixed to the partition member via a sealing member such as an O-ring. It fluctuates considerably. If this frictional force is large, even if the rear electrode plate is displaced, it is difficult for the front electrode plate to follow the displacement. As a result, the central axis of the transfer electrode is tilted with respect to the central axis between the push-out electrode and the pull-in electrode that are parallel to each other in the orthogonal acceleration section, which may lead to deterioration in analytical performance.

In addition, similar problems may occur during transportation of the equipment, not during analysis. That is, when transporting this type of mass spectrometer from a factory to an overseas delivery destination, sea freight or air freight is used, and the temperature inside the container mounted thereon is in a wide range of about 5°C to 50°C. can change with Even if each member expands or contracts due to such temperature changes that occur during the transportation process, and the fixed positions between the members change irreversibly, the central axis of the transfer electrode will tilt in the same manner as described above, resulting in a decrease in analytical performance. may bring about.

The present invention has been made to solve the above problems, and its object is to suppress the inclination of the optical axis of the ion flow incident on the orthogonal acceleration unit due to temperature control and temperature change during analysis. It is an object of the present invention to provide an orthogonal acceleration time-of-flight mass spectrometer capable of securing high analytical performance.

One aspect of the orthogonal acceleration time-of-flight mass spectrometer according to the present invention, which has been made to solve the above problems,
a vacuum chamber having an internal space partitioned into a first vacuum chamber and a second vacuum chamber;
a plurality of electrode plates each having an ion passage opening disposed across the first and second vacuum chambers and connected via insulating spacers for transporting ions from the first vacuum chamber to the second vacuum chamber; a transfer electrode consisting of
an orthogonal acceleration unit disposed in the second vacuum chamber for accelerating ions transported by the transfer electrode in a direction perpendicular to the incident direction;
a rear electrode plate for fixing the rear electrode plate positioned in the second vacuum chamber among the plurality of electrode plates to the vacuum chamber at a position spaced apart in a predetermined direction orthogonal to the central axis of the ion passage aperture; a side fixing member;
A member for positioning a front electrode plate positioned in the first vacuum chamber among the plurality of electrode plates in the first vacuum chamber, the member extending inward from an inner wall surface of the vacuum chamber. It holds the provided extending portion and the spacer fixed to the front electrode plate, and is attached to the extending portion so as to be slidable within a predetermined range in a direction opposite to the predetermined direction. an annular partition member; and an anterior fixation member comprising:
Prepare.

In the orthogonal acceleration time-of-flight mass spectrometer according to the present invention, for example, when the inside of the vacuum chamber is heated to a predetermined temperature higher than room temperature during analysis, the rear side fixing member thermally expands, and as a result, the rear side electrode plate expands. It may move in a direction opposite to the predetermined direction. Since the partition member holding the front electrode plate via the spacer is slidable within a predetermined range in the opposite direction with respect to the extending portion, it is possible to move the rear electrode plate as described above. Following this, the front electrode plate also moves in the same direction. Therefore, the central axis of the transfer electrode is only moved in parallel due to the thermal expansion, and the inclination with respect to the axis of ideal ion incidence to the orthogonal acceleration section is reduced.

Thus, according to the orthogonal acceleration time-of-flight mass spectrometer according to the present invention, it is possible to reduce the tilt of the ion optical axis of the ion flow incident on the orthogonal acceleration part due to temperature control and temperature change during analysis. can be done. As a result, the ion current incident on the orthogonal acceleration section is kept parallel to the electrodes included in the orthogonal acceleration section, so high analytical performance can be achieved.

1 is an overall configuration diagram of a Q-TOF mass spectrometer that is an embodiment of the present invention; FIG. FIG. 2 is an enlarged view of the vicinity of the transfer electrode in the Q-TOF mass spectrometer of the present embodiment; FIG. 3 is an enlarged view of the vicinity of part A in FIG. 2; FIG. 4 is an explanatory diagram of the configuration of the rear-side fixing member in the Q-TOF mass spectrometer of the present embodiment; FIG. 4 is an explanatory diagram of the configuration of the front-side fixing member in the Q-TOF mass spectrometer of the present embodiment; FIG. 2 is a plan view of an electrode plate that constitutes a post-stage transfer electrode in the Q-TOF mass spectrometer of the present embodiment; FIG. 4 is a diagram showing an example (ideal state) of the relationship between the ion optical axis of the rear-stage transfer electrode and the ion optical axis of the orthogonal acceleration section in the Q-TOF mass spectrometer of the present embodiment; FIG. 4 is a diagram showing an example of the relationship between the ion optical axis of the rear-stage transfer electrode and the ion optical axis of the orthogonal acceleration section in the Q-TOF mass spectrometer of the present embodiment (the axis is tilted). FIG. 4 is a diagram showing an example of the relationship between the ion optical axis of the rear-stage transfer electrode and the ion optical axis of the orthogonal acceleration section in the Q-TOF mass spectrometer of the present embodiment (state with parallel axis deviation).

A Q-TOF mass spectrometer according to one embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram of a Q-TOF mass spectrometer according to this embodiment. First, the overall configuration and typical analysis operation of this Q-TOF mass spectrometer will be described.

[Configuration and operation of Q-TOF mass spectrometer]
In this Q-TOF mass spectrometer, an ionization device 10 having an ionization chamber 100 therein is connected to the front of a vacuum chamber 1 . The interior of the vacuum chamber 1 is roughly divided into four chambers, a first intermediate vacuum chamber 11 , a second intermediate vacuum chamber 12 , a first analysis chamber 13 and a second analysis chamber 14 . In this Q-TOF mass spectrometer, the ionization chamber 100 is at substantially atmospheric pressure, and from the ionization chamber 100, the first intermediate vacuum chamber 11, the second intermediate vacuum chamber 12, the first analysis chamber 13, and the second analysis chamber 14 is a configuration of a multi-stage differential pumping system in which the degree of vacuum increases stepwise. In FIG. 1, vacuum pumps for evacuating each chamber are omitted, but generally, the inside of the first intermediate vacuum chamber 11 is evacuated by a rotary pump, and each chamber after that is evacuated. is evacuated by a turbomolecular pump using a rotary pump as a roughing pump.

An electrospray ion (ESI) source 101 is arranged in the ionization chamber 100 to ionize compounds in the sample liquid by atomizing the sample liquid while imparting an electric charge. However, the ionization technique is not limited to this, and other ion sources such as an atmospheric pressure chemical ion source can also be used. Also, an ion source that ionizes a gas sample or a solid sample instead of a liquid sample may be used.

The ionization chamber 100 and the first intermediate vacuum chamber 11 are communicated through a thin desolvation pipe 102 . Ions derived from sample components and minute charged droplets generated in the ionization chamber 100 are mainly desolvated by the difference between the pressure in the ionization chamber 100 (approximately atmospheric pressure) and the pressure in the first intermediate vacuum chamber 11. It is drawn into tube 102 and sent to first intermediate vacuum chamber 11 . The desolvation tube 102 is heated to an appropriate temperature, and the passage of charged droplets through the interior of the desolvation tube 102 accelerates the vaporization of the solvent in the droplets and promotes the generation of ions.

A multipole ion guide 111 is arranged in the first intermediate vacuum chamber 11 to focus the ions near the ion optical axis C1 and pass through the top opening of the skimmer 112 to the second intermediate vacuum chamber. It enters the vacuum chamber 12 . A multipole ion guide 121 is also arranged in the second intermediate vacuum chamber 12 , and ions are sent from the second intermediate vacuum chamber 12 to the first analysis chamber 13 by this multipole ion guide 121 .

In the first analysis chamber 13, a quadrupole mass filter 131 that separates ions according to their mass-to-charge ratio (m/z), a collision cell 133 equipped with a multipole ion guide 132 inside, and A part of the front-stage transfer electrode 134 and the rear-stage transfer electrode 141 for transporting the ions is arranged. The front-stage transfer electrode 134 and the rear-stage transfer electrode 141 are collectively referred to as a transfer electrode 140 .

Ions incident on the first analysis chamber 13 are introduced into the quadrupole mass filter 131, and only ions having a specific mass-to-charge ratio according to the voltage applied to the quadrupole mass filter 131 pass through the quadrupole mass filter. Go through 131. A collision gas such as argon or nitrogen is supplied to the interior of the collision cell 133 continuously or intermittently. Ions that have a predetermined energy and enter the collision cell 133 come into contact with the collision gas and are dissociated by collision-induced dissociation to generate various product ions.

Various product ions emitted from the collision cell 133 are converged by the transfer electrode 140 and sent to the second analysis chamber 14 . In the second analysis chamber 14, the rest of the rear transfer electrode 141, an orthogonal acceleration section 142, an acceleration electrode section 143, a flight tube 144, a reflectron 145, a back plate 146, an ion detector 147, and the like are arranged. The ions introduced into the second analysis chamber 14 as a thin, highly parallel ion stream by the rear-stage transfer electrode 141 are transferred in the orthogonal acceleration section 142 in a direction (Z-axis direction) substantially orthogonal to the incident direction (X-axis direction) of the ion stream. ).

The ions emitted from the orthogonal acceleration section 142 in a pulsed manner, that is, as a group of ion packets, are further accelerated by the acceleration electrode section 143 and introduced into the flight space within the flight tube 144 . The flight tube 144, the reflectron 145, and the back plate 146 form an electric field in the flight space that causes the ions to return and fly along the path indicated by C2 in FIG. As a result, the ions fly back through the flight tube 144 again and reach the ion detector 147 .

The ions ejected from the orthogonal acceleration section 142 fly at a speed corresponding to the mass-to-charge ratio of the ions. Therefore, various ions that are simultaneously accelerated by the orthogonal acceleration section 142 are separated according to their mass-to-charge ratios during flight, and reach the ion detector 147 with a time lag. The ion detector 147 generates a detection signal according to the amount of ions that have arrived. A data processing unit (not shown) creates a mass spectrum (product ion spectrum) in which the flight time is converted to a mass-to-charge ratio based on the detection signal.

[Detailed Configuration of Transfer Electrode and Orthogonal Acceleration Section]
Next, the configurations of the transfer electrode 140, the orthogonal acceleration section 142, and the acceleration electrode section 143 in the Q-TOF mass spectrometer of this embodiment will be described with reference to FIGS. 2 to 6 in addition to FIG. . FIG. 2 is an enlarged view of the vicinity of the transfer electrode 140 in the Q-TOF mass spectrometer of this embodiment. FIG. 3 is an enlarged view of the vicinity of part A in FIG. FIG. 4(A) is a diagram showing only the fixing member for explaining the configuration of the rear side fixing member, and FIG. 4(B) is a cross-sectional view along the arrow line BB' in FIG. 4(A). is. FIG. 5 is a cross-sectional view taken along line DD' in FIG. 2 for explaining the configuration of the front fixing member. FIG. 6 is a plan view of each electrode plate that constitutes the post-stage transfer electrode 141. FIG.

As shown in FIG. 2, the front-stage transfer electrode 134 includes three

electrode plates

1341, 1342, and 1343. These three

electrode plates

1341, 1342 and 1343 are fixed to each other with an insulating spacer 1344 interposed therebetween. An electrode plate 1341 positioned on the frontmost side of the front transfer electrode 134 (the side closest to the collision cell 133) is fixed to the collision cell 133 via a spacer 1344, thereby positioning the front transfer electrode 134. FIG. The collision cell 133 is fixed to the vacuum chamber 1 via a fixing member (not shown).

Each of the three

electrode plates

1341, 1342, and 1343 has a circular ion passage opening formed in its center. The diameter of the ion passage aperture of the electrode plate 1342 located in the center along the ion optical axis C1 is larger than the diameter of the ion passage apertures of the

electrode plates

1341 and 1343 on both sides thereof.

On the other hand, as shown in FIG. 2, the rear transfer electrode 141 includes four

electrode plates

1411, 1412, 1413, and 1414. These four

electrode plates

1411, 1412, 1413, and 1414 are also connected with insulating

spacers

1415 and 1416 sandwiched between adjacent electrode plates along the ion optical axis C1. A spacer 1415 positioned between the

electrode plates

1411, 1412 is annular, and a spacer 1416 positioned between the

electrode plates

1412, 1413, 1414 is rod-shaped.

The frontmost electrode plate 1411 is placed in the first analysis chamber 13, and the remaining three

electrode plates

1412, 1413, and 1414 are placed in the second analysis chamber 14. An annular spacer 1415 that connects the two

front electrode plates

1411 and 1412 is positioned inside a flat cylindrical opening provided in a partition ring 165 that separates the first analysis chamber 13 and the second analysis chamber 14 from each other. It has a contour that fits perfectly around the circumference, and a spacer 1415 is inserted into the opening. Therefore, the spacer 1415 is slidable relative to the partition ring 165 in the direction of the ion optical axis C1 (both positive and negative directions of the X axis).

The electrode plate 1411 arranged in the first analysis chamber 13 is formed with a circular ion passage aperture having a larger diameter than the ion passage aperture of the electrode plate 1343 positioned in front thereof. On the other hand, each of the three

electrode plates

1412, 1413, 1414 arranged in the second analysis chamber 14 is formed with a rectangular ion passage opening (slit). As shown in FIG. 6, the size of the rectangular ion passage aperture is the smallest in the electrode plate 1412 and increases in order of the

electrode plates

1414 and 1413 . The shape of the ion passage aperture corresponds to the shape of the aperture of the ion incident surface of the orthogonal acceleration section 142 located at the subsequent stage.

At a predetermined position 1B on the side wall of the vacuum chamber 1 in the second analysis chamber 14, a conductive plate-like base 150 having a rectangular opening in the center is fixed so as to be substantially horizontal. . Although the base 150 is depicted as a separate member from the vacuum chamber 1 in FIG. 2 and the like, the base 150 may be formed integrally with the vacuum chamber 1 .

As shown in FIG. 4, on the upper surface of the base 150, a total of six cylindrical insulating insulators 151 are fixed, three on each side of the opening of the base 150 in the Y-axis direction. ing. A conductive base plate 152 having two ion passage apertures is fixed on top of these six insulators 151 . Furthermore, a conductive positioning plate 153 in the form of a rectangular plate having an ion passing aperture is fixed to the upper surface of the base plate 152 . The rearmost electrode plate 1414 of the rear transfer electrodes 141 is held by a conductive lens holder 161 . This lens holder 161 is fixed to the positioning plate 153 and the base plate 152 via an insulating lens insulator 160 . This fixation is performed by holder fixing screws 155 made of resin, which is an insulating material.

On the positioning plate 153, in addition to the lens holder 161, the orthogonal acceleration section 142 including the push-out electrode 1421 and the pull-in electrode 1422, and the acceleration electrode section 143 are fixed. An ion detector 147 is fixed above the other opening of the base plate 152 .

The acceleration electrode section 143 is configured by alternately stacking acceleration electrodes 1431 and insulating spacers 1432 , and is fixed to the positioning plate 153 together with the orthogonal acceleration section 142 by a plurality of rod-shaped members 154 .

A partition wall 164 is provided between the first analysis chamber 13 and the second analysis chamber 14 . The partition wall 164 extends inward from the inner wall surface of the vacuum chamber 1 and includes a conductive extension 163 having a substantially circular planar opening, and is attached to the extension 163 from the second analysis chamber 14 side. and the previously described septum ring 165, which is formed by Here, the vacuum chamber 1 and the extension part 163 are described as separate members, but the extension part 163 may be integrated with the vacuum chamber 1 .

As shown in FIGS. 3 and 5, a spacer 1415 sandwiched between two

electrode plates

1411 and 1412 slides in the direction of the ion optical axis C1 (X-axis direction) on the inner peripheral side of the opening of the partition ring 165. possibly embedded. The outer peripheral portion of the partition ring 165 overlaps with the extending portion 163, and in the annular overlapping portion located on the YZ plane, at four positions at approximately equal angular intervals around the ion optical axis C1, Septum rings 165 are attached to extensions 163 by spacer screws 166 respectively.

As shown in FIG. 3, the spacer screw 166 is screwed into the extension 163 with an O-ring 167 as an elastic member interposed between the flange 1661 and the partition ring 165 . A predetermined gap is formed between the flange 1661 and the partition ring 165 when the threaded portion of the spacer screw 166 is maximally screwed into the threaded hole of the extension 163 . The O-ring 167 is crushed in the gap, and the elastic force of the crushed O-ring 167 presses the partition ring 165 against the extending portion 163 . Further, the diameter of the screw through hole 1651 formed in the partition ring 165 is larger than the outer diameter of the spacer portion 1662 of the spacer screw 166 by a predetermined size. Therefore, between the screw through hole 1651 and the spacer portion 1662, there is play (gap) within a predetermined range in a direction substantially orthogonal to the ion optical axis C1.

Since there is almost no difference in the amount of crushing of the O-ring 167 between devices, there is almost no difference between devices regarding the magnitude of force when the partition ring 165 is pressed against the extension 163 . Since the partition ring 165 is made of resin (for example, polyacetal (POM) or polytetrafluoroethylene (PTFE)) and the extension 163 is made of metal (for example, aluminum), the coefficient of static friction at the contact surface between them is small. Therefore, when an appropriate amount of force is applied to move (displace) the partition ring 165 in a direction substantially orthogonal to the ion optical axis C1, the partition ring 165 can move in that direction (arrow in FIG. 3). . In other words, the

electrode plates

1411 and 1412 are slidable within a predetermined range in directions substantially orthogonal to the ion optical axis C1 (both positive and negative directions of the Z axis).

The lens holder 161 is fixed to the surface of the partition ring 165 on the second analysis chamber 14 side by a lens holder fixing member 162 fixed to the rear upper part. In FIG. 5, the mounting position of the lens holder fixing member 162 is indicated by reference numeral 162A. This lens holder fixing member 162 may be an integral member, or may be a combination of a plurality of members. That is, the lens holder 161 is indirectly fixed downward to the vacuum chamber 1 by the holder fixing screw 155 and indirectly fixed to the vacuum chamber 1 via the lens holder fixing member 162 at its upper portion. there is

[Structural Features and Advantages]
The Q-TOF mass spectrometer of this embodiment is usually assembled in a factory under a room temperature environment (eg, 25° C.). On the other hand, during analysis, the temperature of the second analysis chamber 14 is controlled to a predetermined temperature (for example, 42° C.) higher than normal room temperature by a heater (not shown). This is to prevent the distance of the flight paths of ions formed by the flight tube 144 or the like from being affected by fluctuations in the ambient temperature. Therefore, each member arranged in the second analysis chamber 14 expands according to the coefficient of thermal expansion of the material forming each member. Also, when the target temperature for temperature control is changed, or when the temperature changes during transportation of the device, each member expands or contracts according to the coefficient of thermal expansion of the material forming each member.

When the device is assembled in the factory, the central axis of the transfer electrode 140 (the front-stage transfer electrode 134 and the rear-stage transfer electrode 141) is aligned between the facing surfaces of the push-out electrode 1421 and the pull-in electrode 1422 of the orthogonal acceleration section 142 with respect to the facing surface. Transfer electrodes 140 are positioned with high accuracy so that they pass in parallel. At this time, in the rear-stage transfer electrode 141, the central axis of the spacer 1415 arranged to straddle the first analysis chamber 13 and the second analysis chamber 14 with the partition wall 164 interposed therebetween is aligned with the partition ring 165, the extension 163, and a portion of the vacuum chamber 1 (the portion indicated by 1A in FIG. 2; hereinafter, this portion will be referred to as a partial vacuum chamber 1A).

As shown in FIG. 5, the septum ring 165 is fixed by spacer screws 166 to the extension 163 at four positions that are substantially symmetrical about the ion optical axis C1 (except, as noted above, The partition ring 165 is movable within a predetermined range in the YZ plane with respect to the extension 163). Therefore, when the partition ring 165 expands or contracts, the size of the central opening changes, but in principle the central axis does not displace. That is, in the mass spectrometer of the present embodiment, the partition ring 165, the extension 163, and the partial vacuum chamber 1A are included in the front fixing member. It is an element (that is, a first displacement member) that displaces the position of the ion optical axis C1 (C1a) on the electrode plate 1411 due to expansion or contraction according to the expansion coefficient. The displacement of the ion optical axis C1 means the change in the position of the ion optical axis C1 with respect to the predetermined position 1B as a reference position.

On the other hand, the electrode plate 1414 positioned at the rearmost end of the rear transfer electrode 141 is attached to the base 150 fixed to the predetermined position 1B of the vacuum chamber 1 by the lens holder 161, the lens insulator 160, the positioning plate 153, the base plate 152, and fixed via an insulator 151 . That is, in the mass spectrometer of this embodiment, the lens holder 161, the lens insulator 160, the positioning plate 153, the base plate 152, the insulator 151, and the base 150 are included in the rear-side fixing member. is positioned. All of these members included in the rear fixing member are elements (that is, second displacement members) that displace the ion optical axis C1 (C1a) on the electrode plate 1414 by expansion or contraction according to the coefficient of thermal expansion.

FIG. 7 is a schematic diagram showing a state in which the ion optical axis C1a of the rear-stage transfer electrode 141 and the ion optical axis C1b of the orthogonal acceleration section 142 are positioned on a straight line. The ion optical axis C1b of the orthogonal acceleration section 142 may be parallel to the facing surfaces of both the push-out electrode and the pull-in electrode included in the orthogonal acceleration section 142, and should be positioned equidistant from both facing surfaces. is not required. When assembling the device, the positions of the members are basically adjusted so that the state shown in FIG. 7 is achieved.

When heating and temperature control are performed during analysis, both the front side fixing member and the rear side fixing member fixing the rear transfer electrode 141 thermally expand in the same direction. is larger than the amount of thermal expansion of the front fixing member. In this case, the rear-side electrode plate 1414 of the rear-stage transfer electrode 141 moves more in the negative direction of the Z-axis than the front-side electrode plate 1411 . Therefore, the relationship between the ion optical axis C1a of the rear-stage transfer electrode 141 and the ion optical axis C1b of the orthogonal acceleration section 142 is as shown in FIG.

That is, the ion optical axis C1a of the rear-stage transfer electrode 141 is tilted with respect to the ion optical axis C1b of the orthogonal acceleration section 142. Thus, when the ion flow enters the orthogonal acceleration unit 142 along the tilted ion optical axis C1a, the starting position of the ions in the Z-axis direction varies depending on the position in the X-axis direction, and the applied kinetic energy also varies. This reduces mass accuracy and mass resolution. It should be noted that FIG. 8 is an extremely drawn diagram for easy understanding, and actually the inclination of the ion optical axis C1a is so slight that it cannot be visually recognized. Of course, even so, it degrades analytical performance significantly.

In the mass spectrometer of this embodiment, two measures are taken to reduce the inclination of the ion optical axis C1a as described above. One of the countermeasures is to reduce the difference in the amount of thermal expansion between the front-side fixing member and the rear-side fixing member and reduce the inclination of the ion optical axis C1a itself by appropriately selecting the material of each member. is. Another countermeasure is to make the partition ring 165 slidable within a predetermined range in a direction substantially orthogonal to the ion optical axis C1 (that is, the positive and negative directions of the Z axis), as described above. This is to make the

front electrode plates

1411 and 1412 follow the displacement of the rear electrode plate 1414 in the Z-axis direction due to the expansion or contraction of the fixing member, thereby reducing the inclination of the ion optical axis C1a.

In the mass spectrometer of this embodiment, the vacuum chamber 1 (partial vacuum chamber 1A), lens holder 161, positioning plate 153, base plate 152, and base 150 are made of the same conductive material. Here, as an example, aluminum is used as the conductive material. However, it is not an essential requirement that all conductive members be made of the same conductive material, and different types of conductive materials may be used. For example, some or all of the conductive members may be made of stainless steel (SUS).

On the other hand, the lens insulator 160 is made of a first insulating material having a smaller coefficient of thermal expansion than the conductive material, and the insulator 151 is made of a second insulating material having a larger coefficient of thermal expansion than the conductive material. , respectively. For example, when the conductive material is aluminum, polyether ether ketone (PEEK) resin is used as the second insulating material, and it is one of machinable ceramics with good workability as the first insulating material. Nitride machinable ceramics can be used. Boron nitride, for example, can be used as the first insulating material, but machinable ceramics such as nitride-based machinable ceramics and mica-based machinable ceramics are preferably used. Specifically, for example, Photoveil II (registered trademark of Ferrotec Material Technologies Corporation) described in Non-Patent Document 1 can be used as the nitride-based machinable ceramics.

If the same material as the second insulating material, such as PEEK resin, is used as the first insulating material, both the lens insulator 160 and the insulator 151 are made of a material having a larger coefficient of thermal expansion than the above conductive material. It will happen. Therefore, the amount of thermal expansion in the positive and negative directions of the Z axis (the direction orthogonal to the ion optical axis C1) in the front side fixing member composed only of the aluminum member is larger than that of the aluminum member and the PEEK resin member. The amount of thermal expansion in the same direction of the rear side fixing member composed of is considerably larger. As a result, as shown in FIG. 8, the inclination of the ion optical axis C1a may increase.

On the other hand, in the mass spectrometer of the present embodiment, the lens insulator 160 is not made of PEEK resin, but made of, for example, nitride-based machinable ceramics, which has a smaller coefficient of thermal expansion than the above conductive materials. The length of each member according to the coefficient of thermal expansion with the nitride machinable ceramics (the design length in the Z-axis direction of the member located in the range E from the predetermined position 1B to the ion optical axis C1 in FIG. 2 ) are adjusted accordingly.

Specifically, here, the amount of thermal expansion per unit temperature of the displacement element in the front side fixed member (the sum of the product of the length in the Z-axis direction and the coefficient of thermal expansion of each member included in the displacement element) P1 Then, the difference ΔP in the thermal expansion amount P1 per unit temperature of the displacement element in the rear fixing member is suppressed to 30% or less of the thermal expansion amount P1. As a result, the displacement amount of the front electrode plate 1411 in the Z-axis direction due to the thermal expansion of the front side fixing member and the displacement amount of the rear electrode plate 1414 in the Z-axis direction due to the thermal expansion of the rear side fixing member are the same. For example, even if the temperature differs between when the apparatus is manufactured and when the mass spectrometry is performed, the inclination of the ion optical axis C1a can be reduced.

In addition, even when the target temperature of the temperature control of the flight tube 144 is changed, it is possible to suppress the inclination of the ion optical axis C1a. Furthermore, even if each member expands or contracts due to temperature changes during the transport process of the mass spectrometer, the ion optical axis C1a is unlikely to be irreversibly tilted.

Although the tilt of the ion optical axis C1a can be reduced to a considerable extent by the above first measure, due to various design constraints such as cost constraints and the need to secure an electrical insulation distance, the measure In some cases, the inclination of the ion optical axis C1a caused by the expansion/contraction of each member cannot be sufficiently reduced only by the adjustment. Even in such a case, the mass spectrometer of this embodiment can sufficiently reduce the inclination of the ion optical axis C1a by the second countermeasure.

That is, when the amount of thermal expansion of the rear side fixing member is larger than that of the front side fixing member, the electrode plate 1414 held by the lens holder 161 moves in the negative direction of the Z axis.

Electrode plates

1413 and 1412, which are indirectly fixed to electrode plate 1414 via spacers 1416, are also subjected to force to move in the negative direction of the Z axis. Further, a force is applied to the partition ring 165 through the spacer 1415 fixed to the electrode plate 1412 to move it in the negative direction of the Z axis. In addition, since the lens holder 161 and the partition ring 165 are connected via the lens holder fixing member 162, when the lens holder 161 moves in the negative direction of the Z axis due to thermal expansion, A force is also applied to move the partition ring 165 in the same direction.

As described above, the coefficient of static friction at the contact surface between the partition ring 165 and the extending portion 163, which is pressed against the extending portion 163 by the elastic force of the O-ring 167, is small. Upon joining septum ring 165 , septum ring 165 moves in the negative Z-axis direction while maintaining contact with extension 163 . The maximum movable amount corresponds to the gap between the screw through-hole 1651 and the spacer portion 1662 . As a result, the

electrode plates

1411 and 1412 fixed to the spacer 1415 positioned inside the opening of the partition ring 165 also move in the negative direction of the Z axis. Then, the central axis of the rear-stage transfer electrode 141, that is, the ion optical axis C1a, becomes substantially parallel to the ion optical axis C1b of the orthogonal acceleration section 142, as shown in FIG. At this time, although the ion optical axis C1a of the rear transfer electrode 141 deviates from the ion optical axis C1b of the orthogonal acceleration section 142, the amount of deviation is such that the ion flow sent out from the rear transfer electrode 141 can enter the orthogonal acceleration section 142. Therefore, there is no problem in terms of analytical performance.

If the inclination of the ion optical axis C1a caused by the expansion or contraction of each member is reduced to some extent by the above-described first measure, the partition ring 165 moves only slightly in the above-mentioned second measure. Already, parallelism between the ion optical axis C1a and the ion optical axis C1b can be improved. On the other hand, even if the first measure is not taken, or even if it is taken, the effect is not sufficient, the range in which the partition ring 165 can move is widened to some extent in the second measure. By doing so, parallelism between the ion optical axis C1a and the ion optical axis C1b can be sufficiently ensured in practice. Thereby, high mass accuracy, mass resolution, and analytical sensitivity can be achieved in the orthogonal acceleration time-of-flight mass separator.

Moreover, the mass spectrometer of this embodiment can also solve the following problems.
When the vacuum chamber 1 starts to be evacuated and when the vacuum is released and the atmosphere is released, the difference between the pressure in the first analysis chamber 13 and the pressure in the second analysis chamber 14 temporarily becomes large. Sometimes. Then, a force corresponding to the pressure difference is applied in the direction along the ion optical axis C1 to the electrode plate 1412 having the smallest ion passage aperture in the rear-stage transfer electrode 141 . However, the direction of the force at that time differs depending on which of the first analysis chamber 13 and the second analysis chamber 14 has higher pressure.

When the pressure inside the first analysis chamber 13 is higher, a rightward force is applied to the electrode plate 1412 in FIG. If the lens holder fixing member 162 were not present, the rear transfer electrode 141 would be rotated clockwise around the rearmost position (right side in FIG. 2) of the contact portion between the lens insulator 160 and the lens holder 161 due to the above force. A rotating moment acts. The lens holder 161 is fixed by a holder fixing screw 155 that penetrates the positioning plate 153 and reaches the base plate 152. The screw 155 is made of resin and generally has an axial force greater than that of a metal screw. small. Therefore, when the lens holder 161 tries to rotate due to a large pressure difference, an excessive force may be applied to the holder fixing screw 155 and the holder fixing screw 155 may be stretched. As a result, the screw 155 may be irreversibly loosened, or the post-stage transfer electrode 141 may be irreversibly displaced.

On the other hand, in the mass spectrometer of this embodiment, the upper part of the lens holder 161 is fixed to the vacuum chamber 1 by the lens holder fixing member 162 via the partition ring 165 . The direction of this fixation is generally opposite to the direction of action of the force due to the pressure differential as described above, and is the desired direction to resist the force due to the pressure differential. Therefore, even if force due to the pressure difference is applied to the rear-stage transfer electrode 141, the lens holder 161 is unlikely to apply excessive force to the holder fixing screw 155, and the screw 155 can be prevented from stretching. As a result, in the mass spectrometer of the present embodiment, tilting of the lens holder 161 and loosening of the holder fixing screw 155 caused by pressure differences at the start of evacuation and release to the atmosphere can be avoided. The shift and tilt of the ion optical axis C1a of the electrode 141 can also be reduced.

[Modification]
In the mass spectrometer of the above-described embodiment, the elastic force of the O-ring 167 presses the partition ring 165 against the extending portion 163 fixed to or part of the vacuum chamber 1 with a predetermined force. , other elastic members may be used in place of the O-ring 167 . For example, instead of the O-ring 167, a member using mechanical expansion/contraction force such as a compression spring, a disc spring, or a spring washer may be used. Also, instead of the spacer screw 166 as a member for crushing the O-ring 167, a combination of a screw and a spacer may be used.

Further, the number of members included in the front-side fixing member and the rear-side fixing member for positioning the rear-stage transfer electrode 141 and the type of material of each member are not limited to those described in the above embodiment, and the present invention is not limited to those described in the above embodiment. can be changed as appropriate as long as it satisfies the requirements of

Further, in the mass spectrometer of the above-described embodiment, the post-stage transfer electrode 141 is configured to include four electrode plates, but the number can be appropriately selected as long as it is two or more. Further, the electrode plate may be thick enough to be said to be a rod electrode, or may be a multipole rod electrode having a structure divided into a plurality of segments along the ion optical axis C1. .

Also, in the mass spectrometer of the above embodiment, a linear ion trap may be used as the orthogonal acceleration section 142 . This linear ion trap may use either rod-shaped electrodes or plate-shaped electrodes. Also, instead of the reflectron time-of-flight mass separator, a linear time-of-flight mass separator such as a linear type, a multi-turn type, or a multi-reflection type may be used.

In addition, the present invention can be applied to general mass spectrometers including orthogonal acceleration time-of-flight mass separators. Therefore, in addition to the Q-TOF mass spectrometer of the above embodiment, for example, a single orthogonal acceleration time-of-flight mass spectrometer, and an ion trap time-of-flight mass spectrometer combining an ion trap and an orthogonal acceleration time-of-flight mass spectrometer. The present invention can also be applied to mass spectrometers and the like.

Furthermore, the above-described embodiment and various modifications are only examples of the present invention, and any modifications, changes, additions, etc., made appropriately within the scope of the present invention are not included in the scope of the claims of the present application. Naturally.

[Various aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments and variations described above are specific examples of the following aspects.

(Section 1) One aspect of the mass spectrometer according to the present invention is
a vacuum chamber having an internal space partitioned into a first vacuum chamber and a second vacuum chamber;
a plurality of electrode plates each having an ion passage opening disposed across the first and second vacuum chambers and connected via insulating spacers for transporting ions from the first vacuum chamber to the second vacuum chamber; a transfer electrode consisting of
an orthogonal acceleration unit disposed in the second vacuum chamber for accelerating ions transported by the transfer electrode in a direction perpendicular to the incident direction;
a rear electrode plate for fixing the rear electrode plate positioned in the second vacuum chamber among the plurality of electrode plates to the vacuum chamber at a position spaced apart in a predetermined direction orthogonal to the central axis of the ion passage aperture; a side fixing member;
A member for positioning a front electrode plate positioned in the first vacuum chamber among the plurality of electrode plates in the first vacuum chamber, the member extending inward from an inner wall surface of the vacuum chamber. It holds the provided extending portion and the spacer fixed to the front electrode plate, and is attached to the extending portion so as to be slidable within a predetermined range in a direction opposite to the predetermined direction. an annular partition member; and an anterior fixation member comprising:
Prepare.

According to the orthogonal acceleration time-of-flight mass spectrometer described in item 1, it is possible to reduce the inclination of the ion optical axis of the ion flow incident on the orthogonal acceleration part due to temperature control and temperature change during analysis. . As a result, the ion flow incident on the orthogonal acceleration section is kept parallel to the electrodes included in the orthogonal acceleration section, so high analytical performance (mass accuracy, mass resolution, analytical sensitivity) can be achieved.

(Section 2) In the orthogonal acceleration time-of-flight mass spectrometer described in Section 1, the partition member is pressed against the extension by an elastic member and is slidable relative to the extension. can do.

(Section 3) In the orthogonal acceleration time-of-flight mass spectrometer described in Section 2, the elastic member may be an O-ring.

The elastic member may be a member such as an O-ring, which utilizes the elastic force of the material itself, or a member such as a compression spring, disc spring, or spring washer, which utilizes mechanical expansion and contraction force.
According to the orthogonal acceleration time-of-flight mass spectrometers described in paragraphs 2 and 3, the slidability of the partition member on the contact surface between the extending portion and the partition member is ensured while increasing the adhesion between the extension portion and the partition member. be able to. Thereby, the airtightness of each of the first vacuum chamber and the second vacuum chamber can be improved. On the other hand, when the rear electrode plate moves in the direction opposite to the predetermined direction due to expansion/contraction of the rear fixing member, the partition member moves smoothly to reduce the inclination of the ion optical axis. can be done.

(Section 4) In the orthogonal acceleration time-of-flight mass spectrometer described in Section 1, one of the partition member and the extension may be made of resin, and the other may be made of metal.

As the resin, a material having a small coefficient of static friction (that is, having good slidability) such as polyacetal resin or polytetrafluoroethylene resin is preferable.
According to the orthogonal acceleration time-of-flight mass spectrometer according to item 4, when the rear-side electrode plate moves in the direction opposite to the predetermined direction due to expansion/contraction of the rear-side fixing member, the partition member moves smoothly, and the inclination of the ion optical axis can be reduced more reliably.

(Section 5) In the orthogonal acceleration time-of-flight mass spectrometer according to Section 1, the rear fixing member includes a holder that holds at least the rearmost electrode plate among the plurality of electrodes, A holder fixing member for fixing the holder to the partition member may be further provided.

When starting to evacuate the vacuum chamber or releasing the vacuum state, a large difference occurs between the pressure in the first vacuum chamber and the pressure in the second vacuum chamber, and the pressure difference causes the transfer electrode to move. A large force may be applied from the first vacuum chamber side to the second vacuum chamber side. If the holder holding the electrode plate is indirectly fixed to the vacuum chamber by, for example, a screw extending in the predetermined direction, a large force acts on the screw. If screws made of resin are used for electrical insulation, the screws may stretch and become loose, or the holder may rattle.

On the other hand, according to the orthogonal acceleration time-of-flight mass spectrometer described in item 5, since the holder is fixed to the partition member by the holder fixing member, the force due to the pressure difference as described above is applied to the transfer electrode. Even if it works, it is possible to avoid applying excessive force to the resin screws. As a result, loosening of the screws and rattling of the holder can be reduced, and the transfer electrode can be maintained in a properly positioned state.

(Section 6) In the orthogonal acceleration time-of-flight mass spectrometer described in Section 1, the front-side fixing member displaces the inlet-side central axis of the transfer electrode in a direction opposite to the predetermined direction due to thermal expansion. the rear fixing member includes a second displacement member that displaces the center axis of the transfer electrode on the outlet side in a direction opposite to the predetermined direction due to thermal expansion;
The difference between the amount of thermal expansion per unit temperature of the first displacement member and the amount of thermal expansion per unit temperature of the second displacement member is 30% or less of the amount of thermal expansion of the first displacement member. be able to.

According to the orthogonal acceleration time-of-flight mass spectrometer according to item 6, since the difference in thermal expansion or contraction between the front side fixing member and the rear side fixing member is small, the partition member slides with respect to the extension. Even if the movable range is small, the inclination of the ion optical axis in the transfer electrode can be suppressed more reliably.

(Section 7) In the orthogonal acceleration time-of-flight mass spectrometer according to Section 6, the second displacement member includes a first insulation member made of a first insulating material and a second insulation member made of a second insulating material. and a conductive member made of a conductive material, wherein the coefficient of thermal expansion of the first insulating material is smaller than the coefficient of thermal expansion of the conductive member, and the coefficient of thermal expansion of the second insulating material is the above. It can be greater than the coefficient of thermal expansion of the conductive member.

According to the orthogonal acceleration time-of-flight mass spectrometer according to item 7, the rear side fixing member comprises one or more conductive members and a plurality of insulating members each made of an insulating material having a different coefficient of thermal expansion. Since it is included as a displacement member, by appropriately selecting the coefficient of thermal expansion and dimensions of each member, it becomes easy to satisfy the requirements for the amount of thermal expansion in the device described in item 6.

(Section 8) In the orthogonal acceleration time-of-flight mass spectrometer described in Section 7, the first insulating material may be machinable ceramics.

According to the orthogonal acceleration time-of-flight mass spectrometer described in item 8, since machinable ceramic with good workability is used as the first insulating material, the rear side fixing member can be manufactured more easily and with high accuracy. be able to.

Reference Signs List 1 Vacuum chamber 1A Partial vacuum chamber 1B Predetermined position 10 Ionization device 100 Ionization chamber 101 Electrospray ion source 102 Desolvation tube 11 First intermediate vacuum chamber 111 Multipolar ion guide 112 Skimmer 12 Second intermediate vacuum chamber 121 Multipole ion guide 13 First analysis chamber 131 Quadrupole mass filter 132 Multipole ion guide 133 Collision cell 134 Front

stage transfer electrode

1341, 1342, 1343 Electrode plate 1344 Spacer 14 Second analysis chamber 140 Transfer electrode 141

Post-stage transfer electrode

1411, 1412, 1413, 1414

Electrode plate

1415, 1416 Spacer 142 Orthogonal acceleration section 1421 Extrusion electrode 1422 Pull-in electrode 143 Acceleration electrode section 1431 Acceleration electrode 1432 Spacer 144 Flight tube 145 Reflectron 146 Back plate 147 Ion detector 150 Base 151 Insulator 152 Base plate 153 Positioning plate 154 Bar member 155 Holder fixing screw 160 Lens insulator DESCRIPTION OF SYMBOLS 161... Lens holder 162... Lens holder fixing member 163... Extension part 164... Partition part 165... Partition ring 1651... Screw penetration hole 166... Spacer screw 1661... Collar part 1662... Spacer part 167... O-ring

Claims

a vacuum chamber having an internal space partitioned into a first vacuum chamber and a second vacuum chamber;
a plurality of electrode plates each having an ion passage opening disposed across the first and second vacuum chambers and connected via insulating spacers for transporting ions from the first vacuum chamber to the second vacuum chamber; a transfer electrode consisting of
an orthogonal acceleration unit disposed in the second vacuum chamber for accelerating ions transported by the transfer electrode in a direction perpendicular to the incident direction;
a rear electrode plate for fixing the rear electrode plate positioned in the second vacuum chamber among the plurality of electrode plates to the vacuum chamber at a position spaced apart in a predetermined direction orthogonal to the central axis of the ion passage aperture; a side fixing member;
A member for positioning a front electrode plate positioned in the first vacuum chamber among the plurality of electrode plates in the first vacuum chamber, the member extending inward from an inner wall surface of the vacuum chamber. It holds the provided extending portion and the spacer fixed to the front electrode plate, and is attached to the extending portion so as to be slidable within a predetermined range in a direction opposite to the predetermined direction. an annular partition member; and an anterior fixation member comprising:
An orthogonal acceleration time-of-flight mass spectrometer.
The orthogonal acceleration time-of-flight mass spectrometer according to claim 1, wherein the partition member is pressed against the extension by an elastic member and is slidable relative to the extension.
The orthogonal acceleration time-of-flight mass spectrometer according to claim 2, wherein the elastic member is an O-ring.
The orthogonal acceleration time-of-flight mass spectrometer according to claim 1, wherein one of said partition member and said extension is made of resin and the other is made of metal.
2. The rear-side fixing member includes a holder that holds at least the rearmost electrode plate among the plurality of electrodes, and further includes a holder fixing member that fixes the holder to the partition member. The orthogonal acceleration time-of-flight mass spectrometer according to .
The front side fixed member includes a first displacement member that displaces the center axis of the transfer electrode on the inlet side in a direction opposite to the predetermined direction by thermal expansion, and the rear side fixed member displaces the transfer electrode by thermal expansion. including a second displacement member that displaces the central axis on the outlet side of the in a direction opposite to the predetermined direction,
The difference between the amount of thermal expansion per unit temperature of said first displacement member and the amount of thermal expansion per unit temperature of said second displacement member is 30% or less of the amount of thermal expansion of said first displacement member. 2. The orthogonal acceleration time-of-flight mass spectrometer according to 1.
The second displacement member includes a first insulating member made of a first insulating material, a second insulating member made of a second insulating material, and a conductive member made of a conductive material. 7. The orthogonal acceleration time-of-flight type of claim 6, wherein the coefficient of thermal expansion of a material is less than the coefficient of thermal expansion of said conducting member, and the coefficient of thermal expansion of said second insulating material is greater than the coefficient of thermal expansion of said conducting member. Mass spectrometer.
The orthogonal acceleration time-of-flight mass spectrometer according to claim 7, wherein said first insulating material is machinable ceramics.