Mass spectrscope and method for assemblying pre-rods and main rods of mass spectrscope

Abstract

Provided is a mass spectroscope capable of suppressing decreases in spectral sensitivity and resolution due to deformation during assembly of a multipole electrode. A mass spectroscope 28 comprises a multipole rod electrode 1 having a plurality of rod pairs (2A-1, 2A-2 ...). The rod pairs (2A-1, 2A-2 ...) are composed of pre-rods 2A-1 to 2D-1 and main rods 2A-2 to 2D-2 that are connected in the direction of an ion optical axis via an insulation member 6. In the multipole rod electrode 1, the pre-rods 2A-1 to 2D-1 constitute pre-rod electrode portions, and the main rods 2A-2 to 2D-2 constitute main rod electrode portions. The diameter of an inscribed circle 3 on which the pre-rod electrode portions 2A-1 to 2D-1 surround the ion optical axis is equal to the diameter of the inscribed circle 3 on which the main rod electrode portions surround the ion optical axis, and the diameter of all of the pre-rods 2A-1 to 2D-1 of the multipole rod electrode 1 is greater than the diameter of the main rods 2A-2 to 2D-2 connected to the pre-rods 2A-1 to 2D-1.

Description

Mass spectrometer and method for assembling pre-rod and main rod of mass spectrometer

[0001] The present invention relates to a method for assembling a pre-rod and a main rod of a mass spectrometer.

[0002] Mass spectrometers often perform MS / MS analysis, which involves selecting ions of a specific mass from those generated in an ion source, decomposing the ions, and analyzing the masses of the decomposed ions to identify the detailed structure of the sample.

[0003] For example, in the case of a mass spectrometer in which the ion transport section (Q0), the first ion separation section (Q1), the ion dissociation section (Q2), and the second ion separation section (Q3) are all composed of multipole rod electrodes (typically quadrupole rod electrodes), ions generated in the ion source are efficiently transmitted through Q0 and introduced into Q1 by applying a radio frequency (RF) voltage to the multipole rod electrode of Q0.

[0004] Q1 is called a quadrupole mass filter (QMF) because it can transmit only ions with a specific mass from the ions introduced by applying RF and DC voltages to the multipole rod electrodes. The specific ions selected and separated by Q1 are introduced into Q2.

[0005] Q2 is called a collision cell because it has the function of decomposing ions (CID) by colliding them with neutral gases (nitrogen, helium, argon, etc.) in the Q2 atmosphere while allowing ions to pass through by applying RF voltage to the multipole rod electrodes. The ions decomposed in Q2 are introduced into Q3.

[0006] Like Q1, Q3 is also called a QMF because it can separate the introduced ions according to their mass by applying RF and DC voltages to the multipole rod electrodes. The ions separated by Q3 are ejected from the outlet according to their mass and detected by a detector.

[0007] As such a multipole rod electrode, the techniques described in Patent Documents 1 and 2 are known.

[0008] Patent Document 1 states that "the four main rod electrodes (31a to 31d) included in the main electrode section (31) are arranged rotationally symmetrically around the ion optical axis (C), while the four pre-rod electrodes (32a to 32d) included in the pre-electrode section arranged in front of the main electrode section (31) are arranged such that two are tangent to a circle with a radius r0 and the other two are tangent to a circle with a radius R0 larger than r0, and are rotationally asymmetric around the ion optical axis (C).

[0009] As a result, the shape of the acceptance on the xy plane related to the ion position on the pre-electrode portion (32) becomes elliptical. As the ion travels along the ion optical axis (C), the shape of the acceptance can be made gradually flattened, which reduces the mismatch between the emittance of the incident ion and the acceptance on the receiving side and reduces ion loss during ion introduction.

[0010] As a result, it is described that the ion transmittance of the entire quadrupole mass filter can be improved.

[0011] Furthermore, Patent Document 2 discloses a method and apparatus for reducing ion reflection between multipole segments in a mass spectrometer by matching the effective potential between the two segments.

[0012] The mass spectrometer has at least two multipole segments separated from one another along a longitudinal axis of the mass spectrometer such that there is a boundary region where ions are drawn from the upstream segment to the downstream segment, and each multipole segment further includes a set of spaced rod-shaped electrodes arranged around the longitudinal axis and having a field radius defined by an inscribed circle between the innermost portions of each electrode.

[0013] An effective potential match can be achieved by either supplying RF signals of different amplitudes to each segment and / or by modifying the field strength of the segments. In one embodiment, the multipole segments are described as being configured such that the upstream multipole segment has a smaller field radius than the downstream segment.

[0014] International Publication No. 2017 / 094146 Special Publication No. 2022-513801

[0015] In a mass spectrometer, when assembling electrodes that constitute a multipole such as a quadrupole, it is necessary to arrange the main rod and pre-rod in a straight line.

[0016] At this time, it is desirable to connect the main rod and the pre-rod, but if a screw is used in the fixing portion of the connecting portion, deformation may occur due to the torque of the screw.

[0017] In other words, when the connecting part is fixed using a screw, the torque generated when turning the screw may cause the pre-rod, which has a short axial length, to shift its position, potentially causing it to lose linearity with the main rod.

[0018] If the linearity between the main rod and the pre-rod is impaired, there is a risk that the sensitivity and resolution of the detected spectrum will decrease.

[0019] An object of the present invention is to provide a mass spectrometer and a method for assembling a pre-rod and a main rod of the mass spectrometer that can reduce the reduction in spectral sensitivity and resolution due to deformation during assembly of a multipole electrode.

[0020] In order to achieve the above object, the present invention is configured as follows.

[0021] A mass spectrometer includes a multipole rod electrode having a plurality of rod sets, each of which consists of a pre-rod and a main rod connected in the direction of an ion optical axis via an insulating member, and the pre-rods of the multipole rod electrode constitute a pre-rod electrode section and the main rods of the multipole rod electrode constitute a main rod electrode section, wherein the diameter of an inscribed circle formed by the pre-rod electrode sections surrounding the ion optical axis is equal to the diameter of an inscribed circle formed by the main rod electrode sections surrounding the ion optical axis, and the diameters of all the pre-rods constituting the multipole rod electrode are larger than the diameter of the main rods connected to the pre-rods via the insulating member.

[0022] Furthermore, in a method for assembling a pre-rod and a main rod of a mass spectrometer, an end face of the pre-rod and an end face of the main rod are placed opposite each other via an insulating member, the pre-rod, the insulating member, and the main rod are temporarily fixed together with insulating screws, the pre-rod, the insulating member, and the main rod are inserted into a cylindrical assembly guide jig, and the lower side surfaces of the pre-rod and the main rod are aligned with a reference line, a pre-rod position adjustment member is attached to the pre-rod through a pre-rod side position adjustment hole formed in the assembly guide jig, a main rod position adjustment member is attached to the main rod through a main rod side position adjustment hole formed in the assembly guide jig, the pre-rod and the main rod are aligned, the pre-rod and the main rod are fixed together, the pre-rod position adjustment member and the assembly position adjustment jig are removed, and the assembly guide jig is removed from the pre-rod and the main rod.

[0023] According to the present invention, it is possible to provide a mass spectrometer and a method for assembling a pre-rod and a main rod of a mass spectrometer that can reduce the reduction in spectral sensitivity and resolution due to deformation during assembly of a multipole electrode.

[0024] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments.

[0025] 1 is a perspective view of a multipole rod electrode according to an embodiment; a front view of a multipole rod electrode according to an embodiment; a diagram showing a manufacturing method of a rod electrode according to an embodiment; a diagram showing spectrum degradation due to deformation when connecting rods; a more detailed explanatory diagram of a manufacturing method of a rod electrode according to an embodiment; a diagram showing a spectrum after application of an embodiment; a diagram showing the configuration of a mass spectrometer 28 when an ion transmission part 37 functions as an ion transport part Q0;

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] <Ion Transmission Section> An example will be described in which the multipole rod electrode 1 constituting the ion transmission section 37 (shown in FIG. 7) is a quadrupole rod electrode including four rod pairs each consisting of a pre-rod and a main rod.

[0028] 1 and 2 are explanatory diagrams showing the configuration of a quadrupole rod electrode according to an embodiment of the present invention. Fig. 1 is a perspective view of a multipole rod electrode 1, and Fig. 2 is a front view of the multipole rod electrode 1.

[0029] 1 and 2, a multipole rod electrode 1 is composed of four rod electrodes 2A to 2D. Each of the four rod electrodes 2A to 2D is divided into segment rods 2A-1, 2A-2, 2B-1, 2B-2, 2C-1, 2C-2, 2D-1, and 2D-2.

[0030] Of these, the segment rods 2A-1, 2B-1, 2C-1, and 2D-1 arranged upstream in the direction of the ion optical axis are called pre-rods, and the segment rods 2A-2, 2B-2, 2C-2, and 2D-2 arranged downstream in the direction of the ion optical axis are also called main rods.

[0031] The pre-rod 2A-1 and the main rod 2A-2 are connected to each other in the direction of the ion optical axis. Similarly, the pre-rod 2B-1 and the main rod 2B-2, the pre-rod 2C-1 and the main rod 2C-2, and the pre-rod 2D-1 and the main rod 2D-2 are also connected to each other in the direction of the ion optical axis.

[0032] When the multipole rod electrode 1 is used as the ion transmission section 37, ions are introduced from one end of the multipole rod electrode 1 (the pre-rod 2A-1 to 2D-1 side), pass through the multipole rod electrode 1, and are discharged from the other end (the main rod 2A-2 to 2D-2 side).

[0033] Next, a method for applying a voltage to the multipole rod electrode 1 using a power supply and a circuit will be described below.

[0034] High-frequency voltages of opposite phases are applied to rod electrodes 2A and 2B and rod electrodes 2C and 2D, and different DC voltages V1 and V2 are applied to the pre-rod electrode portion consisting of pre-rods 2A-1 to 2D-1 and the main rod electrode portion consisting of main rods 2A-2 to 2D-2, respectively.

[0035] Each of the pre-rods 2A-1 to 2D-1 and main rods 2A-2 to 2D-2 is arranged around the ion optical axis and spaced apart with a field radius defined by an inscribed circle 3 between the innermost portions of each rod.

[0036] The ion transmission section 37 includes a power supply circuit (not shown) that supplies power to the multipole rod electrode 1 so that the effective potential of the pre-rod electrode section exceeds or is substantially equal to the effective potential of the main rod electrode section, so as to reduce reflection of ions transmitted through the boundary region.

[0037] In many cases, the length of the pre-rods 2A-1 to 2D-1 (length in the direction of the ion optical axis) is set to 10 to 20% of the length of the main rods 2A-2 to 2D-2 (length in the direction of the ion optical axis), so long electrodes are used for the main rods 2A-2 to 2D-2.

[0038] As shown in Fig. 3, main rod 2A-2 has screw holes 10 for fixing the electrode and supplying voltage on the side opposite to the surface that generates the quadrupole electric field (the surface on the inscribed circle 3 side in Fig. 2). Even with a rod electrode that has been precisely machined, including these processes, it is difficult to keep the deformation around the machined area to 2 µm or less relative to the diameter.

[0039] On the other hand, if the inscribed circle radius from the main rod inlet portion, where the pre-rods 2A-1 to 2D-1 and the main rods 2A-2 to 2D-2 are fastened with insulating screws 4, to the main rod outlet portion, which is the end face of the main rods 2A-2 to 2D-2, becomes smaller, the amount of ions passing through and the resolution will decrease.

[0040] In this way, when a screw inserted into the screw hole 5 is used to fix the connecting part, deformation occurs due to the torque of the screw. This deformation leads to a decrease in the sensitivity and resolution of the detected spectrum.

[0041] 4 is a diagram showing the spectral degradation due to deformation when pre-rods 2A-1 to 2D-1 and main rods 2A-2 to 2D-2 are connected. In FIG. 4, the line connected by multiple black circles represents the simulated waveform, and the line connected by multiple triangles represents the measured waveform.

[0042] A lump-shaped waveform (peak) that should not occur has occurred in the portion of the measured waveform indicated as the LD hump.

[0043] In this embodiment, taking into consideration the deformation of the rods during manufacturing, the radii of the pre-rods 2A-1 to 2D-1 are made larger than the radii of the main rods 2A-2 to 2D-2 as shown in FIGS.

[0044] Here, the multipole rod electrode 1 is configured so that the diameter of the inscribed circle 3 formed by the group of pre-rods 2A-1 to 2D-1 surrounding the ion optical axis is equal to the diameter of the inscribed circle 3 formed by the group of main rods 2A-2 to 2D-2 surrounding the ion optical axis, and the diameter of all pre-rods 2A-1 to 2D-1 constituting the multipole electrode is larger than the diameter of the main rods 2A-2 to 2D-2 connected to the pre-rods 2A-1 to 2D-1 via insulating members (insulating washers) 6.

[0045] 3, for example, the rod-facing surfaces (surfaces on the inscribed circle 3 side in FIG. 2) of the pre-rod 2A-1 and the main rod 2A-2 are placed opposite each other within the assembly guide jig 7. Then, using gravity, the lower side surfaces of the pre-rod 2A-1 and the main rod 2A-2 are aligned within the assembly guide jig 7 so that they are aligned with the reference line RL.

[0046] This makes it possible to minimize the inclination of the pre-rod 2A-1 and the difference in level between the pre-rod 2A-1 and the main rod 2A-2.

[0047] The pre-rod 2B-1 and main rod 2B-2, the pre-rod 2C-1 and main rod 2C-2, and the pre-rod 2D-1 and main rod 2D-2 are also aligned in the assembly guide jig 7 using gravity in the same manner as the pre-rod 2A-1 and main rod 2A-2.

[0048] FIG. 5 is a diagram for explaining in more detail the method of assembling the pre-rod 2A-1 and the main rod 2A-2.

[0049] In Figure 5, the end face of the main rod 2A-2 and the end face of the pre-rod 2A-1 are placed opposite each other via an insulating member 6, and the pre-rod 2A-1 and the insulating member 6 are lightly tightened with insulating screws 4 to temporarily fix them to the main rod 2A-2.

[0050] Then, the pre-rod 2A-1 and the main rod 2A-2 are inserted into a cylindrical assembly guide jig 7, and the pre-rod 2A-1 and the main rod 2A-2 are aligned.

[0051] That is, gravity is used to align the lower side surfaces of the pre-rod 2A-1 and the main rod 2A-2 within the assembly guide jig 7 so that they are aligned with the reference line RL. This allows the pre-rod 2A-1 and the main rod 2A-2 to be positioned in the positional relationship shown in FIG.

[0052] Next, a resin support (pre-rod position adjustment member) 8 is attached to the screw hole 5 on the pre-rod 2A-1 side via the pre-rod side position adjustment hole 7a formed in the assembly guide jig 7, and an assembly position adjustment jig (main rod position adjustment member) 9 is attached to the screw hole 10 on the main rod 2A-2 side via the main rod side position adjustment hole 7b formed in the assembly guide jig 7, and the tapped hole positions of the pre-rod 2A-1 and main rod 2A-2 are aligned.

[0053] Then, the screws are tightened with a torque driver at a fixed tightening torque via the resin support 8, and the insulating screws 4 are tightened and fixed.

[0054] Next, the resin support 8 and the assembly position adjusting jig 9 are removed from the pre-rod 2A-1 and the main rod 2A-2, and the assembly guide jig 7 is removed from the pre-rod 2A-1 and the main rod 2A-2.

[0055] In the case of a quadrupole rod electrode, the geometric shapes of the pre-rod electrode portion and the main rod electrode portion are in the ratio R / r ０ R is the rod radius and r ０ is the radius of the inscribed circle that touches the electrode tip. In this embodiment, the diameter 2R of the pre-rod electrode portion is set to be at least 0.03% larger than the diameter 2R of the main rod electrode portion.

[0056] FIG. 6 shows actual measurement data when the diameter of the pre-rods 2A-1 to 2D-1 is 9.5 mm and the diameter of the main rods 2A-2 to 2D-2 is 9.498 mm, making the diameter of the pre-rods 2A-1 to 2D-1 0.03% larger.

[0057] The data shown in Figure 6 shows that the lump-like peaks seen in Figure 4 have been eliminated. The diameters of the pre-rods 2A-1 to 2D-1 are preferably 0.03% or more and 0.08% or less than the diameters of the main rods 2A-2 to 2D-2.

[0058] The above-mentioned multi-rod electrode 1 has the configuration shown in Figure 2, and since processing deformation is suppressed, linearity between the main rods 2A-2 to 2D-2 and the pre-rods 2A-1 to 2D-1 is ensured, and a decrease in sensitivity and resolution of the detected spectrum can be suppressed.

[0059] Although a quadrupole rod electrode is used as an example in this embodiment, the technical concept of the present invention is not limited to quadrupoles and can be applied to various multipole rod electrodes, such as hexapoles and octopoles, each of which has a pre-rod electrode portion and a main rod electrode portion.

[0060] <Mass Spectrometer> Hereinafter, a mass spectrometer configured to cause an ion transmission section using the multipole rod electrode 1 as described above to function as an ion transport section (Q0) will be described.

[0061] FIG. 7 shows the configuration of the mass spectrometer 28 when the ion transmission section 37 according to this embodiment functions as the ion transport section Q0.

[0062] 7, the mass spectrometer 28 is mainly composed of an ion source 29 and a vacuum chamber 30. The ion source 29 can be an ion source using APCI, ESI, or any of various other ionization methods.

[0063] The vacuum chamber 30 is divided into a first vacuum chamber 31, a second vacuum chamber 32, and a third vacuum chamber 33, each of which is independently evacuated by a vacuum pump (not shown), and is maintained at a pressure range of several hundred Pa or less, a few Pa or less, and 0.1 Pa or less, respectively.

[0064] Ions generated in the ion source 29 pass through the first aperture 34 and are introduced into the first vacuum chamber 31. Then, the ions pass through the second aperture 35 and are introduced into the second vacuum chamber 32. Then, the ions pass through the ion transport section Q0. The above-described multipole rod electrode 1 can be used for the ion transport section Q0, and the voltage application method is basically the same. However, the voltage conditions for the radio frequency voltage and DC voltage are generally different from when the ion transport section Q0 is used as the ion dissociation section Q2.

[0065] Furthermore, the entrance electrode, exit electrode, pipe 8, case, etc. used in the ion dissociation section Q2 may be omitted.

[0066] Ions that have passed through the ion transport unit Q0 pass through the third aperture 36 and are introduced into the third vacuum chamber 33. The ions then pass through the first ion separation unit Q1. The first ion separation unit Q1 uses a QMF consisting of four rod electrodes or the like, which separates and passes only ions having a specific m / z from the ions introduced into the first ion separation unit Q1.

[0067] Ions of a specific m / z that have passed through the first ion separation unit Q1 are introduced into the ion dissociation unit Q2. Ions that have passed through the ion dissociation unit Q2 are introduced into the second ion separation unit Q3. The second ion separation unit Q3 uses a QMF composed of four rod electrodes or the like, which separates the ions introduced into the second ion separation unit Q3 according to their m / z and passes them through.

[0068] The ions that have passed through the second ion separation section Q3 are detected by a detector 40. The mass spectrometer 28 also includes a control section 41 for receiving instructions input from a user and for controlling voltages and the like.

[0069] According to the present invention, it is possible to provide a mass spectrometer and a method for assembling the pre-rod 2A-1 and main rod 2A-2 of the mass spectrometer, which ensures linearity between the main rods 2A-2 to 2D-2 and the pre-rods 2A-1 to 2D-1 and can reduce the decrease in spectral sensitivity and resolution due to deformation during assembly of the quadrupole electrode.

[0070] In the above example, the ion transmission section 37 is used as the ion transport section Q0, but the ion transmission section 37 according to the present invention can also be applied to the first ion separation section Q1, the ion dissociation section Q2, and the second ion separation section Q3.

[0071] Furthermore, the present invention is applicable to any rod set consisting of a pre-rod and a main rod.

[0072] Furthermore, the present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to an embodiment having all of the described configurations.

[0073] 1... multipole rod electrode, 2A, 2B, 2C, 2D... rod electrodes, 2A-1, 2B-1, 2C-1, 2D-1... pre-rods, 2A-2, 2B-2, 2C-2, 2D-2... main rods, 3... inscribed circle, 4... insulating screw, 5... screw hole, 6... insulating member (insulating washer), 7... assembly guide jig, 7a... pre-rod side position adjustment hole, 7b... main rod side position adjustment hole, 8... resin support (pre-rod position adjustment member), 9... Assembly position adjustment jig (main rod position adjustment member), 10...screw hole, 28...mass spectrometer, 30...vacuum chamber, 31...first vacuum chamber, 32...second vacuum chamber, 33...third vacuum chamber, 34...first aperture, 35...second aperture, 36...third aperture, 37...ion transmission section, 40...detector, 41...control section, Q0...ion transport section, Q1...first ion separation section, Q2...ion dissociation section, Q3...second ion separation section, RL...reference line

Claims

1. a multipole rod electrode having a plurality of rod sets; The rod set includes a pre-rod and a main rod connected in the direction of the ion optical axis via an insulating member, In the multipole rod electrode, the pre-rod constitutes a pre-rod electrode portion, and the main rod constitutes a main rod electrode portion. the diameter of the inscribed circle of the pre-rod electrode portion surrounding the ion optical axis is equal to the diameter of the inscribed circle of the main rod electrode portion surrounding the ion optical axis, A mass spectrometer, characterized in that the diameters of all of the pre-rods constituting the multipole rod electrode are larger than the diameter of the main rod connected to the pre-rods via the insulating member.

2. 10. The mass spectrometer according to claim 1, A mass spectrometer, wherein the difference between the diameter of the pre-rod and the diameter of the main rod is 0.03% or more and 0.08% or less of the diameter of the main rod.

3. A method for assembling a pre-rod and a main rod of a mass spectrometer, comprising: The end surface of the pre-rod and the end surface of the main rod are opposed to each other via an insulating member, and the pre-rod, the insulating member, and the main rod are temporarily fixed together with insulating screws; The pre-rod, the insulating member, and the main rod are inserted into a cylindrical assembly guide jig, and the lower side surfaces of the pre-rod and the main rod are aligned with a reference line. a pre-rod position adjusting member is attached to the pre-rod through a pre-rod side position adjusting hole formed in the assembly guide jig, a main rod position adjusting member is attached to the main rod through a main rod side position adjusting hole formed in the assembly guide jig, and the positions of the pre-rod and the main rod are aligned; The pre-rod and the main rod are fixed, Remove the pre-rod position adjusting member and the main rod position adjusting member; removing the assembly guide jig from the pre-rod and the main rod; A method for assembling a pre-rod and a main rod.

4. 4. The method for assembling a pre-rod and a main rod according to claim 3, A method for assembling a pre-rod and a main rod, wherein the difference between the diameter of the pre-rod and the diameter of the main rod is 0.03% or more and 0.08% or less of the diameter of the main rod.