Method for manufacturing a quadrupole mass filter, and quadrupole mass spectrometer

Abstract

To improve manufacturing yield while maintaining performance such as mass resolution. [Solution] One embodiment of the method for manufacturing a quadrupole mass filter according to the present invention is a method for manufacturing a quadrupole mass filter including four rod electrodes, comprising: a first step (S1, S2) of forming a hyperbolic surface by cutting at least a part of the side surface or circumferential surface of four rod-shaped members, each having a length in the range of 80 mm to 120 mm, in the longitudinal direction; and a second step (S3) of using a holding member to position and fix the four rod-shaped members, each having a hyperbolic surface formed on it, as rod electrodes, so that the four rod electrodes surround a central axis and the hyperbolic surface of each rod electrode faces the central axis.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a quadrupole mass filter used in a mass spectrometer and a quadrupole mass spectrometer using the quadrupole mass filter.

Background Art

[0002] In a general single quadrupole mass spectrometer, various components (compounds) contained in a sample are ionized in an ion source, and the ions generated thereby are separated by a quadrupole mass filter according to the mass-to-charge ratio (m / z), and the separated ions are detected by an ion detector.

[0003] A quadrupole mass filter generally has a configuration in which four rod electrodes having a substantially cylindrical outer shape are arranged parallel to each other and at equal angular intervals (90°) in the circumferential direction so as to contact the outside of an inscribed circle with a predetermined radius centered on a linear axis. Then, a voltage of +(U + Vcosωt), which is obtained by superimposing a high-frequency (RF) voltage +Vcosωt on a DC voltage +U, is applied to two rod electrodes facing each other across the central axis, which is also the ion optical axis. A voltage of -(U + Vcosωt), which is obtained by superimposing an RF voltage -Vcosωt having a phase inverted (180° different) from the above RF voltage +Vcosωt on a DC voltage -U having a polarity different from the above DC voltage +U, is applied to the other two rod electrodes. When the voltage value U of this DC voltage and the amplitude value V of the RF voltage are set to predetermined values according to m / z, only the ions having that m / z selectively pass through the quadrupole electric field in the quadrupole mass filter.

[0004] In quadrupole mass filters, it is known that lengthening the rod electrodes in the axial direction is advantageous for improving mass resolution (mass selectivity). This is because, given the same RF voltage frequency ω, the longer the rod electrodes are in the axial direction, the more vibrations the ions experience as they pass through the space enclosed by the rod electrodes, resulting in more stable vibrations for ions that should pass through (conversely, the vibrations of ions that should not pass through become more reliably unstable). Furthermore, in a quadrupole mass filter, if the curved surface of each rod electrode facing the central axis is a hyperboloid (a surface whose contour on a plane perpendicular to the central axis is hyperbolic), an ideal quadrupole electric field can be formed in the space enclosed by the rod electrodes (see Patent Document 1, etc.), thereby improving mass resolution and resulting in a better peak shape in the mass spectrum. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2018 / 138838 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] As mentioned above, to achieve high mass resolution and good peak shape, it is preferable to use a rod electrode as a quadrupole mass filter whose surface oriented toward the central axis is a hyperbolic surface and is as long as possible in the axial direction. However, machining the side surfaces of the rod electrode requires high precision in the micron range, and forming a hyperbolic surface with high precision is significantly more difficult than forming a simple arc-shaped surface. Therefore, attempting to manufacture a rod electrode whose surface oriented toward the central axis is a hyperbolic surface and is long in the axial direction results in a time-consuming manufacturing process, a low yield, and high costs. On the other hand, in order to reduce manufacturing costs, a rod electrode with a simple cylindrical shape is sometimes used, but in that case, it is unavoidable that the quality of mass resolution and peak shape will be sacrificed.

[0007] The present invention was made to solve these problems, and its main objective is to provide a method for manufacturing a quadrupole mass filter that can reduce manufacturing costs while sufficiently ensuring the performance of the quadrupole mass filter, such as high mass resolution and good peak shape, and a quadrupole mass spectrometer using a quadrupole mass filter manufactured by such a method.

[0008] In this specification, "quadrupole mass spectrometer" includes not only general single-type quadrupole mass spectrometers, but also triple quadrupole mass spectrometers in which quadrupole mass filters are placed before and after a collision cell, and quadrupole-time-of-flight (Q-TOF) mass spectrometers in which a quadrupole mass filter is placed before the collision cell and a time-of-flight mass separator is placed after it, and all other mass spectrometers equipped with quadrupole mass filters. [Means for solving the problem]

[0009] One embodiment of the method for manufacturing a quadrupole mass filter according to the present invention is a method for manufacturing a quadrupole mass filter used in a mass spectrometer, The first step involves forming a hyperbolic surface by machining at least a portion of the side or circumferential surface of each of four rod-shaped members, each having a length between 80 mm and 120 mm, along its entire length in the longitudinal direction. The second step involves using four rod-shaped members, each having a hyperbolic surface formed on it, as rod electrodes, and using a holding member to position and fix each rod electrode so that the four rod electrodes surround a central axis and the hyperbolic surface of each rod electrode faces the central axis. It has.

[0010] Furthermore, one embodiment of the quadrupole mass spectrometer according to the present invention includes a quadrupole mass filter that separates the ions to be measured according to m / z, and the quadrupole mass filter is Four rod electrodes, each having a length along its central axis between 80 mm and 120 mm, and at least one of the surfaces facing the central axis being a hyperbolic surface, A holding member that fixes the four rod electrodes so that the hyperbolic surfaces of each rod electrode face the central axis and surround the central axis, Includes. [Effects of the Invention]

[0011] The inventors of the present invention investigated the manufacturing of rod electrodes with a hyperbolic inner surface from various angles and found that when a hyperbolic surface is formed by machining the side or circumferential surface of a long rod-shaped member, the bending of the rod-shaped member during processing reduces the dimensional accuracy of the hyperbolic surface, which is the main cause of the decrease in manufacturing yield. In other words, by shortening the rod electrode, the bending of the rod-shaped member during processing can be reduced, making it possible to form a hyperbolic surface with greater accuracy. On the other hand, as mentioned above, shortening the rod electrode is disadvantageous in terms of mass resolution because the number of vibrations of ions as they pass through the space enclosed by the rod electrode decreases. Therefore, the inventors of the present invention investigated, through experiments and simulations, a balanced range of rod lengths that can improve manufacturing yield while maintaining performance equivalent to or better than conventional methods, while also considering other parameters such as ion velocity that affect the number of vibrations, and completed the present invention.

[0012] According to the above-described embodiment of the method for manufacturing a quadrupole mass filter and the quadrupole mass spectrometer of the present invention, a highly accurate hyperboloid can be obtained with a cost-satisfactory yield, and the rod length necessary for the separation and selection of the target ions can be secured. As a result, the above-described embodiment of the method for manufacturing a quadrupole mass filter and the quadrupole mass spectrometer of the present invention can improve detection sensitivity while maintaining mass resolution and good peak shape equivalent to or better than conventional methods, while also keeping costs down. [Brief explanation of the drawing]

[0013] [Figure 1] A schematic diagram of the main components of a single quadrupole mass spectrometer, which is one embodiment of the present invention. [Figure 2]Schematic plan view of the quadrupole mass filter in the single quadrupole mass spectrometer of the present embodiment when viewed in the Z-axis direction. [Figure 3] Flowchart showing an example of the manufacturing procedure of the quadrupole mass filter used in the single quadrupole mass spectrometer of the present embodiment. [Figure 4] Schematic diagram showing an example of the processing of the rod electrode. [Figure 5] Schematic diagram showing another example of the processing of the rod electrode. [Figure 6] Diagram showing an actual measurement example of the mass spectrum obtained by analyzing PEG with m / z 1004.6 when using a rod electrode with a rod length of 200 mm (conventional product). [Figure 7] Diagram showing an actual measurement example of the mass spectrum obtained by analyzing PEG with m / z 1004.6 when using a rod electrode with a rod length of 120 mm. [Figure 8] Diagram showing an actual measurement example of the mass spectrum obtained by analyzing PEG with m / z 1004.6 when using a rod electrode with a rod length of 80 mm. [Figure 9] Diagram showing an actual measurement example of the mass spectrum obtained by analyzing PEG with m / z 1893.4 when using a rod electrode with a rod length of 200 mm (conventional product). [Figure 10] Diagram showing an actual measurement example of the mass spectrum obtained by analyzing PEG with m / z 1893.4 when using a rod electrode with a rod length of 120 mm. [Figure 11] Diagram showing an actual measurement example of the mass spectrum obtained by analyzing PEG with m / z 1893.4 when using a rod electrode with a rod length of 80 mm. [Mode for Carrying Out the Invention]

[0014] [Supplementary Explanation of the Above Aspect] The quadrupole mass spectrometer of the above aspect allows the sample to be either a gas, a liquid, or a solid. Naturally, the ionization method varies depending on the form of the sample. That is, the quadrupole mass spectrometer of the above aspect does not particularly limit the method for generating the ions to be measured.

[0015] Moreover, the quadrupole mass spectrometer of the above aspect only needs to use a quadrupole mass filter as at least one of the mass separators. Therefore, this quadrupole mass spectrometer includes not only a very common single-type quadrupole mass spectrometer but also a triple quadrupole mass spectrometer and a quadrupole-time-of-flight mass spectrometer.

[0016] Also, it may be provided with either one or both of a pre-rod electrode and a post-rod electrode before and after the main rod electrodes that contribute to ion mass separation.

[0017] In the method for manufacturing the quadrupole mass filter of the above aspect, the cross-sectional shape of the "rod-shaped member" is not particularly limited. Generally, rod materials with a circular or square cross-section are easily available.

[0018] In the method for manufacturing the quadrupole mass filter of the above aspect, the method of machining the side or circumferential surface of the rod-shaped member along the longitudinal direction to form a hyperboloid is not particularly limited. Naturally, it is preferably a method that can obtain high dimensional accuracy. Specifically, it can be made to use one or a combination of multiple processes including machining such as cutting, grinding, and polishing, electrical discharge machining, and etching.

[0019] [Configuration and Schematic Operation of a Quadrupole Mass Spectrometer in an Embodiment] Hereinafter, a single quadrupole mass spectrometer according to an embodiment of the present invention and the quadrupole mass filter used therein will be described with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of the main part of the single quadrupole mass spectrometer of this embodiment. For convenience of explanation, as shown in FIG. 1, three mutually orthogonal axes of X, Y, and Z are set in space.

[0020] As shown in Figure 1, this quadrupole mass spectrometer has a chamber 1, which is roughly divided into four chambers: an ionization chamber 11, a first intermediate vacuum chamber 12, a second intermediate vacuum chamber 13, and an analysis chamber 14. The inside of the ionization chamber 11 is at approximately atmospheric pressure, and each chamber from the first intermediate vacuum chamber 12 onward is evacuated by a rotary pump (not shown) or a combination of a rotary pump and a turbomolecular pump.

[0021] An electrospray ionization (ESI) probe 2 is located in the ionization chamber 11, and the ionization chamber 11 and the first intermediate vacuum chamber 12 are connected through a desolvation tube 3 that is heated to a high temperature. A first ion guide 4 is located in the first intermediate vacuum chamber 12, and the first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13 are connected through a small hole provided at the top of the skimmer 5. A multipole second ion guide 6, consisting of multiple rod electrodes, is located in the second intermediate vacuum chamber 13. In the analysis chamber 14, a quadrupole mass filter 7 containing four rod electrodes 70 and an ion detector 8 are located along the ion optical axis C.

[0022] During analysis, a predetermined voltage is applied to the ESI probe 2, desolvation tube 3, ion guides 4 and 6, skimmer 5, quadrupole mass filter 7, and ion detector 8 from a power supply circuit (not shown). When a sample solution containing the component to be measured is introduced into the ESI probe 2, a charged sample droplet is sprayed from the tip of the ESI probe 2 into the ionization chamber 11. As the charged droplet collides with the surrounding gas and is atomized, and the solvent in the droplet vaporizes, the component molecules contained in the sample droplet are ionized. The ions thus generated are drawn into the desolvation tube 3 and sent to the first intermediate vacuum chamber 12.

[0023] Ions introduced into the first intermediate vacuum chamber 12 are focused near the small pores of the skimmer 5 by the electric field formed by the first ion guide 4, and pass through these pores into the second intermediate vacuum chamber 13. These ions are then transported while being focused by the electric field formed by the second ion guide 6 and enter the analysis chamber 14. In the analysis chamber 14, ions originating from the sample components are incident on the space surrounded by the four rod electrodes 70 of the quadrupole mass filter 7, and only ions with an m / z corresponding to the voltage applied to these rod electrodes 70 pass through this space and are incident on the ion detector 8. On the other hand, other ions diverge along the way. In other words, ions with a specific m / z are selected in the quadrupole mass filter 7. The ion detector 8 outputs an ion intensity signal of a magnitude corresponding to the amount of incident ions to a data processing unit (not shown).

[0024] [Structure of a quadrupole mass filter] Figure 2 is a schematic plan view of the quadrupole mass filter 7 in Figure 1, viewed from the left in the Z-axis direction. As shown in Figure 2, four rod electrodes 70 (70a, 70b, 70c, 70d; hereafter, the symbols "70a, 70b, 70c, 70d" will be used when referring to individual rod electrodes, and the symbol "70" will be used when referring to a common rod electrode) made of a conductive material such as stainless steel are arranged parallel to each other and at 90° angular intervals in the circumferential direction, so as to be tangent to a virtual circle 75 with radius r0 centered on the central axis, which is also the ion optical axis C. The cross-sectional shape of each rod electrode 70 is approximately cylindrical, but the portion of its circumferential surface facing the ion optical axis C is made into a hyperbolic surface by removing a part of the circle, as will be described later. A hyperbolic surface here is a curved surface in which the outline of the rod electrode 70 on the XY plane is hyperbolic, and this hyperbolic outline is continuously connected in the Z-axis direction between the ends of the rod electrode 70. The maximum distance in the cross-section of each rod electrode 70 is D, and in this case, D is the radius of the circle before it was removed to form the hyperbolic surface.

[0025] The four rod electrodes 70 are held by a roughly annular rod holder (holding member) 71 made of an insulator such as ceramic. The positions of the four rod electrodes 70 around the ion optical axis C are determined by attaching each rod electrode 70 to a predetermined position on the rod holder 71 and fixing them, for example, with screws. As shown in Figure 1, the rod holders 71 are provided at two locations, front and rear, along the Z axis, and these two rod holders 71 are fixed on a base 72.

[0026] Furthermore, the structure for fixing the rod electrodes 70 in a predetermined position is not limited to that described in this example, and various structures can be adopted. For example, instead of holding a part of the circumferential surface of each rod electrode 70 with the rod holder 71 as in this example, a structure may be used that holds both ends or one end of each rod electrode 70. Also, instead of a structure in which the rod electrodes 70 and rod holder 71 are placed on the base 72, it is conceivable to suspend them from above, or to fix the rod electrodes 70 to a wall surface located in front of and / or behind the rod electrodes 70 (in the example of Figure 1, the wall surface separating the second intermediate vacuum chamber 13 and the analysis chamber 14).

[0027] In the quadrupole mass filter 7 of this embodiment, the four rod electrodes 70 having the shape described above are of an appropriate length in the range of 80 mm to 120 mm. This rod length is shorter than that of the rod electrodes that constitute a quadrupole mass filter in a typical quadrupole mass spectrometer. While longer rod electrodes are advantageous for obtaining high mass resolution, as will be described later, the inventors have confirmed that even with such relatively short rod electrodes 70, it is possible to ensure sufficient performance in terms of mass resolution, etc. The radius r0 of the virtual circle 75 that the rod electrodes 70 touch is set in the range of approximately 2 to 6 mm, and the maximum distance D in the cross-section of the rod electrodes 70 is set in the range of approximately 7 to 12 mm.

[0028] The voltage applied to each rod electrode 70 of the quadrupole mass filter 7 with this structure is the same as in the conventional design. Specifically, a voltage of +(U+Vcosωt)+Vbias is applied to a pair of rod electrodes 70a and 70c facing each other across the ion optical axis C, which is a DC voltage +U superimposed with an RF voltage +Vcosωt, and further increased by the addition of a DC bias voltage Vbias. A voltage of -(U+Vcosωt)+Vbias is applied to the other pair of rod electrodes 70b and 70d, which is a DC voltage -U with a different polarity from the DC voltage +U superimposed with an RF voltage -Vcosωt that is inverted in phase with the RF voltage +Vcosωt, and further increased by the addition of a common DC bias voltage Vbias. U and V determine the m / z of the ions that pass through. On the other hand, Vbias affects the velocity of the ions incident on the quadrupole mass filter 7 and, as will be described later, affects the number of oscillations of the ions attempting to pass through the quadrupole mass filter 7. Generally, the frequency of the RF voltage is set in the range of approximately 0.8 to 1.6 MHz, and the DC bias voltage Vbias is set in the range of approximately -1 to -7 V (however, this polarity applies when targeting positive ions; the polarity is different when targeting negative ions).

[0029] [Manufacturing method for quadrupole mass filters] The procedure for manufacturing the quadrupole mass filter 7 described above is explained with reference to Figures 3 to 5. Figure 3 is a flowchart showing an example of the manufacturing procedure, and Figures 4 and 5 are schematic diagrams showing examples of rod electrode processing.

[0030] The manufacturer first prepares four rod-shaped conductive members of a specified length (Step S1). This specified length is a predetermined length within the range of 80 mm to 120 mm. The cross-sectional shape of the rod-shaped members is arbitrary, but the most commonly available is a round bar (made of stainless steel) with a circular cross-section. The left side of Figure 4 shows the cross-section of this rod-shaped member.

[0031] Next, the manufacturer processes a portion of the circumferential or side surface of each rod-shaped member along its entire longitudinal direction using a predetermined method to form a hyperbolic surface (step S2). This rod-shaped member on which the hyperbolic surface is formed is the rod electrode 70. The processing method is not particularly limited as long as it is capable of forming a hyperbolic surface with high precision, but any of the following can be used, including cutting, grinding, polishing, electrical discharge machining, etching, or a combination thereof. The right side of Figure 4 shows a cross-section of a rod-shaped member with a circular cross-section in which a hyperbolic surface has been formed by machining the circumferential surface.

[0032] In conventional quadrupole mass filters, the length of the rod electrodes is 130 mm or more, typically around 200 mm. In contrast, the length of the rod electrodes used here is in the range of 80 mm to 120 mm, which is short, about 1 / 3 to 3 / 5 of the standard rod length. According to the inventor's research, when attempting to machine a portion of the circumferential or side surface of a rod-shaped member of about 200 mm or more in length into a hyperbolic shape along its entire longitudinal direction, as shown in Figure 4, the rod-shaped member is prone to bending during the machining process. This bending leads to a decrease in the accuracy of the hyperbolic shape, significantly reducing the yield during manufacturing. In contrast, if the length of the rod electrodes is 120 mm or less, it is possible to suppress the bending of the rod-shaped member during machining to a substantially acceptable level. As a result, sufficiently high dimensional accuracy can be ensured for the shape of the hyperbolic surface.

[0033] Next, the manufacturer fixes the four rod electrodes 70 using a rod holder 71 (step S3) such that the hyperboloid surfaces of the four rod electrodes 70 each point toward the central axis, the vertices of the hyperboloid surfaces are tangent to the virtual circle 75, the angular spacing between adjacent rod electrodes 70 in the circumferential direction is 90°, and each rod electrode 70 is parallel to the central axis (ion optical axis C). Here, since the rod holder 71 has an arc-shaped rod mounting portion for attaching the four rod electrodes 70, the position and circumferential orientation of each rod electrode 70 can be appropriately determined by attaching each rod electrode 70 to its respective rod mounting portion and fixing it with screws or the like.

[0034] The manufacturer can complete the quadrupole mass filter 7 as shown in Figures 1 and 2 by placing the assembled rod electrodes 70 on the base 72 and fixing them with screws or fastening members (step S4).

[0035] As described above, by forming the rod electrodes 70 using rod-shaped members shorter than conventional ones, at 80-120 mm, a quadrupole mass filter 7 can be obtained in which the surface oriented toward the central axis of each rod electrode 70 is a hyperbolic surface with high dimensional accuracy. This makes it possible to form an ideal quadrupole electric field in the space surrounded by the rod electrodes 70 during analysis. Furthermore, although the rod electrodes 70 are short, as will be described later, by appropriately setting parameters such as the DC bias voltage Vbias, a sufficient number of oscillations of ions attempting to pass through the quadrupole mass filter 7 can be ensured. This makes it possible to improve detection sensitivity while ensuring mass resolution and peak shape quality equivalent to or better than conventional methods. In addition, the yield during the manufacturing of the rod electrodes is improved, and the cost of the rod-shaped members themselves is reduced due to the shorter rod length, thus lowering the cost of the mass spectrometer. Moreover, the short length of the quadrupole mass filter 7 has the advantage of reducing the length (depth) in the Z-axis direction of the mass spectrometer, making the device smaller and lighter.

[0036] [Experiment to determine rod length] To investigate how the length of the rod electrodes affects the performance of mass spectrometry when a quadrupole mass filter is manufactured according to the procedure described above, the inventors fabricated several quadrupole mass filters differing only in rod length and conducted comparative experiments under identical conditions. The main conditions were as follows: • Rod electrode length (L): 80mm, 120mm, 200mm (conventional standard length) • Maximum diameter of the cross-section of the rod electrode: 10 mm • Radius r0 of the virtual circle to which the rod electrode touches: 4 mm • Frequency (f) of the RF voltage applied to the rod electrode: 1.2MHz

[0037] On the other hand, as mentioned above, the length of the rod electrode affects the vibration frequency of ions passing through the space enclosed by the rod electrode, and this vibration frequency affects the mass resolution. Therefore, the value of the DC bias voltage Vbias applied in common to the four rod electrodes was adjusted so that the vibration frequency would be approximately the same even when the lengths of the rod electrodes were different. The reason why changing the DC bias voltage Vbias changes the vibration frequency is that changing the DC bias voltage Vbias changes the potential difference between it and the DC bias voltage applied to the preceding second ion guide 6, that is, the energy received by the ions, and thus changes the velocity of the ions incident on the quadrupole mass filter 7. When the velocity of these ions changes, the residence time of the ions in the space enclosed by the rod electrode 70 changes, and as a result, the vibration frequency also changes. Here, the relative value of the DC bias voltage Vbias when using a rod electrode with a rod length of 200 mm is set to 1, the relative value of the DC bias voltage Vbias when using a rod electrode with a rod length of 120 mm is set to 0.71, and the relative value of the DC bias voltage Vbias when using a rod electrode with a rod length of 80 mm is set to 0.5.

[0038] Figures 6 to 8 show the measured peak waveforms for PEG at m / z 1004.6 when the rod lengths are 200 mm, 120 mm, and 80 mm, respectively. Figures 9 to 11 show the measured peak waveforms for PEG at m / z 1893.4 when the rod lengths are 200 mm, 120 mm, and 80 mm, respectively. The three peaks observed in each figure are the monoisotopic peak and the isotope peak.

[0039] Figures 6 to 11 show that, for both m / z 1004.6 and m / z 1893.4, the signal intensity is increased with rod lengths of 120 mm and 80 mm compared to 200 mm. Furthermore, it can be confirmed that the peak full width at half maximum can be adjusted to approximately 0.7 u for both rod lengths of 120 mm and 80 mm, and that isotopes can be sufficiently separated.

[0040] Now, if we denote the electric charge as e, the ion mass as m, the velocity of the ion passing through the rod electrode as v, and the DC bias voltage (accelerating voltage) as E, then theoretically the following relationship holds: (1 / 2)mv 2 =eE v = √(2eE / m) The number of vibrations N of an ion while passing through the space surrounded by the rod electrodes is: N = ft = fL√(m / 2eE) …(1) This is the result.

[0041] According to equation (1), in order to keep the ion vibration frequency N the same, if the DC bias voltage Vbias (relative value) for a rod length of 200 mm is set to 1, then the DC bias voltage Vbias (relative value) for a rod length of 120 mm is 0.36, and the DC bias voltage Vbias (relative value) for a rod length of 80 mm is 0.16. In other words, in practice, even if the DC bias voltage Vbias is made larger (or not made much smaller) than the theoretical value, it is possible to maintain performance such as high mass resolution and good peak shape. This can be presumed to be due to the fact that the processing accuracy of the hyperboloid surface of the rod electrode has been improved by shortening the length without changing the maximum distance D (cross-sectional diameter of the rod-shaped member) in the cross-section of the rod electrode.

[0042] Although experimental verification has not been conducted for rod lengths other than 200mm, 120mm, and 80mm, the above results suggest that when the rod length exceeds 120mm, the processing accuracy of the hyperbolic surface becomes problematic due to the deflection of the rod-shaped member during hyperbolic surface formation. On the other hand, shortening the rod length beyond 80mm raises concerns that a sufficient number of vibrations affecting mass resolution cannot be secured. Therefore, considering these factors together, it can be concluded that the appropriate range for rod length is between 80mm and 120mm.

[0043] In the above embodiment, the rod electrode 70 was formed from a round bar, but a hyperbolic surface may also be formed by cutting a part of the side surface of a rod-shaped member having a square or rectangular cross-sectional shape (or any other quadrilateral in general), as shown in Figure 5. The cross-sectional shape of the rod-shaped member is not limited to these and is arbitrary.

[0044] Furthermore, the above embodiments are merely examples of the present invention, and it is clear that the claims of this patent application can be extended beyond the various modifications already described, and any modifications, additions, or alterations made within the scope of the spirit of the present invention will also be included.

[0045] [Various forms] Those skilled in the art will understand that the exemplary embodiments described above are specific examples of the following embodiments.

[0046] (Section 1) One embodiment of the method for manufacturing a quadrupole mass filter according to the present invention is a method for manufacturing a quadrupole mass filter used in a mass spectrometer, The first step involves forming a hyperbolic surface by machining at least a portion of the side or circumferential surface of each of four rod-shaped members, each having a length between 80 mm and 120 mm, along its entire length in the longitudinal direction. The second step involves using four rod-shaped members, each having a hyperbolic surface formed on it, as rod electrodes, and using a holding member to position and fix each rod electrode so that the four rod electrodes surround a central axis and the hyperbolic surface of each rod electrode faces the central axis. It has.

[0047] (Section 7) Furthermore, one embodiment of the quadrupole mass spectrometer according to the present invention includes a quadrupole mass filter that separates the ions to be measured according to m / z, and the quadrupole mass filter is Four rod electrodes, each having a length along its central axis between 80 mm and 120 mm, and at least one of the surfaces facing the central axis being a hyperbolic surface, A holding member that fixes the four rod electrodes so that the hyperbolic surfaces of each rod electrode face the central axis and surround the central axis, Includes.

[0048] According to the method for manufacturing a quadrupole mass filter described in paragraph 1 and the quadrupole mass spectrometer described in paragraph 7, by shortening the rod electrode to 120 mm or less compared to conventional quadrupole mass filters, it is possible to obtain a highly accurate hyperbolic surface with a cost-satisfactory yield. Furthermore, by making the rod electrode length 80 mm or more, it is possible to secure the rod length necessary for the separation and selection of the target ions. As a result, the method for manufacturing a quadrupole mass filter described in paragraph 1 and the quadrupole mass spectrometer described in paragraph 7 can improve detection sensitivity while maintaining mass resolution and good peak shape equivalent to or better than conventional methods, while also keeping costs down.

[0049] (Section 2) A method for manufacturing a quadrupole mass filter as described in Section 1, wherein in the second step, the four rod electrodes may be fixed so as to be tangent to a virtual circle with a radius of 2 to 6 mm centered on the central axis.

[0050] (Article 3) A method for manufacturing a quadrupole mass filter as described in Article 2, wherein the four rod electrodes manufactured in the first step may have a maximum distance of 7 to 12 mm in the direction parallel to the tangent between the rod electrode and the virtual circle in the cross-section of each rod electrode.

[0051] (Section 8) In the quadrupole mass spectrometer described in Section 7, the four rod electrodes may be circumscribed around a virtual circle with a radius of 2 to 6 mm centered on the central axis.

[0052] (Section 9) In the quadrupole mass spectrometer described in Section 8, the four rod electrodes may be such that the longest distance in the cross-section of each rod electrode in the direction parallel to the tangent between the rod electrode and the virtual circle is 7 to 12 mm.

[0053] According to the method for manufacturing a quadrupole mass filter described in paragraphs 2 and 3, and the quadrupole mass spectrometer described in paragraphs 8 and 9, the dimensions other than the length of the rod electrode can be made to be similar to those of a conventional mass spectrometer, so the basic configuration and structure of the apparatus can be inherited.

[0054] (Article 4) A method for manufacturing a quadrupole mass filter as described in any one of Articles 1 to 3, wherein the first step may involve forming a hyperbolic surface by machining. Machining here includes grinding and cutting.

[0055] (Clause 5) Furthermore, in the method for manufacturing a quadrupole mass filter described in any one of paragraphs 1 to 3, the first step may involve forming a hyperbolic surface by electrical discharge machining.

[0056] (Clause 6) Furthermore, the method for manufacturing a quadrupole mass filter according to any one of paragraphs 1 to 3, wherein the first step involves forming a hyperbolic surface by etching.

[0057] According to the method for manufacturing a quadrupole mass filter described in any of paragraphs 4 to 6, a good hyperboloid can be formed with high precision.

[0058] (Item 10) The quadrupole mass spectrometer described in any one of items 7 to 9 further comprises a voltage application unit that applies a voltage to each rod electrode of the quadrupole mass filter, and the voltage application unit may apply an RF voltage with a frequency in the range of 0.8 to 1.6 MHz.

[0059] (Clause 11) The quadrupole mass spectrometer described in any one of Clauses 7 to 10 further comprises a voltage application unit that applies a voltage to each rod electrode of the quadrupole mass filter, and the voltage application unit may apply a DC bias voltage with a voltage value of -1 to -7V.

[0060] According to the quadrupole mass spectrometer described in paragraphs 10 and 11, the voltage applied to the rod electrodes can be about the same as that of a conventional mass spectrometer, so the electrical circuits such as the voltage application section can be the same as those of a conventional mass spectrometer.

[0061] (Clause 12) In addition, in the quadrupole mass spectrometer described in any one of Clauses 7 to 11, the maximum value of the m / z range may be in the range of 1000 to 2000.

[0062] (Item 13) In the quadrupole mass spectrometer described in any one of items 7 to 12, the full width at half maximum of the peaks in the mass spectrum may be 0.2 to 1.2 u. [Explanation of Symbols]

[0063] 1... Chamber 11…Ionization Chamber 12, 13…Intermediate vacuum chamber 14…Analysis room 2…ESI probe 3…Desolvation tube 4, 6... Ion Guide 5... Skimmer 7. Quadrupole Mass Filter 70…Rod electrode 71…Rod holder 72... Pedestal 75…Virtual Yen 8…Ion detector C... Ion optical axis (central axis)

Claims

1. A method for manufacturing a quadrupole mass filter used in a mass spectrometer, The first step involves forming a hyperbolic surface by machining at least a portion of the side or circumferential surface of each of four rod-shaped members, each having a length between 80 mm and 120 mm, along its entire length in the longitudinal direction. The second step involves using four rod-shaped members, each having a hyperbolic surface formed on it, as rod electrodes, and using a holding member to position and fix each rod electrode so that the four rod electrodes surround a central axis and the hyperbolic surface of each rod electrode faces the central axis. A method for manufacturing a quadrupole mass filter having the following characteristics.

2. The method for manufacturing a quadrupole mass filter according to claim 1, wherein in the second step, the four rod electrodes are fixed so as to be tangent to a virtual circle with a radius of 2 to 6 mm centered on the central axis.

3. The method for manufacturing a quadrupole mass filter according to claim 2, wherein the four rod electrodes manufactured in the first step have a maximum distance of 7 to 12 mm in the direction parallel to the tangent between the rod electrode and the virtual circle in the cross-section of each rod electrode.

4. The method for manufacturing a quadrupole mass filter according to claim 1, wherein the first step involves forming a hyperbolic surface by machining.

5. The method for manufacturing a quadrupole mass filter according to claim 1, wherein the first step involves forming a hyperbolic surface by electrical discharge machining.

6. The method for manufacturing a quadrupole mass filter according to claim 1, wherein a hyperboloid surface is formed by etching in the first step.

7. The quadrupole mass filter is equipped with a quadrupole mass filter that separates the ions to be measured according to their mass-charge ratio, and the quadrupole mass filter is equipped with a quadrupole mass filter that separates the ions to be measured according to their mass-charge ratio. Four rod electrodes, each having a length along its central axis of 80 mm to 120 mm, and at least one of the surfaces facing the central axis being a hyperbolic surface, A holding member that fixes the four rod electrodes so that the hyperbolic surfaces of each rod electrode face the central axis and surround the central axis, A quadrupole mass spectrometer, including one.

8. The quadrupole mass spectrometer according to claim 7, wherein the four rod electrodes are circumscribed around a virtual circle with a radius of 2 to 6 mm centered on the central axis.

9. The quadrupole mass spectrometer according to claim 8, wherein the longest distance between each of the four rod electrodes in the cross-section of the rod electrode, in a direction parallel to the tangent between the rod electrode and the virtual circle, is 7 to 12 mm.

10. The quadrupole mass spectrometer according to claim 7, further comprising a voltage application unit for applying a voltage to each rod electrode of the quadrupole mass filter, wherein the voltage application unit applies an RF voltage in the frequency range of 0.8 to 1.6 MHz.

11. The quadrupole mass spectrometer according to claim 7, further comprising a voltage application unit for applying a voltage to each rod electrode of the quadrupole mass filter, wherein the voltage application unit applies a DC bias voltage having a voltage value of -1 to -7V.

12. The quadrupole mass spectrometer according to claim 7, wherein the maximum value of the mass-to-charge ratio range is in the range of 1000 to 2000.

13. The quadrupole mass spectrometer according to claim 7, wherein the full width at half maximum of the peaks in the mass spectrum is 0.2 to 1.2 u.

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