Novel ion trap mass analyzer and resolution regulation and control method thereof

Abstract

The invention relates to a novel ion trap mass analyzer and a resolution regulation and control method thereof.The novel ion trap mass analyzer comprises a linear ion trap and regulation and control electrodes, the regulation and control electrodes are arranged in gaps between adjacent electrodes, and radio frequency voltage is applied to the regulation and control electrodes to regulate electric field distribution and content in the ion trap, so that the resolution of the ion trap is regulated and controlled. Therefore, on the basis of not changing the size structure of the ion trap mass analyzer, the electric field distribution and content of the ion trap are optimized by adding the regulation and control electrode, the influence of the content and component of an edge high-order field on the movement of ions is mainly made up, the ions are more stably distributed in the center of the ion trap, and the quality of the ion trap is improved. And the mass resolution and the storage efficiency of the ion trap are improved.

Description

Technical Field

[0001] The invention relates to the technical field of mass spectrometry and ion storage, and in particular to an ion trap mass analyzer and a resolution control method thereof. Background Art

[0002] Mass spectrometer (MS) is a common analytical instrument in modern science, which can be used for material detection and qualitative analysis in many fields such as biology, material science, clinical research, and space exploration. The core of a mass spectrometer is the mass analyzer, which determines the performance of the mass spectrometer. The ion trap mass analyzer has the advantages of simple structure and low dependence on vacuum. It is currently the only mass analyzer that can perform multi-stage mass spectrometry analysis with only a single analysis unit. Linear ion trap (LIT) is an ion trap mass analyzer, whose structure mainly consists of 4 hyperbolic electrodes and 2 planar end cap electrodes. Compared with traditional three-dimensional ion traps, LIT has a simple structure, improved ion storage capacity, and moderate mass resolution, so it has been widely used. The improvement of LIT electrode structure to achieve performance improvement has always been a hot topic in the research of ion trap mass analyzers, and many LITs with excellent performance have been born, such as rectangular ion traps, semicircular arc linear ion traps, and triangular electrode linear ion traps.

[0003] Studies have shown that the performance of an ion trap mass analyzer depends mainly on the electric field distribution in the ion confinement region, and the electric field distribution depends to a large extent on the geometry of the electrodes. The various electrode-shaped LITs developed in recent years have improved their analytical performance, especially mass resolution, because their internal electric field distribution contains multiple components of high-order fields. The internal electric field can be optimized by: (1) applying partial voltages on multiple electrodes; (2) changing the geometric structure of the ion trap. For example, U.S. Patent Publication No. US009735001B2 specifically discloses a planar electrode array ion trap, which optimizes the electric field in the ion trap by applying partial voltages on multiple electrodes to improve performance. U.S. Patent Publication No. US11764051B2 specifically discloses a planar LIT mass analyzer, and the geometric structure of the ion trap includes the electrode geometry, assembly accuracy, etc. These factors will affect the electric field distribution, thereby affecting the performance of the ion trap. China Patent Publication No. CN111816545A specifically discloses a prismatic linear ion trap mass analyzer, which realizes unidirectional excitation of ions and improves mass resolution. The Chinese patent publication number is CN105632986B, which specifically discloses a grid ion trap, which changes the electric field distribution of the ion trap by adjusting the voltage on the grid and the electrode, thereby improving the ejection efficiency of the ions. The Chinese patent publication number is CN104681392A, which specifically discloses a zigzag rod-shaped electrode linear ion trap, which is formed by four rod-shaped electrodes parallel to each other and surrounding a center line, wherein at least one pair of electrodes has a zigzag cross-section toward the center line, and the main goal is to simplify the electrode structure while improving the mass resolution of the ion trap, and reduce the difficulty of processing and assembly. However, these electrode shape improvements and optimizations have the following problems: they are all based on the improvement of the four radial annular electrodes. Once the electrode shape size is adjusted, the entire ion trap mass analyzer needs to be disassembled and reassembled, which not only increases the cost of the experiment, but is also too complicated for the assembly accuracy; in order to control the electric field components, the improvement of the radial four-electrode shape will seriously affect the internal electric field components, which is not conducive to accurately controlling the changes in the internal electric field. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to change the electric field distribution in the ion trap without re-disassembling and changing the size and structure of the ion trap mass analyzer, thereby improving the resolution of the linear ion trap mass analyzer.

[0005] The present invention provides an ion trap mass analyzer, comprising four basic electrodes, four control electrodes, two end cap electrodes and a fixed frame, wherein the interior of the fixed frame (9) is a cavity penetrating along its length direction, the four basic electrodes (1) are uniformly arranged on the inner wall of the cavity around the center line of the length direction of the fixed frame, the basic electrode (1) extends axially along the center line, the two end cap electrodes (3) are arranged at both ends of the length direction of the basic electrode (1), the two end cap electrodes (3) are symmetrically distributed, and the two end cap electrodes (3) are respectively connected to the fixed frame (9). The base electrode (1) and the end cap electrode (3) are fixed together to form an ion trap (5), there are gaps between adjacent base electrodes, the four control electrodes are respectively arranged at the gaps between adjacent base electrodes, mounting brackets are arranged at the cavities at both ends of the fixed frame corresponding to the gaps, the two ends of the control electrode are respectively fixed to the mounting brackets, RF capture voltages with equal amplitudes and opposite phases are applied between adjacent base electrodes, a positive voltage with the same amplitude as the base electrode is applied to the end cap electrode, and radio frequency voltages with equal amplitudes and the same phases are respectively applied to the four control electrodes.

[0006] Compared with the prior art, the ion trap mass analyzer of the present application has the following advantages: by arranging a control electrode in the gap between adjacent basic electrodes and applying a radio frequency voltage, the electric field distribution and content in the ion trap can be adjusted, so that without changing the size structure of the basic electrodes in the ion trap mass analyzer, the electric field distribution and content in the ion trap can be changed by adding the control electrode, so that after the ions enter the ion trap, they first move linearly along the center line, and are distributed along the arc center axis of the quadrupole field under the guidance of the RF capture voltage, and then, under the action of the radio frequency voltage of the control electrode, the kinetic energy of the ions in the X direction is forced to increase rapidly and eject from the ion trap.

[0007] In a possible implementation manner, the sides of the four basic electrodes facing the ion trap are in a curved shape.

[0008] Compared with the prior art, the linear ion trap formed by the curved base electrode and the end cover electrode can form a standard quadrupole field.

[0009] In a possible implementation, an XY coordinate axis is established with the axis of the center line as the origin and the surface perpendicular to the center line as the cross-section, the cross-section of the control electrode on the XY coordinate axis is a hyperbolic arch structure, and the four control electrodes are mirror-stacked on the XY coordinate axis and arranged in the four quadrants of the XY coordinate axis.

[0010] Compared with the prior art, the use of mirror-image-arranged control electrodes can make the control electrodes have a uniform effect on the electric field in the ion trap.

[0011] In a possible implementation, the hyperbolic arch structures of the four control electrodes respectively coincide with the hyperbolic partial trajectories when the focus is on the X-axis, and the curvature of the curved arch structure of the control electrode is the same as the curvature of the hyperbolic surface of the base electrode.

[0012] In a possible implementation, the frequency of the radio frequency voltage on the control electrode is the same as the frequency of the RF capture voltage on the base electrode.

[0013] In a possible implementation manner, the end cap electrode is provided with an ion inlet, the base electrode is provided with an ion outlet, and a detector for capturing ejected ions is provided at the ion outlet.

[0014] In a possible implementation, adjacent base electrodes and base electrodes and end cap electrodes are insulated, the distance between the control electrode and the center line is greater than 3 mm, and the distance between the control horizon and the base electrode is greater than 2 mm, so as to prevent the control electrode from being broken down by the RF capture voltage on the base electrode and improve the rigidity of the control electrode.

[0015] A method for controlling the resolution of an ion trap mass analyzer, wherein the method is based on the above-mentioned ion trap mass analyzer and performs control, and the method comprises: Step 1. Based on the XY coordinate axis, predefine the vertex coordinates (x, y) of the control electrode closest to the origin of the XY coordinate axis, the vertical distance d from the vertex coordinates (x, y) to the origin of the XY coordinate axis, the positive projection length a of the control electrode on the Y axis, and the RF voltage amplitude of the control electrode. V , the distance Rz between the vertex of the hyperbola where the control electrode is located on the X-axis and the center of the central symmetry axis and the thickness △ of the control electrode; locating the position of the control electrode in the ion trap with the vertex coordinates (x, y); Step 2. predefine the working sequence of the ion trap analyzer; Step 3. Adjust the vertical distance d from the vertex coordinate (x, y) of the control electrode to the origin of the XY coordinate axis, and the ion trap mass analyzer works according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; Step 4. On the basis of achieving the optimal mass resolution in step 3, adjusting the distance Rz between the vertex of the hyperbola where the control electrode is located on the X-axis and the centerline axis, the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; Step 5. Based on the optimal mass resolution achieved in step 4, adjust the width of the control electrode , the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer reaches an optimal mass resolution; Step 6. On the basis of achieving the optimal mass resolution in step 5, adjusting the projection length a of the control electrode on the Y axis, and the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; Step 7. Output the optimal mass resolution achieved in step 6 and the corresponding vertical distance d from the vertex coordinates (x, y) of the control electrode to the origin of the XY coordinate axis, the projection length a of the control electrode on the Y axis, the distance Rz between the vertex of the hyperbola where the control electrode is located on the X axis and the center line axis, and the thickness △ of the control electrode.

[0016] Compared with the prior art, the resolution control method of the ion trap mass analyzer of the present application has the following advantages: the resolution of the mass analyzer in the ion trap is adjusted by adjusting the vertical distance d from the vertex coordinates (x, y) to the origin of the XY coordinate axis, the projection length a of the control electrode on the Y axis, the distance Rz between the vertex of the hyperbola where the control electrode is located on the X axis and the center line axis, and the thickness △ of the control electrode, so as to adjust the resolution of the mass analyzer in the ion trap, thereby adjusting the resolution of the ion trap mass analyzer by adding control electrodes and adjusting relevant parameters of the control electrodes without changing the structure of the basic electrodes in the ion trap mass analyzer.

[0017] In a possible implementation manner, predefining the working sequence of the ion trap mass analyzer in step 2 specifically includes: Step 201. In the initial stage, an initial RF trapping voltage with equal amplitude and opposite phase is applied between adjacent base electrodes, a positive voltage is applied to the end cap electrode, and a radio frequency voltage V with equal amplitude and the same phase is applied to the control electrode; ions enter the ion trap from the ion entrance and move stably around the center line under the action of the RF trapping voltage; Step 202: gradually increase the RF capture voltage on the base electrode, keep the positive voltage on the end cap electrode unchanged, and keep the RF voltage V on the control electrode unchanged; the kinetic energy of the ions in the ion trap in the X direction increases under the action of the RF voltage, and they are ejected from the ion exit hole and captured by the detector; Step 203: Lowering the RF capture voltage of the base electrode to the initial RF capture voltage, and at the same time lowering the RF voltage of the control electrode.

[0018] In a possible implementation manner, the method for calculating the mass resolution of the ion trap mass analyzer in steps 3 to 6 includes: a. Obtaining a mass spectrum of the ion trap mass analyzer when it works according to a predefined working sequence; b. Obtain the mass-to-charge ratio m and half-peak width △m of the ion from the mass spectrum. The calculation formula for mass resolution is: . BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic structural diagram of an ion trap mass analyzer in a specific embodiment 1 of the present invention; Figure 2 is a cross-sectional view of the ion trap mass analyzer on the XY coordinate axis in the specific embodiment 1 of the present invention; Figure 3 The mass spectra before and after adding the regulating electrodes in the specific embodiment 1 of the present invention are shown; Figure 4 are various parameters predefined in the XY coordinate axis in the specific embodiment 2 of the present invention; Figure 5 It is a working timing diagram of the predefined ion trap mass analyzer in specific embodiment 2 of the present invention; Figure 6 The mass spectrum obtained by adjusting d in specific embodiment 2 of the present invention; Figure 7 This is a mass resolution diagram obtained by adjusting d in specific embodiment 2 of the present invention; Figure 8 The mass spectrum obtained by adding Rz on the basis of d in specific embodiment 2 of the present invention; Fig. 9 The mass spectrum obtained by reducing Rz on the basis of d in specific embodiment 2 of the present invention is Fig.10 The mass resolution map is obtained by adjusting Rz based on d in the specific embodiment 2 of the present invention; Fig.11 In the specific embodiment 2 of the present invention, the addition of d and Rz is The mass spectra obtained; Fig.12 In the specific embodiment 2 of the present invention, the reduction of d and Rz is The mass spectra obtained; Fig.13 In the specific embodiment 2 of the present invention, d, Rz and The mass spectrum obtained by adjusting a based on the above; Fig.14 In the specific implementation 2 of the present invention, d, Rz and The mass resolution map obtained by adjusting a based on the above results.

[0020] Description of reference numerals: 1. Base electrode; 2. Control electrode; 3. End cap electrode; 4. Mounting bracket; 4.1. Bracket frame; 4.2. Bracket beam; 5. Ion trap; 6. Gap; 7. Ion inlet; 8. Ion outlet; 9. Fixed frame. DETAILED DESCRIPTION

[0021] First, those skilled in the art should understand that these implementations are only used to explain the technical principles of the embodiments of the present application, and are not intended to limit the protection scope of the embodiments of the present application. Those skilled in the art can make adjustments to them as needed to adapt to specific application scenarios.

[0022] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0023] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0024] The present application is further described in detail below with reference to the accompanying drawings and specific embodiments. Specific embodiment 1

[0025] See also Figure 1-2 As shown, an embodiment of the present application discloses an ion trap mass analyzer, including four base electrodes 1, four control electrodes 2, two end cover electrodes 3, two mounting brackets 4 and a fixed frame 9 with a hollow cavity inside. First, the axial direction of the center line of the fixed frame 9 in the length direction is taken as the Z axis, and the XY coordinate axis is established with a plane perpendicular to the center line. In order to accurately calculate the time error, this specific embodiment adopts a Cartesian coordinate system; on the XY coordinate axis, the longitudinal direction is the Y axis and the transverse direction is the X axis.

[0026] Among them, four basic electrodes 1 are evenly arranged on the inner wall surface of the fixed frame 9 around the center line, and the basic electrode 1 is fixed to the inner wall surface of the fixed frame 9 by bolts; at the same time, the basic electrode 1 extends axially along the center line, and two end cover electrodes 3 are respectively arranged at the two ends of the length direction of the basic electrode 1, and the two end cover electrodes are symmetrically distributed. The end cover electrodes 3 are respectively fixed on the fixed frame 9 at the two ends of the length direction of the corresponding basic electrode 1, and the basic electrodes 1 and the end cover electrodes 3 are insulated; the basic electrode 1 and the end cover electrodes 3 are enclosed to form an ion trap 5, and there is a gap 6 between adjacent basic electrodes 1. The four control electrodes 2 are respectively arranged at the gap 6 between adjacent basic electrodes 1. In order to position the control electrode 2 at the gap 6, mounting brackets 4 are provided at the cavity openings at both ends of the fixed frame 9 corresponding to the gap 6. The mounting bracket 4 includes a bracket frame 4.1 and a bracket beam 4.2 arranged corresponding to the gap 6, wherein the bracket frame 4.1 is fixed in the cavities at both ends of the fixed frame 9, one end of the bracket beam 4.2 is integrally formed with the bracket frame 4.1, and both ends of the control electrode 2 are respectively fixedly connected to the corresponding bracket beam 4.2; in this specific embodiment, the four basic electrodes 1 are divided into a pair of X electrodes and a pair of Y electrodes, and there is a gap 6 between the X electrode and the Y electrode, and the control electrode 2 is respectively arranged at the gap 6 between the X electrode and the Y electrode; RF capture voltages with equal amplitude and opposite phases are applied to adjacent X electrodes and Y electrodes, a positive voltage with the same amplitude as that of the basic electrode 1 is applied to the end cap electrode 3, and radio frequency voltages with equal amplitude and the same phase are respectively applied to the four control electrodes 2, and the frequency of the radio frequency voltage on the control electrode 2 is the same as the frequency of the RF capture voltage on the basic electrode 1.

[0027] The ion trap mass analyzer of this specific embodiment is a linear ion trap. Therefore, the four base electrodes 1 have curved surfaces facing the ion trap 5. The two curved surfaces of a pair of X electrodes form a rotating double-leaf hyperboloid, and the curved surface structure of a pair of Y electrodes forms a rotating double-leaf hyperboloid.

[0028] The end cap electrode 3 is provided with an ion inlet 7, the base electrode 1 is provided with an ion outlet 8, and a detector for capturing ejected ions is provided at the ion outlet 8.

[0029] When the ion trap mass analyzer is working, when ions are injected, the foreign ions first move linearly along the axis of the ion trap mass analyzer, and are distributed along the arc center axis of the quadrupole field under the guidance of the RF capture voltage. During this period, the linear ion trap must load a stable RF capture voltage with a certain frequency and amplitude; when the ions are ejected, the voltage on the linear ion trap mass analyzer is scanned, and the RF voltage of the regulating electrode 2 remains constant. This will force the kinetic energy of the stored ions in the x direction to increase rapidly. To a certain extent, the ions are ejected from the x direction of the ion trap mass analyzer and captured by the detector.

[0030] At the same time, in order to allow the radio frequency voltage on the control electrode 2 to affect the distribution of the electric field in the ion trap 5 and increase the content of the electric field in the ion trap 5, this specific embodiment reflects the setting position of the control electrode 2 on the XY coordinate axis, specifically including: The cross section of the control electrode 2 on the XY coordinate axis is a hyperbolic arch structure. The cross section of the control electrode 2 on the XY coordinate axis includes a first curved surface, a second curved surface, and a first straight surface and a second straight surface connecting the first curved surface and the second curved surface.

[0031] The four control electrodes 2 are mirror-stacked on the XY coordinate axis and arranged in four quadrants of the XY coordinate axis. The mirror-set control electrodes 2 can make the control electrodes 2 have a uniform effect on the electric field in the ion trap 5 .

[0032] The hyperbolic arch structures of the four control electrodes 2 respectively coincide with the hyperbolic partial trajectories when the focus is on the X-axis, and the curvature of the curved arch structure of the control electrode 2 is the same as the curvature of the hyperbolic surface of the base electrode 1 .

[0033] The use of a control electrode 2 having a hyperbolic arch structure in cross section and arranged in the four quadrants of the XY coordinate axis in a mirror-symmetrical manner can allow the control electrode 2 to have a positive effect on the electric field in the ion trap 5, thereby increasing the electric field content in the ion trap 5. Figure 3 As shown, the mass spectra were obtained by testing the ion trap mass analyzer before adding the control electrode 2 and the ion trap analyzer after adding the control electrode 2. By comparing the changes in the mass spectrum peaks before and after adding the functional electrode, it can be clearly seen that the resolution of the mass spectrum is improved after adding the functional electrode.

[0034] In addition, the distance between the control electrode 2 and the center line is greater than 3 mm, and the distance between the control horizon and the base electrode 1 is greater than 2 mm, which prevents the control electrode 2 from being broken down by the RF capture voltage on the base electrode 1 and improves the rigidity of the control electrode 2. Specific embodiments

[0035] This specific embodiment discloses a method for controlling the resolution of an ion trap mass analyzer; Before adjusting the resolution of the ion trap mass analyzer, this specific embodiment performs the following tests: Test 1. On the XY coordinate axis where the control electrode 2 is located, the position of the control electrode 2 in the ion trap 5 is located by the vertex (x, y) of the hyperbolic arch structure of the control electrode 2, and the vertical distance d from the vertex coordinate (x, y) to the origin of the XY coordinate axis is defined. The value of d is adjusted, and the change in the content of the high-order field component in the ion trap mass analyzer is shown in Table 1: Table 1 Changes in high-order field content when d changes

[0036] Test 2. Adjust the distance Rz between the vertex of the hyperbola where the control electrode 2 is located on the X-axis and the centerline axis. The change in the content of the high-order field component in the ion trap mass analyzer is shown in Table 2: Table 2 Changes in high-order field content when Rz changes

[0037] It can be seen that when the Rz size changes, the content of the quadrupole field gradually increases.

[0038] Test 3. Adjust the thickness of electrode 2 , the changes in the content of high-order field components in the ion trap mass analyzer are shown in Table 3: Table 3 Changes in high-order field content when changing

[0039] Test 4. Adjust the projection length a of the control electrode 2 on the Y axis. The changes in the content of the high-order field components in the ion trap mass analyzer are shown in Table 4: Table 4 Changes of high-order field content when a changes

[0040] Through test 1 to test 4, the change of high-order field content under different conditions can be obtained, and then the resolution of the ion trap mass analyzer can be adjusted.

[0041] The resolution control method is based on the ion trap mass analyzer of specific embodiment 1 and is controlled. The resolution control method includes: Step 1. Taking the XY coordinate axis as a reference, predefine the vertex coordinate (x, y) of the control electrode 2 closest to the origin of the XY coordinate axis, the vertical distance d from the vertex coordinate (x, y) to the origin of the XY coordinate axis, the positive projection length a of the control electrode 2 on the Y axis, the RF voltage amplitude V of the control electrode 2, the distance Rz between the vertex of the hyperbola on the X axis and the center of the central symmetry axis, and the thickness △ of the control electrode 2; locate the position of the control electrode 2 in the ion trap 5 with the vertex coordinate (x, y); Figure 4 As shown; in this specific embodiment, the initial value of d is 2.5mm, the initial value of Rz is 3.3mm, and the initial value of ∆ is 0.25mm.

[0042] Step 2. Predefine the working sequence of the ion trap analyzer; the working sequence is as follows Figure 5 As shown, including: Step 201. In the initial stage, an initial RF capture voltage with equal amplitude and opposite phase is applied between adjacent base electrodes 1, a positive voltage is applied to the end cap electrode 3, and a radio frequency voltage V with equal amplitude and the same phase is applied to the control electrode 2; ions enter the ion trap 5 from the ion entrance 7 and move stably around the center line under the action of the RF capture voltage; Step 202. gradually increase the RF capture voltage on the base electrode 1, keep the positive voltage on the end cap electrode 3 unchanged, and keep the RF voltage V on the control electrode 2 unchanged; the kinetic energy of the ions in the ion trap 5 in the X direction increases under the action of the RF voltage, and they are ejected from the ion exit hole and captured by the detector; Step 203 : reducing the RF capture voltage of the base electrode 1 to the initial RF capture voltage, and reducing the radio frequency voltage of the control electrode 2 at the same time.

[0043] Step 3. Adjust the vertical distance d from the vertex coordinate (x, y) of the control electrode 2 to the origin of the XY coordinate axis, and the ion trap mass analyzer works according to the predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; the d value of this specific embodiment ranges from 2.5 mm to 3.1 mm, and the mass spectrum obtained is as follows: Figure 6 As shown in the figure, the mass peak mass-to-charge ratio m and half peak width △m of the corresponding ion are obtained from the mass spectrum. The calculation formula for mass resolution is: ; The corresponding mass resolution is Figure 7 As shown in the mass resolution diagram, it can be seen that the best quality resolution is 7612 when d=2.7mm.

[0044] Step 4. Based on the vertical distance d=2.7mm from the vertex coordinates (x, y) corresponding to the optimal mass resolution to the origin of the XY coordinate axis in step 3, adjust the distance Rz between the vertex of the hyperbola on the X-axis where the control electrode 2 is located and the centerline axis, and the ion trap mass analyzer works according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; in this specific embodiment, the value of Rz is first increased and decreased, and the value range of Rz is 2.8mm~3.9mm, wherein the mass spectrum is obtained by increasing Rz as shown in Figure 8 As shown, the mass spectrum obtained by reducing Rz is as follows Fig. 9 As shown, the final mass resolution is Fig.10 As shown in the mass resolution diagram, it can be seen that when d=2.7mm and Rz=3.5mm, the optimal mass resolution is 8808.

[0045] Step 5. Based on the vertical distance d=2.7 from the vertex coordinates (x, y) corresponding to the optimal mass resolution achieved in step 4 to the origin of the XY coordinate axis and the distance Rz=3.5 between the vertex on the X axis and the centerline axis of the hyperbola where the control electrode 2 is located, adjust the width of the control electrode 2 , the ion trap mass analyzer works according to the predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; in this specific embodiment, increasing the width of the control electrode 2 includes increasing the width to the left, increasing the width to the right, decreasing the width to the left and decreasing the width to the right. In this specific implementation, the width of the control electrode 2 varies in the range of 0.1mm to 0.5mm to the left, and the width varies in the range of 0.1mm to 0.5mm to the right. The mass spectrum obtained is as follows Fig.11 and Fig.12 The corresponding mass resolution is shown in Table 5: Table 5 Controlled electrode thickness Change the corresponding resolution

[0046] Combined with Table 5, it can be seen that when d=2.7mm, Rz=3.5mm and =0.25mm, the optimal mass resolution is 8808.

[0047] Step 6. The vertical distance d=2.7mm from the vertex coordinate (x, y) corresponding to the optimal mass resolution achieved in step 5 to the origin of the XY coordinate axis, the distance Rz=3.5mm between the vertex of the hyperbola on the X axis where the control electrode 2 is located and the centerline axis, and the width of the control electrode 2 =0.25mm, the projection length a of the control electrode 2 on the Y axis is adjusted, and the ion trap mass analyzer works according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; in this specific embodiment, the value range of a is 2mm to 7mm, and the mass spectrum obtained is as follows Fig.13 The corresponding mass resolution is shown in Fig.14 As shown, at d=2.7mm, Rz=3.5mm, When a=3, the best resolution is 8808.

[0048] Output the optimal mass resolution 8808 achieved in step 6 and the corresponding vertical distance d=2.7mm from the vertex coordinates (x, y) of the control electrode 2 to the origin of the XY coordinate axis, the projection length a=3mm of the control electrode 2 on the Y axis, the distance Rz=3.5mm between the vertex of the hyperbola where the control electrode 2 is located on the X axis and the centerline axis, and the width of the control electrode 2 .

[0049] In general, the ion trap mass analyzer of the present invention has a simplified appearance and structure by additionally installing two pairs of mirror-symmetrically arranged control electrodes 2 on the basis of the structure of the original linear ion trap mass analyzer. The overall structure is firm and stable, avoiding the problem of repeated disassembly and assembly of the linear ion trap and introducing the problem of performance degradation, while improving the resolution of the linear ion trap mass analyzer. The mass analyzer has a simplified and firm structure, is easy to process and assemble, increases the control variables, and is easy to adjust the electric field distribution and content in the trap. The ion trap mass analyzer of the present invention can be used in analytical testing fields such as mass spectrometry. When used for mass spectrometry, when ions are injected, the foreign ions first move linearly along the axial direction of the ion trap, and are distributed in the arc center axis of the quadrupole field under the guidance of radio frequency. When the ions are ejected, the voltage on the linear ion trap mass analyzer starts to scan, and the voltage on the functional electrode remains unchanged. The radio frequency electric field on the superimposed functional electrode forces the stored ions to rapidly increase their kinetic energy in the x direction. To a certain extent, the ions are ejected from the x direction of the ion trap mass analyzer and captured by the detector.

[0050] In the description of the embodiments of the present application, it should be noted that in the description of the present application, terms such as "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description, and does not indicate or imply that the device or component must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present application.

[0051] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "in the present embodiment", "specific example", or "some examples" etc. means that the specific features, mechanisms, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0052] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. An ion trap mass analyzer, characterized in that: The invention comprises four basic electrodes (1), four regulating electrodes (2), two end cap electrodes (3) and a fixed frame (9), wherein the interior of the fixed frame (9) is a cavity which penetrates along its length direction, the four basic electrodes (1) are evenly arranged on the inner wall of the cavity around the center line of the length direction of the fixed frame, the basic electrode (1) extends axially along the center line, the two end cap electrodes (3) are arranged at two ends of the length direction of the basic electrode (1), the two end cap electrodes (3) are symmetrically distributed, the two end cap electrodes (3) are respectively fixed to the fixed frame (9), and the basic electrode (1) and the end cap electrodes (3) enclose a shape An ion trap (5) is formed, a gap (6) exists between adjacent base electrodes (1), four control electrodes (2) are respectively arranged at the gaps (6) between adjacent base electrodes (1), mounting brackets (4) are arranged at the cavity openings at both ends of the fixed frame (9) corresponding to the gaps (6), the two ends of the control electrode (2) are respectively fixed to the mounting brackets (4), RF capture voltages with equal amplitude and opposite phases are applied between adjacent base electrodes (1), a positive voltage with the same amplitude as that of the base electrode (1) is applied to the end cap electrode (3), and radio frequency voltages with equal amplitude and the same phase are respectively applied to the four control electrodes (2).

2. The ion trap mass analyzer according to claim 1, characterized in that: The sides of the four basic electrodes (1) facing the ion trap (5) are in a curved shape.

3. The ion trap mass analyzer according to claim 2, characterized in that: An XY coordinate axis is established with the axis of the center line as the origin and the surface perpendicular to the center line as the cross section. The cross section of the control electrode (2) on the XY coordinate axis presents a hyperbolic arch structure. The four control electrodes (2) are mirror-imaged and arranged in the four quadrants of the XY coordinate axis.

4. The ion trap mass analyzer according to claim 3, characterized in that: The hyperbolic arch structures of the four control electrodes (2) respectively coincide with the hyperbolic partial trajectories when the focus is on the X-axis, and the curvature of the curved arch structure of the control electrode (2) is the same as the curvature of the hyperbolic surface of the base electrode (1).

5. The ion trap mass analyzer according to claim 1, characterized in that: The frequency of the radio frequency voltage on the control electrode (2) is the same as the frequency of the RF capture voltage on the base electrode (1).

6. The ion trap mass analyzer according to claim 1, characterized in that: The end cap electrode (3) is provided with an ion inlet (7), the base electrode (1) is provided with an ion outlet (8), and a detector for capturing ejected ions is provided at the ion outlet (8).

7. The ion trap mass analyzer according to claim 1, characterized in that: Adjacent base electrodes (1) and base electrodes (1) and end cap electrodes (3) are insulated, the distance between the control electrode (2) and the center line is greater than 3 mm, and the distance between the control horizon and the base electrode (1) is greater than 2 mm.

8. A method for controlling the resolution of an ion trap mass analyzer, the method for controlling the resolution is based on the ion trap mass analyzer according to any one of claims 3 to 7, characterized in that: The resolution control method comprises: Step 1. With the XY coordinate axis as a reference, predefine the vertex coordinates (x, y) of the control electrode (2) closest to the origin of the XY coordinate axis, the vertical distance d from the vertex coordinates (x, y) to the origin of the XY coordinate axis, the positive projection length a of the control electrode (2) on the Y axis, the RF voltage amplitude V of the control electrode (2), the distance Rz between the vertex of the hyperbola on which the control electrode (2) is located on the X axis and the center of the central symmetry axis, and the thickness △ of the control electrode (2); locate the position of the control electrode (2) in the ion trap (5) with the vertex coordinates (x, y); Step 2. predefine the working sequence of the ion trap analyzer; Step 3. adjusting the vertical distance d from the vertex coordinates (x, y) of the control electrode (2) to the origin of the XY coordinate axis, and the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer reaches an optimal mass resolution; Step 4. On the basis of achieving the optimal mass resolution in step 3, adjusting the distance Rz between the vertex of the hyperbola on the X-axis where the control electrode (2) is located and the centerline axis, the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer achieves the optimal mass resolution; Step 5. On the basis of achieving the optimal mass resolution in step 4, adjusting the width ∆ of the control electrode (2), and the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; Step 6. On the basis of achieving the optimal mass resolution in step 5, adjusting the projection length a of the control electrode (2) on the Y axis, and the ion trap mass analyzer operates according to a predefined working sequence until the ion trap mass analyzer reaches the optimal mass resolution; Step 7. Output the optimal mass resolution achieved in step 6 and the corresponding vertical distance d from the vertex coordinates (x, y) of the control electrode (2) to the origin of the XY coordinate axis, the projection length a of the control electrode (2) on the Y axis, the distance Rz between the vertex of the hyperbola where the control electrode (2) is located on the X axis and the center line axis, and the thickness △ of the control electrode (2).

9. The method for controlling the resolution of an ion trap mass analyzer according to claim 8, characterized in that: The predefined working sequence of the ion trap mass analyzer in step 2 specifically includes: Step 201. In the initial stage, an initial RF capture voltage with equal amplitude and opposite phase is applied between adjacent base electrodes (1), a positive voltage is applied to the end cap electrode (3), and a radio frequency voltage V with equal amplitude and the same phase is applied to the control electrode (2); ions enter the ion trap (5) from the ion entrance (7) and move stably around the center line under the action of the RF capture voltage; Step 202. Gradually increase the RF capture voltage on the base electrode (1), keep the positive voltage on the end cap electrode (3) unchanged, and keep the RF voltage V on the control electrode (2) unchanged; the kinetic energy of the ions in the ion trap (5) in the X direction increases under the action of the RF voltage, and they are ejected from the ion exit hole and captured by the detector; Step 203: Lowering the RF capture voltage of the base electrode (1) to the initial RF capture voltage, and at the same time lowering the radio frequency voltage of the control electrode (2).

10. The method for controlling the resolution of an ion trap mass analyzer according to claim 8, characterized in that: The method for calculating the mass resolution of the ion trap mass analyzer in steps 3 to 6 includes: a. Obtaining a mass spectrum of the ion trap mass analyzer when it works according to a predefined working sequence; b. Obtain the mass-to-charge ratio m and half-peak width △m of the ion from the mass spectrum. The calculation formula for mass resolution is: .

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