A novel ion trap mass analyzer and its resolution control method

Abstract

The application relates to a novel ion trap mass analyzer and a resolution regulation method thereof, and comprises a linear ion trap and a regulation electrode, wherein the regulation electrode is mainly arranged in a gap between adjacent electrodes, and a radio frequency voltage is applied to the regulation electrode, so as to adjust the electric field distribution and content in the ion trap, thereby optimizing the electric field distribution and content of the ion trap by adding the regulation electrode on the basis of not changing the size structure of the ion trap mass analyzer, mainly making up the influence of the content and composition of the edge high-order field on the movement of ions, so that the ions are more stably distributed in the center of the ion trap, and the mass resolution and storage efficiency of the ion trap are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of mass spectrometry and ion storage technology, and particularly relates to an ion trap mass analyzer and a resolution regulation method thereof. BACKGROUND

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

[0003] The performance of ion trap mass analyzers mainly depends on the electric field distribution of the ion trapping region, which is largely determined by the geometry of the electrodes. In recent years, various electrode shapes of LIT have been developed, which have improved the analysis performance, especially the mass resolution, due to the internal electric field distribution containing a variety of high-order fields. The electric field distribution in the ion trap can be optimized by: (1) applying a voltage division to multiple electrodes; (2) changing the geometry of the ion trap. For example, US009735001B2 discloses a flat electrode array ion trap, which adjusts and optimizes the electric field in the ion trap by applying a voltage division to multiple electrodes to improve performance. US11764051B2 discloses a flat LIT mass analyzer, the geometry of the ion trap includes electrode geometry, assembly precision, etc., which will affect the electric field distribution and thus the performance of the ion trap. CN111816545A discloses a prismatic linear ion trap mass analyzer, which realizes one-way excitation of ions and improves the mass resolution. CN105632986B discloses a grid ion trap, which adjusts the voltage on the grid and the electrode to change the electric field distribution of the ion trap, thereby improving the ion ejection efficiency. CN104681392A discloses a folded line-shaped rod electrode linear ion trap, which is formed by four rod electrodes that are parallel to each other and surround a center line, at least one pair of electrodes has a folded line-shaped cross section facing the center line. The main goal is to improve the mass resolution of the ion trap while simplifying the electrode structure and reducing the processing and assembly difficulty. However, these electrode shape improvements and optimizations have the following problems: they are based on the improvement of four radial ring-shaped electrodes, and once the electrode size is adjusted, the entire ion trap mass analyzer needs to be disassembled, which not only increases the cost of the experiment, but also makes the assembly precision too complex. In order to control the electric field components, the improvement of the four radial electrode shape will seriously affect the internal electric field components, which is not conducive to the accurate control of the change of the internal electric field. SUMMARY

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

[0005] The application provides an ion trap mass analyzer, which comprises four base electrodes, four control electrodes, two end cover electrodes and a fixed frame, the fixed frame (9) is internally provided with a cavity extending along the length direction thereof, the four base electrodes (1) are uniformly arranged on the inner wall of the cavity along the length direction of the center line of the fixed frame, the base electrodes (1) extend along the axial direction of the center line, the two end cover electrodes (3) are arranged at the two ends of the base electrodes (1) along the length direction, the two end cover electrodes (3) are symmetrically distributed, and the two end cover electrodes (3) are fixed to the fixed frame (9) respectively, the base electrodes (1) and the end cover electrodes (3) form an ion trap (5) by being enclosed, there is a gap between the adjacent base electrodes, the four control electrodes are arranged at the gaps between the adjacent base electrodes respectively, mounting supports are arranged at the gaps corresponding to the cavities at the two ends of the fixed frame, and the two ends of the control electrodes are fixed to the mounting supports respectively, the RF trapping voltages with equal amplitudes and opposite phases are applied between the adjacent base electrodes, the positive voltages with equal amplitudes are applied to the end cover electrodes, and the RF voltages with equal amplitudes and the same phase are applied to the four control electrodes respectively.

[0006] Compared with the prior art, the ion trap mass analyzer has the following advantages: the control electrodes are arranged at the gaps between the adjacent base electrodes, and the RF voltages are applied, so that the electric field distribution and content in the ion trap can be adjusted, the electric field distribution and content in the ion trap are changed by adding the control electrodes without changing the size structure of the base electrodes in the ion trap mass analyzer, after the ions enter the ion trap, the ions firstly move linearly along the center line, are distributed along the axis of the arc of the quadrupole field under the guidance of the RF trapping voltages, and then the kinetic energy of the ions in the X direction is rapidly increased under the action of the RF voltages of the control electrodes and the ions are ejected from the ion trap.

[0007] In a possible implementation, the four base electrodes are in the shape of a curved surface towards the side surface of the ion trap.

[0008] Compared with the prior art, the linear ion trap enclosed by the base electrodes and the end cover electrodes in the shape of a curved surface can form a standard quadrupole field.

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

[0010] Compared with the prior art, the mirror-image arranged control electrodes can uniformly affect the electric field in the ion trap.

[0011] In a possible implementation, the hyperbolic arch structure of the four control electrodes respectively coincides with the hyperbolic curve part track with the focus on the X axis, and the curvature of the arch structure of the control electrode is the same as the curvature of the hyperboloid 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 trapping voltage on the base electrode.

[0013] In a possible implementation, an ion incident port is arranged on the end cover electrode, an ion exit port is arranged on the base electrode, and a detector for capturing ejected ions is arranged at the ion exit port.

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

[0015] A resolution control method of an ion trap mass analyzer, the resolution control method is based on the ion trap mass analyzer described above, and the resolution control method comprises the following steps:

[0016] Step 1. Defining the vertex coordinate (x, y) of the control electrode 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 projection length a of the control electrode on the Y axis, the radio frequency voltage amplitude of the control electrode, the distance Rz between the vertex of the hyperbola on the X axis and the center line axis center of the control electrode, and the thickness Δ of the control electrode based on the XY coordinate axis; positioning the position of the control electrode in the ion trap based on the vertex coordinate (x, y); V

[0017] Step 2. Defining the working timing of the ion trap analyzer;

[0018] Step 3. Adjusting the vertical distance d of the vertex coordinate (x, y) of the control electrode to the origin of the XY coordinate axis, and working the ion trap mass analyzer according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution;

[0019] Step 4. On the basis of reaching the optimal mass resolution in step 3, adjusting the distance Rz between the vertex of the hyperbola on the X axis and the center line axis center of the control electrode, and working the ion trap mass analyzer according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution;

[0020] ​Step 5. On the basis of the optimal mass resolution achieved in step 4, adjust the width of the control electrode Δ, the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution;

[0021] Step 6. On the basis of the optimal mass resolution achieved in step 5, adjust the projection length of the control electrode on the Y axis a, the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution;

[0022] Step 7. Output the optimal mass resolution achieved in step 6 and the corresponding control electrode vertex coordinates (x, y) to the vertical distance d of the XY coordinate axis origin, the projection length of the control electrode on the Y axis a, the distance Rz of the vertex of the hyperbola on which the control electrode is located on the X axis to the center line axis center and the thickness of the control electrode Δ.

[0023] The resolution adjustment method of the ion trap mass analyzer of the present application has the following advantages compared with the prior art: by adjusting the vertical distance d of the vertex coordinates (x, y) to the XY coordinate axis origin, the projection length of the control electrode on the Y axis a, the distance Rz of the vertex of the hyperbola on which the control electrode is located on the X axis to the center line axis center and the thickness of the control electrode Δ, the resolution of the ion trap mass analyzer is adjusted, so that without changing the structure of the basic electrode in the ion trap mass analyzer, the resolution of the ion trap mass analyzer is adjusted by increasing the control electrode and adjusting the related parameters of the control electrode.

[0024] In a possible implementation, the predefined working timing of the ion trap mass analyzer in step 2 specifically includes:

[0025] Step 201. In the initial stage, an initial RF trapping voltage with equal amplitude and opposite phase is applied between adjacent basic electrodes, a positive voltage is applied to the end cap electrode, and a radio frequency voltage V with equal amplitude and same phase is applied to the control electrode; ions enter the ion trap from the ion inlet, and are stably moved around the center line under the action of the RF trapping voltage;

[0026] Step 202. Gradually increase the RF trapping voltage on the basic electrode, the positive voltage on the end cap electrode remains unchanged, and at the same time, the radio frequency voltage V on the control electrode remains unchanged; the kinetic energy of the ions in the ion trap in the X direction increases under the action of the radio frequency voltage, and is ejected from the ion ejection hole and captured by the detector;

[0027] Step 203. Reduce the RF trapping voltage of the basic electrode to the initial RF trapping voltage, and at the same time, reduce the radio frequency voltage of the control electrode.

[0028] In one possible implementation, the calculation method of the mass resolution of the ion trap mass analyzer in steps 3-6 comprises:

[0029] a. obtaining a mass spectrum of the ion trap mass analyzer when working according to the predefined working timing;

[0030] b. obtaining the mass-to-charge ratio of the ion from the mass spectrum and the half-peak width The calculation formula of the mass resolution is: . BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structural schematic diagram of the ion trap mass analyzer in embodiment 1 of the present application;

[0032] Figure 2 is a cross-sectional view of the ion trap mass analyzer in embodiment 1 of the present application on the XY coordinate axis;

[0033] Figure 3 is a mass spectrum obtained by adding a control electrode before and after the control electrode in embodiment 1 of the present application;

[0034] Figure 4 is each parameter predefined in the XY coordinate axis in embodiment 2 of the present application;

[0035] Figure 5 is a working timing diagram of the ion trap mass analyzer predefined in embodiment 2 of the present application;

[0036] Figure 6 is a mass spectrum obtained by adjusting d in embodiment 2 of the present application;

[0037] Figure 7 is a mass resolution diagram obtained by adjusting d in embodiment 2 of the present application;

[0038] Figure 8 is a mass spectrum obtained by increasing Rz on the basis of d in embodiment 2 of the present application;

[0039] Figure 9 is a mass spectrum obtained by reducing Rz on the basis of d in embodiment 2 of the present application

[0040] Figure 10 is a mass resolution diagram obtained by adjusting Rz on the basis of d in embodiment 2 of the present application;

[0041] Figure 11 is a mass spectrum obtained by increasing thickness △ on the basis of d and Rz in embodiment 2 of the present application;

[0042] Figure 12The mass spectrum obtained by reducing the thickness Δ based on d, Rz in the embodiment 2 of the present application;

[0043] Figure 13 The mass spectrum obtained by adjusting a based on d, Rz and width Δ in the embodiment 2 of the present application;

[0044] Figure 14 The mass resolution obtained by adjusting a based on d, Rz and width Δ in the embodiment 2 of the present application.

[0045] Explanation of reference numerals:

[0046] 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 entrance; 8, ion exit; 9, fixed frame. DETAILED DESCRIPTION

[0047] First, those skilled in the art should understand that these embodiments 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 adjust them as needed in order to adapt to specific application occasions.

[0048] In the description of the embodiments of the present application, it should be explained that, unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the embodiments of the present application can be understood according to specific circumstances.

[0049] In the embodiments of the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can be 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, the first feature "above", "above" and "above" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "below" and "below" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0050] The present application will be further described in detail below in combination with the drawings and specific embodiments. Embodiment 1

[0052] Reference should be made to Figures 1-2As shown, the embodiment of the present application discloses an ion trap mass analyzer, which comprises four base electrodes 1, four control electrodes 2, two end cap electrodes 3, two mounting brackets 4 and a fixed frame 9 with a hollow cavity inside. Firstly, the axis of the center line in the length direction of the fixed frame 9 is taken as the Z axis, and the XY coordinate axis is established in the plane perpendicular to the center line. In order to accurately calculate the time error, the Cartesian coordinate system is adopted in the embodiment. On the XY coordinate axis, the longitudinal direction is the Y axis, and the transverse direction is the X axis.

[0053] The four base electrodes 1 are arranged on the inner wall surface of the fixed frame 9 in a circumferential direction around the center line, and the base electrodes 1 are fixed to the inner wall surface of the fixed frame 9 by bolts. Meanwhile, the base electrodes 1 extend along the axis of the center line, and the two end cap electrodes 3 are arranged at the two ends of the base electrodes 1 in the length direction, and the two end cap electrodes are symmetrically distributed. The end cap electrodes 3 are fixed to the fixed frame 9 at the two ends of the base electrodes 1 in the length direction, and the base electrodes 1 are insulated from each other and from the end cap electrodes 3. The base electrodes 1 and the end cap electrodes 3 form an ion trap 5, and there is a gap 6 between adjacent base electrodes 1. The four control electrodes 2 are arranged at the gaps 6 between adjacent base electrodes 1. In order to position the control electrodes 2 at the gaps 6, mounting brackets 4 are arranged at the gaps 6 at the two end cavities of the fixed frame 9. The mounting bracket 4 comprises a bracket frame 4.1 and a bracket beam 4.2 arranged at the gap 6. The bracket frame 4.1 is fixed in the cavity at the two ends of the fixed frame 9, one end of the bracket beam 4.2 is integrally formed with the bracket frame 4.1, and the two ends of the control electrode 2 are fixedly connected with the corresponding bracket beam 4.2. In the embodiment, the four base 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 electrodes and the Y electrodes. The control electrodes 2 are arranged at the gaps 6 between the X electrodes and the Y electrodes. The adjacent X electrodes and Y electrodes are applied with RF trapping voltages with equal amplitude and opposite phase. The end cap electrodes 3 are applied with positive voltages with equal amplitude to the base electrodes 1. The four control electrodes 2 are applied with RF voltages with equal amplitude and the same phase. The frequency of the RF voltage on the control electrode 2 is the same as the frequency of the RF trapping voltage on the base electrode 1.

[0054] The ion trap mass analyzer of the embodiment is a linear ion trap. Therefore, the four base electrodes 1 are in the shape of a curved surface towards the side surface of 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 phase double-leaf hyperboloid.

[0055] The end cap electrode 3 is provided with an ion incident port 7, and the base electrode 1 is provided with an ion exit port 8. A detector for capturing ejected ions is arranged at the ion exit port 8.

[0056] When the ion trap mass analyzer is operating, upon ion implantation, the incoming ions initially move linearly along the axial direction of the ion trap mass analyzer, and are guided by the RF trapping voltage to distribute along the central axis of the quadrupole field. During this period, a stable RF trapping voltage with a constant frequency and amplitude is applied to the linear ion trap. When the ions are ejected, the voltage on the linear ion trap mass analyzer is scanned, and the RF voltage of the control electrode 2 remains constant. This forces the stored ions to rapidly increase their kinetic energy in the x-direction. When this energy reaches a certain level, the ions are ejected from the ion trap mass analyzer in the x-direction and captured by the detector.

[0057] Meanwhile, in order to allow the radio frequency voltage on the control electrode 2 to affect the distribution of the electric field within the ion trap 5 and increase the content of the electric field within the ion trap 5, this specific embodiment shows the setting position of the control electrode 2 on the XY coordinate axis, specifically including:

[0058] The cross-section of the control electrode 2 on the XY coordinate axis has a hyperboloid 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 flat surface and a second flat surface that connect the first curved surface and the second curved surface.

[0059] The four control electrodes 2 are stacked in a mirror image on the XY coordinate axis and arranged in the four quadrants of the XY coordinate axis; the mirror image arrangement of the control electrodes 2 enables the control electrodes 2 to have a uniform influence on the electric field in the ion trap 5.

[0060] The hyperboloid arched structures of the four control electrodes 2 respectively coincide with the hyperboloid partial trajectory when the focus is on the X-axis, and the curvature of the hyperboloid arched structure of the control electrode 2 is the same as the curvature of the hyperboloid of the base electrode 1.

[0061] The control electrode 2, with its hyperboloidal arched cross-section and mirror-symmetrical arrangement in the four quadrants of the XY coordinate axis, can positively influence the electric field within the ion trap 5, thereby increasing the electric field content within the ion trap 5. For example... Figure 3 As shown, mass spectra were obtained by testing the ion trap mass analyzer before and after adding the control electrode 2. The changes in the spectral peaks of the mass spectra before and after adding the functional electrode were compared. It can be clearly seen that the resolution of the mass spectra was improved after adding the functional electrode.

[0062] In addition, the distance between the control electrode 2 and the center line is greater than 3mm, and the distance between the control electrode 2 and the base electrode 1 is greater than 2mm, so as to avoid the control electrode 2 being broken down by the RF trapping voltage on the base electrode 1 and improve the rigidity of the control electrode 2. Specific Implementation Example 2:

[0064] This specific embodiment discloses a method for adjusting the resolution of an ion trap mass analyzer;

[0065] Before the resolution of the ion trap mass analyzer is regulated, the present embodiment is tested as follows:

[0066] Test 1. The position of the regulating electrode 2 in the ion trap 5 is located by the vertex (x, y) of the hyperbolic arch structure of the regulating electrode 2 on the XY coordinate axis, the perpendicular distance d of the vertex coordinate (x, y) to the origin of the XY coordinate axis is defined, the value of d is adjusted, and the change of the high-order field component content in the ion trap mass analyzer is shown in Table 1:

[0067] Table 1 Change of high-order field content when d changes

[0068] ;

[0069] Test 2. The distance Rz of the vertex of the hyperbolic curve on which the regulating electrode 2 is located to the center line axis center on the X axis is adjusted, and the change of the high-order field component content in the ion trap mass analyzer is shown in Table 2:

[0070] Table 2 Change of high-order field content when Rz changes

[0071] ;

[0072] It can be seen that when the Rz size changes, the content of the quadrupole field gradually increases.

[0073] Test 3. The thickness Δ of the regulating electrode 2 is adjusted, and the change of the high-order field component content in the ion trap mass analyzer is shown in Table 3:

[0074] Table 3 Change of high-order field content when thickness Δ changes

[0075] ;

[0076] Test 4. The projection length a of the regulating electrode 2 on the Y axis is adjusted, and the change of the high-order field component content in the ion trap mass analyzer is shown in Table 4:

[0077] Table 4 Change of high-order field content when a changes

[0078] ;

[0079] Through tests 1-4, the change of the high-order field content under different conditions can be obtained, and then the resolution of the ion trap mass analyzer is regulated.

[0080] The resolution regulation method is based on the ion trap mass analyzer of embodiment 1, and the resolution regulation method comprises:

[0081] Step 1. 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 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 from the vertex of the hyperbola on which the control electrode 2 is located to the axis center of the hyperbola on the X axis, and the thickness Δ of the control electrode 2; position the control electrode 2 in the ion trap 5 at the vertex coordinate (x, y); as shown in Figure 4 ; the initial value of d in this embodiment is 2.5 mm, the initial value of Rz is 3.3 mm, and the initial value of the thickness Δ is 0.25 mm.

[0082] Step 2. Predefine the working timing of the ion trap analyzer; the working timing is as shown in Figure 5 ; and includes:

[0083] Step 201. In the initial stage, apply an initial RF trapping voltage with equal amplitude and opposite phase between the adjacent base electrodes 1, apply a positive voltage to the end cover electrode 3, and apply an RF voltage V with equal amplitude and the same phase to the control electrode 2; ions enter the ion trap 5 from the ion inlet 7 and stably move around the center line under the action of the RF trapping voltage;

[0084] Step 202. Gradually increase the RF trapping voltage on the base electrode 1, keep the positive voltage on the end cover electrode 3 unchanged, and keep the RF voltage V on the control electrode 2 unchanged; the ions in the ion trap 5 increase the kinetic energy in the X direction under the action of the RF voltage, and are ejected from the ion ejection hole and captured by the detector;

[0085] Step 203. Reduce the RF trapping voltage of the base electrode 1 to the initial RF trapping voltage, and reduce the RF voltage of the control electrode 2.

[0086] Step 3. Adjust the vertical distance d of 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 timing until the ion trap mass analyzer reaches the optimal mass resolution; the value of d in this embodiment ranges from 2.5 mm to 3.1 mm, and the obtained mass spectrum is as shown in Figure 6 ; the mass-to-charge ratio and the half-peak width of the mass spectrum peak of the corresponding ion are obtained from the mass spectrum, and the calculation formula of the mass resolution is: ;

[0087] The corresponding mass resolution is as shown in Figure 7 ; it can be known from the mass resolution graph that the optimal mass resolution is 7612 when d = 2.7 mm.

[0088] Step 4. On the basis of the vertical distance d = 2.7 mm of the vertex coordinates (x, y) corresponding to the optimal mass resolution to the origin of the XY coordinate axis being reached in step 3, the distance Rz of the vertex of the hyperbola on which the control electrode 2 is located to the axis center of the center line on the X axis is adjusted, and the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution; in this specific embodiment, the value of Rz is first increased and then decreased, the value range of Rz being 2.8 mm to 3.9 mm, wherein the mass spectrum obtained by increasing Rz is as shown in FIG. 8a, the mass spectrum obtained by decreasing Rz is as shown in FIG. 8b, and the finally obtained mass resolution is as shown in FIG. 8c. It can be known from the mass resolution graph that the optimal mass resolution 8808 is reached when d = 2.7 mm and Rz = 3.5 mm. Figure 8 Figure 9 Figure 10

[0089] Step 5. On the basis of the vertical distance d = 2.7 mm of the vertex coordinates (x, y) corresponding to the optimal mass resolution to the origin of the XY coordinate axis and the distance Rz = 3.5 mm of the vertex of the hyperbola on which the control electrode 2 is located to the axis center of the center line on the X axis being reached in step 4, the width Δ of the control electrode 2 is adjusted, and the ion trap mass analyzer works according to the predefined working timing 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, the change range of the width of the control electrode 2 to the left being 0.1 mm to 0.5 mm, the change range of the width to the right being 0.1 mm to 0.5 mm, and the obtained mass spectrum is as shown in FIG. 9a and FIG. 9b, and the corresponding mass resolution is as shown in Table 5. Figure 11

[0090] Table 5. Resolution corresponding to the change of the width Δ of the control electrode

[0091] ;

[0092] It can be known in combination with Table 5 that the optimal mass resolution 8808 is reached when d = 2.7 mm, Rz = 3.5 mm, and Δ = 0.25 mm.

[0093] Step 6. On the basis of the vertical distance d = 2.7 mm of the vertex coordinates (x, y) corresponding to the optimal mass resolution to the origin of the XY coordinate axis, the distance Rz = 3.5 mm of the vertex of the hyperbola on which the control electrode 2 is located to the axis center of the center line on the X axis, and the width Δ = 0.25 mm of the control electrode 2 being reached in step 5, the projection length a of the control electrode 2 on the Y axis is adjusted, and the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution; in this specific embodiment, the value range of a is 2 mm to 7 mm, and the obtained mass spectrum is as shown in FIG. 10a and FIG. 10b.​​​​Figure 12 The corresponding mass resolution is shown as Figure 13 As shown in the figure, the optimal mass resolution is 8808 when d = 2.7 mm, Rz = 3.5 mm, Δ = 0.25 mm, and a = 3.

[0094] The optimal mass resolution 8808 reached by the output step 6 and the corresponding vertical distance d = 2.7 mm of the vertex coordinates (x, y) of the control electrode 2 to the origin of the XY coordinate axis, the projection length a = 3 mm of the control electrode 2 on the Y axis, the distance Rz = 3.5 mm of the vertex of the hyperbola on which the control electrode 2 is located on the X axis from the center line axis center, and the width Δ = 0.25 mm of the control electrode 2.

[0095] In summary, the ion trap mass analyzer of the present application has a simplified shape 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 solid and stable, the problem of performance degradation caused by repeated disassembly and assembly of the linear ion trap is avoided, and the resolution of the linear ion trap mass analyzer is improved. The structure of the mass analyzer is simplified and solid, easy to process and assemble, improves 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 application can be used in the field of analysis and testing such as mass spectrometry. When used for mass spectrometry, when ions are injected, foreign ions first move linearly along the axial direction of the ion trap, and are distributed along the axis of the arc under the guidance of the radio frequency. When the ion ejection stage, the voltage on the linear ion trap mass analyzer begins to scan, and the voltage on the function electrode remains unchanged. The superimposed radio frequency electric field on the function electrode will force the stored ions to rapidly increase the 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.

[0096] In the description of the embodiments of the present application, it should be noted that in the description of the present application, the terms indicating the direction or position relationship are based on the direction or position relationship shown in the drawings, which is only for the convenience of description, and does not indicate or imply that the device or member must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0097] In the description of the application, the description of the terms "one embodiment", "some embodiments", "in this embodiment", "specific example", or "some examples" and the like means that the specific features, mechanisms, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the application. In the description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, mechanisms, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the specification and the features of the different embodiments or examples without contradiction.

[0098] The above description is merely a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An ion-trap mass analyzer characterized by, The ion trap includes four base electrodes (1), four control electrodes (2), two end cap electrodes (3) and a fixed frame (9), the inside of the fixed frame (9) is a cavity through along the length direction, four base electrodes (1) are evenly arranged on the inner wall of the cavity along the length direction of the center line, the base electrodes (1) extend along the axial direction of the center line, two end cap electrodes (3) are arranged at the two ends of the base electrodes (1) along the length direction, the two end cap electrodes (3) are symmetrically distributed, and the two end cap electrodes (3) are fixed with the fixed frame (9), the base electrodes (1) and the end cap electrodes (3) form an ion trap (5), there is a gap (6) between adjacent base electrodes (1), four control electrodes (2) are arranged at the gap (6) between adjacent base electrodes (1), and mounting supports (4) are arranged at the cavities at the two ends of the fixed frame (9) corresponding to the gap (6), the two ends of the control electrodes (2) are fixed with the mounting supports (4), the adjacent base electrodes (1) are applied with RF trapping voltages with equal amplitude and opposite phase, the end cap electrodes (3) are applied with positive voltages with equal amplitude with the base electrodes (1), and the four control electrodes (2) are applied with RF voltages with equal amplitude and the same phase. The center line is taken as the origin, and a plane perpendicular to the center line is taken as the cross section to establish the XY coordinate axis, the cross section of the control electrode (2) on the XY coordinate axis is a hyperbolic arch structure, and the four control electrodes (2) are respectively mirror stacked in the four quadrants of the XY coordinate axis. The hyperbolic arch structure of the four control electrodes (2) respectively coincides with the part of the hyperbolic curve with the focus 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). The frequency of the RF voltage on the control electrode (2) is the same as the frequency of the RF trapping voltage on the base electrode (1).

2. The ion-trap mass analyzer of claim 1, wherein, The side of the four base electrodes (1) facing the ion trap (5) is in a curved surface shape.

3. The ion-trap mass analyzer of claim 1, wherein, The end cap electrode (3) is provided with an ion incident port (7), and the base electrode (1) is provided with an ion ejection port (8), and a detector for capturing ejected ions is arranged at the ion ejection port (8).

4. The ion-trap mass analyzer of claim 1, wherein, The base electrodes (1) and the end cap electrodes (3) are insulated, the distance between the control electrode (2) and the center line is greater than 3mm, and the distance between the control electrode and the base electrode (1) is greater than 2mm.

5. A method of resolution control of an ion-trap mass analyzer, the method of resolution control being based on the ion-trap mass analyzer of any one of claims 1 to 4, characterized in that, The resolution control method comprises: Step 1. Predefine the vertex coordinate (x, y) of the control electrode (2) closest to the origin of the XY coordinate axis, the perpendicular distance d from the vertex coordinate (x, y) to the origin of the XY coordinate axis, the 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 from the vertex of the hyperbola on which the control electrode (2) is located to the center axis on the X axis, and the thickness Δ of the control electrode (2); position the control electrode (2) in the ion trap (5) based on the vertex coordinate (x, y); Step 2. Predefine the working timing of the ion trap analyzer; Step 3. Adjust the perpendicular 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 timing until the ion trap mass analyzer reaches the optimal mass resolution; Step 4. On the basis of reaching the optimal mass resolution in step 3, adjust the distance Rz from the vertex of the hyperbola on which the control electrode (2) is located to the center axis on the X axis, and the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution; Step 5. On the basis of reaching the optimal mass resolution in step 4, adjust the width Δ of the control electrode (2), and the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution; Step 6. On the basis of reaching the optimal mass resolution in step 5, adjust the projection length a of the control electrode (2) on the Y axis, and the ion trap mass analyzer works according to the predefined working timing until the ion trap mass analyzer reaches the optimal mass resolution; Step 7. Output the optimal mass resolution reached in step 6 and the corresponding vertex coordinate (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 from the vertex of the hyperbola on which the control electrode (2) is located to the center axis on the X axis, and the thickness Δ of the control electrode (2).

6. The method of resolution control of an ion trap mass analyzer according to claim 5, wherein, The predefined working timing of the ion trap mass analyzer in step 2 specifically includes: Step 201. In the initial stage, apply an initial RF trapping voltage with equal amplitude and opposite phase between adjacent base electrodes (1), apply a positive voltage to the end cover electrode (3), and apply a RF voltage V with equal amplitude and same phase to the control electrode (2); ions enter the ion trap (5) from the ion inlet (7) and stably move around the center line under the action of the RF trapping voltage; Step 202. Gradually increase the RF trapping voltage on the base electrode (1), keep the positive voltage on the end cover electrode (3) unchanged, and keep the RF voltage V on the control electrode (2) unchanged; the ions in the ion trap (5) increase the kinetic energy in the X direction under the action of the RF voltage, and are ejected from the ion exit hole and captured by the detector; Step 203. Reduce the RF trapping voltage of the base electrode (1) to the initial RF trapping voltage while reducing the radio frequency voltage of the said gate electrode (2).

7. The method of resolution control of an ion trap mass analyzer according to claim 6, wherein, The method for calculating the mass resolution of the ion trap mass analyzer in the steps 3-6 comprises: a. obtaining a mass spectrum of the ion trap mass analyzer when it is operated according to a predefined operation timing; b. obtaining mass-to-charge ratio of the ion from the mass spectrum of the ion and the full width at half maximum The formula for calculating the mass resolution is: .

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