A tripolar ion funnel device for efficient ion transport over a wide mass range

Abstract

This invention relates to mass spectrometry instruments, and more particularly to a tripolar ion funnel device for efficient ion transport over a wide mass range. It includes a fixed base, an insulating support rod, and funnel electrodes. Three funnel electrodes are spaced circumferentially on the fixed base, each connected to the fixed base via an insulating support rod. A triangular truncated space is formed inside the three funnel electrodes. A DC voltage and a radio frequency voltage are applied to each of the three funnel electrodes, and the triangular truncated space serves as an ion pathway. Each funnel electrode comprises multiple stacked electrode plates, with insulating pads between adjacent electrode plates. The insulating support rod passes through the alternately placed funnel electrode plates and the insulating pads. This invention utilizes a hexapole field formed by three radio frequency voltages with a 120° phase difference to achieve efficient ion focusing over a wide mass range. Furthermore, a uniform DC gradient electric field can drive the focused ions to the lower vacuum level, thereby significantly improving sensitivity.

Description

Technical Field

[0001] This invention relates to mass spectrometry instruments, and more particularly to a tripolar ion funnel device for efficient ion transport over a wide mass range. Background Technology

[0002] Mass spectrometry (MS) has been widely used in chemical and biological analysis due to its high sensitivity, specificity, and versatility. In mass spectrometry, the gas pressure in the ionization source section (10⁻¹⁰) 5 The pressure between the Pa and the mass analyzer (<10 Pa) -3 The difference in vacuum levels (Pa) is significant, necessitating the design of differential vacuum chambers to meet vacuum requirements. Ion pathways between different vacuum chambers are often formed by Skimmer orifices. After ions are generated by the ionization source, they must pass through several vacuum orifices to reach the mass analyzer region. During this process, a large number of ions are intercepted by the orifices, leading to a decrease in sensitivity. Furthermore, the significant difference in vacuum levels before and after the orifices causes jet expansion, resulting in ion beam divergence and further affecting instrument performance.

[0003] Therefore, efficient ion transport systems are one of the key technologies for improving mass spectrometry sensitivity. Currently, common ion transport devices include electrostatic lenses, multipole lenses, and ion funnels. The operating gas pressure of electrostatic lenses is around 10... -2 -10 -4 Between Pa; the multipole mainly operates at 10 Pa. -2 Between -10 Pa, an additional axial electric field is needed to provide thrust for operation at higher pressures; while the working pressure of an ion funnel is mainly between 1-1000 Pa, making it suitable as an ion transport device for downward transfer from an ionization source to a lower vacuum. During the operation of an ion funnel, the deep pseudopotential trap at the outlet often traps low mass-to-charge ratio ions, preventing them from being successfully extracted and causing mass discrimination, which limits its application. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a tripolar ion funnel device for efficient ion transport over a wide mass range, thereby solving the problem that existing ion transport devices cannot successfully extract ions, resulting in mass discrimination and limiting their application.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a tripolar ion funnel device for efficient ion transport over a wide mass range, comprising a fixed base, an insulating support rod, and funnel electrodes. The fixed base has three funnel electrodes spaced circumferentially, each funnel electrode being connected to the fixed base via an insulating support rod. The inner sides of the three funnel electrodes form a triangular truncated space. A DC voltage and a radio frequency voltage are applied to each of the three funnel electrodes, and the triangular truncated space serves as an ion pathway.

[0007] The funnel electrode includes multiple stacked electrode plates, with an insulating pad between two adjacent funnel electrode plates, and the insulating support rod passes through the alternately placed funnel electrode plates and each insulating pad in sequence.

[0008] The fixed base is a flat plate structure with a central hole. Three circular through holes are evenly distributed along the circumference of the fixed base. The circular through holes are used to connect the insulating support rod.

[0009] The electrode sheet is a flat plate structure, which is the remaining part after cutting an isosceles triangle with the central angle as the vertex from a sector with a central angle of 120°.

[0010] The electrode sheet has a circular hole near the arc edge, and the center of the circular hole is located on the vertical midline of the bottom edge of the electrode sheet.

[0011] The funnel electrode has N electrode plates stacked on top of each other, where N ≥ 5, and the length of the bottom edge of the N electrode plates decreases sequentially from the outside to the inside.

[0012] The fixed base and the electrode sheet are made of conductive metal or a flat plate with a conductive metal coating on its surface; the insulating support rod and the insulating pad are made of insulating material.

[0013] The thickness of the fixed base is 2-4mm, the diameter of the insulating support rod is 2-6mm, the thickness of the electrode sheet is 0.5-1mm, and the bottom edge length is 2-40mm; the thickness of the insulating pad is 0.5-1.5mm.

[0014] The electrode plates in the three funnel electrodes correspond one-to-one, and the three electrode plates located in the same plane form an electrode group. The DC voltage applied to the three electrode plates in each group is the same. The DC voltage applied to each electrode group decreases sequentially along the ion propagation direction to form a DC gradient electric field with a gradient voltage of 1-20V / cm. A voltage divider resistor with the same resistance value is connected in series between two adjacent electrode groups.

[0015] A radio frequency voltage is applied to each of the funnel electrodes, and the radio frequency voltage amplitude and phase of each electrode in the same column are the same; a decoupling capacitor is connected in series between two adjacent electrode pieces in the same column; the radio frequency voltage amplitude is the same on two adjacent funnel electrodes, the phase difference is 120°, the applied radio frequency is 0.5-5MHz, and the radio frequency peak-to-peak value is 10-800V.

[0016] The advantages and beneficial effects of this invention are: this invention utilizes a hexapole field to focus divergent ions with a wide mass range; in addition, a uniform DC gradient electric field can drive the focused ions to be transported to the lower vacuum level, thereby greatly improving the sensitivity.

[0017] This invention achieves efficient ion focusing and transport by combining radio frequency voltage and DC gradient voltage: the funnel electrode is divided into three columns, the radio frequency voltage amplitude and phase on the funnel electrode in the same column are the same, the radio frequency voltage amplitude on the funnel electrode in adjacent columns are the same, and the phase difference is 120°. Compared with the quadrupole field, the hexapole field can transport a wider range of ion masses, thereby achieving ion focusing over a wider range as much as possible. Attached Figure Description

[0018] Figure 1 This is an isometric view of a tripolar ion funnel device for efficient ion transport over a wide mass range according to the present invention.

[0019] Figure 2 for Figure 1 Enlarged view of a portion of point A in the middle;

[0020] Figure 3 This is a top view of a tripolar ion funnel device for efficient ion transport over a wide mass range, according to the present invention.

[0021] Figure 4 This is a schematic diagram of the structure of the fixed base in this invention;

[0022] Figure 5 This is a schematic diagram of the structure of the funnel electrode sheet in this invention;

[0023] Figure 6 This is a schematic diagram illustrating the method of applying DC voltage to the tripolar ion funnel electrode in this invention;

[0024] Figure 7 This is a schematic diagram illustrating the application method of the radio frequency voltage to the tripolar ion funnel electrode in this invention.

[0025] In the figure: 1-fixed base, 101-center hole, 102-circular through hole, 2-insulating support rod, 3-funnel electrode, 4-insulating gasket, 5-triangular truncated space, 6-electrode plate, 601-circular hole, 7-gap. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] See Figures 1 to 7As shown, the present invention provides a tripolar ion funnel device for efficient ion transport over a wide mass range, comprising a fixed base 1, an insulating support rod 2, and funnel electrodes 3. The fixed base 1 is provided with three funnel electrodes 3 spaced circumferentially, i.e., there is a gap 7 between two adjacent funnel electrodes 3. Each funnel electrode 3 is connected to the fixed base 1 through an insulating support rod 2. A triangular truncated space 5 is formed on the inner side of the three funnel electrodes 3. A DC voltage and a radio frequency voltage are applied to each of the three funnel electrodes 3. The triangular truncated space 5 serves as an ion passage, and the area of ​​the triangular region of the triangular truncated space 5 decreases sequentially along the ion propagation direction.

[0028] See Figure 2 , Figure 3 As shown, in an embodiment of the present invention, the funnel electrode 3 includes a plurality of stacked electrode plates 6, an insulating pad 4 is provided between two adjacent funnel electrode plates 6, and an insulating support rod 2 passes through the alternately placed funnel electrode plates 6 and each insulating pad 4.

[0029] See Figure 4 As shown in the embodiment of the present invention, the fixed base 1 is a flat plate structure with a central hole 101. Three circular through holes 102 are evenly distributed along the circumference of the fixed base 1. The circular through holes 102 are used to connect the insulating support rod 2.

[0030] Specifically, the fixed base 1 is disc-shaped with a radius of R1; the central hole 101 on the fixed base 1 is circular with a radius of R3, and its central axis coincides with the central axis of the fixed base 1; the centers of the three circular through holes 102 are located on a circle with a radius of R2, the plane of which coincides with the upper surface of the fixed base 1, and the center of the circle coincides with the center of the fixed base 1. The angle between the lines connecting any two of the three circular through holes 102 and the center of the fixed base 1 is 120°, and the central axes of all three circular through holes 102 are parallel to the central axis of the fixed base 1.

[0031] Specifically, the insulating support rod 2 is a cylindrical structure, and three insulating support rods 2 are equally spaced at 120° intervals along the circumference of the fixed base 1. The central axis of the insulating support rod 2 coincides with the central axis of the circular through hole 102 on the fixed base 1, and the bottom surfaces of the three insulating support rods 2 are located on the same plane and coincide with the lower surface of the fixed base 1.

[0032] See Figure 5 As shown, in an embodiment of the present invention, the electrode sheet 6 is a flat plate structure. The shape of this flat plate structure is the remaining part after cutting an isosceles triangle with the central angle as the vertex from a sector with a central angle of 120°. The base length of the isosceles triangle is L, that is, the base length of the funnel electrode 3 is L, and the base length of each electrode sheet 6 is different.

[0033] Furthermore, a circular hole 601 is provided on the electrode plate 6 near the edge of the arc, and the center of the circular hole 601 is located on the vertical midline of the bottom edge of the electrode plate 6. The three electrode plates 6 located in the same plane in the three funnel electrodes 3 form an electrode group, and the three electrode plates 6 in the group have completely identical geometric dimensions. The bottom edges of the three electrode plates 6 located in the same plane form an equilateral triangle region, and the vertical spacing between adjacent sides of adjacent electrode plates 6 in each group is the same.

[0034] In an embodiment of the present invention, N electrode plates 6 are stacked in the funnel electrode 3, and N≥5, and the length of the bottom edge of the electrode plate 6 decreases sequentially from the outside to the inside.

[0035] In this embodiment, each funnel electrode 3 has twenty-eight parallel electrode plates 6. Three electrode plates 6 located in the same plane form an electrode group, thus forming twenty-eight electrode groups. The upper surfaces of the electrode plates 6 in each group are all located in the same plane. The only difference between the electrode groups is the size of the base L of the electrode plates 6. The base L of the three electrode plates 6 in each electrode group forms an equilateral triangle region. The electrode groups are placed in parallel at intervals according to the decreasing size of the equilateral triangles formed, from the outside to the inside. The central normal of the equilateral triangles formed by all electrode groups coincides with the central axis of the fixed base 1. The area of ​​the equilateral triangle region formed by the electrode groups gradually decreases with the direction of ion propagation.

[0036] Specifically, the insulating pad 4 has an annular through-hole structure and is placed between any two adjacent electrode plates 6 and between the electrode plate 6 and the fixed base 1. The central axis of the insulating pad 4 coincides with the central axis of the insulating support rod 2. The circular hole 601 of the electrode plate 6, the insulating pad 4, and the insulating support rod 2 are coaxially arranged. The insulating support rod 2 passes through the circular hole 601 of the electrode plate 6 and the through-hole in the middle of the insulating pad 4 to position the electrode.

[0037] Specifically, the thickness of the fixed base 1 is 2-4mm, the radius R1 of the fixed base 1 is 10-40mm, the radius R3 of the center hole 101 is 2.5-20mm, the radius of the circular through hole 102 on the fixed base 1 is 1-3mm, and the radius R2 of the circle where the center of the circular through hole 102 is located is 8-30mm. R1, R2, and R3 should satisfy R1>R2>R3.

[0038] Preferably, the thickness of the fixed base 1 is 4mm, the radius R1 of the fixed base 1 is 33mm, the radius R3 of the central hole 101 is 15mm, the radius of the circular through hole 102 on the fixed base 1 is 3mm, and the radius R2 of the circle where the center of the circular through hole 102 is located is 25mm.

[0039] Specifically, the thickness of the insulating pad 4 is 0.5-1.5mm, and the diameter of the through hole in the middle is 2-6mm; the three insulating support rods 2 have completely identical geometric dimensions and a diameter of 2-6mm; preferably, the diameter is 6mm; the thickness of the electrode sheet 6 is 0.5-1mm, the bottom edge length is 2-40mm, and the diameter of the round hole 601 is 2-6mm; preferably, the thickness of the electrode sheet 6 is 0.5mm, with 1mm intervals, and the diameter of the round hole 601 is 6mm.

[0040] Specifically, the materials of the fixed base 1 and the electrode plate 6 are conductive metals (such as stainless steel) or flat plates with a conductive metal layer on the surface; the insulating support rod 2 and the insulating pad 4 are insulating materials (such as polyetheretherketone or ceramic).

[0041] Specifically, the shape of the electrode plate 6 is not fixed, as long as the base L of the electrode plate 6 can form an equilateral triangle. The working gas pressure of the present invention is between 1-1000 Pa; preferably, the working gas pressure of the integral tripolar ion funnel is 500 Pa.

[0042] See Figure 3 , Figure 6 As shown, in the embodiment of the present invention, the electrode plates 6 in the three funnel electrodes 3 correspond one-to-one, and the three electrode plates 6 located in the same plane form an electrode group. The DC voltage applied to the three electrode plates 6 in each group is the same. The DC voltage applied to each electrode group decreases sequentially along the ion propagation direction to form a DC gradient electric field. The gradient voltage is 1-20V / cm, preferably 10V / cm. A voltage divider resistor with the same resistance value is connected in series between two adjacent electrode groups.

[0043] See Figure 3 , Figure 7 As shown, in the embodiments of the present invention, a radio frequency (RF) voltage is applied to each funnel electrode 3, and the RF voltage amplitude and phase of each electrode piece 6 in the same column are the same; a decoupling capacitor is connected in series between two adjacent electrode pieces 6 in the same column; the RF voltage amplitude is the same on two adjacent funnel electrodes 3, and the phase difference is 120°. The applied RF frequency is 0.5-5MHz, and the RF peak-to-peak value is 10-800V. Preferably, the applied RF frequency is 2MHz, and the RF peak-to-peak value is 600V.

[0044] This invention provides a tripolar ion funnel device for efficient ion transport over a wide mass range. It achieves efficient ion focusing and transport through a combination of radio frequency (RF) voltage and DC gradient voltage. The funnel electrodes are divided into three columns. The RF voltage amplitude and phase on the same column of funnel electrodes are identical, while the RF voltage amplitude on adjacent columns is identical but their phases differ by 120°. This utilizes a hexapole field to focus divergent ions over a wide mass range. Furthermore, the uniform DC gradient electric field promotes the focused ions to transport to the lower vacuum level, thereby significantly improving sensitivity.

[0045] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, extensions, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A tripolar ion funnel device for efficient ion transport over a wide mass range, characterized in that, It includes a fixed base (1), an insulating support rod (2) and funnel electrodes (3). Three funnel electrodes (3) are arranged circumferentially on the fixed base (1). Each funnel electrode (3) is connected to the fixed base (1) through an insulating support rod (2). A triangular truncated space (5) is formed on the inner side of the three funnel electrodes (3). A DC voltage and a radio frequency voltage are applied to the three funnel electrodes (3). The triangular truncated space (5) is used as an ion passage. The funnel electrode (3) includes multiple stacked electrode plates (6), and an insulating pad (4) is provided between two adjacent funnel electrode plates (6). The insulating support rod (2) passes through the alternately placed funnel electrode plates (6) and each insulating pad (4) in sequence. The electrode sheet (6) is a flat plate structure, which is the remaining part after cutting off an isosceles triangle with the central angle as the vertex from a sector with a central angle of 120°. N electrode plates (6) are stacked in the funnel electrode (3), and N≥5. The length of the bottom edge of the N electrode plates (6) decreases sequentially from the outside to the inside. A radio frequency voltage is applied to each of the funnel electrodes (3), and the radio frequency voltage amplitude and phase of each of the electrode pieces (6) in the same column are the same; a decoupling capacitor is connected in series between two adjacent electrode pieces (6) in the same column; the radio frequency voltage amplitude is the same on two adjacent funnel electrodes (3), the phase difference is 120°, the applied radio frequency frequency is 0.5-5 MHz, and the radio frequency peak-to-peak value is 10-800 V.

2. The tripolar ion funnel device for efficient ion transport over a wide mass range according to claim 1, characterized in that, The fixed base (1) is a flat plate structure with a central hole (101). Three circular through holes (102) are evenly distributed along the circumference of the fixed base (1). The circular through holes (102) are used to connect the insulating support rod (2).

3. The tripolar ion funnel device for efficient ion transport over a wide mass range according to claim 1, characterized in that, The electrode sheet (6) has a circular hole (601) near the arc edge, and the center of the circular hole (601) is located on the vertical midline of the bottom edge of the electrode sheet (6).

4. The tripolar ion funnel device for efficient ion transport over a wide mass range according to claim 1, characterized in that, The fixed base (1) and the electrode plate (6) are made of conductive metal or a flat plate with a conductive metal layer on its surface; the insulating support rod (2) and the insulating pad (4) are made of insulating material.

5. The tripolar ion funnel device for efficient ion transport over a wide mass range according to claim 1, characterized in that, The thickness of the fixed base (1) is 2-4 mm, the diameter of the insulating support rod (2) is 2-6 mm, the thickness of the electrode sheet (6) is 0.5-1 mm, and the bottom edge length is 2-40 mm; the thickness of the insulating pad (4) is 0.5-1.5 mm.

6. The tripolar ion funnel device for efficient ion transport over a wide mass range according to claim 1, characterized in that, The electrode plates (6) in the three funnel electrodes (3) correspond one-to-one. The three electrode plates (6) located in the same plane form an electrode group. The DC voltage applied to the three electrode plates (6) in each group is the same. The DC voltage applied to each electrode group decreases sequentially along the direction of ion movement, forming a DC gradient electric field with a gradient voltage of 1-20 V / cm. A voltage divider resistor with the same resistance value is connected in series between two adjacent electrode groups.

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