Ion focusing transmission device based on laminated cluster electrode and preparation method thereof

Abstract

The invention belongs to the technical field of mass spectrometry, and particularly relates to an ion focusing transmission device based on a laminated cluster electrode and a preparation method of the ion focusing transmission device. The device comprises an electrode assembly formed by stacking a plurality of annular electrodes in a crossed mode in the axial direction, and the inner diameter of the electrodes is gradually reduced in the ion transmission direction to form a focusing channel; the electrode assembly is divided into a front area, a middle area and a rear area; a hollow structure is formed between the electrodes in the front section area and is used for extracting neutral particles; an insulating spacer is arranged between the annular electrodes in the middle section area and the rear section area; the adjacent annular electrodes are configured to apply radio frequency voltages with equal amplitudes and opposite phases and a direct current gradient voltage along the axial direction; by optimizing the inner diameter shrinkage curve and the electric field distribution, the transmission efficiency reaches more than 90%. The problems that a traditional ion funnel is complex in machining, high in cost, large in load capacitance, obvious in quality discrimination and the like are solved, and high-efficiency and wide-quality-range ion focusing transmission under high working air pressure is achieved.

Description

Technical Field

[0001] This invention belongs to the field of analytical instrument technology, specifically relating to an ion focusing transmission device in a mass spectrometer and its preparation method. Background Technology

[0002] In mass spectrometry, ion sources typically operate at atmospheric pressure, while mass analyzers need to operate under vacuum. When ions enter the primary vacuum chamber through the interface, they undergo supersonic expansion. Without effective guidance and focusing, this results in significant ion loss. Ion funnel technology is a key solution to this problem. It uses a series of ring electrodes with applied radio frequency voltage to generate a radial confinement electric field, focusing ions onto the central axis and propagating them forward.

[0003] However, traditional ion funnels have several limitations: First, their outlet electrode has a small inner diameter, which easily traps low mass-to-charge ratio ions, leading to severe mass discrimination. Second, to achieve good focusing, a large number of precision-machined electrode sheets and extremely small electrode spacing are usually required, resulting in complex manufacturing and assembly and high costs. Third, the dense electrode structure leads to a huge equivalent load capacitance (up to 1000 pF or more), imposing stringent requirements on the power and frequency of the RF power supply, increasing the cost and complexity of the instrument. In addition, although traditional multipole and other transmission devices are less expensive, they have a narrow operating pressure range (<1 Torr) and low transmission efficiency. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide an ion focusing transport device based on stacked cluster electrodes with optimized structure, superior performance, and lower cost, as well as its preparation method.

[0005] The present invention provides an ion focusing and transport device (SPC series) based on stacked cluster electrodes, comprising: an electrode assembly; the electrode assembly is formed by stacking multiple annular electrodes along the ion transport axis and divided into a front region, a middle region, and a rear region; the annular electrodes in the front and middle regions have the same inner diameter, while the annular electrodes in the rear region have a gradually decreasing inner diameter along the axial direction to form a contraction channel for ion focusing and transport; wherein, no insulating pads are provided between the annular electrodes in the front region, i.e., gaps are provided, so that a hollow structure is formed between adjacent electrodes for the extraction of neutral particles; insulating pads are provided between the annular electrodes in the middle and rear regions (i.e., annular electrodes and insulating pads are alternately arranged); radio frequency voltages of equal amplitude and opposite phase, and a DC gradient voltage along the axial direction are configured to be applied to adjacent annular electrodes.

[0006] Furthermore, the number of ring electrodes in the front region is 9-15, the number of ring electrodes in the middle region is 17-23, and the number of ring electrodes in the rear region is 28-36. The specific number is determined according to actual needs.

[0007] Furthermore, the line width (i.e., ring width) of the annular electrode is 1-4 mm;

[0008] Furthermore, the inner diameter of the annular electrodes in the front and middle sections is 22-30 mm; the decrease in the inner diameter of the annular electrodes in the rear section follows a quadratic polynomial function relationship: y = ax 2 + bx + c.

[0009] Furthermore, the electrode assembly is made of gold-plated copper foil or stainless steel, etc.

[0010] Furthermore, the electrode assembly (a composite electrode composed of multiple ring electrodes stacked along the ion transport axis) is a composite electrode manufactured using a printed circuit board process. Specifically, a negative mold of the electrode assembly is first prepared using an insulating substrate, and then electrode material is electroplated onto the inner wall surface of the negative mold.

[0011] In this invention, the equivalent load capacitance of the ion focusing transport device is less than 300 pF, preferably less than 160 pF.

[0012] This invention also provides a method for preparing the above-mentioned cluster ion focusing and transport device, the specific steps of which are as follows:

[0013] (1) Determine the number, inner diameter variation law and spacing of the ring electrodes according to the target focusing transmission performance;

[0014] (2) Joint simulation of airflow field and electric field to optimize electrode structure parameters;

[0015] (3) Based on the optimized parameters, process the ring electrode and insulating pad;

[0016] (4) The processed annular electrode and insulating pad are cross-stacked and fixed to form the electrode assembly.

[0017] Furthermore, the step of processing the ring electrode is completed using a printed circuit board process, which includes patterning on an insulating substrate and electroplating a metal layer.

[0018] In one embodiment, the ion focusing and transport device (SPC) comprises an electrode assembly consisting of 21 annular electrodes. The front section consists of 5 electrodes, which are perforated (without insulating spacers) and have an equal inner diameter of 15 mm. The middle section consists of 7 electrodes with insulating spacers and also with an equal inner diameter of 15 mm. The rear section consists of 9 electrodes with insulating spacers, and their inner diameters are sequentially: 14.3 mm, 12.9 mm, 11.5 mm, 10.1 mm, 8.7 mm, 7.3 mm, 5.9 mm, 4.5 mm, and 3.1 mm. The inner diameter of the insulating spacers changes synchronously with that of adjacent electrodes. This structure achieves effective ion focusing and transport, with an equivalent load capacitance of approximately 95 pF.

[0019] In another embodiment, the ion focusing transport device (L-SPC) comprises an electrode assembly with a larger number of electrode sheets (e.g., 64 sheets) divided into three functional zones. The front zone consists of 12 electrodes, hollowed out from each other (without insulating pads), and all with an equal inner diameter of 26.4 mm. This design allows the vacuum pump to directly remove neutral molecules and undissolved droplets through the hollowed-out zones, reducing their interference with ion transport. The middle zone consists of 20 electrodes with insulating pads and an equal inner diameter of 26.4 mm. The rear zone consists of 32 electrodes with insulating pads, and their inner diameters decrease according to a quadratic polynomial equation to a smaller outlet inner diameter (1.9 mm), achieving stronger focusing. Although this structure increases the load capacitance, it significantly improves transport efficiency and ion purification effect.

[0020] In another embodiment, the ion focusing transport device (PCB-SPC) uses a ring electrode fabricated using printed circuit board technology. Specifically, a metal electrode layer is laid on the inner ring hole wall and a 2mm wide surface connected to the inner ring on a circular PCB insulating substrate as the actual electrode. This design cleverly combines simulation results: the wide PCB substrate provides good airflow guidance, while the narrow ring metal electrode provides a stable and effective electric field distribution. More importantly, the PCB process greatly simplifies manufacturing and assembly, reducing costs to about 1 / 6 of that of SPC, while keeping the equivalent load capacitance at a low level (about 153 pF), reducing the requirements for the RF power supply.

[0021] This invention optimizes the inner diameter shrinkage profile of the electrode using a specific quadratic polynomial equation, achieving more efficient ion focusing and transmission. Through a pioneering segmented structure of a "front-end hollow area + rear-end focusing area," it integrates ion purification and focusing functions, improving ion beam quality. The device is innovatively manufactured using PCB technology, and a "wide substrate - narrow electrode" composite structure is designed. This significantly reduces costs (to 1 / 6) and simplifies assembly, while unexpectedly achieving a lower equivalent load capacitance, thus reducing the requirements for the RF power supply. Ultimately, this invention successfully achieves an excellent balance between high transmission efficiency (>90%), a wide operating pressure range (~10 Torr), low load capacitance, and low cost, solving a long-standing bottleneck problem in traditional ion funnel technology.

[0022] The main beneficial effects of this invention are:

[0023] (1) High transmission efficiency: Through optimized inner diameter contraction curve and electric field distribution, the transmission efficiency of reserpine (m / z 609) can reach more than 91%.

[0024] (2) Wide working pressure range: It can work stably at pressures up to about 10 Torr and has strong adaptability.

[0025] (3) Low mass discrimination: The optimized electrode structure and electric field parameters reduce the discrimination effect on ions with different mass-to-charge ratios.

[0026] (4) Low load capacitance: Especially in PCB-SPC design, the load capacitance is controlled to less than one-fifth of that of traditional ion funnel, which greatly reduces the difficulty of developing RF power supply and power consumption.

[0027] (5) Low cost and easy processing: The use of PCB technology avoids complex precision machining, significantly reducing costs and making it suitable for mass production.

[0028] (6) Functional integration: The L-SPC design integrates ion focusing and neutral particle removal functions, which improves the overall performance of the system. Attached Figure Description

[0029] Figure 1 This is a structural diagram (side view) of Embodiment 1 (SPC) of the present invention.

[0030] Figure 2 This is a front view of the SPC device according to Embodiment 1 of the present invention.

[0031] Figure 3 It is the circular electrode sheet of Embodiment 1 of the present invention.

[0032] Figure 4 This is a structural diagram (side view) of Embodiment 2 (L-SPC) of the present invention.

[0033] Figure 5 This is a front view of the L-SPC device according to Embodiment 2 of the present invention.

[0034] Figure 6 This is a structural diagram (side view) of Embodiment 3 (PCB-SPC) of the present invention.

[0035] Figure 7 This is a front view of the PCB-SPC device according to Embodiment 3 of the present invention.

[0036] The following labels are used in the diagram: 1 is the SPC electrode assembly, 2 is the SPC insulating gasket assembly, 3 is the SPC insulating retaining collar, 4 is the SPC insulating cover plate, 5 is the SPC clamping lens, 6 is the SPC power interface, 7 is the SPC narrow circular electrode; 8 is the L-SPC electrode assembly, 9 is the L-SPC insulating gasket assembly, 10 is the L-SPC insulating retaining collar, 11 is the L-SPC clamping lens, 12 is the L-SPC insulating cover plate, 13 is the L-SPC power interface; 14 is the PCB-SPC ring electrode assembly, 15 is the PCB-SPC insulating gasket assembly, and 16 is the PCB insulating substrate. Detailed Implementation

[0037] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0038] Specifically, this invention proposes three core implementation methods: a basic stacked cluster electrode ion focusing and transport device (SPC), which achieves effective focusing by decreasing the inner diameter of the electrodes; an improved ion focusing and transport device (L-SPC), which effectively extracts neutral molecules and droplets by adding a large inner diameter electrode area with a hollowed-out front section, and the electrode inner diameter is decreased in a quadratic function manner to improve focusing purity and transport efficiency; and an optimized ion focusing and transport device (PCB-SPC), which uses printed circuit board technology to fabricate electrodes, and lays metal electrodes in a narrow ring form on the surface and inner ring of an insulating substrate, which has excellent airflow guidance, electric field stability and low load capacitance.

[0039] Example 1: Ion Focusing Transport Device (SPC), see Figure 1 , Figure 2 and Figure 3 The system includes an SPC electrode assembly 1, an SPC insulating gasket assembly 2, an SPC insulating retaining collar 3, an SPC insulating cover plate 4, an SPC clamping lens 5, and an SPC power interface 6. The insulating cover plate 4 is annular and contacts the first SPC electrode, serving a fixing and limiting function; it is made of PEEK material. The clamping lens 5 is circular with a 1-2mm hole in the center to allow ions to pass through; it contacts the last insulating gasket and serves a limiting function; it is made of stainless steel. The insulating retaining collar 3 secures the clamping lens 5, and together with the insulating cover plate 4, fixes the SPC in place.

[0040] The SPC device in this embodiment consists of an electrode assembly comprising 21 ring electrodes, each 0.5 mm thick, made of stainless steel and assembled with interleaved stacked insulating pads at designated locations. The first five electrodes are open-ended (without insulating pads) and have the same inner diameter (15 mm). The middle seven electrodes have insulating pads and the same inner diameter (15 mm). The last nine electrodes have insulating pads with inner diameters of 14.3 mm, 12.9 mm, 11.5 mm, 10.1 mm, 8.7 mm, 7.3 mm, 5.9 mm, 4.5 mm, and 3.1 mm, respectively. The inner diameter of the insulating pad is the same as the inner diameter of the adjacent electrode. After assembly, an RF voltage (e.g., 1 MHz, 200 Vpp) of equal amplitude but opposite phase, along with an axial DC gradient voltage (e.g., a 10 V drop from inlet to outlet) provided by a resistor divider network, are applied to adjacent electrodes.

[0041] Example 2: Ion Focusing Transport Device (L-SPC), see Figure 4 and Figure 5 The L-SPC includes an L-SPC electrode assembly 8, an L-SPC insulating gasket assembly 9, an L-SPC insulating retaining collar 10, an L-SPC clamping lens 11, an L-SPC insulating cover plate 12, and an L-SPC power interface 13. Similar to the SPC, the retaining collar 10, clamping lens 11, and insulating cover plate 12 together secure the L-SPC. The power interface 13 is a cylindrical gold-plated power supply interface that provides radio frequency voltage to the L-SPC.

[0042] The L-SPC device in this embodiment consists of 64 narrow stainless steel annular electrodes and 51 PEEK insulating pads. The shape of the annular electrodes is shown in [reference needed]. Figure 3 The first 12 electrodes are hollowed out (without insulating pads) and have an equal inner diameter of 26.4 mm. This design allows the vacuum pump to directly remove neutral molecules and undissolved droplets through the hollowed-out areas, reducing their interference with ion transport. The middle 20 electrodes have insulating pads and an equal inner diameter of 26.4 mm. The rear 32 electrodes have insulating pads and their inner diameters follow a quadratic polynomial equation: y = -0.0004x 2 +0.286x +0.9 gradually decreases from 26.4 mm to 1.9 mm. Here, y is half the inner diameter of the electrode, and x is the distance from each electrode to the last electrode with a 1.9 mm inner diameter; the coefficients are -0.0004, 0.286, and 0.9, respectively, and are calculated values. In the calculation, the inner diameter of the last electrode in the rear section of 32 electrodes is fixed at 1.9 mm, the inner diameter of the first electrode in the rear section of 32 electrodes is fixed at 26.4 mm, and the spacing between adjacent electrodes is 1.5 mm. This design allows for effective removal of neutral interference in the front section and achieves strong focusing in the rear section.

[0043] Example 3: Ion Focusing Transport Device (PCB-SPC), see [link / reference] Figure 6 and Figure 7 It includes a PCB-SPC annular electrode assembly 14 and a PCB-SPC insulating pad assembly 15. The electrode assembly 14 includes a substrate, and the electrode is formed on the substrate.

[0044] The PCB-SPC device in this embodiment is fabricated using PCB technology. The electrode substrate is made of FR-4 material. A 2 mm wide gold-plated copper foil ring is formed on its inner ring hole walls and surface through patterning and electroplating to serve as the effective electrode. Multiple such PCB electrode boards are stacked and fixed together by insulating studs to form a complete electrode assembly. (The first 12 electrodes are hollowed out from each other (without insulating pads) and have the same inner diameter (26.4 mm). This design allows the vacuum pump to directly remove neutral molecules and undissolved droplets through the hollowed-out areas, reducing their interference with ion transport. The middle 20 electrodes have insulating pads and the same inner diameter (26.4 mm). The rear 32 electrodes have insulating pads and their inner diameter gradually decreases from 26.4 mm to 1.9 mm according to the quadratic polynomial equation in Example 2). The variation in electrode inner diameter is achieved by varying the inner diameter of the PCB board. This device combines the airflow advantages of a wide substrate with the electric field advantages of a narrow electrode ring, and its cost is only about 1 / 6 of that of a stainless steel SPC.

[0045] Performance Comparison

[0046] The comparative data in Table 1 clearly demonstrates that the three devices of the present invention, especially the PCB-SPC, achieve a balance between high performance and low cost in terms of transmission efficiency, working air pressure, load capacitance, and cost.

[0047] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0048] Table 1. Comparison of parameters and performance of the three SPC series devices of the present invention.

[0049] .

Claims

1. An ion focusing and transport device based on stacked cluster electrodes, characterized in that, include: An electrode assembly is provided, comprising multiple ring electrodes stacked along the ion transport axis and divided into a front region, a middle region, and a rear region. The ring electrodes in the front and middle regions have the same inner diameter, while the inner diameter of the ring electrodes in the rear region gradually decreases along the axial direction to form a constricted channel for ion focusing and transport. In the front region, no insulating pads are provided between the ring electrodes, i.e., gaps are created, forming a hollow structure between adjacent electrodes for the extraction of neutral particles. Insulating pads are provided between the ring electrodes in the middle and rear regions, i.e., the ring electrodes and insulating pads are alternately arranged. An equal-amplitude, opposite-phase radio frequency voltage and a DC gradient voltage along the axial direction are applied to adjacent ring electrodes.

2. The ion focusing transport device according to claim 1, characterized in that, The number of ring electrodes in the front section is 9-15, the number of ring electrodes in the middle section is 17-23, and the number of ring electrodes in the rear section is 28-36.

3. The ion focusing transport device according to claim 1, characterized in that, The width of the annular electrode line is 1-4 mm.

4. The ion focusing transport device according to claim 1, characterized in that, The inner diameter of the annular electrodes in the front and middle sections is 22-30 mm; the inner diameter of the annular electrodes in the rear section decreases according to a quadratic polynomial function: y = ax 2 + bx + c.

5. The ion focusing transport device according to claim 1, characterized in that, The electrode assembly is made of gold-plated copper foil or stainless steel.

6. The ion focusing transport device according to claim 1, characterized in that, The electrode assembly is a composite electrode manufactured using a printed circuit board process. Specifically, an electrode assembly female mold is first prepared using an insulating substrate, and then electrode material is electroplated onto the inner wall surface of the female mold.

7. The ion focusing transport device according to any one of claims 1-6, characterized in that, The equivalent load capacitance of the ion focusing transport device is less than 300 pF.

8. A method for preparing a cluster ion focusing and transport device as described in any one of claims 1-6, characterized in that, The specific steps are as follows: (1) Determine the number, inner diameter variation law and spacing of the ring electrodes according to the target focusing transmission performance; (2) Joint simulation of airflow field and electric field to optimize electrode structure parameters; (3) Based on the optimized parameters, process the ring electrode and insulating pad; (4) The processed annular electrode and insulating pad are cross-stacked and fixed to form the electrode assembly.

9. The preparation method according to claim 8, characterized in that, The process of fabricating the ring electrode is completed using printed circuit board technology, which includes patterning on an insulating substrate and electroplating a metal layer.

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