A traveling wave ion mobility module without dc protection

Abstract

The application belongs to the technical field of mass spectrum and ion mobility spectrum analysis, and particularly relates to a traveling wave ion mobility module without direct current protection. The application is used for realizing ionized sample separation based on different collision cross sections. The radio frequency restraining electrode and the traveling wave separation electrode on the circuit board are arranged in a specific combination in space, and then a radio frequency signal and an axially periodically changing traveling wave signal are applied, so that the ion is restrained and separated. Compared with the traditional non-destructive ion transmission mobility spectrum based on direct current and traveling wave, the traveling wave ion mobility tube device of the application does not need to apply a direct current protection (guard voltage) electric field, the circuit design is simpler, the required components are less, the expansibility is stronger, and the application range is wider.

Description

Technical Field

[0001] This invention relates to the fields of mass spectrometry and ion mobility spectrometry, and more specifically, to a traveling wave ion mobility module that does not require DC protection. Background Technology

[0002] Traveling-wave ion mobility (TWIM) is a gas-phase ion separation method driven by a dynamic electric field, widely used in mass spectrometry-ion mobility systems to enhance the separation capabilities and analytical dimensionality of complex samples. Unlike traditional drift tube ion mobility techniques that employ a constant DC electric field, TWIM applies a pulsed DC signal with a time-phase delay to a series of spatially distributed electrodes. This creates an axially propagating potential wave in a buffer gas-filled channel, driving ions forward and achieving migration and separation. Because different ions exhibit varying responses to the traveling-wave potential in a gaseous medium, TWIM can effectively distinguish isomers, isomeric isomers, and components in complex mixtures while maintaining high ion throughput. This technique offers advantages such as flexible separation path expansion, high compatibility with various mass spectrometry systems, and suitability for high-resolution and high-throughput analysis, thus demonstrating significant application value in proteomics, metabolomics, environmental analysis, and drug analysis.

[0003] Typically, traveling wave ion mobility requires a stacked ring electrode mechanical structure or a set of mirror-symmetric circuit boards with only specific electrodes as the core ion separation component. However, the former requires a large number of complex mechanical structures, resulting in high installation and maintenance costs and a large number of parts. While the latter simplifies the electrode structure by integrating it onto the circuit board, its double-sided mirror-symmetric structure inevitably lacks lateral electrode arrangement, making it difficult to effectively constrain the radial diffusion of ions between the circuit boards. This necessitates the use of large-area DC electrodes on both sides as protective electrodes to prevent radial ion diffusion, increasing the demands on the circuitry. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention aims to provide a traveling wave ion mobility module for separating ionized samples based on different collision cross-sectional areas without the need for a DC guard voltage. The traveling wave ion mobility tube device of the present invention does not require the application of a DC guard voltage electric field, resulting in a simpler circuit design, fewer required components, greater scalability, and a wider range of applications. It solves the problems of conventional traveling wave ion funnels, which require a DC guard voltage to confine ions, necessitate numerous related accessories, and are cumbersome to assemble and disassemble.

[0005] This invention utilizes a traveling-wave separation electrode array composed of multiple circuit boards to create a pseudopotential field that effectively confines ions and prevents radial diffusion, thus eliminating the need for a DC protection electrode. This device integrates ion transport, separation, and guidance functions. Assembly is completed simply by preparing identical circuit boards for the actual number of multi-electrode arrays and fixing them together. The device then functions by connecting to an external power supply interface via wires and applying a traveling-wave voltage.

[0006] In this invention, multiple sets of metal electrodes are arranged in space, and traveling wave signal voltage and radio frequency signal voltage are applied to the metal electrodes respectively, thereby forming an axially propagating traveling wave electric field and a radio frequency effective potential field that radially confines the ions within the ion transport channel. By applying a force to the ionized sample using the aforementioned electric field, under the presence of a background gas, different ions exhibit different migration behaviors under the combined influence of the electric field force and gas collisions, achieving separation based on the difference in ion collision cross-sectional area. The technical solution of this invention is described in detail below.

[0007] A traveling wave ion mobility module without DC protection includes several circuit boards with traveling wave separation electrodes and radio frequency confinement electrodes drawn on their working surfaces. The circuit boards enclose a spatially symmetrical hollow ion transport channel. The traveling wave separation electrodes are arranged at intervals along the axial direction of the ion transport channel, and the radio frequency confinement electrodes extend radially along the ion transport channel. During operation, a traveling wave voltage signal is applied to the traveling wave separation electrodes, and a radio frequency voltage signal is applied to the radio frequency confinement electrodes, thereby forming an axially propagating traveling wave electric field and a radio frequency confinement electric field that radially confines the ions within the ion transport channel. Ions pass through the geometric center region of the ion transport channel, and the separation process is completed under the combined action of the traveling wave electric field and the radio frequency confinement electric field.

[0008] In this invention, the traveling wave separation electrode is composed of multiple sets of spaced metal electrodes. Starting from any end, n adjacent metal electrodes form a group. The metal electrodes in each group are numbered 1-n. The electrodes in each group are independent and not connected to each other (electrically isolated). Electrodes with the same number in different groups are connected in series to form a circuit.

[0009] In this invention, the traveling wave signal applied to the traveling wave separation electrode is a periodically changing voltage signal, and its waveform can be a periodically changing signal such as a sine wave, square wave, chop wave, or triangular wave. There is a fixed time delay or phase difference between the traveling wave signals of adjacent electrodes, so that the high potential value propagates along the electrode array in the direction of ion transport, thereby forming a dynamic traveling wave electric field with a set propagation speed in space. The propagation speed of the traveling wave is determined by the electrode spacing and the phase delay, and its amplitude is determined by the magnitude of the applied voltage.

[0010] In this invention, the degree of ion separation and throughput are adjusted by regulating the amplitude, propagation speed, and phase difference of the traveling wave voltage.

[0011] In this invention, the radio frequency confinement electrode consists of a set of long strip rod electrodes that are geometrically symmetrical in space, and the electrodes are insulated from each other and independent; a radio frequency signal is applied to it to generate an effective potential well, so as to form a stable radial confinement for charged particles.

[0012] In this invention, the radio frequency (RF) signal applied to the RF confinement electrode is a set of alternating sinusoidal or near-sinusoidal voltage signals with fixed amplitude and frequency. RF signals with 180° phase opposite phase are applied to adjacent or opposing electrodes, thereby forming a radially effective potential well in the ion transport channel, achieving stable ion confinement, and restricting ions to the central region of the traveling wave ion mobility module channel without contacting the electrodes. A DC bias voltage can be selectively superimposed on the RF signal to adjust the ion transport conditions.

[0013] In this invention, the confinement strength of the radio frequency confinement electrode is determined by both the amplitude and frequency of the radio frequency voltage. The frequency is usually several megahertz, and the voltage amplitude is tens to hundreds of volt peak-to-peak values. Specifically, it is determined by factors such as the required mass-to-charge ratio of the confined ions, the ambient air pressure, and the length of the rod electrode.

[0014] In this invention, the cross-section of the hollow ion transport channel can be circular, rectangular, hexagonal, octagonal, or other polygonal structures. The specific polygonal structure depends on the number of multipole rods designed and the actual electrode arrangement of the circuit board. For example, when an octole is used as the ion transport multipole, and two multipole electrodes are drawn on each circuit board, four circuit boards are needed to form a rectangular channel to create the ion transport channel.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention eliminates the need for DC protection electrodes, achieving effective radial confinement of ions through the synergistic effect of radio frequency electric fields and traveling wave electric fields. This avoids the dependence on DC protection electrodes in traditional structures and significantly simplifies electrode structure and circuit design.

[0016] The electrode structure of this invention is simple and highly integrated, and can be directly integrated into a circuit board or modular structure, reducing the number of mechanical parts and lowering processing, assembly and maintenance costs.

[0017] The geometry and size of the ion transport channel of this invention can be flexibly designed according to requirements, and it is easy to integrate with different types of mass spectrometry systems or pre- and post-stage ion optical devices, exhibiting extremely high scalability and compatibility.

[0018] This invention allows for flexible control of ion separation intensity, resolution, and throughput efficiency by adjusting the amplitude, propagation speed, phase difference of the traveling wave voltage, as well as the amplitude and frequency parameters of the radio frequency voltage. It optimizes the trade-off between high-throughput transmission and high-resolution separation, making it suitable for various analytical scenarios and for the migration and separation of ions in various samples. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the axial cross-sectional electrode arrangement in Embodiment 1 of the present invention.

[0020] Figure 2 This is a schematic diagram of the radial cross-section electrode arrangement in Embodiment 1 of the present invention.

[0021] Figure 3 This is a schematic diagram of the three-dimensional cross-sectional electrode arrangement in Embodiment 1 of the present invention.

[0022] Figure 4 This is a schematic diagram of a single-chip circuit board according to Embodiment 1 of the present invention.

[0023] Figure 5 This is a schematic diagram of the circuit board assembly according to Embodiment 1 of the present invention.

[0024] The accompanying figures are labeled as follows: 1-Traveling wave separation electrode, 2-RF constraint electrode, 3-Printed circuit board, 4-Bayonet, 5-Bayonet teeth, 6-Fixing through hole. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0026] Example 1

[0027] like Figures 1-3 As shown, this invention provides a traveling wave ion mobility module design with a channel shape close to a cuboid, requiring no DC protection. The electrode arrangement, viewed in the ion movement direction, consists of traveling wave separation electrodes 1 and radio frequency confinement electrodes 2 spaced apart on all four cross-sections. The radio frequency confinement electrodes 2 limit the radial movement range of ions, preventing collisions between ions and electrodes; the traveling wave separation electrodes 1 generate a periodically changing traveling wave potential in the axial direction, thereby driving ions to move along the channel direction and achieving migration and separation. On any cross-section of the ion movement radially, the electrode arrangement is as follows... Figure 2 As shown, the traveling wave separation electrode 1 and the radio frequency confinement electrode 2 are arranged in the manner illustrated. The final structure is as shown in the figure. Figure 3 As shown in the complete ion channel, ions entering from one end of the channel at the same time will have different trajectories and velocities due to differences in charge, mass, collision cross-sectional area, etc., under the combined action of electric field and gas field. Finally, they will fly out from the other end at different times to achieve separation.

[0028] Of course, depending on the actual design requirements, the electrodes can also be filled in this order to form polygonal and cylindrical channel walls. The specific channel design depends on the number of multipoles used and the electrode arrangement on the circuit board. For example, when using an octupole as the ion transport multipole and drawing two multipole electrodes on each circuit board, four circuit boards are needed to form a rectangular channel to create the ion transport channel; or a flexible circuit board can be used, drawing all the required multipole circuits on the same circuit board and then rolling it into a cylinder. These solutions can also effectively form a separated and confined electric field.

[0029] like Figures 4-5 As shown, this demonstrates how to integrate the electrode design onto a circuit board and assemble it into the desired geometry. Figure 3 The main components of the circuit board 3 shown are the radio frequency constraint electrode 2 and the traveling wave separation electrode 1 arranged in the middle of the board according to the above geometric rules, as well as the bayonet 4 and the tooth 5 for fixed installation.

[0030] Each printed circuit board is divided into two sides: one side is the working side, where electrodes are fabricated and formed using exposed pads. The electrodes are arranged sequentially at equal intervals on the circuit board. The other side is the buried wiring side, where the electrodes are connected internally by wiring.

[0031] The traveling wave separation electrodes on the exposed electrode surface are arranged in groups of eight, starting from any one end. Electrodes within each group are numbered 1 to 8. Electrodes within each group are independent and not connected. Electrodes of the same number from different groups are connected in series via wiring to form a circuit. Each circuit requires an external power signal; that is, each group of mobility transistors requires eight power inputs. Each circuit connection corresponds to a column of series electrodes on the circuit board, and each circuit interface corresponds to one signal in the traveling wave AC signal. In this invention, the traveling wave signal refers to multiple sets of periodically changing AC voltages with the same amplitude and a fixed phase difference applied to electrodes arranged sequentially in a spatial array. The voltage on each electrode changes periodically with time, including but not limited to waveforms such as sine waves, square waves, triangular waves, and choppers. The waveforms of adjacent electrodes are staggered in time, causing the high voltage value to continuously "move" in a predetermined direction within the electrode array, thus forming a dynamic potential wave propagating at a set speed in space. The propagation speed of the traveling wave is determined by the electrode spacing and phase delay, while its amplitude is determined by the pulsed DC voltage. In a specific embodiment, the circuit interfaces on each circuit board can be connected in series with corresponding wires, allowing the same power supply to apply electrical signals to the same column of electrodes on all four circuit boards. The radio frequency confinement electrodes on the exposed electrode surface are elongated electrodes that run through the entire working surface. Radio frequency voltages with a phase difference of 180° are alternately applied to the radio frequency confinement electrodes, thus forming an effective radial confinement of ions.

[0032] Each printed circuit board 3 is rectangular in shape, with a locking mechanism 4 and a locking tooth 5 on each of its two long sides for interlocking and securing. During assembly, simply confirm the working surface and wiring surface of one circuit board, align the locking teeth 4 of the other circuit board, and press it down to lock it in place. Repeat this process for all four circuit boards to complete the installation. The circuit boards have additional through holes 6 for securing the connections with fasteners after the ion mobility tubes are assembled. This prevents loosening or disintegration of the connections due to vibration, external force, twisting, or other unforeseen factors during use.

[0033] During operation, the RF power supply and traveling wave power supply are connected to the assembled ion mobility tube according to the requirements. After pretreatment, the ionized sample is injected in batches at the starting position of one end of the mobility tube using constant pulses. Under the traction of the electric field in the mobility tube, the ions move from one end to the other, completing ion separation and being successively transported out of the mobility tube and transferred to subsequent instruments. When one batch of ions has completely exited the mobility tube, the next batch can be pulsed and injected into the mobility tube. The entire process from the injection of a batch of ions into the mobility tube until their complete exit constitutes a complete working cycle. This achieves the ion mobility separation function.

[0034] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A traveling wave ion mobility module without DC protection, characterized in that, It includes several circuit boards with traveling wave separation electrodes and radio frequency confinement electrodes drawn on their working surfaces. The circuit boards enclose a spatially symmetrical hollow ion transport channel. The traveling wave separation electrodes are arranged at intervals along the axial direction of the ion transport channel, and the radio frequency confinement electrodes extend radially along the ion transport channel. During operation, a traveling wave voltage signal is applied to the traveling wave separation electrodes, and a radio frequency voltage signal is applied to the radio frequency confinement electrodes, thereby forming an axially propagating traveling wave electric field and a radio frequency confinement electric field that radially confines the ions within the ion transport channel, respectively. Ions pass through the geometric center region of the ion transport channel and complete the separation process under the combined action of the traveling wave electric field and the radio frequency confinement electric field.

2. The traveling wave ion mobility module without DC protection according to claim 1, characterized in that, The traveling wave separation electrode consists of multiple groups of spaced metal electrodes. Starting from any end, n adjacent metal electrodes form a group. The metal electrodes in each group are numbered 1-n. The electrodes in each group are independent and not connected to each other. Electrodes with the same number in different groups are connected in series to form a circuit.

3. The traveling wave ion mobility module without DC protection according to claim 1, characterized in that, The traveling wave signal applied to the traveling wave separation electrode is a periodically changing voltage signal with a waveform of sine wave, square wave, chop wave or triangular wave; the traveling wave signals of adjacent electrodes have a fixed time delay or phase difference, so that the high potential value propagates along the electrode array in the direction of ion transport, thereby forming a dynamic traveling wave electric field in space.

4. The traveling wave ion mobility module without DC protection according to claim 1, characterized in that, The degree of ion separation and throughput performance can be adjusted by regulating the amplitude, propagation speed, and phase difference of the traveling wave voltage.

5. The traveling wave ion mobility module without DC protection according to claim 1, characterized in that, The radio frequency confinement electrode consists of a set of long, bar-shaped rod electrodes that are geometrically symmetrical in space and are insulated from each other. Radio frequency signals are applied to the electrodes to generate an effective potential well, thereby forming a stable radial confinement for charged particles.

6. The traveling wave ion mobility module without DC protection according to claim 5, characterized in that, The radio frequency signal applied to the radio frequency confinement electrode is a set of alternating sinusoidal or approximately sinusoidal voltage signals with fixed amplitude and frequency; radio frequency signals with 180° opposite phase are applied to adjacent or opposite electrodes to form a radial effective potential well in the ion transport channel, thereby achieving stable confinement of ions.

7. The traveling wave ion mobility module without DC protection according to claim 6, characterized in that, A DC bias voltage is superimposed on the radio frequency signal to adjust the ion transport conditions.

8. The traveling wave ion mobility module without DC protection according to claim 6, characterized in that, The constraint strength of the radio frequency constraint electrode is determined by both the amplitude and frequency of the radio frequency voltage.

9. The traveling wave ion mobility module without DC protection according to claim 1, characterized in that, The cross-section of the hollow ion transport channel is circular, rectangular, hexagonal, or octagonal.

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