A traveling wave ion guide for simultaneous transmission of positive and negative ions

Abstract

The present invention belongs to the technical field of analytical instruments, and specifically relates to a traveling-wave ion guide for simultaneous transmission of positive and negative ions. The guide comprises a radio frequency electrode group and a traveling-wave electrode group; the radio frequency electrode group comprises at least four parallel radio frequency electrodes, and the traveling-wave electrode group comprises at least one traveling-wave electrode sequence, wherein the traveling-wave electrode sequence is composed of traveling-wave electrodes arranged in sequence; the length direction of the radio frequency electrodes and the length direction of the traveling-wave electrode sequence are mutually parallel. The present invention utilizes a simple structure to achieve multiple functions such as transmission, capture, confinement, mobility separation, and reaction of positive and negative ions, providing more options for the design of instruments such as mass spectrometers and ion mobility spectrometers, and has excellent application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of analytical instruments, and in particular relates to a traveling wave ion guide for simultaneous transmission of positive and negative ions. Background Art

[0002] In the field of mass spectrometry, the analysis of both positive and negative ions has important applications. When analyzing complex samples, no single monopolar mass spectrometer is fully applicable and sensitive enough for both. Therefore, existing mass spectrometers must analyze samples in both positive and negative ion modes.

[0003] However, in applications such as single-cell analysis and tissue imaging, the demand for simultaneous analysis of positive and negative ions is particularly prominent in these applications because the sample amount is very limited and simultaneous mass spectrometry detection of the same sample is more necessary. To achieve simultaneous measurement of positive and negative ions, there are currently two solutions. The first solution is to quickly switch the polarity of the DC voltage applied to the ion source, ion guide system and mass analyzer. However, the rapid switching of the DC voltage polarity will cause instability in the instrument's working conditions, thereby seriously affecting the instrument's working performance. The second solution is to use a bipolar working system, that is, the ion source is located between two devices with different working polarities, but this undoubtedly increases the manufacturing cost and volume of the instrument. Similarly, in the field of ion mobility spectrometry, both of the above solutions have been reported.

[0004] Traveling-wave ion guides are essential components in mass spectrometry and ion mobility spectrometry, guiding and transporting ions. Therefore, to achieve simultaneous analysis of positive and negative ions, the traveling-wave ion guide must be rationally designed to enable simultaneous, lossless transmission of both positive and negative ions. Furthermore, in some applications, the analysis of positive and negative ions requires their separate transmission and separation.

[0005] Since the advent of mass spectrometry, researchers have been studying gas-phase chemical reactions between ions and other particles. Formula (1) is the method for calculating the rate constant k of ion reactions, and formula (2) is the method for calculating the critical distance r for the formation of orbital ion complexes.

[0006] k=v(2π)r 2 (1)

[0007] r=Z1Z2e 2 / 2mv 2 (2)

[0008] Where v is the relative velocity between reactant particles, Z1 and Z2 are the charges of the reactant ions, e is the elementary charge, and m is the reduced mass of the colliding ion pair. Traveling-wave ion guides can increase the density of reactant ions through traveling-wave capture (controlling r), control the relative velocity of reactant ions through wave velocity (controlling v), and obtain reactant ions of interest through mobility separation. Therefore, they are expected to play a significant role in the study of complex gas-phase ion reactions. Based on the above principles, currently, existing traveling-wave ion guides are mainly implemented through the following two schemes. Scheme 1 is the stacked traveling-wave ring ion guide (Waters Technologies Corp. patent US8389932B2). This scheme couples the traveling wave and radio frequency voltage to the same ring electrode, achieving both radio frequency radial confinement of ions and axial ion propulsion by the traveling wave. However, this technique can only confine positive and negative ions simultaneously to the same ion channel for transport, making it difficult to accurately study reactions between positive and negative ions. Scheme 2 is a non-destructive ion manipulation structure (Mobilion Systems Inc. patent AU2020280042A1). This approach utilizes separately placed traveling-wave electrodes, radio frequency electrodes, and direct current electrodes to achieve a traveling-wave ion transport trajectory. However, due to the introduction of the direct current electrodes, this technology can only transport ions of one polarity at a time, making it impossible to simultaneously transport positive and negative ions and study their corresponding reactions.

[0009] In summary, since the simultaneous transmission and separation of positive and negative ions each have strict requirements on the applied electric field, there is no traveling wave ion guide in the prior art that can achieve the simultaneous transmission and separation of positive and negative ions. Summary of the Invention

[0010] In view of the defects of the prior art, the present invention provides a traveling wave ion guide for simultaneous transmission of positive and negative ions, aiming to achieve simultaneous transmission and separation of positive and negative ions.

[0011] A traveling wave ion guide for simultaneous transmission of positive and negative ions, comprising a radio frequency electrode group and a traveling wave electrode group;

[0012] The radio frequency electrode group includes at least three radio frequency electrodes arranged in parallel, the traveling wave electrode group includes at least two traveling wave electrode sequences, and the traveling wave electrode sequences are composed of traveling wave electrodes arranged in sequence;

[0013] The length direction of the radio frequency electrode and the length direction of the traveling wave electrode sequence are parallel to each other.

[0014] Preferably, the radio frequency electrode is a radio frequency multipole or a strip-shaped printed circuit;

[0015] The traveling wave electrode is a metal sheet, a metal rod, a metal block or a printed circuit.

[0016] Preferably, it further includes two parallel printed circuit boards, the radio frequency electrode group includes at least 4 radio frequency electrodes, the radio frequency electrode group is mirrored on the opposite surfaces of the two printed circuit boards, and the traveling wave electrode group includes at least 2 groups of traveling wave electrode sequences, and the traveling wave electrode group is mirrored on the opposite surfaces of the two printed circuit boards.

[0017] Preferably, the radio frequency electrodes and traveling wave electrodes on the same printed circuit board are arranged alternately in sequence.

[0018] Preferably, the distance between adjacent radio frequency electrodes and traveling wave electrode arrays is 0.1 to 10 mm, and the distance between two printed circuit boards is 0.1 to 50 mm;

[0019] The width of the radio frequency electrode is 0.1-100 mm; the width of the traveling wave electrode is 0.1-100 mm; and the length of the traveling wave electrode is 0.1-100 mm.

[0020] Preferably, the number of the radio frequency electrodes is 3, 4, 6, 8 or 12;

[0021] The traveling wave electrode group includes at least 2-10 groups of traveling wave electrode sequences.

[0022] The present invention also provides a method for ion transmission using the above-mentioned traveling wave ion guide, wherein the RF electrode group includes at least four RF electrodes, a RF voltage is applied to the RF electrode group, the RF voltage frequency is 0.1 to 5 MHz, and the amplitude is 0 to 1000 V; in the RF electrode group, the RF voltage applied to adjacent RF electrodes has a phase difference of 180°;

[0023] When the RF electrode group includes at least 3 RF electrodes, a RF voltage is applied to the RF electrode group, the RF voltage frequency is 0.1 to 5 MHz, and the amplitude is 0 to 1000 V; in the RF electrode group, the RF voltage applied to adjacent RF electrodes has a phase difference of 120°;

[0024] A traveling wave voltage is applied to the traveling wave electrode group, wherein the traveling wave voltage has a waveform frequency of 0.1 to 1000 kHz, an amplitude of 0 to 200 V, and a duty cycle of 1 / n to (n-1) / n, where n is the number of traveling wave electrode sequences; and within the traveling wave electrode sequence, the traveling wave voltages applied between adjacent traveling wave electrodes are continuous. Preferably, the RF electrodes in the RF electrode group are arranged in mirror-symmetrical configuration, and a DC bias voltage difference of 0 to 100 V is set on the mirror-symmetrical RF electrodes.

[0025] Preferably, the traveling wave electrode group includes at least two groups of traveling wave electrode sequences that are arranged in mirror symmetry, and a DC bias voltage difference of 0 to 100 V is applied between the traveling wave electrodes that are mirror symmetric to each other.

[0026] The present invention also provides an analytical instrument, which includes the above-mentioned traveling wave ion guide and is a mass spectrometer or an ion mobility spectrometer.

[0027] The present invention provides a traveling wave ion guide with a special electrode structure design and electric field application method, which realizes the mutual coupling of the traveling wave electric field and the radio frequency electric field, thereby collaboratively creating a robust ion transmission track. The traveling wave voltage and the radio frequency voltage are independently applied to the traveling wave electrode and the radio frequency electrode, respectively, without the need for mutual decoupling of the two power supplies, and the power-on parameters can be controlled separately. The traveling wave ion guide does not need to switch the polarity of the applied voltage, and can perform the transmission, capture, confinement, mobility separation and reaction of positive and negative ions simultaneously along the same path and in the same direction. It can be used for a variety of ion guide equipment such as ion drift tubes, ion funnels, gas phase ion reaction cells, ion storage chambers and ion collision cells, thereby providing new ideas for the design of instruments such as mass spectrometers and ion mobility spectrometers. The present invention has good application prospects.

[0028] Obviously, based on the above contents of the present invention, according to common technical knowledge and customary means in this field, without departing from the above basic technical ideas of the present invention, other various forms of modifications, replacements or changes can be made.

[0029] The following further describes the above content of the present invention in detail through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a front view of a printed circuit board of Example 1;

[0031] Figure 2 Schematic diagram of the three-dimensional structure of the device of Example 1;

[0032] Figure 3 The SIMION simulation in Example 1 shows the separation of positive and negative ion transport orbits (preventing positive and negative ion reactions) when the DC bias is on. (A) XY plane view; (B) YZ plane view. Positive ions are blue, negative ions are green, and electric field lines are red.

[0033] Figure 4 When the DC bias is turned off for SIMION simulation, the positive and negative ion transport trajectories merge (ion reaction is enabled); (A) XY plane view; (B) YZ plane view; where positive ions are blue lines, negative ions are green lines, and electric field lines are red lines.

[0034] Among them: 1-printed circuit board, 2-insulating seal, 3-radio frequency electrode group, 4-traveling wave electrode group. DETAILED DESCRIPTION

[0035] Example 1

[0036] This embodiment provides a traveling wave ion guide, the specific structure of which is as follows: Figure 1 、 2 shown.

[0037] It comprises two parallel printed circuit boards 1 , on the opposite sides of the two printed circuit boards 1 a radio frequency electrode group 3 and a traveling wave electrode group 4 are arranged through printed circuit mirroring.

[0038] The RF electrode group 3 includes four parallel RF electrodes, two on each printed circuit board 1. The traveling-wave electrode group 4 includes two traveling-wave electrode sequences, one on each printed circuit board 1. The traveling-wave electrode sequences are composed of traveling-wave electrodes arranged sequentially. The traveling-wave electrode sequence is located between two RF electrodes. The length directions of the RF electrodes and the traveling-wave electrode sequences are parallel to each other.

[0039] The distance between adjacent radio frequency electrodes and traveling wave electrode arrays is 0.1-10 mm, preferably 0.25 mm in this embodiment. The two printed circuit boards 1 are separated by an insulating seal 2, with a distance of 0.1-50 mm, preferably 3 mm in this embodiment.

[0040] The RF electrode has a width of 0.1 to 100 mm, preferably 3 mm in this embodiment. The RF electrode length is determined by the length of the ion transport track and is 45 mm in this embodiment. The traveling-wave electrode is square or rectangular, with a width (the dimension perpendicular to the length of the traveling-wave electrode sequence) of 0.1 to 100 mm and a length (the dimension parallel to the length of the traveling-wave electrode sequence) of 0.1 to 100 mm. In this embodiment, the traveling-wave electrode preferably has a width of 3 mm and a length of 2.5 mm.

[0041] The above-mentioned traveling wave ion guide can realize the functions of transport, capture, confinement, mobility separation and reaction of positive and negative ions. The specific voltage application method is as follows:

[0042] The RF electrode group 3 is used to radially confine the ion beam. A RF voltage is applied to the RF electrode group 3. The RF voltage frequency is 0.1 to 5 MHz, and preferably 1 MHz in this embodiment; the amplitude is 0 to 1000 V, and preferably 200 V in this embodiment; the RF waveform can be a sine wave, a square wave, and a triangular wave, and preferably a sine wave in this embodiment; in the RF electrode group 3, the phase difference of the RF voltage applied to adjacent RF electrodes is 180°.

[0043] The traveling wave electrode group 4 is used to drive the movement of the ion beam or perform mobility separation on the ion beam. A traveling wave voltage is applied to the traveling wave electrode group 4, and the waveform frequency of the traveling wave voltage is 0.1~1000KHz. In this embodiment, the traveling wave voltage can be set to 5KHz (for ion capture) or 75KHz (for ion mobility separation). The amplitude is 0~200V, and in this embodiment, it is preferably 15V. The duty cycle is 1 / n~(n-1) / n, where n is the number of groups in the traveling wave electrode sequence, and in this embodiment, it is preferably 2 / 4; in the traveling wave electrode sequence. The traveling wave voltages applied between adjacent traveling wave electrodes are continuous with each other, that is, the falling edge of the traveling wave voltage on the previous traveling wave electrode is the rising edge of the traveling wave voltage on the next traveling wave electrode. The traveling wave waveform can be a sine wave, a square wave or a triangle wave, and in this embodiment, it is preferably a square wave.

[0044] The RF electrodes in the RF electrode group 3 are arranged in a mirror-symmetrical manner, and a DC bias voltage difference of 0 to 100V is set on the RF electrodes that are mirror-symmetrical to each other. The traveling wave electrode group 4 includes at least two groups of traveling wave electrode sequences that are mirror-symmetrical to each other, and a DC bias voltage difference of 0 to 100V is applied between the traveling wave electrodes that are mirror-symmetrical to each other. In the preferred embodiment of this embodiment, the above voltage difference is 5V when performing positive and negative ion sub-orbital transmission. The SIMION simulation results of the positive and negative ion sub-orbital transmission are as follows: Figure 3 When performing the reaction between positive and negative ions, the voltage difference is set to 0V, and the SIMION simulation results are as follows: Figure 4 shown.

[0045] The traveling wave ion guide provided in this embodiment can be applied to instruments such as mass spectrometers and ion mobility spectrometers that require ion transmission and separation.

[0046] From the above embodiments, it can be seen that the traveling wave ion guide provided by the present invention utilizes a simple structure to realize multiple functions such as transmission, capture, confinement, mobility separation and reaction of positive and negative ions, providing more options for the design of instruments such as mass spectrometers or ion mobility spectrometers, and has good application prospects.

Claims

1. A method for ion transport using a traveling wave ion guide for simultaneous transmission of positive and negative ions, characterized in that: The traveling wave ion guide comprises a radio frequency electrode group (3) and a traveling wave electrode group (4); The radio frequency electrode group (3) includes at least three radio frequency electrodes arranged in parallel, and the traveling wave electrode group (4) includes at least two groups of traveling wave electrode sequences, wherein the traveling wave electrode sequences are composed of traveling wave electrodes arranged in sequence; The length direction of the radio frequency electrode and the length direction of the traveling wave electrode array are parallel to each other; The traveling wave ion guide further comprises two printed circuit boards (1) arranged in parallel, the radio frequency electrode group (3) comprises at least four radio frequency electrodes, the radio frequency electrode group (3) is mirror-arranged on opposite surfaces of the two printed circuit boards (1), and the traveling wave electrode group (4) is mirror-arranged on opposite surfaces of the two printed circuit boards (1); The radio frequency electrodes and the traveling wave electrodes are arranged alternately in sequence on the same printed circuit board (1); The distance between adjacent radio frequency electrodes and traveling wave electrode sequences is 0.1 to 10 mm, and the distance between two printed circuit boards (1) is 0.1 to 50 mm; The width of the radio frequency electrode is 0.1 to 100 mm; the width of the traveling wave electrode is 0.1 to 100 mm; and the length of the traveling wave electrode is 0.1 to 100 mm. When the radio frequency electrode group (3) includes at least four radio frequency electrodes, a radio frequency voltage is applied to the radio frequency electrode group (3), the radio frequency voltage frequency is 0.1 to 5 MHz, and the amplitude is 0 to 1000 V; in the radio frequency electrode group (3), the radio frequency voltage applied to adjacent radio frequency electrodes has a phase difference of 180°; When the radio frequency electrode group (3) includes three radio frequency electrodes, a radio frequency voltage is applied to the radio frequency electrode group (3), the radio frequency voltage frequency is 0.1 to 5 MHz, and the amplitude is 0 to 1000 V; in the radio frequency electrode group (3), the radio frequency voltage applied to adjacent radio frequency electrodes has a phase difference of 120°; A traveling wave voltage is applied to the traveling wave electrode group (4), wherein the waveform frequency of the traveling wave voltage is 0.1 to 1000 kHz, the amplitude is 0 to 200 V, and the duty cycle is 1 / n to (n-1) / n, wherein n is the number of groups in the traveling wave electrode sequence; in the traveling wave electrode sequence, the traveling wave voltages applied between adjacent traveling wave electrodes are continuous with each other.

2. The method according to claim 1, characterized in that: The radio frequency electrode is a radio frequency multipole or a strip-shaped printed circuit; The traveling wave electrode is a metal sheet, a metal rod, a metal block or a printed circuit.

3. The method according to claim 1, wherein: The number of the radio frequency electrodes is 3, 4, 6, 8 or 12; The traveling wave electrode group (4) comprises at least 2-10 groups of traveling wave electrode sequences.

4. The method according to claim 1, wherein: The radio frequency electrodes in the radio frequency electrode group (3) are arranged in a mirror-symmetrical manner, and a direct current bias voltage difference of 0 to 100 V is set on the radio frequency electrodes that are mirror-symmetrical to each other.

5. The method according to claim 1, characterized in that: The traveling wave electrode group (4) comprises at least two groups of traveling wave electrode sequences that are arranged in mirror symmetry, and a DC bias voltage difference of 0 to 100V is applied between the traveling wave electrodes that are mirror symmetric to each other.

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