Linear electrostatic trap and working method thereof

Abstract

The invention provides a linear electrostatic trap and a working method thereof, and the linear electrostatic trap comprises a power supply which applies a radio frequency voltage and a DC voltage to an electrode; the plurality of groups of electrodes comprise a central group of electrodes and peripheral group of electrodes, the central group of electrodes are provided with ion emitting holes, and the peripheral group of electrodes are symmetrically arranged relative to the central group of electrodes; an ion channel is enclosed by each group of electrodes, a linear ion channel is formed by the plurality of groups of electrodes which are arranged in sequence, and the power supply applies radio frequency voltage and direct current voltage to each group of electrodes; the radio frequency voltage Vn of the nth group of electrodes in the direction from the central group of electrodes to the peripheral group of electrodes satisfies a condition. The device has the advantages of simple structure and the like.

Description

Technical Field

[0001] The invention relates to mass spectrometry technology, and in particular to a linear electrostatic trap and a working method thereof. Background Art

[0002] Ion traps, including RF ion traps, are existing devices that allow for the storage of ions and the ejection of the stored ions into a mass analyser such as an ion cyclotron resonance (ICR) analyser.

[0003] S. Michael, M. Chien, D. Lubman described the use of 3D quadrupole ion trap as an accumulator and an injector for TOF mass analyzer in Rev. Sci. Instrum., 1992, 63, 4277-4284, patent US5569917, patent US5763878. However, the volume of the ion cloud in the trap of this prior art is limited, resulting in severe Coulomb interactions between the stored ions, thereby greatly affecting the parameters of the resulting ion beam.

[0004] Linear ion traps and curved ion traps allow the ion cloud volume to increase, thereby reducing the level at which space charge effects begin to affect performance (usually, the number of ions allowed grows by an order of magnitude or more). Therefore, linear ion traps and curved ion traps have been shown to be more suitable for mass spectrometry and for injecting ions into mass analyzers. Senko M.W et al. summarized a range of different traps for FT-ICR mass spectrometers in J.Am.Soc.Mass Spectrom.1997,8,970-976, and described the use of an octopole ion guide as an accumulator, followed by a second octopole as an injector, with ions being transferred from the end of the trap in the direction of the trap axis rather than in a direction perpendicular to the trap axis.

[0005] Patent US6872938 discloses a vertically ejected arcuate multipole trap, specifically an arcuate ion trap that focuses ions through a tiny entrance slit of an orbital trap mass analyzer. Focusing is provided by the shape of the arcuate ion trap itself and by using arcuate focusing and deflection optics between the trap and the orbital trap mass analyzer. Although the resulting construction provides high performance, it has a number of disadvantages, such as: 1. The structure is complicated to manufacture.

[0006] 2. The wide slit required by the construction (the width decreases near the focus point) leads to increased requirements for differential pumping.

[0007] 3. The disadvantage of the well is that its space charge capacity is lower than that of the orbital well itself.

[0008] 4. The lens between the trap and the mass analyzer is arc-shaped and complex to manufacture and calibrate.

[0009] 5. The mass range of ions accumulated and injected into the mass analyzer is limited.

[0010] Makarov et al. provided a curved linear trap, namely C-trap, in patent US8017909B2. It is a storage trap developed based on the principle of ion trap that can store ions and quickly inject ions into the Orbitrap detector. Ions enter the gas-filled curved linear trap (C-Trap) through the gate electrode of the C-trap. The C-trap quadrupole applies RF potential (500-1500Vpp, 3Mhz) to radially capture the ions. The entering ions are reflected by the trap electrode at the other end of the C-trap and begin to lose energy (~1mTorr) in the collision with nitrogen and cool in the C-trap. The ions form a long arc along the curved axis of the C-trap and are axially confined by applying a potential (raised to 200V and increasing the limit on the lifting rate) to the gate electrode and trap electrode of the C-trap at the same time (Makarov et al., 2006a). 1200, 1000 and 1100 volt DC pulses are applied to the push-out electrode (the electrode farthest from the center of curvature of the C-trap), the pull-out electrode (the electrode closest to the center of curvature of the C-trap) and the upper and lower electrodes respectively to focus the ions into a compact ion cloud. The shortcomings of this scheme are: 1. There is only one set of ejection voltage, the voltage cannot be optimized, and the focusing efficiency is low.

[0011] 2. The electrode structure design is complex and difficult to process.

[0012] 3. The ions are compressed by the end cap electrodes, and the ion storage efficiency is low. Summary of the invention

[0013] In order to solve the deficiencies in the above-mentioned prior art solutions, the present invention provides a linear electrostatic trap.

[0014] The objective of the present invention is achieved through the following technical solutions: A linear electrostatic trap, the linear electrostatic trap comprising a power supply, the power supply applying a radio frequency voltage and a direct current voltage to an electrode; the linear electrostatic trap further comprising: A plurality of groups of electrodes, the plurality of groups of electrodes comprising a central group of electrodes and a peripheral group of electrodes, the central group of electrodes having an ion exit hole, the peripheral group of electrodes being symmetrically arranged about the central group of electrodes; each group of electrodes encloses an ion channel, the plurality of groups of electrodes arranged in sequence form a linear ion channel, the power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes; From the central group of electrodes toward the peripheral group of electrodes, the RF voltage V on the nth group of electrodes n satisfy: , (m / z) max is the highest mass-to-charge ratio of the ion packet, (m / z) min is the minimum mass-to-charge ratio of the ion packet, and K is the reference voltage.

[0015] The present invention also aims to provide a method for operating a linear ion trap, which is achieved through the following technical solutions: A method for operating a linear ion trap, the method comprising the steps of: (S1) A power source applies radio frequency voltage to the multiple sets of electrodes, and ions are stored in ion channels formed by the multiple sets of electrodes; The multiple groups of electrodes include a central group of electrodes and a peripheral group of electrodes, the central group of electrodes has an ion exit hole, and the peripheral group of electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes surrounds an ion channel, and the multiple groups of electrodes arranged in sequence form a linear ion channel, and the power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes; From the central group of electrodes toward the peripheral group of electrodes, the RF voltage V on the nth group of electrodes n satisfy: , (m / z) max is the highest mass-to-charge ratio of the ion packet, (m / z) min is the minimum mass-to-charge ratio of the ion packet, and K is the reference voltage.

[0016] (S2) adjusting the DC voltage on the plurality of groups of electrodes so that the ions in the ion channels of the peripheral group of electrodes enter the ion channels of the central group of electrodes along the linear ion channels; (S3) Changing the voltage of the central group electrode to eject ions in the ion channel of the central group electrode, and the ions are ejected from the ion ejection hole.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. Simple structure; By setting the RF voltage on multiple groups of electrodes (or adding the gap setting between multiple groups of electrodes), the same RF field effect as that of a complex structure can be achieved with simple linear electrodes, thus achieving ion cooling and trapping (i.e. storage); the compression of the axial field can be achieved without the gate electrodes on both sides in the prior art; 2. No need for complex ion collection and compression devices; 3. A program-controlled voltage can be applied to the electrode, and the voltage program can be better tuned and modulated according to the instrument status, so that the trap has better transmission efficiency, better compression focusing, and better injection effect; 4. Through low processing precision and simpler structure, combined with more controllable voltage parameters, better focusing effect can be achieved than complex curved arc trap. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The disclosure of the present invention will become easier to understand with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only used to illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention. In the drawings: Figure 1 Schematic diagram of the structure of a linear electrostatic trap according to an embodiment of the present invention. DETAILED DESCRIPTION

[0019] Figure 1 The following description describes optional specific embodiments of the present invention to teach those skilled in the art how to implement and reproduce the present invention. In order to teach the technical solution of the present invention, some conventional aspects have been simplified or omitted. Those skilled in the art will understand that variations or replacements derived from these specific embodiments will be within the scope of the present invention. Those skilled in the art will understand that the following features can be combined in various ways to form multiple variations of the present invention. Thus, the present invention is not limited to the following optional specific embodiments, but is only limited by the claims and their equivalents. Example 1

[0020] A linear electrostatic trap according to an embodiment of the present invention, such as Figure 1 As shown, the linear electrostatic trap comprises: A power source, wherein the power source applies a radio frequency voltage and a direct current voltage to the electrodes; A plurality of groups of electrodes, the plurality of groups of electrodes comprising a central group of electrodes and a peripheral group of electrodes, the central group of electrodes having an ion exit hole, the peripheral group of electrodes being symmetrically arranged about the central group of electrodes; each group of electrodes encloses an ion channel, the plurality of groups of electrodes arranged in sequence form a linear ion channel, the power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes; From the central group of electrodes toward the peripheral group of electrodes, the RF voltage V on the nth group of electrodes n satisfy: , (m / z) max is the highest mass-to-charge ratio of the ion packet, (m / z) min is the minimum mass-to-charge ratio of the ion packet, and K is the reference voltage, which is generally set to 2000V according to the structure of the trap.

[0021] In order to reduce the complexity of the structure, further, each group of electrodes is composed of two pairs of electrodes arranged opposite to each other, and the inner surfaces of the electrodes are plane.

[0022] In order to reduce the complexity of the structure, further, from the central group of electrodes toward the peripheral group of electrodes, the length of each group of electrodes in the direction parallel to the central axis of the ion channel is equal or increases.

[0023] An electrostatic trap working method according to an embodiment of the present invention comprises the following steps: (S1) A power source applies radio frequency voltage to the multiple sets of electrodes, and ions are stored in ion channels formed by the multiple sets of electrodes; The multiple groups of electrodes include a central group of electrodes and a peripheral group of electrodes, the central group of electrodes has an ion exit hole, and the peripheral group of electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes surrounds an ion channel, and the multiple groups of electrodes arranged in sequence form a linear ion channel, and the power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes; From the central group of electrodes toward the peripheral group of electrodes, the RF voltage V on the nth group of electrodes n satisfy: , (m / z) max is the highest mass-to-charge ratio of the ion packet, (m / z) min is the minimum mass-to-charge ratio of the ion packet; K is the reference voltage, which is generally set to 2000V according to the structure of the trap.

[0024] (S2) adjusting the DC voltage on the plurality of groups of electrodes so that the ions in the ion channels of the peripheral group of electrodes enter the ion channels of the central group of electrodes along the linear ion channels; (S3) Changing the voltage of the central group electrode to eject ions in the ion channel of the central group electrode, and the ions are ejected from the ion ejection hole.

[0025] For the purpose of ion storage effect, further, in step (S1), the amplitude of the radio frequency voltage applied to each group of electrodes increases from the central group of electrodes toward the peripheral group of electrodes.

[0026] In order to reduce the complexity of the structure, further, each group of electrodes is composed of two pairs of electrodes arranged opposite to each other, and the inner surfaces of the electrodes are flat or curved.

[0027] In order to reduce the complexity of the structure, further, from the central group of electrodes toward the peripheral group of electrodes, the length of each group of electrodes in the direction parallel to the central axis of the ion channel is equal or increases. Example 2

[0028] An application example of a linear electrostatic trap and a working method thereof according to embodiment 1 of the present invention.

[0029] In this application example, Figure 1As shown, the device includes 5 groups of electrodes arranged in sequence, that is, 2 peripheral groups of electrodes (from the second group of electrodes P2 to the third group of electrodes P3) are arranged on both sides of the central group of electrodes (i.e., the first group of electrodes P1), and the 4 peripheral groups of electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes includes two pairs of relatively parallel (and mutually perpendicular) flat plate electrodes to form a prismatic ion channel; the electrodes of the central group of electrodes are provided with ion exit holes, and the central axis of the exit holes is perpendicular to the central axis of the ion channel.

[0030] In each group of electrodes, the distance between the relatively arranged flat electrodes is a=113mm, the total length of the electrostatic trap is b=40mm, and the gap between adjacent groups of electrodes becomes smaller along the direction from the peripheral group of electrodes to the central group of electrodes, and the gap range is 0.8-1.5mm; The power supply applies radio frequency voltages of different amplitudes to each set of electrodes to achieve ion trapping and transmission. , Ion packet (m / z) max =500, (m / z) min =200, according to the structure of the well, the reference voltage K=2000V. It can be seen that the RF voltage V1=1665V on the first set of electrodes (P1), the RF voltage V2=1685V on the second set of electrodes (P2), V3=1720V, and the RF voltage frequency is 3MHz A working method of a linear electrostatic trap according to an embodiment of the present invention comprises the following steps: (S1) The power supply applies radio frequency voltage to multiple groups of electrodes. The RF voltage on one set of electrodes (P1) is V1=1665V, the RF voltage on the second set of electrodes (P2) is V2=1685V, V3=1720V, the RF voltage frequency is 3MHz, and the ions are stored in the linear ion channel formed by the multiple sets of electrodes; (S2) applying a DC voltage to each group of electrodes step by step from outside to inside (i.e., from the third group of electrodes to the first group of electrodes), so that ions in the ion channels of the peripheral group of electrodes enter the ion channels of the central group of electrodes along the linear ion channels; (S3) Changing the voltage of the central group electrode to eject ions in the ion channel of the central group electrode, and the ions are ejected from the ion ejection hole. Example 3

[0031] An application example of a linear electrostatic trap and a working method thereof according to embodiment 1 of the present invention.

[0032] In this application example, Figure 1As shown, the device includes 15 groups of electrodes arranged in sequence, that is, 7 peripheral groups of electrodes (from the second group of electrodes P2 to the eighth group of electrodes P8) are arranged on both sides of the central group of electrodes (i.e., the first group of electrodes P1), and the 14 groups of peripheral electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes includes two pairs of relatively parallel (and mutually perpendicular) flat plate electrodes to form a prismatic ion channel; the electrodes of the central group of electrodes are provided with ion exit holes, and the central axis of the exit holes is perpendicular to the central axis of the ion channel.

[0033] The length of the flat plate electrodes in the direction parallel to the central axis of the ion channel is c=4 mm, the distance between the flat plate electrodes arranged opposite to each other is a=12 mm, and the total length of the electrostatic trap is b=60 mm; use It can be seen that the gap J1 between the first group of electrodes (P1) and the second group of electrodes (P2) is 1.160 mm, and the gap J2 between the second group of electrodes (P2) and the third group of electrodes (P3) is 1.877 mm.

[0034] The power supply applies radio frequency voltages of different amplitudes to each set of electrodes to achieve ion trapping and transmission. , ion packet (m / z) max =500, (m / z) min =200, reference voltage K=2000V.

[0035] It can be seen that the RF voltage on the first set of electrodes (P1) is V1=1665V, the RF voltage on the second set of electrodes (P2) is V2=1685V, V3=1720V..., and the RF voltage frequency is 3MHz A working method of a linear electrostatic trap according to an embodiment of the present invention comprises the following steps: (S1) The power supply applies radio frequency voltage to the multiple groups of electrodes, the radio frequency voltage V1=1665V on the first group of electrodes (P1), the radio frequency voltage V2=1685V on the second group of electrodes (P2), V3=1720V..., and the ions are stored in the linear ion channel formed by the multiple groups of electrodes; (S2) applying a DC voltage to each group of electrodes step by step from outside to inside (i.e., from the eighth group of electrodes to the first group of electrodes), so that ions in the ion channels of the peripheral group of electrodes enter the ion channels of the central group of electrodes along the linear ion channels; (S3) changing the voltage of the central group electrode to eject the ions in the ion channel of the central group electrode, and the ions are ejected from the ion ejection hole. Example 4

[0036] An application example of a linear electrostatic trap and a working method thereof according to embodiment 1 of the present invention.

[0037] In this application example, Figure 1 As shown, the linear electrostatic trap includes 9 groups of electrodes arranged in sequence, that is, 4 groups of peripheral electrodes (from the second group of electrodes P2 to the fifth group of electrodes P5) are arranged on both sides of the central group of electrodes (i.e., the first group of electrodes P1), and the 8 groups of peripheral electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes includes two pairs of electrodes arranged oppositely (and perpendicular to each other), and the inner surfaces of the electrodes are curved surfaces to form a linear ion channel; the electrodes of the central group of electrodes are provided with ion exit holes, and the central axis of the exit holes is perpendicular to the central axis of the ion channel.

[0038] The lengths of the flat electrodes in the direction parallel to the central axis of the ion channel are different, wherein the length of the first group of electrodes is c1=2.5 mm, the length of the second group of electrodes is c2=2.8 mm, the length of the third group of electrodes is c3=3.15 mm, the length of the fourth group of electrodes is c4=3.5 mm, the length of the fifth group of electrodes is c5=4.0 mm, the minimum distance between the inner surfaces of the electrodes arranged oppositely is a=10 mm, and the total length of the electrostatic trap is b=29.4 mm; use It was found that the gap J1 between the first group of electrodes (P1) and the second group of electrodes (P2) was 0.977 mm, the gap J2 between the second group of electrodes (P2) and the third group of electrodes (P3) was 1.392 mm, the gap J3 between the third group of electrodes (P3) and the fourth group of electrodes (P4) was 1.676 mm, and the gap J4 between the fourth group of electrodes (P4) and the fifth group of electrodes (P5) was 1.900 mm.

[0039] The power supply applies radio frequency voltages of different amplitudes to each set of electrodes to achieve ion trapping and transmission. , ion packet (m / z) min =150, (m / z) max = 1000. It can be seen that the RF voltage V1 on the first set of electrodes (P1) is 1691V, the RF voltage V2 on the second set of electrodes (P2) is 1828V, V3=2072V, V4=2423V…, and the RF voltage frequency is 3MHz.

[0040] The working method of the linear electrostatic trap of the embodiment of the present invention comprises the following steps: (S1) The power supply applies radio frequency voltage to nine groups of electrodes, wherein the radio frequency voltage V1=1691V on the first group of electrodes (P1), the radio frequency voltage V2=1828V, V3=2072V, V4=2423V… on the second group of electrodes (P2), the radio frequency voltage frequency is 3MHz, and ions are stored in a linear ion channel formed by the multiple groups of electrodes; (S2) applying a DC voltage to each group of electrodes step by step from outside to inside (i.e., from the fifth group of electrodes to the first group of electrodes), so that ions in the ion channels of the peripheral group of electrodes enter the ion channels of the central group of electrodes along the linear ion channels; (S3) Changing the voltage of the central group electrode to eject ions in the ion channel of the central group electrode, and the ions are ejected from the ion ejection hole.

Claims

1. A linear electrostatic trap, comprising a power supply, wherein the power supply applies a radio frequency voltage and a direct current voltage to an electrode; characterized in that: The linear electrostatic trap also includes: A plurality of groups of electrodes, the plurality of groups of electrodes comprising a central group of electrodes and a peripheral group of electrodes, the central group of electrodes having an ion exit hole, the peripheral group of electrodes being symmetrically arranged about the central group of electrodes; each group of electrodes encloses an ion channel, the plurality of groups of electrodes arranged in sequence form a linear ion channel, the power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes; From the central group of electrodes toward the peripheral group of electrodes, the RF voltage V on the nth group of electrodes n satisfy: ， (m / z) max is the highest mass-to-charge ratio of the ion packet, (m / z) min is the minimum mass-to-charge ratio of the ion packet, and K is the reference voltage.

2. A linear electrostatic trap according to claim 1, characterized in that: Each set of electrodes consists of two pairs of electrodes arranged opposite to each other, and the inner surfaces of the electrodes are flat or curved.

3. A linear electrostatic trap according to claim 1, characterized in that: From the central group of electrodes toward the peripheral group of electrodes, the length of each group of electrodes in the direction parallel to the central axis of the ion channel is equal or increases.

4. A method for operating a linear ion trap, the method comprising the steps of: (S1) A power source applies radio frequency voltage to the multiple sets of electrodes, and ions are stored in ion channels formed by the multiple sets of electrodes; The multiple groups of electrodes include a central group of electrodes and a peripheral group of electrodes, the central group of electrodes has an ion exit hole, and the peripheral group of electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes surrounds an ion channel, and the multiple groups of electrodes arranged in sequence form a linear ion channel, and the power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes; From the central group of electrodes toward the peripheral group of electrodes, the RF voltage V on the nth group of electrodes n satisfy: , (m / z) max is the highest mass-to-charge ratio of the ion packet, (m / z) min is the minimum mass-to-charge ratio of the ion packet, and K is the reference voltage.

5. (S2) adjusting the DC voltage on the multiple groups of electrodes so that the ions in the ion channels of the peripheral group electrodes enter the ion channels of the central group electrodes along the linear ion channels; (S3) Changing the voltage of the central group electrode to eject ions in the ion channel of the central group electrode, and the ions are ejected from the ion ejection hole.

6. The method for operating a linear ion trap according to claim 4, characterized in that: In step (S1), the amplitude of the radio frequency voltage applied to each group of electrodes increases from the central group of electrodes toward the peripheral group of electrodes.

7. The operating method of the linear ion trap according to claim 4, characterized in that: Each set of electrodes consists of two pairs of electrodes arranged opposite to each other, and the inner surfaces of the electrodes are flat or curved.

8. The operating method of the linear ion trap according to claim 4, characterized in that: From the central group of electrodes toward the peripheral group of electrodes, the length of each group of electrodes in the direction parallel to the central axis of the ion channel is equal or increases.

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