Apparatus and control method for improving ion storage and ejection efficiency of electrostatic field orbitrap mass spectrometer

Abstract

The application provides a device and a control method for improving ion storage and ejection efficiency of an electrostatic field orbitrap mass spectrometer, the device comprising a power supply for applying radio frequency voltage and direct current voltage to electrodes; a plurality of groups of electrodes including a central group of electrodes and a peripheral group of electrodes, the central group of electrodes having an ion exit hole, and the peripheral group of electrodes being symmetrically arranged about the central group of electrodes; each group of electrodes surrounding an ion channel, and the plurality of groups of electrodes being sequentially arranged to form a linear ion channel, the power supply applying radio frequency voltage and direct current voltage to each group of electrodes; the gap J between the nth group of electrodes and the (n+1)th group of electrodes being gradually increased from the central group of electrodes to the peripheral group of electrodes n The application meets the condition and has the advantages of simple structure.

Description

TECHNICAL FIELD

[0001] The present invention relates to mass spectrometry, and in particular to a device and control method for improving ion storage and ejection efficiency of an electrostatic field orbitrap mass spectrometer. BACKGROUND

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

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

[0004] Linear ion traps and curved ion traps allow for an increase in the volume of the ion cloud, thus reducing the level at which space charge effects start to affect performance (typically, the number of allowed ions increases by an order of magnitude or more). Linear ion traps and curved ion traps have thus proven more suitable for mass spectrometry measurements and for the injection of ions into a mass analyzer. Senko M.W. et al. in J. Am. Soc. Mass Spectrom. 1997, 8, 970-976 summarize different traps for FT-ICR mass spectrometers and describe the use of an octapole ion guide as accumulator, followed by a second octapole as injector, with ions being transferred out of the trap ends in the direction of the trap axis, rather than in the direction perpendicular to the trap axis.

[0005] A vertically ejection curved multipole rod trap is disclosed in patent US6872938, in particular a curved ion trap that focuses ions through a small entrance slit of an orbitrap mass analyzer. The focusing is provided by the curved ion trap shape itself and by the use of curved focusing and deflection optics between the trap and the orbitrap mass analyzer. Although the resulting configuration provides high performance, it has many drawbacks, such as:

[0006] 1. The configuration is complex to manufacture.

[0007] 2. The wide slits required by the configuration (width decreases close to the focusing point) lead to an increased requirement for differential pumping.

[0008] 3. The trap has the drawback of having a lower space charge capacity than the space charge capacity of the orbitrap itself.

[0009] 4. The lens between the trap and the mass analyzer is curved, which is complex to manufacture and calibrate.

[0010] 5. The mass range of ions accumulated and injected into the mass analyzer is limited.

[0011] Makarov et al. in patent US8017909B2 provided a curved linear trap, i.e. C-trap, which is a storage trap based on the principle of ion trap and can quickly inject ions into the Orbitrap detector. The ions enter the curved linear trap (C-Trap) filled with gas through the gate electrode of the C-trap, and the C-trap quadrupole applies an RF potential (500-1500Vpp, 3Mhz) to capture the ions radially. The entering ions are reflected by the trap electrode at the other end of the C-trap, and start to lose energy in the collision with nitrogen gas (~1mTorr) to cool in the C-trap. The ions form a long arc along the curved axis of the C-trap, and the ions are axially confined by simultaneously applying potentials on the gate electrode and the trap electrode of the C-trap (lifted to 200V and the lift rate is increased) (Makarov et al., 2006a). The ions are focused into a tight ion cloud by applying 1200, 1000 and 1100 volt DC pulses to the push electrode (the electrode farthest from the center of curvature of the C-trap), the pull electrode (the electrode closest to the center of curvature of the C-trap) and the upper and lower electrodes, respectively. The disadvantages of this scheme are:

[0012] 1. There is only one set of ejection voltage, and the voltage cannot be optimized, resulting in low focusing efficiency.

[0013] 2. The electrode structure design is complex and difficult to process.

[0014] 3. The ions are compressed by the end cap electrode, and the ion storage efficiency is low. SUMMARY

[0015] To solve the above-mentioned deficiencies in the prior art, the present application provides a device for improving the ion storage and ejection efficiency of an electrostatic field orbitrap mass spectrometer.

[0016] The purpose of the present application is achieved by the following technical solutions:

[0017] A device for improving the ion storage and ejection efficiency of an electrostatic field orbitrap mass spectrometer, the device comprising a power supply for applying RF voltage and DC voltage to the electrodes; the device further comprises:

[0018] A plurality of groups of electrodes, the plurality of groups of electrodes comprising a center group of electrodes having an ion exit hole and a plurality of peripheral groups of electrodes symmetrically arranged with respect to the center group of electrodes, each group of electrodes enclosing an ion channel, the plurality of groups of electrodes arranged in sequence forming a linear ion channel, the power supply applying a radio frequency voltage and a direct current voltage to each group of electrodes;

[0019] The gap J between the nth group of electrodes and the (n+1)th group of electrodes from the center group of electrodes towards the peripheral groups of electrodes n Satisfies: a is the minimum distance between the electrodes arranged oppositely in each group of electrodes, b is the total length of the electrostatic trap, c is the length of the nth group of electrodes in the direction parallel to the central axis of the ion channel, k, f, m are constants less than 1.

[0020] The application also provides a control method for improving the ion storage and ejection efficiency of an electrostatic field orbiting trap mass spectrometer.

[0021] A control method for improving the ion storage and ejection efficiency of an electrostatic field orbiting trap mass spectrometer, the control method comprising:

[0022] (S1) The power supply applies a radio frequency voltage to the plurality of groups of electrodes, and ions are stored in the ion channels formed by the plurality of groups of electrodes;

[0023] The plurality of groups of electrodes comprises a center group of electrodes having an ion exit hole and a plurality of peripheral groups of electrodes symmetrically arranged with respect to the center group of electrodes, each group of electrodes enclosing an ion channel, the plurality of groups of electrodes arranged in sequence forming a linear ion channel, the power supply applying a radio frequency voltage and a direct current voltage to each group of electrodes;

[0024] The gap J between the nth group of electrodes and the (n+1)th group of electrodes from the center group of electrodes towards the peripheral groups of electrodes n Satisfies:

[0025] a is the minimum distance between the electrodes arranged oppositely in each group of electrodes, b is the total length of the electrostatic trap, c is the length of the nth group of electrodes in the direction parallel to the central axis of the ion channel, k, f, m are constants less than 1.

[0026] (S2) Adjusting the direct current voltage on the plurality of groups of electrodes so that the ions in the ion channels of the peripheral groups of electrodes enter the ion channel of the center group of electrodes along the linear ion channel;

[0027] (S3) Changing the voltage of the center group of electrodes to eject ions in the ion channel of the center group of electrodes, and the ions are ejected from the ion exit hole.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] 1. simple structure;

[0030] By means of the gap setting of multiple groups of electrodes (or adding the radio frequency voltage setting on the multiple groups of electrodes), the same radio frequency field effect of a complex structure can be realized by simple straight-line electrodes, ion cooling and confinement (i.e. storage) are realized, and the axial field compression can be realized without the gate electrodes on both sides in the prior art;

[0031] 2. without complex ion collection and compression devices;

[0032] 3. a program-controlled voltage can be applied to the electrodes, the voltage program can be better tuned and modulated according to the instrument state, so that the trap has better transmission efficiency, better compression and focusing, and better ejection effect;

[0033] 4. by means of lower machining precision and simpler structure, combined with more controllable voltage parameters, a better focusing effect than the complex curved arc trap can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0034] The disclosure of the application will become more apparent with reference to the accompanying drawings. It is easy for those skilled in the art to understand that the drawings are only used to illustrate the technical solutions of the application, and are not intended to limit the protection scope of the application. In the drawings:

[0035] Figure 1 is a structural schematic view of a device for improving ion storage and ejection efficiency of an electrostatic field orbiting trap mass spectrometer according to an embodiment of the application. DETAILED DESCRIPTION

[0036] Figure 1 The following description describes optional specific embodiments of the application to teach those skilled in the art how to implement and reproduce the application. Some conventional aspects have been simplified or omitted in order to teach the technical solutions of the application. Those skilled in the art should understand that variations or substitutions derived from these specific embodiments will be within the scope of the application. Those skilled in the art should understand that the following features can be combined in various ways to form multiple variations of the application. Therefore, the application is not limited to the following optional specific embodiments, but is only limited by the claims and their equivalents. Example 1

[0037] A device for improving ion storage and ejection efficiency of an electrostatic field orbiting trap mass spectrometer according to an embodiment of the application, as shown in Figure 1 The device comprises:

[0038] a power supply for applying radio frequency voltage and direct current voltage to the electrodes;

[0039] A plurality of groups of electrodes, the plurality of groups of electrodes comprising a center group of electrodes and a plurality of peripheral groups of electrodes, the center group of electrodes having an ion exit hole, the plurality of peripheral groups of electrodes being symmetrically arranged with respect to the center group of electrodes; each group of electrodes encloses an ion channel, and the plurality of groups of electrodes arranged in sequence form a linear ion channel; and a power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes.

[0040] The gap J between the nth group of electrodes and the (n+1)th group of electrodes from the center group of electrodes to the peripheral group of electrodes n Satisfies:

[0041] a is the minimum distance between the electrodes arranged oppositely in each group of electrodes, b is the total length of the electrostatic trap, c is the length of the nth group of electrodes in the direction parallel to the central axis of the ion channel, and k, f, and m are constants less than 1.

[0042] In order to reduce the structural complexity, further, each group of electrodes is composed of two pairs of oppositely arranged electrodes, and the inner surface of the electrodes is a plane.

[0043] In order to reduce the structural complexity, further, from the center group of electrodes to 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.

[0044] The control method for improving the ion storage and ejection efficiency of the electrostatic field orbiting trap mass spectrometer according to the embodiment of the application is as follows:

[0045] (S1) The power supply applies a radio frequency voltage to the plurality of groups of electrodes, and ions are stored in the ion channels formed by the plurality of groups of electrodes;

[0046] A plurality of groups of electrodes, the plurality of groups of electrodes comprising a center group of electrodes and a plurality of peripheral groups of electrodes, the center group of electrodes having an ion exit hole, the plurality of peripheral groups of electrodes being symmetrically arranged with respect to the center group of electrodes; each group of electrodes encloses an ion channel, and the plurality of groups of electrodes arranged in sequence form a linear ion channel; and a power supply applies a radio frequency voltage and a direct current voltage to each group of electrodes.

[0047] The gap J between the nth group of electrodes and the (n+1)th group of electrodes from the center group of electrodes to the peripheral group of electrodes n Satisfies:

[0048] a is the minimum distance between the electrodes arranged oppositely in each group of electrodes, b is the total length of the electrostatic trap, c is the length of the nth group of electrodes in the direction parallel to the central axis of the ion channel, and k, f, and m are constants less than 1.

[0049] (S2) The direct current voltage on the plurality of groups of electrodes is adjusted, so that the ions in the ion channel of the peripheral group of electrodes enter the ion channel of the center group of electrodes along the linear ion channel.

[0050] (S3) Change the voltage of the central electrode group to eject ions in the ion channel of the central electrode group, and the ions are ejected from the ion emission hole.

[0051] To improve ion storage performance, in step (S1), the amplitude of the radio frequency voltage applied to each electrode group is increased from the central electrode group towards the peripheral electrode group.

[0052] To further reduce structural complexity, each set of electrodes consists of two pairs of oppositely arranged electrodes, with the inner surface of the electrodes being either flat or curved.

[0053] To reduce structural complexity, furthermore, from the central electrode group towards the peripheral electrode group, the length of each electrode group in the direction parallel to the central axis of the ion channel is equal or increases. Example 2

[0054] An application example of a device and control method for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer according to Embodiment 1 of the present invention.

[0055] In this application example, such as Figure 1 As shown, the device includes 15 sets of electrodes arranged sequentially, namely, 7 sets of peripheral electrodes (from the second set of electrodes P2 to the eighth set of electrodes P8) are arranged on both sides of the central set of electrodes (i.e., the first set of electrodes P1), and 14 sets of peripheral electrodes are symmetrically arranged about the central set of electrodes; each set of electrodes includes two pairs of relatively parallel (and mutually perpendicular) flat plates forming a prism-shaped ion channel; the electrodes of the central set of electrodes have ion emission holes, and the central axis of the emission holes is perpendicular to the central axis of the ion channel.

[0056] The length of each plate electrode along the direction parallel to the central axis of the ion channel is c=4mm, the distance between the relatively arranged plate electrodes is a=12mm, and the total length of the electrostatic trap is b=60mm.

[0057] 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.

[0058] A radio frequency voltage of 1600V was applied to each group of electrodes.

[0059] An embodiment of the present invention provides a control method for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer, wherein the control method is as follows:

[0060] (S1) The power supply applies RF voltage to the multiple groups of electrodes, and each group of electrodes is applied with 1600V RF voltage, and ions are stored in the linear ion channel formed by the multiple groups of electrodes;

[0061] (S2) The DC voltage is gradually applied to each group of electrodes from outside to inside (i.e. from the eighth group of electrodes to the first group of electrodes), so that the ions in the ion channel of the peripheral group of electrodes enter the ion channel of the central group of electrodes along the linear ion channel;

[0062] (S3) The voltage of the central group of electrodes is changed to eject the ions in the ion channel of the central group of electrodes, and the ions are ejected from the ion ejection hole. Embodiment 3

[0063] According to the application example of the device and control method for improving the ion storage and ejection efficiency of the electrostatic field orbitrap mass spectrometer according to Embodiment 1, which is different from Embodiment 2:

[0064] The power supply applies RF voltages with different amplitudes to each group of electrodes to achieve ion trapping and transmission, wherein from the central group of electrodes to the peripheral group of electrodes, the RF voltage Vn on the nth group of electrodes is n satisfies:

[0065] ,

[0066] (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. In this embodiment, (m / z) max =500, and (m / z) min =200. It can be seen that the RF voltage V1 on the first group of electrodes (P1) is 1665V, the RF voltage V2 on the second group of electrodes (P2) is 1685V, the RF voltage V3 on the third group of electrodes (P3) is 1720V, and the RF voltage frequency is 3MHz. Embodiment 4

[0067] According to the application example of the device and control method for improving the ion storage and ejection efficiency of the electrostatic field orbitrap mass spectrometer according to Embodiment 1.

[0068] In this application example, as shown in Figure 1 , the linear electrostatic trap includes 9 groups of electrodes arranged in sequence, i.e. the central group of electrodes (i.e. the first group of electrodes P1) is arranged on both sides of the 4 groups of peripheral electrodes (from the second group of electrodes P2 to the fifth group of electrodes P5), and the 8 groups of peripheral electrodes are symmetrically arranged about the central group of electrodes; each group of electrodes includes two pairs of oppositely arranged (and perpendicular to each other) electrodes, and the inner surfaces of the electrodes are curved surfaces, forming a linear ion channel; the electrodes of the central group of electrodes have an ion ejection hole, and the central axis of the ejection hole is perpendicular to the central axis of the ion channel.

[0069] The flat electrodes are different in length along the direction parallel to the central axis of the ion channel, wherein the length of the first group of electrodes c1=2.5mm, the length of the second group of electrodes c2=2.8mm, the length of the third group of electrodes c3=3.15mm, the length of the fourth group of electrodes c4=3.5mm, the length of the fifth group of electrodes c5=4.0mm, the minimum distance between the inner surfaces of the oppositely arranged electrodes a=10mm, and the total length of the electrostatic trap b=29.4mm;

[0070] By using It is obtained that the gap J1 between the first group of electrodes (P1) and the second group of electrodes (P2) is 0.977mm, the gap J2 between the second group of electrodes (P2) and the third group of electrodes (P3) is 1.392mm, the gap J3 between the third group of electrodes (P3) and the fourth group of electrodes (P4) is 1.676mm, and the gap J4 between the fourth group of electrodes (P4) and the fifth group of electrodes (P5) is 1.900mm.

[0071] The power supply applies radio frequency voltages with different amplitudes to the electrodes to realize ion trapping and transmission, wherein the radio frequency voltage Vn on the nth group of electrodes is gradually increased from the central group of electrodes to the peripheral group of electrodes. n The following conditions are met: The ion packet (m / z) min =150, (m / z) max =1000, and the reference voltage K is related to the trap structure and is generally 2000V. It can be known that the radio frequency voltage V1 on the first group of electrodes (P1) is 1691V, the radio frequency voltage V2 on the second group of electrodes (P2) is 1828V, V3=2072V, V4=2423V, and so on, and the frequency of the radio frequency voltage is 3MHz.

[0072] The control method for improving the ion storage and ejection efficiency of the electrostatic field orbiting trap mass spectrometer according to the embodiment of the application is as follows:

[0073] (S1) The power supply applies radio frequency voltages to the nine groups of electrodes, wherein the radio frequency voltage V1 on the first group of electrodes (P1) is 1691V, the radio frequency voltage V2 on the second group of electrodes (P2) is 1828V, V3=2072V, V4=2423V, and so on, and the ions are stored in the linear ion channel formed by the multiple groups of electrodes;

[0074] (S2) The direct current voltages are gradually applied to the groups of electrodes from outside to inside (i.e. from the fifth group of electrodes to the first group of electrodes), so that the ions in the ion channel of the peripheral group of electrodes enter the ion channel of the central group of electrodes along the linear ion channel;

[0075] (S3) changing the voltage of the central group of electrodes, ejecting ions within the ion channel of the central group of electrodes, the ions being ejected from the ion exit aperture.

Claims

1. A device for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer, the device comprising a power supply, the power supply applying a radio frequency voltage and a DC voltage to electrodes; characterized in that, The device further includes: Multiple sets of electrodes, including a central set of electrodes and a peripheral set of electrodes, wherein the central set of electrodes has an ion emission port, and the peripheral set of electrodes are symmetrically arranged about the central set of electrodes; each set of electrodes surrounds an ion channel, and the multiple sets of electrodes arranged in sequence form a linear ion channel; the power supply applies radio frequency voltage and DC voltage to each set of electrodes. The gap J between the nth group of electrodes and the (n+1)th group of electrodes is as follows: From the central group of electrodes towards the peripheral group of electrodes... n satisfy: , a is the minimum distance between the electrodes arranged opposite each other in each group of electrodes, b is the total length of the electrostatic trap, c is the length of the nth group of electrodes in the direction parallel to the central axis of the ion channel, and k, f, and m are constants less than 1.

2. The device for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer according to claim 1, characterized in that, Each set of electrodes consists of two pairs of oppositely arranged electrodes, and the inner surface of the electrodes is either flat or curved.

3. The device for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer according to claim 1, characterized in that, From the central electrode group towards the peripheral electrode group, the length of each electrode group is equal or increases in the direction parallel to the central axis of the ion channel.

4. A control method for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer, wherein the control method is as follows: (S1) The power supply applies radio frequency voltage to multiple sets of electrodes, and ions are stored in the ion channels formed by the multiple sets of electrodes; The multiple sets of electrodes include a central set of electrodes and a peripheral set of electrodes. The central set of electrodes has an ion emission port, and the peripheral set of electrodes are symmetrically arranged about the central set of electrodes. Each set of electrodes surrounds an ion channel, and the multiple sets of electrodes arranged in sequence form a linear ion channel. The power supply applies radio frequency voltage and DC voltage to each set of electrodes. The gap J between the nth group of electrodes and the (n+1)th group of electrodes is as follows: From the central group of electrodes towards the peripheral group of electrodes... n satisfy: , a is the minimum distance between the electrodes that are set opposite each other in each group of electrodes, b is the total length of the electrostatic trap, c is the length of the nth group of electrodes in the direction parallel to the central axis of the ion channel, and k, f, and m are constants less than 1; (S2) Adjust the DC voltage on multiple sets of electrodes so that ions in the ion channels of the outer set of electrodes enter the ion channels of the central set of electrodes along the linear ion channels; (S3) Change the voltage of the central electrode group to eject ions in the ion channel of the central electrode group, and the ions are ejected from the ion emission hole.

5. The control method for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer 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.

6. The control method for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer according to claim 4, characterized in that, Each set of electrodes consists of two pairs of oppositely arranged electrodes, and the inner surface of the electrodes is either flat or curved.

7. The control method for improving the ion storage and ejection efficiency of an electrostatic field orbital trap mass spectrometer according to claim 4, characterized in that, From the central electrode group towards the peripheral electrode group, the length of each electrode group is equal or increases in the direction parallel to the central axis of the ion channel.

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