Axial acceleration multipole for enhancing performance of multipole rod-time of flight mass spectrometer

Abstract

The application relates to the technical field of mass spectrometry instruments, and provides an axial acceleration multipole rod for improving the performance of a multipole rod-time-of-flight mass spectrometer, wherein the transmission efficiency of a multipole rod body shows an upward trend with the increase of air pressure; by introducing gas with proper pressure into an ion guiding device of the multipole rod, sample ions can fully collide with gas molecules, so that the kinetic energy of the ions is reduced, the ions gradually converge to the central axis, and the transmission efficiency is improved; however, excessive ion collision can prolong the ion migration time and increase the time spread, not only reducing the analysis speed of tandem mass spectrometry, but also affecting the overall performance of the multipole rod-time-of-flight mass spectrometer. Therefore, a gradient electric field is applied on the axis of the multipole rod body, so that the ions can be accelerated to be released from the multipole rod body, the migration time and the distribution width of the ions in the multipole rod body are reduced, and then the time dispersion degree of the ions reaching the time-of-flight mass spectrometer is compressed, so that the detection sensitivity and the resolution are improved.

Description

Technical Field

[0001] This invention relates to the field of mass spectrometry analysis instrument technology, and more particularly to an axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry. Background Technology

[0002] Paul et al. pioneered the linear quadrupole mass spectrometer, which has been widely used in various analytical scientific instruments. Its basic functions include quadrupole mass analyzer, quadrupole ion guide, and quadrupole ion trap. In 1992, Douglas et al. discovered that the transmission efficiency of the quadrupole increases with increasing gas pressure. By introducing a gas at an appropriate pressure into the quadrupole ion chamber, the sample ions continuously collide with these gas molecules, losing kinetic energy and gradually focusing towards the center—this is the collisional cooling effect. Therefore, the quadrupole plays a crucial role in tandem mass spectrometry instruments, such as quadrupole-time-of-flight mass spectrometers (Q-TOF) and triple quadrupole mass spectrometers (QqQ). It not only serves as an ion cooling device to improve the mass resolution of TOFMS but is also frequently used as a collision cell for ion-molecule reactions or collision-induced dissociation. However, collisional focusing in the collision cell can also have negative effects: due to the lack of forward driving force, ions may essentially stagnate before reaching the exit. Although diffusion and space charge effects may still eventually cause ions to leave, this process leads to a significant increase in ion migration time, which not only reduces the analysis speed of tandem mass spectrometry (MS / MS) but also affects Q. Performance of the TOF analyzer. Summary of the Invention

[0003] To address the aforementioned technical problems, an axially accelerated multipole is provided to improve the performance of multipole-time-of-flight mass spectrometry. By introducing a gas at an appropriate pressure within the multipole ion generator, the transmission efficiency is enhanced through impact cooling. A DC gradient electric field is formed within the multipole body using segmented auxiliary electrodes, accelerating the release of ions from the multipole body. This reduces the migration time and distribution width of ions within the multipole body, thereby compressing the temporal dispersion of ions reaching the time-of-flight mass spectrometer and thus improving detection sensitivity and resolution.

[0004] The technical means employed in this invention are as follows:

[0005] An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry includes a multipole body, which comprises a radio frequency (RF) electrode group, an auxiliary electrode group, an inlet electrode, and an outlet electrode. The RF electrode group consists of 2M RF electrodes uniformly distributed along the circumference (M is a positive integer). An auxiliary electrode group is provided between any two adjacent RF electrodes, and the auxiliary electrode group consists of N auxiliary electrodes uniformly spaced along the axis of the multipole body (N is a positive integer). The N auxiliary electrodes include a first auxiliary electrode E1, a second auxiliary electrode E2, ..., and an (N-1)th auxiliary electrode EN. The first auxiliary electrode E1 and the Nth auxiliary electrode EN, and the second auxiliary electrode E2 to the (N-1)th auxiliary electrode EN. All electrodes are identical and connected in series with resistors, which are connected in parallel with capacitors; an inlet DC voltage and an outlet DC voltage are applied to the inlet electrode and the outlet electrode, respectively; the same RF voltage is applied to the interphase RF electrodes; RF voltages of opposite polarity are applied to adjacent RF electrodes; and the same auxiliary DC voltage is applied to all RF electrodes; a starting DC voltage and a ending DC voltage are applied to the first auxiliary electrode E1 and the Nth auxiliary electrode EN, respectively, to form electrostatic focusing and improve the introduction and extraction efficiency of ions; the second auxiliary electrode E2 and the (N-1)th auxiliary electrode EN are... 1. Applying an intermediate DC voltage creates an axial gradient electric field, accelerating ions away from the multipole body and reducing their residence time in the ion trap; when the voltage of the Nth auxiliary electrode EN is lower than that of the (N-1)th auxiliary electrode EN... When the voltage of 1 and the voltage of the outlet electrode are both present, an axial potential well can be formed at the end of the ion trap, thereby achieving ion enrichment.

[0006] Furthermore, the structure of the multipole body includes a quadrupole structure, a hexapole structure, and an octapole structure; the shape of the multipole body includes a linear multipole and a curved multipole; the cross-sectional shape of the radio frequency electrode includes a circular cross-section, a rectangular cross-section, and a hyperbolic cross-section.

[0007] Furthermore, the distance between the auxiliary electrode group and the center of the multipole body ranges from 0.1 to 10 times the field radius.

[0008] Furthermore, the number of auxiliary electrode groups is at least one, and the number of auxiliary electrodes in the auxiliary electrode groups is at least three.

[0009] Furthermore, the length of the auxiliary electrode ranges from 0.5 to 50 mm.

[0010] Furthermore, the range of both the first DC voltage and the second DC voltage is 0~1000 V.

[0011] Furthermore, the range of both the inlet DC voltage and the outlet DC voltage is 0~1000 V.

[0012] Furthermore, the air pressure adjustment range in the multipole body is 0.01~500 Pa.

[0013] Furthermore, the ion trap driving radio frequency voltage is an arbitrary periodic radio frequency wave, including square waves, triangular waves, and sine waves; the frequency range of the radio frequency voltage is 1~10 MHz, the voltage amplitude range of the radio frequency voltage is 50~1000 V; and the range of the auxiliary DC voltage is 0~1000 V.

[0014] Compared with the prior art, the present invention has the following advantages: In this invention, applying a gradient electric field along the axis of the multipole body can accelerate the release of ions from the multipole body, reduce the migration time and distribution width of ions within the multipole body, thereby compressing the temporal dispersion of ions reaching the time-of-flight mass spectrometer, and thus improving detection sensitivity and resolution. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is an overall structural diagram of an axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to the present invention; wherein, Figure 1 a is a schematic diagram of axially accelerated linear quadrupole-time-of-flight mass spectrometry; Figure 1 b is a cross-sectional view of a linear quadrupole; Figure 1 c is a schematic diagram of the auxiliary electrode assembly; Figure 2 Simulation model diagram of a linear quadrupole with an axial acceleration; Figure 3 The ion migration time distributions are shown at 2.0 Pa and 1.5 Pa. Figure 4 Mass spectra of In samples under different axial electric field gradients; Figure 5 For electric field gradients along different axes 113 In + Local mass spectrum; Reference numerals: 1-Inlet electrode; 2-RF electrode; 3-Auxiliary electrode group; 4-Outlet electrode; 5-Starting auxiliary electrode; 6-End auxiliary electrode; 7-Intermediate auxiliary electrode; 8-Resistor; 9-Capacitor. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0020] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0021] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0022] For ease of description, spatial relative terms such as "above," "over," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation besides the orientation of the device as described in the figures. For example, if the device in the figures is inverted, a device described as "above" or "above" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0023] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0024] Example 1: like Figures 1 to 5 As shown, an axial acceleration multipole for improving the performance of multipole-time-of-flight mass spectrometry includes a multipole body, which comprises a radio frequency electrode group, an auxiliary electrode group 3, an inlet electrode 1, and an outlet electrode 4. The radio frequency electrode group consists of 2M radio frequency electrodes 2 evenly distributed along the circumferential direction (M is a positive integer). An auxiliary electrode group 3 is provided between any two adjacent radio frequency electrodes 2. The auxiliary electrode group 3 consists of N auxiliary electrodes evenly spaced along the axial direction of the multipole body (N is a positive integer). The N auxiliary electrodes include a first auxiliary electrode E1, a second auxiliary electrode E2, ..., and an (N-1)th auxiliary electrode EN. The first auxiliary electrode E1 and the Nth auxiliary electrode EN, and the second auxiliary electrode E2 to the (N-1)th auxiliary electrode EN. All auxiliary electrodes are identical and connected in series by resistors 8, which are connected in parallel with capacitors 9 (the first auxiliary electrode is the starting auxiliary electrode 5, the second auxiliary electrode E2 to the (N-1)th auxiliary electrode are all intermediate auxiliary electrodes 7, and the Nth auxiliary electrode is the ending auxiliary electrode 6); an inlet DC voltage and an outlet DC voltage are applied to the inlet electrode 1 and the outlet electrode 4, respectively; the same radio frequency voltage is applied to the interphase radio frequency electrodes 2; radio frequency voltages of opposite polarity are applied to adjacent radio frequency electrodes 2; and the same auxiliary DC voltage is applied to all radio frequency electrodes 2; a starting DC voltage and an ending DC voltage are applied to the first auxiliary electrode E1 and the Nth auxiliary electrode EN, respectively, to form electrostatic focusing and improve the introduction and extraction efficiency of ions; the second auxiliary electrode E2 and the (N-1)th auxiliary electrode EN are... 1. Applying an intermediate DC voltage creates an axial gradient electric field, accelerating ions away from the multipole body and reducing their residence time in the ion trap; when the voltage of the Nth auxiliary electrode EN is lower than that of the (N-1)th auxiliary electrode EN... When the voltage of electrode 1 and the voltage of outlet electrode 4 are both present, an axial potential well can be formed at the end of the ion trap, thereby achieving ion enrichment.

[0025] Specifically, such as Figure 1 and Figure 2 As shown, this embodiment consists of an inlet electrode 1, four radio frequency electrodes 2, four sets of auxiliary electrodes, and an outlet electrode 4; the field radius r0 = 2.5 mm; the radio frequency electrodes 2 adopt a "T"-shaped cross-section design to improve the ion mass transport range and transport efficiency, and reduce manufacturing costs; the height H of the "T"-shaped quadrupole is 3 mm, and the inner length L of the "T"-shaped quadrupole electrode is... in =2 mm, the outer length L of the "T"-shaped quadrupole electrode out =3 mm; the thickness h of the inner length Lin segment is 1.5 mm; an auxiliary electrode group 3 is provided between any two adjacent RF electrodes 2, with a distance R = 1.5r0 from the center, and the spacing between the auxiliary electrode and the quadrupole electrode is d = 1.2 mm; each auxiliary electrode group 3 consists of thirty-six rectangular electrodes (i.e., E1 to E36) with a length of 3.7 mm and evenly spaced 0.5 mm apart; except for the auxiliary electrode at the beginning (i.e., E1) and the auxiliary electrode at the end (i.e., E36), the remaining auxiliary electrodes are connected in series by 1MΩ resistors 8 to form a DC gradient electric field; and each resistor 8 is connected in parallel with a 10 nF capacitor 9 to prevent RF electric field interference and ensure the stability of the auxiliary DC electric field; all rectangular electrodes, resistors 8 and capacitors 9 are integrated on a printed circuit board that matches the main RF electrode 2, and the thickness of the printed circuit board is 1.6 mm; the inlet electrode 1 and the outlet electrode 4 are both annular electrodes with an inner diameter of 1.5 mm, an outer diameter of 28 mm and a thickness of 2 mm.

[0026] Specifically, an inlet DC voltage DC1 and an outlet DC voltage DC6 are applied to the inlet electrode 1 and outlet electrode 4, respectively; the same RF voltage is applied to the phase-separated RF electrodes 2, and RF voltages with opposite polarities are applied to adjacent RF electrodes 2; the same auxiliary DC voltage float_DC is applied to all four RF electrodes 2; an inlet DC voltage DC2 and an outlet DC voltage DC5 are applied to the auxiliary rectangular electrodes at the beginning and end, respectively; wherein, the inlet DC voltage DC2 is a low voltage, forming an accelerating focusing electric field at the inlet to improve ion implantation efficiency, and the outlet DC voltage DC6 is a low voltage, forming an axial electric field at the outlet to extract ions; a first intermediate DC voltage DC3 and a second intermediate DC voltage DC4 are applied to the second and penultimate auxiliary rectangular electrodes to form an axial gradient electric field at the center of the quadrupole, accelerating ions to leave the curved trap and reducing the residence time of ions in the trap; in addition, this quadrupole system also has an ion storage function; by setting the outlet DC voltage DC5 to 0 V and the outlet DC voltage DC6 and the second intermediate DC voltage DC4 to a high potential, an axial potential trap can be formed at the end of the quadrupole to achieve enrichment and storage of the ion flow.

[0027] In this embodiment, the structure of the multipole body includes a quadrupole structure, a hexapole structure, and an octapole structure; the shape of the multipole body includes a linear multipole and a curved multipole; the cross-sectional shape of the radio frequency electrode 2 includes a circular cross-section, a rectangular cross-section, and a hyperbolic cross-section.

[0028] In this embodiment, the distance between the auxiliary electrode group 3 and the center of the multipole body ranges from 0.1 to 10 times the field radius.

[0029] In this embodiment, the number of auxiliary electrode groups 3 is at least 1, and the number of auxiliary electrodes in the auxiliary electrode group 3 is at least 3.

[0030] In this embodiment, the length of the auxiliary electrode ranges from 0.5 to 50 mm.

[0031] In this embodiment, the range of the first DC voltage and the second DC voltage is both 0~1000 V.

[0032] In this embodiment, the range of the inlet DC voltage and the outlet DC voltage is 0~1000 V.

[0033] In this embodiment, the air pressure adjustment range in the multi-pole body is 0.01~500 Pa.

[0034] In this embodiment, the ion trap driving radio frequency voltage is an arbitrary periodic radio frequency wave, including square waves, triangular waves, and sine waves; the frequency range of the radio frequency voltage is 1~10 MHz, the voltage amplitude range of the radio frequency voltage is 50~1000 V, and the range of the auxiliary DC voltage is 0~1000 V.

[0035] In the experiment, the axial electric field gradient E axial Maintain at 0.08 V / cm; Figure 3 The migration time distribution spectra are shown under conditions of 1.5 Pa and 2.0 Pa; when the pressure increases by 1.4 times, the peak time t peak The peak width at half maximum (FWHM) increased by about 1.4 times (from 1258 μs to 1814 μs).

[0036] Figure 4 It shows electric fields (E) along different axes axial Mass spectrum of indium sample under the following conditions; when the axial electric field is 0 V / cm, 113 In + (m / z 112.9) and 115 In + The signal intensities at (m / z 114.9) were 218 and 3653 counts, respectively. Increasing the axial electric field to 0.10 V / cm increased the signal intensities to 391 and 5079 counts, respectively. When the axial electric field reached 0.22 V / cm, the signal intensities decreased again to 241 and 3610 counts. Without an axial electric field or with a weak field, the time distribution of ions reaching the acceleration region of the time-of-flight mass spectrometry was too wide, leading to a decrease in single-scan sensitivity. A moderate axial electric field can effectively narrow the ion time distribution, thereby enhancing the signal intensity of the quadrupole-time-of-flight mass spectrometry. Conversely, an excessively high axial electric field will form a high barrier at the Q3 inlet through the DC voltage DC2 at the start-up end, hindering ion transport and thus reducing sensitivity. Cluster ions can be detected under 0 V / cm conditions. 115 In + H2O (m / z 132.9) can be detected effectively at 0.10 V / cm and 0.22 V / cm due to collision-induced dissociation.

[0037] Figure 5 show 113 In +The mass resolution exhibits a similar trend to the sensitivity; at axial electric fields of 0, 0.10, and 0.22 V / cm, the corresponding mass resolutions are 9716, 10331, and 8175, respectively. The resolution is slightly improved under moderate axial electric fields, which is attributed to the mitigation of the space charge effect. When the axial electric field exceeds 0.10 V / cm, the resolution decreases due to the intensified kinetic energy dispersion.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry, characterized in that, It includes a multipole body, which includes a radio frequency electrode group, an auxiliary electrode group (3), an inlet electrode (1), and an outlet electrode (4). The radio frequency electrode group consists of 2M radio frequency electrodes (2) evenly distributed along the circumference (M is a positive integer); an auxiliary electrode group (3) is provided between any two adjacent radio frequency electrodes (2), and the auxiliary electrode group (3) consists of N auxiliary electrodes evenly spaced along the axis of the multipole body (N is a positive integer); the N auxiliary electrodes include the first auxiliary electrode E1, the second auxiliary electrode E2, ..., the (N-1)th auxiliary electrode EN. The first auxiliary electrode E1 and the Nth auxiliary electrode EN, and the second auxiliary electrode E2 to the (N-1)th auxiliary electrode EN. All of them are the same and are connected in series by resistors (8), and the resistors (8) are connected in parallel with capacitors (9); An inlet DC voltage and an outlet DC voltage are applied to the inlet electrode (1) and the outlet electrode (4), respectively. The same radio frequency voltage is applied to the interphase radio frequency electrodes (2), and radio frequency voltages of opposite polarity are applied to adjacent radio frequency electrodes (2). The same auxiliary DC voltage is applied to all radio frequency electrodes (2). A starting DC voltage and an ending DC voltage are applied to the first auxiliary electrode E1 and the Nth auxiliary electrode EN, respectively, to form electrostatic focusing and improve the efficiency of ion introduction and extraction. The second auxiliary electrode E2 and the (N-1)th auxiliary electrode EN are also applied...

1. Applying an intermediate DC voltage creates an axial gradient electric field, accelerating ions away from the multipole body and reducing their residence time in the ion trap; when the voltage of the Nth auxiliary electrode EN is lower than that of the (N-1)th auxiliary electrode EN... When the voltage of 1 and the voltage of the outlet electrode (4) are both present, an axial potential well can be formed at the end of the ion trap to achieve ion enrichment.

2. The axial acceleration multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The structure of the multipole body includes a quadrupole structure, a hexapole structure and an octapole structure; the shape of the multipole body includes a linear multipole and a curved multipole; the cross-sectional shape of the radio frequency electrode (2) includes a circular cross-section, a rectangular cross-section and a hyperbolic cross-section.

3. The axial acceleration multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The distance between the auxiliary electrode group (3) and the center of the multipole body is in the range of 0.1 to 10 times the field radius.

4. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The number of auxiliary electrode groups (3) is at least 1, and the number of auxiliary electrodes in the auxiliary electrode groups (3) is at least 3.

5. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The length of the auxiliary electrode ranges from 0.5 to 50 mm.

6. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The range of both the first DC voltage and the second DC voltage is 0~1000 V.

7. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The range of both the inlet DC voltage and the outlet DC voltage is 0~1000 V.

8. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The air pressure adjustment range in the multipole body is 0.01~500 Pa.

9. An axially accelerating multipole for improving the performance of multipole-time-of-flight mass spectrometry according to claim 1, characterized in that, The ion trap driving radio frequency voltage is an arbitrary periodic radio frequency wave, including square waves, triangular waves, and sine waves; the frequency range of the radio frequency voltage is 1~10 MHz, and the voltage amplitude range of the radio frequency voltage is 50~1000V; the range of the auxiliary DC voltage is 0~1000V.

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