Bent multi-pole collision reaction tank and inductively coupled plasma mass spectrometry system

Abstract

A curved multipole collision reaction cell and an inductively coupled plasma mass spectrometry system, the reaction cell comprising: a housing comprising a cell inlet, a cell outlet disposed opposite the cell inlet along a longitudinal axis of the housing, and a gas supply port in communication with an internal structure of the housing; and a curved multi-pole ion guide disposed inside the housing along a longitudinal axis of the housing, the curved multi-pole ion guide configured to generate an RF confinement field effective to constrain ions in a radial direction orthogonal to the longitudinal axis of the housing, while the curved multi-pole ion guide is disposed inside the housing along the longitudinal axis of the housing, and the curved multi-pole ion guide is configured to generate an RF confinement field effective to constrain ions in a radial direction orthogonal to the longitudinal axis of the housing. And separating neutral substances from photons and ions. Besides, by adopting the plasma mass spectrometry system of the collision reaction tank provided by the utility model, the instrument volume of a mass spectrometer can be greatly reduced, and miniaturization is realized.

Description

Technical Field

[0001] This utility model relates to the field of inductively coupled plasma mass spectrometry (ICP-MS), and in particular to a curved multipole collision reaction cell for an ICP-MS. Background Technology

[0002] A typical structure of an inductively coupled plasma mass spectrometry (ICP-MS) system is as follows: Figure 1 As shown, this includes a plasma-based ion source; this ion source is used to generate plasma to break down sample molecules into atoms, which are then ionized to prepare for elemental analysis. In typical operation, the liquid sample is atomized, i.e., converted into an aerosol (fine spray or mist), by a gas-driven (typically argon) nebulizer 401, and coarse aerosols are removed within a nebulization chamber 402, guiding the remaining fine aerosols into the plasma generated by the plasma source. The plasma source is often configured as a flow-through plasma torch 403 with two or more concentric tubes. Typically, a plasma-forming gas (argon) flows through the inner tubes of the torch and is excited into plasma by a suitable energy source, such as a radio frequency (RF) powered load coil 404. The aerosol flows through the coaxial central tube of the torch 403 and is emitted into the generated plasma, where exposure to the plasma breaks down sample molecules into atoms, or alternatively, partially breaks down sample molecules into molecular fragments and ionizes these atoms or molecular fragments; these analyte atoms or molecular fragments are then ionized to generate an ion beam. Since these ions are not generated in a vacuum region, they are gradually transitioned to a high vacuum region via sampling cone 405 and interception cone 406. After entering the high vacuum region, the ion beam is focused by extraction lens group 407 and then enters off-axis or deflection lens group 408. Figure 1The following explanation uses an off-axis lens as an example to illustrate the working principle of ICP-MS. After passing through the off-axis or deflection lens group 408, ions are separated from photons and neutral substances, and then enter the collision reaction cell 412 through the collision reaction cell inlet focusing lens 410 and collision reaction cell inlet lens 411. There is also a slide valve 409 between the off-axis lens group 408 and the collision reaction cell focusing lens. This valve is closed in the instrument's standby state to maintain a high vacuum environment for subsequent components; it automatically opens during analysis. After interference ions are eliminated through collision or reaction, the ion beam undergoes a second off-axis process through the collision reaction cell outlet off-axis lens group 413. This second off-axis process eliminates the influence of neutral substances in the collision reaction cell on subsequent quality screening, improving the signal-to-noise ratio. After passing through the mass analyzer twice off-axis, the ion beam enters the mass analyzer 415. The mass analyzer typically employs a quadrupole structure or other methods such as a sector magnetic field or a time-of-flight (TOF) analyzer. It uses an alternating electric field, or a combination of electric and magnetic fields, to perform spectral decomposition of the ionized ions according to their mass-to-charge ratio (m / z). The quadrupole mass analyzer generally also includes a pre-quadrupole 414. After passing through the mass analyzer 415, the ion detector 416 is able to count each type of ion at a given m / z ratio arriving at the ion detector from the mass analyzer. The intensity of each peak indicates the concentration (or abundance) of the corresponding element in the sample.

[0003] In addition to the inductively coupled plasma mass spectrometer (ICP-MS) consisting of a single quadrupole mass analyzer, a third quadrupole mass analyzer can be added before the collision reaction cell to improve interference elimination capabilities. This pre-separates the ion beam entering the collision reaction cell, allowing only ions with selected mass numbers to enter the subsequent collision reaction cell, thus significantly improving the efficiency of the collision reaction. This is called a triple quadrupole ICP-MS, such as... Figure 2 As shown.

[0004] The plasma used as an ion source in ICP-MS cannot completely decompose all components of the sample into ions. Some undecomposed neutral substances are introduced into the subsequent collisional reaction cell and quadrupole along with the ion beam through the interface. Simultaneously, the high-temperature plasma generates strong photons. These neutral substances can contaminate the subsequent ion microscope and collisional reaction cell, and also produce new interfering ions when colliding with the collisional reaction gas in the collisional reaction cell. Photons also generate significant detection noise. Therefore, effective methods are needed to separate neutral substances and photons from analyte ions before the ion beam enters the collisional reaction cell.

[0005] In addition to methods for separating neutral substances and photons from analyte ions, Figure 1 , Figure 2Besides the off-axis method shown, it is known that in ICP-MS systems, neutral substances and photons can be separated from analyte ions by a 90-degree deflection between the ion source and the collision reaction cell; that is, by using an ion guiding device with a 90-degree deflection. Whether using the off-axis method or the 90-degree deflection method, photons and neutral substances generated in the plasma can be separated from the ion beam, which then continues its flight into the collision reaction cell.

[0006] Existing inductively coupled plasma mass spectrometers all employ linear collisional reaction cells, with multipole configurations including quadrupole, hexapole, and octapole. However, existing collisional reaction cells have two main drawbacks. First, linear collisional reaction cells cannot effectively separate newly produced neutral substances during the reaction or collision. These neutral substances will continue to consume collision or reaction gases and may even collide or react with the analyte ions, leading to a decrease in collisional reaction efficiency. Second, linear multipole collisional reaction cells cannot effectively reduce the vacuum chamber volume, resulting in a large overall instrument size and making miniaturization difficult. Utility Model Content

[0007] To address the aforementioned problems in the existing technology, this utility model provides a curved multi-pole collision reaction cell for an inductively coupled plasma mass spectrometer. The poles of the collision reaction cell are set to a curved shape to further separate neutral substances and analyte ions, and the instrument size of the mass spectrometer is significantly reduced, achieving miniaturization.

[0008] This utility model provides a bent multipole collision reaction cell for an inductively coupled plasma mass spectrometer, characterized in that it includes:

[0009] The housing includes a pool inlet, a pool outlet disposed opposite to the pool inlet along the longitudinal axis of the housing, and a curved multipolar ion guide disposed inside the housing along the longitudinal axis of the housing;

[0010] The curved multipole ion director includes multiple elongated rod electrodes, each of which is a curved structure and is parallel to each other.

[0011] Furthermore, the plurality of rod electrodes are located at a predetermined radial distance orthogonal to the longitudinal axis of the housing, the plurality of rod electrodes being circumferentially spaced from each other around the longitudinal axis, and defining the inlet and outlet of the curved multipole ion guide.

[0012] Furthermore, the longitudinal axis of the rod electrode is arc-shaped, zigzag-shaped, or a combination of arc-shaped and arc-shaped, or a combination of arc-shaped and zigzag-shaped.

[0013] Furthermore, a short section of the front end and / or rear end of the rod electrode is a straight rod to collimate the ions.

[0014] Furthermore, one set of the rod electrodes spaced apart is configured to apply an RF+ potential superimposed on a DC bias potential (U), and another set of the rod electrodes spaced apart is configured to apply an RF- potential superimposed on a DC bias potential (U).

[0015] Among them, the RF+ potential and the RF- potential are radio frequency signals with the same frequency and amplitude but opposite phase, thereby generating an RF confinement field for the ions.

[0016] Furthermore, a negative DC barrier is generated at the outlet of the multipole ion guide to facilitate the smooth extraction of ions from the collision reaction cell.

[0017] Furthermore, the number of rod electrodes is 2N, where N is an integer and N≥2.

[0018] Furthermore, the rod electrode is one of a round rod, a square rod, a hyperboloid rod, or a concave rod.

[0019] Furthermore, it also includes:

[0020] An inlet ion mirror is located on the cell inlet side of the housing; and

[0021] An outlet ion mirror is located on the pool outlet side of the housing.

[0022] This invention also provides an inductively coupled plasma mass spectrometry (ICP-MS) system with a curved multipole collision reaction cell.

[0023] The curved multi-pole collision reaction cell of the inductively coupled plasma mass spectrometer provided by this invention features curved poles that confine ions entering the cell. Neutral substances generated within the cell are not constrained by the electric field and therefore do not change their original flight direction due to the bending of the poles, allowing for separation from the ions. This prevents the neutral substances from consuming collision or reaction gases or colliding or reacting with the analyte ions while flying in the same direction as the ion beam. These neutral substances are expelled by a molecular pump after leaving the cell. A short section of straight pole electrode is provided at the front and rear ends to focus the ion beam passing through this section, ensuring it flies in a straight line from the center of the multiple pole electrodes into the subsequent curved section or exits through the central aperture at the cell outlet. Using the collision reaction cell of this invention, the plasma mass spectrometry analysis system can significantly reduce the instrument size of the mass spectrometer, achieving miniaturization. Attached Figure Description

[0024] Figure 1This is a schematic diagram of a typical inductively coupled plasma mass spectrometry (ICP-MS) system in the prior art;

[0025] Figure 2 This is a schematic diagram of a triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS) system in the prior art;

[0026] Figure 3 This is an explosion diagram of the bent multipole collision reaction cell of the inductively coupled plasma mass spectrometer of this utility model;

[0027] Figure 4 This is a circuit diagram of the rod electrode described in this utility model;

[0028] Figure 5 This is a schematic diagram of the inductively coupled plasma mass spectrometry (ICP-MS) system with a curved multipole collision reaction cell of this utility model;

[0029] Figure 6 This is a simulation diagram of the ion flight trajectory of the inductively coupled plasma mass spectrometry (ICP-MS) system with a curved multipole collision reaction cell of this utility model;

[0030] Figure 7 This is a schematic diagram of the triple quadrupole inductively coupled plasma mass spectrometry analysis system with a curved multipole collision reaction cell of this utility model;

[0031] Figure 8 This is a schematic diagram of another triple quadrupole inductively coupled plasma mass spectrometry analysis system with a curved multipole collision reaction cell according to this utility model.

[0032] In the picture:

[0033] 10. Shell; 1001. Pool inlet; 1002. Pool outlet;

[0034] 20. Bending multipole ion director; 201. Rod electrode;

[0035] 30. Inlet ion microscope;

[0036] 40. Export ion microscope.

[0037] 50. Fixing ring;

[0038] 60. Insulating gaskets;

[0039] 70. Electrode;

[0040] 80. RF+ connection electrode;

[0041] 90. RF - Connecting electrode. Detailed Implementation

[0042] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0043] In the description of this utility model, it should be understood that the terms "longitudinal", "radial", "orthogonal", "opposite", "one end", "the other end", etc., used in this utility model to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to 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 of this utility model.

[0044] The terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of these terms in this utility model based on the specific circumstances.

[0045] like Figure 3 As shown, this utility model provides a bent multipole collision reaction cell for an inductively coupled plasma mass spectrometer, including a housing 10, a bent multipole ion guide 20, an inlet ion mirror 30, and an outlet ion mirror 40; the bent multipole ion guide 20 is disposed inside the housing 10 along the longitudinal axis of the housing 10, and the bent multipole ion guide 20 is connected to the housing 10 by a retaining ring 50. The longitudinal axis refers to the axis of the housing 10 in the length direction.

[0046] Specifically, the housing 10 includes a pool inlet 1001 and a pool outlet 1002 disposed opposite to the pool inlet 1001 along the longitudinal axis of the housing 10; the housing 10 has a gas supply port (not shown in the figure) in the middle for collision or reaction gases to enter the interior of the housing 10. The outer end of the gas supply port is connected to a device for controlling the gas flow rate (such as a proton flow meter) and a switch for selecting the gas type (such as a solenoid valve), and the gas flow rate can be controlled within a range of 0-20 ml / min.

[0047] The housing 10 is preferably made of metal and has an internal structure for fixing the curved multipole ion guide 20. Insulating gaskets 60 are provided at both ends of the housing 10 for fixing the inlet ion mirror 30 and the outlet ion mirror 40.

[0048] The curved multi-stage rod ion guide 20 is configured to generate an RF confinement field that effectively confines ions in a radial direction orthogonal to the longitudinal axis of the housing 10, while simultaneously separating neutral substances and photons from the ions.

[0049] The curved multi-pole ion guide 20 includes multiple elongated rod electrodes 201, each of which is a curved structure. The curvature and degree of curvature of the rod electrodes 201 can be adjusted according to factors such as the spatial arrangement of the plasma mass spectrometer; regarding the curvature shape, the longitudinal axis of the rod electrode 201 can be a broken line, an arc, a combination of arcs, a combination of arcs and straight lines, etc.; regarding the degree of curvature, the degree of curvature of the rod electrode 201 can be small, for example, the angle between the starting end and the ending end can be small; the degree of curvature of the rod electrode 201 can also be large, for example, bent into an S-shape. Figure 3 As shown, the rod electrode 201 is an arc with a bending angle of 90 degrees; as Figure 8 As shown, the rod electrode 201 is an arc with a bending angle of 180 degrees.

[0050] The plurality of rod electrodes 201 are located at a predetermined radial distance orthogonal to the longitudinal axis of the housing 10. The rod electrodes 201 are circumferentially spaced from each other around this longitudinal axis and define the inlet and outlet of the curved multipole ion guide 20. The rod electrodes 201 are parallel to each other. The inlet of the curved multipole ion guide 20 corresponds to the cell inlet 1001, and the outlet of the curved multipole ion guide 20 corresponds to the cell outlet 1002.

[0051] Preferably, the front end of the rod electrode 201 (i.e., the side near the cell inlet 1001) is a short straight section, followed by a curved section. This short straight section on the side of the rod electrode 201 near the cell inlet 1001 allows for the collimation of ions entering the reaction cell from the inlet ion mirror 30.

[0052] Furthermore, a short section of the rear end of the rod electrode 201 (i.e., the side near the cell outlet 1002) is a straight rod. This allows for ion collimation, facilitating entry into the outlet ion mirror 40.

[0053] The number of rod electrodes 201 is 2N (N is an integer and N≥2). Preferably, the bent multi-pole ion guide 20 can be a quadrupole, hexapole, octapole, decapole, dodecapole, etc.

[0054] The rod electrode 201 can be a round rod, a square rod, a hyperboloid rod, a concave rod, or other suitable shape.

[0055] The multiple rod electrodes 201 are configured with a curved structure to constrain ions entering the rod electrodes 201. Neutral substances generated in the collision reaction cell are not constrained by the electric field and therefore do not change their original flight direction due to the bending of the rod electrodes 201, thus allowing for separation from the ions. This prevents the neutral substances from continuing to consume collision or reaction gases, or even colliding or reacting with the analyte ions, when flying in the same direction as the ion beam. This portion of neutral substances is discharged by a molecular pump after leaving the collision reaction cell. Optionally, a short straight rod electrode segment is provided at the front and rear ends of the rod electrodes 201. The purpose of this is to focus the ion beam passing through this segment, allowing it to fly in a straight direction from the center of the multiple rod electrodes 201 into the subsequent curved segment or out through the central hole at the outlet of the collision reaction cell.

[0056] The inlet ion mirror 30 is located on one side of the pool inlet 1001 of the housing 10, and the outlet ion mirror 40 is located on one side of the pool outlet 1002 of the housing 10.

[0057] The inlet ion mirror 30 and the outlet ion mirror 40 are made of metal and have a circular hole in the middle for ions to enter and exit, with a diameter of 1-10 mm. A negative DC voltage can be applied to the inlet ion mirror 30 and the outlet ion mirror 40 to guide ions into and out of the collision reaction cell.

[0058] Furthermore, electrodes 70 may be provided on the inlet ion mirror 30 and the outlet ion mirror 40 to facilitate the application of DC voltage thereon.

[0059] In some implementations, such as Figure 4 As shown, the rod electrodes 201 in the curved multi-pole ion guide 20 are divided into two groups at intervals. One group of rod electrodes 201 is configured to apply an RF+ potential superimposed on a DC bias potential (U). Specifically, one group of rod electrodes is connected to the RF+ connection electrode 80; the other group of rod electrodes is configured to apply an RF- potential superimposed on a DC bias potential (U), specifically, this group of rod electrodes is connected to the RF- connection electrode 90. A certain DC bias voltage (U) can be superimposed on these rod electrodes 201 by one or a group of resistors, thereby adjusting the kinetic energy of ions in the collision reaction cell.

[0060] The aforementioned RF+ and RF- are radio frequency signals with the same frequency and amplitude but opposite phase (180° out of phase). Their frequency can be set from 1 to 200 MHz, thus generating an RF confinement field for the ions. In this way, the ions collide or react with the gas in the collision reaction cell while traveling along the centerline of the curved multipole, thereby eliminating the influence of interfering ions. However, the neutral substances produced during the collision or reaction will fly in a straight line along their own inertia, unconstrained by the electric field and flying along a curve, thus achieving complete separation of the analyte ions from the neutral substances produced during the collision and reaction.

[0061] like Figure 5 The illustration shows a scenario where the curved multipole collision cell of an inductively coupled plasma mass spectrometer provided by this invention is specifically applied to an inductively coupled plasma mass spectrometry (ICP-MS) system. Specifically, it demonstrates an ICP-MS system with a curved multipole collision cell. The liquid sample is atomized by a gas-driven nebulizer 101, converting it into an aerosol (fine spray or mist). Coarse aerosols are removed within the atomization chamber 102, and the remaining fine aerosols are guided into the plasma generated by the plasma source. The plasma source is configured as a flow-through plasma torch 103 with two or more concentric tubes. A plasma-forming gas (argon) flows through the inner tubes of the torch and is excited into plasma by a radio frequency (RF) powered load coil 104, gradually transitioning to a high-vacuum region via a sampling cone 105 and a truncation cone 106. After the ion beam enters the high vacuum region, it is focused by the extraction lens group 107 and then enters the off-axis lens group 108, where it is separated from photons and neutral matter. It then passes through the collision reaction cell inlet focusing lens 110 and the collision reaction cell inlet lens 30 before entering the collision reaction cell. This collision reaction cell is... Figure 3The diagram shows a curved multipole collision reaction cell. Between the off-axis lens group 108 and the focusing lens 30 of the collision reaction cell, there is a slide valve 109. This valve is closed in the instrument standby state to maintain a high vacuum environment for subsequent components; it automatically opens during analysis. After eliminating interfering ions through collision or reaction, the ion beam exits the collision reaction cell through the off-axis lens group 40, causing a secondary off-axis rotation. This second off-axis rotation eliminates the influence of neutral substances in the collision reaction cell on subsequent mass screening, improving the signal-to-noise ratio. The ion beam after the secondary off-axis rotation enters the mass analyzer 115. The mass analyzer typically employs a quadrupole structure or other methods such as a sector magnetic field or a time-of-flight (TOF) analyzer, using an alternating electric field, or a combination of electric and magnetic fields, to perform spectral decomposition of the ionized ions according to their mass-to-charge ratio (m / z). The mass analyzer 115 generally also includes a pre-quadrupole 114. After passing through the mass analyzer 115, the ion detector 116 is able to count each type of ion at a given m / z ratio arriving at the ion detector from the mass analyzer, with the intensity of each peak indicating the concentration (or abundance) of the corresponding element in the sample.

[0062] from Figure 6 The simulated ion flight trajectory shows that, using the inductively coupled plasma mass spectrometry analysis system with a curved multipole collision reaction cell provided by this invention, the ion beam, after being focused into the curved collision reaction cell, is perfectly constrained on the central curve of the multipole ion guide, and flies out from the outlet of the collision reaction cell to enter the subsequent mass analyzer for ion screening.

[0063] Figure 7 This paper presents a triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS) system with a curved multipole collision reaction cell. It can be seen that by utilizing the curved multipole collision reaction cell provided by this invention, the length of the instrument can be greatly reduced, thereby achieving instrument miniaturization.

[0064] Figure 8 This paper presents another triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS) system with a curved multipole collision reaction cell. This system employs another curved multipole collision reaction cell provided by this invention. In this reaction cell, the arcs corresponding to the longitudinal axes of the plurality of rod electrodes 201 in the curved multipole ion guide 20 are 180 degrees. The advantage of using such a curved multipole collision reaction cell is that it allows for further optimization of the arrangement of components in the mass spectrometer, thereby further reducing the size of the mass spectrometer.

[0065] The above description is merely a preferred embodiment of this utility model. It should be noted that, for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of this utility model, and these improvements and substitutions should also be considered within the protection scope of this utility model. The basic principles, main features, and advantages of this utility model have been shown and described above. For those skilled in the art, it is obvious that this utility model is not limited to the details of the above preferred embodiments. The embodiments should be considered exemplary and non-limiting. The scope of this utility model is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included within this utility model.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in the embodiments can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A curved multipole collision cell for an inductively coupled plasma mass spectrometer, characterized in that, include: The housing includes a pool inlet and a pool outlet disposed opposite to the pool inlet along the longitudinal axis of the housing; And a curved multipole ion guide disposed inside the housing along the longitudinal axis of the housing; The curved multipole ion director includes multiple elongated rod electrodes, each of which is a curved structure and is parallel to each other.

2. The reaction tank according to claim 1, characterized in that, The plurality of rod electrodes are located at a predetermined radial distance orthogonal to the longitudinal axis of the housing, the plurality of rod electrodes are circumferentially spaced from each other around the longitudinal axis, and define the inlet and outlet of the curved multipole ion guide.

3. The reaction tank according to claim 1, characterized in that, The longitudinal axis of the rod electrode is arc-shaped, zigzag-shaped, or a combination of arc-shaped and zigzag-shaped, or a combination of arc-shaped and zigzag-shaped.

4. The reaction tank according to claim 1, characterized in that, The front end and / or a short section of the rear end of the rod electrode is a straight rod to collimate the ions.

5. The reaction tank according to claim 1, characterized in that, One set of the rod electrodes spaced apart is configured to apply an RF+ potential superimposed on a DC bias potential (U), and another set of the rod electrodes spaced apart is configured to apply an RF- potential superimposed on a DC bias potential (U). Among them, the RF+ potential and the RF- potential are radio frequency signals with the same frequency and amplitude but opposite phase, thereby generating an RF confinement field for the ions.

6. The reaction tank according to claim 1, characterized in that, A negative DC barrier is generated at the outlet of the multipole ion guide to facilitate the extraction of ions from the collision reaction cell.

7. The reaction tank according to claim 1, characterized in that, The number of rod electrodes is 2N, where N is an integer and N≥2.

8. The reaction tank according to claim 1, characterized in that, The rod electrode is one of a round rod, a square rod, a hyperboloid rod, or a concave rod.

9. The reaction tank according to claim 1, characterized in that, Also includes: An inlet ion mirror is located on the cell inlet side of the housing; and An outlet ion mirror is located on the pool outlet side of the housing.

10. An inductively coupled plasma mass spectrometry (ICP-MS) system having a bent multipole collision reaction cell as described in any one of claims 1-9.

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