Interference ion removal device

Abstract

An interference ion removal device used in a mass spectrometry system or the like comprises a first ion guide and a second ion guide, a DC potential barrier being formed between the first ion guide and the second ion guide. In the first ion guide, collision-induced dissociation (CID) and kinetic energy discrimination (KED) are performed, and in the second ion guide, the velocity distribution of ions is caused to converge.

Description

Interferential ion removal device

[0001] The present invention generally relates to mass spectrometry, and more particularly to interference ion removal devices used in ICP-MS (Inductively Coupled Plasma-Mass Spectrometry) systems and the like. Background Art

[0002] Inductively coupled plasma mass spectrometry (ICP-MS) systems are often used for elemental analysis of samples, such as measuring the concentration of trace metals in a sample. An ICP-MS system includes a plasma-based ion source that generates a plasma to break down the sample molecules into atoms and then ionize the atoms in preparation for elemental analysis. ICP-MS systems generally use argon (Ar) as the plasma generation gas and a high-frequency (typically 27 MHz) ICP as the ion source.

[0003] In an ICP-MS system, during typical operation, a liquid sample is atomized by a nebulizer (generally a pneumatically assisted type), i.e., converted into an aerosol (fine spray or mist), and the aerosolized sample is sent to a plasma plume generated by a plasma source. The plasma source is configured as a flow-through plasma torch with two or more concentric tubes. Generally, a plasma-forming gas such as argon flows through the outer tube of the torch and is energized into a plasma by a suitable energy source (generally a load coil with radio frequency (RF) as the energy source). The aerosolized sample flows through the coaxial central tube (or capillary) of the torch and is released into the generated plasma. Upon exposure to the plasma, the molecules of the sample are broken down into atoms, or alternatively, the molecules of the sample are partially broken down into molecular fragments, and the atoms or molecular fragments are ionized.

[0004] Generally, the ions to be inspected as a result of being positively charged are extracted from the plasma source and sent as an ion beam to the mass spectrometer. The mass spectrometer applies a time-varying electric field or a combination of an electric field and a magnetic field in order to spectrally (spectroscopically) decompose ions of different masses based on their mass-to-charge (m / z) ratio, thereby enabling the ion detector to count each type of ion of a given m / z ratio arriving from the mass spectrometer to the ion detector. As an alternative, the mass spectrometer can be a time-of-flight (TOF) analyzer that calculates the flight speed of ions that acquire a constant kinetic energy by an accelerating electric field from the time required to pass through the flight tube, from which the m / z ratio can then be derived. Next, the ICP-MS system presents the data as a spectrum of peaks of mass (m / z ratio). The intensity of each peak indicates the concentration (abundance) of the corresponding element in the sample.

[0005] In addition to the ions to be inspected for which an analysis is attempted, the plasma generates background (non-inspected) ions. A specific type of non-inspected ions called interference ions may interfere with the analysis of a specific type of inspected ions. Interference ions may be generated from the plasma-forming gas (e.g., argon), the matrix components of the sample, the solvent / acid contained in the sample, or the air (oxygen and nitrogen) mixed into the system. For example, the interference ions may be interfering substances of isomers having the same nominal mass as the inspected ions. Detecting the interference ions associated with the detection of a specific inspected ion leads to spectral overlap in the analysis data, thereby reducing the quality of the analysis. Examples of interference ions are polyatomic ions such as ６３ Cu ＋ interfering with ２３ Na ４０ Ar ＋ since both ions appear at m / z = 63 in the mass spectrum, polyatomic ions such as ７８ Se ＋ interfering with ３８ Ar ４０ Ar ＋Since polyatomic ions like these, and both ions, appear at m / z = 80, selenium isotopes ８０ See ＋ Argon interfering with 40 Ar ４０ Ar ＋ It contains polyatomic ions such as those shown.

[0006] To address the problem of spectral interference and improve the performance of ICP-MS systems, it is known to incorporate a collision / reaction cell between the ion source and the mass spectrometer in an ICP-MS system. This cell includes an ion guide that focuses the ion beam along its central axis. The cell exerts its spectral interference removal function by being filled with a collision gas or reaction gas. By using a collision gas (e.g., helium, He), polyatomic ion interference can be suppressed. In this case, kinetic energy discrimination (KED) and collision-induced dissociation (CID) techniques are generally used within the cell. Both the ion under test and the polyatomic interfering ions within the cell undergo multiple collisions with collision gas molecules, losing kinetic energy (KE) and consequently slowing down. Since the polyatomic interfering ions have a larger collision cross-section than the ion under test, they undergo a greater number of collisions and consequently lose more kinetic energy. Theoretically, in ion-molecular collision processes, the degree of interference reduction increases with the average number of collisions the ions undergo. Therefore, a higher collision gas (e.g., He) density (flow rate) within the cell is preferable. However, for the ions under test to overcome the DC potential barrier, which is set up to prevent the passage of polyatomic interfering ions along the direction of ion beam propagation, they must maintain sufficient kinetic energy (KE) after the collision. For this reason, there is an upper limit to the collision gas density (flow rate), and the performance of such collision / reaction cells has been limited by this limit. In CID, polyatomic interfering ions may dissociate when the internal energy converted and stored by collisions with the collision gas becomes greater than the dissociation energy of the polyatomic interfering ion. To dissociate, it is necessary to increase the internal energy, and consequently, to increase the kinetic energy of the ions entering the cell (i.e., increase the ion velocity).However, if the acceleration rate of the ions injected into the cell is set high, the collision between the collision gas and the ions is a random process, and some ions may enter the subsequent mass spectrometer while maintaining much of their momentum. High-speed ions may pass through the mass spectrometer before mass filtering is complete and proceed to the ion detector, potentially leading to a deterioration in abundance sensitivity.

[0007] Japanese Patent No. 7368945 (U.S. Patent No. 10290482) describes a two-stage KED (Kinetic Energy Deposition) using a two-stage ion guide (tandem collision / reaction cell) including a rod electrode (e.g., quadrupole) to address the problem of the upper limit of the collision gas density (flow rate) in the above-mentioned KED. In the tandem collision / reaction cell of Patent No. 7368945 (U.S. Patent No. 10290482), the DC bias of the first ion guide, into which the ion beam from the ion source enters, is set to be lower in absolute value than the DC bias of the subsequent second ion guide, and the upper limit of the collision gas density (flow rate) can be increased by the second ion guide re-accelerating the ions under test. However, Patent No. 7368945 (U.S. Patent No. 10290482) does not mention the use of the above-mentioned CID (Collision Injection Deposition). Summary of the Invention

[0008] The present invention aims to solve the problems of CID and KED, and to provide an apparatus and method for achieving superior analytical performance compared to conventional collision / reaction cells with a single ion guide, and to the tandem collision / reaction cell of the above-mentioned Japanese Patent No. 7368945 (U.S. Patent No. 10290482), by utilizing CID and KED.

[0009] According to one embodiment, an interference ion removal device is provided. The interference ion removal device includes a housing including an ion beam inlet, an ion beam outlet spaced longitudinally from the ion beam inlet, and a gas supply port communicating with the interior, and at least two ion guides disposed within the housing, the at least two ion guides including a first ion guide and a second ion guide, the first ion guide being configured to generate a first RF confinement field that confines ions radially and to which a first DC potential is applied, the second ion guide being configured to generate a second RF confinement field that confines ions radially and to which a second DC potential is applied, the first DC potential applied to the first ion guide being greater in absolute value than a second DC potential applied to the second ion guide, and a DC potential barrier being formed between the first ion guide and the second ion guide.

[0010] According to one embodiment, in the first ion guide, interfering ions collide with the collision gas and dissociate or lose kinetic energy, and ions under test collide with the collision gas and lose kinetic energy, the DC potential barrier is high enough to prevent interfering ions that did not dissociate from leaving the first ion guide and low enough to allow ions under test to leave the first ion guide, and in the second ion guide, the collision with the collision gas causes the high-speed ions among the ions under test to be significantly slowed down compared to the low-speed ions, thereby converging the ion velocity distribution of the ions under test. The interfering ion removal device further includes a controller, the controller configured to apply a first RF potential superimposed on a first DC potential to the electrodes of the first ion guide to generate a first RF confinement field, and to apply a second RF potential superimposed on a second DC potential to the electrodes of the second ion guide to generate a second RF confinement field. Furthermore, the controller is configured to receive parameters relating to the collision gas species, gas flow rate, the second DC potential, and the height of the DC potential barrier as input, and to synchronize each of these parameters in conjunction with the measurement of the ion under test. Furthermore, the second DC potential has a longitudinal axial DC potential gradient along the length of the second ion guide. Furthermore, the second DC potential has a potential gradient from -50 V / m to 100 V / m.

[0011] According to one embodiment, the first ion guide and the second ion guide are multipole ion guides. Alternatively, one or both of the first ion guide and the second ion guide are quadrupole ion guides. Furthermore, the first ion guide and the second ion guide function as a mass filter by 1) applying a first RF potential superimposed on a first DC potential to the electrode of the first ion guide, 2) applying a second RF potential superimposed on a second DC potential to the electrode of the second ion guide, 3) the first ion guide includes a plurality of elongated first ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced apart from each other in the circumferential direction around the longitudinal axis, and the second ion guide includes a plurality of elongated second ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced apart from each other in the circumferential direction around the longitudinal axis, wherein the second ion guide is positioned forward by an axial gap. 5) The ion guide is separated from the first ion guide, and the first ion guide includes a plurality of elongated first ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced circumferentially apart from each other around the longitudinal axis, and a first auxiliary electrode arranged circumferentially between each of the first ion guide electrodes, and the second ion guide has a configuration selected from the group, wherein the second ion guide is separated from the first ion guide by a longitudinal axial gap.

[0012] According to one embodiment, the first DC potential is in the range of -50V to -200V, and the second DC potential is positively offset by +0.1V to +50V relative to the first DC bias potential. The housing is divided by a partition into a first cell housing the first ion guide and a second cell housing the second ion guide, the partition having an aperture through which an ion beam can pass, the first cell including a first gas supply port communicating with the interior of the first cell, and the second cell including a second gas supply port communicating with the interior of the second cell. Furthermore, the housing consists of at least two housings, the at least two housings including a first housing and a second housing, the first housing including the first ion guide and a first gas supply port, and the second housing including the second ion guide and a second gas supply port.

[0013] According to one embodiment, a mass spectrometry system is provided. The mass spectrometry system includes an interference ion removal device, the interference ion removal device includes a housing, the

[0014] According to one embodiment, the mass spectrometry system further includes a controller configured to apply a first RF potential superimposed on a first DC potential to the electrode of a first ion guide to generate the first RF confinement field, and a second RF potential superimposed on a second DC potential to the electrode of a second ion guide to generate the second RF confinement field. The mass spectrometry system further includes an ion source in communication with the ion beam inlet, the ion source including a plasma torch. The mass spectrometry system further includes a first mass spectrometer configured to receive an ion beam from the ion beam outlet, the first mass spectrometer including a third ion guide electrode configured to filter ions in the ion beam by an m / z ratio. The mass spectrometer further includes a second mass spectrometer between the ion source and the interference ion removal device.

[0015] According to one embodiment, a method is provided for operating an interference ion removal device in a mass spectrometry system. The method involves flowing a collision gas to the interference ion removal device, the interference ion removal device comprising an ion beam inlet, an ion beam outlet spaced longitudinally from the ion beam inlet, a first ion guide between the ion beam inlet and a second ion guide, and a second ion guide between the first ion guide and the ion beam outlet, the device generating a first RF confinement field in the first ion guide to confine ions radially, generating a second RF confinement field in the second ion guide to confine ions radially, and generating a DC potential barrier between the first ion guide and the second ion guide, the DC potential barrier being formed by making the first DC potential applied to the first ion guide significantly greater in absolute value than the second DC potential applied to the second ion guide, the object to be inspected The method includes sending ON and interfering ions to the first ion guide via the ion beam inlet, wherein the ions to be tested and the interfering ions are generated from ionizing the sample to be analyzed, the interfering ions collide with the collision gas and dissociate or lose kinetic energy, the ions to be tested collide with the collision gas and lose kinetic energy, the DC potential barrier is high enough to prevent undissociated interfering ions from leaving the first ion guide and low enough to allow the ions to be tested to leave the first ion guide, and sending the ions to be tested from the first ion guide to the second ion guide, wherein, within the second ion guide, the high-speed ions among the ions to be tested are significantly slowed down compared to the low-speed ions by collision with the collision gas, and the ion velocity distribution of the ions to be tested is converged.

[0016] According to one embodiment, the size of the DC potential barrier is in the range of 0.1 V to 50 V. Furthermore, the second DC potential has an axial DC potential gradient along the length of the second ion guide, and the second DC potential has a potential gradient of -50 V / m to 100 V / m.

[0017] According to one embodiment, the method is: 1) to generate the first RF confinement field, apply a first RF potential superimposed on a first DC potential to the first ion guide; to generate the second RF confinement field, apply a second RF potential superimposed on a second DC potential to the second ion guide; 2) to generate the first RF confinement field, apply a first RF potential superimposed on a first DC potential to the first ion guide; to generate the second RF confinement field, apply a second RF potential superimposed on a second DC potential to the second 1) Apply to the ion guide such that the first DC potential and the second DC potential are negative, 3) In order to generate the first RF confinement field, apply the first RF potential superimposed on the first DC potential to the first ion guide, and in order to generate the second RF confinement field, apply the second RF potential superimposed on the second DC potential to the second ion guide such that the first DC potential is in the range of -50V to -200V, 4) In order to generate the first RF confinement field, apply the first RF potential superimposed on the first DC potential to the first ion guide 5) Applying to the ion guide, a second RF potential superimposed on the second DC potential is applied to the second ion guide to generate the second RF confinement field, and the second DC potential is positively offset from the first DC potential by +0.1V to +50V, 5) Applying to the first ion guide, a first RF potential superimposed on the first DC potential is applied to the first ion guide to generate the first RF confinement field, and applying to the second ion guide, a second RF potential superimposed on the second DC potential is applied to the second ion guide to generate the second RF confinement field, and the first DC The method includes a step selected from a group consisting of: 6) the bias potential being constant along the length of the first ion guide; 7) applying a first RF potential superimposed on a first DC potential to the first ion guide to generate the first RF confinement field, and applying a second RF potential superimposed on a second DC potential to the second ion guide to generate the second RF confinement field, wherein the second DC potential has an axial DC potential gradient along the length of the second ion guide; and 8) two or more combinations of the above.

[0018] According to one embodiment, the interfering ion removal device is divided by a partition into a first cell housing the first ion guide and a second cell housing the second ion guide, the partition having an aperture through which an ion beam can pass, or the housing of the interfering ion removal device consists of at least two housings, the at least two housings including a first housing and a second housing, and the method includes flowing a first impacting gas into the first cell and flowing a second impacting gas into the second cell, or the first housing includes the first ion guide and a first gas supply port, the second housing includes the second ion guide and a second gas supply port, and the method includes flowing a first impacting gas into the first housing and flowing a second impacting gas into the second housing. Furthermore, the first impacting gas is either the same as the second impacting gas, or the first impacting gas is different from the second impacting gas, and the inflow velocity of the first impacting gas is the same as the inflow velocity of the second impacting gas, or the inflow velocity of the first impacting gas is different from the inflow velocity of the second impacting gas.

[0019] According to one embodiment, the method includes performing an operation selected from the group consisting of: 1) generating the target ions by exposing the sample to an inductively coupled plasma before sending the target ions to the interference ion removal device via the ion beam inlet; 2) generating the target ions by exposing the sample to an inductively coupled plasma generated by operating a plasma torch; and 3) generating the target ions by flowing the sample from a nebulizer or spray chamber to a plasma torch and exposing the sample to an inductively coupled plasma generated by operating the plasma torch. The computer program also includes computer-executable instructions configured to cause the processor of the mass spectrometry system to perform the above-described method.

[0020] The present invention provides an interference ion removal device having an ion guide divided into a front and a rear section. By assigning different roles to the front section, which is responsible for interference removal using CID and KED, and the rear section, which equalizes ion velocity and generates heat, it is possible to achieve both superior interference removal performance and sensitivity characteristics compared to conventional collision / reaction cells having only a single ion guide and the tandem collision / reaction cell of the above-mentioned Japanese Patent No. 7368945 (U.S. Patent No. 10290482). The mass filter in the rear section, which does not have the role of KED, allows for optimal voltage setting for mass separation, making it possible to achieve excellent abundance sensitivity.

[0021] This is a schematic diagram of an example of an inductively coupled plasma mass spectrometer (ICP-MS) system according to one embodiment of the present disclosure. This is a schematic perspective view of an example of a tandem ion guide assembly for an interference ion removal device according to one embodiment of the present disclosure. This is a schematic side (longitudinal) view of the tandem ion guide assembly shown in Figure 2. This is a schematic side (longitudinal) view of an example of an interference ion removal device according to one embodiment of the present disclosure, and a plot of the DC potential as a function of axial position. This is a schematic diagram of an interference ion removal device according to another embodiment of the present disclosure. This is a flowchart showing an example of a method for operating an interference ion removal device in an inductively coupled plasma mass spectrometer (ICP-MS) system according to one embodiment of the present disclosure. This is a schematic diagram of an unlimited example of a system controller (or controller or computing device) that may be part of a spectroscopic analysis system, such as the ICP-MS system shown in Figure 1, or that may communicate with such a spectroscopic analysis system. This is a comparison diagram of abundance sensitivity. This is a histogram showing the results of a predictive calculation regarding the energy distribution of ions as they are incident on the second ion guide.

[0022] As used herein, the term “mass spectrometry” may include secondary ion analysis, glow discharge mass spectrometry, spark source mass spectrometry, inductively coupled plasma mass spectrometry, microwave-induced plasma mass spectrometry, and surface ionization mass spectrometry. The present invention will generally be described using inductively coupled plasma mass spectrometry as an example.

[0023] As used herein, the term “fluid” may be used in a general sense to refer to any substance capable of flowing through a conduit. Thus, the term “fluid” may generally mean liquid or gas unless otherwise specified or indicated by the context.

[0024] As used herein, the term “liquid” may generally mean a solution, a turbidity, or an emulsion. Solid particles and / or bubbles may be present in the liquid.

[0025] As used herein, the term “aerosol” may generally mean an aggregate of droplets and / or solid particles that are impregnated in a gaseous medium for a sufficiently long time to be observed and measured. The size of aerosol droplets or particles is generally on the order of micrometers (μm). Thus, an aerosol may be considered to contain droplets and / or solid particles, and the gas that impregnates or carries these droplets and / or solid particles.

[0026] As used herein, the term “atomization” may mean the process of breaking down molecules into atoms. For example, atomization can occur in a plasma-enhanced environment. In the case of liquid samples, “atomization” may necessarily involve atomizing the liquid sample to form an aerosol, which is then followed by exposing the aerosol to or from the plasma.

[0027] As used herein, “liquid sample” may contain one or more different types of test material of interest dissolved in or retained in a liquid matrix. The liquid matrix may contain matrix components. Examples of “matrix (substrate) components” may include, but are not limited to, water and / or other solvents, acids, salts and / or soluble substances such as dissolved solids, insoluble solids or particulates, and any other compounds of no interest in the analysis.

[0028] For the convenience of the present disclosure, unless otherwise specified or the context indicates otherwise, the "interference ion removal device" is a "collision / reaction cell", which may mean a collision cell, a reaction cell, or a collision / reaction cell configured to operate as both a collision cell and a reaction cell by being switchable, for example, between a collision mode, a reaction mode, and a no-gas mode in which no gas flows.

[0029] For the convenience of the present disclosure, unless otherwise specified or the context indicates otherwise, the "collision / reaction gas" may mean an inert collision gas used to collide with such ions without reacting with the ions in the interference ion removal device or without reacting with the reaction gas used to react with the ions to be inspected or interference ions in the interference ion removal device.

[0030] As used herein, the term "ions to be inspected" generally may mean any ions generated by ionizing the components of a sample being analyzed by a mass spectrometry system for which mass spectrum data is sought. For example, in the specific context of mass spectrometry, the ions to be inspected generally may be positive monoatomic ions of elements other than metals or noble gases (e.g., argon), or product ions generated by reacting a collision / reaction gas with positive monoatomic ions of elements other than metals or noble gases. It should be noted that although the ions to be inspected are described as positive ions in this specification, it will be apparent to those skilled in the art that the present invention is equally applicable when the ions to be inspected are negative ions.

[0031] As used herein, the term "interference ions" generally may mean any ions that interfere with the ions to be inspected. Examples of interference ions may include, but are not limited to, positive plasma (e.g., argon) ions, polyatomic ions containing a plasma-forming gas (e.g., argon), and polyatomic ions containing components of the sample. The components of the sample can be non-inspected species that can be derived from the element to be inspected or the matrix components of the sample or other background species.

[0032] As used herein, the term "thermalization" may mean that ions are decelerated by colliding with a collision gas, and the velocity distribution of the ions is narrowed (converged) to a desired range.

[0033] FIG. 1 is a schematic view of an example of an inductively coupled plasma mass spectrometry (ICP-MS) system 100 according to an embodiment. Generally, the structures and operations of various components of an ICP-MS system are known to those skilled in the art, and thus will only be briefly described herein as necessary for understanding the disclosed subject matter.

[0034] In this exemplary embodiment, the ICP-MS system 100 generally includes a sample introduction unit 104, an ion source 108, an interface unit 112, an ion optical unit 114, a first mass spectrometry unit 115, an ion guide unit 116, a second mass spectrometry unit 118, and a system controller 120. The ICP-MS system 100 also includes a vacuum system configured to evacuate various internal regions of the system 100. The vacuum system maintains a desired internal pressure or vacuum level in the internal region and removes neutral molecules that are not the inspection target of interest from the ICP-MS system 100 when doing so. The vacuum system includes appropriate pumps and passages connecting to ports of the regions to be evacuated, as indicated by arrows 128, 131, 132, and 136 in FIG. 1.

[0035] The sample introduction section 104 may include a sample supply conduit 152 for supplying the sample to the ion source 108, which may include a sample supply source 140 for supplying the sample to be analyzed, a pump 144, a nebulizer 148 for converting the sample into an aerosol, a spray chamber 150 for removing larger droplets from the aerosolized sample, and a suitable sample injector. For example, the nebulizer 148 may utilize a flow of argon or other inert gas (atomizing gas) from a gas source 156 (e.g., a pressurized reservoir) to aerosolize the sample, as indicated by the downward arrow. The atomizing gas may be the same gas as the plasmaforming gas used to form plasma in the ion source 108, or a different gas. The pump 144 (e.g., a peristaltic pump, syringe pump, etc.) is connected between the sample supply source 140 and the nebulizer 148 to establish a flow of the liquid sample to the nebulizer 148. The sample flow rate may be in the range of, for example, 0.1 to several milliliters per minute (mL / min). For example, the sample source 140 may include one or more vials. The multiple vials may contain one or more samples, various standard solutions, tuning solutions, calibration solutions, rinsing solutions, etc. The sample source 140 may include an automated device configured to switch between various vials, thereby enabling the selection of a specific vial for current use in the ICP-MS system 100.

[0036] In another embodiment, the sample may be a gas and the nebulizer 148 is not required. In another embodiment, the sample source 140 may be a pressurized reservoir containing a liquid or gaseous sample, or include such a pressurized reservoir and the pump 144 is not required. In another embodiment, the sample source 140 may be the output of an analytical separation instrument, such as a liquid chromatography (LC) or gas chromatography (GC) instrument. Other types of devices and means for introducing samples into an ICP-MS system are known and do not need to be described herein.

[0037] The ion source 108 includes a plasma source for atomizing and ionizing the sample. In the illustrated embodiment, the plasma source is an inflow plasma torch such as the ICP torch 160. In another embodiment, in a MIP-MS (Microwave-Induced Plasma-Mass Spectrometry) system similar to an ICP-MS system, nitrogen (N) is used as the plasma generation gas. ２ The plasma source is a microwave-induced plasma source using microwave (e.g., 2.45 GHz) power. ICP-MS systems and MIP-MS systems are sometimes called spectroscopic analyzers. The ICP torch 160 includes a central or sample injector 164 and one or more outer tubes arranged concentrically around the sample injector 164. In the illustrated embodiment, the ICP torch 160 includes an intermediate tube 168 and an outermost tube 172. The sample injector 164, intermediate tube 168 and outermost tube 172 may be constructed from, for example, quartz, borosilicate glass, or ceramic. Alternatively, the sample injector 164 may be constructed from, for example, a metal such as platinum. The ICP torch 160 is located inside an ionization chamber (or "torch box") 176. The work coil (also called a load coil or RF coil) 180 is coupled to a radio frequency (RF) power supply 185 and is positioned at the discharge end of the ICP torch 160.

[0038] During operation, the gas source 156 supplies a plasma-forming gas to the outermost tube 172. The plasma-forming gas is generally not necessarily argon. RF power is applied to the work coil 180 by the RF power supply 185, while the plasma-forming gas flows through an annular channel formed between the intermediate tube 168 and the outermost tube 172, thereby generating a high-frequency, high-energy electromagnetic field to which the plasma-forming gas is exposed. The work coil 180 operates at a frequency and power effective for generating and maintaining plasma from the plasma-forming gas. As a result, a plasma plume 184 flows from the discharge end of the ICP torch 160 into the sampling cone 188. An auxiliary gas is flowed through an annular channel formed between the sample injector 164 and the intermediate tube 168 to keep the upstream end of the discharge 184 away from the end of the sample injector 164 and the end of the intermediate tube 168. The auxiliary gas may be the same gas as the plasma-forming gas or a different gas. The introduction of gas(s) into the intermediate tube 168 and the outermost tube 172 is shown in Figure 1 by arrows pointing upward from the gas source 156. The sample flows through the sample injector 164, as indicated by arrow 186, and is released from the sample injector 164 into the activated plasma 184. According to principles understood by those skilled in the art, the sample flows through the heating zone of the ICP torch 160 and finally interacts with the plasma 184, where the sample undergoes drying, vaporization, atomization and ionization, thereby generating ions of interest from the components (particularly atoms) of the sample.

[0039] The interface unit 112 provides a first stage of depressurization between the ion source 108, which generally operates at atmospheric pressure (101.3 kPa (760 Torr)) or approximately atmospheric pressure, and the vacuum region of the ICP-MS system 100. For example, the interface unit 112 can be maintained at an operating vacuum of, for example, about 133.3 to 266.6 Pa (1 to 2 Torr) by a mechanical roughing pump (e.g., rotary pump, scroll pump, etc.), while the mass spectrometer 158 can be maintained at, for example, about 1.33 × 10⁻¹⁶ by a high vacuum pump (e.g., turbomolecular pump, etc.). －４ Pa(10 －６The interface section 112 can be maintained in an operating vacuum. The interface section 112 includes a sampling cone 188 positioned across the ionization chamber 176 from the discharge end of the ICP torch 160, and a skimmer cone 192 positioned at a small axial distance from the sampling cone 188. The sampling cone 188 and the skimmer cone 192 have small orifices at the centers of conical structures aligned with each other and with the central axis of the ICP torch 160. The sampling cone 188 and the skimmer cone 192 help extract the plasma 184 from the torch into the vacuum chamber and also function as gas-conducting barriers to limit the amount of gas entering the interface section 112 from the ion source 108. The sampling cone 188 and the skimmer cone 192 can be made of metal (or at least the tips defining their apertures can be made of metal) and can be electrically grounded. Neutral gas molecules and particulate matter entering the interface section 112 can be discharged from the ICP-MS system 100 through a vacuum port 128.

[0040] The ion optics unit 114 may be located between the skimmer cone 192 and the first mass spectrometer 115. The ion optics unit 114 includes a lens assembly 196, which may include a series of (generally electrostatic) ion lenses that help extract ions from the interface unit 112, focus the ions as an ion beam 106, and accelerate the ions to the mass spectrometer 115. The ion optics unit 114 is pumped by a suitable pump (e.g., a turbomolecular pump) to, for example, about 0.133 Pa (10 －３ The operating pressure can be maintained at (Tor). Although not specifically shown in Figure 1, the lens assembly 196 may be configured such that, with the ion beam 106 steered via the offset, the ion optical axis passing through the lens assembly 196 is offset (in the radial direction perpendicular to the longitudinal axis) from the ion optical axis passing through the ion guide 116. Such a configuration facilitates the removal of neutral species and photons from the ion path.

[0041] The first mass spectrometry unit 115 includes a first mass spectrometer 158A. The first mass spectrometer 158A can be any type suitable for ICP-MS. Examples of mass spectrometers include, but are not limited to, multipolar electrode structures (e.g., quadrupole mass filters, linear ion traps, three-dimensional pole traps, etc.), time-of-flight (TOF) analyzers, magnetic field and / or electric field instruments, electrostatic traps (e.g., Kingdon, Knight and ORBITRAP® traps), and ion cyclotron resonance (ICR) traps (FT-ICR or FTMS, also known as Penning traps). The first mass spectrometer 158A, also called the first mass filter (Q1), may operate to allow only ions of a given m / z ratio in the ion beam 106 to pass through. In another embodiment, the first mass spectrometry unit 115 may be omitted. In that case, the ion beam 106 from the ion optics unit 114 is incident on the ion guide unit 116.

[0042] The ion guide unit 116 is positioned between the first mass spectrometry unit 115 and the second mass spectrometry unit 118 and receives the ion beam 107 from the first mass spectrometry unit 115. According to one aspect of the present disclosure, the ion guide unit 116 includes an interference ion removal device 110. The interference ion removal device 110 includes an ion guide assembly 146 positioned within the cell housing 187 between the ion beam inlet and ion beam outlet in the axial direction. In this embodiment, the ion beam inlet and ion beam outlet are provided by ion optical components. Specifically, an ion beam inlet lens 122 is positioned at the ion beam inlet and an ion beam outlet lens 124 is positioned at the ion beam outlet. The ion guide assembly 146 has a tandem configuration in that it includes a first ion guide 174 and a second ion guide 178, and is also called a tandem ion guide assembly. The first ion guide 174 and the second ion guide 178 each have a linear multipole (e.g., quadrupole, sextupole, or octupole) configuration including a plurality (e.g., four, six, or eight) of rod electrodes arranged (generally) parallel to each other along a common longitudinal central axis of the ion guides 174 and 178. Each rod electrode is positioned radially from the longitudinal axis and spaced circumferentially from each other around the longitudinal axis. For simplicity, only two such rod electrodes are shown in Figure 1 for the first ion guide 174 or the second ion guide 178. An RF power supply (described later) applies RF potentials to the rod electrodes of the first ion guide 174 and the second ion guide 178 in known ways that generate a two-dimensional first RF electric field between the rod electrodes of the first ion guide 174 and a two-dimensional second RF electric field between the rod electrodes of the second ion guide 178. These RF electric fields work to focus the ion beam along the longitudinal axis by restricting the radial polarization of ions with respect to the longitudinal axis. In a typical embodiment, the first ion guide 174 and the second ion guide 178 are RF-only devices that do not have mass filtering capabilities.In another embodiment, the first ion guide 174 and / or the second ion guide 178 can function as a mass filter by superimposing a DC potential on the RF potential, as will be understood by those skilled in the art. The ion guide assembly 146 may further include an intermediate electrode (not shown) located near the outlet end of the first ion guide 174.

[0043] The collision / reaction gas source 138 (e.g., a pressurized reservoir) is configured to introduce one or more collision / reaction gases (e.g., a mixture) into the interfering ion removal device 110 via a collision / reaction gas supply conduit and port 142 connected to the inside of the housing 187. The gas flow rate is on the order of milliliters per minute (mL / min) or milligrams per minute (mg / min). The gas flow rate determines the pressure inside the interfering ion removal device 110. For example, the operating pressure of the cell can be in the range of, for example, 0.133 to 26.66 Pa (0.001 to 0.2 Torre). Examples of collision / reaction gases are, but are not limited to, helium, neon, argon, xenon, hydrogen, oxygen, water, ammonia, methane, methane fluoride (CH4). ３ F), and nitrous oxide (N ２ O), and combinations (mixtures) of the above, or two or more of the above. Inert (non-reactive) gases such as helium, neon, argon, and xenon are used as collision gases. The operation of the interference ion removal device 110 according to this disclosure will be described in more detail later.

[0044] The second mass spectrometry unit 118 (also referred to herein as the mass spectrometer) includes a second mass spectrometer 158B and an ion detector 161. The second mass spectrometer 158B can be any type suitable for ICP-MS. The type of the second mass spectrometer 158B may be the same as or different from the first mass spectrometer 158A described above. Similar to the first mass spectrometer 158A, the second mass spectrometer 158B is also referred to as the second mass filter (Q2). The ion detector 161 can be any device configured to collect and measure the flow (or stream) of mass-identified ions output from the second mass spectrometer 158B. Examples of ion detectors include, but are not limited to, electron multiplier tubes, photomultiplier tubes, microchannel plate (MCP) detectors, image current detectors, and Faraday cups. For illustrative purposes in Figure 1, the ion detector 161 (at least the front portion that receives ions) is shown to be oriented at a 90-degree angle to the ion outlet of the mass spectrometer 158. However, in other embodiments, the ion detector 161 may be on axis with the ion outlet of the mass spectrometer 158.

[0045] During operation, the second mass spectrometer 158B receives an ion beam 166 from the interference ion removal device 110 and separates or classifies the ions based on their different mass-to-charge (m / z) ratios. The separated ions pass through the second mass spectrometer 158B and arrive at the ion detector 161. The ion detector 161 detects and counts each ion and outputs an electron detector signal (ion measurement signal) to the data acquisition component of the system controller 120. The mass identification performed by the second mass spectrometer 158B enables the ion detector 161 to detect and count ions with a specific m / z ratio, separate from ions with other m / z ratios (derived from different target elements of the sample), thereby generating an ion measurement signal for each ion mass being analyzed (and consequently, each target element). Ions with various m / z ratios can be detected and counted sequentially. The system controller 120 processes the signals received from the ion detector 161 and generates a mass spectrum showing the relative signal intensity (abundance) of each detected ion. Such signal intensity, measured at a given m / z ratio (and therefore a given element under test), is directly proportional to the concentration of that element in the sample processed by the ICP-MS system 100. In this way, the presence of a chemical element in the sample being analyzed can be confirmed, and the concentration of that chemical element can be determined.

[0046] Although not specifically shown in Figure 1, the ion optical axis passing through the ion guide 146 and the ion beam exit lens 124 can be offset from the ion optical axis passing through the inlet to the second mass spectrometer 158B, and the ion optical system can be configured to steer the ion beam 166 through this offset. This configuration removes further neutral species from the ion path.

[0047] The system controller (or controller, or computing device) 120 may include one or more modules configured to control, monitor, and / or time various functional aspects of the ICP-MS system 100, such as controlling the operation of the sample introduction unit 104, the ion source 108, the ion optics unit 114, the first mass spectrometry unit 115, the ion guide unit 116, and the second mass spectrometry unit 118, as well as controlling the vacuum system and various gas flow rates, temperature and pressure conditions, and any other sample handling components provided between the illustrated devices. The system controller 120 represents electrical circuits (e.g., RF and DC voltage sources) used to operate the interference ion removal device 110. The system controller 120 may also be configured to receive detection signals from the ion detector 161 and perform other tasks related to data acquisition and signal analysis, as needed to generate data (e.g., mass spectra) characterizing the sample under analysis. The system controller 120 may include a persistent computer-readable medium containing persistent instructions for performing any of the methods disclosed herein. The system controller 120 may include one or more types of hardware, firmware and / or software, as well as one or more memories and databases, depending on the need to operate the various components of the ICP-MS system 100. The system controller 120 generally includes a main electronic processor that controls the whole system and may include one or more electronic processors configured for dedicated control operations or specific signal processing tasks.The system controller 120 may also include one or more types of user interface devices, such as user input devices (e.g., keyboards, touch screens, mice, and similar devices), user output devices (e.g., display screens, printers, visible indicators or alarms, audible indicators or alarms, and similar devices), a software-controlled graphical user interface (GUI), and a device for loading media readable by an electronic processor (e.g., persistent logic instructions embodied in software, data, and similar devices). The system controller 120 may also include an operating system (e.g., Microsoft Windows® software) for controlling and managing various functions of the system controller 120.

[0048] As can be seen, Figure 1 is a high-level schematic representation of the ICP-MS system 100 disclosed herein. As will be seen by those skilled in the art, depending on how the ICP-MS system 100 is configured for a given application, other components such as additional structures, devices, and electronic circuits may be included where required for the actual embodiment.

[0049] Figure 2 is a schematic perspective view of an example of a tandem ion guide assembly 246 according to one embodiment. Figure 3 is a schematic side (longitudinal) view of the tandem ion guide assembly 246. The tandem ion guide assembly 246 is configured for the operation of the interference ion removal device 110 described herein and shown in Figure 1. The tandem ion guide assembly 246 includes a first ion guide 274 and a second ion guide 278 positioned between the ion beam inlet and the ion beam outlet. An ion beam inlet lens 222 may be positioned at the ion beam inlet, and an ion beam outlet lens 224 may be positioned at the ion beam outlet.

[0050] The first ion guide 274 includes a plurality of first ion guide electrodes 203 (or "rod electrodes"), and the second ion guide 278 includes a plurality of second ion guide electrodes 205 (or "rod electrodes"). The first ion guide electrodes 203 are arranged circumferentially apart from one another around the longitudinal axis L of the tandem ion guide assembly 246. Each of the first ion guide electrodes 203 is positioned at a radial distance from the longitudinal axis L (perpendicular to the longitudinal axis) and extends along the longitudinal axis L. Accordingly, the first ion guide electrode 203 defines a first ion guide inlet 207 near the ion beam inlet lens 222, the first ion guide outlet 209 is axially separated from the first ion guide inlet 207 by the axial length of the first ion guide electrode 203, and the axially elongated interior 211 of the first ion guide extends from the first ion guide inlet 207 to the first ion guide outlet 209. Similarly, the second ion guide electrodes 205 are arranged circumferentially apart from each other around the longitudinal axis L (generally the same axis as the first ion guide 274), are positioned radially away from (and perpendicular to) the longitudinal axis L, and extend along the longitudinal axis L. The second ion guide electrode 205 defines a second ion guide inlet 213 that is axially separated from the first ion guide outlet 209 by only a small axial gap (space), the second ion guide outlet 215 is axially separated from the second ion guide inlet 213 by the axial length of the second ion guide electrode 205 and is located near the ion beam outlet lens 224, and the axially elongated interior 217 of the second ion guide extends from the second ion guide inlet 213 to the second ion guide outlet 215.

[0051] Figure 2 shows one embodiment in which the first ion guide 274 and the second ion guide 278 each have a quadrupole configuration (four ion guide electrodes). In other embodiments, the first ion guide 274 and the second ion guide 278 may have a higher-order multipolar configuration, such as a hexupole (six ion guide electrodes), an octupole (eight ion guide electrodes), or an even higher-order multipolar configuration. As shown in Figure 2, the first ion guide electrode 203 and the second ion guide electrode 205 may be cylindrical with a circular cross-section. Alternatively, in the case of a quadrupole, the surfaces of the first ion guide electrode 203 and the second ion guide electrode 205 facing the interior 211 of the first ion guide and the interior 217 of the second ion guide may each have a hyperbolic contour. Another alternative is that the first ion guide electrode 203 and the second ion guide electrode 205 may have a polygonal (prismatic) cross-section. In another embodiment, the tandem ion guide assembly 246 may further include an intermediate electrode (not shown) near the first ion guide outlet 209. In another embodiment, the first ion guide 274 may include a first auxiliary electrode (not shown) positioned circumferentially between each of the first ion guide electrodes 203. The second ion guide 278 may also include a second auxiliary electrode (not shown) positioned circumferentially between each of the second ion guide electrodes 205. The auxiliary electrode may assist in accelerating ions in the longitudinal axis direction of the ion guide.

[0052] Figure 3 further schematically illustrates the electronic (electrical) circuits that can be used to apply RF and DC potentials to various components of the tandem ion guide assembly 246. The system controller 120 described above and shown in Figure 1 can be considered to represent such electronic circuits. In Figure 3, the electronic circuits are schematically shown as a first RF source RF1 superimposed on a first DC source DC1 in contact with the first ion guide electrode 203, and a second RF source RF2 superimposed on a second DC source DC2 in contact with the second ion guide 205. The electronic circuits may further include, namely, a third DC source DC3 in contact with the ion beam inlet lens 222, and a fourth DC source DC4 in contact with the ion beam outlet lens 224. The RF and DC sources may also be collectively referred to as "voltage sources (one or more)".

[0053] During operation, the first RF source applies an RF potential RF1 superimposed on the DC bias potential DC1 to the first ion guide electrode 203 (RF1 + DC1) at a frequency and amplitude effective in generating a two-dimensional, time-varying first RF field in the first ion guide 274. Generally, each opposing pair of the first ion guide electrodes 203 are electrically interconnected. The RF potential applied to one opposing pair of the first ion guide electrodes 203 is 180 degrees out of phase with the RF potential (-RF1 + DC1, not shown in Figure 3) applied to an adjacent opposing pair of the first ion guide electrodes 203, as can be understood by those skilled in the art. The RF field confines ions radially in the first ion guide 274, i.e., restricts ion movement in the radial direction, thereby focusing the ions as an ion beam concentrated along the longitudinal axis L. The second RF source similarly applies an RF potential RF2 superimposed on the DC bias potential DC2 to the second ion guide electrode 205, thereby confining ions radially at the second ion guide electrode 278 and generating a two-dimensional, time-varying second RF field in the second ion guide 278 that converges the ions as an ion beam focused along the longitudinal axis L. In this way, the first ion guide 274 and the second ion guide 278 operate as RF-only ion guides, where the RF field functions solely to converge ions along the longitudinal axis L.

[0054] However, in another embodiment in which the first ion guide 274 and / or the second ion guide 278 have a quadrupole electrode structure, DC fields having opposite polarities ±U1 and / or ±U2 can be superimposed on the first RF field and / or the second RF field to enable the first ion guide 274 and / or the second ion guide 278 to function as a mass filter. That is, +RF1+U1+DC1 can be applied to one pair of the first ion guide electrodes 203, -RF1-U1+DC1 can be applied to the other pair of the first ion guide electrodes 203, +RF2+U2+DC2 can be applied to one pair of the second ion guide electrodes 205, and -RF2-U2+DC2 can be applied to the other pair of the second ion guide electrodes 205. According to known principles, by appropriately selecting the operating parameters of the combined RF / DC field (RF amplitude, RF frequency, and DC amplitude), the first ion guide 274 and / or the second ion guide 278 can be configured to impose a mass range (band pass) that allows only a single ion mass or a narrow range of ion masses (from a low mass cutoff point to a high mass cutoff point) to pass through the first ion guide 274 and / or the second ion guide 278. Ions having mass within the mass band pass have a stable flight path and can pass through the entire length of the first ion guide 274 and / or the second ion guide 278. Ions having mass outside the mass band pass have an unstable flight path and are thus removed. That is, such ions are removed from the first ion guide 274 and / or the second ion guide 278 without the possibility of overcoming the RF confinement field and leaving the first ion guide 274 and / or the second ion guide 278. Mass bandpass can be adjusted by tuning one or more operating parameters of the synthesized RF / DC field, thereby enabling the selection of specific ion masses (one or more) to be ejected from the first ion guide 274 and / or the second ion guide 278 at any given time. In some embodiments, this “scanning” function may be implemented to facilitate a process of suppressing the contribution of interfering ions to the mass spectral data, as described elsewhere in this specification.

[0055] Various DC sources are used to apply a DC bias voltage of a desired magnitude and polarity to a component to which various DC sources are coupled. In one embodiment, a first DC source DC1 applies a negative DC bias potential that is constant along the length of a first ion guide electrode 203, and a second DC source DC2 applies a negative DC bias potential that is constant along the length of a second ion guide electrode 205.

[0056] As a non-exclusive example, one or more voltage sources are configured to apply potentials having magnitudes within the following ranges: a first DC bias potential in the range of -50V to -200V, preferably -84V or -98V, and a second DC bias potential set to have a positive offset of +0.1V to +50V relative to the first DC bias potential. A third DC potential (in this case, the on-axis potential applied to the ion beam inlet lens 222 by the third DC source 3) is set to be greater in absolute value than the first DC bias potential. A fourth DC potential (in this case, the on-axis potential applied to the ion beam outlet lens 224 by the fourth DC source DC4) is set to be greater in absolute value than the second DC bias potential, in the range of -120V to -240V, preferably -150V.

[0057] In another embodiment, a first DC source DC1 and / or a second DC source DC2 may be configured to generate an axial DC gradient along the respective lengths of the first ion guide electrode 203 and / or the second ion guide electrode 205. To this end, the first DC source supplies two different DC potentials DC1a and DC1b that can be coupled to the inlet and outlet ends, respectively, of the first ion guide electrode 203, and / or the second DC source supplies two different DC potentials DC2a and DC2b that can be coupled to the inlet and outlet ends, respectively, of the second ion guide electrode 205. For example, DC potentials DC1a and DC1b can be coupled to the conductive or resistive layer of the first ion guide electrode 203 at the inlet and outlet ends, and / or DC potentials DC2a and DC2b can be coupled to the conductive or resistive layer of the second ion guide electrode 205 at the inlet and outlet ends. Applying a longitudinal DC gradient (for example, increasing along the longitudinal axis such that the potential at the outlet end of the second ion guide electrode is greater in absolute value than the potential at its inlet end (see also Figure 4)) can be useful for keeping ions moving in the forward direction and preventing ion backflow. Alternatively, it may be useful for re-accelerating ions that have lost kinetic energy due to collision with the collision gas by moving them in the reverse direction, as will be described later. As an example, the longitudinal DC gradient is in the range of -50 to 100 V / m, preferably 24 V / m.

[0058] To date, the first ion guide 274 and the second ion guide 278 have been primarily described and illustrated as having a linear multipole configuration in which the first ion guide electrode 203 and the second ion guide electrode 205 are parallel to each other and to the longitudinal axes of the first ion guide 274 and the second ion guide 278. However, in other embodiments, the first ion guide electrode 203 and / or the second ion guide electrode 205 do not have to be parallel. Instead, the first ion guide electrode 203 and / or the second ion guide electrode 205 can converge to each other and toward the longitudinal axis, or diverge from each other and away from the longitudinal axis, along their length from the inlet end to the outlet end.

[0059] In yet another embodiment, the first ion guide 274 and / or the second ion guide 278 do not have to have a linear multipolar configuration. More specifically, the first ion guide 274 and the second ion guide 278 may have any configuration for effectively generating a first RF confinement field in the first ion guide 274 and a second RF confinement field in the second ion guide 278, which is compatible with generating a DC potential barrier near the outlet of the first ion guide 274, in accordance with the subject matter disclosed herein. As one non-exclusive alternative embodiment, the first ion guide electrode 203 and / or the second ion guide electrode 205 may be a series (or stack) of rings (or plates with apertures) that coaxially surround the longitudinal axis and are axially separated from each other around the longitudinal axis. In this case, the RF potential applied to a given ring or plate to generate an RF confinement field within the first ion guide 274 and / or the second ion guide 278 may be 180 degrees out of phase with the RF potential applied to the ring(s) or plate(s) directly adjacent to that given ring or plate. The inner diameter of the ring or plate aperture may be constant along the longitudinal axis. Alternatively, the inner diameter of the ring or plate aperture may be successively increased or decreased in a continuous ring or plate in the direction from inlet to outlet, as in an embodiment of an ion funnel. The structure and operation of axially stacked rings or plates and ion funnels for use as ion guides are generally known to those skilled in the art.

[0060] Figure 4 is a schematic side (longitudinal) view of an example of the interference ion removal device 410. The interference ion removal device 410 includes a housing 487 on which a tandem ion guide assembly 246 is mounted to operate. Figure 4 also shows a first mass spectrometer (Q1) 458A and a second mass spectrometer (Q2) 458B. As an example, the first and second mass spectrometers 458A and 458B are shown as quadrupole devices (only a pair of opposing rod electrodes are shown), but they can be any type of mass spectrometer as described herein. Figure 4 further includes plots of the direct current (DC) potentials generated on the axis as a function of the axial position along the length of the first mass spectrometer 458A, the interference ion removal device 410, and the second mass spectrometer 458B.

[0061] In the operation of the ICP-MS system, ideally, only the target ions generated in the plasma-based ion source are sent to the second mass spectrometer 458B. However, as previously stated in this disclosure, the ion source 108 (Figure 1) also generates background (non-target) ions or "interfering ions" that may interfere with the analysis of a given sample. Interfering ions can be generated from plasma-forming gases (e.g., argon), matrix components of the sample, solvents / acids contained in the sample, and air (oxygen and nitrogen) introduced into the system. As previously stated in this disclosure, an example of an interfering ion is a polyatomic interfering substance having the same nominal mass as the monatomic target ion. Detecting interfering ions along with the detection of a specific target ion (which the interfering ion interferes with) leads to partial spectral overlap in the analytical data, thereby degrading the quality of the analysis.

[0062] The interference ion removal device 410 (or 110) described herein is configured to reduce and remove interfering ions (primarily polyatomic interfering materials) by collision-induced dissociation (CID), and also by kinetic energy discrimination (KED), thereby preventing (or at least reducing the amount of interfering ions that are introduced into) the second mass spectrometer 458B. As a result, the operation of the interference ion removal device 410 improves the performance of the ICP-MS system and the quality of the mass spectral data generated thereby. The interference ion removal device 410 can achieve this by performing CID and KED in a multi-stage ion-molecular collision process.

[0063] The operation of the interference ion removal device 410 will be described primarily with reference to Figures 3 and 4. The flow of collision / reaction gas (e.g., helium) to the interference ion removal device 410 is established via the collision / reaction gas source 138 and the supply port 142 (Figure 1). The gas flow rate is set to be optimized for the specific element being measured (the ion under test). The gas flow rate may depend on other factors such as the type of plasma generating gas being used (generally argon) and the type(s) of interference ions(s) expected to be removed. The first ion guide 274 and the second ion guide 278 are actively powered by RF sources RF1 and RF2 to generate the individual first and second RF ion confinement fields as described above. A first DC source DC1 applies a negative first DC bias potential (or guide potential) to the first ion guide electrode 203, and a second DC source DC2 applies a negative second DC bias potential (or guide potential) to the second ion guide electrode 205. The first and second DC bias potentials are both negative numbers, and the magnitude of the second DC bias potential is smaller in absolute value than the first DC bias potential and is positively offset from the first DC bias potential by +2V to +50V. As one non-exclusive example, the first DC bias potential can be -84V and the second DC bias potential can be -66V. As shown in Figure 4, the DC potential barrier (or barrier height) can be defined as the difference between the first DC bias potential at the outlet end of the first ion guide electrode 203 and the second DC bias potential at the inlet end of the second ion guide electrode 205. As a non-exclusive example, the magnitude of the DC potential barrier is in the range of 0.1V to 50V, preferably in the range of 3V to 25V.

[0064] Collision / reaction gases flow into the interference ion removal device 410 and RF and DC fields are generated, while the ion beam 407 is directed to the first ion guide 274 via the ion beam inlet lens 222. The ion beam 407 contains both target ions and background (non-target) ions. Depending on the sample being analyzed and the operating conditions of the sample introduction unit 104 and ion source 108 (Figure 1), some of the non-target ions in the ion beam 406 may become interfering ions. For example, background ions may or may not act as interfering ions for a particular type of target ion being measured. The incoming ions are accelerated to the first ion guide 274 to a kinetic energy of, for example, about 84 eV (in other words, the incoming ions are accelerated to have sufficient kinetic energy to perform CID). Considering that ions are accelerated to a kinetic energy of approximately 22 eV to the first ion guide, as described in Japanese Patent No. 7368945 (U.S. Patent No. 10290482), the ions possess approximately four times that kinetic energy. By significantly accelerating the incoming ions in this way, it becomes possible to set a high collision / reaction gas flow rate in the interfering ion removal device and increase the number of collisions, without the target ions being heated, and to selectively extract them with the DC potential barrier. Furthermore, although the velocity of each incoming ion has variation, this significant acceleration has the advantage of reducing the effect of such variation. Furthermore, in order to achieve such a significant acceleration, the first ion guide 274 is set to a large negative voltage (for example, -84V), which allows for the extraction of more ions from the first mass spectrometry unit 115 (or the ion optics unit 114 if the first mass spectrometry unit 115 is not present) compared to the apparatus of Japanese Patent No. 7368945 (U.S. Patent No. 10290482), and consequently has the advantage of improving analytical accuracy.

[0065] The incident ions are radially confined as a beam along the longitudinal axis L by the first RF field of the first ion guide 274. After entering the interference ion removal device 410 and being focused by the first RF field, polyatomic interference ions may dissociate if the internal energy converted and accumulated by one or more collisions with molecules of the collision / reaction gas is greater than the dissociation energy of the molecular ion. This is known to those skilled in the art as collision-induced dissociation (CID). The first ion guide 274 also functions as a mass filter as described above, and the dissociated ions are removed. In such CID, the dissociated ions may either escape the ion guide trap due to the impact of the collision being too strong, or they may exit the interference ion removal device 410 to the second mass spectrometer (Q2) 158B (Figure 1), but they can be removed by the mass filtering of Q2. Because collisions between polyatomic interfering ions and molecules of the collision / reaction gas are stochastic, polyatomic ions that could not be dissociated by CID are decelerated by collisions (one or more) with molecules of the collision / reaction gas. According to the principle of kinetic energy discrimination (KED), the collision cross-section of a polyatomic interfering ion (e.g., a molecular ion) is larger than that of a monatomic test ion of the same mass as the interfering ion. Therefore, the interfering ion undergoes more collisions with the collision / reaction gas and consequently loses more kinetic energy (KE) than the test ion. The size of the DC potential barrier is high enough to prevent lower-KE interfering ions from moving from the first ion guide 274 to the second ion guide 278 after collision, but low enough to allow higher-energy test ions to move from the first ion guide 274 to the second ion guide 278. In this way, the contribution of interfering ions to the mass spectral data is suppressed.

[0066] The velocity distribution of the target ions that cross the DC potential barrier and proceed to the second ion guide 278 is broader because collisions with collision / reaction gas molecules in the first ion guide 274 are probabilistic. In other words, the target ions that proceed to the second ion guide 278 include both fast and slow target ions. If fast target ions proceed to the second mass spectrometer (Q2) 158B (Figure 1) while maintaining their velocity, they may pass through the second mass spectrometer (Q2) 158B and proceed to the ion detector 161 before mass filtering is completed in the second mass spectrometer (Q2) 158B. As a result, the tail of the peak in the mass spectrum measured by the ion detector 161 broadens, and the proportion of overlap of that tail at adjacent m / z values ​​increases, leading to a deterioration in abundance sensitivity.

[0067] As mentioned above, the DC bias of the second ion guide 278 is set to be smaller in absolute value than the DC bias of the first ion guide 274. In the second ion guide, fast target ions are slowed down more significantly by collisions with the collision / reaction gas compared to slow target ions. On the other hand, slow target ions are slower than fast target ions due to collisions with the collision / reaction gas. The reason for this is that, for example, if we assume that the kinetic energy is halved in one collision, the decrease is greater for ions with higher kinetic energy than for those with lower kinetic energy (a mathematically simplified consideration). Therefore, the second ion guide 278 works to narrow the velocity distribution, which was broad when the target ions entered the second ion guide 278, at the exit of the second ion guide 278, that is, to converge it (i.e., to heat it). In other words, the velocity of each target ion becomes approximately constant at the exit of the second ion guide 278. This improves abundance sensitivity and analytical accuracy. Furthermore, the second analyzer (Q2) 458B shown in Figure 4 is equipped with a third ion guide, and the third DC potential applied to this third ion guide is negative, and can be set to -74V as an example. Moreover, as mentioned above and as shown in the DC potential plot in Figure 4, the second ion guide 278 may have an axial DC gradient. Such an axial DC gradient prevents the target ion from stalling within the second ion guide. As a result, the measurement sensitivity of the target ion in the second mass spectrometer 118 is further improved, and undesirable characteristic changes caused by the retention of the target ion or interfering ions within the second ion guide 278 can be suppressed.

[0068] Figure 5 shows an interference ion removal device 110A within the ion guide section 116 according to another embodiment. The interference ion removal device 110A is similar to the interference ion removal device 110 described above. However, a partition wall 175 divides the housing 187 into a first cell 181 housing the first ion guide 174 and a second cell 183 housing the second ion guide. The partition wall 175 also has an aperture 177 through which an ion beam can pass. A first collision / reaction gas source 138A (e.g., a pressurized reservoir) is configured to introduce a first collision / reaction gas (one or more, e.g., a mixture) into the first cell 181 via a collision / reaction gas supply conduit and port 142A that leads to the inside of the first cell 181. Furthermore, a second collision / reaction gas source 138B (e.g., a pressurized reservoir) is configured to introduce a second collision / reaction gas (one or more, e.g., a mixture) into the second cell 183 via a collision / reaction gas supply conduit and port 142B connected to the interior of the second cell 183. Here, the first collision / reaction gas and the second collision / reaction gas may be the same or different. Also, the flow rates of the first collision / reaction gas and the second collision / reaction gas may be the same or different. Advantageously, by individually optimizing the flow rates of the first collision / reaction gas responsible for interference removal by KED and CID, and the second collision / reaction gas that equalizes the ion velocity, it is possible to further improve the detection limit of the ion under test. Alternatively, the housing 187 may consist of at least two housings (not shown), the at least two housings including a first housing and a second housing. The first housing and the second housing may be arranged at a predetermined distance apart. The first housing houses the first ion guide 174, and the second housing houses the second ion guide 178. The first collision / reaction gas source (e.g., a pressurized reservoir) is configured to introduce the first collision / reaction gas (one or more, e.g., a mixture) into the interior of the first housing via collision / reaction gas supply conduits and ports connected to the interior of the first housing.Furthermore, a second collision / reaction gas source (e.g., a pressurized reservoir) is configured to introduce a second collision / reaction gas (one or more, e.g., a mixture) into the interior of the second housing via collision / reaction gas supply conduits and ports that lead to the interior of the second housing.

[0069] Figure 6 is a flowchart 600 illustrating an example of a method for operating an interference ion removal device in an exemplary inductively coupled plasma mass spectrometry (ICP-MS) system as shown in Figure 1. The collision / reaction gas is flowed into the interference ion removal device (step 602). The interference ion removal device includes an ion beam inlet, an ion beam outlet spaced longitudinally from the ion beam inlet, a first ion guide between the ion beam inlet and a second ion guide, and a second ion guide between the first ion guide and the ion beam outlet. A first RF confinement field is generated within the first ion guide (step 604), and a second RF confinement field is generated within the second ion guide (step 606). The first and second RF electric fields are configured to confine ions in the radial direction perpendicular to the longitudinal axis. The first DC potential applied to the first ion guide is greater in absolute value than the second DC potential applied to the second ion guide, and a potential barrier is formed between the first and second ion guides (step 608). There are no specific restrictions on the order in which steps 602-608 may be started, and two or more steps 602-608 may be started simultaneously or nearly simultaneously. The ion of analysis and interfering ions generated from ionizing the sample under analysis are fed into the first ion guide via the ion beam inlet (step 610). In the first ion guide, polyatomic interfering ions may dissociate (collision-induced dissociation (CID)) if the internal energy converted and accumulated by one or more collisions with molecules of the collision / reaction gas is greater than the dissociation energy of the molecular ion. The first ion guide 274 also functions as a mass filter as described above, and the dissociated ions are removed. Due to reasons such as the stochastic nature of the internal energy converted by collisions between polyatomic interfering ions and molecules of the collision / reaction gas, polyatomic ions that could not be dissociated by CID are slowed down by collisions (one or more) with molecules of the collision / reaction gas. According to the principle of kinetic energy discrimination (KED), the collision cross-section of a polyatomic interfering ion (e.g., a molecular ion) is larger than that of a monatomic ion under test of the same mass as the interfering ion.Consequently, interfering ions undergo more collisions with the collision / reaction gas and, consequently, lose more kinetic energy (KE) compared to the ion under test. The size of the DC potential barrier is set high enough to prevent lower-KE interfering ions from moving from the first ion guide 274 to the second ion guide 278 after collisions, but low enough to allow higher-energy ion under test to move from the first ion guide 274 to the second ion guide 278. The ion under test is fed from the first ion guide to the second ion guide (step 612). The DC bias of the second ion guide 278 is set to be less in absolute value than the DC bias of the first ion guide 274. The second ion guide 278 works to converge (thermalize) the broad velocity distribution of the ion under test as it enters the second ion guide 278 at its exit. The ion under test can then be analyzed by a mass spectrometer and detected and counted by a downstream ion detector.

[0070] In one embodiment, flowchart 600 may represent an interference ion removal device, or an interference ion removal device and associated electronic circuitry, or an interference ion removal device and associated ICP-MS system configured to perform steps 602 to 612. For this purpose, as will be understood by those skilled in the art, a controller (e.g., controller 120 shown in Figure 1) including a processor, memory, and other components may be provided to control the execution of steps 602 to 612 by, for example, controlling the components of the ICP-MS system required to perform steps 602 to 612 (e.g., cells, electronic circuitry, etc.).

[0071] Figure 7 is a schematic diagram of an unrestricted example of a system controller (or controller, or computing device) 120 that may be part of or communicate with a spectroscopic analysis system, such as the ICP-MS system 100 shown in Figure 1. In the illustrated embodiment, the system controller 120 includes a main electronic processor that provides overall control, and one or more electronic processors (generally electronic circuit-based) that can represent dedicated control operations or specific signal processing tasks (e.g., graphics processing unit or GPU, digital signal processor or DSP, application-specific integrated circuit or ASIC, field-programmable gate array or FPGA, etc.). The system controller 120 also includes one or more memories 704 (volatile and / or non-volatile) for storing data and / or software. The system controller 120 may also include one or more device drivers 706 for controlling one or more types of user interface devices and providing an interface between the user interface devices and components of the system controller 120 that communicate with the user interface devices. Such user interface devices may include user input devices 708 (e.g., keyboards, keypads, touchscreens, mice, joysticks, trackballs, and the like) and user output devices 710 (e.g., display screens, printers, visible indicators or alarms, audible indicators or alarms, and the like). In various embodiments, the system controller 120 may be considered to include, or at least communicate with, one or more user input devices 708 and / or user output devices 710. The system controller 120 may also include one or more types of computer programs or software 712 contained in memory and / or one or more types of computer-readable media 714.The computer program or software may include persistence instructions (e.g., logical instructions) for controlling or executing various operations of the ICP-MS system 100. The computer program or software may include application software and system software. The system software may include an operating system (e.g., Microsoft Windows® software) for controlling and managing various functions of the system controller 120, including the interaction between the hardware and the application software. In particular, the operating system may provide a graphical user interface (GUI) that is displayable via the user output device 710 and allows the user to use and interact with the user input device 708. The system controller 120 may also include one or more data acquisition / signal adjustment components (DAQs) 716 (such as those embodied in hardware, firmware, and / or software) for receiving and processing ion measurement signals output by the ion detector 161 (Figure 1), including formatted data for presentation in graphical form via the GUI.

[0072] The system controller 120 may further include a cell controller (or control module) 718 configured to control the operation of the interfering ion removal device 110 (or 410) depending on the type of ion to be tested, and to harmonize and / or synchronize the operation of the interfering ion removal device with the operation of the ion source 108, the ion optics unit 114, the first mass spectrometry unit 115, the second mass spectrometry unit 118, and any other ion processing devices provided in the ICP-MS system 100 shown in Figure 1. Thus, the cell controller 718 may be configured to control or execute all or any part of the methods disclosed herein, including methods for operating the interfering ion removal device 110. For these purposes, the cell controller 718 may be embodied in software and / or electronic circuitry (hardware and / or firmware) as will be understood by those skilled in the art.

[0073] As will be understood, Figure 7 is a high-level schematic depiction of an example of a system controller 120 consistent with the present disclosure. Other components, such as additional structures, devices, electronic circuits, and computer-related or processor-related components, may be included as required in the actual embodiment. Also as will be understood, the system controller 120 is schematically represented in Figure 7 as a functional block intended to represent the structures that may be provided (e.g., circuits, mechanisms, hardware, firmware, software, etc.). Various functional blocks and any signal links between them are arbitrarily placed for illustrative purposes only and do not limit any particular embodiment. As will be understood by those skilled in the art, in practice, the functions of the system controller 120 can be carried out in various embodiments and are not necessarily carried out in the exact embodiments shown in Figure 7 and described by example herein.

[0074] Up to this point, the interfering ion removal device 110 (or 410) has been primarily described in this disclosure as a "tandem" configuration having two stages. However, this disclosure encompasses more than two stages. That is, the interfering ion removal device 110 (or 410) may also include three or more separate ion guides and, optionally, one or more intermediate electrodes, and may generate two or more DC potential barriers. Examples

[0075] In the following embodiment, the ICP-MS system was configured as shown in Figure 1. Three conditions, A to C, were set as follows by changing the DC bias voltage settings of the first ion guide 174 and the second ion guide 178 in the interference ion removal device 110. Condition A assumes a conventional single collision / reaction cell, and the DC bias voltages of the first ion guide 174 and the second ion guide 178 are set to be approximately the same (e.g., -18V). Condition B is set to the DC bias voltage of condition A, for example, -99V, in order to promote collision-induced dissociation (CID). Condition C is set according to the present invention and is a condition that promotes CID and converges the ion velocity distribution. Table 1 below shows the selenium isotope for these conditions A to C.８０ See ＋ The sensitivity of and interfering argon 40 Ar ４０ Ar ＋ The results of measuring the detection limit (DL) to demonstrate the removal performance are shown in Table 1. As can be seen from Table 1, condition C according to the present invention yielded the best results.

[0076]

[0077] Figure 8 shows the measurement results of the abundance sensitivity in the second mass spectrometer (Q2) 158B under the conditions A to C above, when a sample with mass number M is introduced into the ICP-MS system as shown in Figure 1. The vertical axis (normalized signal intensity) in Figure 8 is logarithmic. In condition B, a large acceleration was applied to the ions to promote CID, resulting in a deterioration of the performance of the subsequent mass separator, and the tails on both sides of the peak for mass number M overlap with the adjacent mass numbers M+1 and M-1, causing interference. Condition C according to the present invention, while promoting CID in the same way as condition B, narrows the velocity distribution, resulting in good results almost equivalent to condition A, which does not apply a large initial acceleration. In condition A (the current method without using CID) ８０ See ＋ Argon interfering with 40 Ar ４０ Ar ＋ Because the interference cannot be decomposed and removed, the DL is very high as shown in Table 1, resulting in inferior analytical performance. The present invention (condition C), which focuses energy after performing CID, achieves abundance sensitivity close to condition A, which does not use the conventional method of CID, while simultaneously achieving interference removal performance comparable to condition B, which promotes CID.

[0078] Figure 9 is a histogram of the predicted energy distribution when ions enter the interference ion removal device 110 and reach the second mass spectrometer (Q2) 158B, under the assumption that ions lose a certain percentage of their axial kinetic energy due to collisions with the collision gas in the interference ion removal device 110. It is believed that the fewer high-energy ions there are among the ions entering the second mass spectrometer (Q2) 158B, the more effective the mass filtering becomes and the better the abundance sensitivity. Therefore, comparing the results above +20 eV under conditions A to C, condition C according to the present invention yielded significantly fewer high-energy components compared to condition B. Condition A had even fewer high-energy components, supporting the result in Figure 8 where condition A had slightly better abundance sensitivity than condition C. Furthermore, under condition C, by moving the DC bias voltage of the second mass spectrometer (Q2) 158B in the direction of decreasing its absolute value, there is room to further improve the filtering performance at the expense of a slight decrease in sensitivity. With appropriate adjustment, it is possible to create analytical conditions that are superior to condition A in terms of sensitivity, abundance sensitivity, and interference rejection performance.

[0079] To be understood, one or more of the processes, subprocesses, and process steps described herein may be executed on one or more electronically controlled or digitally controlled devices by hardware, firmware, software, or a combination of two or more thereof. The software may reside in software memory (not shown) in a suitable electronic processing component or system, such as the computing device 120 schematically shown in Figure 1. The software memory may contain an ordered list of executable instructions for performing a logical function (i.e., “logical” may be performed in a digital form such as a digital circuit or source code, or in an analog form such as an analog source such as an analog electrical signal, an audio signal, or a video signal). The instructions may be executed within a processing module including, for example, one or more microprocessors, general-purpose processors, combinations of processors, a digital signal processor (DSP), a field-programmable gate array (FPGA), or an application-specific integrated circuit (ASIC). Furthermore, schematic diagrams describe the logical portion of a function having a physical (hardware and / or software) embodiment that is not limited by the structure or physical layout of the function. The system examples described herein can be implemented in various configurations and can operate as a single hardware / software unit or as a hardware / software component of separate hardware / software units.

[0080] An executable instruction can be realized as a computer program product having internally stored instructions that, when executed by a processing module of an electronic system (e.g., computing device 120 in Figure 1), instruct the electronic system to execute the instruction. The computer program product can be selectively realized in any persistent computer-readable storage medium for use by or connected to an instruction execution system, apparatus, or device, such as an electronic computer-based system, a processor-integrated system, or other system that can selectively fetch instructions from an instruction execution system, apparatus, or device and execute said instructions. In the context of this disclosure, a computer-readable storage medium is any persistent means capable of storing a program for use by or associated with an instruction execution system, apparatus, or device. A persistent computer-readable storage medium can, in part, be an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. A less comprehensive list of more specific examples of persistent computer-readable media includes: electrical connections having one or more wires (electronic); portable floppy disks (magnetic); random-access memory (electronic); read-only memory (electronic); erasable programmable ROM (electronic), such as flash memory; compact disc memory (optical), such as CD-ROM, CD-R, and CD-RW; and digital multi-purpose disc memory, i.e., DVD (optical). It should be noted that persistent computer-readable storage media can even be printed paper or another suitable medium, where the program can be electronically captured, for example, by optical scanning of paper or other medium, then compiled, interpreted, or processed in an appropriate manner as necessary, and then stored in computer memory or machine memory.

[0081] Furthermore, as should be understood, terms such as “communicate” and “communicate with” (for example, “the first component communicates with” or “communicates with” the second component) are used herein to describe structural, functional, mechanical, electrical, signaling, optical, magnetic, electromagnetic, ionic, or fluidic relationships between two or more components or elements. Thus, the fact that one component is said to communicate with a second component is not intended to preclude the possibility that an additional component may exist between the first and second components and / or may be operably associated with or coupled with the first and second components.

[0082] As can be understood, various aspects or details of the present invention may be modified without departing from the scope of the invention. Furthermore, the above description is for illustrative purposes only and not limiting purposes, and the present invention is defined by the claims. Explanation of Symbols

[0083] 100 Inductively Coupled Plasma Mass Spectrometry (ICP-MS) System 104 Sample Introduction Unit 108 Ion Source 110, 410 Interfering Ion Removal Device 112 Interface Unit 114 Ion Optics Unit 115, 118 Mass Spectrometry Unit 116 Ion Guide Unit 120 System Controller 122, 222 Ion Beam Inlet Lens 124, 224 Ion Beam Exit Lens 138, 138A, 138B Collision / Reaction Gas Source 158A, 158B, 458A, 458B Mass Spectrometer 174, 274 First Ion Guide 175 Partition 177 Aperture 178, 278 Second Ion Guide 187 Housing 203 First Ion Guide Electrode 205 Second Ion Guide Electrode

Claims

1. An interference ion removal device comprising: a housing including an ion beam inlet, an ion beam outlet spaced longitudinally from the ion beam inlet, and a gas supply port communicating with the interior; and at least two ion guides disposed within the housing, the at least two ion guides comprising a first ion guide and a second ion guide, wherein the first ion guide is configured to generate a first RF confinement field that confines ions radially and is subjected to a first DC potential; the second ion guide is configured to generate a second RF confinement field that confines ions radially and is subjected to a second DC potential; the first DC potential applied to the first ion guide is greater in absolute value than the second DC potential applied to the second ion guide, and a DC potential barrier is formed between the first ion guide and the second ion guide.

2. In the first ion guide, interfering ions collide with the collision / reaction gas and dissociate or lose kinetic energy, and the ions under test collide with the collision / reaction gas and lose kinetic energy, and the DC potential barrier is high enough to prevent interfering ions that have not dissociated from leaving the first ion guide and low enough to allow the ions under test to leave the first ion guide, and in the second ion guide, the collision with the collision / reaction gas causes the high-speed ions among the ions under test to be significantly slowed down compared to the low-speed ions, thereby converging the ion velocity distribution of the ions under test, as described in claim 1.

3. The interference ion removal device according to claim 1 or 2, further comprising a controller, the controller configured to apply a first RF potential superimposed on a first DC potential to the electrodes of the first ion guide to generate the first RF confinement field, and to apply a second RF potential superimposed on a second DC potential to the electrodes of the second ion guide to generate the second RF confinement field.

4. The interference ion removal device according to any one of claims 1 to 3, wherein the second DC potential has a longitudinal axial DC potential gradient along the length of the second ion guide.

5. The interference ion removal device according to claim 4, wherein the second DC potential has a potential gradient of -50 V / m to 100 V / m.

6. The interference ion removal device according to any one of claims 1 to 5, wherein the first ion guide and the second ion guide are multipolar ion guides.

7. The interference ion removal device according to claim 6, wherein one or both of the first ion guide and the second ion guide are quadrupole ion guides.

8. The first ion guide and the second ion guide function as follows: 1) by applying a first RF potential superimposed on a first DC potential to the electrodes of the first ion guide; 2) by applying a second RF potential superimposed on a second DC potential to the electrodes of the second ion guide; 3) the first ion guide includes a plurality of elongated first ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced circumferentially apart from each other around the longitudinal axis; 4) the second ion guide includes a plurality of elongated second ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced circumferentially apart from each other around the longitudinal axis, and the second ion guide is separated from the first ion guide by a longitudinal axis gap. An interference ion removal device according to any one of claims 1 to 7, having a configuration selected from the group consisting of: 5) the first ion guide includes a plurality of elongated first ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced circumferentially apart from each other around the longitudinal axis, and a first auxiliary electrode arranged circumferentially between each of the first ion guide electrodes; and 6) the second ion guide includes a plurality of elongated second ion guide electrodes arranged at radial distances perpendicular to the longitudinal axis and spaced circumferentially apart from each other around the longitudinal axis, and a second auxiliary electrode arranged circumferentially between each of the second ion guide electrodes, wherein the second ion guide is separated from the first ion guide by a longitudinal axis gap.

9. The interference ion removal device according to claim 3, wherein the first DC potential is in the range of -50V to -200V, and the second DC potential is positively offset from the first DC potential by +0.1V to +50V.

10. The interfering ion removal device according to any one of claims 1 to 9, wherein the housing is divided by a partition wall into a first cell housing the first ion guide and a second cell housing the second ion guide, the partition wall having an aperture through which an ion beam can pass, the first cell including a first gas supply port communicating with the interior of the first cell, and the second cell including a second gas supply port communicating with the interior of the second cell.

11. The interfering ion removal device according to any one of claims 1 to 9, wherein the housing comprises at least two housings, the at least two housings comprising a first housing and a second housing, the first housing comprising a first ion guide and a first gas supply port, and the second housing comprising a second ion guide and a second gas supply port.

12. A mass spectrometry system comprising an interference ion removal device, the interference ion removal device comprising a housing including an ion beam inlet, an ion beam outlet spaced longitudinally from the ion beam inlet, and a gas supply port communicating with the interior, and at least two ion guides disposed within the housing, the at least two ion guides comprising a first ion guide and a second ion guide, wherein the first ion guide is configured to generate a first RF confinement field for radially confining ions and is subjected to a first DC potential, the second ion guide is configured to generate a second RF confinement field for radially confining ions and is subjected to a second DC potential, the first DC potential applied to the first ion guide is greater in absolute value than the second DC potential applied to the second ion guide, and a DC potential barrier is formed between the first ion guide and the second ion guide.

13. The mass spectrometry system according to claim 12, further comprising a controller, the controller configured to apply a first RF potential superimposed on a first DC potential to the electrode of the first ion guide to generate the first RF confinement field, and to apply a second RF potential superimposed on a second DC potential to the electrode of the second ion guide to generate the second RF confinement field.

14. The mass spectrometry system according to claim 12 or 13, further comprising an ion source in contact with the ion beam inlet, wherein the ion source comprises a plasma torch.

15. The mass spectrometry system according to any one of claims 12 to 14, further comprising a first mass spectrometer configured to receive an ion beam from the ion beam outlet, wherein the first mass spectrometer includes a third ion guide electrode configured to filter ions in the ion beam by m / z ratio.

16. The mass spectrometry system according to claim 15, further comprising a second mass spectrometer between the ion source and the interfering ion removal device.

17. A method for operating an interfering ion removal device in a mass spectrometry system, comprising: flowing a collision / reaction gas into the interfering ion removal device, the interfering ion removal device comprising a housing including an ion beam inlet, an ion beam outlet spaced longitudinally from the ion beam inlet, a first ion guide between the ion beam inlet and a second ion guide, and a second ion guide between the first ion guide and the ion beam outlet, wherein a first RF confinement field is generated in the first ion guide to confine ions radially, a second RF confinement field is generated in the second ion guide to confine ions radially, a DC potential barrier is generated between the first ion guide and the second ion guide, the DC potential barrier is formed by making a first DC potential applied to the first ion guide greater in absolute value than a second DC potential applied to the second ion guide. A method comprising sending the ions to be tested and interfering ions to the first ion guide via the ion beam inlet, wherein the ions to be tested and the interfering ions are generated from ionizing a sample to be analyzed, the interfering ions dissociate or lose kinetic energy by colliding with the collision / reaction gas, the ions to be tested lose kinetic energy by colliding with the collision / reaction gas, the DC potential barrier is high enough to prevent undissociated interfering ions from leaving the first ion guide and low enough to allow the ions to be tested to leave the first ion guide, and sending the ions to be tested from the first ion guide to the second ion guide, wherein in the second ion guide, the high-speed ions among the ions to be tested are significantly slowed down compared to the low-speed ions by collision with the collision / reaction gas, and the ion velocity distribution of the ions to be tested is converged.

18. The method according to claim 17, wherein the magnitude of the DC potential barrier is in the range of 0.1V to 50V.

19. The method according to claim 17, wherein the second DC potential has an axial DC potential gradient along the length of the second ion guide.

20. The method according to claim 19, wherein the second DC potential has a potential gradient of -50 V / m to 100 V / m.

21. 1) To generate the first RF confinement field, a first RF potential superimposed on a first DC potential is applied to the electrode of the first ion guide; to generate the second RF confinement field, a second RF potential superimposed on a second DC potential is applied to the electrode of the second ion guide; 2) To generate the first RF confinement field, a first RF potential superimposed on a first DC potential is applied to the electrode of the first ion guide; to generate the second RF confinement field, a second RF potential superimposed on a second DC potential is applied to the electrode of the second ion guide, and the first DC potential and the second DC potential are negative. 3) In order to generate the first RF confinement field, a first RF potential superimposed on a first DC potential is applied to the electrode of the first ion guide, and in order to generate the second RF confinement field, a second RF potential superimposed on a second DC potential is applied to the electrode of the second ion guide, and the first DC potential is in the range of -50V to -200V. 4) In order to generate the first RF confinement field, a first RF potential superimposed on a first DC potential is applied to the electrode of the first ion guide, and in order to generate the second RF confinement field, a second RF potential superimposed on a second DC potential is applied to the electrode of the second ion guide, and the second DC potential is positively offset from the first DC potential by +0.1V to +50V. 5) To generate the first RF confinement field, a first RF potential superimposed on a first DC potential is applied to the electrode of the first ion guide; to generate the second RF confinement field, a second RF potential superimposed on a second DC potential is applied to the electrode of the second ion guide, and the first DC bias potential is constant along the length of the first ion guide; 6) To generate the first RF confinement field, a first RF potential superimposed on a first DC potential is applied to the electrode of the first ion guide; to generate the second RF confinement field, a second RF potential superimposed on a second DC potential is applied to the electrode of the second ion guide, and the second DC potential has an axial DC potential gradient along the length of the second ion guide; and 7) Two or more combinations of the above;The method according to any one of claims 17 to 20, comprising a step selected from the group consisting of the following.

22. The method according to any one of claims 17 to 21, wherein the interfering ion removal device is divided by a partition into a first cell housing the first ion guide and a second cell housing the second ion guide, the partition having an aperture through which an ion beam can pass, and the method comprises flowing a first collision / reaction gas into the first cell and flowing a second collision / reaction gas into the second cell, or the housing of the interfering ion removal device comprises at least two housings, the at least two housings comprising a first housing and a second housing, the first housing comprising the first ion guide and a first gas supply port, and the second housing comprising the second ion guide and a second gas supply port, and the method comprises flowing a first collision / reaction gas into the first housing and flowing a second collision / reaction gas into the second housing.

23. The method according to claim 22, wherein the first collision / reaction gas is the same as the second collision / reaction gas, or the first collision / reaction gas is different from the second collision / reaction gas, and the inflow velocity of the first collision / reaction gas is the same as the inflow velocity of the second collision / reaction gas, or the inflow velocity of the first collision / reaction gas is different from the inflow velocity of the second collision / reaction gas.

24. The method according to any one of claims 17 to 23, comprising performing an operation selected from the group consisting of: 1) generating the ions to be tested by exposing the sample to inductively coupled plasma before sending the ions to be tested to the interference ion removal device via the ion beam inlet; 2) generating the ions to be tested by exposing the sample to inductively coupled plasma generated by operating a plasma torch; and 3) generating the ions to be tested by flowing the sample from a nebulizer or spray chamber to a plasma torch and exposing the sample to inductively coupled plasma generated by operating the plasma torch.

25. A computer program comprising computer-executable instructions configured to cause a processor of a mass spectrometry system to perform a procedure according to any one of claims 17 to 24.

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