Inductively coupled plasma mass spectrometry (ICP-MS) with improved signal-to-noise ratio and signal-to-background ratio

Abstract

The invention relates to inductively coupled plasma mass spectrometry (ICP-MS) with improved signal-to-noise ratio and signal-to-background ratio. In an inductively coupled plasma mass spectrometry (ICP-MS) system, ions are transmitted into a collision / reaction cell. A DC potential of a first magnitude is applied at the exit of the cell to create a DC barrier effective to prevent ions from exiting the cell. The DC potential barrier is maintained to perform the interaction during the limiting period. After the confinement period, the analyte ions or product ions are transmitted to the mass spectrometer by switching the outlet DC potential to a second magnitude effective to allow the analyte ions or product ions to pass through the cell outlet as pulses. The analyte ions or product ions are then counted during the measurement period. The interaction may be an ion-molecule reaction or an ion-molecule collision.

Description

[0001] This application is a divisional application of an invention patent application with an application date of March 18, 2019, application number 201910203635.4, and invention name “Inductively coupled plasma mass spectrometry (ICP-MS) with improved signal-to-noise ratio and signal-to-background ratio”.

[0002] Related Applications

[0003] according to This application claims priority to U.S. Provisional Patent Application Serial No. 62 / 644,896, filed on March 19, 2018, entitled “Inductively Coupled Plasma Mass Spectrometry (ICP-MS) with Improved Signal-to-Noise and Signal-to-Background Ratios,” the contents of which are incorporated herein by reference in their entirety. Technical Field

[0004] The present invention relates generally to inductively coupled plasma mass spectrometry (ICP-MS), and in particular to ICP-MS utilizing a collision / reaction cell. Background Art

[0005] Inductively coupled plasma mass spectrometry (ICP-MS) is generally used for elemental analysis of samples, such as measuring the concentration of trace metals in samples. The ICP-MS system includes a plasma-based ion source, which is used to generate plasma to decompose the molecules of the sample into atoms, and then ionize the atoms to prepare for elemental analysis. In typical operation, the liquid sample is atomized by a nebulizer (usually pneumatic assisted), that is, converted into an aerosol (fine mist or spray), and the aerogelized sample is introduced into the plasma plume (plasma plume) generated by the plasma source. The plasma source is generally configured as a flow-through plasma torch with two or more concentric tubes. Typically, a plasma-forming gas (such as argon) flows through the outer tube of the torch and is activated into a plasma by a suitable energy source (usually a load coil powered by radio frequency (RF)). The aerosolized sample flows through the coaxial central tube (or capillary) of the plasma torch and is emitted into the plasma originally generated. Exposure to plasma decomposes the sample molecules into atoms, or partially decomposes the sample molecules into molecular fragments, and ionizes the atoms or molecular fragments.

[0006] The resulting analyte ions, which are usually positively charged, are extracted from the plasma source and directed into a mass analyzer as an ion beam. The mass analyzer applies a time-varying electric field or a combination of an electric field and a magnetic field to spectrally distinguish ions of different masses according to their mass-to-charge ratio (m / z), so that the ion detector can then count each type of ion of a given m / z ratio that arrives at the ion detector from the mass analyzer. Alternatively, the mass analyzer can be a time-of-flight (TOF) analyzer that measures the flight time of ions drifting through a flight tube, from which the m / z ratio can then be derived. The ICP-MS system then presents the data obtained as a spectrum of mass spectrometry (m / z ratio) peaks. The intensity of each peak represents the concentration (abundance) of the corresponding element of the sample.

[0007] In addition to the analyte ions sought to be analyzed, the plasma also produces background (non-analyte) ions. Certain types of non-analyte ions (called interfering ions) can interfere with the analysis of certain types of analytes. Interfering ions can be produced by plasma-forming gases (such as argon), matrix components of the sample, solvents / acids contained in the sample, or air (oxygen and nitrogen) entrained into the system. For example, an interfering ion can be an isobaric interferent with the same nominal mass as the analyte ion. Detection of such an interfering ion at the same time as a certain analyte ion can result in spectral overlap in the analytical data, thereby reducing the quality of the analysis. Examples of interfering ions include polyatomic ions, such as interfering iron isotopes. 56 Fe + Argon oxide ( 40 Ar 16 O + ) (because both ions show up as m / z = 56 in the mass spectrum) and interfering calcium isotopes 40 Ca + Argon 40 Ar + (Since both ions are shown as m / z=40).

[0008] The known methods for solving the problem of spectral interference and improving the performance of ICP-MS systems involve improving matrix separation, using cold plasma technology and using mathematical correction equations in the processing of analytical data. These methods have known limitations. In order to further solve this problem, it is also known to provide a collision / reaction unit between the ion source and the mass analyzer in the ICP-MS system. The unit includes an ion guide that focuses the ion beam along the central axis of the unit. The unit is filled with collision gas or reaction gas. The use of collision gas (e.g., helium, He) depends on kinetic energy discrimination (KED), which can suppress polyatomic ion interference. The analyte ions and polyatomic interfering ions in the unit all collide with the collision gas molecules for many times, and lose kinetic energy (KE), so they slow down. However, because polyatomic ions have a larger cross section than analyte ions, polyatomic interfering ions experience more collisions and therefore lose more kinetic energy than analyte ions. Such as by biasing the quadrupole electrode of the mass analyzer outside the collision / reaction unit to a few volts more positively than the ion guide of the unit to produce a direct current (DC) barrier of positive magnitude. The magnitude of the DC barrier is set high enough to prevent low energy interfering ions from entering the mass analyzer, but low enough to allow higher energy analyte ions to enter the mass analyzer without interfering ions. In this way, the contribution of interfering ions to the mass spectral data is suppressed.

[0009] Alternatively, the unit is full of reaction gas. According to the chemical property of reaction gas, the reaction gas used is selected to react with interfering ions or analyte ions. In the case of reacting with interfering ions, the reaction converts interfering ions into non-interfering ions (by changing the mass of interfering ions into the mass that does not interfere with the mass of analyte ions) or neutralizes the interfering ions. In the case of reacting with analyte ions, the reaction actually transfers the mass of analyte ions to a higher mass by forming the product ions that the original interfering ions cannot interfere. In all these cases, the unit is full of reaction gas of certain pressure, to obtain the reaction efficiency enough with interfering ions or analyte ions. However, from one element to another element, optimum pressure (or gas density) changes usually. Therefore, when measuring different elements, the flow velocity of reaction gas must be changed, so as to obtain the good signal / background (S / B) ratio of every kind of element.

[0010] Therefore, there remains a need for improved ICP-MS systems and methods of operating the same to address interference issues. Summary of the invention

[0011] To fully or partially solve the above problems and / or other problems that may have been observed by those skilled in the art, the present disclosure provides methods, processes, systems, devices, instruments and / or apparatus as described by examples in the embodiments set forth below.

[0012] According to one embodiment, a method for operating a collision / reaction cell to suppress interferences in an inductively coupled plasma mass spectrometry (ICP-MS) system includes: flowing a collision / reaction gas into a collision / reaction cell, the collision / reaction cell including an inlet, an outlet, and a multipole ion guide located between the inlet and the outlet; transmitting ions through the inlet and into the collision / reaction cell; applying an outlet DC potential at a first magnitude at the outlet to produce a DC barrier that effectively prevents ions from leaving the collision / reaction cell; maintaining the outlet DC potential at the first magnitude during a confinement period; after the confinement period, transmitting analyte ions or product ions generated from the analyte ions to a mass spectrometer by switching the outlet DC potential to a second magnitude that effectively allows the analyte ions or product ions to pass through the outlet as a pulse with a pulse duration; and measuring the analyte ions or product ions during a measurement period having a duration approximately equal to the pulse duration.

[0013] In an embodiment, the method includes performing the interaction between collision / reaction gas and ion during the restricted period. The interaction can be an interaction that effectively suppresses the interfering ion signal intensity (which can be measured by a mass spectrometer). The interaction can be an ion-molecule reaction and / or an ion-molecule collision. Therefore, in one embodiment, the interaction relates to reacting the interfering ion with the collision / reaction gas according to the reaction that effectively converts the interfering ion into a non-interfering ion or a neutral substance, and causing the analyte ion to collide with the collision / reaction gas multiple times to effectively slow down and limit the analyte ion in the collision / reaction unit. In another embodiment, the interaction relates to reacting the analyte ion with the collision / reaction gas according to the reaction that effectively produces the product ion, and causing the product ion to collide with the collision / reaction gas multiple times to effectively slow down and limit the product ion in the collision / reaction unit.

[0014] According to another embodiment, a method for operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system includes: flowing a collision / reaction gas into a collision / reaction cell configured according to any embodiment disclosed herein; transmitting ions through an inlet and into the collision / reaction cell; applying an outlet DC potential at a first magnitude at an outlet to produce a DC barrier that effectively prevents ions from leaving the collision / reaction cell; maintaining the outlet DC potential at the first magnitude during a confinement period; during the confinement period, causing the ions to collide with the collision / reaction gas, wherein the ions undergo multiple collisions to effectively slow down and confine the ions in the collision / reaction cell; after the confinement period, transmitting at least analyte ions of the confined ions or product ions generated from the analyte ions to a mass spectrometer by switching the outlet DC potential to a second magnitude that effectively allows the analyte ions or product ions to pass through the outlet as a pulse with a pulse duration; and measuring the analyte ions or product ions during a measurement period having a duration approximately equal to the pulse duration.

[0015] According to another embodiment, a method for analyzing a sample includes: generating analyte ions from the sample; transmitting the analyte ions to a collision / reaction cell configured according to any embodiment disclosed herein; operating the collision / reaction cell according to any method disclosed herein; and transmitting the analyte ions to a mass analyzer of a mass spectrometer.

[0016] According to another embodiment, an inductively coupled plasma mass spectrometry (ICP-MS) system includes: an ion source configured to generate a plasma and generate analyte ions in the plasma; a collision / reaction cell including an inlet configured to receive analyte ions from the ion source, an outlet spaced apart from the inlet along a longitudinal axis of the collision reaction cell, and a multipole ion guide located between the inlet and the outlet and configured to confine ions in a radial direction perpendicular to the longitudinal axis; a mass spectrometer in communication with the outlet; and a controller including an electronic processor and a memory and configured to control operations including: causing the collision / reaction cell to generate analyte ions; The invention relates to a method for transmitting ions through an inlet and into the collision / reaction cell; applying an outlet DC potential at a first magnitude to produce a DC barrier effective to prevent ions from leaving the collision / reaction cell; maintaining the outlet DC potential at the first magnitude during a confinement period; after the confinement period, transmitting analyte ions or product ions generated from the analyte ions to a mass spectrometer by switching the outlet DC potential to a second magnitude effective to allow the analyte ions or product ions to pass through the outlet as a pulse having a pulse duration; and measuring the analyte ions or product ions during a measurement period having a duration approximately equal to the pulse duration.

[0017] In an embodiment, a controller of the ICP-MS system is configured to control the interaction during the confinement period. In one embodiment, the interaction involves reacting the interfering ions with the collision / reaction gas according to a reaction effective to convert the interfering ions into non-interfering ions or neutral species, and causing the analyte ions to collide with the collision / reaction gas multiple times to effectively slow down and confine the analyte ions in the collision / reaction cell. In another embodiment, the interaction involves reacting the analyte ions with the collision / reaction gas according to a reaction effective to produce product ions, and causing the product ions to collide with the collision / reaction gas multiple times to effectively slow down and confine the product ions in the collision / reaction cell.

[0018] According to another embodiment, an inductively coupled plasma mass spectrometry (ICP-MS) system includes: an ion source, the ion source being configured to generate a plasma and to produce analyte ions in the plasma; a collision / reaction cell according to any embodiment disclosed herein; and a controller, the controller including an electronic processor and a memory and being configured to control the steps of any method disclosed herein.

[0019] Other devices, apparatus, systems, methods, features and advantages of the present invention will be or will become apparent to those skilled in the art by studying the following drawings and detailed description. It should be noted that all such additional systems, methods, features and advantages are included in this description, within the scope of the present invention, and protected by the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention may be better understood by referring to the following drawings. The components in the drawings are not necessarily drawn to scale, but emphasis is placed on illustrating the principles of the present invention. In the drawings, the same reference numerals represent corresponding parts in different views.

[0021] Figure 1 is a schematic diagram of an example of an inductively coupled plasma mass spectrometry (ICP-MS) system according to an embodiment of the present disclosure.

[0022] Figure 2 is a schematic perspective view of an example of an ion guide for a collision / reaction cell according to an embodiment of the present disclosure.

[0023] Figure 3 yes Figure 2 Schematic side (longitudinal) view of the ion guide shown in .

[0024] Figure 4 Shown is the pulse peak value, defined as the ion intensity (in counts per second, or cps) I, as a function of the measurement time (in ms) t, as can be measured by a mass spectrometer.

[0025] Figure 5A Schematic diagram showing an ion guide and a cell exit lens of a collision / reaction cell and a DC potential along the axial length of the ion guide and up to the cell exit lens during a confinement period according to an embodiment of the present disclosure.

[0026] Figure 5B The embodiment according to the present disclosure is shown Figure 5A Schematic diagram of the same collision / reaction cell shown in and the DC potential during the measurement period.

[0027] Fig. 6A is a set of curves representing ion pulses generated from a collision / reaction cell as described herein filled with oxygen, with Co implanted during a confinement period and a subsequent measurement period in accordance with the present disclosure. + , Y + and Tl + ions into the collision / reaction cell.

[0028] Figure 6B Yes means Fig. 6A A set of curves for the trailing edge of the ion pulse shown in .

[0029] Figure 7 is a set of curves showing the following: m / z = 40 from a 0.1 ppb calcium solution in a collision / reaction cell 40 Ca + Ion signal intensity (in cps) as a function of ion confinement duration (or storage time or reaction time in ms), interfering background ions from deionized water (DIW) or blank ( 40 Ar + ion) strength as a function of the duration of ion confinement and the calculated background equivalent concentration or BEC (in ppt) as a function of the duration of ion confinement.

[0030] Figure 8 A flow chart illustrating an example of a method for operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system according to an embodiment of the present disclosure is shown.

[0031] Fig. 9 is a schematic diagram of an example of a system controller (or controller or computing device) that may be a system controller for a spectrometric system such as Figure 1 Part of or in communication with the ICP-MS system shown in FIG.

[0032] Fig.10 is a schematic diagram of an example of an inductively coupled plasma mass spectrometry (ICP-MS) system according to another embodiment of the present disclosure, particularly a system having a triple quadrupole (QQQ) configuration.

[0033] Fig.11 is when unpurified or purified ambient air is introduced into Fig.10 In the reaction unit of the ICP-MS system shown, 40 Ar + Plot of two spectra of ionic intensities (in cps) of product ions (m / z) produced by reactions with components of unpurified ambient air and purified ambient air, respectively.

[0034] Fig.12 A flow chart illustrating an example of a method for operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system according to another embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0035] As used herein, the term "fluid" is used in a general sense to refer to any material that can flow through a conduit. Thus, unless otherwise specified or the context dictates otherwise, the term "fluid" may generally refer to a liquid or a gas.

[0036] As used herein, the term "liquid" may generally refer to a solution, a suspension, or an emulsion. Solid particles and / or gas bubbles may be present in the liquid.

[0037] As used herein, the term "aerosol" generally refers to an assembly of liquid droplets and / or solid particles suspended in a gaseous medium. The size of aerosol droplets or particles is generally in the order of micrometers (μm). See Kulkarni et al., Aerosol Measurement, 3rd edition, John Wiley & Sons, Inc. (2011), p. 821. Thus, an aerosol can be considered to include liquid droplets and / or solid particles and gases that entrain or carry the liquid droplets and / or solid particles.

[0038] As used herein, the term "atomization" refers to the process of breaking molecules into atoms. Atomization can be performed, for example, in a plasma-enhanced environment. In the case of a liquid sample, "atomization" may require atomizing the liquid sample to form an aerosol, which is then exposed to a plasma or heat from the plasma.

[0039] As used herein, a "liquid sample" includes one or more different types of target analytes dissolved or otherwise carried in a liquid matrix. The liquid matrix includes a matrix component. Examples of "matrix components" include, but are not limited to, water and / or other solvents, acids, soluble substances (such as salts) and / or dissolved solids, insoluble solids or particles, and any other compounds that are not of analytical interest.

[0040] For convenience in this disclosure, unless otherwise specified or the context requires otherwise, a "collision / reaction cell" refers to a collision cell, a reaction cell, or a collision / reaction cell that is configured to function as both a collision cell and a reaction cell, for example by being switchable between a collision mode and a reaction mode.

[0041] For convenience in this disclosure, unless otherwise specified or the context dictates otherwise, "collision / reaction gas" refers to an inert collision gas used to collide with ions in a collision / reaction cell without reacting with these ions, or a reaction gas used to react with analyte ions or interfering ions in a collision / reaction cell.

[0042] As used herein, the term "analyte ion" generally refers to any ion produced by ionizing a component of a sample that is to be analyzed by an inductively coupled plasma mass spectrometry (ICP-MS) system and for which mass spectral data is sought. In the specific context of ICP-MS, the analyte ion is generally a positive monatomic ion of a metal or other element other than a noble (precious) gas (e.g., argon), or a product ion produced by reacting a collision / reaction gas with a positive monatomic ion of a metal or other element other than a noble gas.

[0043] As used herein, the term "interfering ion" generally refers to any ion present in a mass spectrometry system that interferes with the analyte ion. Examples of interfering ions include, but are not limited to, positive plasma (e.g., argon) ions, polyatomic ions containing plasma-forming gases (e.g., argon), and doubly charged, isobaric, and polyatomic ions containing sample components. The components of the sample can be analyte elements or non-analyte substances, such as matrix components or other background substances that can be derived from the sample.

[0044] Figure 1 1 is a schematic diagram of an example of an inductively coupled plasma mass spectrometry (ICP-MS) system 100 according to an embodiment. In general, the structure and operation of the various components of an ICP-MS system are known to those skilled in the art and are therefore only briefly described herein as necessary for understanding the disclosed subject matter.

[0045] In this illustrative embodiment, the ICP-MS system 100 generally includes a sample introduction portion 104, an ion source 108, an interface portion 112, an ion optical portion 114, an ion guide portion 116, a mass analysis portion 118, and a system controller 120. The ICP-MS system 100 also includes a vacuum system that is 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 in doing so removes neutral molecules that are not of analytical interest from the ICP-MS system 100. The vacuum system includes appropriate pumps and passages that communicate with ports of the region to be evacuated, such as Figure 1 As shown by arrows 128, 132 and 136 in FIG.

[0046] The sample introduction part 104 may include a sample source 140 for providing a 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 sample supply conduit 152 for supplying the sample to the ion source 108, which may include a suitable sample syringe. The nebulizer 148 may, for example, utilize a flow of argon or other inert gas (nebulizer gas) from a gas source 156 (e.g., a pressurized reservoir) to aerosolize the sample, as shown by a downward arrow. The nebulizer gas may be the same gas as the plasma-forming gas used to generate plasma in the ion source 108, or may be a different gas. A pump 144 (e.g., a peristaltic pump, a syringe pump, etc.) is connected between the sample source 140 and the nebulizer 148 to establish a liquid sample flow to the nebulizer 148. The sample flow rate may be, for example, in the range of 0.1 milliliters per minute (mL / min) to several mL / min. The sample source 140 may, for example, include one or more vials. The plurality of vials may include one or more samples, various standard solutions, conditioning solutions, calibration solutions, flushing solutions, etc. The sample source 140 may include an automated device configured to switch between different vials so that a specific vial can be selected for current use in the ICP-MS system 100.

[0047] In another embodiment, the sample can be a gas and nebulizer 148 is not required. In another embodiment, sample source 140 can be or include a pressurized reservoir containing a liquid or gas sample, and pump 144 is not required. In another embodiment, sample source 140 can be the output of an analytical separation instrument such as a liquid chromatography (LC) instrument or a gas chromatography (GC) instrument. Other types of devices and means for introducing samples into an ICP-MS system are known and need not be described here.

[0048] The ion source 108 includes a plasma source for atomizing and ionizing a sample. In the illustrated embodiment, the plasma source is a flow-through plasma torch, such as an ICP torch 160. The ICP torch 160 includes a center 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, the intermediate tube 168, and the outermost tube 172 can be made of, for example, quartz, borosilicate glass, or ceramic. Alternatively, the sample injector 164 can be made of a metal (such as platinum). The ICP torch 160 is located in an ionization chamber (or "torch box") 176. The working coil 180 (also referred to as a load coil or RF coil) is coupled to a radio frequency (RF) power source 185 and is positioned at the discharge end of the ICP torch 160.

[0049] In operation, the gas source 156 supplies a plasma-forming gas to the outermost tube 172. The plasma-forming gas is typically, but not necessarily, argon. As the plasma-forming gas flows through the annular channel formed between the intermediate tube 168 and the outermost tube 172, RF power is applied to the working coil 180 by the RF power supply 185, thereby generating a high-frequency, high-energy electromagnetic field to which the plasma-forming gas is exposed. The working coil 180 operates at a frequency and power effective for generating and maintaining a plasma from the plasma-forming gas. A spark may be utilized to provide seed electrons for initially striking the plasma. Thus, a plasma plume 184 flows from the discharge end of the ICP torch 160 into the sampling cone 188. An auxiliary gas may flow through the 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 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. In Figure 1 1 and 17. The introduction of gas into the intermediate tube 168 and the outermost tube 172 is depicted in FIG. 1 by arrows pointing upward from the gas source 156. The sample flows through and is emitted from the sample injector 164 and is injected into the active plasma 184 as indicated by arrows 186. As the sample flows through the heated zone of the ICP torch 160 and ultimately interacts with the plasma 184, the sample undergoes drying, evaporation, atomization, and ionization, and analyte ions are generated from components (particularly atoms) of the sample according to principles understood by those skilled in the art.

[0050] The interface portion 112 provides a first depressurization stage between the ion source 108, which typically operates at or about atmospheric pressure (760 Torr), and the evacuated region of the ICP-MS system 100. For example, the interface portion 112 can be maintained at a working vacuum of, for example, about 1-2 Torr by a mechanical roughing pump (e.g., a rotary pump, a vortex pump, etc.), while the mass analyzer 120 can be maintained at a working vacuum of, for example, about 10 Torr by a high vacuum pump (e.g., a turbomolecular pump, etc.). -6 Torr working pressure. Interface portion 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 holes at the center of their conical structures, which are aligned with each other and aligned with the central axis of the ICP torch 160. The sampling cone 188 and the skimmer cone 192 help to extract the plasma 184 from the torch into the vacuum chamber, and also serve as a gas conduction barrier to limit the amount of gas entering the interface portion 112 from the ion source 108. The sampling cone 188 and the skimmer cone 192 can be metal (or at least the tip defining its hole can be metal) and can be electrically grounded. Neutral gas molecules and particles entering the interface portion 112 can be discharged from the ICP-MS system 100 via the vacuum port 128.

[0051] The ion optical section 114 and subsequent ion guide section 116 may be disposed in the second depressurization stage between the skimmer cone 192 and the mass analysis section 118. The ion optical section 114 includes a lens assembly 196, which may include a series of (typically electrostatic) ion lenses that assist in extracting ions from the interface section 112, focusing the ions into the ion beam 106, and accelerating the ions into the ion guide section 116. The ion optical section 114 may be maintained at, for example, about 10 -3 Under the pressure of the entrusted work. Figure 1 106. Although not specifically shown in FIG. 106, lens assembly 196 can be configured such that the ion optical axis passing through lens assembly 196 is offset (in a radial direction perpendicular to the longitudinal axis) from the ion optical axis passing through ion guide portion 116 so that ion beam 106 is steered by the offset. This configuration helps remove neutral species and photons from the ion path.

[0052] The ion guide portion 116 includes a collision / reaction cell (or cell assembly) 110. The collision / reaction cell 110 includes an ion guide 146, which is axially positioned in the cell housing 187 between the cell entrance and the cell exit. In the present embodiment, the cell entrance and the cell exit are provided by ion optical components. That is, the cell entrance lens 122 is located at the cell entrance, and the cell exit lens 124 is located at the cell exit. The ion guide 146 has a linear multipole (e.g., a quadrupole, a hexapole, or an octopole) configuration that includes a plurality of (e.g., four, six, or eight) rod electrodes 103 that are arranged parallel to each other along a common central longitudinal axis of the ion guide 146. The rod electrodes 103 are each positioned at a radial distance from the longitudinal axis and are circumferentially spaced apart from each other around the longitudinal axis. For simplicity, Figure 1 Only two such rod electrodes 103 are shown in FIG. An RF power supply (described further below) applies an RF potential to the rod electrodes 103 of the ion guide 146 in a known manner that produces a two-dimensional RF electric field between the rod electrodes 103. The RF field is used to focus the ion beam 106 along the longitudinal axis by limiting the deviation of the ions in the radial direction relative to the longitudinal axis. In a typical embodiment, the ion guide 146 is an RF-only device without large-scale filtering capabilities. In another embodiment, as understood by those skilled in the art, the ion guide 146 can be used as a mass filter by superimposing a DC potential on the RF potential.

[0053] The collision / reaction gas source 138 (e.g., a pressurized reservoir) is configured to flow one or more collision / reaction gases (e.g., a mixture) into the interior of the collision / reaction cell 110 via a collision / reaction gas feed conduit and port 142 leading to the interior of the cell housing 187. The gas flow rate is in the order of milliliters per minute (mL / min) or milligrams per minute (mg / min). The gas flow rate determines the pressure within the collision / reaction cell 110. The cell operating pressure may be in the range of, for example, 0.001 torr to 0.1 torr. Examples of collision / reaction gases include, but are not limited to, helium, neon, argon, hydrogen, oxygen, water, ammonia, methane, fluoromethane (CH3F) and nitrous oxide (N2O) and combinations (mixtures) of two or more of the foregoing. Inert (non-reactive) gases (such as helium, neon and argon) are used as collision gases. The operation of the collision / reaction cell 110 according to the present disclosure is described in more detail below.

[0054] The mass analysis section 118 (also referred to herein as a mass spectrometer) includes a mass analyzer 158 and an ion detector 161, thereby comprising a third (final) depressurization stage. The mass analyzer 158 can be of any type suitable for ICP-MS. Examples of mass analyzers include, but are not limited to, multipole electrode structures (e.g., quadruple mass filters, linear ion traps, three-dimensional Paul traps, etc.), time-of-flight (TOF) analyzers, magnetic and / or electronic sector instruments, electrostatic traps (e.g., and Traps) and ion cyclotron resonance (ICR) traps (FT-ICR or FTMS, also known as Penning Trap). According to one aspect of the presently disclosed subject matter, the collision / reaction cell 110 is configured to emit ions in the form of ion pulses or ion packets (as further described below), and can also be used in conjunction with a continuous beam (e.g., non-pulsed, non-trapping or non-storage) mass analyzer that receives ion pulses from the collision / reaction cell 110, such as a quadruple mass filter or other multipole device configured for non-pulsed operation, a sector instrument (e.g., containing magnetic and / or electric sectors, including dual focusing instruments), etc. The ion detector 161 can be any device configured to collect and measure the flux (or current) of mass-differentiated ions output from the mass analyzer 158. Examples of ion detectors include, but are not limited to, electron multipliers, photomultiplier tubes, microchannel plate (MCP) detectors, image current detectors, and Faraday cups. For ease of use Figure 1 , the ion detector 161 (receiving at least the front portion of the ions) is oriented at a 90 degree angle to the ion outlet of the mass analyzer 158. However, in other embodiments, the ion detector 161 can be coaxial with the ion outlet of the mass analyzer 158.

[0055] In operation, the mass analyzer 158 receives the ion beam 166 from the collision / reaction unit 110 and separates or sorts the ions based on their different mass-to-charge (m / z) ratios. The separated ions pass through the mass analyzer 158 and arrive at the ion detector 161. The ion detector 161 measures (i.e., detects and counts) each ion and outputs an electronic detector signal (ion measurement signal) to the data acquisition component of the system controller 120. The mass discrimination performed by the mass analyzer 158 enables the ion detector 161 to detect and count ions with a specific m / z ratio separately from ions with other m / z ratios (derived from different analyte elements of the sample), thereby generating an ion measurement signal for each ion group analyzed (and therefore each analyte element). Ions with different m / z ratios can be detected and counted in sequence. The system controller 120 processes the signals received from the ion detector 161 and generates a mass spectrum, which displays the relative signal intensity (abundance) of each ion detected at the mass spectrum. The signal intensity so measured at a given m / z ratio (and therefore a given analyte element) 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 contained in the sample being analyzed can be confirmed, and the concentration of the chemical element can be determined.

[0056] Although not in Figure 1 1, but the ion optical axis passing through the ion guide 146 and the cell exit lens 124 can be offset from the ion optical axis passing through the entrance to the mass analyzer 158, and ion optical devices can be provided to pass the ion beam 166 through this offset. With this configuration, additional neutral species are removed from the ion path.

[0057] 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 section 104, the ion source 108, the ion optical section 114, the ion guide section 116, and the mass analysis section 118, as well as controlling the vacuum system and various gas flow rates, temperature and pressure conditions; and other sample processing components provided in the ICP-MS system 100 that need to be controlled. The system controller 120 represents the circuitry (e.g., RF and DC voltage sources) used to operate the collision / reaction cell 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 non-transitory computer-readable medium that includes non-transitory 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 and one or more memories and databases (as required to operate the various components of the ICP-MS system 100). The system controller 120 typically includes a main electronic processor that provides overall control 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., keypads, touch screens, mice, etc.), user output devices (e.g., display screens, printers, visual indicators or alarms, audible indicators or alarms, etc.), software-controlled graphical user interfaces (GUIs), and devices for loading electronic processor-readable media (e.g., non-transitory logic instructions contained in software, data, etc.). The system controller 120 may include an operating system (e.g., Microsoft Windows XP) for controlling and managing the various functions of the system controller 120. software).

[0058] It should be understood that Figure 1 is a high-level schematic diagram of the ICP-MS system 100 disclosed herein. As will be appreciated 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 electronics may be included as desired for the actual implementation.

[0059] For example, in an embodiment, the ICP-MS system 100 is configured as a triple quadrupole ICP-MS system, and can be referred to as an ICP-MS / MS (tandem MS) or ICP-QQQ system. In such an embodiment, an additional vacuum chamber (not shown) is provided between the ion optical section 114 and the ion guide section 116, and the first (or pre-unit) quadrupole mass filter Q1 (not shown) is positioned in the additional vacuum chamber. The mass analyzer 158 corresponds to the second (final) quadrupole mass filter Q2 in this case. The quadrupole mass filter is briefly described herein and is generally known to those skilled in the art. The ion guide 146 of the collision / reaction cell 110 corresponds to the center "Q" in the QQQ configuration, but can be an octupole or a hexapole instead of a quadrupole as described elsewhere herein. Like the mass analysis section 118 including the mass analyzer 158, the additional vacuum chamber including the first pre-unit mass filter Q1 operates at a very low pressure (high vacuum) to enable the first mass filter to operate (if necessary) with unit mass resolution (1Da mass window). Therefore, the gas-filled collision / reaction cell 110 operates at a higher pressure than the vacuum chamber containing the first pre-cell mass filter Q1 and the mass analysis section 118 containing the second final quadrupole mass filter Q2 (mass analyzer 158). The vacuum system of the ICP-MS system 100 is configured to maintain different pressure conditions in three vacuum stages by utilizing appropriately selected and configured pumps, gas channels, etc.

[0060] In operation, the first pre-cell mass filter Q1 is set to allow only the target analyte ion mass to pass through the collision / reaction cell 110 while rejecting all other ion masses. Therefore, only the target analyte ions and large-mass polyatomic interfering ions (if any) enter the collision / reaction cell 110. This additional pre-cell mass selection step can provide greater predictability, consistency and control over the ion-molecule reaction chemistry that occurs in the collision / reaction cell 110. For example, by rejecting non-target analyte ions and matrix component ions, the first pre-cell mass filter Q1 can prevent the formation of unwanted (and potentially interfering) product ions in the collision / reaction cell 110. Then, the collision / reaction cell 110 removes interference as described herein. In the case where the interfering ions react with the gas in the collision / reaction cell 110, the second final quadrupole mass filter Q2 (mass analyzer 158) is set to allow only the target analyte ions to pass through the ion detector 161. Alternatively, in the event that the target analyte ions react with the gas, the mass analyzer 158 is configured to pass only the target product ions (derived from the original analyte ions by such reaction) through the ion detector 161 .

[0061] In another embodiment, a pre-unit mass filter is provided, but the pre-unit mass filter operates in the form of a bandpass filter with a certain bandpass window, which spans the selected ion mass range, for example, with a window width of 10 Da. The partial mass rejection provided by this embodiment may be useful in some applications. In such an embodiment, the pre-unit mass filter can be positioned in an additional vacuum chamber (not shown) before the ion guide section 116 as described above, or directly positioned in the ion guide section 116 together with the collision / reaction cell 110.

[0062] In applications where pre-cell mass selection is not required or desired, the pre-cell mass filter just described (if provided in the ICP-MS system) can be operated as an RF-only ion guide, which helps guide the ion beam into the collision / reaction cell 110. Examples of the use of pre-cell mass filters in ICP-MS systems are described in U.S. Pat. No. 8,610,053 to Yamada et al.; and McCurdy, Ed., "The Benefits of MS / MS for Reactive Cell Gas Methods in ICP-MS," Agilent ICP-MS Journal, p. 2-3, No. 70, October 2017; the entire contents of these documents are incorporated herein by reference.

[0063] Figure 2 is a schematic perspective view of an example of an ion guide 246 according to an embodiment. Figure 3 2 is a schematic side (longitudinal) view of an ion guide 246. The ion guide 246 is configured for operation in a collision / reaction cell assembly, such as described herein and in Figure 1 2. The collision / reaction cell assembly 110 shown in FIG. 2. An ion guide 246 is located between the cell entrance and the cell exit. A cell entrance lens 222 may be located at the cell entrance, and a cell exit lens 224 may be located at the cell exit.

[0064] The ion guide 246 includes a plurality of ion guide electrodes 203 (or "rod electrodes"). The ion guide electrodes 203 are circumferentially spaced apart from each other around a longitudinal axis L of the ion guide 246. Each ion guide electrode 203 is located at a radial distance from the longitudinal axis L (and is perpendicular to the longitudinal axis L) and is elongated along the longitudinal axis L. Thus, the ion guide electrodes 203 define: an ion guide inlet 207 near a cell entrance lens 222; an ion guide outlet 209 axially spaced apart from the ion guide inlet 207 by the axial length of the ion guide electrode 203 and near a cell exit lens 224; and an axially elongated ion guide interior 211 extending from the ion guide inlet 207 to the ion guide outlet 209.

[0065] Figure 2 One embodiment is shown in which the ion guide 246 has a quadrupole configuration (four ion guide electrodes). In other embodiments, the ion guide 246 can have a higher order multipole configuration, such as a hexapole (six ion guide electrodes), an octupole (eight ion guide electrodes), or an even higher order multipole configuration. Figure 2 As shown, the ion guide electrode 203 may be cylindrical with a circular cross section. Alternatively, in the case of a quadrupole, the surface of the ion guide electrode 203 facing the ion guide interior 211 may have a hyperbolic profile. As another alternative, the ion guide electrode 203 may have a polygonal (prismatic, e.g., square, rectangular, etc.) cross section.

[0066] Figure 3 Also schematically shown are electronic devices (circuits) that can be used to apply RF and DC potentials to the various components. Figure 1 The system controller 120 shown in FIG. 1 may be considered representative of such electronic devices. Figure 3 , the electronics include an RF source (RF) superimposed on a first DC source DC1 in communication with the ion guide electrode 203, as schematically depicted as a voltage source RF+DC1. The electronics also include a second DC source DC2 in communication with the cell exit lens 224, and may also include a third DC source DC3 in communication with the cell entrance lens 222. The various RF and DC sources may also be collectively referred to as a "voltage source" or "multiple voltage sources".

[0067] In operation, the RF+DC1 source applies an RF potential RF (i.e., RF+DC1) superimposed on a DC bias voltage DC1 to the ion guide electrodes 203 at a certain frequency and amplitude to effectively generate a two-dimensional time-varying RF field in the ion guide 246. Typically, each pair of opposing ion guide electrodes 203 are electrically interconnected. The RF potential applied to a pair of opposing ion guide electrodes 203 is the same as the RF potential applied to an adjacent pair of opposing ion guide electrodes 203 (-RF+DC1, Figure 3 The RF potentials of the ion guide 246 (not shown) are 180 degrees out of phase, as understood by those skilled in the art. The RF field radially confines the ions in the ion guide 246, i.e., limits the movement of the ions in the radial direction, thereby focusing the ions into an ion beam centered on the longitudinal axis L. In this manner, the ion guide 246 operates as an RF-only ion guide, wherein the RF field is used only to focus the ions along the longitudinal axis L.

[0068] However, in another embodiment in which the ion guide 246 has a quadrupole electrode structure, a DC field (±U) with opposite polarity can be superimposed on the RF field to enable the ion guide 246 to be used as a mass filter. That is, +RF+U+DC1 can be applied to a pair of ion guide electrodes 203; -RF-U+DC1 can be applied to another pair of ion guide electrodes 203. According to known principles, by appropriately selecting the operating parameters (RF amplitude, RF frequency and DC amplitude) of the composite RF / DC field, the ion guide 246 can be configured to apply a mass range (bandpass) 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 ion guide 246. Ions with masses within the mass bandpass have stable trajectories and are able to traverse the entire length of the ion guide 246. Ions with masses outside the mass bandpass have unstable trajectories and are therefore discarded. That is, such ions will overcome the RF confinement field and be removed from the ion guide 246 without being able to leave the ion guide 246. The mass passband can be adjusted by adjusting one or more operating parameters of the composite RF / DC field, which enables the selection of a particular mass of ions to be transported from the ion guide 246 at any given time. In some embodiments, this "scanning" function can be implemented to facilitate the process of suppressing interfering ions from affecting the mass spectrometry data, as described elsewhere herein.

[0069] In one embodiment, the first DC source DC1 applies a negative DC bias voltage to the ion guide electrodes 203 that is constant along their length.

[0070] In another embodiment, the first DC source DC1 can be configured to generate an axial DC potential gradient along the length of the ion guide electrode 203. For this purpose, the first DC source supplies two different DC potentials DC1a and DC1b, which can be coupled to the entrance and exit ends of the ion guide electrode 203, respectively. For example, the DC potentials DC1a and DC1b can be coupled to the entrance and exit ends of the ion guide electrode 203 made of conductive or resistive materials, respectively. As described, for example, in U.S. Patent No. 6,111,250 (the contents of which are incorporated herein by reference in their entirety), the axial DC potential gradient can also be generated by other techniques, including segmented ion guides or auxiliary electrodes inserted between ion guide rods. Applying an axial DC potential gradient can be used to keep ions moving in the forward direction and prevent ions from escaping the ion guide 246 through the unit entrance lens 222. In addition, the second DC source DC2 applies an exit DC potential to the unit exit lens 224. In addition to or in lieu of the axial DC potential gradient, after ions have been transmitted into the ion guide 246 for a desired amount of time, the DC potential DC3 applied to the cell entrance lens 222 may be increased to prevent ions from escaping the ion guide 246 through the cell entrance lens 222 and to prevent other ions from being transferred from the ion source 108 into the ion guide 246 ( Figure 1 ). In other words, the DC potential DC3 applied to the unit entrance lens 222 can be switched between a first level that produces a DC barrier that effectively prevents ions from entering or leaving the ion guide 246 through the unit entrance lens 222, and a second level that removes (or reduces) the DC barrier to allow ions to enter the ion guide 246.

[0071] In the operation of the ICP-MS system, ideally, only the analyte ions produced in the plasma-based ion source will be transmitted to the mass analyzer. However, as previously described in the present disclosure, the ion source also produces background (non-analyte) ions, some of which can act as "interfering ions" because they interfere with the analysis of a given sample. Interfering ions can be produced by plasma-forming gases (such as argon), matrix components of the sample, solvents / acids contained in the sample, and air (oxygen and nitrogen) entrained into the system. Some interfering ions can be produced directly in the collision / reaction unit. As mentioned above, an example of an interfering ion is a polyatomic interferer with the same mass as a monatomic analyte ion. Detection of such interfering ions and detection of certain analyte ions (interfering ions interfere with it) can result in spectral overlap in the analysis data, thereby reducing the quality of the analysis.

[0072] The collision / reaction cell 110 described herein is configured to remove (reduce or eliminate) interfering ions, thereby preventing interfering ions from being transmitted (or at least reducing the amount of interfering ions transmitted) to the mass analyzer 158. Therefore, the operation of the collision / reaction cell 110 improves the performance of the ICP-MS system 100 and the quality of the mass spectral data generated thereby. The collision / reaction cell 110 can achieve this by implementing a physical, non-reactive ion-molecule collision mechanism or a chemically reactive ion-molecule reaction. In an embodiment, the collision / reaction cell 110 is configured to operate in (and switch between) three different operating modes: a collision mode, in which a collision gas flows into the collision / reaction cell 110; a reaction mode, in which a reaction gas flows into the collision / reaction cell 110; and a "no gas" or standard mode, in which no type of collision / reaction gas flows into the collision / reaction cell 110. The selection of a particular mode can depend on the type of analyte ion to be measured and the type of interfering ions (if any) to be removed. “Type” refers to the chemical (elemental) characteristics of the analyte ion (e.g., calcium, iron, selenium, etc.) and the interfering ions (e.g., Ar + 、ArO + 、Ar2 + In other embodiments, the collision / reaction unit 110 may be configured only (or primarily) for collision operations, or may be configured only (or primarily) for reaction operations.

[0073] In the no-gas mode, the collision / reaction cell 110 is used only as an ion guide to transport analyte ions to the mass analyzer 158. That is, the ion guide 146 is operated without a collision / reaction gas. The no-gas mode may be useful when there are no interfering ions so that collision or reaction operations are not required for suppressing interference.

[0074] In the operation of collision mode or reaction mode, a flow of collision / reaction gas is established in the collision / reaction cell 110 via the collision / reaction gas source 138 and the collision / reaction gas feed pipe and port 142. The gas flow rate can be set to optimize for the specific element (analyte ion) being measured. The gas flow rate can depend on other factors, such as the (one or more) types and (one or more) intensities of the interfering ions expected to be removed. When the collision / reaction gas flows into the collision / reaction cell 110, the ion beam 106 is transmitted to the collision / reaction cell 110 via the cell entrance lens 122 and enters the ion guide 146. The ion beam 106 includes analyte ions and various non-analyte ions. If one of the non-analyte ion materials has the same m / z ratio as the analyte ion to be measured, the non-analyte ion (as a background ion) interferes with the analyte ion detection. Since the formation of each non-analyte ion material depends on the sample in the analysis and the operating conditions of the sample introduction part 104 and the ion source 108, the ion beam 106 may or may not include interfering ions. When the ion beam 106 is transmitted into the collision / reaction cell 110, the ion guide 146 is actively powered to generate the above-mentioned RF confinement field, which radially confines the ion beam 106 along the central longitudinal axis of the ion guide 146. The collision / reaction gas interacts with the ions in the ion beam 106 within the ion guide 146. Depending on the configuration or operating mode of the collision / reaction cell 110, the interaction involves ion-molecule collisions or ion-molecule reactions. The resulting ion beam 166 then leaves the ion guide 146 and the collision / reaction cell 110 via the cell exit lens 124 and is directed into the mass analyzer 158, where the ions are mass analyzed in the manner described above. Ideally, the outflowing ion beam 166 should be free of (or have at least a much lower concentration of) interfering ions from the incident ion beam 106, and should be free of (or have at least a minimal amount of) interfering ions newly formed directly in the collision / reaction cell 110.

[0075] In embodiments, the reaction mode is based on the relative reaction rate of reaction gas and analyte ion and interfering ion. For example, if the reaction with the interfering ion is exothermic, and the reaction with the analyte ion is endothermic, then the reaction with the interfering ion will be very rapid, and the reaction gas does not react with the analyte ion effectively or may not react with the analyte ion completely. The specific type of reaction that occurs (for example, charge transfer, proton transfer, etc.) depends on the type of reaction gas used and the type of interfering ion to be removed. Usually, the reaction converts the interfering ion into non-interfering ion or neutral substance. The interfering ion relates to the composition of changing the interfering ion to the conversion of the non-interfering ion, thereby the mass of the interfering ion is changed to be different from (and therefore no longer interferes with) the mass of the analyte ion. In the case where the interfering ion is converted into a neutral substance, the neutral substance is not affected by the electric field or magnetic field. Therefore, the neutral substance can be removed together with other neutral gas molecules by a vacuum system (for example, via port 132 or port 136), and it is "invisible" to mass analyzer 158 anyway. An example is the use of hydrogen H2 to transfer interfering calcium isotopes via charge transfer from argon ions to hydrogen molecules. 40 Ca + Argon ions 40 Ar + Converted to neutral argon atoms Ar:H2+ 40 Ar + →Ar+H2 + .

[0076] In another embodiment of the reaction mode, the ion-molecule reaction involves the analyte ion rather than the interfering ion. That is, the reaction converts the analyte ion into a new analyte ion substance, that is, changes the composition of the original analyte ion. The mass of the new analyte ion substance is different from (usually higher than) the mass of the original analyte ion substance, and therefore also different from the mass of the interfering ion. The reaction with the analyte ion can also be actually characterized as the conversion of the disturbed ion to the non-interfering ion. The new analyte ion (or "product ion") is detected and becomes part of the mass spectrum and provides useful information because it corresponds to the original monatomic analyte being studied.

[0077] Typically, the reactive mode is a mode in which the collision / reaction gas reacts with the ions of interest, which are either interfering ions or analyte ions, depending on the type of ions with which the gas reacts, as just described. In reactive mode embodiments, in addition to being used as a reaction gas for the ions of interest, the collision / reaction gas also serves as a collision gas for non-reactive ions. Thus, in the case where the gas reacts with interfering ions, the gas can be used as a collision gas for non-reactive analyte ions. On the other hand, in the case where the gas reacts with the analyte ions, the gas can be used as a collision gas for the resulting non-reactive product ions.

[0078] As described earlier in this disclosure, the collision / reaction cell 110 is filled with a reaction gas at a certain pressure to obtain sufficient reaction efficiency with interfering ions or analyte ions (derived from the elements under study). However, the optimal pressure (or gas density) for performing interference suppression reactions generally varies with different elements. Therefore, when measuring different elements, it is conventional to change (adjust) the flow rate of the reaction gas entering the collision / reaction cell so as to obtain an acceptable high signal / background (S / B) ratio for each element. It is also conventional to operate the collision / reaction cell as a continuous beam instrument. That is, the conventional collision / reaction cell is configured to limit ions only in the radial direction (using the RF confinement field generated by the multipole ion guide in the collision / reaction cell), rather than in the axial direction. Therefore, conventionally, the residence time of a given ion in the collision / reaction cell and therefore the reaction time between the collision / reaction gas and the ion is determined by the transit time required for the ion to travel from the cell entrance to the cell exit, and the residence / reaction time cannot be actively controlled.

[0079] According to aspects of the present disclosure, rather than controlling the gas flow rate (and therefore the gas density in the collision / reaction cell 110), the reaction time (i.e., the residence time of the ions in the collision / reaction cell 110) is controlled. In other words, rather than changing the gas flow rate to achieve the optimal reaction conditions for each different element in the analysis, the reaction time is changed (adjusted) as needed to achieve the optimal reaction conditions for each different element in the analysis. The reaction time is extended by limiting the ions in the collision / reaction cell 110 in the axial direction and in the radial direction for a certain confinement period. The confinement period has a required time period for each specific type of analyte ion to be measured to seek to obtain sufficient interference suppression reaction efficiency. According to an embodiment, all ions (analyte and non-analyte) entering the collision / reaction cell 110 are axially confined in the ion guide 146 (or 246) by establishing a high positively charged exit DC potential (DC potential barrier) at the cell exit for the duration of the required (predetermined) confinement period. In an embodiment, the DC barrier is generated by applying an exit DC potential at the cell exit lens 124 (or 224). Additionally, confined ions may be prevented from exiting the collision / reaction cell 110 through the cell entrance during the confinement period by applying an axial DC potential gradient along the ion guide 146, and / or by applying a high entrance DC potential at the cell entrance lens 122 (or 222), as described above in conjunction with Figure 3 In addition, as described above, the ions are radially confined by applying the RF confinement field generated by the ion guide 146. Therefore, the ions are completely confined in the ion guide 146 during the confinement period.

[0080] In this manner, the confinement period of storing ions in the collision / reaction cell 110 for a desired duration can ensure that a sufficient number of reactions have occurred between the collision / reaction gas and the target interfering ions (or analyte ions, depending on the embodiment). Thus, confinement can result in a greater reduction in interferences, and therefore an increased S / B ratio, than in a conventional collision / reaction cell (which, as described above, does not store or confine ions). In addition, the confinement period causes the analyte ions (or analyte product ions, if the reaction is between the analyte ions and the collision / reaction gas) to collide multiple times with the collision / reaction gas molecules, effectively slowing them down by losing kinetic energy, thereby enhancing confinement of the analyte ions (or product ions) in the collision / reaction cell 110 during the confinement period.

[0081] After a sufficient number of reactions with the target interfering ions (or analyte ions, depending on the embodiment) have occurred, the confinement period is terminated by rapidly removing the high DC potential applied to the cell outlet (or rapidly reducing its positive magnitude) to allow the confined ions to flow out of the collision / reaction cell 110 and be mass analyzed and detected / counted during a subsequent measurement period. The mass analyzer 158 can be configured to send only the target analyte ions (or product ions) to the ion detector 161 for measurement, and to discard all other ions received by the mass analyzer 158.

[0082] Thus, the present disclosure includes a method for operating a collision / reaction cell that includes a confinement period followed by a measurement period, wherein the transition between the confinement period and the measurement period requires a very short time interval during which a high exit DC potential (DC barrier) at the cell outlet is removed (or reduced). In an embodiment, the generation and subsequent removal (or reduction) of the high exit DC potential can be characterized by applying an exit DC potential at a first magnitude at the cell outlet to generate a DC barrier that effectively blocks ions from leaving the collision / reaction cell 110, maintaining the exit DC potential at the first magnitude for the duration of the confinement period (the duration being optimal for disturbed analyte ions), and after the confinement period, switching (adjusting) the exit DC potential from the first magnitude to a second magnitude that effectively allows analyte ions to pass through the cell outlet and reach the mass analyzer 158.

[0083] In various embodiments, the first DC potential magnitude and the second DC potential magnitude have one or more of the following properties: the second DC potential magnitude is smaller than the first DC potential magnitude; the first DC potential magnitude is a positive or zero magnitude and the second DC potential magnitude is a negative or zero magnitude; the first DC potential magnitude is in the range of 0V to +100V; and / or the second DC potential magnitude is in the range of -200V to 0V.

[0084] Typically, the duration of the restricted period is determined as required to ensure that the interaction between the collision / reaction gas and the interfering ion or the analyte ion is optimized or maximized to suppress interference. As a non-exclusive example, the duration of the restricted period can be in the range of 0ms to 1000ms, or 5ms to 500ms, or 10ms to 100ms. The duration of the restricted period depends on the analyte ion being analyzed (and therefore can be selected based on the analyte ion), and can be different for different analyte ions. The restricted period duration for different analyte ions can be empirically determined by the appropriate experimental operation of the sample elements of the ICP-MS system 100. The restricted period duration for different analyte ions can be provided by the memory of the system controller 120, for example, in a lookup table or a database stored in the memory of the system controller 120 or accessible by the memory of the system controller 120. The restricted period duration for different analyte ions can depend on the instrument. That is, the confinement period duration for a given analyte element analyzed by one ICP-MS system may be different than the confinement period duration for the same analyte element analyzed by another ICP-MS system, even if the other ICP-MS system is configured identically to the first ICP-MS system.

[0085] Typically, the time interval required to switch the DC potential from the first magnitude to the second magnitude at the cell outlet is limited only by the transient delay exhibited by the electronics used to apply the DC potential. As a non-exclusive example, the switching may have a duration in the range 0.01 ms to 0.1 ms.

[0086] As another aspect of the disclosed subject matter, a sudden switch of the DC potential from a first magnitude to a second magnitude (and the difference between the first magnitude and the second magnitude) causes the analyte ions to exit the collision / reaction cell 110 as pulses having a particular short pulse duration. As a non-exclusive example, the pulse duration may be in the range of 0.1 ms to 1 ms. In an embodiment, the effect of abruptly switching the DC potential in this manner may be characterized as the ejection of ion pulses (or ion packets) from the collision / reaction cell 110.

[0087] In an embodiment, the duration of the measurement period for measuring or counting analyte ions is no longer than or approximately equal to (roughly equivalent to) the pulse duration. In this article, depending on the pulse shape, the pulse duration can be equal to or longer than the full width at half maximum (FWHM) of the pulse peak, but can be equal to or less than about five times the FWHM. "Approximately equal to" (or "approximately equal to", "close to", "about" and similar phrases) can mean that the duration of the measurement period is a value in the range from the FWHM of the pulse peak to five times the FWHM. For example, if the FWHM of the pulse is 0.2ms, the approximately equal measurement period duration can be in the range of 0.2ms to 1.0ms, where the endpoints 0.2ms and / or 1.0ms can be included in the range. Examples of FWHM are Figure 4 shown. Specifically, Figure 4 As can be measured by a mass spectrometer, a pulse peak 402 is defined as the ion intensity (in counts per second, or cps) I as a function of the measurement time (in ms) t. The apex of the pulse peak 402 corresponds to the maximum intensity value I of the ion signal of the pulse peak 402. max Half of the maximum intensity value is denoted as I max / 2. The FWHM of the pulse peak 402 is max The width of the peak at / 2 corresponds to the duration of (t1–t2).

[0088] Setting the measurement period duration to be approximately equal to the pulse duration can help ensure that the S / B ratio is improved due to the implementation of the confinement period disclosed herein. After the pulse duration, the signals of the analyte ions and the interfering ions stabilize at their steady-state levels, providing an unimproved S / B ratio, i.e., an S / B ratio that is the same as the S / B ratio obtained from a conventional collision / reaction cell. Therefore, if the measurement period is extended to the post-pulse period, the S / B ratio will decrease toward the value obtained from a conventional collision / reaction cell. Alternatively, as described in one of the aforementioned embodiments, an increased DC potential DC3 can be applied to the cell entrance lens 222 to prevent additional ions from being transferred to the ion guide 246. If the increased DC potential DC3 is maintained even after the pulse duration, no ion signal will be observed at the end of the pulse. In this case, the measurement after the pulse period is useless.

[0089] When using a continuous beam mass analyzer (e.g., a quadrupole mass filter, a sector instrument, etc.) or a discontinuous beam mass analyzer (e.g., a TOF analyzer, an ion trap-based analyzer, etc.), the measurement period can be controlled to be approximately equal to the pulse duration of the collision / reaction cell 110. In either case, only the pulsed portion of the ion beam from the collision / reaction cell 110 is measured by the mass analyzer, thereby achieving a higher S / B ratio and / or S / N ratio. In this article, the duration of the measurement period can be considered to be the duration of the ion injection mass analyzer, which is limited (at least approximately) to the pulse duration of the collision / reaction cell 110. It will be understood that this pulse duration is not necessarily the same as any "pulsed" operation of the discontinuous beam mass analyzer (such as the extraction pulse that subsequently enters the flight tube of the TOF analyzer, the ion flight time through the flight tube of the TOF analyzer, or the trapping time in a trap-based analyzer).

[0090] As another aspect of the subject matter of the present disclosure, because ions continue to enter the collision / reaction unit 110 from the ion source 108 during the confinement period, they accumulate in the collision / reaction unit 110. As described above, the ion signal obtained after the confinement is a strong short pulse. Depending on the duration of the confinement period, the peak intensity of the pulse is 10 to 300 times higher than the ion signal usually observed without confinement. However, noise (electrical noise and neutral noise from non-ion sources) is not limited or accumulated. Therefore, the signal-to-noise ratio (S / N) is improved by limiting any ion, regardless of whether it is interfered by the spectral line. Ideally, when the analyte concentration is zero (when measuring blank), the spectrometer output should be zero. However, this is not the case in reality. Non-zero output (i.e., so-called "background") is caused by many factors in ICP-MS, such as analyte contamination in the ICP-MS system, interfering ions, stray ions in the vacuum chamber, photons from plasma, high-energy neutral particles (mainly Ar atoms), electrical noise, etc. The high-energy neutral matter produced in the ion optical part 114 can have enough energy to produce secondary particles by colliding with the surface or gas molecules in the vacuum chamber. Secondary particles can be electrons or ions from the surface, and noise will be generated when they reach the ion detector 161. Electrical noise can be the shot noise of the ion detector 161 (for example, spontaneous emission of electrons from the dynode in the electron multiplier), the thermal noise of the ion counting electronic device, or the noise generated by the micro-discharge of the high-voltage component. The background (commonly referred to as "random noise") produced by these non-ion sources (photons, neutral particles, electrical noise) is displayed in the mass spectrogram as a jagged deviation of the mass that is independent of the zero level (not shown as a mass spectrum peak). When the target analyte is affected by interfering ions, the contribution of random noise to the background is usually much smaller than that of the interfering ions. However, for non-interfering analyte ions, random noise may contribute significantly to the background. Unlike ions, random noise is not limited or accumulated in the collision / reaction unit 110. Therefore, the S / N ratio is improved by measuring the limited ions in the form of pulses.

[0091] Therefore, when measuring non-interfering analyte ions in collision mode and when measuring interfered analyte ions in reaction mode, as provided by the embodiments disclosed herein, performing ion confinement and pulsation in the collision / reaction cell in sequence provides advantages. That is, the background of non-interfering analyte ions is mainly due to neutral noise and electrical noise. Since there are no interfering ions, the only ions that are restricted in the collision / reaction cell 110 are analyte ions, while neutral species are not restricted. Therefore, when operating in collision mode, performing ion confinement and pulsation in sequence improves the S / N ratio.

[0092] In an embodiment, by maintaining the inlet DC potential at a second magnitude, ion transport through the cell inlet and into the collision / reaction cell 110 continues to occur during the confinement period. The inlet DC potential at the second magnitude effectively allows ion transport through the cell inlet. That is, after the confinement period begins, ions from the ion source 108 are allowed to continue to enter the collision / reaction cell 110. As a result, analyte ions accumulate in the collision / reaction cell 110, thereby increasing the number of analyte ions in the ion pulse, thereby increasing the peak intensity of the ion pulse that occurs at the end of the confinement period.

[0093] In another embodiment, during at least the second half of the confinement period (i.e., a portion of the confinement period including the end of the confinement period), an entrance DC potential is applied at a first magnitude at the cell entrance (e.g., at the cell entrance lens 122 as described above). The entrance DC potential at the first magnitude is effective to prevent confined analyte ions from leaving the collision / reaction cell 110 through the cell entrance, while preventing interfering ions from entering the collision / reaction cell 110 through the cell entrance.

[0094] Alternatively or additionally, an inlet DC potential may be applied at the cell inlet at a first magnitude during the measurement period.The inlet DC potential at the first magnitude is effective to prevent interfering ions from entering the collision / reaction cell 110 through the inlet.

[0095] The subject matter disclosed at present can be performed in multi-element analysis. Therefore, after analyzing the elements of the first type, the method can be repeated to analyze the elements of the second type, and so on. As described above, the duration of the confinement period for different elements can be different, so it can be adjusted for each type of element to be analyzed. According to the predetermined program developed as part of the method development for sample operation, this adjustment can be much faster than the adjustment of the gas flow rate that usually requires more than a few seconds, and can be affected by the system controller 120 that controls the operation of ICP-MS100. The type of collision / reaction gas to be used can also be different for different elements. Therefore, the method may need to switch the type of collision / reaction gas for different elements, which can also be part of the programming and provided as an operating parameter in the above-mentioned lookup table, database or memory. The system controller 120 can control the collision / reaction gas source 138 for this purpose. It is worth noting that interference suppression may not be required for some elements. In this case, collision / reaction gas is not selected for these elements, but the collision / reaction unit 110 is operated in gas-free mode as an ion guide.

[0096] Therefore, in an embodiment of a method for performing multi-element analysis, the analyte ions include at least a first analyte ion having a first mass and a second analyte ion having a second mass different from the first mass. A flow of a collision / reaction gas into the collision / reaction cell 110 is established. Ions (including at least the analyte ions) are transmitted into the collision / reaction cell 110. An exit DC potential is applied at a first magnitude at the cell outlet during a first confinement period of a first duration, thereby generating a DC barrier as described herein, which effectively prevents ions from leaving the collision / reaction cell 110 during the first confinement period. During the first confinement period, the collision / reaction gas reacts with the first interfering ion that interferes with the first analyte ion, or the collision / reaction gas reacts with the first analyte ion to suppress the interference. That is, effective suppression of the interference generated by the mass spectrometer (e.g., Figure 1 The mass analysis section 118 shown in the figure) is used to measure the interaction of the interfering ion signal intensity measured by the mass analysis section 118 as described herein. The interaction may involve causing the interfering ion to react with the collision / reaction gas in the manner described herein, or causing the analyte ion to react with the collision / reaction gas in the manner described herein. After the first limiting period, the first ion pulse is transmitted to the mass spectrometer. This is accomplished as follows: the outlet DC potential is switched to a second magnitude, which effectively allows the first analyte ion (or the product ion formed by the first analyte ion) to pass through the unit outlet as a pulse. The first pulse includes at least the first analyte ion (or the product ion derived therefrom), but if the mass selection upstream of the (final) mass analyzer 158 is not performed, other ions, such as the second analyte ion, may also be included. Then, at least the first analyte ion (or the product ion derived therefrom) contained in the first pulse is measured by the mass spectrometer. For example, as described herein, mass analyzer 158 may be configured (eg, tuned) to send only the first analyte ion (or product ions derived therefrom) to ion detector 161 for measurement and to discard all other ions received by mass analyzer 158 .

[0097] Continuing with this embodiment, after measuring the first analyte ion contained in the first pulse, the outlet DC potential is again applied at the cell outlet at the first magnitude during a second limiting period of a second duration different from the first duration. During the second limiting period, the collision / reaction gas reacts with the second interfering ion or the second analyte ion that interferes with the second analyte ion to suppress the interference. After the second limiting period, the second pulse is transmitted to the mass spectrometer by switching the outlet DC potential to the second magnitude. The second pulse includes at least the second analyte ion (or the product ion derived therefrom), but if the mass selection upstream of the (final) mass analyzer 158 is not performed, other ions, such as the first analyte ion, may also be included. Then, at least the second analyte ion (or the product ion derived therefrom) contained in the second pulse is measured by the mass spectrometer. For example, at this time, the mass analyzer 158 can be tuned to send only the second analyte ion (or the product ion derived therefrom) to the ion detector 161 for measurement, and all other ions received by the mass analyzer 158 are discarded.

[0098] The method just described can be repeated for additional analyte ions to analyze other elements of the sample.

[0099] In another embodiment of the method for performing multi-element analysis, the method can also perform mass selection before the mass analyzer 158 (such as before the collision / reaction unit 110). For example, the ICP-MS100 can be configured as a QQQ system as described herein. As an example of this embodiment, by performing appropriate mass selection techniques, only the first analyte ion is transmitted to the collision / reaction unit 110, without the second analyte ion or other analyte ions. Then, the first analyte ion (and any first interfering ion that interferes with the first analyte ion) is limited during the first restriction period as described above. During the first restriction period, interference suppression interactions are performed as described above. Subsequently, the first analyte ion (or product ion) is transmitted to the mass spectrometer in the form of a first pulse and measured as described above. After measuring the first analyte ion, the second analyte ion is transmitted to the collision / reaction unit 110 by performing mass selection, without the first analyte ion or other analyte ions. Then the second analyte ion (and any second interfering ion that interferes with the second analyte ion) is limited during the second restriction period. During the second restriction period, interference suppression interactions are performed again. Subsequently, a second analyte ion (or product ion) is transmitted to the mass spectrometer in a second pulse and measured. The method can be repeated for additional analyte ions to analyze other elements of the sample.

[0100] During the confinement period, the reaction of the interfering ions (or analyte ions, depending on the embodiment) with the reaction gas continues, so that the analyte ion signal can be measured with a reduced interfering ion intensity (reduced background). That is, the interfering ion intensity can be reduced without increasing the gas flow rate, or without adjusting the gas flow rate to reduce the interfering ion intensity for different analyte elements to be measured. In other words, using a fixed reaction gas flow rate that is sufficient for the "simplest" element, the other more "difficult" elements can be measured with improved reaction efficiency by confining each of these more "difficult" elements in the collision / reaction cell 110 for the duration of the confinement period applicable to each element. For example, the interfering ions generated in the Ar-plasma 40 Ar + and 40 Ar 16 O + The intensity is usually about 10 10 and 10 7 Counts. Interfered analyte ions 40 Ca + and 56 Fe + The signal intensities of the two species are of the same order of magnitude. Therefore, the interference with Ca is stronger than that with Fe. A higher reaction gas flow rate is required to reduce the Ar + Suppressed to ArO + The same level allows similarly improved S / B ratios to be obtained for Ca and Fe. In this sense, Ca is a more difficult element than Fe. The same reaction gas, such as H2 or NH3 or H2O, can be used to reduce Ar + and ArO + Then, for example, by setting the flow rate of H2O to that of ArO + Go to Fe + (the "easier" element) the best value (lower than Ar + Ca + required value), Ca + Ion pulse measurement followed by Ca + Limitation: Ca analysis can be performed without increasing the H2O flow rate.

[0101] Thus, embodiments of the method require that a collision / reaction gas be flowed into the collision / reaction cell at a specific gas flow rate during a first confinement period (for analyzing a first element), and that a collision / reaction gas be flowed into the collision / reaction cell without changing the gas flow rate during a second confinement period (for analyzing a second element). When analyzing additional elements (third element, fourth element, etc.), the gas flow rate may remain constant, while the duration of the confinement period for each additional element may be adjusted as needed to optimize the reaction conditions for each additional element.

[0102] Operation Example

[0103] Now refer to Figure 5A and 5B One non-exclusive example of operating a collision / reaction cell according to the present disclosure is described. Figure 5A A schematic diagram of the ion guide 546 and the cell exit lens 524 of the collision / reaction cell and the DC potential 531 along the axial length of the ion guide 546 and to the cell exit lens 524 during the confinement period is shown. Figure 5B Yes Description Figure 5A Schematic diagram of the same collision / reaction cell and DC potential 531 during the measurement period shown in FIG. In this example, the portion of DC potential 531 along the axial length of ion guide 546 is an axial DC potential gradient 535 by which the magnitude of DC potential 531 gradually decreases (becomes more negative) along the axis in the direction toward the cell exit lens 524. The DC potential 531 may be measured during the confinement period ( Figure 5A ) and measurement period ( Figure 5B ) during which an axial DC potential gradient of 535 is maintained. Figure 5A and 5B Also depicted is a collision / reaction gas 533 in the housing (not shown) of the collision / reaction cell, with gas molecules represented by dots.

[0104] During the restriction period ( Figure 5A ), ions 506 (analyte ions and interfering ions (if any)) travel into the ion guide 546 and are radially confined by the RF field applied by the rod electrodes of the ion guide 546 as described herein. An exit DC potential of a first magnitude (in this example, +100 V) is applied to the cell exit lens 524, thereby generating a DC barrier 537 at the cell exit lens 524. The ions 506 enter the cell with a certain kinetic energy, travel through the ion guide 546, are reflected by the DC barrier 537, and return toward the entrance of the ion guide 546, as shown by arrow 539. During this journey, the ions are decelerated by multiple collisions with the collision / reaction gas, and some of them are even stopped, thereby being confined in the cell. In addition, if an axial DC potential gradient 535 is generated, some reflected ions are repelled and forced back toward the exit of the ion guide 546, thereby being confined near the cell exit, as shown by another arrow 541. The DC barrier 537 is maintained throughout the confinement period, the duration of which is determined as described elsewhere in this disclosure.

[0105] In the case of the reaction mode of operation, the collision / reaction gas 533 is a reaction gas. The reaction gas reacts with unwanted interfering ions (background ions), but does not react with the analyte ions (signal ions) of the isobaric elements of interference. After sufficient restricted periods (corresponding to the reaction time of the interfering ions), most of the interfering ions have been eliminated by reacting with the gas, and the analyte ions remain limited as described in the preceding paragraph. Therefore, the ratio of the analyte ion density to the interfering ion density increases in the collision / reaction cell, and during the subsequent measurement period, the analyte ions are measured with an improved S / B ratio. Alternatively, the ions measured are product ions produced by the reaction between the analyte ions (in this case, reactive) and the gas. In this case, the analyte ions react with the reaction gas, and during the restricted period, the resulting product ions are no longer restricted in the cell with the gas reaction.

[0106] After a desired amount of confinement period duration, operation of the collision / reaction cell is switched from the confinement period to the measurement period by rapidly removing (or at least lowering) the DC barrier 537 to allow analyte ions 566 to exit the collision / reaction cell and enter a downstream mass analyzer (not shown), as shown in FIG. Figure 5B The DC barrier 537 is removed by rapidly switching the exit DC potential on the cell exit lens 524 from a first magnitude to a lower second magnitude (-50 V in this example). In this way, an intense short ion pulse is obtained during the measurement period, which can be used for ion measurements with an improved S / N ratio.

[0107] An axial DC potential gradient 535 may be applied to improve ion confinement efficiency during the confinement period and ion ejection efficiency during the measurement period.

[0108] Experimental Examples

[0109] Experiments were conducted to evaluate the collision / reaction cell and the method of operation as described herein. Solutions of cobalt (Co), yttrium (Y), and thallium (Tl) at 1 part per billion (ppb) were injected into an argon (Ar) plasma and the resulting ions were transported to the collision / reaction cell. Oxygen (O2) was mixed into the collision / reaction cell at a flow rate of 0.45 standard cubic centimeters per minute (sccm) to examine the generation of short intense ion pulses. O2 acted as a Co + and Tl + collision gas, since these two ions do not react with O2 and serve as Y + of the reaction gas, because Y + Reacts with O2 to form product ion YO which no longer reacts with O2 + . Therefore, during the restricted period implemented as described herein, Co + ,YO +and Tl + Restricted to the unit.

[0110] Fig. 6A and 6B Figure 3 shows the Co ejected from the collision / reaction cell after a 60 ms confinement period by switching the outlet DC potential from +100 V to -50 V in about 0.05 ms. + ,YO + and Tl + Specifically, Fig. 6A It means for Co + Ions (curve 602), YO + ions (curve 604) and Tl + A set of curves of ion pulses measured by ions (curve 606) (ion signal intensity, in counts per second, or cps, as a function of time (in ms) after switching the cell exit potential), Figure 6B Yes means Fig. 6A Figure 1 shows a set of curves for the trailing edges of the three ion pulses shown in Figure 1. During the confinement period and the measurement period, a negative entrance DC potential is applied at the cell entrance lens to allow ions to continue to enter the cell. Approximately 0.1 ms to 0.8 ms after the end of the confinement period (the beginning of the measurement period), ion pulses of sub-ms width are detected. The pulse peak height is for Co + For 4×10 8 Counts / second (cps) for YO + 5×10 8 cps, for Tl+ is 2.8×10 8 cps, such as Fig. 6A These intensities (count rates) are much higher than the steady-state signal levels (1 to 2 x 10 6 cps) by two orders of magnitude, these intensities were observed for the three ions after this pulse, such as Figure 6B As shown (from 1ms to 1.8ms).

[0111] Another experiment was performed to evaluate the collision / reaction cell and the method of operation as described herein. A blank solution (deionized water, DIW) was injected into an argon (Ar) plasma and the resulting ions were transferred to the collision / reaction cell and mass analyzed to measure the m / z = 40 ion ( 40 Ar + ions). Next, 0.1 parts per billion (ppb) of calcium solution was injected into the argon (Ar) plasma, and the resulting ions were transferred to the collision / reaction cell and mass analyzed to measure the m / z = 40 ions ( 40 Ar + and 40 Ca +ions). Therefore, the argon ions 40 Ar + Interfering with calcium ions at m / z = 40 40 Ca + Water vapor (H2O) was used as the reaction gas to suppress this interference. Water vapor was mixed into the collision / reaction cell at a fixed flow rate of 0.1 milligrams per minute (mg / min) along with helium (He). Collisions with this additional helium can promote the Ca + ions for efficient confinement and can help slow down the Ar+ ions for efficient reaction with H2O. 40 Ar + Charge transfer to water molecules, argon ions 40 Ar + is converted into non-interfering neutral argon atoms Ar. On the other hand, water vapor does not react with calcium ions. 40 Ca + Reaction. Therefore, the reaction involved in interference suppression in this example is:

[0112] H2O+Ar + →H2O + +Ar

[0113] H2O+Ca + →No reaction

[0114] Therefore, during the restriction period, Ca + The ions are trapped and accumulated in the cell, and the Ar + The ions react with water, thereby reducing the Ar in the cell. + The exit DC potential applied at the cell exit lens is switched from +100 V to -50 V in about 0.05 ms to start the measurement period. The measurement duration (ion counting period) is set to 0.5 ms, which corresponds to the expected pulse duration, such as Figure 5A shown.

[0115] Figure 7 is a set of curves showing the experimental results. Curve 702 obtained by subtracting the blank signal from the Ca solution signal represents the net m / z = 40 from the 0.1 ppb calcium solution. 40 Ca + Ion signal intensity (in counts per second or cps) as a function of ion confinement duration (or storage time or reaction time, in ms) in the collision / reaction cell. Curve 704 represents interfering background ions ( 40 Ar +ion) intensity as a function of the duration of ion confinement. Curve 706 represents the calculated background equivalent concentration or BEC (in parts per trillion or ppt) as a function of the duration of ion confinement. The BEC is inversely proportional to the S / B ratio as follows:

[0116] BEC = (background intensity / signal intensity) * analyte concentration

[0117] The BEC curve 706 shows that as the duration of ion confinement in the collision / reaction cell (and therefore the reaction time) increases, the S / B ratio increases. Figure 7 The advantages provided by the collision / reaction cell and method of operation disclosed herein are demonstrated.

[0118] Figure 8A flow chart 800 of an example of a method for operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system according to an embodiment is shown. A collision / reaction gas flows into the collision / reaction cell (step 802). The collision / reaction cell includes an inlet, an outlet spaced from the inlet along the longitudinal axis of the collision / reaction cell, and a multipole ion guide between the inlet and the outlet. The multipole ion guide is configured to limit ions in a radial direction perpendicular to the longitudinal axis. Ions are transmitted through the inlet and enter the collision / reaction cell (step 804). The transmitted ions are at least analyte ions generated by ionizing the sample being analyzed. In some embodiments, interfering ions are also generated by the plasma forming gas used to ionize the sample and are also transmitted to the collision / reaction cell. An outlet DC potential is applied at a first magnitude to generate a DC barrier that effectively prevents ions from leaving the collision / reaction cell (step 806). There is no specific restriction on the startup sequence of steps 802-806, and two or more of steps 802-806 can be started simultaneously or almost simultaneously. During the restricted period, the outlet DC potential is maintained at a first value, to perform the interaction between ions and collision / reaction gas (step 808). The type of interaction depends on the operating mode being performed. This interaction can effectively suppress the interfering ion signal intensity measured by mass spectrometer. For example, in a mode (the reaction mode of interfering ions (if any) and the collision mode of analyte ions), interfering ions (if any) react according to the reaction and collision / reaction gas that effectively converts interfering ions into non-interfering ions or neutral substances, and analyte ions collide with collision / reaction gas repeatedly to effectively slow down and limit the analyte ions in the collision / reaction unit. In another mode (the reaction mode of analyte ions and the collision mode of product ions), analyte ions react according to the reaction and collision / reaction gas that effectively produces the product ions measured by mass spectrometer, and product ions collide with collision / reaction gas repeatedly to effectively slow down and limit the product ions in the collision / reaction unit. In a latter mode, interfering ions do not react with collision / reaction gas, so in collision / reaction unit, new ions that can interfere with the product ions derived from analyte are not produced. After the confinement period, the analyte ions or product ions are transmitted to the mass spectrometer by switching the outlet DC potential to a second magnitude effective to allow the analyte ions or product ions to pass through the outlet as a pulse having a pulse duration (step 810). The analyte ions or product ions are then measured or counted during a measurement period (step 812). The measurement period may have a duration approximately equal to the pulse duration.

[0119] In an embodiment, flow chart 800 may represent a collision / reaction cell, or a collision / reaction cell and associated electronics, or a collision / reaction cell and associated ICP-MS system configured to perform steps 802-812. To this end, a controller including a processor, a memory, and other components as understood by those skilled in the art may be provided (e.g., Figure 1 The controller 120 shown in FIG. 1 may control the performance of steps 802-812, for example, by controlling components of the ICP-MS system (eg, units, electronics, etc.) involved in performing steps 802-812.

[0120] Fig. 9 is a schematic diagram of a non-limiting example of a system controller (or controller or computing device) 120, which may be a spectrometric system (such as Figure 1 ) as part of or in communication with the ICP-MS system 100 shown in . In the illustrated embodiment, the system controller 120 includes: a processor 902 (typically based on electronic devices), which can represent a main electronic processor that provides overall control; and one or more electronic processors configured for dedicated control operations or specific signal processing tasks (e.g., a graphics processing unit or GPU, a digital signal processor or DSP, an application-specific integrated circuit or ASIC, a field programmable gate array or FPGA, etc.). The system controller 120 also includes one or more memories 904 (volatile and / or non-volatile) for storing data and / or software. The system controller 120 may also include one or more device drivers 906 for controlling one or more types of user interface devices and providing an interface between the user interface device and the components of the system controller 120 that communicate with the user interface device. Such user interface devices may include user input devices 908 (e.g., keyboards, keypads, touch screens, mice, joysticks, trackballs, etc.) and user output devices 910 (e.g., display screens, printers, visual indicators or alarms, audible indicators or alarms, etc.). In various embodiments, the system controller 120 can be viewed as including, or at least in communication with, one or more of a user input device 908 and / or a user output device 910. The system controller 120 can also include one or more types of computer programs or software 912 contained in memory and / or one or more types of computer readable media 914. The computer program or software can include non-transitory instructions (e.g., logic instructions) for controlling or executing various operations of the ICP-MS system 100. The computer program or software can include application software and system software. The system software can include an operating system (e.g., Microsoft Windows) 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 may be displayed via the user output device 910, and the user may use the graphical user interface to interact with the use of the user input device 908. The system controller 120 may also include one or more data acquisition / signal conditioning components (DAQ) 916 (which may be implemented in hardware, firmware, and / or software) for receiving and processing the ion measurement signals ( Figure 1 ), including formatting data for graphical presentation by the GUI.

[0121] The system controller 120 may also include a cell controller (or control module) 918 that is configured to control the operation of the collision / reaction cell 110 and coordinate the cell operation with the ion source 108, the ion optics section 114, the mass analysis section 118, and the like. Figure 1 The unit controller 918 may be configured to coordinate and / or synchronize operations with any other ion processing devices provided in the illustrated ICP-MS system 100. Thus, the unit controller 918 may be configured to control or execute all or part of any method disclosed herein, including methods for operating the collision / reaction cell 110. For these purposes, the unit controller 918 may be implemented in software and / or electronics (hardware and / or firmware), as will be appreciated by those skilled in the art.

[0122] It should be understood that Fig. 9 1 is a high-level schematic diagram of an example of a system controller 120 consistent with the present disclosure. Other components may be included, such as additional structures, devices, electronic devices, and computer-related or electronic processor-related components, as desired in the actual implementation. It will also be understood that the system controller 120 is not limited to the components of FIG. Fig. 9 Schematically represented in the figure are functional blocks intended to represent structures (e.g., circuits, mechanisms, hardware, firmware, software, etc.) that may be provided. The various functional blocks and any signal links between them are arbitrarily positioned and are used for illustrative purposes only and are not limiting in any way. Those skilled in the art will understand that in practice, the functions of the system controller 120 may be implemented in a variety of ways and not necessarily in a single manner. Fig. 9 The invention is carried out in the precise manner shown in and described by the examples herein.

[0123] Various collision / reaction gases are used to resolve spectral interferences in a quadrupole ICP-MS equipped with a collision / reaction cell. These gases include He, H2, NH3, CH4, O2, N2O, and mixtures of two gases such as NH3 and He, or Ar and H2. It is common and conventional to use high-purity industrial gases as such gases. See PerkinElmer, NexION1000 / 2000ICP-MS, PREPARING YOUR LAB (2018); Quarles, Jr. et al., Analytical method for total chromium and nickel in urine using an inductively coupled plasma-universal cell technology-mass spectrometer (ICP-UCT-MS) in kinetic energydiscrimination (KED) mode, J. Anal. At. Spectrom., Vol. 29, 297-303 (2014); Guo et al., Application of ion molecule reaction to eliminate WO interference on mercurydetermination in soil and sediment samples by ICP-MS; J. Anal. At. Spectrom., Vol. 26, 1198-1203 (2011); and ThermoFisher Scientific,iCAP RQ ICP-MS Pre-Installation Requirements Guide,BRE0009927 Revision A,(November 2016); the entire contents of each of these documents are incorporated herein by reference. High purity industrial gases are usually provided from gas suppliers in the form of pressurized cylinders. For safety reasons, H2 gas has also been available from hydrogen generators or tanks containing hydrogen storage alloys. However, H2 is an exception. For other collision / reaction gases including O2 gas, high pressure industrial gases have been used for reaction cell ICP-MS.

[0124] As a reaction gas, O2 has been used to solve some spectral interference problems in ICP-MS. In the reaction cell, some analyte ions M + Reacts with O2 molecules to produce oxide ions MO + , as shown in the following equation (1). If we have +Interfering ions X with the same m / z + By reacting with O2 (see equation (2) below), no XO is generated. + , then we can measure MO + To determine the element M, since MO + Now not affected by X + The impact of interference.

[0125] M + + O2 → MO + + O (1)

[0126] X + + O2 → No reaction or no production of XO + (2)

[0127] Other industrial gases such as N2O and CO2 can also be used to generate MO in collision / reaction cells. + , as shown in equations (3) and (4) below. See U.S. Patent No. 6,875,618, the contents of which are incorporated herein by reference in their entirety.

[0128] M + + N2O → MO + + N2 (3)

[0129] M + + CO2 → MO + + CO (4)

[0130] Ambient air can generate MO + , because it contains O2 gas. However, ambient air has not been used for this purpose in ICP-MS, despite its safety and cost-free nature. The use of ambient air as a reaction gas may not have been considered due to concerns that the various components that make up ambient air and / or impurities (contaminants) in the ambient air could adversely affect the performance of the reaction unit.

[0131] According to one aspect of the present disclosure, ambient air can be effectively used as a reaction gas in a reaction unit of an ICP-MS system as a substitute or replacement for commercially available conventionally used pure O2 gas (e.g., from an industrial gas supplier). In particular, the inventors have found that ambient air is particularly effective in an ICP-MS system having a triple quadrupole (QQQ) configuration.

[0132] Fig.10 is a schematic diagram of an example of an inductively coupled plasma mass spectrometry (ICP-MS) system 1000 according to another embodiment of the present disclosure, particularly a system having a triple quadrupole (QQQ) configuration. Fig.10As shown in and as previously described in this disclosure, such an ICP-MS system 1000 includes (in order of ion process flow) an ICP ion source 1008, a first (or pre-unit) quadrupole mass filter (Q1) 1026, a reaction unit 1010 (or a "collision / reaction unit" as defined herein), a second (final) quadrupole mass filter (Q2) 1058, and an ion detector 1061. A gas inlet 1042 (e.g., comprising a port, a feed conduit, a pump, etc.) is configured to allow ambient air to flow into the interior of the reaction unit 1010. In some embodiments, the gas inlet 1042 may include a gas purifier configured to remove impurities or contaminants from the incoming ambient air. As a non-exclusive example, the gas purifier may include a purification element (e.g., a filter, a trap, etc.), such as a molecular sieve (e.g., a "molecular sieve" ”, a composite containing silica and alumina and having a pore size of 3 angstroms, etc.), an adsorbent material (such as activated carbon, etc.), or a combination of different types of purification elements. The ICP-MS system 1000 may have the above combined Figure 1 The ICP-MS system 1000 having a triple quadrupole configuration may be operated as previously described in this disclosure.

[0133] Compared with commercially available pure O2 gas, the operation Fig.10 The ICP-MS system 1000 shown in FIG. 1 is an instrument consistent with the ICP-MS system 1000 to evaluate the effectiveness of ambient air as a reaction gas. Specifically, ambient air is introduced into the reaction cell 1010, and phosphorus (P) and sulfur (S) are measured as analytes. 31 P product ion 31 P 16 O + The measurement was performed in the form of , where the first mass filter (Q1) 1026 was set to m / z = 31, and the second mass filter (Q2) 1058 was set to m / z = 47. Similarly, the element 32 S as product ion 32 S 16 O + The measurement is performed in the form of a first mass filter (Q1) 1026 being set to m / z = 32, and a second mass filter (Q2) 1058 being set to m / z = 48. Both the first mass filter (Q1) 1026 and the second mass filter (Q2) 1058 are operated at a certain unit mass resolution.

[0134] P + (m / z=31) and S + Typical interferences (m / z=32) are polyatomic ions 14 N16 OH + and 16 O2 + , these polyatomic ions are generated in the ion source 1008 or just downstream of the ion source 1008. + (m / z=47) and SO + When measuring the (m / z=48) form, the O2 gas in the reaction unit 1010 removes these interferences because the O2 gas is + and S + Reacts efficiently, but not with NOH + and O2 + The reactions are shown in the following equations (5) to (8).

[0135] P + + O2 → PO + + O (5)

[0136] NOH + + O2 → No reaction or NOOH generation + (6)

[0137] S + + O2 → SO + + O (7)

[0138] O2 + + O2 → No reaction or no production of O3 + (8)

[0139] Table 1 below shows the data obtained for sensitivity (in counts per second per part per billion (cps / ppb)) and background equivalent concentration (BEC (in ppb)) for P and S using ambient air as the reaction gas. For comparison, Table 1 also shows the same data obtained for P and S using high purity (100% or close to 100% purity) O2 as the reaction gas.

[0140] Table 1

[0141]

[0142] The flow rates of ambient air and pure O2 gas introduced into the reaction unit 1010 are adjusted so that the oxide ion signal (PO + and SO + The strength of the reaction mixture is maximized. Even though the O2 content in the ambient air is only 21%, the necessary flow rate of the ambient air (0.4 sccm) is almost equal to the flow rate of pure O2 gas (0.3 sccm). This is mainly because the N2 and other inert gas molecules in the ambient air promote the reaction, as described further below.

[0143] The sensitivity of ambient air to P and S, although lower than that of pure O2 gas, is adequate for many analytical purposes. The BECs obtained using ambient air are almost the same or even slightly better (lower) than those obtained with pure O2 gas, indicating that the interference reduction with ambient air is comparable to that with pure O2 gas. Therefore, for P and S determinations, the adverse effect of substances in ambient air other than O2 molecules on the interference reduction is negligible.

[0144] The interpretation of these results is as follows.

[0145] Dry air consists of (approximate percentages) N2 (78%), O2 (21%), Ar (0.93%), CO2 (0.04%), Ne (18 ppm), He (5 ppm), and other minor components at single-digit ppm levels or lower. Ambient air also contains varying concentrations of water vapor (H2O) (0.001% to 5%) and various impurities that may be of anthropogenic origin.

[0146] Although O2 molecules in the air can be used to generate O2 molecules from M in the reaction unit 1010, + generate MO + However, N2, Ar, -Ne and He in the air are inert gases, which act as buffer gases in the reaction unit to promote the reaction of O2 and M + Like O2, CO2 and water (H2O) in the air also react with certain M + Ions react to produce MO + ions, as shown in equation (4) above and equation (9) below, respectively.

[0147] M + + H2O → MO + + H2 (9)

[0148] On the other hand, gaseous impurities B in ambient air j (j=1,2,3,...) (usually water vapor and various hydrocarbons) will be + Ionic substances other than A i + (i=1,2,3,...) to produce various reaction products C ij + and D ij (See equation (10) below). If the product ion species C ij + One of them has the same + The same m / z, MO can no longer be performed + Non-intrusive detection.

[0149] A i + + B j → C ij + + D ij (11)

[0150] Ions generated by impurities in the ambient air were also observed experimentally. The first mass filter (Q1) 1026 was set to m / z = 40 to allow 40 Ar + Entering the reaction cell 1010. The second mass filter (Q2) 1058 is scanned to measure the mass of the reaction cell 1010 that is filled with ambient air. 40 Ar + and B j The different ions produced by the reaction between are shown in the following equation (11).

[0151] 40 Ar + + B j → C j + + D j (11)

[0152] It should be noted that equation (11) is the main reaction, and subsequent reactions may occur between Cj+ and Bj or between 40Ar+ and Dj to produce new ions other than Cj+.

[0153] Fig.11 Shown is a representation of C j + and by 40 Ar + The measurement results of other ions produced by the reaction between and Bj and its subsequent reactions. Using the ambient air introduced into the reaction unit 1010 as is (in its natural state, not purified) and through a molecular sieve The measurement is performed with ambient air introduced by a gas purifier using activated carbon. When the gas purifier is used, the total intensity of the product ions is lower. When two spectra are measured (obtained from the unpurified ambient air and the purified ambient air, respectively), the reaction ions entering the reaction unit 1010 are 40 Ar + The intensity of the product ions is constant. Therefore, the intensity of the product ions reflects the B introduced into the reaction unit 1010. j The observed product ions originate from one ion species, Ar + Reaction with ambient air components. If other ionic species enter the reaction cell 1010, the product ions should be different in intensity and type.

[0154] In addition to P and S, other analytes can be processed in an ICP-MS system using ambient air as the reaction gas. Examples include, but are not limited to, titanium (Ti), arsenic (As), selenium (Se), and uranium (U).

[0155] By having as described herein and as Fig.10 The operation of the reaction unit 1010 in the triple quadrupole configuration of the ICP-MS system 1000 shown can greatly reduce the generation of interfering ions (having the same ions as MO) by impurities reacting with ions. + This is because the first mass filter (Q1) 1026 can be set (or tuned) to limit the ion species entering the reaction unit 1010 to only 1 m / z (M + m / z), thereby suppressing the gas component (B in equation (11) j ) and other intra-cell reactions that would otherwise occur between various ion species that were not ejected prior to reaction cell 1010. For example, when measuring phosphorus ( 31 P), the first quality filter (Q1) 1026 only allows 31 P + and isobaric interfering ions (such as 14 N 16 OH + ) enters the reaction unit 1010. Therefore, for example 40 Ar + The ions are ejected from the ion beam by the first mass filter (Q1) 1026 prior to the reaction cell 1010 and therefore never react to produce Fig.11 In a system without the first mass filter (Q1) 1026 (or in a single quadrupole configuration), the m / z=47 ion from the ion source 1008 is 40 Ar + and other ions will enter the reaction unit 1010 (with P + together) and react with impurity gases to produce various reaction products. + Same m / z, some of these reaction products may interfere with MO + .

[0156] The humidity of the ambient air changes due to changes in environmental conditions. As shown in equation (10), the analyte ion MO +The yield of is affected by the concentrations of H2O and O2 in the reaction unit 1010. In order to ensure the stability of the ion signal even if the weather or laboratory environment changes, purified ambient air can be introduced into the reaction unit 1010. The ambient air can be purified by using a gas purifier before flowing into the reaction unit 1010, so that the ambient air entering the reaction unit 1010 maintains a constant or uniform composition regardless of the environmental conditions. As described above, in Fig.10 In the schematic diagram of FIG. 1040 , an optional (but preferred for some applications) gas purifier can be associated with the gas inlet 1042. As a non-exclusive example, the gas purifier can have a flow-through configuration that includes a molecular sieve (e.g., as a moisture trap) or a combination of a molecular sieve and activated carbon (e.g., as a hydrocarbon trap). Typically, this type of gas purifier is unable to filter out all components except O2 to convert ambient air into pure O2 gas, i.e., is unable to completely separate and allow only O2 molecules to enter the reaction unit 1010. Therefore, for many applications, a triple quadrupole configuration is still required to allow the purified ambient air to function appropriately (or have an acceptable level of effectiveness that is considered for analytical purposes in a given application).

[0157] In the context of the present disclosure, the term "ambient air" generally refers to atmospheric air having the above-mentioned components, i.e., a mixture of primarily N2 and O2 and certain other gases in lower concentrations, and also water vapor in varying concentrations. Ambient air is different from synthetic air produced by mixing high purity nitrogen and high purity oxygen; and is stored in containers for various industrial uses. Ambient air may also contain certain dirt or pollutants (some of which may be particles rather than gas molecules). The ambient air brought into the collision / reaction unit may be unpurified or purified. Unpurified ambient air is ambient air that has not been subjected to a purification (e.g., filtering, trapping, washing, cleaning, etc.) process before being brought into the collision / reaction unit. Purified ambient air is ambient air that has been purified to a certain extent before being brought into the collision / reaction unit in order to remove (or at least reduce the concentration of) one or more components (gases and / or particles) of the ambient air other than O2. The term "ambient air" can refer to air that can be brought into a collision / reaction cell from a local environment outside the collision / reaction cell (or outside an instrument or system of which the collision / reaction cell is a part) without first being stored or confined in a manner such as described above (e.g., a container, such as a gas cylinder, tank, etc., typically obtained from an industrial gas supplier). That is, the source of the ambient air brought into the collision / reaction cell can be the local environment outside the collision / reaction cell, rather than in a container filled with pure O2 gas. The source of the ambient air can be a room or space within a building (e.g., a laboratory) in which the collision / reaction cell operates. For purposes of this disclosure, such an interior room or space is considered an example of a local environment outside the collision / reaction cell and is not considered stored or confined air. An exception to the foregoing definition is that in some embodiments, ambient air (having the multi-component composition described above) can be supplied to the collision / reaction cell from a pressurized container, that is, the source of the ambient air can be compressed air.

[0158] Fig.12 A flowchart 1200 is shown of an example of a method for operating a collision / reaction cell to suppress interferences in an inductively coupled plasma mass spectrometry (ICP-MS) system according to another embodiment. Ambient air flows into the collision / reaction cell (step 1202). After initiating the flow of ambient air into the collision / reaction cell, ions are transmitted into the collision / reaction cell (step 1204). The transmitted ions are at least analyte ions ((M + ), and may also include interfering ions (X + ). The analyte ions react with oxygen molecules (O2) of the ambient air to produce product ions in the collision / reaction cell (step 1206). The product ions are oxide ions (MO +), that is, the oxide of the analyte ion (or the oxidized analyte ion). There are interfering ions (X + ) is reacted under the condition that the mass-to-charge ratio of the interfering ion is equal to the mass-to-charge ratio of the analyte ion. The product ions are then transmitted to a mass spectrometer (step 1208). The mass spectrometer is operated to measure the product ions (step 1210).

[0159] As described above, the ambient air may or may not be purified before flowing into the collision / reaction cell (step 1202). In the latter case, the method includes purifying the ambient air to remove or reduce the concentration of one or more components of the ambient air other than oxygen molecules before flowing into the collision / reaction cell.

[0160] In an embodiment, transmitting ions into the collision / reaction cell (step 1204) includes transmitting only the analyte ions and interfering ions (if any) having a mass-to-charge ratio equal to the mass-to-charge ratio of the analyte ions. Additionally, operation of the mass spectrometer (step 1210) includes measuring only the product ions and other ions (if any) having a mass-to-charge ratio equal to the mass-to-charge ratio of the product ions.

[0161] For example, the method may include transmitting the ions to a first mass filter group to allow only the analyte ions and interfering ions with a mass-to-charge ratio equal to the mass-to-charge ratio of the analyte ions to be transmitted to the collision / reaction cell before transmitting the ions to the collision / reaction cell (step 1204). In addition, transmitting the product ions to the mass spectrometer (step 1208) may include transmitting the product ions to a second mass filter of the mass spectrometer, and the operation of the mass spectrometer (step 1210) may include setting the second mass filter to allow only the product ions and other ions with a mass-to-charge ratio equal to the mass-to-charge ratio of the product ions to be transmitted to an ion detector of the mass spectrometer.

[0162] In another embodiment, when using ambient air as the reaction gas, the above combination can be applied. Figure 1-9 One or more aspects of the described methods.

[0163] In an embodiment, flow chart 1200 may represent a collision / reaction cell, or a collision / reaction cell and associated electronics, or a collision / reaction cell and associated ICP-MS system configured to perform steps 1202-1210. To this end, a controller including a processor, a memory, and other components as understood by those skilled in the art may be provided (e.g., Figure 1 120 ) to control the performance of steps 1202 - 1210 , such as by controlling components of the ICP-MS system (eg, units, electronics, etc.) involved in performing steps 1202 - 1210 .

[0164] Exemplary embodiments

[0165] Exemplary embodiments provided in accordance with the presently disclosed subject matter include, but are not limited to, the following:

[0166] 1. A method of operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system, the method comprising: flowing a collision / reaction gas into the collision / reaction cell, the collision / reaction cell comprising an inlet, an outlet spaced apart from the inlet along a longitudinal axis of the collision / reaction cell, and a multipole ion guide disposed between the inlet and the outlet and configured to confine ions in a radial direction perpendicular to the longitudinal axis; transmitting ions through the inlet and into the collision / reaction cell; applying an outlet DC potential at a first magnitude at the outlet to produce an ion guide effective to prevent the ions from leaving the cell; a DC barrier of the collision / reaction cell; maintaining the outlet DC potential at the first magnitude during a confinement period; causing the ions to collide with the collision / reaction gas during the confinement period, wherein the ions undergo multiple collisions to effectively slow down and confine the ions in the collision / reaction cell; after the confinement period, transmitting at least analyte ions of the confined ions to a mass spectrometer by switching the outlet DC potential to a second magnitude that effectively allows the analyte ions to pass through the outlet as a pulse having a pulse duration; and counting the analyte ions during a measurement period having a duration approximately equal to the pulse duration.

[0167] 2. A method for operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system to suppress interference, the method comprising: flowing a collision / reaction gas into the collision / reaction cell, the collision / reaction cell comprising an inlet, an outlet spaced apart from the inlet along a longitudinal axis of the collision / reaction cell, and a multipole ion guide located between the inlet and the outlet and configured to confine ions in a radial direction perpendicular to the longitudinal axis; transmitting ions through the inlet and into the collision / reaction cell, wherein the ions include analyte ions and interfering ions generated by ionizing a sample under analysis using a plasma-forming gas; applying an outlet DC potential at a first magnitude at the outlet to generate a DC barrier that effectively prevents the ions from leaving the collision / reaction cell; maintaining the outlet DC potential at the first magnitude during a confinement period to perform an interaction that effectively suppresses the intensity of interfering ion signals measured by a mass spectrometer, wherein the ions are generated by ionizing a sample under analysis using a plasma-forming gas; The interaction is selected from the group consisting of: reacting the interfering ions with the collision / reaction gas according to a reaction that effectively converts the interfering ions into non-interfering ions or neutral species, wherein the analyte ions collide with the collision / reaction gas multiple times to effectively slow down and limit the analyte ions in the collision / reaction cell; and reacting the analyte ions with the collision / reaction gas according to a reaction that effectively produces product ions, wherein the product ions collide with the collision / reaction gas multiple times to effectively slow down and limit the product ions in the collision / reaction cell; after the confinement period, transmitting the analyte ions or product ions to the mass spectrometer by switching the outlet DC potential to a second value that effectively allows the analyte ions or the product ions to pass through the outlet as a pulse with a pulse duration; and counting the analyte ions or product ions during a measurement period having a duration approximately equal to the pulse duration.

[0168] 3. A method according to embodiment 1 or 2, wherein the first value and the second value are selected from the group consisting of: the second value is more negative than the first value; the first value is a positive or zero value, and the second value is a negative or zero value; the first value is in the range of 0V to +100V; the second value is in the range of -200V to 0V; and a combination of two or more of the foregoing.

[0169] 4. A method according to any one of the preceding embodiments, wherein the duration of the switching is in the range of 0.01 ms to 0.1 ms.

[0170] 5. A method according to any one of the preceding embodiments, wherein the duration of the restriction period is in the range of 0 ms to 1000 ms.

[0171] 6. The method of any one of the preceding embodiments, wherein the duration of the measurement period is in the range from the FWHM of the peak value of the pulse to five times the FWHM.

[0172] 7. A method according to any of the preceding embodiments, wherein the pulse duration is in the range of 0.01 ms to 1 ms.

[0173] 8. The method according to any of the preceding embodiments, wherein applying the outlet DC potential at the outlet comprises applying the outlet DC potential at an outlet lens of the collision / reaction cell.

[0174] 9. The method of any of the preceding embodiments, comprising applying an axial DC potential gradient along the multipole ion guide, wherein the confined ions are prevented from exiting the collision / reaction cell through the inlet during the confinement period.

[0175] 10. The method according to any one of the preceding embodiments, comprising continuing to transport the ions through the inlet and into the collision / reaction cell during the confinement period.

[0176] 11. According to the method described in any one of embodiments 1 to 9, an inlet DC potential is applied at the inlet during at least the later period of the confinement period to effectively prevent the confined analyte ions from leaving the collision / reaction unit through the inlet and prevent interfering ions from entering the collision / reaction unit through the inlet.

[0177] 12. The method according to any one of the preceding embodiments, comprising applying an inlet DC potential across the inlet during the measurement period to effectively prevent interfering ions from entering the collision / reaction cell through the inlet.

[0178] 13. The method according to any of the preceding embodiments, comprising generating the ions by exposing the sample to an inductively coupled plasma before transmitting the ions through the inlet and into the collision / reaction cell.

[0179] 14. The method of embodiment 13, wherein exposing the sample comprises operating a plasma torch.

[0180] 15. The method of embodiment 13 or 14, comprising flowing the sample from a nebulizer or nebulization chamber into the plasma torch.

[0181] 16. The method of any of the preceding embodiments, comprising selecting the collision / reaction gas based on the chemical characteristics of the analyte ions and the chemical characteristics of the interfering ions.

[0182] 17. A method according to any one of the preceding embodiments, wherein the analyte ion is a first analyte ion having a first mass, the interfering ion is a first interfering ion, the confinement period is a first confinement period having a first duration, the pulse is a first pulse, and the analyte ion also includes a second analyte ion having a second mass different from the first mass, and further includes: after measuring the first analyte ion contained in the first pulse, within a second confinement period having a second duration different from the first duration, again applying an outlet DC potential at the outlet at the first value; during the second confinement period, causing the collision / reaction gas to react with the second interfering ion that interferes with the second analyte ion, or causing the collision / reaction gas to react with the second analyte ion to suppress interference; after the second confinement period, transmitting a second pulse to the mass spectrometer by switching the outlet DC potential to the second value; and measuring the second analyte ion or the product ion formed by the second analyte ion contained in the second pulse.

[0183] 18. A method according to any one of the preceding embodiments, wherein the analyte ion is a first analyte ion having a first mass, the interfering ion is a first interfering ion, the confinement period is a first confinement period having a first duration, and the pulse is a first pulse, and further comprising: after counting the first analyte ion, transmitting a second analyte ion having a second mass different from the first mass and transmitting a second interfering ion that interferes with the second analyte ion through the inlet and into the collision / reaction unit; during a second confinement period having a second duration different from the first duration, applying the outlet DC potential at a first magnitude at the outlet to prevent the second analyte ion and the second interfering ion from leaving the collision / reaction unit during the second confinement period; during the second confinement period, causing the collision / reaction gas to react with the second interfering ion or the second reactant ion to suppress the interfering ion signal intensity; and after the second confinement period, transmitting the second analyte ion or the product ion formed by the second analyte ion as a second pulse through the outlet to the mass spectrometer.

[0184] 19. The method according to embodiment 17 or 18 includes: selecting the first duration based on the chemical characteristics of the first analyte ion and the first interfering ion; and selecting the second duration based on the chemical characteristics of the second analyte ion and the second interfering ion.

[0185] 20. The method according to any one of embodiments 17 to 19 includes: allowing the collision / reaction gas to flow into the collision / reaction unit at a certain flow rate during the first restriction period, and allowing the collision / reaction gas to flow into the collision / reaction unit at the same flow rate during the second restriction period.

[0186] 21. A method according to any of the preceding embodiments, wherein the collision / reaction gas is selected from the group consisting of: helium; neon; argon; hydrogen; oxygen; water; air; ammonia; methane; fluoromethane; nitrous oxide; and combinations of two or more of the foregoing.

[0187] 22. A method according to any of the preceding embodiments, wherein the analyte ions are selected from the group consisting of: positive monatomic ions of metals or other elements except rare gases; and product ions produced by reacting the collision / reaction gas with positive monatomic ions of metals or other elements except rare gases.

[0188] 23. A method according to any of the preceding embodiments, wherein the interfering ions are selected from the group consisting of: positive argon ions; polyatomic ions containing argon; doubly charged ions containing components of the sample; isobaric ions containing components of the sample; and polyatomic ions containing components of the sample.

[0189] 24. A method for analyzing a sample, the method comprising: generating analyte ions from the sample; transmitting the analyte ions to a collision / reaction unit according to any one of the preceding embodiments; operating the collision / reaction unit according to the method of any one of the preceding embodiments; and transmitting the analyte ions to a mass analyzer of the mass spectrometer.

[0190] 25. An inductively coupled plasma mass spectrometry (ICP-MS) system comprising: an ion source configured to generate a plasma and to produce analyte ions in the plasma; a collision / reaction cell according to any of the preceding embodiments; and a controller comprising an electronic processor and a memory and configured to control the steps of the method described in any of the preceding embodiments.

[0191] 26. An inductively coupled plasma mass spectrometry (ICP-MS) system, comprising: an ion source configured to generate a plasma and generate analyte ions in the plasma; a collision / reaction cell, the collision / reaction cell comprising an inlet configured to receive the analyte ions from the ion source, an outlet spaced apart from the inlet along a longitudinal axis of the collision reaction cell, and a multipole ion guide located between the inlet and the outlet and configured to confine ions in a radial direction perpendicular to the longitudinal axis; a mass spectrometer in communication with the outlet; and a controller comprising an electronic processor and a memory and configured to control operations including: flowing a collision / reaction gas into the collision / reaction cell; transmitting ions through the inlet and into the collision / reaction cell, wherein the ions include analyte ions generated in the ion source and interfering ions; applying an outlet DC potential at a first magnitude at the outlet to generate a DC barrier effective to prevent the ions from leaving the collision / reaction cell; maintaining the outlet DC potential at a first magnitude during a confinement period; a magnitude to perform an interaction that effectively suppresses the intensity of an interfering ion signal measured by the mass spectrometer, the interaction being selected from the group consisting of: reacting the interfering ions (if any) with the collision / reaction gas according to a reaction that effectively converts the interfering ions into non-interfering ions or neutral species, wherein the analyte ions collide with the collision / reaction gas multiple times to effectively slow down and confine the analyte ions in the collision / reaction cell; and reacting the analyte ions with the collision / reaction gas according to a reaction that effectively produces product ions to be measured by the mass spectrometer, wherein the product ions collide with the collision / reaction gas multiple times to effectively slow down and confine the product ions in the collision / reaction cell; after the confinement period, transmitting the analyte ions or the product ions to the mass spectrometer by switching the outlet DC potential to a second magnitude that effectively allows the analyte ions or the product ions to pass through the outlet as a pulse having a pulse duration; and measuring the analyte ions or the product ions during a measurement period having a duration approximately equal to the pulse duration.

[0192] 27. An ICP-MS system according to embodiment 25 or 26, wherein the controller is configured to control the application of an axial DC potential gradient along the multipole ion guide, wherein the confined ions are prevented from leaving the collision / reaction cell through the inlet during the confinement period.

[0193] 28. The ICP-MS system of embodiments 25 to 27, comprising an exit lens, wherein the controller is configured to apply the exit DC potential at the exit lens.

[0194] 29. An ICP-MS system according to any one of embodiments 25 to 28, wherein the ion source comprises a plasma torch.

[0195] 30. The ICP-MS system of any one of embodiments 25 to 29, comprising a collision / reaction gas source configured to flow the collision / reaction gas into the collision / reaction cell.

[0196] 31. A method or system according to any of the preceding embodiments, wherein the mass spectrometer is a non-pulsed instrument.

[0197] 32. A method or system according to embodiment 31, wherein the non-pulsed instrument includes a multipolar device or a fan-shaped instrument configured for non-pulsed operation.

[0198] 33. A method of operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system to suppress interferences, the method comprising: flowing ambient air into the collision / reaction cell; transmitting ions into the collision / reaction cell, wherein the ions include analyte ions (M + ); reacting the analyte ions with oxygen molecules (O2) of the ambient air to produce product ions, wherein the product ions are oxide ions (MO + ), the reaction has interfering ions (X + ), and the mass-to-charge ratio of the interfering ions is equal to the mass-to-charge ratio of the analyte ions; transmitting the product ions to a mass spectrometer; and operating the mass spectrometer to measure the product ions.

[0199] 34. A method according to embodiment 33, wherein the ambient air is unpurified before the ambient air is allowed to flow into the collision / reaction unit.

[0200] 35. The method of embodiment 33 comprises purifying the ambient air to remove or reduce the concentration of one or more components in the ambient air other than oxygen molecules before flowing the ambient air into the collision / reaction cell.

[0201] 36. A method according to any one of embodiments 33-35, wherein: the transmitting of ions into the collision / reaction unit includes transmitting only the analyte ions and interfering ions whose mass-to-charge ratio is equal to the mass-to-charge ratio of the analyte ions; and the operation of the mass spectrometer includes measuring only the product ions and other ions (if any) whose mass-to-charge ratio is equal to the mass-to-charge ratio of the product ions.

[0202] 37. A method according to any one of embodiments 33-36, comprising, before transmitting the ions to the collision / reaction unit, transmitting the ions to a first mass filter group to allow only the analyte ions and interfering ions with a mass-to-charge ratio equal to the mass-to-charge ratio of the analyte ions to be transmitted to the collision / reaction unit, wherein: transmitting the product ions to the mass spectrometer includes transmitting the product ions to a second mass filter of the mass spectrometer; and the operation of the mass spectrometer includes setting the second mass filter to allow only the product ions and other ions with a mass-to-charge ratio equal to the mass-to-charge ratio of the product ions to be transmitted to the ion detector of the mass spectrometer.

[0203] 38. A method according to any one of embodiments 33-37, wherein the collision / reaction unit includes: an inlet, into which ions containing analyte ions are transmitted; an outlet, from which the product ions are transmitted to the mass spectrometer; and a multipole ion guide located between the inlet and the outlet.

[0204] 39. The method according to embodiment 38 includes: applying an outlet DC potential at a first value at the outlet to produce a DC potential barrier that effectively prevents the ions from leaving the collision / reaction unit; and maintaining the outlet DC potential at the first value during a confinement period, wherein: reacting the analyte ions with oxygen molecules is completed during the confinement period; and transmitting the product ions to the mass spectrometer is completed after the confinement period, and includes switching the outlet DC potential to a second value that effectively allows the product ions to pass through the outlet as a pulse with a pulse duration.

[0205] 40. A method according to embodiment 39, wherein the operation of the mass spectrometer includes measuring the product ions during a measurement period having a duration approximately equal to the pulse duration.

[0206] 41. A method according to any one of embodiments 33-40, comprising one or more features or steps according to any one of embodiments 3-20, 22 and / or 23.

[0207] 42. A method for analyzing a sample, the method comprising: generating analyte ions from the sample; transmitting the analyte ions to a collision / reaction unit according to any one of embodiments 33-41; operating the collision / reaction unit according to the method according to any one of embodiments 33-41; and transmitting the product ions to a mass analyzer of the mass spectrometer.

[0208] 43. An inductively coupled plasma mass spectrometry (ICP-MS) system comprising: an ion source configured to generate a plasma and to produce analyte ions in the plasma; a collision / reaction cell according to any one of embodiments 33-41; and a controller comprising an electronic processor and a memory and configured to control the steps of the method described in any one of embodiments 33-42.

[0209] It will be understood that one or more of the processes, sub-processes, and process steps described herein may be performed by hardware, firmware, software, or a combination of two or more of the foregoing on one or more electronic or digitally controlled devices. The software may reside in a software memory (not shown) in a suitable electronic processing component or system, such as, Figure 1 1. A computing device 120 schematically depicted in FIG. 1. A software memory may include an ordered list of executable instructions for implementing logical functions (i.e., "logic" that may be implemented in digital form (such as digital circuits or source code) or in analog form (such as an analog source, such as an analog electrical signal, sound signal, or video signal). The instructions may be executed within a processing module that includes, for example, one or more microprocessors, general-purpose processors, combinations of processors, digital signal processors (DSPs), field programmable gate arrays (FPGAs), or application-specific integrated circuits (ASICs). In addition, the schematics depict a logical division of functions with physical (hardware and / or software) implementations (not limited by the architecture or physical layout of the functions). Examples of the systems described herein may be implemented in various configurations and operated as hardware / software components in a single hardware / software unit or in separate hardware / software units.

[0210] Executable instructions may be implemented as a computer program product having instructions stored therein, which when executed by an electronic system (e.g., Figure 1The computer program product may be selectively implemented in any non-transitory computer-readable storage medium for use or in conjunction with an instruction execution system, apparatus, or device, such as an electronic computer-based system, a processor-containing system, or other system that can selectively obtain instructions from an instruction execution system, apparatus, or device and execute instructions. In the context of the present disclosure, a computer-readable storage medium is any non-transitory device that can store a program for use by or in conjunction with an instruction execution system, apparatus, or device. A non-transitory computer-readable storage medium may selectively be, for example, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device. A non-exhaustive list of more specific examples of non-transitory computer-readable media includes: an electrical connection having one or more wires (electronic); a portable computer disk (magnetic); random access memory (electronic); read-only memory (electronic); erasable programmable read-only memory, such as flash memory (electronic); compressed memory, such as CD-ROM, CD-R, CD-RW (optical); and digital versatile disk storage, i.e., DVD (optical). Note that the non-transitory computer-readable storage medium may even be paper or other suitable medium on which the program is printed, as the program may be captured electronically, such as via optical scanning of the paper or other medium, and then compiled, interpreted, or otherwise processed in a suitable manner if necessary, and then stored in computer memory or machine storage.

[0211] It will also be understood that the term "in signal communication" as used herein means that two or more systems, devices, components, modules or submodules can communicate with each other via a signal propagated on a certain type of signal path. The signal can be a communication, power, data or energy signal that communicates information, power or energy from a first system, device, component, module or submodule to a second system, device, component, module or submodule along a signal path between the first and second systems, devices, components, modules or submodules. The signal path can include a physical connection, an electrical connection, a magnetic connection, an electromagnetic connection, an electrochemical connection, an optical connection, a wired connection or a wireless connection. The signal path can also include additional systems, devices, components, modules or submodules between the first and second systems, devices, components, modules or submodules.

[0212] More generally, terms such as "in communication" and "in communication with..." (e.g., a first component "in communication with" or "in communication with" a second component) are used herein to indicate a structural, functional, mechanical, electrical, signal, optical, magnetic, electromagnetic, ionic, or fluid relationship between two or more components or elements. Thus, the fact that one component is described as being in communication with a second component is not intended to exclude the possibility that additional components exist between and / or are operably associated with the first and second components.

[0213] It should be understood that various aspects or details of the present invention may be changed without departing from the scope of the present invention. Furthermore, the foregoing description is for the purpose of illustration only and not for the purpose of limitation - the present invention is defined by the claims.

Claims

1. A method of operating a collision / reaction cell in an inductively coupled plasma mass spectrometry (ICP-MS) system to suppress interferences, the method comprising: Allowing a collision / reaction gas to flow into the collision / reaction cell, wherein the collision / reaction cell comprises an inlet, an outlet, and a multipole ion guide located between the inlet and the outlet; transmitting ions through the inlet and into the collision / reaction cell, wherein the ions include analyte ions and interfering ions; applying an outlet DC potential at a first magnitude at the outlet to produce a DC barrier effective to prevent the ions from exiting the collision / reaction cell; The outlet DC potential is maintained at the first magnitude during the confinement period to perform an interaction effective to suppress interfering ion signal intensities measured by the mass spectrometer, the interaction being selected from the group consisting of: reacting the interfering ions with the collision / reaction gas according to a reaction effective to convert the interfering ions into non-interfering ions or neutral species, wherein the analyte ions collide with the collision / reaction gas multiple times to effectively slow down and confine the analyte ions in the collision / reaction cell; and reacting the analyte ions with the collision / reaction gas according to a reaction effective to produce product ions, wherein the product ions collide with the collision / reaction gas a plurality of times to effectively slow and confine the product ions in the collision / reaction cell; After the confinement period, transmitting the analyte ions or product ions to the mass spectrometer by switching the outlet DC potential to a second magnitude effective to allow the analyte ions or product ions to pass through the outlet as a pulse having a pulse duration; and The analyte ions or product ions are measured during a measurement period having a duration approximately equal to the pulse duration.

2. The method according to claim 1, wherein: The first magnitude and the second magnitude are selected from the group consisting of: the second magnitude is smaller than the first magnitude; The first magnitude is a positive or zero magnitude and the second magnitude is a negative or zero magnitude; The first magnitude is in the range of 0V to +100V; The second magnitude is in the range of -200V to 0V.

3. The method according to claim 1, wherein: The duration of the switching is in the range of 0.01 ms to 0.1 ms.

4. The method according to claim 1, wherein: The duration of the restriction period is in the range of 0 ms to 1000 ms.

5. The method according to claim 1, wherein: The duration of the measurement period ranges from the FWHM of the peak value of the pulse to five times the FWHM.

6. The method according to claim 1, wherein: The pulse duration is in the range of 0.01 ms to 1 ms.

7. The method according to claim 1, wherein: Applying the exit DC potential at the exit includes applying the exit DC potential at an exit lens of the collision / reaction cell.

8. The method of claim 1, comprising continuing to transmit the ions through the inlet and into the collision / reaction cell during the confinement period.

9. The method of claim 1 , comprising applying an axial DC potential gradient along the multipole ion guide, wherein: Confined ions are prevented from exiting the collision / reaction cell through the inlet during the confinement period.

10. The method of claim 1, comprising performing a step selected from the group consisting of: applying an inlet DC potential at the inlet during at least a later period of the confinement period to effectively prevent confined analyte ions from exiting the collision / reaction cell through the inlet and to prevent interfering ions from entering the collision / reaction cell through the inlet; applying an inlet DC potential at the inlet during the measurement period to effectively prevent interfering ions from entering the collision / reaction cell through the inlet; and Both of the above.

11. The method of claim 1 , prior to transmitting the ions through the inlet and into the collision / reaction cell, performing a step selected from the group consisting of: generating the ions by exposing the sample to an inductively coupled plasma; generating the ions by exposing the sample to an inductively coupled plasma, wherein exposing the sample comprises operating a plasma torch; and The sample is flowed from a nebulizer or nebulization chamber into a plasma torch, and the ions are generated by exposing the sample to an inductively coupled plasma generated by the plasma torch.

12. The method of claim 1, comprising selecting the collision / reaction gas based on a chemical characteristic of the analyte ions and a chemical characteristic of the interfering ions.

13. The method according to claim 1, wherein: The analyte ions are first analyte ions having a first mass, the interfering ions are first interfering ions, the confinement period is a first confinement period having a first duration, the pulse is a first pulse, and the analyte ions further include second analyte ions having a second mass different from the first mass, and further including: after measuring the first analyte ions contained in the first pulse, again applying the outlet DC potential at the outlet at a first magnitude for a second confinement period having a second duration different from the first duration; During the second confinement period, causing the collision / reaction gas to react with a second interfering ion interfering with the second analyte ion, or causing the collision / reaction gas to react with the second analyte ion to suppress the interference; After the second confinement period, transmitting a second pulse to the mass spectrometer by switching the outlet DC potential to the second magnitude; and Second analyte ions contained in the second pulse or product ions formed from the second analyte ions are measured.

14. The method according to claim 13, comprising: selecting the first duration based on chemical characteristics of the first analyte ion and the first interfering ion; And the second duration is selected based on chemical characteristics of the second analyte ion and the second interfering ion.

15. The method according to claim 13, comprising: The collision / reaction gas is caused to flow into the collision / reaction cell at a certain flow rate during the first confinement period, and the collision / reaction gas is caused to flow into the collision / reaction cell at the same flow rate during the second confinement period.

16. The method according to claim 1, wherein: The collision / reaction gas is selected from the group consisting of: helium; neon; argon; hydrogen; oxygen; water; air; ammonia; methane; fluoromethane; nitrous oxide; and combinations of two or more of the foregoing.

17. The method according to claim 1, comprising at least one of the following features: The analyte ions are selected from the group consisting of: positive monatomic ions of metals or other elements other than noble gases; and product ions produced by reacting the collision / reaction gas with positive monatomic ions of metals or other elements other than noble gases; The interfering ions are selected from the group consisting of: positive argon ions; polyatomic ions containing argon; doubly charged ions containing components of the sample; isobaric ions containing components of the sample; and polyatomic ions containing components of the sample.

18. A method for analyzing a sample, the method comprising: generating analyte ions from the sample; The method of claim 1, wherein the collision / reaction cell is operated, wherein the analyte ions are transmitted into the collision / reaction cell; and The analyte ions or the product ions are transmitted to the mass spectrometer, wherein transmitting the analyte ions or the product ions to the mass spectrometer includes transmitting the analyte ions or the product ions to a mass analyzer of the mass spectrometer.

19. An inductively coupled plasma mass spectrometry (ICP-MS) system comprising: an ion source configured to generate a plasma and to produce analyte ions in the plasma; A collision / reaction cell, the collision / reaction cell comprising an inlet, an outlet, and a multipole ion guide located between the inlet and the outlet; Mass spectrometer; and A controller comprising A controller comprising an electronic processor and memory and configured to control operations including: allowing a collision / reaction gas to flow into the collision / reaction cell; transmitting ions through an inlet and into a collision / reaction cell, wherein the ions include analyte ions and interfering ions; applying an outlet DC potential at a first magnitude at the outlet to produce a DC barrier effective to prevent the ions from exiting the collision / reaction cell; maintaining the outlet DC potential at the first magnitude during a confinement period to perform an interaction effective to suppress the intensity of an interfering ion signal measured by the mass spectrometer, the interaction selected from the group consisting of: reacting the interfering ions with the collision / reaction gas according to a reaction effective to convert the interfering ions into non-interfering ions or neutral species; and reacting the analyte ions with the collision / reaction gas according to a reaction effective to produce product ions; After the confinement period, transmitting the analyte ions or product ions to the mass spectrometer by switching the outlet DC potential to a second magnitude effective to allow the analyte ions or product ions to pass through the outlet as a pulse having a pulse duration; and The analyte ions or product ions are measured during a measurement period having a duration approximately equal to the pulse duration.

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