Device and method for improving the background equivalent concentration of element species

Abstract

Methods and systems are described that can use a gas containing nitrogen centers introduced upstream of a torch-sustained plasma. In some configurations, the gas containing nitrogen centers can be introduced as a gas upstream of the plasma and through a sample introduction device. Mass spectrometers and optical emission systems are also described that can use the gas containing nitrogen centers.

Description

Technical Field

[0001] Priority Application This application is related to and claims the priority and benefit of U.S. Provisional Application No. 62 / 827,483, filed on April 1, 2019, the entire disclosure of which is incorporated herein by reference for all purposes.

[0002] Specific configurations of devices and methods are described that can reduce plasma interference and / or background signals when detecting one or more elements. In some examples, signals from interfering species and / or background signals can be reduced to improve the background equivalent concentration.

Background Art

[0003] Elemental species in a sample can be analyzed in many different ways. Background signals and interferences often reduce the ability to detect specific elemental species at low levels.

Summary of the Invention

Means for Solving the Problems

[0004] In chemical analysis, various aspects, embodiments, configurations, and examples are described in which a nitrogen-centered gas can be used, such as a gas containing a molecule or compound containing at least one nitrogen atom bonded to another atom. The presence of a nitrogen-centered gas can, for example, reduce the presence of background signals and / or interfering species during the analysis of at least specific elemental species. This reduction can improve the background equivalent concentration of at least specific elemental species.

[0005] In one aspect, the method includes introducing a nitrogen-centered gas, such as a plasma gas, upstream of a torch configured to maintain an inductively coupled plasma, the nitrogen-centered gas being introduced upstream of the sustained inductively coupled plasma. In some embodiments, the nitrogen-centered gas is introduced into a sample introduction device, at a point between the sample introduction device and the plasma, such as into a torch upstream of the plasma. In some configurations, the nitrogen-centered gas is introduced as a separate gas stream from the plasma gas stream and as a separate gas stream from any cooling gas provided to the torch to cool the glassware of the torch.

[0006] In some examples, the nitrogen-centered gas is introduced into the torch as a gas stream that is separate from the plasma gas provided to the torch and also separate from any cooling gas provided to the torch to cool the glassware of the torch.

[0007] In other examples, the method includes introducing a nitrogen-centered gas into a spray chamber disposed upstream of the torch and fluidly coupled to the sample inlet of the torch. In some embodiments, the nitrogen-centered gas is introduced through a secondary port of the spray chamber, or a primary port of the spray chamber, or some other port of the spray chamber. In certain cases, the secondary port of the spray chamber is disposed perpendicular to the longitudinal axis of the spray chamber. In other embodiments, the method includes switching off the introduction of the nitrogen-centered gas into the spray chamber when elements that are difficult to ionize are being analyzed using an inductively coupled plasma. In some examples, the method includes switching on the introduction of the nitrogen-centered gas into the spray chamber when elements other than those that are difficult to ionize are being analyzed using an inductively coupled plasma. In additional examples, the spray chamber is fluidly coupled to a nebulizer, and when switching on and off the introduction of the nitrogen-centered gas into the spray chamber, the flow rate of the sample through the nebulizer is substantially constant.

[0008] In some examples, this method includes configuring an introduced gas containing a nitrogen center to account for up to about 50% by volume of the total gas flow introduced into the torch.

[0009] In certain embodiments, this method includes introducing a gas containing a nitrogen center in a flow that is parallel, perpendicular, or counter - flowing to the direction of the bulk gas flow through the spray chamber.

[0010] Optionally, the gas containing a nitrogen center is a gas containing nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or ammonium ions.

[0011] In certain embodiments, the torch is disposed at an opening of an induction device configured to provide high - frequency energy to the torch to maintain inductively coupled plasma in the torch using argon as a plasma gas, and the spray chamber is configured to provide a laminar flow of the sample to the torch, and the laminar flow of the sample also includes the introduced gas containing a nitrogen center.

[0012] In some examples, power from about 500 watts to about 1800 watts is provided to the induction device to maintain inductively coupled plasma in the torch. In some embodiments, the argon gas introduced into the torch to maintain plasma in the torch has a purity of 99.99% argon to 99.9999% argon.

[0013] In some examples, a mass spectrometer fluidly coupled to the outlet of the torch. In other examples, an optical detector is present and configured to receive optical emission from excited ions in the torch.

[0014] In other embodiments, the method includes introducing a gas containing a nitrogen center into a port of a torch that provides the gas to a central channel of a plasma. In some examples, the gas containing a nitrogen center is nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or a gas containing ammonium ions. In other embodiments, the torch is disposed at an opening of an induction device configured to provide high-frequency energy to the torch to maintain an inductively coupled plasma in the torch using argon as a plasma gas. In some examples, the method includes switching off the introduction of the gas containing a nitrogen center into the torch when an element that is difficult to ionize is being analyzed using an inductively coupled plasma. In other embodiments, the method includes switching on the introduction of the gas containing a nitrogen center into the torch when an element other than an element that is difficult to ionize is being analyzed using an inductively coupled plasma.

[0015] In another aspect, a mass spectrometry system includes a sample introduction device having a first port and a second port, the first port receiving a first gas and the second port receiving a second gas different from the first gas, the second gas containing a nitrogen center; a torch fluidly coupled to the sample introduction device and configured to receive a sample from the sample introduction device at a sample inlet of the torch; an induction device configured to provide high-frequency energy to the torch to maintain an inductively coupled plasma in the torch for ionizing the sample; a mass analyzer fluidly coupled to a sample outlet of the torch and configured to receive ions from the torch; a detector fluidly coupled to the mass analyzer; and a processor configured to prevent introduction of the second gas into the sample introduction device when a sample containing an element that is difficult to ionize is being analyzed using the mass spectrometry system, and to allow the second gas to enter the sample introduction device when an element other than an element that is difficult to ionize is being analyzed using the mass analyzer.

[0016] In certain embodiments, the sample introduction device comprises a spray chamber disposed upstream of the torch and fluidly coupled to the sample inlet of the torch. In other embodiments, the spray chamber comprises a second port into which a second gas is introduced and a first port into which a first gas is introduced. In some examples, the second port of the spray chamber is disposed perpendicular to the longitudinal axis of the spray chamber. In other examples, the second port is orthogonal to the first port. In some embodiments, the processor is further configured to control the amount of the second gas comprising a nitrogen center introduced into the sample introduction device. In some embodiments, the processor is further configured to select a particular gas comprising a nitrogen center from a plurality of gases comprising a nitrogen center based on the analyte being analyzed using a mass spectrometer.

[0017] In some examples, the mass analyzer system further comprises a nebulizer fluidly coupled to the spray chamber. In other embodiments, the spray chamber is configured to provide a laminar flow of the sample to the sample inlet of the torch, and the laminar flow of the sample also comprises a second gas comprising a nitrogen center. In some embodiments, a third port is present on the spray chamber, and the third port receives a gas different from the first gas and the second gas.

[0018] In another aspect, an optical emission spectrometer system includes a sample introduction device having a first port and a second port, where the first port receives a first gas, the second port receives a second gas different from the first gas, the second gas includes a nitrogen center; a torch fluidly coupled to the sample introduction device and configured to receive a sample from the sample introduction device at a sample inlet of the torch; an induction device configured to provide high-frequency energy to the torch to maintain an inductively coupled plasma in the torch for ionizing the sample; an optical detector configured to detect optical emission of an analyte excited in the torch; and a processor configured to prevent introduction of the second gas to the sample introduction device when a sample containing elements that are difficult to ionize is being analyzed using the optical emission spectrometer system, and to allow the second gas to enter the sample introduction device when elements other than the elements that are difficult to ionize are being analyzed using the optical emission spectrometer system.

[0019] In certain embodiments, the sample introduction device comprises a spray chamber disposed upstream of the torch and fluidly coupled to the sample inlet of the torch. In some examples, the spray chamber comprises a second port into which a second gas is introduced and a first port into which a first gas is introduced. In other examples, the second port of the spray chamber is disposed perpendicular to the longitudinal axis of the spray chamber. In other examples, the second port is orthogonal to the first port. In some examples, the processor is further configured to control the amount of the second gas containing a nitrogen center introduced into the sample introduction device. In some examples, the processor is further configured to select a particular gas containing a nitrogen center from a plurality of gases containing a nitrogen center based on the analyte analyzed using the optical emission spectrometer. In other examples, the system further comprises a nebulizer fluidly coupled to the spray chamber. In some embodiments, the spray chamber is configured to provide a laminar flow of the sample at the inlet of the torch, and the laminar flow of the sample also includes a second gas containing a nitrogen center. In other embodiments, a third port is present on the spray chamber, and the third port receives a gas different from the first gas and the second gas.

[0020] In another aspect, a spray chamber is described that is fluidly coupled to a nebulizer at an inlet end of the spray chamber to receive a liquid sample from the nebulizer and to provide an aerosolized sample spray at an outlet end of the spray chamber to an ionization device fluidly coupled to the outlet end of the spray chamber. In some examples, the spray chamber includes an inlet end, an outlet end, and a dual makeup gas inlet port, each configured to receive gas within an outer chamber and provide a tangential gas flow, an outer chamber, an inner chamber within the outer chamber, the inner chamber including a plurality of internal microchannels configured to receive makeup gas introduced from the dual makeup gas inlet port into the outer chamber, the inner chamber sized and arranged to provide a laminar flow between an outer surface of the inner chamber and an inner surface of the outer chamber to reduce droplet deposition on the inner chamber, an inner chamber, and a gas port separated from the dual makeup gas inlet port and configured to receive a nitrogen-centered gas, the spray chamber configured to allow mixing of the received nitrogen-centered gas and the makeup gas introduced into the dual makeup gas inlet port such that the nitrogen-centered gas is present in the aerosolized sample spray exiting the spray chamber at the outlet end of the spray chamber.

[0021] Additional aspects, embodiments, examples, and configurations are described in more detail below. Specific specific configurations are described below with reference to the drawings:

Brief Description of the Drawings

[0022]

Figure 1A

Figure 1B

Figure 1C

Figure 2A

Figure 2B

Figure 2C

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

DETAILED DESCRIPTION OF THE INVENTION

[0023] Considering the advantages of the present disclosure, those skilled in the art will recognize that the components shown in the figures are merely illustrative of the specific components and configurations that can be used.

[0024] To provide an improved detection limit for at least certain elemental species, for example, a particular configuration is described that can use a nitrogen-centered gas such as a gas containing a nitrogen atom covalently bonded to another atom. In some cases, the nitrogen-centered gas can be introduced upstream of the ionization source, directly into the ionization source, or in other ways that can provide the nitrogen-centered gas to the ionization source. Many different gases and gas combinations can be used as needed. The exact amount of the nitrogen-centered gas used can vary and is typically much lower than a small amount of the total gas flow through the system, for example, less than 50 volume %. As described in more detail below, it may be desirable to remove or prevent the introduction of the nitrogen-centered gas when detecting a particular element in a sample. In some cases, the gas is or contains a nitrogen-centered gas, while in other examples, the gas is or contains a molecule or compound containing a nitrogen center. As discussed below, detection can be achieved using a number of devices and systems including mass spectrometers, optical emission devices, atomic absorption devices, time-of-flight devices, or other devices and systems. Without wishing to be bound by any particular theory or configuration, the use of a nitrogen-centered gas can improve the background equivalent concentration (BEC), which is generally defined as the concentration of a given element that exhibits the same intensity as the background, measured at a given wavelength or mass. The BEC is typically calculated according to Equation [1]. [1]

[0025]

Number

[0026] where C 標準 is the standard concentration, I ブランク is the signal intensity of the blank, I 標準is the standard signal intensity. The unit of BEC is the same as the standard unit. BEC is not the detection limit, but the relative size of the signal from the element and the background. Generally, the lower the BEC, the lower the detection limit. If the background signal from interfering species can be reduced, for example, by removing the interfering species or preventing the formation of interfering species, the BEC can be improved.

[0027] In the following specific cases, the phrase "difficult-to-ionize element" refers to specific elemental species for which it is difficult to use an inductively coupled plasma as an ionization source. Examples of difficult-to-ionize elements include, but are not limited to, beryllium, zinc, selenium, and arsenic. The methods and systems described herein can enhance the analysis of difficult-to-ionize elements by selectively using or not using a nitrogen-centered gas. For example, a nitrogen-centered gas can be selectively introduced to reduce interference and / or background signals that may be present during the analysis of specific elemental species. Without wishing to be bound by any particular scientific theory, introducing nitrogen atoms into the ionization source can reduce specific interfering ions and / or interfering ion products, thereby improving the detection limit of specific elements. For example, when ions are detected based on the mass-to-charge (m / z) ratio, specific interferences with the same or similar m / z ratio as the particular analyte of interest can be generated. By introducing a nitrogen-centered gas, the amount of these interfering species may be reduced to any substantial degree or may not be formed at all. In other cases, the introduction of a nitrogen-centered gas may increase the generation of interference or interfering species at specific m / z ratios that may make the detection of specific elements more difficult. Thus, the selective introduction of a nitrogen-centered gas during the detection of specific elements and the removal (or non-introduction) of a nitrogen-centered gas during the detection of other elements can generally improve the detection limits of most, if not all, elements in an analytical sample.

[0028] In certain embodiments, a nitrogen-centered gas can be introduced upstream of the ionization source, for example, into a sample introduction device that is fluidly coupled to the ionization source and disposed upstream of the ionization source. Referring to FIG. 1A, a system 100 is shown that includes a sample introduction device 110 fluidly coupled to a chamber or torch that can be used to maintain a plasma or other ionization source 120. The nitrogen-centered gas can be introduced into the sample introduction device 110 disposed upstream of the ionization source 120. When the ionization source 120 is an inductively coupled plasma, nitrogen atoms in the gas can reduce certain interfering species formed from the argon gas used to maintain the plasma. In some cases, argon is introduced into the torch to maintain the plasma in the torch and includes a purity of 99.99% argon to 99.9999% argon. As further discussed below, a processor or controller can be present in the system 100 and programmed to introduce or not introduce the nitrogen-centered gas depending on the particular element detected. The nitrogen-centered gas is typically introduced into the sample introduction device 110 in a small amount, e.g., less than 50 volume %, so that the sample is not diluted to a substantial extent. The nitrogen-centered gas can be introduced intermittently, continuously, in pulses, or in other ways into the sample introduction device 110. The sample introduction device 110 can take many forms, including a nebulizer, a spray chamber, a spray tip, a spray nozzle, or other forms that can introduce an aerosolized sample into the ionization source 120. Various exemplary and types of ionization sources that can be used with the ionization source 120 are described in more detail below.

[0029] In certain configurations, a nitrogen-centered gas can be introduced at some point between the sample introduction device and the ionization source, for example, through a port, gas line, or device disposed between the sample introduction device and the ionization source. Referring to FIG. 1B, a system 130 is shown comprising a sample introduction device 140 fluidly coupled to an ionization source 150. The nitrogen-centered gas can be introduced into the system 130 between the ionization source 150 and the sample introduction device 140, for example, through a port, spray chamber, flow controller, valve, manifold, etc., disposed between the sample introduction device 140 and the ionization source 150. The gas can be introduced, for example, by adding a nitrogen-centered molecule or compound to the gas stream exiting the sample introduction device 140. In other examples, the nitrogen-centered gas can be introduced into the gas stream exiting the sample introduction device 140. Optionally, a mixing chamber or other device may be present between the sample introduction device 140 and the ionization source 150 to allow for mixing of the nitrogen-centered gas and the sample exiting the sample introduction device 140, such that a substantially homogeneous gas is introduced into the ionization source 150. As further discussed below, a processor or controller can be present in the system 130 and programmed to introduce or not introduce a nitrogen-centered gas depending on the particular element being detected. The nitrogen-centered gas is typically introduced into the gas stream exiting the sample introduction device 140 in a small amount, e.g., less than 50 volume %, so that the sample is not substantially diluted. The sample introduction device 140 can take many forms, including a nebulizer, spray chamber, spray tip, spray nozzle, or other form capable of introducing an aerosolized sample into the ionization source 150. Various exemplary and types of ionization sources that can be used with the ionization source 150 are described in more detail below.

[0030] In some configurations, it may be desirable to introduce a nitrogen-centered gas directly into the ionization source. Referring to FIG. 1C, a system 160 is shown comprising a sample introduction device 170 fluidly coupled to an ionization source 180. The nitrogen-centered gas can be introduced directly into the ionization source 180 to reduce (or prevent) the formation of interferences during the analysis of certain elements. The gas can be introduced directly into the ionization source 180 through a port fluidly coupled to the ionization source 180, a separate spray chamber, a flow controller, a valve, a manifold, etc. For example, if the ionization source 180 includes an inductively coupled plasma (ICP), the nitrogen-centered gas can be introduced into the inner tube of a torch configured to maintain the ICP or directly mixed with the plasma gas so that the gas is mixed with the plasma gas. For example, the nitrogen-centered gas can be mixed with an argon plasma gas stream used in combination with one or more induction devices to maintain the plasma within the torch. Optionally, a mixing chamber or other device may be present so that the nitrogen-centered gas and the plasma gas are mixed and a substantially homogeneous plasma gas mixture is introduced into the ionization source 180 to maintain the plasma. The nitrogen-centered gas is typically not provided to any cooling gas, barrier gas, or other auxiliary gas that may be used in connection with a plasma torch that maintains an inductively coupled plasma. As further discussed below, a processor or controller can be present in the system 160 and programmed to introduce or not introduce the nitrogen-centered gas depending on the particular element being detected. The nitrogen-centered gas is typically introduced into the ionization source 180 in a small amount, e.g., less than 50 volume %, so that the plasma gas is not substantially diluted. The sample introduction device 170 can take many forms, including a nebulizer, a spray chamber, a spray tip, a spray nozzle, or other forms capable of introducing an aerosolized sample into the ionization source 180. Various exemplary and types of ionization sources that can be used with the ionization source 180 are described in more detail below.

[0031] A particular configuration is shown in FIGS. 1A - 1C at different sites or points where a gas containing a nitrogen center can be introduced. Optionally, the gas containing a nitrogen center can be introduced at two or more different sites, or different fluids containing different nitrogen centers can be introduced at two or more different sites. Additionally, as described in more detail below, the gas containing a nitrogen center can also be used by other components of the system, such as a collision cell, reaction cell, or collision - reaction cell located downstream of an ionization source.

[0032] In other examples, the gas containing a nitrogen center can be a gas containing one or more molecules, compounds, or species containing nitrogen atoms. For example, the gas can be nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, gaseous acetonitrile, or a gas containing ammonium ions. Combinations of gases containing nitrogen atoms can also be used. Optionally, two or more different gases containing a nitrogen center can be introduced into the system together, or two or more different gases containing a nitrogen center can be introduced at different sites or points in the system.

[0033] In certain configurations, a nitrogen-centered gas can be introduced into the system using one or more flow controllers. Referring to FIG. 2, a system 200 is shown where a flow controller 230, such as a mass flow controller, is fluidly coupled to a sample introduction device 210 and a gas source 205 configured to provide a nitrogen-centered gas. The flow controller 230 is electrically coupled to a processor 240 (or may include its own processor) to control the amount or volume of the nitrogen-centered gas introduced into the sample introduction device 210. The gas source 205 can introduce a nitrogen-centered gas, can be introduced into the sample introduction device 210, and can be mixed with the sample provided to the downstream ionization source 220. The processor 240 can enable or prevent the gas from the gas source 205 from being introduced into the sample introduction device 210 depending on which particular element is being analyzed. As shown in FIGS. 2B and 2C, the flow controller 230 can instead be fluidly coupled between the sample introduction device 210 and the ionization source 220 (see system 250 in FIG. 2B), or can be directly coupled to the ionization source 220 (see system 260 in FIG. 2C). Alternatively, a nitrogen-centered gas can be introduced at two or more different sites, or different gases containing different nitrogen centers can be introduced at two or more different sites. Additionally, as described in more detail below, the gas source 205 that provides the nitrogen-centered gas can also be used by other components of the system, such as a collision cell, reaction cell, or collision reaction cell located downstream of the ionization source 220.

[0034] In certain configurations, a gas containing a nitrogen center can be introduced into the port of the sample introduction device. An example is shown in FIG. 3A where the sample introduction device 310 includes an inlet 312 configured to receive a sample and an outlet 314 configured to enable an outlet of the sample from the sample introduction device 310. The sample generally flows from the inlet 312 to the outlet 314 within the body of the device 310. The port 320 is present on the sample introduction device 310 and can be fluidly coupled to the gas containing a nitrogen center. The port 320 is shown in a position to introduce the gas containing a nitrogen center in a manner perpendicular to the flow of the sample through the device 310, but this arrangement is not necessary. The gas containing a nitrogen center can be introduced perpendicular to the sample flow or at other angles, in parallel flow, in a convective manner. Although not shown, a valve or other actuating device can be fluidly coupled to the port 320 to enable or prevent the flow of the gas containing a nitrogen center through the port 320. The valve can be, for example, a solenoid valve or can be present in a flow controller.

[0035] In some cases, separate ports can be present on the sample introduction device. For example, in the case of a spray chamber, a separate port can be fluidly coupled to a makeup gas inlet or port. One generalized example is shown in FIG. 3B, where the sample introduction device 330 includes an inlet 332, an outlet 334, a first port 340, and a second port 342. A nitrogen-centered gas can be introduced through port 342 to port 340 to mix before introducing the bulk gas from port 340 into the body of device 330. For example, the first port 340 can receive a gas used to carry a sample analyte through device 330 and / or to assist in the isolation of individual particles, cells, etc. The nitrogen-centered gas can be co-introduced into the body of device 330 along with the gas introduced through the first port 340. Although not shown, a valve or other actuating device can be fluidly coupled to the second port 342 to enable or prevent the flow of the nitrogen-centered gas through the second port 342. The valve can be, for example, a solenoid valve or can be present in a flow controller.

[0036] In other configurations, the sample introduction device can comprise three or more separate ports, one of which can receive a nitrogen-centered gas. An illustration is shown in FIG. 3C where the sample introduction device 350 comprises an inlet 352, an outlet 354, and ports 362, 364, and 366. Ports 362, 364, and 366 are shown to be disposed on the same side or surface of device 350, but this arrangement is not necessary. One or more of ports 362, 364, and 366 can instead be disposed on a different surface or side of device 350. One or more of ports 362, 364, and 366 can be used to introduce a nitrogen-centered gas into device 350; for example, the diameters, shapes, etc. of ports 362, 364, 366 can be the same or different. Although not shown, a valve or other actuating device (or multiple valves or actuating devices) can be fluidly coupled to one or more of ports 362, 364, and 366 to enable or prevent the flow of nitrogen-centered gas through each port. The valve can be, for example, a solenoid valve or can be present in a flow controller.

[0037] In some examples, it may be desirable to introduce a nitrogen-centered gas at the outlet of the sample introduction device. An illustration is shown in FIG. 3D where the sample introduction device 370 comprises an inlet 372, an outlet 374, and a port 376 fluidly coupled to outlet 374. When the analyte exits device 370 through outlet 374, it can be mixed with a nitrogen-centered gas by introducing the nitrogen-centered gas through port 376. Although not shown, the nitrogen-centered gas can instead be introduced at inlet 372 of device 370. Alternatively, the nitrogen center can be introduced upstream of the sample introduction device such that it is already mixed with the sample before being provided to the sample introduction device.

[0038] In some examples, it may be desirable to introduce a nitrogen-centered gas into a mixing chamber disposed between a sample introduction device and an ionization source. Referring to FIG. 4, a system 400 is shown that includes a sample introduction device 410, a mixing chamber 420, an ionization source 430, and a detector 440. The mixing chamber 420 can be configured to receive a nitrogen-centered gas through a port, valve, manifold, or other device. The sample entering the mixing chamber 420 from the sample introduction device 410 can be mixed with the nitrogen-centered gas such that a substantially homogeneous mixture of the sample and the nitrogen-centered gas exits the mixing chamber 420. The mixing chamber 420 can comprise a body or cavity that allows for a linear flow, circular flow, or other gas flow that can mix the sample and the nitrogen-centered gas. In some cases, the mixing chamber 420 can take the form of a spray chamber as described herein. The ionization source 430 can be a plasma or other ionization source. The detector 440 can be a mass spectrometer, an optical emission device, an atomic absorption device, a time-of-flight device, or other detector.

[0039] In a configuration where a sample introduction device is present, the sample introduction device can be a nebulizer, an aerosolizer, a spray nozzle, or a head, or other devices. In some embodiments, the sample introduction device can be configured as a spray chamber, as shown in FIG. 5. The spray chamber 500 generally includes an outer chamber or tube 510 and an inner chamber or tube 520. The outer chamber 510 includes double makeup gas inlets 512, 514, and a drain 518. The makeup gas inlets 512, 514 are typically fluidly coupled to a common gas source, but different gases can be used if desired. For example, one of the gas ports can receive a gas containing a nitrogen center. Although not essential, the makeup gas inlets 512, 514 are shown to be disposed adjacent to the inlet end 511, but alternatively, they can be disposed centrally or towards the outlet end 513. The inner chamber or tube 520 is disposed adjacent to the nebulizer tip 505 and can include two or more microchannels 522, 524 configured to provide a makeup gas flow to reduce or prevent the sample from flowing back and / or depositing on the inner chamber or tube 520. The configuration and arrangement of the inner chamber or tube 520 provide a laminar flow in areas 540, 542 that act to shield the inner surface of the outer chamber 510 from any droplet deposition. The tangential gas flow provided by introducing gas into the spray chamber 500 through inlets 512, 514 can act to select specific droplets. The microchannels 522, 524 in the inner chamber or tube 520 allow the gas flow from the makeup gas inlets 512, 514 and are designed to shield the surface of the inner chamber or tube 520 from droplet deposition. In a particular example, the microchannels 522, 524 can be configured in a similar manner, for example, having the same size and / or diameter, but in other configurations, the microchannels 522, 524 can have different sizes or arrangements. In some cases, at least two, three, four, five, or more separate microchannels can be present in the inner chamber or tube 520.The exact size, morphology, and shape of the microchannels can vary, and each microchannel need not have the same size, morphology, or shape. In some examples, microchannels of different diameters can be present in different radial planes along the longitudinal axis L1 of the inner tube to provide a desired shielding effect. An exemplary spray chamber is described, for example, in U.S. Application No. 15 / 597,608, filed May 17, 2017, the entire disclosure of which is incorporated herein by reference for all purposes. As described in more detail herein, a third port (or additional ports) can be present and used to introduce a nitrogen-centered gas into the spray chamber 500.

[0040] In certain embodiments, the exact dimensions of the spray chamber 500 can vary. In a particular configuration, the longitudinal length from the nebulizer tip 505 to the end of the spray chamber 500 can be from about 10 cm to about 15 cm, for example, about 12 cm or 13 cm. The diameter of the outer tube 510 can vary from about 1 cm to about 5 cm, for example, up to about 3 cm or 4 cm. The maximum diameter of the inner tube 520 can vary from about 0.5 cm to about 4 cm, and the distance between the outer surface of the inner tube 520 and the inner surface of the outer tube 510 can be selected to provide a desired laminar flow rate, for example, the distance can be from about 0.1 cm to about 0.75 cm. In a particular example, the inner tube 520 is shown to have a generally increasing inner diameter along the longitudinal axis of the outer chamber 510, but this dimensional change is not necessary. A portion of the inner tube 520 may be "flat" to enhance laminar flow, or may be substantially parallel to the longitudinal axis L1, or in an alternative configuration, a portion of the inner tube 520 may be substantially parallel to the surface of the outer tube 510 for at least a certain length and may enhance laminar flow. The inner diameter of the outer chamber 510 increases to a point toward the outlet end 513 from the inlet end 511, and then decreases toward the outlet end 513 such that the inner diameter of the outer chamber 510 is smaller at the outlet end 513 than at the inlet end 511. Optionally, the inner diameter of the outer chamber 510 may be maintained constant from the inlet end 511 to the outlet end 513, or may increase from the inlet end 511 to the outlet end 513. Optionally, two or more different spray chambers, the same or different, can be fluidly coupled to each other to assist in the selection of individual cells.

[0041] In certain configurations, the systems described herein may include one or more ionization sources, which may take many different forms and are generally configured to ionize elemental species present in a sample. In some examples, the ionization source can be a high-temperature ionization source having an average temperature of about 4000 Kelvin or greater, such as, for example, a direct current plasma, an inductively coupled plasma, an arc, a spark, or other high-temperature ionization source. The exact ionization source used can vary depending on the particular element and / or cell being analyzed, and exemplary ionization sources include those that can spray and / or ionize the elemental species to be detected, such as ionization sources that can spray and / or ionize metals, metal compounds, and other inorganic or organic species. In other examples, the ionization source can include an electron impact source, a chemical ionization source, a field ionization source, desorption sources such as those configured for fast atom bombardment, field desorption, laser desorption, plasma desorption, thermal desorption, electrohydrodynamic ionization / desorption, a thermal spray or electrospray ionization source, or other types of ionization sources.

[0042] In certain examples, the ionization source may comprise one or more torches and one or more induction devices. Specific components of the ionization source are shown in FIGS. 6-8. Exemplary induction devices and torches are described, for example, in U.S. Pat. Nos. 9,433,073 and 9,360,403, the entire disclosures of which are incorporated herein by reference for all purposes. Referring to FIG. 6, a device is shown that includes a torch 610 in combination with an induction coil 620. The induction coil 620 is typically electrically coupled to a high-frequency generator (not shown) to provide high-frequency energy to the torch 610 and maintain an inductively coupled plasma 650 within some portions of the torch 610. A sample introduction device (not shown) can be used to introduce a sample into the plasma 650 to ionize and / or atomize elemental species present in the sample. As described herein, a nitrogen-centered gas can be introduced upstream of the plasma 650, for example, through a sample introduction device, through a port of the torch, or anywhere in between. For example, nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or a gas containing ammonium ions can be introduced upstream of the plasma 650. The ionized and / or atomized elemental species may be detected within the torch using axial or radial detection, or provided to a downstream chamber or other device, such as a mass spectrometer, for detection or further selection and / or filtering.

[0043] In an alternative configuration, the induction coil 620 of FIG. 6 can be replaced with one or more plate electrodes. For example, referring to FIG. 7, the first plate electrode 720 and the second plate electrode 721 are shown to include an opening through which the torch 710 can receive. For example, the torch 710 can be placed within some regions of the induction device comprising the plate electrodes 720, 721. The plasma 750, or other ionization / atomization source such as, for example, an inductively coupled plasma, can be sustained using the inductive energy from the torch 710 and the plates 720, 721. The high-frequency generator 730 is electrically coupled to each of the plates 720, 721. Optionally, only a single plate electrode can be used instead. A sample introduction device can be used to introduce individual samples into the plasma 750 to ionize and / or atomize the species in the sample. As described herein, a nitrogen-centered gas can be introduced upstream of the plasma 750. For example, nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or a gas containing ammonium ions can be introduced upstream of the plasma 750. Exemplary high-frequency generators are described, for example, in U.S. Pat. Nos. 4,629,940, 6,329,757, and 9,420,679.

[0044] In other configurations, an induction device comprising one or more radial fins can instead be used in the methods and systems described herein. Referring to FIG. 8, a device or system can comprise an induction coil 820 comprising at least one radial fin and a torch 810. For example, a plasma such as an inductively coupled plasma or other ionization / atomization source (not shown) can be maintained using the inductive energy from the torch 810 and the radial fin induction device 820. A high frequency generator (not shown) can be electrically coupled to the induction device 820 and provide high frequency energy to the torch 810. An individual sample can be introduced into the torch 810 using a sample introduction device (not shown). A gas containing a nitrogen center can be introduced upstream of the plasma maintained by the torch 810. For example, a gas containing nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or ammonium ions can be introduced upstream of the plasma maintained by the torch 810. The elemental species in the introduced sample can be ionized or atomized and separated using a downstream mass spectrometer. In other cases, for example, one or more capacitive devices such as a capacitive coil or capacitive plate can be used in the ionization source. Further, other devices can be used that can provide energy to the torch to maintain two or more induction devices, capacitive devices, or atomization / ionization sources such as a plasma.

[0045] In certain embodiments, the systems described herein can be configured as mass spectrometers. Referring to FIG. 9, a mass spectrometer 900 includes a sample introduction device 920 fluidically coupled to an ionization source 930. The ionization source 930 is fluidically coupled to a mass analyzer 940. The mass analyzer is fluidically coupled to a detector 950, which can be integral with or separate from the mass analyzer 940. A processor 960 can be electrically coupled to one or more components of the system 900 to control the various subsystems. As discussed herein, the sample introduction device 920 can be a nebulizer, an aerosolizer, a spray nozzle or head, or other device that can provide a cell to the ionization source 930. The sample introduction device 920 can be, or include, a spray chamber, as shown in FIG. 5. The ionization source 930 can be any of those ionization sources described herein, e.g., any of the induction devices and / or torches shown in FIGS. 6-8. The mass analyzer 940 can generally take a number of forms depending on, for example, the nature of the sample, the desired resolution, etc. In certain embodiments, the mass analyzer 940 can be a scanning mass analyzer, a magnetic sector analyzer (e.g., for use in single and double focusing MS devices), a quadrupole mass analyzer, an ion trap analyzer (e.g., a cyclotron, a quadrupole ion trap), a time-of-flight analyzer, and other suitable mass analyzers that can separate and / or filter (or both) elemental species at different mass-to-charge ratios. The mass analyzer 940 can include two or more different devices arranged in series, e.g., a tandem MS / MS device or a triple quadrupole device, to select and / or identify ions received from the ionization source 930.

[0046] In certain examples, detector 950 can be any suitable detection device that can be used with an existing mass spectrometer, such as an electron multiplier, a Faraday cup, a coated photographic plate, a scintillation detector, etc., and other suitable devices selected by one of ordinary skill in the art, considering the advantages of the present disclosure. Processor 960 typically includes a microprocessor and / or computer and suitable software for analysis of samples introduced into system 900. Optionally, one or more databases can be accessed by processor 960 for determination of the chemical identity of the species introduced into system 900.

[0047] In a specific configuration, the elemental species present in a sample can be detected using optical emission spectroscopy (OES). Referring to FIG. 10, an OES device or system 1000 includes a sample introduction device 1010, an ionization source or device 1020, and a detector or detection device 1030. The sample introduction device 1010 can comprise a spray chamber, nebulizer, or other form. The ionization device 1020 can comprise, for example, one or more components as shown in FIGS. 6 - 8, or other devices and components capable of providing or maintaining an ionization source. The detector or detection device 1030 can take many forms and can be any suitable device capable of detecting optical emission from elemental species, such as optical emission 1025. Optionally, the detection device 1030 can include a suitable optical system such as lenses, mirrors, prisms, windows, band - pass filters, etc. The detection device 1030 can also include a grating such as an echelle grating to provide a multi - channel OES device. A grating such as an echelle grating can enable the detection of multiple emission wavelengths. The grating can be placed within a monochromator or other suitable device for selecting one or more specific wavelengths to monitor. The detection device 1030 can be configured to monitor emission wavelengths over a large wavelength range including, but not limited to, ultraviolet, visible, near - infrared, and far - infrared. The OES device 1000 can further include suitable electronics and suitable circuitry such as a microprocessor and / or a computer to provide a desired signal and / or for data acquisition. Suitable additional devices and circuitry are known in the art and can be found, for example, in commercially available OES devices such as the Optima 2100DV series, Optima 5000DV series OES devices, or the Optima 8000 or 8300 series OES devices commercially available from PerkinElmer Health Sciences, Inc. An optional display screen 1040, which can be a reader, screen, printer, computer, etc., can be present to monitor the detection of elemental species.The OES device may further include autosamplers such as the AS90 and AS93 autosamplers commercially available from PerkinElmer Health Sciences, Inc., or similar devices available from other suppliers. The OES device 1000 can, for example, be calibrated using standard concentrations of elements and particles of known sizes to provide calibration curves for each element that can be used to quantify each element. Optionally, peak height, peak area, or both can be used to determine the amount of each element present in individual particles.

[0048] In certain embodiments, the exact wavelength of the emitted light that is detected can be used to identify specific elemental species present in a sample. Many elements can emit light at multiple single wavelengths. Atomic species can also emit light at wavelengths different from their ionized species. Exemplary optical emission wavelengths for several different elemental species include, but are not limited to, 328.066 nm or 338.288 nm for silver, 396.151 nm or 308.212 nm for aluminum, 188.980 nm or 193.696 nm for arsenic, 249.772 nm or 249.676 nm for boron, 455.402 nm or 233.524 nm for barium, 313.104 nm or 313.042 nm for beryllium, 317.932 nm or 422.673 nm for calcium, 226.502 nm or 214.434 nm for cadmium, 228.615 nm or 230.785 nm for cobalt, 205.560 nm or 267.711 nm for chromium, 324.754 nm or 327.393 nm for copper, 238.201 nm or 239.568 nm for iron, 766.490 nm for potassium, 670.784 nm for lithium, 285.212 nm or 279.076 nm for magnesium, 257.607 nm or 293.305 nm for manganese, 202.032 nm or 203.846 nm for molybdenum, 589.587 nm or 330.237 nm for sodium, 231.604 nm for sodium, 213.617 nm or 178.224 nm for phosphorus, 220.354 nm for lead, 180.671 nm or 181.975 nm for sulfur (as sulfate), 206.834 nm or 217.582 nm for antimony, 196.029 nm for selenium, 251.609 nm or 221.663 nm for silicon, 421.549 nm or 460.733 nm for strontium, 283.730 nm or 401.913 nm for thorium, 334.943 nm or 368.519 nm for titanium, 190.801 nm for thallium, 292.402 nm or 290.880 nm for vanadium, 409.014 nm for uranium, 207.912 nm or 239.708 nm for tungsten, 213.858 nm or 206.199 nm for zinc, and 291.138 nm for lutetium.Considering the advantages of the present disclosure, additional suitable element emission wavelengths are selected by those skilled in the art and depend on the selected detector, use of radial detection, use of axial detection, etc.

[0049] In certain examples, the elemental species present in a sample can be detected using an atomic absorption spectrometer (AAS) by measuring the light absorbed by the different elemental species. Referring to FIG. 11, a single beam AAS device 1100 includes a light source 1110, a sample introduction device 1120, an ionization device or source 1130, and a detection device 1140. The sample introduction device 1120 can be any one or more of those described herein, such as a spray chamber, or other suitable sample introduction device. A power source (not shown) can be configured to supply power to the light source 1110, which provides light 1112 of one or more wavelengths for absorption by the atoms and ions in the ionization source 1130. Suitable light sources include, but are not limited to, mercury lamps, cathode ray lamps, lasers, etc. The light source 1110 may be pulsed using a suitable chopper or pulsed power source, or in examples where a laser is implemented, the laser may be pulsed at a selected frequency, such as 5, 10, or 20 times per second. The exact configuration of the light source 1110 can vary. For example, the light source 1110 may provide light axially along the torch of the ionization device 1130, or may provide light radially along the torch of the ionization device 1130. The example shown in FIG. 11 is configured for axial supply of light from the light source 1110. There may be an advantage in signal-to-noise for axial observation of the signal. Optionally, the light source can provide light to a chamber separate from the ionization source 1130, such as a chamber disposed downstream of the ionization source 1130. For example, the elemental species can be provided to a downstream chamber that is optically coupled from the ionization source 1130 to the light source 1110. Despite the many different configurations possible, the detection device 1140 is optically coupled to the light source 1110 such that the amount of light absorbed by a particular elemental species is detected. In some examples, the light source 1110 can provide light of at least two different wavelengths, where one wavelength is absorbed by a first elemental species and the light of the other wavelength is absorbed by a second elemental species.Optionally, the spectrometer can be present between the light source 1110 and the ionization source 1130 (or secondary chamber) to provide a plurality of different individual light wavelengths for absorption by elemental species. The ionization source 1130 can comprise one or more components as illustrated in FIGS. 6 - 8, or other devices and components that can provide or maintain an ionization source. When the sample is sprayed and / or ionized in the ionization device 1130, the incident light 1112 from the light source 1110 can excite the atoms. That is, some proportion of the light 1112 supplied by the light source 1110 can be absorbed by the atoms and ions in the ionization device 1130. The remaining proportion of the light can be transmitted to the detection device 1140 as wavelength 1132. The detection device 1140 can provide one or more suitable wavelengths using, for example, a prism, lens, grating, and other suitable devices such as those described above with respect to the OES device. To account for the amount of absorption by the sample in the ionization device 1130, a blank such as water or particles lacking any elemental species can be introduced prior to sample introduction to provide a 100% transmittance reference value. The amount of light transmitted when the sample is introduced into the ionization device 1130 can be measured, and the transmittance can be obtained by dividing the amount of light transmitted by the sample by the reference value. The negative logarithm of the transmittance. 10is equal to the absorbance. The AAS device 1100 may further include suitable electronic devices such as a microprocessor and / or a computer and suitable circuitry for providing a desired signal and / or for data acquisition. Suitable additional devices and circuitry may be found, for example, in commercially available AAS devices such as the AAnalyst series spectrometers or the PinAAcle spectrometers commercially available from PerkinElmer Health Sciences, Inc. The AAS device may further include an autosampler known in the art such as the AS-90A, AS-90plus, and AS-93plus autosamplers commercially available from PerkinElmer Health Sciences, Inc. If the ionization source 1130 is configured to maintain an inductively coupled plasma, there may be a high-frequency generator electrically coupled to the induction device. In certain embodiments, instead of a single-beam AAS device, a double-beam AAS device can be used.

[0050] In some examples, the wavelength of the absorbed light can be used to identify the elemental species present in the sample. Many elements can absorb light at two or more different wavelengths. In addition, atomic species can absorb light at wavelengths different from the ionized species. It may be desirable to select monitoring wavelengths that do not overlap with each other when light at two or more wavelengths is provided to the ionized elemental species. Further, when using axial detection and radial detection, the selected wavelengths may be different.Exemplary absorption wavelengths for several different elemental species include, but are not limited to, 328.1 nm for silver, 309.3 nm for aluminum, 193.7 nm for arsenic, 242.8 nm for gold, 249.7 nm for boron, 553.6 nm for barium, 234.9 nm for beryllium, 223.1 nm for bismuth, 422.7 nm for calcium, 228.8 nm for cadmium, 240.7 nm for cobalt, 357.9 nm for chromium, 852.1 nm for cesium, 324.8 nm for copper, 404.6 nm for dysprosium, 400.8 nm for erbium, 459.4 nm for europium, 248.3 nm for iron, 287.4 nm for gallium, 368.4 nm for gadolinium, 265.1 nm for germanium, 286.6 nm for hafnium, 253.7 nm for mercury, 410.4 nm for holmium, 303.9 nm for indium, 264.0 nm for iridium, 766.5 nm for potassium, 550 nm for lanthanum, 670.8 nm for lithium, 336.0 nm for lutetium, 285.2 nm for magnesium, 279.5 nm for manganese, 313.3 nm for molybdenum, 589 nm for sodium, 334.4 nm for niobium, 492.4 nm for neodymium, 232.0 nm for nickel, 290.9 nm for osmium, 213.6 nm for phosphorus, 283.3 nm for lead, 244.8 nm for palladium, 495.1 nm for plutonium, 265.1 nm for platinum, 780.0 nm for rubidium, 346.9 nm for ruthenium, 343.5 nm for rhodium, 349.9 nm for ruthenium, 217.6 nm for antimony, 391.2 nm for scandium, 196.0 nm for selenium, 251.16 nm for silicon, 429.7 nm for samarium, 286.3 nm for tin, 460.7 nm for strontium, 271.5 nm for tantalum, 432.6 nm for thorium, 261.4 nm for technetium, 214.3 nm for tellurium, 364.3 nm for titanium, 267.8 nm for thallium, 371.8 nm for thulium, 351.5 nm for uranium, 318.4 nm for vanadium, 255.1 nm for tungsten, 410.2 nm for yttrium, 398.8 nm for ytterbium, 213.9 nm for zinc, and 360.1 nm for zirconium.

[0051] In certain embodiments, the nitrogen-centered fluid can be selectively switched on or off depending on the particular element being detected. As described herein, during the analysis of certain "difficult-to-ionize" elements, the introduction of a nitrogen-centered gas can create an interference that increases the background signal that can make the detection of difficult-to-ionize elements challenging. Since an analyte sample can contain both difficult-to-ionize and non-difficult-to-ionize elements, it may be desirable to improve the detection limit of non-difficult-to-ionize elements while not altering or reducing the detection limit of difficult-to-ionize elements. By selectively introducing a nitrogen-centered gas for particular elements and not others, the analyte of interest can be detected with an improved signal-to-noise ratio and / or a reduced background signal from interfering species. A processor can be used to correlate the detection of a particular element with the selective introduction (or selective cessation) of a nitrogen-centered gas. For example, the system can be designed to continuously introduce a nitrogen-centered gas into the gas sample unless a difficult-to-ionize element is detected. In such a case, the processor may switch off the flow controller or otherwise stop the flow of the nitrogen-centered gas to enable the detection of difficult-to-ionize elements in the absence of any nitrogen-centered species introduced into the ionization source. The processor can then switch the flow of the nitrogen-centered gas back on during the detection of other elements. In an alternative configuration, for particular elements, the system can be configured to operate without using a nitrogen-centered gas, except when the detection limit is improved in the presence of a nitrogen-centered gas. In such a case, the gas can be switched on during the analysis of these elements and then switched back off during the analysis of other elements. A nitrogen-centered gas is typically not introduced during the detection of difficult-to-ionize elements but can be introduced to provide a differential comparison of signals. For example, a difficult-to-ionize element can be detected in the absence of any nitrogen-centered gas and in the presence of a nitrogen-centered gas.The obtained signal can be compared, for example, to obtain a measure of possible interfering species or to provide some indication of background enhancement of the interference signal. Additionally, differential signals can be compared using fluids having different nitrogen centers to determine whether a particular nitrogen-containing species can function better than other species for a particular element.

[0052] In certain examples, the methods and systems herein may comprise or utilize a processor, which may be part of a system or apparatus, or may be present in an associated device used with the apparatus, such as a computer, laptop, mobile device, etc. For example, a processor can be used to control different components of the system. In certain configurations, the processor may be present in one or more computer systems and / or general hardware circuitry including, for example, a microprocessor and / or suitable software for operating the system, to control, for example, a sample introduction device, ionization source, detector, etc. In some examples, the detection device or the detector itself may be equipped with its own respective processor, operating system, and other functions to enable the detection of various elemental species. The processor can be integrated into the system or may be present on one or more accessory boards, printed circuit boards, or computers electrically coupled to components of the system. The processor is typically electrically coupled to one or more memory units so as to receive data from other components of the system and be able to adjust various system parameters as needed or desired. The processor can be part of a general-purpose computer such as one based on Unix®, an Intel PENTIUM® type processor, Motorola PowerPC, Sun UltraSPARC, a Hewlett-Packard PA-RISC processor, or any other type of processor. One or more of any type of computer system can be used according to various embodiments of the technology. Further, the system may be connected to a single computer or may be distributed among multiple computers attached by a communication network. It should be understood that other functions including network communication can be implemented and that this technology is not limited to having any particular function or set of functions. Various aspects can be implemented as dedicated software executed on a general-purpose computer system.A computer system may include a processor connected to one or more memory devices such as a disk drive, memory, or other device for storing data. Memory is typically used to store programs, calibration curves, emission or absorption wavelengths, and data values during operation of the system. The components of the computer system may be coupled by interconnecting devices including one or more buses (e.g., between components integrated within the same machine) and / or networks (e.g., between components in separate discrete machines). The interconnecting devices provide communication (e.g., signals, data, instructions) exchanged between the components of the system. The computer system can typically receive and / or issue commands within a processing time, e.g., within a few milliseconds, a few microseconds or less, enabling rapid control of the system. For example, computer control can be implemented to control sample introduction, the flow of gases including nitrogen center, detector parameters, etc. The processor is typically electrically coupled to a power source which can be, for example, a direct current power source, an alternating current power source, a battery, a fuel cell, or other power source, or a combination of power sources. The power source can be shared by other components of the system. The system may also include one or more input devices, e.g., a keyboard, a mouse, a trackball, a microphone, a touch screen, a manual switch (e.g., an override switch), and one or more output devices, e.g., a printing device, a display screen, a speaker. Further, the system may contain one or more communication interfaces (in addition to, or as an alternative to, the interconnecting devices) for connecting the computer system to a communication network. The system may also include suitable circuitry for converting signals received from various electrical devices present in the system.Such a circuit can be present on a printed circuit board or, for example, on a separate substrate or device electrically coupled to the printed circuit board through a suitable interface such as a Serial ATA interface, an ISA interface, a PCI interface, or through one or more wireless interfaces such as Bluetooth®, Wi-Fi, Near Field Communication, or other wireless protocols and / or interfaces.

[0053] In certain embodiments, the memory system used in the systems described herein typically includes a computer-readable and writable non-volatile recording medium that can store software code usable by a program executed by a processor, or information stored on or in a medium processed by the program. The medium may be, for example, a hard disk, a solid state drive, or flash memory. The program or instructions executed by the processor may be located locally or remotely and can be retrieved by the processor via an interconnect mechanism, a communication network, or other means as needed. Typically, in operation, the processor causes data to be read from the non-volatile recording medium into another memory that enables faster access to the information from the medium to the processor. This memory is typically a volatile random access memory such as dynamic random access memory (DRAM) or static random access memory (SRAM). It may be located within the memory system or within the storage system. The processor generally operates on the data within the integrated circuit memory and copies the data to the medium after the processing is complete. Various mechanisms are known for managing data movement between the medium and the integrated circuit memory element, and the present technology is not limited thereto. The technology is also not limited to a particular memory system or storage system. In certain embodiments, the system may also include specially programmed dedicated hardware, such as an application specific integrated circuit (ASIC), or a field programmable gate array (FPGA). Aspects of the technology may be implemented in software, hardware, firmware, or any combination thereof. Further, such methods, acts, systems, system elements, and their components may be implemented as part of the systems described above or as independent components. A particular system is described as an example of one type of system on which various aspects of the present technology may be practiced, but it should be understood that the aspects are not limited to being implemented on the systems described. The various aspects may be practiced on one or more systems having different architectures or components.The system may comprise a general-purpose computer system programmable using a high-level computer programming language. The system may also be implemented using specially-programmed dedicated hardware. In the system, the processor is typically a commercially available processor such as a well-known Pentium-class processor available from Intel Corporation. Many other processors are also commercially available. Such processors typically execute an operating system that can be, for example, Windows 95, Windows 98, Windows NT, Windows 2000 (Windows ME), Windows XP, Windows Vista, Windows 7, Windows 8 or Windows 10 operating systems available from Microsoft Corporation, MAC OS X available from Apple, such as Snow Leopard, Lion, Mountain Lion, or other versions, Solaris operating system available from Sun Microsystems, or a UNIX or Linux (registered trademark) operating system available from various suppliers. Many other operating systems may be used and, in certain embodiments, a simple series of commands or instructions may function as an operating system. Further, the processor can be designed as a quantum processor designed to perform one or more functions using one or more quantum bits.

[0054] In certain examples, the processor and the operating system may together define a platform on which application programs are written in a high-level programming language. It should be understood that the technology is not limited to a particular system platform, processor, operating system, or network. Also, considering the advantages of the present disclosure, it should be apparent to those skilled in the art that the technology is not limited to a particular programming language or computer system. Further, it should be understood that other suitable programming languages and other suitable systems may also be used. In certain examples, the hardware or software may be configured to implement a cognitive architecture, a neural network, or other suitable implementation. Optionally, one or more portions of the computer system may be distributed among one or more computer systems coupled to a communication network. These computer systems may also be general-purpose computer systems. For example, various aspects may be provided to one or more client computers as services (e.g., servers), or may be distributed among one or more computer systems configured to perform overall tasks as part of a distributed system. For example, various aspects may be implemented on a client-server or multi-tier system that includes distributed components among one or more server systems that perform various functions according to various embodiments. These components may be executable code, intermediate code (e.g., IL), or interpretable code (e.g., Java (registered trademark)) that communicate over a communication network (e.g., the Internet) using a communication protocol (e.g., TCP / IP). Also, it should be understood that the technology is not limited to running on any particular system or group of systems. Also, it should be understood that the technology is not limited to a particular distributed architecture, network, or communication protocol.

[0055] In some cases, various embodiments may be programmed using an object-oriented programming language such as, for example, SQL, SmallTalk, Basic, Java, Javascript, PHP, C++, Ada, Python, iOS / Swift, Ruby on Rails, or C# (C-Sharp). Other object-oriented programming languages may also be used. Alternatively, a functional, scripting, and / or logic programming language may be used. Various configurations may be implemented in a non-programming environment (e.g., a document created in HTML, XML, or other format that renders a graphical user interface (GUI) aspect or performs other functions when viewed within a browser program window). Certain configurations may be implemented as programmed elements or non-programmed elements, or any combination thereof. In some cases, the system may include a remote interface such as those present on a mobile device, tablet, laptop computer, or other portable device, which can communicate via a wired or wireless interface and enable remote operation of the system as desired.

[0056] In certain examples, the processor may also include or have access to a database of information regarding elemental species, etc., which can include optical emission wavelengths, optical absorption wavelengths, and other general information. For example, a set of calibration curves for different elemental species can be stored in the database and used to estimate the elemental concentration in a sample without the user having to perform the calibration curve for each element. Such a method can be particularly desirable when the amount of sample is limited. Instructions stored in memory can execute software modules or control routines for the system, which can substantially provide a controllable model of the system. The processor can use the information accessed from the database, along with one or more software modules executed by the processor, to determine control parameters or values for different components of the system, such as different gas flow rates, different wavelengths of light being monitored, etc. Using an input interface for receiving control instructions and an output interface linked to different system components in the system, the processor can perform active control of the system. For example, the processor can control detection devices, sample introduction devices, ionization sources, flow controllers, etc.

[0057] In some embodiments, the nitrogen-centered gas can also be introduced into another component of the system downstream of the ionization source. Referring to FIG. 12, a system 1200 is shown where a gas source 1230 containing a gas having a nitrogen center is fluidly coupled to a cell 1240 downstream of a sample introduction device 1210 and an ionization source 1220. Optionally, an optional flow controller 1235 is present and can be used to control the gas flow independently to the sample introduction device 1210 and the cell 1240 from the gas source 1230. In some examples, the cell 1240 can take the form of, for example, a collision cell, a reaction cell, or a collision reaction cell as described in U.S. Patent No. 8,426,804. In certain examples, the gas from the gas source 1230 can also or alternatively be provided to components downstream other than the cell 1240, for example, it can be provided to a detector, a mass spectrometer, or other components downstream from the ionization source 1220.

[0058] Specific specific examples are described below to illustrate some of the novel and inventive aspects of the techniques described herein.

[0059] Example 1 Signals (background signal and element signal) were measured using an inductively coupled mass spectrometry system (NexION ICP-MS) equipped with a spray chamber commercially available from PerkinElmer Health Sciences, Inc., for example, an All Matrix Solution spray chamber. Table 1 below shows the results with values representing counts per second (cps) for each detected element. 100 ppt of each element was introduced separately into the mass spectrometer. The nitrogen-centered gas was not introduced into the spray chamber. The analysis was performed in DRC mode in the presence of ammonia in the reaction cell.

[0060] [Table 1]

[0061] The detection limit was calculated using the standard deviation of the blank signal divided by the analytical signal (3 times the standard deviation of the blank signal). The desired detection limit is 1 ppt or less. The background equivalent concentrations for iron, calcium, and potassium were 10.6, 8.29, and 6.51 ppt, respectively.

[0062] Example 2 Using the same system as used in Example 1, signals (background signal and elemental signals) were measured in the presence of nitrogen gas (1% by volume) introduced into the spray chamber. Table 2 below shows the results with values representing counts per second (cps) for each detected element. 100 ppt of each element was introduced separately into the mass spectrometer.

[0063]

Table 2

[0064] The results were consistent with improved background equivalent concentrations (BEC) in the presence of nitrogen gas introduced into the spray chamber while operating the reaction cell with ammonia gas. The major interference was Ar+, and since nitrogen did not affect this species, the calcium detection limit did not improve. The BEC, and thus the detection limits of the other elements, improved because ArX+ species were not formed (or were formed to a lesser extent) when nitrogen was introduced. The background signal decreased significantly compared to the background signal measured in Example 1. The signal intensities (analytical signal and background signal) for all elements also decreased compared to the signal intensities in Example 1, but at a slower rate compared to the background signal. The background equivalent concentrations (BEC) in the presence of nitrogen gas for iron, calcium, and potassium were 0.59, 7.13, and 1.18 ppt, respectively. The BEC improved for all three elements.

[0065] Example 3 Using the system in Example 1, the background equivalent concentration (BEC) in the absence and presence of nitrogen gas was determined for each element shown in Table 3 in FIG. 13. The elements were present in an aqueous solution of 13% nitric acid. The addition of nitrogen gas improved the BEC for many elements, especially elements that are easily oxidized (uranium, vanadium). The values in Table 3 are expressed as (Log BEC) / ppt.

[0066] When introducing elements of the embodiments disclosed herein, the articles "a", "an", "the", and "said" are intended to mean that one or more of the elements are present. The terms "comprising", "including", and "having" are intended to be open-ended and mean that additional elements other than the recited elements may be present. Considering the advantages of the present disclosure, it will be recognized by those skilled in the art that the various components of the embodiments may be exchanged or substituted with the various components in other embodiments.

[0067] Although specific aspects, examples, and embodiments have been described above, considering the advantages of the present disclosure, it will be recognized by those skilled in the art that additions, substitutions, modifications, and changes to the disclosed exemplary aspects, examples, and embodiments are possible.

Claims

**Claim 1** A method comprising introducing a nitrogen-centered gas upstream of a plasma maintained by a torch, wherein the torch is configured to maintain an inductively coupled plasma using a plasma gas introduced into the torch, the method comprising: switching off the introduction of the nitrogen-centered gas into the spray chamber when an element that is difficult to ionize is being analyzed using an inductively coupled plasma; and further comprising selectively switching on the introduction of the nitrogen-centered gas into the spray chamber when an element other than an element that is difficult to ionize is being analyzed using the inductively coupled plasma, wherein the element that is difficult to ionize includes beryllium, zinc, selenium, or arsenic. **Claim 2** The method of claim 1, wherein the nitrogen-centered gas is introduced into the torch in a gas stream that is separate from the plasma gas provided to the torch and also separate from any cooling gas provided to the torch for cooling the gas appliance of the torch. **Claim 3** The method of claim 1, further comprising introducing the nitrogen-centered gas into a spray chamber disposed upstream of the torch and fluidly coupled to the sample inlet of the torch. **Claim 4** The method of claim 3, wherein the nitrogen-centered gas is introduced through a secondary port of the spray chamber. **Claim 5** The method of claim 4, wherein the secondary port of the spray chamber is disposed perpendicular to the longitudinal axis of the spray chamber. **Claim 6** The method of claim 1, wherein the spray chamber is fluidly coupled to a nebulizer, and the flow rate of the sample through the nebulizer is substantially constant when the on and off switching of the introduction of the nitrogen-centered gas into the spray chamber is performed. **Claim 7** The method of claim 3, further comprising configuring the introduced gas containing nitrogen center to account for up to about 50% by volume of the total gas flow introduced into the torch. **Claim 8** The method of claim 3, further comprising introducing the nitrogen-centered gas in a flow that is parallel, perpendicular, or countercurrent to the flow direction of the bulk gas flow through the spray chamber. **Claim 9** The method according to claim 1, wherein the gas containing the nitrogen center is a gas containing nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or ammonium ions.

10. The method according to claim 3, wherein the torch is disposed at an opening of an induction device configured to provide high-frequency energy to the torch to maintain the inductively coupled plasma in the torch using argon gas as the plasma gas, the spray chamber is configured to provide a laminar flow of a sample to the torch, and the laminar flow of the sample also includes the introduced gas containing the nitrogen center.

11. The method according to claim 10, wherein about 500 watts to about 1800 watts of power is provided to the induction device to maintain the inductively coupled plasma in the torch.

12. The method according to claim 11, wherein the argon gas introduced into the torch to maintain the plasma in the torch has a purity of 99.99% argon to 99.9999% argon.

13. The method according to claim 10, further comprising a mass spectrometer fluidly coupled to an outlet of the torch.

14. The method according to claim 10, further comprising an optical detector configured to receive optical emission from excited ions in the torch.

15. The method according to claim 1, further comprising introducing the gas containing the nitrogen center into a port of the torch that provides the plasma gas to maintain the plasma in the torch.

16. The method according to claim 15, wherein the gas containing the nitrogen center is a gas containing nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, or ammonium ions.

17. The method according to claim 15, wherein the torch is disposed at an opening of an induction device configured to provide high-frequency energy to the torch to maintain the inductively coupled plasma in the torch using argon as the plasma gas.

Images