Patent Description:
Certain configurations are described of devices and methods that can reduce plasma interferences 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 background equivalent concentrations.

Elemental species in samples can be analyzed in many different manners. Background signals and interferences often reduce the ability to detect certain elemental species at low levels.

<NPL>), relates to the use of nitrogen into ICP torches.

<NPL>, relates to the determination of arsenic and selenium in ICP mass spectrometry.

Various aspects, embodiments, configurations and examples are described that can use a gas comprising a nitrogen center, i.e. a gas that comprises a molecule or compound comprising at least one nitrogen atom bonded to another atom, in chemical analyses. The presence of the gas comprising the nitrogen center can, for example, reduce background signals and/or the presence of interfering species during analysis of at least certain elemental species. This reduction can improve background equivalent concentration for at least certain elemental species.

In an aspect, the invention provides a method according to claim <NUM>. In some embodiments, the gas comprising the nitrogen center is introduced into a sample introduction device, at a point between a sample introduction device and a plasma, into the torch upstream of the plasma, etc. In some configurations, a gas comprising the nitrogen center is introduced in a separate gas flow from a plasma gas flow and a separate gas flow from any cooling gases provided to the torch to cool glassware of the torch.

In some examples, the gas comprising the nitrogen center is introduced into the torch in a gas flow that is separate from the plasma gas provided to the torch and is separate from any cooling gases provided to the torch to cool glassware of the torch.

In some embodiments, the gas comprising the nitrogen center 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 instances, the secondary port of the spray chamber is positioned perpendicular to a longitudinal axis of the spray chamber. In additional examples, the spray chamber is fluidically coupled to a nebulizer, and wherein a flow rate of sample through the nebulizer is substantially constant as the switching on and switching off of the gas comprising the nitrogen center into the spray chamber is performed.

In some examples, the method comprises configuring the introduced gas comprising the nitrogen center to comprise up to about <NUM>% by volume of a total gas flow introduced into the torch.

In certain embodiments, the method comprises introducing the gas comprising the nitrogen center in a flow that is a parallel flow, a perpendicular flow or a counter flow to a flow direction of bulk gas flow through the spray chamber.

In some instances, the gas comprising the nitrogen center is nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide or a gas comprising ammonium ions.

In certain embodiments, the torch is positioned in an aperture of an induction device configured to provide radio frequency energy into the torch to sustain the inductively coupled plasma in the torch using argon as the plasma gas, and wherein the spray chamber is configured to provide a laminar flow of sample into the torch, wherein the laminar flow of the sample also comprises the introduced gas comprising the nitrogen center.

In some examples, a power of about <NUM> Watts to about <NUM> Watts is provided to the induction device to sustain the inductively coupled plasma in the torch. In some embodiments, the argon gas introduced into the torch to sustain the plasma in the torch comprises a purity between <NUM>% argon and <NUM>% argon.

In some examples, a mass analyzer fluidically coupled to an outlet of the torch. In other examples, an optical detector is present and is configured to receive an optical emission from excited ions in the torch.

In other embodiments, the method comprises introducing the gas comprising the nitrogen center into a port of the torch that provides a gas to the central channel of the plasma. In some examples, the gas comprising the nitrogen center is nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide or a gas comprising ammonium ions. In other embodiments, the torch is positioned in an aperture of an induction device configured to provide radio frequency energy into the torch to sustain the inductively coupled plasma in the torch using argon as the plasma gas.

In another aspect, the invention provides a mass spectrometer system according to claim <NUM>.

In certain embodiments, the sample introduction device comprises a spray chamber positioned upstream of the torch and fluidically coupled to a sample inlet of the torch. In other embodiments, the spray chamber comprises the second port through which the second gas is introduced and comprises the first port through which the first gas is introduced. In some examples, the second port of the spray chamber is positioned perpendicular to a 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 an amount of the second gas comprising the nitrogen center introduced into the sample introduction device. In some embodiments, the processor is further configured to select a specific gas comprising a nitrogen center from a plurality of gases comprising a nitrogen center based on an analyte to be analyzed using the mass spectrometer.

In some examples, the mass spectrometer system further comprises a nebulizer fluidically coupled to the spray chamber. In other embodiments, the spray chamber is configured to provide a laminar flow of sample into the sample inlet of the torch, wherein the laminar flow of the sample also comprises the second gas comprising the nitrogen center. In some embodiments, a third port is present on the spray chamber, wherein the third port receives a gas different than the first gas and the second gas.

In another aspect, the invention provides an optical emission spectrometer according to claim <NUM>. In some examples, the spray chamber comprises the second port through which the second gas is introduced and comprises the first port through which the first gas is introduced. In other examples, the second port of the spray chamber is positioned perpendicular to a 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 an amount of the second gas comprising the nitrogen center introduced into the sample introduction device. In some examples, the processor is further configured to select a specific gas comprising a nitrogen center from a plurality of gases comprising a nitrogen center based on an analyte to be analyzed using the optical emission spectrometer. In other examples, the system further comprises a nebulizer fluidically coupled to the spray chamber. In some embodiments, the spray chamber is configured to provide a laminar flow of sample into the inlet of the torch, wherein the laminar flow of the sample also comprises the second gas comprising the nitrogen center. In other embodiments, a third port is present on the spray chamber, wherein the third port receives a gas different than the first gas and the second gas.

In another aspect, a spray chamber configured to fluidically couple to a nebulizer at an inlet end of the spray chamber to receive a liquid sample from the nebulizer and provide an aerosolized sample spray at an outlet end of the spray chamber to an ionization device fluidically coupled to the outlet end of the spray chamber is described. In some examples, the spray chamber comprises an outer chamber comprising the inlet end, the outlet end and dual makeup gas inlet ports each configured to receive a gas to provide a tangential gas flow within the outer chamber, an inner chamber within the outer chamber, the inner chamber comprising a plurality of internal microchannels configured to receive makeup gas introduced into the outer chamber from the dual makeup gas inlet ports, in which the inner chamber is 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, and a gas port separate from the dual makeup gas inlet ports and configured to receive a gas comprising a nitrogen center, wherein the spray chamber is configured to permit mixing of the received gas comprising the nitrogen center with makeup gas introduced into the dual makeup gas inlet ports so the gas comprising the nitrogen center is present in the aerosolized sample spray exiting the spray chamber at the outlet end of the spray chamber.

Additional aspects, embodiments, examples and configurations are described in more detail below.

Certain specific configurations are described below with reference to the figures in which:.

It will be recognized by the person of ordinary skill in the art, given the benefit of this disclosure, that the components shown in the figure are merely illustrative of only certain components and configurations that may be used.

Certain configurations are described that use a gas comprising a nitrogen center such as, for example, a gas comprising a nitrogen atom covalently bonded to another atom, to provide improved detection limits at least for certain elemental species. In the present invention, the gas comprising the nitrogen center is introduced upstream of an ionization source, directly into the ionization source or in other manners where the gas comprising the nitrogen center is provided to the ionization source. Many different gases and gas combinations can be used as desired. The exact amount of the gas comprising the nitrogen center that is used may vary and is typically much lower than a minor amount, e.g., much less than <NUM>%, by volume of the total gas flow, e.g., total gas flow, through the system. As noted in more detail below, when detecting certain elements in a sample it may be desirable to remove or prevent introduction of the gas comprising the nitrogen center. In some instances, the gas is or comprises a gas comprising a nitrogen center, whereas in other examples, the gas is or comprises a molecule or compound comprising a nitrogen center. As discussed below, detection can be accomplished using numerous devices and systems including a mass spectrometer, an optical emission device, an atomic absorption device, a time of flight device or other devices and systems. While not wishing to be bound by any particular theory or configuration, use of a gas comprising a nitrogen center can improve a 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. BEC's are typically calculated according to Equation [<NUM>] <MAT> where Cstandard is the concentration of the standard, Iblank is the signal intensity of the blank and Istandard is the signal intensity of the standard. The units of BEC are the same as that of the standard. BEC's are not detection limits but are instead the relative size of the signal from the element and the background. In general, the lower the BEC the lower the detection limit. If background signals from interfering species can be reduced, e.g., by removing or preventing the interfering species from forming, then BEC's can be improved.

The phrase "hard-to-ionize element" refers to certain elemental species where ionization is difficult using an inductively coupled plasma as an ionization source. In the present invention, specifically, hard to ionize elements include beryllium, zinc, selenium and arsenic. The methods and systems described herein can enhance analysis of hard-to-ionize elements by selectively using or not using the gas comprising the nitrogen center. In the present invention, the gas comprising the nitrogen center is selectively introduced to reduce interferences and/or background signals that may exist during analysis of certain elemental species. Without wishing to be bound by any particular scientific theory, by introducing nitrogen atoms into the ionization source certain interfering ions and/or interfering ion products can be reduced to provide improved detection limits for certain elements. For example, when ions are detected based on mass-to-charge (m/z) ratios, certain interferences may be produced that have the same or similar m/z ratio as a particular analyte of interest. By introducing the gas comprising the nitrogen center, an amount of this interfering species may be reduced or otherwise not formed at all to any substantial degree. In other instances, introduction of a gas comprising a nitrogen center can increase interferences or production of interfering species at certain m/z ratios which may make detection of certain elements more difficult. As such, selective introduction of the gas comprising the nitrogen center during detection of certain elements and removal (or non-introduction) of the gas comprising the nitrogen center during detection of other elements can generally improve detection limits for most, if not all, elements in an analytical sample.

In the method of the present invention, the gas comprising the nitrogen center is introduced upstream of an ionization source, i.e., into a sample introduction device fluidically coupled to the ionization source and positioned upstream of the ionization source. Referring to <FIG>, a system <NUM> is shown comprising a sample introduction device <NUM> fluidically coupled to a chamber or torch that is used to sustain a plasma or, in another embodiments not being part of the invention, other ionization source <NUM>. A gas comprising a nitrogen center is introduced into the sample introduction device <NUM>, which is positioned upstream of the ionization source <NUM>. As in the present invention, when the ionization source <NUM> is an inductively coupled plasma, nitrogen atoms in the gas may reduce certain interfering species that form from argon gas used to sustain the plasma. In some instances, the argon has introduced into the torch to sustain the plasma in the torch comprises a purity between <NUM>% argon and <NUM>% argon. As discussed further below, a processor or controller is present in the system <NUM> and programmed to selectively introduce or not introduce the gas comprising the nitrogen center depending on the particular element to be detected. The gas comprising the nitrogen center is typically introduced into the sample introduction device <NUM> in a minor amount, e.g., less than <NUM>% by volume, so the sample is not diluted to a substantial degree. The gas comprising the nitrogen center can be intermittently introduced, continuously introduced, introduced in pulses or in other manners into the sample introduction device <NUM>. The sample introduction device <NUM> may take many forms including a nebulizer, spray chamber, spray tip, spray nozzle or other forms which can introduce an aerosolized sample into the ionization source <NUM>. Various illustrations and types of ionization sources that can be used in the ionization source <NUM> are discussed in more detail below.

In certain configurations, not including the systems of the present invention, the gas comprising the nitrogen center can be introduced at some point between a sample introduction device and an ionization source, e.g., through a port, gas line or a device positioned between a sample introduction device and an ionization source. Referring to <FIG>, a system <NUM> is shown that comprises a sample introduction device <NUM> fluidically coupled to an ionization source <NUM>. A gas comprising a nitrogen center is introduced into the system <NUM> between the ionization source <NUM> and the sample introduction device <NUM>, e.g., through a port, spray chamber as done in the method according to the invention, flow controller, valve, manifold, etc., positioned between the sample introduction device <NUM> and the ionization source <NUM>. The gas can be introduced, for example, by addition of a molecule or compound with a nitrogen center into the gas stream that exits from the sample introduction device <NUM>. In other examples, a gas comprising a nitrogen center can be introduced into a gas stream that exits the sample introduction device <NUM>. If desired, a mixing chamber or other device may be present between the sample introduction device <NUM> and the ionization source <NUM> to permit mixing of the gas comprising the nitrogen center with the sample exiting the sample introduction device <NUM> so a substantially homogeneous gas is introduced into the ionization source <NUM>. As discussed further below, a processor or controller is present in the system <NUM> and programmed to selectively introduce or not introduce the gas comprising the nitrogen center depending on the particular element to be detected. The gas comprising the nitrogen center is typically introduced into the gas stream that exits the sample introduction device <NUM> in a minor amount, e.g., less than <NUM>% by volume, so the sample is not diluted to a substantial degree. The sample introduction device <NUM> may take many forms including a nebulizer, spray chamber, spray tip, spray nozzle or other forms which can introduce an aerosolized sample into the ionization source <NUM>. Various illustrations and types of ionization sources that can be used in the ionization source <NUM> are discussed in more detail below.

In some configurations, not covering the systems of the present invention, it may be desirable to introduce the gas comprising the nitrogen center directly into the ionization source. Referring to <FIG>, a system <NUM> is shown that comprises a sample introduction device <NUM> fluidically coupled to an ionization source <NUM>. A gas comprising a nitrogen center, is introduced directly into the ionization source <NUM> to reduce the formation of interferences (or prevent formation of interferences) during analysis of certain elements. The gas can be introduced directly into the ionization source <NUM> through a port, separate spray chamber as done in the method according to the invention, flow controller, valve, manifold, etc., that is fluidically coupled to the ionization source <NUM>. In the present invention, where the ionization source <NUM> comprises an inductively coupled plasma (ICP), the gas comprising the nitrogen center can be introduced or mixed directly with the plasma gas, e.g., into an inner tube of a torch configured to sustain the ICP so the gas is mixed with the plasma gas. For example, the gas comprising the nitrogen center can be mixed with an argon plasma gas flow that is used in combination with one or more induction devices to sustain a plasma within a torch. If desired, a mixing chamber or other device may be present so the gas comprising the nitrogen center and the plasma gas can be mixed so a substantially homogeneous plasma gas mixture is introduced into the ionization source <NUM> to sustain the plasma. The gas comprising the nitrogen center is typically not provided to any cooling gases, barrier gases or other auxiliary gases that might be used in connection with a plasma torch that sustains an inductively coupled plasma. As discussed further below, a processor or controller is present in the system <NUM> and programmed to selectively introduce or not introduce the gas comprising the nitrogen center depending on the particular element to be detected. The gas comprising the nitrogen center is typically introduced into the ionization source <NUM> in a minor amount, e.g., less than <NUM>% by volume, so the plasma gas is not diluted to a substantial degree. The sample introduction device <NUM> may take many forms including a nebulizer, spray chamber, spray tip, spray nozzle or other forms which can introduce an aerosolized sample into the ionization source <NUM>. Various illustrations and types of ionization sources that can be used in the ionization source <NUM> are discussed in more detail below.

While certain configurations are shown in <FIG> of different sites or points where the gas comprising the nitrogen center can be introduced, if desired, the gas comprising the nitrogen center could be introduced at two or more different sites or different fluids comprising different nitrogen centers can be introduced at two or more different sites. In addition and as noted in more detail below, the gas comprising the nitrogen center may also be used by other components of the system, e.g., by a collision cell, a reaction cell or a collision-reaction cell positioned downstream of the ionization source.

In the present invention, the gas comprising the nitrogen center is a gas that comprises one or more molecules, compounds or species that comprise a nitrogen atom chemically bonded to another atom. For example, the gas may be nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide, gaseous acetonitrile or a gas comprising ammonium ions. Combinations of gases comprising a nitrogen atom can also be used. If desired, two or more different gases comprising a nitrogen center can also be introduced into the system together or two or more different gases comprising a nitrogen center can be introduced at different sites or points in a system.

In certain configurations, the gases comprising the nitrogen center can be introduced into the system using one or more flow controllers. Referring to <FIG>, a system <NUM> is shown where a flow controller <NUM>, e.g., a mass flow controller, is fluidically coupled to a sample introduction device <NUM> and a gas source <NUM> configured to provide a gas comprising a nitrogen center. The flow controller <NUM> is electrically coupled to a processor <NUM> (or may comprise its own processor) to control the amount or volume of gas comprising the nitrogen center that is introduced into the sample introduction device <NUM>. The gas source <NUM> introduces the gas comprising the nitrogen center which is introduced into the sample introduction device <NUM> and mixed with sample that is provided to a downstream ionization source <NUM>. The processor <NUM> selectively permits or prevents the gas from the gas source <NUM> from being introduced into the sample introduction device <NUM> depending on which particular element is being analyzed. As shown in <FIG>, which do not cover the systems of the present invention, the flow controller <NUM> could instead be fluidically coupled between the sample introduction device <NUM> and the ionization source <NUM> (see system <NUM> in <FIG>) or directly to the ionization source <NUM> (see system <NUM> in <FIG>). Alternatively, the gas comprising the nitrogen center could be introduced at two or more different sites or different gases comprising different nitrogen centers can be introduced at two or more different sites. In addition and as noted in more detail below, the gas source <NUM> that provides the gas comprising the nitrogen center may also be used by other components of the system, e.g., by a collision cell, a reaction cell or a collision-reaction cell positioned downstream of the ionization source <NUM>.

In the systems of the present invention, , a gas comprising a nitrogen center is introduced into a port of a sample introduction device. An illustration is shown in <FIG>, where a sample introduction device <NUM> comprises an inlet <NUM> configured to receive a sample, and an outlet <NUM> configured permit exit of the sample from the sample introduction device <NUM>. Sample generally flows from the inlet <NUM> to the outlet <NUM> within the body of the device <NUM>. A port <NUM> can be present on the sample introduction device <NUM> and fluidically coupled to a gas comprising a nitrogen center. While the port <NUM> is shown in a position that introduces the gas comprising the nitrogen center in a manner which is perpendicular to the flow of sample through the device <NUM>, this positioning is not required. The gas comprising the nitrogen center can be introduced in a parallel flow, a counter flow, perpendicular to sample flow or at other angles. While not shown, a valve or other actuating device can be fluidically coupled to the port <NUM> to permit or prevent flow of the gas comprising the nitrogen center through the port <NUM>. The valve may be, for example, a solenoid valve or may be present in a flow controller.

In some instances, a separate port can be present on a sample introduction device. For example, in the case of a spray chamber, a separate port can be fluidically coupled to a makeup gas inlet or port to permit. One generalized illustration is shown in <FIG>, where a sample introduction device <NUM> comprises an inlet <NUM>, an outlet <NUM>, a first port <NUM>, and a second port <NUM>. A gas comprising the nitrogen center can be introduced through the port <NUM> and into the port <NUM> for mixing prior to introduction of the bulk gas from the port <NUM> into the body of the device <NUM>. For example, the first port <NUM> may receive a gas used to carry sample analyte through the device <NUM> and/or to assist in isolation of individual particles, cells, etc. The gas comprising the nitrogen center can be co-introduced into the body of the device <NUM> with the gas introduced through the first port <NUM>. While not shown, a valve or other actuating device can be fluidically coupled to the second port <NUM> to permit or prevent flow of the gas comprising the nitrogen center through the second port <NUM>. The valve may be, for example, a solenoid valve or may be present in a flow controller.

In other configurations, a sample introduction device may comprise three or more separate ports where one of the ports can receive a gas comprising a nitrogen center. An illustration is shown in <FIG>, where a sample introduction device <NUM> comprises an inlet <NUM>, an outlet <NUM>, and ports <NUM>, <NUM> and <NUM>. While ports <NUM>, <NUM> and <NUM> are shown as being positioned on the same side or surface of the device <NUM>, this positioning is not required. One or more of the ports <NUM>, <NUM> and <NUM> could instead be positioned on a different surface or side of the device <NUM>. Any one or more of the ports <NUM>, <NUM> and <NUM> can be used to introduce a gas comprising a nitrogen center into the device <NUM>, e.g., The diameter, shape, etc. of the ports <NUM>, <NUM>, <NUM> can be the same or can be different. While not shown, a valve or other actuating device (or multiples valves or actuating devices) can be fluidically coupled to one or more of the ports <NUM>, <NUM> and <NUM> to permit or prevent flow of the gas comprising the nitrogen center through the respective port. The valve may be, for example, a solenoid valve or may be present in a flow controller.

In some examples, it may desirable to introduce a gas comprising a nitrogen center, at an outlet of the sample introduction device. An illustration is shown in <FIG> where a sample introduction device <NUM> comprises an inlet <NUM>, an outlet <NUM> and a port <NUM> fluidically coupled to the outlet <NUM>. As analyte exits the device <NUM> through the outlet <NUM>, it can be mixed with the gas comprising the nitrogen center by introducing the gas comprising the nitrogen center through the port <NUM>. While not shown, the gas comprising the nitrogen center could instead be introduced into the inlet <NUM> of the device <NUM>. Alternatively, the nitrogen center could be introduced upstream of the sample introduction device so it is already mixed with sample prior to being provided to the sample introduction device.

In some examples, not covering the systems of the present invention, it may be desirable to introduce the gas comprising the nitrogen center into a mixing chamber positioned between a sample introduction device and an ionization source. Referring to <FIG>, a system <NUM> is shown comprising a sample introduction device <NUM>, a mixing chamber <NUM>, an ionization source <NUM> and a detector <NUM>. The mixing chamber <NUM> can be configured to receive a gas comprising a nitrogen center, through a port, valve, manifold or other devices. Sample entering the mixing chamber <NUM> from the sample introduction device <NUM> can be mixed with the gas comprising the nitrogen center so a substantially homogeneous mixture of the sample and the gas comprising the nitrogen center exits the mixing chamber <NUM>. The mixing chamber <NUM> may comprise a body or cavity that permits linear flow, circular flow or other gas flows that can mix the sample and the gas comprising the nitrogen center. In some instances, the mixing chamber <NUM> can take the form of a spray chamber as described herein. The ionization source <NUM> is a plasma or, in embodiments not covered by the present invention, other ionization sources. The detector <NUM> may be a mass spectrometer, an optical emission device, an atomic absorption device, a time of flight device or other detectors.

In configurations where a sample introduction device is present, the sample introduction device may be a nebulizer, aerosolizer, spray nozzle or head or other devices. In some embodiments, the sample introduction device can be configured as a spray chamber as shown in <FIG>. The spray chamber <NUM> generally comprises an outer chamber or tube <NUM> and an inner chamber or tube <NUM>. The outer chamber <NUM> comprises dual makeup gas inlets <NUM>, <NUM> and a drain <NUM>. The makeup gas inlets <NUM>, <NUM> are typically fluidically coupled to a common gas source, though different gases could be used if desired, e.g., one of the gas ports can receive a gas comprising a nitrogen center. While not required, the makeup gas inlets <NUM>, <NUM> are shown as being positioned adjacent to an inlet end <NUM>, though they could instead be positioned centrally or toward an outlet end <NUM>. The inner chamber or tube <NUM> is positioned adjacent to a nebulizer tip <NUM> and may comprise two or more microchannels <NUM>, <NUM> configured to provide a makeup gas flow to reduce or prevent sample from back flowing and/or depositing on the inner chamber or tube <NUM>. The configuration and positioning of the inner chamber or tube <NUM> provides laminar flow at areas <NUM>, <NUM> which acts to shield inner surfaces of the outer chamber <NUM> from any droplet deposition. The tangential gas flow provided by way of gas introduction into the spray chamber <NUM> through the inlets <NUM>, <NUM> can acts to select certain droplets. The microchannels <NUM>, <NUM> in the inner chamber or tube <NUM> also are designed to permit the gas flows from the makeup gas inlets <NUM>, <NUM> to shield the surfaces of the inner chamber or tube <NUM> from droplet deposition. In certain examples, the microchannels <NUM>, <NUM> can be configured in a similar manner, e.g., have the same size and/or diameter, whereas in other configurations the microchannels <NUM>, <NUM> may be sized or arranged differently. In some instances, at least two, three, four, five or more separate microchannels can be present in the inner chamber or tube <NUM>. The exact size, form and shape of the microchannels may vary and each microchannel need not have the same size, form or shape. In some examples, different diameter microchannels may exist at different radial planes along a longitudinal axis L1 of the inner tube to provide a desired shielding effect. Illustrative spray chambers are described, for example, in<CIT>. As noted in more detail herein, a third port (or additional ports) may be present and used to introduce a gas comprising a nitrogen center into the spray chamber <NUM>.

In certain embodiments, the exact dimensions of the spray chamber <NUM> may vary. In certain configurations, a longitudinal length from the nebulizer tip <NUM> to the end of the spray chamber <NUM> may be about <NUM> to about <NUM>, e.g., about <NUM> or <NUM>. The diameter of the outer tube <NUM> may vary from about <NUM> to about <NUM>, e.g., about <NUM> or <NUM>. The largest diameter of the inner tube <NUM> may vary from about <NUM> to about <NUM>, and the distance between outer surfaces of the inner tube <NUM> and inner surfaces of the outer tube <NUM> can be selected to provide a desired laminar flow rate, e.g., the distance may be about <NUM> to about <NUM>. In certain examples, the inner tube <NUM> is shown as having a generally increasing internal diameter along the longitudinal axis of the outer chamber <NUM>, but this dimensional change is not required. Some portion of the inner tube <NUM> may be "flat" or generally parallel with the longitudinal axis L1 to enhance the laminar flow, or in an alternative configuration, some portion of the inner tube <NUM> may generally be parallel to the surface of the outer tube <NUM>, at least for some length, to enhance laminar flow. The inner diameter of the outer chamber <NUM> increases from the inlet end <NUM> toward the outlet end <NUM> up to a point and then decreases toward the outlet end <NUM> such that the inner diameter of the outer chamber <NUM> is smaller at the outlet end <NUM> than at the inlet end <NUM>. If desired, the inner diameter of the outer chamber <NUM> may remain constant from the inlet end <NUM> toward the outlet end <NUM> or may increase from the inlet end <NUM> toward the outlet end <NUM>. If desired, two or more different spray chambers which are the same or different can be fluidically coupled to each other to assist in selection of individual cells.

In certain configurations, the systems described herein comprise one or more ionization sources, which in the present invention are inductively coupled plasma torches configured to ionize the elemental species present in a sample by an inductively coupled plasma. In some examples, the ionization source may be a high temperature ionization source, e.g., one with an average temperature of about <NUM> Kelvin or more, such as, in examples not being covered by the claimed invention, a direct current plasma, an arc, a spark or other high temperature ionization sources. The exact ionization source used in embodiments not being part of the present invention, may vary depending on the particular elements and/or cells to be analyzed, and illustrative ionization sources include those which can atomize and/or ionize the elemental species to be detected, e.g., those ionization sources which can atomize and/or ionize metals, metalloids and other inorganic species or organic species. In other examples, also not being part oc the present invention, the ionization source may comprise an electron impact source, a chemical ionization source, a field ionization source, desorption sources such as, for example, those sources configured for fast atom bombardment, field desorption, laser desorption, plasma desorption, thermal desorption, electrohydrodynamic ionization/desorption, etc., thermospray or electrospray ionization sources or other types of ionization sources.

In the present invention the ionization source comprises one or more torches and one or more induction devices. Certain components of an ionization source are shown in <FIG>. Illustrative induction devices and torches are described, for example, in <CIT> and <CIT>. Referring to <FIG>, a device comprising a torch <NUM> in combination with an induction coil <NUM> is shown. The induction coil <NUM> is typically electrically coupled to a radio frequency generator (not shown) to provide radio frequency energy into the torch <NUM> and sustain an inductively coupled plasma <NUM> within some portion of the torch <NUM>. A sample introduction device (not shown) can be used to introduce sample into the plasma <NUM> to ionize and/or atomize the elemental species present in the sample. As noted herein, a gas comprising a nitrogen center can be introduced upstream of the plasma <NUM>, e.g., through a sample introduction device, through a port of the torch or somewhere in between. For example, nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide or a gas comprising ammonium ions can be introduced upstream of the plasma <NUM>. The ionized and/or atomized elemental species may be detected within the torch using axial or radial detection or can be provided to a downstream chamber or other device, e.g., a mass analyzer, for detection or further selection and/or filtering.

In an alternative configuration, the induction coil <NUM> in <FIG> could be replaced with one or more plate electrodes. For example and referring to <FIG>, a first plate electrode <NUM> and a second plate electrode <NUM> are shown as comprising an aperture that can receive a torch <NUM>. For example, the torch <NUM> can be placed within some region of an induction device comprising plate electrodes <NUM>, <NUM>. A plasma <NUM>, specifically an inductively coupled plasma is sustained using the torch <NUM> and inductive energy from the plates <NUM>, <NUM>. A radio frequency generator <NUM> is electrically coupled to each of the plates <NUM>, <NUM>. If desired, only a single plate electrode could be used instead. A sample introduction device is used to introduce individual sample into the plasma <NUM> to ionize and/or atomize species in the sample. As noted herein, a gas comprising a nitrogen center is introduced upstream of the plasma <NUM>. For example, nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide or a gas comprising ammonium ions can be introduced upstream of the plasma <NUM>. Illustrative radio frequency generators are described, for example in <CIT>, <CIT>, and <CIT>.

In other configurations, an induction device comprising one or more radial fins could instead be used in methods and systems described herein. Referring to <FIG>, a device or system may comprise an induction coil <NUM> comprising at least one radial fin and a torch <NUM>. A plasma or other ionization/atomization source (not shown) such as, for example, an inductively coupled plasma can be sustained using the torch <NUM> and inductive energy from the radially finned induction device <NUM>. A radio frequency generator (not shown) can be electrically coupled to the induction device <NUM> to provide radio frequency energy into the torch <NUM>. A sample introduction device (not shown) can be used to introduce individual sample into the torch <NUM>. A gas comprising a nitrogen center is introduced upstream of a plasma sustained in the torch <NUM>. For example, nitrogen gas, ammonia gas, nitrous oxide, nitrogen dioxide or a gas comprising ammonium ions can be introduced upstream of a plasma sustained in the torch <NUM>. Elemental species in the introduced sample can be ionized or atomized and separated using the downstream mass analyzer. In other instances, not being part of the present invention, one or more capacitive device such as, for example, capacitive coils or capacitive plates can be used in an ionization source. Further two or more induction devices, and in embodiments not being part of the invention, capacitive devices or other devices which can provide energy into the torch to sustain an atomization/ionization source such as a plasma can also be used.

In one aspect of the invention, the systems described herein are configured as a mass spectrometer system. Referring to <FIG>, a mass spectrometer system <NUM> comprises a sample introduction device <NUM> fluidically coupled to an ionization source <NUM>. The ionization source <NUM> is fluidically coupled to a mass analyzer <NUM>. The mass analyzer is fluidically coupled to a detector <NUM>, which can be integral or separate from the mass analyzer <NUM>. A processor <NUM> is electrically coupled to one or more components of the system <NUM> to control the various sub-systems. As discussed herein, the sample introduction device <NUM> may be a nebulizer, aerosolizer, spray nozzle or head or other devices which can provide the cells to the ionization source <NUM>. The sample introduction device <NUM> may be, or may comprise, a spray chamber as shown in <FIG>. The ionization source <NUM> may be any of those ionization sources described herein, e.g., the induction devices and/or torches shown in <FIG>. The mass analyzer <NUM> may take numerous forms depending generally on the sample nature, desired resolution, etc. In certain embodiments, the mass analyzer <NUM> 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., cyclotrons, quadrupole ions traps), time-of-flight analyzers, and other suitable mass analyzers that can separate or filter (or both) elemental species with different mass-to-charge ratios. The mass analyzer <NUM> may comprise two or more different devices arranged in series, e.g., tandem MS/MS devices or triple quadrupole devices, to select and/or identify the ions that are received from the ionization source <NUM>.

In certain examples, the detector <NUM> can be any suitable detection device that can be used with existing mass spectrometers, e.g., electron multipliers, Faraday cups, coated photographic plates, scintillation detectors, etc. and other suitable devices that will be selected by the person of ordinary skill in the art, given the benefit of this disclosure. The processor <NUM> typically includes a microprocessor and/or computer and suitable software for analysis of samples introduced into the system <NUM>. If desired, one or more databases can be accessed by the processor <NUM> for determination of the chemical identity of species introduced into the system <NUM>.

In another aspect of the invention, the elemental species present in the sample can be detected using optical emission spectroscopy (OES). Referring to <FIG>, an OES device or system <NUM> includes a sample introduction device <NUM>, an ionization source or device <NUM> and a detector or detection device <NUM>. The sample introduction device <NUM> may comprise a spray chamber, nebulizer or other forms. The ionization device <NUM> may comprise, for example, one or more components as illustrated in <FIG> or other devices and components which can provide or sustain an ionization source. The detector or detection device <NUM> may take numerous forms but is any suitable device that detects optical emissions from elemental species, such as optical emission <NUM>. If desired, the detection device <NUM> may include suitable optics, such as lenses, mirrors, prisms, windows, band-pass filters, etc. The detection device <NUM> may also include gratings, such as echelle gratings, to provide a multi-channel OES device. Gratings such as echelle gratings may allow for detection of multiple emission wavelengths. The gratings may be positioned within a monochromator or other suitable device for selection of one or more particular wavelengths to monitor. The detection device <NUM> may be configured to monitor emission wavelengths over a large wavelength range including, but not limited to, ultraviolet, visible, near and far infrared, etc. The OES device <NUM> may further include suitable electronics such as a microprocessor and/or computer and suitable circuitry to provide a desired signal and/or for data acquisition. Suitable additional devices and circuitry are known in the art and may be found, for example, on commercially available OES devices such as Optima 2100DV series, Optima <NUM> DV series OES devices or Optima <NUM> or <NUM> series OES devices commercially available from PerkinElmer Health Sciences, Inc. An optional display <NUM>, which may be a readout, screen, printer, computer, etc. may be present to monitor detection of the elemental species. The OES devices may further include autosamplers, such as AS90 and AS93 autosamplers commercially available from PerkinElmer Health Sciences, Inc. or similar devices available from other suppliers. The OES device <NUM> can be calibrated, for example, using standard concentration of elements and particles of known size to provide a calibration curve for each element which can be used to quantify each element. If desired, peak height, peak area or both can be used to determine the amount of each of the elements present in the individual particle.

In certain embodiments, the exact wavelengths of emitted light which are detected can be used to identify the particular elemental species that are present in the sample. Many elements can emit light at more than a single wavelength. Atomic species may also emit light at a different wavelength than ionized species. Illustrative optical emissions wavelengths for some different elemental species include, but are not limited to, <NUM> or <NUM> for silver, <NUM> or <NUM> for aluminum, <NUM> or <NUM> for arsenic, <NUM> or <NUM> for boron, <NUM> or <NUM> for barium, <NUM> or <NUM> for beryllium, <NUM> or <NUM> for calcium, <NUM> or <NUM> for cadmium, <NUM> or <NUM> for cobalt, <NUM> or <NUM> for chromium, <NUM> or <NUM> for copper, <NUM> or <NUM> for iron, <NUM> for potassium, <NUM> for lithium, <NUM> or <NUM> for magnesium, <NUM> or <NUM> manganese, <NUM> or <NUM> for molybdenum, <NUM> or <NUM> for sodium, <NUM> for sodium, <NUM> or <NUM> for phosphorous, <NUM> for lead, <NUM> or <NUM> for sulfur (as sulfate), <NUM> or <NUM> for antimony, <NUM> for selenium, <NUM> or <NUM> for silicon, <NUM> or <NUM> for strontium, <NUM> or <NUM> for thorium, <NUM> or <NUM> for titanium, <NUM> for thallium, <NUM> or <NUM> for vanadium, <NUM> for uranium, <NUM> or <NUM> for tungsten, <NUM> or <NUM> for zinc and <NUM> for lutetium. Additional suitable elemental emission wavelengths will be selected by the person of ordinary skill in the art, given the benefit of this disclosure, and depending on the detector selected, the use of radial detection, the use of axial detection, etc..

In certain examples, the elemental species present in the sample can be detected using an atomic absorption spectrometer (AAS) to measure light absorbed by the different elemental species. Referring to <FIG>, a single beam AAS device <NUM> comprises a light source <NUM>, a sample introduction device <NUM>, an ionization device or source <NUM>, and a detection device <NUM>. The sample introduction device <NUM> may be any one or more of those described herein, e.g., a spray chamber, or other suitable sample introduction devices. A power source (not shown) may be configured to supply power to the light source <NUM>, which provides one or more wavelengths of light <NUM> for absorption by atoms and ions in the ionization source <NUM>. Suitable light sources include, but are not limited to mercury lamps, cathode ray lamps, lasers, etc. The light source <NUM> may be pulsed using suitable choppers or pulsed power supplies, or in examples where a laser is implemented, the laser may be pulsed with a selected frequency, e.g. <NUM>, <NUM>, or <NUM> times/second. The exact configuration of the light source <NUM> may vary. For example, the light source <NUM> may provide light axially along a torch of the ionization device <NUM> or may provide light radially along the torch of the ionization device <NUM>. The example shown in <FIG> is configured for axial supply of light from the light source <NUM>. There can be signal-to-noise advantages using axial viewing of signals. If desired, the light source can provide light to a chamber separate from the ionization source <NUM>, e.g. a chamber positioned downstream of the ionization source <NUM>. For example, the elemental species can be provided from the ionization source <NUM> to a downstream chamber that is optically coupled to the light source <NUM>. Notwithstanding that many different configurations are possible, the detection device <NUM> is optically coupled to the light source <NUM> so that an amount of light absorbed by a particular elemental species is detected. In some examples, the light source <NUM> can provide light of at least two different wavelengths with one wavelength being absorbed by a first elemental species and the other wavelength of light being absorbed by a second elemental species. If desired, a spectrometer can be present between the light source <NUM> and the ionization source <NUM> (or secondary chamber) to provide a plurality of different individual light wavelengths for absorption by the elemental species. The ionization source <NUM> may comprise one or more components as illustrated in <FIG> or other devices and components which can provide or sustain an ionization source. As sample is atomized and/or ionized in the ionization device <NUM>, the incident light <NUM> from the light source <NUM> may excite atoms. That is, some percentage of the light <NUM> that is supplied by the light source <NUM> may be absorbed by the atoms and ions in the ionization device <NUM>. The remaining percentage of the light may be transmitted to the detection device <NUM> as wavelength <NUM>. The detection device <NUM> may provide one or more suitable wavelengths using, for example, prisms, lenses, gratings and other suitable devices such as those discussed above in reference to the OES devices, for example. To account for the amount of absorption by sample in the ionization device <NUM>, a blank, such as water or particles lacking any elemental species, may be introduced prior to sample introduction to provide a <NUM>% transmittance reference value. The amount of light transmitted once sample is introduced into the ionization device <NUM> may be measured, and the amount of light transmitted with sample may be divided by the reference value to obtain the transmittance. The negative log<NUM> of the transmittance is equal to the absorbance. AAS device <NUM> may further include suitable electronics such as a microprocessor and/or computer and suitable circuitry to provide a desired signal and/or for data acquisition. Suitable additional devices and circuitry may be found, for example, on commercially available AAS devices such as AAnalyst series spectrometers or PinAAcle spectrometers commercially available from PerkinElmer Health Sciences, Inc. The AAS devices may further include autosamplers known in the art, such as AS-90A, AS-90plus and AS-93plus autosamplers commercially available from PerkinElmer Health Sciences, Inc. Where the ionization source <NUM> is configured to sustain an inductively coupled plasma, a radio frequency generator electrically coupled to an induction device may be present. In certain embodiments, a double beam AAS device, instead of a single beam AAS device could instead be used.

In some examples, the wavelength of light absorbed can be used to identify the elemental species present in a sample. Many elements may absorb light at two or more different wavelengths. In addition, atomic species may absorb different wavelength of light than ionized species. It may be desirable to select monitoring wavelengths that do not overlap one another when two or more wavelengths of light are being provided to the ionized elemental species. Further, the wavelength selected may differ when using axial detection and radial detection. Illustrative absorption wavelengths for some different elemental species include, but are not limited to, <NUM> for silver, <NUM> for aluminum, <NUM> for arsenic, <NUM> for gold, <NUM> for boron, <NUM> for barium, <NUM> for beryllium, <NUM> for bismuth, <NUM> for calcium, <NUM> for cadmium, <NUM> for cobalt, <NUM> for chromium, <NUM> for cesium, <NUM> for copper, <NUM> for dysprosium, <NUM> for erbium, <NUM> for europium, <NUM> for iron, <NUM> for gallium, <NUM> for gadolinium, <NUM> for germanium, <NUM> for hafnium, <NUM> for mercury, <NUM> for holmium, <NUM> for indium, <NUM> for iridium, <NUM> for potassium, <NUM> for lanthanum, <NUM> for lithium, <NUM> for lutetium, <NUM> for magnesium, <NUM> for manganese, <NUM> for molybdenum, <NUM> for sodium, <NUM> for niobium, <NUM> for neodymium, <NUM> for nickel, <NUM> for osmium, <NUM> for phosphorous, <NUM> for lead, <NUM> for palladium, <NUM> for praseodymium, <NUM> for platinum, <NUM> for rubidium, <NUM> for rhenium, <NUM> for rhodium, <NUM> for ruthenium, <NUM> for antimony, <NUM> for scandium, <NUM> for selenium, <NUM> for silicon, <NUM> for samarium, <NUM> for tin, <NUM> for strontium, <NUM> for tantalum, <NUM> for thorium, <NUM> for technetium, <NUM> for tellurium, <NUM> for titanium, <NUM> for thallium, <NUM> for thulium, <NUM> for uranium, <NUM> for vanadium, <NUM> for tungsten, <NUM> for yttrium, <NUM> for ytterbium, <NUM> for zinc, and <NUM> for zirconium.

In accordance with the invention, the fluids comprising the nitrogen center are selectively switched on or off depending on which particular element is being detected. As noted herein, during analysis of certain "hard-to-ionize" elements, introduction of a gas comprising a nitrogen center may produce interferences that increase background signals that can render detection of the hard-to-ionize elements difficult. Since an analyte sample may comprise both hard-to-ionize elements and non-hard-to-ionize elements, it can be desirable to improve the detection limits for the non hard-to-ionize elements while at the same time not altering or reducing the detection limits for the hard-to-ionize elements. By selectively introducing the gas comprising the nitrogen center for certain elements and not other elements, analytes of interest can be detected with improved signal-to-noise ratios and/or reduced background signals from interfering species. A processor is used to correlate detection of a particular element with selective introduction (or selective halting) of the gas comprising the nitrogen center. For example, the system can be designed to continuously introduce the gas comprising the nitrogen center into the gas sample unless a hard-to-ionize element is to be detected. In such instances, the processor switches off the flow controller or otherwise stop flow of the gas comprising the nitrogen center to permit detection of the hard-to-ionize element in the absence of any nitrogen center introduced into the ionization source. The processor then switches flow of the gas comprising the nitrogen center back on during detection of other elements. In an alternative configuration, not being covered by the present invention, the system can be configured to operate without the gas comprising the nitrogen center unless for certain elements the detection limits would improve in the presence of the gas comprising the nitrogen center. In such instances, the gas can be switched on during analysis of these elements and then switched back off during analysis of other elements. While the gas comprising the nitrogen center is not introduced during detection of hard-to-ionize elements, it is introduced to provide a differential comparison of the signals. For example, a hard-to-ionize element can be detected in the absence of any gas comprising a nitrogen center and in the presence of a gas comprising a nitrogen center. The resulting signals can be compared, for example, to obtain a measure of interfering species that may be present or to provide some indication of background enhancement of interfering signals. In addition, the differential signal can be compared using fluids with different nitrogen centers to determine if a particular nitrogen containing species may work better than other species for certain elements.

In certain examples, the methods and systems herein may comprise or use a processor, which can be part of the system or instrument or present in an associated device, e.g., computer, laptop, mobile device, etc. used with the instrument. For example, the 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 common hardware circuity including, for example, a microprocessor and/or suitable software for operating the system, e.g., to control the sample introduction device, ionization source, detector, etc. In some examples, the detection device or detector itself may comprise its own respective processor, operating system and other features to permit detection of various elemental species. The processor can be integral to the systems or may be present on one or more accessory boards, printed circuit boards or computers electrically coupled to the components of the system. The processor is typically electrically coupled to one or more memory units to receive data from the other components of the system and permit adjustment of the various system parameters as needed or desired. The processor may be part of a general-purpose computer such as those based on Unix, Intel PENTIUM-type processor, Motorola PowerPC, Sun UltraSPARC, Hewlett-Packard PA-RISC processors, or any other type of processor. One or more of any type computer system may be used according to various embodiments of the technology. Further, the system may be connected to a single computer or may be distributed among a plurality of computers attached by a communications network. It should be appreciated that other functions, including network communication, can be performed and the technology is not limited to having any particular function or set of functions. Various aspects may be implemented as specialized software executing in a general-purpose computer system. The 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 for storing programs, calibration curves, emission or absorption wavelengths, and data values during operation of the systems. Components of the computer system may be coupled by an interconnection device, which may include one or more buses (e.g., between components that are integrated within a same machine) and/or a network (e.g., between components that reside on separate discrete machines). The interconnection device provides for communications (e.g., signals, data, instructions) to be exchanged between components of the system. The computer system typically can receive and/or issue commands within a processing time, e.g., a few milliseconds, a few microseconds or less, to permit rapid control of the system. For example, computer control can be implemented to control sample introduction, flow of the gas comprising the nitrogen center, detector parameters, etc. The processor typically is electrically coupled to a power source which can, for example, be a direct current source, an alternating current source, a battery, a fuel cell or other power sources or combinations of power sources. The power source can be shared by the other components of the system. The system may also include one or more input devices, for example, a keyboard, mouse, trackball, microphone, touch screen, manual switch (e.g., override switch) and one or more output devices, for example, a printing device, display screen, speaker. In addition, the system may contain one or more communication interfaces that connect the computer system to a communication network (in addition or as an alternative to the interconnection device). The system may also include suitable circuitry to convert signals received from the various electrical devices present in the systems. Such circuitry can be present on a printed circuit board or may be present on a separate board or device that is electrically coupled to the printed circuit board through a suitable interface, e.g., a serial ATA interface, ISA interface, PCI interface or the like or through one or more wireless interfaces, e.g., Bluetooth, Wi-Fi, Near Field Communication or other wireless protocols and/or interfaces.

In certain embodiments, the storage system used in the systems described herein typically includes a computer readable and writeable nonvolatile recording medium in which codes of software can be stored that can be used by a program to be executed by the processor or information stored on or in the medium to be processed by the program. The medium may, for example, be a hard disk, solid state drive or flash memory. The program or instructions to be executed by the processor may be located locally or remotely and can be retrieved by the processor by way of an interconnection mechanism, a communication network or other means as desired. Typically, in operation, the processor causes data to be read from the nonvolatile recording medium into another memory that allows for faster access to the information by the processor than does the medium. This memory is typically a volatile, random access memory such as a dynamic random access memory (DRAM) or static memory (SRAM). It may be located in the storage system or in the memory system. The processor generally manipulates the data within the integrated circuit memory and then copies the data to the medium after processing is completed. A variety of mechanisms are known for managing data movement between the medium and the integrated circuit memory element and the 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, special-purpose hardware, for example, an application-specific integrated circuit (ASIC) or a field programmable gate array (FPGA). Aspects of the technology may be implemented in software, hardware or firmware, or any combination thereof. Further, such methods, acts, systems, system elements and components thereof may be implemented as part of the systems described above or as an independent component. Although specific systems are described by way of example as one type of system upon which various aspects of the technology may be practiced, it should be appreciated that aspects are not limited to being implemented on the described system. Various aspects may be practiced on one or more systems having a different architecture or components. The system may comprise a general-purpose computer system that is programmable using a high-level computer programming language. The systems may be also implemented using specially programmed, special purpose hardware. In the systems, the processor is typically a commercially available processor such as the well-known Pentium class processors available from the Intel Corporation. Many other processors are also commercially available. Such a processor usually executes an operating system which may be, for example, the Windows <NUM>, Windows <NUM>, Windows NT, Windows <NUM> (Windows ME), Windows XP, Windows Vista, Windows <NUM>, Windows <NUM> or Windows <NUM> operating systems available from the Microsoft Corporation, MAC OS X, e.g., Snow Leopard, Lion, Mountain Lion or other versions available from Apple, the Solaris operating system available from Sun Microsystems, or UNIX or Linux operating systems available from various sources. Many other operating systems may be used, and in certain embodiments a simple set of commands or instructions may function as the operating system. Further, the processor can be designed as a quantum processor designed to perform one or more functions using one or more qubits.

In certain examples, the processor and operating system may together define a platform for which application programs in high-level programming languages may be written. It should be understood that the technology is not limited to a particular system platform, processor, operating system, or network. Also, it should be apparent to those skilled in the art, given the benefit of this disclosure, that the present technology is not limited to a specific programming language or computer system. Further, it should be appreciated that other appropriate programming languages and other appropriate systems could also be used. In certain examples, the hardware or software can be configured to implement cognitive architecture, neural networks or other suitable implementations. If desired, one or more portions of the computer system may be distributed across one or more computer systems coupled to a communications network. These computer systems also may be general-purpose computer systems. For example, various aspects may be distributed among one or more computer systems configured to provide a service (e.g., servers) to one or more client computers, or to perform an overall task as part of a distributed system. For example, various aspects may be performed on a client-server or multi-tier system that includes components distributed among one or more server systems that perform various functions according to various embodiments. These components may be executable, intermediate (e.g., IL) or interpreted (e.g., Java) code which communicate over a communication network (e.g., the Internet) using a communication protocol (e.g., TCP/IP). It should also be appreciated that the technology is not limited to executing on any particular system or group of systems. Also, it should be appreciated that the technology is not limited to any particular distributed architecture, network, or communication protocol.

In some instances, 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, functional, scripting, and/or logical programming languages may be used. Various configurations may be implemented in a non-programmed environment (e.g., documents created in HTML, XML or other format that, when viewed in a window of a browser program, render aspects of a graphical-user interface (GUI) or perform other functions). Certain configurations may be implemented as programmed or non-programmed elements, or any combination thereof. In some instances, the systems may comprise a remote interface such as those present on a mobile device, tablet, laptop computer or other portable devices which can communicate through a wired or wireless interface and permit operation of the systems remotely as desired.

In certain examples, the processor may also comprise, or have access to, a database of information about elemental species and the like, which can include optical emission wavelengths, optical absorption wavelengths and other common information. For example, a collection of calibration curves for different elemental species can be stored in the database and used to estimate elemental concentrations in the sample without the need for the user to perform calibration curves for each of the elements. Such methods may be particularly desirable where the amount of sample is limited. The instructions stored in the memory can execute a software module or control routine for the system, which in effect can provide a controllable model of the system. The processor can use information accessed from the database together with one or software modules executed in the processor to determine control parameters or values for different components of the systems, e.g., different gas flow rates, different light wavelengths to be monitored, etc. Using input interfaces to receive control instructions and output interfaces linked to different system components in the system, the processor can perform active control over the system. For example, the processor can control the detection device, sample introduction devices, ionization sources, flow controllers, etc..

In some embodiments, not being covered by the method of the present invention, the gas comprising the nitrogen center may also be introduced into another component of the system that is downstream of the ionization source. Referring to <FIG>, a system <NUM> is shown where a gas source <NUM> comprising a gas with a nitrogen center is fluidically coupled to a sample introduction device <NUM> and a cell <NUM> downstream of an ionization source <NUM>. If desired, an optional flow controller <NUM> can be present and used to control flow of the gas independently to the sample introduction device <NUM> and the cell <NUM> from the gas source <NUM>. In some examples, the cell <NUM> may take the form of a collision cell, a reaction cell, or a collision-reaction cell as described, for example, in U. Patent No. <NUM>,<NUM>,<NUM>. In certain examples, also not covered by the method of the present invention, the gas from the gas source <NUM> could also or instead be provided to a downstream component other than the cell <NUM>, e.g., it could be provided to a detector, mass analyzer or other components downstream from the ionization source <NUM>.

Certain specific examples are described below to illustrate some of the novel and inventive aspects of the technology described herein.

An inductively coupled mass spectrometer system (NexION ICP-MS) comprising a spray chamber commercially available from PerkinElmer Health Sciences, Inc, e.g., an All Matrix Solution spray chamber, was used to measure signals (background signals and elemental signals). Table <NUM> below shows the results with the values representing the counts per second (cps) for each element detected. <NUM> parts per trillion of each element was separately introduced into the mass spectrometer. No nitrogen center gas was introduced into the spray chamber. Analysis was performed in DRC mode in the presence of ammonia in the reaction cell.

Detection limits were calculated using the standard deviation of the blank signal (3x std. deviation of the blank signal) divided by the analytical signal. A desired detection limit is <NUM> ppt or below. Background equivalent concentrations for the iron, calcium and potassium were <NUM>, <NUM> and <NUM> ppt, respectively.

The same system used in Example <NUM> was used to measure signals (background signals and elemental signals) in the presence of nitrogen gas (<NUM>% by volume) introduced into the spray chamber. Table <NUM> below shows the results with the values representing the counts per second (cps) for each element detected. <NUM> parts per trillion of each element was separately introduced into the mass spectrometer.

The results were consistent with the background equivalent concentrations (BEC) improving in the presence of the nitrogen gas introduced into the spray chamber while operating the reaction cell with ammonia gas. Calcium detection limits did not improve because the primary interference is Ar+ and the nitrogen did not have an effect on this species. The BEC and hence the detection limit for the other elements improved due to the ArX+ species not forming (or forming to a lower degree) when nitrogen is introduced. Background signals decreased significantly compared to the background signals measured in Example <NUM>. Signal intensities for all elements (analytical and background signals) also decreased compared to signal intensities in Example <NUM>, however at reduced rate compared to the background signal. Background equivalent concentrations (BEC's) in the presence of the nitrogen gas for the iron, calcium and potassium were <NUM>, <NUM> and <NUM> ppt, respectively. BEC's improved for all three elements.

Background equivalent concentration (BEC's) in the absence and presence of nitrogen gas were determined for each of the elements shown in Table <NUM> in <FIG> using the system in Example <NUM>. The elements were present in an aqueous solution of <NUM>% nitric acid. Addition of the nitrogen gas improved BEC's for numerous elements particularly those that easily oxidize (Uranium, Vanadium). The values in Table <NUM> are expressed as (Log BEC)/parts per trillion.

When introducing elements of the examples disclosed herein, the articles "a," "an," "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising," "including" and "having" are intended to be open-ended and mean that there may be additional elements other than the listed elements. It will be recognized by the person of ordinary skill in the art, given the benefit of this disclosure, that various components of the examples can be interchanged or substituted with various components in other examples, without departing from the extent of the invention as defined in the appended claims.

Claim 1:
A method comprising:
introducing a gas comprising a nitrogen center into a spray chamber (<NUM>, <NUM>) positioned upstream of an inductively coupled plasma (<NUM>, <NUM>, <NUM>, <NUM>) sustained in a torch (<NUM>, <NUM>, <NUM>), and fluidically coupled to a sample inlet of the torch,
wherein the gas comprising the nitrogen center comprises a molecule or compound comprising at least one nitrogen atom chemically bonded to another atom;
wherein the torch (<NUM>, <NUM>, <NUM>) is configured to sustain the inductively coupled plasma (<NUM>, <NUM>, <NUM>, <NUM>) using a plasma gas introduced into the torch, and wherein elements in a sample introduced into the sustained inductively coupled plasma are ionized by the sustained inductively coupled plasma; the method characterised by
selectively switching off the introduction of the gas comprising the nitrogen center into the spray chamber when a hard-to-ionize element is being analyzed using the inductively coupled plasma, wherein the hard-to-ionize element comprises beryllium, zinc, selenium, or arsenic; and
selectively switching on the introduction of the gas comprising the nitrogen center into the spray chamber when an element other than a hard-to-ionize element is being analyzed using the inductively coupled plasma.