Patent Grant
10834807
Inductively Coupled Plasma (ICP) spectrometry is an analysis technique commonly used for the determination of trace element concentrations and isotope ratios in liquid samples. ICP spectrometry employs electromagnetically generated partially ionized argon plasma which reaches a temperature of approximately 7,000K. When a sample is introduced to the plasma, the high temperature causes sample atoms to become ionized or emit light. Since each chemical element produces a characteristic mass or emission spectrum, measuring the spectra of the emitted mass or light allows the determination of the elemental composition of the original sample.
Sample introduction systems may be employed to introduce the liquid samples into the ICP spectrometry instrumentation (e.g., an Inductively Coupled Plasma Mass Spectrometer (ICP/ICP-MS), an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), or the like) for analysis. For example, a sample introduction system may withdraw an aliquot of a liquid sample from a container and thereafter transport the aliquot to a nebulizer that converts the aliquot into a polydisperse aerosol suitable for ionization in plasma by the ICP spectrometry instrumentation. Prior or during transportation of the aliquot to the nebulizer, the sample aliquot may be mixed with hydride generation reagents and fed into a hydride gas/liquid separator that channels hydride and/or sample gas into the nebulizer. The aerosol generated by the nebulizer is then sorted in a spray chamber to remove the larger aerosol particles. Upon leaving the spray chamber, the aerosol is introduced into the plasma by a plasma torch assembly of the ICP-MS or ICP-AES instruments for analysis. The plasma torch assembly includes an injector for transferring the aerosol from the spray chamber to the analysis site (i.e., into the plasma).
A plasma torch assembly (e.g., for an ICP-MS or ICP-AES instrument) with a retractable injector is disclosed. Variably extending or retracting the injector relative to an auxiliary tube of the torch assembly can be advantageous in certain situations. For example, the torch can be used with a retracted injector when samples with high levels of dissolved solids (<0.1% W/W) are analyzed for increased residence time in the ICP. As another example, when the torch is used with volatile samples, such as organic solvents or solutions with high concentrations of ammonia, it can be operated with the injector in a more extended configuration (e.g., fully extended) to ensure plasma stability.
In embodiments, the torch assembly includes a torch body, an auxiliary tube supported by the torch body, and an injector adjustable to extend or retract relative to the auxiliary tube. The injector can comprise an injector body and an injector tube mounted to the injector body, wherein the injector tube is slidable within a passage of the torch body. The injector body can be actuated to slide the injector tube forward or backward within the passage of the torch body. For example, the injector body may include a threaded portion that is receivable by a threaded coupling for connecting the injector with the torch body, wherein the injector tube is actuatable by rotating the injector body relative to the threaded coupling. The torch assembly also includes an airtight seal between the injector and the torch body to isolate the torch from environmental air external to the torch. In some embodiments, the physical dimensions of the injector body and the passage of the torch body establish the airtight seal when the injector body is coupled to the torch body. In other embodiments, the airtight seal can be formed by a seal element that is coupled to the injector, where the seal element is slidable within the passage of the torch body to maintain the airtight seal when the injector tube is extended/retracted.
This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
The Detailed Description is described with reference to the accompanying figures. The use of the same reference numbers in different instances in the description and the figures may indicate similar or identical items.
Sample introduction systems may be employed to introduce the liquid samples into the ICP spectrometry instrumentation (e.g., an Inductively Coupled Plasma Mass Spectrometer (ICP/ICP-MS), an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), or the like) for analysis. For example, a sample introduction system may withdraw an aliquot of a liquid sample from a container and thereafter transport the aliquot to a nebulizer that converts the aliquot into a polydisperse aerosol suitable for ionization in plasma by the ICP spectrometry instrumentation. Prior or during transportation of the aliquot to the nebulizer, the sample aliquot may be mixed with hydride generation reagents and fed into a hydride gas/liquid separator that channels hydride and/or sample gas into the nebulizer. The aerosol generated by the nebulizer is then sorted in a spray chamber to remove the larger aerosol particles. Upon leaving the spray chamber, the aerosol is introduced into the plasma by a plasma torch assembly of the ICP instrument for analysis.
A plasma torch assembly with a retractable injector is disclosed herein. Having the ability to variably extend or retract the injector relative to an auxiliary tube of the torch assembly can be advantageous in certain situations. For example, the torch can be used with a retracted injector when samples with high levels of dissolved solids (<0.1% W/W) are analyzed for increased residence time in the ICP. As another example, when the torch is used with volatile samples, such as organic solvents or solutions with high concentrations of ammonia, it can be operated with the injector in a more extended configuration (e.g., fully extended) to ensure plasma stability.
According to various embodiments, the torch assembly 100 includes a torch body 104, an auxiliary tube 108 supported by the torch body 104, and an injector adjustable to extend or retract relative to the auxiliary tube 108. The injector can comprise an injector body 118 and an injector tube 120 mounted to the injector body 118, wherein the injector tube 120 is slidable within a passage of the torch body 104. The injector body 118 can be actuated to slide the injector tube 120 forward or backward within the passage of the torch body 104, causing the tip of the injector tube 120 to extend or retract relative to an auxiliary tube 108 situated around the injector tube 120. The injector body 118 and the torch body 104 can be formed from a plastic or polymer material. The injector tube 120 and the auxiliary tube 108 and outer tube 106 of the torch assembly 100 can be formed from a glass or glass-like material that is heat resistant and/or corrosive resistant.
In some embodiments, the torch assembly 100 may include a substantially flat disc shaped (e.g., washer-like) shielding element 122 (
The injector body 118 can include a threaded portion 116 that is receivable by a threaded coupling 112 for connecting the injector body 118 with the torch body 104. For example, the threaded portion 116 can be cooperatively threaded with a threaded portion 124 of the threaded coupling 112, where the injector tube 120 is actuatable by rotating the injector body 118 relative to the threaded coupling 112. When the injector body 118 is turned in a first direction, the injector body 118 is brought into tighter contact with the threaded coupling 112, thereby moving the injector tube 120 to a more extended or less retracted position with respect to the auxiliary tube 108. When the injector body 118 is turned in a second (opposite) direction, the injector body 118 loosened with respect to the threaded coupling 112, thereby moving the injector tube 120 to a retracted or less extended or more retracted position with respect to the auxiliary tube 108.
In some embodiments, the injector body 118 and threaded coupling 112 have fine pitched threading at threaded portions 116 and 124 for accurate positioning of the injector tube 120. For example, the threading can correspond to predetermined positions of the injector tube 120. In some embodiments, a scale printed or etched in proximity of the coupling interface (e.g., between the injector body 118 and the threaded coupling 112). For example, the scale can comprise indicia (e.g., markings) printed or etched on one or more of the components (e.g., as shown in
The threaded coupling 112 can be part of the torch body 104, or it can be distinct from the torch body 104 as illustrated in
The torch assembly 100 also includes an airtight seal between the injector and the torch body 104 to isolate the torch from environmental air external to the torch. In some embodiments, the physical dimensions of the injector body 118 and the passage of the torch body 104 establish the airtight seal when the injector body 118 is coupled to the torch body 104. For example, the injector body 118 and/or the torch body 104 can be tight fit and/or can include ridges, grooves, or other cooperative structural elements that create an airtight seal when they are fit together. In other embodiments, the airtight seal can be formed by a seal element (e.g., polymer washer) that is coupled to the injector, where the seal element is slidable within the passage of the torch body 104 to maintain the airtight seal when the injector tube 120 is extended/retracted. This configuration also allows the components to self-align with one another as a result of the manner by which the components are coupled (i.e., screwed together) along a common axis. In some embodiments, alternative coupling techniques can be implemented, such as snap fitting the components with one another along a common axis. Any such coupling technique can be implemented without departing from the scope of this disclosure.
In some embodiments, the injector tube 120 can be automatically extended/retracted. For example, the torch assembly 100 can further include a motor, servo, or other electronically controlled actuator that rotates the injector body 118 relative to the threaded coupling 112 or otherwise slides the injector tube 120 forward or backwards relative to the auxiliary tube 108. A controller can drive the actuator according to program instructions executable from a non-transitory memory device. The controller can be programmed or otherwise configured to extend or retract the injector tube 120 to a selected position or level or extension/retraction (e.g., a user selected position or a position based on programmed settings for samples/sample solutions being analyzed).
It will be understood by those within the art that, in general, terms used herein, and are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations.
In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.).
In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”
Although particular embodiments of this invention have been illustrated, it is apparent that various modifications and embodiments of the invention may be made by those skilled in the art without departing from the scope and spirit of the foregoing disclosure. Accordingly, the scope of the invention should be limited only by the claims appended hereto.
The present application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 62/316,662, filed Apr. 1, 2017, and titled “ICP TORCH ASSEMBLY WITH RETRACTABLE INJECTOR,” which is incorporated herein by reference in its entirety.
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