Stable cell collection for elemental analysis

Abstract

The invention relates to stable cell collection for elemental analysis. Analysis of a sample injected into an inductively coupled plasma source may be improved by one or more of a stabilizing solution that may be mixed with the sample prior to injection and a heated injector. The stabilized solution can minimize osmotic pressure differences between the solution and the cells with relatively low amounts of dissolved solids (e.g., at or below about 0.2%). The stabilized solution may contain a salt (e.g., ammonium nitrate) present at a concentration of at least 5 mM. The injector may be heated before and / or during the injection. In some cases, heat from adjacent portions may be directed into the injector to improve heating of the injector. The injector heated to a sufficient temperature may minimize solute build-up and may extend the time available between cleaning. These improvements may be particularly useful in elemental analysis such as inductively coupled plasma mass spectrometry or inductively coupled plasma light emission spectroscopy.

Description

[0001] This application is a divisional application of Chinese Patent Application No. 201980039049.9, filed on April 12, 2019, entitled "Stable Cell Collection for Elemental Analysis".

[0002] Citations of relevant applications

[0003] This application claims the benefit of U.S. Provisional Application No. 62 / 657,332, filed April 13, 2018, entitled “Stabilized Cell Acquisition for Elemental Analysis,” which is incorporated herein by reference in its entirety. Technical Field

[0004] This disclosure generally relates to improving signal stability in elemental analysis, and more specifically to improving the ionization of samples in conjunction with elemental analysis. Background Technology

[0005] Inductively coupled plasma (ICP) is a plasma source used in various fields such as elemental analysis. Samples supplied to a plasma generated by an ICP source can be ionized and nebulized prior to analysis, such as by mass spectrometry (MS) or optical emission spectroscopy (OES) (e.g., atomic emission spectroscopy or AES). ICP sources can also be used for other purposes. Samples typically contain substances dissolved in solution, such as suspensions of substances in liquids or solid substances carried in a gas stream.

[0006] In an ICP source (such as an ICP torch), plasma is generated when a gas stream (such as argon) is ionized in a strong electromagnetic field. When optimal plasma temperature and energy density are achieved, a sample introduced into the plasma through the torch can be vaporized, atomized, and ionized. Typically, the conditions for achieving optimal plasma temperature and energy density are reflected by the argon gas flow rate and the power intensity of the electromagnetic field.

[0007] An ICP source may include an induction coil and a set of tubes for supplying gas and sample through a torch region covered by the induction coil. An ICP source typically includes an inner tube that acts as an injector to cover the sample, a middle tube for supplying the gas to be heated and ionized, and an outer tube for providing tangential flow to help maintain the shape of the plasma and protect the torch walls from melting.

[0008] In elemental analysis, a sample supplied to an ICP source is ionized and then transferred to an elemental analyzer. The process of storing the sample and then injecting it into the ICP source can sometimes damage the sample in ways that may reduce the stability or resolution of the determination. Techniques and materials for improving the stability and resolution of ICP-based elemental analysis may be required. Furthermore, conventional ICP-based elemental analyzers become contaminated over time, such as from build-up on the injector. An ICP-based elemental analyzer or ICP source that is resistant to contamination over time may be needed.

[0009] In multielemental analysis of elementally labeled cells (e.g., mass cytometry), cells are suspended in water to avoid background noise from metals or heavy elements during elemental analysis. The absence of solutes also reduces agglomeration on the ICP injector walls, which can clog the jet. Summary of the Invention

[0010] The terms "implementation" and similar terms are intended to refer broadly to all subject matter of this disclosure and the following claims. Statements containing these terms should be understood as not limiting the subject matter described herein or the meaning or scope of the following claims. The embodiments of this disclosure as covered herein are defined by the following claims, not by the content of this invention. The content of this invention is a high-level overview of various aspects of this disclosure and introduces some concepts further described in the following detailed description section. The content of this invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used alone to determine the scope of the claimed subject matter. The subject matter should be understood by referring to appropriate portions of the entire specification of this disclosure, any or all of the accompanying drawings, and each claim.

[0011] Embodiments of this disclosure include a sample comprising: an element-labeled analyte containing an analyte that binds to an element-labeled affinity reagent, wherein the element-labeled affinity reagent comprises an affinity reagent for binding to the analyte and a metal-binding portion for binding to one or more metal elements; and a stabilized solution having a total dissolved solids content of about 0.2% or less, wherein the stabilized solution contains a salt present at a concentration of at least 5 mM.

[0012] In some cases, the salt is a nonmetallic salt. In some cases, the salt does not contain carbon. In some cases, the salt does not contain metals with an atomic mass greater than 80. In some cases, the salt includes nitrogen. In some cases, the salt is ammonium nitrate. In some cases, the salt has a vapor pressure of at least 3 Pa at 100 °C. In some cases, the salt has a vapor pressure of at least 130 Pa at 150 °C. In some cases, the salt has a vapor pressure of at least 250 Pa at 160 °C. In some cases, the salt is ammonium acetate. In some cases, the analyte contains whole cells. In some cases, the stabilizing solution induces a sufficiently low osmotic pressure on the analyte membrane to avoid osmotic lysis. In some cases, the salt is present in the stabilizing solution at a concentration of 1 mM or less than 25 mM. In some cases, the stabilizing solution has a pH between 5 and 9. In some cases, the stabilizing solution has a pH between 6 and 8. In some cases, the metal-binding portion comprises a polymer linked to an affinity reagent and containing at least one metal-binding side group, said metal-binding side group containing at least one metal atom. In some cases, the element-labeled analyte comprises a first analyte labeled with a first element tag and a second analyte labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis. In some cases, the affinity reagent comprises an antibody.

[0013] Embodiments of this disclosure include a sample preparation kit comprising an element-labeled affinity reagent comprising an affinity reagent for binding to an analyte and a metal-binding moiety for binding to one or more metal elements; and a stabilizing solution having a total dissolved solids content of about 0.2% or less, wherein the stabilizing solution contains a salt present at a concentration of at least 5 mM.

[0014] In some cases, the salt is a nonmetallic salt. In some cases, the salt does not contain carbon. In some cases, the salt does not contain metals with an atomic mass greater than 80. In some cases, the salt includes nitrogen. In some cases, the salt is ammonium nitrate. In some cases, the salt has a vapor pressure of at least 3 Pa at 100 °C. In some cases, the salt has a vapor pressure of at least 130 Pa at 150 °C. In some cases, the salt has a vapor pressure of at least 250 Pa at 160 °C. In some cases, the salt is ammonium acetate. In some cases, the affinity reagent can bind to the surface of the whole cell. In some cases, the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the whole cell bound to the affinity reagent to avoid osmotic dissolution of the whole cell. In some cases, the salt is present in the stabilizing solution at a concentration of 1 or less than 25 mM. In some cases, the stabilizing solution has a pH between 5 and 9. In some cases, the stabilizing solution has a pH between 6 and 8. In some cases, the metal-bonded portion comprises a polymer linked to an affinity reagent and containing at least one metal-bonded side group, said metal-bonded side group containing at least one metal atom. In some cases, the element-labeled affinity reagent comprises a first affinity reagent labeled with a first element tag and a second affinity reagent labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis.

[0015] Embodiments of this disclosure include a method comprising: receiving a sample containing an element-labeled analyte and a stabilization solution; transporting the sample downstream toward a plasma source of an inductively coupled plasma source to ionize the sample, wherein transporting the sample includes passing the sample through the inner wall of an injector; ionizing the sample at the plasma; and performing elemental analysis on the ionized sample to detect the element of the element-labeled analyte.

[0016] In some cases, the analyte comprises whole cells, and sample delivery to the plasma includes delivering whole cells to the plasma. In some cases, sample delivery to the plasma includes delivering the sample through an injector with an inner diameter between approximately 0.5 mm and 5 mm. In some cases, the receiving sample also comprises a mixture of elementally labeled analytes and a stabilizing solution. In some cases, the stabilizing solution comprises a salt selected to achieve less than 2% salt deposition during a 48-hour sample run. In some cases, the stabilizing solution comprises a salt selected to maintain a signal drop percentage of 5% or less during elemental analysis during a 48-hour sample run.

[0017] Embodiments of this disclosure include a method comprising providing an element-labeled analyte, wherein the element-labeled analyte comprises a whole-cell sample labeled with an element-labeled affinity reagent, wherein each element-labeled affinity reagent comprises an affinity reagent bound to the sample analyte and a metal-binding moiety bound to one or more metal elements; and mixing the element-labeled analyte with a stabilization solution having a total dissolved solids content of about 0.2% or less, wherein the stabilization solution contains a salt present at a concentration of at least 5 mM.

[0018] In some cases, the salt is a nonmetallic salt. In some cases, the salt does not contain carbon. In some cases, the salt does not contain metals with an atomic mass greater than 80. In some cases, the salt includes nitrogen. In some cases, the salt is ammonium nitrate. In some cases, the salt has a vapor pressure of at least 3 Pa at 100°C. In some cases, the method further includes passing the sample collection solution through an injector heated to at least 100°C. In some cases, the salt has a vapor pressure of at least 130 Pa at 150°C. In some cases, the method further includes passing the sample collection solution through an injector heated to at least 150°C. In some cases, the salt has a vapor pressure of at least 250 Pa at 160°C. In some cases, the method further includes passing the sample collection solution through an injector heated to at least 160°C. In some cases, the salt is ammonium acetate. In some cases, the affinity reagent can bind to the surface of the whole cell. In some cases, the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the whole cell bound to the affinity reagent to avoid osmotic dissolution of the whole cell. In some cases, the salt is present in the stabilization solution at a concentration of 25 mM or less. In some cases, the stabilization solution has a pH between 5 and 9. In some cases, the stabilization solution has a pH between 6 and 8. In some cases, the metal-binding portion comprises a polymer linked to an affinity reagent and containing at least one metal-binding side group, said metal-binding side group containing at least one metal atom. In some cases, the element-labeled affinity reagent comprises a first affinity reagent labeled with a first element tag and a second affinity reagent labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis. In some cases, the salt is selected to obtain less than 2% salt deposition during a 48-hour sample run. In some cases, the stabilization solution includes a salt selected to maintain a signal drop percentage of 5% or less during elemental analysis during a 48-hour sample run.

[0019] Embodiments of this disclosure include a stabilization solution miscible with a sample for use in inductively coupled plasma elemental analysis, the stabilization solution comprising: a solute and a solvent, wherein the solute is a salt present at a concentration of at least 5 mM, wherein the solution has a total dissolved solids of about 0.2% or less, and wherein the solution does not contain metals with an atomic mass greater than 80.

[0020] In some cases, the salt is a nonmetallic salt. In some cases, the salt does not contain carbon. In some cases, the salt includes nitrogen. In some cases, the salt is ammonium nitrate. In some cases, the salt has a vapor pressure of at least 3 Pa at 100 °C. In some cases, the salt has a vapor pressure of at least 130 Pa at 150 °C. In some cases, the salt has a vapor pressure of at least 250 Pa at 160 °C. In some cases, the salt is ammonium acetate. In some cases, the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the whole cells of the sample to avoid osmotic dissolution of the whole cells. In some cases, the salt is present in the stabilizing solution at a concentration of 1 mM or less than 25 mM. In some cases, the stabilizing solution has a pH between 5 and 9. In some cases, the stabilizing solution has a pH between 6 and 8.

[0021] Embodiments of this disclosure include an apparatus comprising: an inductively coupled plasma source for generating plasma; an injector having a sample inlet for receiving a sample containing an elementally labeled analyte, wherein the injector is positioned upstream of the inductively coupled plasma source to supply the sample to the plasma; and a heat source thermally coupled to the injector for heating the injector.

[0022] In some cases, the device also includes a heat transfer device thermally coupled to the injector for transferring heat from a heat source. In some cases, the heat transfer device includes a metallic jacket surrounding at least a portion of the injector. In some cases, the heat source includes at least a portion of a spray chamber located upstream of the injector, such that heat from the spray chamber is transferred to the injector via the heat transfer device. In some cases, the heat source includes plasma. In some cases, the heat source includes a resistance heat source. In some cases, the device also includes one or more heat pipes extending along the length of the injector. In some cases, one or more heat pipes are arranged to conduct thermal energy from a higher temperature portion of the injector to a lower temperature portion of the injector. In some cases, the device also includes a mass spectrometer located downstream of an inductively coupled plasma source for receiving ions from the inductively coupled plasma source. In some cases, the inner diameter of the injector is between approximately 0.5 mm and 5 mm. In some cases, the device also includes a sample source coupled to the injector for providing a sample and a stabilizing solution. In some cases, a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature sufficient to evaporate or sublimate the solute in the stable solution. In other cases, a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature of at least 150°C.

[0023] Embodiments of this disclosure include methods using one or more of the devices disclosed above, the methods comprising: heating an injector with a heat source; passing a sample through the injector to plasma; ionizing the sample; and performing elemental analysis on the ionized sample.

[0024] In some cases, passing a sample through the injector involves passing a solution containing an elementally labeled analyte and a stabilizing solution. In some cases, heating the injector involves heating the injector to a temperature suitable for obtaining less than 2% salt deposition during a 48-hour sample run. In some cases, heating the injector involves passing an electric current through a resistive heat source, wherein the heat source is a resistive heat source. In some cases, heating the injector involves using a heat transfer device to conduct heat from a higher-temperature portion of the injector to a lower-temperature portion of the injector. In some cases, heating the injector involves heating the inner wall to a temperature sufficient to evaporate, sublimate, or decompose the solute in the stabilizing solution.

[0025] Embodiments of this disclosure include a method comprising: receiving a sample containing an element-labeled analyte and a stabilizing solution; transporting the sample downstream toward a plasma source of an inductively coupled plasma source to ionize the sample, wherein transporting the sample includes passing the sample through an inner wall of an injector; and heating the inner wall of the injector.

[0026] In some cases, heating of the inner wall of the injector begins before the sample is delivered to the plasma. In some cases, heating of the inner wall of the injector begins after the first portion of the sample is delivered to the plasma. In some cases, the method further includes passing the sample through a spray chamber, wherein heating the inner wall of the injector includes conducting heat from the spray chamber via a heat transfer device. In some cases, heating the inner wall of the injector includes generating heat at a heat source. In some cases, generating heat at the heat source includes passing an electric current through a resistive heat source. In some cases, heating the inner wall of the injector includes using a heat transfer device to conduct heat from a higher temperature portion of the injector to a lower temperature portion of the injector. In some cases, heating the inner wall of the injector includes heating the inner wall to a temperature sufficient to evaporate or sublimate the solute in the stabilized solution. In some cases, heating the inner wall of the injector includes heating the inner wall to a temperature of at least 150°C. In some cases, the method further includes: delivering ions of an ionized sample to a mass spectrometer; and analyzing the ions via the mass spectrometer. In some cases, the analyte comprises whole cells, and wherein delivering the sample to the plasma includes delivering whole cells to the plasma. In some cases, sample delivery to the plasma involves delivering the sample through an injector with an inner diameter between approximately 0.5 mm and 5 mm. In some cases, the received sample also contains mixed element-labeled analytes and stabilization solutions. In some cases, heating the inner wall of the injector involves heating the inner wall to a temperature suitable for obtaining less than 2% salt deposition during a 48-hour sample run.

[0027] Embodiments of this disclosure include an apparatus comprising: an injector positioned upstream of an inductively coupled plasma source and adapted to deliver a sample to the plasma of the inductively coupled plasma source, the injector having a sample inlet for receiving a sample, wherein the sample comprises an elementally labeled analyte; and a heat source thermally coupled to the injector for heating the injector.

[0028] In some cases, the device also includes a heat transfer device thermally coupled to the injector for transferring heat from a heat source. In some cases, the heat transfer device includes a metal sleeve surrounding at least a portion of the injector. In some cases, the heat source includes at least a portion of a spray chamber positioned upstream of the injector, such that heat from the spray chamber is transferred to the injector via the heat transfer device. In some cases, the heat source includes plasma. In some cases, the heat source includes a resistance heat source. In some cases, the device also includes one or more heat pipes extending along the length of the injector. In some cases, one or more heat pipes are arranged to conduct thermal energy from a higher temperature portion of the injector to a lower temperature portion of the injector. In some cases, the device also includes a mass spectrometer positioned downstream of an inductively coupled plasma source for receiving ions from the inductively coupled plasma source. In some cases, the inner diameter of the injector is between approximately 0.5 mm and 5 mm. In some cases, the device also includes a sample source coupled to the injector for providing a sample and a stabilizing solution. In some cases, a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature sufficient to evaporate or sublimate the solute in the stabilizing solution. In some cases, a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature of at least 150°C. Attached Figure Description

[0029] This specification refers to the following figures, in which the same reference numerals are used in different figures to illustrate the same or similar components.

[0030] Figure 1 This is a schematic diagram depicting an inductively coupled plasma (ICP) system according to certain aspects of this disclosure.

[0031] Figure 2 It is a flowchart depicting a process for ionizing a sample according to certain aspects of this disclosure.

[0032] Figure 3 This is a schematic cross-sectional view depicting an ICP system having a heat transfer device thermally coupled to an injector, according to certain aspects of this disclosure.

[0033] Figure 4 This is a schematic cross-sectional view depicting an ICP system having an injector thermally coupled to a spray chamber according to certain aspects of this disclosure.

[0034] Figure 5 This is a schematic cross-sectional view depicting an ICP system having a heat source thermally coupled to an injector, according to certain aspects of this disclosure.

[0035] Figure 6 This is a schematic front cross-sectional view of an injector having a heat transfer device thermally coupled thereto, according to certain aspects of this disclosure.

[0036] Figure 7 This is a schematic front cross-sectional view depicting an injector having a heat source thermally coupled thereto, according to certain aspects of this disclosure.

[0037] Figure 8 This is a schematic front cross-sectional view depicting an injector having an external heating tube thermally coupled thereto, according to certain aspects of this disclosure.

[0038] Figure 9 This is a schematic front cross-sectional view depicting an injector having an internal heating tube thermally coupled thereto, according to certain aspects of this disclosure.

[0039] Figure 10 It is a flowchart depicting a process for preparing and ionizing a sample according to certain aspects of this disclosure.

[0040] Figure 11 It is a graph depicting the percentage decrease in signal of a set of samples prepared with a 2 mM ammonium nitrate stabilization solution according to certain aspects of this disclosure.

[0041] Figure 12 It is a graph depicting the percentage decrease in signal of a set of samples prepared with a 5 mM ammonium nitrate stabilization solution according to certain aspects of this disclosure.

[0042] Figure 13 It is a graph depicting the percentage decrease in signal of a set of samples prepared with a 10 mM ammonium nitrate stabilization solution according to certain aspects of this disclosure.

[0043] Figure 14 This is a graph depicting the CD44 channel signal of a sample that has been suspended in deionized water and injected into a plasma source.

[0044] Figure 15 It describes, according to certain aspects of this disclosure, that the sample has been suspended in a 25 mM ammonium nitrate stabilization solution and injected into a plasma source. Figure 14 The image shows the CD44 channel signal of the sample.

[0045] Figure 16 This describes a sample that, according to certain aspects of this disclosure, has been suspended in a 25 mM ammonium nitrate-stabilized solution and injected into a plasma source. 165 A diagram of the Ho channel signal.

[0046] Figure 17 It describes certain aspects of this disclosure that have been suspended in a 75 mM ammonium nitrate stabilization solution and injected into a plasma source. Figure 16 The sample 165 A diagram of the Ho channel signal.

[0047] Figure 18It is an image of the buildup on the injector when used without adequate heating of certain aspects of this disclosure.

[0048] Figure 19 This is a flowchart depicting a process for a self-cleaning injector according to certain aspects of this disclosure. Detailed Implementation

[0049] Certain aspects and features of this disclosure relate to improvements in injecting samples into a plasma source, such as an inductively coupled plasma (ICP) source. Improvements may include one or more of a stabilization solution miscible with the sample prior to injection and a heated injector. The sample acquisition solution can be prepared by mixing the sample with the stabilization solution to improve cell stability during injection. Utilizing a relatively low amount of dissolved solids (e.g., at or below about 0.2%), the stabilization solution can minimize osmotic pressure differences between the solution and the cells. The stabilization solution may contain a salt (e.g., ammonium nitrate) present at a concentration of at least 5 mM. The injector can be heated prior to and / or during injection, such as using a heat source or heat transfer device. In some cases, heat from adjacent components can be directed along the injector to improve heating of the injector. Heating the injector to a sufficient temperature during use can minimize buildup and extend the available time between washes. These improvements may be particularly useful in elemental analyses such as inductively coupled plasma mass spectrometry (ICP-MS) or inductively coupled plasma optical emission spectroscopy (ICP-OES). These improvements are particularly useful for ICP systems operating in suspension or solution mode (e.g., when using micro-sprayers).

[0050] Certain aspects of this disclosure are particularly useful for elemental analysis. Elemental analysis can refer to techniques used to determine the elemental composition (e.g., precise or relative) of a sample, or optionally its isotopic composition (e.g., precise or relative). Non-limiting examples of elemental analysis methods include optical atomic spectroscopy, such as flame atomic absorption, graphite furnace atomic absorption, and inductively coupled plasma atomic emission, to detect the external electronic structure of atoms; mass spectrometry, such as inductively coupled mass spectrometry, to detect the mass of atoms; and X-ray fluorescence, particle-induced X-ray emission, X-ray photoelectron spectroscopy, and Auger electron spectroscopy, to detect the internal electronic structure of atoms.

[0051] In some cases, elemental analysis involves the use of inductively coupled plasma mass spectrometry (ICP-MS), a sensitive mass spectrometry-based elemental analyzer. Different ICP-MS configurations are primarily distinguished by the mass selection techniques employed and can be, for example, quadrupole or time-of-flight (ICP-TOF) or magnetic sector (high-resolution ICP-MS). Many commercially available ICP-MS mass spectrometry models offer a wide range of configurations, capabilities, and modifications.

[0052] Elemental analysis can be used to detect elemental tags associated with analytes. Elemental tags, such as element-labeled affinity reagents or element-labeled supports or beads, can be used to label analytes based on the presence or absence of desired biomolecules in the analyte. An elemental tag or label is a chemical component comprising one or more elements, having one or more isotopes (called tag atoms) attached to a supporting molecular structure, or being capable of binding said one or more elements or isotopes. Elemental tags may also include means of attaching the elemental tag to a molecule of interest or a target molecule (e.g., an analyte). Different elemental tags can be distinguished based on the elemental composition of the tag. Elemental tags can contain many copies of a given isotope, and each tag can have a reproducible copy number for each isotope. Suitable elemental tags can include polymers (e.g., linear or branched polymers) having metal-binding side groups such as metal chelate moieties (e.g., tetraxetan (DOTA) or pentetic acid (DTPA)). Elemental tags can be nanoparticles, such as a metal core encapsulated in a polymer shell. Elemental tags are functionally distinguishable from other elemental tags in the same sample because their elemental or isotopic composition differs from other tags. As used herein, the term affinity reagent can refer to a biomolecule capable of tightly binding to a target molecule or analyte. Some non-limiting examples of affinity reagents include aptamers, protein molecules, lectins, and polysaccharides. For example, an affinity reagent can be an antibody that recognizes and binds to a specific antigen (e.g., on a protein) with high affinity. Streptavidin, a protein molecule that specifically binds to biotin, can be considered another example of an affinity reagent. In some cases, affinity reagents are non-oligonucleotide biomolecules.

[0053] Incompatible reagents, such as oligonucleotides used to hybridize with target oligonucleotide sequences (e.g., DNA, RNA), can be element-labeled and can be used to label target oligonucleotides for elemental analysis. Other metal-containing reagents, including DNA chimeras such as iridium and barcoding reagents, can also be detected by the elemental analysis described herein.

[0054] To achieve useful results, it may be necessary to select tag atoms that are not originally present in the potential sample or analyte. For example, certain metals, especially lanthanides, are rare in biological samples and may therefore be particularly suitable for use in elemental tags for determining these biological samples.

[0055] As used herein, the term biological sample or tissue sample can refer to a sample obtained from a biological subject, including samples of biological tissue or fluid origin obtained, reached, or collected in vivo or in situ. Biological samples also include samples from regions of a biological subject containing precancerous or cancerous cells or tissue. Such samples can be, but are not limited to, organs, tissues, fractions, and cells isolated from mammals. Examples of biological samples include, but are not limited to, cell cultures, cell lines, tissues, organs, organelles, and biological fluids. Examples of biological samples include, but are not limited to, skin samples and tissue biopsies.

[0056] As used herein, the term metal may refer to an element having one of the following atomic numbers: 3, 4, 11–13, 19–33, 37–52, 55–84, 87–102. In some cases, a metal may be a transition element. As used herein, the term transition element may refer to an element having one of the following atomic numbers: 21–30, 39–48, 57–80, and 89–92. Transition elements include rare earth metals, lanthanides, and noble metals. As used herein, the term lanthanides can refer to those transition metals having atomic numbers from 57 to 71, including La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium).

[0057] Therefore, in one example, the element-labeled affinity reagent may include a distinguishable element tag (e.g., containing one element or a group of elements) that binds to an antibody that has a high affinity for a specific antigen on the target protein. After incubating the element-labeled affinity reagent with the analyte and washing away unbound reagent, elemental analysis can be used to interrogate the analyte sample to detect the presence of one or more element tags, and thus the presence of the target protein can be inferred.

[0058] In some cases, the target analyte may include biomolecules on or within cells. In other cases, elemental analysis of whole or intact cells may be necessary, such as to determine the presence, amount, or absence of elemental tags associated with individual cells in a sample. For reliable per-cell elemental analysis, it may be necessary to determine the dissolution or other damage to individual cells before ionization in plasma. Damage to cells during cell acquisition via elemental analysis (e.g., per-cell elemental analysis) can result in poor signal stability during sample processing.

[0059] Certain aspects and features of this disclosure relate to the use of stabilizing solutions suitable for maintaining high signal stability of a sample and / or preserving the integrity of individual cells in an ICP system during infusion. As used herein, an ICP system can refer to an inductively coupled plasma source (e.g., an ICP torch), and any additional equipment or components optionally used for operating the ICP source, supplying a sample to the plasma, and / or delivering ions for further analysis. Stabilizing solutions can be selected to minimize osmotic pressure differences between the solution and the cells, which in turn helps maintain cell integrity. Alternatively or additionally, stabilizing solutions can be selected to improve the stability of metal chelates labeled with one or more elements.

[0060] However, in some cases, stabilizing solutions may increase the risk of injector clogging because the solute within the stabilizing solution may condense and accumulate within the injector (e.g., along the inner wall of the injector). In some cases, such accumulation and even clogging can be reduced or prevented by using a heated injector. In some cases, when analyzing samples using an elemental analyzer, the combination of a heated injector and a stabilizing solution according to aspects of this disclosure can improve signal stability.

[0061] In some cases, using a heated injector allows for the use of higher concentrations of stabilizing solution without undesirable negative effects (e.g., no buildup or clogging, no easily noticeable buildup or clogging, or only minimal buildup or clogging, such as that defined by the percentage of injector cross-section). In some cases, with or without a heated injector, using a lower concentration of stabilizing solution minimizes undesirable effects associated with buildup or clogging. In some cases, samples can be taken for 48 hours, 36 hours, 32 hours, 28 hours, 24 hours, 20 hours, 16 hours, 12 hours, 8 hours, 4 hours, 2 hours, and / or 1 hour.

[0062] As used herein, certain aspects of this disclosure can prevent buildup or blockage in the injector. The injector may have a nominal cross-sectional area, which is defined as the cross-sectional area of ​​the injector's inner diameter (e.g., A). 标称 =πr 2 If buildup or blockage occurs within the injector, the injector may have a nominal cross-sectional area smaller than the amount of buildup or blockage (e.g., A). 有效 =πr 2 -A clog A clogThe effective cross-sectional area of ​​the injector is the area of ​​blockage or accumulation. Certain aspects of this disclosure can prevent buildup or blockage of the injector during sample operation, such that the effective cross-sectional area of ​​the injector is maintained at or at least about 99%, 98%, 97%, 96%, 95%, 94%, 93%, 92%, 91%, 90%, 89%, 88%, 87%, 86%, 85%, 84%, 83%, 82%, 81%, 80%, 79%, 78%, 77%, 76%, 75%, 74%, 73%, 72%, 71%, and / or 70% of the nominal cross-sectional area of ​​the injector for continuous instrument non-stop (e.g., continuous) operation for 48 hours, 36 hours, 32 hours, 28 hours, 24 hours, 20 hours, 16 hours, 12 hours, 8 hours, 4 hours, and / or 2 hours. In some cases, certain aspects of this disclosure can prevent buildup or blockage of the injector during sample operation, such that the effective cross-sectional area of ​​the injector remains at or at least about 90% of the nominal cross-sectional area of ​​the injector.

[0063] As used herein, certain aspects of this disclosure can increase the sublimation rate and / or decrease the deposition rate of solution through the injector, thereby preventing long-term deposition of solute on the inner surface of the injector. An increase in the sublimation rate and / or a decrease in the deposition rate may be associated with less overall solute accumulation on the inner surface of the injector during sample operation. The sublimation rate can refer to the rate at which solid solute (e.g., salts stabilizing the solution) deposited on the inner wall of the injector is converted into gas and carried away from the injector. The deposition rate can refer to the rate at which solute (e.g., salts stabilizing the solution) is deposited on the injector. Since sublimation is the primary mode of removal of deposited solute from the injector during operation, the sublimation rate is approximately inversely proportional to the deposition rate. In some cases, as the solution passes through the injector and enters the plasma, sublimation can be described as a percentage of solute deposition rather than ionization. For example, a 5% deposition rate can refer to 5% of the solute in the solution being deposited on the inner wall of the injector. For example, a higher sublimation rate will reduce the amount of solute accumulating on the inner wall of the injector during sample operation. In some cases, approximately 20%, 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.9%, 1.8%, 1.7%, 1.6%, 1.5%, 1.4%, 1.3%, 1.2%, 1.1%, 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2%, or 0.1% or 0% of the solute may deposit on the inner wall of the injector at the end of the sample run. In some cases, sample runs can be 48 hours, 36 hours, 32 hours, 28 hours, 24 hours, 20 hours, 16 hours, 12 hours, 8 hours, 4 hours, 2 hours and / or 1 hour longer.

[0064] Certain stabilization solutions and optionally heated injectors, as described herein, can be used to deliver a mixture containing a sample (e.g., whole cells) and a solute from the stabilization solution (e.g., a salt from the stabilization solution) through the injector into a plasma, for example. In some cases, the mixture exiting the injector contains at least, or about 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 95.5%, 96%, 96.5%, 97%, 97.5%, 98%, 98.1%, 98.2%, 98.3%, 98.4%, 98.5%, 98.6%, 98.7%, 98.8%, 98.9%, 99%, 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9% of the solute that entered the injector. The mixture may be a cell collection solution. The cell collection solution can be entrained in a gas such as argon. After leaving the injector, the cell collection solution can be further entrained in the main gas and / or auxiliary gas.

[0065] In some cases, the sublimation rate can be calculated as the vapor pressure of the solute at the injector (e.g., given the expected vapor pressure of the solute and the injector temperature). Examples of sublimation rates of exemplary solutes are described herein with reference to Table 1.

[0066] The stabilization solution (e.g., the type and concentration of salts in the stabilization solution) and / or the amount of heating in the injector (e.g., no heating or some heating) can be selected to achieve the desired sublimation rate and / or the desired deposition rate.

[0067] The stabilization solution (e.g., the type and concentration of salt in the stabilization solution) and / or the heating amount of the injector can be selected to achieve the desired sublimation rate.

[0068] As used herein, certain aspects of this disclosure can prevent or reduce the percentage of signal drop during a sample run. Signal drop prevention can occur when using a stabilizing solution and / or a heated injector. In some cases, signal drop prevention may be related to keeping the injector free from buildup or blockage. In some cases, according to certain aspects of this disclosure, the percentage of signal drop can be or less than about 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, 1%, or 0.5%. The percentage of signal drop can be calculated over a single sample run or a portion of a single sample run. In some cases, the percentage of signal drop can be calculated over a time period of or about 48 hours, 36 hours, 32 hours, 28 hours, 24 hours, 20 hours, 16 hours, 12 hours, 8 hours, 4 hours, 2 hours, and / or 1 hour. The signal drop percentage can be calculated as the average percentage by which the signal deviates from its initial signal measurement or average value. The signal can be raw data or normalized data. In some respects, the signal drop percentage can be calculated as the average signal drop across all quality channels, the maximum signal drop percentage, or the signal drop percentage of a quality channel relevant to a specific analyte.

[0069] The heated injector can be heated using any suitable technique. In some cases, the heated injector can be directly heated by a heating device. In others, the heated injector can be indirectly heated, such as by drawing heat from other components of the ICP system or an adjacent system. The heating device (e.g., a heat source) can supply heat to the injector. Various types of heating units can be used, such as resistance heating devices, thermoelectric devices, gas-powered heating devices (e.g., direct flame), convection heating devices (e.g., circulating hot fluid, such as air), laser heating devices, or others. In some cases, heat can be applied to a portion of the heated injector (e.g., the upstream portion), allowing another portion of the heated injector (e.g., the downstream portion or the output) to be heated by conduction or convection. For example, a heat pipe can be applied to or incorporated into the injector to conduct heat from the first portion to the second portion. In another example, sufficient heat can be provided to the second portion by convection through the sample fluid within the heated injector.

[0070] In some cases, the injector may be completely or partially surrounded by a heat transfer device. The heat transfer device can be any suitable means capable of conducting heat into and / or along the injector. Examples of suitable heat transfer devices include heat-conducting materials coupled to, disposed within, and / or incorporated into the injector. For example, the injector may be coated with a thin sheet of metal. In some cases, the heat transfer device may thermally couple the injector to a heat source (e.g., a direct or indirect heat source). For example, the heat transfer device may thermally couple the injector to a spray chamber of an ICP system, thereby allowing heat to be transferred from the spray chamber to the injector. In another example, the heat transfer device may be positioned to conduct heat from the plasma into the injector. In some cases, non-metallic heat transfer devices may be used. As used herein, a heat transfer device that thermally couples the injector to another object or element (e.g., a spray chamber or plasma) may include thermal coupling at a higher heat transfer rate than would be achieved without a heat transfer device. In other words, a heat transfer device can increase the rate of heat transfer between the injector and other objects, thus providing faster heat transfer than if no heat transfer device were used (e.g., if the injector were exposed to standard ambient air or gas).

[0071] In some cases, the dimensions (e.g., size and / or shape) of the heat transfer device can be configured to deliver sufficient heat from a stable heat source (e.g., a spray chamber maintained at 200°C) to increase the temperature of the injector (e.g., the temperature of the injector's inner wall) to a minimum set temperature (e.g., 160°C). In such cases, the heat transfer device can result in a temperature gradient along the length of the injector, however, the temperature at any point along the injector's inner wall can be maintained at at least the minimum set temperature. The minimum set temperature can be or approximately 160°C. In some cases, the minimum set temperature can be or at least approximately 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, or 260°C. In some cases, multiple heat transfer devices can be used, such as a first heat transfer device coupled to the injector and a second heat transfer device coupled to or located in conjunction with another element of the ICP system.

[0072] Heated injectors may be particularly useful in certain aspects of this disclosure, such as when a sample is combined with, mixed with, or suspended in a stabilizing solution.

[0073] According to certain aspects of this disclosure, the stabilizing solution may include a salt, such as a nonmetallic salt, such as ammonium nitrate. The salt can be selected to achieve a specific vapor pressure at certain temperatures (such as certain temperatures associated with a heated injector). In some cases, ammonium nitrate is the salt used in the stabilizing solution, although other salts may also be used. In some cases, a chlorine- and / or fluorine-based solute can be used, and a desired vapor pressure can be achieved. Table 1 depicts approximate vapor pressure information related to ammonium nitrate as a function of temperature, where... This is the sublimation rate set for a given purpose, expressed in micrograms per minute.

[0074] Table 1 – Sublimation rate of ammonium nitrate at specific temperatures

[0075]

[0076]

[0077] For ammonium nitrate, the vapor pressure reaches approximately 328 Pa or approximately 0.3% of atmospheric pressure at 433 Kelvin or approximately 160 °C. The mass flow rate of the evaporated solute can be estimated based on the product of the vapor pressure and the gas flow rate. When the injector flow rate is approximately 0.7 slpm (standard liters / min) of argon and the sample flow rate is approximately 45 μL / min, the amount of ammonium nitrate in the carrier gas (argon) can be calculated as 0.003% of the gas volume at a concentration of 20 mM in the solution. Therefore, at this temperature, ammonium nitrate will gradually sublimate from the injector wall and enter the gas flow. The equilibrium between the gas and solid phases of ammonium nitrate can be altered by the surface tension in small crystals. However, experiments have determined that, particularly at the gas flow rates commonly used in inductively coupled plasma sources, 160 °C is sufficient to prevent the injector surface from being “fogged” by ammonium nitrate deposits.

[0078] The injector can be heated to a temperature sufficient to promote the sublimation of the salt in the stabilizing solution. In some cases, the temperature to which the injector is heated can be determined or calculated based on the desired vapor pressure of a particular salt. Techniques for correlating the temperature with vapor pressure of various salts are known in the art, such as those described in Oxley, Jimmie et al., “Determination of Urea Nitrate and Guanidine Nitrate Vapor Pressures by Isothermal Thermogravimetry.” For example, urea nitrate (UN), guanidine nitrate (GN), ammonium nitrate (AN), and triacetone triperoxide (TATP) can have a vapor pressure-temperature relationship that approximately follows the equation below, where P is in Pascals and T is in Kelvin, at least in the range of 300–550 K.

[0079]

[0080] In some cases, the stabilizing solution may include a salt having a vapor pressure of at least 3 Pa at 100 °C, at least 130 Pa at 150 °C, and / or at least 250 Pa at 160 °C. In some cases, salts having the following vapor pressures at 100 °C may be selected: 3 Pa, 8 Pa, 13 Pa, 18 Pa, 23 Pa, 28 Pa, 33 Pa, 38 Pa, 43 Pa, 48 Pa, 53 Pa, 58 Pa, 63 Pa, 68 Pa, 73 Pa, 78 Pa, 83 Pa, 88 Pa, 93 Pa, 98 Pa, 103 Pa, 108 Pa, 113 Pa, 118 Pa, 123 Pa, 128 Pa, 133 Pa, 138 Pa, 143 Pa, 148 Pa, 153 Pa, 158 Pa, 163 Pa, 168 Pa, 173 Pa, 178 Pa. The Pa values ​​are 183 Pa, 188 Pa, 193 Pa, 198 Pa, 203 Pa, 208 Pa, 213 Pa, 218 Pa, 223 Pa, 228 Pa, 233 Pa, 238 Pa, 243 Pa, 248 Pa, 253 Pa, 258 Pa, 263 Pa, 268 Pa, 273 Pa, 278 Pa, 283 Pa, 288 Pa, 293 Pa, 298 Pa, 303 Pa, 308 Pa, 313 Pa, 318 Pa, 323 Pa, 328 Pa, 333 Pa, 338 Pa, 343 Pa, 348 Pa, and / or 350 Pa, but other ranges may also be used. Salts can be selected to provide a suitable sublimation at the injector's operating temperature (e.g., with or without heating) sufficient to prevent deposition on the injector's inner wall.

[0081] In some cases, the stabilization solution may have a neutral or near-neutral pH (e.g., within 1-2 units of neutral pH). At particularly high or low pH levels, the cells in the sample may rupture and / or metals chelated in certain elemental tags may dissociate. In some cases, the stabilization solution may be maintained at a pH between 5-9 (e.g., within 2 units of neutral pH) or 6-8 (e.g., within 1 unit of neutral pH). In some cases, the pH of the stabilizing solution may be or at least about 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, 6.9 and / or 7, and is or below about 9, 8.9, 8.8, 8.7, 8.6, 8.5, 8.4, 8.3, 8.2, 8.1, 8, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1 and / or 7. In some cases, the pH of the stabilizing solution can be within 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and / or 2 units of neutral pH. The pH of the stabilizing solution can be a function of one or more solutes and their concentrations. In some cases, one or more solutes and their concentrations can be selected to achieve the desired pH.

[0082] The salt concentration in the stabilization solution can be high enough to achieve the desired results (e.g., improved stability) but low enough not to introduce unwanted background interference. Too low a salt concentration may provide little or no benefit to cell stability and may even introduce some instability. Too high a salt concentration may provide benefits to cell stability but cause a considerable loss of signal quality due to background interference, especially if the TDS of the salt is greater than a certain value (e.g., 0.2%). In some cases, the stabilization solution may comprise a salt (e.g., ammonium nitrate) with concentrations of 5–25 mM or approximately, such as 6–24 mM, 7–23 mM, 8–22 mM, 9–21 mM, 10–20 mM, 11–19 mM, 12–18 mM, 13–17 mM, 14–16 mM, 5–15 mM, 10–15 mM, 10–25 mM, 15–25 mM, and / or 20–25 mM. In some cases, the stabilizing solution may include salts with concentrations of 5 mM, 6 mM, 7 mM, 8 mM, 9 mM, 10 mM, 11 mM, 12 mM, 13 mM, 14 mM, 15 mM, 16 mM, 17 mM, 18 mM, 19 mM, 20 mM, 21 mM, 22 mM, 23 mM, and / or 24 mM. In some cases, the stabilizing solution may include salts with concentrations of 25 mM, 24 mM, 23 mM, 22 mM, 21 mM, 20 mM, 19 mM, 18 mM, 17 mM, 16 mM, 15 mM, 14 mM, 13 mM, 12 mM, 11 mM, 10 mM, 9 mM, 8 mM, 7 mM, and / or 6 mM. In some cases, other ranges may be used. In some cases, without a heated injector, a stabilizing solution having a salt concentration in the lower part of the aforementioned range (e.g., 5-10 mM, 5-9 mM, 5-8 mM, 5-7 mM, 5-6 mM, or 5 mM) may be used. In some cases, when used with a heated injector, a stabilizing solution having a salt concentration in the upper part of the aforementioned range (e.g., 10-25, 10-25 mM, 11-25 mM, 12-25 mM, 13-25 mM, 14-25 mM, 15-25 mM, 16-25 mM, 17-25 mM, 18-25 mM, 19-25 mM, 20-25 mM, 21-25 mM, 22-25 mM, 23-25 ​​mM, 24-25 mM, or 25 mM) may be most effective. In some cases, higher concentrations can be used, especially when used with a heated injector.

[0083] In some cases, the stabilizing solution may include a nonmetallic salt. In some cases, the salt may have an atomic mass unit of 80 or less. In other words, the salt may not contain any metal or element with an atomic mass unit greater than 80. In some cases, the salt may have an atomic mass unit less than the label atoms of the element label. In some cases, the stabilizing solution may be carbon-free or substantially carbon-free (e.g., less than 1%, 0.95%, 0.9%, 0.85%, 0.8%, 0.75%, 0.7%, 0.65%, 0.6%, 0.55%, 0.5%, 0.45%, 0.4%, 0.35%, 0.3%, 0.25%, 0.2%, 0.15%, 0.1%, 0.05%, and / or 0.01% carbon by weight). As used herein, the term “containing” when referring to a metal or element may exclude such a metal or element or include substantially a small amount of such a metal or element such that it will be undetectable or negligible during elemental analysis of a sample containing an analyte labeled as described herein.

[0084] While ammonium nitrate can be an effective salt, other salts can also be used. In some cases, the salt can be ammonium-based molecules. Ammonium-based salts are highly soluble in water, which can provide beneficial results. In some cases, the salt can be ammonium acetate, ammonium phosphate, ammonium formate, or other such salts. In some cases, the stabilizing solution can include nitrogen or nitrogen-based molecules. In some cases, the stabilizing solution can include azide-based salts.

[0085] In some cases, certain salts may contain elements that degrade overall performance. Examples of performance degradation can include the buildup of carbon residues on the cone, the buildup of salt residues, ion suppression due to high concentrations of easily ionized elements (such as Na and K), channel loss due to the presence of ions in the solution (such as ammonium iodide flooding mass channel 127 or ammonium orthomolybdate containing molybdenum and potentially flooding multiple mass channels between 90 and 100), and other undesirable effects. In some cases, salt selection (e.g., selection of stabilizing solutions) can be made to tailor the specific characteristics of the assay. For example, using ammonium orthomolybdate may not be a problem if there is no interest in the mass channels between 90 and 100 for a specific element label used in the assay.

[0086] Cell stability is desirable in various cell counting techniques; however, ICP-based elemental analysis is limited by total dissolved solids (TDS) due to the use of plasma to probe cells. Therefore, conventional solutions used for cell stabilization in other studies are ineffective or unavailable for use with elemental analysis, at least ICP-based. For example, in standard ICP-MS settings, TDS is kept at 0.2% or below to minimize interference. For a 1x phosphate-buffered saline (PBS) solution, the TDS for NaCl alone is already 0.8%, four times higher than the 0.2% limit. Therefore, PBS cannot be used in ICP-MS settings without undesirable interference. In some cases, the stabilizing solution may have a TDS of 0.2%, 0.19%, 0.18%, 0.17%, 0.16%, 0.15%, 0.14%, 0.13%, 0.12%, 0.11%, 0.1%, 0.09%, 0.08%, 0.07%, 0.06%, 0.05%, 0.04%, 0.03%, 0.02%, and / or 0.01%, but other ranges may be used.

[0087] As used herein, the injector of an ICP system can have any suitable inner diameter. In some cases, the injector can have an inner diameter between 0.5 mm and approximately 5 mm, such as an inner diameter between 1-5 mm or 1.5-5 mm. In some cases, the injector may have an inner diameter of 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm, 2.5 mm, 2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, 3 mm, 3.1 mm, 3.2 mm, 3.3 mm, 3.4 mm, 3.5 mm, 3.6 mm, 3.7 mm, 3.8 mm, 3.9 mm, 4 mm, 4.1 mm, 4.2 mm, 4.3 mm, 4.4 mm, 4.5 mm, 4.6 mm, 4.7 mm, 4.8 mm, or 4.9 mm. In some cases, the injector may have an inner diameter of approximately 5 mm, 4.9 mm, 4.8 mm, 4.7 mm, 4.6 mm, 4.5 mm, 4.4 mm, 4.3 mm, 4.2 mm, 4.1 mm, 4 mm, 3.9 mm, 3.8 mm, 3.7 mm, 3.6 mm, 3.5 mm, 3.4 mm, 3.3 mm, 3.2 mm, 3.1 mm, 3 mm, 2.9 mm, 2.8 mm, 2.7 mm, 2.6 mm, 2.5 mm, 2.4 mm, 2.3 mm, 2.2 mm, 2.1 mm, 2 mm, 1.9 mm, 1.8 mm, 1.7 mm, 1.6 mm, 1.5 mm, 1.4 mm, 1.3 mm, 1.2 mm, 1.1 mm, 1 mm, 0.9 mm, 0.8 mm, 0.7 mm, or 0.6 mm.

[0088] In some cases, using a heated injector can also prevent water droplet formation or aggregation on the injector. At room temperature, especially at higher liquid flow rates (e.g., 60 μL / min) and relatively low gas (e.g., argon) flow rates (e.g., ~0.7 s Lpm), water droplet aggregation (or atomization) on the injector can become a problem. Atomization and droplets on the injector can lead to signal instability and, in some cases, even occasional plasma loss in inductively coupled plasma sources. If plasma is lost, portions of the sample being detected may not be properly ionized and therefore may not be detectable. In some cases, a heated injector can reduce or minimize water droplet formation or aggregation on the injector, which can improve signal stability and plasma reliability.

[0089] These illustrative examples are given to introduce the reader to the general topics discussed herein and are not intended to limit the scope of the disclosed concepts. Various additional features and examples are described below with reference to the accompanying drawings, wherein the same numerals denote the same elements, and directional descriptions are used to describe illustrative embodiments, but, as with the illustrative embodiments, should not be used to limit this disclosure. Elements included in the figures herein may not be drawn to scale.

[0090] Figure 1 This is a schematic diagram depicting an inductively coupled plasma (ICP) system 100 according to certain aspects of this disclosure. The ICP system 100 may include an injector 108 for delivering a sample (e.g., a sample solution or cell collection solution) to a plasma 110. The plasma 110 may be, for example, a spherical, helical, cylindrical, or other shaped plasma generated using an electromagnetically induced stimulation source gas. It should be understood that certain aspects of this disclosure, such as the stabilized solution and / or heated injector, can be advantageously used in conjunction with other techniques for plasma generation. (For illustrative purposes only.) Figure 1 Certain aspects of the standard ICP system 100, such as the gas flow tube, induction coil, and sample cone, are not shown.

[0091] Sample 102 may include intact cells (e.g., whole cells) labeled with element tags. A stabilization solution 104 may be provided as disclosed herein. Stabilization solution 104 may include salts as described herein, such as ammonium nitrate at a concentration of 15 mM. Sample 102 and stabilization solution 104 may be provided separately or pre-mixed. When mixed, sample 102 and stabilization solution 104 may be considered a “sample solution” or a “cell collection solution.” Sample 102 and stabilization solution 104 may be provided to sample source 106 individually or as a mixture of cell collection solutions. Sample source 106 may be any container suitable for storing sample 102 (e.g., cell collection solution) before being introduced into injector 108. In some cases, sample source 106 may be a vial, injector, beaker, a section of tubing, or any other container.

[0092] Injector 108 may receive a cell collection solution from sample source 106. In some cases, the cell collection solution may be atomized by passing it through spray chamber 120 before entering injector 108. Injector 108 may be a section of tubing made of any suitable material such as quartz. Injector 108 may be any suitable shape or profile, such as cylindrical. Injector 108 may introduce the cell collection solution into plasma 110 to ionize sample 102. In some cases, ionization of sample 102 may generate ions (e.g., a group of ions or an ion beam) that may be directed to elemental analyzer 112 (e.g., mass spectrometer) for further analysis. In some cases, ionization of sample 102 may result in light emission that may be directed to and / or sensed by elemental analyzer 112 (e.g., optical emission spectrometer).

[0093] In some alternative cases, heat source 118 may be coupled (e.g., physically) to, positioned around, and / or near injector 108. Heat source 118 may be thermally coupled to injector 108. For example, heat source 118 may be a resistance heater in the form of a metal coil wound around injector 108. Other heat sources 118 may be used. Heat source 118 may extend to the entire length of injector 108 or to a length less than the entire length of injector 108. Heat source 118 may generate heat, such as by using electrical, magnetic, kinetic, or other forms of energy.

[0094] In some alternative cases, the heat transfer device 114 may be coupled (e.g., physically) to, disposed around, and / or near the injector 108. The heat transfer device 114 may be thermally coupled to the injector 108. The heat transfer device 114 may be any suitable device or material capable of transferring heat into and / or along the injector 108. For example, the heat transfer device 114 may transfer heat from one portion of the injector 108 to another portion of the injector 108. In another example, the heat transfer device 114 may transfer heat from another object, such as a heat source 116, into the injector 108. The heat transfer device 114 may extend along the entire length of the injector 108, or extend to a length less than the entire length of the injector 108. In some cases, the injector 108 may include a heat source 118 and the heat transfer device 114. In some cases, the heat transfer device 114 can be incorporated into the injector 108, such as in the form of a heat pipe integrated into or coupled to the body of the injector 108 (e.g., integrated into a channel in a quartz tube or adhered to the surface of the quartz tube using hot paste).

[0095] The heat source 116 can be any suitable heat source that can be thermally coupled to the heat transfer device 114. Examples of suitable heat sources 116 may include resistance heating devices, thermoelectric devices, pneumatic heating devices (e.g., direct flame), convection heating devices (e.g., circulating hot fluid, such as air), laser heating devices, or others.

[0096] In some alternative cases, one or more heat transfer devices 114 may thermally couple the injector 108 to other components of the ICP system 100 or nearby systems (such as the spray chamber 120 or plasma 120), but other sources may also be used. In some cases, these components thermally coupled to the injector 108 may be considered heat sources. When thermally coupled to the spray chamber 120, the heat transfer device 114 can transfer heat energy from the spray chamber 120, which can be maintained at a constant temperature (e.g., 200°C), to the injector 108 at a suitable rate to ensure that the injector 108 is maintained at a temperature of at least a minimum set temperature (e.g., 160°C). When thermally coupled to the plasma 110, the heat transfer device 114 may indirectly receive heat from the plasma 110 (e.g., through convection due to heating of nearby gas or through radiative heat) and transfer heat to the injector 108 at a rate suitable for ensuring that the injector 108 is maintained at at least a minimum set temperature (e.g., 160°C). In some cases, achieving a suitable heat transfer rate in the heat transfer device 114 may include providing the heat transfer device 114 in a suitable size and / or shape to achieve the desired heat transfer rate. In some cases, the heat transfer device 114 may include a heat conduction trap to appropriately slow down heat transfer to the desired rate. The heat conduction trap may include gaps in the material of the heat transfer device 114, which may be filled with a material that is more insulating than the heat transfer device 114 itself, such as a flowing carrier gas or a ceramic material.

[0097] In some cases, the injector 108 of the ICP system 100 is not heated by any heat source 118 or heat transfer device 114. In such cases, the stabilizing solution 104 may comprise a salt at a suitably low concentration or a salt having a sufficiently high vapor pressure at the injector temperature to prevent residues from accumulating within the injector 108.

[0098] In some cases, the injector 108 of the ICP system 100 can be heated, for example by a heat source 118 or a heat transfer device 114, and a sample 102 can be supplied to it without the stabilizing solution 104. In such cases, heating the injector 108 can provide certain benefits, such as reducing the possible accumulation of water / solvent droplets or residues on the injector 108, without the accompanying benefits of the stabilizing solution 104.

[0099] In some cases, the insulation layer 115 may be provided around some or all of the injector 108. The insulation layer 115 may be coupled to or positioned directly around the injector 108, or it may be coupled to or positioned around the heat transfer device 114 and / or the heat source 118. The insulation layer 115 can retain heat within the injector 108 by suppressing radial heat dissipation. The insulation layer 115 can help maintain a constant injector temperature throughout the injector 108. In some cases, the insulation layer 115 may extend completely around the injector 108, but this is not always the case. The insulation layer 115 can be formed of any suitable insulating material, such as glass fiber, para-aramid fiber, or aerogel. In some cases, the insulation layer 115 may be an air gap or a vacuum gap. In some cases, the insulation layer may be solid. In some cases, the insulation layer 115 may be any suitable insulating material that suppresses radial heat dissipation from the injector 108 beyond the heat dissipation achieved by moving the supply gas (e.g., argon) around the plasma generator. In some cases, such as when the amount of gas (e.g., the radial thickness of the gas volume around the injector) is specially tailored to achieve a particular required insulation (e.g., more than in a conventional injector arrangement), the surrounding supply gas (e.g., argon) can be used as insulation layer 115.

[0100] Figure 2 This is a flowchart depicting a process 200 for ionizing a sample according to certain aspects of this disclosure. Process 200 can be performed by any suitable ICP system as described herein (such as...). Figure 1 The ICP system 100 is executed. In box 202, the injector can be heated. The injector can be heated according to any suitable technique (such as those described herein). In some cases, the heated injector at box 202 may include the injector supplied with heat from a directly coupled heat source (e.g., from a resistance heater wound around the injector) at box 214. In some cases, the heated injector at box 202 may include the injector that allows heated fluid to pass through it (e.g., a heated cell collection solution or another heated fluid to pass through it) at box 216.

[0101] In some cases, the heating injector at box 202 may include heat conduction to the injector at box 218. In some cases, heat conduction to the injector at box 218 may include heat conduction along the length of the injector at box 220. In some cases, heat conduction to the injector at box 218 may include heat conduction from the spray chamber of the ICP system at box 222. In some cases, heat conduction to the injector at box 218 may include heat conduction from the plasma generated by the ICP system at box 224.

[0102] At box 204, a sample is received. The sample may optionally include a stabilization solution. In some cases, receiving the sample at 204 may optionally include mixing the stabilization solution with the sample. At box 206, the sample is passed through a heated injector. Passing the sample through the heated injector at box 206 may optionally include passing the sample as part of a cell collection solution containing the sample and the stabilization solution through the heated injector. Passing the sample through the heated injector at box 206 may include directing the sample to the plasma of the ICP system. In some cases, passing the sample through the heated injector at box 206 may include passing intact cells or whole cells through the injector. In some cases, intact cells or whole cells may pass through sequentially.

[0103] At box 208, inductively coupled plasma can be used to ionize the sample. Ionization of the sample at box 208 can result in the release of ions from the sample, such as an ion beam. In some cases, ionization of the sample at box 208 may include ionization of intact cells or whole cells. In some cases, intact cells or whole cells may be ionized sequentially. At box 210, elemental analysis can be performed on the ionized sample. Elemental analysis at box 210 can include any suitable elemental analysis, such as measuring ions using a mass spectrometer (e.g., mass spectrometry) or detecting light emission during sample ionization (e.g., photoemission spectroscopy). At optional box 212, detected elements can be identified based on the measurements of the elemental analysis. Detected elements may be tag atoms from an element tag associated with an element-labeled sample (e.g., a sample labeled with an element tag). In some cases, the detected elements identified at box 212 may be associated with intact cells or whole cells. The identification of detected elements for intact cells or whole cells at box 212 can be repeated for multiple cells in the sample.

[0104] Figure 3 This is a schematic cross-sectional view depicting an ICP system 300 having a heat transfer device 314 thermally coupled to an injector 308 according to certain aspects of this disclosure. The ICP system 300 may include an outer tube 330 for delivering a primary gas 338 (such as argon). In some cases, an intermediate tube 332 may be used, which may deliver an auxiliary gas 336, such as argon. In some cases, the primary gas 338 and the auxiliary gas 336 are the same, optionally with different flow rates. A coil 334 positioned towards the downstream end of the outer tube 330 may be functionalized with a high-frequency current suitable for exciting a gas within an orifice of the coil 334 to generate and / or sustain a plasma 310. A sample 328 (e.g., alone or as part of a cell collection solution along with a stabilization solution) may enter the injector 308 and proceed downstream (e.g., as... Figure 3(The diagram depicts the passage from left to right). Sample 328 can be delivered to plasma 310. The resulting ion, light, or other detectable emission or absorption characteristics can be delivered from plasma 310 to an elemental analyzer. In some cases, injector 308, outer tube 330, and optional intermediate tube 332 are concentric, but this is not always the case.

[0105] like Figure 3 As depicted, the injector 308 may include a heat transfer device 314 physically and thermally coupled thereto. The heat transfer device 314 is shown extending downstream of the injector 308, but this is not always the case. The heat transfer device 314 may be used in conjunction with an additional heat source to heat the injector 308. However, in some cases, the heat transfer device 314 may simply transfer heat through the injector 308.

[0106] In some cases, the auxiliary gas 336 and / or the main gas 338 can be preheated to transfer heat to the injector 308.

[0107] Figure 4 This is a schematic cross-sectional view depicting an ICP system 400 having an injector 408 thermally coupled to a spray chamber 420 according to certain aspects of this disclosure. The ICP system 400 may include an outer tube 430 for delivering a primary gas 438 (such as argon). In some cases, an intermediate tube 432 may be used, which may deliver an auxiliary gas 436, such as argon. In some cases, the primary gas 438 and the auxiliary gas 436 are the same, optionally with different flow rates. A coil 434 positioned towards the downstream end of the outer tube 430 may be functionalized with a high-frequency current suitable for exciting a gas within an orifice of the coil 434 to generate and / or sustain a plasma 410. A sample 428 (e.g., alone or as part of a cell collection solution along with a stabilization solution) may enter the injector 408 and proceed downstream (e.g., as... Figure 4 (The diagram depicts the passage from left to right). Sample 428 can be delivered to plasma 410. The resulting ionic, optical, or other detectable emission or absorption characteristics can be delivered from plasma 410 to an elemental analyzer. In some cases, injector 408, outer tube 430, and optional intermediate tube 432 are concentric, but this is not always the case.

[0108] like Figure 4 As depicted, the injector 408 may include a heat transfer device 414 physically and thermally coupled thereto. The heat transfer device 414 is shown extending from the spray chamber 420 to the downstream end of the injector 408, but in some cases the heat transfer device 414 may not extend the entire length. The heat transfer device 414 can thermally couple the spray chamber 420 to the injector 408, thereby transferring heat from the spray chamber 420 to the injector 408.

[0109] Figure 5 This is a schematic cross-sectional view depicting an ICP system 500 having a heat source 518 thermally coupled to an injector 508 according to certain aspects of this disclosure. The ICP system 500 may include an outer tube 530 for delivering a primary gas 538 (such as argon). In some cases, an intermediate tube 532 may be used, which may deliver an auxiliary gas 536, such as argon. In some cases, the primary gas 538 and the auxiliary gas 536 are the same, optionally with different flow rates. A coil 534 positioned towards the downstream end of the outer tube 530 may be functionalized with a high-frequency current suitable for exciting a gas within an orifice of the coil 534 to generate and / or sustain a plasma 510. A sample 528 (e.g., alone or as part of a cell collection solution along with a stabilization solution) may enter the injector 508 and proceed downstream (e.g., as... Figure 5 (The diagram is shown from left to right). Sample 528 can be delivered to plasma 510. The resulting ion, light, or other detectable emission or absorption properties can be delivered from plasma 510 to an elemental analyzer. In some cases, injector 508, outer tube 530, and optional intermediate tube 532 are concentric, but this is not always the case.

[0110] like Figure 5 As depicted, injector 508 may include a heat transfer device 514 physically and thermally coupled thereto. The heat transfer device 514 is shown extending along the length of injector 508 to its downstream end, but this is not always the case. Resistance heater 542 is depicted as part of injector 508; however, in some cases, resistance heater 542 may extend along the entire length of injector 508. Resistance heater 542 may be powered by power source 540 to generate heat. The generated heat can be transferred to injector 508 via heat transfer device 514. Heat transfer device 514 may facilitate the transfer of heat along the length of injector 508, such as from the portion of resistance heater 542 located around injector 508 to the downstream end of injector 508.

[0111] Figure 6 This is a schematic front cross-sectional view depicting an injector 608 having a heat transfer device 614 thermally coupled thereto, according to certain aspects of this disclosure. The injector 608 may be similar to... Figure 3 The injector 308. The heat transfer device 614 may be physically coupled to the injector 608, or may simply be disposed around or near the injector 608. The heat transfer device 614 may receive heat 644, such as from an external heat source, and transfer heat 644 to the injector 608.

[0112] Figure 7This is a schematic front cross-sectional view depicting an injector 708 having a heat source 718 thermally coupled thereto, according to certain aspects of this disclosure. The injector 708 may be similar to... Figure 5 The injector 708 has no heat transfer device 514. A resistance heater 742 in the form of a coil can be disposed around the injector 708 and optionally physically coupled to the injector 708. When electricity is applied to the resistance heater 742 from the power source 740, the resistance heater 742 can generate heat to heat the injector 708.

[0113] Figure 8 This is a schematic front cross-sectional view depicting an injector 808 having an external heating tube 846 thermally coupled thereto, according to certain aspects of this disclosure. The heating tube 846 may be a heat transfer device type capable of delivering heat 844 into the injector 808. In some cases, the heating tube 846 may be thermally coupled to the injector 808 using hot paste 848. In some cases, the heating tube 846 may be located on an inner surface of the injector 808. The heating tube 846 may extend along part or all of the length of the injector 808.

[0114] Figure 9 This is a schematic front cross-sectional view depicting an injector 908 having an internal heating tube 946 thermally coupled thereto, according to certain aspects of this disclosure. The heating tube 946 may be of the type of heat transfer device capable of delivering heat 944 into the injector 908. In some cases, the heating tube 946 may be thermally coupled to the injector 908 using a hot paste 948. The heating tube 946 may be located within a channel 950 of the injector 908. In some cases, the heating tube 946 may be completely enclosed by the injector 908, including cross-sectional closure and / or longitudinal closure. In some cases, the heating tube 946 may be located within a channel 950 positioned on the inner surface of the injector 908. The heating tube 946 may extend along part or all of the length of the injector 908.

[0115] Figure 10 This is a flowchart depicting a process 1000 for preparing and ionizing a sample according to certain aspects of this disclosure. Process 100 can utilize any suitable ICP system, such as... Figure 1 The ICP system 100. At box 1002, an element-labeled analyte is provided. The element-labeled analyte may include an analyte that has been elementally labeled or traced on or within whole or intact cells. At box 1004, a stabilization solution may be provided. The stabilization solution may be any suitable stabilization solution as described herein, such as a solution containing 15 mM ammonium nitrate. At box 1006, the element-labeled analyte may be mixed with the stabilization solution to produce a sample collection solution (e.g., a cell collection solution).

[0116] The sample collection solution may include intact or whole cells in a suspension containing a stabilizing solution, such as ammonium nitrate, as described herein. The intact or whole cells in the sample collection solution may be labeled with elemental tags, such as by analytes containing elemental tags.

[0117] At box 1008, the sample acquisition solution is transferred into the plasma of the ICP system using the injector located at box 1008. The sample acquisition solution can be pressurized using a fluid (such as the sample acquisition solution and / or a carrier gas) through the injector. In some cases, transferring the sample acquisition solution into the plasma using the injector may include passing the sample acquisition solution through a heated injector and / or heating the injector.

[0118] At box 1010, the ionized sample solution can be analyzed, such as by elemental analysis (e.g., mass spectrometry or optical emission spectroscopy). In some cases, at optional box 1012, the solute retained on the injector, such as a solute from the stabilization solution, can be evaporated or sublimated. Evaporation or sublimation of the solute can be achieved by heating the injector. In some cases, the evaporation or sublimation of the solute at box 1012 can occur after or simultaneously with the transfer of the sample collection solution to the plasma using the injector at box 1008.

[0119] Figure 11-13 The graphs depict the percentage decrease in signal intensity for specific samples when prepared with ammonium nitrate stabilization solutions of varying molar concentrations at 1100, 1200, and 1300. The samples contain various element-labeled affinity reagents and element-labeled beads. The element-labeled affinity reagents in this sample include 145Nd-CD4 (specific to the CD4 antigen and containing an element tag). 145 Nd affinity reagent), 145Nd-CD4 (specific to CD4 antigen and containing element tag) 145 Nd affinity reagent), 146Nd-CD8 (specific to CD8 antigen and contains element tag) 148 Nd affinity reagent), 147Sm-CD20 (specific to CD20 antigen and containing element tag) 147 Sm affinity reagent), 154Sm-CD45 (specific to CD45 antigen and contains element tag) 154 Sm affinity reagent), 155Gd-CD27 (specific to CD27 antigen and containing element tag) 155 Gd affinity reagent), 159Tb-CD11c (specific to CD11c antigen and containing element tag) 159 Tb affinity reagent), 160Gd-CD14 (specific to CD14 antigen and containing element tag) 160Gd affinity reagent), 170Er-CD3 (specific to CD3 antigen and containing element tag) 170 Er's affinity reagent), Ir191 (specific to the first identifiable DNA string and containing an element tag). 191 Ir affinity reagent), and IR193 (specific to the second identifiable DNA string and containing element-tagged elements). 193 (Ir affinity reagent). The element-labeled beads in this sample include those containing known amounts of... 140 Ce、 142 Ce、 151 Eu、 153 Eu、 165 Ho、 175 Lu、 176 Lu beads. Each of the aforementioned elements or isotopes can be measured using an elemental analyzer. In some cases, each of the aforementioned elements or isotopes can be measured using a different channel of an elemental analyzer specific to that element or isotope.

[0120] In each of Figures 1100, 1200, and 1300, the percentage decrease in signal intensity during raw data measurements during a sample run (e.g., a 30-minute sample run) is shown, along with the percentage decrease in signal intensity after the data has been normalized. Data normalization may include adjusting the measured signal intensity of individual channels of the elemental analyzer based on signal drift detected in known standards. In some cases, beads labeled with one or more elements, such as those identified above, can be used as known standards. For example, if using beads containing... 165 If the element-labeled beads of Ho are used as a known standard, then the element-labeled beads may contain a known amount of 165 Ho, and possibly present at a known concentration, should produce a constant signal intensity throughout the sample run. In the event of any detected drift from the expected signal intensity, a correction can be applied to adjust it. 165 The Ho signal returns to the expected signal strength, and similar corrections can be made to other channels of the elemental analyzer. In some cases, even within a common time interval, the element-labeled beads can be normalized to the beads labeled with other elements, such as to explain time-to-time drift in the detectors of the elemental analyzer within said time interval.

[0121] Figure 11This is a figure 1100 depicting the percentage decrease in signal strength of a group of samples prepared with a 2 mM ammonium nitrate stabilization solution according to certain aspects of this disclosure. Figure 1100 shows the percentage decrease in signal strength of many element-labeled affinity reagents when samples are prepared with a 2 mM ammonium nitrate stabilization solution. As depicted in Figure 1100, the percentage decrease in signal strength remains below approximately 15% for almost all channels, and below approximately 10% or 5% for many channels.

[0122] Figure 12 Figure 1200 depicts the percentage decrease in signal intensity for a group of samples prepared with a 5 mM ammonium nitrate stabilization solution according to certain aspects of this disclosure. Figure 1200 shows the percentage decrease in signal intensity for many element-labeled affinity reagents when samples are prepared with a 5 mM ammonium nitrate stabilization solution. When compared to Figure 1100 with a 2 mM ammonium nitrate stabilization solution, it is clear that increasing to a 5 mM ammonium nitrate stabilization solution results in a reduction in signal drift. As depicted in Figure 1200, the percentage decrease in signal intensity remains below approximately 6% for all channels, and below approximately 2% or 3% for most channels.

[0123] Figure 13 Figure 1300 depicts the percentage decrease in signal strength for a group of samples prepared with a 10 mM ammonium nitrate stabilizing solution according to certain aspects of this disclosure. Figure 1300 shows the percentage decrease in signal strength for many element-labeled affinity reagents when samples are prepared with a 10 mM ammonium nitrate stabilizing solution. When compared to Figure 1200 with a 5 mM ammonium nitrate stabilizing solution, it is clear that increasing to a 10 mM ammonium nitrate stabilizing solution does not significantly affect stability. As depicted in Figure 1300, the percentage decrease in signal strength for all channels remains below approximately 4% or 5%, and for most channels it remains below approximately 1% or 2%.

[0124] Figure 14 and 15 The graphs at 1400 and 1500 depict the signal intensity within a specific channel of the elemental analyzer during a 30-minute sample run. In this case, the specific channel was used to identify the CD44 antigen. An affinity reagent specifically labeled with an element for CD44 was used... 171 Yb tag. About Figure 14 and 15 The sample used during the 30-minute sample run contained cells labeled with an affinity reagent for CD44, due to its specificity to this element. The CD44 channel of the elemental analyzer has a value that is or approximately equivalent to... 171Yb or ions with an atomic mass of approximately 171 amu will respond. For each of Figures 1400 and 1500, the x-axis represents time during the elemental analysis process, and the y-axis represents the expression intensity of the selected CD44 channel for the detected event (e.g., the number of tag atoms detected) (each event is represented by a point on the graph). These specific channels, antigens, and / or elements were chosen to provide examples; however, any other suitable channels, antigens, and / or elements may be used.

[0125] Figure 14 This is Figure 1400, depicting the CD44 channel signal of a sample suspended in deionized water and injected into a plasma source. The brighter areas in the measurement band represent the populations of most frequent cellular events. In Figure 1400, the relatively broad variation and downward trend on the y-axis are evident, indicating a degree of instability of the cells during storage and / or injection. This downward trend may also indicate accumulation within the injection tube, which can negatively impact signal intensity over time. Furthermore, if cells in this unstable sample are damaged during storage and / or injection, the element-labeled affinity reagents may have separated from the remaining portion of the cells to which they are attached. This can already cause undesirable fluctuations in signal intensity, as tag atoms that were expected to land on the detector very close in time to other tag atoms of that particular cell may, conversely, land on the detector earlier or later. Therefore, a portion of the signal is not counted in the response to individual events. As a result, the measurements depicted in Figure 1400 can occupy a relatively broad band on the y-axis.

[0126] Figure 15 This is Figure 1500 depicting the CD44 channel signal of a sample that has been suspended in a 25 mM ammonium nitrate stabilization solution according to certain aspects of this disclosure and injected into a plasma source. The brighter areas in the measurement bands represent the populations of the most frequent cellular events. The effect of the stabilization solution is demonstrated by the significantly different clustering of measured signal intensities in Figures 1400 (e.g., without stabilization solution) and 1500 (e.g., with stabilization solution). The bands of the measurement signals depicted in Figure 1500 are much narrower than those depicted in Figure 1400, indicating a significant increase in stability, which may indicate less or no cell damage during storage and / or injection. The bands in Figure 1500 provide a denser combination of measurements and clearer and more accurate averages. Furthermore, the bands in Figure 1500 show a relatively constant horizontal trend, contrary to the downward trend of the bands in Figure 1400.

[0127] Figure 16 and 17Illustrations 1600 and 1700 depict the signal intensity within specific channels of an elemental analyzer during a 30-minute sample run. In this case, the specific channels are used to identify elemental standards in the form of element-marked beads. The element-marked beads used in Illustrations 1600 and 1700 are... 165 Ho. The channel pair used to obtain the signal strength depicted in Figures 1600 and 1700 has a value that is or approximately equivalent to... 165 Ho or ions with an atomic mass of approximately 165 amu have a response. Regarding Figure 16 and 17 The sample used during the 30-minute sample run contained sampled cells and elementally labeled beads. (Select) 165 Ho-labeled beads serve as elemental standards because they are not present in cells or in any element-labeled affinity reagents used with cells. 165 Ho. For each of Figures 1600 and 1700, the x-axis represents the time during the elemental analysis process, and the y-axis represents the time for the selected... 165 The expression intensity of the Ho channel (e.g., the number of detected tag atoms). These specific channels and / or elements are chosen to provide examples; however, any other suitable channels and / or elements may be used. In some cases, beads labeled with elements are chosen as the elemental standard (which may contain any suitable element or isotope (such as those described above)). 165 Ho) can be used to normalize the signal intensity in the detector of an analyzer. Beads labeled with elements containing known amounts of elements or isotopes can be expected to present known amounts of labeled atoms to the detector over a period of time, and therefore, if the signal of the element-labeled beads drops to a lower than expected signal intensity, any drift in the signal intensity due to natural drift in the detector can be identified, and thus the identified drift can be used to correct or normalize the signal intensity in other channels.

[0128] Figure 16 This describes a sample that, according to certain aspects of this disclosure, has been suspended in a 25 mM ammonium nitrate-stabilized solution and injected into a plasma source. 165 Figure 1600 shows the Ho channel signal. The dense measurement set forming a thin band near the top of Figure 1600 represents those events associated with element-labeled beads, and the large measurement band near the bottom of Figure 1600 represents the background noise from cellular events in a 25 mM ammonium nitrate stabilization solution. Since there are no [unclear text - likely referring to a specific type of signal] in the sample cells... 165The source of Ho, the sole source of measurement in the selected channel, should be the element-labeled beads. Therefore, as expected, the background noise in Figure 1600 is relatively minimal, and no high-intensity regions are observed except for the expected intensity of the element-labeled beads and 0 (e.g., the expected atomic intensity of cells in the sample). At 25 mM ammonium nitrate, the background signal does not overwhelm the target signal, and the target signal is clearly distinguishable.

[0129] Figure 17 This describes a sample that, according to certain aspects of this disclosure, has been suspended in a 75 mM ammonium nitrate-stabilized solution and injected into a plasma source. 165 Figure 1700 shows the Ho channel signal. The thin band near the top of Figure 1700 represents those measurements associated with element-labeled beads, and the large measurement band near the bottom of Figure 1700 represents background noise in a 75 mM ammonium nitrate stabilized solution. At 75 mM ammonium nitrate, the background signal begins to overwhelm the target signal and may begin to interfere with the ability to clearly distinguish the target signal. Specifically, a group of readings with expected intensities of 0 or approximately 0 instead show intensities above 0, indicating that the detector detected noise from sources other than element-labeled beads. 165 Ho. Due to the absence of [something] in cells or stabilization solutions. 165 Ho, it is clear that the background signal interfered with the detection in the elemental analyzer.

[0130] Compared to Figure 1600, Figure 1700 shows that when higher concentrations of ammonium nitrate (or other salts) are used, they may begin to cause undesirable background interference. Therefore, it may be desirable to provide a stabilizing solution that is high enough to improve cell stability, but low enough to avoid overwhelming background interference.

[0131] Figure 18 This image depicts an injector 1800 with significant residue buildup due to insufficient heating in certain aspects of this disclosure. The injector 1800 is not heated or is not heated sufficiently, and therefore residue accumulates within the injector. The residue may be a result of salts from the stabilizing solution. When using a stabilizing solution, it may be desirable to heat the injector to prevent residue buildup, such as... Figure 18 The description.

[0132] Figure 19 This is a flowchart depicting a process 1900 for a self-cleaning injector according to certain aspects of this disclosure. Self-cleaning of the injector can be used to remove build-up on the injector of an inductively coupled plasma system, such as residues of salts stabilizing the solution or aggregates of water droplets. In some cases, self-cleaning can occur before, after, or between transferring a sample (e.g., cells) through the injector for ionization by the plasma of the inductively coupled plasma system.

[0133] At optional box 1902, a sample collection solution (e.g., a solution containing cells, and optionally a stabilization solution) can be transferred into the plasma via an injector. During the transfer of the sample collection solution via the injector at box 1902, residues may accumulate on the injector.

[0134] At box 1904, a self-cleaning routine can be performed. In some cases, the self-cleaning routine can be performed automatically after the transfer of sample acquisition solution at box 1902 is completed, such as after a certain amount of sample acquisition solution has been transferred, after all sample acquisition solution has been transferred, or after a period of time has elapsed since the transfer of sample acquisition solution. In some cases, the self-cleaning routine can be performed automatically before the transfer of sample acquisition solution begins at box 1906. At optional box 1904, the sample acquisition solution (e.g., a solution containing cells, and optionally a stabilization solution) can be transferred into the plasma via an injector. In some cases, the sample acquisition solution transferred at box 1904 includes the remainder of the sample acquisition solution that has not yet been transferred at box 1902.

[0135] In some cases, a self-cleaning routine at box 1904 can be triggered. In such cases, the need for self-cleaning can be determined at optional box 1914, and in response to the determination that a need for self-cleaning exists, the self-cleaning routine at box 1904 can be executed automatically. The need for self-cleaning can be based on detected injector condition (e.g., based on a vision sensor associated with the injector) or on inferred injector condition. The inferred injector condition can be based on expected results (e.g., after a preset amount of fluid has passed through the injector or after a preset amount of run time), or it can be based on post-injector measurements (e.g., based on characteristic changes in the expected output of an elemental detector associated with an inductively coupled plasma source). For example, a calibrated sample can be passed through the injector, ionized, and then analyzed by an elemental analyzer. The elemental analyzer measurements can be used to infer that the injector needs self-cleaning. In other cases, when a sample collection solution passes through the injector, is ionized, and is analyzed by an elemental analyzer, the elemental analyzer measurements may change over time in a recognizable pattern, which can be used to infer that the injector needs self-cleaning. In some cases, self-cleaning may be required when the measured or inferred amount of buildup present in the injector is equal to or greater than a threshold amount of buildup, such as based on a percentage of the cross-sectional area without buildup as described herein.

[0136] The self-cleaning routine at box 1904 may include a heated injector at box 1908. At box 1910, at least in part due to the increased temperature of the injector, solutes or other residues on the injector may evaporate or sublimate. At box 1912, fluid may pass through the injector. The fluid passing through the injector at box 1912 may be a sample collection solution (e.g., the sample collection solution of box 1902 or 1906) or another fluid, such as deionized water or argon gas. In some cases, box 1912 may occur simultaneously with and / or after box 1910. In some cases, heated injector 1908 may occur before and / or simultaneously with either box 1910 or 1912.

[0137] In some cases, the transfer of sample collection solution at boxes 1902 and / or 1904 can be performed without heating the injector.

[0138] The foregoing description of the embodiments, including the illustrated embodiments, is for illustrative purposes only and is not intended to exhaustively describe or limit the precise forms disclosed. Many modifications, adaptations, and uses will be apparent to those skilled in the art.

[0139] As used below, any reference to a series of embodiments should be understood as a separate reference to each of those embodiments (e.g., "Embodiments 1-4" should be understood as "Embodiments 1, 2, 3 or 4").

[0140] Example 1 is a sample comprising: an element-labeled analyte containing an analyte binding to an element-labeled affinity reagent, wherein the element-labeled affinity reagent comprises an affinity reagent for binding to the analyte and a metal-binding moiety for binding to one or more metal elements; and a stabilized solution having a total dissolved solids content of about 0.2% or less, wherein the stabilized solution contains a salt. In some cases, the salt in the sample according to Example 1 is present at a concentration of at least 5 mM.

[0141] Example 2 is a sample based on Example 1, wherein the salt is a non-metallic salt.

[0142] Example 3 is a sample based on Example 1 or 2, wherein the salt does not contain carbon.

[0143] Example 4 is a sample based on Examples 1-3, wherein the salt does not contain metals with an atomic mass greater than 80.

[0144] Example 5 is a sample based on Examples 1-4, wherein the salt includes nitrogen.

[0145] Example 6 is a sample based on Examples 1-5, wherein the salt is ammonium nitrate.

[0146] Example 7 is a sample based on Examples 1-6, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0147] Example 8 is a sample based on Examples 1-7, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0148] Example 9 is a sample based on Examples 1-8, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0149] Example 10 is a sample based on Examples 1-5 or 7-9, wherein the salt is ammonium acetate.

[0150] Example 11 is a sample based on Examples 1-10, wherein the analyte comprises whole cells.

[0151] Example 12 is based on the sample of Example 11, wherein the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the analyte to avoid osmotic dissolution of the analyte.

[0152] Example 13 is a sample based on Examples 1-12, wherein the salt is present in the stabilized solution at a concentration of 25 mM or less.

[0153] Example 14 is a sample based on Examples 1-13, wherein the stabilization solution has a pH between 5 and 9.

[0154] Example 15 is a sample based on Examples 1-13, wherein the stabilization solution has a pH between 6 and 8.

[0155] Example 16 is a sample according to Examples 1-15, wherein the metal-binding portion comprises a polymer connected to an affinity reagent and containing at least one metal-binding side group, the metal-binding side group containing at least one metal atom.

[0156] Example 17 is a sample based on Examples 1-16, wherein the element-labeled analytes include a first analyte labeled with a first element tag and a second analyte labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis.

[0157] Example 18 is a sample based on Examples 1-17, wherein the affinity reagent contains an antibody.

[0158] Example 19 is a sample preparation kit comprising an element-labeled affinity reagent comprising an affinity reagent for binding to an analyte and a metal-binding moiety for binding to one or more metal elements; and a stabilizing solution having a total dissolved solids content of about 0.2% or less, wherein the stabilizing solution contains a salt. In some cases, the salt in the sample preparation kit according to Example 19 is present at a concentration of at least 5 mM.

[0159] Example 20 is a sample preparation kit according to Example 19, wherein the salt is a non-metallic salt.

[0160] Example 21 is a sample preparation kit according to Examples 19-20, wherein the salt is carbon-free.

[0161] Example 22 is a sample preparation kit according to Examples 19-21, wherein the salt does not contain metals with an atomic mass greater than 80.

[0162] Example 23 is a sample preparation kit according to Examples 19-22, wherein the salt includes nitrogen.

[0163] Example 24 is a sample preparation kit according to Examples 19-23, wherein the salt is ammonium nitrate.

[0164] Example 25 is a sample preparation kit according to Examples 19-24, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0165] Example 26 is a sample preparation kit according to Examples 19-25, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0166] Example 27 is a sample preparation kit according to Examples 19-26, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0167] Example 28 is a sample preparation kit according to Examples 19-23 or 25-27, wherein the salt is ammonium acetate.

[0168] Example 29 is a sample preparation kit according to Examples 19-28, wherein the affinity reagent can bind to the surface of the whole cell.

[0169] Example 30 is a sample preparation kit according to Example 29, wherein the stabilizing solution induces sufficiently low osmotic pressure on the membrane of whole cells bound to the affinity reagent to avoid osmotic dissolution of the whole cells.

[0170] Example 31 is a sample preparation kit according to Examples 19-29, wherein the salt is present in the stabilization solution at a concentration of 25 mM or less.

[0171] Example 32 is based on the method of Examples 19-31, wherein the stabilizing solution has a pH between 5 and 9.

[0172] Example 33 is based on the method of Examples 19-31, wherein the stabilizing solution has a pH between 6 and 8.

[0173] Example 34 is a sample preparation kit according to Examples 19-33, wherein the metal-binding portion comprises a polymer linked to an affinity reagent and containing at least one metal-binding side group, the metal-binding side group containing at least one metal atom.

[0174] Example 35 is a sample preparation kit according to Examples 19-34, wherein the element-labeled affinity reagent comprises a first affinity reagent labeled with a first element tag and a second affinity reagent labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis.

[0175] Example 36 is a method comprising: receiving a sample containing an element-labeled analyte and a stabilization solution; transporting the sample downstream toward an inductively coupled plasma source to ionize the sample, wherein transporting the sample includes passing the sample through the inner wall of an injector; ionizing the sample at the plasma; and performing elemental analysis on the ionized sample to detect the element of the element-labeled analyte.

[0176] Example 37 is the method according to Example 36, wherein the analyte comprises whole cells, and wherein delivering the sample to the plasma comprises delivering whole cells to the plasma.

[0177] Example 38 is the method according to Example 36 or 37, wherein delivering a sample to the plasma includes delivering the sample through an injector with an inner diameter between approximately 0.5 mm and 5 mm.

[0178] Example 39 is based on the method of Examples 36-38, wherein the receiving sample further includes a mixed element-labeled analyte and a stabilizing solution.

[0179] Example 40 is based on the method of Examples 36-39, wherein the stabilizing solution comprises a salt, which is selected to obtain a salt deposition of less than 2% of the total flow rate of the salt material in the injector during a 48-hour sample run.

[0180] Example 41 is based on the method of Examples 36-40, wherein the stabilizing solution comprises a salt, which is selected to maintain a signal decrease of 5% or less during elemental analysis during a 48-hour sample run.

[0181] Example 42 is a method comprising providing an element-labeled analyte, wherein the element-labeled analyte comprises a sample of whole cells labeled with an element-labeled affinity reagent, wherein each element-labeled affinity reagent comprises an affinity reagent that binds to the analyte in the sample and a metal-binding moiety that binds to one or more metal elements; and mixing the element-labeled analyte with a stabilizing solution having a total dissolved solids of about 0.2% or less, wherein the stabilizing solution contains a salt. In some cases, the salt according to the method of Example 42 is present at a concentration of at least 5 mM.

[0182] Example 43 is based on the method of Example 42, wherein the salt is a nonmetallic salt.

[0183] Example 44 is the method according to Example 42 or 43, wherein the salt does not contain carbon.

[0184] Example 45 is based on the method of Examples 42-44, wherein the salt does not contain metals with an atomic mass greater than 80.

[0185] Example 46 is based on the method of Examples 42-45, wherein the salt includes nitrogen.

[0186] Example 47 is based on the method of Examples 42-46, wherein the salt is ammonium nitrate.

[0187] Example 48 is based on the method of Examples 42-47, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0188] Example 49 is the method according to Example 48, which further includes passing the sample collection solution through an injector heated to a temperature of at least 100°C.

[0189] Example 50 is based on the method of Examples 42-49, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0190] Example 51 is the method according to Example 50, which further includes passing the sample collection solution through an injector heated to a temperature of at least 150°C.

[0191] Example 52 is based on the method of Examples 42-51, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0192] Example 53 is the method according to Example 52, which further includes passing the sample collection solution through an injector heated to a temperature of at least 160°C.

[0193] Example 54 is based on the method of Examples 42-46 or 48-53, wherein the salt is ammonium acetate.

[0194] Example 55 is based on the method of Examples 42-54, wherein the affinity agent can bind to the surface of the entire cell.

[0195] Example 56 is based on the method of Examples 42-55, wherein the stabilizing solution induces sufficiently low osmotic pressure on the membrane of the whole cell bound to the affinity reagent to avoid osmotic dissolution of the whole cell.

[0196] Example 57 is based on the method of Examples 42-56, wherein the salt is present in the stabilized solution at a concentration of 25 mM or less.

[0197] Example 58 is based on the method of Examples 42-57, wherein the stabilizing solution has a pH between 5 and 9.

[0198] Example 59 is based on the method of Examples 42-57, wherein the stabilizing solution has a pH between 6 and 8.

[0199] Example 60 is based on the method of Examples 42-59, wherein the metal-binding portion comprises a polymer connected to an affinity reagent and containing at least one metal-binding side group, the metal-binding side group containing at least one metal atom.

[0200] Example 61 is based on the method of Examples 42-60, wherein the element-labeled affinity reagent comprises a first affinity reagent labeled with a first element tag and a second affinity reagent labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis.

[0201] Example 62 is based on the method of Examples 42-61, wherein the salt is selected to obtain less than 2% salt deposition during a 48-hour sample run.

[0202] Example 63 is based on the method of Examples 42-62, wherein the stabilizing solution comprises a salt, which is selected to maintain a signal decrease of 5% or less during elemental analysis during a 48-hour sample run.

[0203] Example 64 is a stabilization solution miscible with samples used in inductively coupled plasma elemental analysis. The stabilization solution comprises a solute and a solvent, wherein the solute is a salt, the solution has a total dissolved solids content of about 0.2% or less, and the solution does not contain metals with atomic mass units greater than 80. In some cases, the salt in the stabilization solution according to Example 64 is present at a concentration of at least 5 mM.

[0204] Example 65 is a solution according to Example 64, wherein the salt is a nonmetallic salt.

[0205] Example 66 is a solution according to Example 64 or 65, wherein the salt does not contain carbon.

[0206] Example 67 is a solution according to Examples 64-66, wherein the salt includes nitrogen.

[0207] Example 68 is a solution according to Examples 64-67, wherein the salt is ammonium nitrate.

[0208] Example 69 is a solution according to Examples 64-68, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0209] Example 70 is a solution according to Examples 64-69, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0210] Example 71 is a solution according to Examples 64-70, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0211] Example 72 is a solution according to Examples 64-67 or 69-71, wherein the salt is ammonium acetate.

[0212] Example 73 is a solution according to Examples 64-72, wherein the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the whole cells of the sample to avoid osmotic dissolution of the whole cells.

[0213] Example 74 is a solution according to Examples 64-73, wherein the salt is present in the stabilized solution at a concentration of 25 mM or less.

[0214] Example 75 is a solution according to Examples 64-74, wherein the stabilized solution has a pH between 5 and 9.

[0215] Example 76 is a solution according to Examples 64-75, wherein the stabilized solution has a pH between 6 and 8.

[0216] Example 77 is an apparatus comprising: an inductively coupled plasma source for generating plasma; an injector having a sample inlet for receiving a sample containing an element-labeled analyte, wherein the injector is positioned upstream of the inductively coupled plasma source to supply the sample to the plasma; and a heat source thermally coupled to the injector for heating the injector.

[0217] Example 78 is a device according to Example 77, which further includes a heat transfer device thermally coupled to the injector for transferring heat from a heat source.

[0218] Example 79 is an apparatus according to Example 78, wherein the heat transfer device includes a metal sleeve surrounding at least a portion of the injector.

[0219] Example 80 is an apparatus according to Example 78 or 79, wherein the heat source includes at least a portion of a spray chamber located upstream of the injector, such that heat from the spray chamber is transferred to the injector via a heat transfer device.

[0220] Example 81 is a device according to Examples 78-80, wherein the heat source includes plasma.

[0221] Example 82 is a device according to Examples 77-81, wherein the heat source includes a resistive heat source.

[0222] Example 83 is a device according to Examples 77-82, which further includes one or more heat pipes extending along the length of the injector.

[0223] Example 84 is a device according to Example 83, wherein one or more heat pipes are arranged to conduct heat energy from a higher temperature portion of the injector to a lower temperature portion of the injector.

[0224] Example 85 is an apparatus according to Examples 77-84, which further includes a mass spectrometer positioned downstream of an inductively coupled plasma source for receiving ions from the inductively coupled plasma source.

[0225] Example 86 is a device according to Examples 77-85, wherein the injector has an inner diameter between approximately 0.5 mm and 5 mm.

[0226] Example 87 is an apparatus according to Examples 77-86, which further includes a sample source coupled to an injector for providing a sample and a stabilizing solution.

[0227] Example 88 is an apparatus according to Example 87, wherein a heat transfer device is coupled to an injector to heat the inner surface of the injector to a temperature sufficient to evaporate or sublimate the solute in the stable solution.

[0228] Example 89 is an apparatus according to Examples 77-88, wherein a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature of at least 150°C.

[0229] Example 90 is a method using the apparatus according to Examples 77-89, the method comprising: heating the injector with a heat source; passing a sample through the injector to plasma; ionizing the sample; and performing elemental analysis on the ionized sample.

[0230] Example 91 is the method according to Example 90, wherein passing a sample through an injector includes passing a solution containing an element-labeled analyte and a stabilizing solution through the injector.

[0231] Example 92 is the method according to Example 91, wherein heating the injector includes heating the injector to a temperature suitable for obtaining less than 2% salt deposition during a 48-hour sample run.

[0232] Example 93 is a method according to Examples 90-92, wherein the heating injector includes passing current through a resistive heat source, wherein the heat source is a resistive heat source.

[0233] Example 94 is the method according to Examples 90-93, wherein the heating injector includes using a heat transfer device to conduct heat from the higher temperature portion of the injector to the lower temperature portion of the injector.

[0234] Example 95 is the method according to Examples 90-94, wherein the heating injector includes heating the inner wall to a temperature sufficient to evaporate, sublimate, or decompose the solute in the stabilized solution.

[0235] Example 96 is a method comprising: receiving a sample containing an element-labeled analyte and a stabilized solution; transporting the sample downstream toward an inductively coupled plasma source to ionize the sample, wherein transporting the sample includes passing the sample through the inner wall of an injector; and heating the inner wall of the injector.

[0236] Example 97 is the method according to Example 96, wherein the inner wall of the injector is heated before the sample is delivered to the plasma.

[0237] Example 98 is based on the method of Example 96, wherein after the sample is delivered to the plasma, the inner wall of the injector is heated.

[0238] Example 99 is the method according to Examples 96-98, which further includes passing the sample through a spray chamber, wherein the inner wall of the heated injector includes heat conduction from the spray chamber through a heat transfer device.

[0239] Example 100 is the method according to Examples 96-99, wherein heating the inner wall of the injector includes generating heat at a heat source.

[0240] Example 101 is the method according to Example 100, wherein generating heat at the heat source includes passing an electric current through the resistive heat source.

[0241] Example 102 is the method according to Examples 96-101, wherein heating the inner wall of the injector includes using a heat transfer device to conduct heat from the higher temperature portion of the injector to the lower temperature portion of the injector.

[0242] Example 103 is the method according to Examples 96-102, wherein heating the inner wall of the injector includes heating the inner wall to a temperature sufficient to evaporate or sublimate the solute in the stabilized solution.

[0243] Example 104 is the method according to Examples 96-103, wherein heating the inner wall of the injector includes heating the inner wall to a temperature of at least 150°C.

[0244] Example 105 is a method according to Examples 96-104, which further includes: delivering ions of an ionized sample to a mass spectrometer; and analyzing the ions by the mass spectrometer.

[0245] Example 106 is the method according to Examples 96-105, wherein the analyte comprises whole cells, and wherein delivering the sample to the plasma comprises delivering whole cells to the plasma.

[0246] Example 107 is the method according to Examples 96-106, wherein delivering a sample to the plasma includes delivering the sample through an injector with an inner diameter between approximately 0.5 mm and 5 mm.

[0247] Example 108 is based on the method of Examples 96-107, wherein the receiving sample further includes a mixed element-labeled analyte and a stabilizing solution.

[0248] Example 109 is based on the method of Examples 96-108, wherein heating the inner wall of the injector includes heating the inner wall to a temperature suitable for obtaining less than 2% salt deposition during a 48-hour sample run.

[0249] Example 110 is an apparatus comprising: an injector positioned upstream of an inductively coupled plasma source and adapted to deliver a sample into the plasma of the inductively coupled plasma source, the injector having a sample inlet for receiving a sample containing elementally labeled analytes; and a heat source thermally coupled to the injector for heating the injector.

[0250] Example 111 is a device according to Example 110, which further includes a heat transfer device thermally coupled to the injector for transferring heat from a heat source.

[0251] Example 112 is an apparatus according to Example 111, wherein the heat transfer device includes a metal sleeve surrounding at least a portion of the injector.

[0252] Example 113 is an apparatus according to Example 111 or 112, wherein the heat source includes at least a portion of a spray chamber located upstream of the injector, such that heat from the spray chamber is transferred to the injector via a heat transfer device.

[0253] Example 114 is a device according to Examples 111-113, wherein the heat source includes plasma.

[0254] Example 115 is a device according to Examples 110-114, wherein the heat source includes a resistive heat source.

[0255] Example 116 is a device according to Examples 110-115, which further includes one or more heat pipes extending along the length of the injector.

[0256] Example 117 is a device according to Example 116, wherein one or more heat pipes are arranged to conduct heat energy from a higher temperature portion of the injector to a lower temperature portion of the injector.

[0257] Example 118 is an apparatus according to Examples 110-117, which further includes a mass spectrometer that can be positioned downstream of an inductively coupled plasma source for receiving ions from the inductively coupled plasma source.

[0258] Example 119 is a device according to Examples 110-118, wherein the injector has an inner diameter between approximately 0.5 mm and 5 mm.

[0259] Example 120 is an apparatus according to Examples 110-119, which further includes a sample source coupled to an injector for providing a sample and a stabilizing solution.

[0260] Example 121 is an apparatus according to Example 120, wherein a heat transfer device is coupled to an injector to heat the inner surface of the injector to a temperature sufficient to evaporate or sublimate the solute in the stable solution.

[0261] Example 122 is an apparatus according to Examples 110-121, wherein a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature of at least 150°C.

Claims

1. A sample comprising: Element-labeled analytes, wherein the element-labeled analytes include analytes bound to an element-labeled affinity reagent, wherein, The element-labeled affinity reagent includes an affinity reagent for binding to the analyte and a metal-binding portion for binding to one or more metal elements; as well as A stabilizing solution having about 0.2% or less of total dissolved solids, wherein the stabilizing solution contains salt.

2. The sample according to claim 1, wherein, The salt is a non-metallic salt.

3. The sample according to claim 1, wherein, The salt does not contain carbon.

4. The sample according to claim 1, wherein, The salt does not contain any metals having an atomic mass greater than 80.

5. The sample according to claim 1, wherein, The salt includes nitrogen.

6. The sample according to claim 1, wherein, The salt is ammonium nitrate.

7. The sample according to claim 1, wherein, The salt has a vapor pressure of at least 3 Pa at 100°C.

8. The sample according to claim 1, wherein, The salt has a vapor pressure of at least 130 Pa at 150 °C.

9. The sample according to claim 1, wherein, The salt has a vapor pressure of at least 250 Pa at 160°C.

10. A method comprising Provides element-labeled analytes, wherein, The element-labeled analytes comprise samples containing whole cells labeled with element-labeled affinity reagents, wherein each element-labeled affinity reagent comprises an affinity reagent of the analyte bound to the sample and a metal-binding moiety bound to one or more metal elements; and The element-labeled analyte is mixed with a stabilizing solution having a total dissolved solids of about 0.2% or less than about 0.2%, wherein the stabilizing solution contains a salt.

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