Robust cell harvesting for elemental analysis

Abstract

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

Description

[0001] Citations of Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 657,332, filed on April 13, 2018, and entitled “STABILIZED CELL ACQUISITION FOR ELEMENTAL ANALYSIS,” which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates generally to improving signal stability in elemental analysis, and more particularly to improvements in ionizing samples in conjunction with elemental analysis. Background Art

[0004] Inductively coupled plasma (ICP) is a plasma source used in various fields such as elemental analysis. Samples provided to a plasma generated by an ICP source can be ionized and atomized before 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 a solution, such as a suspension of a substance in a liquid or a solid substance carried in a gas stream.

[0005] In an ICP source (e.g., an ICP torch), plasma is generated when a gas stream (such as argon) is ionized in a strong electromagnetic field. When an optimal plasma temperature and energy density are generated, a sample introduced into the plasma by the torch can be evaporated, atomized, and ionized. Typically, the conditions for achieving the optimal plasma temperature and energy density are reflected by the argon gas flow rate and the power intensity of the electromagnetic field.

[0006] The ICP source may include an induction coil and a set of tubes for supplying gas and sample to pass through the torch area covered by the induction coil. The ICP source typically includes an inner tube that acts as an injector to cover the sample, an intermediate tube for supplying the gas to be heated and ionized, and an outer tube for providing a tangential flow to help maintain the shape of the plasma and protect the torch wall from melting.

[0007] In elemental analysis, a sample provided to an ICP source can be 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 a manner that can reduce the stability or resolution of the assay. It may be desirable to provide techniques and materials for improving the stability and resolution of ICP-based elemental analysis. In addition, conventional ICP-based elemental analyzers can become contaminated over time, such as accumulation on the injector. It may be desirable to provide an ICP-based elemental analyzer or ICP source that is resistant to contamination over time.

[0008] In multiple elemental analysis of elementally labeled cells (e.g., mass cytometry), cells are suspended in water to avoid metals or heavy elements that would generate background noise during elemental analysis. The absence of solutes also reduces clumping on the walls of the ICP injector, which could clog the fluidics. Summary of the invention

[0009] The term embodiment and similar terms are intended to refer broadly to all subject matter of the present disclosure and the claims below. Statements containing these terms should be understood not to limit the subject matter described herein or to limit the meaning or scope of the claims below. The embodiments of the present disclosure covered herein are defined by the claims below rather than by this disclosure. This disclosure is a high-level overview of various aspects of the present disclosure and introduces some concepts that are further described in the detailed description section below. This disclosure is not intended to identify the 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 reference to the appropriate portions of the entire specification of the present disclosure, any or all drawings, and each claim.

[0010] Embodiments of the present disclosure include a sample comprising: an element-labeled analyte containing the analyte bound 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 that binds to one or more metal elements; and a stabilizing solution having total dissolved solids at or below approximately 0.2%, wherein the stabilizing solution contains a salt present at a concentration of at least 5 mM.

[0011] In some cases, the salt is a non-metallic salt. In some cases, the salt does not contain carbon. In some cases, the salt does not contain metals with atomic mass units 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 3Pa at 100°C. In some cases, the salt has a vapor pressure of at least 130Pa at 150°C. In some cases, the salt has a vapor pressure of at least 250Pa at 160°C. In some cases, the salt is ammonium acetate. In some cases, the analyte comprises a whole cell. In some cases, the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the analyte to avoid osmotic dissolution (osmotic lysis, osmotic lysis) of the analyte. In some cases, the salt is present in the stabilizing solution at a concentration of or less than 25mM. In some cases, the stabilizing solution has a pH between 5-9. In some cases, the stabilizing solution has a pH between 6-8. In some cases, the metal binding moiety comprises a polymer connected to an affinity reagent and comprising at least one metal binding side group, the metal binding side group comprising at least one metal atom. In some cases, the elementally 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.

[0012] Embodiments of the present 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 portion that binds to one or more metal elements; and a stabilizing solution having a total dissolved solids of or less than approximately 0.2%, wherein the stabilizing solution contains a salt present at a concentration of at least 5 mM.

[0013] In some cases, the salt is a non-metallic salt. In some cases, the salt does not contain carbon. In some cases, the salt does not contain metals with atomic mass units 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 3Pa at 100°C. In some cases, the salt has a vapor pressure of at least 130Pa at 150°C. In some cases, the salt has a vapor pressure of at least 250Pa at 160°C. In some cases, the salt is ammonium acetate. In some cases, the affinity reagent may be bound 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 or less than 25mM. In some cases, the stabilizing solution has a pH between 5-9. In some cases, the stabilizing solution has a pH between 6-8. In some cases, the metal binding moiety comprises a polymer attached to an affinity agent and comprising at least one metal binding side group, the metal binding side group comprising at least one metal atom. In some cases, the element-labeled affinity agent comprises a first affinity agent labeled with a first element tag and a second affinity agent labeled with a second element tag, the second element tag being distinguishable from the first element tag by elemental analysis.

[0014] An embodiment of the present disclosure includes a method comprising: receiving a sample comprising an elementally labeled analyte and a stabilizing solution; transporting the sample in a downstream direction toward a plasma of an inductively coupled plasma source to ionize the sample, wherein transporting the sample comprises passing the sample through an inner wall of an injector; ionizing the sample at the plasma; and performing elemental analysis on the ionized sample to detect elements of the elementally labeled analyte.

[0015] In some cases, the analyte comprises a whole cell, and wherein delivering the sample to the plasma comprises delivering the whole cell to the plasma. In some cases, delivering the sample to the plasma comprises delivering the sample through an injector having an inner diameter between about 0.5 mm and 5 mm. In some cases, the received sample further comprises a mixed elementally labeled analyte and a stabilizing solution. In some cases, the stabilizing solution comprises a salt selected to obtain 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 during elemental analysis at or less than 5% during a 48-hour sample run.

[0016] Embodiments of the present disclosure include 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 sample analyte and a metal binding portion 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 present at a concentration of at least 5 mM.

[0017] In some cases, the salt is a non-metallic salt. In some cases, the salt does not contain carbon. In some cases, the salt does not contain metals with atomic mass units 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 3Pa at 100°C. In some cases, the method further includes passing the sample collection solution through an injector heated to a temperature of at least 100°C. In some cases, the salt has a vapor pressure of at least 130Pa at 150°C. In some cases, the method further includes passing the sample collection solution through an injector heated to a temperature of at least 150°C. In some cases, the salt has a vapor pressure of at least 250Pa at 160°C. In some cases, the method further includes passing the sample collection solution through an injector heated to a temperature of at least 160°C. In some cases, the salt is ammonium acetate. In some cases, the affinity reagent may be bound 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 lysis of the whole cell. In some cases, the salt is present in the stabilizing solution at a concentration of 25 mM or less. In some cases, the stabilizing solution has a pH between 5-9. In some cases, the stabilizing solution has a pH between 6-8. In some cases, the metal binding portion includes a polymer connected to an affinity reagent and comprising at least one metal binding side group, the metal binding side group comprising 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 stabilizing solution includes a salt selected to maintain a signal drop percentage of or less than 5% during the 48-hour sample run during the elemental analysis.

[0018] Embodiments of the present disclosure include a stabilizing solution that can be mixed with a sample for use in inductively coupled plasma elemental analysis, the stabilizing 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 total dissolved solids at or below approximately 0.2%, and wherein the solution does not contain metals with atomic mass units greater than 80.

[0019] In some cases, the salt is a non-metallic 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 3Pa at 100°C. In some cases, the salt has a vapor pressure of at least 130Pa at 150°C. In some cases, the salt has a vapor pressure of at least 250Pa 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 cell of the sample to avoid osmotic lysis of the whole cell. In some cases, the salt is present in the stabilizing solution at a concentration of or less than 25mM. In some cases, the stabilizing solution has a pH between 5-9. In some cases, the stabilizing solution has a pH between 6-8.

[0020] Embodiments of the present disclosure include an apparatus comprising: an inductively coupled plasma source for generating a 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.

[0021] In some cases, the apparatus further comprises a heat transfer device thermally coupled to the injector for transferring heat from the heat source. In some cases, the heat transfer device comprises a metallic jacket surrounding at least a portion of the injector. In some cases, the heat source comprises 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 through the heat transfer device. In some cases, the heat source comprises a plasma. In some cases, the heat source comprises a resistive heat source. In some cases, the apparatus further comprises one or more heat pipes extending along the length of the injector. In some cases, the 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. In some cases, the apparatus further comprises a mass spectrometer positioned downstream of the inductively coupled plasma source for receiving ions from the inductively coupled plasma source. In some cases, the inner diameter of the injector is between about 0.5 mm and 5 mm. In some cases, the apparatus further comprises 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 sublime the solute of the stable 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.

[0022] Embodiments of the present disclosure include methods of using one or more of the apparatus disclosed above, the methods comprising: heating an injector using a heat source; passing a sample through the injector to a plasma; ionizing the sample; and performing elemental analysis on the ionized sample.

[0023] In some cases, passing the sample through the injector includes passing a solution comprising an elementally labeled analyte and a stabilizing solution. In some cases, heating the injector includes 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 includes passing an electric current through a resistive heat source, wherein the heat source is a resistive heat source. In some cases, heating the injector includes conducting heat from a higher temperature portion of the injector to a lower temperature portion of the injector using a heat transfer device. In some cases, heating the injector includes heating an inner wall to a temperature sufficient to evaporate or sublime or decompose a solute of the stabilizing solution.

[0024] An embodiment of the present disclosure includes a method comprising: receiving a sample comprising an elementally labeled analyte and a stabilizing solution; transporting the sample in a downstream direction toward a plasma 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.

[0025] In some cases, heating the inner wall of the injector is initiated before delivering the sample to the plasma. In some cases, heating the inner wall of the injector is initiated after delivering the first portion of the sample to the plasma. In some cases, the method further comprises passing the sample through a spray chamber, wherein heating the inner wall of the injector comprises conducting heat from the spray chamber through a heat transfer device. In some cases, heating the inner wall of the injector comprises generating heat at a heat source. In some cases, generating heat at the heat source comprises passing an electric current through a resistive heat source. In some cases, heating the inner wall of the injector comprises conducting heat from a higher temperature portion of the injector to a lower temperature portion of the injector using a heat transfer device. In some cases, heating the inner wall of the injector comprises heating the inner wall to a temperature sufficient to evaporate or sublimate a solute of the stabilizing solution. In some cases, heating the inner wall of the injector comprises heating the inner wall to a temperature of at least 150° C. In some cases, the method further comprises: delivering ions of the ionized sample to a mass spectrometer; and analyzing the ions by the mass spectrometer. In some cases, the analyte comprises a whole cell, and wherein delivering the sample to the plasma comprises delivering the whole cell to the plasma. In some cases, delivering the sample to the plasma includes delivering the sample through an injector having an inner diameter between about 0.5 mm and 5 mm. In some cases, the received sample also includes a mixed element labeled analyte and a stabilization solution. In some cases, 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.

[0026] Embodiments of the present disclosure include an apparatus comprising: an injector positionable upstream of an inductively coupled plasma source and adapted to deliver a sample to a plasma of the inductively coupled plasma source, the injector having a sample inlet for receiving the sample, wherein the sample comprises an elementally labeled analyte; and a heat source thermally coupled to the injector for heating the injector.

[0027] In some cases, the apparatus further comprises a heat transfer device thermally coupled to the injector for transferring heat from a heat source. In some cases, the heat transfer device comprises a metal sleeve surrounding at least a portion of the injector. In some cases, the heat source comprises at least a portion of a spray chamber positioned upstream of the injector, so that heat from the spray chamber is transferred to the injector through the heat transfer device. In some cases, the heat source comprises plasma. In some cases, the heat source comprises a resistive heat source. In some cases, the apparatus further comprises one or more heat pipes extending along the length of the injector. In some cases, the 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. In some cases, the apparatus further comprises a mass spectrometer positionable downstream of the inductively coupled plasma source for receiving ions from the inductively coupled plasma source. In some cases, the inner diameter of the injector is between about 0.5 mm and 5 mm. In some cases, the apparatus further comprises a sample source coupled to the injector for providing a sample and a stabilizing solution. In some cases, the 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 of the stabilizing solution. In some cases, a heat transfer device is coupled to the injector to heat an interior surface of the injector to a temperature of at least 150°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] This description refers to the following drawings, in which the same reference numerals used in different drawings are intended to describe the same or similar components.

[0029] Figure 1 is a schematic diagram depicting an inductively coupled plasma (ICP) system according to certain aspects of the present disclosure.

[0030] Figure 2 is a flow chart depicting a process for ionizing a sample according to certain aspects of the present disclosure.

[0031] Figure 3 is a schematic cross-sectional diagram depicting an ICP system having a heat transfer device thermally coupled to an injector according to certain aspects of the present disclosure.

[0032] Figure 4 is a schematic cross-sectional diagram depicting an ICP system having an injector thermally coupled to a spray chamber according to certain aspects of the present disclosure.

[0033] Figure 5 is a schematic cross-sectional diagram depicting an ICP system having a heat source thermally coupled to an injector according to certain aspects of the present disclosure.

[0034] Figure 6 is a schematic front cross-sectional view depicting an injector having a heat transfer device thermally coupled thereto, according to certain aspects of the present disclosure.

[0035] Figure 7 is a schematic front cross-sectional view depicting an injector having a heat source thermally coupled thereto, according to certain aspects of the present disclosure.

[0036] Figure 8 is a schematic front cross-sectional view depicting an injector having an external heating tube thermally coupled thereto, according to certain aspects of the present disclosure.

[0037] Fig. 9 is a schematic front cross-sectional view depicting an injector having an internal heating tube thermally coupled thereto, according to certain aspects of the present disclosure.

[0038] Fig.10 is a flow chart depicting a process for preparing and ionizing a sample according to certain aspects of the present disclosure.

[0039] Fig.11 is a graph depicting the percent signal reduction for a set of samples prepared with a 2 mM ammonium nitrate stabilization solution according to certain aspects of the present disclosure.

[0040] Fig.12 is a graph depicting the percent signal reduction for a set of samples prepared with a 5 mM ammonium nitrate stabilization solution according to certain aspects of the present disclosure.

[0041] Fig.13 is a graph depicting the percent signal reduction for a set of samples prepared with a 10 mM ammonium nitrate stabilization solution according to certain aspects of the present disclosure.

[0042] Fig.14 is a graph depicting the CD44 channel signal of a sample that has been suspended in deionized water and injected into a plasma source.

[0043] Fig.15 is a depiction of a plasma source that has been suspended in a 25 mM ammonium nitrate stabilized solution and injected into a plasma source according to certain aspects of the present disclosure. Fig.14 Figure 3. CD44 channel signal of samples.

[0044] Fig.16 is a graph depicting a sample that has been suspended in a 25 mM ammonium nitrate stabilization solution and injected into a plasma source according to certain aspects of the present disclosure. 165 Plot of the Ho channel signal.

[0045] Fig.17 is a depiction of a plasma source that has been suspended in a 75 mM ammonium nitrate stabilized solution and injected into a plasma source according to certain aspects of the present disclosure. Fig.16 Sample 165 Plot of the Ho channel signal.

[0046] Fig.18is an image of the buildup on the injector when used without adequate heating for certain aspects of the present disclosure.

[0047] Fig.19 is a flow chart depicting a process for self-cleaning an injector according to certain aspects of the present disclosure. DETAILED DESCRIPTION

[0048] Certain aspects and features of the present disclosure relate to improving the injection of a sample into a plasma source, such as an inductively coupled plasma (ICP) source. The improvements may include one or more of a stabilizing solution that can be mixed with the sample before injection and a heated injector. The sample collection solution can be prepared by mixing the sample with a stabilizing solution to improve cell stability during injection. The stabilizing solution can minimize the osmotic pressure difference between the solution and the cells using a relatively low amount of dissolved solids (e.g., at or below about 0.2%). The stabilizing solution can contain a salt (e.g., ammonium nitrate) that can be present at a concentration of at least 5 mM. The injector can be heated before 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. Injectors heated to a sufficient temperature during use can minimize accumulation and extend the usable time between cleanings. These improvements may be particularly useful in elemental analysis 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 mode or solution mode (eg, where microsprayer is used).

[0049] Certain aspects of the present disclosure are particularly useful for elemental analysis. Elemental analysis can refer to techniques for determining the elemental composition (e.g., exact or relative) of a sample, or optionally its isotopic composition (e.g., exact 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, which probe the external electronic structure of atoms; mass spectrometry atomic spectroscopy, such as inductively coupled mass spectrometry, which probes the mass of atoms; and x-ray fluorescence, particle induced x-ray emission, x-ray photoelectron spectroscopy, and Auger electron spectroscopy, which probe the internal electronic structure of atoms.

[0050] In some cases, elemental analysis involves the use of an inductively coupled plasma mass spectrometer (ICP-MS), which is an elemental analyzer based on sensitive mass spectrometry. Different ICP-MS configurations are distinguished primarily by the mass selection technique employed, and may be, for example, quadrupole or time-of-flight (ICP-TOF) or magnetic sector (high resolution ICP-MS). There are many commercially available ICP-MS mass spectrometer models with a wide spectrum of configurations, capabilities, and modifications.

[0051] Element analysis can be used to detect element labels related to analyte.Element labels, such as affinity reagents of element labels or support or beads of element labels, can be used to label analyte based on the presence or absence of required biomolecules in analyte.Element label or label is a chemical part, which includes a kind of element or multiple elements, has one or more isotopes (called label atoms) attached to the supporting molecular structure, or can be combined with one or more elements or isotopes.Element label can also include means for attaching element label to molecule of interest or target molecule (for example, analyte).Different element labels can be distinguished based on the element composition of label.Element label can contain many copies of given isotopes, and can have the reproducible copy number of every kind of isotope in each label.Suitable element label can include polymer (for example, straight chain or branched polymer) with metal binding side group such as metal chelating part (for example, tetraxetan (DOTA) or pentetic acid (pentetic acid) (DTPA)).Element label can be nanoparticle, such as metal core packaged in polymer shell. Element tags are functionally distinguishable from other element tags in the same sample because their elemental or isotopic composition is different from other tags. As used herein, the term affinity reagent can refer to a biomolecule that can tightly bind 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 is a protein molecule that specifically binds biotin and can be considered as another example of an affinity reagent. In some cases, an affinity reagent is a non-oligonucleotide biomolecule.

[0052] Non-affinity reagents, such as oligonucleotides for hybridization with target oligonucleotides (e.g., DNA, RNA) sequences, can be elementally labeled and can be used to label target oligonucleotides for elemental analysis. Other metal-containing reagents, including DNA intercalating agents such as iridium and barcoding reagents, can also be detected by elemental analysis as described herein.

[0053] To achieve useful results, it may be necessary to select tag atoms that are not originally present in the underlying sample or analyte. For example, certain metals, particularly lanthanides, are rare in biological samples and may therefore be particularly suitable for use in elemental tags for assays of these biological samples.

[0054] As used herein, the term biological sample or tissue sample may refer to a sample obtained from a biological subject, including a sample of biological tissue or fluid origin obtained, reached or collected in vivo or in situ. Biological samples also include samples from areas of biological subjects containing precancerous or cancerous cells or tissues. Such samples may 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, biological fluids, etc. Examples of biological samples include, but are not limited to, skin samples, tissue biopsies, etc.

[0055] 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, the 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 lanthanide may 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).

[0056] Thus, in one example, an element-labeled affinity reagent can include a distinguishable element tag (e.g., containing an element or a group of elements) that binds to an antibody that has a high affinity for a specific antigen on a target protein. After incubating the element-labeled affinity reagent with the analyte and washing away the unbound reagent, the analyte sample can be interrogated using elemental analysis to detect the presence of one or more element tags, and thus the presence of the target protein can be inferred.

[0057] In some cases, the target analyte may include a biomolecule on or in a cell. In some cases, it may be necessary to perform elemental analysis on whole cells or intact cells, such as to determine the presence, amount or absence of elemental labels associated with individual cells of a sample. In order to achieve reliable elemental analysis of each cell, it may be necessary to determine the dissolution or other damage to individual cells before the cell is ionized in a plasma. In the cell collection by elemental analysis (e.g., elemental analysis of each cell), damage to the cell may result in poor signal stability during the sample.

[0058] Certain aspects and features of the present disclosure relate to the use of a stabilizing solution suitable for maintaining high signal stability of a sample and / or keeping individual cells of the sample intact during injection in an ICP system. As used herein, an ICP system may refer to an inductively coupled plasma source (e.g., an ICP torch), and optionally any additional equipment or components for operating the ICP source, for supplying samples to the plasma, and / or for transporting ions for further analysis. The stabilizing solution may be selected to minimize the osmotic pressure difference between the solution and the cells, which in turn may help keep the cells intact. Alternatively or in addition, the stabilizing solution may be selected to improve the stability of metal chelates of one or more elemental tags.

[0059] However, in some cases, the stabilizing solution may increase the risk of injector clogging because the solutes in the stabilizing solution may condense and accumulate in 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, a combination of a heated injector and a stabilizing solution according to aspects of the present disclosure can improve signal stability when analyzing a sample using an elemental analyzer.

[0060] In some cases, the use of a heated injector can allow the use of a higher concentration of stabilizing solution without undesirable negative effects (e.g., no accumulation or clogging, no easily detectable accumulation or clogging, or only minimal accumulation or clogging, such as defined by a percentage of the injector cross-section). In some cases, undesirable effects associated with accumulation or clogging can be minimized by using a lower concentration of stabilizing solution with or without a heated injector. In some cases, the sample can be or be longer than 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.

[0061] As used herein, certain aspects of the present disclosure can prevent accumulation or clogging in an injector. The injector can have a nominal cross-sectional area, which is defined as the cross-sectional area of ​​the injector inner diameter (e.g., A 标称 =πr 2 If accumulation or blockage occurs within the injector, the injector may have a cross-sectional area smaller than the nominal cross-sectional area (e.g., A) based on the degree of accumulation or blockage. 有效 =πr 2 -A clog , where A clogCertain aspects of the present disclosure can prevent accumulation or clogging of the injector during a sample run such that the effective cross-sectional area of ​​the injector remains 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 48 hours, 36 hours, 32 hours, 28 hours, 24 hours, 20 hours, 16 hours, 12 hours, 8 hours, 4 hours, and / or 2 hours of instrument non-stop (e.g., continuous) operation. In some cases, certain aspects of the present disclosure can prevent buildup or clogging of the injector during a sample run 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.

[0062] As used herein, certain aspects of the present disclosure can increase the sublimation rate and / or reduce the deposition rate of the solution passing through the injector, thereby preventing the long-term deposition of solutes on the inner surface of the injector. The increase in the sublimation rate and / or the reduction in the deposition rate may be associated with less overall solute accumulation on the inner surface of the injector during the sample run. The sublimation rate may refer to the rate at which solid solutes (e.g., salts of stabilizing solutions) deposited on the inner wall of the injector are converted into gases and taken away from the injector. The deposition rate may refer to the rate at which solutes (e.g., salts of stabilizing solutions) are deposited on the injector. Since sublimation is the main mode of removing deposited solutes from the injector during operation, the sublimation rate is approximately inversely proportional to the deposition rate. In some cases, when the solution passes through the injector and enters the plasma, sublimation can be described by the percentage of solute deposition rather than ionization. For example, a 5% deposition rate may refer to 5% of the solutes in the solution deposited on the inner wall of the injector. For example, a higher sublimation rate will reduce the solutes accumulated on the inner wall of the injector during the sample run. 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 solutes may be deposited on the inner wall of the injector at the end of the sample run. In some cases, a sample run may be as long as or longer than 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.

[0063] Certain stabilizing solutions and optionally heated injectors as described herein can be used to deliver a mixture containing a sample (e.g., whole cells) and solutes from the stabilizing solution (e.g., salts from the stabilizing solution) through the injector, such as into a plasma. 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 solutes entering the injector. The mixture can be a cell collection solution. The cell collection solution may be entrained in a gas such as argon. The cell collection solution may be further entrained in a primary gas and / or an auxiliary gas after leaving the injector.

[0064] In some cases, the sublimation rate can be calculated as the vapor pressure of the solute at the injector (eg, the expected vapor pressure of the given solute and the injector temperature). Examples of sublimation rates for exemplary solutes are described herein with reference to Table 1.

[0065] The stabilizing solution (eg, the type and concentration of salt in the stabilizing solution) and / or the amount of heating of the injector (eg, no heating or some heating) can be selected to achieve a desired sublimation rate and / or a desired deposition rate.

[0066] The stabilizing solution (eg, the type and concentration of salt in the stabilizing solution) and / or the amount of heating of the injector can be selected to achieve a desired sublimation rate.

[0067] As used herein, certain aspects of the present disclosure can prevent or reduce the percentage of signal decline during the sample operation process. When using a stabilizing solution and / or a heated injector, the prevention of signal decline can occur. In some cases, the prevention of signal decline may be related to keeping the injector from accumulating or blocking. In some cases, according to certain aspects of the present disclosure, the percentage of signal decline can be or be 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 signal decline percentage can be calculated in a sample run or a part of a sample run. In some cases, the signal decline percentage can be calculated in 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 decrease percentage can be calculated as the average percentage of the amount that the signal deviates from the initial signal measurement or the average value. The signal can be raw data or normalized data. In certain aspects, the signal decrease percentage can be calculated as the average signal decrease over all mass channels, the maximum signal decrease percentage, or the signal decrease percentage for a mass channel associated with a particular analyte of interest.

[0068] The injector of heating can be heated using any suitable technology. In some cases, the injector of heating can be directly heated by a heating device. In some cases, the injector of heating can be indirectly heated such as by guiding heat from other components of the ICP system or adjacent systems. A heating device (such as a heat source) can supply heat to the injector. Various types of heating units can be used, such as a resistance heating device, a thermoelectric device, a gas power heating device (such as a direct flame), a convection heating device (such as a circulating hot fluid, such as air), a laser heating device or other. In some cases, heat can be applied to a part (such as an upstream part) of the injector of heating, thereby allowing the other parts (such as a downstream part or an output end) of the injector of heating to be heated by conduction or convection. For example, a heat pipe can be applied to or incorporated in the injector, so that heat is thermally conducted from the first part to the second part. In another example, by the sample fluid in the injector of heating, enough heat can be provided to the second part by convection.

[0069] In some cases, the injector may be completely or partially surrounded by a heat transfer device. The heat transfer device may be any suitable device capable of conducting heat into the injector and / or along the injector. Examples of suitable heat transfer devices include heat conductive materials coupled to, disposed on and / or incorporated into the injector. For example, the injector may be coated with a metal sheet. In some cases, the heat transfer device may thermally couple the injector to a heat source (e.g., a direct heat source or an 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 to the injector. In some cases, a non-metallic heat transfer device 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 when there is no heat transfer device. In other words, the heat transfer device can increase the rate of heat transfer between the injector and other objects, thereby providing faster heat transfer than if the heat transfer device was not used (eg, if the injector was exposed to standard ambient air or gas).

[0070] In some cases, the heat transfer device can be sized (e.g., in size and / or shape) to deliver sufficient heat from a steady heat source (e.g., a spray chamber maintained at 200°C) to increase the temperature of the injector (e.g., the temperature of the inner wall of the injector) 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, yet the temperature at any point along the inner wall of the injector can be maintained at at least the minimum set temperature. The minimum set temperature can be at or about 160°C. In some cases, the minimum set temperature can be at or about 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 positioned adjacent another element of the ICP system.

[0071] A heated injector may be particularly useful in certain aspects of the present disclosure, such as when the sample is combined with, mixed with, or suspended in a stabilizing solution.

[0072] According to certain aspects of the present disclosure, the stabilization solution can include a salt, such as a non-metallic 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 stabilization solution, although other salts can also be used. In some cases, chlorine and / or fluorine based solutes can be used and the desired vapor pressure can be achieved. Table 1 depicts approximate vapor pressure information associated with ammonium nitrate as a function of temperature, where is the sublimation rate for a given setup in micrograms per minute.

[0073] Table 1 – Sublimation rates of ammonium nitrate at specific temperatures

[0074]

[0075]

[0076] For ammonium nitrate, at 433 Kelvin or about 160°C, the vapor pressure reaches about 328 Pa or about 0.3% of atmospheric pressure. 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 about 0.7 slpm (standard liters per minute) argon and the sample flow rate is about 45 microliters per minute, the amount of ammonium nitrate in the carrier gas (argon) can be calculated as 0.003% of the volume of the gas when the concentration in the solution is 20 mM. Therefore, at this temperature, the ammonium nitrate will gradually sublime from the injector wall and enter the gas flow. The equilibrium between the gas phase and the solid phase of ammonium nitrate can be changed by the surface tension in the small crystals. However, it has been determined experimentally that 160°C is sufficient to keep the injector surface from being "fogged" by ammonium nitrate deposits, especially at gas flow rates commonly used in inductively coupled plasma sources.

[0077] The injector can be heated to a temperature sufficient to promote the sublimation of the salt of the stabilization solution. In some cases, the temperature to which the injector is heated can be determined or calculated based on the required vapor pressure of a specific salt. The technology for associating the temperature of various salts with vapor pressure is known in the art, such as described in Oxley, Jimmie et al. "Determination of UreaNitrate 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 and temperature relationship that approximately follows the following equation, wherein P is in Pascals, and T is in Kelvin, at least in the range of 300-550K.

[0078]

[0079] In some cases, the stabilization solution can 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, a salt having a vapor pressure of at least about 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 at 100° C. , 183Pa, 188Pa, 193Pa, 198Pa, 203Pa, 208Pa, 213Pa, 218Pa, 223Pa, 228Pa, 233Pa, 238Pa, 243Pa, 248Pa, 253Pa, 258Pa, 263Pa, 268Pa, 273Pa, 278Pa, 283Pa, 288Pa, 293Pa, 298Pa, 303Pa, 308Pa, 313Pa, 318Pa, 323Pa, 328Pa, 333Pa, 338Pa, 343Pa, 348Pa, and / or 350Pa, although other ranges may be used. The salt may be selected to provide a suitable sublimation at the operating temperature of the injector (e.g., with or without heating) sufficient to avoid deposition on the inner wall of the injector.

[0080] In some cases, the stabilizing solution can have a neutral pH or a near-neutral pH (e.g., within 1-2 units of neutral pH). At particularly high or low pH, cells of the sample may rupture and / or metals chelated in certain elemental tags may dissociate. In some cases, the stabilizing solution can 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 can be or is 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 is less than 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 one or more concentrations thereof. In some cases, one or more solutes and one or more concentrations thereof can be selected to achieve a desired pH.

[0081] The concentration of salt in the stabilizing solution can be high enough to achieve suitable results (e.g., improved stability), but can be low enough not to produce undesirable background interference. Too low a salt concentration may provide little or no benefit to cell stability, and may instead introduce some instability. Too high a salt concentration may provide benefits to cell stability, but may cause considerable loss of signal quality due to background interference, particularly if the TDS of the salt is greater than a certain value (e.g., 0.2%). In some cases, the stabilizing solution may include a salt (e.g., ammonium nitrate) at a concentration of or about 5-25 mM, 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 a salt having a concentration of or at least about 5mM, 6mM, 7mM, 8mM, 9mM, 10mM, 11mM, 12mM, 13mM, 14mM, 15mM, 16mM, 17mM, 18mM, 19mM, 20mM, 21mM, 22mM, 23mM and / or 24mM. In some cases, the stabilizing solution may include a salt having a concentration of or less than about 25mM, 24mM, 23mM, 22mM, 21mM, 20mM, 19mM, 18mM, 17mM, 16mM, 15mM, 14mM, 13mM, 12mM, 11mM, 10mM, 9mM, 8mM, 7mM and / or 6mM. In some cases, other ranges may be used. In some cases, a stabilizing solution having a salt concentration in the lower portion of the above range (e.g., at or about 5-10 mM, 5-9 mM, 5-8 mM, 5-7 mM, 5-6 mM, or 5 mM) can be used without a heated injector. In some cases, a stabilizing solution having a salt concentration in the upper portion of the above range (e.g., at or about 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 when used with a heated injector. In some cases, higher concentrations may be used, particularly when used with a heated injector.

[0082] In some cases, the stabilization solution may include a non-metallic salt. In some cases, the element of the salt may have an atomic mass unit of 80 or less. In other words, the salt may not contain a metal or element with an atomic mass unit greater than 80. In some cases, the salt may have an atomic mass unit lower than the tag atom of the element tag. In some cases, the stabilization solution may be carbon-free or substantially carbon-free (e.g., 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 "free of" in reference to a metal or element may include no such metal or element or include such metal or element in substantially small amounts such that the metal or element would be undetectable or negligible during elemental analysis of a sample containing an elementally labeled analyte as described herein.

[0083] Although ammonium nitrate can be an effective salt, other salts can also be used. In some cases, the salt can be an ammonium-based molecule. Ammonium-based salts can be 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.

[0084] In some cases, certain salts may have elements that reduce overall performance. Examples of performance degradation may include accumulation of carbon residues on the cones, accumulation of salt residues, ion suppression due to high concentrations of easily ionized elements (such as Na and K), channel loss due to ions present in the solution (such as ammonium iodide that floods mass channel 127 or ammonium orthomolybdate that contains molybdenum and may flood multiple mass channels between 90-100), and other undesirable effects. In some cases, the choice of salt (e.g., the choice of stabilizing solution) can be made to customize the specific characteristics of the assay. For example, if there is no interest in mass channels between 90-100 for a particular element label used in the assay, using ammonium orthomolybdate may not be a problem.

[0085] Cell stability may be desirable in various cytometry techniques, however ICP-based elemental analysis is limited due to the use of plasma to probe the cells, which is fundamentally limited by the total dissolved solids (TDS). Therefore, traditional solutions used to stabilize cells in other studies are ineffective or unusable for use with elemental analysis (at least ICP-based elemental analysis). For example, in a standard ICP-MS setup, in order to reduce the impact of interferences, the TDS is kept at or below 0.2%. For a 1x phosphate buffered saline (PBS) solution, the TDS for the NaCl content alone is already 0.8%, which is four times higher than the 0.2% limit. Therefore, PBS cannot be used in an ICP-MS setup without undesirable interferences. In some cases, the stabilized solution can have a TDS of or less than 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%, although other ranges may be used.

[0086] As used herein, the injector of the ICP system can have any suitable inner diameter. In some cases, the injector can have an inner diameter between or about 0.5 mm and 5 mm, such as at or about 1-5 mm or 1.5-5 mm. In some cases, the injector can have an inner diameter of or at least about 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 can have an inner diameter of or less than about 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.

[0087] In some cases, using a heated injector can also prevent water droplets from forming or gathering 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 sLpm), the gathering (or atomization) of water droplets on the injector can become a problem. Atomization and droplets on the injector can cause signal instability and, in some cases, even cause occasional plasma loss in an inductively coupled plasma source. If the plasma is lost, portions of the sample being detected may not be properly ionized and therefore may not be detected. In some cases, a heated injector can reduce or minimize the formation or gathering of water droplets on the injector, which can improve signal stability and plasma reliability.

[0088] These illustrative examples are given to introduce the reader to the general subject matter discussed herein and are not intended to limit the scope of the disclosed concepts. The following sections describe various additional features and examples with reference to the accompanying drawings, wherein like numbers represent like elements, and directional descriptions are used to describe the illustrative embodiments, but, like the illustrative embodiments, should not be used to limit the present disclosure. The elements included in the illustrations herein may not be drawn to scale.

[0089] Figure 1 1 is a schematic diagram depicting an inductively coupled plasma (ICP) system 100 according to certain aspects of the present disclosure. The ICP system 100 may include an injector 108 for delivering a sample (e.g., a sample solution or a cell collection solution) to a plasma 110. The plasma 110 may be a spherical, toroidal cylindrical, or other shaped plasma generated, for example, by stimulating a source gas using electromagnetic induction. It should be understood that certain aspects of the present disclosure, such as a stabilized solution and / or heated injector, may be advantageously used in conjunction with other techniques for plasma generation. For illustrative purposes, the plasma 110 may be a plasma having a spherical, toroidal cylindrical, or other shape. Figure 1 Certain aspects of the standard ICP system 100 are not shown, such as the gas flow tube, induction coil, and sample cone.

[0090] The sample 102 may include intact cells (e.g., whole cells) labeled with elemental tags. As disclosed herein, a stabilizing solution 104 may be provided. The stabilizing solution 104 may include a salt as described herein, such as ammonium nitrate at a concentration of 15 mM. The sample 102 and the stabilizing solution 104 may be separated or pre-mixed. When mixed, the sample 102 and the stabilizing solution 104 may be considered a "sample solution" or a "cell collection solution." The sample 102 and the stabilizing solution 104 may be provided to a sample source 106 individually or mixed as a cell collection solution. The sample source 106 may be any container suitable for storing the sample 102 (e.g., a cell collection solution) prior to being introduced into the injector 108. In some cases, the sample source 106 may be a vial, an injector, a beaker, a section of tubing, or any other container.

[0091] The injector 108 can receive a cell collection solution from the sample source 106. In some cases, the cell collection solution can pass through a spray chamber 120 before entering the injector 108, such as to atomize the cell collection solution. The injector 108 can be a section of tubing made of any suitable material, such as quartz. The injector 108 can be any suitable shape or shape, such as cylindrical. The injector 108 can introduce the cell collection solution into the plasma 110 to ionize the sample 102. In some cases, the ionized sample 102 can produce ions (e.g., a group of ions or ion beams), which can be directed to an elemental analyzer 112 (e.g., a mass spectrometer) for further analysis. In some cases, the ionized sample 102 can result in light emission, which can be directed to and / or sensed by the elemental analyzer 112 (e.g., a light emission spectrometer).

[0092] In some optional cases, the heat source 118 can be coupled to (e.g., physically), disposed about, and / or disposed near the injector 108. The heat source 118 can be thermally coupled to the injector 108. For example, the heat source 118 can be a resistive heater in the form of a metal coil wrapped around the injector 108. Other heat sources 118 can be used. The heat source 118 can extend to the entire length of the injector 108, or extend to less than the entire length of the injector 108. The heat source 118 can generate heat, such as using electrical, magnetic, kinetic, or other energy.

[0093] In some optional cases, the heat transfer device 114 can be coupled to (e.g., physically), disposed about, and / or disposed near the injector 108. The heat transfer device 114 can be thermally coupled to the injector 108. The heat transfer device 114 can be any suitable device or material capable of transferring heat into and / or along the injector 108. For example, the heat transfer device 114 can transfer heat from one portion of the injector 108 to another portion of the injector 108. In another example, the heat transfer device 114 can transfer heat from another object, such as a heat source 116, to the injector 108. The heat transfer device 114 can extend to the entire length of the injector 108, or to less than the entire length of the injector 108. In some cases, the injector 108 can include a heat source 118 and a 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 thermal paste).

[0094] Heat source 116 may be any suitable heat source that may be thermally coupled to heat transfer device 114. Examples of suitable heat sources 116 may include resistive heating devices, thermoelectric devices, pneumatic heating devices (e.g., direct flames), convection heating devices (e.g., circulating hot fluids such as air), laser heating devices, or others.

[0095] In some optional cases, one or more heat transfer devices 114 can thermally couple the injector 108 to other elements of the ICP system 100 or nearby systems (such as the spray chamber 120 or the plasma 120), although other sources can also be used. In some cases, these elements thermally coupled to the injector 108 can be considered heat sources. When thermally coupled to the spray chamber 120, the heat transfer device 114 can transfer thermal 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 can indirectly receive heat from the plasma 110 (e.g., by convection due to heating of nearby gases or by radiant heat) and transfer the heat to the injector 108 at a rate suitable to ensure 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 heat transfer device 114 can include providing heat transfer device 114 in a suitable size and / or shape that can achieve the desired heat transfer rate. In some cases, heat transfer device 114 can include a thermal conduction trap to appropriately slow the heat transfer to the desired rate. The thermal conduction trap can include gaps in the material of heat transfer device 114, which can be filled with a material that is more thermally insulating than heat transfer device 114 itself, such as a flowing carrier gas or a ceramic material.

[0096] 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 stabilization solution 104 can include salts at suitably low concentrations or salts having sufficiently high vapor pressures at the injector temperature to avoid accumulation of residues within the injector 108.

[0097] In some cases, the injector 108 of the ICP system 100 may be heated, such as by the heat source 118 or the heat transfer device 114, and the sample 102 may be provided thereto without providing the stabilizing solution 104. In such cases, heating the injector 108 may provide certain benefits, such as reducing the possible accumulation of water / solvent droplets or accumulation of residues on the injector 108, without the attendant benefits of the stabilizing solution 104.

[0098] In some cases, the thermal insulation layer 115 can be provided around some or all of the injector 108. The thermal insulation layer 115 can be coupled to the injector 108 or positioned directly around it, or can be coupled to the heat transfer device 114 and / or the heat source 118 or positioned around it. The thermal insulation layer 115 can maintain the heat within the injector 108 by suppressing radial heat dissipation. The thermal insulation layer 115 can help maintain a constant injector temperature throughout the injector 108. In some cases, the thermal insulation layer 115 can extend completely around the injector 108, but this is not always the case. The thermal insulation layer 115 can be formed by any suitable thermal insulation material (such as glass fiber, para-aramid fiber or aerogel). In some cases, the thermal insulation layer 115 can be an air gap or a vacuum gap. In some cases, the thermal insulation layer can be solid. In some cases, the thermal insulation layer 115 can be any suitable thermal insulation material that suppresses radial heat dissipation from the injector 108 beyond the heat dissipation achieved by moving the surrounding supply gas (e.g., argon) to the plasma generator. In some cases, such as where the amount of gas (e.g., the radial thickness of the gas volume surrounding the injector) is specifically tailored to achieve a particular desired amount of insulation (such as more than in conventional injector arrangements), the surrounding supply gas (e.g., argon) can serve as the thermal insulation layer 115.

[0099] Figure 2 2 is a flow chart depicting a process 200 for ionizing a sample according to certain aspects of the present disclosure. The process 200 may be performed by any suitable ICP system as described herein, such as Figure 1 In some cases, heating the injector at block 202 may include supplying heat to the injector from a directly coupled heat source at block 214 (e.g., supplying heat from a resistive heater wrapped around the injector). In some cases, heating the injector at block 202 may include passing a heated fluid through the injector at block 216 (e.g., passing a heated cell collection solution or another heated fluid through the injector).

[0100] In some cases, heating the injector at block 202 may include conducting heat to the injector at block 218. In some cases, conducting heat to the injector at block 218 may include conducting heat along a length of the injector at block 220. In some cases, conducting heat to the injector at block 218 may include conducting heat from a spray chamber of the ICP system at block 222. In some cases, conducting heat to the injector at block 218 may include conducting heat from a plasma generated by the ICP system at block 224.

[0101] At box 204, a sample is received. The sample may optionally include a stabilizing solution. In some cases, receiving the sample at 204 may optionally include mixing the stabilizing solution with the sample. At box 206, the sample is passed through a heated injector. At box 206, passing the sample through the heated injector may optionally include passing the sample through the heated injector as part of a cell collection solution containing the sample and the stabilizing solution. At box 206, passing the sample through the heated injector 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, the intact cells or whole cells may pass through in sequence.

[0102] At box 208, an inductively coupled plasma can be used to ionize the sample. The ionized sample at box 208 can cause ions to be released from the sample, such as an ion beam. In some cases, the ionized sample at box 208 can include ionizing intact cells or whole cells. In some cases, intact cells or whole cells can be ionized in sequence. At box 210, elemental analysis can be performed on the ionized sample. The elemental analysis performed at box 210 can include any suitable elemental analysis, such as using a mass spectrometer to measure ions (e.g., mass spectrometry) or detecting light emission during sample ionization (e.g., light emission spectrum). At optional box 212, the detected element can be identified based on the measurement of elemental analysis. The detected element can be a tag atom from an element tag associated with an element-labeled sample (e.g., a sample labeled with an element tag). In some cases, the detected element identified at box 212 may be associated with an intact cell or a whole cell. The element detected for intact cells or whole cells identified at box 212 can be repeated for multiple cells in the sample.

[0103] Figure 3 is a schematic cross-sectional view of an ICP system 300 having a heat transfer device 314 thermally coupled to an injector 308 according to certain aspects of the present 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 and 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 toward the downstream end of the outer tube 330 may function with a high frequency current suitable for exciting a gas within a bore of the coil 334 to generate and / or maintain a plasma 310. A sample 328 (e.g., alone or as part of a cell collection solution with a stabilization solution) may enter the injector 308 and be discharged in a downstream direction (e.g., as a columnar flow path). Figure 3The sample 328 can be delivered to the plasma 310. The resulting ions, light or other detectable emission or light absorption characteristics can be delivered from the plasma 310 to an elemental analyzer. In some cases, the injector 308, the outer tube 330 and the optional middle tube 332 are concentric, but this is not always the case.

[0104] 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 to the downstream end of the injector 308, but this is not necessarily always the case. The heat transfer device 314 may be used in conjunction with another heat source to heat the injector 308. However, in some cases, the heat transfer device 314 may simply transport heat through the injector 308.

[0105] In some cases, the auxiliary gas 336 and / or the primary gas 338 may be preheated to deliver heat to the injector 308 .

[0106] Figure 4 is a schematic cross-sectional view of an ICP system 400 having an injector 408 thermally coupled to a spray chamber 420 according to certain aspects of the present 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 and 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 toward the downstream end of the outer tube 430 may function with a high frequency current suitable for exciting a gas within a bore of the coil 434 to generate and / or maintain a plasma 410. A sample 428 (e.g., alone or as part of a cell collection solution with a stabilization solution) may enter the injector 408 and be directed in a downstream direction (e.g., as Figure 4 The sample 428 can be delivered to the plasma 410. The resulting ions, light or other detectable emission or light absorption characteristics can be delivered from the plasma 410 to an elemental analyzer. In some cases, the injector 408, the outer tube 430 and the optional middle tube 432 are concentric, but this is not always the case.

[0107] 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 may thermally couple the spray chamber 420 to the injector 408, thereby transferring heat from the spray chamber 420 to the injector 408.

[0108] Figure 5 is a schematic cross-sectional view of an ICP system 500 having a heat source 518 thermally coupled to an injector 508 according to certain aspects of the present 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 and 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 toward the downstream end of the outer tube 530 may function with a high frequency current suitable for exciting a gas within a bore of the coil 534 to generate and / or maintain a plasma 510. A sample 528 (e.g., alone or as part of a cell collection solution with a stabilization solution) may enter the injector 508 and be discharged in a downstream direction (e.g., as a columnar flow path). Figure 5 The sample 528 can be delivered to the plasma 510. The resulting ions, light or other detectable emission or light absorption characteristics can be delivered from the plasma 510 to an elemental analyzer. In some cases, the injector 508, the outer tube 530 and the optional middle tube 532 are concentric, but this is not always the case.

[0109] like Figure 5 As depicted, the 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 the injector 508 up to the downstream end of the injector 508, but this is not necessarily always the case. The resistive heater 542 is depicted as surrounding a portion of the injector 508, however, in some cases, the resistive heater 542 may extend along the entire length of the injector 508. The resistive heater 542 may be powered by a power source 540 to generate heat. The generated heat may be transferred to the injector 508 via the heat transfer device 514. The heat transfer device 514 may help transfer heat along the length of the injector 508, such as from the portion of the injector 508 around which the resistive heater 542 is located to the downstream end of the injector 508.

[0110] Figure 6 is a schematic front cross-sectional view depicting an injector 608 having a heat transfer device 614 thermally coupled thereto in accordance with certain aspects of the present disclosure. The injector 608 may be similar to Figure 3 The heat transfer device 614 can be physically coupled to the injector 608, or can simply be disposed around or near the injector 608. The heat transfer device 614 can receive heat 644, such as from an external heat source, and transfer the heat 644 into the injector 608.

[0111] Figure 7is a schematic front cross-sectional view depicting an injector 708 having a heat source 718 thermally coupled thereto in accordance with certain aspects of the present disclosure. The injector 708 may be similar to Figure 5 The embodiment of the present invention is an injector 508 of the present invention, but without the heat transfer device 514. A resistive heater 742 in the form of a coil can be disposed around the injector 708 and optionally physically coupled to the injector 708. When power is applied to the resistive heater 742 from the power supply 740, the resistive heater 742 can generate heat to heat the injector 708.

[0112] Figure 8 808 having an external heating tube 846 thermally coupled thereto, according to certain aspects of the present disclosure. The heating tube 846 can be a type of heat transfer device capable of transporting heat 844 into the injector 808. In some cases, the heating tube 846 can be thermally coupled to the injector 808 using a thermal paste 848. In some cases, the heating tube 846 can be located on an inner surface of the injector 808. The heating tube 846 can extend along part or all of the length of the injector 808.

[0113] Fig. 9 is a schematic front cross-sectional view of an injector 908 having an internal heating tube 946 thermally coupled thereto according to certain aspects of the present disclosure. The heating tube 946 can be a type of heat transfer device capable of transporting heat 944 into the injector 908. In some cases, the heating tube 946 can be thermally coupled to the injector 908 using a thermal paste 948. The heating tube 946 can be located within a channel 950 of the injector 908. In some cases, the heating tube 946 can be completely enclosed by the injector 908, including cross-sectional closure and / or longitudinal closure. In some cases, the heating tube 946 can be located in a channel 950 positioned on the inner surface of the injector 908. The heating tube 946 can extend along part or all of the length of the injector 908.

[0114] Fig.10 1 is a flow chart depicting a process 1000 for preparing and ionizing a sample according to certain aspects of the present disclosure. Process 100 may utilize any suitable ICP system, such as Figure 1 The ICP system 100 of the present invention is provided. At box 1002, an element-labeled analyte is provided. The element-labeled analyte may include an analyte on or within a whole cell or intact cell that has been labeled or traced with an element tag. At box 1004, a stabilizing solution may be provided. The stabilizing solution may be any suitable stabilizing 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 stabilizing solution to produce a sample collection solution (e.g., a cell collection solution).

[0115] The sample collection solution may include intact or whole cells in suspension with a stabilizing solution containing a salt, such as ammonium nitrate, as described herein. The intact or whole cells of the sample collection solution may be labeled with an elemental tag, such as by including an elementally labeled analyte.

[0116] At block 1008, the sample collection solution is transferred into the plasma of the ICP system using an injector at block 1008. The sample collection solution may be pressurized using a fluid, such as the sample collection solution and / or a carrier gas, through the injector. In some cases, transferring the sample collection solution into the plasma using the injector may include passing the sample collection solution through a heated injector and / or heating the injector.

[0117] At block 1010, the ionized sample solution may be analyzed, such as by elemental analysis (e.g., mass spectrometry or optical emission spectroscopy). In some cases, at optional block 1012, solutes retained on the injector, such as solutes from the stabilization solution, may be evaporated or sublimated. Evaporation or sublimation of the solute may be achieved by heating the injector. In some cases, evaporation or sublimation of the solute at block 1012 may occur after or simultaneously with the transfer of the sample collection solution into the plasma using the injector at block 1008.

[0118] Figure 11-13 Depicted are graphs 1100, 1200, 1300 showing the percentage decrease in signal for a particular sample when prepared with different molar concentrations of ammonium nitrate stabilization solutions. The samples contain various element-labeled affinity reagents and element-labeled beads. The element-labeled affinity reagents in this sample include 145Nd-CD4 (specific for the CD4 antigen and containing an element tag 145 Nd affinity reagent), 145Nd-CD4 (specific for CD4 antigen and contains elemental tags 145 Nd affinity reagent), 146Nd-CD8 (specific for CD8 antigen and contains elemental tags 148 Nd affinity reagent), 147Sm-CD20 (specific for CD20 antigen and contains elemental tags 147 Sm affinity reagent), 154Sm-CD45 (specific for CD45 antigen and contains elemental tag 154 Sm affinity reagent), 155Gd-CD27 (specific for CD27 antigen and contains elemental tags 155 Gd affinity reagent), 159Tb-CD11c (specific for CD11c antigen and contains elemental tags 159 Tb affinity reagent), 160Gd-CD14 (specific for CD14 antigen and contains elemental tags 160Gd affinity reagent), 170Er-CD3 (specific for CD3 antigen and contains elemental tags 170 Er affinity reagent), Ir191 (specific for the first identifiable DNA string and containing an element tag 191 Ir affinity reagent), and IR193 (specific for a second identifiable DNA string and containing an element tag 193 Ir affinity reagent). The element-labeled beads in this sample include 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 by an elemental analyzer. In some cases, each of the aforementioned elements or isotopes can be measured using a different channel of the elemental analyzer that is specific only to the element or isotope.

[0119] In each of the diagrams 1100, 1200, and 1300, the percentage drop in signal in the raw data measurements during a sample run (e.g., a 30 minute sample run) is shown, along with the percentage drop in signal after the data has been normalized. Data normalization may include adjusting the measured signal intensities of various channels of the elemental analyzer based on signal drift detected in known standards. In some cases, one or more element-labeled beads, such as those identified above, may be used as known standards. For example, if a sample containing 165 Ho element-labeled beads as known standards, then the element-labeled beads may contain a known amount of 165 Ho, and may be present at a known concentration, which should produce a constant signal intensity throughout the sample run. In the event that any drift from the expected signal intensity is detected, a correction can be applied to 165 The Ho signal returns to the expected signal strength, and similar corrections can be made to the other channels of the elemental analyzer. In some cases, the element-labeled beads can be normalized to the other element-labeled beads even within a common time interval, such as to account for the moment-to-moment drift in the detector of the elemental analyzer within the time interval.

[0120] Fig.111100 is a graph depicting the percentage drop in signal for a set of samples prepared with a 2 mM ammonium nitrate stabilization solution according to certain aspects of the present disclosure. Graph 1100 shows the percentage drop in signal for many element-labeled affinity reagents when the samples were prepared with a 2 mM ammonium nitrate stabilization solution. As depicted in graph 1100, the percentage drop in signal for almost all channels remained below about 15%, and many channels remained below about 10% or 5%.

[0121] Fig.12 1200 is a graph depicting the percent signal drop for a set of samples prepared with a 5 mM ammonium nitrate stabilization solution in accordance with certain aspects of the present disclosure. Graph 1200 shows the percent signal drop for a number of element labeled affinity reagents when the samples were prepared with a 5 mM ammonium nitrate stabilization solution. When compared to graph 1100 for a 2 mM ammonium nitrate stabilization solution, it is apparent that the increase to a 5 mM ammonium nitrate stabilization solution results in a reduction in signal drift. As depicted in graph 1200, the percent signal drop for all channels remained below approximately 6%, and for most channels remained below approximately 2% or 3%.

[0122] Fig.13 1300 is a graph depicting the percent signal drop for a set of samples prepared with a 10 mM ammonium nitrate stabilization solution in accordance with certain aspects of the present disclosure. Graph 1300 shows the percent signal drop for a number of element labeled affinity reagents when the samples were prepared with a 10 mM ammonium nitrate stabilization solution. When compared to graph 1200 for a 5 mM ammonium nitrate stabilization solution, it is apparent that increasing to a 10 mM ammonium nitrate stabilization solution does not affect stability to any great extent. As depicted in graph 1300, the percent signal drop for all channels remained below approximately 4% or 5%, and for most channels remained below approximately 1% or 2%.

[0123] Fig.14 and 15 Depicted are diagrams 1400, 1500 showing the signal intensity within a particular channel of an elemental analyzer during a 30 minute sample run. In this case, the particular channel was used to identify the CD44 antigen. An elementally labeled affinity reagent specific for CD44 was used 171 Yb mark. About Fig.14 and 15 The samples used during the 30 minute sample run contain cells labeled with an affinity reagent labeled with this element due to its specificity for CD44. The CD44 channel pair of the elemental analyzer has a specificity of or approximately equal to 171Yb or ions with an atomic mass of or about 171 amu are responsive. For each of the diagrams 1400 and 1500, the x-axis represents the time during the elemental analysis, and the y-axis represents the expression intensity (e.g., the number of label atoms detected) for the selected CD44 channel for the detected event (each event is represented by a point on the graph). These specific channels, antigens, and / or elements are selected to provide examples, however any other suitable channels, antigens, and / or elements may be used.

[0124] Fig.14 It is a diagram 1400 depicting the CD44 channel signal of a sample that has been suspended in deionized water and injected into a plasma source. The brighter area in the measurement band represents the population of the most frequent cell events. In the diagram 1400, the relatively wide change and downward trend on the y-axis are obvious, indicating that the cells have a certain degree of instability during storage and / or injection. The downward trend may also indicate that accumulation has occurred in the injection tube, which may have a negative impact on signal intensity over time. In addition, if the cells in this unstable sample are damaged during storage and / or injection, the affinity reagents of the element labels may have been separated from the rest of the cells to which they are attached, which may have produced undesirable fluctuations in signal intensity, because the label atoms that are expected to have fallen on the detector and are very close in time to other label atoms of this particular cell may have the opposite outcome of falling on the detector in advance or postponed. Therefore, a part of the signal is not counted in the reaction of individual events. As a result, the measurement depicted in the diagram 1400 can occupy a relatively wide band on the y-axis.

[0125] Fig.15 1500 is a diagram depicting the CD44 channel signal of a sample that has been suspended in a 25 mM ammonium nitrate stabilizing solution and injected into a plasma source according to certain aspects of the present disclosure. The brighter areas on the measurement band represent the population of the most frequent cell events. The effect of the stabilizing solution is demonstrated by the significantly different clustering of the measured signal intensities in diagram 1400 (e.g., without the stabilizing solution) and 1500 (e.g., with the stabilizing solution). The band of the measurement signal depicted in diagram 1500 is much narrower than the band depicted in diagram 1400, indicating a significant increase in stability, which may indicate that fewer or no cells are damaged during storage and / or injection. The band in diagram 1500 provides a denser combination of measurements and a clearer and more accurate average. In addition, the band in diagram 1500 shows a relatively constant horizontal trend, contrary to the downward trend of the band in diagram 1400.

[0126] Fig.16 and 17Depicted are diagrams 1600, 1700 showing the signal intensity within a particular channel of an elemental analyzer during a 30 minute sample run. In this case the particular channel is used to identify an element standard in the form of element-labeled beads. The element-labeled beads used in diagrams 1600 and 1700 are 165 Ho. The channel pairs used to obtain the signal strengths depicted in diagrams 1600 and 1700 have a value of or approximately equal to 165 Ho or ions with an atomic mass of or about 165 amu respond. Fig.16 and 17 The samples used during the 30-minute sample run contain the cells being sampled and the element-labeled beads. 165 Ho element-labeled beads serve as element standards because they are not present in cells or in any element-labeled affinity reagents used with cells. 165 Ho. For each of the graphs 1600 and 1700, the x-axis represents the time during the element analysis, and the y-axis represents the time for the selected 165 The expression intensity of the Ho channel (e.g., the number of tagged atoms detected). These specific channels and / or elements are selected to provide examples, however any other suitable channels and / or elements may be used. In some cases, element-labeled beads (which may contain any suitable element or isotope (such as those described above)) are selected as element standards. 165 Ho)) can be used to normalize signal intensity in a detector of an analyzer. Element-labeled beads containing a known amount of an element or isotope can be expected to present a known amount of label atoms to the detector over a period of time, and therefore, if the signal of the element-labeled beads drops below the expected signal intensity, any drift in signal intensity due to natural drift in the detector can be identified, and the identified drift can therefore be used to correct or normalize signal intensities in other channels.

[0127] Fig.16 is a graph depicting a sample that has been suspended in a 25 mM ammonium nitrate stabilization solution and injected into a plasma source according to certain aspects of the present disclosure. 165 Graph 1600 of the Ho channel signal. The dense set of measurements forming a thin band near the top of graph 1600 represents those events associated with the elementally labeled beads, and the large band of measurements near the bottom of graph 1600 represents background noise from cellular events in the 25 mM ammonium nitrate stabilization solution. 165The source of Ho, the only measured source in the selected channel should be the element-labeled beads. Therefore, as expected, the background noise in the plot 1600 is relatively minimal, and no areas of high intensity are shown except at the expected intensity of the element-labeled beads and 0 (e.g., the expected atomic intensity of the cells in the sample). At 25 mM ammonium nitrate, the background signal does not overwhelm the signal of interest, and the signal of interest is clearly discernible.

[0128] Fig.17 is a graph depicting a sample that has been suspended in a 75 mM ammonium nitrate stabilization solution and injected into a plasma source according to certain aspects of the present disclosure. 165 Graph 1700 of the Ho channel signal. The thin band near the top of graph 1700 represents those measurements associated with the element-labeled beads, and the large band of measurements near the bottom of graph 1700 represents background noise in a 75 mM ammonium nitrate stabilized solution. At 75 mM ammonium nitrate, the background signal begins to overwhelm the signal of interest and may begin to interfere with the ability to clearly distinguish the signal of interest. Specifically, a population of readings that would be expected to have an intensity of or about 0 instead show an intensity above 0, indicating that the detector detected signals from sources other than the element-labeled beads. 165 Ho. Since there is no 165 Ho, it is obvious that the background signal interferes with the detection in the elemental analyzer.

[0129] Graph 1700 shows that when higher concentrations of ammonium nitrate (or other salts) are used, they may begin to cause undesirable background interference when compared to graph 1600. Therefore, it may be desirable to provide a stabilization solution that is high enough to improve cell stability, but low enough to avoid overwhelming background interference.

[0130] Fig.18 is an image of an injector 1800 depicting a large amount of buildup due to insufficient heating due to certain aspects of the present disclosure. The injector 1800 is not heated or is not heated sufficiently, and therefore residue has accumulated within the injector. The residue may be the result of salts of the stabilizing solution. When using a stabilizing solution, it may be desirable to heat the injector to avoid the buildup of residue, such as Fig.18 Depicted.

[0131] Fig.19 1 is a flow chart depicting a process 1900 for self-cleaning an injector according to certain aspects of the present disclosure. Self-cleaning of an injector can be used to remove accumulation on an injector of an inductively coupled plasma system, such as residues of salts of a stabilizing solution or agglomerates of water droplets. In some cases, self-cleaning can occur before, after, or during transfer of a sample (e.g., a cell) through an injector for ionization by a plasma of an inductively coupled plasma system.

[0132] A sample collection solution (e.g., a solution containing cells, and optionally a stabilizing solution) may be transferred into the plasma through an injector at optional block 1902. During the transfer of the sample collection solution through the injector at block 1902, residue may accumulate on the injector.

[0133] At block 1904, a self-cleaning routine may be performed. In some cases, the self-cleaning routine may be automatically performed after the transfer of the sample collection solution at block 1902 is complete, such as after a certain amount of sample collection solution is transferred, after all of the sample collection solution is transferred, or after a period of time of transferring the sample collection solution. In some cases, the self-cleaning routine may be automatically performed before the transfer of the sample collection solution at block 1906 begins. At optional block 1904, the sample collection solution (e.g., a solution containing cells, and optionally a stabilizing solution) may be transferred to the plasma by an injector. In some cases, the sample collection solution transferred at block 1904 includes a remaining portion of the sample collection solution that was not transferred at block 1902.

[0134] In some cases, the self-cleaning routine performed at block 1904 may be triggered. In such cases, at optional block 1914, the need for self-cleaning may be determined, and in response to determining that there is a need for self-cleaning, the self-cleaning routine at block 1904 may be automatically performed. The need for self-cleaning may be based on a detected injector condition (e.g., based on a visual sensor associated with the injector) or based on an inferred injector condition. The inferred injector condition may be based on an expected result (e.g., after a preset amount of fluid has passed through the injector or after a preset amount of run time), or may be based on a post-injector measurement (e.g., based on a characteristic change in an expected output of an element detector associated with an inductively coupled plasma source). For example, a calibrated sample may be passed through the injector, ionized, and then analyzed by an elemental analyzer. The measured values ​​of the elemental analyzer may be used to generate an inference that the injector needs self-cleaning. In other cases, when the sample collection solution passes through the injector, is ionized, and is analyzed by the elemental analyzer, the measured values ​​of the elemental analyzer may change over time in a recognizable pattern, which may be used to infer that the injector needs self-cleaning. In some cases, a need for self-cleaning may exist when a measured or inferred amount of accumulation present in the injector is equal to or above a threshold amount of accumulation, such as an amount based on a percentage of cross-sectional area without accumulation as described herein.

[0135] The self-cleaning routine at box 1904 may include heating the injector at box 1908. At box 1910, solutes or other residues on the injector may be evaporated or sublimated, at least in part due to the increased temperature of the injector. At box 1912, a 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, heating the injector 1908 may occur before and / or simultaneously with any of boxes 1910 and 1912.

[0136] In some cases, transferring the sample collection solution at block 1902 and / or block 1904 may be performed without heating the injector.

[0137] The foregoing description of the embodiments, including illustrated embodiments, has been presented for purposes of illustration and description only and is not intended to be exhaustive or to limit to the precise form disclosed. Many modifications, adaptations, and uses will be apparent to those skilled in the art.

[0138] As used below, any reference to a series of embodiments should be understood as a reference to each of those embodiments separately (eg, "embodiments 1-4" should be understood as "embodiment 1, 2, 3, or 4").

[0139] Embodiment 1 is a sample comprising: an element-labeled analyte containing the analyte bound 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 that binds to one or more metal elements; and 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 of the sample according to embodiment 1 is present at a concentration of at least 5 mM.

[0140] Example 2 is a sample according to Example 1, wherein the salt is a non-metallic salt.

[0141] Example 3 is a sample according to Example 1 or 2, wherein the salt does not contain carbon.

[0142] Example 4 is a sample according to Example 1-3, wherein the salt does not contain a metal with an atomic mass unit greater than 80.

[0143] Example 5 is a sample according to Example 1-4, wherein the salt includes nitrogen.

[0144] Example 6 is a sample according to Example 1-5, wherein the salt is ammonium nitrate.

[0145] Example 7 is a sample according to Example 1-6, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0146] Example 8 is a sample according to Example 1-7, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0147] Example 9 is a sample according to Example 1-8, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0148] Example 10 is a sample according to Example 1-5 or 7-9, wherein the salt is ammonium acetate.

[0149] Embodiment 11 is a sample according to embodiment 1-10, wherein the analyte comprises whole cells.

[0150] Example 12 is a sample according to 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.

[0151] Example 13 is a sample according to Examples 1-12, wherein the salt is present in the stabilizing solution at a concentration of 25 mM or less.

[0152] Example 14 is a sample according to Example 1-13, wherein the stabilization solution has a pH between 5-9.

[0153] Example 15 is a sample according to Example 1-13, wherein the stabilization solution has a pH between 6-8.

[0154] Embodiment 16 is a sample according to embodiments 1-15, wherein the metal binding portion comprises a polymer attached to the affinity agent and comprising at least one metal binding side group, wherein the metal binding side group comprises at least one metal atom.

[0155] Embodiment 17 is a sample according to embodiments 1-16, wherein the elementally 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.

[0156] Embodiment 18 is a sample according to embodiment 1-17, wherein the affinity reagent comprises an antibody.

[0157] Embodiment 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 portion that binds to one or more metal elements; and 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 of the sample preparation kit according to embodiment 19 is present at a concentration of at least 5 mM.

[0158] Embodiment 20 is a sample preparation kit according to embodiment 19, wherein the salt is a non-metallic salt.

[0159] Embodiment 21 is a sample preparation kit according to embodiments 19-20, wherein the salt does not contain carbon.

[0160] Embodiment 22 is a sample preparation kit according to embodiments 19-21, wherein the salt does not contain a metal with an atomic mass unit greater than 80.

[0161] Embodiment 23 is a sample preparation kit according to embodiments 19-22, wherein the salt comprises nitrogen.

[0162] Embodiment 24 is a sample preparation kit according to embodiments 19-23, wherein the salt is ammonium nitrate.

[0163] Embodiment 25 is a sample preparation kit according to embodiments 19-24, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0164] Embodiment 26 is a sample preparation kit according to embodiments 19-25, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0165] Embodiment 27 is a sample preparation kit according to embodiments 19-26, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0166] Embodiment 28 is a sample preparation kit according to embodiment 19-23 or 25-27, wherein the salt is ammonium acetate.

[0167] Embodiment 29 is a sample preparation kit according to embodiments 19-28, wherein the affinity reagent can be bound to the surface of whole cells.

[0168] Embodiment 30 is a sample preparation kit according to embodiment 29, wherein the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the whole cell bound to the affinity reagent to avoid osmotic lysis of the whole cell.

[0169] Embodiment 31 is a sample preparation kit according to embodiments 19-29, wherein the salt is present in the stabilizing solution at a concentration of 25 mM or less.

[0170] Embodiment 32 is a method according to embodiments 19-31, wherein the stabilizing solution has a pH between 5-9.

[0171] Embodiment 33 is a method according to embodiments 19-31, wherein the stabilizing solution has a pH between 6-8.

[0172] Embodiment 34 is a sample preparation kit according to embodiments 19-33, wherein the metal binding moiety comprises a polymer linked to the affinity reagent and comprising at least one metal binding pendant group, the metal binding pendant group comprising at least one metal atom.

[0173] 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, and the second element tag is distinguishable from the first element tag by elemental analysis.

[0174] Embodiment 36 is a method comprising: receiving a sample comprising an elementally labeled analyte and a stabilizing solution; transporting the sample in a downstream direction toward a plasma of an inductively coupled plasma source to ionize the sample, wherein transporting the sample comprises passing the sample through an inner wall of an injector; ionizing the sample at the plasma; and performing elemental analysis on the ionized sample to detect elements of the elementally labeled analyte.

[0175] Embodiment 37 is a method according to embodiment 36, wherein the analyte comprises a whole cell, and wherein delivering the sample to the plasma comprises delivering the whole cell to the plasma.

[0176] Embodiment 38 is a method according to embodiment 36 or 37, wherein delivering the sample to the plasma comprises delivering the sample through an injector having an inner diameter between approximately 0.5 mm and 5 mm.

[0177] Embodiment 39 is a method according to embodiments 36-38, wherein receiving the sample further comprises mixing the elementally labeled analyte and a stabilizing solution.

[0178] Example 40 is a method according to examples 36-39, wherein the stabilizing solution includes a salt selected to obtain salt deposition of less than 2% of the total flow of salt material in the injector during a 48 hour sample run.

[0179] Embodiment 41 is a method according to embodiments 36-40, wherein the stabilizing solution comprises a salt selected to maintain a percent signal drop during elemental analysis at or less than 5% over a 48 hour sample run.

[0180] Embodiment 42 is a method comprising providing an element-labeled analyte, wherein the element-labeled analyte comprises a sample having whole cells labeled with an element-labeled affinity reagent, wherein each element-labeled affinity reagent comprises an affinity reagent that binds to the analyte of the sample and a metal binding portion 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 embodiment 42 is present at a concentration of at least 5 mM.

[0181] Embodiment 43 is a method according to embodiment 42, wherein the salt is a non-metallic salt.

[0182] Embodiment 44 is the method according to embodiment 42 or 43, wherein the salt contains no carbon.

[0183] Embodiment 45 is the method of embodiments 42-44, wherein the salt does not contain a metal having an atomic mass unit greater than 80.

[0184] Embodiment 46 is the method of embodiments 42-45, wherein the salt comprises nitrogen.

[0185] Embodiment 47 is the method according to embodiments 42-46, wherein the salt is ammonium nitrate.

[0186] Embodiment 48 is the method of embodiments 42-47, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0187] Embodiment 49 is a method according to embodiment 48, further comprising passing the sample collection solution through an injector heated to a temperature of at least 100°C.

[0188] Embodiment 50 is the method according to embodiments 42-49, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0189] Embodiment 51 is a method according to embodiment 50, further comprising passing the sample collection solution through an injector heated to a temperature of at least 150°C.

[0190] Embodiment 52 is the method according to embodiments 42-51, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0191] Embodiment 53 is a method according to embodiment 52, further comprising passing the sample collection solution through an injector heated to a temperature of at least 160°C.

[0192] Embodiment 54 is the method according to embodiment 42-46 or 48-53, wherein the salt is ammonium acetate.

[0193] Embodiment 55 is a method according to embodiments 42-54, wherein the affinity reagent can be bound to the surface of whole cells.

[0194] Embodiment 56 is a method according to embodiments 42-55, wherein the stabilizing solution induces a sufficiently low osmotic pressure on the membrane of the whole cell bound to the affinity reagent to avoid osmotic lysis of the whole cell.

[0195] Embodiment 57 is the method according to embodiments 42-56, wherein the salt is present in the stabilizing solution at a concentration of 25 mM or less.

[0196] Embodiment 58 is a method according to embodiments 42-57, wherein the stabilization solution has a pH between 5-9.

[0197] Embodiment 59 is a method according to embodiments 42-57, wherein the stabilization solution has a pH between 6-8.

[0198] Embodiment 60 is a method according to embodiments 42-59, wherein the metal binding moiety comprises a polymer linked to the affinity agent and comprising at least one metal binding pendant group, the metal binding pendant group comprising at least one metal atom.

[0199] Embodiment 61 is a method according to embodiments 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.

[0200] Example 62 is a method according to Examples 42-61, wherein the salt is selected to obtain less than 2% salt deposition during a 48 hour sample run.

[0201] Embodiment 63 is a method according to embodiments 42-62, wherein the stabilizing solution comprises a salt selected to maintain a percent signal drop during elemental analysis at or less than 5% over a 48 hour sample run.

[0202] Embodiment 64 is a stabilizing solution miscible with a sample for use in inductively coupled plasma elemental analysis, the stabilizing solution comprising: a solute and a solvent, wherein the solute is a salt, wherein the solution has a total dissolved solids at or below about 0.2%, and wherein the solution does not contain metals having atomic mass units greater than 80. In some cases, the salt of the stabilizing solution according to Embodiment 64 is present at a concentration of at least 5 mM.

[0203] Embodiment 65 is a solution according to embodiment 64, wherein the salt is a non-metallic salt.

[0204] Embodiment 66 is a solution according to embodiment 64 or 65, wherein the salt does not contain carbon.

[0205] Embodiment 67 is a solution according to embodiments 64-66, wherein the salt comprises nitrogen.

[0206] Embodiment 68 is a solution according to embodiments 64-67, wherein the salt is ammonium nitrate.

[0207] Embodiment 69 is a solution according to embodiments 64-68, wherein the salt has a vapor pressure of at least 3 Pa at 100°C.

[0208] Embodiment 70 is a solution according to embodiments 64-69, wherein the salt has a vapor pressure of at least 130 Pa at 150°C.

[0209] Embodiment 71 is a solution according to embodiments 64-70, wherein the salt has a vapor pressure of at least 250 Pa at 160°C.

[0210] Embodiment 72 is a solution according to embodiment 64-67 or 69-71, wherein the salt is ammonium acetate.

[0211] Embodiment 73 is a solution according to embodiments 64-72, wherein the stabilizing solution induces a sufficiently low osmotic pressure on the membranes of whole cells of the sample to avoid osmotic lysis of the whole cells.

[0212] Embodiment 74 is a solution according to embodiments 64-73, wherein the salt is present in the stabilizing solution at a concentration of 25 mM or less.

[0213] Embodiment 75 is a solution according to embodiments 64-74, wherein the stabilizing solution has a pH between 5-9.

[0214] Embodiment 76 is a solution according to embodiments 64-75, wherein the stabilizing solution has a pH between 6-8.

[0215] Embodiment 77 is an apparatus comprising: an inductively coupled plasma source for generating a plasma; an injector having a sample inlet for receiving a sample comprising 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.

[0216] Embodiment 78 is an apparatus according to embodiment 77, further comprising a heat transfer device thermally coupled to the injector for transferring heat from the heat source.

[0217] Embodiment 79 is an apparatus according to embodiment 78, wherein the heat transfer device comprises a metal sleeve surrounding at least a portion of the injector.

[0218] Embodiment 80 is an apparatus according to embodiment 78 or 79, wherein the heat source comprises 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.

[0219] Embodiment 81 is an apparatus according to embodiments 78-80, wherein the heat source comprises plasma.

[0220] Embodiment 82 is an apparatus according to embodiments 77-81, wherein the heat source comprises a resistive heat source.

[0221] Embodiment 83 is an apparatus according to embodiments 77-82, further comprising one or more heat pipes extending along the length of the injector.

[0222] Embodiment 84 is an apparatus according to embodiment 83, wherein 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.

[0223] Embodiment 85 is an apparatus according to embodiments 77-84, further comprising a mass spectrometer positioned downstream of the inductively coupled plasma source for receiving ions from the inductively coupled plasma source.

[0224] Embodiment 86 is a device according to embodiments 77-85, wherein the injector has an inner diameter between approximately 0.5 mm and 5 mm.

[0225] Embodiment 87 is an apparatus according to embodiments 77-86, further comprising a sample source coupled to the injector for providing a sample and a stabilizing solution.

[0226] Embodiment 88 is an apparatus according to embodiment 87, wherein a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature sufficient to evaporate or sublime the solute of the stable solution.

[0227] Embodiment 89 is an apparatus according to embodiments 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.

[0228] Example 90 is a method of using the apparatus according to Examples 77-89, the method comprising: heating an injector using a heat source; allowing a sample to reach a plasma through the injector; ionizing the sample; and performing elemental analysis on the ionized sample.

[0229] Embodiment 91 is a method according to embodiment 90, wherein passing the sample through the injector comprises passing a solution comprising an elementally labeled analyte and a stabilizing solution.

[0230] Embodiment 92 is a method according to embodiment 91, wherein heating the injector comprises heating the injector to a temperature suitable for obtaining less than 2% salt deposition during a 48 hour sample run.

[0231] Embodiment 93 is a method according to embodiments 90-92, wherein heating the injector comprises passing an electric current through a resistive heat source, wherein the heat source is a resistive heat source.

[0232] Embodiment 94 is a method according to embodiments 90-93, wherein heating the injector comprises conducting heat from a higher temperature portion of the injector to a lower temperature portion of the injector using a heat transfer device.

[0233] Embodiment 95 is a method according to embodiments 90-94, wherein heating the injector comprises heating the inner wall to a temperature sufficient to evaporate or sublime or decompose the solutes of the stabilization solution.

[0234] Embodiment 96 is a method comprising: receiving a sample comprising an elementally labeled analyte and a stabilizing solution; transporting the sample in a downstream direction toward a plasma of an inductively coupled plasma source to ionize the sample, wherein transporting the sample comprises passing the sample through an inner wall of an injector; and heating the inner wall of the injector.

[0235] Embodiment 97 is a method according to embodiment 96, wherein heating the inner wall of the injector is initiated before delivering the sample to the plasma.

[0236] Embodiment 98 is a method according to embodiment 96, wherein heating the inner wall of the injector is initiated after the sample is delivered to the plasma.

[0237] Embodiment 99 is a method according to embodiments 96-98, further comprising passing the sample through a spray chamber, wherein heating the inner wall of the injector comprises conducting heat from the spray chamber through a heat transfer device.

[0238] Embodiment 100 is a method according to embodiments 96-99, wherein heating the inner wall of the injector includes generating heat at a heat source.

[0239] Embodiment 101 is a method according to embodiment 100, wherein generating heat at a heat source comprises passing an electric current through a resistive heat source.

[0240] Embodiment 102 is a method according to embodiments 96-101, wherein 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.

[0241] Embodiment 103 is a method according to embodiments 96-102, wherein heating the inner wall of the injector comprises heating the inner wall to a temperature sufficient to evaporate or sublime solutes of the stabilizing solution.

[0242] Embodiment 104 is a method according to embodiments 96-103, wherein heating the inner wall of the injector comprises heating the inner wall to a temperature of at least 150°C.

[0243] Embodiment 105 is a method according to embodiments 96-104, which also includes: transporting ions of the ionized sample to a mass spectrometer; and analyzing the ions by the mass spectrometer.

[0244] Embodiment 106 is a method according to embodiments 96-105, wherein the analyte comprises a whole cell, and wherein delivering the sample to the plasma comprises delivering the whole cell to the plasma.

[0245] Embodiment 107 is a method according to embodiments 96-106, wherein delivering the sample to the plasma comprises delivering the sample through an injector having an inner diameter between approximately 0.5 mm and 5 mm.

[0246] Embodiment 108 is a method according to embodiments 96-107, wherein receiving the sample further comprises mixing the elementally labeled analyte and a stabilizing solution.

[0247] Embodiment 109 is a method according to embodiments 96-108, wherein heating the inner wall of the injector comprises heating the inner wall to a temperature suitable for obtaining less than 2% salt deposition during a 48 hour sample run.

[0248] Embodiment 110 is an apparatus comprising: an injector positionable upstream of an inductively coupled plasma source and adapted to deliver a sample into a 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.

[0249] Embodiment 111 is an apparatus according to embodiment 110, further comprising a heat transfer device thermally coupled to the injector for transferring heat from the heat source.

[0250] Embodiment 112 is an apparatus according to embodiment 111, wherein the heat transfer device comprises a metal sleeve surrounding at least a portion of the injector.

[0251] Embodiment 113 is an apparatus according to embodiment 111 or 112, wherein the heat source comprises at least a portion of the spray chamber positioned upstream of the injector, such that heat from the spray chamber is transferred to the injector through the heat transfer device.

[0252] Embodiment 114 is an apparatus according to embodiments 111-113, wherein the heat source comprises plasma.

[0253] Embodiment 115 is an apparatus according to embodiments 110-114, wherein the heat source comprises a resistive heat source.

[0254] Embodiment 116 is an apparatus according to embodiments 110-115, further comprising one or more heat pipes extending along the length of the injector.

[0255] Embodiment 117 is an apparatus according to embodiment 116, wherein 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.

[0256] Embodiment 118 is an apparatus according to embodiments 110-117, further comprising a mass spectrometer positionable downstream of the inductively coupled plasma source for receiving ions from the inductively coupled plasma source.

[0257] Embodiment 119 is an apparatus according to embodiments 110-118, wherein the injector has an inner diameter between approximately 0.5 mm and 5 mm.

[0258] Embodiment 120 is the apparatus according to embodiments 110-119, further comprising a sample source coupled to the injector for providing the sample and the stabilizing solution.

[0259] Embodiment 121 is an apparatus according to embodiment 120, wherein a heat transfer device is coupled to the injector to heat the inner surface of the injector to a temperature sufficient to evaporate or sublime the solute of the stable solution.

[0260] Embodiment 122 is an apparatus according to embodiments 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 preparation kit comprising an element-labeled affinity reagent comprising an affinity reagent for binding to an analyte and a metal binding moiety that binds to one or more metal elements; and A stabilized solution having 0.2% or less total dissolved solids, in, The stabilizing solution has a pH of 5 to 9, and the stabilizing solution contains salt, and the salt is present in the stabilizing solution at a concentration of 5 mM to 25 mM, the salt is selected to reduce signal drop or deposition of the salt on the injector, and the salt is ammonium nitrate; the injector is configured to inject a mixed solution containing the affinity reagent labeled with the element, the stabilizing solution and the analyte into the plasma.

2. The sample preparation kit according to claim 1, in, The salt has a vapor pressure of at least 3 Pa at 100°C.

3. The sample preparation kit according to claim 1, in, The salt has a vapor pressure of at least 130 Pa at 150°C.

4. The sample preparation kit according to claim 1, in, The salt has a vapor pressure of at least 250 Pa at 160°C.

5. The sample preparation kit according to claim 1, in, The affinity reagent may bind to the surface of whole cells.

6. The sample preparation kit according to claim 5, in, The stabilizing solution induces a sufficiently low osmotic pressure on the membrane of whole cells bound to the affinity reagent to avoid osmotic lysis of the whole cells.

7. The sample preparation kit according to claim 1, in, The stabilizing solution has a pH between 6-8.

8. The sample preparation kit according to claim 1, in, The metal binding moiety comprises a polymer attached to the affinity agent and comprising at least one metal binding pendant group comprising at least one metal atom.

9. The sample preparation kit according to claim 1, in, The element-labeled affinity reagent includes a first affinity reagent labeled with a first element tag and a second affinity reagent labeled with a second element tag, wherein the second element tag is distinguishable from the first element tag by elemental analysis.

10. The sample preparation kit according to claim 1, in, The stabilizing solution does not contain carbon or does not contain metals having an atomic mass unit greater than 80.

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