Inert non-adsorbing coiled capillary and device for regulating gas flow in isotope ratio analysis

Abstract

A gas delivery system comprising a capillary for delivering a sample and / or reference gas from a gas source; a first connector for connecting the capillary to the gas source; a second connector for connecting the capillary to the analytical instrument; a crimping device adapted to receive the capillary and adjust the flow of gas into the analytical instrument by crimping the capillary, characterised in that the internal surface of the capillary comprises a coating material to prevent or minimise water adsorption to the surface. Also provided is a device for adjusting the flow of gas in a gas inlet system of an analytical instrument comprising a body member having an internal gas flow passage, and a clamping member for attachment to the body member such that when the clamping member is fastened to the body member, the internal gas flow passage is crimped in an adjustable and reversible manner to adjust the flow of gas therethrough.

Description

[0001] Divisional application

[0002] This application is a divisional application of the invention patent application filed on February 28, 2019, with national application number 201910150653.0, entitled "Inert non-adsorbable coilable capillary tube for isotope ratio analysis and device for regulating gas flow". Technical Field

[0003] This invention relates to gas transport systems for isotope ratio analysis, and more particularly, but not exclusively, to isotope ratio analysis of molecules having more than one rare isotope. The invention also relates to a device for regulating the flow rate in a gas transport system, said device using a capillary tube that cannot be regulated by conventional means. Background Technology

[0004] Isotope ratio analysis is a method used to determine the relative abundance of isotopes, for example, in a gas sample containing CO2. For instance, isotope ratio analysis can be used to determine the isotopic ratio of carbon and oxygen, for example... 13 C / 12 C and / or 18 O / 16 O. Isotope ratio analysis is most commonly performed using spectroscopy and mass spectrometry.

[0005] Precise and accurate isotope ratio measurements often provide the only way to gain deep insights into scientific questions that no other analytical technique can answer.

[0006] By measuring clumped isotopes, that is, determining the presence of more than one rare isotope (e.g., 13 C 18 O 16 The molecules of substances containing O present a particular challenge. For such substances that exist in low abundance, the balance with interfering molecules will alter the isotopic abundance of the analyte isotopes.

[0007] Gas inlet systems for isotope ratio analysis are known in the art, particularly for mass spectrometers. A general review of isotope ratio mass spectrometry and gas inlet systems is provided in Brenna et al., Mass Spectrometry Reviews, 1997, 16: 227-258.

[0008] The determination of the isotope ratio of a sample typically requires a comparative measurement of the isotope ratios of the sample gas and one or more reference gases using known isotope ratios. Therefore, known types of gas inlet systems used for isotope ratio analysis include dual-inlet systems, which consist of a sample gas inlet and a reference gas inlet entering the analyzer.

[0009] The isotope ratio analyzers used in this type of measurement include mass spectrometers or spectrometers. Typically, the sample and reference gas are supplied to these spectrometers from a sample reservoir via a thin capillary. The sample reservoir comprises an adjustable high-vacuum bellows and a small, fixed-size volume.

[0010] To obtain accurate results, sample and reference gases with known isotopic ratios are typically measured one after the other. Advantageously, if the sample quantity allows, sample and reference gases are usually measured alternately. The isotopic ratio of the sample gas is determined by comparing the isotopic abundances of the two different gases. All currently used isotopic ratio analyzers exhibit significant nonlinearity, meaning the measured isotopic ratio varies with absolute signal intensity. To avoid nonlinear bias, the sample and reference must be measured at the same intensity. A common method is to match the sample and reference intensities by adjusting the gas flow rates through the individual capillaries. This is particularly relevant to the long integration intervals used in low-abundance measurements, where the intensities of the sample and reference show a significant decrease during the measurement process.

[0011] In principle, the matching of sample and reference intensities can be achieved in the following ways:

[0012] a) Opening or closing (at least partially) the capillary orifice at a single point.

[0013] b) Precisely adjust the length of the narrow-diameter capillary tube

[0014] c) If possible, readjust the pressure on the capillary reservoir side during measurement.

[0015] Option a) is generally preferred because it allows for online adjustment of the gas flow rate, i.e., simultaneous measurement of signal intensity. Furthermore, closing the inner diameter causes the molecular gas to flow downstream in a coiled manner, while the gas in the upstream portion remains under viscous conditions. This prevents any back-diffusion of gas molecules relative to the gas flow direction, which would otherwise cause fractionation of the analyte gas, i.e., the temporal separation of heavy and light isotopes (WA Brand, Mass Spectrometer Hardware for Analyzing Stable Isotopes, in: Handbook of Stable Isotope Technology, Volume I, Elsevier, 2004).

[0016] Technically, the capillary pore is closed or narrowed by placing a coil at or near the end of the capillary closest to the spectrometer. This coil compresses the capillary, thereby reducing its inner diameter.

[0017] The deviation between the measured abundance of agglomerates and the arithmetic expectation is of particular interest in science (e.g., the measured abundance of agglomerates). 13C 18 O 16 The abundance of O and its relationship with CO2 13 C and 18 The abundance of O is calculated as a bias (the deviation in abundance). Since this bias reflects a non-equilibrium distribution, it can be reset by exchange processes (hybridization) on the surface. A common observation is the exchange of oxygen atoms with CO2 on the surface of commonly used stainless steel capillary tubes, as capillaries made of this material attract water molecules to their surface.

[0018] To avoid contamination, stainless steel capillaries must be heated and kept under vacuum for extended periods (up to several months) before sample measurements can begin. Alternatively, deactivated molten silica capillaries can be used for agglomerated isotope measurements. These capillaries do not draw water onto their surfaces. However, it is not possible to reduce the inner diameter of molten silica capillaries by coiling them.

[0019] In dual-inlet mass spectrometry (MS), there are typically two reservoirs or bellows for introducing the sample gas and reference gas separately into the mass spectrometer. Before introducing the sample and / or reference gas, the bellows are evacuated using a vacuum pump.

[0020] A gas (e.g., CO2) is then applied into the bellows, for example from a canister or other suitable gas source. During the measurement, the gas is allowed to flow from the bellows through a capillary into the ion source of the MS.

[0021] Typically, one bellows contains the sample gas and the second bellows contains the reference gas. To obtain accurate results, the two gases must be measured one after the other or alternately.

[0022] Alternatively, the sample CO2 gas can be generated from a solid sample in the preparation system, such as from Thermo Fisher Scientific. TM The Kiel IV carbonate apparatus is used. Here, carbonate samples such as CaCO3 are treated with phosphoric acid, which causes the release of CO2. Before the released CO2 gas is transported to the ion source through a capillary, two cryogenic cold traps are used to remove water and other contaminants. Summary of the Invention

[0023] This invention addresses how to facilitate accurate measurement of isotope ratios, particularly in the analysis of agglomerated isotopes, by providing a system and apparatus that allows control of gas flow and prevention or reduction of isotope contamination. To this end, the invention provides a gas transport system comprising: at least one coilable capillary for transporting a sample and / or reference gas to a mass spectrometer; and a coiling device for regulating the gas flow to the instrument by coiling the coilable capillary. The inner surface of the capillary is inert relative to any possible isotope contamination, particularly inert to the adsorption of at least water (i.e., the surface does not adsorb or substantially adsorbs water), and preferably sufficiently free of other contaminants, such as metal ions, which could cause changes in the isotopic composition of the sample gas passing through the capillary, i.e., could cause isotope contamination. Desiredly, the inner surface of the capillary is substantially free of contaminants that could cause isotope contamination, such as metal ions. In this way, the measured isotope ratio exhibits reduced isotope mixing effects (compared to isotope ratios measured using capillaries without inert inner surfaces or coatings), and preferably is substantially free of isotope mixing effects. Therefore, the present invention eliminates the need for extended heating of the coilable capillary, while providing precise online regulation of the gas flow rate through the narrow capillary orifice.

[0024] Another aspect of the present invention provides an apparatus for regulating the gas flow rate in a gas inlet system of a mass spectrometer, the apparatus comprising a main body member having an internal airflow channel having an inlet and an outlet adapted to receive a capillary via an airtight connector for receiving and releasing gas, the main body member being further adapted to receive a clamping member at a position on the side of the internal airflow channel, and a clamping member for reversibly attaching to the main body member.

[0025] The signal intensity obtained by measuring the gas in a mass spectrometer depends on the gas flow rate, and therefore on the pressure within the gas source and the diameter of the capillary from which the gas source is introduced into the mass spectrometer. The gas flow rate can be adjusted by controllably compressing or depressurizing the bellows, and thus the signal intensity. However, it is not possible to adjust the gas flow rate very precisely simply by compressing the bellows.

[0026] The above features and other details of the invention are further described in the following examples, which are intended to further illustrate the invention but are not intended to limit its scope in any way.

[0027] This invention describes a gas transport system for transporting gas to a mass spectrometer for isotope ratio analysis, particularly for isotope analysis, wherein the gas transport system includes unmixed measurements of agglomerated isotopes. The system comprises at least one coilable capillary for delivering sample and / or reference gas from at least one gas source to the mass spectrometer; at least one first connector for connecting the at least one capillary to at least one gas source; at least one second connector for connecting the at least one capillary to the mass spectrometer; and at least one coiling device adapted to receive the at least one capillary and to regulate the gas flow rate into the mass spectrometer by coiling the at least one capillary, wherein the inner surface of the coilable capillary comprises a coating material to prevent or minimize the adsorption of water to the surface. The coating material should preferably also be sufficiently free of other contaminants that can cause changes in the isotopic composition of the sample gas passing through the capillary, such as, but not limited to, metal ions.

[0028] Both the first and second connectors can be, independently, any range of conventional connectors known to a person skilled in the art. In some embodiments, the first and / or second connectors include compression fittings, such as Swagelok. TM Accessories.

[0029] As described above, the term reference gas herein refers to a gas containing a substance having a known isotopic composition. This substance may be, but is not limited to, carbon dioxide, carbon monoxide, nitrogen, nitrogen oxides (e.g., N₂O or NOx), hydrogen, or oxygen. In some embodiments, the substance may constitute a minor component (<50 vol%), a fundamental component (e.g., the largest component), and preferably a major component (e.g., >50 vol%), and even more preferably, the sole component of the reference gas.

[0030] The gas source can be a gas cylinder, a gas bellows, a syringe, or other suitable gas storage device. The gas source can have an adjustable volume for the contained gas, such as a bellows or a syringe. The sample gas and reference gas can be provided by the same type of gas source (e.g., a bellows), or they can be provided by different types of gas sources. For example, the sample gas can be provided by a sample preparation device. Such a device generates the sample gas in situ, i.e., through internal sample gas generation. An exemplary sample preparation device is from Thermo Fisher Scientific. TM The Kiel IV carbonate apparatus.

[0031] The coiling device is suitably and preferably adapted to adjust the inner diameter of the capillary by coiling the capillary, thereby regulating the gas flow rate through the capillary and into the mass spectrometer. With this arrangement, the cross-sectional area at the coiling point can be reduced, for example, by at least about 10%, or at least about 20%, or at least about 30%, or at least about 40%, or at least about 50%, or at least about 60%, or at least about 70%, for example, at least about 75%, or at least about 80%, or at least about 90%, or at least about 95%, or more, for example, at least about 97%, or at least about 98%, or at least about 99%.

[0032] In this document, the term "coil" shall be understood to mean the compression or folding of an article, such as a tube, capillary, or channel. Therefore, a "coil device" is a device that functions to compress and / or bend a tube, capillary, or channel. Due to compression or bending, the inner orifice of the tube and / or channel narrows, causing a restriction on the flow rate of fluid through the tube or channel.

[0033] In this document, the term "rollable" should be understood to mean that the structure referred to by the term is flexible, deformable, and / or bendable. For example, in this document, a rollable wall should be understood to mean a method of creating a wall when forces are applied to it, i.e., the wall is bendable, deformable, and / or flexible in response to external forces applied to it.

[0034] In some embodiments, the coilable capillary is a stainless steel, metal, or alloy capillary with the aforementioned coating material coated on its inner surface to prevent or minimize water adsorption to the surface. In some embodiments, the coating is, but is not limited to, a silica-based or silicon-based coating, and in some embodiments, it is deposited on the inner surface by chemical vapor deposition (CVD).

[0035] Depending on the preferred system and / or sample, in some embodiments, the system of the present invention comprises two capillaries for respectively delivering a sample gas and a reference gas into the analytical apparatus. In such embodiments, one, but preferably both, capillaries are arranged with a coiling device as described herein, and one or both capillaries may suitably be constructed of the aforementioned material and have an internal coating as described above. In some embodiments, at least one capillary for delivering a reference gas from at least one reference gas source is received in a coiling device for coiling through the apparatus.

[0036] The gas transport system of the present invention can be suitably used with an isotope ratio mass spectrometer. One or more capillaries of the system are suitably arranged to transport gas to the ion source of the mass spectrometer. Therefore, a second connector in this embodiment can connect one or more capillaries to the ion source.

[0037] In one embodiment of the gas transport system of the present invention, the coiling device includes a first main component and a second main component, the first and second main components being configured to detachably engage with each other. The first main component may have a groove for accommodating a capillary, and the second main component houses a coiling member configured such that, when the components are attached to each other, the coiling member is adjustablely pressed into the capillary, thereby adjustingly coiling the capillary and reducing the cross-sectional area at the coiling point compared to the non-coiled state, thus reducing the gas flow rate through the first main component.

[0038] The first and second body components can be suitably configured to mate with each other using one or more fasteners. For example, the fasteners can be one or more screws or bolts. That is, the first and second body components can be assembled by bolting together or screwing together. Thus, the first and second body components may each have one or more aligned holes to receive corresponding fastening bolts or screws. When using one or more screws, at least one, preferably one or more of the holes in the first and second body components can be threaded or fastened with nuts. In one embodiment, one or more mating screws are used to receive one or more threaded screws by having one or more threaded holes in the first body component and corresponding one or more threaded holes in the second body component to align with one or more threaded holes in the first body component. Thus, one or more fasteners on the first and second body components are forcefully fastened together, thereby coiling the capillary located on the first body component. In an alternative embodiment of fastening the first and second body components together, the first body component may have one or more holes, and the second body component may have one or more corresponding holes for alignment with one or more holes in the first body component, whereby one or more bolts can be arranged through the aligned one or more holes, and bolts are used to fasten the first and second body components together, thereby coiling the capillary located on the first body component.

[0039] The present invention also provides an apparatus for regulating the gas flow rate in the inlet system of a mass spectrometer, the apparatus being advantageously used with a glass capillary or other non-coilable capillary. The apparatus comprises a main body member having an internal airflow channel having an inlet and an outlet for receiving and releasing gas, respectively. The main body member is adapted to receive a clamping member at a location on the side of the internal airflow channel on a coilable portion of the wall of the internal airflow channel, the wall forming part of the main body member and defining the airflow channel and the location for receiving the clamping member. The clamping member of the apparatus is configured to reversibly attach to the main body member at the location, the clamping member comprising at least one coiled portion arranged such that when the clamping member is attached to the main body member, the coiled portion engages with the coilable portion of the wall of the internal airflow channel. The curled portion is adapted such that when the clamping member is attached to the main member and a force is applied to it perpendicular to the internal airflow channel, the curlable portion of the wall of the internal airflow channel is forced inward at the contact point between the curled portion and the wall, thereby reducing the cross-sectional area of ​​the channel at that location, and thus reducing the gas flow rate through the internal airflow channel compared to the non-curled airflow channel.

[0040] In this device, the rollable portion of the wall and the engagement between the rollable portion and the clamping member preferably make the roll reversible. This allows the wall to bend inward elastically, and the clamping member is configured not to cause irreversible bending or other deformation of the wall. In some embodiments, the rollable portion of the wall has a thickness in the range of about 0.5 mm or about 0.75 mm, about 2 mm or about 1.5 mm or about 1.25 mm, for example, about 0.5 mm, about 0.8 mm, or about 1 mm. In one embodiment, the clamping member includes at least two holes for receiving mating clamping screws or bolts, and the body member includes aligned holes for receiving the same screws or bolts, such that when tightened, the screws or bolts press the clamping member into the body member, thereby generating a force on the rollable portion of the wall, causing a reduction in the gas flow through the internal airflow channel. When screws are used, at least the holes in the body member or the clamping member, preferably both, are threaded to receive the screws, or nuts are used to tighten the screws.

[0041] The coiling device is suitably and preferably adapted to adjust the inner diameter of the airflow channel by coiling the wall, which is preferably reversible, thereby regulating the gas flow rate through the airflow channel and into the mass spectrometer. With this arrangement, the cross-sectional area at the coiling point can be reduced, for example, by at least about 10%, at least about 20%, at least about 30%, at least about 40%, at least about 50%, at least about 60%, or at least about 70%, for example, at least about 75%, at least about 80%, at least about 90%, at least about 95%, or at least about 98%.

[0042] In some embodiments, the device may include at least one groove for receiving a curled portion of a clamping member, but is not limited to any particular external shape. This groove is adapted such that at least a portion of the body containing the groove can be deformed by the curled member, the portion comprising a contact point between an airflow passage and the aforementioned curlable portion of the defining wall between the location.

[0043] In some embodiments, the curled portion may include at least a partially cylindrical structure, such as a semi-cylindrical structure, configured such that when attached to the body member, at least the partially cylindrical structure is substantially perpendicular to the internal airflow channel. The cylindrical structure may include a cylindrical or partially cylindrical surface having a radius of curvature, for example, but not limited to, in the range of about 0.5 mm, about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 8 mm, about 6 mm, or about 5 mm, for example, 0.5 to 8 mm, 2-6 mm, or from 3-6 mm, for example, about 2 mm, about 3 mm, about 4 mm, or about 5 mm. The cylindrical structure may be mounted on a plate, thus the cylindrical structure and the plate constitute a clamping member adapted to be clamped to the body by at least two clamping screws.

[0044] One advantage of the present invention is that the internal airflow channel can be configured with a narrow diameter, for example, but not limited to, an inner diameter in the range of about 100 μm, or about 150 μm, or about 200 μm, or about 250 μm, or about 300 μm, to about 800 μm, or about 600 μm, or about 500 μm, or about 400 μm, for example, an inner diameter in the range of 100-800 μm, or 200-600 μm, or 200-500 μm, or 200-400 μm, for example, an inner diameter in the range of about 250 μm, or about 300 μm, or about 350 μm, or about 400 μm. The above ranges refer to the diameter of the flow channel before curling. In some embodiments, the internal airflow channel includes a portion having a diameter narrower than the rest of the channel; in such embodiments, the narrower portion preferably has a diameter within the above ranges and values. Consequently, the narrower portion is preferably located near the curlable portion of the wall of the internal airflow channel, and the curlable portion of the clamping member is adapted to curl the internal airflow channel within the narrower portion. The wider portion may have an inner diameter of about 300 μm, about 400 μm, or about 500 μm, to about 2 mm, or to about 1.5 mm, or to about 1 mm, or to about 800 μm, for example, 300 μm to 2 mm, 500 μm to 2 mm, 300 μm to 1.5 mm, 500 μm to 1.5 mm, 300 μm to 1 mm, or 500 μm to 1 mm.

[0045] In one embodiment of the device, the main body component includes an elongated body, such as, but not limited to, an elongated cylindrical body with an internal airflow channel, the elongated body also including the aforementioned groove and a receiving plate extending radially from the elongated body and located on the side of the groove. The receiving plate in this configuration includes a threaded receiving hole for receiving a clamping screw, such that when the clamping member is mounted on the main body component, the curled portion is located in the groove, and force is applied to the airflow channel by tightening the clamping screw.

[0046] As can be seen from the description of the device above, the inlet is preferably adapted to receive the capillary via an airtight connector, such as, but not limited to, a connector containing a silver ferrule, which can be further connected by a nut, etc. In some embodiments of the device, the inner diameter of the narrower portion of the internal airflow channel is narrower than the outer diameter of the capillary, so that the capillary does not extend into the narrower portion of the airflow channel and therefore does not curl when the airflow channel is forced inward. This configuration can be easily connected to a suitable connector as described.

[0047] The device described herein can be used with non-coilable capillaries, such as, but not limited to, glass capillaries, including capillaries comprising ceramics, silica, and / or other glasses. The capillary should preferably contain at least on its inner surface a material that substantially does not adsorb water onto the surface, or may be made entirely of a material that substantially does not adsorb water onto the surface. The device itself may be made of, but is not limited to, metals or metal alloys, and is preferably made of stainless steel.

[0048] The present invention also provides the use of the above-described apparatus for isotope ratio analysis of gases from a sample. The gas to be analyzed may be from a gaseous sample or from a solid and / or liquid sample, for example, as further described in the detailed description below. Therefore, the use of the apparatus according to the invention is suitable for isotope ratio analysis using an isotope ratio mass spectrometer, for example, but not limited to, isotope ratio analysis of gases selected from carbon dioxide, carbon monoxide, hydrogen, nitrogen, nitrogen oxides (such as N2O or NOx), and sulfur dioxide.

[0049] The present invention also provides a method for isotope ratio analysis of gas samples, comprising: transmitting a sample gas through a capillary tube into an isotope mass spectrometer and performing a first isotope measurement; providing at least one reference gas and transmitting at least one reference gas through a capillary tube into the isotope mass spectrometer and performing a second isotope measurement, wherein the gas flow rate entering the isotope mass spectrometer is adjusted by coiling at least one capillary tube, and by the first and / or second isotope measurements, to obtain substantially equal gas flow rates during the isotope measurements. Preferably, the coiling is used to adjust at least the reference gas flow rate, and optionally the sample and reference gas flow rates. The capillary tube in the method is preferably a stainless steel, metal, or alloy capillary tube with a coating material on its inner surface to prevent or minimize the occurrence of water adsorption to the surface. Alternatively, in other embodiments, the capillary tube is a non-coilable capillary tube, preferably a water-non-adsorbent glass, silica, or ceramic capillary tube. In these embodiments of the method, the use of a non-coilable capillary tube, and the device described above, are suitable for adjusting the gas flow rate, preferably at least the reference gas flow rate. The method is applicable to isotope analysis of gases selected from carbon dioxide, carbon monoxide, hydrogen, nitrogen, nitrogen oxides (e.g., N₂O or NOx), and sulfur dioxide. The method can be used to analyze agglomerated isotopes, i.e., to determine the molecular fraction of a substance containing more than one rare isotope. The method can be used to transport and analyze small-volume samples with low absolute amounts of analyte relative to the inner surface of the sample transport capillary; therefore, it is important to transport the sample to the analyzer without any isotope exchange / mixing between the sample and interfering and / or reactive substances. In some embodiments, the method includes transporting the sample from a sample container selected from microtubes, adjustable gas bellows systems, and gas cylinders. Microtubes may be, for example, but not limited to, micro CaCO₃ decomposition tubes.

[0050] The present invention further provides a method for isotope ratio analysis of a gas sample, comprising: transferring a sample gas from at least one gas source having an adjustable volume through a first capillary to a mass spectrometer and performing a first isotope measurement; providing at least one reference gas from another storage device; transferring the at least one reference gas through a second capillary to the mass spectrometer and performing a second isotope measurement; wherein the gas flow rate entering the isotope analysis instrument is adjusted by means of a coiling device as described herein for the first and / or second isotope measurements to obtain substantially equal gas flow rates during the measurements of the reference gas and the sample gas. Attached Figure Description

[0051] Those skilled in the art will understand that the accompanying drawings described below are for illustrative purposes only. The drawings are not intended to limit the scope of the invention in any way.

[0052] Figure 1 A schematic diagram illustrating a dual-entry IRMS is shown.

[0053] Figure 2 A gas inlet system suitable for isotope ratio instruments is shown.

[0054] Figure 3 (a) shows a side view of the upper part of the coiling device for coiling capillaries, as further described herein; (b) shows a side view of the end.

[0055] Figure 4 A top view of the lower part of the winding device for winding capillaries is shown, as further described herein.

[0056] Figure 5(a) shows a cross-sectional view along the longitudinal axis of the device for regulating gas flow, which includes a main body component with an internal airflow channel and a coiled component. Figure 5(b) shows a top view of the device.

[0057] Figure 6 A three-dimensional cross-sectional view of the device in Figure 5(a) is shown.

[0058] Figure 7 The accompanying drawings show a top view (left) of the main component and a bottom view of the coiled component.

[0059] Figure 8 A view of the assembled device is shown. Detailed Implementation

[0060] In the following description, exemplary embodiments of the invention will be illustrated with reference to the accompanying drawings. These examples are provided to offer a further understanding of the invention without limiting its scope.

[0061] In the following description, a series of steps are described. Those skilled in the art will understand that, unless required by context, the order of the steps is not critical to the resulting configuration and its effects. Furthermore, it will be apparent to those skilled in the art that regardless of the order of the steps, there may or may not be time delays between some or all of the steps.

[0062] It should be understood that this invention is generally applicable to the elemental and isotopic analysis of liquid or gas samples using mass spectrometry. Therefore, the sample being analyzed in the system is typically variable.

[0063] This invention provides a gas inlet system for delivering gas into a mass spectrometer used for isotope ratio measurements. Specifically, this invention provides a solution to the practical problem of regulating the gas flow rate into an isotope ratio mass spectrometer, while simultaneously avoiding or reducing the introduction of artifacts that could affect isotope ratio determinations, such as due to isotope contamination.

[0064] Therefore, this invention is particularly suitable for measuring agglomerated isotopes, such as single molecules like... 13 C 18 O 16 Rare isotopes within O.

[0065] In dual-inlet isotope ratio mass spectrometry (dual-inlet IRMS), the gas flow rate entering the mass spectrometer alternates between the sample gas and the reference (or standard) gas, allowing for comparison of measurements of the two gases. The reference gas can be analyzed before or after the sample gas, or both (so-called bracketed measurements).

[0066] exist Figure 1 A schematic diagram illustrating a dual-inlet IRMS is shown. Sample gas and reference gas can be supplied via gas reservoirs or bellows 12, 13. Gas flow is from the sample bellows through capillaries 2, 2' and into the ion source 11 of the mass spectrometer.

[0067] Alternatively, or additionally, the sample gas can be provided via sample preparation system 9. In such a system, the sample gas is generated or prepared in situ for subsequent analysis in a mass spectrometer. The sample gas is transferred from sample preparation system 9 to ion source 11 via capillary 2". An exemplary sample preparation system is provided by Thermo Fisher Scientific. T The Kiel IV carbonate apparatus is provided. In this apparatus, calcium carbonate is digested using phosphoric acid, resulting in the release of carbon dioxide (CO2) gas. Water and other interfering substances are removed using a cryogenic cold trap before the CO2 gas is transferred to the mass spectrometer through capillary 2". Since this preparation apparatus is typically used with small sample volumes, the resulting sample gas volume can be very small, making it impractical to regulate the gas flow rate by adjusting the bellows. Therefore, the gas flow rate through each capillary must be regulated by coiling.

[0068] refer to Figure 2 The diagram illustrates a gas inlet system for use with a mass spectrometer for isotope ratio measurements, and in some embodiments, the gas inlet system can be configured as follows: Figure 1This is part of a dual-inlet system of the type shown. One end of the gas inlet system is connected to a gas source 14, which may be provided, for example, by a gas cylinder or gas bellows as a sample or reference gas source, or other sample gas source, such as the KielIV sample preparation system. At the other end, the gas inlet system is connected to the inlet 15 of a mass spectrometer for isotope ratio measurement, such as the inlet of a mass spectrometer ion source. The sample and / or reference gas flow rate passes through an internally coated, flexible capillary 2, which has an inner surface coated with a chemically inert or deactivating coating to prevent or reduce such isotope contamination that may be introduced due to water or other substances present on the capillary wall.

[0069] Preferred inert or deactivated surface coatings include: silicon or silicon-based coatings (specific examples include...) 1000 or Silcosteel coated capillaries and 2000 or or Coated capillaries; coatings deposited by chemical vapor deposition (CVD), including, for example, those mentioned. or Coatings such as coatings and coatings applied by thermal decomposition and functionalization of silanes (described in US6444326, incorporated herein by reference). Preferably, the inert or deactivated surface coating does not allow water to adsorb onto its surface or onto other substances that may cause contamination. A capillary made of metal (e.g., steel or nickel) and having an inert or deactivated inner coating is preferred. Such a capillary is flexible but inert on its inner surface.

[0070] The gas flow rate entering the mass spectrometer can be adjusted using a coiling device 20, which is located on the capillary near the spectrometer end of the capillary. The coiling device 20 has a first main body member in the form of a lower part 3 and a second main body member in the form of an upper part 4, and it can be used to coil the capillary 2 to adjust the gas flow rate through the capillary. The coiling of the capillary is adjusted by adjusting the force applied to the capillary by the screw 10 from the coiling device 20. The capillary 2 is located between the upper and lower parts and is held in place by a metal plate 5 having screws for securing the capillary to the coiling device 20 in the appropriate position.

[0071] Metal component 6 can be welded around the capillary and used as an electrical contact. After installation, the capillary can be heated by current from the metal component, the capillary, and the (grounded) mass spectrometer. This ensures complete removal of trace amounts of water remaining in the capillary, regardless of the coating. Furthermore, the capillary is sealed by a silicone tube 7, which provides protection for the capillary 2.

[0072] Metal cylinder 1 is welded to capillary tube 2 and used with connector 8 (e.g., Swagelok).TM (Accessories) Connect one end of the capillary to the mass spectrometer source and the other end to the sample source (e.g., a dual-inlet and / or Kiel IV device, not shown).

[0073] By applying force to a portion of the capillary 2 using the coiling device 20, the gas flow rate through the capillary is regulated by partially closing the capillary. The degree of closure of the capillary at the coiled portion is determined by the torque applied by the coiling device, thereby limiting the gas flow rate through the capillary.

[0074] exist Figure 3 In Figure (a), a side view of the upper portion 4 (second main component) of the coiling device 20 is shown. The upper portion 4 comprises a metal (e.g., steel) block 21 to which a coiling member in the form of a cylinder 22 is attached, and the metal block 21 provides a force to compress the capillary. In some embodiments, the cylinder 22 may be integrally formed as part of the block 21, taking the form of its cylindrical surface portion. When a force is applied to the capillary, the cylinder 22 is long enough to provide a uniform force on the capillary. The cylinder 22 may typically have a length of about 1 / 3 to about 1 / 2 the width of the metal block.

[0075] The upper part 4 also has two holes (in) Figure 3 (Represented by dashed lines), the clamping screw 10 is used to pass through the hole and enter the side of the cylinder 22. Figure 2 (Not shown in the image).

[0076] exist Figure 3 (b) shows an end side view that illustrates how the cylinder 22 is positioned in a shallow recess or groove in the metal block 21 to provide structural support for the cylinder when a force is applied to compress the capillary.

[0077] A top view of the lower part 3 of the curling device is shown below. Figure 4 As shown. The lower part 3 has two larger threaded holes 23 for receiving clamping screws 10. A smaller threaded hole 24 is also shown, which receives screws (not shown) from the fixing plate 5, which secures the capillary tube 2 in place. Along the lower part 3, there is also a groove 25 for securing the capillary tube 2 in place.

[0078] The upper part 4 clamps onto the lower part 3, causing the cylinder 22 to extend perpendicularly to the groove 25, within which the capillary 2 is located. When force is applied to the cylinder 22 by the clamping screw 10, the cylinder 22 causes the capillary to coil, thereby restricting the gas flow rate through the capillary. Therefore, it is possible to regulate the gas flow rate using a chemically inert capillary 2.

[0079] Turning to Figure 5(a), a cross-sectional view of a device 30 for regulating gas flow is shown. The device comprises a main body member 40 having an airflow channel therethrough, and the clamping member in the form of clamping the main body 39. A lower clamping member (not shown in this view) containing a threaded hole for receiving a clamping screw is attached to the main body 40, allowing the clamping member to be attached and secured to the main body. A capillary 31 is attached to the main body 40 of the coiling device 30 by means of a silver ferrule 33, which is fitted onto the capillary and received within the open end of the airflow channel, and a screw 32 is screwed into the internally threaded end of the open end of the airflow channel to secure the capillary 31 to the main body 40. The use of the ferrule allows for vacuum-tight connection of virtually any capillary material to the spectrometer and gas source. Within the device, there is an airflow channel having a narrow portion 34 and a wider diameter main portion 35. The gas flow enters the gas flow channel of the device through the attached capillary tube 31, and exits through its main part 35 after passing through the narrow section 34.

[0080] The inner diameter of the airflow channel in the wider portion is preferably <2 mm, and more preferably <1 mm (e.g., 500 μm to 1 mm). The airflow channel can be manufactured, for example, by eroding the metal of the body using a small forward-moving electrode. The narrow portion 34 preferably has a diameter in the range of 200-500 μm, for example, about 300 μm, about 350 μm, or about 400 μm.

[0081] A groove 41 is provided on the top of the body 40. Due to the groove 41, a wall 42 is formed defining the upper portion of the narrow section 34. The wall thickness is relatively small, for example, in the range of about 0.5 to 2 mm, or in the range of 0.5 to 1.5 mm, or in the range of 0.75 mm to 1.25 mm, for example, about 0.5 or about 1 mm, and as a result, the wall 42 can be deformed by applying an external force to the wall through clamping the body 39. Consequently, the narrow channel 34 can be curled by applying an external force to the wall 42.

[0082] A force is applied to the wall 42 via an upper clamping body 39, which has a body provided as a steel block 36 with two through-holes for inserting clamping screws 37. Only the screw heads of the screws 37 are shown in this cross-sectional view. The clamping screws 37 are screwed into threaded holes on the lower clamping body (not shown in this view). A cylinder 38 extends from the lower surface of the body 36 and is located at the top of the wall 42. By applying the force provided by the clamping screws 37, which are tightened vertically and downward on the channel 34, the channel 34 narrows, resulting in a reduction in the gas flow rate through the channel.

[0083] Turning to Figure 5(b), a top view of the device 30 is shown. In this view, one can see how the clamping screw 37 is arranged on the upper clamping body 39, the screw extending through the upper clamping body and screwed into a threaded hole (not shown in this view) in the lower clamping body, located on the side of the body 40.

[0084] Figure 5(a) shows a cross-sectional view of the device. Figure 6 The coiling device 30 has an upper part 39 and a lower part 45 for clamping bodies, the latter being attached to the main body 40. The upper and lower bodies 39 and 45 are arranged such that when the clamping screw 37 is tightened... Figure 6 When force is applied (not shown), the channel 34 narrows due to the torque applied to the wall 42 by the coiled portion in the form of a cylinder 38, and the clamping screw 37 extends through the hole 46 on the upper clamping body 39 and is screwed into the lower clamping body 45. The cylinder 38 is held in a groove or recess in the upper clamping body 39.

[0085] Figure 7 The device 30 is further shown. The lower clamping body 45 is attached to the body 40. If manufactured separately, the lower clamping body can be welded to the body to produce a single body 40, to which the upper clamping body 39 can be fastened.

[0086] Alternatively, the lower clamping body can be designed and manufactured separately from the body and retain its function in use, for example, if the body 40 rests on the lower clamping body 45, so as to provide structural support when the upper clamping body 39 is connected to the lower clamping body and force is applied to the body located between the two clamping bodies 39, 45.

[0087] The groove 41 in the main body 40 can be considered as a recess or channel entering another generally cylindrical main body. The upper clamping body 39 is attached to the main body, and clamping screws 37 are used to secure and fasten the upper clamping body 39 to the lower clamping body 45. Tightening the clamping screws causes a force perpendicular to the narrow channel direction to be applied within the main body, which in turn causes the cylinder 38 to be pressed into the wall 42. Due to the relatively small thickness of the wall 42, it has the elasticity to allow it to be pressed into the channel 34, thereby curling the channel 34 to restrict the gas flow through the channel. Therefore, the wall around the flow channel is so thin that it can be compressed to narrow the channel.

[0088] Figure 8 The assembled device is shown, with the upper clamping body 39 located on the main body and secured by clamping screws 37. Additionally, a nut (Swagelok nut) 47 for securing the airtight connector to the analytical apparatus (e.g., a mass spectrometer) is shown on the assembly.

[0089] Before using the capillary for measurement, the torque can be adjusted by tightening the clamping screw 37. By doing so, the coiling of all capillaries present on the instrument is adjusted in such a way that, for a given gas pressure in the gas reservoir, the obtained instrument signal (e.g., detector voltage) is approximately the same. Alternatively, the coiling can be adjusted so that, for the same or different gas pressures, the decay of the instrument signal over time is the same for all capillaries. The latter is essential if gas enters the ion source from a finite reservoir (e.g., from a microtube). After adjustment, the coiling typically does not change again, and the capillary can be used for measurement. After measuring a sample gas, which may require continuous measurements for up to 10 minutes or more, a reference gas can be measured.

[0090] As shown in the figure, a capillary and coiling device can be used for sample and reference gas measurements. Alternatively, as in a dual-inlet isotope ratio mass spectrometer, separate capillary tubes and associated coiling devices can be provided for each of the sample gas and reference gas. Further alternatively, for example in another dual-inlet isotope ratio mass spectrometer, separate capillary tubes can be provided for each of the sample gas and reference gas, but only one capillary tube (typically the reference gas capillary) is equipped with a coiling device, thereby allowing the reference gas flow rate to pass through the capillary to match the measured sample gas flow rate.

[0091] exist Figures 5(a) to 8 In the illustrated embodiments, the coil is not placed on the capillary itself, but rather on a small airflow channel within the main body of the coiling device. Therefore, these embodiments of the coiling device can be considered capillary coiling adapters that can use non-coilable capillary tubes, such as glass, silica, or ceramic capillary tubes. Certain such non-coilable capillary tubes with chemically inert inner surfaces are advantageously used, for example, to avoid or reduce isotope mixing effects. The present invention enables the use of such capillary tubes while still allowing control of the gas flow rate through the capillary tube via the coiling mechanism.

[0092] The configuration allows the use of virtually any type of capillary, such as stainless steel capillary with an internal inert coating, for example... or Coatings, or deactivated molten silica capillaries, can be used to create variations that accept capillaries of different diameters.

[0093] In addition, the inner wall of the airflow channel, which constitutes a relatively small portion of the gas flow path inside the coiling device, can be deactivated by an inert coating.

[0094] In summary, the present invention provides many advantages, including:

[0095] a. Improve the accuracy of isotope ratio measurements, especially for agglomerated isotopes, for example, by allowing unmixed measurements of agglomerated isotope abundances;

[0096] b. Use deactivated capillaries to measure isotope ratios that may be affected by trace amounts of water (e.g., in CO2). 18 O / 16 O);

[0097] c. Use a capillary coiling adapter to allow adjustment of gas flow using capillaries that cannot be coiled due to material constraints (e.g., molten silica or capillaries with larger or smaller outer diameters).

[0098] d. Use rings (e.g., silver rings) to seal the capillary, which makes it possible to apply capillary tubes that cannot be welded to provide a hermetically tight connection (e.g., deactivated molten silica).

[0099] As used herein, including in the terms and claims, unless the context otherwise indicates, the singular form of a term should be understood to include the plural form as well, and vice versa. Therefore, it should be noted that, unless the context explicitly states otherwise, the singular forms “a / an” and “the” as used herein include multiple references.

[0100] Throughout the specification and claims, the terms “comprising,” “including,” “having,” and “containing,” and variations thereof, shall be understood to mean “including but not limited to,” and are not intended to exclude other components.

[0101] This invention also covers precise terms, features, values, and ranges, etc., in case these terms, features, values, and ranges are used in combination with terms such as about, around, generally, substantially, substantially, at least, etc. (i.e., "about 3" should also exactly cover 3 or "substantially constant" should also precisely cover).

[0102] The term "at least one" should be understood to mean "one or more," and therefore includes both embodiments comprising one or more components. Furthermore, the appended claims to the independent claim that use "at least one" to describe a feature have the same meaning when the feature is referred to as "the at least one."

[0103] It should be understood that variations can be made to the above embodiments of the present invention, but these variations still fall within the scope of the present invention. Unless otherwise stated, the features disclosed in this specification may be replaced by alternative features for the same, equivalent, or similar purposes. Therefore, unless otherwise stated, each disclosed feature represents an instance of a series of general equivalent or similar features.

[0104] The use of exemplary language, such as "for instance," "such as," "for example," etc., is merely for the purpose of better illustrating the invention and does not imply a limitation on the scope of the invention unless so required. Unless the context clearly indicates otherwise, any steps described in this specification may be performed sequentially or simultaneously.

[0105] Except for at least some mutually exclusive combinations of features and / or steps, all features and / or steps disclosed in the specification can be combined in any combination. In particular, preferred features of the invention are applicable to all aspects and can be used in any combination.

Claims

1. A gas transport system for transporting gas from at least one gas source to a mass spectrometer for isotope ratio analysis of unmixed measurements including agglomerated isotopes, said gas transport system comprising: At least one coilable capillary is used to deliver a sample and / or reference gas from the at least one gas source to the mass spectrometer; At least one first connector for connecting the at least one coilable capillary to the at least one gas source; At least one second connector for connecting the at least one capillary to the mass spectrometer. At least one coiling device is adapted to receive the at least one coilable capillary and to regulate the gas flow rate entering the mass spectrometer by coiling the at least one capillary. The inner surface of the coilable capillary is characterized as being inert to isotopic mixing, wherein the inner surface of the coilable capillary comprises a coating to prevent or minimize the occurrence of water adsorption onto the surface, and the coating is sufficiently free of contaminants that could cause isotopic mixing of agglomerated isotopes.

2. The gas transport system according to claim 1, wherein the coilable capillary is a metal or alloy capillary.

3. The gas transmission system according to claim 2, wherein the coilable capillary is a stainless steel capillary.

4. The gas transmission system according to any one of claims 1 to 3, wherein the coating on the inner surface of the capillary comprises at least one silicon-based coating.

5. The gas transport system according to any one of claims 1 to 3, wherein the coating is deposited on the inner surface by chemical vapor deposition (CVD).

6. The gas transmission system according to any one of claims 1 to 3, wherein the at least one gas source is a gas source having an adjustable volume.

7. The gas transport system according to any one of claims 1 to 3, comprising two coilable capillaries for respectively transporting sample gas and reference gas from two corresponding gas sources to the mass spectrometer.

8. The gas transport system according to any one of claims 1 to 3, wherein the coiling device comprises: i. A first main body component having at least one groove for accommodating at least one capillary tube; ii. A second main body member detachably attached to the first main body member, the second main body member housing a coiling member configured such that when the second main body member is attached to the first main body member, the coiling member is adjustablely pressed onto a capillary in the groove to coil the capillary and thereby reduce the gas flow rate through it.

9. A method for isotope ratio analysis of a gas from a sample containing agglomerated isotopes, comprising: - The gas from at least one gas source is transferred through a first capillary to a mass spectrometer for a first isotope measurement. - At least one reference gas is provided by another storage device. - The at least one reference gas is transmitted to the mass spectrometer through a second capillary for a second isotope measurement. For the first and / or second isotope measurements, the gas flow rate entering the isotope analyzer is adjusted by coiling the capillary to obtain substantially equal gas flow rates during the measurement of the reference gas and the gas from the sample. The first capillary and / or the second capillary are coilable capillary tubes, which are inert to isotopic mixing, and the inner surface of the coilable capillary tube contains a coating to prevent or minimize water adsorption onto the surface, and the coating is sufficiently free of contaminants that could cause isotopic mixing of agglomerated isotopes.

10. The method of claim 9, wherein the coilable capillary is a metal or alloy capillary.

11. The method of claim 10, wherein the coilable capillary is a stainless steel capillary.

12. The method according to any one of claims 9 to 11, wherein the gas flow rate entering the analytical instrument is achieved by the apparatus according to claim 8.

13. The method according to any one of claims 9 to 11, wherein the at least one gas source is a gas source having an adjustable volume.

14. The method according to any one of claims 9 to 11, wherein the gas is selected from carbon monoxide, carbon dioxide, hydrogen, nitrogen, nitrogen oxides and sulfur dioxide.

15. The method according to any one of claims 9 to 11, wherein the gas source is selected from microtubes, adjustable gas bellows systems, syringes, and gas cylinders.

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