Nano-C isotope analysis device

Abstract

The utility model belongs to earth and planet chemical instrument equipment, and discloses a Nano-C isotope analysis device which comprises an element analysis system, a carbon dioxide freezing enrichment system and an isotope mass spectrometry system, the carbon dioxide freezing enrichment system comprises a six-way valve, the six-way valve is communicated with a first freezing assembly and a second freezing assembly, and the second freezing assembly is communicated with the isotope mass spectrometry system; the first freezing assembly comprises a first freezing container, and a first cold trap communicating with the six-way valve is arranged in the first freezing container in a liftable mode. The second freezing assembly comprises a second freezing container, and a second cold trap communicating with the six-way valve is arranged in the second freezing container in a liftable mode. The carbon isotope analyzer is simple and compact in mechanism, convenient to use, capable of analyzing carbon elements in different forms and accurately measuring isotope composition of carbon in different forms at the nanomole level, capable of enriching and purifying a sample to be detected for multiple times, capable of reducing analysis errors and capable of improving measurement sensitivity and precision.

Description

Technical Field

[0001] The utility model belongs to the technical field of earth and planetary chemical instruments and equipment, and in particular relates to a Nano-C isotope analysis device. Background Art

[0002] Carbon is not only one of the most abundant elements on Earth, but also an important element in the composition and evolution of carbon-based life on Earth. Plate subduction provides a driving force for the cycle of carbon in the Earth's interior and on the surface (Dasguptaetal, 2004; Wang et al, 2014; Plank & Manning, 2019), and this carbon cycle has a huge impact on the Earth's climate and the habitability of the surface (Mason et al, 2017). The use of carbon isotopes in natural geological samples can not only trace the source of materials in the carbon cycle, but also trace the specific geological effects in the carbon cycle (Zheng et al. 2000; Galvez et al, 2013; Wang et al, 2014; Zhao et al, 2016; Plank & Manning, 2019). Therefore, accurately determining the carbon isotope composition in natural geological samples is of great scientific significance for studying carbon in the Earth's interior and the global carbon cycle.

[0003] Carbon exists in various forms in natural geological samples, mainly in carbonate and non-carbonate forms; carbonate forms include compounds composed of carbonate and bicarbonate with different cations; non-carbonate forms are mainly elemental carbon (graphite, diamond, etc.). The difference in carbon isotope composition can be used to effectively distinguish the source of carbon, for example, organic carbon (such as graphite, δ 13 C average value - 25‰) and inorganic carbon (such as marine carbonate, δ 13 C average value -0‰). There are two main types of carbon isotope analysis methods for different types of carbon. For carbonate carbon isotope analysis, the acid dissolution method is mainly used (McCrea, 1950; Brenna et al, 1997; Révész & Landwehr, 2002; Paul & Skrzypek, 2006); for non-carbonate carbon isotope analysis, the combustion method is mainly used (Fuex & Bake, 1973; Werner et al, 1999; Zheng et al, 2000; Skrzypek & Paul, 2006).

[0004] The advantages and disadvantages of various analytical methods for different forms of carbon in minerals are as follows:

[0005] McCrea phosphoric acid method is a classic analytical method, which belongs to the acid dissolution method and is suitable for the analysis of constant pure carbonate. This method belongs to the offline analytical method (McCrea, 1950); its advantage is that the analysis result has high accuracy and is applicable to different types of carbonates. However, its disadvantage is that since it is an offline analytical method, it needs to use an isotope gas mass spectrometer for dual-path sampling analysis, and has high requirements for sample volume, generally requiring the sample volume to be higher than 10 mg;

[0006] The Gasbench-MS method also belongs to the acid dissolution method, which mainly uses the online continuous flow analysis method (continuous flow mode, Gasbench-CF-IRMS, abbreviated as Gasbench-MS) of the Gasbench device connected to the isotope gas mass spectrometer (Brenna et al, 1997; Révész & Landwehr, 2002; Paul & Skrzypek, 2006), which is suitable for the analysis of small sample amounts of carbonate; compared with the traditional phosphoric acid method, its advantages are higher accuracy of the analysis results, less sample volume required, and accurate analysis of the isotopic composition of carbon at the micromolar level (Révész & Landwehr, 2002; Paul & Skrzypek, 2006; Zha et al, 2010); not only pure carbonates can be analyzed, but also trace carbonates in silicates can be analyzed (Zha et al, 2010, 2018); however, the disadvantage of this method is that it cannot accurately measure samples with lower carbon content, such as nanomolar carbon;

[0007] The EA-MS method belongs to the combustion oxidation method, which is mainly an online continuous flow analysis method that connects the combustion elemental analyzer with the isotope gas mass spectrometer (Brenna et al., 1997; Werner et al., 1999); this method was mainly used for the analysis of carbon isotopes in organic samples in the early stage, and was also used for the analysis of carbon isotope composition in natural geological samples (Zheng et al., 2000; Skrzypek & Paul, 2006; Zha et al., 2018); the advantage of this method is that it can not only analyze non-carbonate carbon (such as graphite) in geological samples, but also analyze carbonate carbon (Skrzypek & Paul, 2006; Zha et al., 2018); it can accurately determine the isotopic composition of carbon at the micromolar level (Skrzypek & Paul, 2006; Zha et al., 2018); but the disadvantage of this method is that it cannot accurately determine carbon at the nanomolar level (Zha et al., 2018).

[0008] There are two trends in the development of isotope geochemistry and planetary chemistry analysis technology, namely "trace" and "micro-area". "Trace" means that the content of the analyzed object in the sample is lower than the detection limit of the instrument, so it cannot be accurately measured; "micro-area" refers to the direct in-situ analysis of the sample (such as ion probe, etc.). For the isotope analysis of different types of carbon in natural samples, there is also a "trace" technical bottleneck. For example, Zha et al. (2018) found that when the Gasbench-MS method was used to analyze the carbon isotope composition of trace carbonates in silicates, when the amount of carbonate was less than 30 micrograms, the accuracy and precision of the analysis results were relatively poor; when the EA-MS method was used to analyze the isotope composition of non-carbonate carbon in silicates, if the carbon content in the sample was less than 500 ppm, even if the sample weight was optimized, the analysis results were still very unsatisfactory.

[0009] Therefore, the present application designs a Nano-C isotope analysis device to solve the above technical problems. Utility Model Content

[0010] In order to solve the above technical problems, the utility model proposes a Nano-C isotope analysis device to achieve accurate determination of the isotope composition of different forms of carbon in Earth and extraterrestrial samples at the nanomolar level.

[0011] To achieve the above object, the utility model provides a Nano-C isotope analysis device, comprising an element analysis system, a carbon dioxide freezing enrichment system and an isotope mass spectrometry analysis system connected in sequence;

[0012] The carbon dioxide freezing enrichment system comprises a six-way valve connected to the element analysis system, the six-way valve is connected to a first freezing assembly and a second freezing assembly which are independently arranged, and a second port of the second freezing assembly is connected to the isotope mass spectrometry analysis system;

[0013] The first freezing assembly comprises a first freezing container containing a freezing liquid, wherein a first cold trap connected to the six-way valve is arranged in the first freezing container so as to be liftable;

[0014] The second freezing assembly comprises a second freezing container filled with freezing liquid, and a second cold trap connected to the six-way valve is arranged in the second freezing container in a liftable manner.

[0015] Preferably, the elemental analysis system includes an elemental analyzer, which is provided with a reaction tube for converting the carbon element in the raw material to be tested into gaseous carbon dioxide. The second port of the reaction tube is connected to the six-way valve through a ventilation line, and the ventilation line is provided with a first gas supply device for supplying high-speed carrier gas.

[0016] Preferably, a chemical trap is provided on the ventilation pipeline, and the chemical trap is provided between the element analyzer and the six-way valve, the first port of the chemical trap is connected to the second port of the reaction tube, and the second port of the chemical trap is connected to the six-way valve.

[0017] Preferably, two independently arranged branch pipes are provided on the ventilation pipeline, and a first valve and a second valve are provided on the two branch pipes respectively. The first valve is connected to an exhaust device for exhausting the carrier gas, and the second valve is connected to a second gas supply device for supplying auxiliary carrier gas.

[0018] Preferably, when the first cold trap is located below the freezing liquid level in the first freezing container to perform the first freezing of carbon dioxide gas, the second cold trap is separated from the second freezing container, the ventilation line is connected to the first port of the first cold trap through the six-way valve, and the second port of the first cold trap is connected to the exhaust pipe arranged on the six-way valve through the six-way valve.

[0019] Preferably, when the first cold trap is located in the first freezing container to perform the first freezing of carbon dioxide gas, the first port of the second cold trap is connected to a third gas supply device through the six-way valve, and the second port of the second cold trap is connected to the isotope mass spectrometry analysis system.

[0020] Preferably, when the second cold trap is below the freezing liquid level in the second freezing container to perform a second freezing of the carbon dioxide gas, the first cold trap is separated from the first freezing container to ensure that the frozen and enriched carbon dioxide in the first cold trap can be completely frozen and enriched in the second cold trap, and the ventilation pipeline is connected to the exhaust pipe after passing through the six-way valve; the third gas supply device is connected to the second port of the first cold trap through the six-way valve, and the first port of the second cold trap is connected to the first port of the second cold trap through the six-way valve.

[0021] Preferably, when the first cold trap is separated from the first freezing container and the second cold trap is separated from the second freezing container, after the frozen enriched carbon dioxide in the second cold trap is gasified, the low-speed carrier gas provided by the third gas supply device enters the isotope mass spectrometry analysis system.

[0022] Preferably, the isotope mass spectrometry analysis system comprises a four-way valve connected to the second port of the second cold trap, and the second cold trap is connected to the isotope gas mass spectrometer through the four-way valve.

[0023] Preferably, the isotope gas mass spectrometer is connected to the second port of the chemical trap through the four-way valve and directly connected to the element analyzer to achieve constant analysis.

[0024] Compared with the prior art, the utility model has the following advantages and technical effects: the utility model discloses a Nano-C isotope analysis device, which is used to solve the technical bottleneck of isotope analysis of extremely trace carbon and realize the accurate determination of the isotope composition of nanomolar carbon; after the sample to be detected is placed in the element analysis system, the internal mixed air is emptied to reduce the analysis of the detection result by the carbon element in the air; then the carbon element in the sample to be detected is converted into carbon dioxide that can be detected; the generated carbon dioxide enters the carbon dioxide freezing and enrichment system to completely freeze and enrich the carbon dioxide, thereby improving the sensitivity of the isotope mass spectrometry analysis system to the isotope mass spectrometry analysis of carbon dioxide; the first freezing component and the second freezing component work separately to realize the secondary enrichment and purification of the carbon dioxide in the generated gas, thereby avoiding the analysis result caused by the escape of carbon dioxide. Inaccurate, improve the lower limit of analysis, and achieve nanomolar carbon isotope analysis; when carbon dioxide is frozen and purified for the first time, the first freezing component is in working condition, the first cold trap is immersed in the low-temperature freezing liquid in the first freezing container, the mixed gas containing carbon dioxide is frozen in the first cold trap, and the remaining carrier gas is discharged from the six-way valve; when carbon dioxide is frozen and enriched for the second time, the first cold trap is taken out of the low-temperature freezing liquid, and the second freezing liquid is immersed in the low-temperature freezing liquid in the second freezing container. The frozen and liquefied carbon dioxide in the first cold trap is heated and gasified and passes through the six-way valve to enter the second cold trap under a low-flow carrier gas, and is frozen and enriched again to improve the analysis sensitivity; the secondary freezing enrichment can mainly use the low-flow carrier gas after the second freezing to improve the sensitivity of mass spectrometry analysis, and realize the accurate determination of the isotopic composition of different forms of carbon at the nanomolar level in earth and extraterrestrial samples.

[0025] The utility model has a simple and compact structure and is easy to use, and can analyze carbon elements in different forms, thereby realizing accurate determination of isotopic compositions of carbon in different forms at the nanomolar level. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0027] Figure 1 This is a schematic diagram of the structure of the Nano-C isotope analysis device of the utility model;

[0028] Figure 2 This is a schematic diagram of the state of the carbon dioxide freezing and enrichment system of the utility model during the first freezing and separation;

[0029] Figure 3 This is a schematic diagram of the state of the carbon dioxide freezing and enrichment system of the utility model during the second freezing and separation;

[0030] Figure 4 It is a state schematic diagram of the carbon dioxide discharge process of the carbon dioxide freezing and enrichment system of the utility model;

[0031] Figure 5 The calibration and linearity diagram of the Nano-C isotope analysis device of the utility model;

[0032] Figure 6 This is the accuracy analysis diagram of the Nano-C isotope analysis device of the utility model;

[0033] In the figure: 1. Element analysis system; 2. Carbon dioxide freezing enrichment system; 3. Isotope mass spectrometry analysis system; 4. Bypass pipe; 11. Element analyzer; 12. Reaction tube; 13. Chemical trap; 14. Vacuum injector; 15. Vacuum tube; 16. First gas supply pipe; 21. Six-way valve; 22. First freezing container; 23. First cold trap; 24. Second freezing container; 25. Second cold trap; 26. Ventilation pipeline; 27. First gas supply device; 28. Branch pipe; 29, first valve; 210, second valve; 211, emptying device; 212, second gas supply device; 213, first connecting pipe; 214, second connecting pipe; 215, third connecting pipe; 216, fourth connecting pipe; 217, fifth connecting pipe; 218, emptying pipe; 219, third gas supply device; 31, four-way valve; 32, interface device; 33, isotope gas mass spectrometer; 34, sixth connecting pipe; 35, seventh connecting pipe. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0036] Reference Figure 1-Figure 6 As shown, this embodiment provides a Nano-C isotope analysis device, comprising an element analysis system 1, a carbon dioxide freezing enrichment system 2 and an isotope mass spectrometry analysis system 3 which are connected in sequence;

[0037] The carbon dioxide freezing enrichment system 2 includes a six-way valve 21 connected to the element analysis system 1, the six-way valve 21 is connected to a first freezing assembly and a second freezing assembly which are independently arranged, and the second port of the second freezing assembly is connected to the isotope mass spectrometry analysis system 3;

[0038] The first freezing assembly includes a first freezing container 22 containing a freezing liquid, and a first cold trap 23 connected to the six-way valve 21 is arranged in the first freezing container 22 in a liftable manner;

[0039] The second freezing assembly includes a second freezing container 24 containing freezing liquid. A second cold trap 25 connected to the six-way valve 21 is arranged in the second freezing container 24 so as to be liftable.

[0040] The utility model discloses a Nano-C isotope analysis device, which is used to solve the technical bottleneck of isotope analysis of extremely trace carbon and realize the accurate determination of the isotope composition of nanomolar carbon; after the sample to be detected is placed in the element analysis system 1, the mixed air inside is emptied to reduce the analysis of the detection result by the carbon element in the air; then the carbon element in the sample to be detected is converted into carbon dioxide that can be detected; the generated carbon dioxide enters the carbon dioxide freezing enrichment system 2 to completely freeze and enrich the carbon dioxide, which is convenient for isotope mass spectrometry analysis of the carbon dioxide through the isotope mass spectrometry analysis system 3; the first freezing component and the second freezing component work separately to realize the secondary freezing enrichment of the carbon dioxide in the generated gas and improve the analysis sensitivity; when the carbon dioxide is frozen and purified for the first time , the first freezing assembly is in working state, the first cold trap 23 is immersed in the low-temperature freezing liquid in the first freezing container 22, the mixed gas containing carbon dioxide is frozen and liquefied in the first cold trap 23, and the remaining carrier gas is discharged from the six-way valve 21; during the second freezing and purification of carbon dioxide, the first cold trap 23 is taken out from the low-temperature freezing liquid, and the second freezing liquid is immersed in the low-temperature freezing liquid in the second freezing container 24. The frozen and liquefied carbon dioxide in the first cold trap 23 is heated and gasified and enters the second cold trap 25 through the six-way valve 21 under the low-flow carrier gas, and is frozen and enriched again; at the same time, after the secondary freezing and purification, the flow rate of the carrier gas can be adjusted in this process, which is convenient for the mass spectrometry analysis under the low-flow carrier gas in the later stage, and the isotopic composition of different forms of carbon in the earth and extraterrestrial samples at the nanomolar level can be accurately determined. The utility model has a simple and compact structure, is easy to use, can analyze carbon elements in different forms, and can accurately determine the isotopic composition of different forms of carbon at the nanomolar level.

[0041] Furthermore, the cryogenic freezing liquid is liquid nitrogen, dry ice, etc. The cryogenic freezing liquid in this embodiment is liquid nitrogen, which can provide a cryogenic freezing temperature of -196°C.

[0042] A further optimized solution is provided on the ventilation pipeline 26 with a chemical trap 13, which is arranged between the elemental analyzer 11 and the six-way valve 21, the first port of the chemical trap 13 is connected to the second port of the reaction tube 12, and the second port of the chemical trap 13 is connected to the six-way valve 21; two independently arranged branch pipes 28 are provided on the ventilation pipeline 26, and the two branch pipes 28 are respectively provided with a first valve 29 and a second valve 210, the first valve 29 is connected to an exhaust device 211 for carrier gas exhaust, and the second valve 210 is connected to a second gas supply device 212 for supplying auxiliary carrier gas. The reaction tube 12 is arranged in the elemental analyzer 11, and the carbon element in the raw material to be tested is converted into carbon dioxide, and the generated carbon dioxide is input into the six-way valve 21 through the ventilation pipe 26; the first gas supply pipe 16 is used to flush high-speed carrier gas into the device to facilitate the movement of the generated carbon dioxide gas; the function of the chemical trap 13 is to process the gas generated by the reaction tube 12, remove the moisture in the mixed gas, and prevent the moisture in the subsequent low-temperature freezing purification process from affecting the subsequent separation; the first gas supply device 27 provides the system with a high-flow carrier gas through the first gas supply pipe 16; the second gas supply device 212 is used to provide auxiliary carrier gas, and the exhaust device 211 can be set to automatically exhaust to realize automatic exhaust of the system.

[0043] Furthermore, the carrier gas of this embodiment is helium He, whose liquefaction temperature is much lower than the freezing temperature of carbon dioxide. During the cryogenic purification, the helium will not liquefy, thus preventing the carbon dioxide from being affected.

[0044] Furthermore, the flow rate of the high-speed carrier gas in this embodiment is 40-100 ml / min.

[0045] Furthermore, the reaction time and temperature of the sample to be processed need to be calibrated using nanomolar isotope standard substances to determine the appropriate reaction conditions to ensure that the carbon element is completely converted into carbon dioxide. If the sample contains two different types of carbon, carbonate carbon and non-carbonate carbon, nanomolar isotope standard substances can be used to determine the optimal reaction temperature and time for the different types of carbon, respectively, to ensure that the two different types of carbon can be converted into carbon dioxide in steps to achieve the purpose of differentiation.

[0046] Furthermore, the element analysis system 1 of the present embodiment further comprises a vacuum sample injector 14 for placing the sample, and the vacuum sample injector 14 is connected to a vacuum tube 15 for evacuating the vacuum and a first gas supply tube 16 for introducing a high-speed carrier gas.

[0047] Furthermore, when in use, the weighed sample is placed in the vacuum sampler 14, and then the sample in the vacuum sampler 14 is vacuumed and purged with He gas alternately, each vacuuming and purging with He gas lasts for 30 seconds, and the process is alternated 5-10 times to remove the interference of carbon in the air on the sample.

[0048] Further optimizing the scheme, two independently arranged branch pipes 28 are arranged on the ventilation pipeline 26, and the two branch pipes 28 are respectively provided with a first valve 29 and a second valve 210, the first valve 29 is connected to an emptying device 211, and the second valve 210 is connected to a second gas supply device 212 for supplying auxiliary carrier gas. The second gas supply device 212 is used to provide auxiliary carrier gas.

[0049] Furthermore, the auxiliary carrier gas in this embodiment is also helium He.

[0050] Further optimization scheme, when the first cold trap 23 is located in the first freezing container 22 to freeze the carbon dioxide gas for the first time, the second cold trap 25 is separated from the second freezing container 24, the ventilation pipeline 26 is connected to the first port of the first cold trap 23 through the six-way valve 21, and the second port of the first cold trap 23 is connected to the emptying pipe 218 arranged on the six-way valve 21 through the six-way valve 21; when the first cold trap 23 is located in the first freezing container 22 to freeze the carbon dioxide gas for the first time, the first port of the second cold trap 25 is connected to the third gas supply device 219 through the six-way valve 21, and the second port of the second cold trap 25 is connected to the isotope mass spectrometry analysis system 3. The carbon dioxide mixed gas after dehydration by the chemical trap 13 enters the six-way valve 21, and the six-way valve 21 passes the mixed gas into the first cold trap 23 immersed in the low-temperature freezing liquid through the first connecting pipe 213, and the carbon dioxide in the mixed gas is frozen by liquid nitrogen. At this time, the outlet of the first cold trap 23 is connected to the emptying pipe 218 through the second connecting pipe 214 through the six-way valve 21 to ensure the circulation of the carrier gas.

[0051] To further optimize the solution, when the second cold trap 25 is in the second freezing container 24 to perform a second freezing of the carbon dioxide gas, the first cold trap 23 is separated from the first freezing container 22, and the ventilation line 26 is connected to the exhaust pipe 218 after passing through the six-way valve 21; the third air supply device 219 is connected to the second port of the first cold trap 23 through the six-way valve 21, and the first port of the second cold trap 25 is connected to the first port of the second cold trap 25 through the six-way valve 21. When the carbon dioxide is subjected to secondary freezing, the first cold trap 23 is taken out of the low-temperature freezing liquid, and the second cold trap 25 is immersed in the low-temperature freezing liquid; at the same time, the connection relationship of the six-way valve 21 is rotated so that the ventilation pipeline 26 and the exhaust pipe 218 are directly discharged, and the third gas supply device 219 is connected to the six-way valve 21 through the fourth connecting pipe 216 to provide a low-speed carrier gas. The low-speed carrier gas passes through the six-way valve 21 and enters the second port of the first cold trap 23 through the third connecting pipe 215, driving the re-gasified carbon dioxide in the first cold trap 23 to enter the six-way valve 21 through the first connecting pipe 213, and then enters the second cold trap 25 through the fourth connecting pipe 216, and the mixed gas is again cryogenically frozen and enriched; the low-speed carrier gas drives the gasified carbon dioxide to completely enter the second cold trap 25 for freezing and enrichment.

[0052] Furthermore, the flow rate of the low-speed carrier gas in this embodiment is 2-10 ml / min.

[0053] Further optimization scheme, when the first cold trap 23 is separated from the first freezing container 22 and the second cold trap 25 is separated from the second freezing container 24, the carbon dioxide in the second cold trap 25 is gasified and enters the isotope mass spectrometry analysis system 3 under the low flow rate carrier gas; the isotope mass spectrometry analysis system 3 includes a four-way valve 31 connected to the second port of the second cold trap 25, and the second cold trap 25 is connected to the isotope gas mass spectrometer 33 through the four-way valve 31. When performing mass spectrometry analysis, the second cold trap 25 is taken out of the freezing liquid, and the second cold trap 25 is heated to 150°C to completely release the carbon dioxide; then the re-gasified carbon dioxide passes through the fifth connecting pipe 217 four-way valve 31 under the low flow rate carrier gas, and then passes through the four-way valve 31 through the sixth connecting pipe 34 into the interface device 32, and the carbon dioxide is passed into the isotope gas mass spectrometer 33 through the interface device 32, which is convenient for isotope mass spectrometry analysis.

[0054] In a further optimized solution, the isotope gas mass spectrometer 33 is connected to the second port of the chemical trap 13 through the four-way valve 31. In order to improve the practicality of the device, the bypass pipe 4 provided in the present embodiment connects the chemical trap 13 with the four-way valve 31, and then the mixed gas is passed into the interface device 32 through the seventh connecting pipe 35, so as to realize conventional carbon element detection.

[0055] Directions:

[0056] The weighed sample is placed in the vacuum sampler 14, and the sample in the vacuum sampler 14 is subjected to alternate vacuuming and helium purging. Each vacuuming and helium purging lasts for 30 seconds, and the alternating treatment is repeated 5-10 times, which can basically remove the interference of carbon in the air on the sample.

[0057] The processed sample falls into the reaction tube 12 of the elemental analyzer 11, and high-purity oxygen is introduced. At this time, the carrier gas is a carbon element in a high flow rate mode of 40-100 ml / min. The setting of the reaction time and temperature needs to be calibrated using nanomolar isotope standard substances to determine the appropriate reaction conditions to ensure that the carbon element is completely converted into carbon dioxide. If the sample contains two different types of carbon, carbonate carbon and non-carbonate carbon, the nanomolar isotope standard substances can be used to determine the optimal reaction temperature and time for different types of carbon, respectively, to ensure that the two different types of carbon can be converted into carbon dioxide in steps to achieve the purpose of differentiation.

[0058] While the carbon is being oxidized and burned in the reaction tube 12, the six-way valve 21 is set to Figure 2 As shown, the first cold trap 23 is lowered into liquid nitrogen to freeze the carbon dioxide generated by the reaction at -196°C, and at this time, a high-flow helium carrier gas is used. When the reaction is completed and the first cold trap 23 is completely frozen, the first cold trap 23 is raised, and the six-way valve 21 is set to Figure 3 In the state shown, the second cold trap 25 is lowered into liquid nitrogen at the same time, and sufficient time is set to completely freeze the frozen carbon dioxide in the first cold trap 23 into the second cold trap 25. At this time, the helium carrier gas is used at a low flow rate of 2-10ml / min. After the freezing is completed, the second cold trap 25 is lifted and heated to 150°C to ensure that the frozen carbon dioxide is completely released.

[0059] exist Figure 4 In this state, in the low flow rate 2-10 ml / min carbon element helium carrier gas mode, the carbon dioxide sample gas released from the second cold trap 25 is completely introduced into the isotope gas mass spectrometer 33 for carbon isotope analysis. Specific example:

[0060] Three international standard materials of carbon isotopes were selected to verify the method of the utility model. The three materials are IAEA-CO-1 carbonate, δ13C = 2.48‰, USGS24 graphite, δ13C = -15.99‰ and Merck carbonate, δ13C = -35.58‰. Figure 5 As shown in Figure 2, the linearity of the analysis results is very good when the carbon isotope composition is between -40‰ and +10‰. Figure 6As shown in the figure, when the sample weight of carbonate is between 10 nanomoles and 120 nanomoles, the accuracy of carbon isotope analysis is ±0.11‰-±0.22‰, which has a very good analysis accuracy. Therefore, the utility model solves the technical bottleneck of "trace" carbon isotope analysis and successfully realizes the accurate determination of nanomolar carbon isotopes.

[0061] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0062] The embodiments described above are only descriptions of the preferred methods of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A Nano-C isotope analysis device, characterized in that: It comprises an element analysis system (1), a carbon dioxide freezing enrichment system (2) and an isotope mass spectrometry analysis system (3) which are connected in sequence; The carbon dioxide freezing enrichment system (2) comprises a six-way valve (21) connected to the element analysis system (1), the six-way valve (21) being connected to a first freezing assembly and a second freezing assembly which are independently arranged, and a second port of the second freezing assembly being connected to the isotope mass spectrometry analysis system (3); The first freezing assembly comprises a first freezing container (22) containing a freezing liquid, wherein a first cold trap (23) connected to the six-way valve (21) is arranged in the first freezing container (22) so as to be movable upward and downward; The second freezing assembly comprises a second freezing container (24) containing freezing liquid, and a second cold trap (25) connected to the six-way valve (21) is arranged in the second freezing container (24) in a liftable manner.

2. The Nano-C isotope analysis device according to claim 1, characterized in that: The elemental analysis system (1) comprises an elemental analyzer (11), wherein the elemental analyzer (11) is provided with a reaction tube (12) for converting carbon elements in a raw material to be tested into gaseous carbon dioxide, wherein a second port of the reaction tube (12) is connected to the six-way valve (21) via a ventilation line (26), and a first gas supply device (27) for supplying a high-speed carrier gas is provided on the ventilation line (26).

3. The Nano-C isotope analysis device according to claim 2, characterized in that: A chemical trap (13) is provided on the ventilation pipeline (26); the chemical trap (13) is provided between the element analyzer (11) and the six-way valve (21); a first port of the chemical trap (13) is connected to a second port of the reaction tube (12); and a second port of the chemical trap (13) is connected to the six-way valve (21).

4. The Nano-C isotope analysis device according to claim 2, characterized in that: The ventilation pipeline (26) is provided with two independently arranged branch pipes (28), and the two branch pipes (28) are respectively provided with a first valve (29) and a second valve (210), the first valve (29) is connected to an exhaust device (211) for exhausting the carrier gas, and the second valve (210) is connected to a second gas supply device (212) for supplying auxiliary carrier gas.

5. The Nano-C isotope analysis device according to claim 3, characterized in that: When the first cold trap (23) is located below the freezing liquid level in the first freezing container (22) to perform the first freezing of the carbon dioxide gas, the second cold trap (25) is separated from the second freezing container (24), and the ventilation pipeline (26) is connected to the first port of the first cold trap (23) through the six-way valve (21), and the second port of the first cold trap (23) is connected to the drain pipe (218) arranged on the six-way valve (21) through the six-way valve (21).

6. The Nano-C isotope analysis device according to claim 5, characterized in that: When the first cold trap (23) is located in the first freezing container (22) to perform a first freezing on the carbon dioxide gas, the first port of the second cold trap (25) is connected to a third gas supply device (219) via the six-way valve (21), and the second port of the second cold trap (25) is connected to the isotope mass spectrometry analysis system (3).

7. The Nano-C isotope analysis device according to claim 6, characterized in that: When the second cold trap (25) is below the freezing liquid level in the second freezing container (24) to perform a second freezing of the carbon dioxide gas, the first cold trap (23) is separated from the first freezing container (22) to ensure that the frozen and enriched carbon dioxide in the first cold trap (23) can be completely frozen and enriched in the second cold trap (25); the ventilation pipeline (26) is connected to the exhaust pipe (218) after passing through the six-way valve (21); the third air supply device (219) is connected to the second port of the first cold trap (23) through the six-way valve (21), and the first port of the second cold trap (25) is connected to the first port of the second cold trap (25) through the six-way valve (21).

8. The Nano-C isotope analysis device according to claim 7, characterized in that: When the first cold trap (23) is separated from the first freezing container (22) and the second cold trap (25) is separated from the second freezing container (24), the frozen enriched carbon dioxide in the second cold trap (25) is gasified, and the low-speed carrier gas provided by the third gas supply device (219) enters the isotope mass spectrometry analysis system (3).

9. The Nano-C isotope analysis device according to claim 8, characterized in that: The isotope mass spectrometry analysis system (3) comprises a four-way valve (31) connected to the second port of the second cold trap (25); the second cold trap (25) is connected to an isotope gas mass spectrometer (33) via the four-way valve (31).

10. The Nano-C isotope analysis device according to claim 9, characterized in that: The isotope gas mass spectrometer (33) is communicated with the second port of the chemical trap (13) through the four-way valve (31) and is directly connected to the element analyzer (11) to achieve constant analysis.

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