Nano-c isotope analysis device

Abstract

The present invention belongs to earth and planetary chemical instrument apparatuses. Disclosed is a Nano-C isotope analysis device, comprising an element analysis system, a carbon dioxide freezing-enrichment system and an isotope mass-spectrometric analysis system, wherein the carbon dioxide freezing-enrichment system comprises a six-way valve, the six-way valve is in communication with a first freezing assembly and a second freezing assembly, and the second freezing assembly is in communication with the isotope mass-spectrometric analysis system; the first freezing assembly comprises a first freezing container, and a first cold trap in communication with the six-way valve is liftably provided in the first freezing container; and the second freezing assembly comprises a second freezing container, and a second cold trap in communication with the six-way valve is liftably provided in the second freezing container. The present invention has a simple and compact structure, is convenient to use, can analyze carbon elements present in different forms, can accurately determine the isotope composition of carbon in different forms at the nanomolar level, and can perform multiple instances of enrichment and purification on a sample to be tested, thereby reducing analysis errors, and improving measurement sensitivity and precision.

Description

A Nano-C Isotope Analysis Device Technical Field

[0001] This invention belongs to the field of earth and planetary chemistry instrumentation technology, and particularly relates to a Nano-C isotope analysis device. Background Technology

[0002] Carbon is not only one of the most abundant elements on Earth, but also a crucial element in the composition and evolution of carbon-based life. Plate subduction provides the driving force for the carbon cycle within the Earth and on its surface (Dasguptae et al., 2004; Wang et al., 2014; Plank & Manning, 2019), and this carbon cycle has a significant impact on Earth's climate and surface habitability (Masone et al., 2017). Utilizing carbon isotopes in natural geological samples can not only trace the source of materials in the carbon cycle but also the specific geological processes involved (Zheng et al., 2000; Galveze et al., 2013; Wang et al., 2014; Zhao et al., 2016; Plank & Manning, 2019). Therefore, accurately determining the carbon isotopic composition of natural geological samples is of great scientific significance for studying carbon within the Earth and the global carbon cycle.

[0003] Carbon exists in various forms in natural geological samples, mainly divided into carbonate and non-carbonate forms. Carbonate forms include compounds composed of carbonate and bicarbonate ions with different cations; non-carbonate forms are primarily elemental carbon (graphite, diamond, etc.). Differences in carbon isotope composition can effectively distinguish the source of carbon, for example, distinguishing organic carbon (such as graphite, δ¹⁸O₂). 13 C average value -- 25‰) and inorganic carbon (such as marine carbonates, δ 13 The average C value is -0‰. Methods for carbon isotope analysis of different types of carbon are mainly divided into two categories: acid dissolution method (McCrea, 1950; Brenna et al., 1997; Révész & Landwehr, 2002; Paul & Skrzypek, 2006) is mainly used for the analysis of non-carbonate carbon isotopes; and combustion method (Fuex & Bake, 1973; Werner et al., 1999; Zheng et al., 2000; Skrzypek & Paul, 2006) is mainly used for the analysis of non-carbonate carbon isotopes.

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

[0005] The McCrea phosphoric acid method is a classic analytical method, belonging to the acid dissolution method, and is suitable for the analysis of large quantities of pure carbonates. This method is an offline analytical method (McCrea, 1950). Its advantages are high accuracy of analytical results and applicability to different types of carbonates. However, its disadvantages are that, as an offline analytical method, it requires dual-channel sample introduction analysis using an isotope gas mass spectrometer, and it requires a relatively large sample volume, generally higher than 10 mg.

[0006] Gasbench-MS is also an acid-dissolution method, mainly utilizing an online continuous flow analysis method (Gasbench-CF-IRMS, abbreviated as Gasbench-MS) connected to an isotope gas mass spectrometer (Brenna et al., 1997; Révész & Landwehr, 2002; Paul & Skrzypek, 2006). It is suitable for the analysis of small sample amounts of carbonates. Compared with the traditional phosphoric acid method, its advantages are higher analytical precision and a smaller sample volume required. It can accurately analyze the isotopic composition of carbon at the micromolar level (Révész & Landwehr, 2002; Paul & Skrzypek, 2006; Zha et al., 2010). It can analyze not only pure carbonates but also trace amounts of carbonates in silicates (Zha et al., 2010, 2018). However, the limitation of this method is that it cannot accurately determine samples with even lower carbon content, such as nanomolar levels of carbon.

[0007] EA-MS is a combustion oxidation method, primarily utilizing an online continuous flow analysis method that connects a combustion elemental analyzer with an isotope gas mass spectrometer (Brenna et al., 1997; Werner et al., 1999). This method was initially applied mainly to the analysis of carbon isotopes in organic samples, and has also been used to analyze the carbon isotope composition of natural geological samples (Zheng et al., 2000; Skrzypek & Paul, 200). 6; Zha et al., 2018); The advantage of this method is that it can analyze not only non-carbonate carbon (such as graphite) in geological samples, but also 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); However, the disadvantage of this method is that it cannot accurately determine carbon at the nanomolar level (Zha et al., 2018).

[0008] The current development of isotope geochemistry and planetary chemistry analysis techniques follows two trends: "trace amounts" and "micro-regions." "Trace amounts" refers to samples where the content of the analyte is below the instrument's detection limit, making accurate determination impossible. "Micro-regions" refers to direct in-situ analysis of the sample (e.g., using ion probes). For isotope analysis of different types of carbon in natural samples, the "trace amount" technique also presents a bottleneck. For example, Zha et al. (2018) found that when using Gasbench-MS to analyze the carbon isotope composition of trace carbonates in silicates, the accuracy and precision of the analysis results were poor when the carbonate content was below 30 micrograms. Similarly, when using EA-MS to analyze the isotope composition of non-carbonate carbon in silicates, if the carbon content in the sample was below 500 ppm, even with optimized sample weighing, the analytical results remained far from ideal.

[0009] Therefore, this application designs a Nano-C isotope analysis device to solve the above-mentioned technical problems.

[0010] Summary of the Invention

[0011] To address the aforementioned technical problems, this invention proposes a Nano-C isotope analysis device that enables accurate determination of the isotopic composition of carbon in different forms at the nanomolar level in samples from Earth and extraterrestrial sources.

[0012] To achieve the above objectives, the present invention provides a Nano-C isotope analysis device, comprising an elemental analysis system, a carbon dioxide cryogenic enrichment system, and an isotope mass spectrometry analysis system connected in sequence.

[0013] The carbon dioxide cryogenic enrichment system includes a six-way valve connected to the elemental analysis system. The six-way valve is connected to an independently configured first cryogenic component and a second cryogenic component. The second port of the second cryogenic component is connected to the isotope mass spectrometry analysis system.

[0014] The first refrigeration assembly includes a first refrigeration container filled with refrigerant, and a first cold trap connected to the six-way valve is vertically and vertically disposed inside the first refrigeration container.

[0015] The second refrigeration component includes a second refrigeration container filled with refrigerant, and a second cold trap connected to the six-way valve is vertically and retractably installed inside the second refrigeration container.

[0016] Preferably, the elemental analysis system includes an elemental analyzer, which is equipped with a reaction tube for converting carbon 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 gas pipeline, and the gas pipeline is equipped with a first gas supply device for supplying high-speed carrier gas.

[0017] Preferably, a chemical trap is provided on the venting line, the chemical trap is located between the elemental 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.

[0018] Preferably, the ventilation pipeline is provided with two independently configured branch pipes, and the two branch pipes are respectively provided with a first valve and a second valve. The first valve is connected to an exhaust device for venting the carrier gas, and the second valve is connected to a second gas supply device for supplying auxiliary carrier gas.

[0019] 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 venting pipe 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 venting pipe provided on the six-way valve through the six-way valve.

[0020] 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.

[0021] Preferably, when the second cold trap is below the freezing liquid level in the second freezing container to perform a second freezing of carbon dioxide gas, the first cold trap is separated from the first freezing container to ensure that the carbon dioxide frozen and enriched in the first cold trap can be completely frozen and enriched in the second cold trap. The venting pipe is connected to the venting 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.

[0022] 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, the carbon dioxide enriched by freezing in the second cold trap is vaporized and then enters the isotope mass spectrometry analysis system by the low-speed carrier gas provided by the third gas supply device.

[0023] Preferably, the isotope mass spectrometry analysis system includes a four-way valve connected to the second port of the second cold trap, and the second cold trap is connected to an isotope gas mass spectrometer through the four-way valve.

[0024] Preferably, the isotope gas mass spectrometer is connected to the second port of the chemical trap via the four-way valve, and is directly connected to the elemental analyzer to achieve constant analysis.

[0025] Compared with existing technologies, this invention has the following advantages and technical effects: This invention discloses a Nano-C isotope analysis device to solve the technical bottleneck of isotope analysis of trace amounts of carbon, achieving accurate determination of the isotopic composition of nanomolar carbon; after placing the sample to be tested into the elemental analysis system, the mixed air inside is purged to reduce the influence of airborne carbon on the analysis results; then, the carbon in the sample to be tested is converted into detectable carbon dioxide; the generated carbon dioxide enters the carbon dioxide cryogenic enrichment system for complete cryogenic enrichment, improving the sensitivity of the isotope mass spectrometry analysis system for carbon dioxide isotope mass spectrometry analysis; the first and second cryogenic components operate separately to achieve secondary enrichment and purification of carbon dioxide in the generated gas, avoiding inaccurate analysis results caused by carbon dioxide escape. This method improves the analytical limit and enables nanomolar-level carbon isotope analysis. During the first cryogenic purification of carbon dioxide, the first cryogenic component is in operation, and the first cold trap is immersed in the cryogenic liquid in the first cryogenic container. The mixed gas containing carbon dioxide is frozen in the first cold trap, while the remaining carrier gas is discharged through the six-way valve. During the second cryogenic enrichment of carbon dioxide, the first cold trap is removed from the cryogenic liquid, and the second cryogenic liquid is immersed in the cryogenic liquid in the second cryogenic container. The carbon dioxide liquefied in the first cold trap is heated and vaporized, then passes through the six-way valve and enters the second cold trap under low-flow-rate carrier gas for another cryogenic enrichment, thus improving analytical sensitivity. The secondary cryogenic enrichment mainly utilizes the low-flow-rate carrier gas after the second cryogenic process to improve the sensitivity of mass spectrometry analysis, enabling accurate determination of the isotopic composition of different forms of carbon in samples from Earth and extraterrestrial sources at the nanomolar level.

[0026] The invention has a simple and compact structure, is easy to use, and can analyze carbon in different forms, achieving accurate determination of the isotopic composition of carbon in different forms at the nanomolar level. Attached Figure Description

[0027] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0028] Figure 1 is a schematic diagram of the Nano-C isotope analysis device of the present invention;

[0029] Figure 2 is a schematic diagram of the state during the first freezing separation of the carbon dioxide cryogenic enrichment system of the present invention;

[0030] Figure 3 is a schematic diagram of the state during the second freezing separation of the carbon dioxide cryogenic enrichment system of the present invention;

[0031] Figure 4 is a schematic diagram of the carbon dioxide discharge process of the carbon dioxide cryogenic enrichment system of the present invention.

[0032] Figure 5 shows the calibration and linearity graph of the Nano-C isotope analysis device of the present invention;

[0033] Figure 6 is a precision analysis diagram of the Nano-C isotope analysis device of the present invention;

[0034] In the diagram: 1. Elemental analysis system; 2. Carbon dioxide cryogenic enrichment system; 3. Isotope mass spectrometry analysis system; 4. Bypass tube; 11. Elemental analyzer; 12. Reaction tube; 13. Chemical trap; 14. Vacuum sampler; 15. Vacuum tube; 16. First gas supply line; 21. Six-way valve; 22. First cryogenic container; 23. First cold trap; 24. Second cryogenic container; 25. Second cold trap; 26. Ventilation line; 27. First gas supply device; 28. 29. Branch pipe; 210. First valve; 211. Second valve; 212. Vent device; 213. Second gas supply device; 214. First connecting pipe; 215. Second connecting pipe; 216. Third connecting pipe; 217. Fourth connecting pipe; 218. Fifth connecting pipe; 219. Vent pipe; 210. 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 Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] Referring to Figures 1-6, this embodiment provides a Nano-C isotope analysis device, including an elemental analysis system 1, a carbon dioxide cryogenic enrichment system 2, and an isotope mass spectrometry analysis system 3 connected in sequence.

[0038] The carbon dioxide cryogenic enrichment system 2 includes a six-way valve 21 connected to the elemental analysis system 1. The six-way valve 21 is connected to an independently configured first cryogenic component and a second cryogenic component. The second port of the second cryogenic component is connected to the isotope mass spectrometry analysis system 3.

[0039] The first refrigeration component includes a first refrigeration container 22 containing refrigerant, and a first cold trap 23 connected to a six-way valve 21 is vertically and vertically disposed inside the first refrigeration container 22.

[0040] The second refrigeration assembly includes a second refrigeration container 24 containing refrigerant, and a second cold trap 25 connected to a six-way valve 21 is vertically and vertically disposed inside the second refrigeration container 24.

[0041] This invention discloses a Nano-C isotope analysis device to overcome the technical bottleneck of isotope analysis of trace amounts of carbon, achieving accurate determination of the isotopic composition of nanomolar carbon. After the sample to be tested is placed in the elemental analysis system 1, the mixed air inside is purged to reduce the influence of airborne carbon on the analysis results. Then, the carbon in the sample is converted into detectable carbon dioxide. The generated carbon dioxide enters the carbon dioxide cryogenic enrichment system 2 for complete cryogenic enrichment, facilitating isotope mass spectrometry analysis by the isotope mass spectrometry system 3. The first and second cryogenic components operate separately to achieve secondary cryogenic enrichment of carbon dioxide in the generated gas, improving analytical sensitivity. During the first cryogenic purification of carbon dioxide... The first freezing component is in operation. The first cold trap 23 is immersed in the cryogenic liquid within the first freezing container 22. The mixed gas containing carbon dioxide is liquefied in the first cold trap 23, while the remaining carrier gas is discharged through the six-way valve 21. During the second freezing purification of carbon dioxide, the first cold trap 23 is removed from the cryogenic liquid, and the second cryogenic liquid is immersed in the cryogenic liquid within the second freezing container 24. The carbon dioxide liquefied in the first cold trap 23 is heated and vaporized, then enters the second cold trap 25 through the six-way valve 21 under low-flow carrier gas conditions for further freezing and enrichment. Simultaneously, the secondary freezing purification process allows for adjustment of the carrier gas flow rate, facilitating subsequent mass spectrometry analysis under low-flow carrier gas conditions, enabling accurate determination of the isotopic composition of different forms of carbon at the nanomolar level in samples from Earth and extraterrestrial environments. This invention features a simple and compact mechanism, is easy to use, and can analyze carbon in different forms, achieving accurate determination of the isotopic composition of different forms of carbon at the nanomolar level.

[0042] Furthermore, the cryogenic fluid is liquid nitrogen, dry ice, etc. In this embodiment, the cryogenic fluid is liquid nitrogen, which can provide a cryogenic freezing temperature of -196°C.

[0043] Further optimizing the scheme, a chemical trap 13 is installed on the ventilation pipeline 26. The chemical trap 13 is located 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 configured branch pipes 28 are provided on the ventilation pipeline 26. A first valve 29 and a second valve 210 are respectively installed on the two branch pipes 28. The first valve 29 is connected to an exhaust device 211 for venting the carrier gas, and the second valve 210 is connected to a second gas supply device 212 for supplying auxiliary carrier gas. The reaction tube 12 is installed inside the elemental analyzer 11, converting the carbon element in the raw material to be tested into carbon dioxide, and inputting the generated carbon dioxide into the six-way valve 21 through the gas pipeline 26; the first gas supply pipe 16 is used to inject high-speed carrier gas into the device to facilitate the movement of the generated carbon dioxide gas; the chemical trap 13 is used to treat the gas generated by the reaction tube 12, removing moisture from the mixed gas to prevent moisture from affecting the subsequent separation during the low-temperature cryogenic purification process; the first gas supply device 27 provides high-flow-rate carrier gas to the system 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 the gas to realize the automatic exhaust of the system.

[0044] Furthermore, in this embodiment, helium (He) is chosen as the carrier gas because its liquefaction temperature is much lower than that of carbon dioxide. During cryogenic purification, helium will not liquefy, thus preventing any impact on carbon dioxide.

[0045] Furthermore, in this embodiment, the flow rate of the high-speed carrier gas is 40-100 ml / min.

[0046] Furthermore, the reaction time and temperature of the sample to be processed need to be calibrated using nanomolar-level isotopic standards to determine suitable reaction conditions and ensure that carbon is completely converted into carbon dioxide. If the sample contains two different types of carbon, carbonate carbon and non-carbonate carbon, the optimal reaction temperature and time for each type of carbon can be determined using nanomolar-level isotopic standards to ensure that the two different types of carbon can be converted into carbon dioxide stepwise, thus achieving the purpose of differentiation.

[0047] Furthermore, the elemental analysis system 1 of this embodiment also includes a vacuum sampler 14 for placing into the sample, the vacuum sampler 14 being connected to a vacuum tube 15 for evacuating a vacuum and a first gas supply tube 16 for introducing high-speed carrier gas.

[0048] Furthermore, during use, the weighed sample is placed into the vacuum sampler 14, and then the sample in the vacuum sampler 14 is subjected to alternating vacuuming and He gas purging. Each vacuuming and He gas purging process takes 30 seconds, and the process is repeated 5-10 times to remove the interference of carbon in the air on the sample.

[0049] In a further optimized design, the ventilation pipe 26 is equipped with two independently configured branch pipes 28. Each branch pipe 28 is equipped with a first valve 29 and a second valve 210. The first valve 29 is connected to a venting 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 the auxiliary carrier gas.

[0050] Furthermore, the auxiliary carrier gas in this embodiment is also helium (He).

[0051] Further optimization of the scheme: When the first cold trap 23 is located inside the first freezing container 22 and performs the first freezing of carbon dioxide gas, the second cold trap 25 is separated from the second freezing container 24. The vent pipe 26 is connected to the first port of the first cold trap 23 through a six-way valve 21, and the second port of the first cold trap 23 is connected to the vent pipe 218 set on the six-way valve 21 through the six-way valve 21. When the first cold trap 23 is located inside the first freezing container 22 and performs the first freezing of carbon dioxide gas, the first port of the second cold trap 25 is connected to a 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 being dehydrated by the chemical trap 13 enters the six-way valve 21. The six-way valve 21, through the first connecting pipe 213, vents the mixed gas into the first cold trap 23 immersed in the cryogenic freezing liquid. 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 vent pipe 218 through the second connecting pipe 214 and the six-way valve 21 to ensure the flow of carrier gas.

[0052] In a further optimized scheme, when the second cold trap 25 is in the second freezing container 24 and the carbon dioxide gas is being frozen for the second time, the first cold trap 23 is separated from the first freezing container 22, and the ventilation pipe 26 is connected to the vent pipe 218 after passing through the six-way valve 21; the third gas 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 carbon dioxide is subjected to secondary freezing, the first cold trap 23 is removed from the cryogenic freezing liquid, and the second cold trap 25 is immersed in the cryogenic freezing liquid. At the same time, the connection of the six-way valve 21 is rotated so that the vent pipe 26 and the vent pipe 218 can be directly discharged. 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 then enters the second port of the first cold trap 23 through the third connecting pipe 215. This carries the carbon dioxide that has been re-vaporized in the first cold trap 23 through the first connecting pipe 213 into the six-way valve 21, and then through the fourth connecting pipe 216 into the second cold trap 25, where the mixed gas is again cryogenically frozen and enriched. The carbon dioxide that has been vaporized by the low-speed carrier gas completely enters the second cold trap 25 for cryogenic enrichment.

[0053] Furthermore, in this embodiment, the flow rate of the low-speed carrier gas is 2-10 ml / min.

[0054] In a further optimized 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 vaporizes and enters the isotope mass spectrometry analysis system 3 under 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 removed from the freezing liquid and heated to 150°C to completely release the carbon dioxide. Then, the re-vaporized carbon dioxide, under low-flow-rate carrier gas, passes through the fifth connecting pipe 217 and the four-way valve 31, and then through the four-way valve 31 and the sixth connecting pipe 34 to the interface device 32. The interface device 32 then introduces the carbon dioxide into the isotope gas mass spectrometer 33 for convenient isotope mass spectrometry analysis.

[0055] In a further optimized design, the isotope gas mass spectrometer 33 is connected to the second port of the chemical trap 13 via a four-way valve 31. To improve the practicality of this device, a bypass pipe 4 is provided in this embodiment to connect the chemical trap 13 to the four-way valve 31, and then the mixed gas is introduced into the interface device 32 through the seventh connecting pipe 35, enabling conventional carbon element detection.

[0056] How to use:

[0057] The weighed sample is placed in the vacuum sampler 14. The sample in the vacuum sampler 14 is subjected to alternating vacuuming and helium purging. Each vacuuming and helium purging process takes 30 seconds. The alternating process is repeated 5-10 times, which can basically remove the interference of carbon in the air on the sample.

[0058] The processed sample falls into the reaction tube 12 of the elemental analyzer 11, and high-purity oxygen is introduced. At this point, the carrier gas is in high-flow-rate mode (40-100 ml / min for carbon). The reaction time and temperature need to be calibrated using nanomolar-level isotope standards to determine suitable reaction conditions and ensure complete conversion of carbon to carbon dioxide. If the sample contains both carbonate and non-carbonate carbon, nanomolar-level isotope standards can be used to determine the optimal reaction temperature and time for each type of carbon, ensuring that the two types of carbon can be converted to carbon dioxide stepwise for differentiation.

[0059] While carbon is oxidizing and burning in reaction tube 12, the six-way valve 21 is set as shown in Figure 2, and the first cold trap 23 is lowered into liquid nitrogen to freeze the carbon dioxide generated by the reaction to -196°C. At this time, a high-flow-rate helium carrier gas is used. When the reaction is complete and the first cold trap 23 is frozen, the first cold trap 23 is raised, the six-way valve 21 is set to the state shown in Figure 3, and the second cold trap 25 is lowered into liquid nitrogen. A sufficient time is set to completely freeze the carbon dioxide frozen in the first cold trap 23 into the second cold trap 25. At this time, a low-flow-rate helium carrier gas of 2-10 ml / min is used. After freezing is complete, the second cold trap 25 is raised and heated to 150°C to ensure that the frozen carbon dioxide is completely released.

[0060] In the state shown in Figure 4, under a low flow rate of 2-10 ml / min in carbon-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:

[0061] Three international standard reference materials for carbon isotopes were selected to verify the method of this invention. These three materials were IAEA-CO-1 carbonate (δ¹³C = 2.48‰), USGS24 graphite (δ¹³C = -15.99‰), and Merck carbonate (δ¹³C = -35.58‰). As shown in Figure 5, the linearity of the analytical results was excellent when the carbon isotope composition was between -40‰ and +10‰. As shown in Figure 6, when the carbonate sample amount was between 10 nanomoles and 120 nanomoles, the accuracy of the carbon isotope analysis was ±0.11‰ to ±0.22‰, demonstrating excellent analytical precision. Therefore, this invention solves the technical bottleneck of "trace" carbon isotope analysis and successfully achieves accurate determination of carbon isotopes at the nanomolar level.

[0062] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0063] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A Nano-C isotope analysis device, characterized in that: It includes an elemental analysis system (1), a carbon dioxide cryogenic enrichment system (2), and an isotope mass spectrometry analysis system (3) connected in sequence; The carbon dioxide cryogenic enrichment system (2) includes a six-way valve (21) connected to the elemental analysis system (1). The six-way valve (21) is connected to an independently configured first cryogenic component and a second cryogenic component. The second port of the second cryogenic component is connected to the isotope mass spectrometry analysis system (3). The first refrigeration assembly includes a first refrigeration container (22) containing a refrigerant, and a first cold trap (23) connected to the six-way valve (21) is provided in the first refrigeration container (22) in a height-adjustable manner. The second refrigeration assembly includes a second refrigeration container (24) containing refrigerant, and a second cold trap (25) connected to the six-way valve (21) is provided in the second refrigeration container (24) in a height-adjustable manner.

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

4. The Nano-C isotope analysis device according to claim 2, characterized in that: The ventilation pipe (26) is provided with two independently configured 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 venting 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 carbon dioxide gas, the second cold trap (25) is separated from the second freezing container (24), the vent pipe (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 vent pipe (218) provided 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 freeze 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).

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 carbon dioxide gas, the first cold trap (23) is separated from the first freezing container (22), ensuring that the carbon dioxide frozen and enriched in the first cold trap (23) can be completely frozen and enriched in the second cold trap (25). The ventilation pipe (26) is connected to the vent pipe (218) after passing through the six-way valve (21). The third gas 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 carbon dioxide enriched by freezing in the second cold trap (25) is vaporized and then 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) 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 an isotope gas mass spectrometer (33) through 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 connected to the second port of the chemical trap (13) through the four-way valve (31), and is directly connected to the elemental analyzer (11) to realize constant analysis.

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