Device and method for combined nitrogen and carbon isotope testing of trace samples

Abstract

The present invention discloses a device and method for the combined testing of nitrogen and carbon isotopes in trace samples. The device comprises a laser sample tray, a vacuum system, a CuO furnace, an air standard sample, a CT quartz cold trap, an ion pump and a rare gas mass spectrometer. The device utilizes laser heating to release nitrogen and CO2 in the sample, and then controls the internal volume to divide the generated gas into two parts according to a certain ratio, thereby obtaining nitrogen and CO2 samples respectively. The device can use one sample to simultaneously analyze nitrogen and carbon isotopes in the sample, thereby saving sample usage and ensuring sample consistency.

Description

Technical Field

[0001] The present invention relates to the technical field of isotope detection, and in particular to a device and method for joint testing of nitrogen and carbon isotopes of trace samples. Background Art

[0002] Currently, stable isotope mass spectrometry analysis requires large sample volumes. Analyzing the isotopic composition of fluid inclusions in rock samples often requires dozens of grams of sample. However, this amount is often insufficient for precious samples, such as drill cores. Furthermore, two isotopes must be analyzed on two separate systems, requiring the sample to be split into two parts, further increasing the sample size and ensuring consistency between the two samples. Summary of the Invention

[0003] The purpose of the present invention is to provide a device and method for the joint testing of nitrogen and carbon isotopes in trace samples to solve the problems existing in the above-mentioned prior art. It can use one sample to simultaneously analyze the nitrogen and carbon isotopes in the sample, save sample usage, and ensure sample consistency.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The invention provides a device for combined testing of nitrogen and carbon isotopes of trace samples, comprising a laser sample tray, a vacuum system, a CuO furnace, an air standard sample, a CT quartz cold trap, an ion pump and a rare gas mass spectrometer. The laser sample tray is connected to the rare gas mass spectrometer via a main pipe, and the vacuum system, the CuO furnace, the air standard sample, the CT quartz cold trap and the ion pump are sequentially connected to the main pipe from the head end to the tail end. A first valve is provided on the main pipe at the outlet of the laser sample tray, a second valve is provided between the vacuum system and the main pipe, a third valve is provided between the CuO furnace and the main pipe, a fourth valve and a fifth valve are provided between the air standard sample and the main pipe, a sixth valve is provided on the main pipe between the CT quartz cold trap and the ion pump, a seventh valve is provided between the ion pump and the main pipe, and an eighth valve is provided on the main pipe at the inlet of the rare gas mass spectrometer.

[0006] Preferably, a diamond sample window is provided above the laser sample disk, and the infrared laser can heat or even melt the sample through the sample window.

[0007] Preferably, the vacuum system is a double-stage vacuum structure of dry pump plus molecular pump, which can pump the air pressure of the pipeline to 1*10 -6 Below Pa.

[0008] Preferably, the CuO furnace is a quartz tube with a CF16 metal interface, 2-5 g of CuO powder is arranged in the quartz tube, and a muffle furnace is arranged on the outer shell of the quartz tube, and the muffle furnace can heat the quartz tube to 1000°C.

[0009] Preferably, a quantitative pipeline is provided between the valve four and the valve five.

[0010] Preferably, the CT quartz cold trap is a quartz tube with a CF16 metal interface, and the outer surface of the quartz tube is provided with a thermos cup filled with liquid nitrogen for adsorbing chemically generated CO2 gas.

[0011] Based on the above-mentioned device for combined nitrogen and carbon isotope testing of trace samples, the present invention also provides a method for combined nitrogen and carbon isotope testing of trace samples, including two processes: sample analysis and air analysis calibration;

[0012] Sample analysis includes the following steps:

[0013] 1) Open valves 1, 2, 3 and 6, keep other valves closed, and use the vacuum system to pump vacuum into the entire pipeline;

[0014] 2) Close valve 1 and use laser to heat the sample to be analyzed;

[0015] 3) Close valve 2 and valve 6, open valve 1 to allow the heated gas sample to diffuse freely into the CuO furnace, and close valve 3;

[0016] 4) Open valve 2 to remove the remaining gas, and at the same time use the muffle furnace to heat the CuO furnace;

[0017] 5) Close valves 1 and 2, open valves 3 and 6, and allow the gas sample to diffuse freely into the CT quartz cold trap. Use liquid nitrogen to cool the CT quartz cold trap. The inner wall of the CT quartz cold trap can adsorb CO2 generated by the reaction with CuO.

[0018] 6) Open valve 8 to allow the remaining adsorbed gas to diffuse freely into the noble gas mass spectrometer for N isotope analysis until the measurement is completed;

[0019] 7) Open valve 7 to remove all the gas analyzed in step 6);

[0020] 8) Close valves 6, 7, and 8, remove the liquid nitrogen outside the CT quartz cold trap to restore the room temperature, and release the adsorbed CO2 from the tube wall;

[0021] 9) Open valve 8 to allow the released CO2 to diffuse freely into the mass spectrometer for N isotope analysis until the measurement is completed; finally, the gas analysis data is used to correct the sample analysis results;

[0022] Air analysis includes the following steps:

[0023] 1) Open valves 1, 2, 3 and 6, keep other valves closed, and use the vacuum system to pump vacuum into the entire pipeline;

[0024] 2) Open valve 4, and the gas diffuses freely to valves 4 and 5;

[0025] 3) Close valve 1 and valve 4, open valve 5 to allow the heated gas sample to diffuse freely into the CuO furnace, and close valve 3;

[0026] 4) Open valve 2 to remove the remaining gas, and at the same time use the muffle furnace to heat the CuO furnace;

[0027] 5) Close valves 1 and 2, open valves 3 and 6, and allow the gas sample to diffuse freely into the CT quartz cold trap. Use liquid nitrogen to cool the CT quartz cold trap. The inner wall of the CT quartz cold trap can adsorb CO2 generated by the reaction with CuO.

[0028] 6) Open valve 8 to allow the remaining adsorbed gas to diffuse freely into the noble gas mass spectrometer for N isotope analysis until the measurement is completed;

[0029] 7) Open valve 7 to remove all the gas analyzed in step 6);

[0030] 8) Close valves 6, 7, and 8, remove the liquid nitrogen outside the CT quartz cold trap to restore the room temperature, and release the adsorbed CO2 from the tube wall;

[0031] 9) Open valve eight and allow the released CO2 to diffuse freely into the mass spectrometer for N isotope analysis until the measurement is completed; finally, use the gas analysis data to correct the sample analysis results.

[0032] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0033] The present invention provides an apparatus and method for the combined testing of nitrogen and carbon isotopes in trace samples. The apparatus and method utilize laser heating to release nitrogen and CO2 from the sample, then control the internal volume and divide the generated gas into two parts according to a certain ratio, thereby obtaining nitrogen and CO2 samples respectively. The apparatus and method can simultaneously analyze nitrogen and carbon isotopes in a sample using one sample, thereby saving sample usage and ensuring sample consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 Schematic diagram of the structure of the device for combined testing of nitrogen and carbon isotopes in trace samples of the present invention;

[0036] In the figure: 1-laser sample tray, 2-vacuum system, 3-CuO furnace, 4-air standard, 5-CT quartz cold trap, 6-ion pump, 7-rare gas mass spectrometer, 8-valve one, 9-valve two, 10-valve three, 11-valve four, 12-valve five, 13-valve six, 14-valve seven, 15-valve eight. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] The purpose of the present invention is to provide a device and method for the combined testing of nitrogen and carbon isotopes in trace samples, so as to solve the problems existing in the prior art.

[0039] 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 with reference to the accompanying drawings and specific embodiments.

[0040] The device for combined nitrogen and carbon isotope testing of trace samples in this embodiment is as follows: Figure 1 As shown, it includes a laser sample tray 1, a vacuum system 2, a CuO furnace 3, an air standard sample 4, a CT quartz cold trap 5, an ion pump 6 and a rare gas mass spectrometer 7; wherein the laser sample tray 1 is connected to the rare gas mass spectrometer 7 through a main pipe, and the vacuum system 2, the CuO furnace 3, the air standard sample 4, the CT quartz cold trap 5 and the ion pump 6 are sequentially connected to the main pipe from the head end to the tail end; a valve 1 8 is provided on the main pipe at the outlet of the laser sample tray 1, a valve 2 9 is provided between the vacuum system 2 and the main pipe, a valve 3 10 is provided between the CuO furnace 3 and the main pipe, a valve 4 11 and a valve 5 12 are provided between the air standard sample 4 and the main pipe, a valve 6 13 is provided on the main pipe between the CT quartz cold trap 5 and the ion pump 6, a valve 7 14 is provided between the ion pump 6 and the main pipe, and a valve 8 15 is provided on the main pipe at the entrance of the rare gas mass spectrometer 7.

[0041] In this specific embodiment, a diamond sample window is provided above the laser sample disk 1 , and the infrared laser can heat or even melt the sample through the sample window.

[0042] In this embodiment, the vacuum system 2 is a double-stage vacuum structure of a dry pump plus a molecular pump, which can pump the air pressure of the pipeline to 1*10 -6 Below Pa.

[0043] In this specific embodiment, the CuO furnace 3 is a quartz tube with a CF16 metal interface. 2-5g of CuO powder is set in the quartz tube. A muffle furnace is arranged outside the quartz tube. The muffle furnace can heat the quartz tube to 1000°C.

[0044] In this specific embodiment, a quantitative pipeline is provided between valve four 11 and valve five 12.

[0045] In this specific embodiment, the CT quartz cold trap 5 is a quartz tube with a CF16 metal interface. A thermos cup filled with liquid nitrogen is sheathed outside the quartz tube for adsorbing chemically generated CO2 gas.

[0046] Based on the above-mentioned device for combined nitrogen and carbon isotope testing of trace samples, this embodiment further provides a method for combined nitrogen and carbon isotope testing of trace samples, including two processes: sample analysis and air analysis calibration.

[0047] Sample analysis includes the following steps:

[0048] 1) Open valve 1 8, valve 2 9, valve 3 10, and valve 6 13, keep the other valves closed, and use vacuum system 2 to evacuate the entire pipeline;

[0049] 2) Close valve 18 and use laser to heat the sample to be analyzed;

[0050] 3) Close valve two 9 and valve six 13, open valve one 8 to allow the gas sample released by heating to diffuse freely into the CuO furnace 3, and close valve three 10;

[0051] 4) Open valve 29 to remove the remaining gas, and at the same time use a muffle furnace to heat the CuO furnace, first heating to 850°C and holding for 15 minutes, then reducing the temperature to 600°C and holding for 15 minutes, and finally reducing the temperature to 450°C and holding for 15 minutes;

[0052] 5) Close valve 1 8 and valve 2 9, open valve 3 10 and valve 6 13, and allow the gas sample to diffuse freely into the CT quartz cold trap 5. Use liquid nitrogen to cool the CT quartz cold trap 5. The inner wall of the CT quartz cold trap 5 can adsorb the CO2 generated by the reaction with CuO. To ensure the effectiveness of adsorption, the adsorption time needs to be maintained for 20 minutes.

[0053] 6) Open valve 8 15 to allow the remaining adsorbed gas (mainly nitrogen) to diffuse freely into the noble gas mass spectrometer 7 for N isotope analysis until the measurement is completed;

[0054] 7) Open valve 7 14 to remove all the gas analyzed in step 6);

[0055] 8) Close valve six 13, valve seven 14 and valve eight 15, remove the liquid nitrogen outside the CT quartz cold trap 5 to restore the room temperature, and release the adsorbed CO2 from the tube wall;

[0056] 9) Open valve 8 15 to allow the released CO2 to diffuse freely into the mass spectrometer for N isotope analysis until the measurement is completed; finally, the gas analysis data is used to correct the sample analysis results;

[0057] Air analysis includes the following steps:

[0058] 1) Open valve 1 8, valve 2 9, valve 3 10, and valve 6 13, keep the other valves closed, and use vacuum system 2 to evacuate the entire pipeline;

[0059] 2) Open valve 4 11, and the gas freely diffuses to valve 4 11 and valve 5 12;

[0060] 3) Close valve 1 8 and valve 4 11, open valve 5 12 to allow the heated and released gas sample to diffuse freely into the CuO furnace 3, and close valve 3 10;

[0061] 4) Open valve 29 to remove the remaining gas, and at the same time use a muffle furnace to heat the CuO furnace, first heating to 850°C and holding for 15 minutes, then reducing the temperature to 600°C and holding for 15 minutes, and finally reducing the temperature to 450°C and holding for 15 minutes;

[0062] 5) Close valve 1 8 and valve 2 9, open valve 3 10 and valve 6 13, and allow the gas sample to diffuse freely into the CT quartz cold trap 5. Use liquid nitrogen to cool the CT quartz cold trap 5. The inner wall of the CT quartz cold trap 5 can adsorb the CO2 generated by the reaction with CuO. To ensure the effectiveness of adsorption, the adsorption time needs to be maintained for 20 minutes.

[0063] 6) Open valve 8 15 to allow the remaining adsorbed gas (mainly nitrogen) to diffuse freely into the noble gas mass spectrometer 7 for N isotope analysis until the measurement is completed;

[0064] 7) Open valve 7 14 to remove all the gas analyzed in step 6);

[0065] 8) Close valve six 13, valve seven 14 and valve eight 15, remove the liquid nitrogen outside the CT quartz cold trap 5 to restore the room temperature, and release the adsorbed CO2 from the tube wall;

[0066] 9) Open valve 8 15 to allow the released CO2 to diffuse freely into the mass spectrometer for N isotope analysis until the measurement is completed; finally, use the gas analysis data to correct the sample analysis results.

[0067] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A device for combined nitrogen and carbon isotope testing of trace samples, characterized by: The invention comprises a laser sample tray, a vacuum system, a CuO furnace, an air standard sample, a CT quartz cold trap, an ion pump and a rare gas mass spectrometer; wherein the laser sample tray is connected to the rare gas mass spectrometer via a main pipe, and the vacuum system, the CuO furnace, the air standard sample, the CT quartz cold trap and the ion pump are sequentially connected to the main pipe from the head end to the tail end; a valve 1 is provided on the main pipe at the outlet of the laser sample tray, a valve 2 is provided between the vacuum system and the main pipe, a valve 3 is provided between the CuO furnace and the main pipe, valves 4 and 5 are provided between the air standard sample and the main pipe, a valve 6 is provided on the main pipe between the CT quartz cold trap and the ion pump, a valve 7 is provided between the ion pump and the main pipe, and a valve 8 is provided on the main pipe at the inlet of the rare gas mass spectrometer.

2. The device for combined nitrogen and carbon isotope testing of trace samples according to claim 1, characterized in that: A diamond sample window is provided above the laser sample disk, and the infrared laser can heat or even melt the sample through the sample window.

3. The device for combined nitrogen and carbon isotope testing of trace samples according to claim 1, characterized in that: The vacuum system is a double-stage vacuum structure of dry pump plus molecular pump, which can pump the air pressure of the pipeline to 1*10 -6 Below Pa.

4. The device for combined nitrogen and carbon isotope testing of trace samples according to claim 1, characterized in that: The CuO furnace is a quartz tube with a CF16 metal interface. 2 to 5 g of CuO powder is arranged in the quartz tube. A muffle furnace is arranged on the outer shell of the quartz tube. The muffle furnace can heat the quartz tube to 1000°C.

5. The device for combined nitrogen and carbon isotope testing of trace samples according to claim 1, characterized in that: A quantitative pipeline is provided between the valve 4 and the valve 5.

6. The device for combined nitrogen and carbon isotope testing of trace samples according to claim 1, characterized in that: The CT quartz cold trap is a quartz tube with a CF16 metal interface. The outer surface of the quartz tube is covered with a thermos cup filled with liquid nitrogen for adsorbing chemically generated CO2 gas.

7. A method for combined nitrogen and carbon isotope testing of trace samples, using the apparatus for combined nitrogen and carbon isotope testing of trace samples according to any one of claims 1 to 6, characterized in that: It includes two processes: sample analysis and air analysis calibration; Sample analysis includes the following steps: 1) Open valves 1, 2, 3 and 6, keep other valves closed, and use the vacuum system to pump vacuum into the entire pipeline; 2) Close valve 1 and use laser to heat the sample to be analyzed; 3) Close valve 2 and valve 6, open valve 1 to allow the heated gas sample to diffuse freely into the CuO furnace, and close valve 3; 4) Open valve 2 to remove the remaining gas, and at the same time use the muffle furnace to heat the CuO furnace; 5) Close valves 1 and 2, open valves 3 and 6, and allow the gas sample to diffuse freely into the CT quartz cold trap. Use liquid nitrogen to cool the CT quartz cold trap. The inner wall of the CT quartz cold trap can adsorb CO2 generated by the reaction with CuO. 6) Open valve 8 to allow the remaining adsorbed gas to diffuse freely into the noble gas mass spectrometer for N isotope analysis until the measurement is completed; 7) Open valve 7 to remove all the gas analyzed in step 6); 8) Close valves 6, 7, and 8, remove the liquid nitrogen outside the CT quartz cold trap to restore the room temperature, and release the adsorbed CO2 from the tube wall; 9) Open valve 8 to allow the released CO2 to diffuse freely into the mass spectrometer for N isotope analysis until the measurement is completed; finally, the gas analysis data is used to correct the sample analysis results; Air analysis includes the following steps: 1) Open valves 1, 2, 3 and 6, keep other valves closed, and use the vacuum system to pump vacuum into the entire pipeline; 2) Open valve 4, and the gas diffuses freely to valves 4 and 5; 3) Close valve 1 and valve 4, open valve 5 to allow the heated gas sample to diffuse freely into the CuO furnace, and close valve 3; 4) Open valve 2 to remove the remaining gas, and at the same time use the muffle furnace to heat the CuO furnace; 5) Close valves 1 and 2, open valves 3 and 6, and allow the gas sample to diffuse freely into the CT quartz cold trap. Use liquid nitrogen to cool the CT quartz cold trap. The inner wall of the CT quartz cold trap can adsorb CO2 generated by the reaction with CuO. 6) Open valve 8 to allow the remaining adsorbed gas to diffuse freely into the noble gas mass spectrometer for N isotope analysis until the measurement is completed; 7) Open valve 7 to remove all the gas analyzed in step 6); 8) Close valves 6, 7, and 8, remove the liquid nitrogen outside the CT quartz cold trap to restore the room temperature, and release the adsorbed CO2 from the tube wall; 9) Open valve eight and allow the released CO2 to diffuse freely into the mass spectrometer for N isotope analysis until the measurement is completed; finally, use the gas analysis data to correct the sample analysis results.

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