Device and method for synchronously measuring N2 and N2O isotopes in gas sample

Abstract

The invention discloses a device and a method for synchronously measuring N2 and N2O isotopes in a gas sample, and relates to the field of stable isotope analysis, the device comprises a sample introduction device, a first switching valve, a first chromatographic column, a quantitative loop, a gas separation device and a detection device, the first switching valve has a first state and a second state, and when the first switching valve is in the first state, the first chromatographic column is in the second state; the sampling device and the quantitative ring can be communicated through a first switching valve; when the first switching valve is in a second state, the first external carrier gas source, the quantitative loop and the first chromatographic column can be communicated through the first switching valve, and the sampling device and the gas separation device can be communicated through the first switching valve; a gas outlet of the first chromatographic column and a gas outlet of the gas separation device are connected with the detection device; the first chromatographic column can be used for separating N2 in a gas sample, and the gas separation device can be used for separating N2O in the gas sample. The device can ensure the working efficiency, reduce the measurement workload and reduce the probability of polluting gas samples in the sampling process.

Description

Technical Field

[0001] The present invention relates to the technical field of stable isotope analysis, and in particular to a device and method for synchronously determining N2 and N2O isotopes in a gas sample. Background Art

[0002] Nitrogen is a ubiquitous key nutrient and a limiting factor for primary productivity in terrestrial ecosystems. In nature, nitrogen exists in the form of organic nitrogen, inorganic nitrogen, and molecular nitrogen, and the interconversion between these three forms constitutes the nitrogen cycle. The nitrogen cycle in terrestrial ecosystems primarily involves nitrogen fixation, ammoniation, nitrification, and denitrification.

[0003] Denitrification is a microbial process of nitrate nitrogen reduction. It is a key process of nitrogen transformation in the biosphere and plays an important role in the closing process of the global nitrogen cycle. N2O is the intermediate product of this reaction and N2 is the final product of this reaction. Nitrogen isotopes mainly include 14 N and 15 N, in the tracer research in biology, ecology, agriculture and other fields, due to 15 The natural abundance of N is low. 15 After N marks a specific compound or substance, it is easier to track its whereabouts and changes in a complex system.

[0004] Due to the high background concentration of N2 in the atmosphere and the spatiotemporal heterogeneity of N2 emissions in different ecosystems, it is difficult to measure N2 emissions. Only a few methods can quantify N2 and N2O in soil, one of which is 15 N gas flux method. 15 The N2 gas flux method can be used to study denitrification and quantify the associated N2 and N2O emissions in terrestrial and aquatic environments. 15 The basic principle of the N-labeled gas flux method is to inject a certain amount of high-abundance nitrogen into the soil or water in a closed container. 15 N-labeled compound solution, the gas at the top of the container is collected regularly. The isotope mass spectrometer is used to measure the gas content. 15 N-N2 or 15 N-N2O. 15 The N-labeled gas flux method is a good technical means to distinguish the release of N2 and N2O from different pathways with high accuracy.

[0005] Currently, the N2O and N2 in the test gas samples 15 When measuring N isotopes, different test modes of the same instrument are generally used to measure N2O. 15 N isotopes and N2 15 N isotopes, or using different instruments to measure N2O 15 N isotopes and N2 15N isotopes, so the same gas sample needs to be prepared twice, and the sampling preparation work needs to be carried out separately, which results in a large workload for testing; the number of sampling times increases, and even if a gas-tight syringe is used to take gas during the sampling process, a small amount of air will enter, affecting the composition ratio of the gas sample and increasing the probability of the gas sample being contaminated. Summary of the Invention

[0006] The purpose of the present invention is to provide a device and method for synchronously determining N2 and N2O isotopes in a gas sample, thereby realizing the synchronous determination of N2 and N2O isotopes in the gas sample to solve the problems existing in the above-mentioned prior art, thereby ensuring work efficiency, simplifying the test process, reducing the measurement workload, and reducing the probability of contaminating the gas sample during the sampling process.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a device for synchronously determining N2 and N2O isotopes in a gas sample, comprising a sampling device, a first switching valve, a first chromatographic column, a quantitative loop, a gas separation device, and a detection device. Five ports of the first switching valve are respectively connected to a gas outlet of the sampling device, two ports of the quantitative loop, a gas inlet of the first chromatographic column, and a gas inlet of the gas separation device; another port of the first switching valve is used to connect to a first external carrier gas source; the first switching valve has a first state and a second state. When the first switching valve is in the first state, the sampling device and the quantitative loop can be connected through the first switching valve; when the first switching valve is in the second state, the first external carrier gas source, the quantitative loop, and the first chromatographic column can be connected through the first switching valve, and the sampling device and the gas separation device can be connected through the first switching valve; the gas outlet of the first chromatographic column and the gas outlet of the gas separation device are both connected to the detection device; the first chromatographic column can separate N2 from the gas sample, and the gas separation device can separate N2O from the gas sample.

[0009] Preferably, the gas separation device includes a purification device and a second chromatographic column, the gas inlets of the first switching valve and the second chromatographic column can be connected to the purification device, and the gas outlet of the second chromatographic column is connected to the detection device; when the first switching valve is in the second state, the sampling device and the purification device can be connected through the first switching valve, the purification device can enrich and purify the gas sample, and the second chromatographic column can separate N2O in the gas sample.

[0010] Preferably, the purification device includes a second switching valve, a first cold trap device and a second cold trap device, the four ports of the second switching valve are respectively connected to the first switching valve, the two ports of the first cold trap device and the air inlet of the second cold trap device, and the other port of the second switching valve is used to connect to a second external carrier gas source; the second switching valve has a third state and a fourth state, when the second switching valve is in the third state, the first switching valve and the first cold trap device can be connected through the second switching valve; when the second switching valve is in the fourth state, the second external carrier gas source, the first cold trap device and the second cold trap device can be connected in sequence through the second switching valve; both the first cold trap device and the second cold trap device can enrich and purify the gas sample.

[0011] Preferably, the first cold trap device includes a first lifting device, a first cold trap, a first liquid nitrogen cooling device and a first heating device, the first cold trap is fixedly connected to the first lifting device, the first lifting device can drive the first cold trap to descend so that the first cold trap is immersed in the liquid nitrogen of the first liquid nitrogen cooling device, the first liquid nitrogen cooling device can cool the first cold trap, the first lifting device can drive the first cold trap to ascend so that the first cold trap is separated from the liquid nitrogen of the first liquid nitrogen cooling device, and the first heating device can heat the first cold trap;

[0012] The second cold trap device includes a second lifting device, a second cold trap, a second liquid nitrogen cooling device and a second heating device. The second cold trap is fixedly connected to the second lifting device. The second lifting device can drive the second cold trap to descend so that the second cold trap is immersed in the liquid nitrogen of the second liquid nitrogen cooling device. The second liquid nitrogen cooling device can cool the second cold trap. The second lifting device can drive the second cold trap to ascend so that the second cold trap is separated from the liquid nitrogen of the second liquid nitrogen cooling device. The second heating device can heat the second cold trap.

[0013] Preferably, it further comprises a first drying tube, which is arranged on the pipeline between the sampling device and the first switching valve, and is used to remove moisture and CO2 in the gas sample.

[0014] Preferably, it further includes a second drying tube, which is arranged on the pipeline between the first switching valve and the gas separation device, and is used to remove moisture and CO2 from the gas sample.

[0015] Preferably, a third switching valve is also included, and the gas outlet of the first chromatographic column, the gas outlet of the gas separation device and the gas inlet of the detection device are all connected to the third switching valve, and the third switching valve can connect the first chromatographic column or the gas separation device with the detection device.

[0016] Preferably, the first switching valve and the second switching valve are both six-way valves, and the third switching valve is a four-way valve; the sampling device is an automatic sampling device; and the detection device is a mass spectrometer.

[0017] The present invention also provides an isotope determination method based on the above-mentioned device for synchronously determining N2 and N2O isotopes in a gas sample, comprising the following steps:

[0018] S1, placing the first switching valve in the first state, allowing the gas sample of the injection device to enter the quantitative loop through the first switching valve;

[0019] S2. Switching the first switching valve to the second state, introducing carrier gas into the first switching valve through the first external carrier gas source, allowing the carrier gas to enter the quantitative loop, backflushing the gas sample in the quantitative loop into the first chromatographic column, separating nitrogen in the gas sample by the first chromatographic column, and determining the isotope of nitrogen in the gas sample by the detection device;

[0020] At the same time, the gas sample in the sampling device enters the gas separation device through the first switching valve, the N2O in the gas sample is separated by the gas separation device, and the isotope of N2O in the gas sample is measured by the detection device.

[0021] Preferably, the gas separation device includes a second switching valve, a first cold trap device, a second cold trap device and a second chromatographic column, the four ports of the second switching valve are respectively connected to the first switching valve, two ports of the first cold trap device, and the air inlet of the second cold trap device, and the other port of the second switching valve is used to connect to a second external carrier gas source; the second switching valve has a third state and a fourth state, when the second switching valve is in the third state, the first switching valve and the first cold trap device can be connected through the second switching valve; when the second switching valve is in the fourth state, the second external carrier gas source, the first cold trap device and the second cold trap device can be connected in sequence through the second switching valve; the first cold trap device and the second cold trap device can both enrich and purify the gas sample; the second chromatographic column can separate N2O in the gas sample;

[0022] S2 also includes: after the gas sample is introduced into the quantitative loop for a set time, switching the first switching valve to the second state, placing the second switching valve in the third state, allowing the gas sample in the injection device to enter the first cold trap device through the first switching valve and the second switching valve, and the first cold trap device performs a first enrichment and purification on the gas sample; after the first enrichment and purification is completed, switching the second switching valve to the fourth state, allowing the carrier gas of the second external carrier gas source to enter the first cold trap device through the second switching valve, and carrying the gas sample in the first cold trap device into the second cold trap device, and the second cold trap device performs a second enrichment and purification on the gas sample; after the second enrichment and purification is completed, allowing the gas sample in the second cold trap device to enter the second chromatographic column, and the second chromatographic column to separate N2O in the gas sample.

[0023] Compared with the prior art, the present invention has achieved the following technical effects:

[0024] The present invention provides a device and method for synchronously determining N2 and N2O isotopes in a gas sample. The device comprises a sampling device, a first switching valve, a first chromatographic column, a quantitative loop, a gas separation device, and a detection device. Five ports of the first switching valve are respectively connected to a gas outlet of the sampling device, two ports of the quantitative loop, a gas inlet of the first chromatographic column, and a gas inlet of the gas separation device. Another port of the first switching valve is used to connect to a first external carrier gas source. The first switching valve has a first state and a second state. When the first switching valve is in the first state, the sampling device and the quantitative loop can be connected through the first switching valve. When the first switching valve is in the second state, the first external carrier gas source, the quantitative loop, and the first chromatographic column can be connected through the first switching valve, and the sampling device and the gas separation device can be connected through the first switching valve. The gas outlet of the first chromatographic column and the gas outlet of the gas separation device are both connected to the detection device. The first chromatographic column can separate N2 from the gas sample, and the gas separation device can separate N2O from the gas sample.

[0025] The first switching valve is placed in a first state, allowing the gas sample from the sampling device to enter the quantitative loop through the first switching valve; after a certain period of time, the first switching valve is switched to a second state, allowing the carrier gas to enter the quantitative loop through the first switching valve, and backflushing the gas sample in the quantitative loop into the first chromatographic column, separating N2 in the gas sample through the first chromatographic column, and passing the gas sample to the detection device, which determines the isotope of N2 in the gas sample; at the same time, the gas sample enters the gas separation device through the sampling device and the first switching valve, separating N2O in the gas sample through the gas separation device, and passing the gas sample to the detection device, which determines the isotope of N2O in the gas sample. By switching the first switching valve, the isotopes of N2 and N2O separated successively from the gas sample can be measured in a single test process, thus achieving simultaneous measurement, simplifying the test process, and reducing the measurement workload. Furthermore, while the gas sample in the backflush quantitative loop is being subjected to the first chromatographic column for N2 separation, the gas sample can simultaneously enter the gas separation device through the first switching valve for N2O separation, thereby ensuring test efficiency. Only one sampling is required, which can reduce the probability of contamination of the gas sample during the sampling process. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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.

[0027] Figure 1 A gas path diagram for synchronously measuring N2 and N2O isotopes in a gas sample when the first switching valve is in a first state and the second switching valve is in a third state;

[0028] Figure 2 A gas path diagram for synchronously measuring N2 and N2O isotopes in a gas sample when the first switching valve is in the second state and the second switching valve is in the third state;

[0029] Figure 3 A gas path diagram for synchronously measuring N2 and N2O isotopes in a gas sample when the first switching valve is in the second state and the second switching valve is in the fourth state;

[0030] Figure 4 This is a peak graph obtained by detecting a gas sample using the device for simultaneously determining N2 and N2O isotopes in a gas sample according to Example 1;

[0031] Figure 5 This is a linear graph of test data of isotopes in N2O detected by the apparatus for simultaneously determining N2 and N2O isotopes in a gas sample of Example 1;

[0032] Figure 6 Linearity graph of test data for isotope detection in N2O using existing equipment (GCMS-QP2020);

[0033] In the figure: 100, device for synchronously determining N2 and N2O isotopes in a gas sample; 1, sampling device; 2, first switching valve; 3, first chromatographic column; 4, quantitative loop; 5, gas separation device; 501, second chromatographic column; 502, second switching valve; 503, first cold trap; 504, second cold trap; 6, detection device; 7, first drying tube; 8, second drying tube; 9, third switching valve. DETAILED DESCRIPTION

[0034] 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.

[0035] The purpose of the present invention is to provide a device and method for synchronously determining N2 and N2O isotopes in a gas sample, thereby realizing the synchronous determination of N2 and N2O isotopes in the gas sample to solve the problems existing in the above-mentioned prior art, thereby ensuring work efficiency, simplifying the test process, reducing the measurement workload, and reducing the probability of contaminating the gas sample during the sampling process.

[0036] 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.

[0037] Example 1

[0038] This embodiment provides a device 100 for synchronously determining N2 and N2O isotopes in a gas sample, comprising a sampling device 1, a first switching valve 2, a first chromatographic column 3, a quantitative loop 4, a gas separation device 5, and a detection device 6. The five ports of the first switching valve 2 are respectively connected to the gas outlet of the sampling device 1, the two ports of the quantitative loop 4, the gas inlet of the first chromatographic column 3, and the gas inlet of the gas separation device 5; another port of the first switching valve 2 can be connected to a first external carrier gas source; the first switching valve 2 has a first state and a second state, and the first switching valve 2 has a first state and a second state. When the valve 2 is in the first state, the sampling device 1 and the quantitative loop 4 can be connected through the first switching valve 2; when the first switching valve 2 is in the second state, the first external carrier gas source, the quantitative loop 4 and the first chromatographic column 3 can be connected through the first switching valve 2, and the sampling device 1 and the gas separation device 5 can be connected through the first switching valve 2; the gas outlet of the first chromatographic column 3 and the gas outlet of the gas separation device 5 are both connected to the detection device 6; the first chromatographic column 3 can separate N2 in the gas sample, and the gas separation device 5 can separate N2O in the gas sample.

[0039] The first switching valve 2 is placed in a first state, allowing the gas sample from the sampling device 1 to enter the quantitative loop 4 through the first switching valve 2; after a certain period of time, the first switching valve 2 is switched to a second state, allowing the carrier gas to enter the quantitative loop 4 through the first switching valve 2, and backflushing the gas sample in the quantitative loop 4 into the first chromatographic column 3, separating N2 in the gas sample through the first chromatographic column 3, and passing the gas sample to the detection device 6, which determines the isotope of N2 in the gas sample; at the same time, the gas sample enters the gas separation device 5 through the sampling device 1 and the first switching valve 2, separating N2O in the gas sample through the gas separation device 5, and passing the gas sample to the detection device 6, which determines the isotope of N2O in the gas sample. By switching the first switching valve 2, the isotopes of N2 and N2O separated successively from the gas sample can be measured in one test process, that is, synchronous measurement is achieved, the test process is simplified, and the measurement workload is reduced; and when the gas sample in the backflush quantitative loop 4 is subjected to the first chromatographic column 3 for N2 separation, the gas sample can simultaneously enter the gas separation device 5 through the first switching valve 2 for N2O separation, thereby ensuring test efficiency; only one sampling is required, which can reduce the probability of contamination of the gas sample during the sampling process.

[0040] Furthermore, the gas separation device 5 includes a purification device and a second chromatographic column 501. The outlet of the first switching valve 2 and the inlet of the second chromatographic column 501 can both be connected to the purification device, and the outlet of the second chromatographic column 501 is connected to the detection device 6. When the first switching valve 2 is in the second state, the sampling device 1 and the purification device can be connected through the first switching valve 2. The purification device can freeze and purify the gas sample, and the second chromatographic column 501 can separate NO from the gas sample. The purification device can enrich and purify the gas to be measured, enabling the measurement of low-concentration gas samples.

[0041] Furthermore, the purification device includes a second switching valve 502, a first cold trap device, and a second cold trap device. The four ports of the second switching valve 502 are respectively connected to the first switching valve 2, the two ports of the first cold trap device, and the air inlet of the second cold trap device. The other port of the second switching valve 502 is used to connect to the second external carrier gas source; the second switching valve 502 has a third state and a fourth state. When the second switching valve 502 is in the third state, the first switching valve 2 and the first cold trap device can be connected through the second switching valve 502; when the second switching valve 502 is in the fourth state, the second external carrier gas source, the first cold trap device, and the second cold trap device can be connected in sequence through the second switching valve 502; the first cold trap device and the second cold trap device can both enrich and purify the gas sample. It should be noted that the first external carrier gas source and the second external carrier gas source can be the same gas source or different gas sources, preferably the same gas source.

[0042] Furthermore, the first cold trap device includes a first lifting device, a first cold trap 503, a first liquid nitrogen cooling device, and a first heating device. The first cold trap 503 is fixedly connected to the first lifting device. The first lifting device can drive the first cold trap 503 to descend so that the first cold trap 503 is immersed in the liquid nitrogen of the first liquid nitrogen cooling device. The first liquid nitrogen cooling device can cool the first cold trap 503. The first lifting device can drive the first cold trap 503 to ascend so that the first cold trap 503 is separated from the liquid nitrogen of the first liquid nitrogen cooling device. The first heating device can heat the first cold trap 503. As a preferred embodiment, the first liquid nitrogen cooling device is filled with liquid nitrogen at -180°C. When the first cold trap 503 is immersed in liquid nitrogen, the liquid nitrogen can cool the first cold trap 503, and components such as N2O and CO2 in the gas sample are frozen and enriched in the first cold trap 503, and other components in the gas sample are discharged through the second switching valve 502; after the enrichment and purification are completed, the first cold trap 503 is lifted by the first lifting device to separate it from the liquid nitrogen, and the first cold trap 503 is heated and thawed by the first heating device, so that components such as N2O and CO2 in the first cold trap 503 can be discharged.

[0043] The second cold trap device includes a second lifting device, a second cold trap 504, a second liquid nitrogen cooling device, and a second heating device. The second cold trap 504 is fixedly connected to the second lifting device. The second lifting device can drive the second cold trap 504 downward so that the second cold trap 504 is immersed in the liquid nitrogen of the second liquid nitrogen cooling device. The second liquid nitrogen cooling device can cool the second cold trap 504. The second lifting device can drive the second cold trap 504 upward so that the second cold trap 504 is separated from the liquid nitrogen of the second liquid nitrogen cooling device. The second heating device can heat the second cold trap 504. As a preferred embodiment, the second liquid nitrogen cooling device is filled with liquid nitrogen at -180°C. Similarly, when the second cold trap 504 is immersed in liquid nitrogen, the liquid nitrogen can cool the second cold trap 504, and components such as N2O and CO2 in the gas sample are frozen and enriched in the second cold trap 504, while other components in the gas sample are discharged after passing through the second chromatographic column 501. After the enrichment and purification are completed, the second cold trap 504 is raised by the second lifting device and heated and thawed by the second heating device. Components such as N2O and CO2 in the second cold trap 504 can be discharged and enter the second chromatographic column 501. The second chromatographic column 501 can separate N2O from components such as N2O and CO2, and then the isotopes in the N2O are measured by the detection device 6. This embodiment enriches and purifies the gas sample twice using the first cold trap 503 and the second cold trap 504, which can increase the concentration of the gas to be measured and ensure the accuracy of the measurement.

[0044] Furthermore, this embodiment also includes a first drying tube 7, which is arranged on the pipeline between the sampling device 1 and the first switching valve 2. The gas sample of the sampling device 1 enters the first switching valve 2 through the first drying tube 7. The first drying tube 7 is used to remove moisture and CO2 in the gas sample.

[0045] Furthermore, this embodiment also includes a second drying tube 8, which is arranged on the pipeline between the first switching valve 2 and the gas separation device 5. The gas sample enters the first cold trap 503 from the sampling device 1 through the first switching valve 2, the second drying tube 8, and the second switching valve 502. The second drying tube 8 is used to remove moisture and CO2 from the gas sample, thereby reducing the impact of moisture and CO2 on the isotope detection in N2O.

[0046] Furthermore, this embodiment includes a third switching valve 9. The gas outlet of the first chromatographic column 3, the gas outlet of the gas separation device 5, and the gas inlet of the detection device 6 are all connected to the third switching valve 9. The third switching valve 9 can connect the first chromatographic column 3 or the gas separation device 5 with the detection device 6. When N2 is separated by the first chromatographic column 3, the third switching valve 9 connects the first chromatographic column 3 with the detection device 6, allowing the N2 to enter the detection device 6 for measurement. When N2O is separated by the second chromatographic column 501, the third switching valve 9 connects the second chromatographic column 501 with the detection device 6, allowing the N2O to enter the detection device 6 for measurement.

[0047] Furthermore, the first switching valve 2 is a six-way valve having ports A to F. The six ports of the first switching valve 2 are respectively connected to the gas outlet of the sample injection device 1, the two ports of the quantitative loop 4, the gas inlet of the first chromatographic column 3, the second switching valve 502, and the first external carrier gas source; the second switching valve 502 is a six-way valve having ports A to F. The five ports of the second switching valve 502 are respectively connected to the first switching valve 2, the two ports of the first cold trap device, the gas inlet of the second cold trap device, and the second external carrier gas source. Specifically, as Figure 1 As shown, when the first switching valve 2 is in the first state and the second switching valve 502 is in the third state, the gas sample in the sampling device 1 can enter the quantitative loop 4 through the first drying tube 7, the A port of the first switching valve 2, and the B port of the first switching valve 2; after a certain period of time, the first switching valve 2 is switched to the second state, as shown in FIG. Figure 2 As shown, at this time, the D port of the first switching valve 2, the E port of the first switching valve 2, the quantitative ring 4, the B port of the first switching valve 2, the C port of the first switching valve 2, the first chromatographic column 3 and the detection device 6 can be connected in sequence to form a first gas path; and the sampling device 1, the first drying tube 7, the A port of the first switching valve 2, the F port of the first switching valve 2, the second drying tube 8, the A port of the second switching valve 502, the F port of the second switching valve 502, the first cold trap 503, and the C port of the second switching valve 502 can be connected in sequence to form a second gas path; after the first cold trap 503 completes the enrichment and purification, the second switching valve 502 is switched to the fourth state, as shown Figure 3 As shown, at this time, the D port of the second switching valve 502, the C port of the second switching valve 502, the first cold trap 503, the F port of the second switching valve 502, the E port of the second switching valve 502, the second cold trap 504, the second chromatographic column 501 and the detection device 6 can be connected in sequence to form a third gas path.

[0048] Furthermore, the third switching valve 9 is a four-way valve, and the three ports of the four-way valve are respectively connected to the gas outlet of the first chromatographic column 3 , the gas outlet of the second chromatographic column 501 and the gas inlet of the detection device 6 .

[0049] Furthermore, the sample injection device 1 is an automatic sample injection device.

[0050] Furthermore, the detection device 6 is a mass spectrometer, and the carrier gas is helium.

[0051] Further, the first drying tube 7 is a thin drying tube (inner diameter 3mm), which can better reduce the impact of the peak width of moisture and carbon dioxide on nitrogen detection, and the second drying tube 8 is a thick drying tube (inner diameter 9mm). Both the first drying tube 7 and the second drying tube 8 contain magnesium perchlorate and sodium hydroxide, and magnesium perchlorate is used to absorb moisture in the gas sample, and sodium hydroxide is used to absorb carbon dioxide in the gas sample. The quantitative loop 4 has a capacity of 50 μL and the second chromatographic column 501 is 30m long.

[0052] As a preferred embodiment, this embodiment is used for N2 and N2O in gas samples. 15 It should be noted that this embodiment can also be used to determine the N isotope in N2 and N2O. 15 During the determination of N isotopes, the N2O in the gas sample is 18 O isotope determination.

[0053] Example 2

[0054] This embodiment provides an isotope determination method based on the apparatus 100 for simultaneously determining N2 and N2O isotopes in a gas sample according to embodiment 1, comprising the following steps:

[0055] S1, placing the first switching valve 2 in a first state, allowing the gas sample of the injection device 1 to enter the quantitative loop 4 through the first switching valve 2;

[0056] S2, switching the first switching valve 2 to the second state, introducing carrier gas into the first switching valve 2 through the first external carrier gas source, and allowing the carrier gas to enter the quantitative loop 4, backflushing the gas sample in the quantitative loop 4 into the first chromatographic column 3, separating N2 in the gas sample by the first chromatographic column 3, and measuring the isotope of N2 in the gas sample by the detection device 6;

[0057] Simultaneously, the gas sample in the sampling device 1 enters the gas separation device 5 through the first switching valve 2. The gas separation device 5 separates the N2O in the gas sample, and the N2O isotopes in the gas sample are measured by the detection device 6. The isotope measurement method of this embodiment can simplify the testing process, reduce the measurement workload, improve testing efficiency, reduce the workload of equipment debugging, and reduce the probability of contamination of the gas sample during the sampling process.

[0058] Furthermore, S2 also includes: after the gas sample is passed into the quantitative ring 4 for a set time, switching the first switching valve 2 to the second state, making the second switching valve 502 in the third state, so that the gas sample in the injection device 1 enters the first cold trap device through the first switching valve 2 and the second switching valve 502, and the first cold trap device enriches and purifies the gas sample for the first time; after the first enrichment and purification is completed, switching the second switching valve 502 to the fourth state, so that the carrier gas of the second external carrier gas source enters the first cold trap device through the second switching valve 502, and carries the gas sample in the first cold trap device into the second cold trap device, and the second cold trap device enriches and purifies the gas sample for the second time; after the second enrichment and purification is completed, the gas sample in the second cold trap device enters the second chromatographic column 501, and the second chromatographic column 501 separates N2O in the gas sample, and finally the isotopes in N2O are measured by the detection device 6.

[0059] Furthermore, S1 also includes: placing the first switching valve 2 in the first state and the second switching valve 502 in the third state, and introducing a gas sample into the quantitative ring 4; S2 also includes: after the gas sample in the quantitative ring 4 is filled for about 20s, switching the first switching valve 2 to the second state, introducing a carrier gas into the first gas path, and carrying the gas sample to circulate in the first gas path to perform the determination of the isotope in N2; at the same time, the remaining gas sample in the sampling device 1 can enter the first cold trap 503 through the second gas path for the first freeze purification, and the freezing time is optimized. Select 240s; then, the first cold trap 503 body is lifted and heated to room temperature, and the second switching valve 502 is switched to the fourth state, and the carrier gas is introduced into the third gas path, so that the carrier gas carries the gas sample in the first cold trap 503 into the second cold trap 504 for freezing and purification, and the freezing time is preferably 120s. Then, the second cold trap 504 body is lifted and heated to room temperature, so that the carrier gas carries the gas sample in the second cold trap 504 into the second chromatographic column 501 for separation, and finally the isotope in N2O is measured by the detection device 6. After the detection device 6 completes the measurement, it can obtain the following information: Figure 4 Peak shape diagram shown.

[0060] The test gas sample was tested using the apparatus 100 for simultaneously determining N2 and N2O isotopes in a gas sample according to Example 1 and an existing instrument to verify the test accuracy of the apparatus 100 for simultaneously determining N2 and N2O isotopes in a gas sample according to Example 1, as follows:

[0061] Nitrate standards with different abundance gradients were prepared by the denitrifying bacteria method. The cultured bacterial solution was concentrated and then transferred to the headspace bottle. After the bacterial solution was purged with high-purity nitrogen for 2 hours, nitrate standard gas samples of the same concentration and different abundance were added. The gas sample was placed on a shaker for reaction. The shaker parameters were set to 28 degrees Celsius and 120 rpm. After 16 hours of reaction, it was terminated with 10M NaOH solution. The gas after the reaction was used as the gas sample, and 0.5 mL was extracted from the headspace bottle with an airtight syringe. The test was performed on the existing GCMS-QP2020 instrument. The remaining gas in the headspace bottle was tested by the device 100 for synchronous determination of N2 and N2O isotopes in the gas sample in Example 1, and the corresponding test data were obtained respectively. Among them, Figure 5 This is a linear graph of test data of isotopes in N2O detected by the apparatus for simultaneously determining N2 and N2O isotopes in a gas sample in Example 1. Figure 6 Table 1 shows the linear graph of the test data of N2O isotopes detected by the existing equipment (GCMS-QP2020). Table 1 shows the N2O-δ in the gas sample tested by the apparatus 100 for synchronously determining N2 and N2O isotopes in the gas sample of Example 1 and the existing GCMS-QP2020 instrument. 15 A comparison table of coefficients of variation for N isotopes shows that the slopes of the standard curves for the two methods are not significantly different, at 1.0783 and 1.0071, respectively. However, the coefficient of variation for the device in Example 1 is significantly smaller than that of GC-MS, demonstrating superior repeatability. Therefore, the test results for the device for simultaneous determination of N2 and N2O isotopes in gas samples in this example meet the requirements.

[0062] Table 1. N2O-δ in gas samples measured by the apparatus 100 for simultaneous determination of N2 and N2O isotopes in gas samples according to Example 1 and by the existing GCMS-QP2020 instrument. 15 N isotope coefficient of variation comparison table

[0063]

[0064] During the preparation of nitrate standard samples by the denitrifying bacteria method, high-purity N2 is used for purging. After the purging is terminated, the headspace bottle mainly contains a mixed gas of N2 and N2O. The device 100 for synchronously determining N2 and N2O isotopes in the gas sample of Example 1 is used for testing. 29 N2 / 28 N2 and 30 N2 / 28The test accuracy of N2 is 0.4‰ and 0.2‰ respectively. At the same time, different concentrations of nitrogen were used as gas samples for testing: after the 20mL headspace bottle was evacuated, different volumes (10ml, 15ml) of high-purity N2 were injected, and the atmospheric pressure in the bottle was balanced with high-purity He. Each concentration of gas sample was sampled separately, and the device 100 for synchronous determination of N2 and N2O isotopes in gas samples in Example 1 and the existing instrument precis ION IsoFlow were used for testing, and the coefficients of variation shown in Table 2 were obtained respectively. By comparison, it can be seen that the difference in coefficient of variation between the device in Example 1 and the existing instrument precis ION IsoFlow is small, the repeatability of the device in Example 1 meets the requirements, and the test results of the device 100 for synchronous determination of N2 and N2O isotopes in gas samples in Example 1 meet the requirements.

[0065] Table 2 Comparison of coefficients of variation of N2 isotope ratios in gas samples measured by the apparatus 100 for simultaneous determination of N2 and N2O isotopes in gas samples according to Example 1 and the existing precis-ION IsoFlow instrument

[0066]

[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 construed as limiting the present invention.

Claims

1. A device for synchronously determining N2 and N2O isotopes in a gas sample, characterized in that: The invention comprises a sample injection device (1), a first switching valve (2), a first chromatographic column (3), a quantitative ring (4), a gas separation device (5) and a detection device (6); the five ports of the first switching valve (2) are respectively connected to the gas outlet of the sample injection device (1), the two ports of the quantitative ring (4), the gas inlet of the first chromatographic column (3) and the gas inlet of the gas separation device (5); the other port of the first switching valve (2) is used to be connected to a first external carrier gas source; the first switching valve (2) has a first state and a second state; when the first switching valve (2) is in the first state, the sample injection device (1) and the quantitative ring (4) are in the first state. 4) can be connected through the first switching valve (2); when the first switching valve (2) is in the second state, the first external carrier gas source, the quantitative loop (4) and the first chromatographic column (3) can be connected through the first switching valve (2), and the injection device (1) and the gas separation device (5) can be connected through the first switching valve (2); the gas outlet of the first chromatographic column (3) and the gas outlet of the gas separation device (5) are both connected to the detection device (6); the first chromatographic column (3) can separate N2 in the gas sample, and the gas separation device (5) can separate N2O in the gas sample.

2. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: The gas separation device (5) comprises a purification device and a second chromatographic column (501); the gas inlets of the first switching valve (2) and the second chromatographic column (501) can be connected to the purification device, and the gas outlet of the second chromatographic column (501) is connected to the detection device (6); when the first switching valve (2) is in a second state, the injection device (1) and the purification device can be connected through the first switching valve (2), the purification device can enrich and purify the gas sample, and the second chromatographic column (501) can separate N2O in the gas sample.

3. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 2, characterized in that: The purification device comprises a second switching valve (502), a first cold trap device and a second cold trap device, wherein the four ports of the second switching valve (502) are respectively connected to the first switching valve (2), the two ports of the first cold trap device and the air inlet of the second cold trap device, and the other port of the second switching valve (502) is used to connect to a second external carrier gas source; the second switching valve (502) has a third state and a fourth state, and when the second switching valve (502) is in the third state, the first switching valve (2) and the first cold trap device can be connected through the second switching valve (502); when the second switching valve (502) is in the fourth state, the second external carrier gas source, the first cold trap device and the second cold trap device can be connected in sequence through the second switching valve (502); the first cold trap device and the second cold trap device can both enrich and purify the gas sample.

4. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 3, characterized in that: The first cold trap device comprises a first lifting device, a first cold trap (503), a first liquid nitrogen cooling device and a first heating device, the first cold trap (503) is fixedly connected to the first lifting device, the first lifting device can drive the first cold trap (503) to descend so that the first cold trap (503) is immersed in the liquid nitrogen of the first liquid nitrogen cooling device, the first liquid nitrogen cooling device can cool the first cold trap (503), the first lifting device can drive the first cold trap (503) to ascend so that the first cold trap (503) is separated from the liquid nitrogen of the first liquid nitrogen cooling device, and the first heating device can heat the first cold trap (503); The second cold trap device comprises a second lifting device, a second cold trap (504), a second liquid nitrogen cooling device and a second heating device, the second cold trap (504) is fixedly connected to the second lifting device, the second lifting device can drive the second cold trap (504) to descend so that the second cold trap (504) is immersed in the liquid nitrogen of the second liquid nitrogen cooling device, the second liquid nitrogen cooling device can cool the second cold trap (504), the second lifting device can drive the second cold trap (504) to ascend so that the second cold trap (504) is separated from the liquid nitrogen of the second liquid nitrogen cooling device, and the second heating device can heat the second cold trap (504).

5. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: It also includes a first drying tube (7), which is arranged on the pipeline between the sampling device (1) and the first switching valve (2), and the first drying tube (7) is used to remove moisture and CO2 in the gas sample.

6. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: It also includes a second drying tube (8), which is arranged on the pipeline between the first switching valve (2) and the gas separation device (5), and the second drying tube (8) is used to remove moisture and CO2 in the gas sample.

7. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 3, characterized in that: The invention also comprises a third switching valve (9), the gas outlet of the first chromatographic column (3), the gas outlet of the gas separation device (5) and the gas inlet of the detection device (6) are all connected to the third switching valve (9), and the third switching valve (9) can connect the first chromatographic column (3) or the gas separation device (5) with the detection device (6).

8. The device for synchronously determining N2 and N2O isotopes in a gas sample according to claim 7, characterized in that: The first switching valve (2) and the second switching valve (502) are both six-way valves, and the third switching valve (9) is a four-way valve; the injection device (1) is an automatic injection device; and the detection device (6) is a mass spectrometer.

9. An isotope determination method based on the device for synchronously determining N2 and N2O isotopes in a gas sample according to any one of claims 1 to 8, characterized in that: The steps include: S1, placing the first switching valve (2) in the first state, so that the gas sample of the sampling device (1) enters the quantitative loop (4) through the first switching valve (2); S2, switching the first switching valve (2) to the second state, introducing carrier gas into the first switching valve (2) through the first external carrier gas source, and allowing the carrier gas to enter the quantitative loop (4), back-flushing the gas sample in the quantitative loop (4) into the first chromatographic column (3), separating N2 in the gas sample through the first chromatographic column (3), and determining the isotope of N2 in the gas sample by the detection device (6); At the same time, the gas sample in the sampling device (1) enters the gas separation device (5) through the first switching valve (2), the N2O in the gas sample is separated by the gas separation device (5), and the isotope of the N2O in the gas sample is determined by the detection device (6).

10. The isotope determination method according to claim 9, characterized in that: The gas separation device (5) comprises a second switching valve (502), a first cold trap device, a second cold trap device and a second chromatographic column (501), wherein four ports of the second switching valve (502) are respectively connected to the first switching valve (2), two ports of the first cold trap device and an air inlet of the second cold trap device, and another port of the second switching valve (502) is used to connect to a second external carrier gas source; the second switching valve (502) has a third state and a fourth state, and when the second switching valve (502) is in the third state, the first switching valve (2) and the first cold trap device can be connected through the second switching valve (502); when the second switching valve (502) is in the fourth state, the second external carrier gas source, the first cold trap device and the second cold trap device can be connected in sequence through the second switching valve (502); the first cold trap device and the second cold trap device can both enrich and purify the gas sample; and the second chromatographic column (501) can separate N2O from the gas sample; S2 also includes: after the gas sample is introduced into the quantitative ring (4) for a set time, switching the first switching valve (2) to the second state, making the second switching valve (502) in the third state, making the gas sample in the injection device (1) enter the first cold trap device through the first switching valve (2) and the second switching valve (502), and the first cold trap device performs a first enrichment and purification on the gas sample; after the first enrichment and purification is completed, switching the second switching valve (502) to the fourth state, making the carrier gas of the second external carrier gas source enter the first cold trap device through the second switching valve (502), and carrying the gas sample in the first cold trap device into the second cold trap device, and the second cold trap device performs a second enrichment and purification on the gas sample; after the second enrichment and purification is completed, making the gas sample in the second cold trap device enter the second chromatographic column (501), and the second chromatographic column (501) separates N2O in the gas sample.

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