Device for synchronously measuring N2 and N2O isotopes in gas sample

Abstract

The utility model discloses a device for synchronously measuring N2 and N2O isotopes in a gas sample, which relates to the field of stable isotope analysis, and comprises a sampling 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 second switching valve 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 sampling 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] This invention relates to the field of stable isotope analysis technology, and in particular to a device for simultaneously determining N2 and N2O isotopes in a gas sample. Background Technology

[0002] Nitrogen is a critical nutrient element and a limiting factor for primary productivity, ubiquitous in terrestrial ecosystems. In nature, nitrogen exists in the forms of organic nitrogen, inorganic nitrogen, and molecular nitrogen, and the interconversion processes among these three forms constitute the nitrogen cycle. The nitrogen cycle in terrestrial ecosystems mainly includes processes such as nitrogen fixation, ammonification, nitrification, and denitrification.

[0003] Denitrification is a microbial process of nitrate reduction, a key process in nitrogen transformation in the biosphere, and plays an important role in the closure of the global nitrogen cycle. N₂O is an intermediate product of this reaction, and N₂ is the final product. Nitrogen isotopes mainly include... 14 N and 15 N, in tracer studies in fields such as biology, ecology, and agriculture, because 15 The natural abundance of N is low, so when using 15 After labeling a specific compound or substance with nitrogen (N), it becomes easier to track its whereabouts and changes in complex systems.

[0004] Due to the high background concentration of N2 in the atmosphere and the spatiotemporal heterogeneity of N2 emissions across different ecosystems, measuring N2 emissions is quite challenging. Only a few methods can quantify N2 and N2O in soil, one of which is... 15 Nitrogen gas flux method. 15 The N gas flux method can be used to study denitrification in terrestrial and aquatic environments and to quantify related N2 and N2O emissions. 15 The basic principle of nitrogen-labeled gas flux method is to inject a certain amount of high-abundance nitrogen into soil or water in a sealed container. 15 A solution of N-labeled compound was used to collect gas at the top of a container at regular intervals. The concentration of N-labeled compound in the gas was determined using an isotope mass spectrometer. 15 N-N2 or 15 N-N2O. 15 The N-labeled gas flux method is an excellent technique for distinguishing between N2 and N2O releases from different pathways, and it is highly accurate.

[0005] Currently testing gas samples for N2O and N2 15 When measuring nitrogen isotopes, different test modes of the same instrument are generally used to measure N₂O. 15 N isotopes and N2 15 N isotopes, or N2O measured separately using different instruments. 15 N isotopes and N2 15The N isotope, so two samples of the same gas sample need to be prepared, and the sample injection preparation work needs to be carried out respectively, and the test workload is large; the sampling frequency is increased, and even if an airtight syringe is used to take the gas, a small amount of air will enter in the sampling process, which affects the component ratio of the gas sample and increases the probability of contamination of the gas sample. Practical new type content

[0006] The utility model discloses a kind of devices for synchronously determining N2 and N2O isotopes in gas sample, realize the synchronous determination of N2 and N2O isotopes in gas sample, to solve the problems existing in the above prior art, can guarantee work efficiency, simplify test procedure, reduce determination workload, can reduce the probability of contaminating gas sample in sampling process.

[0007] To achieve the above object, the utility model provides the following scheme:

[0008] The utility model provides a kind of devices for synchronously determining N2 and N2O isotopes in gas sample, including sample introduction device, first switching valve, first chromatographic column, quantitative ring, gas separation device and detection device, five ports of the first switching valve are connected with the gas outlet of the sample introduction device, two ports of the quantitative ring, the gas inlet of the first chromatographic column and the gas inlet of the gas separation device respectively;Another port of the first switching valve is used to be connected with first external carrier gas source;The first switching valve has first state and second state, when the first switching valve is in the first state, the sample introduction device and the quantitative ring can be communicated by the first switching valve;When the first switching valve is in the second state, the first external carrier gas source, the quantitative ring and the first chromatographic column can be communicated by the first switching valve, and the sample introduction device and the gas separation device can be communicated by the first switching valve;The gas outlet of the first chromatographic column, the gas outlet of the gas separation device are connected with the detection device;N2 in gas sample can be separated by the first chromatographic column, and N2O in the gas sample can be separated by the gas separation device.

[0009] Preferably, the gas separation device includes purification device and second chromatographic column, the gas inlet of the first switching valve and the second chromatographic column can be connected with the purification device, and the gas outlet of the second chromatographic column is connected with the detection device;When the first switching valve is in the second state, the sample introduction device and the purification device can be communicated by 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 comprises a second switching valve, a first cold trap device and a second cold trap device, four ports of the second switching valve are connected with the first switching valve, two ports of the first cold trap device, an inlet of the second cold trap device respectively, and another port of the second switching valve is used for connecting with 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 communicated 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 communicated 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.

[0011] Preferably, the first cold trap device comprises 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 with the first lifting device, the first lifting device can drive the first cold trap to descend so as to immerse the first cold trap in 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 as to separate the first cold trap 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 comprises 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 with the second lifting device, the second lifting device can drive the second cold trap to descend so as to immerse the second cold trap in 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 as to separate the second cold trap from the liquid nitrogen of the second liquid nitrogen cooling device, and the second heating device can heat the second cold trap.

[0013] Preferably, a first drying tube is arranged on a pipeline between the sample inlet device and the first switching valve, and the first drying tube is used for removing water and CO2 in the gas sample.

[0014] Preferably, a second drying tube is arranged on a pipeline between the first switching valve and the gas separation device, and the second drying tube is used for removing water and CO2 in the gas sample.

[0015] Preferably, a third switch valve is further included, 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 connected with the third switch valve, and the third switch valve can make the first chromatographic column or the gas separation device communicate with the detection device.

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

[0017] Preferably, the sample injection device is an automatic sample injection device.

[0018] Preferably, the detection device is a mass spectrometer.

[0019] The device for synchronously determining N2 and N2O isotopes in a gas sample has the following technical effects compared with the prior art:

[0020] The utility model discloses a kind of devices for synchronously determining N2 and N2O isotopes in a gas sample, including sample injection device, first switch valve, first chromatographic column, quantitative ring, gas separation device and detection device, five ports of first switch valve are respectively connected with the gas outlet of sample injection device, two ports of quantitative ring, the gas inlet of first chromatographic column and the gas inlet of gas separation device;Another port of first switch valve is used to be connected with first external carrier gas source;First switch valve has first state and second state, when first switch valve is in first state, sample injection device and quantitative ring can be communicated by first switch valve;When first switch valve is in second state, first external carrier gas source, quantitative ring and first chromatographic column can be communicated by first switch valve, and sample injection device and gas separation device can be communicated by first switch valve;The gas outlet of first chromatographic column, the gas outlet of gas separation device are connected with detection device;N2 in first chromatographic column can be separated from gas sample, and N2O in gas separation device can be separated from gas sample.

[0021] The first switching valve is in the first state, and the gas sample of the sample inlet device enters the quantitative ring through the first switching valve; after a certain time, the first switching valve is switched to the second state, the carrier gas enters the quantitative ring through the first switching valve, and the gas sample in the quantitative ring is back-flushed into the first chromatographic column, N2 in the gas sample is separated through the first chromatographic column, and is input into the detection device, and the isotopes of N2 in the gas sample are measured by the detection device; at the same time, the gas sample enters the gas separation device through the sample inlet device and the first switching valve, N2O in the gas sample is separated through the gas separation device, and is input into the detection device, and the isotopes of N2O in the gas sample are measured by the detection device. By switching the first switching valve, the isotopes of N2 and N2O separated in the gas sample can be measured through one test process, that is, synchronous measurement is realized, the test process is simplified, and the measurement workload is reduced; when the gas sample in the back-flushed quantitative ring is separated by the first chromatographic column, the gas sample can enter the gas separation device through the first switching valve at the same time to separate N2O, so that the test efficiency is ensured; only one sampling is needed, and the probability of contaminating the gas sample in the sampling process can be reduced. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0023] Figure 1 The gas path diagram for synchronously measuring N2 and N2O isotopes in a gas sample when the first switching valve is in the first state and the second switching valve is in the third state;

[0024] Figure 2 The 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;

[0025] Figure 3 The 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;

[0026] Figure 4 The peak shape diagram obtained by detecting a gas sample by the device for synchronously measuring N2 and N2O isotopes in a gas sample in embodiment 1;

[0027] Figure 5 The test data linear diagram for detecting isotopes in N2O by the device for synchronously measuring N2 and N2O isotopes in a gas sample in embodiment 1;

[0028] Figure 6 Test data linear graph for detecting isotopes in N2O by using existing equipment (GCMS-QP2020) ;

[0029] In the figure: 100, a device for synchronously determining isotopes of N2 and N2O in a gas sample; 1, a sampling device; 2, a first switching valve; 3, a first chromatographic column; 4, a quantitative ring; 5, a gas separation device; 501, a second chromatographic column; 502, a second switching valve; 503, a first cold trap; 504, a second cold trap; 6, a detection device; 7, a first drying tube; 8, a second drying tube; 9, a third switching valve. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0031] The purpose of the present application is to provide a device for synchronously determining isotopes of N2 and N2O in a gas sample, which realizes synchronous determination of isotopes of N2 and N2O in a gas sample, solves the problems existing in the prior art, guarantees work efficiency, simplifies the test process, reduces the determination workload, and reduces the probability of contaminating the gas sample during sampling.

[0032] In order to make the above-mentioned purposes, features and advantages of the present application more apparent and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0033] Embodiment 1

[0034] The embodiment provides a device 100 for synchronously determining isotopes of N2 and N2O in a gas sample, which comprises a sampling device 1, a first switching valve 2, a first chromatographic column 3, a quantification ring 4, a gas separation device 5 and a detection device 6, five ports of the first switching valve 2 are connected with a gas outlet of the sampling device 1, two ports of the quantification ring 4, a gas inlet of the first chromatographic column 3 and a gas inlet of the gas separation device 5 respectively; another port of the first switching valve 2 can be connected with 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 sampling device 1 and the quantification ring 4 can be communicated through the first switching valve 2; when the first switching valve 2 is in the second state, the first external carrier gas source, the quantification ring 4 and the first chromatographic column 3 can be communicated through the first switching valve 2, and the sampling device 1 and the gas separation device 5 can be communicated through the first switching valve 2; a gas outlet of the first chromatographic column 3 and a gas outlet of the gas separation device 5 are connected with 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.

[0035] The first switching valve 2 is in the first state, the gas sample of the sampling device 1 enters the quantification ring 4 through the first switching valve 2; after a certain time, the first switching valve 2 is switched to the second state, the carrier gas enters the quantification ring 4 through the first switching valve 2, and the gas sample in the quantification ring 4 is back-flushed to the first chromatographic column 3, N2 in the gas sample is separated through the first chromatographic column 3 and enters the detection device 6, and the isotopes of N2 in the gas sample are determined by the detection device 6; at the same time, the gas sample enters the gas separation device 5 through the sampling device 1 and the first switching valve 2, N2O in the gas sample is separated through the gas separation device 5 and enters the detection device 6, and the isotopes of N2O in the gas sample are determined by the detection device 6. By switching the first switching valve 2, the isotopes of N2 and N2O separated in the gas sample in turn can be determined through one test process, that is, synchronous determination is realized, the test process is simplified, and the determination workload is reduced; when the gas sample in the back-flushed quantification ring 4 is separated for N2 through the first chromatographic column 3, the gas sample can enter the gas separation device 5 for N2O separation through the first switching valve 2 at the same time, so that the test efficiency is ensured; only one sampling is needed, and the probability of contaminating the gas sample in the sampling process can be reduced.

[0036] Further, the gas separation device 5 comprises a purification device and a second chromatographic column 501, the gas outlet of the first switching valve 2 and the gas inlet of the second chromatographic column 501 can be connected with the purification device, and the gas outlet of the second chromatographic column 501 is connected with 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 communicated through the first switching valve 2, the purification device can perform cryogenic purification on the gas sample, and the second chromatographic column 501 can separate N2O in the gas sample. By enriching and purifying the to-be-measured gas through the purification device, the determination of the low-concentration gas sample can be realized.

[0037] Further, the purification device comprises a second switching valve 502, a first cold trap device and a second cold trap device, four ports of the second switching valve 502 are respectively connected with the first switching valve 2, two ports of the first cold trap device and the gas inlet of the second cold trap device, and the other port of the second switching valve 502 is used for being connected with 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 communicated 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 sequentially communicated 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, and preferably the same gas source is adopted.

[0038] Further, 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 with 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. As a preferred embodiment, the first liquid nitrogen cooling device is filled with liquid nitrogen at-180℃. When the first cold trap 503 is immersed in the liquid nitrogen, the liquid nitrogen can cool the first cold trap 503, and N2O and CO2 and other components 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 be separated from the liquid nitrogen, and the first cold trap 503 is heated and thawed by the first heating device, and N2O and CO2 and other components in the first cold trap 503 can be discharged.

[0039] 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 with 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. 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℃. Similarly, when the second cold trap 504 is immersed in the liquid nitrogen, the liquid nitrogen can cool the second cold trap 504. The components such as N2O and CO2 in the gas sample are frozen and enriched in the second cold trap 504. 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 lifted by the second lifting device, and the second cold trap 504 is thawed by the second heating device. The 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 the components such as N2O and CO2. Then, the isotopes in N2O are measured by the detection device 6. In this embodiment, the gas sample is enriched and purified twice by the first cold trap 503 and the second cold trap 504, which can improve the concentration of the gas to be measured and ensure the accuracy of the measurement.

[0040] Further, the embodiment also comprises a first drying tube 7. The first drying tube 7 is arranged on the pipeline between the sample inlet device 1 and the first switching valve 2. The gas sample of the sample inlet device 1 enters the first switching valve 2 through the first drying tube 7. The first drying tube 7 is used to remove water and CO2 in the gas sample.

[0041] Further, the embodiment also comprises a second drying tube 8. The second drying tube 8 is arranged on the pipeline between the first switching valve 2 and the gas separation device 5. The gas sample of the sample inlet device 1 enters the first cold trap 503 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 water and CO2 in the gas sample, so as to reduce the influence of water and CO2 on the detection of isotopes in N2O.

[0042] Further, the embodiment further comprises a third switching valve 9, the outlet of the first chromatographic column 3, the outlet of the gas separation device 5 and the inlet of the detection device 6 are connected with the third switching valve 9, and the third switching valve 9 can make the first chromatographic column 3 or the gas separation device 5 communicate with the detection device 6. When N2 is separated by the first chromatographic column 3, the first chromatographic column 3 is connected with the detection device 6 through the third switching valve 9, so that N2 enters the detection device 6 for measurement; when N2O is separated by the second chromatographic column 501, the second chromatographic column 501 is connected with the detection device 6 through the third switching valve 9, so that N2O enters the detection device 6 for measurement.

[0043] Further, the first switching valve 2 is a six-way valve, having A-F ports, and the six ports of the first switching valve 2 are respectively connected with the outlet of the sample injection device 1, the two ports of the constant volume loop 4, the 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 A-F ports, and the five ports of the second switching valve 502 are respectively connected with the first switching valve 2, the two ports of the first cold trap device, the inlet of the second cold trap device and the second external carrier gas source. Specifically, as shown in Figure 1 , 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 sample injection device 1 can pass through the first drying tube 7, the A port of the first switching valve 2, the B port of the first switching valve 2 and enter the constant volume loop 4; after a certain time, the first switching valve 2 is switched to the second state, as shown in Figure 2 , at this time, the D port of the first switching valve 2, the E port of the first switching valve 2, the constant volume loop 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 sequentially communicated and form a first gas path; and the sample injection 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, the C port of the second switching valve 502 can be sequentially communicated and form a second gas path; after the first cold trap 503 completes enrichment and purification, the second switching valve 502 is switched to the fourth state, as shown in Figure 3 , 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 sequentially communicated and form a third gas path.

[0044] Further, the third switching valve 9 is a four-way valve, and the three ports of the four-way valve are respectively connected with the outlet of the first chromatographic column 3, the outlet of the second chromatographic column 501 and the inlet of the detection device 6.

[0045] Further, the sample injection device 1 is an automatic sample injection device.

[0046] Further, the detection device 6 is a mass spectrometer, and the carrier gas is helium.

[0047] Further, the first drying tube 7 is a thin drying tube (inner diameter 3 mm), which can better reduce the influence of the peak width of water and carbon dioxide on the detection of nitrogen, and the second drying tube 8 is a thick drying tube (inner diameter 9 mm). The first drying tube 7 and the second drying tube 8 both contain magnesium perchlorate and sodium hydroxide, the magnesium perchlorate is used to absorb water in the gas sample, and the sodium hydroxide is used to absorb carbon dioxide in the gas sample. The capacity of the quantitative ring 4 is 50 μL, and the length of the second chromatographic column 501 is 30 m.

[0048] As a preferred embodiment, the embodiment is used for the determination of N2 and N2O in a gas sample. 15 N isotopes. It should be noted that the embodiment can also be used in the determination of N2 and N2O in a gas sample. 15 N isotopes. It should be noted that the embodiment can also be used in the determination of N2 and N2O in a gas sample. 18 O isotopes.

[0049] Embodiment 2

[0050] The embodiment provides an isotopic determination method based on the device 100 for simultaneously determining N2 and N2O isotopes in a gas sample according to the embodiment 1, which comprises the following steps:

[0051] S1, the first switching valve 2 is in the first state, and the gas sample of the sampling device 1 enters the quantitative ring 4 through the first switching valve 2;

[0052] S2, the first switching valve 2 is switched to the second state, the carrier gas is introduced into the first switching valve 2 through the first external carrier gas source, and the carrier gas enters the quantitative ring 4, the gas sample in the quantitative ring 4 is back-flushed into the first chromatographic column 3, N2 in the gas sample is separated by the first chromatographic column 3, and the isotopes of N2 in the gas sample are determined by the detection device 6.

[0053] At the same time, the gas sample in the sampling device 1 enters the gas separation device 5 through the first switching valve 2, N2O in the gas sample is separated by the gas separation device 5, and the isotopes of N2O in the gas sample are determined by the detection device 6.

[0054] The isotopic determination method of the embodiment can simplify the test process, reduce the determination workload, improve the test efficiency, reduce the workload of equipment debugging, and reduce the pollution probability of the gas sample in the sampling process.

[0055] Further, S2 further comprises: after the gas sample is introduced into the quantitative ring 4 for a set time, the first switching valve 2 is switched to the second state, the second switching valve 502 is switched to the third state, the gas sample in the sample inlet device 1 enters the first cold trap device through the first switching valve 2 and the second switching valve 502, and the gas sample is first enriched and purified by the first cold trap device; after the first enrichment and purification is completed, the second switching valve 502 is switched to the fourth state, 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 gas sample is secondly enriched and purified by the second cold trap device; after the second enrichment and purification is completed, the gas sample in the second cold trap device enters the second chromatographic column 501, and N2O in the gas sample is separated by the second chromatographic column 501, and finally the isotopes in N2O are determined by the detection device 6.

[0056] Further, S1 further comprises: the first switching valve 2 is in the first state, the second switching valve 502 is in the third state, and the gas sample is introduced into the quantitative ring 4; S2 further comprises: after the gas sample in the quantitative ring 4 is filled for about 20 s, the first switching valve 2 is switched to the second state, the carrier gas is introduced into the first gas path, and the gas sample is carried in the first gas path to determine the isotopes in N2; at the same time, the remaining gas sample in the sample inlet device 1 can enter the first cold trap 503 through the second gas path to be first frozen and purified, and the freezing time is preferably 240 s; 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, the carrier gas is introduced into the third gas path, the carrier gas carries the gas sample in the first cold trap 503 into the second cold trap 504 to be frozen and purified, the freezing time is preferably 120 s, then the second cold trap 504 body is lifted and heated to room temperature, the carrier gas carries the gas sample in the second cold trap 504 into the second chromatographic column 501 to be separated, and finally the isotopes in N2O are determined by the detection device 6. After the detection device 6 completes the determination, the peak shape diagram as shown in FIG. 6 can be obtained. Figure 4

[0057] The device 100 for simultaneously determining N2 and N2O isotopes in a gas sample in embodiment 1 and the existing instrument are used to test the test gas sample to verify the test accuracy of the device 100 for simultaneously determining N2 and N2O isotopes in a gas sample in embodiment 1, and the specific process is as follows:

[0058] ​The different abundance gradient nitrate standard samples were prepared by the denitrifying bacteria method. The cultured bacteria liquid was concentrated and then transferred to a headspace bottle. After purging the bacteria liquid with high-purity nitrogen for 2 hours, the same concentration and different abundance nitrate standard gas samples were added. The gas samples were placed in a shaking bed with a parameter setting of 28 degrees Celsius and 120 revolutions per minute. After 16 hours of reaction, the reaction was terminated with 10M NaOH solution. The reacted gas was used as the gas sample. 0.5mL was extracted from the headspace bottle with a gas-tight syringe and tested on the existing GCMS-QP2020 instrument. The remaining gas in the headspace bottle was tested by the device 100 for simultaneous determination of N2 and N2O isotopes in the gas sample of embodiment 1. Corresponding test data were obtained respectively. Among them, Figure 5 is the test data linear graph of the isotope in N2O detected by the device for simultaneous determination of N2 and N2O isotopes in the gas sample of embodiment 1, Figure 6 is the test data linear graph of the isotope in N2O detected by the existing equipment (GCMS-QP2020), and table 1 is the N2O-δ 15 coefficient of variation of N isotope. By comparison, the slopes of the standard curves of the two are not much different, which are 1.0783 and 1.0071 respectively, but the coefficient of variation of the device in embodiment 1 is much smaller than that of GC-MS, and the repeatability is better than that of GC-MS. Therefore, the test results of the device for simultaneous determination of N2 and N2O isotopes in the gas sample of the embodiment meet the requirements.

[0059] Table 1 is the N2O-δ 15 coefficient of variation of N isotope

[0060]

[0061] In the process of preparing nitrate standard samples by denitrifying bacteria method, high-purity N2 was used for purging. After termination, the main gas in the headspace bottle was N2 and N2O mixture, which was tested by the device 100 for simultaneous determination of N2 and N2O isotopes in the gas sample of embodiment 1, 29 N2 / 28 N2 and 30 N2 / 28The test precisions of N2 are 0.4 ‰ and 0.2 ‰ respectively. Meanwhile, nitrogen gas with different concentrations is used as the gas sample for testing: 20 mL of headspace bottle is vacuumed, and then different volumes (10 mL, 15 mL) of high-purity N2 is injected, and high-purity He is used to balance the atmospheric pressure in the bottle. For each concentration of gas sample, sampling is performed respectively, and the device 100 for simultaneously determining the isotopes of N2 and N2O in the gas sample of embodiment 1 and the existing instrument precis ION IsoFlow are used for testing respectively, and the coefficients of variation shown in Table 2 are obtained. By comparison, it can be seen that the coefficients of variation of the device of embodiment 1 and the existing instrument precis ION IsoFlow are less different, the repeatability of the device of embodiment 1 meets the requirements, and the testing results of the device 100 for simultaneously determining the isotopes of N2 and N2O in the gas sample of embodiment 1 meet the requirements.

[0062] Table 2 Comparison table of coefficients of variation of N2 isotope ratio tested by the device 100 for simultaneously determining the isotopes of N2 and N2O in the gas sample of embodiment 1 and the existing precis-ION IsoFlow instrument

[0063]

[0064] The principles and implementation manners of the present application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the present application and its core idea; meanwhile, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manners and application ranges. In conclusion, the content of the present application should not be understood as a limitation of the present application.

Claims

1. A device for the simultaneous determination of N2 and N2O isotopes in a gas sample, characterized in that: The gas separation device (5) comprises a purification device and a second chromatographic column (501), the first switching valve (2) and the gas inlet of the second chromatographic column (501) can be connected with the purification device, and the gas outlet of the second chromatographic column (501) is connected with the detection device (6); when the first switching valve (2) is in the second state, the sample 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.

2. The apparatus for simultaneous determination of N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: The purification device comprises a second switching valve (502), a first cold trap device and a second cold trap device, four ports of the second switching valve (502) are respectively connected with the first switching valve (2), two ports of the first cold trap device and the gas inlet of the second cold trap device, and another port of the second switching valve (502) is used for being connected with a 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 sequentially connected through the second switching valve (502); and the first cold trap device and the second cold trap device can both enrich and purify the gas sample.

3. The apparatus for simultaneous determination of 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, four ports of the second switching valve (502) are respectively connected with the first switching valve (2), two ports of the first cold trap device and the gas inlet of the second cold trap device, and another port of the second switching valve (502) is used for being connected with a 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 sequentially connected through the second switching valve (502); and the first cold trap device and the second cold trap device can both enrich and purify the gas sample.

4. The apparatus for simultaneous determination of 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 with 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 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 with 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 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 apparatus for simultaneous determination of N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: The first drying pipe (7) is arranged on a pipeline between the sample inlet device (1) and the first switching valve (2), and is used for removing water and CO2 in the gas sample.

6. The apparatus for simultaneous determination of N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: The second drying pipe (8) is arranged on a pipeline between the first switching valve (2) and the gas separation device (5), and is used for removing water and CO2 in the gas sample.

7. The apparatus for simultaneous determination of N2 and N2O isotopes in a gas sample according to claim 3, characterized in that: The third switching valve (9) is connected with an outlet of the first chromatographic column (3), an outlet of the gas separation device (5) and an inlet of the detection device (6), and can make the first chromatographic column (3) or the gas separation device (5) communicate with the detection device (6).

8. The apparatus for simultaneous determination of 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 six-way valves, and the third switching valve (9) is a four-way valve; the sample inlet device (1) is an automatic sample inlet device; and the detection device (6) is a mass spectrometer.

9. The apparatus for simultaneous determination of N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: The sample inlet device (1) is an automatic sample inlet device.

10. The apparatus for simultaneous determination of N2 and N2O isotopes in a gas sample according to claim 1, characterized in that: The detection device (6) is a mass spectrometer.

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