CN111983007A - For determining nitric acid or nitrate15Method and apparatus for N isotope abundance - Google Patents
For determining nitric acid or nitrate15Method and apparatus for N isotope abundance Download PDFInfo
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- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 title claims abstract description 47
- 229910017604 nitric acid Inorganic materials 0.000 title claims abstract description 47
- 238000006243 chemical reaction Methods 0.000 claims abstract description 122
- 239000007789 gas Substances 0.000 claims abstract description 77
- 238000000034 method Methods 0.000 claims abstract description 71
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 65
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 57
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims abstract description 57
- 230000000155 isotopic effect Effects 0.000 claims abstract description 37
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 29
- 238000007789 sealing Methods 0.000 claims abstract description 29
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 9
- 238000011068 loading method Methods 0.000 claims abstract description 6
- 239000000523 sample Substances 0.000 claims description 155
- 150000002500 ions Chemical class 0.000 claims description 18
- 238000001514 detection method Methods 0.000 claims description 15
- 239000002689 soil Substances 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 claims description 8
- 239000003153 chemical reaction reagent Substances 0.000 claims description 8
- 239000007788 liquid Substances 0.000 claims description 8
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 6
- QVQLCTNNEUAWMS-UHFFFAOYSA-N barium oxide Chemical compound [Ba]=O QVQLCTNNEUAWMS-UHFFFAOYSA-N 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 6
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 5
- 239000000395 magnesium oxide Substances 0.000 claims description 5
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 5
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 5
- 238000005070 sampling Methods 0.000 claims description 5
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 4
- QPLDLSVMHZLSFG-UHFFFAOYSA-N Copper oxide Chemical compound [Cu]=O QPLDLSVMHZLSFG-UHFFFAOYSA-N 0.000 claims description 4
- 239000005751 Copper oxide Substances 0.000 claims description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 claims description 4
- 239000000292 calcium oxide Substances 0.000 claims description 4
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 4
- 229910000431 copper oxide Inorganic materials 0.000 claims description 4
- KKCBUQHMOMHUOY-UHFFFAOYSA-N sodium oxide Chemical compound [O-2].[Na+].[Na+] KKCBUQHMOMHUOY-UHFFFAOYSA-N 0.000 claims description 4
- 229910001948 sodium oxide Inorganic materials 0.000 claims description 4
- 239000011787 zinc oxide Substances 0.000 claims description 4
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 3
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 3
- 239000012472 biological sample Substances 0.000 claims description 3
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 3
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 3
- 239000000463 material Substances 0.000 claims description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims 1
- 239000011521 glass Substances 0.000 claims 1
- 230000035484 reaction time Effects 0.000 claims 1
- 238000012360 testing method Methods 0.000 abstract description 17
- 230000008569 process Effects 0.000 abstract description 14
- 238000002347 injection Methods 0.000 abstract description 7
- 239000007924 injection Substances 0.000 abstract description 7
- 238000005086 pumping Methods 0.000 description 12
- 239000001273 butane Substances 0.000 description 8
- 238000004949 mass spectrometry Methods 0.000 description 8
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 8
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 8
- 238000002360 preparation method Methods 0.000 description 8
- 229910001873 dinitrogen Inorganic materials 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 6
- 238000005259 measurement Methods 0.000 description 6
- 239000000126 substance Substances 0.000 description 5
- 239000000243 solution Substances 0.000 description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 3
- IOVCWXUNBOPUCH-UHFFFAOYSA-M Nitrite anion Chemical compound [O-]N=O IOVCWXUNBOPUCH-UHFFFAOYSA-M 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- GRYLNZFGIOXLOG-OUBTZVSYSA-N 43625-06-5 Chemical compound O[15N+]([O-])=O GRYLNZFGIOXLOG-OUBTZVSYSA-N 0.000 description 2
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 150000003863 ammonium salts Chemical class 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000012298 atmosphere Substances 0.000 description 2
- ZCCIPPOKBCJFDN-UHFFFAOYSA-N calcium nitrate Chemical compound [Ca+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O ZCCIPPOKBCJFDN-UHFFFAOYSA-N 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000002203 pretreatment Methods 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 239000012266 salt solution Substances 0.000 description 2
- CRWJEUDFKNYSBX-UHFFFAOYSA-N sodium;hypobromite Chemical compound [Na+].Br[O-] CRWJEUDFKNYSBX-UHFFFAOYSA-N 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 241000894006 Bacteria Species 0.000 description 1
- 241000108664 Nitrobacteria Species 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- ZCCIPPOKBCJFDN-IMSGLENWSA-N calcium;dioxido(oxo)azanium Chemical compound [Ca+2].[O-][15N+]([O-])=O.[O-][15N+]([O-])=O ZCCIPPOKBCJFDN-IMSGLENWSA-N 0.000 description 1
- 239000012468 concentrated sample Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000004720 fertilization Effects 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 238000003141 isotope labeling method Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- -1 nitrogen-containing compound Chemical class 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000002688 persistence Effects 0.000 description 1
- 239000000700 radioactive tracer Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000006479 redox reaction Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
Images
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
Abstract
The invention relates to a method for determining nitric acid or nitrate15A method and apparatus for N isotopic abundance, the method comprising the steps of: (1) get15Loading the N-labeled nitric acid or nitrate sample, oxide and reducing agent into a reaction tube, vacuumizing and sealing; (2) heating the reaction tube to generate reaction15N marks nitrogen; (3) after the reaction tube is cooled to room temperature, the reaction tube is placed into a sample injection tube, and then the sample injection tube and a sample injection pipeline of a gas isotope mass spectrometer connected with the sample injection tube are continuously vacuumized; (4) breaking the reaction tube to make it inside15N-labeled nitrogen is introduced into the gas isotope mass spectrometer; (5) detecting and recording the relative intensities of the mass numbers 28, 29 and 30 respectively, and calculating to obtain the intensity of the light wave in the sample15The abundance of the N isotope. Compared with the prior art, the method has the advantages of simple operation process, low economic cost, high accuracy and precision of test data and the like, and the sample pretreatment time can be greatly shortened when the sample amount is more than or equal to 5.
Description
Technical Field
The invention belongs to15The technical field of N isotope abundance detection, and relates to a method for determining nitric acid or nitrate15Method and apparatus for N isotopic abundance.
Background
Nitrogen circulation refers to a substance circulation process of an ecosystem in a process of interconversion between a nitrogen simple substance and a nitrogen-containing compound in the nature, and is an important component of the whole biosphere substance energy circulation, nitrogen enters a land ecosystem through fertilization, nitrogen sedimentation and plant nitrogen fixation, is subjected to a nitrobacteria and denitrifying bacteria conversion process in soil, and then leaves the land ecosystem through eluviation or a gas form, the nitrogen circulation mainly comprises nitrogen fixation, ammoniation, nitrification, assimilation and denitrification, and the processes are circularly reciprocated in the ecosystem, so that nitrogen is continuously migrated and converted in an ecosystem formed by atmosphere, water, soil and organisms, and finally life and life persistence on the earth is built, and the ecological system becomes a bobble of bobble in a solar system. Stable isotopes15The tracer effect of N in these studies was not replaceable.
In the nitrogen circulation process of the water body ecological system, the nitrification and denitrification processes are key links,15the N isotope labeling method can better track the migration and transformation processes of water nitrogen, and is widely applied to the research of nitrogen circulation processes in the atmosphere, land and aquatic ecosystems, so that nitric acid or nitrate in samples of environment, soil, water quality and the like15Accurate detection of N-isotopic abundance is key to nitrogen cycling studies.
The existing method for measuring nitric acid or nitrate in samples15The method of N isotope abundance is gas isotope mass spectrometry, and pretreatment usually requires that the N isotope abundance in a sample is subjected to gas isotope mass spectrometry15Conversion of N-labelled nitric acid or nitrate with azotometric alloy under alkaline conditions15N-labelled ammonia gas, generated during the distillation, absorbed by the acid15Formation of N-labelled Ammonia15N-labelled ammonium salt solution, after further concentration15The N-marked ammonium salt solution reacts with the sodium hypobromite solution to generate15N-labelled nitrogen gas, will15N-labeled nitrogen is introduced into a gas isotope mass spectrometer for isotope abundance determination. The test time increases in proportion to the increase of the sample amount, certain optimization is required in the aspect of high-throughput sample detection, and15the consumption of N marked samples is large, and the relative cost is high.
CN 110763535A discloses a method for determining nitrite15The preparation method of the sample with the N isotopic abundance comprises the following steps: loading a sample, mixing15N marked samples to be prepared and aqueous solution of a reducing agent are filled into a first bulb of a double-bulb reaction tube, and acidic substances are filled into a second bulb of the double-bulb reaction tube; preparation 15NO gas, the vacuum degree is kept, and meanwhile, acidic substances in the second bulb are added into the first bulb to generate15NO; detecting, namely reducing the vacuum degree of the pipeline between the vacuum plug valve and the gas isotope mass spectrometer to 2 multiplied by 10-5When the pressure is lower than Pa, the vacuum plug valve is opened to enable the first bulb to be in the first bulb15Introducing NO into a gas isotope mass spectrometer; setting detection parameters of a gas isotope mass spectrometer, detecting the relative strength of the mass number of 30 and 31, and testing for multiple times in parallel; computing15N isotope abundance value.
Related to invention disclosed in CN 110763535A15The N-marked nitrite and the reducing agent are generated by oxidation-reduction reaction15NO, by detection15Isotopic abundance of NO is obtained15Isotopic abundance of N-labeled nitrite in the invention disclosed in CN 110763535A15N-labeled nitrate does not react with the reducing agent and is not suitable for15And (4) detecting N-labeled nitrate.
Disclosure of Invention
The invention aims to provide a method for measuring nitric acid or nitrate15The method and the device for N isotope abundance have simple operation process, can greatly shorten the sample pretreatment time when the sample amount is more than or equal to 5, and have low economic cost and accurate test data.
The purpose of the invention can be realized by the following technical scheme:
one of the technical schemes of the invention provides a method for measuring nitric acid or nitrate15A method of N isotopic abundance comprising the steps of:
(1) in the liquid or solid state15Loading the N-labeled nitric acid or nitrate sample, oxide and reducing agent into a reaction tube, vacuumizing and sealing the reaction tube;
(2) heating the reaction tube to generate reaction15N marks nitrogen;
(3) after the reaction tube is cooled to room temperature, the reaction tube is placed into a sample introduction tube connected with a sample introduction system of the gas isotope mass spectrometer, and then the sample introduction tube and a sample introduction pipeline of the gas isotope mass spectrometer connected with the sample introduction tube are continuously vacuumized;
(4) breaking the reaction tube to make it inside15N marked nitrogen is released into the sample introduction pipe and is introduced into the gas isotope mass spectrometer;
(5) detecting and recording the relative intensities of the mass numbers (i.e. mass to charge ratios) of 28, 29 and 30 respectively, and calculating to obtain the corresponding nitric acid or nitrate in the sample15The abundance of the N isotope.
Further, in the step (1),5the N-labeled nitric acid or nitrate sample is15N-labeled nitric acid or nitrate chemical reagent,15N-labeled biological sample,15Nitric acid or nitrate in N-labelled soil or15One or more of the N-labeled water quality samples.
Further, in the step (1), the oxide is one or more of magnesium oxide, copper oxide, chromium oxide, sodium oxide, barium oxide, iron oxide, calcium oxide, aluminum oxide or zinc oxide.
Further, in the step (1), the reducing agent is one or more of zinc powder, iron powder, magnesium powder, copper powder, chromium powder or aluminum powder.
Further, in the step (1), when15When the N-labeled nitric acid or nitrate sample is a liquid sample, the method is carried out by mixing the liquid sample with an oxide and a reducing agentThe addition ratio is (1-100) mu L: (1-100) mg: (1-100) mg;
15when the nitrate sample marked by N is a solid sample, the mass ratio of the nitrate sample marked by N to the oxide and the reducing agent is (1-100) mg: (1-100) mg: (1-100) mg.
Further, in the step (2), the temperature of the heating reaction in the reaction tube is 300-.
Further, in the step (1), vacuumizing the reaction tube until the vacuum degree is below 50 Pa;
in the step (3), the sampling tube is vacuumized until the vacuum degree is reduced to 2 multiplied by 10-5Pa or less.
Further, in the step (3), the detection parameters of the gas isotope mass spectrometer are set as follows: bombarding an ion source (EI) with electrons; the scanning range is 18-45 m/z; the temperature of the ion source is 80-200 ℃; the electron bombardment energy is 50 eV-120 eV; the high voltage is 3kV to 10kV, and the trap voltage is 80V to 200V; the detector is a faraday cup or an electron multiplier tube.
Further, in step (5), in the nitric acid or nitrate sample15The calculation formula of the N isotopic abundance E is as follows:
1) when the isotopic abundance is 0.365-20 (i.e. in the range of more than or equal to 0.365 and less than 20), then
2) When the isotopic abundance is in the range of 20-30 (i.e. in the range of 20-30), then
3) When the isotopic abundance is in the range of 30-99.9 (i.e., in the range of 30-99.9 inclusive), the isotopic abundance is in the range of 30-99.9 inclusive
Wherein E represents15The N isotopic abundance is calculated by atom%15N；
I28Represents a relative strength,%, by mass number of 28;
I29represents a relative strength,%, by mass number of 29;
I30represents a relative strength,%, by mass number of 30.
Note: there are two isotopes of nitrogen in nature,14the N content is 99.635%,15The N content was 0.365%, i.e., sample15The abundance of N isotope is (0.365-99.9) atom%15And N is between.
The second technical proposal of the invention provides a method for measuring nitric acid or nitrate15An apparatus for measuring N-isotopic abundance, which is used for implementing the measuring method, comprises a gas isotope mass spectrometer, a sample inlet pipe and a reaction pipe, wherein one end of the reaction tube is opened, the other end is processed into a fragile section, a tube sealing section is arranged on the position of the reaction tube close to the opening end, the sample inlet pipe consists of a sample inlet pipe section and a sample inlet pipe section which are mutually connected in a sealing way, the sample inlet pipe section is provided with an interface which is connected with a sample inlet system of the gas isotope mass spectrometer in a sealing way, one side end part of the sample inlet pipe section is sealed, an adjusting pipe section is vertically and outwardly led out from the middle position of the first section of the sample inlet pipe and is communicated with the first section of the sample inlet pipe, still sealed arrangement has an adjustment handle on adjusting the pipeline section, adjustment handle's top is passed adjust the pipeline section and stretch into one section inside of appearance pipe, still processes the round hole that has the breakable section that can supply the reaction tube to stretch into on adjustment handle's top. When the reaction tube is arranged in the sampling tube, the fragile section of the reaction tube extends into the round hole, and when the adjusting handle rotates, the fragile section can be broken, so that the gas in the reaction tube is released.
Furthermore, the adjusting handle and the adjusting pipe section are sealed through a frosting surface.
Compared with the prior art, the invention has the following advantages:
1) when the sample amount is more than or equal to 5, the pretreatment time of the sample can be greatly shortened, the efficiency is improved, and high-throughput detection is realized. According to the invention, batch processing operation of a group of 5 samples can be simultaneously carried out in the pre-treatment process of vacuumizing and sealing the reaction tube, the time consumption of the group of 5 samples is less than 0.5h, 2.5h is consumed by utilizing the prior art, and 2h is shortened on a par with 2 h.
2) Developed by the technical scheme15The pretreatment method of the N-labeled nitric acid or nitrate sample is simple to operate,15the method has the advantages of less consumption of N marked samples, low economic cost, high accuracy and precision of test data and the like.
3) The reagent consumption in the experimental process is low, and corrosive reagents of sodium hydroxide and sodium hypobromite solution are not used, so that a large amount of laboratory waste liquid is avoided.
Drawings
FIG. 1 is a schematic view of the structure of a reaction tube used in the present invention;
FIG. 2 is a schematic view of a sample introduction tube in the apparatus of the present invention;
the notation in the figure is:
1-reaction tube, 2-sample injection tube, 3-fragile section, 4-seal tube section, 5-sample injection tube section, 6-sample injection tube section, 7-adjusting handle and 8-round hole.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.
In the following examples, unless otherwise specified, all the conventional commercially available raw materials or conventional processing techniques in the art are indicated.
The invention provides a method for measuring nitric acid or nitrate15A method of N isotopic abundance comprising the steps of:
(1) in the liquid or solid state15Loading the N-labeled nitric acid or nitrate sample, oxide and reducing agent into a reaction tube 1, vacuumizing and sealing the reaction tube 1;
(2) heating the reaction tube 1 to cause the reaction to generate15N marks nitrogen;
(3) after the reaction tube 1 is cooled to room temperature, the reaction tube is placed into a sample inlet tube 2 connected with a sample inlet system of the gas isotope mass spectrometer, and then the sample inlet tube 2 and a sample inlet tube 2 path of the gas isotope mass spectrometer connected with the sample inlet tube are continuously vacuumized;
(4) breaking the reaction tube 1 to make it inside15N-labeled nitrogen is released into the sample introduction pipe 2 and introduced into the gas isotope mass spectrometer;
(5) detecting and recording the relative intensities of the mass numbers (i.e. mass to charge ratios) of 28, 29 and 30 respectively, and calculating to obtain the corresponding nitric acid or nitrate in the sample15The abundance of the N isotope.
In a specific embodiment of the present invention, in step (1),5the N-labeled nitric acid or nitrate sample is15N-labeled nitric acid or nitrate chemical reagent,15N-labeled biological sample,15Nitric acid or nitrate in N-labelled soil or15One or more of the N-labeled water quality samples.
In a specific embodiment of the present invention, in step (1), the oxide is one or more of magnesium oxide, copper oxide, chromium oxide, sodium oxide, barium oxide, iron oxide, calcium oxide, aluminum oxide, or zinc oxide.
In a specific embodiment of the invention, in the step (1), the reducing agent is one or more of zinc powder, iron powder, magnesium powder, copper powder, chromium powder or aluminum powder.
In a specific embodiment of the present invention, in step (1), when15When the N-labeled nitric acid or nitrate sample is a liquid sample, the ratio of the amount of the nitric acid or nitrate sample to the amount of the oxide or the reducing agent added is (1-100) mu L: (1-100) mg: (1-100) mg;
15when the nitrate sample marked by N is a solid sample, the mass ratio of the nitrate sample marked by N to the oxide and the reducing agent is (1-100) mg: (1-100) mg: (1-100) mg.
In a specific embodiment of the present invention, in the step (2), the temperature of the heating reaction in the reaction tube 1 is (300-.
In a specific embodiment of the present invention, in the step (1), the inside of the reaction tube 1 is evacuated to a vacuum degree of 50Pa or less;
in the step (3), the sampling tube 2 is vacuumized until the vacuum degree is reduced to 2 x 10-5Pa or less.
In a specific embodiment of the present invention, in step (3), the detection parameters of the gas isotope mass spectrometer are set as: bombarding an ion source with electrons; the scanning range is 18-45 m/z; the temperature of the ion source is 80-200 ℃; the electron bombardment energy is 50 eV-120 eV; the high voltage is 3kV to 10kV, and the trap voltage is 80V to 200V; the detector is a faraday cup or an electron multiplier tube.
In one embodiment of the present invention, in step (5), the nitric acid or nitrate is in a sample15The calculation formula of the N isotopic abundance E is as follows:
2) when the isotopic abundance is 0.365-20 (i.e. in the range of more than or equal to 0.365 and less than 20), then
2) When the isotopic abundance is in the range of 20-30 (i.e. in the range of 20-30), then
3) When the isotopic abundance is in the range of 30-99.9 (i.e., in the range of 30-99.9 inclusive), the isotopic abundance is in the range of 30-99.9 inclusive
Wherein E represents15The N isotopic abundance is calculated by atom%15N；
I28Represents a relative strength,%, by mass number of 28;
I29represents a relative strength,%, by mass number of 29;
I30represents a relative strength,%, by mass number of 30.
Note: there are two isotopes of nitrogen in nature,14the N content is 99.635%,15The N content was 0.365%, i.e., sample15The abundance of N isotope is (0.365-99.9) atom%15And N is between.
In addition, in order to match the measuring method, the invention also provides a method for measuring nitric acid or nitrate15The N isotope abundance device is shown in fig. 1 and fig. 2, and comprises a gas isotope mass spectrometer, a sample inlet pipe 2 and a reaction pipe 1, wherein one end of the reaction pipe 1 is open, the other end of the reaction pipe 1 is processed into a fragile section 3, a pipe sealing section 4 is arranged on the reaction pipe 1 near the open end of the reaction pipe, the sample inlet pipe 2 consists of a sample inlet pipe section 5 and a sample inlet pipe section 6 which are hermetically connected with each other, an interface which is hermetically connected with a sample inlet system of the gas isotope mass spectrometer is arranged on the sample inlet pipe section 5, one side end of the sample inlet pipe section 6 is sealed, an adjusting pipe section 9 is vertically and outwardly led out from the middle position of the sample inlet pipe section 5, the adjusting pipe section 9 is communicated with the sample inlet pipe section 5, an adjusting handle 7 is hermetically arranged on the adjusting pipe section 9, and the top end of the adjusting handle 7 penetrates through the adjusting pipe section 9 and extends into the sample inlet pipe section 5, a round hole 8 for the fragile section of the reaction tube to extend into is also processed at the top end of the adjusting handle 7. When the reaction tube 1 is arranged in the sampling tube, the fragile section 3 of the reaction tube 1 extends into the round hole 8, and when the adjusting handle 7 rotates, the fragile section can be broken, so that gas in the reaction tube is released.
Furthermore, the adjusting handle 7 and the adjusting pipe section 9 are sealed through a frosted surface.
In addition, the open end of the reaction tube 1 can be connected with a vacuum-pumping system, and the tube-sealing section 4 can be made of a meltable material and can be fused and sealed when being calcined by a butane gas flame gun.
The above embodiments or examples may be implemented individually, or in any combination of two or more.
The above embodiments will be described in more detail with reference to specific examples.
Example 1:
0.5mol/L nitric acid-15N chemical reagent isotopic abundance analysis, comprising the following steps:
(1) preparation of15N-labeled nitrogen gas
The reaction equipment adopted in this embodiment is a reaction tube 1 as shown in fig. 1, an isotope labeled sample, an oxide and a reducing agent can be filled in the reaction tube 1, meanwhile, the open end position of the reaction tube 1 can be communicated with other external equipment, and after the vacuum degree meets the requirement, a butane gas flame gun is used for sealing the tube at the position of a tube sealing section 4 of the reaction tube 1.
As shown in fig. 2, a sample inlet tube 2 adopted in this embodiment is configured by placing a reaction tube 1 in the sample inlet tube 2, extending a fragile section 3 into a circular hole 8 of an adjusting handle 7 located in the sample inlet tube 2, connecting a first section 5 of the sample inlet tube with a second section 6 of the sample inlet tube, connecting a sample inlet system of a gas isotope mass spectrometer with the first section 5 of the sample inlet tube, and continuously vacuumizing a pipeline between the sample inlet tube 2 and the gas isotope mass spectrometer by the isotope mass spectrometer; the maintenance of the vacuum degree is realized. The adjusting handle 7 is rotated to break and release the breakable section 315N marks nitrogen and is introduced into a gas isotope mass spectrometer;
respectively filled with 100mg of copper oxide, 50mg of iron powder and 10 μ L of nitric acid-15And (3) putting the N sample in the reaction tube 1, connecting a vacuum-pumping system with the reaction tube 1, reducing the vacuum degree in the reaction tube 1 to be below 50Pa through the vacuum-pumping system, vacuumizing, and sealing the tube at the position of a tube sealing section 4 by using a butane gas flame gun. Putting the reaction tube 1 after tube sealing into a muffle furnace for reaction at the high temperature of 400 ℃ for 1h to generate15N marks nitrogen;
(2) instrument parameter setting
Electron impact ion source (EI); the scanning range (m/z) is 18-45; the ion source temperature is 100 ℃; the electron energy is 70 eV; the high voltage is 6kV, and the trap voltage is 100V; the signal receiver is a Faraday cage.
(3) Calculation of isotopic abundance
After the reaction tube 1 is cooled to room temperature, the reaction tube 1 is placed into the first section 5 of the sample inlet tube, the first section 5 of the sample inlet tube is connected with the second section 6 of the sample inlet tube, a sample inlet system of the gas isotope mass spectrometer is connected with the first section 5 of the sample inlet tube, and the sample inlet tube 2 and the gas isotope mass spectrometer are connected through the isotope mass spectrometerContinuously vacuumizing the pipeline between the spectrometers; the vacuum degree of the pipeline between the sample tube 2 to be sampled and the gas isotope mass spectrometer is reduced to 2 multiplied by 10-5When the pressure is lower than Pa, the frangible section 3 of the reaction tube 1 is broken by rotating the adjusting handle 7 and is released15N2And introducing into a gas isotope mass spectrometer; setting detection parameters of a gas isotope mass spectrometer, detecting the relative intensities of 28, 29 and 30 mass numbers, and performing parallel test twice, wherein the relative intensities of 28 mass numbers are all less than 1%; the mass number is 29, and the relative strength is respectively: 1.670%, 1.643%; the relative intensities for a mass number of 30 are: 100 percent and 100 percent. The data shows that the relative intensity of 30 mass percent is 100 percent at most, and the relative intensity is substituted into the formula
The calculated E values are 99.172atom percent respectively15N、99.185atom％15N, average 99.18 atom%15And N is added. Meets the limit requirement of isotope in the range of 30-99.9.
Meanwhile, the results of parallel tests by the existing gas isotope mass spectrometry are 99.196atom percent respectively15N and 99.120 atom%15N, average 99.16 atom%15N, the determination results of the two methods are basically equivalent, and the isotope abundance determination method also has very high measurement accuracy.
Example 2:
8mol/L nitric acid-15N chemical reagent isotopic abundance analysis, comprising the following steps:
(1) preparation of15N-labeled nitrogen gas
Respectively filled with 50mg of calcium oxide, 50mg of copper powder and 5 mu L of nitric acid-15And (3) putting the N sample in the reaction tube 1, connecting a vacuum-pumping system with the reaction tube 1, reducing the vacuum degree in the reaction tube 1 to be below 50Pa through the vacuum-pumping system, vacuumizing, and sealing the tube at the position of a tube sealing section 4 of the reaction tube 1 by using a butane gas flame gun. The reaction tube 1 after being sealed is put into a muffle furnace to react for 3 hours at the high temperature of 650 DEG C15N2；
(2) Instrument parameter setting
Electron impact ion source (EI); the scanning range (m/z) is 18-45; the ion source temperature is 100 ℃; the electron energy is 70 eV; the high voltage is 6kV, and the trap voltage is 100V; the signal receiver is a Faraday cage.
(3) Calculation of isotopic abundance
After the reaction tube 1 is cooled to room temperature, the reaction tube 1 is placed into the sample inlet tube section 5, the sample inlet tube section 5 is connected with the sample inlet tube section 6, a sample inlet system of the gas isotope mass spectrometer is connected with the sample inlet tube section 5, and a pipeline between the sample inlet tube 2 and the gas isotope mass spectrometer is continuously vacuumized through the isotope mass spectrometer; the vacuum degree of the pipeline between the sample tube 2 to be sampled and the gas isotope mass spectrometer is reduced to 2 multiplied by 10-5When the pressure is lower than Pa, the frangible section 3 of the reaction tube 1 is broken by rotating the adjusting handle 7 and is released15N2And introducing into a gas isotope mass spectrometer; setting detection parameters of a gas isotope mass spectrometer, detecting the relative intensities of 28, 29 and 30 mass numbers, and performing parallel test twice, wherein the relative intensities of 28 mass numbers are all less than 1%; the mass number is 29, and the relative strength is respectively: 1.751%, 1.772%; the relative intensities for a mass number of 30 are: 100 percent and 100 percent. The data show that the relative intensity of 30 mass is 100% at the maximum, and the relative intensity is substituted into the formula
The calculated E values are 99.132atom percent respectively15N、99.122atom％15N, average 99.13 atom%15And N is added. Meets the limit requirement of isotope in the range of 30-99.9.
Meanwhile, the results of parallel tests by the existing gas isotope mass spectrometry are 99.014atom percent respectively15N and 99.288 atom%15N, average 99.15 atom%15N, the determination results of the two methods are basically equivalent, and the isotope abundance determination method also has very high measurement accuracy.
Example 3:
nitrate in water quality samples15N isotopic abundance analysis, comprising the steps of:
(1) pretreatment of water quality samples
When a small amount of magnesium oxide solution is required to be added into a water sample to ensure that the pH value is 7-9 and the nitrate content is lower than 0.1% (volume is more than 10mL), heating and concentrating at 90 ℃ to about 1 mL.
(2) Preparation of15N-labeled nitrogen gas
50mg of alumina, 50mg of zinc powder and 15 mu L of water quality sample are respectively filled into a reaction tube 1, a vacuumizing system is connected with the reaction tube 1, the vacuum degree in the reaction tube 1 is reduced to below 50Pa through the vacuumizing system, vacuumizing is carried out, and a tube sealing is carried out at the position of a tube sealing section 4 of the reaction tube 1 by using a butane gas flame gun.
The reaction tube 1 after being sealed is put into a muffle furnace to react for 3 hours at the high temperature of 750 ℃ to generate15N marks nitrogen;
(3) instrument parameter setting
Electron impact ion source (EI); the scanning range (m/z) is 18-45; the ion source temperature is 100 ℃; the electron energy is 70 eV; the high voltage is 9kV, and the trap voltage is 100V; the signal receiver is a Faraday cage.
(4) Calculation of isotopic abundance
After the reaction tube 1 is cooled to room temperature, the reaction tube 1 is placed into the sample inlet tube section 5, the sample inlet tube section 5 is connected with the sample inlet tube section 6, a sample inlet system of the gas isotope mass spectrometer is connected with the sample inlet tube section 5, and a pipeline between the sample inlet tube 2 and the gas isotope mass spectrometer is continuously vacuumized through the isotope mass spectrometer; the vacuum degree of the pipeline between the sample tube 2 to be sampled and the gas isotope mass spectrometer is reduced to 2 multiplied by 10-5When the pressure is lower than Pa, the frangible section 3 of the reaction tube 1 is broken by rotating the adjusting handle 7 and is released15N2And introducing into a gas isotope mass spectrometer; setting the detection parameters of the gas isotope mass spectrometer, detecting the relative intensities of the mass numbers 28, 29 and 30, and carrying out parallel test twice, wherein the relative intensities of the mass numbers 28 are respectively as follows: 100 percent and 100 percent; the relative intensities for a mass number of 29 are: 17.393 percent and 17.468 percent, and the relative strength is less than 5 percent when the mass number is 30. The data show that the relative intensity of 28 mass is 100% maximum, which is substituted into the formula
The calculated E values are 8.001atom percent respectively15N、8.032atom％15N, average 8.02 atom%15And N is added. The method meets the limit requirement of isotope in the range of 0.365-20.
Meanwhile, the results of parallel tests by the existing gas isotope mass spectrometry are 8.176atom percent respectively15N and 7.965 atom%15N, average 8.07 atom%15N, the determination results of the two methods are basically equivalent, and the isotope abundance determination method also has very high measurement accuracy.
Example 4:
nitrate in soil samples15N isotopic abundance analysis, comprising the steps of:
(1) pretreatment of soil samples
Drying the soil sample at 70 ℃, crushing and grinding the soil sample after 3 hours, sieving the ground soil sample through a soil sieve with the aperture of 0.25mm, and sealing the ground soil sample for later use;
(2) preparation of15N-labeled nitrogen gas
Respectively loading 50mg of magnesium oxide, 50mg of chromium powder and 100mg of soil sample into a reaction tube 1, connecting a vacuum pumping system with the reaction tube 1, reducing the vacuum degree in the reaction tube 1 to below 50Pa through the vacuum pumping system, vacuumizing, and sealing the tube at the position of a tube sealing section 4 of the reaction tube 1 by using a butane gas flame gun. The reaction tube 1 after being sealed is put into a muffle furnace to react for 5 hours at the high temperature of 700 ℃ to generate15N marks nitrogen;
(3) instrument parameter setting
Electron impact ion source (EI); the scanning range (m/z) is 18-45; the ion source temperature is 100 ℃; the electron energy is 70 eV; the high voltage is 9kV, and the trap voltage is 100V; the signal receiver is a Faraday cage.
(4) Calculation of isotopic abundance
After the reaction tube 1 is cooled to room temperature, the reaction tube 1 is placed into the sample inlet tube section 5, the sample inlet tube section 5 is connected with the sample inlet tube section 6, a sample inlet system of the gas isotope mass spectrometer is connected with the sample inlet tube section 5, and a pipeline between the sample inlet tube 2 and the gas isotope mass spectrometer is continuously vacuumized through the isotope mass spectrometer; the vacuum degree of the pipeline between the sample tube 2 to be sampled and the gas isotope mass spectrometer is reduced to 2 multiplied by 10-5At Pa below, rotateThe adjusting handle 7 breaks the frangible section 3 of the reaction tube 1 and releases the frangible section15N2And introducing into a gas isotope mass spectrometer; setting detection parameters of a gas isotope mass spectrometer, detecting relative intensities of 28 and 29 mass numbers, and performing parallel test twice, wherein the relative intensities of 28 mass numbers are respectively as follows: 100 percent and 100 percent; the relative intensities for a mass number of 29 are: 2.823 percent and 2.705 percent, and the relative strength is less than 1 percent when the mass number is 30. The data show that the relative intensity of 28 mass is 100% maximum, which is substituted into the formula
The calculated E values were 1.392 atom% respectively15N、1.334atom％15N, average 1.36 atom%15And N is added. The method meets the limit requirement of isotope in the range of 0.365-20.
Meanwhile, the results of parallel tests by the existing gas isotope mass spectrometry are respectively 1.385 atom%15N and 1.340 atom%15N, average 1.36 atom%15N, the determination results of the two methods are basically equivalent, and the isotope abundance determination method also has very high measurement accuracy.
Example 5:
nitrate in cell samples15N isotopic abundance analysis, comprising the steps of:
(1) pretreatment of cell samples
Carrying out ultrasonic crushing treatment on a cell sample, centrifuging, taking supernate, adding the supernate into 2mL of aqueous solution, adjusting the pH value to 7-9 by using sodium carbonate, sealing for later use, and heating and concentrating to 0.5 mL;
(2) preparation of15N-labeled nitrogen gas
50mg of zinc oxide and 50mg of aluminum powder are respectively filled, 10 mu L of cell concentrated sample is put into a reaction tube 1, a vacuum pumping system is connected with the reaction tube 1, the vacuum degree in the reaction tube 1 is reduced to below 50Pa through the vacuum pumping system, vacuum pumping is carried out, and a butane gas flame gun is used for sealing the tube at the position of a tube sealing section 4 of the reaction tube 1. Putting the reaction tube 1 after tube sealing into a muffle furnace for reaction at the high temperature of 550 ℃ for 6h to generate15N marks nitrogen;
(3) instrument parameter setting
Electron impact ion source (EI); the scanning range (m/z) is 18-45; the ion source temperature is 120 ℃; the electron energy is 70 eV; the high voltage is 7kV, and the trap voltage is 110V; the signal receiver is a Faraday cage.
(4) Calculation of isotopic abundance
After the reaction tube 1 is cooled to room temperature, the reaction tube 1 is placed into the sample inlet tube section 5, the sample inlet tube section 5 is connected with the sample inlet tube section 6, a sample inlet system of the gas isotope mass spectrometer is connected with the sample inlet tube section 5, and a pipeline between the sample inlet tube 2 and the gas isotope mass spectrometer is continuously vacuumized through the isotope mass spectrometer; the vacuum degree of the pipeline between the sample tube 2 to be sampled and the gas isotope mass spectrometer is reduced to 2 multiplied by 10-5When the pressure is lower than Pa, the frangible section 3 of the reaction tube 1 is broken by rotating the adjusting handle 7 and is released15N2And introducing into a gas isotope mass spectrometer; setting detection parameters of a gas isotope mass spectrometer, detecting relative intensities of 28 and 29 mass numbers, and performing parallel test twice, wherein the relative intensities of 28 mass numbers are respectively as follows: 100 percent and 100 percent; the relative intensities for a mass number of 29 are: 1.865 percent and 1.802 percent, and the relative strength is less than 1 percent when the mass number is 30. The data show that the relative intensity of 28 mass is 100% maximum, which is substituted into the formula
The calculated E values are respectively 0.924 atom%15N、0.893atom％15N, average 0.91 atom%15And N is added. The method meets the limit requirement of isotope in the range of 0.365-20.
Meanwhile, the results of the parallel tests by the existing gas isotope mass spectrometry are respectively 0.877 atom%15N and 1.013 atom%15N, average 0.94 atom%15N, the determination results of the two methods are basically equivalent, and the isotope abundance determination method also has very high measurement accuracy.
Example 6:
calcium nitrate-15N2Chemical reagent isotopic abundance analysis, comprising the steps of:
(1) preparation of15N-labeled nitrogen gas
50mg of sodium oxide, 50mg of zinc powder and 5mg of calcium nitrate15N2And putting the sample in a reaction tube 1, connecting a vacuum-pumping system with the reaction tube 1, reducing the vacuum degree in the reaction tube 1 to be below 50Pa through the vacuum-pumping system, vacuumizing, and sealing the tube at the position of a tube sealing section 4 of the reaction tube 1 by using a butane gas flame gun.
The reaction tube 1 after being sealed is put into a muffle furnace to react for 3 hours at the high temperature of 250 ℃ to generate15N marks nitrogen;
(2) instrument parameter setting
Electron impact ion source (EI); the scanning range (m/z) is 18-45; the ion source temperature is 100 ℃; the electron energy is 70 eV; the high voltage is 6kV, and the trap voltage is 100V; the signal receiver is a Faraday cage.
(3) Calculation of isotopic abundance
After the reaction tube 1 is cooled to room temperature, the reaction tube 1 is placed into the sample inlet tube section 5, the sample inlet tube section 5 is connected with the sample inlet tube section 6, a sample inlet system of the gas isotope mass spectrometer is connected with the sample inlet tube section 5, and a pipeline between the sample inlet tube 2 and the gas isotope mass spectrometer is continuously vacuumized through the isotope mass spectrometer; the vacuum degree of the pipeline between the sample tube 2 to be sampled and the gas isotope mass spectrometer is reduced to 2 multiplied by 10-5When the pressure is lower than Pa, the frangible section 3 of the reaction tube 1 is broken by rotating the adjusting handle 7 and is released15N2And introducing into a gas isotope mass spectrometer; setting the detection parameters of the gas isotope mass spectrometer, detecting the relative intensities of the mass numbers 28, 29 and 30, and carrying out parallel test twice, wherein the relative intensities of the mass numbers 28 are respectively as follows: 100 percent and 100 percent; the relative intensities for a mass number of 29 are: 55.431%, 55.529%; the mass number of 30 and the relative strength are respectively as follows: 7.763% and 7.689%. The data show that the relative intensity of 28 mass is 100% maximum, which is substituted into the formula
The calculated E values are 21.701atom percent respectively15N、21.731atom％15N, average 21.72 atom%15And N is added. Non-isotopic content of 0.365 ℃A restriction within 20. Substituting into formula
The calculated E values are 21.740atom percent respectively15N、21.722atom％15N, average 21.73 atom%15And N is added. The method meets the limitation requirement that the isotope is within the range of 20-30.
Meanwhile, the results of parallel tests by the existing gas isotope mass spectrometry are 21.858atom percent respectively15N and 21.693 atom%15N, average 21.78 atom%15N, the determination results of the two methods are basically equivalent, and the isotope abundance determination method also has very high measurement accuracy.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. For determining nitric acid or nitrate15A method of N isotopic abundance, comprising the steps of:
(1) in the liquid or solid state15Loading the N-labeled nitric acid or nitrate sample, oxide and reducing agent into a reaction tube, vacuumizing and sealing the reaction tube;
(2) heating the reaction tube to generate reaction15N marks nitrogen;
(3) after the reaction tube is cooled to room temperature, the reaction tube is placed into a sample introduction tube connected with a sample introduction system of the gas isotope mass spectrometer, and then the sample introduction tube and a sample introduction pipeline of the gas isotope mass spectrometer connected with the sample introduction tube are continuously vacuumized;
(4) breaking the reaction tube to make it inside15N markReleasing nitrogen into the sample introduction tube and introducing the nitrogen into the gas isotope mass spectrometer;
(5) detecting and recording the relative intensities of the mass numbers of 28, 29 and 30 respectively, and calculating to obtain the corresponding nitric acid or nitrate in the sample15The abundance of the N isotope.
2. The method according to claim 1 for determining nitric acid or nitrate15The method for N isotope abundance is characterized in that in the step (1),5the N-labeled nitric acid or nitrate sample is15N-labeled nitric acid or nitrate chemical reagent,15N-labeled biological sample,15Nitric acid or nitrate in N-labelled soil or15One or more of the N-labeled water quality samples.
3. The method according to claim 1 for determining nitric acid or nitrate15The method for N isotopic abundance is characterized in that in the step (1), the oxide is one or more of magnesium oxide, copper oxide, chromium oxide, sodium oxide, barium oxide, iron oxide, calcium oxide, aluminum oxide or zinc oxide;
the reducing agent is one or more of zinc powder, iron powder, magnesium powder, copper powder, chromium powder or aluminum powder.
4. The method according to claim 1 for determining nitric acid or nitrate15The method for N isotope abundance is characterized in that in the step (1), the15When the N-labeled nitric acid or nitrate sample is a liquid sample, the ratio of the amount of the nitric acid or nitrate sample to the amount of the oxide or the reducing agent added is (1-100) mu L: (1-100) mg: (1-100) mg;
15when the nitrate sample marked by N is a solid sample, the mass ratio of the nitrate sample marked by N to the oxide and the reducing agent is (1-100) mg: (1-100) mg: (1-100) mg.
5. The method according to claim 1 for determining nitric acid or nitrate15The method for N isotope abundance is characterized in that in the step (2), the reaction is carried outThe temperature of the heating reaction in the tube is 300-900 ℃, the material of the reaction tube is a glass tube or a quartz glass tube, and the reaction time is 0.5-8 h.
6. The method according to claim 1 for determining nitric acid or nitrate15The method for N isotope abundance is characterized in that in the step (1), the reaction tube is vacuumized until the vacuum degree is below 50 Pa;
in the step (3), the sampling tube is vacuumized until the vacuum degree is reduced to 2 multiplied by 10-5Pa or less.
7. The method according to claim 1 for determining nitric acid or nitrate15The method for N isotope abundance is characterized in that in the step (3), the detection parameters of the gas isotope mass spectrometer are set as follows: bombarding an ion source (EI) with electrons; the scanning range is 18-45 m/z; the temperature of the ion source is 80-200 ℃; the electron bombardment energy is 50 eV-120 eV; the high voltage is 3kV to 10kV, and the trap voltage is 80V to 200V; the detector is a faraday cup or an electron multiplier tube.
8. The method according to claim 1 for determining nitric acid or nitrate15The method for determining the abundance of N isotopes is characterized in that, in the step (5), the N isotopes are contained in a nitric acid or nitrate sample15The calculation formula of the N isotopic abundance E is as follows:
1) when the isotopic abundance is 0.365-20, the method is used
2) When the isotopic abundance is within the range of 20-30, the isotopic abundance is
3) When the isotopic abundance is within the range of 30-99.9, the method
Wherein E represents15The N isotopic abundance is calculated by atom%15N；
I28Represents a relative strength,%, by mass number of 28;
I29represents a relative strength,%, by mass number of 29;
I30represents a relative strength,%, by mass number of 30.
9. For determining nitric acid or nitrate15The N isotope abundance device is used for implementing the method according to any one of claims 1 to 8, and is characterized by comprising a gas isotope mass spectrometer, a sample inlet pipe and a reaction pipe, wherein one end of the reaction pipe is opened, the other end of the reaction pipe is processed into a fragile section, a pipe sealing section is arranged on the reaction pipe close to the opening end of the reaction pipe, the sample inlet pipe consists of a sample inlet pipe section and a sample inlet pipe section which can be mutually and hermetically connected, an interface which can be hermetically connected with a sample inlet system of the gas isotope mass spectrometer is arranged on the sample inlet pipe section, one side end part of the sample inlet pipe section is sealed, an adjusting pipe section is further vertically and outwards led out from the middle position of the sample inlet pipe section, the adjusting pipe section is communicated with the sample inlet pipe section, an adjusting handle is further hermetically arranged on the adjusting pipe section, and the top end of the adjusting handle penetrates through the adjusting pipe section and extends into the sample inlet pipe section, the top end of the adjusting handle is also provided with a round hole for the fragile section of the reaction tube to extend into.
10. The method according to claim 9 for determining nitric acid or nitrate15The device for N isotope abundance is characterized in that the adjusting handle and the adjusting pipe section are sealed by a frosted surface.
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