CN112986453A - Method and system for high-resolution determination of organic carbon isotopes in stalagmite - Google Patents
Method and system for high-resolution determination of organic carbon isotopes in stalagmite Download PDFInfo
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- CN112986453A CN112986453A CN202110509034.3A CN202110509034A CN112986453A CN 112986453 A CN112986453 A CN 112986453A CN 202110509034 A CN202110509034 A CN 202110509034A CN 112986453 A CN112986453 A CN 112986453A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/08—Preparation using an enricher
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/14—Preparation by elimination of some components
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/62—Detectors specially adapted therefor
- G01N30/72—Mass spectrometers
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N2030/067—Preparation by reaction, e.g. derivatising the sample
Abstract
The invention discloses a method and a system for high-resolution determination of organic carbon isotopes in stalagmite, wherein the method comprises the steps of filling a stalagmite powder sample into an inverted Y-shaped sample bottle; at the bottom of the first branch, 1mol/L hydrochloric acid is added to the stalagmite powder sample; after chromic acid is added to the bottom of the second branch, a bottle gasket and a bottle cap for sealing are screwed on the first branch; connecting the first branch with a vacuum pipeline of a vacuum system; separating the vacuum system from the first branch and then piercing the double-bore needle into the bottle cap and the bottle pad; filling helium gas into sample bottle by using double holes(ii) a Fully mixing chromic acid in the second branch with the acidified stalagmite powder sample in the first branch; pricking the double-hole needle into the bottle cap and the bottle pad again; organic CO flowing through silver wire purifying tube2After enrichment and purification, introducing a mass spectrometer to measure the carbon isotope composition of the sample, thereby realizing the high-resolution determination of the organic carbon isotope in the stalagmite powder sample.
Description
Technical Field
The invention relates to the field of mass spectrometry detection, in particular to a method and a system for performing high-resolution determination on an organic carbon isotope in a stalagmite bamboo shoot.
Background
The main component of the stalagmite is calcium carbonate, wherein carbon and oxygen isotopes mainly originate from CO generated by plant respiration or plant residue decomposition in soil2It is usually used to reflect the changes of ancient vegetation, and then used to reconstruct ancient environment.
There are two main sources of carbon stores in stalagmites: inorganic carbon in calcium carbonate and carbon in organic matter. At present, in the prior art, the carbon isotope of inorganic carbonate of the stalagmite bamboo shoot is mainly used as a commonly used substitute index, because in the determination method, the carbon isotope of the inorganic carbonate of the stalagmite bamboo shoot is simply and quickly tested, and only dozens of micrograms of powder of the stalagmite bamboo shoot can be used for determination, so that high-resolution record of the carbon isotope of the inorganic carbonate of the stalagmite bamboo shoot can be provided. However, the carbon isotope composition of the inorganic carbonate of the stalagmite is easily interfered by various factors of a cave system in the process from soil to a cave (karst cave), so that the climate and environmental significance of the composition is not clear, and the application is very limited.
The research on the organic carbon isotopes of the stalagmite is less because the organic matter content of the stalagmite is very low (generally, the organic carbon content is 0.1-3 per mill), and the research on the organic carbon isotopes of the stalagmite is not widely carried out due to the limitation of technical means. However, compared with the carbon isotope of inorganic carbonate of the stalagmite, the information carried by the organic matter in the stalagmite is hardly changed in the whole migration process, and the original carbon isotope composition information of the surface soil and the vegetation can be stored, so that uncertain factors of response of the carbon isotope of the inorganic carbonate to the climate can be avoided.
At present, the organic carbon isotope of the sample is generally completed by an element analyzer and a gas isotope ratio mass spectrometer in an on-line way. The specific method comprises the following steps: putting the sample powder into a centrifuge tube, and removing inorganic carbonate by using dilute hydrochloric acid; centrifuging in centrifuge, removing supernatant, and oven drying the lower layer precipitateDry grinding into powder; and finally, measuring the carbon isotope composition by using an element analyzer-gas isotope ratio mass spectrometer. As shown in FIG. 1, when the elemental analyzer-gas isotope ratio mass spectrometer is used for measurement, the treated powder is tightly wrapped by a tin cup, then is fed into an oxidation furnace (filled with chromium oxide and silver-plated cobalt oxide in sequence from top to bottom) at 960 ℃ through an automatic sample injector, and is instantaneously combusted at high temperature under the condition of oxygen introduction to form CO2Then the mixture flows through a reducing furnace (filled with copper wires) at 680 ℃ under the carrying of high-purity helium gas, and H is removed through magnesium perchlorate2O, finally separating and purifying by a chromatographic packed column, introducing into a gas isotope ratio mass spectrometer through a specific interface, and finally obtaining CO2And (3) the carbon isotope composition.
However, the above conventional organic carbon isotope assay technology requires a very large amount of samples (at least 2g of samples are required), and the conventional analysis method cannot realize high-resolution analysis of the organic carbon isotope of the stalagmite bamboo shoot because the organic content of the stalagmite bamboo shoot is too low. For example, Li et al (Li X L, Hu C Y, Huang J H, et al 2014. A9000-year carbon isomeric recorded of acid-soluble organic matter in a stable from Heshang Cave, Central China: Paleoylimate experiments [ J ]. Chemical geography, 388: 71-77.) digests the stalactite powder with hydrochloric acid, evaporates the supernatant to dryness, and determines the carbon isotope of acid-soluble organic matter by a conventional elemental analyzer-isotope ratio mass spectrometer (EA-IRMS). The method has the advantages that the sample consumption is large (2 g), the analysis error is large (0.2-0.4 per mill), and the analysis error is far larger than the analysis error of the inorganic carbon isotope (< 0.08 per mill).
After searching, internationally, scholars have tried to determine the organic carbon isotopes of the stalagmite powder by using a small amount of the stalagmite powder. For example, Blyth (Blyth A J, Shutova Y, Smith C. 2013b. delta13C analysis of bulk Organic matter in spore microorganisms using liquid chromatography-isotope ratio mass spectrometry, Organic Geochem, 55: 22-25), et al, determined the Organic carbon isotopes of the stalagmite powder by liquid chromatography-isotope ratio mass spectrometry (LC-IRMS), namely: firstly, the stalagmite powder is digested by phosphoric acid and then is put inProduction of CO from carbonate under air2Removing; then passing through dilute H2SO4The sample was taken as a mobile phase to LC-IRMS for determination of its organic carbon isotope. The method needs 200mg (23 mu g TOC) of the stalagmite powder, and the precision is +/-0.2 per mill. However, the method needs a relatively large sample amount, only acid-soluble organic matters can be analyzed, the carbon isotopes of the whole rock organic matters of the stalagmite cannot be measured, and partial information of the organic matters can be ignored.
As another example, Lechleitner et al (Lechleitner, FA, Lang, SQ, Haghipour, N, McIntyre, C, Baldini, JUL, Prufer, KM, Eglinton, TI. 2019 Towards organic carbon iso-tope receptors from stands: coupled delta13C and 14C analysis using wet chemical oxidation, Radiocaron. 61(3): 749-764) reported a method for rapid determination of organic carbon isotopes of stalagmites, namely: firstly, acidifying a sample by using phosphoric acid, removing inorganic carbon, and then converting organic carbon of the stalagmite into CO by adopting a wet chemical method2Oxidizing the mixture at 100 ℃ for 1 hour by using sodium persulfate as an oxidizing agent, and oxidizing the organic carbon to obtain CO2Is introduced into a gas isotope ratio mass spectrometer to measure the carbon isotope composition. The method is simple and quick, the background control is low, the dosage is 50mg (5 mu g TOC) of the stalagmite, but the method has the problem that although the authors try several methods, the method still cannot ensure the generation of CO from inorganic carbon2Thorough removal, which greatly disturbs the organic carbon CO2The measurement of (2) and the use amount is relatively large, which limits the high-resolution sampling of the stalagmite.
The inventor has invented a method and system for measuring carbon and oxygen isotopes (CN 109557225B), but the structure and method are not suitable for high resolution measurement of organic carbon isotopes in stalagmite, because CN109557225B is only suitable for measuring inorganic carbon isotopes in carbonate samples, and the principle is to react inorganic carbon in carbonate samples with phosphoric acid to generate CO2The carbon isotope composition of the product was determined after purification. The invention focuses on measuring the organic carbon isotope of the stalagmite bamboo shoot, so that the inorganic carbonation of the stalagmite bamboo shoot is firstly removed, which obviously has a significant difference from CN109557225B in principleAnd (3) distinguishing. In terms of system structure, if a sample bottle in CN109557225B is used and an oxidant is added into the sample bottle through a bottle pad by a syringe, organic matters in the bottle pad may be oxidized and brought into the sample to cause pollution, and the sealing effect of the bottle pad is also affected, which is obviously not suitable for high-resolution determination of organic carbon isotopes in the stalagmite. Moreover, the determination process of the organic carbon isotope of the stalagmite bamboo shoot has more interference elements, and the purification step in CN109557225B does not remove the elements. In addition, the sample ring in CN109557225B needs a large sample amount (at least 150 micrograms of stalagmite powder corresponding to 15 micrograms of C) because there is no liquid nitrogen cold trap, while near 150mg of stalagmite powder is needed to contribute 15 micrograms of organic C in stalagmite, so CN109557225B cannot realize high-resolution sampling of stalagmite.
In summary, the methods provided in the prior art have relatively large sample usage amount, and are not favorable for the application of the high-resolution organic carbon isotope record of the stalagmite bamboo shoot in the ancient environment. Therefore, the accurate determination of the trace organic carbon isotope in the stalagmite through the new method is a technical problem which needs to be solved urgently.
Disclosure of Invention
The invention mainly aims to provide a method and a system for performing high-resolution determination on an organic carbon isotope in a stalagmite bamboo shoot.
In a first aspect of the invention, a method for high resolution determination of organic carbon isotopes in stalagmite is provided, which is used for determining organic carbon isotopes in a stalagmite powder sample; the method comprises the following steps:
loading the stalagmite shoot powder sample into an inverted Y-shaped sample bottle, wherein the inverted Y-shaped sample bottle comprises a first branch and a second branch, and the first branch and the second branch are communicated with each other; the bottom of the first branch is used for placing the stalagmite powder sample, and the bottom of the second branch is closed and is downward;
at the bottom of the first branch, adding 1mol/L hydrochloric acid into the stalagmite powder sample, and reacting for 24 hours to acidify the stalagmite powder sample to remove inorganic carbon in the stalagmite powder sample;
after chromic acid is added to the bottom of the second branch, a bottle gasket and a bottle cap for sealing are screwed on the first branch;
connecting the first branch with a vacuum pipeline of a vacuum system, wherein the vacuum system vacuumizes the sample bottle through the vacuum pipeline to exhaust air in the sample bottle and inorganic CO dissolved in liquid after the stalagmite powder sample is acidified2；
Separating the vacuum system from the first branch, and then puncturing a double-hole needle into the bottle cap and the bottle pad, wherein the double-hole needle comprises a first pipeline and a second pipeline which are positioned inside, helium is introduced into the first pipeline, so that gas in the sample bottle flows out of the sample bottle through the second pipeline;
filling helium into the sample bottle for 5min by using the double holes, wherein the flow rate is 100ml/min, the helium is introduced into the sample bottle through the first pipeline, and gas in the sample bottle flows out of the sample bottle through the second pipeline so as to reduce background interference in the sample bottle;
pulling out the double-hole needle, fully mixing chromic acid in the second branch with the acidified stalagmite powder sample in the first branch, and then heating at 100 ℃ for 1 hour to oxidize organic carbon in the stalagmite powder sample into organic CO2；
Pricking the double-hole needle into the bottle cap and the bottle pad again, and introducing helium gas into the first pipeline of the double-hole needle at a flow rate of 1.5ml/min to introduce the organic CO2Leading the sample to a silver wire purification tube so as to remove impurities generated in the sample bottle;
organic CO flowing through the silver wire purification tube2And introducing the enriched and purified product into a mass spectrometer so as to measure the organic carbon isotopes in the stalagmite powder sample.
According to an embodiment of the present invention, the organic CO to be flowed through the silver wire purification tube2Introducing the enriched and purified powder into a mass spectrometer so as to measure the organic carbon isotopes in the powder sample,the method comprises the following steps:
the organic CO passing through the silver wire purifying tube is subjected to pair treatment by utilizing a first eight-way valve and a first sample ring2Collecting, wherein the first sample ring is an 1/8-inch stainless steel tube; in the first enrichment mode, the first eight-way valve routes the organic CO according to the path of 7-6-3-22Collecting the sample in the first sample ring, and carrying out primary enrichment through a first liquid nitrogen cold trap; and
removing the first liquid nitrogen cold trap, and placing the first sample ring in a liquid nitrogen-alcohol cold trap with the temperature of-85 ℃; in a first release mode, the first eight-way valve routes the organic CO in the first sample ring by 5-6-3-42Carrying the organic CO into a gas chromatographic column by carrier gas for separation and purification, and then carrying out separation and purification on the organic CO through an open shunt tube2The resulting mixture was introduced into the mass spectrometer to measure the organic carbon isotope.
According to an embodiment of the invention, the first eight-way valve routes the organic CO in the first sample ring by 5-6-3-4 in the first release mode2Carrying the organic CO into a gas chromatographic column by carrier gas for separation and purification, and then carrying out separation and purification on the organic CO through an open shunt tube2The method for measuring the organic carbon isotope by introducing into the mass spectrometer, further comprises:
placing the gas chromatography column in a liquid nitrogen-ethylene glycol cold trap at a temperature of-15 ℃ and passing the organic CO out of the gas chromatography column2Performing secondary enrichment through a second eight-way valve and a second sample ring, wherein the second sample ring is a capillary tube with the outer diameter of 1 mm; in the second enrichment mode, the second eight-way valve routes the organic CO according to the path of 7-6-3-22Collecting the sample in the second sample ring, and performing secondary enrichment through a second liquid nitrogen cold trap; and
removing the second liquid nitrogen cold trap and heating the second sample ring to 30 ℃; in a second release mode, the second eight-way valve routes the organic CO in the second sample ring by 5-6-3-42The organic carbon is measured by the carrier gas brought into the open shunt pipe and led into the mass spectrometer after passing through the open shunt pipeSite element; the mass spectrometer is a Delta V Plus type isotope ratio mass spectrometer.
According to an embodiment of the invention, said connecting said first branch with a vacuum line of a vacuum system comprises:
the bottle cap and the bottle pad are pricked by using a porous needle, so that the vacuum pipeline is communicated with the first branch, a silicone tube close to the first branch is arranged on the vacuum pipeline, one end of the porous needle is pricked into the silicone tube and communicated with the vacuum pipeline, the other end of the porous needle is pricked into the bottle cap and the bottle pad, and the porous needle comprises a communicating pipeline used for communicating the vacuum pipeline with the first branch.
According to an embodiment of the invention, said separating said vacuum system from said first branch comprises:
pulling the porous needle out of the bottle cap and the bottle gasket to separate the vacuum line and the first branch from each other.
According to the embodiment of the invention, the first pipeline is provided with a first hole part on the side surface of the double-hole needle, and is provided with a stainless steel pipe at the top end of the double-hole needle, and the helium gas is introduced into the sample bottle from the first hole part through the stainless steel pipe;
the second pipeline is provided with a second hole part at the bottom of the double-hole needle and a capillary at the top end of the double-hole needle, and the organic CO is2Through the second aperture and out of the capillary tube.
According to an embodiment of the invention, wherein: the silver wire purifying tube is a glass tube filled with silver wires, is in gas communication with the second pipeline and is used for removing impurities generated in the sample bottle; the impurities comprise sulfides and halides; the chromic acid is H2SO4-CrO3Solution, test accuracy of said method<±0.1‰。
In a second aspect of the invention, there is provided a system for high resolution determination of organic carbon isotopes in stalagmite, using the determination of organic carbon isotopes in a sample of stalagmite powder according to the method described above; the system comprises an inverted Y-shaped sample bottle, a vacuum system, a perforated needle, a double-perforated needle, a silver wire purification tube, a first eight-way valve, a first sample ring, a first liquid nitrogen cold trap, a gas chromatographic column, a liquid nitrogen-ethylene glycol cold trap, a second eight-way valve, a second sample ring, a second liquid nitrogen cold trap, an open shunt tube and a mass spectrometer; wherein:
the inverted Y-shaped sample bottle comprises a first branch and a second branch, and the first branch and the second branch are communicated with each other; the first branch is used for placing the stalagmite shoot powder sample, and 1mol/L hydrochloric acid is added to acidify and remove inorganic carbon in the stalagmite shoot powder sample; the second branch is closed at the bottom and is downward, so as to directly contain and place chromic acid as an oxidant; the first branch is provided with a bottle gasket and a bottle cap for sealing;
the vacuum system comprises a vacuum pipeline communicated with the sample bottle, and the vacuum system vacuumizes the sample bottle through the vacuum pipeline to exhaust air in the sample bottle and inorganic CO dissolved in liquid after the stalagmite powder sample is acidified2(ii) a Wherein a silicone tube close to the first branch is arranged on the vacuum pipeline;
the inner part of the porous needle comprises a communication pipeline for communicating the vacuum pipeline with the first branch, when in use, one end of the porous needle is pricked into the silicone tube and communicated with the vacuum pipeline, and the other end of the porous needle is pricked into the bottle cap and the bottle pad;
the double-hole needle comprises a first pipeline and a second pipeline which are positioned inside, and helium is introduced into the first pipeline so that gas in the sample bottle flows out of the sample bottle through the second pipeline;
the silver wire purifying tube is a glass tube filled with silver wires and is in gas communication with the second pipeline so as to be used for removing impurities generated in the sample bottle.
The first eight-way valve is a valve with eight connectors, and the first sample ring is a stainless steel tube of 1/8 inches; in the first enrichment mode, the first eight-way valve routes the organic CO according to the path of 7-6-3-22Is collected at the placeThe first sample ring is subjected to primary enrichment through the first liquid nitrogen cold trap; when the first eight-way valve is in a first release mode, the first liquid nitrogen cold trap is removed, the first sample ring is placed in a liquid nitrogen-alcohol cold trap with the temperature of-85 ℃, and the organic CO in the first sample ring is placed in a path of 5-6-3-42Carrying the carrier gas into a gas chromatographic column for separation and purification;
the gas chromatographic column is placed in the liquid nitrogen-glycol cold trap at the temperature of-15 ℃;
the second eight-way valve is a valve with eight interfaces, and the second sample ring is a capillary tube with the outer diameter of 1 mm; in the second enrichment mode, the second eight-way valve routes the organic CO according to the path of 7-6-3-22Collecting the sample in the second sample ring, and performing secondary enrichment through the second liquid nitrogen cold trap; when the second eight-way valve is in the second release mode, the second liquid nitrogen cold trap is removed, the second sample ring is heated to 30 ℃, and the organic CO in the second sample ring is heated to 5-6-3-42Carried into the open shunt tube by a carrier gas;
the open shunt tube is used for enabling the organic CO flowing out of the second eight-way valve2Introducing the sample into the mass spectrometer to measure the organic carbon isotope in the stalagmite shoot powder sample.
According to the embodiment of the invention, the first pipeline is provided with a first hole part on the side surface of the double-hole needle, and is provided with a stainless steel pipe at the top end of the double-hole needle, and the helium gas is introduced into the sample bottle from the first hole part through the stainless steel pipe;
the second pipeline is provided with a second hole part at the bottom of the double-hole needle and a capillary at the top end of the double-hole needle, and the organic CO is2Through the second aperture and out of the capillary tube.
According to an embodiment of the invention, the chromic acid is H2SO4-CrO3Solution, test accuracy of said method<Plus or minus 0.1 per thousand, and the mass spectrometer is a Delta V Plus type isotope ratio mass spectrometer.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art system for determining the carbon isotope composition using an elemental analyzer-gas isotope ratio mass spectrometer;
fig. 2 is a schematic structural diagram of a system for performing high-resolution determination on an organic carbon isotope in a stalagmite shoot according to an embodiment of the present invention.
Fig. 3 is a schematic structural diagram of the connection between the sample bottle and the vacuum system according to the present invention.
Fig. 4 is a schematic structural diagram of the first eight-way valve or the second eight-way valve in fig. 2 in the enrichment mode.
Fig. 5 is a schematic structural diagram of the first eight-way valve or the second eight-way valve in fig. 2 in a release mode.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by a person skilled in the art without any inventive work based on the embodiments of the present invention belong to the protection scope of the present invention.
In order to solve the problems mentioned in the background of the invention, as shown in fig. 2 to 5, embodiments of the present invention provide a system for performing high resolution determination on an organic carbon isotope in a stalagmite shoot, which can perform accurate determination on a trace amount of the organic carbon isotope in the stalagmite shoot. The system comprises an inverted Y-shaped sample bottle 1, a vacuum system 2, a porous needle 3, a double-porous needle 4, a silver wire purification tube 5, a first eight-way valve 61, a first sample ring 71, a first liquid nitrogen cold trap 81, a gas chromatographic column 9, a liquid nitrogen-ethylene glycol cold trap 91, a second eight-way valve 62, a second sample ring 72, a second liquid nitrogen cold trap 82, an open shunt tube 10 and a mass spectrometer 11.
Referring to fig. 2, the inverted "Y" shaped sample bottle 1 includes a first branch 11 and a second branch 12, the first branch 11 and the second branch 12 communicating with each other; the first branch 11 is used for placing a stalagmite powder sample, and 1mol/L hydrochloric acid is added to acidify and remove inorganic carbon in the stalagmite powder sample; the second branch 12 is closed at the bottom and is directed downwards to directly contain and place chromic acid as an oxidizing agent; the first branch 11 is provided with a bottle gasket 13 and a bottle cap 14 for sealing. The bottle cap 14 can be of a structure with a hole in the middle, and the bottle pad 13 is arranged inside the bottle cap 14 and made of rubber and used for sealing the sample bottle 1.
The invention aims to meet the requirement of a method for performing high-resolution determination on organic carbon isotopes in stalagmite, and particularly designs an inverted Y-shaped sample bottle, which is different from the Y-shaped sample bottle in CN109557225B in structure, and is characterized in that a second branch is a closed branch pipe (no bottle pad or bottle cap is arranged), and the direction of the second branch is downward, so that the whole sample bottle is inverted Y-shaped. The structural design of the inverted Y-shaped sample bottle is unique in the invention, because the second branch with the closed bottom can directly contain and place chromic acid (the chromic acid is H)2SO4-CrO3Solution) as an oxidizing agent, and since chromic acid is very corrosive as an oxidizing agent, the corrosive effects of chromic acid can be prevented from affecting the test method of the present invention. On the contrary, if the second branch pipe of CN109557225B (on which the bottle pad and the bottle cap are disposed) is adopted, very strong corrosion will occur, organic matters in the bottle pad will be oxidized and brought into the sample to cause contamination, and the sealing effect of the bottle pad will be affected, so that the overall measuring method of the present invention cannot achieve the expected effect due to the influence of corrosion.
Referring to fig. 3, the vacuum system 2 in the embodiment of the present invention includes a vacuum pipeline 21 communicated with the sample bottle 1, the vacuum system 2 vacuumizes the sample bottle 1 through the vacuum pipeline 21 to exhaust air in the sample bottle 1, and inorganic CO dissolved in liquid after the stalagmite powder sample is acidified2(ii) a Wherein a vacuum is providedA silicone tube 23 is arranged on the pipe 21 close to the first branch. The vacuum system 2 can be controlled to be closed/opened by a valve 24, and the vacuum pumping can be set to 10-3mbar. The silicone tube 23 can be sleeved on the vacuum pipeline 21 below the valve 24 (and sealed with the valve 24 by a sealant), and the bottom of the silicone tube 23 is sealed.
In the embodiment of the invention, the inside of the porous needle 3 comprises a communication pipeline for communicating the vacuum pipeline 21 with the first branch 11, when in use, one end of the porous needle 3 is inserted into the silicone tube 23 and communicated with the vacuum pipeline 21, and the other end is inserted into the bottle cap 14 and the bottle pad 13. Here, one end of the porous needle 3 pierces the silicone tube 23 (e.g., the bottom of the silicone tube 23) and communicates with the vacuum line 21, and the other end pierces the cap and the bottle pad of the first branch 11, thereby achieving the effect of gas communication.
It should be noted that, unlike the connection structure of the sample bottle shaped like the letter "Y" in CN109557225B and the vacuum system, since the sample bottle shaped like the letter "Y" is used in the present invention and the bottom of the second branch 12 is closed and the direction is downward, when the connection structure is connected to the vacuum system, the present invention especially designs the structure that the first branch 11 and the vacuum system are communicated with each other through the holed needle 3, and this structure is easier and more convenient to install and convenient to operate in practice because the sample bottle 1 is kept upright and the structure including the silicone tube 23 and the valve 24 is also kept upright. In addition, CN109557225B is only suitable for measuring inorganic carbon isotope in carbonate sample, and its principle is to react inorganic carbon in carbonate sample with phosphoric acid to generate CO2The carbon isotope composition of the product was determined after purification. The system and the method focus on measuring the organic carbon isotope of the stalagmite bamboo shoot, firstly, the inorganic carbonation of the stalagmite bamboo shoot is removed, and then the organic carbon is oxidized into CO by the oxidant2And the carbon isotope composition of the carbon is determined after the carbon is purified, which is obviously different from CN109557225B in principle.
With continued reference to fig. 2, the dual-hole needle 4 of the present embodiment includes a first tube (not shown) and a second tube (not shown) inside, the first tube being filled with helium gas to allow the gas in the sample bottle 1 to flow out of the sample through the second tubeProduct bottle 1. The first pipeline has a first hole part (not shown) on the side of the double-hole needle 4, and a stainless steel pipe (not shown) on the top end of the double-hole needle 4, and helium gas is introduced into the sample bottle 1 from the first hole part through the stainless steel pipe; the second pipe has a second hole part (not shown) at the bottom of the double-hole needle 4 and a capillary tube at the top of the double-hole needle 4, and the organic CO is2Through the second aperture and out of the capillary tube into the sample vial 1.
For example, the double-hole needle 4 is a needle-type structure having a hole at the bottom and at the side, and the double-hole needle 4 penetrates through the bottle pad 13 in the bottle cap 14 to extend into the sample bottle 1 in use. The top end of the double-hole needle 4 is connected with a stainless steel tube and a capillary tube, helium is introduced into the inverted Y-shaped sample bottle 1 from the stainless steel tube through a small hole on the side surface, and gas (including air or CO) in the inverted Y-shaped sample bottle 12Sample gas) is discharged from the small hole at the bottom through a capillary tube (namely before reaction, the inverted Y-shaped sample bottle 1 discharges air in a helium purging mode, the He discharging process reaches 600s for example, and the flow rate is about 100ml/min for example; after reaction, the inverted Y-shaped sample bottle 1 discharges CO in a helium headspace mode2The gas is discharged, for example at a flow rate of about 1.5 ml/min). In this way, CO in the sample vial 1 can be introduced through the double-bore needle 42And (6) exporting. The stainless steel tube of the double-hole needle 4 is connected with a He gas port at the flow rate of 1.5ml/min, and the capillary tube is communicated with the silver wire purification tube 5 through a port. Pricking the double-hole needle 4 into a bottle pad 13 of the sample bottle 1, and introducing helium into the sample bottle 1 from a first hole part through a stainless steel pipe; CO in sample bottle 12The sample gas is led out from the capillary through the second hole portion, thereby realizing the circulation of the gas.
Referring to fig. 2, the silver wire purification tube 5 according to the embodiment of the present invention is a glass tube filled with silver wires and is in gas communication with the second line for removing impurities generated in the sample bottle 1. For example, CO derived from the double-hole needle 42And removing impurities such as sulfide, halide and the like which may exist through a silver wire purifying pipe 5.
Referring to fig. 2, 4 and 5, the first eight-way valve 61 in this embodiment of the invention is a valve with eight ports, and the first sample ring 71 is a stainless steel tube of 1/8 inches; in the first enrichment mode, the first eight-way valve 61 is pressedOrganic CO is introduced according to the route of 7-6-3-22Collected in the first sample loop 71 and subjected to primary enrichment by a first liquid nitrogen cold trap 81; in the first release mode of the first eight-way valve 61, the first liquid nitrogen-cooled trap 81 is removed, the first sample ring 71 is placed in a liquid nitrogen-alcohol-cooled trap (not shown) with a temperature of-85 ℃, and the organic CO in the first sample ring 71 is treated in a route of 5-6-3-42The carrier gas is carried into a gas chromatographic column 9 for separation and purification.
As shown in FIG. 2, the gas chromatography column 9 in the present example was placed in a liquid nitrogen-ethylene glycol cold trap 91 at a temperature of-15 ℃. Referring to fig. 4 and 5, second eight-way valve 62 in the embodiment of the present invention is a valve having eight ports, and second sample ring 72 is a capillary having an outer diameter of 1 mm; in the second enrichment mode, the second eight-way valve 62 routes the organic CO through the 7-6-3-2 path2Collected in the second sample loop 72 and subjected to secondary enrichment by a second liquid nitrogen cold trap 82; in the second release mode, second eight-way valve 62 removes second liquid nitrogen-cooled trap 82, heats second sample ring 72 to 30 deg.C, and routes organic CO from second sample ring 72 in the 5-6-3-4 direction2Carried into the open shunt 10 by the carrier gas.
It should be noted that the sample bottle of the present invention has more interfering elements than CN109557225B, which interfere with the measurement of sample gas, and the purification step of CN109557225B does not remove these elements, and thus is not suitable for high resolution measurement of organic carbon isotopes in stalagmite. The sample ring in CN109557225B has no liquid nitrogen cold trap and collects only a part of sample CO2The method does not play a role in total enrichment, the required sample amount is large (at least 150 micrograms of the stalagmite powder is required, corresponding to 15 micrograms of C), and if 15 micrograms of organic C in the stalagmite is contributed, nearly 150mg of the stalagmite powder is required, so that the high-resolution sampling work of the stalagmite cannot be realized. In contrast, the method adds a secondary enrichment process, so that the organic CO generated by the stalagmite shoot sample can be enriched2All the components are collected, and organic CO can be realized2High resolution determination of microgram grade samples.
With continued reference to fig. 2, an open shunt 10 in an embodiment of the invention is used to divert flow out of a second sample loop72 organic CO2The sample is introduced into a mass spectrometer 11 to measure the organic carbon isotope in the stalagmite powder sample. The mass spectrometer 11 here may be an isotope ratio mass spectrometer of the Delta V Plus type.
Through the system structure, the measuring system and the measuring method in the embodiment of the invention can realize the carbon isotope measurement of the micro-gram-grade stalagmite bamboo shoot powder, and the measuring precision is less than +/-0.1 per mill, so that the analysis work of the high-resolution organic carbon isotope of the stalagmite bamboo shoot can be carried out.
The embodiment of the invention also provides a method for performing high-resolution determination on an organic carbon isotope in a stalagmite bamboo shoot, which uses the system (shown in fig. 2) for performing high-resolution determination on the organic carbon isotope in the stalagmite bamboo shoot to determine the organic carbon isotope in a stalagmite bamboo shoot powder sample, and the method comprises the following steps:
202, filling a stalagmite powder sample into an inverted Y-shaped sample bottle 1, wherein the inverted Y-shaped sample bottle 1 comprises a first branch 11 and a second branch 12, and the first branch 11 and the second branch 12 are mutually communicated; the bottom of the first branch 11 is used for placing the stalagmite powder sample, and the bottom of the second branch 12 is closed and the direction is downward.
Step 204, adding 1mol/L hydrochloric acid to the stalagmite powder sample at the bottom of the first branch 11, and reacting for 24 hours to acidify the stalagmite powder sample to remove inorganic carbon in the stalagmite powder sample. For example, a sample of a stalagmite powder is loaded into the first branch 11 of a sample vial 1 (i.e., a reaction vial), reacted for 24 hours with 1mol/L hydrochloric acid, and acidified to remove inorganic carbon.
After adding chromic acid to the bottom of the second branch 12, the gasket 13 and the cap 14 for sealing are screwed onto the first branch 11, step 206. For example, chromic acid (H) is added in the second branch 122SO4-CrO3Solution), the bottle gasket 13 and the bottle cap 14 are tightened.
Step 208, connecting the first branch 11 with a vacuum pipeline 21 of a vacuum system 2, and vacuumizing the sample bottle 1 by the vacuum system 2 through the vacuum pipeline 21 to completely exhaust air in the sample bottle 1 and inorganic CO dissolved in liquid after the stalagmite powder sample is acidified2. For example, the sample bottle 1 is put inVacuum is pumped in the vacuum system 2, the sample bottle 1 is vacuumized to exhaust the air in the sample bottle 1, and the inorganic CO2 dissolved in the liquid after the sample is acidified.
According to some embodiments of the invention, connecting the first branch with a vacuum line of a vacuum system comprises: the bottle cap 14 and the bottle pad 13 are inserted by the porous needle 3, so that the vacuum pipeline 21 and the first branch 11 are communicated with each other, wherein the vacuum pipeline 21 is provided with a silicone tube 23 close to the first branch 1, one end of the porous needle 3 is inserted into the silicone tube 23 and communicated with the vacuum pipeline 21, the other end is inserted into the bottle cap 14 and the bottle pad 13, and the porous needle 3 internally comprises a communication pipeline (not shown) for communicating the vacuum pipeline 21 and the first branch 11.
In step 210, the vacuum system 2 is separated from the first branch 11, and then the two-hole needle 4 is inserted into the bottle cap 14 and the bottle pad 13, wherein the two-hole needle 4 includes a first pipe (not shown) and a second pipe (not shown) inside, and the first pipe is filled with helium gas to make the gas in the sample bottle 1 flow out of the sample bottle through the second pipe.
According to some embodiments of the invention, separating the vacuum system 2 from the first branch 11 comprises: the perforated needle 3 is pulled out from the bottle cap and the bottle gasket so that the vacuum line and the first branch are separated from each other. The first pipeline is provided with a first hole part on the side surface of the double-hole needle 4, the top end of the double-hole needle 4 is provided with a stainless steel pipe, and helium gas is introduced into the sample bottle 1 from the first hole part through the stainless steel pipe; the second pipeline has a second hole part at the bottom of the double-hole needle 4, and has a capillary tube at the top of the double-hole needle 4 for organic CO2Through the second aperture and out of the capillary tube into the sample vial 1.
And 212, filling helium into the sample bottle 1 for 5min by using the double-hole needle 4, wherein the flow rate is 100ml/min, the helium is introduced into the sample bottle 1 through the first pipeline, and gas in the sample bottle 1 flows out of the sample bottle 1 through the second pipeline, so that the positive pressure state in the sample bottle 1 is ensured, and the background interference in the sample bottle 1 is further reduced.
For example, the sample vial 1 is filled with helium gas for 5min using the double-hole needle 4. The stainless steel tube of the double-hole needle 4 at this time was connected to the He port at a flow rate of 100ml/min, and the capillary was exposed to air. The double-hole needle 4 is inserted into a bottle cap 14 and a bottle pad 13 of the sample bottle 1, the first pipeline is provided with a first hole part (not shown) on the side surface of the double-hole needle 4, the top end of the double-hole needle 4 is provided with a stainless steel pipe (not shown), and helium is introduced into the sample bottle 1 from the first hole part through the stainless steel pipe; the second line has a second hole portion (not shown) at the bottom of the double-hole needle 4 and a capillary tube (not shown) at the top end of the double-hole needle 4, and the gas in the sample bottle 1 flows through the second hole portion and flows out of the capillary tube to be discharged into the air. Thus, the pressure in the sample bottle 1 is kept in a positive pressure state, and the gas of the subsequent reaction in the sample bottle 1 is ensured not to leak, so that the isotope is fractionated; meanwhile, the device plays a role in further emptying, and the background in the sample bottle 1 is low.
Step 214, pulling out the double-hole needle 4, fully mixing chromic acid in the second branch 12 with the acidified stalagmite bamboo shoot powder sample in the first branch 11, and then heating at 100 ℃ for 1 hour to oxidize organic carbon in the stalagmite bamboo shoot powder sample into organic CO2. For example, after the inflation with He gas, the double-hole needle 4 is pulled out, the chromic acid in the second branch 12 is mixed with the sample in the first branch 11, and the mixture is heated at 100 ℃ for 1 hour to oxidize the organic carbon in the sample to CO2。
Step 216, the double-hole needle 4 is inserted into the bottle cap 14 and the bottle pad 13 again, and helium gas is introduced into the first pipeline of the double-hole needle 4 at a flow rate of 1.5ml/min, so as to introduce organic CO2And led out to the silver wire purification tube 5, thereby removing impurities generated in the sample bottle 1. For example, the silver wire purifying tube 5 is a glass tube filled with silver wires, is in gas communication with the second pipeline, and is used for removing impurities generated in the sample bottle 1; the impurities include sulfides and halides. For example, the silver wire purification tube 5 is a glass tube filled with silver wires, and one end of the glass tube is connected with the capillary tube of the double-hole needle 4 through a port to remove impurities such as sulfide and halide generated in the sample bottle 1.
Step 218, pass the organic CO through the silver wire purification tube 52After enrichment and purification, the product is introduced into a mass spectrometer 11, so that the organic carbon isotopes in the powder sample can be measured.
As an example, step 218 further comprises, for example: 220, utilize the first eight way valve 61 and 71 pairs of organic CO after passing through a silver wire purification tube 52The collection was performed with the first sample ring 71 being an 1/8 inch stainless steel tube; in the first enrichment mode, the first eight-way valve 61 routes the organic CO in the 7-6-3-2 path2Collected in the first sample loop 71 and subjected to primary enrichment by a first liquid nitrogen cold trap 81; and removing the first liquid nitrogen cold trap 81 and placing the first sample ring 71 in a liquid nitrogen-alcohol cold trap at a temperature of-85 ℃; in the first release mode, the first eight-way valve 61 routes the organic CO in the first sample ring 71 by 5-6-3-42The carrier gas is carried into the gas chromatographic column 9 for separation and purification (water and other impurities are remained in the first sample ring 71), and then the separated and purified organic CO is separated and purified by the open shunt pipe 102The sample was introduced into a mass spectrometer 11 to measure the organic carbon isotope.
As an example, step 220 further comprises: step 222, placing the gas chromatographic column 9 in a liquid nitrogen-ethylene glycol cold trap 91 (for removing various impurities in the gas) with the temperature of-15 ℃, and discharging the organic CO flowing out of the gas chromatographic column 92Performing secondary enrichment through the second eight-way valve 62 and the second sample ring 72, wherein the second sample ring 72 is a capillary tube with an outer diameter of 1mm (the tube diameter is very small, so that the sample gas pressure is large enough to improve the ion current intensity entering the mass spectrometer, and thus the required sample amount is reduced); in the second enrichment mode, the second eight-way valve 62 routes the organic CO through the 7-6-3-2 path2Collected in the second sample loop 72 and subjected to secondary enrichment by a second liquid nitrogen cold trap 82; and removing second liquid nitrogen cold trap 82 and heating second sample ring 72 to 30 ℃; in the second release mode, the second eight-way valve 62 routes the organic CO in the second sample loop 72 by 5-6-3-42The carrier gas is brought into the open shunt pipe 10 and is led into a mass spectrometer 11 after passing through the open shunt pipe 10 to measure the organic carbon isotope; the mass spectrometer 11 is a Delta V Plus type isotope ratio mass spectrometer.
For example, each of the first eight-way valve 61 and the second eight-way valve 62 may be a valve having eight ports, and the structure thereof is as shown in fig. 4 and 5. An ion source in the mass spectrometer 11 (e.g., a gas isotope ratio mass spectrometer) can separate the gasThe ions are ionized and the ionized gas enters the flight tube at an initial velocity through an accelerating electric field. The flight pipe is bent, the magnet is arranged above the flight pipe, charged molecules are separated due to different mass-to-charge ratios, and the bending degree of molecules containing heavy isotopes (large mass-to-charge ratio) is smaller than that of molecules containing light isotopes (small mass-to-charge ratio). Because there is a Faraday cup collector at the end of the flight tube, it can be used to measure the ion beam intensity with a specific mass after magnet separation, and finally obtain CO2Isotope of carbon in gas (. delta.)13C) And (4) forming.
Through the system structure and the determination method, the determination system and the determination method in the embodiment of the invention can acidify the stalagmite powder to remove inorganic carbon, and oxidize organic carbon into CO by chromic acid2Then, the carbon isotope composition is measured by introducing the carbon isotope composition into a gas isotope ratio mass spectrometer. The measuring system and the measuring method can realize the carbon isotope measurement of the microgram-grade stalagmite bamboo shoot powder and have the advantages of high measuring precision<Plus or minus 0.1 per mill, so that the analysis work of the high-resolution organic carbon isotope of the stalagmite bamboo shoot can be carried out.
From the above description of the embodiments, it will be clear to those skilled in the art that the present invention may be implemented by other structures, and the features of the present invention are not limited to the above preferred embodiments. Any changes or modifications that can be easily conceived by those skilled in the art are also intended to be covered by the scope of the present invention.
Claims (10)
1. A method for carrying out high-resolution determination on an organic carbon isotope in a stalagmite bamboo shoot is used for determining the organic carbon isotope in a stalagmite bamboo shoot powder sample; the method comprises the following steps:
loading the stalagmite shoot powder sample into an inverted Y-shaped sample bottle, wherein the inverted Y-shaped sample bottle comprises a first branch and a second branch, and the first branch and the second branch are communicated with each other; the bottom of the first branch is used for placing the stalagmite powder sample, and the bottom of the second branch is closed and is downward;
at the bottom of the first branch, adding 1mol/L hydrochloric acid into the stalagmite powder sample, and reacting for 24 hours to acidify the stalagmite powder sample to remove inorganic carbon in the stalagmite powder sample;
after chromic acid is added to the bottom of the second branch, a bottle gasket and a bottle cap for sealing are screwed on the first branch;
connecting the first branch with a vacuum pipeline of a vacuum system, wherein the vacuum system vacuumizes the sample bottle through the vacuum pipeline to exhaust air in the sample bottle and inorganic CO dissolved in liquid after the stalagmite powder sample is acidified2；
Separating the vacuum system from the first branch, and then puncturing a double-hole needle into the bottle cap and the bottle pad, wherein the double-hole needle comprises a first pipeline and a second pipeline which are positioned inside, helium is introduced into the first pipeline, so that gas in the sample bottle flows out of the sample bottle through the second pipeline;
filling helium into the sample bottle for 5min by using the double holes, wherein the flow rate is 100ml/min, the helium is introduced into the sample bottle through the first pipeline, and gas in the sample bottle flows out of the sample bottle through the second pipeline so as to reduce background interference in the sample bottle;
pulling out the double-hole needle, fully mixing chromic acid in the second branch with the acidified stalagmite powder sample in the first branch, and then heating at 100 ℃ for 1 hour to oxidize organic carbon in the stalagmite powder sample into organic CO2；
Pricking the double-hole needle into the bottle cap and the bottle pad again, and introducing helium gas into the first pipeline of the double-hole needle at a flow rate of 1.5ml/min to introduce the organic CO2Leading the sample to a silver wire purification tube so as to remove impurities generated in the sample bottle;
organic CO flowing through the silver wire purification tube2And introducing the enriched and purified product into a mass spectrometer so as to measure the organic carbon isotopes in the stalagmite powder sample.
2. The method for high resolution determination of organic carbon isotopes in stalagmite as claimed in claim 1 wherein the organic CO to be passed through the silver wire purification tube2After enrichment and purification, introducing the obtained product into a mass spectrometer so as to measure the organic carbon isotopes in the stalagmite powder sample, wherein the method comprises the following steps:
the organic CO passing through the silver wire purifying tube is subjected to pair treatment by utilizing a first eight-way valve and a first sample ring2Collecting, wherein the first sample ring is an 1/8-inch stainless steel tube; in the first enrichment mode, the first eight-way valve routes the organic CO according to the path of 7-6-3-22Collecting the sample in the first sample ring, and carrying out primary enrichment through a first liquid nitrogen cold trap; and
removing the first liquid nitrogen cold trap, and placing the first sample ring in a liquid nitrogen-alcohol cold trap with the temperature of-85 ℃; in a first release mode, the first eight-way valve routes the organic CO in the first sample ring by 5-6-3-42Carrying the organic CO into a gas chromatographic column by carrier gas for separation and purification, and then carrying out separation and purification on the organic CO through an open shunt tube2The resulting mixture was introduced into the mass spectrometer to measure the organic carbon isotope.
3. The method for high resolution determination of organic carbon isotopes in stalagmite as claimed in claim 2, wherein said first eight-way valve routes said organic CO in said first sample ring in a 5-6-3-4 way in said first release mode2Carrying the organic CO into a gas chromatographic column by carrier gas for separation and purification, and then carrying out separation and purification on the organic CO through an open shunt tube2The method for measuring the organic carbon isotope by introducing into the mass spectrometer, further comprises:
placing the gas chromatography column in a liquid nitrogen-ethylene glycol cold trap at a temperature of-15 ℃ and passing the organic CO out of the gas chromatography column2Performing secondary enrichment through a second eight-way valve and a second sample ring, wherein the second sample ring is a capillary tube with the outer diameter of 1 mm; in the second enrichment mode, the second eight-way valve is according to 7-6-3-2 route to the organic CO2Collecting the sample in the second sample ring, and performing secondary enrichment through a second liquid nitrogen cold trap; and
removing the second liquid nitrogen cold trap and heating the second sample ring to 30 ℃; in a second release mode, the second eight-way valve routes the organic CO in the second sample ring by 5-6-3-42The carrier gas is carried into the open shunt pipe, and the carrier gas is guided into the mass spectrometer after passing through the open shunt pipe to measure the organic carbon isotope; the mass spectrometer is a Delta V Plus type isotope ratio mass spectrometer.
4. The method of claim 1, wherein the connecting the first branch to a vacuum line of a vacuum system comprises:
the bottle cap and the bottle pad are pricked by using a porous needle, so that the vacuum pipeline is communicated with the first branch, a silicone tube close to the first branch is arranged on the vacuum pipeline, one end of the porous needle is pricked into the silicone tube and communicated with the vacuum pipeline, the other end of the porous needle is pricked into the bottle cap and the bottle pad, and the porous needle comprises a communicating pipeline used for communicating the vacuum pipeline with the first branch.
5. The method of claim 4, wherein the separating the vacuum system from the first branch comprises:
pulling the porous needle out of the bottle cap and the bottle gasket to separate the vacuum line and the first branch from each other.
6. The method for high resolution determination of organic carbon isotopes in stalagmite as claimed in claim 1 wherein said first conduit has a first bore section at the side of said double-bore needle and a stainless steel tube at the tip of said double-bore needle, said helium gas passing through said stainless steel tube from said first bore section into said sample vial;
the second pipeline is provided with a second hole part at the bottom of the double-hole needle and a capillary at the top end of the double-hole needle, and the organic CO is2Through the second aperture and out of the capillary tube.
7. The method for high resolution determination of isotopes of organic carbon in stalagmite as claimed in claim 1, wherein:
the silver wire purifying tube is a glass tube filled with silver wires, is in gas communication with the second pipeline and is used for removing impurities generated in the sample bottle; the impurities comprise sulfides and halides; the chromic acid is H2SO4-CrO3Solution, test accuracy of said method<±0.1‰。
8. A system for high resolution determination of organic carbon isotopes in stalagmites, using the method according to any one of claims 1-7 for determining organic carbon isotopes in a sample of stalagmite powder; the system comprises an inverted Y-shaped sample bottle, a vacuum system, a perforated needle, a double-perforated needle, a silver wire purification tube, a first eight-way valve, a first sample ring, a first liquid nitrogen cold trap, a gas chromatographic column, a liquid nitrogen-ethylene glycol cold trap, a second eight-way valve, a second sample ring, a second liquid nitrogen cold trap, an open shunt tube and a mass spectrometer; wherein:
the inverted Y-shaped sample bottle comprises a first branch and a second branch, and the first branch and the second branch are communicated with each other; the first branch is used for placing the stalagmite shoot powder sample, and 1mol/L hydrochloric acid is added to acidify and remove inorganic carbon in the stalagmite shoot powder sample; the second branch is closed at the bottom and is downward, so as to directly contain and place chromic acid as an oxidant; the first branch is provided with a bottle gasket and a bottle cap for sealing;
the vacuum system comprises a vacuum pipeline communicated with the sample bottle, and the vacuum system is connected with the sample bottle through the vacuum pipelineVacuumizing the sample bottle to exhaust air in the sample bottle and inorganic CO dissolved in liquid after the stalagmite powder sample is acidified2(ii) a Wherein a silicone tube close to the first branch is arranged on the vacuum pipeline;
the inner part of the porous needle comprises a communication pipeline for communicating the vacuum pipeline with the first branch, when in use, one end of the porous needle is pricked into the silicone tube and communicated with the vacuum pipeline, and the other end of the porous needle is pricked into the bottle cap and the bottle pad;
the double-hole needle comprises a first pipeline and a second pipeline which are positioned inside, and helium is introduced into the first pipeline so that gas in the sample bottle flows out of the sample bottle through the second pipeline;
the silver wire purifying tube is a glass tube filled with silver wires and is in gas communication with the second pipeline so as to remove impurities generated in the sample bottle;
the first eight-way valve is a valve with eight connectors, and the first sample ring is a stainless steel tube of 1/8 inches; in the first enrichment mode, the first eight-way valve routes the organic CO according to the path of 7-6-3-22Collecting the sample in the first sample ring, and performing primary enrichment through the first liquid nitrogen cold trap; when the first eight-way valve is in a first release mode, the first liquid nitrogen cold trap is removed, the first sample ring is placed in a liquid nitrogen-alcohol cold trap with the temperature of-85 ℃, and the organic CO in the first sample ring is placed in a path of 5-6-3-42Carrying the carrier gas into a gas chromatographic column for separation and purification;
the gas chromatographic column is placed in the liquid nitrogen-glycol cold trap at the temperature of-15 ℃;
the second eight-way valve is a valve with eight interfaces, and the second sample ring is a capillary tube with the outer diameter of 1 mm; in the second enrichment mode, the second eight-way valve routes the organic CO according to the path of 7-6-3-22Collecting the sample in the second sample ring, and performing secondary enrichment through the second liquid nitrogen cold trap; when the second eight-way valve is in the second release mode, the second liquid nitrogen cold trap is removed, the second sample ring is heated to 30 ℃, and 5-6-3-4 pathway of the organic CO in the second sample Ring2Carried into the open shunt tube by a carrier gas;
the open shunt tube is used for flowing the organic CO out of the second sample ring2Introducing the sample into the mass spectrometer to measure the organic carbon isotope in the stalagmite shoot powder sample.
9. The system for high resolution determination of organic carbon isotopes in stalagmite as claimed in claim 8 wherein said first conduit has a first bore portion at the side of said double-bore needle and a stainless steel tube at the tip of said double-bore needle, said helium gas passing through said stainless steel tube from said first bore portion into said sample vial;
the second pipeline is provided with a second hole part at the bottom of the double-hole needle and a capillary at the top end of the double-hole needle, and the organic CO is2Through the second aperture and out of the capillary tube.
10. The system for high resolution determination of organic carbon isotopes in stalagmites according to claim 8, wherein the chromic acid is H2SO4-CrO3Solution, test accuracy of said method<Plus or minus 0.1 per thousand, and the mass spectrometer is a Delta V Plus type isotope ratio mass spectrometer.
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