CN111965282A - Ultra-micro sulfur isotope analysis system and analysis method - Google Patents

Ultra-micro sulfur isotope analysis system and analysis method Download PDF

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CN111965282A
CN111965282A CN202010830113.XA CN202010830113A CN111965282A CN 111965282 A CN111965282 A CN 111965282A CN 202010830113 A CN202010830113 A CN 202010830113A CN 111965282 A CN111965282 A CN 111965282A
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gas
valve port
concentration
port
helium
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CN111965282B (en
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范昌福
武晓珮
胡斌
高建飞
李延河
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Institute of Mineral Resources of Chinese Academy of Geological Sciences
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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
    • 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
    • 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
    • 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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Abstract

The invention discloses an ultra-micro sulfur isotope analysis system and an analysis method, belongs to the technical field of stable isotope testing, and solves the problems that the existing analysis method is large in sample consumption, low in actual sample utilization rate, high in material consumption cost and incapable of realizing ultra-micro sulfur isotope analysis testing. The ultra-micro sulfur isotope analysis system comprises an element analyzer, a first gas pre-concentration and purification device, a chromatographic column, a second gas pre-concentration and purification device and a mass spectrometer; the element analyzer is connected with a first gas pre-concentration and purification device, the first gas pre-concentration and purification device is connected with a second gas pre-concentration and purification device through a chromatographic column, and the second gas pre-concentration and purification device is connected with a mass spectrometer through a universal interface. The invention has the advantages of less sample consumption, high analysis efficiency, low material consumption cost, capability of realizing ultra-micro sulfur isotope analysis test, analysis precision superior to 0.40 thousandth (1 sigma) and capability of reaching the advanced level of international similar laboratories.

Description

Ultra-micro sulfur isotope analysis system and analysis method
Technical Field
The invention relates to the technical field of stable isotope testing, in particular to an ultra-micro sulfur isotope analysis system and an analysis method.
Background
Sulfur exists in various forms in geological processes and has great isotope fractionation. Sulfur isotope analysis is commonly used to indicate the origin and behavior of sulfur-containing geological materials and is widely used as a tracing method in the study of igneous rock, sediments, hydrothermal fluid and biological processes on earth.
Since the 70's of the 20 th century, the measurement technology of sulfur isotopes has been advancing. Offline SO from initially adopted double entry System (DI-IRMS) isotope Mass spectrometers2Since pretreatment, developments were made to allow the on-line preparation and purification of SO using continuous flow technology2Recent years have seen the development of laser-based in situ analysis allowing higher spatial resolution, but EA-IRMS technology remains an important method for sulfur isotope measurement. EA-IRMS for sulfur isotope measurement generally requires 0.01-0.1mg of sulfur (Flash 2000HT elemental analyzer, Thermo Fisher Scientific), but with the diversification of sulfur isotope analysis materials, including exotic samples, organic and inorganic sediment samples, and other samples requiring high resolution analysis, etc., this method no longer meets the test requirements of researchers for these geological materials.
Sulfur isotope ratio for low sulfur content materials or very small sulfur samples: (34S/32S) measurements have been very challenging due to: the sulfur content of low sulfur material samples is relatively low and sulfur isotope analysis requires large sample volumes to ensure that the IRMS has sufficient SO2For analysis. Therefore, reducing the amount of samples required for EA-IRMS has become a primary problem for expanding the application of this technology.
However, in conventional EA-IRMS analysis, sulfur-containing samples combust in EA to produce SO2The gas is carried by carrier gas with flow rate of 100mL/min, while the mass spectrometer needs to maintain normal working vacuum degree, the flow rate of the capillary tube entering the ion source needs to be controlled at 0.3mL/min, and 99.7 percent of SO generated by burning the sulfur-containing sample is generated due to the mismatching of the flow rates of the carrier gases required by EA and IRMS2The gas is discharged through the shunt interface and is not utilized. The actual utilization of the sulfur-containing sample was only 0.3%. Therefore, how to reduce the loss of the sample and improve the utilization rate of the sample in the analysis process is the key to solve how to reduce the required amount of the sample to meet the ultra-micro sulfur isotope analysis test.
Disclosure of Invention
In view of the above, the present invention provides an ultra-micro sulfur isotope analysis system and an analysis method, so as to solve the problems of the existing analysis method, such as large sample usage, low actual sample utilization rate, high material cost, and incapability of realizing an ultra-micro sulfur isotope analysis test.
The purpose of the invention is mainly realized by the following technical scheme:
in one aspect, an ultra-micro sulfur isotope analysis system is provided, which comprises an element analyzer, a first gas pre-concentration and purification device, a chromatographic column, a second gas pre-concentration and purification device and a mass spectrometer; the element analyzer is connected with a first gas pre-concentration and purification device, the first gas pre-concentration and purification device is connected with a second gas pre-concentration and purification device through a chromatographic column, and the second gas pre-concentration and purification device is connected with a mass spectrometer through a universal interface.
Further, the first gas pre-concentration and purification device is used for carrying out pre-concentration and purification on SO generated in the element analyzer2Carrying out primary enrichment and purification on the gas; the second gas pre-concentration and purification device is used for separating and purifying SO of the chromatographic column2And enriching and purifying the gas again.
Further, the first gas pre-concentration and purification device comprises a first six-way valve and a first liquid nitrogen gas collection assembly; the first liquid nitrogen gas collection assembly comprises a first cold trap and a first liquid nitrogen barrel; the first six-way valve is provided with a first valve port a, a second valve port a, a third valve port a, a fourth valve port a, a fifth valve port a and a sixth valve port a; the first valve port a is an exhaust port and is connected with a first exhaust pipe; the second valve port a is an air inlet and is connected with an air outlet of the oxidation-reduction pipe through a pipeline; the third valve port a and the sixth valve port a are both connected with the first cold trap through external pipelines; the fourth valve port a is a back-blowing helium port and is connected with a helium source through a first back-blowing helium pipe; the fifth valve port a is connected with the chromatographic column through a pipeline.
Further, the second gas pre-concentration and purification device comprises a second six-way valve and a second liquid nitrogen gas collection assembly; the second liquid nitrogen gas collection assembly comprises a second cold trap and a second liquid nitrogen barrel; the second six-way valve is provided with a first valve port b, a second valve port b, a third valve port b, a fourth valve port b, a fifth valve port b and a sixth valve port b; the first valve port b is an exhaust port and is connected with the second exhaust pipe 2; the second valve port b is an air inlet and is connected with the chromatographic column through a pipeline; the third valve port b and the sixth valve port b are both connected with the second cold trap through pipelines; the fourth valve port b is a back-blowing helium port and is connected with a helium source through a second back-blowing helium pipe; the fifth valve port b is connected with the universal interface through a pipeline, and the mass spectrometer is connected with the opening shunting device of the universal interface through a capillary tube.
Further, the first cold trap is a Teflon cold trap; the second cold trap is a stainless steel cold trap, and a quartz fusion capillary tube is arranged in the stainless steel cold trap.
Further, in the test process, the first six-way valve and the second six-way valve have two working modes: a gas enrichment mode and a helium blowback mode.
Further, when the first six-way valve is in the gas enrichment mode, the second valve port a is communicated with the third valve port a, the fourth valve port a is communicated with the fifth valve port a, and the first valve port a is communicated with the sixth valve port a; when the first six-way valve is in a helium back-blowing mode, the first valve port a is communicated with the second valve port a, the third valve port a is communicated with the fourth valve port a, the fifth valve port a is communicated with the sixth valve port a, and back-blowing helium is supplied from the fourth valve port a;
further, when the second six-way valve is in the gas enrichment mode, the second valve port b is communicated with the third valve port b, the fourth valve port b is communicated with the fifth valve port b, and the first valve port b is communicated with the sixth valve port b; when the second six-way valve is in a helium back-blowing mode, the first valve port b is communicated with the second valve port b, the third valve port b is communicated with the fourth valve port b, the fifth valve port b is communicated with the sixth valve port b, and back-blowing helium is supplied from the fourth valve port b.
Further, the elemental analyzer comprises an autosampler and a redox tube, wherein one end of the redox tube is connected with the autosampler, and the other end of the redox tube is connected with the first gas pre-concentration and purification device.
Furthermore, a water trap is arranged on a pipeline connecting the redox pipe and the first gas pre-concentration and purification device.
Furthermore, the lower part of the oxidation-reduction tube is filled with an oxidant and a reducing agent, and the upper part of the oxidation-reduction tube is reserved with a mixing space of helium carrier gas and oxygen.
On the other hand, the method for analyzing the ultra-small amount of sulfur isotope is based on the above system for analyzing the ultra-small amount of sulfur isotope, and comprises the following steps:
the method comprises the following steps: preparing a sample to be detected;
step two: SO generated by reaction in the oxidation-reduction tube by utilizing a first gas pre-concentration and purification device2Performing primary enrichment and purification;
step three: utilizing a second gas pre-concentration and purification device to carry out primary enrichment and purification on SO2Carrying out enrichment and purification again to obtain pure SO2A solid frozen material;
step four: adding SO2Sublimating the solid frozen product to obtain pure SO2Gas and adding purified SO2The gas is fed into a mass spectrometer for testing, and a sulfur isotope test result is obtained.
Further, in the second step, SO is treated2The steps for carrying out primary enrichment and purification are as follows:
the first six-way valve is set to be in a gas enrichment mode, and the automatic sample injector sends a sample to be detected into the oxidation-reduction tube to react to generate SO2Gas, SO2And other impurity gases which can be frozen by liquid nitrogen form solid frozen matters in the first cold trap to finish SO2And (5) primary enrichment and purification of the gas.
Further, in step three, for SO2The steps for carrying out enrichment and purification again comprise:
switching the first six-way valve into a helium back flushing mode, and simultaneously moving the first cold trap out of the first liquid nitrogen barrel and heating to sublimate solid frozen matters in the first cold trap into SO containing target gas2Mixed gas of (2) containing target gas SO2The mixed gas enters a second valve port b of the second six-way valve after being separated and purified by a chromatographic column under the transportation of helium; at the moment, the second six-way valve is in a gas enrichment mode, and the purified SO is separated and purified by a chromatographic column2The gas is frozen and enriched in the second cold trap to form pure SO2Freezing the solid to complete SO2And (4) re-enriching the gas.
Further, in step four, SO is added2Sublimating the solid frozen product to obtain pure SO2In the gas process, the second six-way valve is switched from the gas enrichment mode to the helium back flushing mode, and the second cold trap is removed from the second liquid nitrogen barrel and heated, SO that SO in the second cold trap2Sublimating the solid frozen material into pure SO2A gas.
Compared with the prior art, the invention has at least one of the following beneficial effects:
a) the ultra-micro sulfur isotope analysis system provided by the invention has the advantages that the gas pre-concentration purification device is arranged between the element analyzer and the universal interface, SO that SO generated by burning of a sample to be detected2The gas can be completely collected by freezing, thereby solving the problem of trailing phenomenon caused by incomplete instantaneous combustion of the sample and improving the precision of the test result.
b) According to the ultramicro sulfur isotope analysis system provided by the invention, the six-way valve is connected with back-flushing helium flow in a helium back-flushing mode, SO that SO is reduced2The waste of gas, the utilization ratio of the sample to be tested is improved by 20-100 times, the reduction of the dosage of the sample to be tested not only improves the service life of the oxidation-reduction tube and reduces the ash removal frequency, but also obviously improves the experimental efficiency and reduces the experimental cost.
c) The ultra-micro sulfur isotope analysis method provided by the invention is based on an ultra-micro sulfur element analysis system provided with two gas pre-concentration purification devices, and canCan remove SO generated in the system2The total collection and purification are carried out, so that the utilization rate of a sample to be detected is improved by 20-100 times, the sulfur demand of a system is reduced to 1-5 mug, the service life of a redox tube can be prolonged, the ash removal frequency is reduced, the working efficiency is improved, the analysis precision is better than 0.40 thousandth (1 sigma), and the international leading level is reached.
In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and drawings.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.
FIG. 1 is a schematic view showing the start of the primary enrichment and purification mode of the ultra-trace sulfur isotope analysis system according to the present invention;
FIG. 2 is a schematic view showing the start of the system for analyzing ultra-trace sulfur isotopes according to the present invention entering a re-enrichment and purification mode;
FIG. 3 is a schematic view of the first six-way valve of the present invention in the enrichment mode in the connected state;
FIG. 4 is a schematic view of the first six-way valve of the present invention in a helium blowback mode;
FIG. 5 is a schematic view of the second six-way valve of the present invention in the enrichment mode in the connected state;
FIG. 6 is a schematic view of the second six-way valve of the present invention in the helium blowback mode;
FIG. 7 is a schematic view of the valve port communication states of the first and second six-way valves of FIG. 1;
fig. 8 is a schematic view illustrating the valve port communication states of the first and second six-way valves in fig. 2.
Reference numerals:
1. an autosampler; 1-1, helium carrier gas inlet; 1-2, an oxygen inlet; 2. a redox tube; 3. a first gas pre-concentration purification device; 4-a chromatographic column; 5. a first six-way valve; 5-1, a first valve port a; 5-2, a second valve port a; 5-3, a third valve port a; 5-4, a fourth valve port a; 5-5, a fifth valve port a; 5-6, a sixth valve port a; 6. a first liquid nitrogen gas collection assembly; 6-1, a first cold trap; 6-2, a first liquid nitrogen barrel; 7. a second gas pre-concentration and purification device; 8. a second six-way valve; 8-1 and a first valve port b; 8-2 and a second valve port b; 8-3 and a third valve port b; 8-4, a fourth valve port b; 8-5, a fifth valve port b; 8-6 and a sixth valve port b; 9. a second liquid nitrogen gas collection assembly; 9-1, a second cold trap; 9-2, a second liquid nitrogen barrel; 10. a water trap; 11-a universal interface; 12. an oxidizing agent; 13. a reference gas sample introduction system; 14. a first back-flushing helium pipe; 15. a first exhaust pipe; 16. a mass spectrometer; 17. reducing the copper wire; 18. quartz wool; 19. a second back-blowing helium pipe; 20. a second exhaust pipe.
Detailed Description
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.
Example 1
In one embodiment of the present invention, an ultra-micro sulfur isotope analysis system for analyzing and testing ultra-micro sulfur isotopes in sulfur-containing substances (e.g., rocks, soil, plants, food, etc.) is disclosed, as shown in fig. 1 to 2, and includes an analysis system along an SO line2The gas flow direction pipeline is sequentially provided with an element analyzer, a first gas pre-concentration and purification device 3, a chromatographic column 4, a second gas pre-concentration and purification device 7 and a mass spectrometer 16; the element analyzer is connected with a first gas pre-concentration and purification device 3, the first gas pre-concentration and purification device 3 is connected with a second gas pre-concentration and purification device 7 through a chromatographic column 4, and the second gas pre-concentration and purification device 7 is connected with a mass spectrometer 16 through a universal interface 11.
In this embodiment, the elemental analyzer includes an autosampler 1 and a redox tube 2, and the autosampler 1 is used to sample a sample to be measuredThe sample is sent into a redox tube 2, and an automatic sample injector 1 is provided with a helium carrier gas inlet 1-1 for supplying helium carrier gas and an oxygen inlet 1-2 for supplying oxygen; the redox tube 2 is used for carrying out redox reaction on a sample to be detected to obtain SO2One end of the redox tube 2 is connected with the automatic sample injector 1 through a pipeline, the other end of the redox tube is connected with the first gas pre-concentration and purification device 3 through a pipeline, and a water trap 10 is arranged on the pipeline connecting the redox tube 2 and the first gas pre-concentration and purification device 3.
In this embodiment, the first gas pre-concentration and purification device 3 is used for primarily enriching and purifying the SO generated in the redox tube 22The first gas pre-concentration and purification device 3 comprises a first six-way valve 5 and a first liquid nitrogen gas collection assembly 6; the second gas pre-concentration and purification device 7 is used for enriching and purifying SO obtained by the first gas pre-concentration and purification device 3 and separating and purifying the SO by the chromatographic column 42The gas is enriched and purified again, and the second gas pre-concentration and purification device 7 comprises a second six-way valve 8 and a second liquid nitrogen gas collection component 9.
In this embodiment, the liquid nitrogen gas collection assembly includes a cold trap and a liquid nitrogen barrel, liquid nitrogen is filled in the liquid nitrogen barrel, the liquid nitrogen barrel is of an open structure, and the cold trap can be inserted into or removed from the liquid nitrogen barrel. When enriching SO2When in use, the cold trap is stretched into liquid nitrogen in a liquid nitrogen barrel, and SO is added2Freezing in a cold trap; complete SO2After enrichment, the cold trap was removed from the liquid nitrogen drum to allow solid SO2Returning to the gaseous state. To accelerate solid SO2Changing into gas state, the cold trap has heating function, and independent heating device is arranged in the cold trap to freeze SO2The cold trap is put into a heating device for heating to ensure that solid SO is obtained2Accelerating to become gaseous; or, the outer wall of the cold trap is wound with a heating wire, and the heating wire is electrified and heated to raise the temperature, SO that the SO frozen by the liquid nitrogen in the cold trap2And other gases are heated to a gaseous state.
In this embodiment, the first liquid nitrogen gas collecting assembly 6 is used for freezing and enriching SO generated in the redox tube 22The gas comprises a first cold trap 6-1 and a first liquid nitrogen barrel 6-2, wherein the first cold trap 6-1 is a Teflon cold trap, and the outer diameter of the first cold trap is 1/16 inches; the second liquid nitrogen gas collection component 9 is used for freezing and enriching the first gas againSO which is heated and sublimated in the body pre-concentration and purification device 3 and is separated and purified by the chromatographic column 42The gas comprises a second cold trap 9-1 and a second liquid nitrogen barrel 9-2, wherein the second cold trap 9-1 is a stainless steel cold trap, the outer diameter of the second cold trap is 1/16 inches, the second cold trap 9-1 is directly connected with a second six-way valve 8 after penetrating through a stainless steel protective sleeve through a whole quartz fused capillary tube with the length of 3m, the stainless steel sleeve plays a role in protecting the quartz fused capillary tube, and the outer diameter of the quartz fused capillary tube is 0.32 mm. The whole capillary tube is arranged to reduce the possible air leakage at the joint, and the small-volume quartz fused capillary tube can lead the target gas SO2More concentrated, all gases can reach the ion source in a short time, and the peak shape is narrower.
Primary enrichment and purification of SO2When in use, the first cold trap 6-1 is extended into the liquid nitrogen in the first liquid nitrogen barrel 6-2, and SO generated in the oxidation-reduction tube 2 is oxidized2Freezing in the first cold trap 6-1 to complete SO2Primary enrichment and purification;
complete SO2After primary enrichment and purification, the first cold trap 6-1 is removed from the liquid nitrogen barrel 6-2 to ensure that solid SO is obtained2Returning to the gaseous state, gaseous SO containing impurity gases2Entering a chromatographic column 4, separating by controlling the airflow direction of the second six-way valve 8 and the time of immersing the second cold trap 9-1 into liquid nitrogen, and separating and purifying the SO2The gas enters the second liquid nitrogen gas collection assembly 9 for secondary enrichment.
When SO is enriched again2When in use, the second cold trap 9-1 is extended into the liquid nitrogen in the second liquid nitrogen barrel 9-2, and the SO separated and purified by the chromatographic column 4 is treated2The gas is frozen in the second cold trap 9-1 to form pure SO2A solid frozen material; complete SO2After the secondary enrichment, the second cold trap 9-1 is removed from the second liquid nitrogen bucket 9-2, SO that the pure SO is obtained2The solid frozen substance is restored to the gaseous state again to obtain pure gaseous SO2Mass spectrometer 16 for pure SO2The gas is subjected to isotope ratio determination.
In this embodiment, the first six-way valve 5 and the second six-way valve 8 have the same structure, and are provided with six valve ports and a rotatable valve core, and two adjacent valve ports are connected or disconnected by rotating the valve core, and the first six-way valve 5 and the second six-way valve 8 both include two working modes in the test process: a gas enrichment mode and a helium blowback mode.
As shown in fig. 3 to 4, the first six-way valve 5 is provided with a first port a5-1, a second port a5-2, a third port a5-3, a fourth port a5-4, a fifth port a5-5 and a sixth port a 5-6. The first valve port a5-1 of the first six-way valve 5 is an exhaust port and is connected with the first exhaust pipe 15; the second valve port a5-2 is an air inlet and is connected with the air outlet of the oxidation-reduction tube 2 through a pipeline; the third valve port a5-3 and the sixth valve port a5-6 are both connected with the first cold trap 6-1 through an external pipeline; the fourth valve port a5-4 is a blowback helium port and is connected with a helium source through a first blowback helium pipe 14; the fifth valve port a5-5 is connected with the chromatographic column 4 through a pipeline.
When the first six-way valve 5 is in the gas enrichment mode, the communication states of the ports are as shown in fig. 3, the second port a5-2 is communicated with the third port a5-3, the fourth port a5-4 is communicated with the fifth port a5-5, the first port a5-1 is communicated with the sixth port a5-6, because the third port a5-3 and the sixth port a5-6 are both connected with the first cold trap 6-1 through external pipelines, SO2And other gases that can be frozen by liquid nitrogen are cryogenically concentrated in the first cold trap 6-1, and helium and other gases that cannot be frozen by liquid nitrogen are discharged through the first valve port a 5-1.
When the first six-way valve 5 is in the helium blowback mode, the communication state of the ports is as shown in fig. 4, the first port a5-1 is communicated with the second port a5-2, the third port a5-3 is communicated with the fourth port a5-4, the fifth port a5-5 is communicated with the sixth port a5-6, blowback helium is supplied from the fourth port a5-4, and the blowback helium carries SO carried with the SO2And other impurity gases reach a sixth valve port a5-6 after passing through a third valve port a5-3 and a first cold trap 6-1, and as the sixth valve port a5-6 is communicated with a fifth valve port a5-5, mixed gas flows out of the fifth valve port a5-5 and enters a chromatographic column 4, SO2And other impurity gases are separated and purified by the time difference of the chromatographic column 4 and the passing time ratio SO2The short gas is directly discharged from the second port b8-2 and the first port b8-1 of the second six-way valve, SO2When the gas passes through the chromatographic column, the second six-way valve 8 switches the gas flow to be in a gas enrichment mode in the reverse direction, SO2The gas is trapped in the second cold trap 9-1 after passing through the second cold trap 9-1 immersed in liquid nitrogen, and the impurity gas and the helium carrier gas which can not be frozen are discharged from the first valve port b8-1 after passing through the second cold trap 9-1; when all SO is present2After the gas passes through the chromatographic column 4, the gas flow direction of the second six-way valve 8 is switched, and the gas which does not pass through is directly discharged from the second valve port b8-2 and the first valve port b8-1 of the second six-way valve 8 and does not enter the second cold trap 9-1, SO that the purpose that the target gas SO is obtained2Purification of (4).
As shown in fig. 5 to 6, the second six-way valve 8 is provided with a first port b8-1, a second port b8-2, a third port b8-3, a fourth port b8-4, a fifth port b8-5 and a sixth port b 8-6. The first valve port b8-1 of the second six-way valve 8 is an exhaust port and is connected with the second exhaust pipe 20; the second valve port b8-2 is an air inlet and is connected with the chromatographic column 4 through a pipeline; the third valve port b8-3 and the sixth valve port b8-6 are both connected with the second cold trap 9-1 through pipelines; the fourth valve port b8-4 is a back-blowing helium port and is connected with a helium source through a second back-blowing helium pipe 19; the fifth valve port b8-5 is connected with the universal interface 11 through a pipeline, and the mass spectrometer 16 is connected with the opening shunt device of the universal interface 11 through a capillary tube.
When the second six-way valve 8 is in the gas enrichment mode, the communication states of the ports are as shown in fig. 5, the second port b8-2 is communicated with the third port b8-3, the fourth port b8-4 is communicated with the fifth port b8-5, the first port b8-1 is communicated with the sixth port b8-6, and since the third port b8-3 and the sixth port b8-6 are both connected with the second cold trap 9-1 through external pipes, SO is that2And other gases that can be frozen by liquid nitrogen are cryogenically concentrated in the second cold trap 9-1, and helium and other gases that cannot be frozen by liquid nitrogen are discharged through the first valve port b 8-1.
When the second six-way valve 8 is in the helium blowback mode, the communication state of the ports is as shown in fig. 6, the first port b8-1 is communicated with the second port b8-2, the third port b8-3 is communicated with the fourth port b8-4, the fifth port b8-5 is communicated with the sixth port b8-6, blowback helium is supplied from the fourth port b8-4, and the blowback helium carries SO2The gas reaches a sixth port b8-6 after passing through a third port b8-3 and a second cold trap 9-1, and SO is generated because the sixth port b8-6 is communicated with a fifth port b8-52The gas flows out into the universal port 11 through the fifth valve port b 8-5.
In the embodiment, the redox tube 2 is made of quartz material, the lower part of the redox tube 2 is filled with an oxidant 12 and a reducing agent, the upper part is reserved with a mixed space of helium carrier gas and oxygen, a sample to be tested is subjected to combustion reaction in the mixed space, the reducing agent adopts a reducing copper wire 17, and the oxidant 12 adopts WO with the granularity of 0.85-1.7mm3. Specifically, a reducing copper wire 17 and an oxidant 12 are arranged upwards from the bottom surface of the redox tube 2, and the oxidant 12 and the reducing copper wire 17 are separated by quartz wool 18. Quartz wool 18 is laid on the top surface of the oxidant 12 and below the reducing copper wire 17.
In this embodiment, the chromatographic column 4, the first cold trap 6-1 and the connecting pipeline are made of teflon, SO that the occurrence of SO is avoided2The gas has viscosity and is easy to adhere to the pipe wall, so that the testing precision is influenced, and the influence of the memory effect is reduced.
In this embodiment, the column 4 is placed in a column box having a heating function, and the column box can set a heating temperature so that the heating temperature is kept constant. The column 4 was a teflon tube packed with Poropak QS packing, and the column 4 was 1/8 inches in outside diameter and 30cm long.
In this embodiment, the mass spectrometer 16 and the universal interface 11 were a MAT253 gas isotope mass spectrometer and a Conflo IV universal interface from Thermo Fisher Scientific.
During implementation, the aluminum cup wrapping the sample to be detected is placed in the sample tray of the automatic sample injector 1, the sample tray is vacuumized and purified by helium purging (2-3 times), then the automatic sample injector 1 sends the aluminum cup wrapping the sample to be detected into the redox tube 2, the aluminum cup wrapping the sample to be detected rapidly flashes in a high-temperature oxygen injection environment, and the sample to be detected and excessive oxygen generate SO3，SO3Reduced copper wire 17 to SO2All SO in the redox flow tubes 22The gas is carried out of the redox tube 2 by the helium gas, enters the second valve port a5-2 of the first six-way valve 5 through the water trap 10, at this time, the first six-way valve 5 is in a gas enrichment mode, and since the second valve port a5-2 and the third valve port a5-3 are connected, SO generated in the redox tube 22And others can beThe gas frozen by the liquid nitrogen enters the first cold trap 6-1 and is frozen and enriched into solid frozen matters, helium and other gas which can not be frozen by the liquid nitrogen are discharged from the first valve port a5-1, and SO is finished2Primary enrichment and purification.
When the first cold trap 6-1 in the liquid nitrogen collects all SO2After the gas is generated, the first cold trap 6-1 is removed from the first liquid nitrogen barrel 6-2 and heated, SO that the solid frozen substance in the first cold trap 6-1 is sublimated to contain SO2The first six-way valve 5 is switched to a helium back-blowing mode at the same time, and the back-blown helium carries SO2The mixed gas containing other impurity gases enters from a fourth valve port a5-4 of the first six-way valve 5, sequentially flows through a third valve port a5-3, a first cold trap 6-1, a sixth valve port a5-6 and a fifth valve port a5-5, enters the chromatographic column 4, and contains SO2And the mixed gas of other impurity gases enters the first valve port of the second six-way valve 8 after being separated in the chromatographic column 4, and at the moment, the second six-way valve 8 is in a gas enrichment mode. Since the second valve port b8-2 is connected with the third valve port b8-3, the SO separated and purified by the chromatographic column 42The gas enters the second cold trap 9-1 and is frozen and enriched into solid frozen matters, helium and other gases which cannot be frozen by liquid nitrogen are discharged from the first valve port b8-1, and SO is finished2And enriching and purifying again.
When the second cold trap 9-1 in the liquid nitrogen collects all SO2After the gas is generated, the second cold trap 9-1 is moved out of the second liquid nitrogen barrel 9-2 and heated, and meanwhile, the second six-way valve 8 is switched to a helium back-blowing mode, and back-blowing helium carries SO2Gas enters from a fourth valve port b8-4 of the second six-way valve 8, sequentially flows through a third valve port b8-3, a second cold trap 9-1, a sixth valve port b8-6 and a fifth valve port b8-5 to enter the universal interface 11, and the mass spectrometer 16 is connected with an opening diverter of the universal interface 11 through a capillary tube to connect SO2The gas is introduced into the mass spectrometer 16 for isotope ratio determination.
Compared with the prior art, the system for analyzing the ultra-micro sulfur isotope provided by the embodiment is a key improvement on the basis of a sulfur isotope on-line analysis system of a conventional element analyzer, and two gas pre-concentration and purification devices are arranged between the element analyzer and a universal interfaceTwo gas pre-concentration and purification devices are connected through a chromatographic column to realize the purpose of generating SO2Performing enrichment and purification twice, specifically arranging two six-way valves, two cold traps and a chromatographic column between the element analyzer and the universal interface, wherein the cold trap with the heating function can enrich SO by freezing liquid nitrogen in a gas enrichment mode2The gas is enriched and purified twice to ensure SO generated by burning the sample to be detected2The gas can be completely frozen and collected, so that the tailing phenomenon caused by the fact that the sample cannot be instantly and completely combusted is solved, and other impurity gases which cannot be frozen by liquid nitrogen can be carried by helium and discharged through an exhaust port of the six-way valve; the six-way valve plays a role in switching the gas flow direction and the helium carrier gas flow rate when the gas enrichment mode is changed into a helium back-blowing mode, and SO enriched in the cold trap is carried out by back-blowing helium carrier gas (0.3mL/min) matched with the low-flow-rate interface of the universal interface2All gas is sent into the universal interface, SO that the SO generated by burning the sample to be detected before entering the universal interface2The gas is completely collected, and the back-blowing helium flow accessed through the six-way valve greatly reduces SO2The waste of gas improves the utilization rate of the sample to be measured by more than 20 times, and the minimum amount of the sample to be measured is reduced to below 1/20 of the conventional method, and only about 1-5 mu g of sulfur is needed. The reduction of the dosage of the sample to be tested not only improves the service life of the oxidation-reduction tube and reduces the ash removal frequency, but also obviously improves the experimental efficiency. The analysis system of the embodiment is used for testing, the analysis precision is better than 0.40 thousandth (1 sigma), the difference between the measured value and the true value is within 1 thousandth, and the advanced level of the international similar laboratory is achieved.
Example 2
In another embodiment of the present invention, an ultra-low sulfur isotope analysis method is disclosed, which is based on the ultra-low sulfur isotope analysis system of embodiment 1, and implements an analysis test of ultra-low sulfur isotopes in sulfur-containing substances (such as rocks, soil, plants, food, etc.), and the ultra-low sulfur isotope analysis method includes the following steps:
the method comprises the following steps: preparing a sample to be tested.
Before carrying out a sulfur isotope test experiment on a trace sample, preparing a sample to be testedAnd grinding the sample to be detected to be more than 200 meshes by using the sulfide or sulfate as the sample to be detected. Wherein, a sulfide sample is directly wrapped in an aluminum cup after being ground to 200 meshes, and V with the weight 5 times that of the sulfate sample is added after being ground to 200 meshes2O5Powder, sulfate sample and added V2O5The powder is evenly mixed and then wrapped in an aluminum cup. The amount of the sulfide sample ranges from 15 to 40 mug and the amount of the sulfate sample ranges from 7 to 36 mug.
Step two: SO generated by the reaction in the oxidation-reduction tube 2 is concentrated and purified by the first gas pre-concentration and purification device 32And carrying out primary enrichment and purification.
Specifically, the first six-way valve 5 is set to be in a gas enrichment mode, and the automatic sample injector 1 sends a sample to be detected into the oxidation-reduction tube 2 to react to generate SO2A gas; collecting SO generated in the redox tube 2 by using the first cold trap 6-12Gases and other contaminant gases which can be frozen by liquid nitrogen, SO2And other impurity gases which can be frozen by liquid nitrogen form solid frozen matters in the first cold trap 6-1 to finish SO2And (5) primary enrichment and purification of the gas.
After the work is started, a plurality of samples to be detected wrapped by the aluminum cups are sequentially placed in the sample tray of the automatic sample injector 1, repeated vacuumizing and helium purging purification treatment is carried out on an analysis system, impurity gases are removed, and the background is reduced. The specific implementation process is as follows: closing the helium purging valve, and opening the vacuum pumping valve; and then closing the vacuum air exhaust valve, opening the helium purging valve, repeating the process for 2-3 times, and closing the vacuum air exhaust valve and the helium purging valve to finish the processes of system vacuumizing and helium purging purification treatment.
After the process of vacuumizing the system and purging and purifying helium gas is finished, the automatic sample injector 1 sends the aluminum cup wrapped with the sample to be detected into the redox tube 2, the sample to be detected is filled into the redox tube 2 by the automatic sample injector 1 and simultaneously injected with oxygen for flash combustion, the redox tube 2 is in a high-temperature oxygen-rich environment, the sample to be detected rapidly and fully burns under the flash combustion of the aluminum cup, and the sample to be detected flashes under the peroxy environment to generate SO3And SO2In which SO3SO is generated under the reduction action of the reduced copper wire 172Generation of the target gas SO2And exits the redox tube 2 by being carried by the helium carrier gas through the water trap 10 into the second port a5-2 of the first six-way valve 5. At the moment, the first six-way valve 5 is in a gas enrichment mode, the second valve port a5-2 is communicated with the third valve port a5-3, the fourth valve port a5-4 is communicated with the fifth valve port a5-5, the first valve port a5-1 is communicated with the sixth valve port a5-6, and as the third valve port a5-3 and the sixth valve port a5-6 are both connected with the first cold trap 6-1 through external pipelines, SO is generated in the first six-way valve2And other impurity gases which can be frozen by liquid nitrogen are frozen and enriched in the first cold trap 6-1 to form solid freezers, and helium and other gases which cannot be frozen by liquid nitrogen are discharged from the first valve port a 5-1.
In the second step, to SO2In the process of primary enrichment and purification of the gas, the first six-way valve 5 keeps a gas enrichment mode, the first cold trap 6-1 is always positioned in liquid nitrogen in the gas enrichment mode, or the first cold trap 6-1 descends and is immersed in the liquid nitrogen after a sample to be detected reacts in the redox tube 2 for 30s until all SO generated in the redox tube 22The gas was frozen to a solid state in the first cold trap 6-1(-196 c) in liquid nitrogen. In the primary enrichment process, the second six-way valve 8 is in a gas blowback mode, as shown in fig. 1, that is, the first cold trap 6-1 is in a gas enrichment process, the second cold trap 9-1 is in a purging mode, and the system is purged completely through gas blowback.
Further, in the second step, the reaction temperature of the redox tube was 1020 ℃ and the flow rate of the helium carrier gas was 100 mL/min.
Further, in the second step, the first cold trap 6-1 is kept in liquid nitrogen in the liquid nitrogen barrel 6-2 for 240 +/-10 s to collect all SO generated by the reaction2A gas.
Step three: the SO enriched and purified for the first time is concentrated and purified by a second gas pre-concentration and purification device 72Carrying out enrichment and purification again to obtain pure SO2Freezing the solid.
Specifically, the first six-way valve 5 is switched to a helium back flushing mode, and meanwhile, the first cold trap 6-1 is moved out of the first liquid nitrogen barrel 6-2 and starts to be heated, SO that solid frozen matters in the first cold trap 6-1 are sublimated into solid frozen matters containing target gas SO2Mixed gas of (2) containing the target gasBody SO2The separation and purification are realized by the time difference of the mixed gas passing through the chromatographic column 4 under the transportation of helium. Transit time ratio SO2The short gas is directly discharged from the second port b8-2 and the first port b8-1 of the second six-way valve, SO2When gas passes through the chromatographic column, the second six-way valve switches the gas flow to be in a gas enrichment mode in the reverse direction, as shown in fig. 2, the second valve port b8-2 is communicated with the third valve port b8-3, the fourth valve port b8-4 is communicated with the fifth valve port b8-5, the first valve port b8-1 is communicated with the sixth valve port b8-6, and as the third valve port b8-3 and the sixth valve port b8-6 are both connected with the second cold trap 9-1 through external pipelines, SO is that2The gas is trapped in the cold trap after passing through a second cold trap 9-1 immersed in liquid nitrogen, and the impurity gas and helium carrier gas which can not be frozen are discharged from a first valve port b8-1 after passing through the cold trap; when all SO is present2After the gas passes through the chromatographic column 4, the gas flow direction of the second six-way valve is switched, and the gas which does not pass through is directly discharged from the second valve port b8-2 and the first valve port b8-1 of the second six-way valve and does not enter the second cold trap 9-1, SO that the purpose that the target gas SO is obtained2And (4) enriching and purifying again.
Further, in step three, the flow rate of the helium carrier gas was 100 mL/min.
Further, in the third step, the second cold trap 9-1 is kept in liquid nitrogen in the second liquid nitrogen barrel 9-2 for 240 +/-10 seconds to collect all SO generated by the reaction2A gas.
Further, in the third step, the flow rate of the back-flushing helium gas is 10mL/min, and when the mixed gas which is frozen and enriched by the first cold trap 6-1 and recovered to be gaseous is carried by the back-flushing helium gas to enter the chromatographic column 4, the temperature of the chromatographic column 4 is 90-110 ℃.
Step four: mixing pure SO2Sublimating the solid frozen product to obtain pure SO2Gas and adding purified SO2The gas is fed to a mass spectrometer 16 for testing, resulting in sulfur isotope test results.
Specifically, the second six-way valve 8 is switched from the gas enrichment mode to the helium back-flushing mode, and meanwhile, the frozen SO is discharged2The second cold trap 9-1 is moved out of the second liquid nitrogen barrel 9-2, and the heating wire wound on the second cold trap 9-1 is electrified and heated to ensure that SO in the second cold trap 9-12The solid frozen substance is quickly sublimated into pure SO2A gas; because the second six-way valve 8 is in the helium back-blowing mode, back-blowing helium enters from the fourth valve port b8-4, and the back-blowing helium carries pure SO2The gas reaches a sixth valve port b8-6 after passing through a third valve port b8-3 and a second cold trap 9-1, and pure SO is generated because a fifth valve port b8-5 is communicated with the sixth valve port b8-6 in a helium back-blowing mode2Gas flows out of the fifth valve port b8-5 into the universal interface 11, the mass spectrometer 16 is connected with the opening shunt device of the universal interface 11 through the capillary tube to connect SO2The gas is introduced into the mass spectrometer 16 for isotope ratio determination to obtain a sulfur isotope test result. Isotope mass spectrometer tests SO with mass numbers of 64 and 662Obtained by calculation34And obtaining a sulfur isotope test result by using the ratio of S. Further, the second six-way valve 8 is in a helium back-blowing mode, and the flow rate of back-blowing helium gas is 0.3-1.0 mL/min.
In this embodiment, when the automatic sample injector 1 starts to feed a sample into the reaction tube 2, the system automatically starts timing. When the test is carried out to the 60s-160s, three groups of reference gases are sent to the mass spectrometer through the two-way reference gas sampling system, the sampling time of each group of reference gases is 20s, and the interval time of each two groups of reference gases is 20 s. When the test is carried out to 240s, the first six-way valve 5 is switched to a helium back flushing mode, the first cold trap 6-1 is removed from the first liquid nitrogen barrel 6-2, the cold trap 6-1 is heated to sublimate the solid frozen object into mixed gas, and the mixed gas passes through the chromatographic column 4 and the second six-way valve 8 in sequence, and then SO is added2The gas freezes to the second cold trap 9-1. And when the test is carried out to 600s, switching the second six-way valve 8 to a helium back flushing mode, simultaneously removing the second cold trap 9-1 from the liquid nitrogen, and heating the second cold trap 9-1 to sublimate the solid frozen object into gas. Heated sublimed pure SO by back-blowing helium carrier gas matched with high-flow-rate channel of universal interface 112The gas is fed into the universal interface 11 for mass spectrometry analysis.
The peak time of the sample to be tested is 600s, the data acquisition time in the test process is 700s, the background is reduced by prolonging the data acquisition time, and the interference of the background on the next sample is reduced.
Compared with the prior art, the method for analyzing ultra-trace sulfur isotope provided by the embodiment utilizes the first gas pre-concentration and purification device, the chromatographic column and the second gas pre-concentration and purification device to react with the sample to be detected to generate the SO2Performing enrichment and purification twice, and when the six-way valve is in a gas enrichment mode, utilizing liquid nitrogen to carry out SO2Freezing the gas in cold trap, removing impurity gas, heating and recovering to gaseous SO2The six-way valve plays a role in switching the flow rate and the flow direction of the helium carrier gas when the gas enrichment mode is changed into the helium back-blowing mode, and SO enriched in the cold trap is subjected to back-blowing helium carrier gas matched with the universal interface2Gas is fed into the universal interface, thereby ensuring SO generated by sample combustion before entering the universal interface2The gas is collected completely, the utilization rate of the sample can be improved by 20 times, the sulfur demand of the system is reduced to 1-5 mu g, the service life of the oxidation-reduction tube can be prolonged, the ash removal frequency is reduced, and the working efficiency is improved. Meanwhile, the generation of tailing peaks is effectively avoided, the result precision is improved, the analysis precision is better than 0.40 thousandth (1 sigma), the difference between a measured value and a true value is within 1 thousandth, and the advanced level of the international similar laboratory is achieved.
Example 3
In order to verify that the present invention can satisfy the analysis requirements of ultra-trace sulfur isotopes in precious samples and micro-area samples and that the test results reach the international advanced level, the present example is based on the analysis system of example 1 and the analysis method of example 2 is used to test sulfide and sulfate standard substances.
The selected national sulfide sulfur isotope standard substances are GBW04414 and GBW04415 and the international sulfide sulfur isotope standard substance IAEA-S-3, and the component is Ag2S; selecting international sulfate sulfur isotope standard substances IAEA-SO-5, IAEA-SO-6 and NBS-127, wherein the component is BaSO4(ii) a The purity of the selected standard sulfide and sulfate samples is more than 99.9 percent, the sample weights are respectively 15-40 mu g and 7-36, the selected standard substance samples are ground to be more than 200 meshes, and the samples are wrapped in an aluminum cup for determination. Wherein V which is 5 times of the weight of the standard sulfate sample is added into the standard sulfate sample2O5And (3) powder.
The test was performed using a Thermo Finnigan model MAT-253 stable isotope mass spectrometer (IRMS) in combination with an Elemental Analyzer (EA). And wrapping the sample to be detected in an aluminum cup and placing the sample to be detected in an automatic sample injector. After the start of the work, the aluminum cup wrapping the standard sample to be detected is sent into the oxidation-reduction tube 2 by the automatic sample injector, and the standard sample to be detected is rapidly and fully combusted under the flash combustion of the aluminum cup in the atmosphere of oxygen-enriched gas to generate SO3And SO2，SO3SO is generated under the reduction action of the reduced copper wire 172Generation of the target gas SO2Passing through a first six-way valve 5, a first cold trap 6-1, a chromatographic column 4 and a second six-way valve 8 in sequence under the transportation of helium carrier gas (100mL/min), and finally entering a second cold trap 9-1 in a liquid nitrogen barrel 9-2 to form solid SO2. Solid SO in the second Cold trap2In the heating mode, pure SO is carried by a back-flushing helium carrier gas (0.3mL/min) matched with the high-flow channel of the universal interface 112Gas is sent into a universal interface 11 for mass spectrometry analysis, and the purity of He steel cylinder gas>99.999％。
The working parameters are as follows: initial He gas flow rate of 100mL/min, O2The flow rate is 150mL/min, and the gas purity is more than 99.999 percent; the temperature of the oxidation-reduction tube 2 is set to 1020 ℃, the temperature of the chromatographic column is set to 90 ℃, and SO of the standard sample to be measured2The peak began to appear at 600s, with an overall detection time of 700 ± 10 s. The reference gas sampling system 13 adopts a two-way sampling system, and the ion current intensity of 66 mass numbers in three groups of reference gases is kept at 4-6V.
The working standard used in mass spectrometry is national sulfide sulfur isotope standard substances GBW04414 and GBW04415 and international sulfide sulfur isotope standard substance IAEA-S-3, and the component is Ag2S，34SV-CDTThe actual values are respectively-0.07 ‰, +22.15 ‰, -32.49 ‰. International standard substances IAEA-SO-5, IAEA-SO-6 and NBS-127 of sulfate sulfur isotopes comprise BaSO4，34SV-CDTThe actual values are respectively-0.5 per mill, -34.1 per mill and 20.3 per mill.
TABLE 1 statistical table of the test results of sulfide sulfur isotope standard substance
Figure BDA0002637643060000191
Figure BDA0002637643060000201
TABLE 2 statistical table of the test results of sulfate sulfur isotope standard substance
Figure BDA0002637643060000202
The results of the sulfur isotope test obtained by the analytical method of example 2 are shown in tables 1 to 2. By comparison, the standard sample to be tested34SV-CDTMeasured value and34SV-CDTthe difference of the true values is between 0.0 and 1.00 per mill, the standard deviation is less than 0.40 per mill (1SD), and the advanced level of the international similar laboratory is reached.
It should be noted that the system and method for analyzing ultra-trace sulfur isotopes of the present invention can be used not only for analyzing sulfur isotopes of sulfur-containing minerals such as sulfide and sulfate in rock and soil, but also for analyzing sulfur isotopes of other sulfur-containing substances (such as plants and food).
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

Claims (10)

1. An ultra-micro sulfur isotope analysis system is characterized by comprising an element analyzer, a first gas pre-concentration and purification device (3), a chromatographic column (4), a second gas pre-concentration and purification device (7) and a mass spectrometer (16);
the element analyzer is connected with the first gas pre-concentration and purification device (3), the first gas pre-concentration and purification device (3) is connected with the second gas pre-concentration and purification device (7) through the chromatographic column (4), and the second gas pre-concentration and purification device (7) is connected with the mass spectrometer (16) through a universal interface (11).
2. The ultra-trace sulfur isotope analysis system according to claim 1, characterized in that said first gas pre-concentration purification apparatus (3) comprises a first six-way valve (5) and a first liquid nitrogen gas-collecting assembly (6);
the first liquid nitrogen gas collection assembly (6) comprises a first cold trap (6-1) and a first liquid nitrogen barrel (6-2);
the first six-way valve (5) is provided with a first valve port a (5-1), a second valve port a (5-2), a third valve port a (5-3), a fourth valve port a (5-4), a fifth valve port a (5-5) and a sixth valve port a (5-6);
the first valve port a (5-1) is an exhaust port and is connected with a first exhaust pipe 15; the second valve port a (5-2) is an air inlet and is connected with an air outlet of the oxidation-reduction pipe (2) through a pipeline; the third valve port a (5-3) and the sixth valve port a (5-6) are connected with the first cold trap (6-1) through external pipelines; the fourth valve port a (5-4) is a back-blowing helium port and is connected with a helium source through a first back-blowing helium pipe (14); the fifth valve port a (5-5) is connected with the chromatographic column (4) through a pipeline.
3. The ultra-trace sulfur isotope analysis system according to claim 2, characterized in that said second gas pre-concentration purification apparatus (7) comprises a second six-way valve (8) and a second liquid nitrogen gas collection assembly (9);
the second liquid nitrogen gas collection assembly (9) comprises a second cold trap (9-1) and a second liquid nitrogen barrel (9-2);
the second six-way valve (8) is provided with a first valve port b (8-1), a second valve port b (8-2), a third valve port b (8-3), a fourth valve port b (8-4), a fifth valve port b (8-5) and a sixth valve port b (8-6);
the first valve port b (8-1) is an exhaust port and is connected with a second exhaust pipe (20); the second valve port b (8-2) is an air inlet and is connected with the chromatographic column (4) through a pipeline; the third valve port b (8-3) and the sixth valve port b (8-6) are connected with a second cold trap (9-1) through pipelines; the fourth valve port b (8-4) is a back-flushing helium port and is connected with a helium source through a second back-flushing helium pipe (19); the fifth valve port b (8-5) is connected with the universal interface (11) through a pipeline, and the mass spectrometer 16 is connected with the opening shunting device of the universal interface (11) through a capillary tube.
4. The ultra-trace sulfur isotope analysis system according to claim 3, characterized in that during the test, the first and second six-way valves (5, 8) each have two operating modes: a gas enrichment mode and a helium blowback mode.
5. The ultra-trace sulfur isotope analysis system according to any one of claims 1 to 4, characterized in that said elemental analyzer comprises an autosampler (1) and a redox tube (2), and one end of said redox tube (2) is connected to said autosampler (1) and the other end is connected to said first gas pre-concentration and purification apparatus (3).
6. The system for ultra-trace sulfur isotope analysis according to claim 5, characterized in that a water trap (10) is provided on a pipeline connecting the redox tube (2) and the first gas pre-concentration and purification apparatus (3).
7. The system for ultra-trace sulfur isotope analysis according to claim 6, characterized in that the lower portion of said redox tube (2) is filled with an oxidizing agent (12) and a reducing agent, and the upper portion is reserved with a mixing space for helium carrier gas and oxygen.
8. An ultra-trace sulfur isotope analysis method based on the ultra-trace sulfur isotope analysis system according to claims 1 to 7, comprising the steps of:
the method comprises the following steps: preparing a sample to be detected;
step two: SO generated by the reaction is concentrated and purified by a first gas pre-concentration and purification device (3)2Performing primary enrichment and purification;
step three: the SO enriched and purified for the first time is concentrated and purified by a second gas pre-concentration and purification device (7)2Carrying out enrichment and purification again to obtain pure SO2A solid frozen material;
step four: mixing pure SO2Sublimating the solid frozen product to obtain pure SO2Gas and adding purified SO2The gas is fed into a mass spectrometer (16) for testing, and sulfur isotope test results are obtained.
9. The method for ultra-trace sulfur isotope analysis according to claim 8, wherein in step two, SO is subjected to2The steps for carrying out primary enrichment and purification are as follows:
the first six-way valve (5) is set to be in a gas enrichment mode, and the automatic sample injector (1) sends a sample to be detected into the oxidation-reduction tube (2) to react to generate SO2Gas, SO2And other impurity gases which can be frozen by liquid nitrogen form solid frozen matters in the first cold trap (6-1) to finish SO2And (5) primary enrichment and purification of the gas.
10. The method for ultra-trace sulfur isotope analysis according to claim 8, wherein SO is analyzed in step three2The steps for carrying out enrichment and purification again comprise:
the first six-way valve (5) is switched to a helium back flushing mode, and the first cold trap (6-1) is removed from the first liquid nitrogen barrel (6-2) and heated, SO that solid frozen matters in the first cold trap (6-1) are sublimated into solid frozen matters containing target gas SO2Mixed gas of (2) containing target gas SO2The mixed gas enters a second valve port b (8-2) of a second six-way valve (8) after being separated and purified by a chromatographic column (4) under the conveying of helium gas; at the moment, the second six-way valve (8) is in a gas enrichment mode, and the purified SO separated and purified by the chromatographic column (4)2The gas is frozen and enriched in the second cold trap (9-1) to form pure SO2Freezing the solid to complete SO2And (4) re-enriching the gas.
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CN112730587A (en) * 2021-01-18 2021-04-30 天津师范大学 Tracing method for sulfur element in sludge in river engineering and application
CN113049665A (en) * 2021-04-20 2021-06-29 深圳海关食品检验检疫技术中心 Equipment and method for measuring sulfur isotope content
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