CN111965282B - Ultra-trace sulfur isotope analysis system and analysis method - Google Patents
Ultra-trace sulfur isotope analysis system and analysis method Download PDFInfo
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- CN111965282B CN111965282B CN202010830113.XA CN202010830113A CN111965282B CN 111965282 B CN111965282 B CN 111965282B CN 202010830113 A CN202010830113 A CN 202010830113A CN 111965282 B CN111965282 B CN 111965282B
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Abstract
The invention discloses an ultra-trace 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 consumable cost and incapable of realizing ultra-trace sulfur isotope analysis test. The ultra-trace sulfur isotope analysis system comprises an elemental 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 the mass spectrometer through a universal interface. The invention has the advantages of less sample consumption, high analysis efficiency and low consumable cost, can realize ultra-trace sulfur isotope analysis and test, has the analysis precision superior to 0.40 per mill (1 sigma), and reaches the advanced level of the international similar laboratory.
Description
Technical Field
The invention relates to the technical field of stable isotope testing, in particular to an ultra-trace sulfur isotope analysis system and an analysis method.
Background
Sulfur exists in a variety of forms in geologic processes with significant isotopic fractionation. Sulfur isotope analysis is commonly used to indicate the origin and behavior of sulfur-containing geologic materials and is widely used as a tracer method for the study of igneous rocks, sediments, hydrothermal solutions, and biological processes on earth.
Measurement techniques for sulfur isotopes have been advancing since the 70 s of the 20 th century. Offline SO from a dual inlet system (DI-IRMS) isotope mass spectrometer employed initially 2 Pretreatment has evolved to allow on-line production and purification of SO using continuous flow techniques 2 Recent developments based on laser in situ analysis have allowed for higher spatial resolution, but EA-IRMS technology remains an important method for sulfur isotope measurement. EA-IRMS for sulfur isotope measurement typically require 0.01-0.1mg sulfur (Flash 2000HT elemental analyzer, thermo Fisher Scientific), but with the diversification of sulfur isotope analysis materials, including foreigner samples, organic and inorganic sediment samples, and other samples requiring high resolution analysis, etc., the method no longer meets the test requirements of researchers for these geologic materials.
Sulfur isotope ratio for low sulfur content materials or very small sulfur samples 34 S/ 32 S) measurement has been very challenging due to: the relatively low sulfur content of the low sulfur material sample requires a large sample size for sulfur isotope analysis to ensure sufficient SO for IRMS 2 For analysis. Thus, reducing the sample size required for EA-IRMS has become a primary issue in expanding the application of this technology.
However, in conventional EA-IRMS analysis, the SO generated by combustion of the sulfur-containing sample in EA 2 The gas is carried by carrier gas with flow rate of 100mL/min, while the mass spectrometer needs to maintain normal working vacuum, the capillary flow rate into the ion source needs to be controlled at 0.3mL/min, and because the flow rates of carrier gas needed by EA and IRMS are not matched, 99.7% of SO generated by burning sulfur-containing sample is generated 2 The gas is discharged through the split-flow interface and is not utilized. The actual utilization of the sulfur-containing sample was only 0.3%. Therefore, in the analysis process, how to reduce the loss of the sample and improve the utilization rate of the sample is to solve the problem of how to reduce the sampleThe amount is required to meet the key of ultra-trace sulfur isotope analysis test.
Disclosure of Invention
In view of the above, the present invention aims to provide an ultra-trace sulfur isotope analysis system and an analysis method, which are used for solving the problems of large sample consumption, low actual sample utilization rate, high consumable cost and incapability of realizing ultra-trace sulfur isotope analysis test in the existing analysis method.
The aim of the invention is mainly realized by the following technical scheme:
in one aspect, an ultra-trace sulfur isotope analysis system is provided, comprising an elemental analyzer, a first gas pre-concentration purification device, a chromatographic column, a second gas pre-concentration 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 the mass spectrometer through a universal interface.
Further, the first gas pre-concentration and purification device is used for purifying SO generated in the elemental analyzer 2 Carrying out primary enrichment and purification on the gas; the second gas pre-concentration purification device is used for separating and purifying SO after the chromatographic column 2 The gas is enriched and purified again.
Further, the first gas pre-concentration purification device comprises a first six-way valve and a first liquid nitrogen collection component; the first liquid nitrogen 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 tube through a pipeline; the third valve port a and the sixth valve port a are 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 purification device comprises a second six-way valve and a second liquid nitrogen gas collection component; the second liquid nitrogen 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 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 an opening shunt 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 melting capillary tube is arranged in the stainless steel cold trap.
Further, during the test, 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 a 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 flushing 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 flushing helium is supplied by the fourth valve port a;
Further, when the second six-way valve is in a 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 flushing 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 flushing helium is supplied by 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 purification device.
Further, a water trap is arranged on a pipeline connected with the redox tube and the first gas pre-concentration purification device.
Further, the lower part of the oxidation-reduction tube is filled with an oxidant and a reducing agent, and the upper part is reserved with a mixing space of helium carrier gas and oxygen.
On the other hand, the ultra-trace sulfur isotope analysis method is provided, and the ultra-trace sulfur isotope analysis system comprises the following steps:
step one: preparing a sample to be tested;
step two: SO generated by the reaction in the oxidation-reduction tube by utilizing the first gas pre-concentration and purification device 2 Performing primary enrichment and purification;
step three: utilizing a second gas pre-concentration purification device to perform primary enrichment purification on SO 2 Enriching and purifying again to obtain pure SO 2 Solid frozen matter;
step four: SO is put into 2 Sublimating the solid frozen matter to obtain pure SO 2 Gas and clean SO 2 And (5) feeding the gas into a mass spectrometer for testing to obtain a sulfur isotope testing result.
Further, in the second step, the SO 2 The steps of the primary enrichment and purification are as follows:
setting a first six-way valve to be in a gas enrichment mode, and sending a sample to be detected into an oxidation-reduction tube by an automatic sampler to react to generate SO 2 Gas, SO 2 And other impurity gases which can be frozen by liquid nitrogen form solid frozen matters in the first cold trap to finish SO 2 And (5) gas primary enrichment and purification.
Further, in step three, for SO 2 The steps of enrichment and purification again are as follows:
switching the first six-way valve into a helium back-flushing mode, and simultaneously removing the first cold trap from the first liquid nitrogen barrel and heating to sublimate solid frozen matters in the first cold trap into target gas SO 2 Is a mixed gas of (1) a target gas SO 2 The mixed gas of (2) enters a second valve port b of a 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 pure SO purified by chromatographic column separation 2 The gas is frozen and enriched in a second cold trap to form pure SO 2 Solid frozen matter, finish SO 2 And (5) gas is enriched again.
Further, in the fourth step, SO is added 2 Sublimating the solid frozen matter to obtain pure SO 2 In the gas process, the second six-way valve is switched from a gas enrichment mode to a helium back-flushing mode, and meanwhile, the second cold trap is removed from the second liquid nitrogen barrel and heated, SO that SO in the second cold trap is realized 2 Sublimation of solid frozen matter into pure SO 2 And (3) gas.
Compared with the prior art, the invention has at least one of the following beneficial effects:
a) According to the ultra-trace sulfur isotope analysis system provided by the invention, the SO generated by burning the sample to be detected is enabled by arranging the gas pre-concentration purification device between the elemental analyzer and the universal interface 2 The gas can be completely frozen and collected, so that the tailing phenomenon caused by the fact that the sample cannot be instantaneously and completely combusted is solved, and the precision of a test result is improved.
b) According to the ultra-trace 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 reduced 2 The waste of gas and the utilization rate of the sample to be tested are improved by 20-100 times, and the consumption of the sample to be tested is reduced, so that the service life of the redox tube is prolonged, the ash cleaning frequency is reduced, the experimental efficiency is obviously improved, and the experimental cost is reduced.
c) The ultra-trace sulfur isotope analysis method provided by the invention is based on an ultra-trace sulfur element analysis system provided with two gas pre-concentration and purification devices, and can be used for enabling SO generated in the system to be generated 2 The method is characterized in that the method is used for collecting and purifying all samples, so that the utilization rate of the samples 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 cleaning frequency is reduced, the working efficiency is improved, the analysis precision is better than 0.40 per mill (1 sigma), and the international leading level is reached.
In the invention, the technical schemes can be mutually combined 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 may 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, like reference numerals being used to refer to like parts throughout the several views.
FIG. 1 is a schematic diagram of the structure of an ultra-trace sulfur isotope analysis system of the present invention beginning to enter a primary enrichment and purification mode;
FIG. 2 is a schematic diagram of the structure of the ultra-trace sulfur isotope analysis system of the present invention beginning to enter a re-enrichment purification mode;
FIG. 3 is a schematic illustration of the first six-way valve of the present invention in a connected state in an enrichment mode;
FIG. 4 is a schematic illustration of the first six-way valve of the present invention in a helium blowback mode;
FIG. 5 is a schematic illustration of the second six-way valve of the present invention in a connected state in an enrichment mode;
FIG. 6 is a schematic illustration of a second six-way valve of the present invention in a helium blowback mode;
FIG. 7 is a schematic diagram showing a valve port communication state of the first six-way valve and the second six-way valve in FIG. 1;
fig. 8 is a schematic diagram of a valve port communication state of the first six-way valve and the second six-way valve 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-chromatography 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, fifth valve port a;5-6, a sixth valve port a; 6. a first liquid nitrogen collection assembly; 6-1, a first cold trap; 6-2, a first liquid nitrogen barrel; 7. a second gas pre-concentration purification device; 8. a second six-way valve; 8-1, a first valve port b;8-2, a second valve port b;8-3, a third valve port b;8-4, a fourth valve port b;8-5, fifth valve port b;8-6, a sixth valve port b; 9. a second liquid nitrogen collection assembly; 9-1, a second cold trap; 9-2, a second liquid nitrogen barrel; 10. a water trap; 11-universal interfaces; 12. an oxidizing agent; 13. a reference gas injection system; 14. a first back-flushing helium pipe; 15. a first exhaust pipe; 16. a mass spectrometer; 17. reducing copper wires; 18. quartz cotton; 19. a second back-flushing helium pipe; 20. and a second exhaust pipe.
Detailed Description
The following detailed description of preferred embodiments of the application is made in connection with the accompanying drawings, which form a part hereof, and together with the description of the embodiments of the application, are used to explain the principles of the application and are not intended to limit the scope of the application.
Example 1
In one embodiment of the present application, an ultra-trace sulfur isotope analysis system is disclosed for analysis testing of ultra-trace sulfur isotopes in sulfur-containing materials (e.g., rock, soil, plants, food, etc.), as shown in FIGS. 1-2, comprising along SO 2 The element analyzer, the first gas pre-concentration and purification device 3, the chromatographic column 4, the second gas pre-concentration and purification device 7 and the mass spectrometer 16 are sequentially arranged on a pipeline of the gas flow direction; the elemental 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 the embodiment, the elemental analyzer comprises an autosampler 1 and a redox tube 2, wherein the autosampler 1 is used for feeding a sample to be measured into the redox tube 2, and the autosampler 1 is provided with a helium carrier gas inlet 1-1 for feeding helium carrier gas and an oxygen inlet 1-2 for feeding oxygen; the redox tube 2 is used for carrying out redox reaction on a sample to be detected to obtain SO 2 One end of the oxidation-reduction tube 2 is connected with the automatic sampler 1 through a pipeline, the other end 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 oxidation-reduction tube 2 with the first gas pre-concentration and purification device 3.
In this embodiment, the first gas preconcentration and purification device 3 is used for primary enrichment and purification of the produced in the redox tube 2SO 2 The gas, the first gas pre-concentration purification device 3 comprises a first six-way valve 5 and a first liquid nitrogen collection component 6; the second gas pre-concentration and purification device 7 is used for enriching and purifying the SO after purification by the first gas pre-concentration and purification device 3 and separating and purifying the SO by the chromatographic column 4 2 The 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 assembly 9.
In this embodiment, the liquid nitrogen gas collection subassembly includes cold trap and liquid nitrogen bucket, and the liquid nitrogen is equipped with in the liquid nitrogen bucket, and the liquid nitrogen bucket is open structure, and the cold trap can insert or remove the liquid nitrogen bucket. When enriching SO 2 When the cold trap is stretched into liquid nitrogen in the liquid nitrogen barrel, SO is carried out 2 Freezing in a cold trap; completion of SO 2 After enrichment, the cold trap is removed from the liquid nitrogen barrel to enable solid SO 2 And returning to the gaseous state. To accelerate solid SO 2 The cold trap is changed into a gaseous state, has a heating function, is matched with an independent heating device and is used for freezing SO 2 Is put into a heating device for heating SO as to lead the solid SO 2 Accelerating to become gaseous; or, the outer wall of the cold trap is wound with a heating wire, and the heating wire is electrified to heat up SO that SO frozen by liquid nitrogen in the cold trap 2 And other gases to be heated to a gaseous state.
In this embodiment, a first liquid nitrogen gas collection module 6 is used to freeze enrich SO generated in the redox tube 2 2 The 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 is 1/16 inch; the second liquid nitrogen gas collection assembly 9 is used for freezing and enriching SO which is heated and sublimated in the first gas pre-concentration purification device 3 and separated and purified by the chromatographic column 4 again 2 The 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 is 1/16 inch, the second cold trap 9-1 is directly connected with the second six-way valve 8 after passing 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 0.32mm. The possible gas leakage at the joint is reduced by arranging the whole capillary tube, and the small-volume quartz melting capillary tube can lead the target gas SO 2 The utility model is more concentrated in that,all gases can reach the ion source in a short time, and the peak type is narrower.
Primary enrichment and purification of SO 2 When the first cold trap 6-1 is extended into the liquid nitrogen in the first liquid nitrogen barrel 6-2, SO generated in the oxidation-reduction tube 2 is generated 2 Freezing in the first cold trap 6-1 to complete SO 2 Primary enrichment and purification;
completion of SO 2 After primary enrichment and purification, the first cold trap 6-1 is removed from the liquid nitrogen barrel 6-2 to enable solid SO 2 Gaseous SO containing impurity gas recovered to gaseous state 2 Enters the chromatographic column 4, and is separated and purified SO by controlling the air flow direction of the second six-way valve 8 and the time of immersing the second cold trap 9-1 in liquid nitrogen 2 The gas enters a second liquid nitrogen gas collection assembly 9 for secondary enrichment.
When enriching SO again 2 When in use, the second cold trap 9-1 is extended into the liquid nitrogen in the second liquid nitrogen barrel 9-2, and SO after separation and purification by the chromatographic column 4 is obtained 2 The gas is frozen in the second cold trap 9-1 to form pure SO 2 Solid frozen matter; completion of SO 2 After re-enrichment, the second cold trap 9-1 is removed from the second liquid nitrogen barrel 9-2 to enable the pure SO to be obtained 2 Recovering the solid frozen matter to the gaseous state again to obtain pure gaseous SO 2 Mass spectrometer 16 is directed to pure SO 2 The gas was 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 comprise two working modes in the testing 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 valve port a5-1, a second valve port a5-2, a third valve port a5-3, a fourth valve port a5-4, a fifth valve port a5-5 and a sixth valve port a5-6. 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 an air outlet of the redox tube 2 through a pipeline; the third valve port a5-3 and the sixth valve port a5-6 are connected with the first cold trap 6-1 through external pipelines; the fourth valve port a5-4 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 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 state of each valve port is shown in figure 3, 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 because the third valve port a5-3 and the sixth valve port a5-6 are connected with the first cold trap 6-1 through external pipelines, SO 2 And other gases which can be frozen by the liquid nitrogen are frozen and enriched in the first cold trap 6-1, and helium and other gases which cannot be frozen by the liquid nitrogen are discharged from the first valve port a 5-1.
When the first six-way valve 5 is in the helium back-flushing mode, the communication state of the valve ports is shown in fig. 4, the first valve port a5-1 is communicated with the second valve port a5-2, the third valve port a5-3 is communicated with the fourth valve port a5-4, the fifth valve port a5-5 is communicated with the sixth valve port a5-6, back-flushing helium is supplied by the fourth valve port a5-4, and the back-flushing helium carries SO (SO) 2 And other impurity gases reach the sixth valve port a5-6 after passing through the third valve port a5-3 and the first cold trap 6-1, and as the sixth valve port a5-6 is communicated with the fifth valve port a5-5, the mixed gases flow out into the chromatographic column 4 through the fifth valve port a5-5 and SO 2 And other impurity gases pass through the chromatographic column 4 in a time difference to realize separation and purification, and the passing time ratio SO 2 The gas with short gas is directly discharged from the second valve port b8-2 and the first valve port b8-1 of the second six-way valve SO 2 When the gas passes through the chromatographic column, the second six-way valve 8 switches the gas flow to be in a gas enrichment mode reversely SO 2 The gas is captured in the second cold trap 9-1 after being immersed in the liquid nitrogen, and the impurity gas and helium carrier gas which cannot be frozen are discharged from the first valve port b8-1 after passing through the second cold trap 9-1; when all SO 2 After the gas passes through the chromatographic column 4, the gas flow direction of the second six-way valve 8 is switched, and all 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, thereby realizing the target gas SO 2 Is purified by the purification method.
As shown in fig. 5 to 6, the second six-way valve 8 is provided with a first valve port b8-1, a second valve port b8-2, a third valve port b8-3, a fourth valve port b8-4, a fifth valve port b8-5, and a sixth valve port b8-6. 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 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 an 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 state of each valve port is shown in FIG. 5, 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 because the third valve port b8-3 and the sixth valve port b8-6 are connected with the second cold trap 9-1 through external pipelines, SO 2 And other gases which can be frozen by liquid nitrogen are frozen and enriched in the second cold trap 9-1, and helium and other gases which cannot be frozen by liquid nitrogen are discharged from the first valve port b 8-1.
When the second six-way valve 8 is in the helium back-flushing mode, the communication state of the valve ports is shown in fig. 6, the first valve port b8-1 is communicated with the second valve port b8-2, the third valve port b8-3 is communicated with the fourth valve port b8-4, the fifth valve port b8-5 is communicated with the sixth valve port b8-6, back-flushing helium is supplied by the fourth valve port b8-4, and the back-flushing helium carries SO 2 The gas reaches the sixth valve port b8-6 after passing through the third valve port b8-3 and the second cold trap 9-1, and the sixth valve port b8-6 is communicated with the fifth valve port b8-5 SO 2 The gas flows out from the fifth valve port b8-5 and enters the universal joint 11.
In this embodiment, the redox tube 2 is made of quartz material, the lower part of the redox tube 2 is filled with oxidant 12 and reductant, the upper part is reserved with a mixing space of helium carrier gas and oxygen, the sample to be tested is subjected to combustion reaction in the mixing space, the reductant adopts reduction copper wires 17, and the oxidant 12 adopts WO with granularity of 0.85-1.7mm 3 . Specifically, the reduced copper wires 17 and the oxidizing agent 12 are arranged upward from the bottom surface of the redox tube 2, and the oxidizing agent 12 is separated from the reduced copper wires 17 by quartz wool 18. The top surface of the oxidant 12 and the lower part of the reduction copper wire 17 are paved with Quartz wool 18.
In this embodiment, the chromatographic column 4, the first cold trap 6-1 and the connecting pipeline are made of Teflon material, SO that SO is avoided 2 The gas has viscosity and is easy to adhere to the pipe wall, so that the testing precision is affected, 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, which can set a heating temperature so that the heating temperature is kept constant. The column 4 used a teflon tube filled with Poropak QS packing, and the column 4 had a gauge of 1/8 inch outer diameter and a length of 30cm.
In this embodiment, the mass spectrometer 16 and the universal interface 11 are a MAT253 gas isotope mass spectrometer of Thermo Fisher Scientific company and a Conflo IV universal interface.
During implementation, the aluminum cup wrapped with the sample to be tested is placed in a sample tray of the automatic sampler 1, the sample tray is vacuumized and purged with helium (2-3 times), then the automatic sampler 1 sends the aluminum cup wrapped with the sample to be tested into the redox tube 2, the aluminum cup wrapped with the sample to be tested is flash-burned rapidly in a high-temperature oxygen injection environment, and the sample to be tested and excessive oxygen generate SO 3 ，SO 3 Is reduced by the reduced copper wire 17 to SO 2 All SO's in the redox tube 2 2 The gas is carried out of the redox tube 2 by helium gas and enters the second valve port a5-2 of the first six-way valve 5 through the water trap 10, at the moment, the first six-way valve 5 is in a gas enrichment mode, and SO generated in the redox tube 2 is generated due to the connection of the second valve port a5-2 and the third valve port a5-3 2 And other gases which can be frozen by liquid nitrogen enter the first cold trap 6-1 and are frozen and enriched into solid frozen matters, helium and other gases which can not be frozen by liquid nitrogen are discharged from the first valve port a5-1, SO that SO is completed 2 And (5) primary enrichment and purification.
When the first cold trap 6-1 in the liquid nitrogen collects all SO 2 After the gas is discharged, the first cold trap 6-1 is removed from the first liquid nitrogen barrel 6-2 and heated, SO that the solid frozen matters in the first cold trap 6-1 are sublimated into SO-containing matters 2 Simultaneously switching the first six-way valve 5 to a helium blowback mode, wherein the blowback helium carries SO-containing gas 2 Mixed gas of other impurity gasesThe body enters from the fourth valve port a5-4 of the first six-way valve 5 and flows through the third valve port a5-3, the first cold trap 6-1, the sixth valve port a5-6 and the fifth valve port a5-5 in sequence to enter the chromatographic column 4, and the chromatographic column contains SO 2 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 the second six-way valve 8 is in a gas enrichment mode. The second valve port b8-2 is connected with the third valve port b8-3, SO that the purified SO is separated by the chromatographic column 4 2 The gas enters a 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 a first valve port b8-1, SO that SO is completed 2 Enriching and purifying again.
When the second cold trap 9-1 in the liquid nitrogen collects all SO 2 After the gas is discharged, the second cold trap 9-1 is removed from the second liquid nitrogen barrel 9-2 and heated, and the second six-way valve 8 is switched to a helium back-flushing mode, wherein the back-flushing helium carries SO 2 The gas enters from the fourth valve port b8-4 of the second six-way valve 8, flows through the third valve port b8-3, the second cold trap 9-1, the sixth valve port b8-6 and the fifth valve port b8-5 in sequence and enters the universal interface 11, the mass spectrometer 16 is connected with an opening split device of the universal interface 11 through a capillary tube to carry out SO (sulfur dioxide) separation 2 The gas is introduced into a mass spectrometer 16 for isotope ratio determination.
Compared with the prior art, the ultra-trace sulfur isotope analysis system provided by the embodiment performs key improvement on the basis of the conventional elemental analyzer sulfur isotope online analysis system, and two gas pre-concentration and purification devices are arranged between the elemental analyzer and the universal interface and are connected through a chromatographic column SO as to realize the production of SO (sulfur dioxide) 2 Carrying out enrichment and purification twice, in particular to a cold trap with a heating function which can enrich SO through freezing of liquid nitrogen in a gas enrichment mode by arranging two six-way valves, two cold traps and a chromatographic column between an element analyzer and a universal interface 2 The SO generated by burning the sample to be tested is ensured by the gas after the gas is enriched and purified twice 2 The gas can be completely frozen and collected, the tailing phenomenon caused by the fact that the sample cannot be instantaneously and completely combusted is solved, and other impurity gases which cannot be frozen by liquid nitrogen can be carried through by heliumDischarging through an exhaust port of the six-way valve; the six-way valve plays a role in switching the airflow direction and the helium carrier gas flow rate when the gas enrichment mode is changed into the helium back-flushing mode, and enriched SO in the cold trap is carried out through back-flushing helium carrier gas (0.3 mL/min) matched with the universal interface low-flow rate interface 2 The gas is fully sent into the universal interface, SO that SO generated by the combustion of the sample to be tested before entering the universal interface 2 The gas is completely collected, and the back-blowing helium flow is connected through the six-way valve, SO that SO is greatly reduced 2 The 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 less than 1/20 of that of the conventional method, and only about 1-5 mug of sulfur is needed. The reduction of the consumption of the sample to be tested not only improves the service life of the redox 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 permillage (1 sigma), and the difference between the measured value and the true value is within 1 permillage, so that the advanced level of the international similar laboratory is achieved.
Example 2
In still another embodiment of the present invention, an analysis method of ultra-trace sulfur isotopes is disclosed, based on the analysis system of ultra-trace sulfur isotopes of embodiment 1, for realizing analysis and test of ultra-trace sulfur isotopes in sulfur-containing substances (such as rock, soil, plants, food, etc.), the analysis method of ultra-trace sulfur isotopes comprises the steps of:
step one: and preparing a sample to be tested.
Before a trace sample sulfur isotope test experiment is carried out, preparing a sample to be tested, wherein the sample to be tested is sulfide or sulfate, and grinding the sample to be tested to more than 200 meshes. Wherein, the sulfide sample is directly wrapped in an aluminum cup after being ground to 200 meshes, and V with the weight of 5 times is added after the sulfate sample is ground to 200 meshes 2 O 5 Powder, sulfate sample and added V 2 O 5 The powder is wrapped in an aluminum cup after being evenly mixed. The sulfide sample amount is 15-40 mug, and the sulfate sample amount is 7-36 mug.
Step two: SO generated by the reaction in the oxidation-reduction tube 2 is subjected to a pre-concentration and purification device 3 for the first gas 2 And (5) performing primary enrichment and purification.
Specifically, the first six-way valve 5 is set to be in a gas enrichment mode, and the automatic sampler 1 sends a sample to be detected into the oxidation-reduction tube 2 to react to generate SO 2 A gas; collecting SO generated in the redox tube 2 by means of the first cold trap 6-1 2 Gases and other impurity gases which can be frozen by liquid nitrogen, SO 2 And other impurity gases which can be frozen by liquid nitrogen form solid frozen matters in the first cold trap 6-1 to finish SO 2 And (5) gas primary enrichment and purification.
After starting to work, a plurality of samples to be tested wrapped by the aluminum cup are sequentially placed in a sample tray of the automatic sampler 1, repeated vacuumizing and helium purging purification treatment are carried out on an analysis system, impurity gas is removed, and background is reduced. The specific implementation process is as follows: closing a helium purging valve and opening a vacuum pumping valve; and then closing the vacuum extraction valve, opening the helium purging valve, repeating the process for 2-3 times, and closing the vacuum extraction valve and the helium purging valve to finish the processes of vacuumizing the system and purging and purifying the helium.
After the system vacuumizing and helium purging purification treatment processes are completed, the automatic sampler 1 sends an aluminum cup wrapping a sample to be tested into the redox tube 2, the sample to be tested is filled into the redox tube 2 by the automatic sampler 1 and simultaneously is injected with oxygen for flash combustion, a high-temperature and oxygen-enriched air environment is arranged in the redox tube 2, the aluminum cup of the sample to be tested is rapidly and fully combusted under the flash combustion, and the sample to be tested is flashed under the peroxy environment to generate SO (sulfur dioxide) 3 And SO 2 Wherein SO 3 The reduced copper wire 17 generates SO under the reduction effect 2 The generated target gas SO 2 Flows out of the oxidation-reduction tube 2 under the transportation of helium carrier gas, and 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, 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 the third valve port a5-3 and the sixth valve port a5-6 are connected with the first cold trap 6-1 through external pipelines SO 2 And other impurity gases which can be frozen by liquid nitrogen are frozen and enriched in the first cold trap 6-1 to form solid frozen matters, and helium and other gases which can not be frozen by liquid nitrogen are discharged from the first valve port a5-1And (5) outputting.
In the second step, for SO 2 In the process of carrying out primary enrichment and purification on the gas, the first six-way valve 5 keeps a gas enrichment mode, and 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 dips into the liquid nitrogen after the sample to be detected reacts for 30 seconds in the redox tube 2 until all SO generated in the redox tube 2 2 The gas is frozen in solid form in a first cold trap 6-1 (-196 ℃) in liquid nitrogen. During the primary enrichment process, the second six-way valve 8 is in a gas back-flushing mode, as shown in fig. 1, that is, the first cold trap 6-1 is in a purging mode during the enrichment process of gas, and the system is purged by gas back-flushing.
Further, in the second step, the reaction temperature of the redox tube was 1020℃and the flow rate of helium carrier gas was 100mL/min.
Further, in the second step, the first cold trap 6-1 is kept in the liquid nitrogen barrel 6-2 for 240+ -10 s to collect all SO generated by the reaction 2 And (3) gas.
Step three: the second gas pre-concentration purification device 7 is utilized to perform primary enrichment purification on SO 2 Enriching and purifying again to obtain pure SO 2 Solid frozen matter.
Specifically, the first six-way valve 5 is switched to a helium back-flushing mode, and simultaneously the first cold trap 6-1 is removed from the first liquid nitrogen barrel 6-2 and begins to heat, SO that solid frozen matters in the first cold trap 6-1 sublimate into target gas SO 2 Is a mixed gas of (1) a target gas SO 2 The time difference of passing the mixed gas of the chromatographic column 4 under the helium transportation is used for realizing separation and purification. Transit time ratio SO 2 The gas with short gas is directly discharged from the second valve port b8-2 and the first valve port b8-1 of the second six-way valve SO 2 When gas passes through the chromatographic column, the second six-way valve switches the gas flow to be in a gas enrichment mode reversely, 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 because the third valve port b8-3 and the sixth valve port b8-6 are connected with the second cold trap 9-1 through external pipelines, SO 2 Gas and its preparation methodThe impurity gas and helium carrier gas which are immersed in liquid nitrogen and then trapped in the cold trap are discharged from the first valve port b8-1 after passing through the cold trap; when all SO 2 After the gas passes through the chromatographic column 4, the gas flow direction of the second six-way valve is switched, and all 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, thereby realizing the target gas SO 2 Is enriched and purified again.
Further, in step three, the flow rate of helium carrier gas was 100mL/min.
Further, in the third step, the second cold trap 9-1 is kept in the liquid nitrogen in the second liquid nitrogen barrel 9-2 for 240.+ -. 10s to collect all SO generated by the reaction 2 And (3) gas.
Further, in the third step, the flow rate of the back-blowing helium gas is 10mL/min, and when the mixed gas which is frozen, enriched and recovered to be in a gaseous state through the first cold trap 6-1 is carried into the chromatographic column 4 by the back-blowing helium gas, the temperature of the chromatographic column 4 is 90-110 ℃.
Step four: pure SO 2 Sublimating the solid frozen matter to obtain pure SO 2 Gas and clean SO 2 The gas is fed to a mass spectrometer 16 for testing to obtain sulfur isotope test results.
Specifically, the second six-way valve 8 is switched from the gas enrichment mode to the helium blowback mode, and the SO is frozen 2 Is removed from the second liquid nitrogen barrel 9-2, and the heating wire wound on the second cold trap 9-1 is electrified to heat SO as to enable SO in the second cold trap 9-1 2 Fast sublimation of solid frozen matter into pure SO 2 A gas; because the second six-way valve 8 is in the helium blowback mode, blowback helium enters from the fourth valve port b8-4, and the blowback helium carries pure SO 2 The gas reaches the sixth valve port b8-6 after passing through the third valve port b8-3 and the second cold trap 9-1, and the fifth valve port b8-5 is communicated with the sixth valve port b8-6 in the helium back blowing mode, SO that the pure SO is obtained 2 The gas flows out from the fifth valve port b8-5 and enters the universal interface 11, the mass spectrometer 16 is connected with an opening shunt device of the universal interface 11 through a capillary tube, and SO is discharged 2 The gas is introduced into a mass spectrometer 16 for isotope ratio measurement to obtain sulfur isotopeResults of plain test. Isotope mass spectrometers were tested for SO with mass numbers of 64 and 66 2 Delta is obtained by calculation 34 S ratio, and obtaining sulfur isotope test results. Further, the second six-way valve 8 is in a helium blowback mode, and the flow rate of the blowback helium is 0.3-1.0mL/min.
In this embodiment, when the autosampler 1 starts feeding the sample into the reaction tube 2, the system automatically starts timing. When the test is carried out to 60s-160s, three groups of reference gases are sent into the mass spectrometer through the double-path reference gas sample injection system, the sample injection time of each group of reference gases is 20s, and the interval time of each two groups of reference gases is 20s. When the test is carried out until 240s, the first six-way valve 5 is switched to a helium back-blowing 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 matter into mixed gas, and after the mixed gas passes through the chromatographic column 4 and the second six-way valve 8 in sequence, SO is pumped out 2 The gas freezes to the second cold trap 9-1. When the test proceeds to 600s, the second six-way valve 8 is switched to the helium blowback mode while the second cold trap 9-1 is removed from the liquid nitrogen and the second cold trap 9-1 is heated to sublimate the solid frozen matter into a gas. Pure SO sublimated by heating through back-blowing helium carrier gas matched with high-flow-rate channel of universal interface 11 2 The gas is fed into the universal interface 11 for mass spectrometry.
Because 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 to the next sample is reduced.
Compared with the prior art, the ultra-trace sulfur isotope analysis method provided by the embodiment utilizes the SO generated by the reaction of the first gas pre-concentration and purification device, the chromatographic column and the second gas pre-concentration and purification device to the sample to be detected 2 Performing enrichment and purification twice, and using liquid nitrogen to perform SO when the six-way valve is in a gas enrichment mode 2 The gas is frozen in a cold trap, and the temperature is raised to be recovered to gaseous SO after removing the impurity gas 2 The six-way valve plays a role in switching the flow speed and the flow direction of helium carrier gas when the gas enrichment mode is changed into the helium back-blowing mode, and the helium carrier gas is back-blown to enrich the cold trap through matching with the universal interface SO of the set 2 The gas is sent into the universal interface SO as to ensure SO generated by the combustion of the sample before entering the universal interface 2 The gas is fully collected, so that the utilization rate of a sample can be improved by 20 times, the sulfur demand of the system is reduced to 1-5 mug, the service life of an oxidation-reduction tube can be prolonged, the ash cleaning frequency is reduced, and the working efficiency is improved. Meanwhile, the generation of tailing peaks is effectively avoided, the precision of results is improved, the analysis precision is better than 0.40 per mill (1 sigma), the difference between measured values and true values is within 1 per mill, and the advanced level of the international similar laboratory is achieved.
Example 3
In order to verify that the invention can meet the analysis requirements of the ultrafine sulfur isotopes in the precious samples and the micro-area samples, and the test results reach the international advanced level, the example is based on the analysis system of the example 1, and the sulfide and sulfate standard substances are tested by using the analysis method of the example 2.
The selected national sulfide sulfur isotope standard substances are GBW04414, GBW04415 and international sulfide sulfur isotope standard substance IAEA-S-3, and the components are Ag 2 S, S; selected international sulfate sulfur isotope standard substances IAEA-SO-5, IAEA-SO-6 and NBS-127, and the components are BaSO 4 The method comprises the steps of carrying out a first treatment on the surface of the The purity of the selected sulfide and sulfate standard samples is more than 99.9%, the sample weights are respectively 15-40 mug and 7-36, the selected standard substance samples are ground to more than 200 meshes, and the standard substance samples are wrapped in an aluminum cup for measurement. Wherein, V is added into the sulfate standard sample by 5 times of the weight of the sulfate standard sample 2 O 5 And (3) powder.
Testing 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 tested in an aluminum cup and placing the aluminum cup in an automatic sampler. After starting to work, an aluminum cup wrapping the standard sample to be tested is sent into the oxidation-reduction tube 2 by an automatic sampler, and the standard sample to be tested is quickly and fully combusted under the flash of the aluminum cup in the atmosphere of oxygen-enriched gas to generate SO 3 And SO 2 ，SO 3 Generates SO under the reduction of the reduced copper wire 17 2 The generated target gas SO 2 Sequentially passing through a first six-way valve 5 and a second six-way valve under the delivery of helium carrier gas (100 mL/min)A cold trap 6-1, a chromatographic column 4 and a second six-way valve 8, finally enter a second cold trap 9-1 positioned in a liquid nitrogen barrel 9-2 to form solid SO 2 . Solid SO in the second cold trap 2 In heating mode, pure SO is obtained by back-flushing helium carrier gas (0.3 mL/min) matched with the high-flow channel of the universal interface 11 2 The gas is sent into a universal interface 11 for mass spectrometry, and the purity of the He steel bottle gas is improved>99.999％。
The working parameters are as follows: the initial He gas flow rate is 100mL/min, O 2 The flow rate is 150mL/min, and the gas purity is more than 99.999 percent; the temperature of the redox tube 2 is set to 1020 ℃, the chromatographic column temperature is set to 90 ℃, and the SO of the standard sample to be measured is set to be the SO of the standard sample to be measured 2 The peak starts to appear at 600s and the overall detection time is 700.+ -.10 s. The reference gas sample injection system 13 adopts a double-path sample injection system, and the ion current intensity of 66 mass numbers in three groups of reference gases is kept between 4 and 6V.
The working standard used in mass spectrometry is national sulfide sulfur isotope standard substances GBW04414, GBW04415 and international sulfide sulfur isotope standard substance IAEA-S-3, and the components are Ag 2 S，δ 34 S V-CDT The true values are-0.07%o, +22.15%o and-32.49%o respectively. International sulfate sulfur isotope standard substances IAEA-SO-5, IAEA-SO-6 and NBS-127, and the components are BaSO 4 ，δ 34 S V-CDT The true values are-0.5 per mill, -34.1 per mill, and 20.3 per mill respectively.
TABLE 1 statistics of test results for sulfide sulfur isotope standard substances
TABLE 2 statistics of sulfate sulfur isotope standard substance test results
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 delta of the standard sample to be tested can be known 34 S V-CDT Measurement value delta 34 S V-CDT The difference of the true values is 0.0.0-1.00 per mill, and the standard deviation is less than 0.40 per mill (1 SD), thereby reaching the advanced level of the international similar laboratory.
The system and the method for analyzing the ultra-trace sulfur isotopes can be used for analyzing and testing sulfur isotopes of sulfur-containing minerals such as sulfides, sulfates and the like in rock and soil, and also can be used for analyzing and testing sulfur isotopes in other sulfur-containing substances (such as plants, foods and the like).
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (7)
1. An ultra-trace sulfur isotope analysis method is characterized in that an analysis test of ultra-trace sulfur isotopes in sulfur-containing substances is performed based on an ultra-trace sulfur isotope analysis system, and the ultra-trace sulfur isotope analysis system comprises a sulfur-doped oxygen (SO) along the SO 2 The gas flow pipeline is sequentially provided with an elemental 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 elemental 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);
the first gas pre-concentration purification device (3) comprises a first six-way valve (5) and a first liquid nitrogen gas collection 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 second gas pre-concentration purification device (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) is used for freezing and enriching SO which is sublimated by heating in the first gas pre-concentration purification device (3) and separated and purified by the chromatographic column (4) again 2 The gas comprises a second cold trap (9-1) and a second liquid nitrogen barrel (9-2); the second cold trap (9-1) comprises a whole quartz melting capillary tube with the length of 3m, the quartz melting capillary tube passes through a stainless steel protective sleeve and is directly connected with a second six-way valve (8), and the outer diameter of the quartz melting capillary tube is 0.32mm;
the ultra-trace sulfur isotope analysis method comprises the following steps:
step one: preparing a sample to be measured, and wrapping the sample to be measured in an aluminum cup;
step two: SO generated by the reaction is purified by a first gas pre-concentration device (3) 2 Performing primary enrichment and purification;
step three: freezing and enriching SO after heating sublimation and separation and purification by a chromatographic column (4) in the first gas pre-concentration and purification device (3) again by using a second gas pre-concentration and purification device (7) 2 The gas is purified SO 2 Solid frozen matter;
step four: pure SO 2 Sublimating the solid frozen matter to obtain pure SO 2 The gas is used for blowing helium carrier gas reversely at 0.3 mL/min which is matched with the low-flow interface of the universal interface (11) to enrich pure SO in the second cold trap (9-1) 2 The gas is all sent to a universal interface (11) and purified SO is sent 2 The gas is fed into a mass spectrometer (16) for testing, and a sulfur isotope test result is obtained;
in the second step, for SO 2 The steps of the 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 sampler (1) sends an aluminum cup which wraps a sample to be detected into the redox tube (2) to react to generate SO 2 Gas, SO 2 And other impurity gases which can be frozen by liquid nitrogen form solid frozen matters in the first cold trap (6-1) to finish SO 2 Primary enrichment and purification of gas;
in the third step, for SO 2 The steps of enrichment and purification again are as follows:
the first six-way valve (5) is switched into a helium back-blowing mode, the flow rate of back-blowing helium is 10mL/min, and simultaneously 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 target gas SO 2 Is a mixed gas of (1) a target gas SO 2 The mixed gas of (2) 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 transportation of helium; at the moment, the second six-way valve (8) is in a gas enrichment mode, and pure SO purified by separation of the chromatographic column (4) 2 The gas is frozen and enriched in a second cold trap (9-1) to form pure SO 2 Solid frozen matter, finish SO 2 And (5) gas is enriched again.
2. The ultra-micro sulfur isotope analysis method according to claim 1, wherein 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 redox tube (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-micro sulfur isotope analysis method according to claim 2, wherein 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 the second cold trap (9-1) through pipelines; the fourth valve port b (8-4) 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 b (8-5) is connected with the universal interface (11) through a pipeline, and the mass spectrometer (16) is connected with an opening shunt device of the universal interface (11) through a capillary tube.
4. A method of ultra-micro sulfur isotope analysis according to claim 3, wherein during the test, the first six-way valve (5) and the second six-way valve (8) each have two modes of operation: a gas enrichment mode and a helium blowback mode.
5. The ultra-micro sulfur isotope analysis method according to any one of claims 1 to 4, wherein the elemental analyzer comprises an autosampler (1) and a redox tube (2), one end of the redox tube (2) is connected to the autosampler (1), and the other end is connected to the first gas pre-concentration purification device (3).
6. The method for analyzing ultra-trace sulfur isotopes according to claim 5, characterized in that the oxidation-reduction tube (2) is provided with a water trap (10) on the pipeline connected with the first gas pre-concentration purification device (3).
7. The method for analyzing ultra-trace sulfur isotopes according to claim 6, wherein the redox tube (2) is filled with an oxidizing agent (12) and a reducing agent at the lower portion thereof and a helium carrier gas and oxygen mixing space is reserved at the upper portion thereof.
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