CN106769346B - Method for analyzing hydrogen isotopes in water - Google Patents

Abstract

The invention relates to the technical field of isotope analysis, and discloses a method for analyzing hydrogen isotopes in water. The method comprises the following steps: (i) sealing both ends of a capillary tube for collecting water samples and then placing them into a first collection tube; (ii) after placing the first collection tube in step (i) into the second collection tube (10) containing chromium powder and performing vacuum treatment, the second collection tube (10) is melted and sealed; (iii) The capillary in the first collection tube is broken, and under the condition of heating, the chromium powder in the second collection tube (10) is reacted with the water sample in the capillary; (iv) the chromium powder in the step (iii) and the After the water sample reaction is completed, the second collection tube (10) is put into the third collection tube, and then the third collection tube is connected with the analysis device, the hydrogen in the second collection tube (10) is released, and hydrogen isotope analysis is performed to obtain hydrogen in water isotope ratio. The method provided by the invention has the advantages of high precision and good repeatability.

Description

Methods for analyzing hydrogen isotopes in water

technical field

The invention relates to the technical field of stable isotope analysis, in particular to a method for analyzing hydrogen isotopes in water.

Background technique

With the development of isotope analysis technology, stable isotope analysis of water has gradually become one of the modern research methods in the field of water science. The stable isotopic composition of water is considered to be the "fingerprint" of water and plays an increasingly important role in the analysis of dynamic processes such as water source, transport and mixing. D and ¹⁸ O, in particular, are considered to be stable in the absence of high-temperature hydrolithogenesis and intense evaporation, and are ideal environmental isotopes for tracing hydrodynamic processes.

The hydrogen isotope analysis method of water, the isotope laboratory at home and abroad generally adopts a metal method that uses some active metal elements as reducing agents to convert water into hydrogen: metal + water = metal oxide + hydrogen, and then the hydrogen generated by the reaction is used. Isotope analysis was performed with a gas isotope mass spectrometer. At present, metal zinc and uranium methods are widely used in isotope laboratories of various countries.

The metal zinc reduction method was first established by Friedman, and its analysis methods mainly include: (1) flow method, using two cold traps to make the water sample pass through a zinc furnace at 400 °C in the form of steam, and then the generated hydrogen is adsorbed and collected by activated carbon. Mass spectrometry analysis was performed in the gas sample tube. (2) The reaction tube method with a grease-free high-vacuum piston, the water sample and zinc are directly loaded, and the reaction is carried out at 450 ° C after degassing, and the generated hydrogen can be directly introduced into the mass spectrometer for analysis. However, due to the poor activity of zinc metal, the reproducibility of metal zinc reduction method is not good, the precision is not high enough, and the analysis data is not accurate enough. Craig established the uranium reduction method. Although the uranium reduction method has fast reaction speed, high precision, and accurate analysis data, the radioactive properties of metallic uranium and the disposal of radioactive waste generated in the experiment all have an impact on the work and ecological environment.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the existing hydrogen isotope analysis method and technology of water in the analysis of trace water samples due to few samples and weak signal, resulting in poor repeatability of the hydrogen isotope ratio in the analyzed water, not high enough precision, and poor analysis. Due to the inaccurate data and unfriendly environment, a method for analyzing hydrogen isotopes in water is provided. In addition, the method is simple and convenient to operate, and can prepare multiple samples at the same time by means of separate packaging, which has stronger operability and higher analysis efficiency than the traditional off-line analysis and detection method.

In order to achieve the above object, the present invention provides a method for analyzing hydrogen isotopes in water, the method comprising the following steps:

(i) put into the first collection tube after the two ends of the capillary tube for collecting the water sample are melted and sealed;

(ii) after putting the first collection pipe in step (i) into the second collection pipe equipped with chromium powder and carrying out vacuum treatment, the second collection pipe is melted and sealed;

(iii) breaking the capillary in the first collection tube, and under heating, the chromium powder in the second collection tube (10) reacts with the water sample in the capillary;

(iv) until the reaction of the chromium powder and the water sample in the step (iii) ends, put the second collection tube into the third collection tube, then connect the third collection tube with the analysis device, and release the hydrogen in the second collection tube, Hydrogen isotope analysis was performed to obtain the hydrogen isotope ratio in water.

Through the above technical solution, hydrogen isotopes in water can be analyzed quickly and efficiently. During the analysis process, the reaction speed is fast, the sample consumption is small, the precision is high, the analysis results are accurate, and the repeatability is good. The method is simple and convenient to operate, environmentally friendly, and uses a separate package. The method can prepare multiple samples at the same time, which is more operable and more efficient than the traditional offline analysis and detection method.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention. In the attached image:

Fig. 1 is the structural representation of the pretreatment stage;

FIG. 2 is a schematic view of the structure of the second collection pipe.

Description of reference numerals

1. Vacuum line interface 2. Vacuum connection line 3. Pressure gauge

4. The first cold trap 5. The second cold trap 6. The absorption tube

7. Vacuum gauge 8. Vacuum pump 9. Two-way piston

10. Second collection tube 11. LPG gun 12. Expanding section

13. Reaching into the segment

Detailed ways

The endpoints of ranges and any values disclosed herein are not limited to the precise ranges or values, which are to be understood to encompass values proximate to those ranges or values. For ranges of values, the endpoints of each range, the endpoints of each range and the individual point values, and the individual point values can be combined with each other to yield one or more new ranges of values that Ranges should be considered as specifically disclosed herein.

The invention provides a method for analyzing hydrogen isotopes in water, the method comprising the following steps:

(i) put into the first collection tube after the two ends of the capillary tube for collecting the water sample are melted and sealed;

(ii) after putting the first collecting pipe in step (i) into the second collecting pipe 10 containing the chromium powder and performing vacuum treatment, the second collecting pipe 10 is melted and sealed;

(iii) breaking the capillary in the first collection tube, and under heating, the chromium powder in the second collection tube 10 is reacted with the water sample in the capillary;

(iv) After the reaction between the chromium powder and the water sample in step (iii) is completed, put the second collection tube 10 into the third collection tube, then connect the third collection tube to the analysis device, and release the second collection tube 10. Hydrogen, hydrogen isotope analysis was performed to obtain the hydrogen isotope ratio δD in water.

According to the present invention, in order to facilitate the packaging of the collected water samples, and in order to facilitate the outflow of the water samples to react with the chromium powder in subsequent operations, the capillary tube for collecting the water sample may be a quartz glass capillary tube; the size of the capillary tube is not particularly limited, It can be prepared by a conventional glass drawing process, for example, the length of the capillary can be 5-8 cm, and the inner diameter can be 1-2 mm.

According to the present invention, the water sample can be collected by injecting it into the capillary tube through a micro-syringe. When collecting the water sample, it is necessary to ensure that the water sample can flow continuously and without faults in the capillary tube.

According to the present invention, in order to prevent the capillary tube that collected the water sample from being adsorbed to the container wall, which is not conducive to breaking when the water sample needs to be released later, it is preferable to use a first collection tube to store the capillary tube, and then put it into the first collection tube containing the chromium powder. Two collection tubes for subsequent operations. The material of the first collection tube is not particularly limited, for example, it may be a quartz collection tube. The shape and size of the first collection tube are not particularly limited, as long as the capillary tube can be accommodated. For example, the first collection tube may be a flat-mouthed round-bottomed collection tube, the length may be 4-5 cm, and the inner diameter may be 4-5 cm. 5-6mm.

According to the present invention, the operation process of melting and sealing is not particularly limited, and can be a conventional practice in the field. For example, a liquefied gas gun can be used to heat a collection tube made of glass or quartz to melt and seal it. For the fusing and sealing of the capillary, the fusing operation is to carry out fusing sealing at both ends after the water sample has been collected, and after ensuring that the water sample flows continuously in the capillary without faults; for the fusing of the second collection tube 10, due to Its bottom end is a closed structure, and when the second collection tube 10 is vacuumed, its top end is connected to the vacuum pipeline interface 1 of the pre-processing stage. Therefore, the melting and sealing operation is to use a liquefied gas gun to connect the second collection tube 10 and the second collection tube 10. The part below the connection of the vacuum line interface 1 of the pretreatment stage and above the open end of the first collection pipe placed inside the second collection pipe 10 is heated to melt and seal the second collection pipe 10 .

According to the present invention, before the water sample reacts with the chromium powder, the collection tube containing it needs to be evacuated. In this way, it can be ensured that all the hydrogen samples for final analysis come from the reaction between the water sample and the chromium powder. The hydrogen isotopes used for analysis are all from the collected water samples.

According to the present invention, the vacuuming process of step (ii) is processed by using a pre-processing stage, as shown in FIG. 1 , the pre-processing stage includes: a vacuum pipeline interface 1, a vacuum communication pipeline 2, a pressure gauge 3, a first cooling system Trap 4, second cold trap 5, absorption tube 6, vacuum gauge 7, vacuum pump 8 and two-way piston 9, wherein the vacuum line interface 1, pressure gauge 3, first cold trap 4, second cold trap 5, The absorption pipe 6, the vacuum gauge 7 and the vacuum pump 8 are arranged in sequence along the suction direction of the vacuum pump of the vacuum communication pipeline 2, and a two-way piston 9 is arranged between the first cold trap 4 and the second cold trap 5, so A two-way piston 9 is provided between the vacuum gauge 7 and the vacuum pump 8, a two-way piston 9 is provided between the pressure gauge 3 and the first cold trap 4, and the vacuum line interface 1 is 10-20 These are arranged in sequence and at equal intervals along the suction direction of the vacuum pump of the vacuum communication pipeline 2 , and a two-way piston 9 is correspondingly arranged on each of the vacuum pipeline interfaces 1 .

According to the present invention, in order to facilitate the access of the device to be evacuated to the pretreatment station and to ensure good air tightness when the vacuum pipeline interface 1 is connected to the device to be evacuated, the lower end of the vacuum pipeline interface 1 in the pretreatment platform A silicone tube is preferably provided for connection to the device to be evacuated.

According to the present invention, the method of breaking the capillary in the first collection tube in step (iii) is not particularly limited. For example, the second collection tube 10 can be shaken to drive the vibration of the first collection tube, so that the capillary is broken and released. The water sample in the capillary is in contact with the chromium powder and reacts under heating. The reaction of the water sample and the chromium powder is carried out according to the following formula:

It can be seen that under the premise of complete reaction of the water sample and good airtightness of the device, all the hydrogen elements in the water sample are finally converted into hydrogen, that is, all the hydrogen isotopes used for analysis come from the collected water sample.

According to the present invention, in order to improve the accuracy of the method for analyzing hydrogen isotopes in water, and to facilitate the operation of releasing hydrogen from the second collection pipe 10 in step (iv), as shown in FIG. 2 , the second collection pipe The lower end of 10 is preferably formed with a protruding section 13 , and the remaining part of the upper end of the second collecting pipe 10 is a diameter-expanding section 12 . The size of the enlarged diameter section 12 and the protruding section 13 is not particularly limited, as long as the enlarged diameter section 12 is sufficient to accommodate the first collecting tube, and the protruding section 13 can be easily broken when hydrogen is required to be released That is, for example, the length ratio of the enlarged diameter section 12 and the extending section 13 may be 3-4:1, and the inner diameter ratio of the enlarged diameter section 12 and the extending section 13 may be 7-9 :1.

In a preferred case, the length of the enlarged diameter section 12 of the second collection tube 10 may be 16.5-18 cm, and the inner diameter may be 8-15 mm; the length of the extending section 13 of the second collection tube 10 may be 5-15 mm. 6cm, the inner diameter can be 1-2mm.

According to the present invention, the third collection tube is connected to the analysis device and is used for sample sending and analysis, as long as the airtightness during the sample sending and analysis process can be guaranteed, and the third collection tube may be a glass sleeve. Preferably, the third collection tube includes a glass tube body and a glass piston, the glass piston is used to control the connection or disconnection between the glass tube body and the analysis device, and the lower half of the glass tube body is provided with a soft Tube. The hose is not particularly limited as long as it has elasticity. For example, the hose can be at least one of a metal hose, a glass hose, a rubber hose, a plastic hose, and a silicone hose.

According to the present invention, the size of the third collection pipe is not particularly limited, as long as the second collection pipe 10 can be accommodated and the protruding section of the second collection pipe 10 is satisfied when the second collection pipe 10 is put into it. 13 can pass through the inner cavity of the hose of the third collection tube. According to the size of the second collection tube 10, the length of the third collection tube may be 25-30 cm, and the inner diameter may be 25-30 mm.

According to the present invention, in order to facilitate the release of hydrogen from the second collection tube 10 when sample injection and analysis are required, the method of placing the second collection tube 10 into the third collection tube in step (iv) is as follows: The protruding section 13 protrudes into and penetrates the inner cavity of the hose of the third collection pipe; the method of releasing the hydrogen in the second collection pipe 10 is: bending the hose of the third collection pipe, so that the hose extends into and penetrates through the third collection pipe. The extending section 13 of the second collection tube 10 in the inner cavity of the flexible tube is broken, thereby releasing hydrogen gas, which is sent to the analysis device for analysis of hydrogen isotopes.

According to the present invention, the analysis device for analyzing hydrogen isotopes may be an analysis device conventionally used in the art for analyzing various stable isotope gases, for example, the analysis device may be a mass spectrometer. In the method provided by the present invention, when a mass spectrometer is used to analyze a sample, the third collection tube is first connected to the dual-channel sampling system of the mass spectrometer, the glass piston is opened, and the glass tube body of the third collection tube is placed in the same position as the mass spectrometer. When the vacuum degree is stable between 10 ^-7 -10 ^-8 Pa, close the glass piston, so that the glass body of the third collection tube is in the dual-channel injection system with the mass spectrometer. In the disconnected state, bend the hose part of the third collection tube, break the extending section 13 of the second collection tube 10, release the hydrogen gas, and then open the glass piston, so that the glass tube body of the third collection tube is in contact with the mass spectrometer. When the dual-channel injection system is connected, the injection is completed.

According to the present invention, the amount of the chromium powder is not particularly limited, as long as it is slightly excessive to make the water sample completely react. For example, the amount of the chromium powder can satisfy: the weight ratio of the chromium powder to the water sample 1000-1500:1.

According to the present invention, the heating conditions of step (iii) are not particularly limited, as long as the temperature required for the reaction between chromium powder and water is reached, and the heating time is sufficient for the entire reaction of the water sample. For example, the heating operation can be performed in In a muffle furnace, the specific heating conditions may include: the heating temperature is 800-900°C, and the heating time is 15-30min; preferably, the heating conditions may include: the heating temperature is 840-860°C, and the heating time is 15 minutes -20min.

In a preferred embodiment, the method for analyzing hydrogen isotopes in water may include the following steps: firstly, the two ends of the capillary tube from which the water sample was collected are melted and sealed, and then put into the first collection tube, and then the first collection tube Put it into the second collection tube 10 filled with chromium powder, then connect the second collection tube 10 with the vacuum pipeline interface 1 of the pre-processing stage through the silicone tube, and close the corresponding vacuum pipeline interface 1 connected with the second collection tube 10. The set two-way piston 9, open the vacuum pump 8, and cover the liquid nitrogen cup at the first cold trap 4 and the second cold trap 5, open the two-way piston 9 between the vacuum gauge 7 and the vacuum pump 8, the first cold trap 8 in turn The two-way piston 9 between the trap 4 and the second cold trap 5, the two-way piston 9 between the pressure gauge 3 and the first cold trap 4, and the two-way piston 9 correspondingly arranged on the vacuum line interface 1, pass the pressure gauge 3 and the vacuum gauge 7 to detect the vacuum degree of the pre-treatment table, until the vacuum degree reaches 0.01Pa, use the liquefied gas gun to put the second collection tube 10 and the vacuum pipeline interface 1 of the pre-treatment table below the junction, put into the first The part above the open end of the first collection pipe inside the second collection pipe 10 is heated, so that the second collection pipe 10 is fused and sealed. Then, the second collection tube 10 is shaken, thereby driving the vibration of the first collection tube, so as to rupture the capillary tube and release the water sample in the capillary tube. After that, the second collection tube 10 was placed in the muffle furnace, and the muffle furnace was heated to 850 °C at a heating rate of 15 °C/min, and kept at this temperature, so that the chromium powder and the water sample were contacted and reacted. After the second collection tube 10 is cooled to room temperature, the second collection tube 10 is put into the third collection tube, so that the protruding section 13 of the second collection tube 10 extends into and penetrates the third collection tube the tube lumen. Then connect the third collection tube to the dual-channel sampling system of the mass spectrometer, open the glass piston, make the glass body of the third collection tube in a state of communication with the mass spectrometer, and then perform vacuum treatment until the vacuum degree is stabilized at 10 Between ^-7 and -10 ^-8 Pa, close the glass piston, keep the glass body of the third collection tube disconnected from the dual-channel sampling system of the mass spectrometer, bend the hose part of the third collection tube, and break it The protruding section 13 of the second collection tube 10 releases hydrogen gas, and then opens the glass piston, so that the glass tube body of the third collection tube is in a state of communication with the dual-channel sampling system of the mass spectrometer, the sample injection is completed, and the hydrogen isotope analysis is carried out. Obtain the hydrogen isotope ratio in the hydrogen gas prepared from the tested water sample.

According to the present invention, when using a mass spectrometer for hydrogen isotope composition analysis, dual receivers are used to simultaneously collect sample hydrogen and standard hydrogen (hydrogen prepared from water samples according to international standards or national standards, and The ¹ H ⁺ and ² H ⁺ in the hydrogen calibration cylinder hydrogen) prepared with these standard water samples, the sample hydrogen enters the sample compartment when the sample is injected, and the standard hydrogen enters the standard compartment. The analysis results are compared, and the δD value (‰) of the hydrogen isotope composition of the tested water sample relative to the standard water sample is directly calculated, and expressed as the ratio of the corresponding isotope in the standard water sample, specifically calculated according to the following formula get:

In the formula: SA represents the water sample to be tested, and ST represents the standard water sample.

According to the present invention, due to the ingenious design of the second collection pipe 10 and the third collection pipe, the air tightness in the process of hydrogen generation and sample injection analysis is effectively guaranteed, and compared with the traditional analysis method, the air tightness is effectively guaranteed. Different samples use the same vacuum processing device and adopt separate packaging means to effectively avoid mutual contamination between different samples. Therefore, the error of the hydrogen isotope ratio in the water obtained in the step (iv) is minimized, so that the The error is -1‰-1‰, and the error is statistically obtained from the difference between the results obtained by analyzing a large number of standard water samples and the standard value of the standard water sample.

The present invention will be described in detail below by means of examples.

In the following examples, the mass spectrometer is a Delta S mass spectrometer produced by Thermo Fisher Company, and the H sample to be tested is detected by the _dual -inlet system (Dual-Inlet) of the mass spectrometer, and the sample is detected at a signal intensity of 7000mV. Measurement, each sample was tested 6 times, and the average value was taken.

In the following examples, the international standard material is Standard Mean Ocean Water (SMOW), and the δD value (‰) of the tested water sample represents the hydrogen isotope composition of the tested water sample, and its average value relative to the standard The ratio of the corresponding isotopes in ocean water (V-SMOW) is expressed, and is calculated according to the following formula:

where SA represents the sample and SMOW represents the standard mean ocean water.

Examples 1-10

The two ends of the capillary tube that collected the water sample are melted and sealed and put into the first collection tube, then the first collection tube is put into the second collection tube 10 containing the chromium powder, and then the second collection tube 10 is passed through the silica gel. The pipe is communicated with the vacuum line interface 1 of the pretreatment stage, close the two-way piston 9 correspondingly provided on the vacuum line interface 1 communicated with the second collection pipe 10, turn on the vacuum pump 8, and connect the first cold trap 4 and the second cold trap. Put liquid nitrogen cups on 5 places, open the two-way piston 9 between the vacuum gauge 7 and the vacuum pump 8, the two-way piston 9 between the first cold trap 4 and the second cold trap 5, and the pressure gauge 3 and the first cold trap. The two-way piston 9 between the traps 4 and the corresponding two-way piston 9 on the vacuum pipeline interface 1 are used to detect the vacuum degree of the pretreatment table through the pressure gauge 3 and the vacuum gauge 7. When the vacuum degree reaches 0.01Pa, Use a liquefied gas gun to heat the part below the connection between the second collection pipe 10 and the vacuum line interface 1 of the pre-processing stage, and above the opening end of the first collection pipe placed inside the second collection pipe 10, so that the second collection pipe 10 is heated. Tube 10 is fused and sealed. Then, the second collection tube 10 is shaken, thereby driving the vibration of the first collection tube, so as to rupture the capillary tube and release the water sample in the capillary tube. Then, the second collection tube 10 is placed in a muffle furnace for heating, so that the chromium powder and the water sample are contacted and reacted. After all the water samples have reacted, the second collection tube 10 is cooled to room temperature, and then placed in the Three collecting tubes, so that the protruding section 13 of the second collecting tube 10 extends into and penetrates the inner cavity of the hose of the third collecting tube. Then connect the third collection tube to the dual-channel sampling system of the mass spectrometer through the tee joint, and then carry out vacuum treatment. After the vacuum degree is stabilized at 10 ^-7 Pa, rotate the sealing piston to make the sealing piston in the double-channel with the mass spectrometer. When the sampling system is disconnected, bend the hose part of the third collection tube, break the extending section 13 of the second collection tube 10, release the hydrogen gas, and then rotate the sealing piston, so that the sealing piston is in the dual-channel connection with the mass spectrometer. When the sampling system is connected, the sampling is completed, and the hydrogen isotope analysis is carried out to obtain the hydrogen isotope ratio in the hydrogen obtained from the tested water sample, so as to obtain the tested water with a hydrogen isotope ratio equivalent to the hydrogen isotope ratio in the hydrogen obtained from the tested water sample. The hydrogen isotope ratio in the sample.

Table 1 lists the types and amounts of materials used in Examples 1-10, as well as the test results and the standard values of the hydrogen isotope ratios in the water samples. Table 2 shows the specific analysis results of the samples tested 6 times in Examples 1-10.

Comparative Examples 1-10

According to the method for testing hydrogen isotopes in natural water, mineral inclusions and hydrogen-containing minerals by metal zinc method (Zhou Yamin, Minerals and Geology, 1995(S1): 398-403.), the online method was adopted. The same water samples as in Examples 1-10 were tested.

Table 1 lists the types and amounts of materials used in Comparative Examples 1-10, as well as the test results and the standard values of the hydrogen isotope ratios in the water samples.

Table 1

Table 2

It can be seen from the results in Table 1 and Table 2 that when using the method provided by the present invention to analyze hydrogen isotopes in water, the method of separate packaging is used, which effectively avoids the traditional analysis method when testing different samples using the same vacuum treatment device. Mutual contamination, the final obtained hydrogen isotope ratio data in water has higher accuracy and better reproducibility. The method provided by the present invention also has the advantages of less water sample consumption, fast reaction speed, high precision and environmental friendliness. In addition, the method provided by the present invention simplifies the sample preparation process, improves the sample preparation efficiency, saves the pretreatment time, and can meet the needs of industrial analysis of large quantities of samples.

In Comparative Examples 1-8, two cold traps were used to make the water sample pass through a zinc furnace at 400°C in the form of steam, and then the generated hydrogen was adsorbed and collected in a gas sample tube for mass spectrometry analysis. The operation process was complicated and tedious, and the determination of When the hydrogen isotope ratio in water is used, the amount of water sample is large, the data accuracy is low, and the reproducibility is poor.

The preferred embodiments of the present invention have been described above in detail, however, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, a variety of simple modifications can be made to the technical solutions of the present invention, including the combination of various technical features in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed in the present invention. All belong to the protection scope of the present invention.

Claims (4)

1. A method of analyzing hydrogen isotopes in water, said method comprising the steps of:

two ends of a capillary tube for collecting a water sample are sealed by melting and then are placed into a first collecting pipe, the first collecting pipe is placed into a second collecting pipe (10) filled with chromium powder, the second collecting pipe (10) is communicated with a vacuum pipeline interface (1) of a pretreatment table through a silicone tube, a two-way piston (9) correspondingly arranged on the vacuum pipeline interface (1) communicated with the second collecting pipe (10) is closed, a vacuum pump (8) is opened, liquid nitrogen cups are sleeved at a first cold trap (4) and a second cold trap (5), the two-way piston (9) between a vacuum gauge (7) and the vacuum pump (8), the two-way piston (9) between the first cold trap (4) and the second cold trap (5), the two-way piston (9) between a pressure gauge (3) and the first pressure gauge cold trap (4) and the two-way piston (9) correspondingly arranged on the vacuum pipeline interface (1) are sequentially opened, detecting the vacuum degree of the pretreatment table through a pressure gauge (3) and a vacuum gauge (7), and heating a part below the joint of the second collecting pipe (10) and the vacuum pipeline interface (1) of the pretreatment table and above the opening end of the first collecting pipe placed in the second collecting pipe (10) by using a liquefied gas fire gun until the vacuum degree reaches 0.01Pa, so that the second collecting pipe (10)Fusing and sealing, then shaking second collecting pipe (10), thereby driving the vibrations of first collecting pipe, thereby make the capillary break, release the water sample in the capillary, later place second collecting pipe (10) in the muffle furnace and heat, make chromium powder and water sample contact and reaction, treat that the water sample is whole to react, after cooling second collecting pipe (10) to room temperature, put into third collecting pipe with second collecting pipe (10), make stretch into section (13) of stretching into of second collecting pipe (10) and stretch into and run through the hose inner chamber of third collecting pipe, then pass through three way connection with the third collecting pipe and insert the double-circuit sampling system of mass spectrograph, then carry out the evacuation and handle, treat that vacuum is stable at 10^-7Pa, rotating the sealing piston to enable the sealing piston to be in a state of being disconnected with a two-way sampling system of the mass spectrometer, bending a hose part of a third collecting pipe, breaking an extending section (13) of a second collecting pipe (10), releasing hydrogen, rotating the sealing piston again to enable the sealing piston to be in a state of being communicated with the two-way sampling system of the mass spectrometer, completing sampling, and performing hydrogen isotope analysis to obtain a hydrogen isotope ratio in hydrogen prepared from a water sample to be detected, so that a hydrogen isotope ratio in the water sample to be detected which is equivalent to the hydrogen isotope ratio in the hydrogen prepared from the water sample to be detected is obtained;

wherein the water sample is injected into the capillary through a micro-injector, the continuous flow of the water sample in the capillary is ensured during the collection of the water sample, no fault is generated,

the capillary tube is 5-8cm in length and 1-2mm in inner diameter, the first collecting tube is a quartz tube with a flat opening and a round bottom, the first collecting tube is 4-5cm in length and 5-6mm in inner diameter;

the second collecting pipe (10) comprises an expanding section (12) and an extending section (13), one end of the extending section (13) is sealed, the other end of the extending section is communicated with the expanding section (12), the length ratio of the expanding section (12) to the extending section (13) is 3-4:1, the inner diameter ratio of the expanding section (12) to the extending section (13) is 7-9:1, the length of the expanding section (12) of the second collecting pipe (10) is 16.5-18cm, and the inner diameter is 8-15 mm; the length of an extending section (13) of the second collecting pipe (10) is 5-6cm, and the inner diameter is 1-2 mm;

wherein the heating conditions in the muffle furnace comprise: the heating temperature is 800-900 ℃, and the heating time is 15-30 min.

2. The method according to claim 1, wherein the error in the ratio of hydrogen isotopes in the measured water is obtained from-1% to 1%.

3. The method as claimed in claim 1 or 2, wherein the weight ratio of the chromium powder to the water sample is 1000-1500: 1.

4. the method of claim 1 or 2, wherein the conditions of heating in the muffle comprise: the heating temperature is 840-860 ℃, and the heating time is 15-20 min.

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