Water sample purging and sampling device and isotope detection instrument

Abstract

The invention discloses a water sample purging and sampling device and an isotope detection instrument.The water sample purging and sampling device comprises a six-way valve, a heat preservation box, a flow limiting pipe, a sample collecting pipe and a water sample preparation device, the six-way valve is provided with six connecting points, and when the six-way valve is switched between a sampling state and a sampling state, the six connecting points are connected with the heat preservation box; the method comprises the following steps of: freezing a water sample in a sample collection pipe in a water sample preparation device, instantly and completely unfreezing and vaporizing the water sample after a sample introduction instruction is given, and completely introducing water vapor into a TC / EA device under the purging of helium flow. The device can ensure that water in the pipeline runs in a water vapor state, the memory effect possibly caused by water vapor condensation is greatly reduced, and the test accuracy is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and particularly to a water sample purge injection device and an isotope detection instrument. Background Art

[0002] The research on stable hydrogen and oxygen isotopes in water has been widely applied in the fields of geochemistry, life science, etc. There are many testing devices and related testing methods for the ratio of hydrogen and oxygen isotopes in water. Among them, the TC / EA high-temperature pyrolyzer is a testing device for the ratio of hydrogen and oxygen isotopes in water that has been widely used in recent years. Its principle is that water undergoes a pyrolysis reaction with carbon particles in a reaction furnace (1400 °C) to generate gases such as CO and H2. The pyrolyzed gases are separated by chromatography and then enter an isotope mass spectrometer to complete the detection of stable hydrogen and oxygen isotopes. This device has been adopted by many domestic and foreign laboratories due to its advantages of complete, rapid, stable, and continuous on-line pyrolysis. However, the TC / EA has a relatively large memory effect on the sample testing instrument.

[0003] In 2013, Sun Weizhen, Yu Haitang et al. developed a "pre-stage device for testing hydrogen and oxygen isotopes in salty and organic matter-containing water" (Patent No.: ZL.201310025226.3), which is mainly aimed at the determination of high-salt content water samples such as plateau lake water and river water in arid areas, as well as plant extracts rich in organic matter. This set of devices can reduce the influence of salts and organic matter on the device and results, and also reduce the memory effect. However, it still cannot meet the scientific research needs for the testing of samples with similar isotope values. Especially for the detection of ice core samples (with an interval of 1-2 cm between two adjacent ones), its memory effect often exceeds the accuracy requirements of the instrument.

[0004] Based on the above requirements, through multiple experiments and method improvements, the present invention has developed a water sample purge injection device of the present invention, which is installed at the liquid injection port of a TC / EA elemental analyzer and is used for on-line analysis of hydrogen and oxygen isotopes in water samples. The application scope includes the detection of all types of water samples, including "brine" desalination and organic matter water. Summary of the Invention

[0005] The object of the present invention is to provide a water sample purge injection device to address the technical defects existing in the prior art. This device is directly connected to a TC / EA elemental analyzer, effectively removing salts and organic matter impurities in water while reducing the influence of the memory effect of the instrument on the test results.

[0006] Another object of the present invention is to provide an isotope detection instrument based on the above water sample purge injection device.

[0007] The technical solution adopted to achieve the object of the present invention is as follows: A water sample purge injection device includes a six-way valve, an incubator, a flow limiting tube, and a water sample preparation device, wherein: The six-way valve is provided with six contacts, namely a first contact, a second contact, a third contact, a fourth contact, a fifth contact and a sixth contact that are adjacent to each other in sequence and arranged in a ring. When the six-way valve switches between the sampling state and the injection state, each contact is selectively connected to its adjacent contact; The first contact is connected to a first helium gas pipeline. The second contact is connected to the inlet of a flow-limiting tube through a pipeline. The outlet of the flow-limiting tube is connected to the fifth contact through a pipeline. The sixth contact is connected to a He exhaust pipe. The third contact is connected to a second helium gas pipeline. The fourth contact is used to connect to a sample output pipeline. The six-way valve and its six contacts, the first helium gas pipeline, the second helium gas pipeline, the flow-limiting tube, the pipeline between the second contact and the flow-limiting tube, and the pipeline between the flow-limiting tube and the fifth contact are all arranged in an incubator; A sample collection tube is provided in the water sample preparation device. A first upper valve is provided on the pipeline between the inlet of the sample collection tube and the inlet of the flow-limiting tube. A second upper valve is provided on the pipeline between the outlet of the sample collection tube and the outlet of the flow-limiting tube. A sample inflow tube is also connected to the inlet of the sample collection tube. A first lower valve is provided on the sample inflow tube. A sample outflow tube is also connected to the outlet of the sample collection tube. A second lower valve is provided on the sample outflow tube.

[0008] In the above technical solution, the first helium gas pipeline, the second helium gas pipeline, the He exhaust pipe, the sample inflow tube, the sample outflow tube, the sample output pipeline, and each pipeline for connection are all quartz capillary tubes. The ratio of the flow rate of the flow-limiting tube to the flow rate of the sample collection tube is 1:(10 - 12).

[0009] On the other hand, the present invention also includes the working method of the water sample purging and injection device: Water sample collection and freezing process: The six-way valve is in the sampling state. The first upper valve and the second upper valve in the water sample preparation device are closed, and the first lower valve and the second lower valve are opened. The water sample preparation device enters the condensation state. The sample enters the sample collection tube through the sample inflow tube and is all condensed in the sample collection tube. At the same time, a stream of helium gas is introduced from the first helium gas pipeline through the first contact of the six-way valve, enters the flow-limiting tube through the second contact of the six-way valve, then passes through the fifth contact of the six-way valve and the sixth contact of the six-way valve, and finally is discharged from the He exhaust pipe. This stream of helium gas flow passes through the flow-limiting tube to maintain the cleanliness of the sampling pipeline. A stream of helium gas is output from the second helium gas pipeline through the third contact of the six-way valve and the fourth contact of the six-way valve by the sample output pipeline to keep the system clean; After the condensation is completed, the first upper valve is opened, the second upper valve is closed, and the first lower valve and the second lower valve remain open. A large flow of helium gas is purged to let the impurities in the sample collection tube be discharged from the first lower valve and the second lower valve respectively; Sample collection tube equilibration process: When the water sample collection and freezing are completed, close the first lower valve and the second lower valve inside the water sample preparation device, and open the first upper valve and the second upper valve to ensure that the sample collection tube is in a helium gas flow environment and the frozen water sample in the sample collection tube is in a stable equilibrium state; Water sample output process: When the six-way valve is in the injection state, start the heating program of the water sample preparation device to rapidly heat up the sample collection tube. The water sample in the sample collection tube is instantaneously and completely thawed and vaporized. A stream of helium gas enters the sample collection tube from the second helium gas pipeline through the third contact point of the six-way valve, the second contact point of the six-way valve, and the first upper valve. After purging the water vapor in the sample collection tube, it then passes through the second upper valve, the fifth contact point of the six-way valve, and the fourth contact point of the six-way valve. The helium gas carries the vaporized water sample and is output via the sample output pipeline.

[0010] Another aspect of the present invention further includes an isotope detection instrument based on the above water sample purge injection device.

[0011] Another aspect of the present invention, an isotope detection instrument includes the above water sample purge injection device and a TC / EA device, and the outlet of the sample output pipeline is connected to the interface of the TC / EA device.

[0012] In the above technical solution, the TC / EA device includes a TC / EA injection port, a TC / EA reaction tube, a chromatographic separation column, a continuous flow device, and a gas stable isotope mass spectrometer. The sample output pipeline is connected to the TC / EA injection port, the TC / EA injection port is connected to the inlet of the TC / EA reaction tube through a pipeline, the outlet of the TC / EA reaction tube is connected to the inlet of the chromatographic separation column through a pipeline, and the outlet of the chromatographic separation column is connected to the injection port of the gas stable isotope mass spectrometer through the continuous flow device.

[0013] In the above technical solution, the TC / EA reaction tube is filled with quartz wool and carbon particles.

[0014] In the above technical solution, the packing in the chromatographic separation column is 5A molecular sieve.

[0015] In the above technical solution, the six-way valve is communicatively connected to the control system of the gas stable isotope mass spectrometer.

[0016] In the above technical solution, the water sample preparation device is communicatively connected to the control system of the gas stable isotope mass spectrometer.

[0017] In the above technical solution, the incubator is communicatively connected to the control system of the gas stable isotope mass spectrometer.

[0018] Another aspect of the present invention further includes a detection method for the above isotope detection instrument, including the following steps: Step 1, water sample collection and freezing process: The six-way valve is in the sampling state. The first upper valve and the second upper valve in the water sample preparation device are closed, and the first lower valve and the second lower valve are opened. The water sample preparation device enters the condensation state. The sample enters the sample collection tube through the sample inlet tube and is completely condensed in the sample collection tube. At the same time, a stream of helium gas is introduced from the first helium gas pipeline through the first contact point of the six-way valve, enters the flow restrictor through the quartz capillary and the second contact point of the six-way valve, then passes through the flow restrictor, the fifth contact point of the six-way valve, the sixth contact point of the six-way valve, and finally discharges from the He exhaust pipe. This stream of helium gas passes through the flow restrictor to maintain the cleanliness of the sampling pipeline; a stream of helium gas is output from the second helium gas pipeline through the third contact point and the fourth contact point of the six-way valve through the sample output pipeline, enters the TC / EA reaction tube from the TC / EA injection port, and then enters the gas stable isotope mass spectrometer through the chromatographic separation column and the continuous flow device. This stream of helium gas maintains the helium gas flow state of the TC / EA device; After the condensation is completed, the first upper valve is opened, the second upper valve is closed, and the first lower valve and the second lower valve remain open. High-flow helium gas purging is used to discharge the impurities in the sample collection tube from the first lower valve and the second lower valve respectively; Step 2, sample collection tube equilibration process: When the water sample collection and freezing are completed, the first lower valve and the second lower valve in the water sample preparation device are closed, and the first upper valve and the second upper valve are opened to ensure that the sample collection tube is in a helium gas flow environment and the frozen water sample in the sample collection tube is in a stable equilibrium state; Step 3, TC / EA pyrolysis and isotope detection process: The six-way valve is in the injection state. The heating program of the water sample preparation device is started to rapidly heat the sample collection tube. The water sample in the sample collection tube is instantaneously and completely thawed and vaporized. A stream of helium gas enters the sample collection tube from the second helium gas pipeline through the third contact point, the second contact point of the six-way valve, and the first upper valve. After purging the water vapor in the sample collection tube, it passes through the second upper valve, the fifth contact point of the six-way valve, the fourth contact point of the six-way valve, and enters the TC / EA reaction tube through the TC / EA injection port for high-temperature pyrolysis. The gas generated after pyrolysis passes through the chromatographic separation column and the continuous flow device, and finally enters the gas stable isotope mass spectrometer for hydrogen and oxygen stable isotope ratio detection.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. In the present invention, the water sample in the sample collection tube is first frozen, instantaneously and completely thawed and vaporized after the injection command is issued, and then the prepared water sample is completely purged into the TC / EA device with helium gas for high-temperature pyrolysis reaction to measure its hydrogen and oxygen stable isotope ratios; 2. The present invention can effectively avoid the water vapor fractionation that may be caused by the injection process and the sealing performance of the device, reduce the influence of the adhesion of salts and organic substances on the inner wall of the sample collection tube on the test results, and can be extended to the detection application range of all types of water samples. In particular, it has a significant improvement in reducing the memory effect of the instrument, and greatly improves the stability of analysis and the test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The sampling principle diagram of the present invention is shown.

[0021] Figure 2 The sample injection principle diagram of the present invention is shown.

[0022] In the figure: 1 - first contact point, 2 - second contact point, 3 - third contact point, 4 - fourth contact point, 5 - fifth contact point, 6 - sixth contact point, 7 - six-way valve, 8 - incubator, 9 - flow limiting tube, 10 - sample collection tube, 11 - water sample preparation device, 12 - first helium gas pipeline, 13 - second helium gas pipeline, 14 - He exhaust pipe, 15 - TC / EA injection port, 16 - TC / EA reaction tube, 17 - chromatographic separation column, 18 - continuous flow device, 19 - gas stable isotope mass spectrometer, 20 - sample inflow tube, 21 - sample outflow tube, 22 - sample output pipeline; V1 - first upper valve, V2 - second upper valve, V3 - first lower valve, V4 - second lower valve. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] Embodiment 1 As Figure 1 - Figure 2 shown, a water sample purge injection device includes a six-way valve 7, an incubator 8, a flow limiting tube 9, and a water sample preparation device 11, wherein: Six contact points are provided on the six-way valve 7, which are respectively the first contact point 1, the second contact point 2, the third contact point 3, the fourth contact point 4, the fifth contact point 5, and the sixth contact point 6 that are adjacent in sequence and arranged in a ring. When the six-way valve 7 switches between the sampling state and the injection state, each contact point is selectively connected to its adjacent contact point. Specifically, when the six-way valve 7 is in the sampling state A, the first contact point 1 is connected to the second contact point 2, the third contact point 3 is connected to the fourth contact point 4, and the fifth contact point 5 is connected to the sixth contact point 6. When the six-way valve 7 is in the injection state B, the first contact point 1 is connected to the sixth contact point 6, the fifth contact point 5 is connected to the fourth contact point 4, and the third contact point 3 is connected to the second contact point 2.

[0025] A first helium gas pipeline 12 is connected to the first contact point 1. The second contact point 2 is connected to the inlet of a flow-limiting pipe 9 through a pipeline. The outlet of the flow-limiting pipe 9 is connected to the fifth contact point 5 through a pipeline. A He exhaust pipe 14 is connected to the sixth contact point 6. A second helium gas pipeline 13 is connected to the third contact point 3. The fourth contact point 4 is used to connect to a sample output pipeline 22. The six-way valve 7 and its six contact points, the first helium gas pipeline 12, the second helium gas pipeline 13, the flow-limiting pipe 9, the pipeline between the second contact point 2 and the flow-limiting pipe 9, and the pipeline between the flow-limiting pipe 9 and the fifth contact point 5 are all arranged in a heat preservation box 8; A sample collection pipe 10 is arranged in the water sample preparation device 11. A first upper valve V1 is arranged on the pipeline between the inlet of the sample collection pipe 10 and the inlet of the flow-limiting pipe 9. A second upper valve V2 is arranged on the pipeline between the outlet of the sample collection pipe 10 and the outlet of the flow-limiting pipe 9. A sample inflow pipe 20 is further connected to the inlet of the sample collection pipe 10. A first lower valve V3 is arranged on the sample inflow pipe 20. A sample outflow pipe 21 is further connected to the outlet of the sample collection pipe 10. A second lower valve V4 is arranged on the sample outflow pipe 21.

[0026] Preferably, the first helium gas pipeline 12, the second helium gas pipeline 13, the He exhaust pipe 14, the sample inflow pipe 20, the sample outflow pipe 21, the sample output pipeline 22, and each pipeline for connection are all quartz capillary tubes.

[0027] Example 2 This embodiment provides a working method of the water sample purging and injection device described in Example 1: Water sample collection and freezing process: As Figure 1 shown, the six-way valve 7 is in the sampling state A. The first upper valve V1 and the second upper valve V2 in the water sample preparation device 11 are closed, and the first lower valve V3 and the second lower valve V4 are opened. The water sample preparation device 11 enters the condensation state. The sample enters the sample collection pipe 10 through the sample inflow pipe 20 and is all condensed in the sample collection pipe 10. At the same time, a stream of helium gas is introduced from the first helium gas pipeline 12 through the first contact point 1 of the six-way valve 7, enters the flow-limiting pipe 9 through the second contact point 2 of the six-way valve 7, then passes through the fifth contact point 5 of the six-way valve 7 and the sixth contact point 6 of the six-way valve 7, and finally is discharged from the He exhaust pipe 14. This stream of helium gas flow passes through the flow-limiting pipe 9 to maintain the cleanliness of the sampling pipeline. The flow rate of the flow-limiting pipe 9 ≤ 10 ml / min. A stream of helium gas is output from the second helium gas pipeline 13 through the third contact point 3 of the six-way valve 7, the fourth contact point 4 of the six-way valve 7, and the sample output pipeline 22 to keep the system clean; After condensation is completed, open the first upper valve V1, close the second upper valve V2, and keep the first lower valve V3 and the second lower valve V4 open. Purge with a large flow of helium gas (flow rate of 100 - 120 ml / min) so that the impurities in the sample collection tube 10 are discharged from the first lower valve V3 and the second lower valve V4 respectively, reducing the entry of possible impurities in the sample collection tube 10 into the six-way valve 7 or clogging or contaminating the pipeline; Equilibration process of the sample collection tube 10: When the water sample collection and freezing are completed, close the first lower valve V3 and the second lower valve V4 in the water sample preparation device 11, and open the first upper valve V1 and the second upper valve V2 to ensure that the sample collection tube 10 is in an environment of helium gas flow (flow rate of 100 - 120 ml / min), and the frozen water sample in the sample collection tube 10 is in a stable equilibrium state; Water sample output process: As Figure 2 shown, the six-way valve 7 is in the injection state B. Start the heating program of the water sample preparation device 11 to quickly heat up the sample collection tube 10. The water sample in the sample collection tube 10 is instantly and completely thawed and vaporized. A stream of helium gas (flow rate of 100 - 120 ml / min) is introduced from the second helium pipeline 13 through the third contact 3 of the six-way valve 7, enters the sample collection tube 10 through the second contact 2 of the six-way valve 7 and the first upper valve V1, purges the water vapor in the sample collection tube 10, and then passes through the second upper valve V2, the fifth contact 5 of the six-way valve 7, and the fourth contact 4 of the six-way valve 7. The helium gas carries the vaporized water sample and is output through the sample output pipeline 22. During this process, the flow rate of the flow-limiting tube 9 ≤ 10 ml / min, which will not affect the sample flow rate and the actual amount of sample carried.

[0028] Example 3 This example provides an isotope detection instrument based on the above water sample purge injection device.

[0029] An isotope detection instrument includes the water sample purge injection device as described in Example 1 and a TC / EA device. The outlet of the sample output pipeline 22 is connected to the interface of the TC / EA device. The water sample purge injection device is directly connected to the interface of the TC / EA device, which is convenient for installation and use and has good application and promotion value.

[0030] Preferably, the TC / EA device includes a TC / EA injection port 15, a TC / EA reaction tube 16, a chromatographic separation column 17, a continuous flow device 18, and a gas stable isotope mass spectrometer 19. Among them, the sample output pipeline 22 is connected to the TC / EA injection port 15, the TC / EA injection port 15 is connected to the inlet of the TC / EA reaction tube 16 through a pipeline, the outlet of the TC / EA reaction tube 16 is connected to the inlet of the chromatographic separation column 17 through a pipeline, and the outlet of the chromatographic separation column 17 is connected to the injection port of the gas stable isotope mass spectrometer 19 through the continuous flow device 18.

[0031] Preferably, quartz wool and carbon particles are contained in the TC / EA reaction tube 16.

[0032] Preferably, the packing material in the chromatographic separation column 17 is 5A molecular sieve.

[0033] Preferably, the continuous flow device 18 and the gas stable isotope mass spectrometer 19 are both commercially available accessories or instruments.

[0034] Preferably, the six-way valve 7 is communicatively connected to the control system of the gas stable isotope mass spectrometer 19, the water sample preparation device 11 is communicatively connected to the control system of the gas stable isotope mass spectrometer 19, and the incubator 8 is communicatively connected to the control system of the gas stable isotope mass spectrometer 19.

[0035] The switching of the working state of the six-way valve 7, the temperature rising program of the water sample preparation device 11, and the heating temperature of the incubator 8 are all controlled by the control system of the gas stable isotope mass spectrometer 19, ensuring the reliability of data acquisition.

[0036] Example 4 A detection method of an isotope detection instrument based on the water sample purge injection device as described in Example 3 includes the following steps: Step 1, the water sample collection and freezing process: As Figure 1 shown, the six-way valve 7 is in the sampling state A, the first upper valve V1 and the second upper valve V2 in the water sample preparation device 11 are closed, the first lower valve V3 and the second lower valve V4 are opened, the water sample preparation device 11 enters the condensation state, the sample enters through the sample inflow pipe 20 and is completely condensed in the sample collection tube 10. At the same time, a stream of helium gas is introduced from the first helium gas pipeline 12 through the first contact point 1 of the six-way valve 7, enters the flow limiting tube 9 through the quartz capillary and the second contact point 2 of the six-way valve 7, then passes through the flow limiting tube 9, the fifth contact point 5 of the six-way valve 7, the sixth contact point 6 of the six-way valve 7, and finally is discharged from the He exhaust pipe 14. This stream of helium gas passes through the flow limiting tube 9 to maintain the cleanliness of the sampling pipeline, and the flow rate of the flow limiting tube 9 ≤ 10 ml / min; a stream of helium gas is output from the second helium gas pipeline 13 through the third contact point 3 of the six-way valve 7 and the fourth contact point 4 of the six-way valve 7 through the sample output pipeline 22, enters the TC / EA reaction tube 16 from the TC / EA injection port 15, then passes through the chromatographic separation column 17 and the continuous flow device 18 and enters the gas stable isotope mass spectrometer 19. This stream of helium gas maintains the helium gas flow state of the TC / EA device; After condensation is completed, open the first upper valve V1, close the second upper valve V2, and keep the first lower valve V3 and the second lower valve V4 open. Purge the impurities in the sample collection tube 10 with helium at a large flow rate (flow rate of 100 - 120 ml / min) so that the impurities are discharged from the first lower valve V3 and the second lower valve V4 respectively, reducing the entry of possible impurities in the sample collection tube 10 into the six-way valve 7 or clogging or contaminating the pipeline; Step 2, the equilibration process of the sample collection tube 10: When the water sample collection and freezing are completed, close the first lower valve V3 and the second lower valve V4 in the water sample preparation device 11, and open the first upper valve V1 and the second upper valve V2 to ensure that the sample collection tube 10 is in an environment of helium gas flow (flow rate of 100 - 120 ml / min), and the frozen water sample in the sample collection tube 10 is in a stable equilibrium state; Step 3, the TC / EA pyrolysis and isotope detection process: As Figure 2 shown, when the six-way valve 7 is in the injection state B, start the heating program of the water sample preparation device 11 to rapidly heat up the sample collection tube 10. The water sample in the sample collection tube 10 is instantly and completely thawed and vaporized. A stream of helium gas (flow rate of 100 - 120 ml / min) enters the sample collection tube 10 from the second helium gas pipeline 13, through the third contact point 3 of the six-way valve 7, the second contact point 2 of the six-way valve 7, and the first upper valve V1. After purging the water vapor in the sample collection tube 10, it passes through the second upper valve V2, the fifth contact point 5 of the six-way valve 7, the fourth contact point 4 of the six-way valve 7, and enters the TC / EA reaction tube 16 through the TC / EA injection port 15 for high-temperature pyrolysis. The gas generated after pyrolysis passes through the chromatographic separation column 17 and the continuous flow device 18, and finally enters the gas stable isotope mass spectrometer 19 for hydrogen and oxygen stable isotope detection.

[0037] In the above steps, the working state of the six-way valve 7, the control of the freezing and vaporization temperatures of the water sample in the sample collection tube 10, and the temperature adjustment of the incubator 8 are given signal instructions by the gas stable isotope mass spectrometer 19 to ensure the reliability of data acquisition.

[0038] The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A water sample purge injection device, characterized in that: It includes a six-way valve, an insulated box, a flow limiting tube and a water sample preparation device, wherein: The six-way valve is provided with six contacts, namely, a first contact, a second contact, a third contact, a fourth contact, a fifth contact and a sixth contact, which are arranged in a ring in sequence and adjacent to each other. When the six-way valve is switched between the sampling state and the injection state, each contact is selectively connected to its adjacent contact. The first connection point is connected to a first helium pipeline, the second connection point is connected to an inlet of a flow limiting tube through a pipeline, the outlet of the flow limiting tube is connected to a fifth connection point through a pipeline, the sixth connection point is connected to a He gas release tube, the third connection point is connected to a second helium pipeline, the fourth connection point is used to connect a sample output pipeline, the six-way valve and its six connections, the first helium pipeline, the second helium pipeline, the flow limiting tube, the pipeline between the second connection point and the flow limiting tube, and the pipeline between the flow limiting tube and the fifth connection point are all arranged in an incubator; A sample collecting tube is provided in the water sample preparation device, a first upper valve is provided on the pipeline between the inlet of the sample collecting tube and the inlet of the flow limiting tube, a second upper valve is provided on the pipeline between the outlet of the sample collecting tube and the outlet of the flow limiting tube, a sample inlet tube is also connected to the inlet of the sample collecting tube, a first lower valve is provided on the sample inlet tube, a sample outflow tube is also connected to the outlet of the sample collecting tube, and a second lower valve is provided on the sample outflow tube.

2. The water sample purge injection device according to claim 1, characterized in that: The first helium pipeline, the second helium pipeline, the He venting pipe, the sample inlet pipe, the sample outlet pipe, the sample output pipe and each pipe used for connection are all quartz capillaries, and the ratio of the flow rate of the limiting tube to the flow rate of the sample collection tube is 1: (10-12).

3. An isotope detection instrument, characterized in that: It comprises the water sample purge injection device as described in claim 1 or 2.

4. An isotope detection instrument as claimed in claim 3, characterized in that: It comprises the water sample purge sampling device and the TC / EA device, and the outlet of the sample output pipeline is connected to the interface of the TC / EA device.

5. An isotope detection instrument as claimed in claim 4, characterized in that: The TC / EA device comprises a TC / EA injection port, a TC / EA reaction tube, a chromatographic separation column, a continuous flow device and a gas stable isotope mass spectrometer, wherein the sample output pipeline is connected to the TC / EA injection port, the TC / EA injection port is connected to the inlet of the TC / EA reaction tube through a pipeline, the outlet of the TC / EA reaction tube is connected to the inlet of the chromatographic separation column through a pipeline, and the outlet of the chromatographic separation column is connected to the sample inlet of the gas stable isotope mass spectrometer through the continuous flow device.

6. An isotope detection instrument as claimed in claim 5, characterized in that: The TC / EA reaction tube is filled with quartz wool and carbon particles.

7. An isotope detection instrument as claimed in claim 5, characterized in that: The filler in the chromatographic separation column is 5A molecular sieve.

8. An isotope detection instrument as claimed in claim 5, characterized in that: The six-way valve is communicatively connected with a control system of a gas stable isotope mass spectrometer.

9. An isotope detection instrument as claimed in claim 5, characterized in that: The water sample preparation device is communicatively connected with a control system of a gas stable isotope mass spectrometer.

10. An isotope detection instrument as claimed in claim 3, characterized in that: The incubator is communicatively connected with a control system of a gas stable isotope mass spectrometer.

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